JPH05212828A - Composite sheet - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a composite sheet in which a PVA-based sheet is laminated with a protective layer excellent in transparency, durability at high temperature and high humidity, heat resistance, physical strength and the like with good adhesiveness. A composite sheet comprising a polyvinyl alcohol-based sheet, a thermoplastic saturated norbornene-based resin sheet laminated on at least one side of an acrylic pressure-sensitive adhesive layer, and heat-pressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite sheet obtained by integrally bonding a polyvinyl alcohol sheet and a thermoplastic saturated norbornene resin sheet. The composite sheet of the present invention can be suitably used, for example, as a polarizing film for liquid crystal displays and the like.

[0002]

2. Description of the Related Art Polarizing films take advantage of various functions such as removal of reflected light and light lockability, and are used, for example, in sunglasses, filters for cameras, sports goggles, gloves for lighting, anti-glare coatings for automobile headlights, and interior perspective prevention. It is used in a wide range of fields such as light intensity adjustment filters, fluorescent display contrastars, translucency continuous change plates, and polarizing films for microscopes. Recently, it has been used in a liquid crystal display (LCD) and its functionality has been highlighted.

The polarizing film for LCD has a function of blocking transmission of light, and has a role of displaying electric signals together with liquid crystal having a function of switching light.
In order to exhibit such functionality, the optical properties, durability, and other required quality of the polarizing film are becoming severe.

In most of the polarizing films, a polarizing film in which a transparent polymer film is molecularly aligned in a certain direction and a dichroic substance is adsorbed in a gap between micelles is used.
For such a polarizing film, a thin sheet (film) of polyvinyl alcohol (hereinafter abbreviated as PVA) is generally used as a polymer film.

However, a polarizing film made of a PVA type film has weak mechanical strength in the direction of the transmission axis, and is easily contracted by heat or moisture, or the polarizing function is easily deteriorated. The protective layer is laminated with an adhesive to ensure durability and mechanical strength. This laminated body is called a polarizing film or a polarizing plate.

The polarizing film for LCD is attached to a liquid crystal substrate via an adhesive in order to prevent reflection loss of light at the interface with the liquid crystal cell. Therefore, in a normal polarizing film, the pressure-sensitive adhesive layer is provided on one surface of the protective layer, and from the viewpoint of protection and workability of the pressure-sensitive adhesive layer, a release film (separator) is formed on the pressure-sensitive adhesive layer. It is provided. The release film is peeled off when the polarizing film is bonded to the liquid crystal substrate.

The protective layer has no birefringence, high transmittance, good heat resistance and moisture absorption resistance, high mechanical strength, and low shrinkage due to temperature / humidity change.
Performances such as a smooth surface, high resolution, good adhesiveness with an adhesive, and excellent appearance are required. Conventionally, as a protective layer, a solution cast film of cellulose triacetate (hereinafter, abbreviated as TAC) having low birefringence and good appearance is mainly used.

However, the PVA film constituting the polarizing substrate has a water vapor permeability of 25 μm at 25 ° C. and 90%.
1000-1200g / m ² · 24hr under RH environment
On the other hand, the TAC film of the protective layer has a water vapor permeability of about 700 g / m ² · 24 hr under the same conditions, and is insufficient in moisture resistance. Therefore, T
A polarizing film having an AC film as a protective layer has poor durability at high temperature and high humidity, and is deteriorated in 100 hours or less under an environment of 80 ° C. and 90% RH, for example, and the polarization performance is rapidly lowered.

The TAC film also has an insufficient gas barrier property, and dichroic substances such as iodine and dye are likely to be deteriorated by permeated oxygen. In addition, since the TAC film contains a plasticizer for forming a film, it does not have sufficient heat resistance. Further, the TAC film has a tensile strength of 6
There is only about 11 kg / mm ² and the physical strength is insufficient. Therefore, the TAC film has a low strength and durability in a thin film of 40 μm or less, and therefore it is usually 80 μm.
The thing of thickness is used.

Since the TAC film has a large photoelastic coefficient, it tends to have a large birefringence when an external force is applied or there is residual stress during molding. Therefore, the TAC film has low birefringence and good appearance, and can be produced only by the solution casting method with small residual stress.

The polarizing film is laminated on a liquid crystal substrate, a phase plate or the like via an adhesive layer, but there is a problem in the adhesiveness between the TAC film and the adhesive, and the T film is peeled off due to moisture or heat.
Air bubbles called a tunnel are easily generated between the AC film and the adhesive layer. Further, when an acrylic pressure-sensitive adhesive layer is laminated on the TAC film, there is a problem that the TAC film is decomposed by acrylic acid.

