KR101374511B1 - Adhesive, double-sided adhesive sheet and display - Google Patents

Abstract

The present invention can provide a pressure-sensitive adhesive layer that can form a pressure-sensitive adhesive layer that is difficult to peel even when the adherend is deformed, and exhibits sufficient adhesive strength even when the thickness of the pressure-sensitive adhesive layer is reduced to about 10 μm. The pressure-sensitive adhesive of the present invention includes an acrylic ester resin having a weight average molecular weight of 500,000 to 1.5 million, a tackifying resin having an alcoholic hydroxyl group having a hydroxyl value of 35 or more, and a terpene phenol resin measured as polystyrene reduced molecular weight by GPC method. The gel fraction is 5 to 40% by weight.

Adhesive, double sided adhesive sheet, display device

Description

Adhesive, Double Sided Adhesive Sheet, and Display Device {ADHESIVE, DOUBLE-SIDED ADHESIVE SHEET AND DISPLAY}

According to the present invention, a pressure-sensitive adhesive capable of forming an adhesive layer that is difficult to be peeled off even when the adherend is deformed, a double-sided adhesive sheet containing the pressure-sensitive adhesive layer made of the pressure-sensitive adhesive, and a double-sided adhesive sheet are bonded to the display panel and the backlight. It relates to a display device.

Recently, liquid crystal displays (LCD modules) have been used in many electric devices such as televisions, personal computers and mobile phones. This liquid crystal display device is comprised by members, such as a liquid crystal panel, a drive circuit (driver IC) arrange | positioned in the periphery of a liquid crystal panel, and the backlight etc. which adhere to the back surface of a liquid crystal panel.

The said backlight is a member used as a light source of a liquid crystal display device, and optical sheets, such as a cold cathode tube, a reflecting plate, a light guide plate, a diffuser plate, and a prism sheet, are arrange | positioned in this order in a backlight body. The surface of the backlight is in a state where the optical sheet is exposed from the opening of the backlight housing.

In addition, since a thickness and width can be easily controlled and can be made to stick easily, the double-sided adhesive sheet is used for adhesion | attachment with a liquid crystal panel and a backlight at the time of manufacture of the said liquid crystal display device. In the adhesion method between the liquid crystal panel and the backlight by the double-sided adhesive sheet, the back surface of the double-sided adhesive sheet punched in a frame shape so as to have a width of 0.5 to 1.0 mm on both surfaces of the backlight and the optical body and optical sheet; Adhesive to touch. Moreover, the surface of a double-sided adhesive sheet is stuck to the back surface of a liquid crystal panel. Thus, the method of sticking a liquid crystal panel and a backlight through a double-sided adhesive sheet is used. Here, the double-sided adhesive sheet not only serves to adhere the liquid crystal panel and the backlight but also has a role of fixing the position of the optical sheet exposed from the opening of the backlight housing.

In recent years, with the miniaturization and thickness reduction of liquid crystal display device mounting apparatuses, such as a mobile telephone, the small size and thin liquid crystal display device is calculated | required, and the miniaturization and thickness reduction are also required also in the double-sided adhesive sheet which comprises a liquid crystal display device.

And since the member which comprises a liquid crystal display device tends to generate | occur | produce distortion, such as curvature, by its thinning, in the double-sided adhesive sheet corresponding to miniaturization and thinning of a liquid crystal display device, it is suitable for the deformation of a liquid crystal panel and a backlight. It is necessary to be able to withstand the peeling stress which arises. Moreover, since high precision is calculated | required by the dimension of the adhesion position of a liquid crystal panel and a backlight by miniaturization of a liquid crystal display device, the double-sided adhesive sheet which is hard to be deformed by the shear force applied at the time of punching process is calculated | required.

As a double-sided adhesive sheet which can respond to the miniaturization and thinning of such a liquid crystal display device, Patent Document 1 describes an acrylic copolymer having a weight average molecular weight of 80 to 1.5 million on both sides of the base material, and an unbalanced rosin ester, a polymerized rosin ester, and a petroleum resin. The double-sided adhesive tape which has the adhesive layer which consists of 1 or more types of tackifying resin chosen from is proposed.

However, when the said double-sided adhesive tape is thinned to about 10 micrometers in thickness, it becomes easy to peel by the peeling stress which arises by deformation of a liquid crystal panel or a backlight. In addition, there arises a problem that deformation occurs due to the shear force applied during punching. Therefore, it has not been able to sufficiently cope with the recent downsizing and thinning of the liquid crystal display device.

Patent Document 1: Japanese Patent Laid-Open No. 2005-97393

DISCLOSURE OF THE INVENTION <

[PROBLEMS TO BE SOLVED BY THE INVENTION]

This invention can form the adhesive layer which is hard to peel even if a to-be-adhered body deform | transforms, The adhesive double-sided adhesive sheet which consists of an adhesive which expresses sufficient adhesive force even if it makes thin the thickness of an adhesive layer to about 10 micrometers, and the said adhesive layer is contained. And a liquid crystal display device having excellent reliability in which a display panel and a backlight are adhered to each other through the double-sided adhesive sheet.

MEANS FOR SOLVING THE PROBLEMS [

The pressure-sensitive adhesive of the present invention is an acrylic ester resin having a weight average molecular weight of 500,000 to 1.5 million and an alcoholic hydroxyl group measured as polystyrene reduced molecular weight by GPC (gel permeation chromatography) method, and having a hydroxyl value of 35 or more. And a terpene phenol resin, and the gel fraction is 5 to 40% by weight.

