CN106928868B

CN106928868B - Pressure-sensitive adhesive and preparation method thereof

Info

Publication number: CN106928868B
Application number: CN201710200648.7A
Authority: CN
Inventors: 泽登纯一; 冈琦哲也; 陈维; 姜云; 陈田安; 高昂; 杨春强; 江华; 邹学良; 周玉波
Original assignee: Suzhou And West Mstar Technology Ltd
Current assignee: Suzhou And West Mstar Technology Ltd
Priority date: 2017-03-30
Filing date: 2017-03-30
Publication date: 2020-02-18
Anticipated expiration: 2037-03-30
Also published as: JP2020507665A; JP6830281B2; CN106928868A; WO2018177288A1

Abstract

The invention provides an optical acrylate pressure-sensitive adhesive and a preparation method thereof. The pressure-sensitive adhesive disclosed by the invention has a lower dielectric constant under the condition of 1 kHz-1 MHz, and has the advantages of high peeling strength, high transmittance and the like, so that the application prospect is wider. A pressure-sensitive adhesive is prepared by polymerizing one or more acrylate monomers and oligomers under the action of a photoinitiator; the acrylate monomer is acrylic acid saturated alcohol ester or alkyl acrylic acid saturated alcohol ester; the weight ratio of the acrylate monomer is more than 10%, preferably more than 15%, more preferably more than 20%; the molecular weight of the oligomer is more than 20000, and the oligomer is selected from one or more of acrylate prepolymer, epoxy prepolymer, organosilicon prepolymer, polyurethane prepolymer, polyether prepolymer, polyhydroxy polyolefin oligomer, polybutadiene prepolymer and fluorine modified prepolymer.

Description

Pressure-sensitive adhesive and preparation method thereof

Technical Field

The invention relates to the field of optical display, in particular to an optical pressure-sensitive adhesive for bonding a display device and a preparation method thereof.

Background

With the wide application and rapid development of optical displays, the requirements for optical pressure-sensitive adhesives are increasing. Acrylic resin is one of the commonly used pressure-sensitive adhesives, and is widely used because of its many advantages: 1. exhibits high adhesion to a transparent material such as a PET optical film or glass; 2. the appearance is colorless and transparent and has good weather resistance; 3. no additive is needed, and the formula is simple; 4. the pressure-sensitive adhesive meeting various performance requirements can be prepared by utilizing copolymerization and crosslinking.

However, with the rapid development of electronic products, acrylic adhesives still have certain limitations. For example, in a specific application, the adhesive is required to have a low dielectric constant (usually, Dk is 2-3 under the condition of 1 kHz-1 MHz), but the traditional acrylic resin has double bonds and a high dielectric constant, so that the requirement is difficult to meet.

In view of the above, the present invention is particularly proposed.

Disclosure of Invention

The first purpose of the invention is to provide a pressure-sensitive adhesive, which has a relatively low dielectric constant under the condition of 1 kHz-1 MHz, and has the advantages of high peel strength, high transmittance and the like, and the application prospect is wider.

The second purpose of the invention is to provide the preparation method of the pressure-sensitive adhesive, which has simple process and convenient preparation, so that a new product is easier to popularize.

In order to achieve the above purpose, the invention provides the following technical scheme:

a pressure-sensitive adhesive is mainly prepared by polymerizing one or more acrylate monomers and oligomers under the action of a photoinitiator;

the acrylate monomer is acrylic acid saturated alcohol ester or alkyl acrylic acid saturated alcohol ester;

in the polymer, the weight ratio of the acrylate monomer is 10% or more, preferably 15% or more, and more preferably 20% or more;

the molecular weight of the oligomer is more than 20000, and the oligomer is selected from one or more of acrylate prepolymer, epoxy prepolymer, organosilicon prepolymer, polyurethane prepolymer, polyether prepolymer, polyhydroxy polyolefin oligomer, polybutadiene prepolymer and fluorine modified prepolymer.

The invention solves the technical problem that the dielectric constant can not adapt to new technology products, and the main principle for solving the problem is as follows: the number of double bonds in the adhesive is reduced to reduce the dielectric constant.

In practical studies, it has been found that a good effect cannot be obtained by merely reducing the number of double bonds without considering other factors, and the effect is mainly manifested by extremely low peel strength, loss of practical value, or a great decrease in other properties such as transmittance. In order to obtain the adhesive with practical value, a specific type and a specific content of acrylate monomers are required to be selected for copolymerization with a specific type of prepolymer while the number of double bonds is reduced.

Through research, the adhesive prepared by the formula has excellent comprehensive properties: the peel strength is maintained at 8N/25mm or more (180 DEG), the dielectric constant at 1 kHz-1 MHz is maintained at 2-3, and the transmittance at wavelength of 550nm is 99% or more.

