CN112882134A

CN112882134A - Resin lens for head-mounted display

Info

Publication number: CN112882134A
Application number: CN202010127434.3A
Authority: CN
Inventors: 吉田淳一; 稻川雄一郎; 多田裕
Original assignee: Asahi Kasei Corp
Current assignee: Asahi Kasei Corp; Asahi Chemical Industry Co Ltd
Priority date: 2019-11-29
Filing date: 2020-02-28
Publication date: 2021-06-01
Also published as: CN112882135A; JP2021092767A

Abstract

The present invention aims to provide a resin lens for a head-mounted display that can obtain a clear image even in an optical system using polarized light. The lens for a head-mounted display is characterized in that the average value of the absolute values of the phase differences within the effective diameter is 5nm or less, and the concentration-intensity of an ethanol solution using fluorescein is determined from the fluorescence intensity at a wavelength of 530nm when a 2.0 mass% solution obtained by dissolving chloroform is measured at an excitation wavelength of 436nmThe content of the fluorescent substance determined by the formula of degree conversion is 0.1 × 10^‑9～4.0×10^‑9mol/L。

Description

Resin lens for head-mounted display

Technical Field

The present invention relates to a resin lens for a head-mounted display.

Background

In recent years, various electronic technologies called VR (Virtual Reality) and AR (Augmented Reality) have been rapidly developed, and Head Mounted Display (HMD) products have become popular as image Display devices thereof. Since a head-mounted display is an image display device used while wearing a head, it is required to be small and light and to have less discomfort when worn.

As a means for miniaturizing the head-mounted display, the following methods are proposed: the lenses are combined with 1/4 wavelength plates, reflective polarizers, and the like, and the polarization state of light passing through the lenses is changed to switch between reflection and transmission, thereby making an image half-way back and forth in one lens (patent documents 1 to 2).

The method has the following structure: an 1/4 wavelength plate and a reflective polarizing plate are arranged on the back surface of the lens with the front surface partially coated in a reflective manner, and light entering as circularly polarized light from the front surface of the lens passes through the lens and then is converted into linearly polarized light by a 1/4 wavelength plate; the linearly polarized light is reflected by the reflection type polarizer, converted into a circularly polarized light opposite to the original one by the 1/4 wavelength plate again, and enters the lens from the back surface to reach the front partial reflection coating part; the light reflected by the partial reflection coating section and coming out of the back surface of the lens passes through the 1/4 wavelength plate to become linearly polarized light having a different orientation from the first 90 °, passes through the reflection type polarizer plate, and enters the glasses as an image. Thus, a wide field of view with high magnification can be obtained even in a thin optical module.

Documents of the prior art

Patent document

Patent document 1: U.S. patent No. 6563638.

Patent document 2: japanese patent laid-open publication No. 2017-21321.

Disclosure of Invention

However, if the polarization state of light is changed while passing through the lens in the head-mounted display, for example, a part of light passes through the reflective polarizer after passing through the lens once, and thus a low-magnification image and a high-magnification image are superimposed on each other, and it is difficult to obtain a clear image. A clear image is obtained by using a glass lens having a small birefringence, but the weight is increased, which is not preferable. Therefore, a clear image is desired to be obtained even in a resin lens which is lightweight but is generally likely to cause birefringence.

Accordingly, an object of the present invention is to provide a resin lens for a head-mounted display that can obtain a clear image even in an optical system using polarized light.

The present inventors have conducted intensive studies to solve the above problems, and as a result, have found that the phase difference within the effective diameter due to the birefringence of the resin lens and the content of a fluorescent substance unexpectedly contained in the resin lens affect the sharpness of an image of a head-mounted display, and have completed the present invention.

That is, the present invention is as follows.

[1] A resin lens for a head-mounted display, characterized in that,

the average value of the absolute values of the phase differences within the effective diameter is 5nm or less,

the content of the fluorescent substance determined by using the concentration-intensity conversion formula of the ethanol solution of fluorescein from the fluorescence intensity at 530nm when the 2.0 mass% solution obtained by dissolving chloroform was measured at an excitation wavelength of 436nm was 0.1X 10^-9～4.0×10^-9mol/L。

[2] The resin lens for a head-mounted display according to [1], characterized in that a glass transition temperature Tg is more than 120 ℃ and 160 ℃ or less.

[3]According to [1]Or [2]]The resin lens for a head-mounted display is characterized in that the absolute value of the photoelastic coefficient is 3.0 x 10^-12Pa^-1The following.

[4] The resin lens for a head-mounted display according to any one of [1] to [3], characterized by comprising a methacrylic resin.

[5] The resin lens for a head-mounted display according to [4], wherein the methacrylic resin contains a methacrylic resin having a structural unit X, and the structural unit X is a structural unit having a ring structure in a main chain.

[6] The resin lens for a head-mounted display according to [5], wherein the structural unit X comprises at least one structural unit selected from the group consisting of a structural unit derived from an N-substituted maleimide monomer, a glutarimide-based structural unit, and a lactone ring-based structural unit.

[7] The resin lens for a head-mounted display according to [5], wherein the structural unit X comprises a structural unit derived from an N-substituted maleimide monomer.

[8] The resin lens for a head-mounted display according to [5], wherein the structural unit X comprises a glutarimide-based structural unit.

According to the present invention, it is possible to provide a resin lens for a head-mounted display that can obtain a clear image even in an optical system using polarized light.

Drawings

Fig. 1 is a schematic diagram of a simulation apparatus for reproducing the principle of a head-mounted display described in japanese patent application laid-open No. 2017-21321. In the examples, the evaluation of the sharpness of the image was performed using the simulation apparatus.

Wherein the reference numerals are explained as follows.

1: a liquid crystal display; 2: a polarizing plate; 3: 1/4 wavelength plates; 4: a semi-transparent mirror; 5: a resin lens; 6: 1/4 wavelength plates; 7: a reflective polarizing plate.

Detailed Description

The present embodiment (hereinafter, referred to as "the present embodiment") will be described in detail below, but the present invention is not limited to the following description, and can be carried out by being variously modified within the scope of the gist thereof.

[ resin lens for head-mounted display ]

The resin lens for a head-mounted display according to the present embodiment is characterized in that the average value of the absolute values of the phase differences within the effective diameter is 5nm or less, and the excitation wavelength 436n is determined from a 2.0 mass% solution obtained by dissolving chloroformThe fluorescence intensity at 530nm in the measurement of m is 0.1X 10 as the content of the fluorescent substance determined by using the concentration-intensity conversion formula of the ethanol solution of fluorescein^-9～4.0×10^-9mol/L。

Phase differences within the effective diameter-

In the resin lens for a head-mounted display according to the present embodiment, the average value of the absolute values of the phase differences within the effective diameter of the resin lens is 5nm or less, preferably 4nm or less, and more preferably 3nm or less. The average value of the absolute values of the phase differences is 5nm or less, and thus the image is clearly visible without being a double image.

Here, the effective diameter of the resin lens indicates a range in which an image can be recognized when the lens is assembled to a housing of a head-mounted display, and is represented by the diameter of a circle centered on the optical axis of the lens. The phase difference in the effective diameter of the resin lens can be measured specifically by the method described in the examples described later.

Content of fluorescent luminescent substances-

In the resin lens for a head-mounted display according to the present embodiment, the content of the fluorescent substance determined by using the concentration-intensity conversion equation of the ethanol solution of fluorescein from the fluorescence intensity at a wavelength of 530nm when a 2.0 mass% solution obtained by dissolving the resin lens in chloroform was measured at an excitation wavelength of 436nm was 0.1 × 10^-9～4.0×10^-9mol/L, preferably 0.2X 10^-9～3.5×10^-9mol/L, more preferably 0.3X 10^-9～3.0×10^-9mol/L, more preferably 0.3X 10^-9～2.5×10^-9mol/L. The content of the fluorescent substance is not more than the upper limit, whereby the image can be clearly distinguished without blurring. In addition, the content of the fluorescent substance is not less than the lower limit, and thus light of a low wavelength harmful to the naked eye can be suppressed from entering the naked eye more than necessary.

The reason why the image is seen blurrily when the fluorescence intensity is high (the content of the fluorescent substance is large) is not clear, but it is estimated that when fluorescence is generated by light transmitted through the lens, the light also goes in a direction other than the traveling direction of the original transmitted light, and the image is seen blurrily. It is assumed that in a head-mounted display lens that repeatedly reflects polarized light and transmits the polarized light through the lens twice or more, the optical path length in the transmissive lens becomes long, and the blur of the image becomes more conspicuous by further increasing the deviation from the original light traveling direction by the reflective polarizer and the partial reflection coating.

The content of the fluorescent substance can be measured specifically by the method described in the examples below.

Glass transition temperature-

The glass transition temperature (Tg) of the resin lens for a head-mounted display in the present embodiment is preferably greater than 120 ℃ and 160 ℃ or lower.

From the viewpoint of heat resistance against heat generation from electronic devices of the head-mounted display and the occurrence of photoelastic birefringence associated with dimensional change, the glass transition temperature of the resin lens for the head-mounted display is preferably greater than 120 ℃. The glass transition temperature (Tg) is more preferably 125 ℃ or higher, and still more preferably 130 ℃ or higher, from the viewpoint of dimensional stability at the use environment temperature.

On the other hand, when the glass transition temperature (Tg) is 160 ℃ or lower, melt processing at an extremely high temperature can be avoided, thermal decomposition of a resin or the like can be suppressed, and a good product can be obtained. The glass transition temperature (Tg) is preferably 150 ℃ or lower, and more preferably 140 ℃ or lower, from the viewpoint of further obtaining the above-described effects.

The glass transition temperature (Tg) can be determined by measurement according to JIS-K7121. Specifically, it can be determined by the method described in the examples below.

Photoelastic coefficient C_R-

Photoelastic coefficient C of the resin lens for a head-mounted display of the present embodiment_RAbsolute value of | C_RL, preferably 3.0 × 10^-12Pa^-1Hereinafter, more preferably 2.0 × 10^-12Pa^-1Hereinafter, more preferably 1.5 × 10^-12Pa^-1Hereinafter, more preferably 1.0 × 10^-12Pa^-1The following. Regarding the photoelastic coefficient, it is described in various documents (for example, refer to "general chemical introduction", No.39,1998 (issued by academic Press center)), and is defined by the following formulae (i-a) and (i-b). The photoelastic coefficient C can be known_RThe closer to zero the value of (b), the smaller the birefringence change due to external force.

|C_R|＝|Δn|/σ_R (i-a)

|Δn|＝|nx-ny| (i-b)

(in the formula, C_RDenotes the photoelastic coefficient, σ_RRepresents a tensile stress, | Δ n | represents an absolute value of birefringence, nx represents a refractive index in a stretching direction, and ny represents a refractive index in a direction perpendicular to the stretching direction in a plane. )

As long as the photoelastic coefficient C of the resin lens of the present embodiment_RAbsolute value of | C_RI is 3.0X 10^-12Pa^-1As described below, a resin lens in which stress generated when the lens is fixed and photoelastic birefringence caused by a change in dimensional temperature are sufficiently small and a clear image can be obtained.

The photoelastic coefficient C is_RThe measurement of (3) was carried out by finely cutting the resin lens and then forming a pressed film by using a vacuum compression molding machine. Specifically, it was determined by the method described in the examples below.

Transmittance of light-

In the resin lens for a head-mounted display according to the present embodiment, the ratio (T450/T680) of the transmittance at a wavelength of 450nm (T450) to the transmittance at a wavelength of 680nm (T680) in the light transmittance in the thickest part measured with a D65 light source field of view of 10 ° using a spectrocolorimeter is preferably 0.95 to 1.03, more preferably 0.97 to 1.01, and still more preferably 0.98 to 1.00. If the ratio (T450/T680) is within the above range, an image with a good color tone can be obtained.

The light transmittance can be measured specifically by the method described in the examples below.

Molecular weight and molecular weight distribution

The weight average molecular weight (Mw) of the resin lens for a head mount display in the present embodiment, as measured by Gel Permeation Chromatography (GPC), in terms of polymethyl methacrylate, is preferably in the range of 100,000 to 170,000, more preferably in the range of 100,000 to 150,000, and still more preferably in the range of 120,000 to 150,000. When the weight average molecular weight (Mw) is in the above range, the balance between mechanical strength and fluidity is also excellent.

The weight average molecular weight (Mw), the number average molecular weight (Mn), and the Z average molecular weight (Mz) of the resin lens can be measured by the following apparatus and conditions.

The measurement device: gel permeation chromatography (HLC-8320GPC) available from Tosoh corporation.

The measurement conditions are as follows.

A chromatographic column: one TSKguardcolumn SuperH-H, two TSKgel SuperHM-M and one TSKgel SuperH2500 are connected in series in sequence for use.

Temperature of the column: at 40 ℃.

Developing agent: tetrahydrofuran, flow rate: 0.6mL/min, 2, 6-di-tert-butyl-4-methylphenol (BHT) was added as an internal standard at 0.1 g/L.

A detector: an RI (differential refraction) detector.

Detection sensitivity: 3.0 mV/min.

Sample preparation: 0.02g of a tetrahydrofuran 20mL solution of a resin lens.

Sample introduction amount: 10 μ L.

Standard sample for calibration curve: ten types of polymethyl methacrylates (manufactured by Polymer laboratories, PMMA Calibration Kit M-M-10) having known monodisperse weight peaks and different molecular weights were used.

Weight Peak molecular weight (Mp)

Standard test specimen 1	1,916,000
		Standard specimen 2	625,500
Standard specimen No.3	298,900
		Standard test specimen 4	138,600
Standard test specimen 5	60,150
		Standard specimen 6	27,600
Standard specimen 7	10,290
		Standard specimen 8	5,000
Standard specimen 9	2,810
		Standard test specimen 10	850

Under the above conditions, the RI detection intensity with respect to the elution time of the resin lens was measured.

As described above, the weight average molecular weight (Mw), the number average molecular weight (Mn), and the Z average molecular weight (Mz) of the resin lens were obtained based on each calibration curve obtained by measurement of a calibration standard sample for calibration curve, and the molecular weight distribution (Mw/Mn) and (Mz/Mw) were determined using the values thereof.

Methanol insoluble fraction-

The amount of the methanol-insoluble component of the resin lens for a head-mounted display in the present embodiment is preferably 95% by mass or more, more preferably 95.5% by mass or more, further preferably 96% by mass or more, further preferably 96.5% by mass or more, particularly preferably 97% by mass or more, and most preferably 97.5% by mass or more, relative to the ratio of the amount of the methanol-insoluble component to the total amount of the methanol-soluble component of 100% by mass. By setting the ratio of the amount of the methanol-insoluble component to 95% by mass or more, troubles in molding such as occurrence of crazing at the time of injection molding can be suppressed.

The methanol-insoluble component and the methanol-soluble component are components obtained by dissolving a resin lens for a head-mounted display in chloroform to prepare a chloroform solution, then reprecipitating the solution by dropping the solution into a large excess of methanol, distinguishing a filtrate from a residue, and thereafter drying each.

Specifically, it can be obtained as follows. After 5g of the resin lens was dissolved in 100mL of chloroform, the solution was added to a dropping funnel, and dropped into 1L of methanol stirred with a stirrer for about 1 hour to reprecipitate. After the entire amount was added dropwise, the mixture was left to stand for 1 hour, and then subjected to suction filtration using a membrane filter (made by Toyo Kagaku K.K. (アドバンテック Toyo Co., Ltd., T050A 090C)) as a filter. The residue was dried under vacuum at 60 ℃ for 16 hours as a methanol-insoluble fraction. Further, the bath temperature of the rotary evaporator was set to 40 ℃ and the degree of vacuum was gradually decreased from 390Torr, which was initially set, to 30Torr, and the solvent was removed, and then the soluble fraction remaining in the eggplant type flask was recovered as a methanol-soluble fraction. The mass of each of the methanol-insoluble component and the mass of the methanol-soluble component was weighed, and the ratio (mass%) of the amount of the methanol-soluble component to the total amount (100 mass%) of the amount of the methanol-soluble component and the amount of the methanol-insoluble component (methanol-soluble component fraction) was calculated.

[ resin composition ]

The resin lens for a head-mounted display according to the present embodiment is preferably composed of a resin composition containing a methacrylic resin.

[ methacrylic resin ]

The methacrylic resin included in the resin lens for a head-mounted display according to the present embodiment preferably includes a methacrylic resin having a structural unit X having a ring structure in a main chain and a structural unit derived from a methacrylate monomer. By including a methacrylic resin, particularly a methacrylic resin including a structural unit X having a ring structure in its main chain and a methacrylate ester monomer unit, a resin lens having a sufficiently small phase difference within the effective diameter of the lens and a sufficiently small photoelastic coefficient can be obtained.

Hereinafter, each constituent unit will be described.

Structural units derived from methacrylate monomers

Examples of the structural unit derived from a methacrylate ester monomer include structural units derived from monomers selected from the following methacrylate esters. Examples of the methacrylic acid ester include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, 2-ethylhexyl methacrylate, cyclopentyl methacrylate, cyclohexyl methacrylate, cyclooctyl methacrylate, tricyclodecyl methacrylate, bicyclooctyl methacrylate, tricyclodecyl methacrylate, isobornyl methacrylate, phenyl methacrylate, benzyl methacrylate, 1-phenylethyl methacrylate, 2-phenoxyethyl methacrylate, 3-phenylpropyl methacrylate, and 2,4, 6-tribromophenyl methacrylate.

These monomers may be used alone or in combination of two or more.

As the structural unit derived from the above-mentioned methacrylate ester monomer, a structural unit derived from methyl methacrylate and benzyl methacrylate is preferable in terms of excellent transparency and weather resistance of the obtained methacrylic resin.

The structural unit derived from the methacrylate ester monomer may contain one kind or two or more kinds.

In the resin lens for a head-mount display according to the present embodiment, the ratio of the structural unit X having a ring structure in the main chain to the structural unit derived from a methacrylate monomer is appropriately adjusted, whereby birefringence caused by orientation and residual stress at the time of molding is reduced, and the resin lens for a head-mount display having an average value of absolute values of phase differences within the effective diameter of 5nm or less can be obtained. In addition, by appropriately adjusting the above ratio, heat resistance can be sufficiently imparted to the methacrylic resin. From these viewpoints, the content of the structural unit derived from a methacrylate ester monomer is preferably 50to 97% by mass, more preferably 55 to 97% by mass, even more preferably 55 to 95% by mass, even more preferably 60 to 93% by mass, and particularly preferably 60 to 90% by mass, based on 100% by mass of the methacrylic resin.

The content of the structural unit derived from the methacrylate ester monomer may be determined by¹H-NMR measurement and¹³determined by C-NMR measurement. For example, CDCl can be used as a solvent for measurement₃Or DMSO-d₆At a measurement temperature of 40 DEG C¹H-NMR measurement and¹³C-NMR measurement.

Hereinafter, the structural unit X having a ring structure in its main chain will be described.

The structural unit X having a ring structure in its main chain preferably includes at least one structural unit selected from the group consisting of a structural unit derived from an N-substituted maleimide monomer, a glutarimide structural unit, and a lactone ring structural unit, and more preferably includes only at least one structural unit selected from the group consisting of a structural unit derived from an N-substituted maleimide monomer, a glutarimide structural unit, and a lactone ring structural unit. The structural unit X having a ring structure in the main chain may be one kind or plural kinds may be combined.

Structural units derived from N-substituted maleimide monomers

Next, the structural unit derived from the N-substituted maleimide monomer will be described.

The structural unit derived from the N-substituted maleimide monomer may be at least one structural unit selected from the group consisting of structural units represented by the following formula (1) and structural units represented by the following formula (2), and preferably, is formed of two structural units of structural units represented by the following formula (1) and the following formula (2).

[ chemical formula 1]

In the formula (1), R¹R represents any one of an arylalkyl group having 7 to 14 carbon atoms and an aryl group having 6 to 14 carbon atoms²And R³Each independently represents any one of a hydrogen atom, an oxygen atom, a sulfur atom, an alkyl group having 1 to 12 carbon atoms, or an aryl group having 6 to 14 carbon atoms.

In addition, in R²Or R³In the case of aryl, R²Or R³A halogen atom may be contained as a substituent.

In addition, R¹May be substituted with a substituent such as a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a nitro group, a benzyl group, etc.

