JP2003050313A - Polarizing plate and liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing plate improving warpage of a liquid crystal cell with plastics substrates generated by expansion and contraction of the polarizing plate to a level without any practical problem and a liquid crystal display element using the same. SOLUTION: An adhesive layer of 25 μm thickness with >=30 μm/h creep shift length (25 deg.C) generated by loading 500 gf (gram-force) tensile shear stress for one hour with respect to 10-mm-square adhesion area is laminated on at least one surface of the polarizing plate. >=0.10 mm dimensional shift length of the polarizing plate is observed in the case of sticking the polarizing plate to the plastics substrate with >=8 inches width across corner and left standing for 24 hours in the stuck state under 40 deg.C and 92% RH(relative humidity) condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing plate used in a liquid crystal display device (hereinafter sometimes abbreviated as LCD) and a liquid crystal display element using the polarizing plate.

[0002]

2. Description of the Related Art Liquid crystal display devices are used for desk computers, electronic clocks, personal computers, word processors,
It is used for measuring instruments of automobiles and machines, and a polarizing plate is used for this liquid crystal display device. As a polarizing plate,
Generally, triacetyl cellulose (hereinafter sometimes abbreviated as TAC) is formed on both surfaces of a polarizing film made of a polyvinyl alcohol (hereinafter sometimes abbreviated as PVA) film in which iodine or a dichroic dye is adsorbed and oriented. .) Is used as a laminate of protective films.

Conventionally, as a method for producing a polarizing plate, a polyvinyl alcohol film has been dyed mainly with dichroic iodine or a dichroic dye, and stretched 5 times or more in order to arrange molecules, and then stretched. In order to maintain the above state, the film is cross-linked with a cross-linking agent such as boric acid or borax, dried to prepare a polarizing film, and a protective film is attached thereto.
The steps of dyeing, crosslinking and stretching need not be performed separately and may be performed simultaneously, and the order of each step may be arbitrary.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the polarizing film formed by dyeing, crosslinking, stretching and drying the film, the stress generated during the stretching remains. Therefore, when the polarizing plate is exposed to heating and humidifying conditions, the polarizing film does not withstand the residual stress and contracts, deforms, etc., causing the polarizing plate itself to change its dimensions. However, there is a problem that the hue of the liquid crystal display device is changed.

In particular, a plastic liquid crystal cell using a plastic substrate is more flexible than a glass substrate, so that the liquid crystal cell warps due to contraction of the polarizing plate. Such a phenomenon becomes more remarkable as the size of the plastic substrate forming the liquid crystal cell increases. Therefore, depending on the application, there is a problem that the plastic substrate cannot be used for assembling the liquid crystal panel due to the warp generated in the liquid crystal cell.

Therefore, in order to solve the above-mentioned conventional problems, the present invention utilizes the stress relaxation property of the pressure-sensitive adhesive interposed between the liquid crystal cell substrate and the polarizing plate, and thus the plastic substrate liquid crystal generated by the expansion and contraction of the polarizing plate. Warp of the cell,
It is an object of the present invention to provide a polarizing plate and a liquid crystal display device using the polarizing plate, which can be improved to a level that causes no practical problems.

[0007]

The present invention generally uses a pressure-sensitive adhesive as a means for bonding a liquid crystal cell substrate and a polarizing plate, and the pressure-sensitive adhesive layer formed from this pressure-sensitive adhesive has stress relaxation properties. Focusing on, the adhesive that shows a creep characteristic (deviation amount) of a certain size or more is interposed between the liquid crystal cell substrate and the polarizing plate to follow the dimensional behavior of the polarizing plate, such as contraction and deformation of the polarizing plate. Based on the finding that if the adhesive is designed to move, the stress generated when the polarizing plate behaves in a dimensional manner can be relieved and the addition to the plastic substrate can be reduced to reduce the warpage. It was done.

To achieve the above object, the polarizing plate of the present invention is a polarizing plate in which an adhesive layer is laminated on at least one side, and the adhesive layer has a thickness of 25 μm and an adhesive area of 10 mm square and a tensile strength of 500 gf. The creep shift amount (25 ° C.) when a breaking stress is applied for 1 hour is 30 μm / H or more.

In the above polarizing plate, this is set at a diagonal distance of 8
The size deviation of the polarizing plate is preferably 0.10 mm or more when bonded to a plastic substrate of inch or more and left in the bonded state under the conditions of 40 ° C. and 92% RH for 24 hours. At this time, it is preferable that the maximum warp amount of the four corners of the plastic substrate is suppressed to 35 mm or less.

The pressure-sensitive adhesive layer is preferably formed of an acrylic pressure-sensitive adhesive and has a thickness of 5 to 30 μm.

Further, the present invention is characterized in that the polarizing plate is laminated with at least one optical layer selected from a retardation plate, a reflection plate, a semi-transmissive reflection plate, a viewing angle compensation film and a brightness enhancement film. Provide a polarizing plate.

Next, the liquid crystal display device of the present invention is characterized in that the polarizing plate of the present invention is bonded to at least one surface of a liquid crystal cell. In particular, the object of the present invention is most effectively achieved in a combination of the polarizing plate of the present invention and a liquid crystal cell made of a plastic substrate.

