JP2007025643A - Polarizing plate, its working and manufacturing method and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing plate which can improve a light leakage phenomenon occurring in a liquid crystal display device and, does not degrade display quality, and also to provide a working and manufacturing method of the polarizing plate. <P>SOLUTION: The polarizing plate has a void part (A) such as grooves, holes, or hollows parallel to sides of the outer periphery in a transparent protective film or an optical compensation film between a polarizing film and the liquid crystal cell. When the dies-cutting of the polarizing plate into a desirable form is performed, the void part (A) such as groove is formed on the transparent protective film or the optical compensation film. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a polarizing plate used on at least one of the upper and lower surfaces or one surface of a liquid crystal cell in a liquid crystal display device, and a liquid crystal display device using the same, and particularly to avoid a light leakage phenomenon that becomes noticeable in a black display state. The present invention relates to a polarizing plate that can be manufactured, a process for producing the same, and a liquid crystal display device using the polarizing plate.

  The liquid crystal display device includes, for example, a liquid crystal cell, a linear polarizing plate, an optical compensation film, and a drive circuit. In the transmissive liquid crystal display device, two polarizing plates are arranged on both sides of the liquid crystal cell, and one or two optical compensation films are arranged between the liquid crystal cell and the polarizing plate. In a reflective liquid crystal display device, a reflector, a liquid crystal cell, a single optical compensation film, and a single polarizing plate are arranged in this order. The polarizing plate is composed of a transparent protective film and a polarizing film. In some cases, an elliptically polarizing plate having an optical compensation film as the transparent protective film of the polarizing plate may be used. The liquid crystal cell is composed of a rod-like liquid crystal molecule, two substrates for enclosing it, and an electrode layer for applying a voltage to the rod-like liquid crystal molecule. The liquid crystal cell is different in the alignment state of rod-like liquid crystal molecules. As for the transmission type, TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), OCB (Optically Compensatory Bend), STN (STN) Various display modes such as TN, HAN (Hybrid Aligned Nematic), and GH (Guest-Host) have been proposed for Supper Twisted Nematic (VA), VA (Vertically Aligned), ECB (Electrically Controlled Birefringence), and reflective types. .

  Of the polarizing plates above and below the transmissive liquid crystal cell, the polarizing plate on the backlight side partially absorbs light from the light source and converts light incident on the liquid crystal cell into linearly polarized light. The polarizing plate on the output side allows the polarized light component parallel to the transmission axis to pass through the light passing through the liquid crystal cell and absorbs the polarized light component in the absorption axis direction. The optical compensation film is disposed between the polarizing plate and the liquid crystal cell in order to eliminate image coloring and expand the viewing angle, and converts linearly polarized light by the polarizing plate into elliptically polarized light. That is, the linearly polarizing plate and the optical compensation film become an elliptically polarizing plate. As the optical compensation film, an optical compensation film having an optically anisotropic layer formed from a discotic compound or a liquid crystalline molecule on a transparent support, such as a stretched birefringent polymer film, is generally used. The optical properties of the optical compensation film are determined according to the optical properties of the liquid crystal cell, specifically, the display mode differences as described above. Various optical compensation films corresponding to various display modes have been proposed.

  In recent years, the size of liquid crystal display devices has been increased, and accordingly, particularly in the state of displaying black, light is directed to the top and bottom, left and right edges, or the four corners of the display screen regardless of the image signal for display. There is a tendency for the phenomenon of leakage to be noticeable. Regardless of the display image, since light leaks in a specific viewing direction, the display quality is remarkably deteriorated. In the case of a TN liquid crystal display, the absorption axis of the polarizing plate is in the direction of ± 45 ° with respect to the top and bottom of the display surface, whereas the light leakage phenomenon can be seen on the top and bottom, left and right of the display surface. In the case of the apparatus, the absorption axis of the polarizing plate is in the directions of 0 ° and 90 ° with respect to the top and bottom of the display screen, whereas light leaks in the four corner directions of the display screen. FIG. 2 schematically shows the light leakage phenomenon when it occurs vertically and horizontally. FIG. 3 schematically shows a case where the noise occurs in the four corner directions.

Regarding display unevenness due to light leakage, Patent Document 1 discloses that the product of the photoelastic coefficient (m ² / N) of the retardation film and the elastic modulus (N / m ² ) of the adhesive layer is 1.2 × 10 ⁻⁵ or less. By doing so, there is a method for improving unevenness due to birefringence that occurs when the retardation film is distorted due to the action of heat and humidity during the adhesive lamination of the optical compensation film or subsequent heating / humidification treatment or practical use. It is disclosed. In Patent Document 2, in the polarizing plate with an optical compensation film, the elastic modulus of the adhesive layer between the polarizing plate and the optical compensation film is 0.06 MPa or less, and the elastic modulus of the adhesive layer between the optical compensation film and the liquid crystal cell is 0. A method for improving the phenomenon that the stress due to the difference in dimensional change between the polarizing plate and the optical compensation film is generated by the heat generated from the backlight or the like by setting the pressure to 0.08 MPa or less, and the resulting birefringence causes display unevenness is disclosed. Yes. In Patent Document 3, the product of the linear expansion coefficient of the polarizing plate protective layer and the elastic modulus of the pressure-sensitive adhesive is set to 1.0 × 10 ⁻⁵ (° C. ⁻¹ · MPa) or less, whereby the polarizing plate is made into a liquid crystal cell. Patent Document 4 discloses a product of the photoelastic coefficient of the polarizing plate protective layer and the elastic modulus of the adhesive, which is 8.0 × 10 ^−. A method of avoiding light leakage unevenness caused by stress applied to the polarizing plate when the polarizing plate is attached to the liquid crystal cell by disposing ¹² (m ² / N · MPa) or less is disclosed.

JP 2001-264538 A JP 2001-272542 A JP 2002-122739 A JP 2002-122740 A

  Among the transmissive liquid crystal display devices, the absorption axes of two polarizing plates arranged on the front and back of the liquid crystal cell are arranged at approximately 45 ° or approximately −45 ° clockwise with respect to the vertical direction of the display screen of the liquid crystal display device. In the case of a general TN mode liquid crystal display device, as shown schematically in FIG. 2, light leakage occurs vertically and horizontally with respect to the display screen. When black is displayed, the luminance level of the black increases, causing a decrease in contrast, and the display quality is significantly reduced.

This light leakage phenomenon occurs when, for example, a liquid crystal display device stored in a high humidity state with a humidity of 60% or more is moved to a low humidity environment. The remarkable light leakage phenomenon then gradually recovers in a high humidity environment. This light leakage phenomenon is considered to be caused by photoelastic deformation accompanying moisture absorption and desorption of the film material constituting the polarizing plate sandwiched between the two polarizing films arranged in crossed Nicols.
The object of the present invention is to improve the light leakage phenomenon caused by the elastic deformation of the film material due to this environmental change and the photoelasticity caused by the stress strain generated between the glass substrate and the adhesive, and to lower the display quality. An object of the present invention is to provide a polarizing plate, an elliptically polarizing plate and a method for producing the same, and a liquid crystal display device using the polarizing plate.

Conventionally, a polarizing plate bonded to a liquid crystal display device with an adhesive is approximately the same size as the display area of the liquid crystal cell, and each layer constituting the polarizing plate and each film are a uniform layer having the same thickness. It is made by laminating the materials that become. On the other hand, the light leakage phenomenon occurs by drawing an arc in the display center direction with respect to a horizontally long and rectangular display area (Active Area). The shape of the light leakage of the arc shrinks when the cellulose acylate film between the upper and lower polarizing films and the substrate of the liquid crystal cell is dehumidified suddenly from the state of absorbing moisture, and the distortion caused thereby. It is thought to be created by the photoelastic effect due to stress.
A method of reducing elastic stress without degrading display quality was examined using the finite element method. In practice, a transparent material composed of cellulose acylate, etc., placed inside the polarizing film and between the liquid crystal cell substrate. It has been found that a shrinkage stress depending on the shape of the polarizing plate is generated in the protective film. Each point of the transparent protective film shrinks, and the closer to the outer periphery of the polarizing plate shape, the larger the shrinkage stress toward the center of the polarizing plate than in the outer peripheral direction. On the other hand, the center of the polarizing plate contracts substantially uniformly in the vertical and horizontal directions. As a result, an elastic deformation that is biased and contracted occurs near the outer periphery depending on the shape of the polarizing plate.
As a result of intensive studies, the inventors of the present invention have provided holes, grooves, dents and other portions that become voids in the transparent protective layer or the optical compensation film disposed between the polarizing film and the transparent substrate constituting the liquid crystal cell. It was found that this stress can be effectively relieved. This is presumably because the portion including the locally provided gap is easier to extend than the other portions, and thereby the stress toward the center is relieved at that point.

  The inventors of the present invention studied optimization of the depth and shape of the void portion in order to more effectively relieve stress. As a result, discontinuous holes, continuous or discontinuous grooves and dents, etc. are effective as the void portions, and when the dents are provided in the entire layer to reduce the elastic modulus, or grooves parallel to the outer periphery of the polarizing plate As a result, the present invention has been completed. (Note that the “polarizing plate” in the present invention includes an elliptically polarizing plate having an optical compensation film in addition to the linear polarizing plate.) That is, means for solving the above-described problems are the following [1] to [[ 12].

[1]
A polarizing plate having a polarizing film and at least one transparent protective film or an optical compensation film, wherein the transparent protective film or the optical compensation film is provided with a gap portion.
[2]
The said gap part is a discontinuous hole, or a continuous or discontinuous groove | channel or a hollow, It is set as the polarizing plate as described in said [1] characterized by the above-mentioned.
[3]
The void portion is filled with a substance having a refractive index within ± 1% with respect to the refractive index of the transparent protective film or the optical compensation film, according to the above [1] or [2] A polarizing plate is used.
[4]
The said gap part is provided in parallel with the edge | side of a polarizing plate outer periphery, It is set as the polarizing plate in any one of said [1]-[3] characterized by the above-mentioned.
[5]
The said gap part is provided in the outer peripheral part of the polarizing plate, It is set as the polarizing plate in any one of said [1]-[4] characterized by the above-mentioned.
[6]
The said gap part is provided in the whole surface of a polarizing plate, It is set as the polarizing plate in any one of said [1]-[4] characterized by the above-mentioned.
[7]
A liquid crystal cell in which a liquid crystal cell bonded with the polarizing plate according to any one of [1] to [6] is incorporated so that the gap portion is between the polarizing film and the liquid crystal cell. A display device is used.
[8]
The liquid crystal display device according to [7], wherein the gap portion of the polarizing plate according to [5] is disposed outside a display region.
[9]
The liquid crystal display device according to [7], wherein the gap portion of the polarizing plate according to [6] is disposed in a display region.
[10]
The liquid crystal display device according to [7], wherein the gap is a groove having a width equal to or smaller than a display pixel pitch of the liquid crystal cell.
[11]
Any one of the above [1] to [6], wherein when the polarizing plate is die-cut into a desired shape, the gap is also formed in the transparent protective film or the optical compensation film of the polarizing plate at the same time. The method for producing the described polarizing plate is used.
[12]
The method for producing a polarizing plate according to any one of [1] to [6], wherein the void portion is formed in the transparent protective film or the optical compensation film by ablation processing by laser irradiation.

According to the polarizing plate and the liquid crystal display device of the present invention, it is possible to reduce the light leakage phenomenon occurring at the top, bottom, left and right or four corners of the display surface, thereby preventing the image quality from deteriorating.
The method of the present invention can be advantageously used for OCB (Optically Compensatory Bend), VA (Vertically Aligned), IPS (In Plane Switching), ECB (Electrically Controlled Birefring, etc.) in addition to a TN mode liquid crystal display device.
Furthermore, this invention also provides the manufacturing method of the polarizing plate for processing and manufacturing the above polarizing plates.