As the acrylate ester resin constituting the pressure-sensitive adhesive, an acrylate alkyl ester resin obtained by homopolymerizing an alkyl acrylate ester monomer, a methacrylic acid alkyl ester resin obtained by homopolymerizing an alkyl methacrylate monomer, and two or more kinds of acrylate alkyl ester monomers Acrylate alkylester resin formed by copolymerizing, methacrylate alkylester resin formed by copolymerizing two or more kinds of methacrylic acid alkylester monomers, copolymers of acrylate alkylester monomers and methacrylic acid alkylester monomers, acrylate alkylester monomers or And copolymers of any one or both of the methacrylic acid alkyl ester monomers with other vinyl monomers copolymerizable therewith, and alkyl acrylate ester monomers or methacrylic acid alkyl esters. And either or both of the dimer, are preferred copolymers of this and the other copolymerizable vinyl monomer.

Although it does not specifically limit as said alkyl acrylate monomer, What is obtained by esterification of the primary or secondary alkyl alcohol of C1-C12 of an alkyl group with acrylic acid is preferable, Specifically, ethyl acrylate and acrylic acid Butyl, 2-ethylhexyl acrylate, etc. are mentioned, It is preferable to contain ethyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate. In addition, the said alkyl acrylate monomer may be used independently and 2 or more types may be used together.

When there is little content of the ethyl acrylate component in the said acrylate ester resin, it may become easy to peel from a to-be-adhered body by the peeling stress which arises by the deformation of a to-be-adhered body, and when too much, the viscosity of an adhesive is too high 5-30 weight% is preferable and 8-25 weight% is more preferable because it may become high and coatability may fall or the adhesive layer formed may become too hard.

The other vinyl monomer copolymerizable with the alkyl acrylate ester monomer or the methacrylic acid alkyl ester monomer may be modified by copolymerizing any one or both of the alkyl acrylate ester monomer or the acrylic acid alkyl ester monomer with another vinyl monomer copolymerizable therewith. It is added in order to raise the cohesion force of the adhesive obtained, For example, to raise the glass transition temperature (Tg) of an acrylic ester resin, to contribute to forming a crosslinked structure between the principal chains of an acrylic ester resin, etc. This is used.

Moreover, it does not specifically limit as a vinyl monomer which raises the glass transition temperature (Tg) of the said acrylic acid ester resin, For example, Carboxylic-containing monomers, such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid; hydroxyl group-containing monomers such as n-methylol acrylamide; Maleic anhydride, vinyl acetate, styrene, etc. are mentioned. As a vinyl monomer, since it is hard to affect the control of the molecular weight of acrylic acid ester resin, and excellent in the adhesiveness of the adhesive obtained, acrylic acid is preferable.

Since the total content of the vinyl monomer component which raises a glass transition temperature is low, the glass transition temperature of the adhesive obtained may become low too much, and the cohesion force of an adhesive may fall, and in many cases, the adhesive force and tag of the adhesive obtained may fall, 0.01-10 weight% is preferable in acrylic ester resin, and 0.05-5 weight% is more preferable.

Although it does not specifically limit as a vinyl monomer which contributes to forming a crosslinked structure between the principal chains of acrylic acid ester resin, A hydroxyl group containing acrylic acid ester and a hydroxyl group containing methacrylic acid ester are preferable.

By using either or both of the hydroxyl group-containing acrylic acid ester monomer or the hydroxyl group-containing methacrylic acid ester and the isocyanate crosslinking agent described later, it is easy to adjust the gel fraction of the pressure-sensitive adhesive to 5 to 40% by weight, and the repulsion resistance and peeling performance This excellent adhesive can be obtained.

Examples of the hydroxyl group-containing acrylic acid ester monomers include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, and 4-hydroxybutyl acrylate. And the addition of caprolactone to acrylic acid-2-hydroxypropyl.

As a hydroxyl-containing methacrylic acid ester monomer, methacrylic acid-2-hydroxyethyl, methacrylic acid-2-hydroxypropyl, methacrylic acid-3-hydroxypropyl, methacrylic acid-2-hydride, for example Addition of caprolactone to hydroxybutyl, 4-hydroxy methacrylate, 2-hydroxypropyl methacrylic acid, etc. are mentioned.

0.01-0.5 weight% is preferable and, as for the total content of a hydroxyl-containing acrylic acid ester monomer component and a hydroxyl-containing methacrylic acid ester monomer component, 0.05-0.3 weight% is more preferable.

When the total content of the hydroxyl group-containing acrylic acid ester monomer component and the hydroxyl group-containing methacrylic acid ester monomer component is small, it is difficult to increase the gel fraction of the pressure-sensitive adhesive, and a large amount of crosslinking agent is required to adjust the gel fraction of the pressure-sensitive adhesive to an appropriate gel fraction. The crosslinking of the resin proceeds with time, and the repulsion resistance of the pressure sensitive adhesive becomes unstable.

When the total content of the hydroxyl group-containing acrylic acid ester monomer component and the hydroxyl group-containing methacrylic acid ester monomer component is large, the gel fraction of the pressure sensitive adhesive tends to be increased, and it is necessary to perform with a small amount of crosslinking agent to adjust the gel fraction of the pressure sensitive adhesive to an appropriate gel fraction. This is because the variation in the gel fraction due to the variation in the amount of the crosslinking agent in the pressure-sensitive adhesive increases, so that a uniform crosslinked structure may not be obtained.

In addition, the weight average molecular weight measured as polystyrene conversion molecular weight by GPC (Gel Permeation Chromatography) method of the said acrylic acid ester resin is small, and the peeling stress which the adhesive layer formed when small is formed by deformation of a to-be-adhered body It becomes easy to peel from a to-be-adhered body, but when it is large, the adhesive force of an adhesive falls and also the adhesive layer formed becomes easy to peel from an to-be-adhered body by the peeling stress which arises by deformation of a to-be-adhered body, 500,000-150 It is limited only to 500,000-1 million, and 550,000-900,000 are more preferable.

