JP2001081428A - Adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive sheet which strongly adheres to a light transmission plastic film even in a high temperature atmosphere in a manufacturing process for liquid crystal display panels without occurrence of air involvement caused by the volatilization of volatile components and smoothly enables the progression of precision operations in the step of manufacturing liquid crystal display panels. SOLUTION: An adhesive sheet has a substrate resin sheet and a pressure- sensitive adhesive layer formed thereon, and strongly adheres to a light transmission plastic film to be placed thereon before irradiation with ultraviolet rays and reduces the adhesive power after the irradiation with ultraviolet rays to enable easy peeling from the light transmission plastic film, and the content of volatile components in the pressure-sensitive adhesive which are volatilized on heating the adhesive sheet before the irradiation with ultraviolet rays is not more than 3 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an adhesive sheet used for producing a liquid crystal display panel.

[0002]

2. Description of the Related Art Conventionally, in a liquid crystal display panel,
Glass, resin sheets, and the like are used for substrates, but the amount of resin sheets used has been gradually increasing due to recent demands for lighter, thinner and smaller electronic devices.

When a liquid crystal display panel is manufactured using a resin sheet, a light-transmitting metal oxide electrode, an alignment film, and the like are formed directly on two resin sheets to form a laminate. After processing, etc., the spacers are sprayed, followed by superposition of these two laminates and sealing of the peripheral part with an adhesive, injection of liquid crystal and sealing of the injection port, lamination of a polarizing plate and a color filter, etc. Had been performed.

However, when a high-precision large-area liquid crystal display panel is manufactured on a flexible resin sheet, when electrodes are formed directly on the resin sheet as in the conventional case, the Since the sheet is apt to bend, it is difficult to maintain a constant shape in a three-dimensional sense, and as a result, high-precision processing cannot be performed like processing on a glass substrate. However, there is a problem that it is difficult to secure the accuracy and to achieve automation.

[0005] Therefore, an extremely flat translucent plastic film is placed on a predetermined substrate and brought into close contact with the substrate, and various layers such as a translucent metal oxide electrode are formed on the translucent plastic film. The way was being taken. In this method, first, a light-transmitting metal oxide electrode is formed on a light-transmitting plastic film adhered to a substrate, and then an alignment film and the like are formed to form a first laminated substrate. And a spacer is placed on the alignment film. On the other hand, except that the spacers are not sprayed, a second laminated substrate is produced in the same manner as the above method, a sealing agent layer or the like is formed around the second laminated substrate, and the second laminated substrate on which the sealing agent layer is formed is formed. Then, a liquid crystal display panel is manufactured by laminating and bonding a first laminated substrate, and injecting a liquid crystal and sealing an injection port.

The substrate used in the above process does not basically constitute a liquid crystal display panel, and must be removed by peeling off at any stage of the manufacturing process. Therefore, after laminating the second laminated substrate and the first laminated substrate and then bonding and removing the two substrates, or
The substrate is peeled off and removed from one of the laminated substrates in a process before bonding, and after laminating the second laminated substrate and the first laminated substrate, the other laminated substrate is peeled off and removed. Was taking the way.

In the manufacturing process of such a liquid crystal display panel, after a light-transmitting plastic film is brought into close contact with a substrate, a process of removing the substrate from the laminated substrate is performed.
A transparent plastic film must be firmly fixed on the substrate in order to smoothly carry out precise work.

If the translucent plastic film is weakly fixed to the substrate, the translucent plastic film may be wrinkled or broken, making precise work difficult. On the other hand, after the injection of the liquid crystal and the sealing of the injection port are performed, the substrate is not required. Therefore, it is necessary to easily peel the substrate from the translucent plastic film and the laminated substrate formed thereon. There is.

[0009]

Therefore, when performing various operations on the light-transmitting plastic film, the adhesiveness with the light-transmitting plastic film is high. By irradiating ultraviolet rays, a method was adopted in which the adhesive sheet, which facilitates peeling, was fixed by inserting it between the translucent plastic film and the substrate, but such an adhesive sheet was used. Even in this case, air bubbles (hereinafter, referred to as air bites) are formed between the light-transmitting plastic film and the adhesive sheet in the heating step for forming the alignment film, and the subsequent steps require precise work. There was a problem that it became difficult.

[0010]

Means for Solving the Problems The present inventors have made intensive studies in view of the above, and have found that, in general, the pressure-sensitive adhesive layer for bonding a light-transmitting plastic film formed on an adhesive sheet is used. It has been found that the volatile component is contained, and that the volatile component is volatilized by heating or the like, thereby causing air biting, thereby completing the present invention.

