CN107735435B

CN107735435B - Resin film, laminate, optical member, display member, and front panel

Info

Publication number: CN107735435B
Application number: CN201680034930.6A
Authority: CN
Inventors: 安井未央; 野殿光纪; 樱井孝至
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: mgc; Sumitomo Chemical Co Ltd
Priority date: 2015-07-22
Filing date: 2016-07-21
Publication date: 2021-05-25
Anticipated expiration: 2036-07-21
Also published as: JP7055166B2; KR20180025964A; JP6709220B2; JP2020149064A; CN107735435A; KR102002611B1; KR20190087663A; TW201708318A; JPWO2017014279A1; WO2017014279A1; TWI694096B; TW202031732A; KR102276382B1

Abstract

Disclosed is a resin film (10) containing a polyimide polymer. When the resin film 10 is subjected to a light irradiation test by irradiating a predetermined light from the main surface 10a side, the resin film satisfies the following conditions: (i) the resin film after the light irradiation test has a transmittance of 85% or more for 550nm light; and (ii) the resin film before the light irradiation test has a yellowness index of 5 or less, and the difference between the yellowness indexes of the resin film before and after the light irradiation test is less than 2.5.

Description

Resin film, laminate, optical member, display member, and front panel

Technical Field

The invention relates to a resin film, a laminate, an optical member, a display member, and a front panel.

Background

Glass has been used as a base material for display members of various display devices such as solar cells and displays, a base material for optical members, and a material for front panels. However, glass has the disadvantage of being prone to breakage and heavy. In recent years, glass substrates and glass front panels have not been provided with sufficient material properties for thinning, weight reduction, and flexibility of displays. Therefore, studies have been made on acrylic resins and laminates for imparting scratch resistance to resins as materials or substrates to replace glass. Composite materials of an organic material and an inorganic material, such as a mixed film containing polyimide and silica, have also been studied (see, for example, patent documents 1 and 2).

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2008-163309

Patent document 2: specification of U.S. Pat. No. 8207256

Disclosure of Invention

Problems to be solved by the invention

The present inventors have found that a resin film containing a polyimide-based polymer has high transparency and can realize excellent bendability. However, a resin film containing a polyimide-based polymer may change in contrast and hue when bent, and further improvement is required in this respect. Resin films suitable for use as substrates for display members of flexible devices, substrates for optical members, and/or front panels are required to have good visibility when bent.

Therefore, the main objects of the present invention are: a resin film containing a polyimide polymer and having high transparency is improved in visibility at the time of bending.

Means for solving the problems

The resin film according to one embodiment of the present invention contains a polyimide polymer. When the resin film was subjected to a light irradiation test by irradiating the resin film with light of 313nm for 24 hours from one main surface side of the resin film by a light source having an output of 40W provided at a distance of 5cm from the resin film, the resin film satisfied the following conditions:

(i) the resin film after the light irradiation test has a transmittance of 85% or more for 550nm light; and the number of the first and second groups,

(ii) the resin film before the light irradiation test has a yellowness index of 5 or less, and the difference between the yellowness index of the resin film before and after the light irradiation test is less than 2.5.

The resin film satisfying the above conditions (i) and (ii) is less likely to change in contrast or hue when bent, and can maintain good visibility.

The present invention provides a laminate comprising the resin film and a functional layer provided on at least one surface side of the resin film. The functional layer may be a layer having at least 1 function selected from the group consisting of ultraviolet absorption, adhesion, and a function of exhibiting high hardness on the surface.

The laminate may further have a primer coating layer disposed between the resin film and the functional layer.

The substrate and the front panel of the optical member or the display member according to one aspect of the present invention have the resin film or the laminate. When applied to a flexible device, the material is useful for excellent visibility during bending.

Effects of the invention

The present invention can improve visibility at bending of a transparent resin film containing a polyimide-based polymer.

Drawings

FIG. 1 is a cross-sectional view showing one embodiment of a resin film.

FIG. 2 is a sectional view showing an embodiment of a laminate.

FIG. 3 is a sectional view showing an embodiment of a laminate.

FIG. 4 is a schematic cross-sectional view showing an embodiment of a display device.

Detailed Description

Hereinafter, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments. In the drawings, the same or corresponding elements are denoted by the same reference numerals, and redundant description thereof may be omitted.

[ resin film ]

Fig. 1 is a sectional view showing an embodiment of a resin film. The resin film 10 shown in fig. 1 contains a polyimide-based polymer and has a pair of

main surfaces

10a and 10b facing each other.

When a light irradiation test is performed by irradiating the resin film 10 with light of 313nm for 24 hours from the main surface 10a side by a light source having an output of 40W provided at a distance of 5cm from the resin film 10, the resin film 10 satisfies the following conditions:

(ii) the resin film before the light irradiation test has a yellowness index (YI value) of 5 or less, and the difference in yellowness index between the resin film before and after the light irradiation test is less than 2.5.

The resin film satisfying the conditions (i) and (ii) can be easily obtained by using a polyimide-based polymer having high transparency and by incorporating an ultraviolet absorber in the resin film, for example. Specific examples of the polyimide-based polymer having high transparency and the ultraviolet absorber are described below.

The transmittance of the resin film 10 after the light irradiation test to 550nm light is preferably 90% or more, and usually 100% or less, and may be 95% or less. The haze of the resin film 10 after the light irradiation test is preferably 0.9 or less, and may be 0.1 or more. The resin film 10 before the light irradiation test can have a transmittance of 85% or more with respect to 550nm light. The transmittance of the resin film to light of a predetermined wavelength is: a ratio of the intensity of the light of the predetermined wavelength transmitted through the resin film to the intensity of the light of the predetermined wavelength incident on the resin film. Haze may be measured according to JIS K7105: 1981. The details of the method for measuring the transmittance and the haze are described in the following examples.

The yellowness index of the resin film 10 before the light irradiation test is preferably 4 or less, more preferably 3 or less, and may be 0.5 or more. The yellowness index before the light irradiation test was YI₀The yellow index after light irradiation is YI₁In this case, the difference Δ YI between the yellowness indices of the resin film before and after the light irradiation test can be represented by the formula "Δ YI ═ YI₁－YI₀And calculating. Δ YI is preferably 2.3 or less, more preferably 2.0 or less, and may be 0.1 or more. The details of the method for measuring the yellowness index are described in the following examples.

The resin film 10 contains a polyimide-based polymer. In the present specification, the polyimide-based polymer means: a polymer having at least 1 or more repeating structural unit represented by formula (PI), formula (a') or formula (b). When the repeating structural unit represented by the formula (PI) is a main structural unit of the polyimide-based polymer, it is preferable from the viewpoint of strength and transparency of the film. The repeating structural unit represented by the formula (PI) is preferably 40 mol% or more, more preferably 50 mol% or more, even more preferably 70 mol% or more, particularly preferably 90 mol% or more, and even more preferably 98 mol% or more of the total repeating structural units of the polyimide-based polymer.

[ chemical formula 1]

In the formula (PI), G represents a 4-valent organic group, and A represents a 2-valent organic group. G in the formula (a)²Represents a 3-valent organic group, A²Represents a 2-valent organic group. G in the formula (a')³Represents a 4-valent organic group, A³Represents a 2-valent organic group. G in the formula (b)⁴And A⁴Each represents a 2-valent organic group.