[ chemical formula 2]

In the formula (2), R⁴Represents any one of a hydrogen atom, a cycloalkyl group having 3 to 12 carbon atoms and an alkyl group having 1 to 12 carbon atoms, R⁵And R⁶Each independently represents any one of a hydrogen atom, an oxygen atom, a sulfur atom, an alkyl group having 1 to 12 carbon atoms, or an aryl group having 6 to 14 carbon atoms.

Specific examples are shown below.

Examples of the monomer forming the structural unit represented by the formula (1) (e.g., N-arylmaleimides, N-aromatic-substituted maleimides, etc.) include N-phenylmaleimide, N-benzylmaleimide, N- (2-chlorophenyl) maleimide, N- (4-bromophenyl) maleimide, N- (2-methylphenyl) maleimide, N- (2, 6-dimethylphenyl) maleimide, N- (2-ethylphenyl) maleimide, N- (2-methoxyphenyl) maleimide, N- (2-nitrophenyl) maleimide, N- (2,4, 6-trimethylphenyl) maleimide, N-arylmaleimides, etc.), N- (4-benzylphenyl) maleimide, N- (2,4, 6-tribromophenyl) maleimide, N-naphthylmaleimide, N-anthrylmaleimide, 3-methyl-1-phenyl-1H-pyrrole-2, 5-dione, 3, 4-dimethyl-1-phenyl-1H-pyrrole-2, 5-dione, 1, 3-diphenyl-1H-pyrrole-2, 5-dione, 1,3, 4-triphenyl-1H-pyrrole-2, 5-dione, and the like.

Among these monomers, N-phenylmaleimide and N-benzylmaleimide are preferable from the viewpoint that the methacrylic resin obtained is excellent in heat resistance, birefringence and other optical properties.

These monomers may be used alone or in combination of two or more.

Examples of the monomer forming the structural unit represented by the formula (2) include N-methylmaleimide, N-ethylmaleimide, N-N-propylmaleimide, N-isopropylmaleimide, N-N-butylmaleimide, N-isobutylmaleimide, N-sec-butylmaleimide, N-tert-butylmaleimide, N-N-pentylmaleimide, N-N-hexylmaleimide, N-N-heptylmaleimide, N-N-octylmaleimide, N-laurylmaleimide, N-cyclopentylmaleimide, N-cyclohexylmaleimide, 1-cyclohexyl-3-methyl-1H-pyrrole-2, 5-dione, N-isopropylmaleimide, N-butylmaleimide, N-isobutylmaleimide, N-sec-butylmaleimide, N-tert-butylmaleimide, N-N-pentylmaleimide, N-N-hexylmaleimide, N-N-heptylmaleimide, N-, 1-cyclohexyl-3, 4-dimethyl-1H-pyrrole-2, 5-dione, 1-cyclohexyl-3-phenyl-1H-pyrrole-2, 5-dione, 1-cyclohexyl-3, 4-diphenyl-1H-pyrrole-2, 5-dione, and the like.

Among these monomers, N-methylmaleimide, N-ethylmaleimide, N-isopropylmaleimide and N-cyclohexylmaleimide are preferable from the viewpoint of excellent weather resistance of methacrylic resins, and N-cyclohexylmaleimide is particularly preferable from the viewpoint of excellent low hygroscopicity which has been required for optical materials in recent years.

These monomers may be used alone, or two or more of them may be used in combination.

In the methacrylic resin of the present embodiment, it is particularly preferable to use a combination of the structural unit represented by formula (1) and the structural unit represented by formula (2) in order to exhibit highly controlled birefringence characteristics.

The molar ratio (X1/X2) of the content (X1) of the structural unit represented by formula (1) to the content (X2) of the structural unit represented by formula (2) is preferably greater than 0 and 15 or less, more preferably greater than 0 and 10 or less.

When the molar ratio (X1/X2) is within this range, the resin lens of the present embodiment maintains transparency without accompanying yellowing, and does not deteriorate environmental resistance, exhibits good heat resistance and good photoelastic characteristics.

The content of the structural unit derived from the N-substituted maleimide monomer is preferably 5to 40% by mass, more preferably 5to 35% by mass, based on 100% by mass of the methacrylic resin.

When the amount is within this range, the methacrylic resin can obtain a more sufficient effect of improving heat resistance, and can also obtain more preferable effects of improving weather resistance, low water absorption, and optical characteristics. It is effective to prevent the decrease in physical properties of the methacrylic resin due to the decrease in reactivity of the monomer components and the increase in the amount of unreacted and remaining monomer during the polymerization reaction, and to set the content of the structural unit derived from the N-substituted maleimide monomer to 40 mass% or less.

Further, by appropriately adjusting the content of the structural unit derived from the N-substituted maleimide monomer within this range, birefringence due to orientation and residual stress at the time of molding can be reduced, and a resin lens for a head mount display having an average value of absolute values of retardation within an effective diameter of 5nm or less can be obtained. The content of the most suitable structural unit derived from the N-substituted maleimide monomer varies depending on the kind of the N-substituted maleimide monomer, and for example, when methyl methacrylate is used as the methacrylate monomer and N-phenylmaleimide and N-cyclohexylmaleimide are used as the N-substituted maleimide monomer, it is preferable to adjust the content in the range of 79 to 83 mass% of the structural unit derived from methyl methacrylate, 6 to 8 mass% of the structural unit derived from N-phenylmaleimide and 11 to 13 mass% of the structural unit derived from N-cyclohexylmaleimide.

The methacrylic resin having a structural unit derived from an N-substituted maleimide monomer constituting the resin lens for a head-mounted display according to the present embodiment may contain a structural unit derived from another monomer copolymerizable with a methacrylate monomer and an N-substituted maleimide monomer, within a range not to impair the object of the present invention.

Examples of the other copolymerizable monomer include aromatic vinyl groups; an unsaturated nitrile; an acrylate having a cyclohexyl group, a benzyl group, or an alkyl group having 1 to 18 carbon atoms; a glycidyl compound; unsaturated carboxylic acids; and the like.

Examples of the aromatic vinyl group include styrene, α -methylstyrene, and divinylbenzene.

Examples of the unsaturated nitrile include acrylonitrile, methacrylonitrile, and ethacrylonitrile.

Examples of the acrylic acid ester include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, and butyl acrylate.

Examples of the glycidyl compound include glycidyl (meth) acrylate and the like.

Examples of the unsaturated carboxylic acids include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and half-esters and anhydrides thereof.

The copolymerizable structural unit derived from another monomer may be one type or two or more types.

The content of the copolymerizable structural unit derived from another monomer is preferably 0to 10% by mass, more preferably 0to 9% by mass, and still more preferably 0to 8% by mass, based on 100% by mass of the methacrylic resin.

When the content of the structural unit derived from another monomer is within this range, the moldability and mechanical properties of the resin can be improved without impairing the original effect of introducing a ring structure into the main chain, and therefore, it is preferable.

The content of the structural unit derived from the N-substituted maleimide monomer and the content of the structural unit derived from another copolymerizable monomer may be determined by¹H-NMR measurement and¹³determined by C-NMR measurement. For example, CDCl can be used as a solvent for measurement₃Or DMSO-d₆At a measurement temperature of 40 DEG C¹H-NMR measurement and¹³C-NMR measurement.

Structural units of the glutarimide system

Examples of the methacrylic resin having a glutarimide-based structural unit in the main chain include methacrylic resins having a glutarimide-based structural unit described in, for example, japanese patent laid-open nos. 2006-249202, 2007-009182, 2007-009191, 2011-186482, and 2012/114718, and can be formed by the method described in these publications.

The glutarimide-based constituent unit constituting the methacrylic resin of the present embodiment may be formed after polymerization of the resin.

Specifically, the glutarimide-based structural unit may be represented by the following general formula (3).

[ chemical formula 3]

In the above general formula (3), R is preferably⁷And R⁸Each independently is a hydrogen atom or a methyl group, R⁹Is any of a hydrogen atom, a methyl group, a butyl group and a cyclohexyl group, and more preferably R⁷Is methyl, R⁸Is a hydrogen atom, R⁹Is methyl.

The glutarimide-based structural unit may include only a single species or may include a plurality of species.

In the methacrylic resin having a glutarimide-based structural unit, the content of the glutarimide-based structural unit is preferably in the range of 3 to 70% by mass, more preferably in the range of 3 to 60% by mass, based on 100% by mass of the methacrylic resin.

When the content of the glutarimide-based structural unit is in the above range, a resin having good moldability, heat resistance and optical properties can be obtained, and therefore, the content is preferable.

Further, by appropriately adjusting the content of the glutarimide-based structural unit within this range, birefringence due to orientation and residual stress at the time of molding can be reduced, and a resin lens for a head-mounted display in which the average value of the absolute values of retardation within the effective diameter is 5nm or less can be obtained. The most suitable content of glutarimide-based structural unit is represented by R of the general formula (3)⁷～R⁹The substituents of (A) differ from one another, e.g. in R⁷And R⁸Is a hydrogen atom, R⁹In the case of methyl, when the content of the glutarimide-based structural unit is in the range of 3 to 10% by mass, birefringence due to orientation and residual stress at the time of molding is reduced, and a resin lens for a head-mounted display in which the average value of absolute values of retardation in the effective diameter is 5nm or less can be obtained.

The content of glutarimide-based structural units in the methacrylic resin can be determined by the method described in the above patent document.

The methacrylic resin having a glutarimide-based structural unit may further contain an aromatic vinyl monomer unit, if necessary.

The aromatic vinyl monomer is not particularly limited, and may be styrene or α -methylstyrene, with styrene being preferred.

The content of the aromatic vinyl unit in the methacrylic resin having a glutarimide-based structural unit is not particularly limited, and is preferably 0to 20% by mass based on 100% by mass of the methacrylic resin having a glutarimide-based structural unit.

When the content of the aromatic vinyl unit is within the above range, it is preferable because heat resistance and excellent photoelastic properties can be achieved at the same time.

For example, when a methyl methacrylate-styrene copolymer obtained by copolymerizing methyl methacrylate as a methacrylate monomer and styrene as an aromatic vinyl monomer is glutarimidized to obtain a resin, birefringence due to orientation and residual stress at the time of molding is reduced by adjusting the content within the range of 65 to 90 mass% of a methyl methacrylate-derived structural unit, 5to 15 mass% of a styrene-derived structural unit, and 5to 20 mass% of a glutarimide-based structural unit, and a resin lens for a head-mounted display having an average value of absolute values of retardation in an effective diameter of 5nm or less can be obtained.

Lactone ring structural units

Methacrylic resins having a lactone ring structure unit in the main chain can be formed by the methods described in, for example, Japanese patent laid-open Nos. 2001-151814, 2004-168882, 2005-146084, 2006-96960, 2006-171464, 2007-63541, 2007-297620, 2010-180305 and the like.

The lactone ring structure unit constituting the methacrylic resin of the present embodiment may be formed after polymerization of the resin.

The lactone ring structure unit in the present embodiment is preferably a six-membered ring in view of excellent stability of the ring structure.

The lactone ring structure unit having a six-membered ring is particularly preferably a structure represented by the following general formula (4), for example.

[ chemical formula 4]

In the above general formula (4), R¹⁰、R¹¹And R¹²Independently of each other, a hydrogen atom or an organic residue having 1 to 20 carbon atoms.

Examples of the organic residue include saturated aliphatic hydrocarbon groups having 1 to 20 carbon atoms (such as alkyl groups) such as methyl, ethyl and propyl groups; an unsaturated aliphatic hydrocarbon group (e.g., alkenyl group) having 2 to 20 carbon atoms such as a vinyl group and a propenyl group; an aromatic hydrocarbon group having 6 to 20 carbon atoms (e.g., an aryl group) such as a phenyl group or a naphthyl group; one or more hydrogen atoms in the saturated aliphatic hydrocarbon group, unsaturated aliphatic hydrocarbon group, and aromatic hydrocarbon group are substituted with at least one group selected from the group consisting of a hydroxyl group, a carboxyl group, an ether group, and an ester group; and the like.

For example, a lactone ring structure unit can be formed by introducing a hydroxyl group and an ester group or a carboxyl group into a molecular chain by copolymerizing an acrylic monomer having a hydroxyl group and a methacrylic acid ester monomer such as methyl methacrylate, and then subjecting the hydroxyl group and the ester group or the carboxyl group to dealcoholization (esterification) or dehydration condensation (hereinafter, also referred to as "cyclized condensation reaction").

Examples of the acrylic monomer having a hydroxyl group used in the polymerization include 2- (hydroxymethyl) acrylic acid, 2- (hydroxyethyl) acrylic acid, and alkyl 2- (hydroxymethyl) acrylates (for example, methyl 2- (hydroxymethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, isopropyl 2- (hydroxymethyl) acrylate, n-butyl 2- (hydroxymethyl) acrylate, tert-butyl 2- (hydroxymethyl) acrylate), and alkyl 2- (hydroxyethyl) acrylates, and monomers having a hydroxyalkyl moiety, that is, 2- (hydroxymethyl) acrylic acid and alkyl 2- (hydroxymethyl) acrylate are preferable, and methyl 2- (hydroxymethyl) acrylate and ethyl 2- (hydroxymethyl) acrylate are particularly preferable.

The content of the lactone ring structure unit in the methacrylic resin having a lactone ring structure unit in the main chain is preferably 5to 40% by mass, more preferably 5to 35% by mass, based on 100% by mass of the methacrylic resin.

When the content of the lactone ring structural unit is within this range, a ring structure-introducing effect such as an improvement in solvent resistance and an improvement in surface hardness can be exhibited while maintaining moldability. Further, by appropriately adjusting the content of the lactone ring structural unit within this range, birefringence due to orientation and residual stress at the time of molding can be reduced, and a resin lens for a head-mounted display in which the average value of absolute values of retardation in the effective diameter is 5nm or less can be obtained.

The content of the lactone ring structure in the methacrylic resin can be determined by the method described in the above patent document.

The methacrylic resin having a lactone ring structural unit in its main chain may have a structural unit derived from another monomer copolymerizable with the above methacrylate ester monomer and the acrylic monomer having a hydroxyl group.

Examples of such other copolymerizable monomers include monomers having a polymerizable double bond such as styrene, vinyltoluene, α -methylstyrene, α -hydroxymethylstyrene, α -hydroxyethylstyrene, acrylonitrile, methacrylonitrile, methallyl alcohol, ethylene, propylene, 4-methyl-1-pentene, vinyl acetate, 2-hydroxymethyl-1-butene, methylvinylketone, N-vinylpyrrolidone, and N-vinylcarbazole.

These other monomers (constituent units) may be present in only one kind, or may be present in two or more kinds.

The content of the structural unit derived from another copolymerizable monomer is preferably 0to 20% by mass based on 100% by mass of the methacrylic resin, and more preferably less than 10% by mass, and even more preferably less than 7% by mass, from the viewpoint of weather resistance.

The methacrylic resin in the present embodiment may have only one kind of the structural unit derived from the other copolymerizable monomer or two or more kinds of the structural units derived from the other copolymerizable monomer.

The methacrylic resin in the present embodiment preferably has at least one structural unit selected from the group consisting of a structural unit derived from an N-substituted maleimide monomer, a glutarimide structural unit, and a lactone ring structural unit, and particularly preferably has a structural unit derived from an N-substituted maleimide monomer, since it is easy to control optical characteristics such as photoelastic coefficient and the like in a high level without mixing with other thermoplastic resins. In particular, from the viewpoint of obtaining a resin lens having high strength, a resin lens having a glutarimide-based structural unit is particularly preferable.

[ method for producing methacrylic resin ]

The method for producing the methacrylic resin of the present embodiment will be described below.

Process for producing methacrylic resin comprising structural units derived from N-substituted maleimide monomer

The method for producing a methacrylic resin having a structural unit derived from an N-substituted maleimide monomer in the main chain (hereinafter, sometimes referred to as "maleimide copolymer") includes any of bulk polymerization, solution polymerization, suspension polymerization, precipitation polymerization and emulsion polymerization, and from the viewpoint of reducing the amount of residual monomers and impurities contained in the resin lens, suspension polymerization, bulk polymerization and solution polymerization are preferred, and solution polymerization is more preferred.

In the production method of the present embodiment, as the polymerization method, for example, any of a batch polymerization method, a semi-batch method, and a continuous polymerization method can be used.

In the present embodiment, from the viewpoint of being able to reduce the amount of residual maleimide at the time of termination of polymerization and to reduce the fluorescence intensity (reduce the content of a fluorescent substance), it is preferable to use a so-called semi-batch polymerization method in which a part of monomers is charged into a reactor before the start of polymerization, polymerization is started by adding a polymerization initiator, and then the remaining part of the monomers is supplied.

In the methacrylic resin having a structural unit derived from an N-substituted maleimide monomer, as a method for controlling the obtained resin lens so that it exhibits a predetermined fluorescence intensity (the content of a fluorescent substance falls within a predetermined range), at least one selected from the group consisting of (1) to (3) and the like is performed: (1) as a raw material, an N-substituted maleimide monomer in which the content of specific impurities is controlled; (2) a polymerization method which reduces the amount of the unreacted N-substituted maleimide remaining after the completion of the polymerization; (3) suitable for devolatilization with reduced shear. Among them, it is preferable to select the production methods of the combinations (1) and (3) or to select the production methods of the combinations of the three.

(1) Control of impurities in N-substituted maleimides

One of the impurities in the N-substituted maleimide which provides a fluorescent emission property to the methacrylic resin is 2-amino-N-substituted succinimide produced by reacting the N-substituted maleimide with a primary amine. Examples of the 2-amino-N-substituted succinimide include 2-cyclohexylamino-N-cyclohexylsuccinimide, 2-anilino-N-phenylsuccinimide, and the like. It has been clarified through studies by the inventors that 2-amino-N-substituted succinimide not only has a fluorescence itself but also has a fluorescence, and it has been found that a thermal modification product having a fluorescence is produced when the 2-amino-N-substituted succinimide is heated at 300 ℃ or higher or supplied to a devolatilizer having a shear, although the detailed modification mechanism is not clear. That is, in order to control the fluorescence intensity of the methacrylic resin and the obtained resin lens, it is preferable to reduce the 2-amino-N-substituted succinimide contained in the N-substituted maleimide and to perform devolatilization at 300 ℃ or lower using a devolatilization apparatus having no rotating part in the production of the methacrylic resin.

Examples of a method for controlling impurities in the N-substituted maleimide include a pretreatment step in which the N-substituted maleimide is subjected to water washing (water washing step) and/or dehydration (dehydration step).

The pretreatment step may be water washing alone or a combination of water washing and dehydration. In addition, the washing and the dehydration may be performed once or twice or more. In the pretreatment step, a concentration adjustment step of adjusting the concentration of the N-substituted maleimide solution obtained in the dehydration step may be further provided.

In the present embodiment, for example, 2-amino-N-substituted succinimide in N-substituted maleimide is removed by a water washing step shown below, followed by removal of water in a dehydration step, whereby an N-substituted maleimide solution suitable for producing a methacrylic resin having controlled fluorescence intensity and good color tone can be obtained.

In the water washing step, for example, the following method can be employed: dissolving N-substituted maleimide in a water-insoluble organic solvent, separating into an organic layer and an aqueous layer, mixing and washing the organic layer with one or more of an acidic aqueous solution, water and an alkaline aqueous solution in a stepwise manner, a continuous manner or both, and separating the organic layer and the aqueous layer.

When the amount of the N-substituted maleimide in the organic layer is 100% by mass, the amount of the 2-amino-N-substituted succinimide in the organic layer after the water washing step is preferably 5 ppm by mass or less, more preferably 0.1 ppm by mass or more and 1 ppm by mass or less. When the amount of the 2-amino-N-substituted succinimide in the organic layer is within this range, the concentration of the fluorescent light-emitting substance in the methacrylic resin and the obtained resin lens can be controlled within the above range, and a resin lens for a head-mounted display that can obtain a clear image can be obtained, and therefore, this is preferable. Further, it is also preferable from the viewpoint of cost in cleaning. In the case where the dehydration step is not provided, the organic layer containing the N-substituted maleimide obtained in the water washing step may be used as an N-substituted maleimide solution in the polymerization step.

The amount of the 2-amino-N-substituted succinimide in the organic layer can be measured, for example, by a gas chromatograph, a liquid chromatograph, or the like using isopropyl benzoate as an internal standard substance, specifically, by the method described in the examples described later.

