JP2008260824A - Optical pressure-sensitive adhesive composition and optical functional film - Google Patents

Abstract

Provided is an optical pressure-sensitive adhesive composition for forming a pressure-sensitive adhesive layer capable of absorbing internal stress resulting from expansion and contraction of an optical functional film and preventing occurrence of color unevenness and white spots in a liquid crystal display device. thing.
An acrylic copolymer (A) having a weight average molecular weight of 800,000 or more and a glass transition temperature (Tg) (calculated value) of −30 ° C. to 50 ° C., a plasticizer (B), and The crosslinking agent (C) and the silane coupling agent (D) are contained, and the content of the plasticizer is 40 to 120 parts by mass per 100 parts by mass of the acrylic copolymer (A). An optical pressure-sensitive adhesive composition.
[Selection figure] None

Description

  The present invention relates to an optical pressure-sensitive adhesive composition and an optical functional film. More specifically, in a liquid crystal display device, an optimal pressure-sensitive adhesive composition for an optical functional film used for adhering an optical functional film such as a polarizing plate or a retardation plate to an optical component such as a liquid crystal cell, and the The present invention relates to an optical functional film in which an adhesive layer is laminated with a composition.

  The liquid crystal display device has a structure in which a liquid crystal material oriented in a predetermined direction is sandwiched between two glass substrates, and a polarizing plate, a retardation film, a viewing angle expansion film, or the like is provided on the surface of the substrate. The optical functional film is laminated with an adhesive.

  In recent years, this liquid crystal display device has become thinner and larger, and is widely used for various applications such as mounting on vehicles, outdoor instruments, PC displays, or TV displays. There is an increasing trend. With the spread of this application, the environment in which the liquid crystal display device is used has become very harsh. Therefore, the adhesive used for the above-mentioned application does not adhere even when exposed to high temperature or high temperature and high humidity conditions. A characteristic (durability) is required in which foaming does not occur in the agent layer and the attached film does not peel off from the substrate.

  A polarizing plate used in a liquid crystal display device has a three-layer structure in which both surfaces of a polyvinyl alcohol polarizer are sandwiched between triacetyl cellulose protective films, but has poor dimensional stability due to the characteristics of these materials. In addition, since an optical functional film such as a polarizing plate is formed by stretching, it tends to expand and contract over time. For this reason, in the liquid crystal display device, the internal stress generated by the expansion and contraction of the optical functional film cannot be absorbed and relaxed by the adhesive layer, and the distribution of residual stress acting on the optical functional film becomes non-uniform, In particular, stress concentrates on the peripheral edge. As a result, the peripheral edge of the liquid crystal display device becomes brighter or darker than the center, which causes color unevenness and white spots in the liquid crystal display device.

  Many means have been studied to solve the above problems. For example, in Patent Document 1, an optical functional film is characterized in that the pressure-sensitive adhesive layer of an optical functional film is composed of a main polymer having a weight average molecular weight of 60 to 2 million and 0.1 to 60 parts by weight of a plasticizer. It is disclosed. However, since the technology for setting the Tg of the main polymer higher than that of a general pressure-sensitive adhesive has not been shown, the amount of plasticizer added cannot be increased sufficiently, and the balance between durability and whiteout is achieved. It is not possible.

  In Patent Document 2, 100% by mass of a high molecular weight (meth) acrylic copolymer having a weight average molecular weight of 1 million or more and a low molecular weight (meth) acrylic copolymer 20 having a weight average molecular weight of 30,000 or less. An invention of a pressure-sensitive adhesive composition for a polarizing plate comprising ˜200 mass% and 0.005 to 5 mass% of a polyfunctional compound is disclosed. The invention describes that a pressure-sensitive adhesive layer that can follow the dimensional change of the polarizing plate is formed, and color unevenness and white spots are unlikely to occur in the liquid crystal element. However, as a result of studies by the present inventors, there is no technique for setting the Tg of the polymer higher than that of a general pressure-sensitive adhesive. Therefore, durability when color unevenness and white spot phenomenon are less likely to occur is exhibited. Still not enough.