In addition, the weight average molecular weight measured as polystyrene conversion molecular weight by the GPC method of the said acrylic acid ester resin is 50-times dilution liquid obtained by diluting acrylic acid ester resin with tetrahydrofuran (THF) with the filter, and the obtained filtration It can obtain by measuring the polystyrene conversion molecular weight of acrylic ester-type resin by gel permeation chromatography based on liquid. As the gel permeation chromatography, for example, those sold under the trade name "2690 Separations Model" by Water, Inc. can be used.

In order to obtain the acrylate ester resin, any one or both of an acrylate alkyl ester monomer or a methacrylic acid alkyl ester monomer may be copolymerized with any one or both of an acrylate alkyl ester monomer or a methacrylic acid alkyl ester monomer, if necessary. With other vinyl monomers possible, radical reactions can be carried out in the presence of a polymerization initiator. Moreover, as a polymerization method, a conventionally well-known method is used, For example, solution polymerization, emulsion polymerization, suspension polymerization, block polymerization, etc. are mentioned.

The polymerization initiator is not particularly limited, and for example, 1,1-bis (t-hexyl peroxy) -3,3,5-trimethylcyclohexane, t-hexyl peroxy pivalate, t-butylper Oxypivalate, 2,5-dimethyl-2,5-bis (2-ethylhexanoylperoxy) hexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexano And t-butylperoxy isobutyrate, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate, and the like, and 1,1-bis (t-hexylpere). Oxy) -3,3,5-trimethylcyclohexane and t-hexylperoxy pivalate are preferred. In addition, the said polymerization initiator may be used independently and 2 or more types may be used together.

The adhesive of this invention contains tackifying resin which has an alcoholic hydroxyl group, in order to form the adhesive layer which is hard to peel even if a to-be-adhered body deform | transforms an adhesive.

It does not specifically limit as tackifying resin which has the said alcoholic hydroxyl group, For example, rosin ester-type resin, hydrogenated terpene phenol resin, etc. are mentioned, Rosin ester-type resin is preferable.

The rosin ester-based resin is a dimer (polymerized rosin resin) of resins such as rosin resins, disproportionated rosin resins and hydrogenated rosin resins containing abiic acid as a main component, abiate acid, and the like. It is resin obtained by esterification, and some hydroxyl groups of alcohols used for esterification are contained in resin rather than being used for esterification. Esterized rosin resin esterified rosin ester resin, disproportionated rosin resin esterified disproportionated rosin ester resin, hydrogenated rosin resin esterified hydrogenated rosin ester resin, polymerization rosin resin Rosin ester resin.

Moreover, as alcohols used for the said esterification, polyhydric alcohols, such as ethylene glycol, glycerin, pentaerythritol, are mentioned.

Moreover, as said hydrogenated terpene phenol resin, resin obtained by hydrogenating the terpene phenol resin obtained by superposing | polymerizing a terpene in presence of phenol, for example is mentioned.

The hydroxyl value of the said tackifying resin is limited to 35 or more, and 40-60 are preferable. The adhesive layer formed when the hydroxyl value of the said tackifying resin is small easily peels from a to-be-adhered body by peeling stress generate | occur | produced by the deformation | transformation of a to-be-adhered body, and when too large, an isocyanate type crosslinking agent is added as mentioned later, and an adhesive This is because crosslinking defects may occur in the case of crosslinking. In addition, the hydroxyl value of the said tackifying resin says the value measured based on JISK0070.

And when there is little content of tackifying resin in the said adhesive, the adhesive layer formed may become easy to peel from a to-be-adhered body by the peeling stress generate | occur | produced by the deformation | transformation of a to-be-adhered body, and in many cases, an adhesive becomes hard and adhesive force and Since a tag may fall, 5-40 weight part is preferable with respect to 100 weight part of acrylic ester resin, and 8-35 weight part is more preferable.

Moreover, the adhesive of this invention contains terpene phenol resin for the purpose of improving adhesive force, especially adhesive force with respect to polycarbonate resin. The said terpene phenol resin is resin obtained by superposing | polymerizing a terpene in presence of a phenol, and the hydrogenated terpene phenol resin formed by hydrogenating a terpene phenol resin is excluded. This is because it is assumed that the ring having aromaticity in the terpene phenol resin contributes to the improvement of the adhesive force, in particular, the interaction with the polycarbonate resin.

In addition, as described above, it is assumed that the ring having an aromaticity in the terpene phenol contributes to the improvement of the adhesive strength, in particular to the interaction with respect to the polycarbonate resin. Therefore, the possibility that the other compound containing the ring which has aromaticity can be used instead of the said terpene phenol resin is also suggested.

If the softening point of the said terpene phenol resin is low, since the heat resistance of an adhesive may fall, 140 degreeC or more is preferable, and when too high, an adhesive becomes hard, adhesive force and a tag fall, and the adhesive layer formed further of the adherend Since peeling from a to-be-adhered body may become easy by peeling stress generate | occur | produced by a deformation | transformation, 145-170 degreeC is more preferable. In addition, the softening point of the said terpene phenol resin says what was measured based on JISK2207.