In the formula (PI), examples of the organic group of the 4-valent organic group represented by G (hereinafter, sometimes referred to as an organic group of G) include groups selected from acyclic aliphatic groups, cyclic aliphatic groups, and aromatic groups. From the viewpoint of transparency and bendability of the resin film 10, the organic group of G is preferably a 4-valent cyclic aliphatic group or a 4-valent aromatic group. Examples of the aromatic group include monocyclic aromatic groups, condensed polycyclic aromatic groups, and non-condensed polycyclic aromatic groups having 2 or more aromatic rings and connected to each other directly or through a linking group. From the viewpoint of transparency and suppression of coloring of the resin film, the organic group of G is preferably a cyclic aliphatic group, a cyclic aliphatic group having a fluorine-based substituent, a monocyclic aromatic group having a fluorine-based substituent, a condensed polycyclic aromatic group having a fluorine-based substituent, or a non-condensed polycyclic aromatic group having a fluorine-based substituent. In the present specification, the fluorine-based substituent means a group containing a fluorine atom. The fluorine-based substituent is preferably a fluorine group (fluorine atom, -F) and a perfluoroalkyl group, and more preferably a fluorine group and a trifluoromethyl group.

More specifically, the organic group of G may be selected from, for example, the following groups: a saturated or unsaturated cycloalkyl group, a saturated or unsaturated heterocycloalkyl group, an aryl group, a heteroaryl group, an arylalkyl group, an alkylaryl group, a heteroarylalkyl group, and a group having any 2 groups (which may be the same) therein and being linked to each other directly or through a linking group. Examples of the linking group include-O-, an alkylene group having 1 to 10 carbon atoms, and-SO₂-, -CO-or-CO-NR- (R represents an alkyl group having 1 to 3 carbon atoms such as a methyl group, an ethyl group or a propyl group, or a hydrogen atom).

The number of carbon atoms of the 4-valent organic group represented by G is usually 2 to 32, preferably 4 to 15, more preferably 5 to 10, and further preferably 6 to 8. When the organic group of G is a cyclic aliphatic group or an aromatic group, at least 1 of carbon atoms constituting these groups may be replaced with a hetero atom. Examples of the heteroatom include O, N and S.

Specific examples of G include groups represented by the following formula (20), formula (21), formula (22), formula (23), formula (24), formula (25) or formula (26). Wherein represents a bonding site. Z in formula (26) represents a single bond, -O-, -CH₂－、－C(CH₃)₂－、－Ar－O－Ar－、－Ar－CH₂－Ar－、－Ar－C(CH₃)₂-Ar-or-Ar-SO₂-Ar-. Ar represents an aryl group having 6 to 20 carbon atoms, and may be a phenylene group, for example. At least 1 of the hydrogen atoms of these groups may be substituted with a fluorine-based substituent.

[ chemical formula 2]

In the formula (PI), examples of the organic group of the 2-valent organic group represented by a (hereinafter, sometimes referred to as an organic group of a) include groups selected from acyclic aliphatic groups, cyclic aliphatic groups, and aromatic groups. The 2-valent organic group represented by a is preferably selected from a 2-valent cyclic aliphatic group and a 2-valent aromatic group. Examples of the aromatic group include monocyclic aromatic groups, condensed polycyclic aromatic groups, and non-condensed polycyclic aromatic groups having 2 or more aromatic rings and connected to each other directly or through a linking group. From the viewpoint of transparency and suppression of coloring of the resin film, it is preferable to introduce a fluorine-based substituent into the organic group of a.

More specifically, the organic group of a may be selected from, for example, the following groups: a saturated or unsaturated cycloalkyl group, a saturated or unsaturated heterocycloalkyl group, an aryl group, a heteroaryl group, an arylalkyl group, an alkylaryl group, a heteroarylalkyl group, and a group having any 2 groups (which may be the same) therein and being linked to each other directly or through a linking group. The heteroatom includes O, N or S, and the linking group includes-O-, an alkylene group having 1 to 10 carbon atoms, and-SO₂-, -CO-or-CO-NR- (R includes an alkyl group having 1 to 3 carbon atoms such as a methyl group, an ethyl group, a propyl group, etc., or a hydrogen atom).

The number of carbon atoms of the 2-valent organic group represented by A is usually 2 to 40, preferably 5 to 32, more preferably 12 to 28, and further preferably 24 to 27.

Specific examples of A include groups represented by the following formula (30), formula (31), formula (32), formula (33) or formula (34). Wherein represents a bonding site. Z¹～Z³Each independently represents a single bond, -O-, -CH₂－、－C(CH₃)₂－、－SO₂-, -CO-or-CO-NR- (R represents an alkyl group having 1 to 3 carbon atoms such as a methyl group, an ethyl group or a propyl group, or a hydrogen atom). In the following radicals, for Z¹And Z²And, Z²And Z³Preferably, the ring is in the meta or para position with respect to each ring. For Z¹Single bond to terminal, Z²A single bond to the terminal, and Z³The single bond to the terminal is preferably in the meta or para position, respectively. In 1 instance of A, Z¹And Z³is-O-, and Z²is-CH₂－、－C(CH₃)₂-or-SO₂-. 1 or 2 or more of the hydrogen atoms of these groups may be substituted with a fluorine-based substituent.

[ chemical formula 3]

At least 1 hydrogen atom of the hydrogen atoms constituting at least one of A and G may be substituted with at least 1 functional group selected from a fluorine-based substituent, a hydroxyl group, a sulfonic acid group, an alkyl group having 1 to 10 carbon atoms, and the like. When the organic group of a and the organic group of G are each a cyclic aliphatic group or an aromatic group, at least one of a and G preferably has a fluorine-based substituent, and more preferably both a and G have a fluorine-based substituent.

G in the formula (a)²Is a 3-valent organic group. The organic group may be selected from the same groups as those of G in formula (PI), except that it is a 3-valent group. As G²Examples of (3) include: specific examples of G include groups in which 1 arbitrary of 4 bonding sites of the groups represented by the formulae (20) to (26) is substituted with a hydrogen atom. A in the formula (a)²May be selected from the same groups as A in formula (PI).

G in the formula (a')³May be selected from the same groups as the organic group of G in formula (PI). A in the formula (a')³May be selected from the same groups as A in formula (PI).

G in the formula (b)⁴Is a 2-valent organic group. The organic group may be selected from the same groups as those of G in formula (PI), except that it is a 2-valent group. As G⁴Examples of (3) include: specific examples of G include groups in which 2 of the 4 bonding sites of the groups represented by the formulae (20) to (26) are substituted with hydrogen atoms. A in the formula (b)⁴May be selected from the same groups as A in formula (PI).

The polyimide-based polymer contained in the resin film 10 may be a condensation-type polymer obtained by polycondensing at least 1 of diamines and tetracarboxylic acid compounds (including tetracarboxylic acid compound analogs such as acid chloride compounds and tetracarboxylic acid dianhydrides) or tricarboxylic acid compounds (including tricarboxylic acid compound analogs such as acid chloride compounds and tricarboxylic acid anhydrides). Further, dicarboxylic acid compounds (including acid chloride compounds and the like) may be polycondensed. The repeating structural unit represented by the formula (PI) or the formula (a') can be generally derived from diamines and tetracarboxylic acid compounds. The repeating structural unit represented by the formula (a) can be generally derived from diamine and tricarboxylic acid compounds. The repeating structural unit represented by the formula (b) can be generally derived from diamines and dicarboxylic acid compounds.