In Patent Document 3, a. The base polymer comprises (1) about 50-70% by weight high Tg monomer component, wherein the homopolymer formed from the high Tg comonomer component has at least about 20 ° C., and (2) based on the total weight of the base copolymer. From about 30% by weight of an acidic comonomer, and (3) about 30-50% by weight of one or more low Tg (meth) acrylate comonomers, wherein the Tg of the homopolymer of the low Tg comonomer is less than about 20 ° C. About 100 parts by weight of a base copolymer formed and having a Tg greater than about 0 ° C., and b. A pressure sensitive adhesive is disclosed comprising about 1 to 100 parts by weight of a non-reactive non-acrylic plasticizer based on the base copolymer. However, since the pressure-sensitive adhesive disclosed in the present invention has no consideration on the molecular weight of the main polymer, the durability becomes insufficient when used as an optical pressure-sensitive adhesive.
Japanese Patent No. 3272721 Japanese Patent No. 3533589 Special table 2002-540245 gazette

  An object of the present invention is an adhesive used for a liquid crystal cell constituting a liquid crystal display device, which absorbs internal stress due to expansion and contraction of an optical functional film, and causes color unevenness and white spot phenomenon of the liquid crystal display device. It is providing the optical adhesive composition for forming the adhesive layer which can prevent.

In order to solve the above-mentioned problems, the present inventors have conducted intensive research and found that the above-described problems can be solved by the following present invention.
That is, the present invention relates to an acrylic copolymer (A) having a weight average molecular weight of 800,000 or more and a glass transition temperature (Tg) (calculated value) of −30 ° C. to 50 ° C., and a plasticizer (B ), A crosslinking agent (C), and a silane coupling agent (D), and the content of the plasticizer is 40 to 120 parts by mass per 100 parts by mass of the acrylic copolymer (A). An optical pressure-sensitive adhesive composition is provided.

  In the present invention, the plasticizer (B) is a benzoic acid ester-based, phosphoric acid-based or phthalic acid-based plasticizer; the acrylic copolymer (A) is an alkyl having 1 to 18 carbon atoms (meta It is preferably a copolymer of an acrylate monomer (a) and a functional group-containing monomer (b) copolymerizable with the monomer (a).

  Moreover, in the said invention, content of a crosslinking agent (C) is 0.01-5 mass parts per 100 mass parts of acrylic copolymers (A); Inclusion of a silane coupling agent (D) The amount is preferably 0.01 to 5 parts by mass per 100 parts by mass of the acrylic copolymer (A).

  Moreover, this invention provides the optical functional film characterized by having the adhesive layer which consists of an optical adhesive composition of the said invention on an at least one surface.

  According to the present invention, an optical pressure-sensitive adhesive composition for forming a pressure-sensitive adhesive layer that absorbs internal stress due to expansion and contraction of an optical functional film and can prevent occurrence of uneven color and white spots in a liquid crystal display device. Can be provided.

Next, the present invention will be described in more detail with reference to the best mode for carrying out the invention. The term “(meth) acryl” in the claims and the specification of the present invention means both “acryl” and “methacryl”, and the term “(meth) acrylate” ”And“ methacrylate ”.
The acrylic copolymer used in the present invention needs to have a weight average molecular weight of 800,000 or more, and a preferable weight average molecular weight is 800 to 2,000,000. When the weight average molecular weight is less than 800,000, when the pressure-sensitive adhesive composition is formed and the pressure-sensitive adhesive layer is formed, the durability of the pressure-sensitive adhesive layer becomes insufficient. On the other hand, if the weight average molecular weight exceeds 2 million, it is not preferable because the suppression of the occurrence of uneven color and white spots is insufficient.

  The acrylic copolymer used in the present invention has the above molecular weight, and the glass transition temperature (Tg) (calculated value) of the copolymer needs to be −30 ° C. to 50 ° C. If the Tg of the copolymer is lower than −30 ° C., when the plasticizer is added to the copolymer, the copolymer is too soft, and the copolymer is used as a pressure-sensitive adhesive composition. When the agent layer is formed, the durability of the pressure-sensitive adhesive layer becomes insufficient. In this case, if the amount of the plasticizer to be added is reduced to suppress peeling or foaming of the pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer has insufficient followability to the contraction of the polarizing plate, and white spots are not generated. It cannot be prevented.

  On the other hand, if the Tg of the copolymer exceeds 50 ° C., when the molecular weight of the copolymer is increased to 800,000 or more, even if a plasticizer is added to the copolymer, the copolymer does not exhibit adhesiveness. Therefore, the performance as a preferable pressure-sensitive adhesive cannot be obtained. In addition, Tg in this invention is a calculated value from the monomer used for the synthesis | combination of a copolymer.