According to the polarizing plate and the liquid crystal display device of the present invention, the transparent protective film or the optical compensation film disposed between the pressure-sensitive adhesive and the polarizing film is usually provided near the outer periphery by providing a gap portion for relaxing stress. It becomes possible to suppress the light leakage phenomenon that becomes apparent. It is sufficient that the gap portion is disposed between the adhesive and the polarizing film, and any shape can be used as the shape of the gap portion. For example, the “hole” shape that penetrates the film of the transparent protective film or the optical compensation film in the film thickness direction, the “groove” shape that does not penetrate the film, the “dent” shape provided on the film surface, etc. are easy to process. Although it is typical, it is not necessarily limited to these. For example, a hollow shape may be used, and various shapes such as a shape formed in a tunnel shape in parallel with the film surface inside the film and a shape in which a large number of small bubbles gathered in a linear shape are possible. Further, the inside of the gap portion may be filled with another material within a range not departing from the purpose. In that case, it is preferable that the transparent protective film or the optical compensation film is filled with a substance having a refractive index within ± 1% with respect to the refractive index.
Examples of the shape of the typical void portion include a discontinuous hole, a continuous or discontinuous groove, or a depression as described above. When holes, grooves, dents and the like as void portions are provided in the vicinity of the outer periphery of the polarizing plate, the holes are preferably provided in parallel with the sides and particularly preferably in a groove shape. Moreover, when providing in the whole surface of a polarizing plate, it is preferable that it is a fine hole, a hollow shape, or a thin groove shape.
In the present specification, parallel does not necessarily need to be completely parallel in a strict sense, and may be substantially parallel.

FIG. 1, FIG. 7, FIG. 8, FIG. 9, and FIG. 10 show schematic diagrams of examples of the polarizing plate of the present invention.
1 shows an example in which grooves parallel to the outer periphery are provided, FIG. 7 shows an example in which holes parallel to the outer periphery are provided discontinuously, FIG. 8 shows an example in which recesses parallel to the outer periphery are provided discontinuously, and FIG. FIG. 10 schematically shows an example in which the gap width of the gap is equal to or smaller than the display pixel pitch.
In the case of providing grooves parallel to the outer periphery shown in FIG. Here, the term “parallel” means that it is parallel to the outer peripheral side in a range of ± 10 °, preferably ± 5 °. For example, the position (xd, yd) of the groove is preferably yd of 3% to 15% of the vertical screen dimension in the vertical direction of the display, and is xd of 3% to 15% of the horizontal screen dimension in the horizontal direction. It is desirable. A plurality of grooves may be provided in the range of 3% to 30% in the vertical and horizontal directions, and the larger the number, the similar effect is exhibited even when the depth of the groove is shallow. In addition to the grooves parallel to the outer periphery, the same effect is exhibited even in continuous or discontinuous recesses. An example of this is shown in FIG.
The depth of the groove or the like may be an appropriate depth that can achieve the purpose, but a depth of 50% or more of the film thickness of the transparent protective film or the optical compensation film is desirable.
Various cross-sectional shapes, such as grooves, are possible. For example, any of a rectangular recessed groove, a V-shaped groove, a U-shaped groove, and the like is effective. In the case of a groove having a corner, such as a rectangular groove or a V-shaped groove, the polarization state easily changes, causing a difference in the amount of light transmitted through the polarizer between the non-grooved part and the groove part. It will stand out. Therefore, when a groove is provided over the display region, it is desirable that the groove has a shape that does not have a corner and the polarization state does not change significantly from a portion without the groove. Furthermore, when the difference in refractive index between the pressure-sensitive adhesive and the transparent protective film or the optical compensation film is small, the change in the polarization state due to the presence of the groove becomes small, making it difficult to visually recognize the groove. Therefore, the refractive index of the pressure-sensitive adhesive layer is preferably in the range of ± 2%, more preferably in the range of ± 1% with respect to the refractive index of the transparent protective film or the optical compensation film. In order to adjust the refractive index, the refractive index can be adjusted to be large (small) by mixing, for example, a fine (high) (low) filler having a small refractive index of several μm.

  In the case where the grooves are arranged in the display area, the influence on the display quality can be reduced by providing a large number of thin grooves below the pitch of the display pixels in the transparent protective film or the optical compensation film. For example, when one pixel of the display pixel is 0.3 mm in the vertical direction and 0.1 mm in the horizontal direction, the width of the depression (groove) is set to about 30 μm and distributed over the entire display surface. In this case, by providing a large number of concave portions, a structural mechanical effect close to that obtained when the elastic modulus of the transparent protective film or the optical compensation film is lowered or the average thickness is reduced is exhibited. The photoelastic effect generated in the transparent protective film or the optical compensation film is reduced, and the light leakage phenomenon can be reduced.

In order to form a desired depression or groove, for example, an ultra-thin blade that has been devised so as not to cut deeper than the thickness of the protective layer, a punching blade with an adjusted height, or a Thomson blade can be used. . It can also be formed by a rotary blade having a V shape, a U shape, or a rectangle.
Regarding a polarizing plate formation method, it can be made into a desired shape by various methods, such as a Thomson blade, punching, a rotation tooth, a slice cutter, a laser cutter.
The polarizing plate of the present invention is formed by punching a polarizing plate from a large plate, a base plate, and a roll-shaped large plate of a polarizing plate by using a punching processing apparatus (for example, a sheet cutter manufactured by Sakamoto Construction Co., Ltd.), and at the same time half-cut ( This can be done by a process called half-cutting. Thus, a grooved polarizing plate can be continuously produced. In general, half-cut refers to a process in which only a layer to be die-cut out of a laminated material laminated is die-cut, and a base material (paper, film, adhesive layer, etc.) is not die-cut. The thickness of the layer to be left uncut is possible from 0.01 mm or more, and the depth of the half cut can be adjusted with high accuracy.

In addition to providing grooves and recesses on the periphery of the display screen, in the case where the recesses are distributed over the entire display surface, before processing into a polarizing plate, the transparent protective film or optical compensation film is continuously rolled. It is possible to provide a recess as shown in FIG. In the middle of the film production process, it is possible to continuously form the depressions by nipping with an embossed roller unit with a heater provided with irregularities while maintaining the film at a high temperature.
Furthermore, it is possible to form a polarizing plate or a transparent protective film constituting the polarizing plate, an optical compensation film, a single layer of the polarizing film by continuously dispersing concave portions or penetrating holes by ablation processing by laser irradiation. . For example, using an ArF excimer laser (wavelength 193 nm), continuously forming fine holes of φ10 μm to φ50 μm with an irradiation intensity of 50 to 300 mJ / cm ² , an irradiation repetition frequency of 10 to 60 Hz, and an irradiation time of 5 to 100 ns. Can do. The film processing by this method is detailed in the report shown in Reference 1 below.
[Reference 1]: Optical Review (2005) Vol. 12, no. 6 p. 427-441

In order to bond a polarizing plate to a liquid crystal cell, a pressure-sensitive adhesive sheet having a refractive index adjusted is first bonded onto the substrate of the liquid crystal cell, and a polarizing plate having a transparent protective film or an optical compensation film in which grooves are formed in advance. It can be easily realized by bonding to the adhesive sheet.
When incorporating a liquid crystal cell with a polarizing plate into a liquid crystal display device, adjust the screen size (display area) of the liquid crystal display device so that the grooves are arranged outside the display area. Can be made invisible.
Since the light leakage phenomenon is improved in the center direction of the display from the stress relaxation groove, it is possible to make the light leakage phenomenon invisible by hiding only the groove portion with the frame of the display device.

  The polarizing plate of the present invention is a liquid crystal display device in which the absorption axis of the polarizing plate is arranged at 45 ° or −45 ° clockwise relative to the vertical direction of the display screen, as in the TN liquid crystal display device. In addition to exerting an effect on the light leakage phenomenon (see FIG. 2) that occurs in an arc from the top and bottom of the outer periphery and from the left and right, also in the OCB mode liquid crystal display device, VA mode display device, IPS mode display device, and ECB mode display device Demonstrate the effect.

[Polarizer]
Below, the polarizing plate of this invention is demonstrated.
The polarizing plate is composed of a polarizing film and at least one transparent protective film disposed on one side thereof.
Usually, a polarizing plate consists of a polarizing film and two transparent protective films arrange | positioned at the both sides. In the case of a wide viewing angle polarizing plate or an elliptical polarizing plate, it has an optical compensation film described later, but it is preferable to use the optical compensation film as one protective film. As the normal protective film, a normal polymer film having a light transmittance of 80% or more can be used. A cellulose acetate film is preferably used as the polymer film. About a cellulose acetate film, the same thing as what is described as a support body used for an optical compensation film can be used.
The elliptically polarizing plate or the wide viewing angle polarizing plate has a layer structure in which a transparent protective film 3, a polarizing film 2, an optical compensation film 1 (transparent support 12, optically anisotropic layer 11), and an adhesive layer 4 are sequentially laminated. It is preferable (FIG. 5). The polarizing plate is attached to the liquid crystal cell through the adhesive layer.
The polarizing plate according to the present invention is preferably when the absorption axis direction of the polarizing plate is substantially 45 ° or −45 ° clockwise relative to the vertical direction of the display screen of the liquid crystal display device. Here, 45 ° and −45 ° mean substantially, preferably 45 ° ± 10 ° or −45 ° ± 10 °, more preferably 45 ° ± 5 ° or −45 ° ± 5 °.

  Examples of the polarizing film include an iodine polarizing film, a dye polarizing film using a dichroic dye, and a polyene polarizing film. The iodine polarizing film and the dye polarizing film are generally produced using a polyvinyl alcohol film. As a manufacturing method, a conventionally known method can be applied. For example, it is described in Patent Document 1.

[Adhesive]
As the adhesive used in the pressure-sensitive adhesive layer constituting the polarizing plate of the present invention, it is preferable that the absolute value of the photoelastic coefficient of ^{800 × 10 -12 (1 / Pa} ) or less, 600 × 10 ^-12 (1 / Pa) or less, more preferably 400 × 10 ⁻¹² (1 / Pa) or less. If the condition is satisfied, it can be used without particular limitation. Moreover, the absolute value of the photoelastic coefficient of an adhesive is so preferable that it becomes smaller, and it is more preferable that the photoelastic coefficient is positive.
As the material of the pressure-sensitive adhesive, pressure-sensitive pressure-sensitive adhesives such as rubber-based pressure-sensitive adhesives, acrylic pressure-sensitive adhesives, silicone-based pressure-sensitive adhesives, urethane-based pressure-sensitive adhesives, polyether-based pressure-sensitive adhesives, and polyester-based pressure-sensitive adhesives are preferable.

In the case of an acrylic pressure-sensitive adhesive, monomers used in the base polymer acrylic polymer include various (meth) acrylic acid esters [(meth) acrylic acid esters include acrylic acid esters and methacrylic acid esters. This is a generic expression, and the following compound names with (meth) have the same meaning. ] Can be used. Specific examples of such (meth) acrylic acid esters include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and the like. Can be used alone or in combination. Further, in order to impart polarity to the resulting acrylic polymer, a small amount of (meth) acrylic acid can be used instead of a part of the (meth) acrylic acid ester. Furthermore, glycidyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, N-methylol (meth) acrylamide and the like may be used in combination as the crosslinkable monomer. Furthermore, if desired, other copolymerizable monomers such as vinyl acetate and styrene may be used in combination as long as the adhesive properties of the (meth) acrylic acid ester polymer are not impaired.
Examples of the base polymer of the rubber adhesive include natural rubber, isoprene rubber, styrene-butadiene rubber, recycled rubber, polyisobutylene rubber, styrene-isoprene-styrene rubber, and styrene-butadiene-styrene rubber. Etc.
Examples of the base polymer of the silicone pressure-sensitive adhesive include dimethylpolysiloxane and diphenylpolysiloxane.
Examples of the base polymer of the polyether-based pressure-sensitive adhesive include polyvinyl ethyl ether, polyvinyl butyl ether, polyvinyl isobutyl ether and the like.

In order to adjust the photoelastic coefficient of the pressure-sensitive adhesive layer to a desired value, there is a method of selecting a polymer as a main agent used in the pressure-sensitive adhesive. Other than this, the following method is conceivable, but is not limited to this method. One of them is a method of adjusting the optical anisotropy, that is, the intrinsic birefringence of the resin molecule itself, which is an effective means. As a method for adjusting the intrinsic birefringence, “Optical Transparent Resin”, Technical Information Association, (2001), page 20, (1) Modification of molecular structure, (2) Random copolymerization method, (3) Alloy Chemical methods are described, and these methods can also be applied in the present invention.
Further, an anisotropic low-molecular doping method as described in Molding, (2003), Vol. 15, No. 3, page 196 can be preferably used.
Further, the anisotropic inorganic particle doping method disclosed in SCIENCE, (2003), VOL301, P812 can be particularly preferably used.
In order to adjust the elastic modulus of the pressure-sensitive adhesive layer to a desired value, the molecular weight of the polymer used for the pressure-sensitive adhesive may be adjusted, or the mixing ratio of the materials may be adjusted.

