JP2007078854A - Polarizing plate and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing plate which has a transparent protective film protecting a polarizer on a side facing a liquid crystal cell (LC) and can effectively compensate variation of optical characteristics of liquid crystal during oblique observation, and a liquid crystal display device which uses the same and has a wide view angle range of good visual inspection. <P>SOLUTION: Disclosed are: the polarizing plate such that the transparent protective film on the one surface side is a uniaxial phase difference film which has birefringence characteristics generating an in-plane phase difference in a (x, y) direction as a main axis and meets a condition of ny=nz, where nx and ny (nx>ny) are main refractive indexes in an x-y plane and nz is a refractive index in a thickness direction, and a slow axis of the unixial phase difference film is almost in parallel relation with an absorption axis of the polarizer; and the liquid crystal device using the same. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a polarizing plate that can compensate for changes in the optical characteristics of liquid crystal when observed obliquely, and a liquid crystal display device that uses the polarizing plate and has a wide viewing angle range with good visibility.

The liquid crystal display device can be directly connected to an IC with low voltage and low power consumption, and has many features such as various display functions, light weight, and easy miniaturization. Therefore, OA equipment such as word processors and personal computers, Widely used as various display means such as color televisions, car navigation monitors and aircraft cockpit monitors.
In such a liquid crystal display device, a polarizing plate is used in order to visualize the change in orientation of the liquid crystal. A polarizing plate is usually configured by laminating a transparent protective film made of TAC (triacetyl cellulose) or the like on a polarizer. FIG. 12A shows a typical polarizing plate structure. The polarizer 1 divides incident light into two polarization components orthogonal to each other, passes only one of them (a component whose vibration direction is parallel to the transmission axis of the polarizer), and the other component (the vibration direction is absorption by the polarizer 1). This is an optical element that absorbs or disperses the component parallel to the axis 1A, and is manufactured through a process of adsorbing iodine or the like on the surface of the polymer film and stretching. The transparent protective film 2 of the polarizing plate serves to protect the polarizer 1 with the polarizer 1 interposed therebetween. In general, a polarizing plate has a pressure-sensitive adhesive layer on one side and a surface protective film on the opposite side, and is attached to a liquid crystal cell via the pressure-sensitive adhesive layer.

  FIG. 12B schematically shows the configuration of a transmissive liquid crystal display (LCD). In FIG. 12B, 3 indicates a liquid crystal cell and 4 indicates a backlight. A liquid crystal material 32 is sealed in the space formed between the glass substrates 31. The transmissive liquid crystal display device includes a liquid crystal cell 3 sandwiched between polarizing plates 33 from both sides in the thickness direction. In the polarizing plates 33 on both sides, the absorption axes 1A of the pair of polarizers are generally orthogonal to each other (see FIG. 13A), and this arrangement is called a crossed Nicols type.

  In general, the optical characteristics of the pair of polarizers 1 have a viewing angle dependency, and even when the pair of polarizers 1 are arranged so that the absorption axes 1A are orthogonal to each other, they are observed obliquely (viewing angle θ> 0 °). In some cases, as the viewing angle θ increases, the amount of deviation from 90 ° of the angle between the absorption axes 1A viewed from the oblique direction increases as shown in FIG. Changes. For this reason, when the display light in the polarization state that has passed through the liquid crystal cell is directly incident on the polarizer 1 on the observation side, the orthogonal transmittance deteriorates and the amount of light leakage increases as the viewing angle θ increases. Become. Thereby, it is said that the display brightness of the liquid crystal display device (LCD) becomes insufficient, color changes such as a decrease in contrast and coloring occur, and the good viewing range is narrowed.

  Conventionally, in order to realize a liquid crystal display device with a wide viewing angle range with good visual recognition, it is essential to develop a polarizing plate that reduces the viewing angle dependency of the polarizer and generates almost no light leakage, that is, a wide viewing angle polarizing plate. There have been several proposals so far. Each of the wide viewing angle polarizing plates is configured by superposing a polarizer 1 (also referred to as a polarizing film) and one or two retardation films. FIG. 14 shows an optical system using the polarizing plate 33 of Conventional Example 1 and a pair of polarizers 1 arranged in a crossed Nicol type and its optical characteristics.

  The polarizing plate 33 of Conventional Example 1 has an in-plane retardation of 0.8 nm on both surfaces of the polarizer 1 and an optical value of Nz defined by (nx−nz) / (nx−ny) of 50 to 80. A transparent protective film (TAC) 2 having characteristics is overlaid. FIG. 14B is a spectrum obtained by changing the azimuth angle φ from the absorption axis 1A to 45 ° and the viewing angle θ to 0, 20, 40, 60 ° stepwise. In the spectrum, the incident angle of the incident light Lin from the light source is changed in steps of 0, 20, 40, and 60 degrees according to the viewing angle θ, and the incident light Lin is applied to the polarizing plate 33 on the incident light side. The obtained polarized light passes through the polarizing plate 33 on the observation side, and is obtained by measuring the leaked light Lout that leaks out by the light receiver.

  In the case of Conventional Example 1, it can be seen that there is a problem because the leakage light Lout is large when the viewing angle θ is large, for example, when oblique observation is performed at θ = 60 °, and both the wavelength dependency and the viewing angle dependency are large. For this reason, when a transmissive liquid crystal display device is configured by sandwiching the liquid crystal cell 3 (LC) between two polarizing plates 33, as shown in FIGS. 17A and 17B, the viewing angle θ = The transmittance change in the visible light band when observed obliquely at 60 ° is about 1.8%, and the transmittance at a wavelength of 550 nm when observed obliquely at a viewing angle θ = 60 ° is 1.0%. Therefore, it is evaluated that the viewing angle range for good visual recognition is narrow.

  A polarizing plate that suppresses leakage light Lout in a specific wavelength of this visible light band (wavelength is 370 to 780 nm, that is, wavelength is 550 nm) is disclosed in Conventional Example 2 (Non-Patent Document 1). In Conventional Example 2, uniaxial retardation films called A-plate 21 and C-plate 22 are used and overlapped on the observation-side polarizer 1 having a protective film (TAC) 2 as shown in FIG. The polarizing plate 35 is combined with the polarizing plate 34 on the incident light side having the protective film (TAC) 2. The slow axis 21A of the A plate 21 is orthogonal to the transmission axis of the polarizer 1 on the incident light side (parallel to the absorption axis 1A of the polarizer 1 on the incident light side). The shaft 22A is laminated so as to face the thickness direction of the film, and the in-plane retardation of the A plate 21 and the retardation of the C plate 22 in the thickness direction are 137 nm and 80 nm, respectively.