  Examples of the copolymer satisfying the above conditions include a copolymer of an alkyl (meth) acrylate monomer (a) having 1 to 18 carbon atoms and a functional group-containing monomer (b) copolymerizable with the monomer (a). Can be mentioned. When the use ratio of the monomer (a) and the monomer (b) is 100% by mass, the monomer (a) is 90 to 99.8% by mass and the monomer (b) is 10 to 0. It is preferable that it is 2 mass%. When the amount of the monomer (b) used is less than 0.2% by mass, the durability becomes insufficient when the pressure-sensitive adhesive composition formed by the copolymer (A) is used. Moreover, when it exceeds 10 mass%, when the adhesive composition formed with a copolymer (A) is used, generation | occurrence | production of a color nonuniformity and a white spot phenomenon cannot be suppressed.

  Examples of the monomer (a) include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, Examples include alkyl (meth) acrylate monomers such as octyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, and lauryl (meth) acrylate. These may be used alone or in combination.

  The monomer (b) to be copolymerized with the monomer (a) is a carboxyl group, hydroxyl group, acetyl group, amide group or substituted amide group, amino group or substituted amino group, epoxy group or reactive group with the crosslinking agent (C). It is a monomer containing a functional group such as a mercapto group. Typically, it is a carboxyl group-containing monomer such as (meth) acrylic acid or carboxyethyl acrylate, or a hydroxyl group-containing monomer such as hydroxyethyl acrylate. These may be used alone or in combination. These monomers (b) are all known in the field of pressure-sensitive adhesives, and any known monomer (b) can be used in the present invention.

  The said copolymer (A) can contain monomers other than the said monomer (a) and the said monomer (b) as needed in the range which does not impair the effect of this invention. For example, aromatic group-containing monomers such as styrene, methylstyrene, phenoxyethyl (meth) acrylate or benzyl (meth) acrylate, vinyl acetate, (meth) acrylonitrile and the like can be contained, and these can be used alone or in combination. Good.

  A copolymer that satisfies the above conditions can be produced by ordinary solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization, or the like, but it must be produced by solution polymerization in which the copolymer (A) is obtained as a solution. Is preferred. By obtaining the copolymer (A) as a solution, it can be used as it is for the production of the pressure-sensitive adhesive composition of the present invention. Examples of the solvent used for the solution polymerization include organic solvents such as ethyl acetate, toluene, n-hexane, acetone, and methyl ethyl ketone.

  Examples of the polymerization initiator used in the polymerization include peroxides such as benzoyl peroxide and lauryl peroxide, azobis compounds such as azobisisobutyronitrile and azobisvaleronitrile, and polymer azo polymerization initiators. These can be used alone or in combination. Moreover, in the said superposition | polymerization, in order to adjust the molecular weight of a copolymer (A), a conventionally well-known chain transfer agent can be used.

  The plasticizer (B) used in the present invention may be any conventionally known plasticizer, but preferably includes benzoate-based, phosphoric acid-based and phthalic acid-based plasticizers. Examples of the benzoate plasticizer include diethylene glycol dibenzoate, dipropylene glycol dibenzoate, benzyl benzoate, and 1,4-cyclohexanedimethanol dibenzoate. Particularly preferred benzoate plasticizers include Examples thereof include dipropylene glycol dibenzoate and benzyl benzoate.

  Examples of the phosphoric acid plasticizer include trimethyl phosphate, triethyl phosphate, tris (butoxyethyl) phosphate, tricresyl phosphate, trixylenyl phosphate, cresyl diphenyl phosphate, 2-ethylhexyl diphenyl phosphate, etc. Preferred phosphoric acid plasticizers include cresyl diphenyl phosphate, tricresyl phosphate, triethyl phosphate, and the like. Examples of the phthalic acid plasticizer include dimethyl phthalate, diethyl phthalate, dibutyl phthalate, butyl benzyl phthalate, dicyclohexyl phthalate, and ethyl phthalyl ethyl glycolate. Particularly preferred phthalic acid plasticizers include, for example, , Butylbenzyl phthalate, dicyclohexyl phthalate and the like.