Further, the liquid crystal display element of the present invention is a liquid crystal display element in which a polarizing plate and a plastic substrate having a diagonal distance of 8 inches or more are bonded via an adhesive layer, and the adhesive layer has a thickness of 25 μm. 500g in 10mm square area
When the amount of creep displacement (25 ° C.) when the tensile breaking stress of f is applied for 1 hour is 30 μm / H or more, and the liquid crystal display element is placed under the conditions of 40 ° C. and 92% RH for 24 hours, The dimensional deviation of the polarizing plate is 0.10 mm or more. In this liquid crystal display element, the maximum warp amount of the four corners of the plastic substrate is 35
It is preferable to be suppressed to mm or less.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The polarizing plate of the present invention is obtained by laminating a pressure-sensitive adhesive layer having specific creep characteristics on a polarizing plate produced by a conventional method on at least one surface of the polarizing plate. , With a thickness of 25 μm and an adhesion area of 10 mm square,
The amount of creep deviation (25 ° C.) when a tensile breaking stress of 500 gf is applied for 1 hour is 30 μm / H or more, preferably 33 μm / H or more. When the polarizing plate is attached to a plastic substrate having a diagonal distance of 8 inches or more, and the attached state is left under the conditions of 40 ° C. and 92% RH for 24 hours, the positional deviation amount of the polarizing plate is 0.10 mm. It is preferably not less than 0.15 mm, more preferably not less than 0.15 mm. As a result, the dimensional change of the polarizing plate caused by the residual stress inherent in the polarizing film can be alleviated by the adhesive layer, so that the warpage of the plastic substrate constituting the liquid crystal cell is reduced.

The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited, and those having the above-mentioned characteristics can be used appropriately. For example, adhesives such as acrylic polymers, urethane polymers, silicone polymers, polyesters and polyethers can be mentioned. Among them, acrylic pressure-sensitive adhesives are preferable because they have excellent optical transparency, pressure-sensitive adhesive properties and weather resistance. Alternatively, the pressure-sensitive adhesive may contain fine particles to form a light-diffusing pressure-sensitive adhesive layer.

The pressure-sensitive adhesive layer may be provided on at least one side of the polarizing plate, and if necessary, the pressure-sensitive adhesive layer may be provided on one side or both sides of the protective layer. The thickness of the adhesive layer is not particularly limited, but is preferably 5 to 30 μm, more preferably 10 to 25 μm, and particularly preferably 15 to 25 μm.
It should be By setting the thickness of the pressure-sensitive adhesive layer in this range, the stress generated when the polarizing plate behaves in a dimensional manner can be relaxed, and the phenomenon that the pressure-sensitive adhesive causes stains on the surface of the polarizing plate can be prevented.

The polarizing plate used in the present invention is formed by dyeing, crosslinking, stretching and drying a synthetic resin film, and is formed on one side or both sides of a polarizer made of a polyvinyl alcohol type polarizing film containing a dichroic substance. The transparent protective film serving as a protective layer is adhered via the adhesive layer of (1), for example, an adhesive layer composed of a vinyl alcohol polymer or the like.

As the polarizer (polarizing film), a synthetic resin film may be subjected to a suitable treatment such as a dyeing treatment with a dichroic substance such as iodine or a dichroic dye, a stretching treatment and a crosslinking treatment in an appropriate order or It is possible to use an appropriate material which is applied by a method and which transmits linearly polarized light when natural light is made incident, and in particular, one having excellent light transmittance and polarization degree is preferable.
The thickness of the polarizer is not particularly limited, but 1 to
The thickness is generally 80 μm, and particularly preferably 5 to 40 μm. This is because when the thickness is less than 5 μm, the mechanical strength decreases, and when it exceeds 40 μm, the optical characteristics deteriorate.

As the synthetic resin film, for example, a hydrophilic polymer film such as polyvinyl alcohol or partially formalized polyvinyl alcohol is preferable, and a polyvinyl alcohol film is particularly preferable because it has a good dyeing property with iodine. The polyvinyl alcohol-based film is a casting method in which a polyvinyl alcohol-based resin is cast to form an undiluted solution obtained by dissolving it in water or an organic solvent.
A film formed by any method such as an extrusion method can be appropriately used. The degree of polymerization of the polyvinyl alcohol resin used is preferably 100 to 5000, and 1400 to 4
000 is more preferable. The thickness of the polyvinyl alcohol-based film is generally 80 μm or less, and preferably 35 to 76 μm. When it exceeds 80 μm, the color change of the display panel becomes large when it is mounted on the liquid crystal display device, while when it is too thin, the stretching becomes difficult.

The polarizing film can be manufactured, for example, by the following method.

In the dyeing step, the polyvinyl alcohol film is usually immersed in a dyeing bath containing iodine or a dichroic dye at 20 to 70 ° C. for 1 to 20 minutes to adsorb the iodine or the dichroic dye. , 2 to 4 times. The concentration of iodine or dichroic dye in the dyeing bath is usually 0.1 to 1.0 part by mass per 100 parts by mass of water. 2 to 20 parts by mass of an auxiliary agent such as potassium iodide may be added to the dyeing bath, and a small amount of an organic solvent compatible with water may be contained in addition to the water solvent. Further, the polyvinyl alcohol-based film is dyed in an aqueous solution containing iodine or a dichroic dye at 20 to 60 ° C. in a water bath or the like before dyeing in an aqueous solution containing iodine.
Swelling treatment may be performed for 1 to 10 minutes.