That is, the adhesive sheet of the present invention comprises a base resin sheet and a pressure-sensitive adhesive layer formed thereon. Before irradiation with ultraviolet rays, the adhesive sheet is strongly adhered to the translucent plastic film placed thereon. On the other hand, after being irradiated with ultraviolet light, the adhesive sheet has a reduced adhesive strength, and is an adhesive sheet configured to be easily peeled off from the light-transmitting plastic film. The content of a volatile component in the pressure-sensitive adhesive layer, which volatilizes when the conductive sheet is heated, is 3% by weight or less. Hereinafter, the present invention will be described in detail.

The adhesive sheet of the present invention comprises a base resin sheet and a pressure-sensitive adhesive layer formed thereon, and before irradiation with ultraviolet rays, a translucent plastic for a liquid crystal display panel mounted thereon. The adhesive sheet is configured so that it adheres firmly to the film and, after irradiation with ultraviolet rays, has a reduced adhesive strength and can be easily peeled off from the light-transmitting plastic film.

The adhesive sheet comprises a base resin sheet made of a usual material that can transmit ultraviolet rays, and an adhesive layer formed on the base resin sheet, the adhesiveness of which changes when irradiated with ultraviolet rays in a specific wavelength range.

The base resin sheet is not particularly limited as long as it is a resin sheet capable of transmitting ultraviolet rays. Examples thereof include vinyl chloride resin, vinyl chloride-vinylidene chloride copolymer resin, and vinyl chloride-vinyl acetate copolymer. Resin sheets made of resin, polyvinylidene chloride resin, polyolefin, polyvinyl alcohol, polyamide, polyester, polycarbonate, acetyl cellulose and the like can be mentioned.

The pressure-sensitive adhesive layer is preferably composed of, for example, an acrylic resin-based pressure-sensitive adhesive, an ultraviolet-crosslinkable compound, a polymerization initiator, and the like. Examples of the acrylic resin-based pressure-sensitive adhesive include a copolymer of an acrylate monomer and another copolymerizable monomer. The copolymer of the acrylate monomer and another copolymerizable monomer uses the acrylate monomer having a low glass transition point as a main monomer to impart tackiness, while the Other copolymerizable monomers include a monomer capable of forming a hard polymer having a high glass transition point for imparting cohesiveness, and a carboxylic acid group and an amide for improving crosslinkability and adhesion. It can be obtained by using a monomer having a functional group such as a group, a glycidyl group, and a hydroxyl group.

Examples of the UV-crosslinkable compound include acrylic or methacrylic esters as oligomers or monomers which are crosslinked by irradiation with ultraviolet rays in a specific wavelength range. It preferably has an acryloyl group or a methacryloyl group.

Examples of the oligomer include oligoester acrylate, and examples of the monomer include 1,6-hexanediol acrylate, trimethylolpropane triacrylate, and the like.
Ester of polyhydric alcohol such as tetramethylol methane tetraacrylate, dipentaerythritol hexaacrylate and acrylic acid, or 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, tetramethylol methane tetraacrylate, dipentaerythritol hexaacrylate An ester of a polyhydric alcohol such as acrylate and methacrylic acid can be exemplified. In addition, urethane acrylate, epoxy acrylate and the like can also be mentioned.

In preparing the pressure-sensitive adhesive layer, for example,
It is preferable to add 5-150 parts by weight of the above-mentioned ultraviolet-crosslinkable compound to 100 parts by weight of the acrylic resin-based pressure-sensitive adhesive. In addition, a weight part shows the ratio of the weight of a solid content. More preferably, 10 to 100 parts by weight are added.

The polymerization initiator is used to promote crosslinking of the ultraviolet-crosslinkable compound by irradiation with ultraviolet rays. In the present invention, a conventionally known polymerization initiator can be used. Examples of these polymerization initiators include benzoin alkyl ethers such as benzoin methyl ether and benzoin propyl ether, aromatic oxyketones such as benzoin, benzyl and benzophenone, aromatic ketones, benzyl dimethyl ketal, and polyvinyl benzophenone. be able to. The amount of the polymerization initiator is preferably 0.1 to 20 parts by weight based on 100 parts by weight of the elastic polymer. More preferably,
0.5 to 10 parts by weight.