  Content of the said plasticizer needs to be 40-120 mass parts per 100 mass parts of said acrylic copolymers (A), and preferable content is 50 per 100 mass parts of copolymers (A). ˜110 parts by mass. If the amount of the plasticizer used is too small, the occurrence of uneven color and white spots is insufficiently suppressed. On the other hand, if the amount of the plasticizer used is too large, the durability is insufficient.

  Examples of the crosslinking agent (C) used in the present invention include a polyglycidyl compound having two or more glycidyl groups in one molecule, a polyisocyanate compound having two or more isocyanate groups in one molecule, and aziridinyl in one molecule. A polyaziridine compound having two or more groups, a polyoxazoline compound having two or more oxazoline groups in a molecule, a metal chelate compound or a butylated melamine compound can be used. A polyglycidyl compound, a polyisocyanate compound, or a polyaziridine compound is preferably used in that the durability of the pressure-sensitive adhesive composition can be further improved. These crosslinking agents are all known in the field of pressure-sensitive adhesives, and any known crosslinking agent can be used in the present invention.

  It is preferable that content of the said crosslinking agent (C) is 0.01-5 mass parts with respect to 100 mass parts of said copolymers (A), More preferably, it is 0.02-4 mass parts. . When the said content is less than 0.01 mass part, the cohesion force of an adhesive composition becomes low and durability is inferior compared with the said range. On the other hand, when the amount used exceeds 5 parts by mass, the resulting pressure-sensitive adhesive composition has excessive cohesive strength, which causes peeling of the optical functional film to be adhered.

  Moreover, in this invention, durability of the adhesive layer formed from an adhesive composition can further be improved by containing a silane coupling agent (D). These silane coupling agents are all known in the field of pressure-sensitive adhesives, and any known silane coupling agent can be used in the present invention. It is preferable that content of a silane coupling agent (D) is 0.01-5 mass parts with respect to 100 mass parts of acrylic copolymers (A). When the content is less than 0.01 parts by mass, the adhesive strength of the copolymer (A) cannot be appropriately reduced, and the reworkability is inferior compared with the above range. When the content exceeds 5 parts by mass, the adhesive strength of the copolymer (A) is reduced, but the durability is inferior compared with the above range.

  Moreover, the adhesive composition of this invention may mix | blend various additives in the range which does not impair the effect of this invention according to required characteristics, such as the objective of adjusting adhesive force. For example, terpene, terpene-phenol, coumarone indene, styrene, rosin, xylene, phenol, or petroleum tackifier resins, antioxidants, UV absorbers, fillers, pigments, etc. can do. The production method of the pressure-sensitive adhesive composition of the present invention may be a known method and is not particularly limited, but is preferably in the form of a solution containing an organic solvent. In this case, the pressure-sensitive adhesive layer can be easily formed.

  The optical functional film of the present invention is characterized in that the pressure-sensitive adhesive composition of the present invention is laminated on one side or both sides of an optical functional film (raw film) on which no pressure-sensitive adhesive layer is formed. For this reason, the optical functional film of the present invention does not peel off from the glass substrate or the like even under high temperature or high temperature and high humidity, and does not cause foaming in the pressure-sensitive adhesive layer (durability), and has a long time. It can be easily peeled off even after a lapse of time, and also has a property (reworkability) that does not cause residue on the substrate after peeling.

  Although there is no limitation in particular as the kind of said raw film, For example, a film light-guide plate, an antireflection film, an electroconductive film, a viewing angle expansion film, a phase difference film, a polarizing plate, or the film which combined these etc. are mentioned. . Moreover, in order to improve the adhesiveness with respect to the original film of the said adhesive composition, surface treatments, such as a corona treatment, can be performed to the surface of an original film.

  Moreover, there is no restriction | limiting in particular in the thickness of the said raw film, Although any thing can be used, For example, the thing of 5 micrometers-300 micrometers can be used, These differ with uses or the objectives.

  The optical functional film of the present invention is coated by applying the pressure-sensitive adhesive composition of the present invention on one or both sides of the original film using a commonly used coating apparatus such as a roll coating apparatus. It can be produced by drying the layer. If necessary, the pressure-sensitive adhesive layer can be subjected to heat crosslinking or curing with light such as ultraviolet rays. The optical functional film of the present invention is prepared by first applying an adhesive composition to a protective film such as a polyethylene terephthalate film (PET film) coated with a release agent such as a silicone resin and drying the adhesive layer. After forming, it can also be produced by laminating the original film on the pressure-sensitive adhesive layer.