  However, in Conventional Example 2, as shown in FIG. 15 (b), the leakage light Lout at a wavelength of 550 nm can be suppressed, but the effect of improving the wavelength dependency is insufficient, and the drawback that the wavelength dependency is large remains. As a result, when the liquid crystal cell 3 (LC) is sandwiched between two polarizing plates 34 and 35 to constitute a liquid crystal display device, in the case of oblique incident light, the direction of polarized light incident on the liquid crystal cell 3 (LC) differs depending on the wavelength. As a result, as shown in FIG. 18 (b), the transmittance change in the visible light band when observed obliquely at a viewing angle θ = 60 ° is 1% or more, and a wide viewing angle cannot be achieved. There is. FIG. 18A shows a schematic configuration of a liquid crystal display device using a polarizing plate 35 in which a uniaxial retardation film called an A plate 21 and a C plate 22 is superimposed on a viewing-side polarizer 1.

Therefore, in order to compensate for changes in the optical characteristics of the liquid crystal when observed obliquely and to realize a liquid crystal display device with a wide viewing angle range, the visible light is observed when oblique incident light is observed at a large viewing angle. It is desired for the polarizing plate that the change in transmittance in the band can be reduced and the transmittance at a wavelength of 550 nm can be reduced.
In addition, the definition formula of the birefringence characteristic of refractive-index anisotropic bodies, such as above-mentioned retardation film and a liquid crystal, is shown in FIG. FIG. 21 shows a three-dimensional schematic diagram of the viewing angle θ and the azimuth angle φ (observation azimuth) during the oblique observation described above.

In addition to the above, wide viewing angle polarizing plates composed by laminating the polarizer 1 and one or two retardation films have been proposed (Patent Documents 1 to 3). The characteristics were examined.
J. Chen et al: SID'98 Digest (1998), p315 Japanese Patent Laid-Open No. 9-325216 JP-A-10-48420 Japanese Patent Laid-Open No. 10-14423

  However, according to the theoretical calculation by the present inventors, in Conventional Example 3 (the one described in Non-Patent Document 1 above), the slow axis direction of the biaxial retardation film 23 is defined as the absorption axis of the polarizing plate. The optical characteristics as shown in FIGS. 16 and 19 can be obtained even when orthogonal or parallel, but in the polarizing plates 34 and 36, the transparent protection that protects the polarizer 1 on the side facing the liquid crystal cell 3 (LC) Since there is no film, there is a problem that the surface of the polarizer 1 facing the liquid crystal cell 3 (LC) is not sufficiently protected. That is, the transparent protection for protecting the polarizer 1 on the polarizing plate 34 on the surface opposite to the incident light side of the polarizer 1 and the polarizing plate 36 on the surface on the opposite side of the viewing side of the polarizer 1, respectively. The films are not superposed.

  Here, Patent Document 1 has a transparent protective film layer on both sides of the polarizing film, and at least one transparent protective film layer exhibits birefringence with an in-plane retardation of 50 to 200 nm, and the transparent protective film. A polarizing plate is disclosed in which the slow axis of the layer is parallel or orthogonal to the transmission axis of the polarizing film (the axis perpendicular to the absorption axis of the polarizing film). The transparent protective film on one side has birefringence in which an in-plane retardation is 50 to 200 nm, and the main refractive index in the xy plane is nx and ny (nx> ny), and the refractive index in the thickness direction. When the rate is nz, the film having the Nz value defined by (nx−nz) / (nx−ny) in the range of −1 to 3 is used to enlarge the good visibility region of the liquid crystal display device. (Relationship between each axis and its refractive index: see FIG. 20).

Patent Document 2 discloses a polarizing plate in which the transparent protective film described above is superimposed on one side of a polarizing layer.
In Patent Document 3, on one side of the polarizing layer, the refractive index in the slow axis direction is nx, the refractive index in the fast axis direction is ny, the refractive index in the thickness direction is nz, and the film thickness is d. nz) · d has a thickness direction retardation of 300 nm or less, and (nx−ny) · d has an in-plane retardation of 20 nm or less, and the in-plane retardation is 50 nm. A birefringent layer B having a value of Nz defined by (nx-nz) / (nx-ny) of 0.8 to 3.5 at ˜200 nm, and the slow axis of the latter birefringent layer B And a wide viewing angle polarizing plate in which the transmission axis of the polarizing layer is parallel or orthogonal.

The present invention solves the above-mentioned problems of the prior art, has a transparent protective film for protecting the polarizer on the side facing the liquid crystal cell (LC), and effectively changes the optical characteristics of the liquid crystal when observed obliquely. It is an object of the present invention to provide a polarizing plate that can be compensated, and a liquid crystal display device that uses the polarizing plate and has a wide viewing angle range with good visibility.
Specifically, as described in the examples, when a liquid crystal display device is formed using a polarizing plate and the transmittance change when viewed obliquely at a viewing angle θ = 60 ° is 0.6% or less, the wavelength dependence When the transmittance at a wavelength of 550 nm when viewed obliquely at a viewing angle θ = 60 ° is 1.0% or less, the viewing angle dependency is sufficiently improved. It was evaluated as a polarizing plate.

As a result of intensive studies, the present inventors have obtained the knowledge that the change in the optical characteristics of the liquid crystal when obliquely observed can be effectively compensated by the following types of polarizing plates, and have made the present invention. .
The present invention is as follows.
1. A polarizing plate in which a transparent protective film for protecting the polarizer is superimposed on one or both sides of a polarizer, and the transparent protective film on one side produces an in-plane retardation with the x and y directions as principal axes. It has birefringence characteristics, and the uniaxiality condition satisfying the condition of ny = nz when the main refractive index in the xy plane is nx and ny (nx> ny) and the refractive index in the thickness direction is nz. An A-type polarizing plate, which is a retardation film, wherein a slow axis of the uniaxial retardation film is substantially parallel to an absorption axis of the polarizer.

  2. A polarizing plate in which a transparent protective film for protecting the polarizer is superimposed on one or both sides of a polarizer, the transparent protective film on one side having a birefringence characteristic that produces an in-plane retardation, and x A uniaxial retardation film satisfying the condition of ny = nz, where nx and ny (nx> ny) are the main refractive indices in the -y plane, and nz is the refractive index in the thickness direction. A B-type polarizing plate, wherein a slow axis of the retardation film is substantially orthogonal to an absorption axis of the polarizer.