The above-mentioned pressure-sensitive adhesive layer may further contain a tackifier and the like. The tackifier is not particularly limited,
What has been conventionally used as an adhesive can be used. As such a tackifier, for example,
Modified rosin resins such as xylene resin, rosin and polymerized rosin, hydrogenated rosin and rosin ester, terpene resins such as terpene resin, terpene phenol resin and rosin phenol resin, aliphatic, aromatic and alicyclic petroleum resin,
Coumarone resin, styrene resin, alkylphenol resin and the like can be mentioned. The amount of the tackifier is preferably 1 to 100 parts by weight based on 100 parts by weight of the elastic polymer. More preferably, it is 5 to 50 parts by weight.

An appropriate amount of an organic solvent, such as an aromatic hydrocarbon, which dissolves each of the components constituting the pressure-sensitive adhesive layer, is used.
By adding and dissolving a ketone or a mixture thereof, a solution composition having a uniform composition for forming an adhesive layer can be obtained. The above pressure-sensitive adhesive layer can be formed by applying and drying by a more known method.

The adhesive sheet is firmly adhered to a light-transmitting plastic film placed thereon before irradiation with ultraviolet light, while the adhesive force is reduced after irradiation with ultraviolet light, and It is configured so that it can be easily peeled off from the film.

Examples of the translucent plastic film include polycarbonate, polyether sulfone, polyarylate, polyethylene terephthalate, polyethylene-2,6-naphthalate, polyether-ether ketone, and the like.

In the manufacturing process of the liquid crystal display panel, when various layers are formed on the translucent plastic film by using a physical method or a chemical method, various forces are applied to the translucent plastic film. Acts on conductive plastic films.

When forming an alignment film, it is necessary to heat these systems, so that the temperature of the entire system including the adhesive sheet rises.
Even at a temperature of 0 ° C., the adhesive strength between the translucent plastic film and the adhesive sheet is configured to be strong.

However, the pressure-sensitive adhesive layer formed on the base resin sheet contains a volatile component even after drying, and the volatile component volatilizes when the temperature is increased as described above. As a result, an air bite is formed between the adhesive sheet and the translucent plastic film.

Therefore, in the present invention, the amount of the volatile component in the pressure-sensitive adhesive layer, which volatilizes when the adhesive sheet is heated, is reduced to 3% by weight.
It was decided to reduce to below. At this time, when the content of the volatile component is around 3% by weight, a very small air bite may be generated. In this case, however, in a later step, the light-transmitting plastic film adhered to the adhesive sheet is displaced. No peeling or the like occurs and there is no practical problem.

By reducing the amount of the volatile component as described above, it is possible to prevent air from being caught between the adhesive sheet and the translucent plastic film when a liquid crystal display panel is manufactured. When the content of the volatile component exceeds 3% by weight, a considerable amount of the volatile component is volatilized during the production of the liquid crystal display panel, thereby causing air biting. In order to completely eliminate the occurrence of air entrapment, the content of the volatile component is more preferably 1% by weight or less. When measuring the content of volatile components, the heating temperature is usually 10
0 ° C. or higher is required, and 100 to 200 ° C. is more preferable.

The method for reducing the amount of the volatile component in the pressure-sensitive adhesive layer is not particularly limited. For example, a method for selecting the type and amount of the material used in preparing the pressure-sensitive adhesive layer and the type of the organic solvent , A method of adjusting the amount of the organic solvent, a method of selecting drying conditions, and the like.

In the adhesive sheet of the present invention, since the amount of the volatile component is greatly reduced, even at a high temperature of 100 to 200 ° C., the adhesive sheet and the light-transmitting plastic film adhere firmly, No air bites are formed.

Thereafter, various layers are formed on the translucent plastic film constituting the adhesive sheet. At this time, there is a gap between the translucent plastic film and the adhesive sheet. Peeling does not occur, and a layer having a correct shape can be formed at a correct position.

On the other hand, when the adhesive sheet of the present invention is irradiated with ultraviolet light, the adhesive force between the adhesive sheet of the present invention and the light-transmitting plastic film decreases, and the adhesive sheet of the present invention is removed from the light-transmitting plastic film. The flexible sheet can be easily peeled off.

As a result of the decrease in the adhesive strength of the adhesive sheet, for example, when the steps of forming a plurality of layers on the translucent plastic film and manufacturing the liquid crystal display panel are completed, for example, By irradiating ultraviolet rays using a high-pressure mercury lamp, the adhesive sheet of the present invention can be easily peeled off, and a target laminate for a liquid crystal display panel can be easily obtained.