Examples of the tetracarboxylic acid compound include aromatic tetracarboxylic acid compounds, alicyclic tetracarboxylic acid compounds, and acyclic aliphatic tetracarboxylic acid compounds. These tetracarboxylic acid compounds may be used in combination of 2 or more. The tetracarboxylic acid compound is preferably a tetracarboxylic acid dianhydride, and examples of the tetracarboxylic acid dianhydride include an aromatic tetracarboxylic acid dianhydride, an alicyclic tetracarboxylic acid dianhydride, and an acyclic aliphatic tetracarboxylic acid dianhydride.

The tetracarboxylic acid compound is preferably selected from alicyclic tetracarboxylic acid compounds and aromatic tetracarboxylic acid compounds from the viewpoint of solubility of the polyimide-based polymer in a solvent, and transparency and bendability when the resin film 10 is formed. The tetracarboxylic acid compound is preferably selected from alicyclic tetracarboxylic acid compounds having a fluorine-based substituent and aromatic tetracarboxylic acid compounds having a fluorine-based substituent, and more preferably alicyclic tetracarboxylic acid compounds having a fluorine-based substituent, from the viewpoint of suppressing the transparency and coloration of the resin film.

Examples of the tricarboxylic acid compound include an aromatic tricarboxylic acid, an alicyclic tricarboxylic acid, an acyclic aliphatic tricarboxylic acid, and a chloride compound or an acid anhydride similar thereto. The tricarboxylic acid compound is preferably selected from aromatic tricarboxylic acids, alicyclic tricarboxylic acids, acyclic aliphatic tricarboxylic acids, and their analogous acid chloride compounds. The tricarboxylic acid compound may be used in combination of 2 or more.

The tricarboxylic acid compound is preferably selected from alicyclic tricarboxylic acid compounds and aromatic tricarboxylic acid compounds, from the viewpoint of solubility of the polyimide-based polymer in a solvent, and transparency and bendability in forming the resin film 10. From the viewpoint of transparency and suppression of coloring of the resin film, the tricarboxylic acid compound is preferably selected from an alicyclic tricarboxylic acid compound having a fluorine-based substituent and an aromatic tricarboxylic acid compound having a fluorine-based substituent.

Examples of the dicarboxylic acid compound include aromatic dicarboxylic acids, alicyclic dicarboxylic acids, acyclic aliphatic dicarboxylic acids, and their analogous acid chloride compounds and acid anhydrides. The dicarboxylic acid compound is preferably selected from aromatic dicarboxylic acids, alicyclic dicarboxylic acids, acyclic aliphatic dicarboxylic acids, and their analogous acid chloride compounds. The dicarboxylic acid compound may be used in combination of 2 or more.

The dicarboxylic acid compound is preferably selected from alicyclic dicarboxylic acid compounds and aromatic dicarboxylic acid compounds from the viewpoint of solubility of the polyimide-based polymer in a solvent, and transparency and flexibility in forming the resin film 10. From the viewpoint of transparency and suppression of coloring of the resin film, the dicarboxylic acid compound is preferably selected from an alicyclic dicarboxylic acid compound having a fluorine-based substituent and an aromatic dicarboxylic acid compound having a fluorine-based substituent.

Examples of the diamine include aromatic diamines, alicyclic diamines, and aliphatic diamines. The diamine may be used in combination of 2 or more. The diamine is preferably selected from alicyclic diamines and aromatic diamines having a fluorine-based substituent, from the viewpoint of solubility of the polyimide-based polymer in a solvent and transparency and flexibility in forming the resin film 10.

When the polyimide-based polymer is used, a resin film having particularly excellent bendability, high light transmittance (for example, 85% or more, preferably 88% or more with respect to light of 550 nm), low yellow index (YI value, for example, 5 or less, preferably 3 or less), and low haze (for example, 1.5% or less, preferably 1.0% or less) can be easily obtained.

The polyimide-based polymer may be a copolymer containing a plurality of different types of the above-described repeating structural units. The weight average molecular weight of the polyimide polymer is usually 10,000 to 500,000. The weight average molecular weight of the polyimide polymer is preferably 50,000 to 500,000, more preferably 70,000 to 400,000. The weight average molecular weight is a molecular weight in terms of standard polystyrene measured by Gel Permeation Chromatography (GPC). When the weight average molecular weight of the polyimide polymer is large, high bendability tends to be easily obtained, but when the weight average molecular weight of the polyimide polymer is too large, viscosity of varnish tends to be high, and processability tends to be low.

The polyimide-based polymer may contain a halogen atom such as a fluorine atom which can be introduced by the fluorine-based substituent or the like. The polyimide-based polymer contains a halogen atom, and thus can improve the elastic modulus of the resin film and reduce the yellow index. This can suppress scratches, wrinkles, and the like generated in the resin film, and can improve the transparency of the resin film. The halogen atom is preferably a fluorine atom. The content of the halogen atom in the polyimide-based polymer is preferably 1 to 40% by mass, more preferably 1 to 30% by mass, based on the mass of the polyimide-based polymer.

The resin film 10 may contain 1 or 2 or more kinds of ultraviolet absorbers. The ultraviolet absorber may be appropriately selected from those generally used as ultraviolet absorbers in the field of resin materials. The ultraviolet absorber may contain a compound that absorbs light having a wavelength of 400nm or less. Examples of the ultraviolet absorber that can be appropriately combined with the polyimide-based polymer include at least 1 compound selected from benzophenone-based compounds, salicylate-based compounds, benzotriazole-based compounds, and triazine-based compounds.

In the present specification, the term "related compound" refers to a derivative of a compound to which the "related compound" is attached. For example, the "benzophenone-based compound" refers to a compound having benzophenone as a matrix skeleton and a substituent bonded to benzophenone.

The amount of the ultraviolet absorber to be blended may be such that the resin film 10 satisfies the above conditions (i) and (ii). Specifically, the amount of the ultraviolet absorber is usually 1% by mass or more, preferably 2% by mass or more, preferably 3% by mass or more, usually 10% by mass or less, preferably 8% by mass or less, preferably 6% by mass or less, based on the entire mass of the resin film.

The resin film 10 may further contain an inorganic material such as inorganic particles. The inorganic material is preferably a silicon material containing silicon atoms. The resin film 10 can obtain a particularly excellent effect in terms of bendability by containing an inorganic material such as a silicon material.

Examples of the silicon material containing a silicon atom include silicon dioxide particles, quaternary alkoxysilane such as Tetraethylorthosilicate (TEOS), and a silicon compound such as a silsesquioxane derivative. Among these silicon materials, silica particles are preferable from the viewpoint of transparency and flexibility of the resin film 10.

The average primary particle diameter of the silica particles is usually 100nm or less. When the average primary particle diameter of the silica particles is 100nm or less, the transparency tends to be improved.