  3. A polarizing plate in which a transparent protective film for protecting the polarizer is superimposed on one or both sides of a polarizer, and the transparent protective film on one side produces an in-plane retardation with the x and y directions as principal axes. It has birefringence characteristics, and the uniaxiality condition satisfying the condition of ny = nz when the main refractive index in the xy plane is nx and ny (nx> ny) and the refractive index in the thickness direction is nz. The retardation film is a retardation film, and the slow axis of the uniaxial retardation film is substantially parallel to the absorption axis of the polarizer, and the surface opposite to the polarizer overlapping surface of the uniaxial retardation film is A C-type or I-type polarizing plate, wherein a biaxial retardation film is superposed so that a slow axis thereof is substantially parallel to an absorption axis of the polarizer.

  4). A polarizing plate in which a transparent protective film for protecting the polarizer is superimposed on one or both sides of a polarizer, and the transparent protective film on one side produces an in-plane retardation with the x and y directions as principal axes. It has birefringence characteristics, and the uniaxiality condition satisfying the condition of ny = nz when the main refractive index in the xy plane is nx and ny (nx> ny) and the refractive index in the thickness direction is nz. The retardation film is a retardation film, and the slow axis of the uniaxial retardation film is substantially parallel to the absorption axis of the polarizer, and the surface opposite to the polarizer overlapping surface of the uniaxial retardation film is A D-type or J-type polarizing plate, wherein a biaxial retardation film is superposed so that its slow axis is substantially perpendicular to the absorption axis of the polarizer.

  5. A polarizing plate in which a transparent protective film for protecting the polarizer is superimposed on one or both sides of a polarizer, and the transparent protective film on one side produces an in-plane retardation with the x and y directions as principal axes. It has birefringence characteristics, and the uniaxiality condition satisfying the condition of ny = nz when the main refractive index in the xy plane is nx and ny (nx> ny) and the refractive index in the thickness direction is nz. The retardation film is a retardation film, and the slow axis of the uniaxial retardation film is substantially parallel to the absorption axis of the polarizer, and the surface opposite to the polarizer overlapping surface of the uniaxial retardation film is Two types of biaxial retardation films are superposed so that their slow axes are substantially parallel to each other and substantially parallel to the absorption axis of the polarizer. Polarizer.

  6). A polarizing plate in which a transparent protective film for protecting the polarizer is superimposed on one or both sides of a polarizer, and the transparent protective film on one side produces an in-plane retardation with the x and y directions as principal axes. It has birefringence characteristics, and the uniaxiality condition satisfying the condition of ny = nz when the main refractive index in the xy plane is nx and ny (nx> ny) and the refractive index in the thickness direction is nz. The retardation film is a retardation film, and the slow axis of the uniaxial retardation film is substantially parallel to the absorption axis of the polarizer, and the surface opposite to the polarizer overlapping surface of the uniaxial retardation film is Two types of biaxial retardation films are superposed so that their slow axes are substantially parallel to each other and are substantially orthogonal to the absorption axis of the polarizer. Polarizer.

  7). A polarizing plate in which a transparent protective film for protecting the polarizer is superimposed on one or both sides of a polarizer, and the transparent protective film on one side produces an in-plane retardation with the x and y directions as principal axes. It has birefringence characteristics, and the uniaxiality condition satisfying the condition of ny = nz when the main refractive index in the xy plane is nx and ny (nx> ny) and the refractive index in the thickness direction is nz. The retardation film is a retardation film, and the slow axis of the uniaxial retardation film is substantially parallel to the absorption axis of the polarizer, and the surface opposite to the polarizer overlapping surface of the uniaxial retardation film is Two biaxial retardation films have their slow axes almost orthogonal to each other and the slow axes of the biaxial retardation films arranged on the side closer to the polarizer are used as the absorption axes of the polarizer. G type polarizing plate characterized by being superimposed so as to be substantially parallel to each other

  8). A polarizing plate in which a transparent protective film for protecting the polarizer is superimposed on one or both sides of a polarizer, and the transparent protective film on one side produces an in-plane retardation with the x and y directions as principal axes. It has birefringence characteristics, and the uniaxiality condition satisfying the condition of ny = nz when the main refractive index in the xy plane is nx and ny (nx> ny) and the refractive index in the thickness direction is nz. The retardation film is a retardation film, and the slow axis of the uniaxial retardation film is substantially parallel to the absorption axis of the polarizer, and the surface opposite to the polarizer overlapping surface of the uniaxial retardation film is Two biaxial retardation films have their slow axes almost orthogonal to each other and the slow axes of the biaxial retardation films arranged on the side closer to the polarizer are used as the absorption axes of the polarizer. An H-type polarizing plate characterized by being superimposed so as to be substantially orthogonal to each other

  9. A polarizing plate in which a transparent protective film for protecting the polarizer is superimposed on one or both sides of a polarizer, the transparent protective film on one side having a birefringence characteristic that produces an in-plane retardation, and x A uniaxial retardation film satisfying the condition of ny = nz, where nx and ny (nx> ny) are the main refractive indices in the -y plane, and nz is the refractive index in the thickness direction. The retardation axis of the retardation film is substantially parallel to the absorption axis of the polarizer, and the uniaxial retardation film has a uniaxial retardation film on the surface opposite to the polarizer overlapping surface. A K-type polarizing plate, wherein an A plate is superposed so that its slow axis is substantially orthogonal to the absorption axis of the polarizer.

  10. A polarizing plate in which a transparent protective film for protecting the polarizer is superimposed on one or both sides of a polarizer, the transparent protective film on one side having a birefringence characteristic that produces an in-plane retardation, and x A uniaxial retardation film satisfying the condition of ny = nz, where nx and ny (nx> ny) are the main refractive indices in the -y plane, and nz is the refractive index in the thickness direction. The retardation axis of the retardation film is substantially parallel to the absorption axis of the polarizer, and the retardation axis of the surface of the uniaxial retardation film opposite to the polarizer overlap surface is the thickness direction. An L-type polarizing plate, wherein the formed C plates are superposed.

  11. A polarizing plate in which a transparent protective film for protecting the polarizer is superimposed on one or both sides of a polarizer, the transparent protective film on one side having a birefringence characteristic that produces an in-plane retardation, and x A uniaxial retardation film satisfying the condition of ny = nz, where nx and ny (nx> ny) are the main refractive indices in the -y plane, and nz is the refractive index in the thickness direction. The retardation axis of the retardation film is substantially parallel to the absorption axis of the polarizer, and the retardation axis of the uniaxial retardation film on the surface opposite to the polarizer overlapping surface is the polarization axis. A plate which is a uniaxial retardation film arranged so as to be substantially orthogonal to the absorption axis of the polarizer and a C plate whose slow axis is in the thickness direction are superposed in this order from the side closer to the polarizer. An M-type polarizing plate characterized by the above.