In the crosslinking step, the dyed polyvinyl alcohol film is usually stretched in a boron compound-containing aqueous solution at a total stretching ratio of 5 to 7 times. The composition of the boron compound-containing aqueous solution to be crosslinked is usually 100% water.
1 to 1 parts by weight of PVA crosslinking agent such as boric acid, borax, glyoxal, glutaraldehyde, etc., alone or as a mixture
It is 0 part by mass. An auxiliary agent such as potassium iodide may be added to the crosslinking bath in an amount of 0.05 to 15% by mass, which is particularly preferable from the viewpoint of obtaining uniform in-plane characteristics. The temperature of the aqueous solution is usually 2
It is in the range of 0 to 70 ° C, preferably 40 to 60 ° C. The immersion time is not particularly limited, but is usually 1 second to 15 minutes. In addition to the water solvent, a small amount of an organic solvent compatible with water may be contained.

When the polyvinyl alcohol film is stretched, the stretching method, the number of times of stretching and the like are not particularly limited, and may be performed in each step of dyeing and crosslinking,
It may be performed only in any one step. Moreover, you may perform in the same process multiple times.

A polyvinyl alcohol-based film that has been subjected to an iodine adsorption orientation treatment or the like is further placed in an aqueous iodide solution such as potassium iodide having a water temperature of 10 to 60 ° C., preferably 30 to 40 ° C. and a concentration of 0.1 to 10% by mass. After dipping for 1 second to 1 minute, it is washed with water and dried at 20 to 80 ° C. for 1 minute to 10 minutes to obtain a polarizing film. An auxiliary agent such as zinc sulfate or zinc chloride may be added to the iodide aqueous solution.

The water content of the polarizing film when bonded to the protective film (the weight ratio of water in the polarizing film to the total weight of the polarizing film) is generally 15 to 25 mass, although it depends on the thickness of the polarizing film. It is preferable to set in the range of%. If the water content is less than 15% by mass,
The appearance after bonding the protective film deteriorates, 25% by mass
If it exceeds, the amount of change in water content after the production of the polarizing plate will increase and the dimensional change will increase.

An appropriate transparent film can be used as the protective film material which is a transparent protective layer provided on both sides of the polarizer (polarizing film). Above all, a film made of a polymer having excellent transparency, mechanical strength, thermal stability, moisture shielding property and the like is preferably used. Examples of the polymer include polyester resin, acetate resin, polynorbornene resin, polyether sulfone resin, polycarbonate resin, polyamide resin, polyimide resin, polyolefin resin, acrylic resin, or acrylic resin. Examples thereof include thermosetting or ultraviolet curable resins such as resins, urethanes, epoxies, and silicones. Among them, an acetate resin is preferable from the viewpoint of transparency, and a triacetyl cellulose film whose surface is saponified with alkali or the like is particularly preferable from the viewpoint of polarization characteristics and durability.

The thickness of the transparent protective film is arbitrary, but generally 500 μm or less for the purpose of thinning the polarizing plate,
The thickness is preferably 5 to 300 μm. When transparent protective films are provided on both sides of the polarizing film, transparent protective films made of different polymers may be used on the front and back sides. Further, the transparent protective film used for the protective layer,
As long as the object of the present invention is not impaired, a hard coat treatment, an antireflection treatment, a treatment for the purpose of preventing sticking, diffusion or antiglare, or the like may be applied.

The adhesive treatment between the polarizing film and the transparent protective film as the protective layer is not particularly limited, but for example, an adhesive made of a vinyl alcohol polymer, boric acid, borax, or glutaraldehyde. Alternatively, it can be carried out via an adhesive or the like made of at least a water-soluble cross-linking agent of a vinyl alcohol polymer such as melamine or oxalic acid. Such an adhesive layer can be formed as a coating / drying layer of an aqueous solution, but other additives and a catalyst such as an acid can be blended, if necessary, in the preparation of the aqueous solution. In particular, it is preferable to use an adhesive made of polyvinyl alcohol because it has the best adhesiveness with PVA (polarizing film).

FIG. 1 is a schematic sectional view showing a state in which the polarizing plate of the present invention is attached to a plastic substrate. The adhesive layer 2 is formed on one surface of the polarizing plate 1, and the plastic substrate 3 is bonded via the adhesive layer 2. The laminated liquid crystal display element was put under the condition of 40 ° C. and 92% RH.
By leaving it for 4 hours, the polarizing plate 1 undergoes a dimensional change, and the adhesive layer 2 causes creep displacement accordingly, and the plastic substrate 3 warps. Warpage amount of plastic substrate 4
Can be obtained by placing the substrate on a horizontal table and measuring the distance between the tip of the substrate and the horizontal table. Of the four corners of the board, the amount of warpage at the portion with the largest amount of warpage is the maximum amount of warpage.

In order to reduce the hue change of the liquid crystal display device, the polarizing plate is attached to a plastic substrate having a diagonal distance of 8 inches or more, and the attached state is 40 ° C. and 92% R.
The maximum warp amount of the four corners of the plastic substrate when placed under the condition of H for 24 hours is preferably 35 mm or less, more preferably 30 mm or less, particularly preferably in the case of a plastic substrate having a diagonal distance of 8 inches or more. Is 2
It is 5 mm or less. This is because when the maximum warp amount is 35 mm or less, the hue change of the liquid crystal display device does not pose a practical problem. When the polarizing plate of the present invention is bonded to a liquid crystal cell to form a liquid crystal display element, the size of the plastic substrate is preferably 8 inches or more and 15 inches or less, particularly 8 inches or more 11 inches. It is preferably less than or equal to inches.