When the content of the terpene phenol resin in the pressure-sensitive adhesive is small, the heat resistance and adhesive force of the pressure-sensitive adhesive may decrease, while in many cases, the pressure-sensitive adhesive hardens, the pressure-sensitive adhesiveness and tag decrease, and the pressure-sensitive adhesive layer further formed is formed of the adherend. Since it may become easy to peel from a to-be-adhered body by the peeling stress generate | occur | produced by a deformation | transformation, 3-20 weight part is preferable with respect to 100 weight part of acrylic ester resin, and 5-15 weight part is more preferable.

Moreover, in the said adhesive, it is preferable to form a crosslinked structure between the principal chains of resin which comprises a crosslinking agent and comprises an adhesive. By adjusting the kind and quantity of a crosslinking agent suitably, it becomes easy to adjust the gel fraction of an adhesive to a desired range. It does not specifically limit as said crosslinking agent, For example, an isocyanate type crosslinking agent, an aziridine type crosslinking agent, an epoxy type crosslinking agent, a metal chelate type crosslinking agent, etc. are mentioned, An isocyanate type crosslinking agent is preferable. This isocyanate group in an isocyanate type crosslinking agent, and alcoholic hydroxyl group in above-mentioned tackifying resin react, and a urethane bond is formed. Therefore, it is because the adhesive layer formed by an adhesive can be made to be difficult to peel from an adherend by the peeling stress generate | occur | produced by the deformation | transformation of a to-be-adhered body.

If the amount of the crosslinking agent is small, the crosslinking of the adhesive may be insufficient. If the amount of the crosslinking agent is large, 0.5 to 1.7 parts by weight is preferable, and 0.7 to 0.7 to 100 parts by weight of the acrylic ester resin. 1.5 weight part is more preferable.

That is, even if the gel fraction of the pressure-sensitive adhesive is high or low, since the pressure-sensitive adhesive layer formed is easily peeled from the adherend due to the peeling stress generated by the deformation of the adherend, it is limited to 5 to 40% by weight, and is 10 to 40% by weight. Is preferable, and 15-35 weight% is more preferable.

As a measuring method of the gel fraction of the said adhesive, a double-sided adhesive sheet obtained as mentioned later is cut | disconnected in the plane rectangle of 50 mm x 100 mm, and a test piece is manufactured, This test piece is ethyl acetate at 23 degreeC for 24 hours. After immersion, the test piece was taken out of ethyl acetate and dried for 1 hour under the condition of 110 ° C. And the weight of the test piece after drying is measured, and a gel fraction is computed using the following formula. In addition, the release film as mentioned later shall not be laminated | stacked on the said test piece.

Gel fraction (% by weight) = 100 × (W ₂ -W ₀ ) / (W ₁ -W ₀ )

(W ₀ : weight of base material, W ₁ : weight of test piece before dipping, W ₂ : weight of test piece after dipping and drying)

Moreover, additives, such as a plasticizer, an emulsifier, a softener, a filler, a pigment, and a dye, can also be added to the adhesive of this invention as needed.

Next, the double-sided adhesive sheet by which the adhesive layer which consists of an adhesive mentioned above on both surfaces of a base material is laminated | stacked is demonstrated. It does not specifically limit as said base material, For example, Polyolefin resin films, such as a polyethylene film and a polypropylene film, Polyester resin films, such as a polyethylene terephthalate film, Ethylene-vinyl acetate copolymer film, Polyvinyl chloride-type resin A film, a polyurethane resin film, etc. are mentioned, A polyester resin film is preferable. In addition, the substrate may be black printed to prevent light transmission, white printed or metal deposited to improve light reflectivity.

When the thickness of the base material is thin, the mechanical strength of the double-sided adhesive sheet may be reduced or the handleability may be reduced, while when the thickness of the base material is thick, the elasticity of the double-sided adhesive sheet is excessively strong, and the adhesive is adhered to the adherend according to the shape of the adherend. Since it may become difficult, 3-30 micrometers is preferable and 5-25 micrometers is more preferable.

Further, if the thickness of the pressure-sensitive adhesive layer on both sides of which is laminated on both surfaces of the substrate is thick, the pressure-sensitive adhesive layer is deformed when shear stress is applied to both sides of the pressure-sensitive adhesive layer with respect to the pressure-sensitive adhesive layer, and the bonding site using the double-sided adhesive sheet. Since the thickness of both adhesive layers is 30 micrometers or less, since it may cause a shift | offset | difference in all, and if it is too thin, a double-sided adhesive sheet will become easy to peel from an adherend by the peeling stress which arises by deformation of a to-be-adhered body. In some cases, the thickness of both pressure-sensitive adhesive layers is more preferably 10 to 25 µm.

And the said double-sided adhesive sheet is normally laminated | stacked so that a release film may be peeled off on the surface of an adhesive layer in order to prevent an adhesive layer from sticking to a separate member, or to adhere dust to an adhesive layer before use. As said mold release film, the film similar to the base material mentioned above can be used, The mold release process is given to the surface which contact | connects an adhesive layer.

Next, the manufacturing method of a double-sided adhesive sheet is demonstrated. As a manufacturing method of a double-sided adhesive sheet, a solvent is added to an adhesive, for example, an adhesive solution is manufactured, this adhesive solution is apply | coated on the surface of a base material, the solvent in an adhesive solution is completely dried and removed, and an adhesive layer is formed. Next, the mold release film is overlaid on the formed adhesive layer in the state which the mold release process surface opposed the adhesive layer. Subsequently, a release film separate from the release film was prepared, the pressure-sensitive adhesive solution was applied to the release treatment surface of the release film, and the solvent in the pressure-sensitive adhesive solution was completely dried to remove the pressure-sensitive adhesive layer on the surface of the release film. A laminated film is produced. This laminated | multilayer film is laminated | stacked on the back surface of the said base material in the state which opposed the back surface of a base material, and a laminated body is manufactured. And the method of obtaining the double-sided adhesive sheet by which the pressure-sensitive adhesive layer is integrally laminated on both surfaces of the base material and the release film is laminated on the surface of the pressure-sensitive adhesive layer so as to be peelable by pressing the laminate with a rubber roller or the like is mentioned.

