JP2000098370A - Adhesive composition for liquid crystal display device and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure reworkability to release a polarizing plate from a cell in a state where an adhesive is remaining stuck to the polarizing plate at the time when the polarizing plate is desired to be released without loading a burden on the cell by utilizing a polymer with a reactive functional group or a polymer compounded with a compound having a reactive functional group as a principal component of an adhesive composition. SOLUTION: When a liquid crystal display device, provided with a liquid crystal cell 1 equipped with a liquid crystal layer on the surface of a substrate via a transparent electrode and an alignment layer, and polarizing plates 10, 12 stuck to both surfaces of the substrate is manufactured, a polymer with a reactive functional group or a polymer compounded with a compound having a reactive functional group as a principal component of adhesive layers 22, 24 is utilized in the adhesive layers 22, 24 used to bind the substrates and the polarizing plates 10, 12. In this case, hydroxyl, carbonyl, carboxyl, an acyl and an amino groups can be mentioned as reactive functional groups. A glass transition temperature of the polymer which is the principal component of the adhesive layers is <=20 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal display device comprising a liquid crystal cell having a liquid crystal layer provided on one surface of a substrate via a transparent electrode and an alignment layer, and a polarizing plate adhered to the other surface of the substrate. The present invention relates to an adhesive composition for bonding a substrate and a polarizing plate, and a liquid crystal display device in which the substrate and the polarizing plate are bonded using the adhesive.

[0002]

2. Description of the Related Art A liquid crystal cell substrate constituting a liquid crystal display device has conventionally been formed of glass. Recently, however, a plastic liquid crystal cell substrate has been used to reduce the weight. It has become

For this reason, when the liquid crystal cell substrate is made of plastic, if the liquid crystal cell substrate is bonded to the above-mentioned polarizing plate with an acrylic adhesive or a thermosetting adhesive, the polarizing plate may be misaligned or foreign matter may be mixed. It is very difficult to remove it, or the adhesive remains on the substrate even if it comes off,
There is a problem that the cell is destroyed, and it has been desired to solve this problem.

The present invention has been made in order to meet the above-mentioned demand. In the above-mentioned adhesive composition for a liquid crystal display device, the adhesive force of the polarizing plate to the cell is appropriately controlled, and the polarizing plate is peeled off. An adhesive composition for a liquid crystal display device having a rework property capable of separating a polarizing plate from a cell in a state where an adhesive is adhered to the polarizing plate without applying a load to the cell when desired. It is an object to provide a liquid crystal display device.

[0005]

Means for Solving the Problems and Embodiments of the Invention In order to achieve the above object, the present invention provides a liquid crystal cell having a liquid crystal layer provided on one surface of a substrate via a transparent electrode and an alignment layer. When manufacturing a liquid crystal display device having a polarizing plate bonded to the other surface of the substrate, in the adhesive composition used for bonding the substrate and the polarizing plate, the main component of the adhesive composition, An adhesive composition for a liquid crystal display device, comprising a polymer having a reactive functional group or a compound having a reactive functional group in a polymer, wherein the polymer of the main component has a glass transition temperature of 20 ° C. or lower. The adhesive composition according to claim 1, which is a polymer of Claim 3, wherein the polymer of the main component has rubber elasticity,
Its elastic modulus is 1 × 10 ⁵ to 1 × 10 ¹⁰ dyne / cm
The adhesive composition according to claim 1 or 2, which is ² (25 ° C); the adhesive composition according to claim 1, 2 or 3 containing a hydrocarbon resin; the silane coupling agent. 5. The method according to claim 1, wherein
6. The adhesive composition according to any one of claims 1 to 5, wherein the adhesive composition comprises a plasticizer. 7. The transparent electrode and the alignment layer on one surface of the substrate. 7. A liquid crystal display device comprising: a liquid crystal cell provided with a liquid crystal layer via a liquid crystal layer; and a polarizing plate adhered to the other surface of the substrate, wherein the substrate and the polarizing plate are arranged in accordance with one of claims 1 to 6. Provided is a liquid crystal display device characterized by being adhered with an adhesive composition.

According to the present invention, the main component of the adhesive composition is a polymer having a reactive functional group or a mixture of a polymer and a compound having a reactive functional group. The plate can be peeled off smoothly from the cell without applying a load. At this time, the adhesive can be peeled off while being adhered to the polarizing plate side, so that the cell can be reused.

Hereinafter, the present invention will be described in more detail.

[0008] The adhesive composition for a liquid crystal display device of the present invention comprises:
The main component is a polymer having a reactive functional group or a polymer having no reactive functional group in combination with a polymer having no reactive functional group.

