JP2007264595A - Polarizing plate and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display having highly improved gray scale inversion by improving not only display quality but also a viewing angle characteristic with a simple configuration, particularly, an ECB type, TN type or IPS type liquid crystal display. <P>SOLUTION: A polarizing plate for the liquid crystal display includes a first protective film, a polarizing film, a second protective film and a light diffusion layer in order. The light diffusion layer is a layer including a translucent resin and translucent particles having a refractive index different from a refractive index of the translucent resin. The internal haze of the light diffusion layer is 45% to 80%. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polarizing plate comprising a polarizing film sandwiched between protective films and a liquid crystal display device using the polarizing plate.

Liquid crystal display elements (also called liquid crystal display panels), electroluminescent elements (separated into organic and inorganic types depending on the fluorescent material used, hereinafter referred to as EL elements), field emission elements (Field)
A display device using an Emission Device (hereinafter referred to as FED element), an electrophoretic element, or the like is a space (such as a cathode ray tube (CRT)) for two-dimensionally scanning an electron beam on the back side of a display screen (CRT: Cathode Ray Tube). Image display can be performed without providing a vacuum housing. Therefore, these display devices are characterized by being thinner and lighter and having lower power consumption than a cathode ray tube. These display devices are sometimes referred to as flat panel displays because of their appearance characteristics.

  A display device using a liquid crystal display element, an EL element, a field emission element, or the like uses a cathode ray tube in various applications such as notebook computers, OA devices such as personal computer monitors, portable terminals, and televisions because of the above-described advantages over the cathode ray tube. It is becoming widespread instead of display devices. Technological innovations such as viewing angle characteristics of liquid crystal display elements and EL elements and image quality improvement such as expansion of the display color reproducibility area are behind the progress of replacement of CRTs with flat panel displays. Recently, with the widespread use of multimedia and the Internet, there has been an improvement in video display performance. In addition, there are also fields that cannot be realized with CRT, such as electronic paper, large public, and advertising information displays.

  The liquid crystal display device includes a liquid crystal cell, a drive circuit that sends a display signal voltage to the liquid crystal cell, a backlight (back light source), and a signal control system that sends an input image signal to the drive circuit. These are collectively called a liquid crystal module.

  A liquid crystal cell is usually composed of liquid crystal molecules, two substrates for enclosing and sandwiching the liquid crystal molecules, and an electrode layer for applying a voltage to the liquid crystal molecules, and a polarizing plate is disposed on the outside thereof. The polarizing plate is usually composed of a protective film and a polarizing film, and is obtained by dyeing a polarizing film made of a polyvinyl alcohol film with iodine, stretching, and laminating both surfaces with a protective film. In the transmissive liquid crystal display device, the polarizing plate is attached to both sides of the liquid crystal cell, and one or more optical compensation sheets may be disposed. In a reflective liquid crystal display device, usually, a reflector, a liquid crystal cell, one or more optical compensation sheets, and a polarizing plate are arranged in this order.

  The liquid crystal cell performs ON / OFF display depending on the alignment state of liquid crystal molecules, and can be applied to both transmission type and reflection type, TN (Twisted Nematic), IPS (In-Plane Switching), OCB (Optically Compensatory). Display modes such as Bend, VA (Vertically Aligned), and ECB (Electrically Controlled Birefringence) have been proposed.

Optical compensation films are used in various liquid crystal display devices in order to eliminate image coloring and to widen the viewing angle. As the optical compensation film, a stretched birefringent polymer film has been conventionally used. Further, it has been proposed to use an optical compensation film having an optical compensation layer formed of low-molecular or high-molecular liquid crystalline molecules on a transparent support, instead of the optical compensation film made of a stretched birefringent film. Since liquid crystalline molecules have various alignment forms, the use of liquid crystalline molecules can realize optical properties that cannot be obtained with conventional stretched birefringent polymer films. Furthermore, a structure that serves as both a protective film and an optical compensation film has been proposed by adding birefringence to the protective film of the polarizing plate.

  The optical properties of the optical compensation film are determined according to the optical properties of the liquid crystal cell, specifically, the display mode difference as described above. When liquid crystalline molecules are used, optical compensation films having various optical properties corresponding to various display modes of the liquid crystal cell can be produced. Optical compensation films using liquid crystal molecules have already been proposed for various display modes.