The water-insoluble organic solvent to be used is not particularly limited as long as it dissolves the N-substituted maleimide and the 2-amino-N-substituted succinimide, undergoes phase separation from water, and has an azeotropic point with water. Specifically, for example, aromatic hydrocarbons such as toluene and xylene; aliphatic hydrocarbons such as n-hexane and cyclohexane; halogenated hydrocarbons such as chloroform and dichloroethane; and the like.

The water used may be any of sewage, pure water, and tap water.

The acidity of the acidic aqueous solution or the basic aqueous solution is not particularly limited.

The concentration of the N-substituted maleimide in the organic layer before the water washing step is preferably 0.5 to 30 mass%, more preferably 10to 25 mass%, and still more preferably 20 to 25 mass%.

The temperature for mixing and washing the organic layer and the aqueous layer may be 40 ℃ or higher, preferably 40 ℃ to 80 ℃ or lower, and more preferably 50 ℃ to 60 ℃ or lower.

When the mass of the organic layer is 100 mass%, the mass ratio of the aqueous layer to the organic layer is preferably 5to 300 mass%, more preferably 10to 200 mass%, and still more preferably 30to 100 mass%.

When the concentration of the N-substituted maleimide in the organic layer, the liquid temperature at the time of washing and the mass ratio of the aqueous layer are in these ranges, the reaction of the N-substituted maleimide with water is difficult to proceed, and the 2-amino-N-substituted succinimide is easily extracted to the aqueous layer side, and therefore, this is preferable.

When the washing is performed in a stepwise manner, the reaction vessel to be used may be made of stainless steel or glass-lined steel, or may be any other reaction vessel. In addition, the shape of the stirring blade is not particularly limited. As a specific stirring blade, for example, three sweepback blades, four paddle blades, four tilt paddle blades, six turbine blades, and anchor blades may be used, and further, twins (Twin Star, ツインスター) and universes (Full zone, フルゾーン) manufactured by the neuroson environment solution company (neuroson environment ソリューション) may be used.

The stirring time is preferably 10 minutes to 120 minutes, more preferably 30 minutes to 60 minutes. In addition, as for the stirring speed, a speed at which the mixed liquid is in a turbulent state and does not emulsify is appropriately selected. When the stirring time and the stirring speed are within these ranges, the stirring efficiency and the extraction efficiency of the 2-amino-N-substituted succinimide into the aqueous layer can be improved, and the 2-amino-N-substituted succinimide in the N-substituted maleimide can be further reduced, which is preferable.

When the washing is performed continuously, an empty column, a packed column or a plate column may be used, and a static mixer such as a static mixer or a rotary mixer such as a dynamic mixer may be used.

The contact time of the organic layer and the aqueous layer is preferably set to 1 second to 60 minutes, more preferably 30 seconds to 10 minutes. When the contact time is in this range, the reaction of the N-substituted maleimide with water is difficult to proceed, and the 2-amino-N-substituted succinimide is easily extracted to the water layer side, and therefore, it is preferable.

In the dehydration step, the organic layer is supplied to the reaction tank, and water is removed by heating under reduced pressure. The pressure and temperature are not particularly limited as long as the solvent used and water form an azeotropic component.

The moisture content in the organic layer after the dehydration step is preferably 100 mass ppm or less, assuming that the mass of the organic layer is 100 mass%. When the water content after the dehydration step is within this range, deterioration in color tone due to water at the time of polymerization of the methacrylic resin can be suppressed, and the amount of the solvent distilled off together with water can be reduced, which is also preferable from the viewpoint of cost.

The organic layer containing N-substituted maleimide obtained in the dehydration step may be used in the polymerization step as an N-substituted maleimide solution, or an N-substituted maleimide solution whose concentration has been adjusted in the concentration adjustment step may be used in the polymerization step.

In the concentration adjustment step, for example, the organic layer of the N-substituted maleimide obtained in the dehydration step or the like may be diluted with the water-insoluble organic solvent. The water-insoluble organic solvent used in the concentration adjustment step is preferably the same as the water-insoluble organic solvent used in the water washing step.

The N-substituted maleimide solution obtained in the pretreatment step is preferably a solution (organic layer) of the water-insoluble organic solvent.

In the N-substituted maleimide solution obtained in the pretreatment step, the mass ratio of the 2-amino-N-substituted succinimide contained in the N-substituted maleimide solution to 100 mass% of the N-substituted maleimide contained in the N-substituted maleimide solution is preferably 5 mass ppm or less, and more preferably 0.1 mass ppm or more and 1 mass ppm or less.

The water content in the N-substituted maleimide solution obtained in the pretreatment step is preferably 200 mass ppm or less, more preferably 100 to 200 mass ppm, based on 100 mass% of the N-substituted maleimide solution.

The mass ratio of the N-substituted maleimide contained in the N-substituted maleimide solution obtained in the pretreatment step is preferably 5to 30 mass%, more preferably 5to 25 mass%, relative to 100 mass% of the N-substituted maleimide solution. In the case where the concentration is within this range, it is preferable that the N-substituted maleimide is difficult to precipitate and can be transported in a uniform solution.

In the case where a plurality of kinds of N-substituted maleimide solutions are used in the polymerization step, it is preferable that a mixture of the plurality of kinds of N-substituted maleimide solutions satisfies the mass ratio of the 2-amino-N-substituted succinimide, the water content and/or the mass ratio of the N-substituted maleimide, and it is more preferable that each of the N-substituted maleimide solutions satisfies the mass ratio of the 2-amino-N-substituted succinimide, the water content and/or the mass ratio of the N-substituted maleimide.

The use of the above-mentioned water washing step and dehydration step of the N-substituted maleimide is preferable because it is possible to reduce the amount of the 2-amino-N-substituted succinimide having a fluorescent light-emitting property and to remove moisture which causes deterioration in color tone of the methacrylic resin, and it is possible to obtain a methacrylic resin having a good color tone even in a lens having a long optical path length and a composition of the resin.

In the polymerization step, a methacrylate monomer, an optional other monomer, a polymerization initiator, a polymerization solvent, a chain transfer agent, and the like are mixed with the N-substituted maleimide solution obtained in the pretreatment step to prepare a monomer mixture, and then the mixture is used for polymerization.

(2) Reduction of unreacted N-substituted maleimide at the end of polymerization

The present inventors have found that, although the detailed mechanism is not clear, if unreacted N-substituted maleimide exists at the end of the polymerization of a methacrylic resin, a reaction by-product having a low molecular weight and a fluorescence emission property is generated as a structural unit thereof in a heated devolatilizer or the like.

In order to control the content of the fluorescent light-emitting substance in the methacrylic resin and the obtained resin lens within the above range, the total mass of the unreacted N-substituted maleimide remaining after completion of the polymerization is preferably 1000 mass ppm or less, more preferably 10 mass ppm or more and 500 mass ppm or less, with respect to 100 mass% of the polymerization solution at the time of completion of the polymerization.

When an N-arylmaleimide such as N-phenylmaleimide is used as the N-substituted maleimide, the total mass of unreacted N-arylmaleimides remaining after completion of the polymerization is preferably 500 mass ppm or less, more preferably 10to 500 mass ppm, and still more preferably 10to 50 mass ppm, based on 100 mass% of the polymerization solution at the time of completion of the polymerization.

In the case of these ranges, the content of the fluorescent substance in the methacrylic resin and the obtained resin lens can be controlled to be within the above-mentioned range, which is preferable. Further, in order to reduce the amount of unreacted N-substituted maleimide to less than 10 mass ppm, it is necessary to increase the polymerization temperature or increase the amount of a polymerization initiator, and therefore, the maleimide thermal-denatured product and the active radical increase, which is not preferable because they cause deterioration in the color tone of the methacrylic resin.

As a means for controlling the amount of the unreacted N-substituted maleimide after completion of the polymerization within the above range, a semi-batch polymerization method can be mentioned. In the semi-batch polymerization method, it is preferable to additionally add 5to 35 mass% of a methacrylate monomer based on 100 mass% of the total mass of all monomers (for example, a methacrylate, an N-substituted maleimide and any other monomer) to be polymerized after 30 minutes from the start of addition of a polymerization initiator in the polymerization step. In other words, it is preferable that 65 to 95 mass% of the total mass of all monomers to be polymerized is charged into the reactor before the addition of the polymerization initiator, and the remaining part of 5to 35 mass% of the methacrylate ester monomer is additionally added after 30 minutes from the start of the addition of the polymerization initiator. The amount of the methacrylic acid ester monomer to be additionally added is preferably 10to 30% by mass based on 100% by mass of the total mass of all monomers to be polymerized. When the amount of the additionally added methacrylate monomer is within the above range, the unreacted N-substituted maleimide reacts with the additionally added methacrylate monomer, and the amount of the unreacted N-substituted maleimide after completion of the polymerization can be controlled within the above range, which is preferable.

The timing of starting the addition of the monomer, the rate of the addition, and the like may be appropriately selected depending on the polymerization conversion. In addition, a monomer mixture containing an N-substituted maleimide monomer and other monomers may be additionally added in addition to the methacrylate monomer in a range not hindering the effect of the present invention and not hindering the reduction of the amount of unreacted N-substituted maleimide.

The use of the semi-batch polymerization method as described above is preferable because the amount of unreacted N-substituted maleimide monomer in the latter half of the polymerization can be reduced, the formation of a fluorescent substance in the devolatilization step can be minimized, and a methacrylic resin having a good color tone even in a lens having a long optical path length and a composition of the resin can be obtained.

Hereinafter, a case of production by radical polymerization in a semi-batch manner using a solution polymerization method will be specifically described as an example of a method for producing a methacrylic resin having a structural unit derived from an N-substituted maleimide monomer.

In the semi-batch polymerization method, it is preferable to additionally add 5to 35 mass% of a methacrylate monomer based on 100 mass% of the total mass of all monomers (methacrylate, N-substituted maleimide and any other monomer) to be polymerized 30 minutes after the start of the addition of the polymerization initiator. In other words, it is preferable that 65 to 95 mass% of the total mass of all monomers to be polymerized is charged into the reactor before the start of polymerization, and the remainder of 5to 35 mass% of the methacrylate ester monomer is additionally added after 30 minutes from the start of addition of the polymerization initiator.

The amount of the methacrylic acid ester monomer to be additionally added is preferably 10to 30% by mass based on 100% by mass of the total mass of all monomers to be polymerized.

The timing of starting the addition of the monomer, the rate of the addition, and the like may be appropriately selected depending on the polymerization conversion.

In addition, a monomer mixture containing an N-substituted maleimide monomer and other monomers may be additionally added in addition to the methacrylate monomer in a range that does not inhibit the effect of the present invention and does not inhibit the improvement of the conversion of the N-substituted maleimide monomer.

The use of the semi-batch polymerization method as described above is preferable because the conversion of the N-substituted maleimide monomer in the latter half of the polymerization can be increased, the content of the fluorescent substance can be reduced, and a resin having excellent light transmittance for a lens having a long optical path length, easy control of the molecular weight distribution of the obtained polymer, and fluidity particularly suitable for injection molding, and a composition of the resin can be obtained.

The polymerization solvent to be used is not particularly limited as long as it is a solvent that appropriately maintains the viscosity of the reaction solution for the purpose of enhancing the solubility of the maleimide copolymer obtained by polymerization, preventing gelation, and the like.

Specific examples of the polymerization solvent include aromatic hydrocarbons such as toluene, xylene, ethylbenzene, and cumene; ketones such as methyl isobutyl ketone, butyl cellosolve, methyl ethyl ketone, and cyclohexanone; polar solvents such as dimethylformamide and 2-methylpyrrolidone.

These may be used alone or in combination of two or more.

In addition, an alcohol such as methanol, ethanol, or isopropanol may be used as a polymerization solvent in a range not to inhibit the dissolution of the polymerization product during the polymerization.

The amount of the solvent used in the polymerization is not particularly limited as long as the solvent can be easily removed without causing precipitation of the copolymer or the monomer used during the production by allowing the polymerization to proceed, and is preferably 10to 200% by mass, for example, when the total amount of the monomers to be blended is 100% by mass. More preferably 25 to 150% by mass, still more preferably 40to 100% by mass, and still more preferably 50to 100% by mass.

In the present embodiment, it is also preferable to use a method in which the amount of the solvent during polymerization is in the range of 100% by mass or less when the total amount of the monomers to be blended is 100% by mass, and polymerization is performed while appropriately changing the solvent concentration during polymerization.

More specifically, a method of blending 40to 60% by mass at the initial stage of polymerization, blending the remaining 60 to 40% by mass during the polymerization, and finally setting the total amount of the monomers blended to 100% by mass, and setting the solvent amount to a range of 100% by mass or less, can be exemplified.

This method is preferable because it can improve the polymerization conversion rate, control the molecular weight distribution, and obtain a resin and a resin composition which have excellent injection moldability, reduce the content of a fluorescent substance, and obtain a good color tone even when a lens having a long optical path length is produced.

In the solution polymerization, it is important to reduce the dissolved oxygen concentration in the polymerization solution as much as possible, for example, the dissolved oxygen concentration is preferably 10ppm or less. The dissolved oxygen concentration can be measured, for example, using a dissolved oxygen meter DO meter B-505 (manufactured by Kashima electronics Co., Ltd.). As a method for reducing the dissolved oxygen concentration, a method of bubbling an inert gas into a polymerization solution, a method of repeating an operation of pressurizing a vessel containing a polymerization solution with an inert gas to about 0.2MPa and then releasing the pressure before polymerization, a method of introducing an inert gas into a vessel containing a polymerization solution, and the like can be appropriately selected.

The polymerization temperature is not particularly limited as long as the polymerization is carried out, and is preferably 70 to 180 ℃, more preferably 80 to 160 ℃, even more preferably 90to 150 ℃, and further more preferably 100 to 150 ℃. From the viewpoint of productivity, it is preferably 70 ℃ or higher, and in order to suppress side reactions during polymerization and obtain a polymer having a desired molecular weight and quality, it is preferably 180 ℃ or lower.

The polymerization time is not particularly limited as long as the desired degree of polymerization can be obtained at a desired conversion rate, and is preferably 2 to 15 hours, more preferably 3 to 12 hours, and still more preferably 4 to 10 hours from the viewpoint of productivity and the like.

As the polymerization initiator, any initiator generally used for radical polymerization can be used, for example, organic peroxides such as cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-t-butyl peroxide, lauroyl peroxide, benzoyl peroxide, t-butyl peroxyisopropyl carbonate, t-amyl peroxy-2-ethylhexanoate, t-amyl peroxyisononanoate, and 1, 1-di (t-butylperoxy) cyclohexane; azo compounds such as 2,2 '-azobis (isobutyronitrile), 1' -azobis (cyclohexanecarbonitrile), 2 '-azobis (2, 4-dimethylvaleronitrile), and dimethyl-2, 2' -azobisisobutyrate; and the like.

These may be used alone or in combination of two or more.

The amount of the polymerization initiator to be added may be in the range of 0.01 to 1% by mass, preferably 0.05 to 0.5% by mass, based on 100% by mass of the total amount of the monomers used in the polymerization.

The method of adding the polymerization initiator is not particularly limited as long as it is not a constant addition rate but is a variable addition according to the concentration of the monomer remaining in the polymerization solution, and it may be continuously or intermittently added. In the case of intermittently adding the polymerization initiator, the time of non-addition does not take into account the amount added per unit time.

In the present embodiment, it is preferable to select the kind and the amount of the polymerization initiator, the polymerization temperature, and the like appropriately so that the ratio of the total amount of radicals generated by the polymerization initiator to the total amount of unreacted monomers remaining in the reaction system is always a constant value or less.

By using these methods, the amount of oligomers and low molecular weight substances produced in the post-polymerization stage can be suppressed, or the polymerization stability can be improved by suppressing overheating during the polymerization.

In the polymerization reaction, a chain transfer agent may be added as necessary to carry out the polymerization.

As the chain transfer agent, chain transfer agents used in usual radical polymerization can be used, and examples thereof include thiol compounds such as n-butyl mercaptan, n-octyl mercaptan, n-decyl mercaptan, n-dodecyl mercaptan, and 2-ethylhexyl thioglycolate; halogen compounds such as carbon tetrachloride, methylene chloride and bromoform; unsaturated hydrocarbon compounds such as α -methylstyrene dimer, α -terpinene, dipentene, terpinolene, etc.; and the like.

These may be used alone or in combination of two or more.

The chain transfer agent may be added at any stage during the polymerization reaction, and is not particularly limited.

The amount of the chain transfer agent to be added may be 0.01 to 1% by mass, preferably 0.05 to 0.5% by mass, based on 100% by mass of the total amount of the monomers used in the polymerization.

As a method for recovering a polymer from a polymerization solution obtained by solution polymerization, there is a method for recovering a polymerization product by separating a polymerization solvent and an unreacted monomer through a step called a devolatilization step. The devolatilization step is a step of removing volatile components such as a polymerization solvent, residual monomers, and reaction by-products under heating and reduced pressure.

In the present embodiment, the content of the unreacted N-substituted maleimide monomer contained in the polymerization solution containing the methacrylic resin supplied to the devolatilization step is preferably controlled to a predetermined concentration or less. As detailed in the above-mentioned "(2) reduction of unreacted N-substituted maleimide at the end of polymerization", in addition to the above-mentioned methods, for example, it is possible to use: a method of polymerizing by extending the polymerization time as long as possible or by changing the addition rate of a polymerization initiator according to the concentration of unreacted monomers in the polymerization solution in order to increase the conversion rate of the monomers; a method of carrying out polymerization while appropriately changing the solvent concentration during the polymerization; a method of additionally adding another monomer having high reactivity with the residual N-substituted maleimide monomer in the latter half of the polymerization; and a method of adding a compound having high reactivity with an N-substituted maleimide, such as α -terpinene, at the end of polymerization.

Residual amount of N-substituted maleimide monomer

As a method for determining the residual amount of the N-substituted maleimide monomer remaining in the polymerization solution containing the methacrylic resin, for example, a part of the polymerization solution is collected and weighed, the sample is dissolved in chloroform to prepare a 5 mass% solution, N-decane is added as an internal standard substance, and the concentration of the N-substituted maleimide monomer remaining in the sample is measured by using a gas chromatograph (manufactured by shimadzu corporation, GC-2010) to determine the residual amount of the N-substituted maleimide monomer. More specific measurement conditions may be those described in the examples below.

(3) Devolatilization process with reduced shear

As the apparatus used in the devolatilization step, it is preferable to use a devolatilization apparatus mainly composed of a heat exchanger and a pressure reduction vessel and having no rotating portion as its structure. By not providing a rotating portion, shear during devolatilization can be reduced, and a resin with lower fluorescence can be obtained.

Specifically, a devolatilization apparatus comprising a devolatilization vessel in which a heat exchanger is disposed at the upper part and a depressurization unit is added to a depressurization vessel having a devolatilizable size, and a discharge device such as a gear pump for discharging the devolatilized polymer can be used.

The devolatilization apparatus is configured to supply the polymerization solution to a heat exchanger disposed above the decompression vessel and heated, for example, a multitubular heat exchanger, a fin-type heat exchanger, a flat plate heat exchanger having a flat plate flow path and a heater, to preheat the polymerization solution, and then to supply the preheated polymerization solution to a devolatilization vessel under heating and decompression, to separate and remove the polymerization solvent, the unreacted raw material mixture, the polymerization by-products, and the like from the polymer. By using the devolatilization apparatus having no rotating portion as described above, it is possible to suppress reaction by-products having a low molecular weight and a fluorescence from unreacted N-substituted maleimide, and it is possible to control the fluorescence intensity (content of a fluorescence-emitting substance) in the methacrylic resin and the obtained resin lens within a predetermined range, and therefore, it is preferable. In addition, methacrylic resins having good color tone can be obtained, and therefore, such resins are preferable.

Examples of the device having the rotary part include thin film evaporators such as wprene (ワイプレン) and exeva (エクセバ) manufactured by deity steel environment solution company (deity steel environment ソリューション), KONTRO (コントラ) and inclined blade KONTRO (コントラ) manufactured by hitachi; extruders with vent holes, and the like.

In the devolatilization step in the present embodiment, the shear rate applied to the polymerization solution is preferably set to 20 seconds^-1More preferably 10s below^-1Hereinafter, it is more preferably 0.1s^-1Above 10s^-1The following embodiment is performed. By setting the shear rate to 0.1s^-1As described above, the flow of the molten resin is not excessively slow, and deterioration in color tone due to an increase in residence time can be suppressed. In addition, the time is set to 20s^-1The generation of a reaction by-product having a fluorescence emission property due to shearing can be suppressed as follows.