As described above, the PVA-based sheet (sheet or film) is widely used, for example, as a polarizing film, but is excellent in transparency, durability, heat resistance, physical strength and the like for the purpose of protection and the like. There is a demand for a composite sheet in which protective layers are laminated with good adhesiveness.

[0013]

The object of the present invention is to provide PV
A type sheet has transparency, durability at high temperature and high humidity, heat resistance,
It is to provide a composite sheet in which a protective layer excellent in physical strength and the like is laminated with good adhesiveness. The present inventors have noticed that a sheet made of a thermoplastic saturated norbornene resin is excellent in transparency, low birefringence, moisture resistance, water resistance, heat resistance, physical strength, etc. We carried out intensive research to create a composite with the seat. As a result, when a PVA-based sheet and a thermoplastic saturated norbornene-based resin sheet are bonded with an acrylic pressure-sensitive adhesive and then heated and pressed, a composite sheet having high adhesive strength between them and excellent transparency and the like can be obtained. I found it. When a polarizing film is used as the PVA-based sheet in this composite sheet, a polarizing film having excellent optical characteristics, durability and the like can be obtained. The present invention has been completed based on these findings.

[0014]

Thus, according to the present invention, a thermoplastic saturated norbornene resin sheet is laminated on at least one surface of a polyvinyl alcohol sheet through an acrylic pressure-sensitive adhesive layer, and thermocompression bonded. A composite sheet characterized by the above is provided.

The present invention will be described in detail below. (PVA-based sheet) The PVA-based sheet used in the present invention is not particularly limited as long as it is a sheet (sheet or film) formed using PVA. When the composite sheet of the present invention is used as various polarizing films, PVA
A polarizing film is used as the system sheet.

A polarizing film made of a PVA type sheet includes
There is no particular limitation as long as it has a function as a polarizer, and for example, a PVA / iodine-based polarizing film that is uniaxially stretched in a boric acid bath after adsorbing iodine on the PVA film; Highly direct dye is diffusely adsorbed and then uniaxially stretched PVA / dye-based polarizing film; PVA
PVA / polyvinylene-based polarizing film having a polyvinylene structure by adsorbing iodine on the film and stretching; PVA / metal-based polarizing film having PVA film adsorbing metal such as gold, silver, mercury, iron; PVA film on potassium iodide And a near-ultraviolet polarizing film treated with a boric acid solution containing sodium thiosulfate; a polarizing film having a dichroic dye on the surface and / or inside of a PVA-based film composed of modified PVA containing a cationic group in the molecule; Can be mentioned.

The method for producing the PVA type polarizing film is not particularly limited, and for example, a method of adsorbing iodine ions after stretching the PVA type film; a method of dyeing the PVA type film with a dichroic dye and then stretching; PVA Method of dyeing dichroic dye after stretching the base film; dichroic dye is PVA
Examples of the method include a method of printing on a base film and then stretching; a method of printing a dichroic dye after stretching a PVA film.
More specifically, iodine is dissolved in a potassium iodine solution to form a higher order iodine ion, which is adsorbed on a PVA film and stretched, and then a 1 to 4% boric acid aqueous solution having a bath temperature of 30 to 40. A method of producing a polarizing film by immersing the film in a temperature of 50 ° C., or a PVA film is similarly treated with boric acid and stretched uniaxially by about 3 to 7 times, and then added to a dichroic dye aqueous solution of 0.05 to 5% at a bath temperature of 30 There is a method of producing a polarizing film by immersing at -40 ° C to adsorb the dye, drying at 80-100 ° C and heat fixing.

(Thermoplastic Saturated Norbornene Resin Sheet) In the present invention, a sheet made of a thermoplastic saturated norbornene resin is laminated on one side or both sides of the PVA sheet. The thermoplastic saturated norbornene-based resin of the present invention is disclosed in JP-A-3-14882 and JP-A-3-122137.
Known resins such as ring-opening polymer hydrogenated products of norbornene-based monomers, addition-type polymers of norbornene-based monomers, addition-type polymers of norbornene-based monomers and olefins, and polymers thereof. And the like.