The basic scheme can be further improved to achieve more technical effects, such as:

preferably, the alkyl group is selected from C1-C10 alkyl groups, preferably C1-C6 alkyl groups. That is, the substituent on the acrylic acid may be selected from methyl, ethyl, propyl, butyl, isobutyl, etc.,

preferably, the saturated alcohol is selected from saturated monohydric or polyhydric alcohols from C1 to C18, preferably saturated monohydric or polyhydric alcohols from C2 to C8, preferably saturated monohydric or polyhydric alcohols from C4 to C8. For example, methanol, ethanol, propanol, propylene glycol, n-butanol, isobutanol, butylene glycol, n-octanol, isooctanol, hexadecanol, octadecanol and the like. The saturated alcohol used herein refers to the saturated alcohol used in all the esters above, and it should be noted that the kind of the saturated alcohol selected for each compound is independent, that is, any one of the above kinds is independently selected.

The monomer type has a great influence on the peel strength of the adhesive and, secondly, on the dielectric constant.

In order to obtain larger peel strength and lower dielectric constant, preferably, the acrylate monomer is a mixture of isooctyl acrylate and 4-hydroxybutyl acrylate, and the weight ratio of the two is preferably below 1:1, i.e. the amount of 4-hydroxybutyl acrylate is preferably less than that of isooctyl acrylate.

Preferably, the oligomer is selected from one or a mixture of acrylate prepolymer and polyurethane prepolymer.

Preferably, the molecular weight of the oligomer is 20000-40000, or 30000-60000, or 40000-70000.

The type and molecular weight of the oligomer mainly affect the peel strength of the adhesive, and if the selection is reasonable, the peel strength is far higher than that of the existing product.

Preferably, the oligomer is present in a weight ratio of 20% or more, preferably 25% or more, more preferably 30% or more.

The weight ratio of the oligomer has an important influence on both the peel strength and the dielectric constant of the adhesive, and is preferably 20% or more, for example, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, and the like.

In order to improve the stability of the adhesive, a proper amount of additives selected from one or more of a cross-linking agent, a tackifier, a plasticizer, an antistatic agent, a softening agent, a coloring agent, an antioxidant, a leveling agent, a light stabilizer, a defoaming agent, a stabilizer and a preservative may be further introduced at the time of polymerization.

Preferably, the additive is present in an amount of 10 to 50 wt%.

Preferably, the additive comprises a tackifier.

Preferably, the additives include tackifiers, light stabilizers, defoamers.

The various additives mentioned above may be of conventional type, but the effect of type and amount on peel strength and dielectric constant is very different for the purposes of the present invention.

Preferably, the tackifier is preferably selected from terpene phenolic resins, and the content of the tackifier is preferably more than 15 wt%, preferably more than 20 wt%, and more preferably more than 25 wt%;

when the dosage and the type of the tackifier are different, the dielectric constant is improved, the stability is reduced, and the peel strength is not obviously improved. If the above types and amounts are used, they can be avoided.

Preferably, the light-resistant agent is selected from phenoxy triazines in an amount of 0.1 to 0.3 wt%, preferably 0.1 to 0.2 wt%.

Preferably, the defoaming agent is selected from polysiloxane, and the content is 0.1-0.3 wt%, preferably 0.1-0.2 wt%.

Preferably, the cross-linking agent is a polyol acrylate, and/or a polyol methacrylate; the polybasic group before the acid here means that there are a plurality of ester groups.

Preferably, the polyol is selected from the group consisting of diols, triols, tetrols or polyethylene glycols, preferably saturated or cycloalkyl alcohols, more preferably one or more of 1, 4-butanediol, 1, 6-hexanediol, 1, 9-nonanediol, tripropylene glycol, tricyclodecane dimethanol, 1, 10-decanediol, polyethylene glycol 200, polyethylene glycol 400, trimethylolpropane, ditrimethylolpropane, ethoxylated pentaerythritol, dipentaerythritol.

Preferably, the weight ratio of the cross-linking agent in the polymer is 0.1-3 wt%.

In addition, the pressure-sensitive adhesive disclosed by the invention has another advantage that: the hot pressing and curing process of the existing product can be adopted, so that the cost of upgrading the product (including equipment replacement, process condition control, operator training and the like) is reduced.