  12 A polarizing plate in which a transparent protective film for protecting the polarizer is superimposed on one or both sides of a polarizer, the transparent protective film on one side having a birefringence characteristic that produces an in-plane retardation, and x A uniaxial retardation film satisfying the condition of ny = nz, where nx and ny (nx> ny) are the main refractive indices in the -y plane, and nz is the refractive index in the thickness direction. The retardation axis of the retardation film is substantially parallel to the absorption axis of the polarizer, and the retardation axis of the surface of the uniaxial retardation film opposite to the polarizer overlap surface is the thickness direction. The C plate and the A plate, which is a uniaxial retardation film having a slow axis substantially parallel to the absorption axis of the polarizer, are superposed in this order from the side near the polarizer. An N-type polarizing plate characterized by

13. Above 1. -12. The polarizing plate according to any one of the above, wherein the in-plane retardation of the transparent protective film on one side superimposed on the polarizer is 0 to 200 nm.
14 Above 1. -13. A liquid crystal display device, wherein one or two polarizing plates selected from the polarizing plates according to any one of the above are disposed on one side or both sides of a liquid crystal cell.

  Here, the substantially parallel relationship means that the angle between the axes is preferably within 2.5 degrees, more preferably within 1.0 degree, and the substantially orthogonal relationship is preferably a deviation from 90 degrees. It means within a degree, more preferably within 1.0 degree.

  According to the present invention, since the transparent protective film for protecting the polarizer 1 is provided on the side facing the liquid crystal cell 3 (LC), the surface of the polarizer 1 on the side facing the liquid crystal cell 3 (LC) is sufficiently protected. And a polarizing plate selected from the above polarizing plates can effectively compensate for changes in the optical characteristics of the liquid crystal when observed obliquely. It can be realized.

First, a structure of a polarizing plate suitable for a liquid crystal display device will be described with reference to FIG. 1 (a) and 1 (b) are diagrams schematically showing the structure of a polarizing plate according to the present invention. In the figure, the direction of the absorption axis 1A of the polarizer 1 (also referred to as a polarizing film) and the direction of the slow axis 10A, 11A, 12A, 13A, 14A, 15A of each retardation film are clearly shown. Showed away.
Here, the transparent protective films 10 and 20 stacked on both sides of the polarizer 1 have a function of protecting the polarizer 1, and the transparent protective film 10 on one surface side has an in-plane retardation with the x and y directions as main axes. Uniaxiality that satisfies the condition of ny = nz when the main refractive index in the xy plane is nx and ny (nx> ny) and the refractive index in the thickness direction is nz. A type of polarizing plate according to the present invention is a retardation film having a slow axis 10A of the uniaxial retardation film substantially parallel to the absorption axis 1A of the polarizer 1. That is, in the A-type polarizing plate according to the present invention, the transparent protective film 10 overlaid on one surface side (downward in FIG. 1 (a)) of the polarizer 1 has the optical characteristics described above, and a liquid crystal display device. When applied to (see FIGS. 2 to 7), the liquid crystal cell 3 (LC) and the polarizer 1 are disposed. Therefore, when the A-type polarizing plate is applied to the liquid crystal display device, the transparent protective film 10 is disposed between the liquid crystal cell 3 (LC) and the polarizer 1, so that the side facing the liquid crystal cell 3 (LC) It is possible to sufficiently protect one surface of the polarizer.

  Further, in all of the polarizing plates according to the present invention including the B to N type polarizing plates described below, one side of the polarizer 1 (the lower side of the polarizer 1 in FIGS. 1A and 1B). The transparent protective film 10 overlying the uniaxiality satisfying the condition of ny = nz when the main refractive index in the xy plane is nx and ny (nx> ny) and the refractive index in the thickness direction is nz. Retardation film. However, in the B type polarizing plate, the transparent protective film 10 having the optical characteristics described above is superimposed on one side of the polarizer 1 so that the slow axis 10A is substantially orthogonal to the absorption axis 1A of the polarizer 1. The C to N type polarizing plate has a three-layer structure including the polarizer 1 and the transparent protective films 10 and 20 on both sides of the four or five layers. It is the same as the board.

  As described above, in all the polarizing plates according to the present invention, the transparent protective film 10 overlaid on one surface side of the polarizer 1 has a main refractive index in the xy plane of nx and ny (nx> ny), and a thickness direction. The reason why the film is a uniaxial retardation film satisfying the condition of ny = nz when the refractive index is nz is that of Nz defined by (nx−nz) / (nx−ny) among the optical characteristics. Since the value is substantially 1 (constant), two polarizing plates selected from A to N type polarizing plates are used, and a pair of polarizers 1 are arranged in a crossed Nicols arrangement (FIG. 2). When a reflective liquid crystal display device (see FIG. 8) is formed using a single polarizing plate, the polarization state of light emitted from the polarizer is changed over a wide angle range. Without the effect of protecting the polarizer without This is because a polarizing plate having a large effect of improving the wavelength dependency can be obtained, and a change in the optical characteristics of the liquid crystal when obliquely observed can be effectively compensated.

  Such a uniaxial retardation film in which the transparent protective film 10 satisfies the condition of nx> ny = nz is different from a transparent protective film having optical isotropy, for example, triacetylcellulose (TAC), Zeonoa Arton, etc. The film having optical isotropy made in (1) can be produced by uniaxial stretching (Y. Ito etal: SID05 Digest (2005) p. 986). In addition, since optical devices such as liquid crystal display devices require an accuracy of ± 0.0001 in terms of refractive index relative to the retardation film (Liquid Crystal Display Technology—Active Matrix LCD—, Shoichi Matsumoto, Sangyo Tosho Co., Ltd. 1996.11.8, p232), the refractive index of the uniaxial retardation film satisfying the condition of ny = nz has an in-plane refractive index difference (ny−nz) of ± 0.0001 or less in terms of accuracy control. Is preferred. The material of the transparent protective film 20 is not limited as long as it has a function of protecting the other surface side of the polarizer 1. For example, polyether sulfone (PES), glass sheet, Acetyl cellulose (TAC), Zeonoa Arton, etc. can be used. Note that 20 of the transparent protective films 10 and 20 can be omitted.

  Here, the optical characteristics of the transmissive liquid crystal display device formed using the A and B type polarizing plates shown in FIG. 2 were examined, and the results are shown in FIG. From the examination results of the optical characteristics of the liquid crystal display device shown in FIG. 9, when the A and B type polarizing plates are used, the change in transmittance in the visible light region when observed obliquely at a viewing angle θ = 60 ° is 0. Since it is .6% or less, it can be evaluated that the polarizing plate has a large effect of improving wavelength dependency. However, since the transmittance at a wavelength of 550 nm when obliquely observed at a viewing angle θ = 60 ° greatly exceeds 1.0%, it is evaluated that the effect of improving the viewing angle dependency is insufficient. The in-plane retardation (nx−ny) · d of the transparent protective film 10 overlaid on one surface side of the polarizer 1 (the lower side of the polarizer 1 in FIGS. 1A and 1B) is 0. It is preferable to limit to the range of ˜200 nm.

