JP2003342546A - Optical adhesive with regulated refractive index, and optical adhesive sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical adhesive preventing reflection by the interface caused at the stuck interface of an optical film and an adhesive layer, halation at the adhesive layer face and reduction of transmission, caused when the adhesive layer is used for sticking various kinds of the optical films, by reducing the difference of the refractive indexes between the optical film and the adhesive layer, having excellent heat resistance, light resistance, resistance to hot moisture, and optical characteristics in a high-degree reliability test, and further having adhesive durability by which peeling and foaming are prevented, and to provide an optical adhesive sheet having the optical adhesive sandwiched by a releasing sheet and a resin sheet. <P>SOLUTION: The adhesive is obtained by adding ≤65% agent for regulating refractive index, having ≤900 weight average molecular weight and containing styrene as a monomer unit based on the amount of a principal ingredient of the adhesive comprising an acrylic resin. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

The present invention relates to an optically anisotropic film,
The present invention relates to a pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet, and a pressure-sensitive adhesive layer used for laminating films and plate materials for optical and electronic materials such as diffusion films, antireflection films, glass and the like. In particular, it is used for applications that require adjustment of the refractive index between adherends via an adhesive layer in optical design.

[0002]

2. Description of the Related Art Optical light guide plates, optical films such as antireflection films, and optical pressure-sensitive adhesive compositions and optical pressure-sensitive adhesive sheets used for bonding electronic materials are transparent, have few appearance defects, and have a light transmittance. In addition to high durability, it is required to have durability characteristics over time that adhesive strength, appearance and optical distortion are not caused by light, high temperature, low temperature, heat and humidity, and time. In order to solve such a problem, there is an acrylic resin-based pressure-sensitive adhesive having a specified molecular weight as disclosed in JP-A-1-66283.

[0003]

However, when an adhesive layer is used for laminating various optical films and the difference in the refractive index between the optical film and the adhesive layer is large, the optical interface at the laminating interface between the optical film and the adhesive layer is Interfacial reflection occurs, halation occurs on the adhesive layer surface, and the transmittance decreases. Generally, the refractive index of the acrylic adhesive resin is 1.46 to 1.
In contrast to 47, the refractive index of the resin used for the optical film is, for example, 1.50 of triacetylacetate polymer and 1.49 of acrylic resin.

In order to solve such a problem, an adhesive having a refractive index adjusted according to the adherend by an additive such as tackifier having a refractive index adjusting function is disclosed in, for example, Japanese Patent Laid-Open No. 2002-014225. Open 2000-321
There is a 960 publication. However, in the conventional refractive index adjusting agent, the compatibility of the refractive index adjusting agent with the adhesive is poor, and when the addition amount of the refractive index adjusting agent is large, the refractive index adjusting agent bleeds out in the adhesive layer or crystallizes. And cause optical anomalies such as uneven reflection and reduced light transmittance. In particular, when the compatibility is poor, the refractive index adjusting agent separates in the pressure-sensitive adhesive layer, and a whitening phenomenon occurs. Therefore, there is a limit to the amount of the refractive index adjusting agent added, and there is also a limit to the adjustment of the refractive index difference with the optical film.

[0005]

[Means for Solving the Problems] In view of such a situation,
Excellent transparency, light resistance, heat resistance, peeling at the interface between the pressure-sensitive adhesive layer and the adherend in an advanced reliability test such as heat and humidity resistance, and an adhesive main agent with adhesion durability that can prevent foaming, As a result of studying a refractive index adjusting agent having good compatibility with an optical adhesive main agent, the present invention has been completed. That is, by adding a refractive index adjusting agent having a weight average molecular weight of 900 or less and styrene as a monomer unit to a pressure-sensitive adhesive main agent made of an acrylic resin, the refractive index is 1.47.
An optical pressure-sensitive adhesive and an optical pressure-sensitive adhesive which can be arbitrarily adjusted up to 1.53, and have excellent heat resistance, light resistance, heat and humidity resistance, excellent optical characteristics in advanced reliability tests, and adhesion and durability that can prevent peeling and foaming. It is possible to obtain an optical pressure-sensitive adhesive sheet characterized in that the pressure-sensitive adhesive for use is sandwiched between the release sheet and the resin sheet.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Acrylic resin is used as a resin used as a base material of an optical pressure-sensitive adhesive used in the present invention in view of optical characteristics, light resistance, weather resistance, heat resistance and transparency. Monomers constituting the acrylic resin used in the present invention include, for example, ethyl acrylate, butyl acrylate, amyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, cyclohexyl acrylate, benzyl acrylate, and other alkyl acrylates. Esters, alkyl methacrylates such as butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate and benzyl methacrylate, ethyl methacrylate, and vinyl acetate, vinyl propionate, vinyl ether, styrene, acrylonitrile, methacrylonitrile. You may copolymerize vinyl group containing compounds, such as. Further, in order to improve the adhesion durability performance and suppress the generation of outgas, it is preferable that the main component of the optical adhesive is an acrylic resin, the weight average molecular weight is 500,000 or more, and the polydispersity is 5 or less.