Here, the reactive functional groups include a hydroxyl group, a carbonyl group, a carboxyl group, an acyl group, an amino group, an N-alkylamino group, an azo group, a diazo group, an azoxy group, an amide group, an imide group, and a mercapto group. Group, a thio group, a dithio group, a sulfino group, a sulfo group, a sulfamoyl group, a sulfonyl group, a sulfinyl group, a nitro group, a nitroso group, and the like. Among them, a hydroxy group, a carboxyl group, an amino group, and a nitro group having polarity are preferable. .

In addition, the polymer modified or unmodified with the above functional group has a Tg value from the viewpoint of exhibiting cold flow properties and relaxing strain caused by contraction and expansion of the substrate.
Is 20 ° C. or lower, preferably 0 ° C. or lower, more preferably −
It is preferable to use a polymer having a temperature of 20 ° C. or lower, preferably a polymer having rubber elasticity. When Tg exceeds 20 ° C., the effect of relaxing strain may not be obtained.
Specifically, as a base polymer, natural rubber, styrene-butadiene rubber, butadiene rubber, isoprene rubber, acrylonitrile-butadiene rubber, chloroprene rubber, ethylene-propylene rubber, ethylene-propylene terpolymer, butyl rubber, acrylic rubber, silicone rubber, Epichlorohydrin rubber or the like can be used.

The above polymer has an elastic modulus at 25 ° C. of 1 × 10 ⁵ to 1 × 10 ¹⁰ dyne / cm ² , particularly 1 × 10 ⁵ dyne / cm ² .
It is preferably in the range of × 10 ⁵ to 1 × 10 ⁸ dyne / cm ² . If it is less than 1 × 10 ⁵ dyne / cm ^2, it is too soft,
If the workability is poor, and if it exceeds 1 × 10 ¹⁰ dyne / cm ² , it is too hard to obtain a warp prevention effect, and the effect of Tg is delayed.

In the present invention, a polymer obtained by modifying the above-mentioned polymer with the above-mentioned reactive functional group is used, or when an unmodified polymer is used, a compound having the above-mentioned reactive functional group is used in combination.

In this case, as the compound having the reactive functional group, specifically, a polymer having the above functional group (modified), a carboxylic acid or the like is suitably used.

It is an object of the present invention to provide the compound having a reactive functional group in an amount of 0.1 to 100 parts, especially 1 to 50 parts, per 100 parts (parts by weight, hereinafter the same) of the polymer. It is preferable from the point of achieving.

It is preferable that the adhesive composition of the present invention contains a hydrocarbon resin, whereby the processability and the processability such as bonding can be improved. in this case,
The hydrocarbon resin to be added may be either a natural resin type or a synthetic resin type. Rosin, rosin derivatives, and terpene resins are preferably used in the natural resin system. For rosin, gum-based resins, tall oil-based resins, and wood-based resins can be used. As the rosin derivative, rosin obtained by hydrogenation, heterogeneization, polymerization, esterification, and metal salification can be used. As the terpene-based resin, terpene-based resins such as α-pinene and β-pinene, as well as terpene phenol resins can be used. Also, dammar, corval, and shellac may be used as other natural resins. On the other hand, in the case of synthetic resins, petroleum resins, phenol resins, and xylene resins are preferably used. Petroleum resins include aliphatic petroleum resins, aromatic petroleum resins, alicyclic petroleum resins, copolymer petroleum resins, hydrogenated petroleum resins,
Pure monomer petroleum resins and coumarone indene resins can be used. As the phenolic resin, an alkylphenol resin and a modified phenol resin can be used. As the xylene-based resin, a xylene resin or a modified xylene resin can be used.

The amount of the hydrocarbon resin to be added is appropriately selected, but is preferably 1 to 200 parts per 100 parts of the base polymer (the polymer having the reactive functional group or the compound having the compound having the reactive functional group). Parts, more preferably 5 to 150 parts.