This is because the in-plane retardation (nx−ny) · d of the transparent protective film 10 superimposed on one surface side of the polarizer 1 is not smaller than 0, whereas the in-plane retardation (nx−ny) · d is 200 nm
This is because the wavelength dispersion due to the difference in birefringence becomes excessive and a color change such as coloring occurs, which makes it difficult to expand the viewing angle with good visibility. However, d represents the thickness of a retardation film.
Next, a description will be given of the configuration of a polarizing plate that can reduce the transmittance at a wavelength of 550 nm when viewed obliquely at a viewing angle θ = 60 ° to 1.0% or less.

  1 (a) 4 layer and 5 layer structure (C to H type polarizing plate) or 4 layer and 5 layer structure (I to N type polarization) shown in FIG. 1 (b) The viewing angle dependency can be effectively improved by forming a liquid crystal display device using a plate. The biaxial retardation films 11 and 12 used for the C to H type polarizing plates have different optical characteristics. In addition to the A-type polarizing plate having the three-layer structure described above, the C to H type polarizing plate has one or two sheets on the surface opposite to the polarizer overlapping surface of the uniaxial retardation film 10. It is a polarizing plate formed by stacking biaxial retardation films.

 That is, in the C type polarizing plate, a single biaxial retardation film 11 has a slow axis 11A on the surface opposite to the polarizer overlapping surface of the uniaxial retardation film 10 and the polarizer 1 has the slow axis 11A. Are superimposed so as to be substantially parallel to the absorption axis 1A. The biaxial retardation film 11 has an xy in-plane retardation of 200 to 350 nm, main refractive indices in the xy plane of nx and ny (nx> ny), and a refractive index in the thickness direction. When nz is set, the value of Nz defined by (nx−nz) / (nx−ny) is preferably in the range of 0.5 to 1. This is because when the xy in-plane retardation of the biaxial retardation film 11 is out of the range of 200 to 350 nm, the Nz value of the biaxial retardation film 11 is 0.5 to 0.5. This is because if the angle is outside the range 1, the change in the slow axis and the change in the phase difference due to the viewing angle become large and the range of the viewing angle that can be compensated is narrowed, making it difficult to widen the viewing angle.

  In the D type polarizing plate, a single biaxial retardation film 12 absorbs the slow axis 12A of the polarizer 1 on the surface of the uniaxial retardation film 10 opposite to the polarizer overlapping surface. It is overlapped so as to be substantially orthogonal to the axis 1A. The biaxial retardation film 12 has an xy in-plane retardation of 200 to 350 nm, main refractive indices in the xy plane of nx and ny (nx> ny), and a refractive index in the thickness direction. When nz, the value of Nz defined by (nx−nz) / (nx−ny) is preferably in the range of 0.05 to 0.5. This is because when the xy in-plane retardation of the biaxial retardation film 12 is out of the range of 200 to 350 nm, the Nz value of the biaxial retardation film 12 is 0.05 to This is because if the angle is out of the range of 0.5, the change of the slow axis and the change of the phase difference due to the viewing angle become large and the range of the viewing angle that can be compensated is narrowed, and it becomes difficult to widen the viewing angle.

In addition, the E to H type polarizing plate having a five-layer structure includes the biaxial retardation films 11 and 12 having the optical characteristics described above, one each, or two of them, a uniaxial retardation film 10. Is superimposed on the surface opposite to the polarizer overlapping surface.
That is, the E and F type polarizing plates have two biaxial retardation films 11 and 12 on the surface opposite to the polarizer overlapping surface of the uniaxial retardation film 10 and the slow axes 11A, 12A is overlapped so as to be substantially parallel to each other and substantially parallel to the absorption axis 1A of the polarizer 1, and 12A is overlapped so as to be substantially orthogonal. The G and H type polarizing plates have two biaxial retardation films 11 or 12 on the opposite side of the uniaxial retardation film 10 on the side where the polarizer is overlapped, and the slow axes 11A and 12A. The slow axis 11A or 12A of the biaxial retardation film arranged almost orthogonal to each other and close to the polarizer is superposed so as to be substantially parallel to the absorption axis 1A of the polarizer 1 And superimposed so as to be orthogonal. The C and D type polarizing plates are described as four layers, and the E to H type polarizing plates are described as five layers. However, the transparent protective film 20 can be omitted in any type.

  Next, the structure of a liquid crystal display device formed using C to H type polarizing plates and its optical characteristics will be described. 3 to 5 show a schematic configuration of a transmission type liquid crystal display device using C to H type polarizing plates, and FIG. 8 shows a reflection type liquid crystal display using C type and D type polarizing plates. A schematic configuration of the apparatus is shown. In FIG. 8, 24 indicates a quarter-wave retardation film bonded to the liquid crystal cell (LC) 3 with an adhesive, and 5 indicates a reflector. The transmissive liquid crystal display device is formed by arranging a pair of polarizers 1 in crossed Nicols with a liquid crystal cell (LC) 3 interposed therebetween. As an example, a liquid crystal display device using F type and A type polarizing plates. Were examined under the same conditions as in Conventional Example 1, and the results are shown in FIG. As is apparent from FIG. 10, when a transmissive liquid crystal display device is formed using F type and A type polarizing plates (liquid crystal display device corresponding to FIG. 3A), the viewing angle θ is 60 °. Since the transmittance change when obliquely observed is 0.6% or less, it can be evaluated as a polarizing plate having a large effect of improving wavelength dependency, and the wavelength when obliquely observed at a viewing angle θ = 60 ° is 550 nm. It can be seen that the transmittance can be 1.0% or less, and the effect of improving the viewing angle dependency is sufficient. In addition, in FIG. 11, the result of having investigated the optical characteristic of what used the F type and A type polarizing plate and arrange | positioned a pair of polarizer 1 in crossed Nicols was shown.

  Incidentally, when the polarizing plate 33 of Conventional Example 1 shown in FIG. 17 is used to form a transmissive liquid crystal display device, the transmittance change when viewed obliquely at a viewing angle θ = 60 ° is 1.8%. Is slightly over. Moreover, since the transmittance at a wavelength of 550 nm when observed obliquely at a viewing angle θ = 60 ° exceeds 1.0%, the liquid crystal display device using the polarizing plate 33 of Conventional Example 1 has a good visual field. The angular range is narrow.