If necessary, a crosslinking agent, a catalyst, a UV absorber, an antioxidant, a coloring pigment, glass beads, a filler,
A flame retardant, an antibacterial agent, a light stabilizer, a colorant, a fluidity improver, a lubricant, an antiblocking agent, an antistatic agent, a crosslinking aid and the like can be added. These may be used alone or 2
You may use together 1 or more types. The cross-linking agent can be used without particular limitation as long as it does not impair the required properties. Examples thereof include polyisocyanate, chelate, epoxy resin, melamine resin, and amide resin.

The refractive index adjusting agent used in the present invention is required to have compatibility with the base material of the pressure-sensitive adhesive because of its optical characteristics. Therefore, it is preferable that it has an aromatic ring in its molecular structure and preferably has styrene as a monomer unit. . For example, there are coumarone resin and styrene resin, which may have a tackifying function.
A styrene resin is preferable as a resin that does not yellow due to the color of the resin itself.

Further, the lower the molecular weight of the refractive index adjusting agent is, the better the compatibility with the pressure-sensitive adhesive is because of the compatibility with the main agent of the pressure-sensitive adhesive.
In the case of the refractive index adjusting agent used in the present invention, the weight average molecular weight is preferably 900 or less. The appropriate addition amount of the refractive index adjusting agent depends on the compatibility with the optical pressure-sensitive adhesive, but the refractive index adjusting function is proportional to the amount of the refractive index adjusting agent. If the amount is small, the refractive index adjusting function is not exhibited, and the refractive index of the optical pressure-sensitive adhesive depends on the refractive index of the main agent. When the selection of the refractive index adjusting agent is different from the above selection conditions or when it is added excessively, the refractive index adjusting agent is not compatible with the pressure-sensitive adhesive in the liquid and a whitening phenomenon occurs.

Even when the whitening phenomenon does not occur, the refractive index adjusting agent bleeds out in the optical adhesive,
Non-uniformity of optical properties due to separation of adhesive or crystallization
Floating and uneven adhesive characteristics for optical use will occur. In the case of the present invention, in consideration of weather resistance, light resistance, and stability over time, up to 65% by weight can be added to the optical pressure-sensitive adhesive main agent.

If necessary, the diluent solvent can be used without particular limitation. An organic solvent is particularly desirable, and examples thereof include toluene, xylene, hexane, cyclohexanone, ethyl acetate, methyl ethyl ketone and the like. The pressure-sensitive adhesive used in the optical pressure-sensitive adhesive layer preferably has a solvent content of 0.5% or less in the dried layer. When such a material is used, it is possible to further prevent the generation of voids due to foaming between the adhered film, plate material and glass, which brings about a preferable result, and prevents foaming due to outgas generated from the adhesive layer in adhesion durability. Can be prevented.

In the present invention, the thickness of the optical pressure-sensitive adhesive layer may be arbitrarily set, but is preferably 10 to 50 μm. The sheet-like material used as the substrate for providing the optical pressure-sensitive adhesive layer is not particularly limited, for example, glass,
Polyester resin sheet, olefin resin sheet,
There are polyphenylene sulfide resin sheet, triacetate resin sheet, acrylic resin sheet, polyimide resin sheet, polycarbonate resin sheet and norbornene resin sheet. The thickness of the sheet is not particularly limited, but is preferably less than 500 μm, more preferably 10 to 50 μm. In order to protect the optical pressure-sensitive adhesive layer, it can be used in combination with a release liner or the like, if necessary. The release liner is not particularly limited, for example,
Examples thereof include paper, cloth, glass, ceramics, metal plates, antireflection films, acrylic plates, PET films, olefin resin films, PPS resin films, TAC films, acrylic resin films, and those obtained by subjecting these to release treatment. It is also possible to reduce the outgas during use by performing heat treatment at a temperature higher than the process temperature when the release liner or the material to be conveyed is attached. Release liner
The thickness is not particularly limited, but is preferably less than 500 μm, and more preferably 10 to 50 μm.