In addition, two laminated | multilayer films are manufactured by the method similar to the above, These laminated | multilayer film are overlapped in the state which the adhesive layer of laminated | multilayer film opposed to the base material on each of both surfaces of a base material, and a laminated body is manufactured, This laminated body The pressure sensitive adhesive layer is laminated on both surfaces of the base material by pressurizing a rubber roller or the like, and a double-sided pressure-sensitive adhesive sheet can be produced in which a release film is laminated on the surface of the pressure-sensitive adhesive layer so as to be peeled off.

In addition, the pressure-sensitive adhesive solution is applied to the surface of the substrate, and the solvent in the pressure-sensitive adhesive solution is completely dried to form a pressure-sensitive adhesive layer. Then, the release film is overlaid on the pressure-sensitive adhesive layer in a state in which the release-treated surface faces the pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer and the release film are laminated on each of both sides of the substrate by subsequently forming a pressure-sensitive adhesive layer on the back surface of the substrate and superimposing the release film on the pressure-sensitive adhesive layer in a state in which the release treatment surface faces the pressure-sensitive adhesive layer. It is also possible to produce a double-sided pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer is integrally laminated on both surfaces of the base material and a release film is laminated on the surface of the pressure-sensitive adhesive layer so that the release film can be peeled off by pressing the laminate with a rubber roller or the like. have.

In addition, in the above, although the double-sided adhesive sheet by which the adhesive layer is laminated | stacked and integrated on both surfaces of the base material formed in the sheet form was demonstrated, it can also be used as a double-sided adhesive tape by cutting the said double-sided adhesive sheet into a rectangle.

The double-sided adhesive sheet of this invention can be used as a double-sided adhesive sheet for display device manufacture, It is used for sticking the display panel and backlight of a display device specifically ,. Next, the method of manufacturing a display apparatus by integrating a display panel and a backlight using the double-sided adhesive sheet of this invention is demonstrated. First, a backlight is manufactured by arranging a reflecting plate, a cold cathode tube, a light guide plate, a diffusion plate, and a prism sheet in this order in the backlight housing. The prism sheet is exposed in the opening of the backlight housing of the backlight. Moreover, a liquid crystal display panel etc. are mentioned as a display panel.

Then, a double-sided pressure-sensitive adhesive sheet punched into a frame is prepared, and the back surface of the double-sided pressure-sensitive adhesive sheet is adhered to be in contact with at least one of the backlight housing and prism sheet on the surface of the backlight. Then, by preparing a display panel provided with a driving circuit and adhering the surface of the double-sided adhesive sheet to the back surface of the display panel, a display device in which the display panel and the backlight are adhered through the double-sided adhesive sheet can be manufactured.

EFFECTS OF THE INVENTION [

The pressure-sensitive adhesive of the present invention includes a acrylate ester resin having a weight average molecular weight of 500,000 to 1.5 million, a tackifying resin having an alcoholic hydroxyl group and a hydroxyl value of 35 or more, and a terpene phenol resin measured as polystyrene reduced molecular weight by GPC method. At the same time, the gel fraction is 5 to 40% by weight. Therefore, even if it is thin, the said adhesive can form the adhesive layer which is hard to peel by the peeling stress which arises by deformation of a to-be-adhered body.

And since the adhesive layer of this invention can make the adhesive layer thin, there is little case that a punching part generate | occur | produces at the time of punching of a sheet | seat, and workability hardly falls, and a double-sided adhesive sheet is carried out. Can be suitably used, for example, in the manufacture of a display device punched into a frame.

And since the adhesive layer of this invention is excellent in adhesive force, the adhesive layer can be made thin, and the thickness of the whole double-sided adhesive sheet is also thin, the use which manufactures a small display apparatus and a thin display apparatus is sufficient. It can be used preferably.

In addition, the display device of the present invention firmly integrates both of the double-sided adhesive sheets used for adhesion between the display panel and the backlight despite the peeling stress generated due to deformation of the display panel and the backlight. Maintains good quality over a long period of time.

1 is a diagram illustrating a test method of peeling stress.

2 is a diagram illustrating a test method of the resistance to repulsion.

BRIEF DESCRIPTION OF THE DRAWINGS FIG.

1: polycarbonate resin plate

2: test piece

3: trial sample

4:50 g weight

5: test piece

6: aluminum plate

7: polycarbonate resin plate

8: trial sample

9: jig

L: Maximum length of the peeled off part (mm)

H: The gap height between the aluminum plate and the polycarbonate resin plate (mm)

BEST MODE FOR CARRYING OUT THE INVENTION [

Although an Example is given to the following and the aspect of this invention is demonstrated in more detail, this invention is not limited only to these Examples.