Here, the plastic substrate is not particularly limited, and any conventionally known one can be used. Examples of the resin forming the plastic substrate include thermoplastic resins such as polycarbonate, polyarylate, polyethersulfone, polyester, polysulfone, polymethylmethacrylate, polyetherimide, polyamide, epoxy resin, unsaturated polyester, and polydiallyl. Examples thereof include thermosetting resins such as phthalate and polyisobornyl methacrylate. 1 such resin
One kind or two or more kinds can be used, and they can also be used as a copolymer or a mixture with other components.

Among the above-mentioned resin for forming a substrate, it is excellent in transparency and impact resistance, and in view of durability in the case of a liquid crystal cell, chemical resistance, optical isotropy, low absorption, low moisture permeability, From the viewpoint of excellent gas barrier properties against oxygen and the like, it is preferable to use an epoxy resin (particularly an alicyclic epoxy resin) and a cured product of an epoxy composition containing an acid anhydride curing agent and a phosphorus curing catalyst. . As the alicyclic epoxy resin, various kinds can be used and are not particularly limited.

Examples of the acid anhydride type curing agent include phthalic anhydride, maleic anhydride, trimellitic anhydride, pyromellitic anhydride, nadic acid anhydride, glutaric anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic acid. Anhydrous, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, methyl nadic acid anhydride, dodecenyl succinic anhydride, dichlorosuccinic anhydride, benzophenone tetracarboxylic acid anhydride, chlorendic acid anhydride, etc. Can be mentioned. In particular, colorless or pale yellow acid anhydrides such as tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, and methylhexahydrophthalic anhydride are preferable. The compounding amount of the acid anhydride curing agent is preferably 0.5 to 1.3 equivalents per 1 epoxy equivalent of the epoxy resin.

Examples of phosphorus-based curing catalysts include alkylphosphines, phosphine oxides, and phosphonium salts. The blending amount is 0.2 to 10 parts by mass, preferably 0.5 to 4 parts by mass, per 100 parts by mass of the acid anhydride curing agent curing agent.

The plastic substrate is formed by an appropriate method such as casting molding method, casting molding method, injection molding method, roll coating molding method, extrusion molding method, transfer molding method, and reaction injection molding method (RIM). It can be carried out. In the formation thereof, if necessary, additives such as dyes, modifiers, discoloration preventing agents, antioxidants, ultraviolet absorbers, release agents, reactive diluents and non-reactive diluents may be added to improve transparency. It can be blended within a range that does not impair it.

In the present invention, the thickness of the plastic substrate is 5 in view of thinning, lightness, strength, deformation prevention and the like.
0 μm or more and 800 μm or less, preferably 100 μm
m or more and 700 μm or less. Therefore, the thickness of the plastic substrate may be achieved as a laminate of two layers or three or more layers made of the same or different resins.

The polarizing plate and the liquid crystal display device of the present invention can be used as an optical member laminated with another optical layer in practical use. The optical layer is not particularly limited, and may be, for example, a reflection plate, a semi-transmission reflection plate, a retardation plate (1/2 wavelength plate, 1
(Including a λ plate such as a / 4 wavelength plate), a viewing angle compensation film, a brightness enhancement film, and the like, and one or two or more suitable optical layers that may be used for forming a liquid crystal display device can be used. . In particular, a polarizing plate comprising the polarizing film of the present invention described above and a protective film, a reflection type polarizing plate or a semi-transmissive reflection type polarizing plate obtained by further laminating a reflecting plate or a semi-transmissive reflecting plate, the above-mentioned polarizing film and protection. An elliptical polarizing plate or a circular polarizing plate in which a retardation plate is further laminated on a polarizing plate comprising a film, and a viewing angle compensation film is further laminated on a polarizing plate comprising the above-mentioned polarizing film and a protective film. Alternatively, a polarizing plate in which a brightness enhancement film is further laminated on the polarizing plate composed of the polarizing film and the protective film described above is preferable.

A reflective polarizing plate or a semi-transmissive reflective plate type polarizing plate in which a reflective plate or a semi-transmissive reflective plate is further laminated on the above-mentioned polarizing plate will be described.

The reflection plate is provided on the polarizing plate to form a reflection type polarizing plate. The reflective polarizing plate is usually disposed on the back side of the liquid crystal cell, and forms a liquid crystal display device (reflective liquid crystal display device) of the type that reflects and displays incident light from the viewing side (display side). The reflective polarizer is
It has an advantage that a light source such as a backlight can be omitted and the liquid crystal display device can be easily thinned. The reflective polarizing plate can be formed by an appropriate method such as a method in which a reflective layer made of metal or the like is attached to one surface of the polarizing plate. Specific examples thereof include a transparent protective film that is mat-treated if necessary, and a reflective layer formed by attaching a foil or a vapor deposition film made of a reflective metal such as aluminum to one surface of the transparent protective film.

Further, there may be mentioned a reflection type polarizing plate having a reflective layer reflecting the fine concavo-convex structure on the transparent protective film containing fine particles and having a fine concavo-convex structure on the surface. The reflective layer having a fine surface irregularity structure has an advantage of diffusing incident light by diffuse reflection, preventing directivity and glare, and suppressing uneven brightness. The transparent protective film can be formed by a method of directly attaching a metal to the surface of the transparent protective film by an appropriate method such as a vacuum vapor deposition method, an ion plating method, a vapor deposition method such as a sputtering method or a plating method. .