The norbornene-based monomer is a monomer known in the above publications, JP-A-2-227424 and JP-A-2-276842, and examples thereof include norbornene and
Substituted derivatives of its alkyl, alkylidene, aromatic, etc.,
Halogen, hydroxyl group, ester group, alkoxy group, cyano group, amide group of these substituted or unsubstituted olefins,
Polar substituents such as imide group and silyl group, for example, 5-methyl-2-norbornene, 5,5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-
2-norbornene, 5-ethylidene-2-norbornene, 5methoxycarbonyl-2-norbornene, 5-cyano-2-norbornene, 5-methyl-5methoxycarbonyl-2-norbornene, 5-phenyl-2-norbornene, 5- Phenyl-5-methyl-2-norbornene, etc .; dicyclopentadiene, derivatives and substitution products thereof similar to the above, for example, 2,3-dihydrodicyclopentadiene, etc .; dimethanooctahydronaphthalene, similar to the above. Derivatives and substituted compounds such as 6-methyl-1,
4: 5,8-Dimethano-1,4,4a, 5,6,7,
8,8a-octahydronaphthalene, 6-ethyl-1,
4: 5,8, dimethano-1,4,4a, 5,6,7,
8,8a-octahydronaphthalene, 6-ethylidene-
1,4: 5,8, dimethano-1,4,4a, 5,6
7,8,8a-octahydronaphthalene, 6-chloro-
1,4: 5,8, dimethano-1,4,4a, 5,6
7,8,8a-octahydronaphthalene, 6-cyano-
1,4: 5,8-dimethano-1,4,4a, 5,6
7,8,8a-octahydronaphthalene, 6-pyridyl-1,4: 5,8-dimethano-1,4,4a, 5,6
7,8,8a-octahydronaphthalene, 6-methoxycarbonyl-1,4: 5,8-dimethano-1,4,4
a, 5,6,7,8,8a-octahydronaphthalene or the like; an adduct of cyclopentadiene and tetrahydroindene or the like, a derivative or a substitution product similar to the above, for example,
1,4-Dimethano-1,4,4a, 4b, 5,8,8
a, 9a-octahydrofluorene, 5,8-methano-
1,2,3,4,4a, 5,8,8a-octahydro-
2,3-cyclopentadienonaphthalene, etc .; multimers of cyclopentadiene, derivatives and substitution products similar to the above, for example, 4,9: 5,8-dimethano-3a, 4,4
a, 5,8,8a, 9,9a-octahydro-1H-benzoindene, 4,11: 5,10: 6,9-trimethano-3a, 4,4a, 5,5a, 6,9,9a, 10 ，
And the like.

The norbornene-based monomer may be polymerized by a known method. If necessary, the norbornene-based monomer may be copolymerized with another copolymerizable monomer or may be hydrogenated to obtain a thermoplastic norbornene-based thermoplastic norbornene-based resin. It may be a hydrogenated polymer. Further, a polymer or a polymer hydrogenated product is subjected to a method known in JP-A-3-95235 or the like to obtain an α, β-unsaturated carboxylic acid and / or a derivative thereof, a styrene-based hydrocarbon, an olefin-based unsaturated bond and a hydrolyzed product. It may be modified by using an organosilicon compound having a decomposable group, an unsaturated epoxy monomer or the like.

The thermoplastic saturated norbornene-based resin used in the present invention has a number average molecular weight of usually 25,000 to 100,000, preferably 3 as measured by a gel permeation chromatography (GPC) method using a toluene solvent.
10,000-80,000, more preferably 35,000
The range of 0 to 70,000 is desirable. If the number average molecular weight is too small, the physical strength will be poor, and if it is too large, the operability during molding will be poor.

When the thermoplastic saturated norbornene-based resin is obtained by hydrogenating a ring-opening (co) polymer of a norbornene-based monomer, the hydrogenation rate is from the viewpoint of heat deterioration resistance and light deterioration resistance. It is usually 90% or more, preferably 95% or more, more preferably 99% or more.

The thermoplastic saturated norbornene-based resin is excellent in transparency, heat resistance, moisture resistance, physical strength, durability against an adhesive and the like. A sheet having a thickness of 25 μm, a hygroscopic property of usually 0.05% or less, preferably 0.01% or less, and a water vapor transmission rate of 25 ° C. and 20% RH in an environment of 90% RH.
It is possible to easily obtain those having a viscosity of ² · 24 hours or less. The photoelastic coefficient is 3 to 9 × 10 ⁻¹⁵ cm ² / dyn.
Since it is as small as e, the influence on the retardation is small even if external force is applied or there is residual stress, and it is suitable for the production of an optically uniform film.