The average primary particle diameter of the silica particles in the resin film can be determined by observation with a Transmission Electron Microscope (TEM). The primary particle diameter of the silica particles may be set to a unidirectional particle diameter measured by a Transmission Electron Microscope (TEM). The primary particle size at 10 points was measured by TEM observation, and the average value of these was determined as the average primary particle size. The particle distribution of the silica particles before forming the resin film can be determined by a commercially available laser diffraction particle size distribution meter.

In the resin film 10, the mixing ratio of the polyimide-based polymer and the inorganic material is preferably 1: 9-10: 0, more preferably 3: 7-10: 0, more preferably 3: 7-8: 2, more preferably 3: 7-7: 3. the proportion of the inorganic material is usually 20 mass% or more, preferably 30 mass% or more, usually 90 mass% or less, preferably 70 mass% or less, based on the total mass of the polyimide-based polymer and the inorganic material. When the mixing ratio of the polyimide-based polymer and the inorganic material is within the above range, the transparency and mechanical strength of the resin film tend to be improved.

The resin film 10 may further contain other components within a range in which transparency and bendability are not significantly impaired. Examples of the other components include colorants such as antioxidants, mold release agents, stabilizers, bluing agents, flame retardants, lubricants, and leveling agents. The proportion of the components other than the polyimide-based polymer and the inorganic material is preferably more than 0% and 20% by mass or less, and more preferably more than 0% and 10% by mass or less, relative to the mass of the resin film 10.

When the resin film 10 contains a polyimide-based polymer and a silicon material, the atomic ratio of silicon atoms to nitrogen atoms, i.e., Si/N, in at least one main surface 10a is preferably 8 or more. The atomic ratio Si/N is a value calculated based on the amount of silicon atoms and the amount of nitrogen atoms obtained by evaluating the composition of the main surface 10a with an X-ray photoelectron spectroscopy (XPS).

When the Si/N ratio in the main surface 10a of the resin film 10 is 8 or more, sufficient adhesion to the functional layer 20 described below can be obtained. From the viewpoint of adhesion, Si/N is more preferably 9 or more, still more preferably 10 or more, preferably 50 or less, and more preferably 40 or less.

The thickness of the resin film 10 can be appropriately adjusted depending on the flexible device to which the laminate 30 is applied, and is preferably 10 to 500 μm, more preferably 15 to 200 μm, and still more preferably 20 to 100 μm. The resin film 10 having the above-described configuration has particularly excellent bendability.

Next, an example of a method for producing the resin film 10 of the present embodiment will be described. The polyimide-based polymer varnish used for the production of the resin film can be produced by dissolving a solvent-soluble polyimide-based polymer polymerized by a known method for synthesizing a polyimide-based polymer in a solvent. The solvent may be any solvent that dissolves the polyimide-based polymer, and examples thereof include Dimethylacetamide (DMAC), Dimethylformamide (DMF), dimethyl sulfoxide (DMSO), γ -butyrolactone (GBL), and a mixed solvent thereof.

In the preparation of an inorganic material-containing resin film, an inorganic material is added to a polyimide-based polymer varnish, and the mixture is stirred and mixed by a known stirring method to uniformly disperse the inorganic material, thereby preparing a dispersion. When an ultraviolet absorber is blended, an ultraviolet absorber may be added to the dispersion.

The polyimide-based polymer varnish or dispersion may further contain an additive. Examples of the additives include colorants such as antioxidants, mold release agents, stabilizers, bluing agents, flame retardants, lubricants, tackifiers, and leveling agents. The polyimide-based polymer varnish or dispersion may contain a compound such as alkoxysilane having 1 or 2 or more metal alkoxy groups, which contributes to the bonding of the inorganic particles to each other. Examples of the above compound include alkoxysilanes having an amino group. By using the polyimide-based polymer varnish or dispersion containing the compound, the blending ratio of the inorganic particles can be increased while maintaining the optical properties such as transparency of the resin film.

The polyimide-based polymer varnish or dispersion may further contain water. The water content is usually 0.1 to 10% by mass based on the mass of the polyimide-based polymer varnish or dispersion.

The resin film can be produced by an appropriate known method. Examples of the production method include the following methods. The polyimide-based polymer varnish or dispersion is applied to a substrate by a known roll-to-roll (batch) or batch process to form a coating film. The coating film is dried to form a film. Then, the film is peeled off from the substrate, whereby the resin film 10 can be obtained. Examples of the substrate include a polyethylene terephthalate (PET) substrate, a stainless steel (SUS) tape, and a glass substrate.

The coating film may be heated in order to dry and/or bake the coating film. The heating temperature of the coating film is usually 50 to 350 ℃. The heating of the coating film may be performed in an inert atmosphere or under reduced pressure. The solvent can be removed by evaporating the coating film by heating. The resin film can be formed by a method comprising a step of drying the coating film at 50 to 150 ℃ and a step of drying the dried coating film at 180 to 350 ℃.

Next, a surface treatment may be performed on at least one main surface of the resin film. The surface treatment is preferably a UV ozone treatment. By the UV ozone treatment, Si/N can be easily adjusted to 8 or more. However, the method of making Si/N8 or more is not limited to the UV ozone treatment. The main surface 10a and/or 10b of the resin film 10 may be subjected to a surface treatment such as a plasma treatment or a corona discharge treatment in order to improve adhesion to a functional layer described below.

For the UV ozone treatment, a known ultraviolet light source containing a wavelength of 200nm or less can be used. Examples of the ultraviolet light source include a low-pressure mercury lamp. As the ultraviolet light source, various commercially available devices having an ultraviolet light source can be used. An example of a commercially available apparatus is an Ultraviolet (UV) ozone cleaning apparatus UV-208 manufactured by TECHNOLOGIEVISION.

The resin film 10 of the present embodiment obtained as described above is excellent in bendability. In addition, when the atomic ratio of silicon atoms to nitrogen atoms, Si/N, is 8 or more in at least one main surface 10a, excellent adhesion to the functional layer 20 described below can be obtained.

[ laminate ]

Fig. 2 is a sectional view showing an embodiment of the laminate. The laminate 30 shown in fig. 2 is a laminate having a resin film 10 and a functional layer 20 laminated on one main surface 10a of the resin film 10.

The functional layer 20 may be a layer for imparting further functions (performances) to the laminated body 30 when the laminated body 30 is used as a substrate of an optical member or a display member of a flexible device or a front panel. In the present specification, the optical member refers to a sensor portion such as a touch sensor or a signal emitting portion in a display device, and the display member refers to an image display portion such as an organic EL device or a liquid crystal display device in the display device.

The functional layer 20 is preferably a layer having at least 1 function selected from the group consisting of ultraviolet absorption, a function of imparting high hardness to the surface, adhesion, hue adjustment, and refractive index adjustment.

The layer having an ultraviolet absorbing function (ultraviolet absorbing layer) as the functional layer 20 can be composed of a main material selected from an ultraviolet curable transparent resin, an electron beam curable transparent resin, and a thermosetting transparent resin, and an ultraviolet absorber dispersed in the main material, for example. By providing the ultraviolet absorbing layer as the functional layer 20, a change in yellow index caused by light irradiation can be easily suppressed.