  For example, an optical compensation film for a TN type liquid crystal cell performs optical compensation of an alignment state tilted on the substrate surface while eliminating the twisted structure of the liquid crystal molecules by applying a voltage, and contrast by preventing light leakage in an oblique direction during black display. (See Patent Document 1). The optical compensation film for the parallel alignment liquid crystal cell also serves to improve the viewing angle characteristics of the optical compensation of the liquid crystal molecules aligned in parallel to the substrate surface and the orthogonal transmittance of the polarizing plate during black display when no voltage is applied. Reference 2).

  However, even if an optical compensation film in which a discotic liquid crystalline compound is uniformly hybrid-aligned is used, it is very difficult to completely optically compensate the liquid crystal cell without any problem. For example, in a TN liquid crystal cell, a gradation inversion phenomenon occurs in which the transmittance at each gradation is inverted when observed from an oblique direction. A method for limiting the tilt angle range of liquid crystal molecules in a liquid crystal cell is known in order to prevent gradation inversion (see Non-Patent Document 1).

On the other hand, in the TN liquid crystal display device, the viewing angle characteristics are improved by the above method. However, the polarizing plate contracts in a severe use environment, for example, a high temperature or high humidity environment, and light leaks around the polarizing plate. Was not solved. This light leakage is caused by contraction of the polarizing plate, and there is an example that can be improved by selecting a material for the pressure-sensitive adhesive of the polarizing plate (see Patent Document 3).
JP-A-6-214116 Japanese Patent No. 3342417 JP 2004-516359 A “Technical Report of IEICE”, EID2001-108, p. 47-52

The present invention has been made in view of the above-described problems, and is a liquid crystal display device with a simple structure, improved viewing angle characteristics, and markedly improved gradation inversion, particularly a parallel liquid crystal layer having no twisted structure. It is an object of the present invention to provide an alignment type ECB type or IPS type liquid crystal display device or a TN type liquid crystal display device having a twisted structure.
Furthermore, the present invention provides a liquid crystal display device with improved reliability in harsh environments.

The object of the present invention has been achieved by the following means.
[1] A polarizing plate for a liquid crystal display device having a first protective film, a polarizing film, a second protective film, and a light diffusing layer in this order, wherein the light diffusing layer includes a translucent resin and a translucent A polarizing plate for a liquid crystal display device, which is a layer containing translucent fine particles having a refractive index different from the refractive index of the resin, and the internal haze of the light diffusion layer is 45% or more and 80% or less.
[2] A polarizing plate for a liquid crystal display device, wherein the polarizing plate according to [1] further has an optical compensation layer.
[3] The [1] or [3] above, wherein the light diffusion layer has a scattered light intensity of 30 ° with respect to the light intensity at an output angle of 0 ° of the scattered light profile of the goniophotometer in the range of 0.05 to 0.3% 2
] The polarizing plate for liquid crystal display devices of description.
[4] A liquid crystal layer comprising a pair of opposed substrates having electrodes on one side and a nematic liquid crystal material sandwiched between the substrates and oriented substantially parallel to the surfaces of the pair of substrates when no voltage is applied And a polarizing plate disposed on at least one surface outside the liquid crystal cell, wherein the polarizing plate includes a first protective film, a polarizing film, a second protective film, and a light diffusion layer. In this order, the diffusion layer is a layer containing a translucent resin and translucent fine particles having a refractive index different from the refractive index of the translucent resin, and the internal haze of the light diffusion layer is A liquid crystal display device of 45% to 80%.
[5] The liquid crystal display device, wherein the polarizing plate according to [4] further includes an optical compensation layer.
[6] The liquid crystal display device according to [4] or [5], wherein the absorption axis of the polarizing film and the horizontal direction of the screen of the display device are parallel or vertical.
[7] The liquid crystal display device according to any one of [4] to [6], wherein the liquid crystal display device is an ECB type liquid crystal display device.
[8] The liquid crystal display device according to any one of [4] to [6], wherein the liquid crystal display device is a TN liquid crystal display device.
[9] The liquid crystal display device according to any one of [4] to [6], wherein the liquid crystal display device is an IPS liquid crystal display device.