The pressure-sensitive adhesive can contain a crosslinking agent.
Examples of the crosslinking agent include polyisocyanate compounds, polyamine compounds, melamine resins, urea resins, and epoxy resins.
Furthermore, the pressure-sensitive adhesive may be appropriately selected from conventionally known tackifiers, plasticizers, fillers, antioxidants, ultraviolet absorbers, and the like, as necessary, without departing from the object of the present invention. It can also be used.
The method for forming the pressure-sensitive adhesive layer on the polarizing plate is not particularly limited. Conventional methods such as a method of applying a pressure-sensitive adhesive solution to the polarizing plate and drying, a method of transferring with a release sheet provided with a pressure-sensitive adhesive layer, and the like. Known methods are listed.
Although the thickness of an adhesive layer is not specifically limited, It is preferable to set it as about 10-40 micrometers with a dry film thickness.
The pressure-sensitive adhesive used for the pressure-sensitive adhesive layer constituting the polarizing plate of the present invention has a storage elastic modulus of 1.5 × 10 ⁴ to 1.5 × 10 ⁵ Pa and a yield strength of 0.9 × 10 ^{4 to} 0. If it can form the adhesive layer which will be .9 * 10 < ⁵ > Pa, it can be used without a restriction | limiting in particular.
The storage elastic modulus is an index representing the ease of deformation of the material. When the storage elastic modulus of the pressure-sensitive adhesive layer is 1.5 × 10 ⁴ to 1.5 × 10 ⁵ Pa, one optical compensation sheet is obtained. In this way, it becomes easy to deform and a preferable result is obtained. The storage elastic modulus is more preferably 1.5 × 10 ^{4 to} 1.3 × 10 ⁵ Pa, and still more preferably 1.5 × 10 ^{4 to} 1.2 × 10 ⁵ Pa.
Moreover, when the yield strength of the pressure-sensitive adhesive layer is 0.9 × 10 ⁴ to 0.9 × 10 ⁵ Pa, the pressure-sensitive adhesive layer is more easily deformed, and a preferable result is obtained. The yield strength is more preferably 0.9 × 10 ^{4 to} 0.8 × 10 ⁵ Pa, and still more preferably in the range of 0.9 × 10 ^{4 to} 0.7 × 10 ⁵ Pa.

  In order to set the storage elastic modulus and yield strength of the pressure-sensitive adhesive layer within the above ranges, the molecular weight of the polymer used in the pressure-sensitive adhesive may be adjusted, or the mixing ratio of the materials may be adjusted.

  As described above, the pressure-sensitive adhesive layer is provided on the upper surface (the surface having the optically anisotropic layer) of the optical compensation film of the polarizing plate to obtain the polarizing plate with the pressure-sensitive adhesive layer.

[Optical compensation film]
The optical compensation film in the present invention is disposed between a polarizing plate and a liquid crystal cell of a liquid crystal display device. Examples of the optical compensation film used in the present invention include a compensation film (for example, Japanese Patent No. 2587398) in which a discotic liquid crystal compound is hybrid-aligned and fixed on a transparent support, as well as triacetylcellulose and norbornene. High-molecular optical compensation films such as polymers of the same kind can be used.

(Optical compensation film, transparent support, transparent protective film for polarizing plate)
The optical compensation film and the transparent support for the optical compensation film can be used without any particular limitation, but it is preferable to use a polymer film having a light transmittance of 80% or more.
Moreover, as a transparent protective film of a polarizing plate, the same thing as the said optical compensation film and the transparent support body of an optical compensation film can be used.
Examples of the polymer constituting the polymer film include cellulose ester (eg, cellulose acetate, cellulose diacetate, cellulose triacetate (triacetyl cellulose)), polyolefin (eg, norbornene-based polymer), polycarbonate, and polysulfone. Commercially available polymers (for norbornene polymers, Arton (manufactured by JSR), Zeonore (manufactured by Nippon Zeon), etc.) may be used.

As the transparent support, it is preferable to use a support made mainly of triacetylcellulose or norbornene. In this specification, “mainly” means that the polymer is 50% or more in the polymer film as the support.
Of these, a cellulose ester is particularly preferable, and a lower fatty acid ester of cellulose is more preferable. Lower fatty acid means a fatty acid having 6 or less carbon atoms. The number of carbon atoms is preferably 2 (cellulose acetate), 3 (cellulose propionate) or 4 (cellulose butyrate). Cellulose acetate is particularly preferred. Mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate may be used. Most preferably, the lower fatty acid ester of cellulose is cellulose acetate.
The acetylation degree of cellulose acetate is preferably 55.0 to 62.5%, and more preferably 59.0 to 61.5%. The degree of acetylation means the amount of bound acetic acid per unit mass of cellulose. The degree of acetylation follows the measurement and calculation of the degree of acetylation in ASTM D-817-91 (test method for cellulose acetate and the like).

The viscosity average degree of polymerization (DP) of cellulose acetate (also referred to as acetyl cellulose) is preferably 250 or more, and more preferably 290 or more.
The cellulose ester (cellulose acetate) used in the present invention preferably has a narrow molecular weight distribution of Mw / Mn (Mw is mass average molecular weight, Mn is number average molecular weight) by gel permeation chromatography. The specific value of Mw / Mn is preferably in the range of 1.0 to 1.7, more preferably in the range of 1.3 to 1.65, and in the range of 1.4 to 1.6. Most preferably.

  In general, the 2, 3, and 6 hydroxyl groups of cellulose acetate are not evenly distributed by 1/3 of the total substitution degree, and the substitution degree of the 6-position hydroxyl group tends to be small. In the present invention, it is preferable that the substitution degree of the 6-position hydroxyl group of cellulose acetate is larger than that of the 2- and 3-positions. The hydroxyl group at the 6-position with respect to the total substitution degree is preferably substituted with 30% or more, more preferably 31% or more, particularly preferably 32% or more. Furthermore, the substitution degree of the 6-position acetyl group of cellulose acetate is preferably 0.88 or more. In addition to the acetyl group, the 6-position hydroxyl group is substituted with a propionyl group, butyroyl group, valeroyl group, benzoyl group, acryloyl group or the like, which is an acyl group having 3 or more carbon atoms. I can do it. The degree of substitution at each position can be determined by NMR. As the cellulose acetate of the present invention, Synthesis Example 1 described in paragraph Nos. 0043 to 0044 of JP-A No. 11-5851, Synthesis Example 2 described in paragraph Nos. 0048 to 0049, and Synthesis examples described in paragraph Nos. 0051 to 0052 The cellulose acetate obtained by the method 3 can be used.

The photoelastic coefficient of the cellulose acetate film is preferably 50 × 10 ⁻¹² (1 / Pa) or less. It is more preferably 30 × 10 ⁻¹² (1 / Pa) or less, and further preferably 20 × 10 ⁻¹² (1 / Pa) or less. As a specific measuring method, a tensile stress is applied to the major axis direction of a 12 mm × 120 mm cellulose acetate film sample, and the retardation at that time is measured with an ellipsometer (M150, JASCO Corporation). The photoelastic coefficient was calculated from the amount of change in retardation.

(Retardation raising agent)
When a cellulose acetate film is used as a support for an optical compensation film, it is preferable to use an aromatic compound having at least two aromatic rings as a retardation increasing agent in order to adjust the retardation of the support. The aromatic compound is preferably used in the range of 0.01 to 20 parts by mass, more preferably in the range of 0.05 to 15 parts by mass, with respect to 100 parts by mass of cellulose acetate. It is more preferable to use in the range of 10 to 10 parts by mass. Two or more aromatic compounds may be used in combination. The aromatic ring of the aromatic compound includes an aromatic hetero ring in addition to the aromatic hydrocarbon ring.

  The aromatic hydrocarbon ring is particularly preferably a 6-membered ring (that is, a benzene ring). The aromatic heterocycle is generally an unsaturated heterocycle. The aromatic heterocycle is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring. Aromatic heterocycles generally have the most double bonds. As the hetero atom, a nitrogen atom, an oxygen atom and a sulfur atom are preferable, and a nitrogen atom is particularly preferable. Examples of aromatic heterocycles include furan ring, thiophene ring, pyrrole ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, imidazole ring, pyrazole ring, furazane ring, triazole ring, pyran ring, pyridine ring , Pyridazine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring. As the aromatic ring, benzene ring, furan ring, thiophene ring, pyrrole ring, oxazole ring, thiazole ring, imidazole ring, triazole ring, pyridine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring are preferable, More preferred are a benzene ring and a 1,3,5-triazine ring. It is particularly preferred that the aromatic compound has at least one 1,3,5-triazine ring.

  The number of aromatic rings contained in the aromatic compound is preferably 2 to 20, more preferably 2 to 12, still more preferably 2 to 8, and most preferably 2 to 6. . The bonding relationship between two aromatic rings can be classified into (a) when a condensed ring is formed, (b) when directly linked by a single bond, and (c) when linked via a linking group (for aromatic rings). , Spiro bonds cannot be formed). The connection relationship may be any of (a) to (c).

Examples of the condensed ring of (a) (condensed ring of two or more aromatic rings) include an indene ring, a naphthalene ring, an azulene ring, a fluorene ring, a phenanthrene ring, an anthracene ring, an acenaphthylene ring, a naphthacene ring, a pyrene ring, Indole ring, isoindole ring, benzofuran ring, benzothiophene ring, indolizine ring, benzoxazole ring, benzothiazole ring, benzimidazole ring, benzotriazole ring, purine ring, indazole ring, chromene ring, quinoline ring, isoquinoline ring, quinolidine Ring, quinazoline ring, cinnoline ring, quinoxaline ring, phthalazine ring, pteridine ring, carbazole ring, acridine ring, phenanthridine ring, xanthene ring, phenazine ring, phenothiazine ring, phenoxathiin ring, phenoxazine ring and thianthrene ring Be Naphthalene ring, azulene ring, indole ring, benzoxazole ring, benzothiazole ring, benzimidazole ring, benzotriazole ring and quinoline ring are preferred.
The single bond (b) is preferably a bond between carbon atoms of two aromatic rings. Two aromatic rings may be bonded with two or more single bonds to form an aliphatic ring or a non-aromatic heterocyclic ring between the two aromatic rings.

The linking group in (c) is preferably bonded to carbon atoms of two aromatic rings. The linking group is preferably an alkylene group, an alkenylene group, an alkynylene group, —CO—, —O—, —NH—, —S—, or a combination thereof. Examples of linking groups composed of combinations are shown below. In addition, the relationship between the left and right in the following examples of the linking group may be reversed.
c1: -CO-O-
c2: —CO—NH—
c3: -alkylene-O-
c4: —NH—CO—NH—
c5: —NH—CO—O—
c6: —O—CO—O—
c7: -O-alkylene-O-
c8: -CO-alkenylene-
c9: -CO-alkenylene-NH-
c10: -CO-alkenylene-O-
c11: -alkylene-CO-O-alkylene-O-CO-alkylene-
c12: -O-alkylene-CO-O-alkylene-O-CO-alkylene-O-
c13: -O-CO-alkylene-CO-O-
c14: -NH-CO-alkenylene-
c15: -O-CO-alkenylene-

The aromatic ring and the linking group may have a substituent. Examples of the substituent include halogen atom (F, Cl, Br, I), hydroxyl, carboxyl, cyano, amino, nitro, sulfo, carbamoyl, sulfamoyl, ureido, alkyl group, alkenyl group, alkynyl group, aliphatic acyl group , Aliphatic acyloxy group, alkoxy group, alkoxycarbonyl group, alkoxycarbonylamino group, alkylthio group, alkylsulfonyl group, aliphatic amide group, aliphatic sulfonamido group, aliphatic substituted amino group, aliphatic substituted carbamoyl group, aliphatic Substituted sulfamoyl groups, aliphatic substituted ureido groups and non-aromatic heterocyclic groups are included.
In the present specification, when a hydrogen atom is substituted with an atom other than a hydrogen atom, an atom other than the hydrogen atom is also treated as a substituent for convenience.

The alkyl group preferably has 1 to 8 carbon atoms. A chain alkyl group is preferable to a cyclic alkyl group, and a linear alkyl group is particularly preferable. The alkyl group may further have a substituent (eg, hydroxy, carboxy, alkoxy group, alkyl-substituted amino group). Examples of alkyl groups (including substituted alkyl groups) include methyl, ethyl, n-butyl, n-hexyl, 2-hydroxyethyl, 4-carboxybutyl, 2-methoxyethyl and 2-diethylaminoethyl.
The alkenyl group preferably has 2 to 8 carbon atoms. A chain alkenyl group is preferable to a cyclic alkenyl group, and a linear alkenyl group is particularly preferable. The alkenyl group may further have a substituent. Examples of alkenyl groups include vinyl, allyl and 1-hexenyl. The alkynyl group preferably has 2 to 8 carbon atoms. A chain alkynyl group is preferable to a cyclic alkynyl group, and a linear alkynyl group is particularly preferable. The alkynyl group may further have a substituent. Examples of alkynyl groups include ethynyl, 1-butynyl and 1-hexynyl.