The ultraviolet-curable, electron beam-curable, or heat-curable transparent resin as a main material of the ultraviolet absorbing layer is not particularly limited, and may be, for example, poly (meth) acrylate. The ultraviolet absorber may be selected from the same compounds as those listed as the ultraviolet absorber that can be contained in the resin film 10.

The ultraviolet absorbing layer may be a layer that absorbs 95% or more of light having a wavelength of 400nm or less (for example, light having a wavelength of 313 nm). In other words, the ultraviolet absorbing layer may have a transmittance of light having a wavelength of 400nm or less (for example, light having a wavelength of 313 nm) of less than 5%. The ultraviolet absorbing layer may contain an ultraviolet absorber at a concentration that can provide the above transmittance. From the viewpoint of suppressing an increase in the yellow index of the laminate caused by light irradiation, the content of the ultraviolet absorber in the ultraviolet absorbing layer (functional layer 20) is usually 1 mass% or more, preferably 3 mass% or more, usually 10 mass% or less, and preferably 8 mass% or less, based on the mass of the ultraviolet absorbing layer.

The layer (hard coat layer) having a function of imparting a high hardness to the surface of the functional layer 20 is, for example, a layer in which a surface having a higher pencil hardness than the pencil hardness of the surface of the resin film is provided to the laminate. The hard coat layer is not particularly limited, and includes an ultraviolet-curable, electron beam-curable, or heat-curable resin represented by poly (meth) acrylates. The hard coat layer may contain a photopolymerization initiator and an organic solvent. The poly (meth) acrylate is, for example, a poly (meth) acrylate formed from 1 or more (meth) acrylates selected from urethane (meth) acrylate, epoxy (meth) acrylate, and other polyfunctional poly (meth) acrylates. The hard coat layer may contain an inorganic oxide such as silica, alumina, or polyorganosiloxane in addition to the above components.

The layer (adhesive layer) having an adhesive function as the functional layer 20 has a function of bonding the laminate 30 to another member. Examples of the material for forming the adhesive layer include a thermosetting resin composition and a photocurable resin composition.

The adhesive layer may be composed of a resin composition containing a component having a polymerizable functional group. In this case, after the laminate 30 is brought into close contact with other members, the resin composition constituting the adhesive layer is further polymerized, whereby strong adhesion can be achieved. The adhesive strength between the resin film 10 and the adhesive layer is preferably 0.1N/cm or more, and more preferably 0.5N/cm or more.

The adhesive layer may contain a thermosetting resin composition or a photocurable resin composition as a material. In this case, the resin composition can be cured by polymerizing the polymer by supplying energy afterwards.

The Pressure-Sensitive Adhesive layer may be a layer called a Pressure-Sensitive Adhesive (PSA) that adheres to an object by pressing. The pressure-sensitive adhesive may be an adhesive of "a substance having adhesiveness at normal temperature and adhering to an adherend under slight pressure" (JIS K6800), or may be a capsule adhesive of "an adhesive in which a specific component is placed in a protective film (microcapsule) and which can maintain stability until the film is broken by an appropriate means (pressure, heat, etc.)" (JIS K6800).

The layer having a color adjusting function (color adjusting layer) as the functional layer 20 is a layer capable of adjusting the laminate 30 to a target color. The hue adjustment layer may be a layer containing a resin and a colorant, for example. Examples of the colorant include: inorganic pigments such as titanium oxide, zinc oxide, red iron oxide, titanium oxide-based calcined pigments, ultramarine, cobalt aluminate, and carbon black; organic pigments such as azo-based compounds, quinacridone-based compounds, anthraquinone-based compounds, perylene-based compounds, isoindolinone-based compounds, phthalocyanine-based compounds, quinophthalone-based compounds, threne-based compounds, and diketopyrrolopyrrole-based compounds; bulk pigments such as barium sulfate and calcium carbonate; basic dyes, acid dyes, mordant dyes and the like.

The layer having a refractive index adjusting function (refractive index adjusting layer) as the functional layer 20 is a layer having a refractive index different from that of the resin film 10 and capable of giving a predetermined refractive index to the laminated body. The refractive index adjusting layer may be, for example, a resin layer containing an appropriately selected resin and a pigment if necessary, or may be a metal thin film.

Examples of the pigment for adjusting the refractive index include silicon oxide, aluminum oxide, antimony oxide, tin oxide, titanium oxide, zirconium oxide, and tantalum oxide. The average particle diameter of the pigment is preferably 0.1 μm or less. By setting the average particle diameter of the pigment to 0.1 μm or less, diffuse reflection of light transmitted through the refractive index adjustment layer can be prevented, and deterioration in transparency can be prevented.

Examples of the metal usable for the refractive index adjustment layer include metal oxides and metal nitrides such as titanium oxide, tantalum oxide, zirconium oxide, zinc oxide, tin oxide, silicon oxide, indium oxide, titanium oxynitride, titanium nitride, silicon oxynitride, and silicon nitride.

The functional layer 20 has the above-described functions as appropriate depending on the use of the laminate 30. The functional layer 20 may be a single layer or a plurality of layers. Each layer may have 1 function or more than 2 functions.

The functional layer 20 preferably has a function of imparting high hardness to the surface and a function of absorbing ultraviolet rays. In this case, the functional layer 20 preferably includes "a single layer having a function of imparting high hardness to the surface and a function of absorbing ultraviolet rays", "a multilayer including a layer having a function of imparting high hardness to the surface and a layer having ultraviolet rays absorption", or "a multilayer including a single layer having a function of imparting high hardness to the surface and a layer having ultraviolet rays absorption".

The thickness of the functional layer 20 can be appropriately adjusted according to the flexible device to which the laminate 30 is applied, and is preferably 1 to 100 μm, and more preferably 2 to 80 μm. Typically, the functional layer 20 is thinner than the resin film 10.

The laminate 30 can be obtained by forming the functional layer 20 on the main surface 10a of the resin film 10. The functional layer 20 may be formed by a known roll-to-roll method or a batch method.

The ultraviolet absorbing layer as the functional layer 20 may be formed, for example, as follows: a dispersion liquid (the dispersion liquid contains an ultraviolet absorber and a main material such as a resin capable of dispersing the ultraviolet absorber) is applied to the main surface 10a of the resin film 10 to form a coating film, and the coating film is dried and cured.

The hard coat layer as the functional layer 20 may be formed, for example, as follows: a solution containing a resin for forming a hard coat layer is applied to the main surface 10a of the resin film 10 to form a coating film, and the coating film is dried and cured.

The adhesive layer serving as the functional layer 20 may be formed, for example, as follows: a solution containing a binder for forming an adhesive layer is applied to the main surface 10a of the resin film 10 to form a coating film, and the coating film is dried and cured.

The color adjusting layer as the functional layer 20 may be formed, for example, as follows: a dispersion liquid (the dispersion liquid contains a pigment or the like forming the color adjusting layer and a main material such as a resin capable of dispersing the pigment or the like) is applied to the main surface 10a of the resin film 10 to form a coating film, and the coating film is dried and cured.

The refractive index adjustment layer as the functional layer 20 may be formed, for example, as follows: a dispersion liquid (the dispersion liquid contains inorganic particles or the like forming the refractive index adjustment layer and a main material such as a resin capable of dispersing the inorganic particles or the like) is applied to the main surface 10a of the resin film 10 to form a coating film, and the coating film is dried and cured.