  3 includes a liquid crystal display device shown in FIG. 3A, and a polarizing plate structure capable of forming a transmission type liquid crystal display device having a large effect of improving wavelength dependency, as shown in an embodiment described later. showed that. 4 and 5 show a configuration of a polarizing plate that can form a transmission type liquid crystal display device having a moderate wavelength dependency improvement effect. On the other hand, FIGS. 6 and 7 show a configuration of a polarizing plate that can form a transmissive liquid crystal display device with a small effect of improving wavelength dependency.

Next, I to N type polarizing plates used in forming the transmission type liquid crystal display device shown in FIGS. 6 and 7 will be described (see FIG. 1B).
The I type polarizing plate is biaxial on the surface opposite to the polarizer overlapping surface of the uniaxial retardation film 10 instead of the biaxial retardation film 11 constituting the C type polarizing plate. The retardation film 13 is superposed so that its slow axis 13A is substantially parallel to the absorption axis 1A of the polarizer 1. The biaxial retardation film 13 has an xy in-plane retardation of 200 to 350 nm, main refractive indices in the xy plane of nx and ny (nx> ny), and a refractive index in the thickness direction of nz. In this case, the film is formed of a film having an Nz value defined by (nx−nz) / (nx−ny) in the range of 0.25 to 0.75.

The J-type polarizing plate is replaced with the biaxial retardation film 12 constituting the D-type polarizing plate described above on the surface opposite to the polarizer overlapping surface of the uniaxial retardation film 10. The axial retardation film 13 is formed by superimposing the slow axis 13A so as to be substantially orthogonal to the absorption axis 1A of the polarizer 1.
The K-type polarizing plate has a uniaxial retardation film 10 on the side opposite to the polarizer overlapping surface of the uniaxial retardation film 10 and an A plate 14 which is a uniaxial retardation film. It is overlapped so as to be substantially orthogonal to 1A. The A plate 14 is formed of a uniaxial film in which ny = nz (see FIG. 20), and the xy in-plane retardation is preferably 50 to 150 nm from the viewpoint of visual compensation.

  The L-type polarizing plate is formed by superposing a C plate 15 having a slow axis 15A in the thickness direction on the surface of the uniaxial retardation film 10 opposite to the polarizer overlapping surface. The C plate 15 is formed of a uniaxial film with nx = ny (see FIG. 20). The M-type polarizing plate is a uniaxial film in which a slow axis 14A is arranged on the surface opposite to the polarizer overlapping surface of the uniaxial retardation film 10 so as to be substantially orthogonal to the absorption axis 1A of the polarizer 1. A plate 14 which is a phase difference film and a C plate 15 having a slow axis 15A in the thickness direction are overlapped in this order from the side closer to the polarizer 1.

The N-type polarizing plate has a C-plate 15 having a slow axis 15A in the thickness direction on the surface opposite to the polarizer overlapping surface of the uniaxial retardation film 10 and a slow axis 14A of the polarizer 1. The A plate 14 which is a uniaxial retardation film disposed so as to be substantially parallel to the absorption axis 1A is superposed in this order from the side close to the polarizer 1.
According to the above described I to N type polarizing plates, although the effect of improving the wavelength dependency is small, the change in the optical characteristics of the liquid crystal when observed obliquely can be effectively compensated for, so the viewing angle dependency is improved. A liquid crystal display device having a sufficient effect and a wide viewing angle range for good visual recognition can be realized.

  Here, the polarizing plate according to the present invention can be formed by a conventionally known appropriate laminating operation. At this time, the parallel relationship and the orthogonal relationship are not limited to the parallel or orthogonal state in a strict sense, and are expressed as “almost” parallel relationship and “almost” orthogonal relationship in the sense that work placement errors are allowed. ing. Further, the liquid crystal display device according to the present invention can be constituted by a usual method. In general, a liquid crystal display device is formed by appropriately assembling components such as a polarizing plate, a liquid crystal cell 3 (LC), and illumination means if necessary, and further incorporating a drive circuit. Here, in the transmission type liquid crystal display device shown in FIGS. 2 to 7, incident light from a backlight (not shown) as illumination means is incident light from either the upper side or the lower side in each figure. It is comprised so that it may inject with respect to the polarizing plate 1 of the side. By using the A to N type polarizing plate according to the present invention, a reflection type liquid crystal display device having a backlight or a natural light is used to reflect light passing through the polarizing plate and the liquid crystal cell 3 (LC). An appropriate liquid crystal display device such as a reflective liquid crystal display device using a plate can be configured.

  The forming parts of the liquid crystal display device may be laminated and integrated, or may be in a separated state. In configuring the liquid crystal display device, for example, appropriate optical elements such as a diffusion plate, an antiglare layer, an antireflection film, and a color filter can be appropriately disposed. The A to N type polarizing plates according to the present invention are various displays such as TFT type and MIM type using liquid crystal cells showing birefringence such as VA (vertical alignment) type and IPS (in-plane-switching) type. It can be preferably used in an apparatus.

  Using films having the characteristics shown in Table 1, A to N type polarizing plates were prepared, and the liquid crystal display devices shown in FIGS. 2 to 8 were formed to examine the transmittance. The cell thickness of the liquid crystal cell 3 (LC) was set to 5.2 μm. The transmittance of the transmissive liquid crystal display device is measured under the same conditions as in the conventional example 1, that is, under the condition that the liquid crystal cell 3 (LC) is in a dark state, and the incident angle of the incident light Lin from the light source is the viewing angle θ. The incident light Lin is applied to the incident light side polarizing plate by changing it stepwise to 0, 20, 40, 60 ° according to the incident light, and the obtained polarized light passes through the observation side polarizing plate and leaks out. The incoming light leakage Lout was measured with a light receiver, and the obtained spectrum was used. In the case of a reflection type liquid crystal display device, a light source was arranged on one side, and light leakage reflected from the reflection plate and leaking to one side was measured in the same manner using a light receiver. In addition, the A to N type polarizing plates shown in FIGS. 1A and 1B were formed by a conventionally known appropriate lamination operation.

  The liquid crystal display device using an A to N type polarizing plate was set to Experimental Examples 1 to 17, and the wavelength dependency improvement effect and the viewing angle dependency improvement effect were evaluated by the evaluation methods shown in Tables 3 and 4. . Simultaneously, using the films having the characteristics shown in Table 2, polarizing plates of Conventional Examples 1 to 3 were prepared, and liquid crystal display devices using the polarizing plates were also evaluated by the same evaluation method.