The method for providing the optical pressure-sensitive adhesive layer on the substrate or the release film is not particularly limited, and may be a bar, an applicator, a brush, a spray, a roller, a gravure coater, a die coater, a lip coater, a comma coater, The coating method using a knife coater, a reverse coater, a spin coater, etc. is illustrated. The drying method is not particularly limited, and examples thereof include hot air drying, infrared rays, and a method using a reduced pressure method. The drying condition depends on the curing form of the optical pressure-sensitive adhesive, the film thickness and the selected solvent, but it is 60-
It may be about 180 ° C.

There is no particular limitation on the structure of the optical adhesive thus coated. Examples include release liner / optical pressure-sensitive adhesive layer / release liner, release liner / optical pressure-sensitive adhesive layer / various optical films, release liner / optical pressure-sensitive adhesive layer / light guide plate, release liner / optical pressure-sensitive adhesive layer / liquid crystal cell, and the like. To be In particular, in the case of the structure of release liner / optical pressure-sensitive adhesive layer / release liner, the optical pressure-sensitive adhesive layer surface is smooth, so that it has excellent optical characteristics, and after peeling off the release liner, it is transferred to a substrate and an adherend. By doing so, the optical pressure-sensitive adhesive layer can be provided regardless of the substrate. The method of sticking the optical pressure-sensitive adhesive layer and the base material is not particularly limited, and examples thereof include pressure bonding using a roll.

[0015]

EXAMPLES Example 1 Weight average molecular weight (Mw) 500,000, polydispersity (Mw / M
n) 65 parts by weight of a styrene polymer (Picolastic A-5, manufactured by Eastman Chemical Co.) having a weight average molecular weight (Mw) of 430 per 100 parts by weight of an acrylic resin of 3.5 and toluene / ethyl acetate as a diluting solvent = 105 parts by weight of the 1/1 mixed solvent was mixed to obtain an optical pressure-sensitive adhesive. The optical pressure-sensitive adhesive is applied to a silicone-treated polyester film using an applicator, and a hot air drier is used to obtain 100
After drying at 1 ° C. for 1 minute to provide an optical pressure-sensitive adhesive layer having a thickness of 27.5 μm, a silicone-treated polyester film was laminated using a laminator to prepare an optical pressure-sensitive adhesive sheet. The optical pressure-sensitive adhesive sheet thus prepared was evaluated in the following items 1 to 6, and the results are shown in Table 1.

Example 2 Weight average molecular weight (Mw) 750,000, polydispersity (Mw / M
n) 65 parts by weight of a styrene polymer (Picolastic A-5, manufactured by Eastman Chemical Co.) having a weight average molecular weight (Mw) of 430 per 100 parts by weight of an acrylic resin of 3.5 and toluene / ethyl acetate as a diluting solvent = 105 parts by weight of the 1/1 mixed solvent was mixed to obtain an optical pressure-sensitive adhesive. The optical pressure-sensitive adhesive is applied to a silicone-treated polyester film using an applicator, and a hot air drier is used to obtain 100
After drying at 1 ° C. for 1 minute to provide an optical pressure-sensitive adhesive layer having a thickness of 27.5 μm, a silicone-treated polyester film was laminated using a laminator to prepare an optical pressure-sensitive adhesive sheet. Add the following 1 to the optical pressure-sensitive adhesive sheet thus created.
Evaluations from 6 to 6 were made, and the results are shown in Table 1.

Example 3 Weight average molecular weight (Mw) 500,000, polydispersity (Mw / M
n) 40 parts by weight of a styrene polymer (Picolastic A-5, manufactured by Eastman Chemical Co.) having a weight average molecular weight (Mw) of 430 per 100 parts by weight of an acrylic resin of 3.5 and toluene / ethyl acetate = as a diluting solvent. 105 parts by weight of the 1/1 mixed solvent was mixed to obtain an optical pressure-sensitive adhesive. The optical pressure-sensitive adhesive is applied to a silicone-treated polyester film using an applicator, and a hot air drier is used to obtain 100
After drying at 1 ° C. for 1 minute to provide an optical pressure-sensitive adhesive layer having a thickness of 27.5 μm, a silicone-treated polyester film was laminated using a laminator to prepare an optical pressure-sensitive adhesive single-layer sheet. The optical pressure-sensitive adhesive sheet thus prepared was evaluated in the following items 1 to 6, and the results are shown in Table 1.