The single layer having a function of imparting high hardness to the surface and a function of absorbing ultraviolet rays as the functional layer 20 may be formed as follows: a dispersion (the dispersion contains a main material such as an ultraviolet absorber and a resin capable of dispersing the ultraviolet absorber, and a resin for forming a hard coat layer) is applied to the main surface 10a of the resin film 10 to form a coating film, and the coating film is dried and cured. The resin used as the main material and the resin forming the hard coat layer may be the same.

The multilayer functional layer including a layer having a function of imparting high hardness to the surface and a layer having ultraviolet absorption can be formed by the following method.

A dispersion liquid (containing an ultraviolet absorber and a main material such as a resin capable of dispersing the ultraviolet absorber) is applied to the main surface 10a of the resin film 10 to form a coating film, and the coating film is dried and cured to form an ultraviolet absorbing layer. Next, a solution containing a resin for forming a hard coat layer is applied to the ultraviolet absorbing layer to form a coating film, and the coating film is dried and cured to form a hard coat layer. By this method, a multilayer functional layer including a layer having a function of rendering the surface high in hardness and a layer having ultraviolet absorption can be formed.

The multilayer including a single layer having a function of imparting high hardness and an ultraviolet absorbing function to the surface and a layer having a function of imparting high hardness to the surface can be formed by the following method.

A hard coat layer can be formed by applying a dispersion (containing an ultraviolet absorber, a main material such as a resin capable of dispersing the ultraviolet absorber, and a resin for forming a hard coat layer) to the main surface 10a of the resin film 10 to form a coating film, drying and curing the coating film to form a single layer having a function of imparting high hardness to the surface and an ultraviolet absorbing function, applying a solution containing a resin for forming a hard coat layer to the single layer to form a coating film, and drying and curing the coating film. By this method, a multilayer functional layer including a layer having a function of imparting high hardness to the surface and a function of absorbing ultraviolet rays and a layer having a function of imparting high hardness to the surface can be formed.

The laminate 30 of the present embodiment obtained as described above is excellent in bendability. The laminate 30 can have functions such as transparency and ultraviolet resistance required for an optical member or a base material of a display member or a front panel of a flexible device, and a function of imparting high hardness to the surface. In the laminate 30, when the Si/N ratio of the main surface 10a of the resin film 10 is 8 or more, the adhesion between the resin film 10 and the functional layer 20 is also excellent.

Fig. 3 is a sectional view showing an embodiment of the laminate. The laminate 30 shown in fig. 3 includes a primer coat layer 25 provided between the resin film 10 and the functional layer 20, in addition to the resin film 10 and the functional layer 20 similar to those of the laminate of fig. 2. The primer coat layer 25 is laminated on one main surface 10a of the resin film 10. The functional layer 20 is laminated on the main surface 25a of the primer coat layer 25 on the opposite side from the main surface contacting the resin film 10.

The primer coat layer 25 is a layer formed of a primer, and preferably contains a material capable of improving adhesion to the resin film 10 and the functional layer 20. The compound contained in the primer coating layer 25 may be chemically bonded to a polyimide-based polymer or a silicon material contained in the resin film 10 at the interface.

Examples of the primer include ultraviolet-curable, thermosetting, and two-pack curable epoxy-based compounds. The primer may be a polyamic acid. These primers are preferable because they can improve adhesion to the resin film 10 and the functional layer 20.

The primer may also contain a silane coupling agent. The silane coupling agent may be chemically bonded to the silicon material contained in the resin film 10 through a condensation reaction. The silane coupling agent can be suitably used particularly when the compounding ratio of the silicon material contained in the resin film 10 is high.

Examples of the silane coupling agent include compounds having an alkoxysilyl group (which has a silicon atom and 1 to 3 alkoxy groups covalently bonded to the silicon atom). The compound having a structure in which 2 or more alkoxy groups are covalently bonded to a silicon atom is preferable, and the compound having a structure in which 3 alkoxy groups are covalently bonded to a silicon atom is more preferable. Examples of the alkoxy group include a methoxy group, an ethoxy group, an isopropoxy group, an n-butoxy group, and a tert-butoxy group. Among them, methoxy and ethoxy groups are preferable because reactivity with a silicon material can be improved.

The silane coupling agent preferably has a substituent having high affinity with the resin film 10 and the functional layer 20. The substituent group of the silane coupling agent is preferably an epoxy group, an amino group, a ureido group, or an isocyanate group from the viewpoint of affinity with the polyimide-based polymer contained in the resin film 10. When the functional layer 20 contains a (meth) acrylate, the silane coupling agent used in the primer coating layer 25 preferably has an epoxy group, a methacrylic group, an acrylic group, an amino group, or a styryl group because of its improved affinity. Among these, a silane coupling agent having a substituent selected from a methacrylic group, an acrylic group, and an amino group is preferable because it tends to have excellent affinity with the resin film 10 and the functional layer 20.

The thickness of the primer coat layer 25 may be appropriately adjusted depending on the functional layer 20, and is preferably 0.01nm to 20 μm. When the primer of the epoxy-based compound is used, the thickness of the primer coat layer 25 is preferably 0.01 to 20 μm, and more preferably 0.1 to 10 μm. When the silane coupling agent is used, the thickness of the primer coating layer 25 is preferably 0.1nm to 1 μm, and more preferably 0.5nm to 0.1 μm.

The laminate 30 of fig. 3 can be produced, for example, by a method including: a solution in which a primer is dissolved is applied to the main surface 10a of the resin film 10 to form a coating film, and the formed coating film is dried and cured to form a primer coating layer. The other parts are formed in the same manner as the laminate 30 of fig. 2. The primer coating 25 may be cured simultaneously with the functional layer 20 or may be separately cured prior to forming the functional layer 20.

The resin film and the laminate of the present embodiment have high transparency and can maintain excellent visibility when bent. In addition, the resin film and the laminate may have excellent bendability. When a primer coat layer is provided between the resin film and the functional layer, the adhesion between the resin film and the functional layer is improved. The resin film and the laminate may have functions such as transparency, ultraviolet ray resistance, and a function of imparting high hardness to the surface, which are required when applied to a substrate of an optical member or a display member of a flexible device, or a front panel.

The resin film and the laminate can be appropriately deformed. For example, functional layers may be provided on both sides of the resin film, respectively. In this case, a primer coat layer may be provided between each functional layer and the resin film.

[ display device (Flexible device) ]

Fig. 4 is a cross-sectional view showing one embodiment of a display device. The display device 100 shown in fig. 4 has the organic EL device 50, the touch sensor 70, and the front panel 90. They are typically housed in a housing. The organic EL device 50 and the touch sensor 70, and the touch sensor 70 and the front panel 90 may be bonded together with an Optical Adhesive (not shown), for example.

The organic EL device 50 is a display member having an organic EL element 51, a 1 st substrate 55, a 2 nd substrate 56, and a sealing member 59.

The organic EL element 51 includes a pair of electrodes (a 1 st electrode 52 and a 2 nd electrode 53) and a light-emitting layer 54. The light-emitting layer 54 is disposed between the 1 st electrode 52 and the 2 nd electrode 53.