[Examples 1-3, 6-28, Comparative Examples 1-6, 8-12]

(Production of Acrylic Ester Resin)

A reactor equipped with a thermometer, a stirrer, and a cooling tube was prepared, and a predetermined amount of ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, 2-hydroxy acrylate, and the like are shown in Tables 1 to 4 below. Ethyl, 4-hydroxybutyl acrylate, acrylic acid ester-containing acrylate ester G (what added caprolactone to 2-hydroxyethyl acrylate, trade name "Fraccel FA-2D" manufactured by Daicel Chemical Corporation), hydroxyl-containing methacryl Acid ester H (what added caprolactone to 2-hydroxyethyl methacrylate, "Fraccel FM-2D" by Daicel Chemical Corporation), acrylic acid, and the predetermined amount of ethyl acetate shown in Tables 1-4 After addition, the reactor was heated to initiate reflux. Subsequently, 0.01 weight part of 1,1-bis (t-hexylperoxy) -3,3,5-trimethylcyclohexane was added as a polymerization initiator in the said reactor, and superposition | polymerization was started under reflux. Subsequently, 1,1-bis (t-hexylperoxy) -3,3,5-trimethylcyclohexane is added in 0.01 parts by weight even after 1 hour and 2 hours after the start of the polymerization, and further 4 hours after the start of the polymerization. 0.05 weight part of hexyl peroxy pivalate was added to continue the polymerization reaction. And 8 hours after the start of polymerization, ethyl acetate was added to the reactor and cooled with dilution to obtain an acrylic ester resin solution having a solid content of 30% by weight.

[Examples 4 and 5 and Comparative Example 7]

A reactor equipped with a thermometer, a stirrer, and a cooling tube was prepared, and a predetermined amount of ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, and the like shown in Tables 1 and 4 were prepared in the reactor. After adding acrylic acid and the predetermined amount of ethyl acetate shown in Tables 1 and 4, nitrogen was blown in the reactor over 30 minutes, and the air in the reactor was nitrogen-substituted.

Subsequently, 0.01 part by weight of 1,1-bis (t-hexylperoxy) -3,3,5-trimethylcyclohexane was added as a polymerization initiator in the reactor, and polymerization was started at 70 ° C. Subsequently, 0.01 part by weight of 1,1-bis (t-hexylperoxy) -3,3,5-trimethylcyclohexane was added after 1 hour and 2 hours after the start of the polymerization, and further 4 hours after the start of the polymerization. 0.05 weight part of hexyl peroxy pivalate was added to continue the polymerization reaction. In addition, when the viscosity of the reaction solution became too high during the polymerization reaction, a small amount of ethyl acetate was added into the reactor as needed to dilute the reaction solution. And 8 hours after the start of superposition | polymerization, ethyl acetate was added and dilute | cooled in a reactor, and it cooled, and obtained the acrylic acid ester resin solution of 30 weight% of solid content.

(Production of double-faced pressure-sensitive adhesive sheet)

The predetermined amount of polymerization rosin ester resin A (hydroxy group value: 46, softening point: 152 ° C.) and hydrogen shown in Tables 1 to 4 with respect to 100 parts by weight of the acrylic acid ester resin solid content in the acrylic acid ester resin solution obtained as described above. Addition rosin ester resin B (Arakawa Chemical Co., Ltd. brand name "fine crystal KE359", hydroxyl value: 40, softening point: 100 degreeC), disproportionated rosin ester resin C (Arakawa Chemical Co., Ltd. brand name "superester A125", hydroxyl group value : 15, softening point: 125 degreeC), polymerization rosin ester resin D (Arakawa Chemical Co., Ltd. brand name "Pencel D125", hydroxyl value: 32, softening point: 125 degreeC), terpene phenol resin E (Yasuhara Chemical company make brand name "Mighty Ace G150 ", softening point: 150 degreeC), terpene phenol resin F (trade name" YS Polystar T130 "by Yashara Chemical Co., Ltd., softening point: 130 degreeC), and petroleum resin (Mitsui Sekiyu Chemical Co., Ltd. make phase) Name "FTR6100", a softening point: 100 DEG C) was added, ethyl acetate was added and stirred, and a predetermined amount of an isocyanate-based crosslinking agent (trade name "Colonate L45" manufactured by Nippon Polyurethane Co., Ltd.) was further added to Tables 1 to 4, By stirring, an adhesive solution having a solid content of 20% by weight was obtained. In addition, the quantity of the isocyanate type crosslinking agent in Tables 1-4 shows the weight part of solid content of an isocyanate type crosslinking agent.

Subsequently, the pressure-sensitive adhesive solution was applied to the surface of a polyethylene terephthalate film having a thickness of 23 μm as a base material, dried at 100 ° C. for 5 minutes to remove ethyl acetate in the pressure-sensitive adhesive solution, and the pressure-sensitive adhesive layer A shown in Tables 1 to 4 After the formation, the polyethylene terephthalate film having a thickness of 50 µm to be a release film was superimposed on the pressure-sensitive adhesive layer A in such a manner that the release treatment surface thereof faced the pressure-sensitive adhesive layer A.

Subsequently, a polyethylene terephthalate film having a thickness of 50 µm to be a release film, which is different from the polyethylene terephthalate film superimposed on the pressure-sensitive adhesive layer A, was prepared, and the pressure-sensitive adhesive solution was applied to the release treatment surface of the film, By drying at 100 degreeC for 5 minutes, and removing ethyl acetate in an adhesive solution, the laminated film by which the adhesive layer B of the thickness shown in Tables 1-4 is formed in the mold release process surface of the 50-micrometer-thick polyethylene terephthalate film was produced.

Then, the pressure-sensitive adhesive layer of the laminated film is overlaid in the state facing the rear surface of the polyethylene terephthalate film serving as the base material to produce a laminate, and a 2 kg rubber roller is placed on the laminate at a speed of 300 mm / min. After reciprocating once and curing for 7 days at 23 degreeC, the double-sided adhesive sheet by which the adhesive layers A and B of the thickness shown in Tables 1-4 were laminated on both surfaces of the base material was laminated. Moreover, the release film of thickness 50micrometer was laminated | stacked so that peeling was possible on the adhesive layers A and B of a double-sided adhesive sheet.