Further, the reflection plate may be used as a reflection sheet or the like in which a reflection layer is provided on an appropriate film conforming to the transparent protective film instead of directly attaching to the transparent protective film of the polarizing plate. it can. Since the reflective layer of the reflective plate is usually made of metal, the use form in which the reflective surface is covered with a film or a polarizing plate is to prevent reduction of the reflectance due to oxidation, and thus to maintain the initial reflectance for a long time. Also, it is preferable from the viewpoint of avoiding the additional provision of the protective layer.

The semi-transmissive polarizing plate is a semi-transmissive reflective layer in the above reflective polarizing plate, and examples thereof include a half mirror that reflects and transmits light at the reflective layer.
The semi-transmissive polarizing plate is usually provided on the back side of the liquid crystal cell, and when a liquid crystal display device is used in a relatively bright atmosphere, it reflects incident light from the viewing side (display side) to display an image. In a relatively dark atmosphere, a liquid crystal display device of the type that displays an image using a built-in light source such as a backlight built in the back side of a semi-transmissive polarizing plate is formed. That is, the semi-transmissive polarizing plate is useful for forming a liquid crystal display device of a type that can save energy for using a light source such as a backlight in a bright atmosphere and can be used with a built-in light source in a relatively dark atmosphere. Is.

Next, an elliptically polarizing plate or a circularly polarizing plate in which a retardation plate or a λ plate is further laminated on the above-mentioned polarizing plate will be described.

The retardation plate is used for converting linearly polarized light into elliptically polarized light or circularly polarized light, changing elliptically polarized light or circularly polarized light into linearly polarized light, or changing the polarization direction of linearly polarized light. In particular, a so-called quarter-wave plate (also referred to as a λ / 4 plate) is used as a retardation plate that changes linearly polarized light into elliptically polarized light or circularly polarized light, or changes elliptically polarized light or circularly polarized light into linearly polarized light. Half-wave plate (also called λ / 2 plate)
Is usually used when changing the polarization direction of linearly polarized light.

The above elliptically polarizing plate compensates (prevents) coloring (blue or yellow) generated by the birefringence of the liquid crystal layer of the super twisted nematic (STN) type liquid crystal display device to obtain a black and white display without the coloring. It is effectively used when doing. Further, the one in which the three-dimensional refractive index is controlled is preferable because it can also compensate (prevent) coloring that occurs when the screen of the liquid crystal display device is viewed from an oblique direction. Further, the circularly polarizing plate is effectively used, for example, when adjusting the color tone of an image of a reflective liquid crystal display device in which an image is displayed in color, and also has a function of preventing reflection.

As the retardation plate, a birefringent film obtained by stretching a polymer film such as polycarbonate, polyvinyl alcohol, polystyrene, polymethylmethacrylate, polypropylene and other polyolefins, polyarylate, polyamide, polynorbornene, Examples include an oriented film of a liquid crystal polymer and a film in which an oriented layer of a liquid crystal polymer is supported.

The retardation plate is used for various purposes such as various wavelength plates such as 1/2 or 1/4, and those for the purpose of compensating for coloring due to birefringence of the liquid crystal layer and compensating for viewing angle such as widening of viewing angle. It may have a corresponding retardation, and may be a tilt-oriented film having a controlled refractive index in the thickness direction. Also,
It may be one in which two or more kinds of retardation plates are laminated to control optical characteristics such as retardation.

The tilt-oriented film may be formed by, for example, adhering a heat-shrinkable film to a polymer film and subjecting the polymer film to a stretching treatment and / or a shrinking treatment under the action of the shrinkage force caused by heating, or a method in which a liquid crystal polymer is slanted. It can be obtained by a method of orienting.

Next, a polarizing plate in which a viewing angle compensation film is further laminated on the above-mentioned polarizing plate will be described.

The viewing angle compensating film is a film for widening the viewing angle so that an image can be seen relatively clearly even when the screen of the liquid crystal display device is viewed from a slightly oblique direction, not perpendicular to the screen. As such a viewing angle compensation film, a triacetyl cellulose film coated with a discotic liquid crystal or a retardation plate is used.
Ordinary retardation plate, uniaxially stretched in its plane direction, while a polymer film having birefringence is used,
The retardation plate used as a viewing angle compensation film has a birefringent polymer film biaxially stretched in the plane direction and a refractive index in the thickness direction uniaxially stretched in the plane direction and also in the thickness direction. A bidirectionally stretched film such as the above-mentioned inclined orientation polymer film is used. As the inclined orientation film, for example, a film obtained by adhering a heat-shrinkable film to a polymer film and subjecting the polymer film to a stretching treatment and / or a shrinking treatment under the action of its shrinkage force by heating, or a liquid crystal polymer which is obliquely oriented, etc. Is mentioned. As the raw material polymer of the retardation plate, the same polymer as that used in the above retardation plate is used.

Next, a polarizing plate in which a brightness enhancement film is further laminated on the above-mentioned polarizing plate will be described.