The 1 st electrode 52 is formed of a light-transmitting conductive material. The 2 nd electrode 53 may have a light-transmitting property. As the 1 st electrode 52 and the 2 nd electrode 53, known materials can be used.

The light-emitting layer 54 may be formed by a known light-emitting material constituting an organic EL element. The luminescent material may be low molecular compound or high molecular compound.

When power is supplied between the 1 st electrode 52 and the 2 nd electrode 53, carriers (electrons and holes) are supplied to the light-emitting layer 54, and light is generated in the light-emitting layer 54. The light generated in the light-emitting layer 54 is emitted to the outside of the organic EL device 50 through the 1 st electrode 52 and the 1 st substrate 55.

The 1 st substrate 55 is made of a material having light transmittance. The 2 nd substrate 56 may have light transmittance. The 1 st substrate 55 and the 2 nd substrate 56 are bonded together with a sealing material 59 disposed so as to surround the organic EL element. The 1 st substrate 55, the 2 nd substrate 56, and the sealing member 59 form a sealing structure in which organic EL elements are sealed. The 1 st substrate 55 and/or the 2 nd substrate 56 are mostly made of a gas barrier material.

As a material for forming one or both of the 1 st substrate 55 and the 2 nd substrate 56, an inorganic material such as glass or a known transparent resin such as an acrylic resin can be used. As the above member, the resin film or laminate of the present embodiment described above may be used.

The 1 st substrate 55 and the 2 nd substrate 56, which can be used as the laminate of the present embodiment, correspond to the base material or the gas barrier material of the display member in the present embodiment. The organic EL device 50 having the 1 st substrate 55 and the 2 nd substrate 56 is excellent in flexibility because the resin film or laminate of the present embodiment is used.

The touch sensor 70 is an optical member having a touch sensor base 71 and an element layer 72 having a detection element formed on the touch sensor base 71.

The touch sensor base 71 may be formed of a material having light transmittance. As the touch sensor substrate 71, an inorganic material such as glass, or a known transparent resin such as an acrylic resin can be used. The resin film or laminate of the present embodiment described above may be used as the touch sensor substrate 71.

A known detection element composed of a semiconductor element, a wiring, a resistor, and the like is formed in the element layer 72. As the configuration of the detection element, a configuration that can realize a known detection system, such as a matrix switch, a resistive film system, or an electrostatic capacitance system, can be adopted.

The touch sensor base 71 to which the laminate of the present embodiment can be applied corresponds to an optical member in the present embodiment. The touch sensor 70 having the touch sensor base 71 is excellent in bendability because the resin film or laminate of the present embodiment is used.

The front panel 90 is formed of a material having light transmittance. The front panel 90 is positioned on the outermost layer on the display screen side of the display device, and functions as a protective member for protecting the display device. The front panel is sometimes also referred to as a window film. As the front panel 90, an inorganic material such as glass, or a known transparent resin such as an acrylic resin can be used. The resin film or laminate of the present embodiment described above may be used as the front panel 90. When a laminate is used as the front panel 90, the laminate is usually disposed in such a direction that the functional layer is positioned outside the display device.

The front panel 90 to which the resin film or laminate of the present embodiment can be applied has excellent bendability because the resin film or laminate of the present embodiment is applied.

When the display device 100 uses the resin film or laminate of the present embodiment as 1 or more of the constituent members selected from the organic EL device 50, the touch sensor 70, and the front panel 90, the display device can have excellent flexibility as a whole. That is, the display device 100 may be a flexible device.

A device (flexible device) to which the resin film and the laminate of the present embodiment can be applied is not limited to the display device described above. For example, the present invention can be applied to a solar cell having a substrate on which a photoelectric conversion element is formed and a front panel provided on a surface of the substrate. In this case, when the resin film or the laminate of the present embodiment is used as a substrate or a front panel of a solar cell, the solar cell as a whole can have excellent flexibility.

Examples

The present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[ example 1]

A nitrogen-purged polymerization vessel was charged with the compound represented by the formula (1), the compound represented by the formula (2), the compound represented by the formula (3), a catalyst, and a solvent (gamma butyrolactone and dimethylacetamide). The addition amount is as follows: 75.0g of the compound represented by the formula (1), 36.5g of the compound represented by the formula (2), 76.4g of the compound represented by the formula (3), 1.5g of a catalyst, 438.4g of gamma-butyrolactone, and 313.1g of dimethylacetamide. The molar ratio of the compound represented by formula (2) to the compound represented by formula (3) is 3: 7, the molar ratio of the total of the compound represented by the formula (2) and the compound represented by the formula (3) to the compound represented by the formula (1) is 1.00: 1.02.

[ chemical formula 4]

After the mixture in the polymerization vessel was stirred to dissolve the raw materials in the solvent, the mixture was heated to 100 ℃ and then to 200 ℃ and kept warm for 4 hours to polymerize polyimide. In this heating, water is removed from the liquid. Then, the polyimide was obtained by purification and drying.

Next, a polyimide γ -butyrolactone solution adjusted to a concentration of 20 mass%, a dispersion in which silica particles having a solid content concentration of 30 mass% were dispersed in γ -butyrolactone, a dimethylacetamide solution of an alkoxysilane having an amino group, a triazine-based ultraviolet absorber (TINUVIN (registered trademark) 479, manufactured by BASF) and water were mixed, and stirred for 30 minutes. The stirring was carried out according to the method described in U.S. Pat. No. 5, 8207256, 2.

Here, the mass ratio of the silica particles to the polyimide was set to 60: 40, the amount of the alkoxysilane having an amino group was 1.67 parts by mass with respect to 100 parts by mass of the total of the silica particles and the polyimide, the amount of the triazine-based ultraviolet absorber was 3 parts by mass with respect to 100 parts by mass of the total of the silica particles and the polyimide, and the amount of water was 10 parts by mass with respect to 100 parts by mass of the total of the silica particles and the polyimide.

The mixed solution was applied to a glass substrate, and dried by heating at 50 ℃ for 30 minutes and 140 ℃ for 10 minutes. Then, the film was peeled off from the glass substrate, a metal frame was mounted, and heating was performed at 210 ℃ for 1 hour, thereby obtaining a resin film having a thickness of 80 μm. The content of the silica particles in the resin film was 60 mass%.

Example 2 (laminate)

A two-pack curable primer (trade name: ARACOAT AP2510, available from Seikagawa chemical industries, Ltd.) was applied as a primer coat layer to one surface of the resin film produced in example 1 to form a coating film, and the coating film was dried and cured to form a primer coat layer having a thickness of 1 μm.