  The coating amount of the pressure-sensitive adhesive composition of the present invention is preferably such that the thickness of the pressure-sensitive adhesive layer after drying is 10 to 50 μm. By setting the thickness of the pressure-sensitive adhesive layer within the above range, an optical functional film having a better balance between durability and reworkability is obtained.

  The above-mentioned optical functional film of the present invention can be stuck on a glass substrate of a liquid crystal display device by means usually used. Further, the optical functional film of the present invention can be further laminated and stuck on the optical functional film stuck on the glass substrate.

  EXAMPLES Next, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited by the following Example, unless the summary is exceeded. In the text, “parts” and “%” are based on mass unless otherwise specified.

  In this example, the value of the weight average molecular weight (MW) is a polystyrene equivalent molecular weight measured by a GPC (GEL Permeation Chromatography) method. Specifically, the coating film obtained by drying the copolymer at room temperature was dissolved in tetrahydrofuran, and measured with a high performance liquid chromatograph (manufactured by Shimadzu Corporation, LC-10ADvp, column KF-G + KF-806 × 2). The weight average molecular weight (MW) in terms of polystyrene was determined.

<Preparation of acrylic copolymer>
[Production Examples 1 to 13]
Nitrogen gas was introduced into a reaction apparatus equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube, and the air in the reaction apparatus was replaced with nitrogen gas. Thereafter, 58 parts of butyl acrylate, 40 parts of methyl acrylate, 2 parts of acrylic acid, 0.1 part of azobisisobutyronitrile and 100 parts of ethyl acetate were added to the reactor. While stirring, this was reacted at 68 ° C. for 8 hours in a nitrogen gas stream. After completion of the reaction, the solution was diluted with ethyl acetate to obtain a copolymer solution 1 having a solid content of 20%, a weight average molecular weight of 1.6 million, and a theoretical Tg of 29.1 ° C. (Production Example 1). In the same manner as in Production Example 1, polymerization was carried out in the same manner with the monomer compositions shown in Table 1 to obtain copolymer solutions 2 to 13. The copolymer solutions 12 and 13 correspond to comparative examples. The numerical value of the composition in Table 1 is the number of parts.

MA: methyl acrylate (Tg of homopolymer: 8 ° C.)
EA: ethyl acrylate (Tg of homopolymer: −22 ° C.)
BA: butyl acrylate (Tg of homopolymer: -55 ° C)
MMA: methyl methacrylate (Tg of homopolymer: 105 ° C.)
VAc: Vinyl acetate (Tg of homopolymer: 30 ° C.)
AA: Acrylic acid (Tg of homopolymer: 106 ° C.)
HEA: hydroxyethyl acrylate (Tg of homopolymer: -15 ° C)
HEAA: hydroxyethylacrylamide (homopolymer Tg: 98 ° C.)
DMAA: dimethylacrylamide (homopolymer Tg: 119 ° C)

<Production and evaluation of pressure-sensitive adhesive composition and optical functional film>
[Examples 1 to 18, Comparative Examples 1 to 4]
50 parts of a plasticizer, 0.8 part of a crosslinking agent and 0.3 part of a silane coupling agent were mixed with 100 parts of the solid content of the copolymer solution 1 to obtain a pressure-sensitive adhesive composition of Example 1. In the same manner as in Example 1, the components described in Table 2 were mixed to obtain pressure-sensitive adhesive compositions of Examples 2 to 18 and Comparative Examples 1 to 4.

BPDP: dipropylene glycol dibenzoate BB: benzyl benzoate CDP: cresyl diphenyl phosphate TCP: tricresyl phosphate BBP: butylbenzyl phthalate DCHP: dicyclohexyl phthalate coronate L (trade name): manufactured by Nippon Polyurethane Industry Co., Ltd., polyisocyanate Takenate D-110N (trade name): manufactured by Mitsui Takeda Chemical Co., Ltd., polyisocyanate KBM-803 (trade name): manufactured by Shin-Etsu Chemical Co., Ltd., γ-mercaptopropylmethyltrimethoxysilane KBM-408 (trade name): Shin-Etsu Chemical industry, γ-glycidoxypropyltrimethoxysilane

  Next, the obtained pressure-sensitive adhesive compositions of Examples 1 to 18 and Comparative Examples 1 to 4 were applied onto a PET film coated with a silicone resin, and the solvent was removed at 90 ° C., followed by drying and a crosslinking reaction. As a result, a pressure-sensitive adhesive layer having a thickness of 25 μm was formed. A polarizing plate having a thickness of 180 μm was bonded to the surface on which the pressure-sensitive adhesive layer was formed to produce an optical functional film. After this optical functional film was cured at 23 ° C. and 50% RH for 7 days, white spots, durability and adhesive strength were evaluated by the test methods described later. The evaluation results of the examples were good in all items. The evaluation results are shown in Table 3.