  As a result of research, the present inventors have adjusted the materials and manufacturing methods of the polarizing plate protective film, the light diffusing layer, the surface film, and the liquid crystal cell, so that the liquid crystal cell is optically structured with the same configuration as the conventional liquid crystal display device. We succeeded in manufacturing a polarizing plate that also has a function to compensate. Furthermore, when this polarizing plate was attached to an ECB type, IPS type, or TN type liquid crystal cell and used in a liquid crystal display device, not only the display quality but also the viewing angle was remarkably improved. Moreover, the process of laminating | stacking, adjusting the angle of the conventional 1 or several retardation film and polarizing plate exactly becomes unnecessary, and manufacture of the polarizing plate by a roll to roll became possible. That is, according to the present invention, it is possible to provide a liquid crystal display device with a simple configuration and with not only display quality but also a significantly improved viewing angle. In addition, according to the present invention, not only has a polarization function, but also contributes to widening the viewing angle of a liquid crystal display device, reduces gradation inversion, and highly realizes prevention of reflection of external light, and is easily manufactured. A possible polarizing plate can be provided.

Terms used in this specification will be described.
[Explanation of terms]
[Retardation, Re, Rth]
In this specification, Re (λ) and Rth (λ) represent in-plane retardation and retardation in the thickness direction at the wavelength λ, respectively. Re (λ) is measured by making light having a wavelength of λ nm incident in the normal direction of the film in “KOBRA 21ADH” or “KOBRA 21WR” (manufactured by Oji Scientific Instruments).

  When the film to be measured is represented by a uniaxial or biaxial refractive index ellipsoid, Rth (λ) is calculated by the following method.

  Rth (λ) is obtained by using Re (λ) as a tilt axis (rotation axis) with an in-plane slow axis (determined by “KOBRA 21ADH” or “KOBRA 21WR”) (when there is no slow axis). Is an arbitrary direction in the film plane), and the film normal direction is 10 ° step from the normal direction to 50 ° on one side, and light of wavelength λ nm is incident from each inclined direction. Then, “KOBRA 21ADH” or “KOBRA 21WR” is calculated based on the measured retardation value, the assumed average refractive index value, and the input film thickness value.

  In the above, in the case of a film having a direction in which the retardation value is zero at a certain tilt angle with the in-plane slow axis as the rotation axis from the normal direction, the retardation at a tilt angle larger than the tilt angle. The value is calculated by “KOBRA 21ADH” or “KOBRA 21WR” after changing the sign to negative.

In addition, the retardation value is measured from the two inclined directions, with the slow axis as the tilt axis (rotation axis) (when there is no slow axis, the arbitrary direction in the film plane is the rotation axis), Based on the value, the assumed value of the average refractive index, and the input film thickness value, Rth can also be calculated from the following formulas (1) and (2).
Formula (1):

  The above Re (θ) represents a retardation value in a direction inclined by an angle θ from the normal direction. In formula (1), nx represents the refractive index in the slow axis direction in the plane, ny represents the refractive index in the direction perpendicular to nx in the plane, and nz represents the refractive index in the direction perpendicular to nx and ny. . d represents the film thickness of the film.

  Formula (2): Rth = [(nx + ny) / 2−nz] × d

  When the film to be measured is a film that cannot be expressed by a uniaxial or biaxial refractive index ellipsoid, that is, a film without a so-called optical axis, Rth (λ) is calculated by the following method.

Rth (λ) is the above-mentioned Re (λ) with respect to the film normal direction with the in-plane slow axis (determined by “KOBRA 21ADH” or “KOBRA 21WR”) as the tilt axis (rotation axis). In 11 degrees from −50 ° to + 50 °, light at a wavelength of λ nm was incident from each inclined direction, measured at 11 points, and the measured retardation value and assumed average refractive index were input. “KOBRA 21ADH” or “KOBRA” based on the film thickness
21WR "is calculated.

In the above measurement, the assumed value of the average refractive index can be the value of “Polymer Handbook” (John Wiley & Sons, Inc.) and catalogs of various optical films. Those whose average refractive index is not known can be measured with an Abbe refractometer. Examples of the average refractive index values of main optical films are given below:
Cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), and polystyrene (1.59).

  By inputting the assumed value of the average refractive index and the film thickness, “KOBRA 21ADH” or “KOBRA 21WR” calculates nx, ny, and nz. Nz = (nx−nz) / (nx−ny) is further calculated from the calculated nx, ny, and nz.