Then, a coating film was formed on the primer coat layer by applying a solution prepared by mixing 47.5 parts by mass of a 4-functional acrylate (trade name: A-TMMT, manufactured by Newzhongcun Chemical Co., Ltd.), 47.5 parts by mass of a 3-functional acrylate (trade name: A-TMPT, manufactured by Newzhongcun Chemical Co., Ltd.), 12.5 parts by mass of a reactive polyurethane polymer (trade name: 8 BR-600, manufactured by Dachen Fine Chemical Co., Ltd., 40% by mass of a product), 3 parts by mass of a triazine-based ultraviolet absorber (TINUVIN (registered trade name), manufactured by BASF Co., Ltd.), 8 parts by mass of a photopolymerization initiator (IRGACURE (registered trade name) 184, manufactured by Ciba Specialty Chemical Co., Ltd.), 0.6 parts by mass of a leveling agent (trade name: CheK-350, manufactured by BYK-Mie Japan Co., Ltd.), and 107 parts by mass of methyl ethyl ketone. The coating film was dried and cured to form a functional layer having a thickness of 10 μm as a "functional layer having a function of imparting high hardness to the surface and a function of absorbing ultraviolet rays", thereby obtaining a laminate of example 2.

Comparative example 1

A resin film having a thickness of 80 μm was obtained in the same manner as in example 1, except that the triazine-based ultraviolet absorber was not added to the mixed solution for forming a resin film.

Comparative example 2

A polyimide having a glass transition temperature of 390 ℃ was prepared ("Neopulim" manufactured by Mitsubishi GAS chemical corporation). This polyimide was mixed with a gamma butyrolactone solution having a concentration of 20 mass%, a dispersion in which silica particles having a solid content concentration of 30 mass% were dispersed in gamma butyrolactone, a dimethylacetamide solution of an alkoxysilane having an amino group, and water, and stirred for 30 minutes to obtain a mixed solution. The mass ratio of the silica particles to the polyimide was 55: 45, the amount of the alkoxysilane having an amino group is 1.67 parts by mass with respect to 100 parts by mass of the total of the silica particles and the polyimide, and the amount of water is 10 parts by mass with respect to 100 parts by mass of the total of the silica particles and the polyimide. Using the mixed solution, a resin film having a thickness of 80 μm was obtained in the same manner as in example 1.

(evaluation)

1) Optical Properties (yellow index (YI value))

The yellowness Index (YI value) of each of the resin films of examples and comparative examples was measured by an ultraviolet-visible near-infrared spectrophotometer V-670 manufactured by Japan Spectroscopy. After background measurement in the absence of the sample, the resin film was placed in a sample holder, and the transmittance of the resin film to light of 300nm to 800nm was measured to obtain a tristimulus value (X, Y, Z). The YI value was calculated based on the following formula.

YI＝100×(1.2769X－1.0592Z)/Y

2) Transmittance of light

The transmittance for light having a wavelength of 550nm was calculated by measuring the transmittance for light having a wavelength of 300nm to 800nm using an ultraviolet-visible near-infrared spectrophotometer V-670 manufactured by Japan Spectroscopy.

3) Haze degree

The resin films of examples and comparative examples were set in a sample holder by a fully automatic direct reading haze computer HGM-2 DP manufactured by Suga testing machine, and the haze of the resin films was measured.

4) Light irradiation test

The resin films of examples and comparative examples were subjected to a light irradiation test using UVCON manufactured by Atras corporation. The light source was UV-B313 nm, the output was 40W, and the distance between the resin film and the light source was set to 5 cm. The resin film was irradiated with ultraviolet rays for 24 hours. After the ultraviolet irradiation, the optical properties (YI value, transmittance) were evaluated as described above.

5) Visibility of

The film before the light irradiation test was bent, and the state of appearance of contrast and color phase at that time was confirmed, and the visibility was determined according to the following criteria.

A: no change in contrast or hue was observed.

C: changes in appearance such as changes in contrast and hue were observed.

[ Table 1]

The evaluation results are shown in table 1. The resin film of the example subjected to the light irradiation test satisfied the above conditions (i) and (ii), and it was confirmed that the resin film and the laminate having the resin film had high visibility when bent.

Description of the reference numerals

10 … resin film, 20 … functional layer, 25 … primer coating, 30 … laminate (laminate), 50 … organic EL device, 70 … touch sensor, 90 … front panel, 100 … display device.

Claims

1. A front panel of a flexible device having a resin film containing a polyimide polymer,

the polyimide polymer is a polymer having at least 1 or more kinds of repeating structural units represented by the following formula (PI), wherein the structural units represented by the formula (PI) are 40 mol% or more relative to all the repeating units of the polyimide polymer,

in the formula (PI), G is any one group selected from the group consisting of groups represented by each of the formula (20), the formula (21), the formula (22), the formula (23), the formula (24), the formula (25) and the formula (26),

in the formulae (20) to (26), the bond site is represented by,

z in formula (26) represents a single bond, -O-, -CH₂－、－C(CH₃)₂－、－Ar－O－Ar－、－Ar－CH₂－Ar－、－Ar－C(CH₃)₂-Ar-or-Ar-SO₂-Ar-, Ar represents an aryl group having 6 to 20 carbon atoms, at least 1 of the hydrogen atoms of which may be substituted by a fluorine-based substituent,

a is any one selected from the group consisting of groups represented by the following formulae (30), (31), (32), (33) and (34),

in the formulae (30) to (34), the bond site is represented by,

in the formula (32), Z¹Represents a single bond, -O-, -CH₂－、－C(CH₃)₂－、－SO₂-, -CO-or-CO-NR-, wherein R represents an alkyl group having 1 to 3 carbon atoms or a hydrogen atom,

in the formula (33), Z¹And Z²Each independently represents a single bond, -O-, -CH₂－、－C(CH₃)₂－、－SO₂-, -CO-or-CO-NR-, wherein R represents an alkyl group having 1 to 3 carbon atoms or a hydrogen atom,

the group represented by the above formula (30), formula (31), formula (32) and formula (33) may have a fluorine-based substituent introduced therein,

in the formula (34), Z¹And Z³Each independently represents a single bond, -O-, or,－CH₂－、－C(CH₃)₂－、－SO₂-, -CO-or-CO-NR-, wherein R represents an alkyl group having 1 to 3 carbon atoms or a hydrogen atom; z²Represents a single bond, -CH₂－、－C(CH₃)₂－、－SO₂-, -CO-or-CO-NR-, wherein R represents an alkyl group having 1 to 3 carbon atoms or a hydrogen atom,

when a light irradiation test was performed by irradiating light of 313nm for 24 hours from a side of the resin film facing the resin film with a light source having an output of 40W provided at a distance of 5cm from the resin film, the resin film satisfied the following conditions:

(i) the resin film after the light irradiation test has a transmittance of 85% or more for light of 550 nm; and the number of the first and second groups,

(ii) the resin film before the light irradiation test has a yellowness index of 5 or less, the difference between the yellowness index of the resin film before and after the light irradiation test is less than 2.5,

the resin film after the light irradiation test has a haze of 0.8% or less,

the resin film contains silica particles, and the proportion of the silica particles is 20 mass% or more and 70 mass% or less relative to the total mass of the polyimide polymer and the silica particles.

2. The front plate of a flexible device according to claim 1, wherein said resin film further contains an ultraviolet absorber.

3. The front panel of a flexible device according to claim 1 or 2, which has a laminate body having the resin film and a functional layer provided on at least one surface side of the resin film.

4. The front plate of a flexible device according to claim 3, wherein the functional layer is a layer having at least 1 function selected from the group consisting of ultraviolet absorption, adhesion, and a function of exhibiting high hardness at the surface.

5. The front panel of a flexible device according to claim 3, further comprising a primer coating disposed between the resin film and the functional layer.