実験例１〜１７の評価結果を表５〜８に、従来例１〜３の評価結果を表９に示す。但し、従来例１〜３の測定結果はそれぞれ図１７〜１９に示したとおりであり、実験例１、２の測定結果はそれぞれ図９、１０に示したとおりである。

The evaluation results of Experimental Examples 1 to 17 are shown in Tables 5 to 8, and the evaluation results of Conventional Examples 1 to 3 are shown in Table 9. However, the measurement results of Conventional Examples 1 to 3 are as shown in FIGS. 17 to 19, respectively, and the measurement results of Experimental Examples 1 and 2 are as shown in FIGS.

表５〜８の評価結果と表９とを対比することにより、実験例１〜１７は、従来例１、２（波長依存性の改善効果が認められない場合）に比べて、波長依存性の改善効果があることがわかる。また実験例１を除く、実験例２〜１７は、視野角依存性の改善効果が十分であることもわかる。

By comparing the evaluation results in Tables 5 to 8 with Table 9, Experimental Examples 1 to 17 are more wavelength-dependent than Conventional Examples 1 and 2 (when the effect of improving wavelength dependency is not observed). It can be seen that there is an improvement effect. It can also be seen that Experimental Examples 2 to 17 except Experimental Example 1 have a sufficient effect of improving the viewing angle dependency.

It is a schematic diagram which shows the structure of the polarizing plate which concerns on this invention. It is a schematic diagram which shows the structure of the other polarizing plate which concerns on this invention. It is a schematic diagram which shows the structure of an example liquid crystal display device using the polarizing plate which concerns on this invention. It is a schematic diagram which shows the structure of the other liquid crystal display device using the polarizing plate which concerns on this invention. It is a schematic diagram which shows the structure of the other liquid crystal display device using the polarizing plate which concerns on this invention. It is a schematic diagram which shows the structure of the other liquid crystal display device using the polarizing plate which concerns on this invention. It is a schematic diagram which shows the structure of the other liquid crystal display device using the polarizing plate which concerns on this invention. It is a schematic diagram which shows the structure of the other liquid crystal display device using the polarizing plate which concerns on this invention. It is a schematic diagram which shows the structure of the other liquid crystal display device using the polarizing plate which concerns on this invention. (A) is the schematic diagram of the optical system which investigates the characteristic of the liquid crystal display device based on this invention, (b) is the characteristic view. (A) is the schematic diagram of the optical system which investigates the characteristic of the liquid crystal display device based on this invention, (b) is the characteristic view. (A) is the schematic diagram of the optical system which investigates the characteristic of the polarizing plate used for the liquid crystal display device of FIG. 10, (b) is the characteristic view. (A) is a schematic cross-sectional view showing the basic structure of a polarizing plate, and (b) is a schematic view showing the structure of a transmissive liquid crystal display device (LCD). It is a schematic diagram for demonstrating the problem of the polarizing plate which concerns on a prior art example. (A) is the schematic diagram of the optical system which investigates the characteristic of the polarizing plate which concerns on the prior art example 1, (b) is the characteristic figure. (A) is the schematic diagram of the optical system which investigates the characteristic of the polarizing plate which concerns on the prior art example 2, (b) is the characteristic figure. (A) is the schematic diagram of the optical system which investigates the characteristic of the polarizing plate which concerns on the prior art example 3, (b) is the characteristic figure. (A) is the schematic diagram of the optical system which investigates the characteristic of the liquid crystal display device which concerns on the prior art example 1, (b) is the characteristic figure. (A) is the schematic diagram of the optical system which investigates the characteristic of the liquid crystal display device which concerns on the prior art example 2, (b) is the characteristic figure. (A) is the schematic diagram of the optical system which investigates the characteristic of the liquid crystal display device which concerns on the prior art example 3, (b) is the characteristic figure. It is a schematic diagram explaining the definition of the optical anisotropy in retardation film. It is a schematic diagram explaining the definition of viewing angle (theta) and azimuth angle (phi) in an observation surface.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polarizer 1A Absorption axis of polarizer 1, 2, 20 Transparent protective film 3 Liquid crystal cell (LC)
4 Backlight 5 Reflector
10 Uniaxial retardation film
11, 12, 13 Biaxial retardation film
10A, 11A, 12A Slow axis of each retardation film θ Viewing angle (angle formed with respect to normal direction of observation surface)
φ Observation direction
21 A plate (uniaxial retardation film)
22 C plate (uniaxial retardation film)
23 Biaxial retardation film
21A, 22A, 23A Slow axis of each retardation film
24 1/4 wavelength retardation film
31 Glass substrate
32 Liquid crystal materials
33, 34, 35 Conventional polarizing plate

Claims (14)