[Molecular orientation axis]
Phase difference when 70 mm × 100 mm sample is conditioned at 25 ° C. and 65% RH for 2 hours, and the incident angle at normal incidence is changed with an automatic birefringence meter {“KOBRA21DH”, Oji Scientific Co., Ltd.} From this, the molecular orientation axis was calculated.

[Transmissivity]
The transmittance of visible light (615 nm) was measured on a 20 mm × 70 mm sample at 25 ° C. and 60% RH with a transparency measuring device (“AKA Phototube Colorimeter”, KOTAKI Corporation).

[Spectral characteristics]
A sample 13 mm × 40 mm was measured for transmittance at a wavelength of 300 to 450 nm with a spectrophotometer {“U-3210”, Hitachi, Ltd.} at 25 ° C. and 60% RH. The inclination width was obtained at a wavelength of 72% -5%. The limit wavelength was expressed by a wavelength of (gradient width / 2) + 5%. The absorption edge is represented by a wavelength with a transmittance of 0.4%. From this, the transmittance | permeability of 380 nm and 350 nm was evaluated.

  In the present specification, regarding the angle, “+” means the counterclockwise direction, and “−” means the clockwise direction. Further, when the upper direction of the liquid crystal display device is 12 o'clock and the lower direction is 6 o'clock, the absolute value 0 ° direction in the angular direction means the 3 o'clock direction (right direction of the screen). Further, the “slow axis” means a direction in which the refractive index is maximized. The “visible light region” means 380 nm to 780 nm. Further, the measurement wavelength of the refractive index is a value at λ = 550 nm in the visible light region unless otherwise specified.

  In addition, regarding the angle between each axis and direction, “parallel”, “vertical”, “45 °”, etc. means “approximately parallel”, “approximately vertical”, “approximately 45 °”, and is not exact. . Some deviation is allowed within the range to achieve each purpose. For example, “parallel” means that the crossing angle is approximately 0 °, and is −10 ° to 10 °, preferably −5 ° to 5 °, more preferably −3 ° to 3 °. “Vertical” means that the crossing angle is approximately 90 °, and is 80 ° to 100 °, preferably 85 ° to 95 °, more preferably 87 ° to 93 °. “45 °” means that the crossing angle is approximately 45 °, and is 35 ° to 55 °, preferably 40 ° to 50 °, more preferably 42 ° to 48 °.

  Further, in this specification, unless otherwise specified, the “polarizing plate” is cut into a size that can be incorporated into a long polarizing plate and a liquid crystal device (in this specification, “cutting” includes “punching” and The term “includes“ cutout ”and the like” is used to include both polarizing plates. Further, in this specification, “polarizing film” and “polarizing plate” are distinguished from each other, and “polarizing plate” is a laminate having a protective film for protecting the polarizing film on at least one surface of the “polarizing film”. Shall mean. Further, the polarizing plate may include an optical compensation film. In this case, the protective film may also serve as the optical compensation film. When the optical compensation film is formed by laminating an optically anisotropic layer having liquid crystal molecules on a support, the protective film may also serve as the support for the optical compensation film. Furthermore, the polarizing plate of the present invention may include a support. The “optical compensation film” is sometimes used synonymously with the optically anisotropic layer or the optical compensation film.

The present invention will be described in detail below.
<Liquid crystal display device>
[Configuration of liquid crystal display device]
The liquid crystal display device of the present invention includes a pair of opposed substrates having electrodes on one side, and a nematic liquid crystal material that is sandwiched between the substrates and is aligned substantially parallel to the surfaces of the pair of substrates when no voltage is applied. And a polarizing plate disposed on at least one side outside the liquid crystal cell, the polarizing plate being a first protective film, a polarizing film, and a second protective film The light diffusing layer in this order, the diffusing layer is a layer containing a translucent resin and translucent fine particles having a refractive index different from the refractive index of the translucent resin, and the light diffusion The internal haze of the layer is 45% or more and 80% or less.

  As the liquid crystal display device of the present invention, it is preferable to use a TN liquid crystal display device, an ECB liquid crystal display device, or an IPS liquid crystal display device.

  The ECB type liquid crystal display device has a normally white display in which white display is performed when no voltage is applied, and black is displayed with reduced transmittance when a high voltage is applied. Black display is obtained when the Re value of the optical compensation film matches the retardation value of the liquid crystal layer in the voltage application state. In such a configuration, a wide range of high-contrast images can be obtained, and gradation inversion does not occur in the halftone display area.