The method of irradiating the pressure-sensitive adhesive layer with ultraviolet rays is not particularly limited, and a conventionally used method can be used. For example, a xenon lamp, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, or an ultra-high-pressure A method of irradiating for several seconds to several minutes using an ultraviolet light source such as a mercury lamp can be used.

The configuration of the surface of the adhesive sheet of the present invention that is in contact with the substrate is not particularly limited as long as the adhesive sheet retains such an adhesive strength that it is not easily peeled off from the substrate even after irradiation with ultraviolet rays.
Examples of such a surface configuration include, for example, an embodiment in which an adhesive layer formed by removing the polymerization initiator from the pressure-sensitive adhesive layer is formed on the substrate-side surface of the resin base sheet. Can be.

FIG. 1 shows one embodiment in which a translucent plastic film is fixed on a substrate using the adhesive sheet of the present invention. An adhesive sheet 20 including an adhesive layer 12, a base resin sheet 13, and an adhesive layer 14 is attached to a base 11 made of glass or the like such that the adhesive layer 12 side is in contact with the adhesive sheet. Thereafter, the translucent plastic film 15 is placed on the pressure-sensitive adhesive layer 14, and the substrate 1 is placed via the adhesive sheet 20.
A translucent plastic film 15 is fixed on 1. Before irradiation with ultraviolet light, the transparent plastic film 15 is attached to the adhesive sheet 2 at the time of heating and at room temperature.
Although the adhesive layer 14 is firmly adhered to the base 11 via the adhesive layer 14, the transparent plastic film 15 can be easily peeled off from the adhesive sheet 20 and the base 11 by irradiating the pressure-sensitive adhesive layer 14 with ultraviolet rays.

[0037]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In addition, regarding the compounding amount of each component in the following Examples and Comparative Examples, those other than the solvent are parts by weight of solid content.

Example 1 First, 100 parts by weight of an acrylic resin-based pressure-sensitive adhesive (Alontack S-1601 manufactured by Toa Gosei Chemical Co., Ltd.) and an ultraviolet-crosslinkable compound (Aronix M-400 manufactured by Toa Gosei Chemical Co., Ltd.) 5
0 parts by weight, 1.6 parts by weight of a photopolymerization initiator (manufactured by Ciba Specialty Chemicals, Irgacure 500), 16 parts by weight of a tackifier (manufactured by Arakawa Chemical Industries, KE-604), and 33 parts by weight of methyl ethyl ketone The parts were mixed in the above ratio in a container to prepare a solution composition for forming an adhesive layer.

Next, the obtained solution composition was applied to a thickness of 38
μm polyethylene terephthalate (PET) and dried at 120 ° C. for 1 minute to obtain 20 μm
A pressure-sensitive adhesive layer having a thickness of 2 was formed to prepare an adhesive sheet.

With respect to the obtained adhesive sheet, release PE
After peeling off T, the adhesive strength at room temperature before UV irradiation, the presence or absence of air bite at 130 ° C. before UV irradiation, and the adhesive strength with polycarbonate (PC) film at room temperature after UV irradiation Was measured using the method described below and evaluated. The results are shown in Table 1.

[Evaluation Method] (1) Measurement of Volatile Component Content 7 to 9 mg of the pressure-sensitive adhesive layer was weighed from the adhesive sheet, and held at 130 ° C. for 1 hour using TG / DTA manufactured by Seiko Co., Ltd. Was measured.

(2) Measurement of Adhesive Strength Before Irradiation with Ultraviolet Light The obtained adhesive sheet was cut into a width of 25 mm and a length of 100 mm. The sample was left and right at room temperature for 20 minutes to form a test piece. Next, using an Instron 1175 type testing machine, at room temperature,
The test piece was subjected to a 90 ° peel test under the condition of a tensile speed of 300 mm / min, and the adhesive strength was measured.

(3) Measurement of Air Bite at 130 ° C. Before Irradiation with Ultraviolet Light The adhesive sheet was cut into a width of 50 mm and a length of 100 mm.
This was superimposed on a PC film in such a manner that no air bubbles were formed, and reciprocated 5 times with a 3 kg roller to be pressed and adhered. Thereafter, the adhesive sheet adhered to the PC film in the above step and the fixing glass were adhered with a two-component curable epoxy-based adhesive, and left for 1 hour to obtain a test piece.