Here, the shear rate γ in the extruder is calculated by the following formula, for example.

γ＝(π×D×N)/H

(wherein D represents a screw diameter (m), N represents a screw rotation speed per 1 second, and H represents a screw groove depth (m))

In the case of a flat plate-type flow path, the shear rate γ is calculated by the following equation.

γ＝(6×Q)/(w×h²)

(in the formula, Q represents a volume flow rate (m) passing through the flat plate-type flow path³And/s), w represents the width (m) of the flat plate type flow path, and h represents the distance (m) between the flat plates. )

In the present embodiment, a plate heat exchanger having a plate flow channel and a heater is preferably used as the heat exchanger disposed at the upper portion of the pressure reduction vessel. More preferably, the flat plate heat exchanger has a flat plate type flow path having a laminated structure having a plurality of slit-shaped flow paths having a rectangular cross section on the same plane, and a heater.

The polymerization solution supplied to the devolatilization apparatus is sent from the center of the heat exchanger to the slit-shaped flow path and heated. The heated polymerization solution is supplied from the slit-shaped flow path into a reduced-pressure vessel integrated with the heat exchanger under reduced pressure, and is flashed.

Such a devolatilization method may be referred to as flash devolatilization, and in the present invention, it will be referred to as flash devolatilization hereinafter.

It is also possible to adopt a method of performing devolatilization in two or more stages by installing two or more of the above devolatilization apparatuses in series.

The temperature range for heating by the heat exchanger with a devolatilization apparatus may be from 100 ℃ to 300 ℃, preferably from 100 ℃ to Tg +160 ℃, more preferably from Tg +110 ℃ to Tg +150 ℃, of the methacrylic resin. The temperature range of the heated and maintained devolatilization vessel may be from 100 ℃ to 300 ℃, preferably from Tg +100 ℃ to Tg +160 ℃, and more preferably from Tg +110 ℃ to Tg +150 ℃. When the temperature of the heat exchanger and the devolatilization vessel is in this range, thermal modification of the remaining 2-amino-N-substituted succinimide can be suppressed, and generation of a fluorescent substance can be suppressed, which is preferable. Further, it is preferable to effectively prevent the increase of the residual volatile components and to improve the thermal stability and the product quality of the obtained methacrylic resin.

The degree of vacuum in the devolatilization vessel may be set to a range of 5to 300Torr, and preferably 10to 200 Torr. When the degree of vacuum is 300Torr or less, the unreacted monomer or the mixture of the unreacted monomer and the polymerization solvent can be efficiently separated and removed, and the thermal stability and quality of the obtained thermoplastic copolymer are not deteriorated. When the degree of vacuum is 5Torr or more, industrial implementation is easier.

The average residence time in the devolatilization vessel may be 5to 60 minutes, preferably 5to 45 minutes. When the average residence time is within this range, the devolatilization can be efficiently performed, and coloring and decomposition due to thermal modification of the polymer can be suppressed, which is preferable.

The polymer recovered through the devolatilization step is processed into pellets in a step called a pelletizing step.

In the pelletizing step, the resin in a molten state is extruded in a strand form by at least one conveying and pelletizing device selected from a gear pump, a single-shaft extruder, a twin-shaft extruder, and the like, which have a porous die as an accessory, and is processed into pellets by a cold cutting method, an air hot cutting method, an underwater strand cutting method, and an underwater cutting method. From the viewpoint of controlling the generation of a reaction by-product having a fluorescence emission due to shearing, it is preferable to select a conveying apparatus having a low shearing rate without using an extruder.

In the present embodiment, in order to obtain a highly controlled resin composition, it is preferable to use a granulation method in which the resin composition in a molten state at a high temperature is cooled and solidified quickly while being kept as free from contact with air as possible.

In this case, it is more preferable to lower the temperature of the molten resin within a possible range, to minimize the residence time from the outlet of the porous die to the surface of the cooling water, and to granulate the molten resin at a higher temperature within a possible range under conditions that can be carried out.

For example, the temperature of the molten resin is preferably 220 to 280 ℃, more preferably 230 to 270 ℃, the residence time from the outlet of the porous die to the surface of the cooling water is preferably within 5 seconds, more preferably within 3 seconds, and the temperature of the cooling water is preferably 30to 80 ℃, more preferably within the range of 40to 60 ℃.

By carrying out the treatment in the ranges of the molten resin temperature and the cooling water temperature, a methacrylic resin having less coloration and a low water content and a composition thereof can be obtained, which is preferable.

From the viewpoint of thermal stability and product quality, the smaller the content of the residual monomer in the methacrylic resin after the devolatilization step is, the more preferable. Specifically, the content of the methacrylate ester monomer is preferably 3000 ppm by mass or less, and more preferably 2000 ppm by mass or less. The content of the N-substituted maleimide monomer is preferably 200 mass ppm or less, more preferably 100 mass ppm or less, in terms of the total amount.

The content of the residual polymerization solvent is preferably 500 mass ppm or less, and more preferably 300 mass ppm or less.

Process for producing methacrylic resin comprising glutarimide-based structural unit

The method for producing a methacrylic resin having a glutarimide structural unit in the main chain includes any of bulk polymerization, solution polymerization, suspension polymerization, precipitation polymerization and emulsion polymerization, and is preferably suspension polymerization, bulk polymerization or solution polymerization, and more preferably solution polymerization.

In the production method of the present embodiment, a method of polymerizing a monomer by radical polymerization is preferable.

Methacrylic resins having glutarimide-based structural units in the main chain may be, for example, methacrylic resins having glutarimide-based structural units described in, for example, Japanese patent laid-open Nos. 2006-249202, 2007-one 009182, 2007-one 009191, 2011-one 186482, and International publication No. 2012/114718, and may be formed by the method described in these publications.

Hereinafter, a case of producing a methacrylic resin having a glutarimide-based structural unit by a batch radical polymerization method using a solution polymerization method will be specifically described as an example of the production method.

First, a (meth) acrylate polymer is produced by polymerizing a (meth) acrylate such as methyl methacrylate. When the methacrylic resin having a glutarimide-based structural unit contains an aromatic vinyl unit, a (meth) acrylate and an aromatic vinyl (for example, styrene) are copolymerized to produce a (meth) acrylate-aromatic vinyl copolymer.

Examples of the solvent used in the polymerization include aromatic hydrocarbons such as toluene, xylene, and ethylbenzene; ketones such as methyl ethyl ketone and methyl isobutyl ketone; and the like.

These solvents may be used alone or in combination of two or more.

The amount of the solvent used in the polymerization is not particularly limited as long as the solvent can be easily removed without causing precipitation of the copolymer or the monomer used during the production by allowing the polymerization to proceed, and is preferably 10to 200% by mass, for example, when the total amount of the monomers to be blended is 100% by mass. More preferably 25 to 200 mass%, still more preferably 50to 200 mass%, and still more preferably 50to 150 mass%.

The polymerization temperature is not particularly limited as long as the polymerization is carried out, and is preferably 50to 200 ℃ and more preferably 80 to 200 ℃. More preferably 90to 150 ℃, still more preferably 100 to 140 ℃, and still more preferably 100 to 130 ℃. From the viewpoint of productivity, it is preferably 70 ℃ or higher, and in order to suppress side reactions during polymerization and obtain a polymer having a desired molecular weight and quality, it is preferably 180 ℃ or lower.

The polymerization time is not particularly limited as long as the desired conversion rate is satisfied, but is preferably 0.5 to 15 hours, more preferably 2 to 12 hours, and still more preferably 4 to 10 hours from the viewpoint of productivity and the like.

In the polymerization reaction, a polymerization initiator and a chain transfer agent may be added as necessary to carry out the polymerization.

The polymerization initiator is not particularly limited, and for example, the polymerization initiator disclosed in the method for producing a methacrylic resin having a structural unit derived from the above-mentioned N-substituted maleimide monomer, and the like can be used.

These polymerization initiators may be used alone or in combination of two or more.

These polymerization initiators may be added at any stage as long as the polymerization reaction proceeds.

The amount of the polymerization initiator to be added is not particularly limited as long as it is appropriately set according to the combination of monomers, reaction conditions, and the like, and may be 0.01 to 1% by mass, preferably 0.05 to 0.5% by mass, assuming that the total amount of the monomers used in the polymerization is 100% by mass.

As the chain transfer agent, a chain transfer agent used in general radical polymerization can be used, and for example, a chain transfer agent disclosed in a method for producing a methacrylic resin having a structural unit derived from the above-mentioned N-substituted maleimide monomer, and the like can be used.

These may be used alone or in combination of two or more.

These chain transfer agents may be added at any stage as long as the polymerization reaction proceeds, and are not particularly limited.

The amount of the chain transfer agent to be added is not particularly limited as long as it is within a range that allows a desired degree of polymerization to be obtained under the polymerization conditions to be used, and is preferably 0.01 to 1% by mass, more preferably 0.05 to 0.5% by mass, assuming that the total amount of the monomers used in the polymerization is 100% by mass.

The method of adding a polymerization initiator and a chain transfer agent suitable for the polymerization step may be, for example, the method described in the method of producing a methacrylic resin having a structural unit derived from the above-mentioned N-substituted maleimide monomer.

The dissolved oxygen concentration in the polymerization solution may be, for example, a value disclosed in the production method of a methacrylic resin having a structural unit derived from the above-mentioned N-substituted maleimide monomer.

Next, the (meth) acrylate polymer or the methacrylate-aromatic vinyl copolymer is reacted with an imidizing agent to perform imidization (imidization step). Thereby, a methacrylic resin having a glutarimide-based structural unit can be produced.

The imidizing agent is not particularly limited as long as it is an imidizing agent capable of forming glutarimide-based structural units represented by the above general formula (3).

As the imidizing agent, specifically, ammonia or a primary amine can be used. Examples of the primary amine include primary amines having an aliphatic hydrocarbon group such as methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, tert-butylamine, and n-hexylamine; alicyclic hydrocarbon group-containing primary amines such as cyclohexylamine; and the like.

Among the above imidizing agents, ammonia, methylamine and cyclohexylamine are preferably used from the viewpoint of cost and physical properties, and methylamine is particularly preferably used.

In this imidization step, the content of the glutarimide-based unit in the obtained methacrylic resin having a glutarimide-based unit can be adjusted by adjusting the addition ratio of the imidizing agent.

The method for carrying out the imidization reaction is not particularly limited, and conventionally known methods can be used, and the imidization reaction can be carried out by using an extruder or a batch reactor, for example.

The extruder is not particularly limited, and for example, a single-screw extruder, a twin-screw extruder, a multi-screw extruder, or the like can be used.

Among them, a twin-screw extruder is preferably used. According to the twin-screw extruder, the mixing of the base polymer and the imidizing agent can be promoted.

Examples of the twin-screw extruder include a non-intermeshing type corotating type, an intermeshing type corotating type, a non-intermeshing type counter-rotating type, and an intermeshing type counter-rotating type.

The above-described extruders can be used alone or in combination of a plurality of extruders.

In addition, it is particularly preferable to use an extruder equipped with a vent port capable of reducing the pressure to atmospheric pressure or lower, since the reaction can be conducted without using any by-products or monomers such as imidizing agents and methanol.

When a methacrylic resin having a glutarimide-based structural unit is produced, the method may include, in addition to the imidization step, an esterification step of treating a carboxyl group of the resin with an esterifying agent such as dimethyl carbonate. In this case, the treatment may be carried out by using a catalyst such as trimethylamine, triethylamine or tributylamine.

The esterification step can be carried out by using an extruder or a batch reactor, for example, as in the imidization step.

In addition, for the purpose of removing the excessive esterification agent, methanol and other by-products or monomers, it is preferable to install a vent port capable of reducing the pressure to atmospheric pressure or lower in the apparatus used.

The methacrylic resin having undergone the imidization step and, if necessary, the esterification step is melted and extruded in a strand form from an extruder with a porous die, and processed into pellets by a cold cutting method, an air hot cutting method, an underwater strand cutting method, an underwater cutting method, or the like.

In order to reduce the amount of foreign substances in the resin, it is also preferable to use a method in which a methacrylic resin is dissolved in an organic solvent such as toluene, methyl ethyl ketone, or methylene chloride, the obtained methacrylic resin solution is filtered, and then the organic solvent is devolatilized.

From the viewpoint of reducing the fluorescence intensity (the content of the fluorescent substance), it is preferable to imidize the polymerization solution after completion of the polymerization in a batch reaction tank without using a twin screw extruder which is subjected to a shearing force.

The imidization is preferably carried out at 130 to 250 ℃, more preferably at 150 to 230 ℃, and still more preferably at 170 to 190 ℃. The reaction time is preferably 10 minutes to 5 hours, and more preferably 30 minutes to 2 hours.

From the viewpoint of reducing the fluorescence intensity, it is preferable that after the imidization step, if necessary after the esterification step, the devolatilization is carried out by (3) the shear-reducing devolatilization method described in the above-mentioned method for producing a methacrylic resin having a structural unit derived from an N-substituted maleimide monomer, and then the granulation (ペレタイズ) is carried out.

Method for producing methacrylic resin containing lactone ring structural unit

As a method for producing a methacrylic resin having a lactone ring structure unit in its main chain, a method of forming a lactone ring structure by a cyclization reaction after polymerization can be used, and it is preferable to polymerize a monomer by radical polymerization in a solution polymerization method using a solvent in addition to promoting the cyclization reaction.

Methacrylic resins having a lactone ring structure unit in the main chain can be formed by, for example, the methods described in Japanese patent laid-open Nos. 2001-151814, 2004-168882, 2005-146084, 2006-96960, 2006-171464, 2007-63541, 2007-297620, 2010-180305 and the like.

Hereinafter, a case of production by radical polymerization in a batch manner using a solution polymerization method will be specifically described as an example of a method for producing a methacrylic resin having a lactone ring structure unit.

As a method for producing a methacrylic resin having a lactone ring structure unit, a method of forming a lactone ring structure by a cyclization reaction after polymerization can be used, and solution polymerization using a solvent in addition to promoting the cyclization reaction is preferable.

These solvents may be used alone or in combination of two or more.

The amount of the solvent used in the polymerization is not particularly limited as long as the polymerization proceeds and gelation can be suppressed, and for example, when the total amount of the monomers to be blended is 100% by mass, the amount is preferably 50to 200% by mass, and more preferably 100 to 200% by mass.

In order to sufficiently suppress gelation of the polymerization liquid and promote the cyclization reaction after polymerization, it is preferable to carry out polymerization so that the concentration of the polymer produced in the reaction mixture obtained after polymerization becomes 50 mass% or less. It is preferable to control the concentration of the polymerization solvent to 50% by mass or less by appropriately adding the polymerization solvent to the reaction mixture.

The method of adding the polymerization solvent to the reaction mixture is not particularly limited, and for example, the polymerization solvent may be continuously added or may be intermittently added.

The polymerization solvent to be added may be a single solvent or a mixed solvent of two or more kinds.

The polymerization temperature is not particularly limited as long as the polymerization is carried out, and is preferably 50to 200 ℃ and more preferably 80 to 180 ℃ from the viewpoint of productivity.

The polymerization time is not particularly limited as long as the desired conversion rate is satisfied, and is preferably 0.5 to 10 hours, and more preferably 1 to 8 hours from the viewpoint of productivity and the like.

The amount of the polymerization initiator to be added is not particularly limited as long as it is appropriately set according to the combination of monomers, reaction conditions, and the like, and may be 0.05 to 1% by mass when the total amount of the monomers used in the polymerization is 100% by mass.

These may be used alone or in combination of two or more.

The amount of the chain transfer agent to be added is not particularly limited as long as it is within a range that allows a desired degree of polymerization to be obtained under the polymerization conditions used, and is preferably 0.05 to 1% by mass, assuming that the total amount of monomers used in the polymerization is 100% by mass.

The methacrylic resin having a lactone ring structure unit in the present embodiment can be obtained by performing a cyclization reaction after the completion of the polymerization reaction. Therefore, it is preferable to supply the lactone to the cyclization reaction in a state of containing a solvent without removing the polymerization solvent from the polymerization reaction liquid.

The copolymer obtained by polymerization is subjected to a heat treatment to cause a cyclized condensation reaction between a hydroxyl group (hydroxyl group) present in the molecular chain of the copolymer and an ester group, thereby forming a lactone ring structure.

In the heat treatment for forming the lactone ring structure, a reaction apparatus equipped with a vacuum apparatus or a devolatilization apparatus for removing an alcohol which may be by-produced by the cyclized condensation, an extruder equipped with a devolatilization apparatus, or the like may be used.

In the formation of the lactone ring structure, a cyclized condensation reaction is promoted by heating with a cyclized condensation catalyst as necessary.

Specific examples of the cyclized condensation catalyst include monoalkyl, dialkyl, and triesters of phosphorous acid such as methyl phosphite, ethyl phosphite, phenyl phosphite, dimethyl phosphite, diethyl phosphite, diphenyl phosphite, trimethyl phosphite, and triethyl phosphite; monoalkyl, dialkyl or trialkyl phosphates such as methyl phosphate, ethyl phosphate, 2-ethylhexyl phosphate, octyl phosphate, isodecyl phosphate, lauryl phosphate, stearyl phosphate, isostearyl phosphate, dimethyl phosphate, diethyl phosphate, di-2-ethylhexyl phosphate, diisodecyl phosphate, dilauryl phosphate, distearyl phosphate, diisostearyl phosphate, trimethyl phosphate, triethyl phosphate, triisodecyl phosphate, trilauryl phosphate, tristearyl phosphate, triisostearyl phosphate, etc.; organic zinc compounds such as zinc acetate, zinc propionate, and octyl zinc; and the like.

These may be used alone or in combination of two or more.

The amount of the cyclized condensation catalyst used is not particularly limited, and is, for example, preferably 0.01 to 3% by mass, and more preferably 0.05 to 1% by mass, based on 100% by mass of the methacrylic resin.

When the amount of the catalyst used is 0.01% by mass or more, the reaction rate of the cyclized condensation reaction is effectively increased, and when the amount of the catalyst used is 3% by mass or less, the obtained polymer is effectively prevented from being colored, crosslinked, and thus melt-molded.

The addition timing of the cyclized condensation catalyst is not particularly limited, and for example, the catalyst may be added at the initial stage of the cyclized condensation reaction, may be added in the middle of the reaction, or may be added at both stages.

The cyclized condensation reaction may be carried out in the presence of a solvent, and the devolatilization may be carried out simultaneously.

The apparatus used in the case of simultaneously performing the cyclized condensation reaction and the devolatilization step is not particularly limited, and may be a devolatilization apparatus comprising a heat exchanger and a devolatilization vessel, or an extruder with a vent hole.

The vent-equipped twin screw extruder used is preferably a vent-equipped extruder having a plurality of vent ports.

The reaction treatment temperature in the case of using an extruder with a vent is preferably 150 to 350 ℃, and more preferably 200to 300 ℃. When the reaction treatment temperature is less than 150 ℃, the cyclized condensation reaction becomes insufficient and the residual volatile matter becomes large. On the contrary, when the reaction treatment temperature is more than 350 ℃, coloration and decomposition of the obtained polymer are caused.

The degree of vacuum in the case of using an extruder with a vent is preferably 10to 500Torr, and more preferably 10to 300 Torr. When the degree of vacuum is more than 500Torr, volatile components may easily remain. In contrast, when the degree of vacuum is less than 10Torr, industrial implementation sometimes becomes difficult.

In carrying out the above-mentioned cyclized condensation reaction, it is also preferable to add an alkaline earth metal and/or an amphoteric metal salt of an organic acid during granulation for the purpose of deactivating the remaining cyclized condensation catalyst.

Examples of the alkaline earth metal and/or amphoteric metal salt of an organic acid include calcium acetoacetate, calcium stearate, zinc acetate, zinc octoate, and zinc 2-ethylhexanoate.

After the cyclized condensation reaction step, the methacrylic resin was melted and extruded in a strand-like manner from an extruder with a porous die, and processed into pellets by a cold cutting method, an air hot cutting method, an underwater strand cutting method, and an underwater cutting method.

The lactonization for forming the lactone ring structure unit may be performed after the production of the resin and before the production of the resin composition (described later), or may be performed together with the melt-kneading of the resin and components other than the resin during the production of the resin composition.