The aliphatic acyl group preferably has 1 to 10 carbon atoms. Examples of the aliphatic acyl group include acetyl, propanoyl and butanoyl.
The aliphatic acyloxy group preferably has 1 to 10 carbon atoms. Examples of the aliphatic acyloxy group include acetoxy.
The number of carbon atoms of the alkoxy group is preferably 1 to 8. The alkoxy group may further have a substituent (eg, alkoxy group). Examples of alkoxy groups (including substituted alkoxy groups) include methoxy, ethoxy, butoxy and methoxyethoxy.
The alkoxycarbonyl group preferably has 2 to 10 carbon atoms. Examples of the alkoxycarbonyl group include methoxycarbonyl and ethoxycarbonyl.
The number of carbon atoms of the alkoxycarbonylamino group is preferably 2 to 10. Examples of the alkoxycarbonylamino group include methoxycarbonylamino and ethoxycarbonylamino.

The alkylthio group preferably has 1 to 12 carbon atoms. Examples of the alkylthio group include methylthio, ethylthio and octylthio.
The alkylsulfonyl group preferably has 1 to 8 carbon atoms. Examples of the alkylsulfonyl group include methanesulfonyl and ethanesulfonyl.
The aliphatic amide group preferably has 1 to 10 carbon atoms. Examples of the aliphatic amide group include acetamide.
The aliphatic sulfonamide group preferably has 1 to 8 carbon atoms. Examples of the aliphatic sulfonamido group include methanesulfonamido, butanesulfonamido and n-octanesulfonamido.
The number of carbon atoms of the aliphatic substituted amino group is preferably 1 to 10. Examples of the aliphatic substituted amino group include dimethylamino, diethylamino and 2-carboxyethylamino.
The aliphatic substituted carbamoyl group preferably has 2 to 10 carbon atoms. Examples of the aliphatic substituted carbamoyl group include methylcarbamoyl and diethylcarbamoyl.
The aliphatic substituted sulfamoyl group preferably has 1 to 8 carbon atoms. Examples of the aliphatic substituted sulfamoyl group include methylsulfamoyl and diethylsulfamoyl.
The number of carbon atoms in the aliphatic substituted ureido group is preferably 2 to 10. Examples of the aliphatic substituted ureido group include methylureido.
Examples of non-aromatic heterocyclic groups include piperidino and morpholino.

  The molecular weight of the retardation increasing agent is preferably 300 to 800. Specific examples of the retardation increasing agent include compounds described in JP-A Nos. 2000-1111914, 2000-275434, and WO 2000/065384.

(Manufacture of cellulose acetate film)
Next, the manufacturing method of a cellulose acetate film is described. As the method and equipment for producing the cellulose acetate film, a conventionally known solution casting film forming method and solution casting film forming apparatus for use in producing a cellulose acetate film are used.
Especially, it is preferable to manufacture a cellulose acetate film by a solvent cast method. In the solvent cast method, a film is produced using a solution (dope) in which cellulose acetate is dissolved in an organic solvent. The organic solvent is a solvent selected from ethers having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, esters having 3 to 12 carbon atoms, and halogenated hydrocarbons having 1 to 6 carbon atoms. It is preferable to contain. The ether, ketone and ester may have a cyclic structure. A compound having two or more functional groups of ether, ketone and ester (that is, —O—, —CO— and —COO—) can also be used as the organic solvent. The organic solvent may have another functional group such as an alcoholic hydroxyl group. In the case of an organic solvent having two or more types of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group.

Examples of the ether having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole.
Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone and methylcyclohexanone.
Examples of the esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate.
Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.
The number of carbon atoms of the halogenated hydrocarbon is preferably 1 or 2, and most preferably 1. The halogen of the halogenated hydrocarbon is preferably chlorine. The proportion of halogenated hydrocarbon hydrogen atoms substituted with halogen is preferably 25 to 75 mol%, more preferably 30 to 70 mol%, and more preferably 35 to 65 mol%. More preferably, it is 40 to 60 mol%, and most preferably. Methylene chloride is a typical halogenated hydrocarbon.
Two or more organic solvents may be mixed and used.

  A cellulose acetate solution can be prepared by a general method. The general method here means that the treatment is performed at a temperature of 0 ° C. or higher (room temperature or high temperature). The solution can be prepared using a dope preparation method and apparatus in a normal solvent cast method. In the case of a general method, it is preferable to use a halogenated hydrocarbon (particularly methylene chloride) as the organic solvent. The amount of cellulose acetate is preferably adjusted so as to be 10 to 40% by mass in the obtained cellulose acetate solution, and more preferably 10 to 30% by mass. Arbitrary additives described later may be added to the organic solvent (main solvent). The solution can be prepared by stirring cellulose acetate and an organic solvent at room temperature (0 to 40 ° C.). High concentration solutions may be stirred under pressure and heating conditions. Specifically, cellulose acetate and an organic solvent are placed in a pressure vessel and sealed, and stirred while heating to a temperature not lower than the boiling point of the solvent at normal temperature and in a range where the solvent does not boil. The heating temperature is usually 40 ° C. or higher, preferably 60 to 200 ° C., more preferably 80 to 110 ° C.

  Each component may be coarsely mixed in advance and then placed in a container. Moreover, you may put into a container sequentially. The container is preferably configured so that it can be stirred. The container can be pressurized by injecting an inert gas such as nitrogen gas. Moreover, you may utilize the raise of the vapor pressure of the solvent by heating. Or after sealing a container, you may add each component under pressure. When heating, it is preferable to heat from the outside of the container. For example, a jacket type heating device can be used. The entire container can also be heated by providing a plate heater outside the container and piping to circulate the liquid. It is preferable to provide a stirring blade inside the container and stir using this. The stirring blade preferably has a length that reaches the vicinity of the wall of the container. A scraping blade is preferably provided at the end of the stirring blade in order to renew the liquid film on the vessel wall. Instruments such as a pressure gauge and a thermometer may be installed in the container. Each component can be dissolved in a solvent in the container. The prepared dope may be taken out of the container after cooling, or may be cooled using a heat exchanger or the like after taking out.

  A solution can also be prepared by a cooling dissolution method. In the cooling dissolution method, cellulose acetate can be dissolved in an organic solvent that is difficult to dissolve by a normal dissolution method. In addition, even if it is a solvent which can melt | dissolve a cellulose acetate with a normal melt | dissolution method, according to the cooling melt | dissolution method, there exists an effect that a uniform solution can be obtained rapidly and it is preferable. In the cooling dissolution method, usually, cellulose acetate is first gradually added to an organic solvent with stirring at room temperature. The amount of cellulose acetate is preferably adjusted so as to be contained in the mixture at 10 to 40% by mass. The amount of cellulose acetate is more preferably 10 to 30% by mass. Furthermore, you may add the arbitrary additive mentioned later in a mixture.

  The mixture is then cooled to -100 to -10 ° C (preferably -80 to -10 ° C, more preferably -50 to -20 ° C, most preferably -50 to -30 ° C). The cooling can be performed, for example, in a dry ice / methanol bath (−75 ° C.) or a cooled diethylene glycol solution (−30 to −20 ° C.). When cooled in this way, the mixture of cellulose acetate and organic solvent solidifies. The cooling rate is preferably 4 ° C./min or more, more preferably 8 ° C./min or more, and most preferably 12 ° C./min or more. The faster the cooling rate, the better. However, 10,000 ° C./second is the theoretical upper limit, 1000 ° C./second is the technical upper limit, and 100 ° C./second is the practical upper limit. The cooling rate is a value obtained by dividing the difference between the temperature at the start of cooling and the final cooling temperature by the time from the start of cooling until the final cooling temperature is reached.

  Furthermore, when this is heated to 0 to 200 ° C. (preferably 0 to 150 ° C., more preferably 0 to 120 ° C., most preferably 0 to 50 ° C.), cellulose acetate is dissolved in the organic solvent. The temperature can be raised by simply leaving it at room temperature or in a warm bath. The heating rate is preferably 4 ° C./min or more, more preferably 8 ° C./min or more, and most preferably 12 ° C./min or more. The higher the heating rate, the better. However, 10,000 ° C./second is the theoretical upper limit, 1000 ° C./second is the technical upper limit, and 100 ° C./second is the practical upper limit. The heating rate is a value obtained by dividing the difference between the temperature at the start of heating and the final heating temperature by the time from the start of heating until the final heating temperature is reached. . A uniform solution is obtained as described above. If the dissolution is insufficient, the cooling and heating operations may be repeated. Whether the dissolution is sufficient or not can be judged by observing the appearance of the solution by visual observation.

In the cooling dissolution method, it is desirable to use a sealed container in order to avoid moisture mixing due to condensation during cooling. In the cooling and heating operation, when the pressure is applied during cooling and the pressure is reduced during heating, the dissolution time can be shortened. In order to perform pressurization and decompression, it is desirable to use a pressure-resistant container.
In addition, for example, according to differential scanning calorimetry (DSC), a 20% by mass solution of cellulose acetate having an acetylation degree of 60.9% and a viscosity average polymerization degree of 299 dissolved in methyl acetate by a cooling dissolution method, There is a quasi-phase transition point between a sol state and a gel state in the vicinity of 33 ° C., and a uniform gel state is obtained below this temperature. Therefore, this solution needs to be maintained at a temperature equal to or higher than the pseudo phase transition temperature, preferably about the gel phase transition temperature plus about 10 ° C. However, this pseudo phase transition temperature varies depending on the degree of acetylation of cellulose acetate, the degree of viscosity average polymerization, the concentration of the solution, and the organic solvent used.

  As described above, it is preferable to produce a cellulose acetate film from the prepared cellulose acetate solution (dope) by a solvent cast method. In the case of producing cellulose acetate used as a support for the optical compensation sheet, it is preferable to add the above-mentioned retardation increasing agent to the dope. The dope is cast on a drum or band and the solvent is evaporated to form a film. It is preferable to adjust the concentration of the dope before casting so that the solid content is 18 to 35%. The surface of the drum or band is preferably finished in a mirror state. The casting and drying methods in the solvent casting method are described in U.S. Pat. No. 736892, JP-B Nos. 45-4554, 49-5614, JP-A-60-176834, No. 60-203430, and No. 62-115035. The dope is preferably cast on a drum or band having a surface temperature of 10 ° C. or less. After casting, it is preferable to dry it by applying air for 2 seconds or more. The obtained film can be peeled off from the drum or band, and further dried by high-temperature air whose temperature is successively changed from 100 to 160 ° C. to evaporate the residual solvent. The above method is described in JP-B-5-17844, and this method is preferable because it can shorten the time from casting to stripping. In order to carry out this method, it is necessary for the dope to gel at the surface temperature of the drum or band during casting.

  It is also possible to form a film by casting two or more layers using the adjusted cellulose acetate solution (dope). In this case, it is preferable to produce a cellulose acetate film by a solvent cast method. The dope is cast on a drum or band and the solvent is evaporated to form a film. It is preferable to adjust the concentration of the dope before casting so that the solid content is in the range of 10 to 40%. The surface of the drum or band is preferably finished in a mirror state.

  When casting a plurality of cellulose acetate liquids of two or more layers, it is possible to cast a plurality of cellulose acetate solutions, and cellulose acetate from a plurality of casting openings provided at intervals in the traveling direction of the support. A film may be produced while casting and laminating solutions each containing. For example, the methods described in JP-A-61-158414, JP-A-1-122419, and JP-A-11-198285 can be used. It can also be formed into a film by casting a cellulose acetate solution from two casting ports. For example, JP-B-60-27562, JP-A-61-94724, JP-A-61-947245, JP-A-61-104413, JP-A-61-158413, and JP-A-6-134933. The method described in each publication can be used. Further, a cellulose acetate film casting method is disclosed in which a flow of a high-viscosity cellulose acetate solution described in JP-A-56-162617 is wrapped with a low-viscosity cellulose acetate solution, and the high- and low-viscosity cellulose acetate solution is simultaneously extruded. It can also be used.