Comparative Example 1 Weight average molecular weight (Mw) 750,000, polydispersity (Mw / M
n) 40 parts by weight of a styrene polymer (Picolastic A-75, manufactured by Eastman Chemical Co.) having a weight average molecular weight (Mw) of 1350 and 100 parts by weight of an acrylic resin of 3.5 and toluene / ethyl acetate = as a diluting solvent. 105 parts by weight of the 1/1 mixed solvent was mixed to obtain an optical pressure-sensitive adhesive. The optical pressure-sensitive adhesive is applied to a silicone-treated polyester film by using an applicator, and a hot air dryer is used to
After drying at 00 ° C for 1 minute to provide an optical adhesive layer having a thickness of 27.5 µm, a silicone-treated polyester film was laminated using a laminator to prepare an optical adhesive sheet. The optical pressure-sensitive adhesive sheet thus prepared was evaluated in the following items 1 to 6, and the results are shown in Table 1.

Comparative Example 2 Weight average molecular weight (Mw) 500,000, polydispersity (Mw / M
n) 20 parts by weight of a rosin ester resin (Pine Crystal KE-100, manufactured by Arakawa Chemical Industries, Ltd.) having a weight average molecular weight (Mw) of 840 per 100 parts by weight of an acrylic resin of 3.5 and toluene / ethyl acetate = 1 as a diluting solvent. 105 parts by weight of the / 1 mixed solvent was mixed to obtain an optical pressure-sensitive adhesive. The optical pressure-sensitive adhesive is applied to a silicone-treated polyester film using an applicator, and a hot air drier is used to obtain 100
After drying at 1 ° C. for 1 minute to provide an optical pressure-sensitive adhesive layer having a thickness of 27.5 μm, a silicone-treated polyester film was laminated using a laminator to prepare an optical pressure-sensitive adhesive sheet. Add the following 1 to the optical pressure-sensitive adhesive sheet thus created.
An evaluation of ~ 6 was performed. The results are shown in Table 1.

Comparative Example 3 Weight average molecular weight (Mw) 500,000, polydispersity (Mw / M
n) 40 parts by weight of a rosin ester resin (Pine Crystal KE-100, manufactured by Arakawa Chemical Industries, Ltd.) having a weight average molecular weight (Mw) of 840 in 100 parts by weight of an acrylic resin of 3.5 and toluene / acetic acid as a diluent solvent. Ethyl = 1
105 parts by weight of the / 1 mixed solvent was mixed to obtain an optical pressure-sensitive adhesive. The optical pressure-sensitive adhesive is applied to a silicone-treated polyester film using an applicator, dried at 100 ° C. for 1 minute using a hot air drier to provide an optical pressure-sensitive adhesive layer having a thickness of 27.5 μm, and then a laminator is used. Then, a silicone-treated polyester film was laminated to prepare an optical pressure-sensitive adhesive sheet. The optical pressure-sensitive adhesive sheet thus prepared was evaluated in the following items 1 to 6, and the results are shown in Table 1.

Evaluation item 1 (appearance at the time of coating) The optical adhesive coatings of Examples 1 to 3 and Comparative Examples 1 to 3 were visually observed after drying, and those having transparency were evaluated as good. The white turbid material was whitened.

Evaluation item 2 (refractive index) Regarding the optical pressure-sensitive adhesive sheet having good evaluation 1, the optical pressure-sensitive adhesive sheet side was peeled off using an Abbe refractometer (manufactured by Atago Co., Ltd.) after peeling off the silicone-treated polyester film. The refractive index of the optical adhesive layer was measured from.

Evaluation Item 3 (Visible Light Transmittance) With respect to the optical pressure-sensitive adhesive sheet having a good evaluation 1, a total light transmittance measuring device (model UV-160A, manufactured by Shimadzu Corporation) was used after peeling off the silicone-treated polyester film. The total light transmittance was measured.

Evaluation item 4 (heat resistance test) With respect to the optical pressure-sensitive adhesive sheet having good evaluation 1, the silicone-treated polyester film was peeled off, and then laminated on the polycarbonate and the transparent acrylic plate by using a laminator and set to 80 ° C. Vessel (model FC-41
0, manufactured by ADVANTEC Co., Ltd.) for 500 hours, and visually observed for appearance change such as floating, peeling, generation of bubbles, color tone, and turbidity from the optical pressure-sensitive adhesive sheet. The item was marked as x.