From the viewpoint of reducing the fluorescence intensity (the content of the fluorescent substance), it is preferable to cyclize the lactone in the polymerization solution after completion of the polymerization in a batch reaction tank without using a biaxial extruder subjected to a shearing force. From the viewpoint of reducing the fluorescence intensity, it is preferable that after the lactone cyclization step, the pellets are produced after devolatilization by the shear-reducing devolatilization method (3) described in the above-mentioned method for producing a methacrylic resin having a structural unit derived from an N-substituted maleimide monomer.

[ additives ]

The resin composition constituting the resin lens for a head-mounted display according to the present embodiment may contain various additives within the range not significantly impairing the effects of the present invention as described above.

The additives are not particularly limited, and examples thereof include softening agents/plasticizers such as antioxidants, light stabilizers such as hindered amine light stabilizers, ultraviolet absorbers, mold release agents, other thermoplastic resins, paraffin process oils, naphthene process oils, aromatic process oils, paraffins, organopolysiloxanes, mineral oils, inorganic fillers such as pigments such as flame retardants, antistatic agents, organic fibers, iron oxides, reinforcing agents such as glass fibers, carbon fibers, metal whiskers, and coloring agents; organic phosphorus compounds such as phosphites, phosphonites and phosphates, other additives, and mixtures thereof.

Antioxidants-

The resin composition constituting the resin lens for a head-mounted display according to the present embodiment preferably contains an antioxidant for suppressing deterioration and coloring during molding or during use.

Examples of the antioxidant include, but are not limited to, hindered phenol antioxidants, phosphorus antioxidants, and sulfur antioxidants.

One or two or more of these antioxidants may be used.

In addition, from the viewpoint of improving the thermal stability and suppressing the molding defect, it is preferable to use a plurality of heat stabilizers in combination, for example, it is preferable to use at least one selected from the group consisting of a phosphorus antioxidant and a sulfur antioxidant and a hindered phenol antioxidant in combination.

Examples of the hindered phenol-based antioxidant include pentaerythritol tetrakis [3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate ], thiodiethylene bis [3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate ], octadecyl-3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate, 3 ', 5,5 ' -hexa-t-butyl-a, a ' - (mesitylene-2, 4, 6-triyl) tri-p-cresol, 4, 6-bis (octylthiomethyl) -o-cresol, 4, 6-bis (dodecylthiomethyl) -o-cresol, ethylenebis (oxyethylenebis [3- (5-t-butyl-4-hydroxy-m-tolyl) propionate ]), Hexamethylenebis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ], 1,3, 5-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) -1,3, 5-triazine-2, 4,6(1H,3H,5H) -trione, 1,3, 5-tris [ (4-tert-butyl-3-hydroxy-2, 6-xylyl) methyl ] -1,3, 5-triazine-2, 4,6(1H,3H,5H) -trione, 2, 6-di-tert-butyl-4- (4, 6-bis (octylthio) -1,3, 5-triazin-2-ylamino) phenol, 2- [1- (2-hydroxy-3, 5-di-t-pentylphenyl) ethyl ] -4, 6-di-t-pentylphenyl ester, 2-t-butyl-4-methyl-6- (2-hydroxy-3-t-butyl-5-methylbenzyl) phenyl acrylate, and the like, but are not limited to these hindered phenol-based antioxidants.

Particularly preferred are pentaerythrityl tetrakis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ], octadecyl-3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate and 2- [1- (2-hydroxy-3, 5-di-tert-pentylphenyl) ethyl ] -4, 6-di-tert-pentylphenyl acrylate.

Further, as the hindered phenol-based antioxidant of the above-mentioned antioxidants, commercially available phenol-based antioxidants can be used, and examples of such commercially available phenol-based antioxidants include Irganox 1010(イルガノックス 1010: pentaerythrityl tetrakis [3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate ], manufactured by BASF corporation, Irganox 1076(イルガノックス 1076: octadecyl-3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate, manufactured by BASF corporation), Irganox 1330(イルガノックス 1330: 3,3 ', 5,5 ' -hexa-t-butyl-a, a ' - (mesitylene-2, 4, 6-triyl) tri-p-cresol, manufactured by BASF corporation), and the like, Irganox 3114(イルガノックス 3114: 1,3, 5-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) -1,3, 5-triazine-2, 4,6(1H,3H,5H) -trione, manufactured by basf), Irganox 3125(イルガノックス 3125, manufactured by basf), ADK STAB AO-60(アデカスタブ AO-60) (pentaerythritol tetrakis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ], manufactured by ADEKA), ADK STAB AO-80(アデカスタブ AO-80) (3, 9-bis {2- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy ] -1, 1-dimethylethyl } -2,4,8, 10-tetraoxaspiro [5.5] undecane, manufactured by ADEKA Co., Ltd.), Sumilizer BHT (スミライザー BHT, manufactured by Sumitomo chemical Co., Ltd.), Cyanox 1790(シアノックス 1790, manufactured by Newcastle (SITECH, サイテック)), Sumilizer GA-80(スミライザー GA-80, manufactured by Sumitomo chemical Co., Ltd.), Sumilizer GS (スミライザー GS: acrylic acid 2- [1- (2-hydroxy-3, 5-di-t-pentylphenyl) ethyl ] -4, 6-di-t-pentylphenyl ester, manufactured by Sumitomo chemical Co., Ltd.), submillizer GM (スミライザー GM: 2-tert-butyl-4-methyl-6- (2-hydroxy-3-tert-butyl-5-methylbenzyl) phenyl acrylate, Sumitomo chemical Co., Ltd.), vitamin E (manufactured by Wei Material Co., Ltd. (Eisai, エーザイ), and the like, but are not limited thereto.

Among these commercially available phenol antioxidants, Irganox 1010(イルガノックス 1010), ADK STAB AO-60(アデカスタブ AO-60), ADK STAB AO-80(アデカスタブ AO-80), Irganox 1076(イルガノックス I1076), and Sumilizer GS (スミライザー GS) are preferable from the viewpoint of the effect of imparting thermal stability to the resin.

These may be used alone or in combination of two or more.

Further, examples of the phosphorus-based antioxidant as the above-mentioned antioxidant include tris (2, 4-di-t-butylphenyl) phosphite, bis (2, 4-bis (1, 1-dimethylethyl) -6-methylphenyl) ethyl phosphite, tetrakis (2, 4-di-t-butylphenyl) (1, 1-biphenyl) -4,4 '-diyl diphosphonite, bis (2, 4-di-t-butylphenyl) pentaerythritol diphosphite, bis (2, 6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite, bis (2, 4-dicumylphenyl) pentaerythritol diphosphite, tetrakis (2, 4-t-butylphenyl) (1, 1-biphenyl) -4, 4' -diyl diphosphonite, and the like, Di-tert-butyl-m-tolyl phosphonite, 4- [3- [ (2,4,8, 10-tetra-tert-butyldibenzo [ d, f ] [1,3,2] dioxaphosphino cycloheptyl) -6-yloxy ] propyl ] -2-methyl-6-tert-butylphenol, and the like, but are not limited thereto.

Further, as the phosphorus-based antioxidant, commercially available phosphorus-based antioxidants can be used, and examples of such commercially available phosphorus-based antioxidants include Irgafos168(イルガフォス 168: tris (2, 4-di-t-butylphenyl) phosphite, manufactured by basf), Irgafos 12(イルガフォス 12: tris [2- [ [2,4,8, 10-tetra-t-butyldibenzo [ d, f ] [1,3,2] dioxaphosphepin-6-yl ] oxy ] ethyl ] amine, manufactured by basf), Irgafos 38(イルガフォス 38: bis (2, 4-bis (1, 1-dimethylethyl) -6-methylphenyl) ethyl phosphite, manufactured by basf), ADK STAB-229K (manufactured by アデカスタブ 329K, ADEKA), ADK STAB PEP-36(アデカスタブ PEP-36), Manufactured by ADEKA), ADK STAB PEP-36A (manufactured by アデカスタブ PEP-36A, ADEKA), ADK STAB PEP-8(アデカスタブ PEP-8, manufactured by ADEKA), ADK STAB HP-10(アデカスタブ HP-10, manufactured by ADEKA), ADK STAB 2112(アデカスタブ 2112, manufactured by ADEKA), ADK STAB 1178(アデカスタブ 1178, manufactured by ADEKA), ADK STAB 1500(アデカスタブ 1500, manufactured by ADEKA), Sandstab P-EPQ (CLARIANT, manufactured by CLARIANT クラリアント), Weston 618(ウェストン 618, manufactured by GE), Weston 619G (ウェストン 619G, GE), Ultranox 626(ウルトラノックス 626, manufactured by GE), Suizer GP (スミライザー GP: 4- [3- [ (2,4,8, 10-tetra-tert-butylbenzo [ d, f ] [1,3,2] dioxaphosphorin-6-yloxy ] propyl ] -2-methyl-6-tert-butylphenol, manufactured by Sumitomo chemical Co., Ltd.), HCA (9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, manufactured by Sanko Co., Ltd.), and the like, but not limited thereto.

Among these commercially available phosphorus antioxidants, Irgafos168(イルガフォス 168), ADK STAB PEP-36(アデカスタブ PEP-36), ADK STAB PEP-36A (アデカスタブ PEP-36A), ADK STAB HP-10(アデカスタブ HP-10), and ADK STAB 1178(アデカスタブ 1178), and particularly ADK STAB PEP-36A (アデカスタブ PEP-36A) and ADK STAB PEP-36(アデカスタブ PEP-36) are preferable from the viewpoint of an effect of imparting thermal stability to the resin and an effect of combining a plurality of antioxidants.

These phosphorus antioxidants may be used alone or in combination of two or more.

Examples of the sulfur-based antioxidant include 2, 4-bis (dodecylthiomethyl) -6-methylphenol (Irganox 1726(イルガノックス 1726), manufactured by BASF corporation), 2, 4-bis (octylthiomethyl) -6-methylphenol (Irganox 1520L (イルガノックス 1520L), manufactured by BASF corporation), 2-bis { [3- (dodecylthio) -1-oxopropoxy ] methyl } propane-1, 3-diylbis [ 3-dodecylthio ] propionate ] (ADK STAB AO-412S (アデカスタブ AO-412S), manufactured by ADEKA corporation), 2-bis { [3- (dodecylthio) -1-oxopropoxy ] methyl } propane-1, 3-diylbis [ 3-dodecylthio ] propionate ] (KEMINOXPLS (ケミノックス PLS), CHEMICPRO CHEMIPRO chemical Co., Ltd. (ケミプロ chemical Co., Ltd.), ditridecyl 3, 3' -thiodipropionate (AO-503, manufactured by ADEKA) and the like, but the present invention is not limited thereto.

Among these commercially available sulfur antioxidants, ADK STAB AO-412S (アデカスタブ AO-412S) and KEMINOX PLS (ケミノックス PLS) are preferable from the viewpoints of an effect of imparting thermal stability to the resin, an effect of combining a plurality of antioxidants, and handling properties.

These sulfur-based antioxidants may be used alone or in combination of two or more.

The content of the antioxidant is preferably 5% by mass or less, more preferably 3% by mass or less, further preferably 1% by mass or less, further more preferably 0.8% by mass or less, further preferably 0.01 to 0.8% by mass, and particularly preferably 0.01 to 0.5% by mass, based on 100% by mass of the methacrylic resin, because an excessive content may cause problems such as bleeding during processing.

The timing of adding the antioxidant is not particularly limited, and examples thereof include: a method of starting polymerization after adding to a monomer solution before polymerization; a method of adding the polymer solution to the polymerized polymer solution, mixing the polymer solution and the polymer solution, and then supplying the mixture to a devolatilization step; a method of adding and mixing the devolatilized molten polymer and then granulating the resulting mixture; and a method of adding and mixing the devolatilized and granulated pellets at the time of melt extrusion again. Among these, from the viewpoint of preventing thermal deterioration and coloration in the devolatilization step, a method is preferred in which an antioxidant is added to and mixed with the polymer solution after polymerization, and then the mixture is supplied to the devolatilization step after the antioxidant is added before the devolatilization step.

Hindered amine light stabilizers-

The resin composition constituting the resin lens for a head-mounted display according to the present embodiment may contain a hindered amine light stabilizer.

The hindered amine-based light stabilizer is not particularly limited, and is preferably a compound having three or more ring structures. Here, the ring structure is preferably at least one selected from the group consisting of an aromatic ring, an aliphatic ring, an aromatic heterocyclic ring and a non-aromatic heterocyclic ring, and when two or more ring structures are included in one compound, the ring structures may be the same or different from each other.

Specific examples of the hindered amine-based light stabilizer include bis (1,2,2,6, 6-pentamethyl-4-piperidyl) [ [3, 5-bis (1, 1-dimethylethyl) -4-hydroxyphenyl ] methyl ] butyl malonate, a mixture of bis (1,2,2,6, 6-pentamethyl-4-piperidyl) sebacate and methyl 1,2,2,6, 6-pentamethyl-4-piperidyl sebacate, bis (2,2,6, 6-tetramethyl-4-piperidyl) sebacate, N '-bis (2,2,6, 6-tetramethyl-4-piperidyl) -N, N' -diformylhexamethylenediamine, dibutylamine 1,3, 5-triazine N, a polycondensate of N' -bis (2,2,6, 6-tetramethyl-4-piperidyl) -1, 6-hexamethylenediamine with N- (2,2,6, 6-tetramethyl-4-piperidyl) butylamine, poly [ {6- (1,1,3, 3-tetramethylbutyl) amino-1, 3, 5-triazine-2, 4-diyl } { (2,2,6, 6-tetramethyl-4-piperidyl) imino } hexamethylene { (2,2,6, 6-tetramethyl-4-piperidyl) imino } ], tetrakis (1,2,2,6, 6-pentamethyl-4-piperidyl) butane-1, 2,3, 4-tetracarboxylic acid ester, tetrakis (2,2,6, 6-tetramethyl-4-piperidyl) butane-1, 2,3, 4-tetracarboxylic acid ester, a reaction product of 1,2,2,6, 6-pentamethyl-4-piperidinol and β, β, β ', β' -tetramethyl-2, 4,8, 10-tetraoxaspiro [5.5] undecane-3, 9-diethanol, a reaction product of 2,2,6, 6-tetramethyl-4-piperidinol and β, β, β ', β' -tetramethyl-2, 4,8, 10-tetraoxaspiro [5.5] undecane-3, 9-diethanol, bis (1-undecyloxy-2, 2,6, 6-tetramethylpiperidin-4-yl) carbonate, 1,2,2,6, 6-pentamethyl-4-piperidyl methacrylate, 2,2,6, 6-tetramethyl-4-piperidyl methacrylate, and the like, but is not limited thereto.

Among them, preferred are bis (1,2,2,6, 6-pentamethyl-4-piperidyl) [ [3, 5-bis (1, 1-dimethylethyl) -4-hydroxyphenyl ] methyl ] butyl malonate, dibutylamine-1, 3, 5-triazine-N, N' -bis (2,2,6, 6-tetramethyl-4-piperidyl) -1, 6-hexamethylenediamine and N- (2,2,6, 6-tetramethyl-4-piperidyl) butylamine, poly [ {6- (1,1,3, 3-tetramethylbutyl) amino-1, 3, 5-triazine-2, 4-diyl } { (2,2,6, 6-tetramethyl-4-piperidyl) imino } hexamethylene { (2,2,6, 6-tetramethyl-4-piperidyl) imino } ], a reaction product of 1,2,2,6, 6-pentamethyl-4-piperidinol and β, β, β ', β' -tetramethyl-2, 4,8, 10-tetraoxaspiro [5.5] undecane-3, 9-diethanol, a reaction product of 2,2,6, 6-tetramethyl-4-piperidinol and β, β, β ', β' -tetramethyl-2, 4,8, 10-tetraoxaspiro [5.5] undecane-3, 9-diethanol.

The content of the hindered amine-based light stabilizer is not limited as long as the effect of improving light stability can be obtained, and when the content is excessive, problems such as bleeding may occur during processing, and therefore, the content is preferably 5% by mass or less, more preferably 3% by mass or less, further preferably 1% by mass or less, further more preferably 0.8% by mass or less, further preferably 0.01 to 0.8% by mass, and particularly preferably 0.01 to 0.5% by mass, relative to 100% by mass of the methacrylic resin.

UV absorbers

The resin composition constituting the resin lens for a head-mounted display according to the present embodiment may contain an ultraviolet absorber.

The ultraviolet absorber is not particularly limited, but is preferably an ultraviolet absorber having a maximum absorption wavelength of 280 to 380nm, and examples thereof include benzotriazole compounds, benzotriazine compounds, benzophenone compounds, oxybenzophenone compounds, benzoate compounds, phenol compounds, oxazole compounds, cyanoacrylate compounds, and benzoxazinone compounds.

Examples of the benzotriazole-based compound include 2, 2' -methylenebis [4- (1,1,3, 3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol ], 2- (3, 5-di-tert-butyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 2- (2H-benzotriazol-2-yl) -p-cresol, 2- (2H-benzotriazol-2-yl) -4, 6-bis (1-methyl-1-phenylethyl) phenol, 2-benzotriazol-2-yl-4, 6-di-tert-butylphenol, 2- [ 5-chloro (2H) -benzotriazol-2-yl ] -4-methyl-6-tert-butylphenol, and mixtures thereof, 2- (2H-benzotriazol-2-yl) -4, 6-di-tert-butylphenol, 2- (2H-benzotriazol-2-yl) -4- (1,1,3, 3-tetramethylbutyl) phenol, 2- (2H-benzotriazol-2-yl) -4-methyl-6- (3,4,5, 6-tetrahydrophthalimidomethyl) phenol, the reaction product of methyl 3- (3- (2H-benzotriazol-2-yl) -5-tert-butyl-4-hydroxyphenyl) propionate and polyethylene glycol 300, 2- (2H-benzotriazol-2-yl) -6- (linear and branched dodecyl) -4-methylphenol, and mixtures thereof, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [ 2-hydroxy-3, 5-bis (. alpha.,. alpha. -dimethylbenzyl) phenyl ] -2H-benzotriazole, 3- (2H-benzotriazol-2-yl) -5- (1, 1-dimethylethyl) -4-hydroxy-C7-9 branched and straight chain alkyl esters.

Of these, benzotriazole-based compounds having a molecular weight of 400 or more are preferable, and examples of commercially available compounds include Kemisorb (registered trademark) 2792 (manufactured by CHEMIPRO chemical synthesis (ケミプロ chemical synthesis)), ADK STAB (アデカスタブ) (registered trademark) LA31 (manufactured by ADEKA corporation), Tinuvin (チヌビン) (registered trademark) 234 (manufactured by basf corporation), and the like.

Examples of the benzotriazine-based compound include a 2-mono (hydroxyphenyl) -1,3, 5-triazine compound, a 2, 4-bis (hydroxyphenyl) -1,3, 5-triazine compound, and a 2,4, 6-tris (hydroxyphenyl) -1,3, 5-triazine compound, and specific examples thereof include 2, 4-diphenyl-6- (2-hydroxy-4-methoxyphenyl) -1,3, 5-triazine, 2, 4-diphenyl-6- (2-hydroxy-4-ethoxyphenyl) -1,3, 5-triazine, 2, 4-diphenyl- (2-hydroxy-4-propoxyphenyl) -1,3, 5-triazine, and, 2, 4-diphenyl- (2-hydroxy-4-butoxyphenyl) -1,3, 5-triazine, 2, 4-diphenyl-6- (2-hydroxy-4-hexyloxyphenyl) -1,3, 5-triazine, 2, 4-diphenyl-6- (2-hydroxy-4-octyloxyphenyl) -1,3, 5-triazine, 2, 4-diphenyl-6- (2-hydroxy-4-dodecyloxyphenyl) -1,3, 5-triazine, 2, 4-diphenyl-6- (2-hydroxy-4-benzyloxyphenyl) -1,3, 5-triazine, 2, 4-diphenyl-6- (2-hydroxy-4-butoxyethoxy) -1,3, 5-triazine, 2, 4-bis (2-hydroxy-4-butoxyphenyl) -6- (2, 4-dibutoxyphenyl) -1, 3-5-triazine, 2,4, 6-tris (2-hydroxy-4-methoxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-4-ethoxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-4-propoxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-4-butoxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-4-hexyloxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-4-octyloxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-4-dodecyloxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-4-benzyloxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-4-ethoxyethoxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-4-butoxyethoxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-4-propoxyethoxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-4-methoxycarbonylpropoxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-4-ethoxycarbonylethoxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-4- (1- (2-ethoxyhexyloxy) -1-oxopropane-2- Aryloxy) phenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-3-methyl-4-methoxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-3-methyl-4-ethoxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-3-methyl-4-propoxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-3-methyl-4-butoxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-3-methyl-4-hexyloxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-3-methyl-4-octyloxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-3-methyl-4-dodecyloxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-3-methyl-4-benzyloxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-3-methyl-4-ethoxyethoxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-3-methyl-4-butoxyethoxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-3-methyl-4-propoxyethoxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-3-methyl-4-methoxycarbonylpropoxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-3-methyl-4-ethoxycarbonylethoxyphenyl) -1,3, 5-triazine, 2,4, 6-tris (2-hydroxy-3-methyl-4- (1- (2-ethoxyhexyloxy) -1- Oxopropan-2-yloxy) phenyl) -1,3, 5-triazine, and the like.