  Also, using two casting ports, the film formed on the support by the first casting port is peeled off, and the second casting is performed on the side that was in contact with the support surface to produce a film. You can also For example, the method described in Japanese Patent Publication No. 44-20235 can be mentioned. As the cellulose acetate solution to be cast, the same solution may be used, or different cellulose acetate solutions may be used. In order to give a function to a plurality of cellulose acetate layers, a cellulose acetate solution corresponding to the function may be pushed out from each casting port. Furthermore, the cellulose acetate solution can be cast simultaneously with other functional layers (for example, an adhesive layer, a dye layer, an antistatic layer, an antihalation layer, an ultraviolet absorbing layer, a polarizing layer).

  In the conventional single-layer liquid, it is necessary to extrude a cellulose acetate solution having a high concentration and a high viscosity in order to obtain a necessary film thickness. In such a case, the stability of the cellulose acetate solution is poor and solid matter is generated, which often causes problems such as defects in the surface and poor flatness. As a solution to this problem, by casting a plurality of cellulose acetate solutions from the casting port, it is possible to extrude a highly viscous solution onto the support at the same time. Not only can it be produced, but also the use of a concentrated cellulose acetate solution can achieve a reduction in drying load and increase the production speed of the film.

(Additive)
Polyester urethane is preferably added to the cellulose acetate film in order to improve mechanical properties. The polyester urethane is preferably a reaction product of a polyester diol represented by the following general formula (1) and a diisocyanate, and is preferably soluble in dichloromethane.
General formula (1):

_{H - (- O- (CH 2} ) p -OOC- (CH 2) m -CO) n -O- (CH 2) p -OH

In general formula (1), p represents an integer of 2 to 4; m represents an integer of 2 to 4; and n represents an integer of 1 to 100.
More specifically, in the constituent polyester, the glycol component is ethylene glycol, 1,3-propanediol, or 1,4-butanediol, and the dibasic acid component is succinic acid, glutaric acid, or adipine. It is a polyester having hydroxyl groups at both ends made of an acid, and the degree of polymerization n is in the range of 1-100. The optimum degree of polymerization varies slightly depending on the type of glycol and dibasic acid used, and the molecular weight of the polyester is particularly preferably in the range of 1000 to 4500.
The dichloromethane-soluble polyester urethane resin is a compound having a repeating unit represented by the following general formula (2), which is obtained by the reaction of the polyester of the general formula (1) and diisocyanate.

General formula (2):

-CONH-R-NHCO- (O- ( CH 2) p -OOC- (CH 2) m -CO) n -O- (CH 2) p -O) -

In general formula (2), p represents an integer of 2 to 4; m represents an integer of 2 to 4; n represents an integer of 1 to 100; R represents a divalent atomic group residue Represents. Examples of the divalent atomic group residue include those represented by the following formula, for example.

Examples of the diisocyanate component used in the polyurethane compound include polymethylene diisocyanate represented by ethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (general formula: OCN (CH ₂ ) _p NCO (p represents an integer of 2 to 8)), p-phenylene diisocyanate, tolylene diisocyanate, p, p′-diphenylmethane diisocyanate, 1,5-naphthylene diisocyanate Aromatic diisocyanates such as narate, m-xylylene diisocyanate and the like can be mentioned, but are not limited thereto. Among these, tolylene diisocyanate, m-xylylene diisocyanate, and tetramethylene diisocyanate are readily available, relatively stable and easy to handle, and cellulose acetate when polyurethaneized. This is preferable because of its excellent compatibility.

The molecular weight of the polyester urethane resin is preferably in the range of 2,000 to 50,000, and can be appropriately selected depending on the type or molecular weight of the component polyesters or the diisocyanate component that is a linked group thereof. The molecular weight of the polyester urethane resin is more preferably in the range of 5,000 to 15,000 in terms of improving the mechanical properties of the cellulose acetate film and compatibility with the cellulose acetate. The synthesis of the dichloromethane-soluble polyester urethane can be easily obtained by mixing the polyester diol represented by the general formula (1) and diisocyanate and heating with stirring. The polyester diol represented by the general formula (1) is a hot melt condensation method by a polyesterification reaction or transesterification reaction between a corresponding dibasic acid or an alkyl ester thereof and a glycol, or an acid of these acids. It can be easily synthesized by appropriately adjusting the terminal group to be a hydroxyl group by any of the interfacial condensation methods of chloride and glycols.
The dichloromethane-soluble polyester urethane resin used in the present invention is extremely compatible with cellulose acetate having an acetylation degree of 58% or more. Although a slight difference is recognized depending on the structure of the resin, when the molecular weight of the polyester urethane is 10,000 or less, even 200 parts by mass of the polyester urethane is compatible with 100 parts by mass of the cellulose acetate.

  Therefore, when polyester urethane resin is mixed with cellulose acetate to improve the mechanical properties of the film, the content of polyester urethane resin is appropriately determined according to the type of urethane resin, molecular weight, and desired mechanical properties. That's fine. In order to improve mechanical properties while maintaining the properties of cellulose acetate, it is preferable to contain 10 to 50% by mass of polyester urethane resin with respect to cellulose acetate. This polyester urethane resin is stable and does not thermally decompose up to at least 180 ° C. This dichloromethane-soluble polyester urethane is extremely compatible with cellulose acetate having a degree of acetylation of 58% or more. Therefore, when both are mixed and formed into a film, a film with extremely high transparency can be obtained. Moreover, since these polyester urethanes have a high average molecular weight, they are hardly volatile even at high temperatures, unlike conventional low-molecular plasticizers. Therefore, the film obtained by forming a film from these mixtures has less inconvenience due to the volatilization and migration of the plasticizer found in the conventional plasticizer in the subsequent processing.

Addition of polyester urethane to the cellulose acetate film is preferable because the folding strength and tear strength at high and low temperatures are increased, and the film is difficult to tear.
Conventionally, low molecular plasticizers have been used to improve the bending strength and tear strength of a film. This method is effective to some extent at room temperature and high humidity, but the film is not flexible at low temperature and high humidity, and satisfactory results are not always obtained. Furthermore, when an attempt was made to improve mechanical properties with a low molecular plasticizer, it was common that the mechanical properties such as tensile strength significantly decreased with the amount of plasticizer added. When dichloromethane-soluble polyester urethane resin is added to cellulose acetate, a slight decrease in tensile strength is observed with the amount of resin added, but there is clearly little decrease in strength compared to the addition of low molecular plasticizer, A tough film having a high bending strength almost equal to the case of no addition can be obtained.
Furthermore, the migration of the plasticizer at low temperature and high humidity can be prevented by mixing polyester urethane. Therefore, a transparent and glossy film that does not adhere to each other, is very flexible, and does not cause wrinkles can be obtained.

In order to improve the mechanical properties of the cellulose acetate film, the following plasticizer can be used in place of the polyester urethane or in combination with the polyester urethane.
As the plasticizer, phosphoric acid ester or carboxylic acid ester is used. Examples of phosphate esters include triphenyl phosphate (TPP) and tricresyl phosphate (TCP). Representative examples of the carboxylic acid ester include phthalic acid esters and citric acid esters. Examples of phthalic acid esters include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and diethyl hexyl phthalate (DEHP). Examples of citrate esters include triethyl O-acetylcitrate (OACTE) and tributyl O-acetylcitrate (OACTB). Examples of other carboxylic acid esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic acid esters. Phthalate plasticizers (DMP, DEP, DBP, DOP, DPP, DEHP) are preferably used. DEP and DPP are particularly preferred. The addition amount of the plasticizer is preferably 0.1 to 25% by mass, more preferably 1 to 20% by mass, and most preferably 3 to 15% by mass of the amount of the cellulose ester.

  Degradation inhibitors (eg, antioxidants, peroxide decomposers, radical inhibitors, metal deactivators, acid scavengers, amines) may be added to the cellulose acetate film. The deterioration preventing agents are described in JP-A-3-199201, JP-A-51907073, JP-A-5-194789, JP-A-5-271471, and JP-A-6-107854. The addition amount of the deterioration preventing agent is preferably 0.01 to 1% by mass of the solution (dope) to be prepared, and more preferably 0.01 to 0.2% by mass. When the addition amount is less than 0.01% by mass, the effect of the deterioration preventing agent is hardly recognized. When the addition amount exceeds 1% by mass, bleed-out (bleeding) of the deterioration preventing agent to the film surface may be observed. Examples of particularly preferred deterioration inhibitors include butylated hydroxytoluene (BHT) and tribenzylamine (TBA).

(Biaxial stretching)
The cellulose acetate film is preferably stretched in order to reduce virtual strain. Since the virtual strain in the stretching direction can be reduced by stretching, biaxial stretching is more preferable in order to reduce the strain in all directions in the plane. Biaxial stretching includes simultaneous biaxial stretching and sequential biaxial stretching, but sequential biaxial stretching is preferred from the viewpoint of continuous production, and after casting the dope, the film is peeled off from the band or drum, After stretching in the width direction (longitudinal method), the film is stretched in the longitudinal direction (width direction). Methods for stretching in the width direction are described in, for example, JP-A-62-115035, JP-A-4-152125, JP-A-2842211, JP-A-298310, and JP-A-11-48271. Yes.
The film is stretched at room temperature or under heating conditions. The heating temperature is preferably not higher than the glass transition temperature of the film. The film can be stretched by a treatment during drying, and is particularly effective when the solvent remains. In the case of stretching in the longitudinal direction, for example, the film is stretched by adjusting the speed of the film transport roller so that the film winding speed is higher than the film peeling speed. In the case of stretching in the width direction, the film can also be stretched by conveying while holding the width of the film with a tenter and gradually widening the width of the tenter. After the film is dried, it can be stretched using a stretching machine (preferably uniaxial stretching using a long stretching machine). The stretch ratio of the film (the ratio of the increase due to stretching relative to the original length) is preferably in the range of 5 to 50%, more preferably in the range of 10 to 40%, and in the range of 15 to 35%. Most preferably.

  These steps from casting to post-drying may be performed in an air atmosphere or an inert gas atmosphere such as nitrogen gas. The winder used for producing the cellulose acetate film used in the present invention may be a commonly used winder such as a constant tension method, a constant torque method, a taper tension method, a program tension control method with a constant internal stress, or the like. It can be wound up by the method.

(Surface treatment of cellulose acetate film)
The cellulose acetate film is preferably subjected to a surface treatment. Specific examples include corona discharge treatment, glow discharge treatment, flame treatment, acid treatment, alkali treatment, and ultraviolet irradiation treatment. It is also preferable to provide an undercoat layer as described in JP-A-7-333433. From the viewpoint of maintaining the flatness of the film, the temperature of the cellulose acetate film in these treatments is preferably Tg (glass transition temperature) or less, specifically 150 ° C. or less.
When using a cellulose acetate film as a transparent protective film of a polarizing plate, it is particularly preferable to carry out an acid treatment or an alkali treatment, that is, a saponification treatment on cellulose acetate, from the viewpoint of adhesiveness with a polarizing film. The surface energy is preferably 55 mN / m or more, and more preferably 60 mN / m or more and 75 mN / m or less.

  Hereinafter, the alkali saponification treatment will be specifically described as an example. The alkali saponification treatment of the cellulose acetate film is preferably performed in a cycle in which the film surface is immersed in an alkaline solution, neutralized with an acidic solution, washed with water and dried. Examples of the alkaline solution include a potassium hydroxide solution and a sodium hydroxide solution, and the prescribed concentration of hydroxide ions is preferably in the range of 0.1 to 3.0 mol / L, and preferably 0.5 to 2.0. More preferably, it is in the range of mol / L. The alkaline solution temperature is preferably in the range of room temperature to 90 ° C, and more preferably in the range of 40 to 70 ° C.

The surface energy of a solid can be determined by a contact angle method, a wet heat method, and an adsorption method as described in “Basics and Applications of Wetting” (issued by Realize 1989.12.10). In the case of the cellulose acetate film of the present invention, it is preferable to use a contact angle method. Specifically, two types of solutions having known surface energies are dropped on a cellulose acetate film, and at the intersection between the surface of the droplet and the surface of the film, the angle formed by the tangent line drawn on the droplet and the film surface The surface angle of the film can be calculated by defining the angle containing the droplet as the contact angle.
The thickness of the support is preferably 10 to 200 μm, and more preferably 20 to 150 μm.