Subsequently, the gel fraction of the pressure-sensitive adhesive obtained as described above was measured in the above-described manner, and at the same time, the weight average molecular weight of the acrylic ester resin and the adhesive force, peeling stress, repulsion resistance, punching resistance, and shear resistance of the double-sided adhesive sheet were measured. About the measurement by the following method, the result is shown to Tables 1-4.

(Weight average molecular weight of acrylic acid ester resin)

The measurement sample was manufactured by filtering the dilution liquid obtained by diluting 50-times of obtained acrylic acid ester resin with tetrahydrofuran (THF) with the filter (material: polytetrafluoroethylene, pore diameter: 0.2 micrometer). Subsequently, this measurement sample is supplied to gel permeation chromatography (Water brand name "2690 Separations Model"), GPC measurement is carried out under the conditions of a sample flow rate of 1 ml / min, column temperature 40 ℃, The polystyrene conversion molecular weight of acrylic acid ester resin was measured, and this value was made into the weight average molecular weight of acrylic acid ester resin. In the above GPC measurement, a column commercially available from Showa Denko Co., Ltd. under the trade name "GPC LF-804" was used, and a differential refractometer was used as a detector.

(adhesiveness)

The obtained double-sided adhesive sheet was cut out to the rectangle of 25 mm width, the test piece was produced, the release film on the adhesive layer A of this test piece was peeled off, and the adhesive layer was exposed. Subsequently, after placing the said test piece on the polycarbonate resin board so that the adhesive layer may be in the state which opposes the polycarbonate resin board, a 2 kg rubber roller was applied on the test piece at the speed | rate of 300 mm / min. By reciprocating once, the test piece and the polycarbonate resin plate were made to stick, and it stood still at 23 degreeC for 30 minutes, and manufactured the test sample. And about this test sample, the tensile test of 180 degree directions was performed at 300 mm / min of peeling rate according to JISZ0237, and adhesive force (N / 25mm) was measured.

(Peel resistance)

As shown in Fig. 1, the obtained double-sided pressure-sensitive adhesive sheet was cut into a rectangle having a width of 20 mm to prepare a test piece 1, the release film was peeled off and removed from the surface of the test piece 1, and the pressure-sensitive adhesive layer was exposed. It mounted on the carbonate resin plate 2 so that an adhesive layer might be in the state which opposes.

Subsequently, after peeling off and removing a release film from the back surface of the said test piece 1, and laminating | stacking a polyethylene terephthalate film with a thickness of 23 micrometers on the exposed adhesive layer, 300 mm / min on the back surface of the said test piece 1 The test sample (1) and the polycarbonate resin plate (2) were adhered to each other by reciprocating the rubber roller of 2 kg at a rate of 1 time and allowed to stand for 24 hours under the condition of 23 ° C and a relative humidity of 50%. 3) was prepared.

Subsequently, the test sample 3 was placed in an oven at 85 ° C., and as shown in FIG. 1, at one end of the test piece 1 of the test sample 3 in the direction perpendicular to the adhesive face to the test piece 1. After attaching 50 g weight (4) and letting it stand over 24 hours so that a load might be applied, the maximum length L (mm) of the part which the test piece 1 peeled from the polycarbonate resin plate 2 was measured.

(Repulsion resistance)

As shown in Fig. 2, the obtained double-sided pressure-sensitive adhesive sheet was cut into a flat rectangular shape having a width of 25 mm × 150 mm to prepare a test piece 5, and the release film provided on both sides of the test piece 5 was peeled off. The pressure-sensitive adhesive layer was exposed.

Thereafter, an aluminum plate 6 having a width of 25 mm × 150 mm × 0.3 mm in thickness is placed on the surface of the test piece 5, and a polycar of 25 mm in width × 200 mm in height × 1 mm in thickness on the back surface of the test piece 5. The bonate resin plates 7 were superimposed. In addition, it adjusted so that the test piece 5 may be located in the center part of the longitudinal direction of the polycarbonate resin plate 7.

Subsequently, a 2 kg rubber roller was reciprocated once on the polycarbonate resin plate 7 at a speed of 300 mm / min, and the polycarbonate resin plate 7 and the aluminum plate 6 were tested. The test sample is formed by integrating through and incorporating at 23 ° C. over 24 hours so that the aluminum plate 6 is integrally bonded to the central portion of the polycarbonate resin plate 7 in the longitudinal direction via the test piece 5. (8) was prepared.

Subsequently, as shown in FIG. 2, the test sample 8 is set to a jig 9, and the test sample 8 is applied by applying a bending stress in the longitudinal direction of the test sample 8. The polycarbonate resin sheet 7 is deformed in an arcuate state so that the distance between both ends in the longitudinal direction becomes 180 mm, and in this state, the test sample 8 is placed in an oven at 85 ° C. for 24 hours. I was stationed.

Thereafter, the test sample 8 was taken out of the oven as it was in an arc shape, and the gap H between the aluminum plate 6 and the polycarbonate resin plate 7 (mm) was measured by a calipers. The value was made into the value of evaluation of repulsion force.

Here, the lifting height H (mm) between the aluminum plate 6 and the polycarbonate resin plate 7 of the test sample 8 is the aluminum plate 6 in the direction perpendicular to the upper surface of the jig 9. ) And the surface between the opposing surfaces of the polycarbonate resin plate 7 specify the position at which the maximum value is obtained, and the aluminum plate 6 and the polycarbonate in the direction perpendicular to the upper surface of the jig 9 at this position. The value which subtracted the thickness of the test piece 5 from the space | interval between the opposing surfaces of the nate resin plate 7 is said.