As the benzotriazine compound, commercially available products can be used, and examples thereof include Kemisorb102 (manufactured by ケミプロ Kasei corporation), LA-F70 (manufactured by ADEKA Co., Ltd.), LA-46 (manufactured by ADEKA Co., Ltd.), Tinuvin405(チヌビン 405) (manufactured by BASF corporation), Tinuvin460(チヌビン 460) (manufactured by BASF corporation), Tinuvin479(チヌビン 479) (manufactured by BASF corporation), Tinuvin1577FF (チヌビン 1577FF) (manufactured by BASF corporation), and the like.

Among them, from the viewpoint of high compatibility with acrylic resins and excellent ultraviolet absorption characteristics, it is more preferable to use an ultraviolet absorber having a 2, 4-bis (2, 4-dimethylphenyl) -6- [ 2-hydroxy-4- (3-alkoxy-2-hydroxypropoxy) -5- α -cumylphenyl ] -s-triazine skeleton ("alkoxy" means a long-chain alkoxy group such as an octyloxy group, a nonyloxy group, or a decyloxy group).

The ultraviolet absorber is preferably a benzotriazole compound or a benzotriazine compound having a molecular weight of 400 or more, particularly from the viewpoint of compatibility with a resin and volatility upon heating, and is particularly preferably a benzotriazine compound from the viewpoint of suppressing decomposition by heating at the time of extrusion processing of the ultraviolet absorber itself.

The melting point (Tm) of the ultraviolet absorber is preferably 80 ℃ or higher, more preferably 100 ℃ or higher, still more preferably 130 ℃ or higher, and yet more preferably 160 ℃ or higher.

When the temperature of the ultraviolet absorber is raised from 23 ℃ to 260 ℃ at a rate of 20 ℃/min, the weight loss ratio is preferably 50% or less, more preferably 30% or less, still more preferably 15% or less, still more preferably 10% or less, and still more preferably 5% or less.

These ultraviolet absorbers may be used alone or in combination of two or more. By using two types of ultraviolet absorbers having different structures in combination, ultraviolet rays in a wide wavelength range can be absorbed.

The content of the ultraviolet absorber is not particularly limited as long as the effect of the present invention is exhibited without impairing heat resistance, moist heat resistance, heat stability and moldability, and is preferably 0.1 to 5% by mass, preferably 0.2 to 4% by mass or less, more preferably 0.25 to 3% by mass, and still more preferably 0.3 to 3% by mass, relative to 100% by mass of the methacrylic resin. When within this range, the balance of ultraviolet absorption properties, moldability, and the like is excellent.

Mold release agents-

The resin composition constituting the resin lens for a head-mounted display according to the present embodiment may contain a release agent. Examples of the release agent include, but are not limited to, fatty acid esters, fatty acid amides, fatty acid metal salts, hydrocarbon-based lubricants, alcohol-based lubricants, polyalkylene glycols, carboxylic acid esters, hydrocarbon-based paraffin mineral oils, and the like.

The fatty acid ester that can be used as the release agent is not particularly limited, and conventionally known fatty acid esters can be used.

Examples of the fatty acid ester include ester compounds of fatty acids having 12 to 32 carbon atoms such as lauric acid, palmitic acid, margaric acid, stearic acid, oleic acid, arachidic acid, and behenic acid, and monovalent aliphatic alcohols such as palmitic alcohol, stearyl alcohol, and behenic alcohol, and polyvalent aliphatic alcohols such as glycerin, pentaerythritol, dipentaerythritol, and sorbitan; and complex ester compounds of fatty acids and polyvalent organic acids with monovalent aliphatic alcohols or polyvalent aliphatic alcohols.

As such a fatty acid ester, for example, examples thereof include cetyl palmitate, butyl stearate, stearyl citrate, glyceryl monocaprylate, glyceryl monodecanoate, glyceryl monolaurate, glyceryl monopalmitate, glyceryl dipalmitate, glyceryl monostearate, glyceryl distearate, glyceryl tristearate, glyceryl monooleate, glyceryl dioleate, glyceryl trioleate, glyceryl monolinoleate, glyceryl monobehenate, glyceryl mono 12-hydroxystearate, glyceryl di 12-hydroxystearate, glyceryl tri 12-hydroxystearate, glyceryl diacetyl monostearate, glyceryl citric acid fatty acid ester, pentaerythritol adipic acid stearate, montanic acid partial saponification ester, pentaerythritol tetrastearate, dipentaerythritol hexastearate, sorbitan tristearate, and the like.

These fatty acid esters may be used alone or in combination of two or more.

Examples of commercially available products include RIKEMAL (リケマール), POEM (ポエム), RIKESTAR (リケスター), RIKEMASTER (リケマスター), EXCEL (エキセル), RHEODOL (レオドール), EXCEPARL (エキセパール), and COCONAD (ココナード), more specifically RIKEMAL S-100(リケマール S-100), RIKEMAL H-100(リケマール H-100), POEM V-100(ポエム V-100), RIKEMAL B-100(リケマール B-100), RIKEMAL HC-100(リケマール HC-100), RIKEMAL S-200(リケマール S-200), POEM B-200(ポエム B-200), and so on, RIKESTAR EW-200(リケスター EW-200), RIKESTAR EW-400(リケスター EW-400), EXCEL S-95(エキセル S-95), RHEODOL MS-50(レオドール MS-50), etc.

The fatty acid amide is not particularly limited, and conventionally known fatty acid amides can be used.

Examples of the fatty acid amide include saturated fatty acid amides such as lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, and hydroxystearic acid amide; unsaturated fatty acid amides such as oleamide, erucamide, and ricinoleamide; substituted amides such as N-stearyl stearic acid amide, N-oleyl oleic acid amide, N-stearyl oleic acid amide, N-oleyl stearic acid amide, N-stearyl erucamide, and N-oleyl palmitic acid amide; methylolamides such as methylolstearic acid amide and methylolbehenic acid amide; saturated fatty acid bisamides such as methylene bisstearamide, ethylene bisdecanoic acid amide, ethylene bislauric acid amide, ethylene bisstearamide (ethylene bisstearyl amide), ethylene bisisostearamide, ethylene bishydroxystearic acid amide, ethylene bisbehenic acid amide, hexamethylene bisstearamide, hexamethylene bisbehenic acid amide, hexamethylene bishydroxystearic acid amide, N '-distearyladipic acid amide, and N, N' -distearylsebacic acid amide; unsaturated fatty acid bisamides such as ethylenebisoleic acid amide, hexamethylenebisoleic acid amide, N '-dioleyl adipic acid amide, and N, N' -dioleyl sebacic acid amide; and aromatic bisamides such as m-xylylene bisstearic acid amide and N, N' -distearyl isophthalic acid amide.

These fatty acid amides may be used alone or in combination of two or more.

Examples of commercially available products include DIAMIDO (ダイヤミッド) (manufactured by Nikka chemical Co., Ltd.), Amide (manufactured by Nikka Amide (ニッカアマイド) (manufactured by Nikka chemical Co., Ltd.), methylolamide, bisamide, Suripakkusu (スリパックス) (manufactured by Nikka chemical Co., Ltd.), Kao wax (manufactured by Kao corporation), fatty acid Amide (manufactured by Kao corporation), and ethylene bisstearamide (manufactured by Dari chemical Co., Ltd.).

The fatty acid metal salt is a metal salt of a higher fatty acid, and examples thereof include lithium stearate, magnesium stearate, calcium laurate, calcium ricinoleate, strontium stearate, barium laurate, barium ricinoleate, zinc stearate, zinc laurate, zinc ricinoleate, zinc 2-ethylhexanoate, lead stearate, lead distearate, lead naphthenate, calcium 12-hydroxystearate, and lithium 12-hydroxystearate.

Examples of commercially available products include SZ series, SC series, SM series, and SA series made by Sakai chemical industry Co.

The content of the fatty acid metal salt is preferably 0.2% by mass or less based on 100% by mass of the resin composition from the viewpoint of maintaining transparency.

The release agent may be used alone or in combination of two or more.

The release agent to be used is preferably one having a decomposition initiation temperature of 200 ℃ or higher. Here, the decomposition start temperature can be determined by a temperature based on 1% mass reduction of TGA.

The content of the release agent is not limited as long as the effect as a release agent can be obtained, and when the content is excessive, problems such as bleeding during processing and poor extrusion due to sliding of a screw may occur, and therefore, the content is preferably 5% by mass or less, more preferably 3% by mass or less, further preferably 1% by mass or less, further more preferably 0.8% by mass or less, further preferably 0.01 to 0.8% by mass, and particularly preferably 0.01 to 0.5% by mass, relative to 100% by mass of the methacrylic resin. When the amount is added in the above range, the decrease in transparency due to the addition of the release agent is suppressed, and the release failure at the time of injection molding tends to be suppressed, so that the above-mentioned case is preferable.

Other thermoplastic resins

The resin composition constituting the resin lens for a head mount display according to the present embodiment may contain a thermoplastic resin other than a methacrylic resin for the purpose of adjusting the birefringence and improving the flexibility, as long as the object of the present invention is not impaired.

Examples of the other thermoplastic resin include polyacrylates such as polybutyl acrylate; styrene polymers such as polystyrene, styrene-methyl methacrylate copolymers, styrene-butyl acrylate copolymers, styrene-acrylonitrile copolymers, and acrylonitrile-butadiene-styrene block copolymers; further, for example, there may be mentioned acrylic rubber particles having a3 to 4-layer structure as described in, for example, Japanese patent application laid-open Nos. 59-202213, 63-27516, 51-129449, 52-56150; rubbery polymers disclosed in Japanese Kokoku publication Sho-60-17406 and Japanese patent application laid-open No. Hei 8-245854; graft copolymer particles containing a methacrylic rubber obtained by multistage polymerization as described in International publication No. 2014-002491; and the like.

Among them, from the viewpoint of obtaining good optical properties and mechanical properties, styrene-acrylonitrile copolymers and rubber-containing graft copolymer particles having a surface layer having a graft portion composed of a composition compatible with a methacrylic resin containing a structural unit X having a ring structure in the main chain are preferable.

The average particle diameter of the acrylic rubber particles, the graft copolymer particles containing a methacrylic rubber, and the rubbery polymer is preferably 0.03 to 1 μm, and more preferably 0.05 to 0.5 μm, from the viewpoint of improving the impact strength and optical properties of the film obtained from the composition of the present embodiment.

The content of the other thermoplastic resin is preferably 0to 50% by mass, more preferably 0to 25% by mass, when the methacrylic resin is 100% by mass.

[ method for producing resin composition ]

The method for producing the resin composition constituting the resin lens for a head-mounted display according to the present embodiment is not particularly limited as long as the composition satisfying the conditions of the present invention can be obtained. For example, a method of kneading the mixture using a kneading machine such as an extruder, a heating roll, a kneader, a roll mixer, or a banbury mixer is mentioned. Among them, kneading by an extruder is preferable from the viewpoint of productivity. The kneading temperature may be set in accordance with a preferable processing temperature of the polymer constituting the methacrylic resin and the other resin to be mixed, and may be 140 to 300 ℃ as a reference, and preferably 180 to 280 ℃. Further, for the purpose of reducing volatile components, it is preferable to provide vent ports in the extruder.

Here, in the resin composition constituting the resin lens for a head-mounted display according to the present embodiment, the amount of the solvent remaining (the amount of the solvent remaining) is preferably less than 1000 mass ppm, more preferably less than 800 mass ppm, and still more preferably less than 700 mass ppm.

The residual solvent used herein means a polymerization solvent used in polymerization (excluding alcohols) and a solvent used in dissolving a resin obtained by polymerization again into a solution, and specifically, aromatic hydrocarbons such as toluene, xylene, ethylbenzene, and cumene; ketones such as methyl isobutyl ketone, butyl cellosolve, methyl ethyl ketone, and cyclohexanone; polar solvents such as dimethylformamide and 2-methylpyrrolidone; examples of the solvent used for redissolution include toluene, methyl ethyl ketone, and methylene chloride.

In the resin composition constituting the resin lens for a head-mounted display according to the present embodiment, the amount of alcohol remaining (amount of alcohol remaining) is preferably less than 500 mass ppm, more preferably less than 400 mass ppm, and still more preferably less than 350 mass ppm.

The residual alcohol is an alcohol by-produced by the cyclized condensation reaction, and specifically, an aliphatic alcohol such as methanol, ethanol, or isopropanol may be used.

The amount of the residual solvent and the amount of the residual alcohol can be measured by a gas chromatograph.

In the case of selecting any method, it is preferable to prepare the composition on the basis of minimizing oxygen and water.

For example, the dissolved oxygen concentration in the polymerization solution during solution polymerization is preferably less than 300ppm in the polymerization step, and the oxygen concentration in the extruder in the production method using an extruder or the like is preferably less than 1% by volume, and more preferably less than 0.8% by volume. The water content of the methacrylic resin is preferably adjusted to 1000 mass ppm or less, more preferably 500 mass ppm or less.

Within these ranges, it is advantageous to produce a composition satisfying the requirements of the present invention relatively easily.

[ method for producing resin lens for head-mounted display ]

The resin lens for a head-mounted display according to the present embodiment is obtained by molding the resin composition. As a method for manufacturing the resin lens for a head-mounted display of the present embodiment, a molding method such as injection molding, compression molding, or extrusion molding can be used. Among them, injection molding is preferable from the viewpoint of productivity.

Generally, the injection molding method is composed of the following steps: (1) an injection step of melting a resin and filling the molten resin into a cavity of a temperature-controlled mold; (2) a pressure maintaining step of applying a pressure to the cavity until the gate is sealed, and injecting a resin in an amount corresponding to an amount of the molten resin filled in the injection step, which is cooled and contracted by contacting the molten resin with the mold; (3) a cooling step of holding the molded article until the resin is cooled after the pressure is released; (4) and opening the mold to take out the cooled molded article.

In this case, the molding temperature may be in the range of Tg +100 to Tg +160 ℃ based on the glass transition temperature (Tg) of the resin composition, and preferably in the range of Tg +110 to Tg +150 ℃. Here, the molding temperature refers to a control temperature of a tape heater wound around the injection nozzle. A resin lens having a lower phase difference can be obtained at a higher molding temperature, but coloring due to thermal degradation when the resin lens is retained in a molding machine is promoted at a high temperature, and therefore, it is necessary to appropriately select the molding temperature.

The mold temperature is preferably in the range of Tg-70 to Tg, more preferably in the range of Tg-50 to Tg-20 ℃ based on the glass transition temperature (Tg) of the resin composition.

The injection speed may be appropriately selected according to the thickness and size of the resin lens to be obtained, and may be appropriately selected in the range of 200to 1000 mm/sec, for example.

The pressure for holding the pressure may be appropriately selected according to the shape of the resin lens to be obtained, and may be appropriately selected, for example, in the range of 30to 120 MPa.

Here, the pressure for holding pressure refers to a pressure held by a screw for feeding out the molten resin further from the gate after filling the molten resin.

In addition, an annealing process may be performed to relieve residual stress caused by injection molding and reduce the phase difference of the resin lens. The temperature at the time of annealing is preferably in the range of Tg-50 to Tg, more preferably in the range of Tg-30 to Tg-10 ℃ based on the glass transition temperature (Tg) of the resin composition.

The surface of the resin lens for a head-mounted display according to the present embodiment may be further subjected to surface functionalization treatment such as hard coating treatment, antireflection treatment, transparent conductive treatment, electromagnetic wave shielding treatment, and gas barrier treatment. The thickness of these functional layers is not particularly limited, but is usually in the range of 0.01 to 10 μm.

The hard coating layer to be provided on the surface thereof is formed by, for example, applying a coating solution prepared by dissolving or dispersing a silicone-based curable resin, a curable resin containing organic polymer composite inorganic fine particles, an acrylate such as urethane acrylate, epoxy acrylate, or polyfunctional acrylate, and a photopolymerization initiator in an organic solvent, onto a film or a sheet obtained from the resin composition of the present embodiment by a conventionally known coating method, drying the coating solution, and photocuring the coating solution.

In order to improve the adhesiveness, for example, a method of forming a hard coating layer after providing an easy adhesion layer containing inorganic fine particles in its components, an undercoat layer, an anchor layer, and the like in advance before applying the hard coating layer may be used.

The antiglare layer provided on the surface thereof is formed by forming fine particles of silica, melamine resin, acrylate resin, or the like into ink (ink), applying the ink onto another functional layer by a conventionally known coating method, and thermally curing or photocuring the ink.

Examples of the anti-reflective layer provided on the surface thereof include anti-reflective layers formed of thin films of inorganic substances such as metal oxides, fluorides, silicides, borides, nitrides, and sulfides; a resin having different refractive indices such as an acrylic resin and a fluororesin may be used in a single layer or a multilayer anti-reflection layer, or an anti-reflection layer obtained by laminating a thin layer containing composite fine particles of an inorganic compound and an organic compound may be used.

[ examples ]

The present invention will be described in detail below with reference to examples and comparative examples. The present invention is not limited to the following examples.

< 1. determination of the amount of 2-cyclohexylamino-N-cyclohexylsuccinimide in N-cyclohexylmaleimide >

N-cyclohexylmaleimide or an N-cyclohexylmaleimide/m-xylene solution was collected and weighed, a 25 mass% m-xylene solution of N-cyclohexylmaleimide was prepared, isopropyl benzoate was added as an internal standard substance, and the solution was measured by a gas chromatograph (manufactured by Shimadzu corporation, GC-2014) under the following conditions.

A detector: FID.

Using a chromatographic column: HP-5 ms.

The measurement conditions were as follows: after the temperature was maintained at 80 ℃ for 5 minutes, the temperature was raised to 300 ℃ at a temperature raising rate of 10 ℃/minute, and thereafter, the temperature was maintained for 5 minutes.

[2] determination of the amount of 2-anilino-N-phenylsuccinimide in N-phenylmaleimide >

The N-phenylmaleimide solution or the N-phenylmaleimide/m-xylene solution was collected and weighed, a 10 mass% m-xylene solution of N-phenylmaleimide was prepared, isopropyl benzoate was added as an internal standard substance, and the solution was measured by a liquid chromatograph (UPLC H-class, manufactured by Waters corporation) under the following conditions.

A detector: PDA (detection wavelength: 210 nm-300 nm).

Using a chromatographic column: ACQUITY UPLC HSS T3.

Temperature of the column: at 40 ℃.

Mobile phase: 50% aqueous acetonitrile containing 0.1% formic acid.

Flow rate: 0.4 mL/min.

Determination of the residual amount of N-substituted maleimide monomer

A part of the analysis object (polymerization solution after polymerization or methacrylic resin particles) was collected and weighed, and this sample was dissolved in chloroform to prepare a 5 mass% solution, and n-decane was added as an internal standard substance, and the solution was measured by a gas chromatograph (manufactured by shimadzu corporation, GC-2010) under the following conditions.

A detector: FID.

Using a chromatographic column: ZB-1.

The measurement conditions were as follows: after holding at 45 ℃ for 5 minutes, the temperature was raised to 300 ℃ at a rate of 20 ℃/minute, and then held for 15 minutes.

< 4. analysis of structural units >

Each structural unit in the methacrylic resins produced in the production examples and comparative examples described later was, unless otherwise specified, represented by¹H-NMR measurement and¹³C-NMR measurement was carried out to identify each structural unit of the methacrylic resin and the methacrylic resin composition, and the amount thereof present was calculated.¹H-NMR measurement and¹³the measurement conditions for the C-NMR measurement are as follows.