Further, a plasticizer can be added to the adhesive composition, whereby the processability is improved and the strain relaxation of the adhesive can be improved. Examples of the plasticizer include phthalic acid esters such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dihexyl phthalate, dioctyl phthalate, and di-2-ethylhexyl phthalate; phosphate esters such as tricresyl phosphate, trioctyl phosphate, and triphenyl phosphate. , Dioctyl adipate, diisooctyl adipate, adipates such as di-n-octyl adipate, dibutyl sebacate, sebacates such as dioctyl sebacate, dioctyl azelate,
Azelate esters such as dihexyl azelate, citrate esters such as triethyl citrate and acetyl triethyl citrate, glycolate esters such as methyl phthalyl ethyl glycolate and ethyl phthalyl ethyl glycolate, and trioctyl trimellitate , Bird
Trimellitic acid esters such as n-octyl-n-decyl trimellitate, phthalic acid isomers such as diocicle isophthalate and diocicle terephthalate, and ricinoleic acid esters such as methyl acetyl ricinolate and butyl acetyl ricinolate Polyesters such as, polypropylene adipate, polypropylene sebacate,
Epoxys such as epoxidized soybean oil and epoxybutyl stearate, and chlorinated paraffins and chlorinated fatty acid esters are also included.

The compounding amount of the plasticizer is as follows.
1 to 200 parts, more preferably 5 to 150 parts per 00 parts
Part is preferable, and when it is out of this range, workability,
It is difficult to obtain lamination properties.

Further, a silane coupling agent can be added to the adhesive composition, whereby the adhesiveness and moisture resistance can be improved. As the silane coupling agent, vinyl triethoxysilane, vinyl tris (β
-Methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, γ-glycidoxypropyltrimethoxysilane, γ
-Glycidoxypropyltriethoxysilane, β-
(3,4-epoxycyclohexyl) ethyltrimethoxysilane, vinyltrichlorosilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane, etc. Or a mixture of two or more of the above. The compounding amount of the silane coupling agent is
It is preferably 0.01 to 10 parts, more preferably 0.01 to 5 parts, based on 100 parts of the base polymer.

Further, an antioxidant, a UV absorber, a crosslinking agent such as an organic peroxide, and other additives can be added to the adhesive composition as required.

The adhesive composition of the present invention can be used for bonding a polarizing plate and a substrate of a liquid crystal cell having a liquid crystal layer provided on one surface of a substrate via a transparent electrode and an alignment layer. In this case, as shown in FIG. 1, the liquid crystal cell 1 includes two substrates 2 having transparent electrodes 3, 3 ′ and alignment layers 4, 4 ′ on one surface.
2 'may be arranged such that the alignment layers 4 and 4' face each other, and the liquid crystal layer 5 is interposed therebetween.
The substrate is made of polycarbonate, polyethersulfone, polyarylate, norbornene, etc.
A plastic film of about 500 μm can be used.

Further, the polarizing plate may be, for example, a structure in which both surfaces of a polarizing film are covered and protected with protective films. Preferably, a transparent plastic barrier film is laminated on the surface of the polarizing plate and, if necessary, on both front and back surfaces. The polarizing plate and further the liquid crystal cell substrate are restrained and moisture-proof by the lamination of the plastic barrier film, and the warpage of the cell substrate and the entire liquid crystal display device due to the shrinkage of the polarizing film also from this point. It can be prevented as much as possible.

In this case, as the polarizing film, a known film obtained by adsorbing and orienting and stretching iodine or a dichroic dye on a hydrophilic polymer film such as a polyvinyl alcohol film or a saponified ethylene-vinyl acetate copolymer film is used. The thickness is usually 50 to 250 μm, especially 120 to 1 μm.
80 μm.

As the protective film for covering and protecting the polarizing film, a cellulose film, a polyester film, a polyacryl film, a polycarbonate film, a polyether sulfone, etc. are used. This thickness is usually from 5 to 250 μm, especially from 10 to 180 μm.

The plastic barrier film to be laminated on the polarizing plate is transparent and has a water vapor barrier property, and has a glass transition temperature of 60 ° C. or higher. Specifically, a polyester film, a polystyrene film, a polyacrylonitrile film, Examples include a polycarbonate film and a polyacryl film.

With respect to the transparency of such a plastic barrier film, those having a light transmittance of 70% or more, particularly 90% or more are preferable from the viewpoint of maintaining the performance of the liquid crystal display device.
The haze value is preferably 12% or less from the viewpoint of visibility.

[0027] In addition, the water vapor permeability of 500g / m ² · ²
It is preferably 4 hours or less, particularly preferably 10 g / m ² · 24 hours or less. Further, the glass transition temperature of the barrier film is 60 ° C. or higher, preferably 100 ° C. or higher. The thickness is 10 μm or more, preferably 25 μm.
５００500 μm, especially 50-200 μm.

In this case, the adhesion between the barrier film and the polarizing plate can be performed using an acrylic, urethane or epoxy adhesive, but the adhesive composition of the present invention is preferably used.

In the present invention, the structure of the liquid crystal display device is not limited, and it can be a display device of a transmission type, a reflection type, a transflective type, etc.