(Punching property)

The obtained double-sided adhesive sheet was cut | disconnected with the cutter knife, and it left still over 3 hours at 23 degreeC as these cut | disconnected surfaces were bonded, and after that, cut | disconnected surfaces were separated by hand. When the cutting surfaces were separated from each other, the situation of the ordinary yarns generated between the cutting surfaces was visually observed, and the case where no ordinary example was recognized was evaluated as ○, the case where a slight ordinary example was recognized as △, and the severe case was evaluated as x.

(Shear resistance)

The obtained double-sided adhesive sheet was cut into a flat square of 20 mm on one side to prepare a test piece, the release film was peeled off from the surface of the test piece to expose the pressure-sensitive adhesive layer, and the test piece was placed on the polycarbonate resin plate. It was placed to be in the opposite state.

Subsequently, the release film was peeled off from the back surface of the test piece, and a 23 μm-thick polyethylene terephthalate film was laminated on the exposed pressure-sensitive adhesive layer, and then, on the back surface of the test piece, 2 kg of By reciprocating a rubber roller once, the test piece and the polycarbonate resin plate were made to stick, and the test sample was produced by standing still at 23 degreeC over 24 hours.

Subsequently, a weight was attached to the test piece of the test sample, and the test piece was allowed to stand at 23 ° C. over 3 hours so that a load of 200 g was applied in the direction along the adhesive surface of the test piece. Then, before and after attaching a weight to a test piece, the twist length of the test piece on a polycarbonate resin plate was measured using the loupe.

Although Examples 1-5 have the same composition of the monomer component of acrylic acid ester resin, the weight average molecular weight of acrylic acid ester resin differs. In Example 1, since the weight average molecular weight of acrylate ester resin is less than the minimum of the more preferable range, the value of peeling-resistant stress is large compared with Examples 2-4. Since Examples 3-5 exceeded the upper limit of a more preferable range, compared with Examples 1 and 2, adhesive force fell and the value of the repulsion resistance became large.

Examples 6 and 7 differ from each other in the amount of 2-hydroxyethyl acrylate. In Example 6, the amount of 2-hydroxyethyl acrylate is the lower limit of a more preferable range. Therefore, although many crosslinking agents are mix | blended than Example 7, the gel fraction of an adhesive became small and it is less than the minimum of a preferable range.

Examples 10 and 11 differ from each other in the amount of isocyanate crosslinking agent. In Example 11, the amount of the isocyanate crosslinking agent is below the preferred range, the gel fraction of the pressure-sensitive adhesive is below the preferred range, and the peeling stress is a large value.

Examples 12-16 differ in the amount of ethyl acrylate. In Example 12, since the amount of ethyl acrylate is less than a preferable range, the peeling stress is a large value. In Examples 15 and 16, since the amount of ethyl acrylate exceeded the upper limit of a more preferable range, the repulsion resistance is large. It is inferred that this is because the pressure-sensitive adhesive layer is hardened.

In Examples 17-19, the compounding quantity of rosin ester differs. In Examples 17 and 19, the amount of the rosin ester-based resin is out of a more preferable range, so that the value of the repulsion resistance is large.

Although Examples 26-28 differ in the kind of hydroxyl group containing acrylic acid ester monomer, the quantity of hydroxyl group containing acrylic acid ester monomer is all in the more preferable range. In Examples 26 to 28, the gel fraction of the pressure-sensitive adhesive is in a more preferred range.

In Comparative Examples 1 and 12, the gel fraction of the pressure-sensitive adhesive is too high, and the value of the repulsion resistance is large. In Comparative Examples 2 and 6, the weight average molecular weight of the acrylic acid ester resin is too small and the peeling stress is a large value.

Since Comparative Example 3, 4, 8-9 is not mix | blended with tackifying resin whose hydroxyl value is 35 or more, it becomes a value with large peeling resistance. In Comparative Example 7, the weight average molecular weight of the acrylate ester resin is too large, and the adhesive force of the pressure-sensitive adhesive is lowered, and the peeling stress is a large value. In Comparative Example 11, the gel fraction was too small and the peeling stress was large.

Even if the adhesive of this invention is thin, it can form the adhesive layer which is hard to peel by the peeling stress which arises by deformation of a to-be-adhered body. Therefore, the adhesive of this invention can be used suitably for manufacture of a display apparatus, especially a small display apparatus and a thin display apparatus.

Claims (9)

On both sides of the substrate, a weight average molecular weight measured as a polystyrene reduced molecular weight by the GPC method is 500,000 to 1.5 million, and an acrylic acid ester resin having 5 to 30% by weight of an ethyl acrylate component, an alcoholic hydroxyl group, and a hydroxyl value A pressure-sensitive adhesive layer having a thickness of 30 μm or less, comprising a tackifying resin having a thickness of 35 or more and a terpene phenol resin having a softening point of 145 to 170 ° C., and having a gel fraction of 5 to 40 wt%, is laminated and integrated. Adhesive sheet. The double-sided adhesive sheet according to claim 1, wherein the tackifying resin is a rosin ester resin. The double-sided adhesive sheet according to claim 1, wherein the weight average molecular weight measured as polystyrene reduced molecular weight by GPC method of acrylic ester resin is 500,000 to 1 million and gel fraction is 10 to 40% by weight. The double-sided adhesive sheet according to claim 2, which comprises 5 to 40 parts by weight of the rosin ester resin and 3 to 20 parts by weight of the terpene phenol resin with respect to 100 parts by weight of the acrylic acid ester resin. The double-sided adhesive sheet according to any one of claims 1 to 4, which is used for the manufacture of a display device. A display panel and a backlight are adhered to each other via the double-sided adhesive sheet according to claim 5. delete delete delete

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