If desired, the thermoplastic saturated norbornene-based resin used in the present invention may include a phenol-based or phosphorus-based antiaging agent; a phenol-based thermal deterioration inhibitor; an amine-based antistatic agent; an aliphatic alcohol. And various additives such as lubricants such as esters of polyhydric alcohols, partial esters of polyhydric alcohols and partial ethers thereof may be added.

Further, since the liquid crystal is usually deteriorated by ultraviolet rays, an ultraviolet absorber should be added if it is used for a liquid crystal display but no other protective means such as laminating an ultraviolet protection filter is taken. Is preferred. As the UV absorber, a benzophenone-based UV absorber, a benzotriazole-based UV absorber, an acrylonitrile-based UV absorber, or the like can be used. Among these, benzophenone-based UV absorbers are preferable,
The addition amount depends on the thickness of the thermoplastic saturated norbornene-based resin sheet, but is usually 10 to 100,000 ppm, preferably 100 to 10,000 ppm. The thinner the sheet, the more UV absorber is required.

Furthermore, in order to reduce the surface roughness, it is preferable to add a leveling agent. As the leveling agent, for example, a fluorine-based nonionic surfactant, a special acrylic resin-based leveling agent, a coating leveling agent such as a silicone-based leveling agent can be used, and among them, those having good compatibility with a solvent are preferable, The addition amount is usually 5
50,000ppm, preferably 10-20,000p
pm.

When the thermoplastic saturated norbornene-based resin sheet used in the present invention is used as a protective layer for a PVA-based polarizing film, it is preferably produced by a solution casting method.
Since it is a resin having a small photoelastic coefficient, unlike the case of TAC, a sheet having a sufficiently small birefringence can be obtained even if the sheet is produced by a melt molding method.

In order to perform solution casting of the thermoplastic saturated norbornene resin, the resin is dissolved in a solvent. The solvent used preferably has a boiling point of 100 ° C. or higher, and 120 ° C.
The above is more preferable. In particular, a solvent that can uniformly dissolve the thermoplastic saturated norbornene resin even at a solid content concentration of 10% by weight or more at 25 ° C. is preferable.

Examples of such a solvent include toluene, xylene, ethylbenzene, chlorobenzene, trimethylbenzene, diethylbenzene, isopropylbenzene, chlorobenzene and the like, and among them, xylene, ethylbenzene and chlorobenzene are preferable. Further, as long as it dissolves the thermoplastic saturated norbornene-based resin, dichlorohexane, chloroform, benzene, cyclic ethers such as tetrahydrofuran and dioxane, linear hydrocarbons such as n-hexane and n-octane, etc. may be added to these solvents. May be included. Those which satisfy these conditions well include those containing 50% or more of an aromatic solvent having a boiling point of 100 ° C. or more, such as xylene and ethylbenzene.

The resin concentration in the solution used for casting is usually 5
-60% by weight, preferably 10-50% by weight, more preferably 20-45% by weight. If the concentration of the resin is too low, it is difficult to adjust the thickness of the sheet because the viscosity is low, and if the concentration is too high, the viscosity is high and the film-forming property is poor, and a film having good appearance cannot be obtained.

The method for casting the resin solution is not particularly limited, and a general solution casting method can be used. Specifically, the resin solution is applied with a bar coater, a T-die, a T-die with a bar, a doctor knife, a meer bar, a roll coat,
A method of casting on a heat resistant material such as polyethylene terephthalate, a steel belt, a flat plate such as a metal foil or a roll using a die coat or the like can be used.

The sheet produced by the solution casting method is dried to a residual solvent concentration of 2% by weight or less. If the residual solvent concentration is too high, the heat resistance is poor, and when used in a high temperature environment, the residual solvent evaporates, which adversely affects the surroundings and causes deformation.

The sheet is usually preferably dried in two stages. First, as the first stage of drying, a flat plate or a sheet on a roll is heated at 30 to 100 ° C., preferably 4
Drying is performed in the temperature range of 0 to 80 ° C. until the residual solvent temperature becomes 10% by weight or less, preferably 5% by weight or less. In this case, if the drying temperature is too high, the sheet foams when the solvent volatilizes. Then, the sheet is peeled from the flat plate or roll, and as the second stage drying, from room temperature to 60 ° C. or higher,
Preferably, the temperature is raised to a temperature range from 70 ° C. to the glass transition temperature (Tg) of the resin until the residual solvent concentration becomes 2% by weight or less, preferably 1% by weight or less, more preferably 0.5% by weight or less. dry.