Here, the transmission type shown in FIG. 2 can be used, and the reflection type shown in FIG.
The one shown in FIG. 3 can be used. In addition, FIG.
In 3, 3, 12, 14, 16 are polarizing plates, 18 is a reflective layer, 20 is a barrier film, 22, 24, 2
Reference numerals 6, 28, and 30 denote adhesive layers, and in the present invention, these adhesive layers are preferably the above-mentioned adhesive composition.

[0031]

EXAMPLES The present invention will be described below in detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

Example 1, Comparative Examples 1 and 2 A liquid crystal display device shown in FIG. 2 was prepared according to the following specifications. Liquid crystal cell substrate Amorix AM301 manufactured by Fujimori Industry Co., Ltd.
5E Thickness 320 μm Polarizer PLN-12432Z adhesive layer manufactured by Nippon Synthetic Chemical Industry Co., Ltd. <Example 1> Butadiene rubber (BR-01 manufactured by JSR) 100 parts by weight Tg: -102 ° C Elasticity: 1.2 × 10 ⁶ dyne / cm ² (25 ° C.) Polybutadiene modified with terminal carboxylic acid (10 parts by weight, manufactured by Ube Industries, Ltd., HYCAR CT polymer CTB2000 × 162) Petroleum resin (Alcon P-125 manufactured by Arakawa Chemical Co., Ltd.) 50 parts by weight Plasticizer DDP 10 parts by weight Antioxidant BHT 2 parts by weight <Comparative Example 1> Acrylic adhesive 1831 manufactured by Soken Chemical Co., Ltd. (25% of non-volatile content) 100 parts by weight Hardening agent E-AX manufactured by Soken Chemical Company 2 parts by weight <Comparative Example 2> An adhesive composition having the same composition as in Example 1 except that the terminal carboxylic acid-modified polybutadiene is not blended.

In this case, in Example 1 and Comparative Example 2, the above adhesive composition was dissolved in toluene and coated on a polarizing plate so as to have a thickness of 30 μm using a coating machine. Were adhered to the upper and lower sides of a plastic liquid crystal cell such that the absorption axes were perpendicular to each other to obtain a liquid crystal display.

In Comparative Example 1, the above-mentioned adhesive composition was applied to a thickness of 30 μm using a coating machine, and was cured for about 7 days to obtain an acrylic pressure-sensitive adhesive. A liquid crystal display device was obtained by bonding to a plastic liquid crystal cell.

With respect to the film-form liquid crystal display device, the peeling force between the polarizing plate and the cell was measured. Table 1 shows the results.

[0036]

[Table 1]

[0037]

According to the present invention, it is possible to obtain a liquid crystal display device having a reworking property capable of easily peeling off the polarizing plate.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of a liquid crystal cell.

FIG. 2 is a cross-sectional view illustrating an example of a liquid crystal display device.

FIG. 3 is a sectional view showing another example of the liquid crystal display device.

[Description of Signs] 1 Liquid crystal cell 2, 2 'substrate 3, 3' Transparent electrode 4, 4 'Alignment layer 5 Liquid crystal layer 10, 12, 14, 16 Polarizer 18 Reflective layer 20 Barrier film 22, 24, 26, 28 , 30 adhesive layer

Claims (7)

[Claims] When manufacturing a liquid crystal display device comprising: a liquid crystal cell having a liquid crystal layer provided on one surface of a substrate via a transparent electrode and an alignment layer; and a polarizing plate bonded to the other surface of the substrate. In an adhesive composition used for bonding a substrate and a polarizing plate, a main component of the adhesive composition is a liquid crystal display in which a polymer having a reactive functional group or a compound having a reactive functional group is blended with a polymer. An adhesive composition for a device. 2. The adhesive composition according to claim 1, wherein the polymer as the main component is a polymer having a glass transition temperature of 20 ° C. or lower. 3. The polymer of the main component has rubber elasticity, and has an elastic modulus of 1 × 10 ⁵ to 1 × 10 ¹⁰ dyne / c.
^3. The adhesive composition according to claim 1, which has a m ² (25 ° C.). 4. The method according to claim 1, which comprises a hydrocarbon resin.
The adhesive composition as described in the above. 5. The adhesive composition according to claim 1, further comprising a silane coupling agent. 6. The adhesive composition according to claim 1, further comprising a plasticizer. 7. A liquid crystal display device comprising: a liquid crystal cell having a liquid crystal layer provided on one surface of a substrate via a transparent electrode and an alignment layer; and a polarizing plate adhered to the other surface of the substrate. 7. A liquid crystal display device comprising: a liquid crystal display device;