This polarizing plate is usually used by being provided on the back side of the liquid crystal cell. The brightness enhancement film has a property of reflecting linearly polarized light of a predetermined polarization axis or circularly polarized light of a predetermined direction when natural light is incident, due to reflection from a backlight of a liquid crystal display device or the back side, and transmitting other light. Is. Inject light from a light source such as a backlight,
The transmitted light having a predetermined polarization state is obtained, and the light other than the predetermined polarization state is reflected without being transmitted. The light reflected on the surface of the brightness enhancement film is further re-incident on the brightness enhancement plate by reversing it through a reflection layer or the like provided on the back side thereof, and a part or all of the light is transmitted as light having a predetermined polarization state, The brightness can be improved by increasing the amount of light transmitted through the brightness enhancement film and by supplying polarized light that is difficult to be absorbed by the polarizer to increase the amount of light that can be used for liquid crystal image display and the like. When light enters from the back side of the liquid crystal cell through a polarizer without using a brightness enhancement film, almost all light with a polarization direction that does not match the polarization axis of the polarizer is absorbed by the polarizer. It will not be transmitted through the polarizer. That is, although depending on the characteristics of the polarizer used, about 50% of light is absorbed by the polarizer, and the amount of light that can be used for liquid crystal image display and the like is reduced accordingly, and the image becomes dark. The brightness enhancement film allows light having a polarization direction that is absorbed by the polarizer to be reflected by the brightness enhancement film once without entering the polarizer and then inverted through a reflection layer or the like provided behind it. And then re-incident on the brightness enhancement plate. Then, the polarization direction of the light reflected and inverted between the both is transmitted only to the polarization whose polarization direction is such that it can pass through the polarizer, and is supplied to the polarizer. It can be efficiently used for displaying an image on a liquid crystal display device, and the screen can be brightened.

The brightness enhancement film is not particularly limited, and may be one that transmits linearly polarized light of a predetermined polarization axis, such as a multilayer thin film of a dielectric or a multilayer laminate of thin films having different refractive index anisotropies. The light may be one that exhibits a characteristic of being reflected. In addition, a cholesteric liquid crystal layer, in particular, an oriented film of a cholesteric liquid crystal polymer or one in which the oriented liquid crystal layer is supported on a film substrate, shows a property of reflecting circularly polarized light on one of the left and right sides and transmitting other light. May be.

Therefore, in a brightness enhancement film of a type that transmits linearly polarized light having a predetermined polarization axis, the transmitted light is directly incident on the polarizing plate with the polarization axis aligned, and the absorption loss due to the polarizing plate is suppressed and the efficiency is improved. Can be transmitted. On the other hand, in a brightness enhancement film of a type that transmits circularly polarized light like a cholesteric liquid crystal layer, it can be directly incident on a polarizer, but from the viewpoint of suppressing absorption loss, the transmitted circularly polarized light is linearly polarized through a retardation plate. It is preferable that the light is incident on the polarizing plate. By using a ¼ wavelength plate as the retardation plate, circularly polarized light can be converted into linearly polarized light.

The retardation plate that functions as a quarter-wave plate in a wide wavelength range such as a visible light region is a retardation layer that functions as a quarter-wave plate for monochromatic light such as light having a wavelength of 550 nm. It can be obtained by a method of superimposing a retardation layer showing the retardation characteristic of (for example, a retardation layer functioning as a half-wave plate). Therefore, the retardation plate disposed between the polarizing plate and the brightness enhancement film may be one layer or two or more retardation layers. The cholesteric liquid crystal layers can also have a structure in which two or more layers are superposed by combining layers having different reflection wavelengths. Thereby, it is possible to obtain a circularly polarized light that reflects in a wide wavelength range such as a visible light region, and based on that, it is possible to obtain a transmitted circularly polarized light in a wide wavelength range.

Further, the polarizing plate may be formed by laminating a polarizing plate and two or three or more optical layers. Therefore, it may be a reflective elliptical polarizing plate or a semi-transmissive elliptical polarizing plate in which the above reflective polarizing plate or semi-transmissive polarizing plate is combined with a retardation plate.

The optical member in which two or three or more optical layers are laminated can be formed by a method of sequentially laminating separately in the manufacturing process of a liquid crystal display device or the like. The optical member is excellent in quality stability and assembling workability, and has an advantage of being able to improve manufacturing efficiency of liquid crystal display devices and the like. In addition, an appropriate adhesion means such as an adhesive layer can be used for the lamination.

When the pressure-sensitive adhesive layer provided on the polarizing plate or the like is exposed on the surface, it is preferable to cover the pressure-sensitive adhesive layer with a separator for the purpose of preventing contamination until practical use. The separator is formed by a method in which a suitable thin sheet conforming to the above-mentioned transparent protective film or the like is provided with a release coat using a suitable release agent such as silicone-based or long-chain alkyl-based, fluorine-based or molybdenum sulfide as necessary. be able to.

Each layer such as the polarizing film and the transparent protective film forming the polarizing plate and the optical member, the optical layer and the adhesive layer is, for example, a salicylate compound, a benzophenone compound, a benzotriazole compound or a cyanoacrylate compound. It may be one having an ultraviolet absorbing ability by an appropriate method such as a method of treating with an ultraviolet absorber such as a compound or a nickel complex salt compound.

The polarizing plate and the liquid crystal display element of the present invention can be preferably used for forming various devices such as a liquid crystal display device. For example, a polarizing plate or a reflective type in which a polarizing plate is arranged on one side or both sides of a liquid crystal cell is used. It can be used for a semi-transmissive type or a transmissive / reflective type liquid crystal display device. The liquid crystal cell forming the liquid crystal display device is arbitrary, and an appropriate type such as an active matrix drive type represented by a thin film transistor type, a simple matrix drive type represented by a twist nematic type or a super twist nematic type, etc. The liquid crystal cell may be used.