The measurement device: JNM-ECZ400S, manufactured by Nippon electronics Co., Ltd.

Determination of the solvent: CDCl₃Or d₆-DMSO。

Measurement temperature: at 40 ℃.

< 5. molecular weight and molecular weight distribution >

The weight average molecular weight (Mw), the number average molecular weight (Mn), and the Z average molecular weight (Mz) of the methacrylic resin compositions produced in the production examples and the production comparative examples described below were measured by the following apparatus and conditions.

Measurement conditions:

Temperature of the column: at 40 ℃.

Developing solvent: tetrahydrofuran, flow rate: 0.6mL/min 2, 6-di-tert-butyl-4-methylphenol (BHT) was added as an internal standard at 0.1 g/L.

A detector: an RI (differential refraction) detector.

Detection sensitivity: 3.0 mV/min.

Sample preparation: 0.02g of a tetrahydrofuran 20mL solution of a methacrylic resin composition.

Sample introduction amount: 10 μ L.

Weight Peak molecular weight (Mp)

Under the above conditions, the RI detection intensity with respect to the elution time of the methacrylic resin composition was measured.

Based on each calibration curve obtained by measurement of the standard sample for calibration curve described above, the weight average molecular weight (Mw), the number average molecular weight (Mn), and the Z average molecular weight (Mz) of the methacrylic resin composition were obtained, and the molecular weight distribution (Mw/Mn) and (Mz/Mw) were determined using the values.

< 6. phase difference within effective diameter of resin lens >

The resin lenses obtained in examples and comparative examples were measured for the surface distribution of the retardation of the lens from the optical axis direction at a wavelength of 520nm using a birefringence evaluation system PA-200-L manufactured by Photonic Lattice co., フォトニックラティス, and the average value (nm) of the absolute values of the retardation was determined by specifying the region within the effective diameter (Φ 41mm) of the lens.

< 7. content of fluorescent substance in resin lens >

The resin lenses obtained in examples and comparative examples were finely cut, a glass sample bottle was weighed, chloroform was added thereto, and the solution was shaken with a shaker at a speed of 800 times per minute for 30 minutes to prepare a chloroform solution of 2.0 mass% resin lenses, and the fluorescence intensity was measured using a spectrofluorometer (horiba, gabbitt, yon, manufactured by horiba, Jobin Yvon corporation, Fluorolog 3-22).

The measurement conditions were measured by using a xenon lamp as a light source, a PMT as a detector, an excitation wavelength of 436nm, a slit width of 2nm on both the excitation side and the observation side, and a time constant of 0.2s, in a measurement mode of Sc/Rc in which the emission intensity was normalized by the excitation light intensity of each wavelength, and by performing 90 ° observation using a quartz cuvette having an optical path length of 1 cm.

The obtained fluorescence intensity in the wavelength of 530nm was normalized using the fluorescence intensity of a fluorescein/ethanol solution. Specifically, the following is described.

To obtain the respective ratios of ethanol and 5X 10^-8mol/L and 1X 10^-6When the fluorescence intensity at a wavelength of 530nm was analyzed by spectroscopic analysis using a fluorescein/ethanol solution of mol/L at an excitation wavelength of 436nm, the blank of ethanol was subtracted therefrom to prepare a concentration-intensity conversion equation. Measuring fluorescence emission spectrum of chloroform from 2.0 mass% of the treeThe content (mol/L) of the fluorescent substance was determined by subtracting the emission intensity of chloroform at 530nm from the emission intensity of chloroform at 530nm in the chloroform solution in the resin lens, and using the concentration-intensity conversion formula for the previously determined fluorescein/ethanol solution.

< 8. glass transition temperature of resin lens >

The glass transition temperature (Tg) (. degree. C.) of the resin lens was measured in accordance with JIS-K7121.

First, as a test piece, about 10mg was cut out from each of four points (four points) of a resin lens conditioned in a standard state (23 ℃ C., 50% RH) (left at 23 ℃ C., for 1 week).

Next, in a DSC curve drawn during the complete melting of the sample by using a differential scanning calorimeter (Diamond DSC, manufactured by perkin elmer japan ltd., パーキンエルマージャパン, inc.) under a nitrogen flow rate of 25 mL/min, the temperature was raised from room temperature (23 ℃) to 200 ℃ at 10 ℃/min (primary temperature rise), the temperature was maintained at 200 ℃ for 5 minutes, the temperature was lowered from 200 ℃ to 40 ℃ at 10 ℃/min, the temperature was maintained at 40 ℃ for 5 minutes, and the temperature was further raised again under the temperature rise condition (secondary temperature rise), and in the DSC curve drawn during this time, the intersection point (middle glass transition temperature) between the curve of the step-like change portion at the secondary temperature rise and the straight line equidistant from the extension lines of the respective base lines in the vertical axis direction was measured as the glass transition temperature (Tg) (° c). Four points were measured for each sample, and the arithmetic average of the four points (rounded up or down in decimal places) was defined as the measured value.

< 9 photoelastic coefficient of resin lens >

After the resin lenses obtained in examples and comparative examples were finely cut, a film was formed using a vacuum compression molding machine, thereby obtaining a sample for measurement.

As a concrete sample preparation condition, a vacuum compression molding machine (SFV-30, product of the Shenteng Metal industry) was used, the resin lens was preheated at 260 ℃ under reduced pressure (about 10kPa) for 10 minutes, then compressed at 260 ℃ under about 10MPa for 5 minutes, and after the reduced pressure and the compression pressure were released, the resin lens was moved to a compression molding machine for cooling and solidified. The pressed film thus obtained was aged in a constant temperature and humidity chamber adjusted to 23 ℃ and a humidity of 60% for 24 hours or more, and then a test piece for measurement (thickness: about 150 μm, width: 6mm) was cut out.

The photoelastic coefficient C was measured using a birefringence measurement apparatus described in detail in Polymer Engineering and Science (1999,39,2349-_R(Pa^-1)。

The film-like test piece was placed in a film stretching apparatus (manufactured by wellmaking) also installed in a constant temperature and humidity chamber so that the distance between chucks became 50 mm. Next, the apparatus was disposed so that the laser beam path of a birefringence measurement apparatus (RETS-100, manufactured by Otsuka Denshi) was positioned at the center of the film, and the birefringence of the test piece was measured while applying a tensile stress at a deformation rate of 50%/min (between chucks: 50mm, chuck movement rate: 5 mm/min).

Birefringence (. DELTA.n) and tensile stress (. sigma.) obtained from the measurement_R) The slope of the straight line is obtained by approximation by the minimum two-way multiplication, and the photoelastic coefficient (C) is calculated_R)(Pa^-1). In the calculation, a tensile stress of 2.5 MPa. ltoreq. sigma._RData less than or equal to 10 MPa.

C_R＝Δn/σ_R

Here, the birefringence (Δ n) is a value shown below.

Δn＝nx-ny

(nx: refractive index in stretching direction, ny: refractive index in a direction perpendicular to the stretching direction in plane)

< 10. light transmittance of resin lens >

The resin lenses obtained in examples and comparative examples were measured for transmittance (%) at 5nm over a wavelength range of 380 to 780nm with a D65 light source at 10 ℃ by passing a light source through the thickest part of the lens in the thickness direction using a spectrocolorimeter (SD-5000, manufactured by Nippon Denshoku industries Co., Ltd.). Using the measured values, the ratio (T450/T680) of the transmittance at a wavelength of 450nm (T450) to the transmittance at a wavelength of 680nm (T680) was determined.

< 11. definition of image >

A simulator for reproducing the principle of the head-mounted display described in japanese patent laid-open publication No. 2017-21321 shown in fig. 1 was fabricated in a dark room using the resin lenses obtained in the examples and comparative examples.

In this simulation apparatus, a liquid crystal display 1, a polarizing plate 2, an 1/4 wavelength plate 3, a half mirror 4, resin lenses 5 obtained in examples and comparative examples, a 1/4 wavelength plate 6, and a reflective polarizing plate 7 were disposed coaxially in this order. When light along the optical axis from the liquid crystal display 1 passes through the polarizing plate 2, 1/4 wavelength plate 3, half mirror 4, resin lens 5, 1/4 wavelength plate 6 and reaches the reflective polarizing plate 7, the light is reflected by the reflective polarizing plate 7 (first reflection), then passes through the 1/4 wavelength plate 6 and resin lens 5 and reaches the half mirror 4, is reflected by the half mirror 4 (second reflection), passes through the resin lens 5, 1/4 wavelength plate 6 again, and reaches the human eye. The half mirror 4 can reflect a part of the light and transmit the remaining light. The light adds a phase lag of 90 degrees each time it passes through the 1/4 wavelength plate. The image is magnified by the two reflections described above to reach the human eye.

The still image displayed on the liquid crystal display 1 was observed by the simulation device, and the sharpness of the image was evaluated by the following evaluation criteria.

[ evaluation standards ]

Good: the image was magnified and no bleeding and blurring were observed.

And (delta): when an image with a low magnification is superimposed on the enlarged image, the image becomes slightly unclear.

X: an image with a low magnification is mainly observed, and becomes unclear.

[ raw materials ]

The raw materials used in examples and comparative examples described below are as follows.

[ [ monomer ] ]

Methyl Methacrylate (MMA): asahi Kasei K.K.K.

N-cyclohexylmaleimide (chMI): manufactured by japan catalyst corporation.

(the mass ratio of 2-cyclohexylamino-N-cyclohexylsuccinimide (CCSI) relative to the mass of chMI is 80 mass ppm)

N-phenylmaleimide (phMI): manufactured by japan catalyst corporation.

(the mass ratio of 2-anilino-N-phenylsuccinimide (APSI) to the mass of phMI is 60 mass ppm)

Pretreatment of N-substituted maleimide (chMI, phMI) (water washing step and dehydration step) -removal of 2-amino-N-substituted succinimide (CCSI, APSI) and removal of water content were carried out by subjecting the above-mentioned N-cyclohexylmaleimide (chMI) and N-phenylmaleimide (phMI) to the following water washing and dehydration steps.

Water washing and dehydration of-N-cyclohexylmaleimide (chMI)

Reduction of CCSI in N-cyclohexylmaleimide to 5 mass ppm or less

250.0kg of chMI and 750.0kg of m-xylene (hereinafter referred to as "mXy") were measured and added to a 2.0m stirring blade having a temperature control device based on a jacket and three sweepback blades as stirring blades³In the reactor made of glass-lined, steam was blown into the sheath to raise the temperature of the solution in the reactor to 56 ℃ and the solution was stirred to obtain an organic layer. Next, 350.0kg of 2 mass% sulfuric acid water was measured and added to the reactor, and the solution temperature was maintained at 56 ℃ and stirred at 100rpm for 10 minutes. Stirring was stopped, the mixture was allowed to stand for 10 minutes, and the aqueous layer was taken out into a drum.

The same operation was repeated twice more, and the organic layer was washed with sulfuric acid water three times in total. The CCSI content in the organic layer was determined by gas chromatography, and the result was 4.9 mass ppm relative to the chMI in the organic layer.

Thereafter, 350.0kg of ion-exchanged water was added to the reactor, and the solution temperature was maintained at 55 ℃ and stirred at 100rpm for 10 minutes. Stirring was stopped, the mixture was allowed to stand for 20 minutes, and the aqueous layer was taken out into a drum.

The same operation was repeated once more, and the operation of washing the organic layer with ion-exchanged water was performed twice in total. The CCSI amount in the organic layer was quantified by gas chromatography, and the result was 4.6 mass ppm relative to chMI in the organic layer.

Then, the pressure in the reactor was gradually reduced while stirring at 100rpm while maintaining the solution temperature at 50 ℃ so that the pressure in the reactor was 5 kPa. Thereafter, the temperature of the solution was raised to 60 ℃ to conduct an azeotropic dehydration operation. 131.6kg of the water/mXy mixed solution was distilled off, and the water concentration in the organic layer was determined by a Karl Fischer moisture meter, and as a result, the mass was 102 mass ppm with respect to the mass of the organic layer.

mXy for concentration adjustment was added to the organic layer to obtain 1034.3kg of an organic layer having a chMI of 24.0 mass%, a water concentration of 191 mass ppm, and a CCSI of 4.6 mass ppm with respect to the mass of chMI.

Reduction of CCSI in N-cyclohexylmaleimide to 1 mass ppm or less

80.0kg of chMI and 240.0kg of mXy were measured and added to 0.50m of a Full area (Full zone, フルゾーン) with a jacket-based thermostat and a blade-based solution (blade-based environment ソリューション)³In the reactor made of glass-lined, steam was blown into the sheath to raise the temperature of the solution in the reactor to 55 ℃ and the solution was stirred to obtain an organic layer. Next, 112.0kg of 2 mass% sulfuric acid water was measured and added to the reactor, and the solution temperature was maintained at 55 ℃ and stirred at 100rpm for 30 minutes. Stirring was stopped, the mixture was allowed to stand for 10 minutes, and the aqueous layer was taken out into a drum.

The same operation was repeated three more times, and the organic layer was washed with sulfuric acid water 4 times in total. The CCSI content in the organic layer was determined by gas chromatography, and the result was 0.57 ppm by mass relative to the chMI in the organic layer.

Thereafter, 112.0kg of ion-exchanged water was added to the reactor, and the solution temperature was maintained at 55 ℃ and stirred at 100rpm for 30 minutes. The stirring was stopped, the mixture was allowed to stand for 10 minutes, and the aqueous layer was taken out of the drum.

The pressure in the reactor was gradually reduced while stirring at 100rpm while maintaining the solution temperature at 50 ℃ so that the pressure in the reactor became 5 kPa. Thereafter, the temperature of the solution was raised to 60 ℃ to conduct an azeotropic dehydration operation. 54kg of the water/mXy mixed solution was distilled off, and the water concentration in the organic layer was determined by a Karl Fischer moisture meter, and as a result, it was 46 mass ppm based on the mass of the organic layer.

mXy for concentration adjustment was added to the organic layer to obtain 384.0kg of an organic layer having a chMI of 20.3 mass%, a water concentration of 125 mass ppm, and a CCSI of 0.60 mass ppm with respect to the mass of the chMI.

Water washing and dehydration of-N-phenylmaleimide (phMI) -

Reduction of APSI in N-phenylmaleimide to 5 mass ppm or less

150.0kg phMI and 720.0kg mXy were measured and added to a 2.0m blade with a jacket-based thermostat and three sweepback blades as stirring blades³In the reactor made of glass-lined, steam was blown into the sheath to raise the temperature of the solution in the reactor to 55 ℃ and the solution was stirred to obtain an organic layer. Next, 336.0kg of 7 mass% sodium bicarbonate water was measured and added to the reactor, and the solution temperature was maintained at 55 ℃ and stirred at 100rpm for 10 minutes. Stirring was stopped, the mixture was allowed to stand for 10 minutes, and the aqueous layer was taken out into a drum.

Next, 336.0kg of ion-exchanged water was added to the reactor, and the solution temperature was maintained at 55 ℃ and stirred at 100rpm for 10 minutes. Stirring was stopped, the mixture was allowed to stand for 10 minutes, and the aqueous layer was taken out into a drum.

Thereafter, 336.0kg of 2 mass% sulfuric acid water was measured and added to the reactor, and the solution temperature was maintained at 55 ℃ and stirred at 100rpm for 10 minutes. Stirring was stopped, the mixture was allowed to stand for 10 minutes, and the aqueous layer was taken out into a drum.

In the same manner as described above, the operation of washing with ion-exchanged water was further performed twice.

The amount of APSI in the organic layer was determined by liquid chromatography, and as a result, the phMI in the organic layer was 3.6 mass ppm.

Then, the pressure in the reactor was gradually reduced while stirring at 100rpm while maintaining the solution temperature at 50 ℃ so that the pressure in the reactor was 5 kPa. Thereafter, the temperature of the solution was raised to 55 ℃ to conduct an azeotropic dehydration operation. 190kg of the water/mXy mixed solution was distilled off, and the water concentration in the organic layer was determined by a Karl Fischer moisture meter, and as a result, it was 47 mass ppm with respect to the mass of the organic layer.

mXy for concentration adjustment was added to the organic layer to obtain 1340.7kg of an organic layer having a phMI of 10.8 mass%, a water concentration of 170 mass ppm, and an APSI of 3.4 mass ppm relative to the mass of phMI.

Reduction of APSI in N-phenylmaleimide to 1 mass ppm or less

50.0kg phMI and 240.0kg mXy were measured and added to 0.50m of a Full area (Full zone, フルゾーン) with a jacket-based thermostat and a blade-based blade-mix system (Steel Environment ソリューション)³In the reactor made of glass-lined, steam was blown into the sheath to raise the temperature of the solution in the reactor to 55 ℃ and the solution was stirred to obtain an organic layer. Next, 112.0kg of 7 mass% sodium bicarbonate water was measured and added to the reactor, and the solution temperature was maintained at 55 ℃ and stirred at 100rpm for 15 minutes. Stirring was stopped, the mixture was allowed to stand for 10 minutes, and the aqueous layer was taken out into a drum. The same operation was repeated once more, and the operation of washing the organic layer with sodium bicarbonate was performed twice in total.

Next, 112.0kg of ion-exchanged water was added to the reactor, and the solution was stirred at 100rpm for 30 minutes while maintaining the temperature at 55 ℃. Stirring was stopped, the mixture was allowed to stand for 10 minutes, and the aqueous layer was taken out into a drum.

Thereafter, 112.0kg of 2 mass% sulfuric acid water was measured and added to the reactor, and the solution temperature was maintained at 55 ℃ and stirred at 100rpm for 30 minutes. Stirring was stopped, the mixture was allowed to stand for 10 minutes, and the aqueous layer was taken out into a drum. The same operation was repeated twice more, and the operation of washing the organic layer with sulfuric acid water was performed three times in total.

The APSI content in the organic layer was determined by liquid chromatography, and the result was 0.37 mass ppm relative to the phMI in the organic layer.

The pressure in the reactor was gradually reduced while stirring at 100rpm while maintaining the solution temperature at 50 ℃ so that the pressure in the reactor became 5 kPa. Thereafter, the temperature of the solution was raised to 55 ℃ to conduct an azeotropic dehydration operation. 72kg of the water/mXy mixed solution was distilled off, and the water concentration in the organic layer was determined by a Karl Fischer moisture meter, and as a result, the mass of the organic layer was 60 mass ppm.

mXy for concentration adjustment was added to the organic layer to obtain 432.8kg of an organic layer having a phMI of 10.3 mass%, a water concentration of 180 mass ppm, and an APSI of 0.42 mass ppm relative to the mass of phMI.

[ [ polymerization initiator ] ]

1, 1-bis (tert-butylperoxy) cyclohexane: "PERHEXA C (パーヘキサ C)" manufactured by Nichigan oil Co., Ltd.

[ [ chain transfer agent ] ]

N-octyl mercaptan: manufactured by kao corporation.

[ [ hindered phenol-based antioxidant ] ]

Irganox 1010(イルガノックス 1010): manufactured by basf corporation.

[ [ phosphorus-based antioxidant ] ]

Irgafos168(イルガフォス 168) (melting point 180-190 ℃): manufactured by basf corporation.

[ methacrylic resin composition ]

Production example 1

374.8kg of mXy solution (APSI of 0.42 mass ppm based on the phMI) having a phMI of 10.3 mass% and 323.6kg of mXy solution (CCSI of 0.60 mass ppm based on the chMI) having a chMI of 20.3 mass% and having a water washing step and a dehydrating step were measured and added to a 1.25m stirring blade equipped with a temperature control device using a jacket³160.8kg of mXy was distilled off under reduced pressure while stirring in a reactor at a solution temperature of 60 ℃ and a reactor pressure of 5 kPa. Next, the reaction vessel was returned to normal pressure, and 16.7kg of mXy was added to prepare a mixed solution of 38.6kg of phMI, 65.7kg of chMI, and 450.0kg of mXy. 445.7kg of MMA and 0.413kg of n-octylmercaptan as a chain transfer agent were weighed out, and charged and stirred to obtain a monomer mixed solution.

Nitrogen-based bubbling was performed at a rate of 30L/min for 1 hour for the liquid content of the reactor, thereby removing dissolved oxygen.