If the drying temperature is too low, the drying does not proceed, and if the temperature is too high, foaming occurs. After the first stage drying, the sheet is peeled from the flat plate or roll after the completion of the drying, and even after the second stage drying, or after the first stage drying, the sheet is cooled and the sheet is peeled from the flat plate or roll. The second stage drying may be performed.

When the sheet is produced by the melt molding method, T
There are a method using a die, a melt extrusion method such as an inflation method, a calender method, a hot press method, and an injection molding method. Among them, the melt extrusion method using a T die, which has small thickness unevenness, can be easily processed into a thickness of about 10 to 500 μm, and can reduce the absolute value of retardation and its variation, is preferable.

The conditions of the melt molding method are the same as the general conditions used for an optical material having a similar Tg. For example, in the melt extrusion method using a T die, a resin temperature of 240 is used.
~ 300 ℃, take-up roll temperature 100 ~ 1
It is preferable to select conditions under which the resin sheet can be gradually cooled at a relatively high temperature of about 50 ° C. Further, in order to reduce surface defects such as the die line, it is necessary for the die to have a structure in which the retention portion is reduced as much as possible, and it is preferable to use a die that has as few scratches as possible on the inside and lips.

The thickness of the thermoplastic saturated norbornene resin sheet is usually 5 to 500 μm, preferably 10 to 150.
μm, and more preferably 20 to 100 μm. If the thickness of the sheet is too thin, the strength will decrease. On the other hand, if the sheet is too thick, the transparency is poor, the birefringence is high, the appearance is deteriorated, and it is difficult to dry when the sheet is produced by the solution casting method. However, in the case of TAC film, in order to have sufficient moisture resistance and strength, it is usually 80μ.
Whereas the thermoplastic norbornene-based resin sheet has a thickness of about 30 μm, the thermoplastic norbornene-based resin sheet can have moisture resistance, heat resistance, and strength equal to or higher than that of a TAC film having a thickness of 80 μm. Even if it is thin, it functions sufficiently as a protective layer even if it is thin, and has good visual dependency.

The thickness unevenness of the sheet is usually within ± 5%, preferably within ± 3%, and more preferably within ± 2% of the average thickness over the entire surface. If the sheet has a large thickness unevenness, it causes image distortion and variation in retardation, and is not preferable as a protective layer for the uneven film for liquid crystal displays.

The light transmittance of the thermoplastic saturated norbornene resin sheet is usually 80% or more, preferably 85% or more, more preferably 90% or more.

The heat resistance of this sheet is determined by the type of thermoplastic saturated norbornene-based resin, the type of solvent used, and the residual solvent concentration when produced by the solution casting method.
The higher the residual solvent concentration, the lower the heat resistance. The thermoplastic saturated norbornene-based resin used to form the sheet has a Tg of usually 90 ° C. or higher, preferably 110 ° C. or higher, and particularly preferably 120 ° C. or higher.

(Acrylic Adhesive) As the acrylic adhesive used in the present invention, a solution prepared by dissolving one or more (co) polymers of acrylic ester in an organic solvent such as toluene or ethyl acetate, or these ( An aqueous emulsion of a co) polymer can be used.

The acrylic pressure-sensitive adhesive is generally used as a main constituent monomer as a homopolymer glass transition temperature (T).
Those having g) of -50 ° C or lower (low Tg monomer) are used, and an appropriate comonomer is selected for adjusting the Tg and adhesive properties of the copolymer. Specifically, a low Tg monomer that imparts tackiness, such as butyl acrylate or 2-ethylhexyl acrylate, is mainly used, and these monomers,
Examples thereof include copolymers with a high Tg monomer such as vinyl acetate, methyl methacrylate, styrene, unsaturated carboxylic acid, and acrylonitrile, which give adhesiveness and cohesive force. The acrylic pressure-sensitive adhesive may be used in combination with a crosslinking agent such as isocyanate or butylated melamine. In that case, it is mixed with the crosslinking agent before coating.

By the way, as described above, the liquid crystal is deteriorated by ultraviolet rays. Therefore, when the composite sheet is used for a polarizing film for liquid crystal displays, it is preferable that the composite sheet does not transmit ultraviolet rays. When UV absorber is added to thermoplastic saturated norbornene resin,
If the resin sheet is thin, it will not absorb enough ultraviolet light unless a large amount of UV absorber is added, and the strength of this resin sheet will be insufficient due to the thinness and the addition of a large amount of UV absorber. There is. However, when the ultraviolet absorber is added to the acrylic pressure-sensitive adhesive, only a small amount of the ultraviolet absorber is added to the thermoplastic saturated norbornene-based resin sheet, or even when not added at all, the composite sheet of the present invention, It is possible to effectively suppress the transmission of ultraviolet rays.