When polarizing plates and optical members are provided on both sides of the liquid crystal cell, they may be the same or different. Further, when forming the liquid crystal display device, one or two or more layers can be arranged at appropriate positions with appropriate components such as a prism array sheet, a lens array sheet, a light diffusion plate, and a backlight.

[0062]

EXAMPLES Next, the present invention will be described with reference to Examples and Comparative Examples.
A more specific description will be given. In the following examples and the like, "mass%" and "parts by mass" are abbreviated as "%" and "parts", respectively, unless otherwise specified.

Production Example 1 Isooctyl Acrylate 10
0 parts, 6 parts of 6-hydroxyhexyl acrylate, and 0.5 parts of 2,2′-azobisisobutyronitrile were added to 4 flasks together with 200 parts of ethyl acetate, and the mixture was stirred at about 60 ° C. for 6 hours. After reacting for a time, a polymer solution was obtained. An acrylic pressure-sensitive adhesive was prepared by adding 0.5 part of an isocyanate-based crosslinking agent (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name: Coronate L) to 100 parts of the solid content of the obtained polymer solution. The amount of creep displacement of the obtained adhesive is 7
It was 9 μm / H.

(Production Example 2) Isooctyl acrylate and 6
Preparation of an acrylic pressure-sensitive adhesive according to Example 1 except that 100 parts of butyl acrylate and 5 parts of acrylic acid were used in place of hydroxyhexyl acrylate and 5 parts of an isocyanate-based crosslinking agent was added. did. The creep shift amount of the obtained pressure-sensitive adhesive was 20 μm / H.

(Creep test) The adhesive area of the adhesive was set to 10
The amount of deviation (μm) after 1 hour at room temperature when a force of 500 gf was applied was set to mm square and measured.

Example 1 A polyvinyl alcohol film (PVA) film having a thickness of 75 μm was swollen in a warm water bath at 30 ° C., and then, about 30 ° C. in a dyeing bath at 30 ° C. containing an aqueous solution of iodine and potassium iodide. Stretched 3 times and then
It was stretched and crosslinked in a crosslinking bath composed of an aqueous boric acid solution at 50 ° C. so that the total stretching ratio was 6 times. This was immersed in an aqueous potassium iodide solution at 35 ° C. for 10 seconds to adjust the hue. Further, it was washed with water and dried to obtain a polarizing film having a thickness of 16 μm. The water content of this polarizing film was 15% by mass.

Next, an adhesive consisting of a 7 mass% PVA aqueous solution was applied to both sides of this polarizing film, and two protective triacetyl acetate sheets having a thickness of 80 μm were saponified with a caustic soda aqueous solution as protective films. Cellulose (TA
C) The polarizing film was laminated so as to be sandwiched between the films to prepare a polarizing plate having a total thickness of 176 μm. The resulting polarizing plate has a single transmittance of 43.4% and a polarization degree of 99.9.
%Met.

The acrylic pressure-sensitive adhesive obtained in Production Example 1 was applied to a separator made of a polyester film provided with a surface coating of a silicone-based release agent, and heat-treated at 150 ° C. for 5 minutes to give a pressure-sensitive adhesive having a thickness of 25 μm. A layer was provided, and this was adhered to one surface of the above polarizing plate to obtain an optical member.

Example 2 A mixture of 100 parts of an alicyclic epoxy resin represented by the following formula (Formula 1), 125 parts of methylhexahydrophthalic anhydride, and 1 part of tri-N-butyloctylphosphonium bromide was prepared. Pour into mold 1
Curing treatment was performed at 20 ° C. for 2 hours to obtain a resin substrate having a thickness of 0.4 mm. Subsequently, a urethane acrylate resin represented by the following formula (Formula 2) is applied to one surface of this resin substrate by a spin coating method, irradiated with ultraviolet rays to be cross-linked, and a thickness of 5 is obtained.
A coat layer having a thickness of μm was formed to obtain a cell substrate. The optical member produced in Example 1 was laminated on this in the manner shown in FIG.

[0070]

[Chemical 1]

[0071]

[Chemical 2]

Comparative Example 1 A polarizing plate was prepared in the same manner as in Example 1. The acrylic pressure-sensitive adhesive obtained in Production Example 2 was applied to a separator made of a polyester film provided with a surface coating of a silicone-based release agent, and heat-treated at 150 ° C. for 5 minutes to form a pressure-sensitive adhesive layer having a thickness of 25 μm. This was adhered to one surface of the above polarizing plate to obtain an optical member. The obtained optical member was laminated on the substrate in the same manner as in Example 2 to obtain a laminated body.

(Comparative Example 2) An optical member and a laminate were obtained in the same manner as in Comparative Example 1 except that the thickness of the adhesive layer was 15 μm.

Comparative Example 3 An optical member and a laminated body were obtained in the same manner as in Comparative Example 1 except that the thickness of the adhesive layer was 5 μm.