The test piece was placed in an oven at 130 ° C. for 2 hours and then taken out. The presence or absence of air biting was visually observed using a loupe, and evaluated according to the following criteria. ◎: Air bite is not observed at all ○: 1 to 3 air bites are observed ×: 5 or more air bites are observed

(4) Measurement of Adhesion Force after Irradiation with Ultraviolet Light A test piece similar to the test piece used at the time of measurement of the adhesion force before irradiation with ultraviolet light was prepared, and a main wavelength of 365 nm, 120 W was applied to this test piece from the polyethylene terephthalate side. / Cm for 7 seconds. Then, Instron 1175
The test piece was subjected to a 90 ° peel test at room temperature at a tensile speed of 300 mm / min using a mold type testing machine, and the adhesive strength was measured.

Example 2 The procedure of Example 1 was repeated, except that Dytocure IP was used as the photopolymerization initiator instead of using Irgacure 500 manufactured by Ciba Specialty Chemicals.
An adhesive sheet having a pressure-sensitive adhesive layer formed on a PET film was prepared, and various characteristics were measured in the same manner as in Example 1.
An evaluation was performed. The results are shown in Table 1.

Example 3 A PET film was formed on a PET film in the same manner as in Example 1 except that 10 parts by weight of Dytocure IP was used as the photopolymerization initiator instead of using Irgacure 500 manufactured by Ciba Specialty Chemicals. An adhesive sheet having a pressure-sensitive adhesive layer formed thereon was prepared, and various characteristics were measured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1 The procedure of Example 1 was repeated except that 200 parts by weight of Aronix M-9050 manufactured by Toa Gosei Chemical Co., Ltd. were used instead of Alonix M-400 manufactured by Toa Gosei Chemical Co., Ltd. as the ultraviolet-crosslinkable compound. Similarly, an adhesive sheet having a pressure-sensitive adhesive layer formed on a PET film was produced, and various properties were measured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0049]

[Table 1]

As shown in Table 1 above, the adhesive sheet used in the examples had a volatile component content of 3% by weight or less in the pressure-sensitive adhesive layer at a temperature of 130 ° C. The adhesive strength between the conductive sheet and the translucent plastic film is very large, and no air biting occurs between them due to volatilization of volatile components. Therefore, even in the step of manufacturing the liquid crystal display panel, the translucent plastic film is not displaced or peeled off, and the liquid crystal display panel can be satisfactorily manufactured.

[0051]

Since the adhesive sheet of the present invention has the above-mentioned structure, the adhesive sheet and the light-transmitting plastic film are strongly adhered to each other, and the volatile component can be obtained even in a high-temperature atmosphere in the process of manufacturing a liquid crystal display panel. Due to the volatilization of
No air biting occurs. As a result, precise operations in the process of manufacturing the liquid crystal display panel can be smoothly performed.

[Brief description of the drawings]

FIG. 1 is a view showing an embodiment in which a light-transmitting plastic film is fixed on a substrate using an adhesive sheet of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Base 12 Adhesive layer 13 Base resin sheet 14 Adhesive layer 15 Translucent plastic film 20 Adhesive sheet

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yoshio Taguchi 3-2-15 Meiwadori, Hyogo-ku, Kobe Bando Chemical Co., Ltd. F-term (reference) 4F100 AK01A AK25 AK42 AR00B BA02 CA16 CA30 GB41 JB14B JB20B JL00 JL01 JL13B JL14B YY00B 4J004 AA01 AA10 AA17 AB01 CA02 CA03 CA04 CA05 CA06 CC02 FA10

Claims (3)

[Claims] 1. A method comprising a base resin sheet and a pressure-sensitive adhesive layer formed thereon, and before being irradiated with ultraviolet light, while firmly adhering to a light-transmitting plastic film placed thereon,
After the ultraviolet irradiation, the adhesive force is reduced, the adhesive sheet is configured so that it can be easily peeled from the translucent plastic film, and before the ultraviolet irradiation, the adhesive sheet was heated. The adhesive sheet, wherein the content of the volatile component in the pressure-sensitive adhesive layer volatilized at that time is 3% by weight or less. 2. The adhesive according to claim 1, wherein the content of a volatile component in the pressure-sensitive adhesive layer, which is volatilized when the adhesive sheet is heated before irradiation with ultraviolet rays, is 1% by weight or less. Sheet. 3. The temperature for heating the adhesive sheet is 100.
The adhesive sheet according to claim 1, wherein the temperature is −200 ° C. 3.