  When an ECB type liquid crystal display device is used as the liquid crystal display device, the crossing angle between the absorption axis of the polarizing film and the alignment treatment direction of the liquid crystal layer is preferably in the range of 40 to 50 °, and preferably 45 °. Is more preferable.

  The TN type liquid crystal display device is normally white display in which white display is performed when no voltage is applied, and black display is performed due to a decrease in transmittance when a high voltage is applied. Black display is obtained when the Re value of the optical compensation film matches the retardation value of the liquid crystal layer in the voltage application state. With this configuration, a wide range of high contrast can be obtained. When the polarizing film absorption axis is 45 ° or −45 ° with respect to the horizontal direction of the screen, the crossing angle between the absorption axis of the polarizing film and the alignment treatment direction of the liquid crystal layer is preferably in the range of −10 to 10 °. ° is more preferred. When the polarizing film is parallel to the horizontal direction of the screen or 90 °, the crossing angle between the absorption axis of the polarizing film and the alignment direction of the liquid crystal layer is in the range of 20 to 70 ° in order to make the viewing angle symmetrical. Is preferred.

  In addition, the IPS liquid crystal display device has a normally black display in which black is displayed when no voltage is applied, and black and white display is obtained with increased transmittance when a high voltage is applied. Viewing angle expansion for black display can be realized by optimizing the Re value and Rth of the optical compensation film. In this configuration, in the polarizing plate closer to the viewer than the liquid crystal cell, the crossing angle between the absorption axis of the polarizing film and the initial alignment treatment direction of the liquid crystal layer is preferably in the range of 80 to 100 °, more preferably 90 °. In the polarizing plate far from the viewer side across the liquid crystal cell, the intersection angle between the absorption axis of the polarizing film and the initial alignment treatment direction of the liquid crystal layer is preferably in the range of −10 ° to 10 °, more preferably 0 °. .

  A specific light diffusion layer is laminated on the second protective film. This light diffusion layer has the effect of widening the contrast viewing angle, reducing the change in the tint viewing angle, reducing the gradation inversion, and reducing display unevenness.

  Furthermore, in the liquid crystal display device of the present invention, it is preferable that at least one optical compensation film is disposed between the polarizing plate and the liquid crystal layer.

  The optical compensation film is not particularly limited and may have any configuration as long as it has optical compensation capability. Examples thereof include a birefringent polymer film, and a laminated body of a transparent support and an optical compensation layer composed of liquid crystalline molecules formed on the transparent support. In the latter embodiment, the transparent protective film on the side close to the liquid crystal layer of the polarizing plate may also serve as the support for the optical compensation film. In other words, the polarizing plate may have an optical compensation layer.

  The optical compensation film for a TN type or ECB type liquid crystal display device is preferably an optical compensation film comprising a discotic structural unit. In the present invention, the orientation control direction of the optical compensation film composed of the discotic structural unit is preferably substantially parallel to the absorption axis of the polarizing film of the polarizing plate.

In the liquid crystal device of the present invention, the disc surface of the discotic structural unit is inclined with respect to the polarizing film (or transparent support surface), and the disc surface of the discotic structural unit and the polarizing film (or transparent support surface) It is preferable that the angle formed between the optical compensation film and the optical compensation film changes in a direction perpendicular to the film surface (thickness direction). In such a liquid crystal display device, it is possible to obtain a display with no contrast viewing angle and gradation inversion.

  The optical compensation film used in the present invention is not only composed of a transparent support subjected to orientation treatment and a compound having a discotic structural unit provided on the support, but also composed of a stretched film. An optical compensation film may be used. The optical compensation film is such that the normally black display liquid crystal cell that displays black when no voltage is applied has two or more pixel regions, each of which is an initial molecule of the nematic liquid crystal material. An oblique direction of black display for a liquid crystal display device having two or more regions different from each other, or two or more regions different from each other in which the alignment direction of molecules of the nematic liquid crystal material continuously changes in a voltage application state. There is also an effect of reducing the leakage light.

  Further, in the liquid crystal display device of the present invention, whether one pixel of the liquid crystal cell further has two or more pixel regions, and the initial alignment states of the liquid crystalline molecules in the respective regions in the pixel region are different from each other. Alternatively, a configuration may be adopted in which the orientation directions of the liquid crystal molecules in the two or more pixel regions are different from each other in a voltage application state, and further change continuously.