<Test methods and evaluation criteria>
[White spot test]
Two of the same samples after the 80 ° C. endurance test using the optical functional films in Examples and Comparative Examples were bonded together in crossed Nicols, placed on the backlight of a liquid crystal monitor, and the white spots were observed visually.
-Evaluation criteria ○: No white spots were observed in the optical functional film.
Δ: Slight white spots were observed in the optical functional film.
X: White spots were observed in the optical functional film.

[Durability test]
The optical functional films in Examples and Comparative Examples were each cut to 200 mm × 300 mm, and after the PET film was peeled off, it was affixed on a glass substrate and subjected to autoclave treatment to produce an evaluation sample. About the obtained sample for evaluation, the test of the following item was performed, respectively.
(1) 80 ° C
The sample for evaluation was allowed to stand in an atmosphere of 80 ° C. (DRY) for 500 hours, and then visually confirmed for foaming and peeling. The evaluation criteria are as follows.
(2) 60 ° C / 95% RH
The sample for evaluation was allowed to stand in an atmosphere of 60 ° C. and 95% RH for 500 hours, and then visually confirmed for foaming and peeling. The evaluation criteria are as follows.

Evaluation criteria (1) Foaming ○: Foaming is not confirmed in the optical functional film.
Δ: Slight foaming was confirmed in the optical functional film (practical level).
X: Foaming was confirmed in the optical functional film.
(2) Peeling ○: Peeling is not confirmed on the optical functional film.
Δ: Slight peeling was confirmed on the optical functional film (practical level).
X: Peeling was confirmed on the optical functional film.

[Adhesion test]
(1) Initial adhesive strength The optical functional films in Examples and Comparative Examples were each cut into 25 mm × 120 mm, and the adhesive strength was measured according to JIS Z 0237 and JIS Z 0238. A glass plate was used as the adherend.
(2) Heat-adhesive strength Each of the optical functional films in Examples and Comparative Examples was cut into 25 mm × 120 mm, allowed to stand at 70 ° C. for 6 hours, and then allowed to cool to 23 ° C. to JIS Z 0237 and JIS Z 0238. The adhesive strength was measured accordingly. A glass plate was used as the adherend.

  According to the present invention, an optical pressure-sensitive adhesive composition for forming a pressure-sensitive adhesive layer that absorbs internal stress due to expansion and contraction of an optical functional film and can prevent occurrence of uneven color and white spots in a liquid crystal display device. Can be provided.

Claims (6)

  An acrylic copolymer (A) having a weight average molecular weight of 800,000 or more and a glass transition temperature (Tg) (calculated value) of −30 ° C. to 50 ° C., a plasticizer (B), a crosslinking agent ( C) and a silane coupling agent (D), and the plasticizer content is 40 to 120 parts by mass per 100 parts by mass of the acrylic copolymer (A). Pressure-sensitive adhesive composition.   The optical pressure-sensitive adhesive composition according to claim 1, wherein the plasticizer (B) is a benzoic acid ester-based, phosphoric acid-based or phthalic acid-based plasticizer.   The acrylic copolymer (A) is a copolymer of an alkyl (meth) acrylate monomer (a) having 1 to 18 carbon atoms and a functional group-containing monomer (b) copolymerizable with the monomer (a). The optical pressure-sensitive adhesive composition according to claim 1 or 2.   Content of a crosslinking agent (C) is 0.01-5 mass parts per 100 mass parts of acrylic copolymers (A), The optical adhesive composition of any one of Claims 1-3. .   The optical pressure-sensitive adhesive according to any one of claims 1 to 4, wherein the content of the silane coupling agent (D) is 0.01 to 5 parts by mass per 100 parts by mass of the acrylic copolymer (A). Composition.   An optical functional film comprising a pressure-sensitive adhesive layer comprising the optical pressure-sensitive adhesive composition according to claim 1 on at least one surface.