The ultraviolet absorber is preferably a benzophenone type, a benzotriazole type, or a salicylate type, and these may be used in combination. The amount of the ultraviolet absorber added to the acrylic adhesive depends on the type of the adhesive and the thickness of the adhesive layer, but is usually about 1 to 20 parts by weight with respect to 100 parts by weight of the resin in the adhesive. It is desirable to do.

(Composite Sheet and Manufacturing Method Thereof) The composite sheet of the present invention is obtained by laminating a thermoplastic saturated norbornene resin sheet on one or both sides of a PVA sheet through an acrylic pressure-sensitive adhesive layer, followed by thermocompression bonding. It will be.

Generally, the acrylic adhesive is a toluene-based adhesive.
It is a solution type using an ethyl acetate mixed solvent as a solvent.
Since toluene is a good solvent for the thermoplastic saturated norbornene-based resin, when the solution-type acrylic pressure-sensitive adhesive is directly applied to the thermoplastic saturated norbornene-based resin sheet, the surface of the sheet may be dissolved, which may cause optical unevenness. is there.

Therefore, in order to bond the PVA-based sheet and the thermoplastic saturated norbornene-based resin sheet, (1) a method of bonding using an aqueous emulsion-type acrylic adhesive, and (2) a solution-type PVA-based sheet. A method of applying an acrylic pressure-sensitive adhesive, volatilizing the solvent, and then laminating it with a thermoplastic saturated norbornene-based sheet, (3) ester-based such as ethyl acetate or methyl ethyl ketone, ketone-based,
A method of using an acrylic pressure-sensitive adhesive which is a poor solvent for a thermoplastic saturated norbornene-based resin such as alcohol and in which the acrylic pressure-sensitive adhesive is soluble, (4) Solution type acrylic pressure-sensitive adhesive After applying it to (separator) and volatilizing the solvent, transfer it to a thermoplastic saturated norbornene-based resin sheet and attach it to a PVA-based sheet (transfer method). It is preferable to prevent dissolution of the surface of the norbornene-based sheet.

When the transfer method is adopted, the method is not particularly limited, and it can be carried out by using an apparatus used for transferring a general pressure-sensitive adhesive or the like. The application of the acrylic pressure-sensitive adhesive is not particularly limited, such as brush coating, a method using a gun spray, a method using a spin coater, a bar coater, etc., but a method that can be easily and uniformly applied is preferable. It is preferable to use a bar coater.
In order to reduce optical refraction unevenness and the like, it is preferable to reduce unevenness in the coating thickness of the acrylic pressure-sensitive adhesive. Similarly, the release film used in the transfer method preferably has excellent surface smoothness.

The coating thickness of the acrylic adhesive is usually 10
˜50 μm, preferably 15˜30 μm. After application, the solvent and water are volatilized. In the case of a solution type acrylic pressure-sensitive adhesive, 60 to 110 ° C., preferably 70 after application.
The solvent is volatilized by drying at -100 ° C for 1 to 5 minutes, preferably 1.5 to 10 minutes.

In the present invention, a thermoplastic saturated norbornene resin sheet is laminated on at least one surface of the PVA sheet via an acrylic pressure-sensitive adhesive layer, and then heated and pressed to bond (heat compression bonding). Specifically, a PVA-based sheet and a thermoplastic saturated norbornene-based resin sheet are stuck together, and usually 50 to 120 ° C., preferably 80 to 100.
Heat in the temperature range of ℃, 1 to 5 minutes, preferably 1.5
By holding for 3 minutes and then adhering under pressure of 1-10 kg / cm ² , preferably 4-7 kg / cm ² , a composite sheet having excellent interlaminar adhesive strength can be obtained.

The composite sheet of the present invention has excellent transparency, interlayer adhesion strength and durability, and also has the low birefringence, moisture resistance, and inherent properties of a thermoplastic saturated norbornene resin sheet.
Since it has properties such as water resistance, heat resistance and physical strength, it is useful as a polarizing film in various fields.