(Alignment film)
The optical compensation film is provided with an optically anisotropic layer formed from a liquid crystalline compound on a support (which will be described below using a cellulose acetate film which is a preferred example of the support as a representative of the support). Although it is produced by this, an orientation film can be provided between the optically anisotropic layers provided on a cellulose acetate film. Thus, in this specification, “on the support” means not only directly on the support but also includes a case where the support is provided via another layer such as an alignment film.
The alignment film functions to align the liquid crystalline compound used for the optically anisotropic layer in a certain direction. Therefore, an alignment film is essential for producing an optical compensation film. However, if the alignment state is fixed after aligning the liquid crystalline compound, the alignment film plays its role and is not particularly necessary for the optical compensation film itself. It is not an essential component. Therefore, once the optical anisotropic layer is aligned on the alignment film, the formed alignment state is fixed, and only the optical anisotropic layer on the alignment film in which the alignment state is fixed is transferred onto the cellulose acetate film. It is also possible to produce an optical compensation film comprising a support without an alignment film and an optically anisotropic layer.

  The alignment film has a function of defining the alignment direction of the liquid crystalline compound. The alignment film is an organic compound (eg, ω-tricosanoic acid) formed by rubbing treatment of an organic compound (preferably polymer), oblique deposition of an inorganic compound, formation of a layer having a microgroove, or Langmuir-Blodgett method (LB film). , Dioctadecylmethylammonium chloride, methyl stearylate). Furthermore, an alignment film in which an alignment function is generated by application of an electric field, application of a magnetic field, or light irradiation is also known.

  The alignment film is preferably formed by polymer rubbing treatment. Polyvinyl alcohol is a preferred polymer. Particularly preferred is a modified polyvinyl alcohol to which a hydrophobic group is bonded. The alignment film can be formed from one type of polymer, but is more preferably formed by rubbing a layer composed of two types of crosslinked polymers. As the at least one polymer, it is preferable to use either a polymer that can be crosslinked by itself or a polymer that is crosslinked by a crosslinking agent. The alignment film is formed by reacting a polymer having a functional group or a polymer into which a functional group is introduced by polymerizing the polymer by light, heat, pH change, or the like; or a cross-linking agent that is a compound having high reaction activity Can be formed by introducing a linking group derived from a cross-linking agent between polymers to cross-link between the polymers.

  Such crosslinking is carried out by applying an alignment film coating solution containing the polymer or a mixture of a polymer and a crosslinking agent on a cellulose acetate film and then heating the coating film. Since it is only necessary to ensure the durability of the optical compensation film, the cross-linking treatment may be performed at any stage after the alignment film is coated on the cellulose acetate film until the optical compensation film is obtained. Considering the orientation of the liquid crystal compound layer (optically anisotropic layer) formed on the alignment film, it is also preferable to sufficiently crosslink after aligning the liquid crystal compound. In general, the alignment film is crosslinked by applying an alignment film coating solution on a cellulose acetate film and drying by heating. It is preferable that the heating temperature of the coating solution is set low so that the alignment film is sufficiently cross-linked at the stage of the heat treatment when forming the optically anisotropic layer described later.

  As the polymer used for the alignment film, either a polymer that can be crosslinked by itself or a polymer that is crosslinked by a crosslinking agent can be used. Of course, some polymers are possible. Examples of polymers include polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleimide copolymer, polyvinyl alcohol and modified polyvinyl alcohol, poly (N-methylol acrylamide), styrene / vinyl toluene copolymer, Polymers such as chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, carboxymethyl cellulose, polyethylene, polypropylene, and polycarbonate, Mention may be made of compounds such as gelatin and silane coupling agents. Examples of preferable polymers include water-soluble polymers such as poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvinyl alcohol, and modified polyvinyl alcohol. Gelatin, polyvinyl alcohol and modified polyvinyl alcohol are preferably used, and polyvinyl alcohol and modified polyvinyl alcohol are more preferably used. It is most preferable to use two types of polyvinyl alcohol or modified polyvinyl alcohol having different degrees of polymerization.

Examples of polyvinyl alcohol include polyvinyl alcohol having a saponification degree in the range of 70 to 100%. Generally, the degree of saponification is in the range of 80 to 100%, and more preferably in the range of 85 to 95%. The polymerization degree of polyvinyl alcohol is preferably in the range of 100 to 3000. Examples of the modified polyvinyl alcohol include polyvinyl alcohol modified by copolymerization, modification by chain transfer, or modification by block polymerization. Examples of the modifying group in the case of copolymerization modification include COONa, Si (OH) ₃ , N (CH ₃ ) ₃ .Cl, C ₉ H ₁₉ COO, SO ₃ , Na, C ₁₂ H _{25 and the} like. Examples of the modifying group in the case of the modification with chain transfer, COONa, SH, and the like C ₁₂ H _25. Examples of the modifying group in the case of modification by block polymerization include COOH, CONH ₂ , C ₆ H _{5 and the} like. Among these, unmodified or modified polyvinyl alcohol having a saponification degree in the range of 80 to 100% is preferable. Further, unmodified polyvinyl alcohol and modified polyvinyl alcohol having a saponification degree in the range of 85 to 95% are more preferable.

  As the modified polyvinyl alcohol, it is particularly preferable to use a modified product of polyvinyl alcohol modified with a compound represented by the following general formula. Hereinafter, this modified polyvinyl alcohol is referred to as a specific modified polyvinyl alcohol.

In the formula, R ¹ represents an alkyl group, an acryloylalkyl group, a methacryloylalkyl group, or an epoxyalkyl group; W represents a halogen atom, an alkyl group, or an alkoxy group; X represents an active ester, an acid anhydride, Or represents a group of atoms necessary to form an acid halide; p represents 0 or 1; and n represents an integer of 0 to 4. The specific modified polyvinyl alcohol is preferably a modified product of polyvinyl alcohol by a compound represented by the following general formula.

In the formula, X ¹ represents an atomic group necessary for forming an active ester, an acid anhydride, or an acid halide, and m represents an integer of 2 to 24.

  Examples of the polyvinyl alcohol used for reacting with the compounds represented by these general formulas include the above-mentioned unmodified polyvinyl alcohol and those modified by copolymerization, that is, modified by chain transfer, modified by block polymerization. A modified product of polyvinyl alcohol, such as those obtained. Preferred examples of the specific modified polyvinyl alcohol are described in detail in JP-A-9-152509. A method for synthesizing these polymers, a method for measuring a visible absorption spectrum, a method for determining a modification group introduction rate, and the like are described in detail in JP-A-8-338913.

  Examples of crosslinking agents include aldehydes, N-methylol compounds, dioxane derivatives, compounds that act by activating carboxyl groups, active vinyl compounds, active halogen compounds, isoxazoles, and dialdehyde starch. Can do. Examples of aldehydes include formaldehyde, glyoxal, and glutaraldehyde. Examples of N-methylol compounds include dimethylol urea and methylol dimethyl hydantoin. Examples of dioxane derivatives include 2,3-dihydroxydioxane. Examples of compounds that act by activating the carboxyl group include carbenium, 2-naphthalenesulfonate, 1,1-bispyrrolidino-1-chloropyridinium, and 1-morpholinocarbonyl-3- (sulfonatoaminomethyl). Can be mentioned. Examples of active vinyl compounds include 1,3,5-triacroyl-hexahydro-s-triazine, bis (vinylsulfone) methane, and N, N′-methylenebis- [β- (vinylsulfonyl) propionamide]. . An example of the active halogen compound is 2,4-dichloro-6-hydroxy-s-triazine. These can be used alone or in combination. These are preferable when used in combination with the above water-soluble polymer, particularly polyvinyl alcohol and modified polyvinyl alcohol (including the above-mentioned specific modified products). In view of productivity, it is preferable to use an aldehyde having a high reaction activity, particularly glutaraldehyde.

  There is no particular limitation on the amount of crosslinking agent added to the polymer. The moisture resistance tends to be improved by adding more crosslinking agent. However, when the crosslinking agent is added in an amount of 50% by mass or more based on the polymer, the alignment ability as the alignment film is lowered. Accordingly, the amount of the crosslinking agent added to the polymer is preferably in the range of 0.1 to 20% by mass, and more preferably in the range of 0.5 to 15% by mass. The alignment film contains a certain amount of the crosslinking agent that has not reacted even after the crosslinking reaction is completed. The amount of the crosslinking agent is preferably 1.0% by mass or less in the alignment film. More preferably, it is 5 mass% or less. When the amount of the unreacted crosslinking agent in the alignment film is within the above range, reticulation occurs when used in a liquid crystal display device, when used for a long time, or when left in a high temperature and high humidity atmosphere for a long time. However, sufficient durability is obtained, which is preferable.

The alignment film can be formed by applying a solution containing the polymer or a solution containing the polymer and a crosslinking agent on the cellulose acetate film, followed by drying by heating (crosslinking) and rubbing treatment. The cross-linking reaction may be performed at any time after the coating solution is coated on the cellulose acetate film. When a water-soluble polymer such as polyvinyl alcohol is used as the alignment film forming material, the solvent for preparing the coating solution is an organic solvent such as methanol having a defoaming action, or a mixture of an organic solvent and water. It is preferable to use a solvent. When methanol is used as the organic solvent, the mass ratio of water: methanol is generally 0: 100 to 99: 1, and more preferably 0: 100 to 91: 9. Thereby, generation | occurrence | production of a bubble is suppressed and the defect of the surface of an alignment film and also an optical anisotropic layer reduces remarkably.
Examples of the coating method include a spin coating method, a dip coating method, a curtain coating method, an extrusion coating method, a bar coating method, and an E type coating method. Among these, the E type coating method is particularly preferable.

  The thickness of the alignment film is preferably in the range of 0.1 to 10 μm. The heat drying can be performed at a heating temperature in the range of 20 to 110 ° C. In order to form sufficient crosslinking, the heating temperature is preferably in the range of 60 to 100 ° C, and preferably in the range of 80 to 100 ° C. The drying time can be 1 minute to 36 hours. Preferably it is 5 to 30 minutes. The pH is also preferably set to an optimum value for the crosslinking agent to be used. When glutaraldehyde is used, it is preferably in the range of pH 4.5 to 5.5, particularly preferably pH 5.

  For the rubbing treatment, a treatment method widely adopted as a liquid crystal alignment treatment step of the liquid crystal display device can be used. That is, a method of obtaining alignment by rubbing the surface of the alignment film in a certain direction using paper, gauze, felt, rubber, nylon, polyester fiber or the like can be used. In general, it is carried out by rubbing several times using a cloth in which fibers having a uniform length and thickness are flocked on average.

[Optically anisotropic layer]
The optically anisotropic layer formed from the liquid crystalline compound is formed on the cellulose acetate film directly or via another layer such as an alignment film. As the liquid crystalline compound having a polymerizable group used in the optically anisotropic layer, a rod-like liquid crystalline compound and a discotic liquid crystalline compound are used. The optically anisotropic layer is formed by applying a liquid crystal compound and, if necessary, a coating liquid containing a polymerizable initiator and optional components on the alignment film, and fixing the alignment of the liquid crystal compound by a polymerization reaction. Can be formed.

As a solvent used for adjusting the coating solution, an organic solvent is preferably used. Examples of organic solvents include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethyl sulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, benzene, hexane), alkyl halides (eg, , Chloroform, dichloromethane, tetrachloroethane), esters (eg, methyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane). Alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination. The coating liquid can be applied by a known method (eg, wire bar coating method, extrusion coating method, direct gravure coating method, reverse gravure coating method, die coating method).
The thickness of the optically anisotropic layer is preferably 0.1 to 20 μm, more preferably 0.5 to 15 μm, and most preferably 1 to 10 μm. Examples of the liquid crystalline compound used in the present invention include rod-shaped liquid crystalline compounds and discotic liquid crystalline compounds, and it is particularly preferable to use discotic liquid crystalline compounds.

(Bar-shaped liquid crystalline compound)
Examples of rod-like liquid crystalline compounds include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines. , Phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used. The rod-like liquid crystalline compound includes a metal complex.
As for the rod-like liquid crystalline compounds, Chapter 4, Chapter 7 and Chapter 11 of the “Chemical Review of Vol. 22” published by the Chemical Society of Japan (1994), and “Liquid Crystal” of the 142th Committee of the Japan Society for the Promotion of Science. It is described in Chapter 3 of “Device Handbook”. The birefringence of the rod-like liquid crystalline compound is preferably in the range of 0.001 to 0.7. The rod-like liquid crystalline compound needs to have a polymerizable group in order to fix its alignment state. Examples of the polymerizable group (Q) are shown below.