  A polarizing plate in which a transparent protective film for protecting the polarizer is superimposed on one or both sides of a polarizer, and the transparent protective film on one side produces an in-plane retardation with the x and y directions as principal axes. It has birefringence characteristics, and the uniaxiality condition satisfying the condition of ny = nz when the main refractive index in the xy plane is nx and ny (nx> ny) and the refractive index in the thickness direction is nz. A polarizing plate characterized in that it is a phase difference film, and the slow axis of the uniaxial phase difference film is substantially parallel to the absorption axis of the polarizer.   A polarizing plate in which a transparent protective film for protecting the polarizer is superimposed on one or both sides of a polarizer, the transparent protective film on one side having a birefringence characteristic that produces an in-plane retardation, and x A uniaxial retardation film satisfying the condition of ny = nz, where nx and ny (nx> ny) are the main refractive indices in the -y plane, and nz is the refractive index in the thickness direction. A polarizing plate, wherein a slow axis of the retardation film is substantially orthogonal to an absorption axis of the polarizer.   A polarizing plate in which a transparent protective film for protecting the polarizer is superimposed on one or both sides of a polarizer, and the transparent protective film on one side produces an in-plane retardation with the x and y directions as principal axes. It has birefringence characteristics, and the uniaxiality condition satisfying the condition of ny = nz when the main refractive index in the xy plane is nx and ny (nx> ny) and the refractive index in the thickness direction is nz. The retardation film is a phase difference film, and the slow axis of the uniaxial retardation film is substantially parallel to the absorption axis of the polarizer, and the opposite surface of the uniaxial retardation film to the polarizer overlapping surface is A polarizing plate, wherein a biaxial retardation film is superposed so that a slow axis thereof is substantially parallel to an absorption axis of the polarizer.   A polarizing plate in which a transparent protective film for protecting the polarizer is superimposed on one or both sides of a polarizer, and the transparent protective film on one side produces an in-plane retardation with the x and y directions as principal axes. It has birefringence characteristics, and the uniaxiality condition satisfying the condition of ny = nz when the main refractive index in the xy plane is nx and ny (nx> ny) and the refractive index in the thickness direction is nz. The retardation film is a phase difference film, and the slow axis of the uniaxial retardation film is substantially parallel to the absorption axis of the polarizer, and the opposite surface of the uniaxial retardation film to the polarizer overlapping surface is A polarizing plate, wherein a biaxial retardation film is superposed so that its slow axis is substantially orthogonal to the absorption axis of the polarizer.   A polarizing plate in which a transparent protective film for protecting the polarizer is superimposed on one or both sides of a polarizer, and the transparent protective film on one side produces an in-plane retardation with the x and y directions as principal axes. It has birefringence characteristics, and the uniaxiality condition satisfying the condition of ny = nz when the main refractive index in the xy plane is nx and ny (nx> ny) and the refractive index in the thickness direction is nz. The retardation film is a phase difference film, and the slow axis of the uniaxial retardation film is substantially parallel to the absorption axis of the polarizer, and the opposite surface of the uniaxial retardation film to the polarizer overlapping surface is A polarizing plate, wherein two biaxial retardation films are superposed so that their slow axes are substantially parallel to each other and substantially parallel to the absorption axis of the polarizer.   A polarizing plate in which a transparent protective film for protecting the polarizer is superimposed on one or both sides of a polarizer, and the transparent protective film on one side produces an in-plane retardation with the x and y directions as principal axes. It has birefringence characteristics, and the uniaxiality condition satisfying the condition of ny = nz when the main refractive index in the xy plane is nx and ny (nx> ny) and the refractive index in the thickness direction is nz. The retardation film is a phase difference film, and the slow axis of the uniaxial retardation film is substantially parallel to the absorption axis of the polarizer, and the opposite surface of the uniaxial retardation film to the polarizer overlapping surface is A polarizing plate characterized in that two biaxial retardation films are superposed such that their slow axes are substantially parallel to each other and substantially orthogonal to the absorption axis of the polarizer.   A polarizing plate in which a transparent protective film for protecting the polarizer is superimposed on one or both sides of a polarizer, and the transparent protective film on one side produces an in-plane retardation with the x and y directions as principal axes. It has birefringence characteristics, and the uniaxiality condition satisfying the condition of ny = nz when the main refractive index in the xy plane is nx and ny (nx> ny) and the refractive index in the thickness direction is nz. The retardation film is a phase difference film, and the slow axis of the uniaxial retardation film is substantially parallel to the absorption axis of the polarizer, and the opposite surface of the uniaxial retardation film to the polarizer overlapping surface is Two biaxial retardation films having their slow axes almost orthogonal to each other and the slow axes of the biaxial retardation films arranged on the side closer to the polarizer as the absorption axis of the polarizer A polarizing plate, wherein the polarizing plates are stacked so as to be substantially parallel to each other.   A polarizing plate in which a transparent protective film for protecting the polarizer is superimposed on one or both sides of a polarizer, and the transparent protective film on one side produces an in-plane retardation with the x and y directions as principal axes. It has birefringence characteristics, and the uniaxiality condition satisfying the condition of ny = nz when the main refractive index in the xy plane is nx and ny (nx> ny) and the refractive index in the thickness direction is nz. The retardation film is a phase difference film, and the slow axis of the uniaxial retardation film is substantially parallel to the absorption axis of the polarizer, and the opposite surface of the uniaxial retardation film to the polarizer overlapping surface is Two biaxial retardation films having their slow axes almost orthogonal to each other and the slow axes of the biaxial retardation films arranged on the side closer to the polarizer as the absorption axis of the polarizer A polarizing plate, wherein the polarizing plates are stacked so as to be substantially orthogonal to each other.   A polarizing plate in which a transparent protective film for protecting the polarizer is superimposed on one or both sides of a polarizer, the transparent protective film on one side having a birefringence characteristic that produces an in-plane retardation, and x A uniaxial retardation film satisfying the condition of ny = nz, where nx and ny (nx> ny) are the main refractive indices in the -y plane, and nz is the refractive index in the thickness direction. The slow axis of the retardation film is substantially parallel to the absorption axis of the polarizer, and the surface opposite to the polarizer overlapping surface of the uniaxial retardation film is a uniaxial retardation film. A polarizing plate, wherein a certain A plate is superposed so that a slow axis thereof is substantially orthogonal to an absorption axis of the polarizer.   A polarizing plate in which a transparent protective film for protecting the polarizer is superimposed on one or both sides of a polarizer, the transparent protective film on one side having a birefringence characteristic that produces an in-plane retardation, and x A uniaxial retardation film satisfying the condition of ny = nz, where nx and ny (nx> ny) are the main refractive indices in the -y plane, and nz is the refractive index in the thickness direction. The retardation axis of the retardation film is substantially parallel to the absorption axis of the polarizer, and the retardation axis of the uniaxial retardation film on the side opposite to the polarizer stacking surface is the thickness direction. A polarizing plate comprising a plurality of C plates stacked together.   A polarizing plate in which a transparent protective film for protecting the polarizer is superimposed on one or both sides of a polarizer, the transparent protective film on one side having a birefringence characteristic that produces an in-plane retardation, and x A uniaxial retardation film satisfying the condition of ny = nz, where nx and ny (nx> ny) are the main refractive indices in the -y plane, and nz is the refractive index in the thickness direction. The retardation axis of the retardation film is substantially in parallel with the absorption axis of the polarizer, and the retardation axis of the uniaxial retardation film on the surface opposite to the polarizer overlapping surface is set to the polarization axis. A plate which is a uniaxial retardation film arranged so as to be substantially orthogonal to the absorption axis of the polarizer and a C plate whose slow axis is in the thickness direction are superposed in this order from the side closer to the polarizer. A polarizing plate characterized by comprising:   A polarizing plate in which a transparent protective film for protecting the polarizer is superimposed on one or both sides of a polarizer, the transparent protective film on one side having a birefringence characteristic that produces an in-plane retardation, and x A uniaxial retardation film satisfying the condition of ny = nz, where nx and ny (nx> ny) are the main refractive indices in the -y plane, and nz is the refractive index in the thickness direction. The retardation axis of the retardation film is substantially parallel to the absorption axis of the polarizer, and the retardation axis of the uniaxial retardation film on the side opposite to the polarizer stacking surface is the thickness direction. The C plate and the A plate, which is a uniaxial retardation film having a slow axis substantially parallel to the absorption axis of the polarizer, are superposed in this order from the side close to the polarizer. A polarizing plate characterized by comprising:   The polarizing plate according to any one of claims 1 to 12, wherein the in-plane retardation of the transparent protective film on one side superimposed on the polarizer is 0 to 200 nm. 14. A liquid crystal display device, wherein one or two polarizing plates selected from the polarizing plates according to claim 1 are disposed on one side or both sides of a liquid crystal cell.

Images