When the composite sheet of the present invention is used as a polarizing film for a liquid crystal display, for example, a thermoplastic saturated norbornene resin sheet as a protective layer is attached to one side or both sides of a PVA type polarizing film. When the protective layer is provided on one surface, the protective layer is located outside the polarizing film in the production of the liquid crystal display in order to protect the polarizing film from the ambient temperature of the liquid crystal display. In order to maintain the quality of the polarizing film before manufacturing the liquid crystal display, prevent moisture absorption of the polarizing film in the manufacturing process, prevent deterioration of the polarization degree due to heating, etc., and protect from scratches, it is preferable to attach protective layers to both surfaces. A protective layer made of a conventionally known material may be provided on one surface.

When the composite sheet of the present invention is mainly used as a polarizing film for a liquid crystal display, in order to facilitate the laminating work on the liquid crystal substrate and the transparent electrode layer,
When a protective layer is provided on both sides, on one protective layer side,
When the protective layer is provided on one surface, it is preferable that a pressure-sensitive adhesive layer for adhering the polarizing film is laminated on the surface having no protective layer. Further, it is preferable that a release film such as release paper or release film is laminated on the pressure-sensitive adhesive layer.

[0054]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. In addition, part and% are
Unless otherwise specified, it is based on weight.

The methods of measuring the physical properties in the following examples and comparative examples are as follows. (1) The number average molecular weight was measured by the GPC method using toluene as a solvent. (2) The hydrogenation rate was measured by ¹ H-NMR. (3) The glass transition temperature (Tg) was measured by the DSC method. (4) Retardation is Belek with a wavelength of 550 nm.
It was measured by a Convensator. (5) The thickness of the sheet and the film was measured with a dial type thickness gauge. (6) In Example 1 and Comparative Examples 1 to 3, the light transmittance was measured with a spectrophotometer by continuously changing the wavelength in the wavelength range of 400 to 700 nm, and the minimum transmittance was obtained. And rate. Example 1 and Comparative Examples 1-
In No. 3, the minimum transmittance was shown at 400 nm. In addition, in Example 2, by using a spectrophotometer,
The light transmittance was measured by continuously changing the wavelength in the range of 700 nm. (7) The residual solvent concentration of the sheet was measured by gas chromatography at a temperature of 200 ° C. (8) The adhesive strength is measured by the T-peel peel test (JIS Z-0
237).

Reference Example 1 (Synthesis of Thermoplastic Saturated Norbornene Resin) 6-Methyl-1,4,5,8-dimethano-1,4,4
To a, 5,6,7,8,8a-octahydronaphthalene, 10 parts of a 15% cyclohexane solution of triethylaluminum, 5 parts of triethylamine, and 10 parts of a 20% cyclohexane solution of titanium tetrachloride were added as a polymerization catalyst, The ring-opening polymerization was carried out in cyclohexane, and the obtained ring-opening polymer was hydrogenated with a nickel catalyst to obtain a polymer solution. The polymer solution was coagulated in isopropyl alcohol and dried to obtain a powdery resin. The number average molecular weight of this resin was 40,000, the hydrogenation rate was 99.8% or more, and the Tg was 142 ° C.

[Example 1] 15 g of the resin obtained in Reference Example 1 was dissolved in 85 g of xylene, and a leveling agent (Sumitomo 3M, Florard FC-430) 500 pp was added thereto.
m was added to obtain a resin solution composition. This resin solution composition was placed on a glass plate whose surface had been polished, and an appropriate amount was cast by a bar coater to a width of about 300 mm and a length of 500 mm. This is the first stage of drying, and the whole glass plate is heated from 20 ° C to 50 ° C in an air-refluxing oven.
The temperature was raised over 0 minutes and dried. Then, in the second stage of drying, the resin film was peeled from the glass plate, dried in an oven at 90 ° C. for 30 minutes, cooled to room temperature, and then cut off at a width of 10 mm to obtain a thermoplastic saturated norbornene-based resin sheet. The residual solvent concentration of this sheet was 1.0% by weight.

The surface of this sheet was observed visually and by an optical microscope, but no foaming, lines, scratches, etc. were observed. The Tg was 139 ° C., the average thickness was 50 μm, the thickness unevenness was ± 4 μm or less at the maximum, the light transmittance was 98.5%, and the absolute value of the retardation value was 3 nm or less on the entire surface. The water vapor permeability of this sheet was 5.2 g / m ² · 24 hr (converted to a thickness of 25 μm, about 12 g / m ² · 24 hr) in an environment of 25 ° C. and 90% RH.