  The polymerizable group (Q) is preferably an unsaturated polymerizable group (Q1 to Q7), an epoxy group (Q8) or an aziridinyl group (Q9), more preferably an unsaturated polymerizable group, and an ethylenic group. Most preferably, it is an unsaturated polymerizable group (Q1 to Q6). The rod-like liquid crystalline compound preferably has a molecular structure that is substantially symmetrical with respect to the minor axis direction. For that purpose, it is preferable to have a polymerizable group at both ends of the rod-like molecular structure. Below, the example of a rod-shaped liquid crystalline compound is shown.

  The optically anisotropic layer is composed of a rod-like liquid crystalline compound or a polymerizable initiator described later, and any conventionally known additive (eg, plasticizer, monomer, surfactant, cellulose ester, 1,3,5-triazine compound). And a liquid crystal composition (coating solution) containing a chiral agent) is applied on the alignment film, and the alignment of the liquid crystalline compound is fixed by a polymerization reaction.

(Discotic liquid crystalline compounds)
Examples of discotic liquid crystalline compounds include C.I. Destrade et al., Mol. Cryst. 71, 111 (1981), benzene derivatives described in C.I. Destrade et al., Mol. Cryst. 122, 141 (1985), Physics lett, A, 78, 82 (1990); Kohne et al., Angew. Chem. 96, page 70 (1984) and the cyclohexane derivatives described in J. Am. M.M. Lehn et al. Chem. Commun. , 1794 (1985), J. Am. Zhang et al., J. Am. Chem. Soc. 116, page 2655 (1994), and azacrown-based and phenylacetylene-based macrocycles. In addition, the discotic liquid crystalline compounds generally have a structure in which these are used as the mother nucleus at the center of the molecule, and linear alkyl groups, alkoxy groups, substituted benzoyloxy groups, etc. are radially substituted as the linear chains. Is also included and exhibits liquid crystallinity. However, the molecule itself is not limited to these as long as it has negative uniaxiality and can give a certain orientation.

  In order to fix the discotic liquid crystalline compound by polymerization, it is necessary to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystalline compound. However, when the polymerizable group is directly connected to the disc-shaped core, it becomes difficult to maintain the orientation state in the polymerization reaction. Therefore, a linking group is introduced between the discotic core and the polymerizable group. Therefore, the discotic liquid crystalline compound having a polymerizable group is preferably a compound represented by the following general formula (3).

General formula (3): D (-LP) _n

In the general formula (3), D is a discotic core; L is a divalent linking group, P is a polymerizable group, and n is an integer of 4 to 12. An example of the general formula (3) is shown below. In each of the following examples, LP (or PL) means a combination of a divalent linking group (L) and a polymerizable group (P).

  In the general formula (3), the divalent linking group (L) is selected from the group consisting of an alkylene group, an alkenylene group, an arylene group, —CO—, —NH—, —O—, —S—, and combinations thereof. It is preferable that it is a bivalent coupling group. The divalent linking group (L) is a divalent combination of at least two divalent groups selected from the group consisting of an alkylene group, an arylene group, -CO-, -NH-, -O-, and -S-. More preferably, it is a linking group. The divalent linking group (L) is most preferably a divalent linking group in which at least two divalent groups selected from the group consisting of an alkylene group, an arylene group, -CO- and -O- are combined. . The alkylene group preferably has 1 to 12 carbon atoms. The alkenylene group preferably has 2 to 12 carbon atoms. The number of carbon atoms in the arylene group is preferably 6 to 10.

Examples of the divalent linking group (L) are shown below. The left side is bonded to the discotic core (D), and the right side is bonded to the polymerizable group (P). AL represents an alkylene group or an alkenylene group, and AR represents an arylene group. The alkylene group, alkenylene group and arylene group may have a substituent (eg, an alkyl group).
L1: -AL-CO-O-AL-
L2: -AL-CO-O-AL-O-
L3: -AL-CO-O-AL-O-AL-
L4: -AL-CO-O-AL-O-CO-
L5: -CO-AR-O-AL-
L6: -CO-AR-O-AL-O-
L7: -CO-AR-O-AL-O-CO-
L8: -CO-NH-AL-
L9: -NH-AL-O-
L10: -NH-AL-O-CO-
L11: -O-AL-
L12: -O-AL-O-
L13: -O-AL-O-CO-
L14: -O-AL-O-CO-NH-AL-
L15: -O-AL-S-AL-
L16: -O-CO-AR-O-AL-CO-
L17: -O-CO-AR-O-AL-O-CO-
L18: -O-CO-AR-O-AL-O-AL-O-CO-
L19: -O-CO-AR-O-AL-O-AL-O-AL-O-CO-
L20: -S-AL-
L21: -S-AL-O-
L22: -S-AL-O-CO-
L23: -S-AL-S-AL-
L24: -S-AR-AL-

  The polymerizable group (P) of the general formula (3) can be determined according to the type of polymerization reaction. Examples of the polymerizable group (P) are shown below.

The polymerizable group (P) is preferably an unsaturated polymerizable group (P1, P2, P3, P7, P8, P15, P16, P17) or an epoxy group (P6, P18). More preferably, it is most preferably an ethylenically unsaturated polymerizable group (P1, P7, P8, P15, P16, P17).
In the general formula (3), as described above, n is an integer of 4 to 12. Specific numbers can be determined according to the type of the disk-shaped core (D). In addition, although the combination of several L and P may differ, it is preferable that it is the same.

  When the discotic liquid crystalline compound is used, the optically anisotropic layer is a layer having negative birefringence, and the surface of the discotic structural unit is inclined with respect to the surface of the cellulose acetate film and the discotic structural unit. The angle formed between the surface and the surface of the cellulose acetate film is preferably changed in the depth direction of the optically anisotropic layer.

  The surface angle (tilt angle) of the disk-like structural unit generally increases or decreases in the depth direction of the optically anisotropic layer and with an increase in the distance from the bottom surface of the optically anisotropic layer. The tilt angle preferably increases with increasing distance. In addition, changes in the inclination angle include continuous increase, continuous decrease, intermittent increase, intermittent decrease, change including continuous increase and continuous decrease, and intermittent change including increase and decrease. it can. The intermittent change includes a region where the inclination angle does not change in the middle of the thickness direction. Even if the tilt angle includes a region where the tilt angle does not change, the tilt angle preferably increases or decreases as a whole. Further, the inclination angle is preferably increased as a whole, and particularly preferably continuously changed.

  The tilt angle of the disk-shaped unit on the support side can be generally adjusted by selecting a disk-like liquid crystalline compound or a material for the alignment film, or by selecting a rubbing treatment method. Further, the inclination angle of the disk-like unit on the surface side (opposite to the support) can generally be adjusted by selecting a discotic liquid crystalline compound or another compound used together with the discotic liquid crystalline compound. Examples of the compound used together with the discotic liquid crystalline compound include conventionally known compounds such as a plasticizer, a surfactant, a polymerizable monomer and a polymer. Further, the degree of change in the tilt angle can be adjusted by the same selection as described above.

  The plasticizer, surfactant, and polymerizable monomer used together with the discotic liquid crystalline compound are compatible with the discotic liquid crystalline compound and can change the tilt angle of the discotic liquid crystalline compound or can be aligned. Any compound can be used as long as it does not inhibit Among these, polymerizable monomers (eg, compounds having a vinyl group, a vinyloxy group, an acryloyl group, and a methacryloyl group) are preferable. The amount of the compound added is generally in the range of 1 to 50% by mass and preferably in the range of 5 to 30% by mass with respect to the discotic liquid crystalline compound.

  As the polymer used together with the discotic liquid crystalline compound, any polymer can be used as long as it is compatible with the discotic liquid crystalline compound and can change the tilt angle of the discotic liquid crystalline compound. A cellulose ester can be mentioned as an example of a polymer. Preferred examples of the cellulose ester include cellulose acetate, cellulose acetate propionate, hydroxypropyl cellulose, and cellulose acetate butyrate. In order not to inhibit the orientation of the discotic liquid crystalline compound, the amount of the polymer added is generally in the range of 0.1 to 10% by mass with respect to the discotic liquid crystalline compound, and in the range of 0.1 to 8% by mass. It is more preferable that it is in the range of 0.1 to 5% by mass.

  The optically anisotropic layer is generally formed by applying a solution obtained by dissolving a discotic liquid crystalline compound and other compounds in a solvent onto an alignment film, drying it, and then heating it to a discotic nematic phase formation temperature, and then aligning it (disco It can be obtained by cooling while maintaining the (tick nematic phase). Alternatively, the optically anisotropic layer is formed by applying a solution obtained by dissolving a discotic liquid crystalline compound and another compound (for example, a polymerizable monomer, a photopolymerization initiator) in a solvent onto the alignment film, and then drying, It is obtained by heating to a discotic nematic phase formation temperature, polymerizing (by irradiation with UV light or the like), and further cooling. The discotic nematic liquid crystal phase-solid phase transition temperature of the discotic liquid crystalline compound used in the present invention is preferably 70 to 300 ° C, particularly preferably 70 to 170 ° C.

(Fixing the alignment state of liquid crystalline compounds)
In the present invention, since the liquid crystalline compound has a polymerizable group, the alignment state of the aligned liquid crystalline compound can be maintained and fixed, and thereby the alignment of the optically anisotropic layer is fixed. The The immobilization is preferably performed by a polymerization reaction. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator. A photopolymerization reaction is preferred.
Examples of the photopolymerization initiator include α-carbonyl compounds (described in US Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (described in US Pat. No. 2,448,828), α-hydrocarbon substituted aromatics. Group acyloin compounds (described in US Pat. No. 2,722,512), polynuclear quinone compounds (described in US Pat. Nos. 3,046,127 and 2,951,758), combinations of triarylimidazole dimers and p-aminophenyl ketone (US patents) No. 3549367), acridine and phenazine compounds (JP-A-60-105667, US Pat. No. 4,239,850) and oxadiazole compounds (US Pat. No. 4,221,970).
The amount of the photopolymerization initiator used is preferably in the range of 0.01 to 20% by mass, more preferably in the range of 0.5 to 5% by mass, based on the solid content of the coating solution.
Light irradiation for the polymerization of the liquid crystalline compound is preferably performed using ultraviolet rays. The irradiation energy is preferably in the range of 20 mJ / cm ² to 50 J / cm ^2, more preferably in the range of 20 to 5000 mJ / cm ^2, and still more preferably in the range of 100 to 800 mJ / cm ² . In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions. A protective layer may be provided on the optically anisotropic layer. As described above, an optical compensation sheet can be produced by providing an optically anisotropic layer on a cellulose acetate film.

[Liquid Crystal Display]
The polarizing plate of the present invention is advantageously used for a liquid crystal display device, particularly a TN mode transmissive liquid crystal display device.
In a TN mode liquid crystal cell, rod-like liquid crystalline molecules are substantially horizontally aligned when no voltage is applied, and are twisted and aligned at 60 to 120 °. The TN mode liquid crystal cell is most frequently used as a color TFT liquid crystal display device, and is described in many documents.
In addition to the TN mode liquid crystal cell, the polarizing plate of the present invention is also used in OCB (Optically Compensatory Bend), VA (Vertically Aligned), IPS (In Plane Switching), ECB (Electrically Controlled Birefringence Display), etc. Available.

  The present invention will be described more specifically with reference to the following examples. The materials, operations, test conditions, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the following examples.

[Example 1]
In order to compare the light leakage phenomenon in the liquid crystal display panel, verification was performed using a glass plate (Corning # 1737) having a length of 350 mm, a width of 430 mm, and a thickness of 1.1 mm. A thin razor prepared by preparing a commercially available polarizing plate (SUNRITZ HLC2-5618) with a length of 280 mm and a width of 370 mm, peeling off all the adhesive, and adjusting the depth from about 4 μm from the top, bottom, left, and right to the inside of 10 mm to a depth of about 60 μm. A groove that did not reach the polarizing film was formed by the groove forming jig used. This polarizing plate was bonded to the above-mentioned glass plate using an adhesive sheet (Soken Chemicals SK-1478). The absorption axes of the front and back polarizing films were bonded to crossed Nicols at an angle of 45 ° with respect to the long side of the glass plate. This glass plate was placed on a Schaukasten with a luminance of 2600 cd / m ² , and the luminance of the leaked light on the top, bottom, left and right was measured.
Next, the glass plates with the polarizing plates bonded to the front and back are left in an environment of 25 ° C. and 60% for 6 hours, placed in a 60 ° C. dry temperature oven for about 20 hours, and returned to room temperature. Leakage was again measured with a luminance meter.

  Luminance measurement points are points on the top, bottom, left, and right, near the center of each of the four sides, and 5 mm inside from the end.