(Dimensional Amount of Displacement) A laminate of the polarizing plate, the adhesive and the plastic cell substrate (diagonal distance 8 inches) produced by the above method was heated at a temperature of 50 ° C. and a pressure of 5 × 10 ⁵ Pa for 15 times. After autoclaving for a minute, as shown in FIG. 2, the distance between the resin substrate and the polarizing plate is marked with a biaxial microscope. This is left for 24 hours under humidified conditions of 40 ° C./92% RH. After taking out from the humidified condition and leaving it for 30 minutes, the distance between the X mark between the resin substrate and the polarizing plate is measured with a biaxial microscope. The distance between the X marks before charging under humidified conditions,
The difference in the distance between the X marks after adding the humidifying conditions is determined and used as the amount of deviation of the polarizing plate under the humidifying conditions.

Table 1 shows the amount of dimensional deviation of the polarizing plate and the amount of substrate warpage in Examples and Comparative Examples.

[0077]

Table 1 Dimensional deviation amount (mm) Substrate warpage amount (mm) Example 1 0.178 21.7 Comparative example 1 0.030 36.3 Comparative example 2 0.069 39.5 Comparative example 3 0.092 41 .8

As is clear from Table 1, since the polarizing plate of Example 1 uses the pressure-sensitive adhesive having a creep displacement of 30 μm / H or more, the dimensional displacement of the polarizing plate is as large as 0.10 mm or more. Substrate warpage is small. On the other hand, in the polarizing plate of the comparative example, the amount of creep deviation of the adhesive used was 30 μm.
Since it is less than m / H, the dimensional deviation of the polarizing plate is small and the amount of substrate warpage is large. Also, the thinner the pressure-sensitive adhesive layer,
Since the amount of deviation and the amount of warpage are large, it can be seen that the thickness of the pressure-sensitive adhesive layer influences the improvement of dimensional deviation and warpage.

[0079]

As described above, in the polarizing plate of the present invention, a pressure sensitive adhesive having a creep shift amount of 30 μm / H or more is used, and the dimensional shift amount of the polarizing plate is increased to 0.10 mm or more, so that a plastic substrate is obtained. It is possible to reduce the amount of applied stress and reduce the amount of warpage of the substrate. for that reason,
When mounted on a liquid crystal display device, it is possible to provide a display display with little change in hue. Therefore, it becomes possible to realize a liquid crystal display using a large-sized plastic substrate, which is of great industrial value.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a bonded state of a polarizing plate of the present invention and a plastic substrate.

FIG. 2A is a diagram showing a state in which a substrate and a polarizing plate are bonded together. (B) It is a partial enlarged view showing a dimensional deviation of a polarizing plate.

[Explanation of symbols]

1 Polarizer 2 Adhesive layer (adhesive) 3 plastic substrates 4 Warp amount

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor ▲ Hama ▼ Eiji             1-2 1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto             Electric Works Co., Ltd. (72) Inventor Seiichi Kusumoto             1-2 1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto             Electric Works Co., Ltd. (72) Inventor Yuji Suiki             1-2 1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto             Electric Works Co., Ltd. (72) Inventor Masayuki Satake             1-2 1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto             Electric Works Co., Ltd. F-term (reference) 2H049 BA02 BA06 BA27 BB33 BB41                       BB43 BB52 BB63 BC03 BC10                       BC14 BC22                 2H090 JB03 LA06 LA09 LA20                 2H091 FA08X FA08Z FD15 GA01                       GA17 LA02                 5C094 AA03 AA34 BA43 DA01 DA06                       FB01 FB06 JA01 JA08

Claims (9)

[Claims] 1. A polarizing plate in which an adhesive layer is laminated on at least one side of a polarizing plate, wherein the adhesive layer has a thickness of 25 μm and a thickness of 10 μm.
When the tensile breaking stress of 500 gf is applied for 1 hour with the adhesion area of mm square, the creep shift amount (25 ° C) is 30μ.
A polarizing plate having a ratio of m / H or more. 2. The polarizing plate is attached to a plastic substrate having a diagonal distance of 8 inches or more, and 40 is attached to the plastic substrate.
The dimensional deviation amount of the polarizing plate is 0.10 mm or more when left for 24 hours under conditions of ° C and 92% RH.
The polarizing plate described in. 3. The polarizing plate according to claim 2, wherein the maximum warp amount of the four corners of the plastic substrate is 35 mm or less. 4. The pressure-sensitive adhesive layer is formed of an acrylic pressure-sensitive adhesive and has a thickness of 5 to 30 μm.
The polarizing plate according to any one of 3 above. 5. The polarizing plate according to claim 1, and at least one optical layer selected from a retardation plate, a reflection plate, a semi-transmissive reflection plate, a viewing angle compensation film and a brightness enhancement film. A polarizing plate characterized by the above. 6. A liquid crystal display device comprising the polarizing plate according to claim 1 attached to at least one surface of a liquid crystal cell. 7. The liquid crystal display device according to claim 6, wherein the substrate forming the liquid crystal cell is a plastic substrate. 8. A liquid crystal display device comprising a polarizing plate and a plastic substrate having a diagonal distance of 8 inches or more bonded to each other through an adhesive layer, wherein the adhesive layer has a thickness of 25 μm and an adhesive area of 10 mm square. When the amount of creep deviation (25 ° C.) when a tensile breaking stress of 500 gf is applied for 1 hour is 30 μm / H or more, and the liquid crystal display element is left under the conditions of 40 ° C. and 92% RH for 24 hours. A liquid crystal display device, wherein the dimensional deviation of the polarizing plate is 0.10 mm or more. 9. The liquid crystal display element according to claim 8, wherein the maximum warp amount of the four corners of the plastic substrate is 35 mm or less.