  Such a configuration is a particularly effective aspect in an ECB type liquid crystal display device in which liquid crystal molecules are inclined with respect to the substrate normal line by applying a voltage. The unevenness of brightness and color tone can be reduced by configuring one pixel with two or more (preferably two or four or more) pixel regions having different initial alignment states and averaging.

  The present invention also relates to the liquid crystal display device, wherein the absorption axis of the polarizing film and the screen left-right direction of the display device are parallel or vertical.

  In a conventional liquid crystal display device, the polarizing plate contracts in a harsh environment. In particular, the shrinkage in the direction parallel to the long and short sides of the screen is maximized. Thus, when an elastic force such as shrinkage or elongation is applied to the film used for the polarizing plate, a retardation change occurs. In the configuration in which the polarizing plate absorption axis intersects at 45 ° with the retardation generation direction, the light transmission is maximized and is observed as leakage light.

  In the conventional ECB type liquid crystal display device or TN type liquid crystal display device, the polarizing plate absorption axis intersects with the horizontal direction of the screen, that is, the polarizing plate end long side direction at 45 °. Since the contraction direction of the polarizing plate is parallel to the long side and short side directions of the end portion of the polarizing plate, leakage light is maximized in this arrangement. Therefore, as described above, by making the polarizing plate absorption axis parallel or perpendicular to the horizontal direction of the screen, that is, the long side direction of the polarizing plate end, light leakage can be improved particularly in an ECB type liquid crystal display device or a TN type liquid crystal display device. I found it. An example of such an ECB type liquid crystal display device will be described later with reference to FIG.

  The TN type liquid crystal display device employs TFT driving in order to perform high definition and high contrast high quality display. In TFT driving, gate wiring and signal (or source) wiring are arranged in the horizontal and vertical directions of the screen. Since the polarizing plate shrinkage direction is parallel or perpendicular to this wiring, even if the polarizing plate absorption axis is arranged parallel or perpendicular to this wiring, the maximum shrinking direction of the polarizing plate, that is, the long side and short side of the polarizing plate end The light leakage can be improved by arranging them substantially parallel or perpendicular to the direction. An example of such a TN liquid crystal display device will be described later with reference to FIG.

On the other hand, in a liquid crystal display device having a conventional configuration, when the configuration in which the absorption axis of the polarizing film and the horizontal direction of the screen of the display device are parallel or vertical as described above, the angle range from the front with a contrast of 10 ° or more is used. Alternatively, the left-right symmetry of the color change when the screen is viewed from an oblique direction with respect to the front may be reduced. However, the liquid crystal display device of the present invention includes a light diffusing layer having specific characteristics, and it has been confirmed that the right-and-left object property is improved by using the configuration.

  Furthermore, the configuration of the liquid crystal display device of the present invention can be applied to an IPS liquid crystal display device. By applying the configuration of the present invention to an IPS liquid crystal display device, it has been found that the color of leakage light from the oblique direction during black display in the conventional IPS liquid crystal display device can be averaged and achromatic. An example of such an IPS liquid crystal display device will be described later with reference to FIG.

[Embodiment of Liquid Crystal Display Device of the Present Invention]
Hereinafter, embodiments of the liquid crystal display device of the present invention will be sequentially described in detail with reference to the drawings.

[ECB type liquid crystal display]
FIG. 1 is a schematic view of a preferred example of the liquid crystal display device according to the present invention, particularly when the liquid crystal display device is an ECB type liquid crystal display device.

  In FIG. 1, the liquid crystal display device includes liquid crystal cells 5 to 7 and a pair of polarizing plates 1 and 2 disposed on both sides of the liquid crystal cell. The polarizing plate is sandwiched between a polarizing film and a pair of protective films. A light diffusion layer (not shown) is formed on the upper side (viewing side) of the upper polarizing plate 1 from the polarizing film 12 on the outer side, or on the outer side of the lower polarizing plate 2 viewed from the polarizing film 22 of the lower protective film 21. Is arranged. The protective film 11 and the protective film 21 also serve as a support for the light diffusion layer. Further, an upper optical compensation film 14 and a lower optical compensation film 24 having an optical compensation capability are disposed between the liquid crystal cell and the pair of polarizing plates. The lower protective film 13 of the upper polarizing plate 1 may also serve as a support for the upper optical compensation film 14. The upper polarizing plate is incorporated in the liquid crystal display device as a structure in which the light diffusion layer, the members 11 to 13, and more preferably 14 are integrally laminated. On the other hand, the upper protective film 23 of the lower polarizing plate may also serve as a support for the lower optical compensation film 24. The lower polarizing plate is incorporated in the liquid crystal display device as a structure in which the light diffusion layer, the members 21 to 23, and more preferably 24 are integrally laminated.