[Conventional example 1]
Similar to Example 1, the adhesive was removed from a commercially available polarizing plate (Sunlitz Corporation HLC2-5618) having a length of 280 mm and a width of 370 mm, and using the same pressure-sensitive adhesive sheet (Soken Chemical SK-1478) as in Example, A polarizing plate on the front and back sides was bonded to crossed Nicols on a glass plate (Corning Inc. # 1737) having a width of 430 mm and a thickness of 1.1 mm at an oblique angle of 45 ° with respect to the long side. After this glass plate was placed on the Schaukasten and the leaked light intensity was measured on the top, bottom, left, and right, it was left in an environment of 25 ° C. and 60% for 6 hours, put into a 60 ° C. dry temperature oven for about 20 hours, and returned to room temperature. Thereafter, the luminance was measured again.

  Similar to the first embodiment, the luminance measurement points are the upper, lower, left, and right sides, the approximate center of each of the four sides, and a point 5 mm inside from the end.

Normal polarizer whereas (Conventional Example 1) In the light leakage light is also increased 0.92cd / m ² with respect to the initial state, in the first embodiment the groove is formed on a transparent protective film of a polarizing plate It was confirmed that the light leakage light increased only 0.11 cd / m ^{2 with} respect to the initial state.

  FIG. 6 shows a comparison between the vertical position of the glass plate in which the polarizing plate is pasted on the crossed Nicols in Example 1 and Conventional Example 1 and the leakage light using the Schaukasten as a light source. It can be seen that the maximum value of the amount of leakage light is lower than that of the polarizing plate of Conventional Example 1 in Example 1.

By having a groove parallel to the outer periphery, the portion where light leakage becomes prominent, that is, when the absorption axis is ± 45 °, the stress in the horizontal direction and the vertical direction generated in the transparent protective film near the upper, lower, left and right outer periphery. It is considered that the difference in stress is reduced, and as a result, the phase difference generated by the photoelastic effect is reduced and light leakage is reduced.
In Example 1 and Conventional Example 1, the effect was confirmed by bonding a polarizing plate to crossed Nicols using a glass plate. This is equivalent to verifying light leakage in a normal normally white type TN liquid crystal display device when a wide viewing angle optical compensation film is not used and when a black voltage is applied (ON state). To do.

  In this embodiment, the display screen size is approximately 17 inches. However, the present invention is not limited to this display size, and the aspect ratio is also limited to 5: 4 in this example. is not.

[Example 2]
In the case where the optical compensation film has a large number of holes, the case where the optical compensation film has a thin groove having a pixel pitch or less was compared with a normal case.
Triacetyl cellulose film: Fujitac TD-80U was prepared as a transparent support, and surface saponification treatment was performed in the same manner as the saponification treatment described in Example 1 of International Publication No. 2002/46809 using an alkaline solution having the following contents. . The contact angle between the film surface and water was 32 degrees, and the surface energy was 61 mN / m. This was designated as a transparent support (TK-1).
Alkaline solution:
5.6 parts by mass of potassium hydroxide, 65.5 parts by mass of isopropyl alcohol, 12 parts by mass of ethylene glycol, 1.0 part by mass of a fluoroaliphatic group-containing copolymer (Megafac F780 manufactured by Dainippon Ink Co., Ltd.) and water 11.4 parts by mass of mixed solution

(Formation of alignment film)
On the transparent support subjected to the surface saponification treatment, a coating solution having the following composition was coated with a # 16 wire bar coater at a coating amount of 28 ml / m ² , and then heated with 60 ° C. hot air for 60 seconds, and further 90 It was dried for 150 seconds with warm air of ° C. A rubbing treatment was performed in a direction parallel to the slow axis of the transparent support to obtain an alignment film.

<Alignment film coating solution composition>
Modified polyvinyl alcohol having the following structure 10 parts by weight Water 371 parts by weight Methanol 119 parts by weight Glutaraldehyde (crosslinking agent) 0.5 parts by weight

(Formation of optically anisotropic layer)
90 parts by mass of liquid crystalline discotic compound (A), 10 parts by mass of ethylene oxide-modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.), melamine formaldehyde / acrylic acid copolymer (Aldrich reagent) 0.6 Part by mass, 3.0 parts by mass of a photopolymerization initiator (Irgacure 907, manufactured by Nippon Ciba Geigy Co., Ltd.) and 1.0 part by mass of a photosensitizer (Kaya Cure DETX, manufactured by Nippon Kayaku Co., Ltd.) are dissolved in methyl ethyl ketone. A solution having a solid content concentration of 38% by mass was prepared as a coating solution.

  This coating solution was continuously applied onto the alignment film with a # 5.4 wire bar and heated at 130 ° C. for 2 minutes to align the liquid crystalline discotic compound.

  Next, UV irradiation was performed for 1 minute using a 120 W / cm high pressure mercury lamp at 100 ° C. to polymerize the liquid crystalline discotic compound. Then, it stood to cool to room temperature. Thus, an optical compensation film with an optically anisotropic layer (KH-1) was produced.

The optical compensation film (KH-1) is divided into three rolls, and on one film, an excimer laser irradiation device (Lumonis PulseMaster PM-848) is formed with about 1 hole in a 1 mm square and a diameter of about 100 μm. ) To form continuously. (Irradiation conditions: irradiation wavelength 193 nm, irradiation power 50 mJ / cm ² , repetition frequency 20 Hz, pulse duration 18 ns) This was designated as (KH-1A).
In the next film, fine grooves with a distance of 10 mm, a width of 30 μm, and a depth of 10 to 30 μm are formed on the entire surface of the optically anisotropic layer side and the liquid crystal disk-like compound surface by excimer laser irradiation in parallel with the roll winding direction. Formed. Irradiation device (Lumonis PulseMaster PM-848, irradiation wavelength 193 nm, irradiation power 3 mJ / cm ² , repetition frequency 20 Hz, pulse duration 10 ns) The fine grooves made on the entire surface are very thin and visible. I confirmed it was difficult. This film was designated as (KH-1B).

(Production of polarizer)
PVA having an average polymerization degree of 4000 and a saponification degree of 99.8 mol% was dissolved in water to obtain a 4.0% aqueous solution. This solution was band-cast using a die having a taper and dried to form a film so that the width before stretching was 110 mm, the thickness was 120 μm at the left end, and 135 μm at the right end.
The film was peeled off from the band, obliquely stretched in the 45 ° direction in a dry state, and immersed in an aqueous solution of iodine 0.5 g / L and potassium iodide 50 g / L for 1 minute at 30 ° C., and then boric acid 100 g / L. L, immersed in an aqueous solution of 60 g / L of potassium iodide at 70 ° C. for 5 minutes, further washed with water at 20 ° C. for 10 seconds and then dried at 80 ° C. for 5 minutes to obtain an iodine-based polarizer (HF-1). Obtained. The polarizer had a width of 660 mm and a thickness of 20 μm on both the left and right sides.

(Preparation of polarizing plate)
Three types of KH-1A, KH-1B and KH-1 were attached to one side of the polarizer (HF-1) on the transparent support (TK-1) surface using a polyvinyl alcohol-based adhesive. Again, a surface saponification treatment was performed on another triacetyl cellulose film: Fujitac TD-80U in the same manner as the saponification treatment described in Example 1 of WO 2002/46809 pamphlet, and a polyvinyl alcohol-based adhesive was used. Affixed to the opposite side of the polarizer.
The transmission axis of the polarizer and the slow axis of the transparent support were arranged in parallel. The triacetyl cellulose film was arranged so as to be orthogonal to the slow axis. In this way, a polarizing plate (HB-1A) provided with a large number of fine holes by laser in the optical compensation film, a polarizing plate (HB-1B) having fine grooves of a display pixel pitch or less at an interval of 10 mm, and a normal A polarizing plate (HB-1) was produced.

(Creation of liquid crystal display device)
From the polarizing plates (HB-1A), (HB-1B), and (HB-1), a 17-inch size (270 mm long, 337 mm wide) with a side that forms an angle of 45 ° with the absorption axis of the polarizing plate is 2 Cut out one by one.
Commercially available liquid crystal display device (Nippon Samsung Co., Ltd. SyncMaster 172X) The polarizing plates on the front and back of the three liquid crystal panels were peeled off. Instead, the above-mentioned 6 polarizing plates were attached to the front and back surfaces (Soken Chemicals SK-1478). It was pasted using. A display device combining (HB-1A) having fine holes, a display device combining (HB-1B) having fine grooves, and a display device combining normal viewing angle widening films were produced. . The polarizing plate was bonded to crossed Nicols so that the absorption axis of the polarizing plate was ± 45 ° with respect to the vertical direction of the display surface.
A display device (1) combining (HB-1A), a display device (2) combining (HB-1B) and a display device (3) combining (HB-1), respectively, at 40 ° C. After being stored in a 95% constant temperature and humidity chamber for about 20 hours and taken out, it was allowed to pass for 72 hours at 25 ° C. and 60%, and the occurrence of light leakage phenomenon and display quality of the display device were compared.
As a result, the display device (1) in which (HB-1A) is combined, and then the display device (2) in which (HB-1B) is combined is more than the display device (3) using a normal viewing angle widening polarizing plate. The frame-like light leakage phenomenon was confirmed to be mild.

Explanatory drawing when grooves are provided in the transparent protective film or optical compensation film of the polarizing plate Schematic diagram of general light leakage phenomenon found in TN liquid crystal display devices Schematic diagram of general light leakage phenomenon found in VA liquid crystal display devices An example of a Thomson blade type that forms grooves in a transparent protective film and molds a polarizing plate Schematic diagram of preferred layer structure of wide viewing angle polarizing plate Comparison of leakage light luminance after taking out from high temperature soot at 60 ℃ Explanatory drawing when a hole is provided in the transparent protective film or optical compensation film of the polarizing plate Explanatory drawing when a depression is provided in the transparent protective film or optical compensation film of the polarizing plate Schematic diagram of an optical compensation film with depressions distributed over the entire display surface Schematic diagram of an optical compensation film provided with grooves having a width less than the display pixel pitch Schematic diagram of liquid crystal display panel configuration

Explanation of symbols

xd: position of horizontal grooves, holes, dents, etc. in the display area yd; position A of vertical grooves, holes, dents, etc. in the display area; continuous or discontinuous grooves B; discontinuous holes C; discontinuous A recess D; a discontinuous gap E; a display pixel F; grooves a and b on the optical compensation film; a light leakage region c; a blade d for punching the polarizing plate; and a groove in the transparent protective film of the polarizing plate. Blade 1; Optical compensation film 11; Optical anisotropic layer 12; Transparent support 2; Polarizing film 3; Transparent protective film 4; Adhesive layer 5; Liquid crystal cell 6;

Claims (12)

  A polarizing plate having a polarizing film and at least one transparent protective film or an optical compensation film, wherein the transparent protective film or the optical compensation film is provided with a gap portion.   The polarizing plate according to claim 1, wherein the void portion is a discontinuous hole, or a continuous or discontinuous groove or depression.   The polarizing plate according to claim 1, wherein the void portion is filled with a substance having a refractive index within ± 1% with respect to the refractive index of the transparent protective film or the optical compensation film.   The polarizing plate according to claim 1, wherein the gap portion is provided in parallel with a side of the outer periphery of the polarizing plate.   The said space | gap part is provided in the outer peripheral part of the polarizing plate, The polarizing plate in any one of Claims 1-4 characterized by the above-mentioned.   The polarizing plate according to claim 1, wherein the gap portion is provided on the entire surface of the polarizing plate.   A liquid crystal display device in which a liquid crystal cell to which the polarizing plate according to claim 1 is bonded is incorporated so that the gap portion is between the polarizing film and the liquid crystal cell.   The liquid crystal display device according to claim 7, wherein the gap portion of the polarizing plate according to claim 5 is disposed outside the display region.   The liquid crystal display device according to claim 7, wherein the gap portion of the polarizing plate according to claim 6 is disposed in a display region.   The liquid crystal display device according to claim 7, wherein the gap portion is a groove having a width equal to or smaller than a display pixel pitch of the liquid crystal cell.   The polarized light according to any one of claims 1 to 6, wherein when the polarizing plate is die-cut into a desired shape, the gap is also formed in the transparent protective film or the optical compensation film of the polarizing plate at the same time. A method of manufacturing a board.   The method for producing a polarizing plate according to claim 1, wherein the gap is formed in the transparent protective film or the optical compensation film by ablation processing by laser irradiation.

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