Wherein, during the polymerization, the photoinitiator is benzil dimethyl ether, dialkoxy acetophenone, methyl benzoylformate, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-methyl-1- (4-methylthiophenyl) -2-morpholine-1-propanone, 2-benzyl-2-dimethylamine-1- (4-morpholine benzyl phenyl) butanone, 2,4, 6-trimethylbenzoyl phenyl phosphine, 2,4, 6-trimethylbenzoyl diphenyl phosphine oxide, ethyl 2,4, 6-trimethylbenzoyl phenyl phosphonate, benzophenone, 4,4' -bis (diethylamino) benzophenone, 2-isopropyl thioxanthone, one or two or a mixture of more than two of 4-dimethylamino-ethyl benzoate, preferably 2,4, 6-trimethylbenzoylphenylphosphine and methyl benzoylformate; preferably, the weight ratio of the two components is 1-2: 1.

In summary, compared with the prior art, the invention achieves the following technical effects:

(1) the comprehensive performance of the adhesive is improved, including the peel strength, the dielectric constant, the transmittance, the stability of the dielectric constant and the like.

(2) The application range of the adhesive is wider.

(3) The production process has low requirement.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a graph showing the change of dielectric constant with frequency of the adhesives obtained in the examples of the present invention and the comparative examples.

Detailed Description

The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and the detailed description, but those skilled in the art will understand that the following described embodiments are some, not all, of the embodiments of the present invention, and are only used for illustrating the present invention, and should not be construed as limiting the scope of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

The invention solves the technical problem that the dielectric constant can not adapt to new technology products, and the main principle for solving the problem is as follows: the number of double bonds in the adhesive is reduced to reduce the dielectric constant. In practical studies, it has been found that a good effect cannot be obtained by merely reducing the number of double bonds without considering other factors, and the effect is mainly manifested by extremely low peel strength, loss of practical value, or a great decrease in other properties such as transmittance. In order to obtain the adhesive with practical value, a specific type and a specific content of acrylate monomers are required to be selected for copolymerization with a specific type of prepolymer while the number of double bonds is reduced. The basic scheme is as follows:

mainly polymerized by one or more saturated acrylate monomers and oligomers under the action of a photoinitiator;

the saturated acrylate monomer is generated by acrylic acid or alkyl acrylic acid and saturated alcohol;

the molecular weight of the oligomer is more than 20000, and the oligomer is selected from one or more of urethane prepolymer, acrylate prepolymer, epoxy prepolymer, organic silicon prepolymer, polyester prepolymer, polyether prepolymer, polyhydroxy polyolefin oligomer, polybutadiene prepolymer and fluorine modified prepolymer.

Based on the aim, the invention optimizes the types and the use amounts of the monomers and the oligomers, simultaneously introduces the additive, optimizes the type and the addition amount of the additive, obtains more excellent comprehensive performance, and has the following optimization results:

the alkyl acrylic acid is selected from C1-C10 alkyl substituted acrylic acid, preferably C1-C6 alkyl substituted acrylic acid;

preferably, the saturated alcohol is selected from saturated monohydric or polyhydric alcohols from C1 to C18, preferably saturated monohydric or polyhydric alcohols from C2 to C8, preferably saturated monohydric or polyhydric alcohols from C4 to C8;

preferably, the saturated acrylate monomer is a mixture of 4-hydroxybutyl acrylate and isooctyl acrylate, and the weight ratio of the two is preferably below 1: 1.

Preferably, the molecular weight of the oligomer is 20000-40000, or 30000-60000, or 40000-70000;

Preferably, the polymerization is also added with a proper amount of additives, and the additives are selected from one or more of cross-linking agents, adhesion promoters, plasticizers, antistatic agents, softening agents, coloring agents, antioxidants, leveling agents, light stabilizers, defoaming agents, stabilizing agents and preservatives;

preferably, the additive is present in an amount of 10 to 50 wt%.

Preferably, the additive comprises a tackifier.

Preferably, the additives include tackifiers, light stabilizers, defoamers.

preferably, the light-resistant agent is selected from phenoxy triazines, and the content is 0.1-0.3 wt%, preferably 0.1-0.2 wt%;

Preferably, the cross-linking agent is a polyol acrylate, and/or a polyol methacrylate;

preferably, the polyol is selected from a diol, triol, tetraol or polyethylene glycol, preferably a saturated alcohol or a cycloalkyl alcohol, more preferably one or more of 1, 4-butanediol, 1, 6-hexanediol, 1, 9-nonanediol, tripropylene glycol, tricyclodecane dimethanol, 1, 10-decanediol, polyethylene glycol 200, polyethylene glycol 400, trimethylolpropane, ditrimethylolpropane, ethoxylated pentaerythritol, dipentaerythritol;

Preferably, the photoinitiator is 2,4, 6-trimethylbenzoylphenylphosphine and/or methyl benzoylformate, preferably a mixture of the two; preferably, the weight ratio of the two components is 1-2: 1.

Based on the above basic and optimized schemes, the present invention provides the following examples.

Examples 1 to 6

Preparation of adhesive

The formulation is shown in table 1.