Thereafter, 0.23kg of a polymerization initiator solution prepared by dissolving 0.23kg of 1, 1-di (t-butylperoxy) cyclohexane in 2.77kg of mXy was added at a rate of 0.5 kg/hr while stirring at 50rpm while raising the temperature of the solution in the reactor to 125 ℃ by blowing steam into the jacket, thereby starting the polymerization, and the addition was stopped 6 hours after the start of the polymerization.

It should be noted that the temperature of the solution in the reactor was controlled to 125. + -. 2 ℃ by using jacket-based temperature regulation in the polymerization.

From the start of the polymerization to after 8 hours have elapsed, a polymerization solution containing a methacrylic resin having a ring structure in the main chain was obtained.

The amount of the N-substituted maleimide contained in the obtained polymerization solution was evaluated, and as a result, 1340 mass ppm of phMI and 4390 mass ppm of chMI were contained.

To this polymerization solution, Irganox 1010(イルガノックス 1010) in an amount of 0.1 mass% and Irgafos168(イルガフォス 168) in an amount of 0.05 mass% relative to 100 mass% of the polymer contained in the solution were added under stirring.

The polymerization solution containing the antioxidant was filtered through a filter having a filtration accuracy of 2 μm made of a metal fiber made of SUS 316L.

In order to recover the polymer from the polymerization solution, a device used in the devolatilization step was constituted by a plate heat exchanger having a plate slit-type flow path and a heat medium flow path and an internal volume of about 0.3m³The devolatilization apparatus of (1) above, which comprises a pressure reducing vessel (hereinafter, referred to as a devolatilization vessel) with an SUS heating medium jacket.

The solution containing the polymer obtained by polymerization was supplied to a heat exchanger provided in the upper part of a vacuum vessel at a rate of 30 liters/hour, heated to 260 ℃ and then supplied to a devolatilization vessel heated and depressurized to an internal temperature of 260 ℃ and a vacuum degree of 30Torr, thereby carrying out devolatilization treatment. The shear rate in the devolatilizer was calculated from the shape of the apparatus and the operating conditions and found to be 5.3 seconds^-1。

The devolatilized polymer was pressurized from the bottom of the devolatilization vessel by a gear pump, extruded from a strand die, water-cooled, and pelletized to obtain a methacrylic resin composition a.

The composition of the methacrylic resin composition a was confirmed, and as a result, the constituent units derived from the MMA, phMI, and chMI monomers were 81.2 mass%, 7.1 mass%, and 11.7 mass%, respectively. Further, the weight average molecular weight Mw was 148,000, Mw/Mn was 2.12, Mz/Mw was 1.63, and the glass transition temperature was 133 ℃.

Production example 2

352.4kg of mXy solution (APSI of 0.42 mass ppm based on the phMI) having a phMI of 10.3 mass% and 310.3kg of mXy solution (CCSI of 0.60 mass ppm based on the chMI) having a chMI of 20.3 mass% and having a water washing step and a dehydrating step were measured and added to a 1.25m stirring blade equipped with a temperature control device using a jacket³The reactor was purged with 335.4kg of mXy under reduced pressure while stirring at a solution temperature of 60 ℃ and a reactor pressure of 5 kPa. Next, the reaction vessel was returned to normal pressure, and 8.9kg of mXy was added to prepare a mixed solution of 36.3kg of phMI, 63.0kg of chMI, and 236.9kg of mXy. 340.7kg of MMA and 0.275kg of n-octylmercaptan as a chain transfer agent were measured out, and charged and stirred to obtain a monomer mixed solution.

Next, 123.1kg of mXy was measured and added to tank 1.

Further, 110.0kg of MMA and 90.0kg of mXy were weighed and stirred in tank 2 as a monomer solution for additional addition.

Nitrogen bubbling was performed at a rate of 30L/min for 1 hour for the liquid in the reactor, and nitrogen bubbling was performed at a rate of 10L/min for 30 minutes for each of tank 1 and tank 2, thereby removing dissolved oxygen.

Thereafter, the temperature of the solution in the reactor was raised to 128 ℃ by blowing steam into the jacket, and while stirring at 50rpm, 0.37kg of a polymerization initiator solution prepared by dissolving 1, 1-bis (t-butylperoxy) cyclohexane in 3.005kg of mXy was added at a rate of 1 kg/hour to start the polymerization. After 0.5 hour from the start of the polymerization, mXy was added at 35.2 kg/hour from tank 1 for 3.5 hours while the rate of addition of the initiator solution was decreased to 0.25 kg/hour.

It should be noted that the temperature of the solution in the reactor was controlled to 128. + -. 2 ℃ by using jacket-based temperature regulation in the polymerization.

Next, while changing the rate of addition of the initiator solution to 0.75 kg/hr 4 hours after the start of polymerization, a monomer solution containing MMA was added from the tank 2 at a rate of 100.0 kg/hr for 2 hours.

Further, the rate of addition of the initiator solution was decreased to 0.5 kg/hr 6 hours after the start of the polymerization, and the addition was stopped 7 hours after the start of the polymerization. The polymerization was further continued for 1 hour to obtain a polymerization solution containing a methacrylic resin having a ring structure unit in its main chain.

The amount of the N-substituted maleimide contained in the obtained polymerization solution was evaluated, and as a result, it contained 220 mass ppm of phMI and 1070 mass ppm of chMI.

In order to recover the polymer from the polymerization solution, a device used in the devolatilization step was constituted by a plate heat exchanger having a plate slit-type flow path and a heat medium flow path and an internal volume of about 0.3m³The devolatilization apparatus of (1) above, which is composed of a pressure reducing vessel with a SUS heating medium jacket (hereinafter referred to as a devolatilization vessel), is not provided with a rotating part.

The devolatilized polymer was pressurized from the lower part of the devolatilization vessel by a gear pump, extruded from a strand die, water-cooled, and pelletized to obtain a methacrylic resin composition B.

The composition of the methacrylic resin composition B was confirmed, and as a result, the constituent units derived from the monomers MMA, phMI, and chMI were 80.9 mass%, 7.0 mass%, and 12.1 mass%, respectively. Further, the weight average molecular weight Mw was 142,000, Mw/Mn was 2.32, Mz/Mw was 1.75, and the glass transition temperature was 134 ℃.

[ production example 3]

Methacrylic resin composition C was obtained in the same manner as in production example 2, except that mXy solution (APSI 3.4 mass ppm based on the phMI) at 10.8 mass% was used for phMI subjected to the water washing step and the dehydration step, and mXy solution (CCSI 4.6 mass ppm based on the chMI) at 24.0 mass% was used for chMI subjected to the water washing step and the dehydration step, and the composition of the mixed solution prepared in the reactor was adjusted to that of production example 2.

The amount of the N-substituted maleimide contained in the obtained polymerization solution was evaluated, and as a result, it contained 210 mass ppm of phMI and 1090 mass ppm of chMI.

The composition of the methacrylic resin composition C was confirmed, and as a result, the constituent units derived from the monomers MMA, phMI, and chMI were 80.8 mass%, 7.1 mass%, and 12.1 mass%, respectively. The weight-average molecular weight Mw was 141,000, Mw/Mn was 2.31, Mz/Mw was 1.75, and the glass transition temperature was 134 ℃.

[ production example 4]

In a reactor equipped with a jacket-based temperature control device and a stirring blade, 40 parts by mass of MMA, 60 parts by mass of mXy, and 0.08 part by mass of n-octyl mercaptan as a chain transfer agent were charged, and bubbling with nitrogen was performed for 1 hour to remove dissolved oxygen. Thereafter, steam was blown into the jacket to raise the temperature of the solution in the reactor to 120 ℃, and 0.02 part by mass of 1, 1-bis (t-butylperoxy) cyclohexane in 0.10 part by mass of mXy as a polymerization initiator solution was added at a constant rate for 5 hours while stirring at 50rpm, thereby carrying out polymerization, followed by aging at 120 ℃ for 3 hours to complete the polymerization after 8 hours from the start of the polymerization, thereby obtaining a mXy solution of PMMA. After the polymerization was complete, the liquid temperature was lowered to 50 ℃.

Next, a mixed solution composed of 12 parts by mass of monomethylamine and 12 parts by mass of methanol was added dropwise into the reactor at room temperature, and the temperature of the solution was raised to 170 ℃ and stirred under pressure for 1 hour, thereby conducting glutarimide cyclization reaction. The liquid temperature was lowered to 120 ℃, and the inside of the reactor was depressurized to distill off unreacted monomethylamine and methanol and a part of mXy, to obtain mXy solution of glutarimide-cyclized methacrylic acid-based polymer of about 50 mass%.

A solution containing a polymer obtained by polymerization was supplied at a rate of 30 liters/hr to a heat exchanger provided in the upper part of a vacuum vessel, heated to 260 ℃ and then supplied to a devolatilization vessel heated and depressurized to an internal temperature of 260 ℃ and a vacuum degree of 30Torr, to carry out devolatilization treatment. The shear rate in the devolatilizer was calculated from the shape of the apparatus and the operating conditions and found to be 5.3 seconds^-1。

The devolatilized polymer was pressurized from the lower part of the devolatilization vessel by a gear pump, extruded from a strand die, water-cooled, and pelletized to obtain a methacrylic resin composition D.

The composition of the obtained methacrylic resin composition D was confirmed, and as a result, the imidization rate was 3.2% and the amount of the glutarimide structural unit was 5.1% by mass. The weight average molecular weight Mw was 93,000, Mw/Mn was 1.79, Mz/Mw was 1.51, and the glass transition temperature was 122 ℃.

[ production example 5]

A methacrylic resin composition E was obtained in the same manner as in production example 2, except that the amounts of the monomers in the solution prepared in the reactor were changed to 39.3kg of phMI, 46.5kg of chMI, and 354.2kg of MMA.

The composition of the methacrylic resin composition E was confirmed, and as a result, the constitutional units derived from the monomers MMA, phMI, and chMI were 83.2 mass%, 7.6 mass%, and 9.2 mass%, respectively. The weight average molecular weight Mw was 143,000, Mw/Mn was 2.35, Mz/Mw was 1.81, and the glass transition temperature was 132 ℃.

Production comparative example 1

352.4kg of mXy solution (APSI of 0.42 mass ppm based on the phMI) having a phMI of 10.3 mass% and 310.3kg of mXy solution (CCSI of 0.60 mass ppm based on the chMI) having a chMI of 20.3 mass% and having a water washing step and a dehydrating step were measured and added to a 1.25m stirring blade equipped with a temperature control device using a jacket³The reactor was purged with 335.4kg of mXy under reduced pressure while stirring at a solution temperature of 60 ℃ and a reactor pressure of 5 kPa. Next, the autoclave was returned to normal pressure, and 8.9kg of mXy was added to prepare a mixed solution of 36.3kg of phMI, 63.0kg of chMI, and 236.9kg of mXy. 340.7kg of MMA and 0.275kg of n-octylmercaptan as a chain transfer agent were measured out, and charged and stirred to obtain a monomer mixed solution.

Next, 123.1kg of mXy was measured and added to tank 1.

It should be noted that the temperature of the solution in the reactor was controlled to 128. + -. 2 ℃ by using jacket-based temperature regulation during the polymerization.

To this polymerization solution, 0.1 mass% of Irganox 1010(イルガノックス 1010) and 0.05 mass% of Irgafos168(イルガフォス 168) were added under stirring with respect to 100 mass% of the polymer contained in the solution.

Subsequently, the obtained polymerization solution was introduced into a twin-screw extruder equipped with a plurality of vent ports for devolatilization, thereby carrying out devolatilization. The obtained polymerization solution was fed to the twin-screw extruder so that the concentration of the polymerization solution was 10 kg/hr in terms of resin, and the conditions of a cylinder temperature of 260 ℃, a screw rotation speed of 150rpm and a vacuum degree of 10to 40Torr were set. Extruding from strand dieThe resin devolatilized in a twin-screw extruder was water-cooled and pelletized to obtain a methacrylic resin composition F. The shear rate in the devolatilizer was calculated from the shape of the apparatus and the operating conditions and found to be 80 seconds^-1。

The composition of the methacrylic resin composition F was confirmed, and as a result, the constituent units derived from the monomers MMA, phMI, and chMI were 80.9 mass%, 7.0 mass%, and 12.1 mass%, respectively. The weight average molecular weight Mw was 136,000, Mw/Mn was 2.35, Mz/Mw was 1.81, and the glass transition temperature was 134 ℃.

Production comparative example 2

A methacrylic resin composition G was obtained in the same manner as in production example 2, except that a mixed solution of 36.3kg of phMI, 63.0kg of chMI, and 236.9kg of mXy was prepared by using a commercially available product as it was in an unrefined state for phMI and chMI. The shear rate in the devolatilizer was calculated from the shape of the apparatus and the operating conditions and found to be 5.3 seconds^-1。

The amount of the N-substituted maleimide contained in the obtained polymerization solution was evaluated, and as a result, the solution contained 220 ppm by mass of phMI and 1070 ppm by mass of chMI.

The compositions of the obtained granular polymers were confirmed, and as a result, the constitutional units derived from the MMA, phMI, and chMI monomers were 80.9 mass%, 7.1 mass%, and 12.1 mass%, respectively. Further, the weight average molecular weight Mw was 142,000, Mw/Mn was 2.32, Mz/Mw was 1.75, and the glass transition temperature was 134 ℃.

Production comparative example 3

As the phMI and the chMI, commercially available products were used as they were without purification, and 38.6kg of phMI, 65.7kg of chMI, 450.0kg of mXy, 445.7kg of MMA, and 0.413kg of n-octylmercaptan were measured as chain transfer agents, and the measured substances were charged into a 1.25m tank equipped with a temperature control device and a stirring blade, which were covered with a sheath³The reactor was stirred to obtain a monomer mixture solution.

Nitrogen bubbling was performed at a rate of 30L/min for 1 hour for the liquid in the reactor, and dissolved oxygen was removed.

Thereafter, 0.23kg of a polymerization initiator solution prepared by dissolving 0.23kg of 1, 1-di (t-butylperoxy) cyclohexane in 2.77kg of mXy was added at a rate of 0.5 kg/hr while stirring at 50rpm while raising the temperature of the solution in the reactor to 125 ℃ by blowing steam into the jacket, to start the polymerization, and the addition was stopped 6 hours after the start of the polymerization.

The polymerization solution added with this antioxidant was supplied to a concentration device constituted by a tubular heat exchanger and a gasification tank which had been heated to 170 ℃ in advance, the concentration of the polymer contained in the solution was increased to 70 mass%, and then the obtained polymerization solution was supplied to a heat transfer area of 0.2m²The thin film evaporator having a rotating part of (1) for devolatilization.

In this case, the internal temperature of the apparatus was 280 ℃, the supply amount was 30L/hr, the rotation speed was 400rpm, the vacuum degree was 30Torr, the devolatilized polymer was pressurized by a gear pump, extruded from a strand die, water-cooled, and pelletized to obtain a methacrylic resin composition H. The shear velocity in a thin film evaporator having a rotating portion was calculated from the shape of the apparatus and the operating conditions and was 3200s^-1。

The compositions of the obtained granular polymers were confirmed, and as a result, the constitutional units derived from the MMA, phMI, and chMI monomers were 81.0 mass%, 7.2 mass%, and 11.8 mass%, respectively. Further, the weight average molecular weight Mw was 136,000, Mw/Mn was 2.21, Mz/Mw was 1.71, and the glass transition temperature was 134 ℃.

Production comparative example 4

Methacrylic resin composition I was obtained in the same manner as in production example 2, except that the amounts of the monomers in the solution prepared in the reactor were changed to 41.3kg of phMI, 41.3kg of chMI, and 357.5kg of MMA.

The composition of the methacrylic resin composition I was confirmed, and as a result, the constituent units derived from the MMA, phMI, and chMI monomers were 84.1 mass%, 8.0 mass%, and 7.9 mass%, respectively. Further, the weight average molecular weight Mw was 145,000, Mw/Mn was 2.31, Mz/Mw was 1.77, and the glass transition temperature was 130 ℃.

Production comparative example 5

Polymethyl methacrylate was imidized with monomethylamine using a co-rotating twin-screw extruder to obtain a methacrylic resin composition J having glutarimide structural units.

Specifically, a co-rotating twin-screw extruder having a screw diameter of 40mm was used, the extruder cylinder temperature was 270 ℃ and the screw rotation speed was 150rpm, and polymethyl methacrylate having a weight-average molecular weight Mw of 10.8 ten thousand was supplied through a hopper at 20kg/h, and nitrogen was passed through the extruder at a flow rate of 200 mL/min. After the resin was melted and filled in the kneading blocks, 1.8 parts by mass of monomethylamine per 100 parts by mass of the raw material resin was injected from a nozzle to perform imidization. The resin was filled by placing a reverse flight at the end of the reaction zone (just before the vent orifice). The pressure at the vent was reduced to 50Torr to remove by-products after the reaction and excess methylamine. The resin strand discharged from a die provided at the outlet of the extruder was cooled in a water tank, and then pelletized by a pelletizer, thereby obtaining an imide resin.

Then, using a co-rotating twin screw extruder having a screw diameter of 40mm, the obtained imide resin was supplied at 20kg/hr with the barrel temperature of the extruder set to 250 ℃ and the screw rotation speed set to 150rpm, and after the resin was melted and filled by a kneading block, a mixed solution of dimethyl carbonate and triethylamine was injected as an esterifying agent from a nozzle to reduce the carboxylic acid groups in the resin. Dimethyl carbonate was 3.2 parts by mass and triethylamine was 0.8 part by mass per 100 parts by mass of the imide resin. The resin was filled by placing a reverse screw at the end of the reaction zone. The pressure at the vent port was reduced to 50Torr, and by-products after the reaction and excess dimethyl carbonate were removed. The resin strand discharged from a die provided at the outlet of the extruder was cooled in a water tank and then pelletized by a pelletizer, thereby obtaining a methacrylic resin composition J having a glutarimide structure.

The imidization ratio of this resin composition was 3.3%, and the content of glutarimide-based structural units was 5.2% by mass. The shear rate in the twin-screw extruder was calculated to be about 80 seconds according to the shape of the apparatus and the operating conditions^-1。

Further, the weight average molecular weight Mw was 96,000, Mw/Mn was 1.82, Mz/Mw was 1.48, and the glass transition temperature was 122 ℃.

Examples 1 to 5 and comparative examples 1 to 5

Using the methacrylic resin compositions a to J obtained in production examples and production comparative examples, resin lenses were injection-molded by the following methods, and various properties were measured. The results are shown in Table 1.

Molding of resin lens

After the methacrylic resin compositions A to J were dried at 100 ℃ for 4 hours in a forced air circulation dryer, injection molding was carried out using a mold having a spherical plano-convex lens (thickness: 3.2mm, side gate (thickness: 0.95mm, width: 5.0 mm)) of diameter 41mm and R98mm, at a cylinder temperature of 270 ℃, a mold temperature of 116 ℃ and an injection speed of 10mm/s, at a cylinder temperature of 50T, using a mold clamping force of 50T, at a first stage of 50MPa for 4 seconds, and at a second stage of 30MPa for 3 seconds, and at a cooling time of 400 seconds.

Further, annealing was performed in an oven set to a temperature 25 ℃ lower than the glass transition temperature of the methacrylic resin composition for 3 hours.

[ Table 1]

The resin lens for a head-mounted display according to the present invention can obtain a clear image even in an optical system using polarized light, and thus can contribute to downsizing and weight reduction of the head-mounted display.

Claims

1. A resin lens for a head-mounted display, characterized in that,

2. The resin lens for a head-mounted display according to claim 1,

the glass transition temperature Tg is greater than 120 ℃ and below 160 ℃.

3. The resin lens for a head-mounted display according to claim 1 or 2, wherein,

the absolute value of the photoelastic coefficient was 3.0X 10^-12Pa^-1The following.

4. The resin lens for a head-mounted display according to any one of claims 1 to 3,

comprises a methacrylic resin.

5. The resin lens for a head-mounted display according to claim 4,

the methacrylic resin includes a methacrylic resin having a structural unit X having a ring structure in a main chain.

6. The resin lens for a head-mounted display according to claim 5,

the structural unit X includes at least one structural unit selected from the group consisting of a structural unit derived from an N-substituted maleimide monomer, a glutarimide structural unit, and a lactone structural unit.

7. The resin lens for a head-mounted display according to claim 5, wherein,

the above structural unit X comprises a structural unit derived from an N-substituted maleimide monomer.

8. The resin lens for a head-mounted display according to claim 5,

the structural unit X includes a glutarimide-based structural unit.