Evaluation item 5 (heat and humidity resistance test) Regarding the optical pressure-sensitive adhesive sheet with good evaluation 1, the silicone-treated polyester film was peeled off, and then laminated on the polycarbonate and the transparent acrylic plate using a laminator, and set at 60 ° C. 90%. After putting it in the constant temperature and humidity layer (model LHL-12, manufactured by Tabashi Co., Ltd.) for 500 hours, visually observing the appearance change such as floating, peeling, bubble generation, color tone, and turbidity from the optical adhesive sheet. , Those with no change were marked with ○.

Evaluation item 6 (Change in color with time) With respect to the products evaluated as ◯ in the evaluations 4 and 5, the silicone-treated polyester film was peeled off, and then laminated on the polycarbonate and the transparent acrylic plate by using a laminator, and the temperature was 80 ° C. , Humidity set to 95%, 250
The optical adhesive film that had been subjected to the time treatment was evaluated with a ΔE value with a spectrocolorimeter (model H-CT, manufactured by Suga Test Instruments Co., Ltd.) to evaluate the change in color with time.

[Table 1] From Evaluation 1, the optical pressure-sensitive adhesive sheets of Examples 1 to 3 and Comparative Example 2 having a molecular weight of 900 or less were not whitened until the mixture amount of the refractive index adjusting agent was 0 to 20 Phr for both the styrene resin and the rosin ester resin. Can be dispersed, but Comparative Example 1
Of an optical pressure-sensitive adhesive sheet having a molecular weight of 900 or more, and Comparative Example 3
It can be seen that the optical pressure-sensitive adhesive sheet using the refractive index adjusting agent of rosin-based ester resin described above becomes white when the mixed amount exceeds 40 Phr.

From the evaluation 2, the mixture amount of the refractive index adjusting agent is 40
Example 1 in which the refractive index adjusting agent is a styrene-based resin when Phr is used
The optical pressure-sensitive adhesive sheets of Nos. 3 to 3 have a refractive index of 1.5 or more, but the optical pressure-sensitive adhesive of Comparative Example 2 of rosin ester could only be increased to about 1.48. Further, the optical adhesives of Examples 1 and 2 of styrene resin having a molecular weight of 900 or less can be mixed up to 65 Phr, so that the refractive index could be increased to 1.518.

From the evaluation 3, the refractive index adjusting agent having a rosin ester resin is 94.0% when the amount of 40 Phr is mixed, while the molecular weight is 900 or less and the optical properties of Examples 1 to 3 of the styrene resin are shown. It was found that the adhesive sheet can maintain the total light transmittance of 94.1% even when mixed up to 65 Phr.

Heat resistance and heat and humidity evaluations were carried out on the evaluations from Evaluations 4 and 5 to Evaluations 1 to 3, and as shown in Examples 1 to 3, the refractive index adjusting agent of styrene resin having a molecular weight of 900 or less was obtained. The optical pressure-sensitive adhesive sheet using is 20 to 65
80 ℃ × 500hr ・ 6 even if the mixing amount is adjusted up to Phr
While no change in appearance was observed after 0 ° C x 90% x 500 hours, the optical adhesion using the rosin ester of Comparative Example 2 with the refractive index adjuster caused floating, peeling, and air bubbles between the polycarbonate / optical adhesion layers. did.

According to the evaluation 6, those of Examples 1 to 3 are 60 ° C.
It was found that there was no significant change even when the changes in the color after 90% × 250 hours were compared.

Claims (4)

[Claims] 1. An optical pressure-sensitive adhesive comprising a pressure-sensitive adhesive base material made of an acrylic resin and having a weight average molecular weight of 900 or less and a refractive index adjusting agent having styrene as a monomer unit up to 65% by weight. Agent. 2. The optical pressure-sensitive adhesive according to claim 1, wherein the acrylic resin has a weight average molecular weight of 500,000 or more. 3. Polydispersity of acrylic resin (Mw / Mn)
Is 5 or less, The optical pressure-sensitive adhesive according to claim 1 or 2, characterized in that. 4. An optical pressure-sensitive adhesive sheet, characterized in that the optical pressure-sensitive adhesive according to any one of claims 1 to 3 is sandwiched between a release sheet and / or a base material.