TABLE 1

Note: the oligomers described in table 1 are acrylate prepolymers.

The preparation method comprises the following steps:

the components are fully stirred, mixed and vacuumized, so that the liquid pressure-sensitive adhesive composition is obtained, can be directly applied to a substrate and is cured by uv irradiation.

Comparative example 1

The only difference from example 1 is that the prepolymer was replaced with an acrylate prepolymer having a molecular weight of 15000.

Comparative examples 2 to 6

The formulations of comparative examples 2 to 6 are shown in Table 2, and the preparation methods are the same as in example 1.

TABLE 2

Note: the oligomers described in table 2 are acrylate prepolymers.

The adhesive obtained in all the above examples and comparative examples was tested for properties and is shown in tables 3 and 4 below, and the results show that the adhesive obtained in examples 3 to 16 all maintained peel strength at 8N or more, dielectric constant at 1kHz to 1MHz was maintained between 2 and 3, and transmittance at wavelength 550nm was 99% or more.

In addition, the adhesive of the present invention can maintain a stable dielectric constant over a wide frequency range, such as the trend of example 1 and comparative examples 3 and 5, as shown in fig. 1.

In conclusion, the adhesive disclosed by the invention has excellent comprehensive performance.

TABLE 3

TABLE 4

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. The pressure-sensitive adhesive is characterized by being mainly prepared by polymerizing one or more acrylate monomers and oligomers under the action of a photoinitiator;

the acrylate monomer is a mixture of isooctyl acrylate and 4-hydroxybutyl acrylate, and the weight ratio of the 4-hydroxybutyl acrylate to the isooctyl acrylate is below 1: 1;

in the polymer, the weight ratio of the acrylate monomer is more than 10%;

the molecular weight of the oligomer is 20000 or more, and the oligomer is selected from one or a mixture of two of acrylate prepolymer and polyurethane prepolymer;

the photoinitiator is a mixture of 2,4, 6-trimethyl benzoyl phenyl phosphine and methyl benzoylformate, and the mixing weight ratio of the two is 1-2: 1.

2. The pressure-sensitive adhesive of claim 1, wherein the oligomer has a molecular weight of 20000 to 40000, or 30000 to 60000, or 40000 to 70000.

3. The pressure sensitive adhesive of claim 2 wherein the oligomer is present in an amount of 20% by weight or more.

4. The pressure sensitive adhesive according to any of claims 1 to 3, wherein an appropriate amount of additives selected from one or more of cross-linking agents, tackifiers, plasticizers, antistatic agents, softeners, colorants, antioxidants, leveling agents, light stabilizers, defoamers, stabilizers, and preservatives are further introduced during the polymerization.

5. The pressure sensitive adhesive of claim 4 wherein the additive is present in an amount of 10 to 50 wt%.

6. The pressure sensitive adhesive of claim 4 wherein the additive comprises a tackifier.

7. The pressure sensitive adhesive of claim 4 wherein the additives are tackifiers, light stabilizers, and defoamers.

8. The pressure sensitive adhesive of claim 4 wherein the tackifier is selected from terpene phenolic resins, and the tackifier content is 15 wt% or more.

9. The pressure-sensitive adhesive of claim 4 wherein the light stabilizer is selected from phenoxytriazines in an amount of 0.1 to 0.3 wt.%.

10. The pressure-sensitive adhesive as claimed in claim 4, wherein the defoaming agent is selected from polysiloxane, and the content of the defoaming agent is 0.1-0.3 wt%.

11. The pressure sensitive adhesive of claim 4 wherein the crosslinker is a polyol polyacrylate and/or a polyol methacrylate; "polybasic" before the acid means that there are a plurality of ester groups.

12. The pressure sensitive adhesive of claim 11 wherein the polyol of the crosslinker is selected from the group consisting of diols, triols, tetraols, and polyethylene glycols.

13. The pressure sensitive adhesive of claim 12 wherein the polyol in the crosslinker is a saturated or cycloalkyl alcohol.

14. The pressure sensitive adhesive of claim 13 wherein the polyol in the crosslinker is one or more of 1, 4-butanediol, 1, 6-hexanediol, 1, 9-nonanediol, tripropylene glycol, tricyclodecane dimethanol, 1, 10-decanediol, polyethylene glycol 200, polyethylene glycol 400, trimethylolpropane, ditrimethylolpropane, ethoxylated pentaerythritol, pentaerythritol and dipentaerythritol.

15. The pressure-sensitive adhesive of claim 4, wherein the weight ratio of the crosslinking agent in the polymer is 0.1-3 wt%.

16. The method of making a pressure sensitive adhesive according to any of claims 1-15 comprising the steps of:

according to the formula, all the raw materials are mixed and polymerized under the action of a photoinitiator.