An acrylic adhesive (Nogawa Chemical Co., DD-) was applied to the surface of the release film (Fujimori Kogyo Co., Ltd., Vina sheet).
624) was applied to a thickness of 20 μm using a bar coater, dried at 80 ° C. for 2 minutes, and transferred to the thermoplastic saturated norbornene resin sheet. Next, a PVA-based polarizing film (thickness of about 100 μm) that is uniaxially stretched by adsorbing iodine
The above-mentioned transfer sheet was attached to both surfaces of the above with an acrylic pressure-sensitive adhesive layer interposed between them, and kept at 90 ° C. for 2 minutes to bond them by applying 5 kg / cm ^{2 of} pressure.

Immediately after adhesion, 200 cycles of a heat cycle in which holding at 80 ° C. and 90 RH% for 1 hour and holding at −40 ° C. for 1 hour were alternately repeated, adhesive strength was measured, and the results are shown in Table 1. It was Further, the transfer sheet and the thermoplastic saturated norbornene-based resin sheet were bonded together via an acrylic pressure-sensitive adhesive layer, kept at 90 ° C. for 2 minutes, and bonded by applying 5 kg / cm ^{2 of} pressure. Immediately after the adhesion and after 200 heat cycles, the light transmittance was measured, and the results are shown in Table 1.

[Comparative Example 1] The transfer sheet of Example 1, which was obtained by transferring an acrylic pressure-sensitive adhesive to a thermoplastic saturated norbornene-based resin sheet, was attached to both surfaces of a PVA-based polarizing film, and then the sheet was not heated. , Keep at room temperature for 2 minutes, 5kg / c
Adhesion was performed by pressurizing with m ² , and the adhesive strength was measured in the same manner as in Example 1. The results are shown in Table 1. The transfer sheet and the thermoplastic saturated norbornene-based resin sheet were adhered, and the light transmittance was measured in the same manner as in Example 1.

Comparative Example 2 The procedure of Comparative Example 1 was repeated except that a special synthetic rubber adhesive (DA-753 manufactured by Nogawa Chemical Co., Ltd.) was used as the adhesive.

Comparative Example 3 The procedure of Comparative Example 1 was repeated except that a hot melt adhesive (DH-597A, manufactured by Nogawa Chemical Co., Ltd.) was used as the adhesive.

[0064]

[Table 1]

Example 2 Benzophenone UV Absorber (Kyoyaku Co., Ltd., Viosorb 110) and Benzotriazole UV Absorber (Kyoyaku Co., Ltd., Vios)
orb 583) was mixed at a weight ratio of 8: 2 and added at a ratio of 4.7% to an acrylic pressure-sensitive adhesive (Nogawa Chemical Co., DD-624; resin concentration 47%) as an adhesive. P is the same as in Example 1 except that
A composite sheet in which a transfer sheet was bonded to both sides of a VA-based sheet, and a sheet in which a transfer sheet was bonded to a thermoplastic saturated norbornene-based resin sheet were produced.

The adhesive strength of the obtained composite sheet was 5.3 kg / 25 mm immediately after the adhesion and after the heat cycle test.
Therefore, no difference was observed from the case where no ultraviolet absorber was added. The sheet having the transfer sheet adhered to the thermoplastic saturated norbornene-based resin sheet did not show a difference in light transmittance at a wavelength of about 420 to 700 nm from that without addition of an ultraviolet absorber, but at a wavelength of 400 nm it had about 89. It is as low as 9%, and about 50% at wavelength of 380 nm and wavelength of 23
It was 0% at 0 to 350 nm.

[0067]

EFFECTS OF THE INVENTION According to the present invention, a composite sheet obtained by laminating a PVA-based sheet and a thermoplastic saturated norbornene-based resin sheet, which is excellent in transparency, durability under high temperature and high humidity, heat resistance, physical strength, etc. Will be provided. The composite sheet of the present invention is
Excellent inter-layer adhesion, low birefringence inherent in thermoplastic saturated norbornene resin sheet, moisture resistance,
Since it has properties such as water resistance, heat resistance and physical strength, it is useful as a polarizing film in various fields.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Izu Natsume 1-2-1 Yokou, Kawasaki-ku, Kawasaki-shi, Kanagawa Inside Zeon Corporation R & D Center

Claims (2)

[Claims] 1. A composite sheet comprising a polyvinyl alcohol-based sheet, a thermoplastic saturated norbornene-based resin sheet laminated on at least one surface of the polyvinyl alcohol-based sheet via an acrylic pressure-sensitive adhesive layer, and heat-pressed. 2. The composite sheet according to claim 1, wherein the polyvinyl alcohol-based sheet is a polarizing film.