  In the present invention, at least one of the polarizing plates is a laminate of a light diffusing layer and a polarizing plate, more preferably an optical compensation film (for example, as an upper polarizing plate, the light diffusing layer and the members 11 to 13, more preferably 14) may be used, and it is not necessary for both polarizing plates to have the above-described structure as shown in FIG. That is, the liquid crystal display device only needs to have a structure in which a light diffusion layer, a polarizing film, and preferably an optical compensation film are integrally laminated. Therefore, the configuration is not limited to that shown in FIG.

  In the liquid crystal display device of the present invention, the support of the light diffusing layer can also serve as a protective film on one side of the polarizing film, and more preferably, the transparent support of the optical compensation film is used as the other side of the polarizing film. A light diffusion layer, a protective film (also used as a support), a polarizing film and a protective film (preferably used as a transparent support), and more preferably an optical compensation film. An integrated polarizing plate laminated in order can be used. The polarizing plate not only has a polarizing function, but also contributes to an increase in viewing angle, in particular, an increase in contrast viewing angle, a decrease in change in tint viewing angle, a decrease in gradation inversion, and a reduction in display unevenness. Furthermore, it is preferable that the polarizing plate is provided with an optical compensation film having optical compensation ability, and the liquid crystal display device can be optically compensated accurately with a simple configuration. In the liquid crystal display device, it is preferable that the light diffusion layer, the protective film, the polarizing film, the transparent support, and more preferably the optical compensation film are laminated in this order from the outside of the device (the side far from the liquid crystal cell).

Regarding the absorption axes 12D and 22D of the polarizing films 12 and 22, the alignment direction RD of the optical compensation films 14 and 24, and the alignment direction of the liquid crystalline molecules 6, the materials used in each member, the display mode, the laminated structure of the members, etc. It can be adjusted to the optimum range accordingly. In order to obtain a high contrast, the absorption axes 12D and 22D of the polarizing films 12 and 22 are arranged so as to be substantially orthogonal to each other. However, the liquid crystal display device of the present invention is not limited to this configuration.

  Next, the specific configuration of the liquid crystal display device shown in FIG. 1 will be described in more detail, and the operation thereof will be described.

  The rubbing direction 5RD of the upper substrate 5 of the liquid crystal cells 5 to 7 and the rubbing direction 7RD of the lower substrate 7 are set in parallel, and the liquid crystal layer has a parallel alignment without a twist structure. The upper substrate 5 and the lower substrate 7 each have an alignment film (not shown) and an electrode layer (not shown). The alignment film has a function of aligning the liquid crystal molecules 6. The electrode layer has a function of applying a voltage to the liquid crystal molecules 6. For example, transparent indium tin oxide (ITO) can be used as the electrode layer. In the parallel mode, a liquid crystal (for example, “MLC-9100” manufactured by Merck) of Δn = 0.0854 (589 nm, 20 ° C.) and Δε = + 8.5 can be used between the upper and lower substrates.

  Here, the brightness at the time of white display changes depending on the magnitude of the product Δn · d of the thickness d and the refractive index anisotropy Δn. Therefore, in order to obtain the maximum brightness, it is preferable to set the value of Δn · d to be in the range of 0.2 to 0.4 μm. At least one polarizing film absorption axis intersects with the liquid crystal cell alignment direction (rubbing direction RD) adjacent thereto at approximately 45 °, and the crossing angle between the upper and lower polarizing film absorption axes (12D and 22D) is approximately 90 ° crossed Nicols. is there.

  In the non-driving state in which the driving voltage is not applied to the respective transparent electrodes (not shown) of the liquid crystal cell substrates 5 and 7, the liquid crystal molecules 6 in the liquid crystal layer are aligned substantially parallel to the surfaces of the substrates 5 and 7. As a result, the light passing therethrough changes its polarization state due to the birefringence effect of the liquid crystalline molecules 6 and passes through the polarizing film 12. At this time, the value of Δn · d of the liquid crystal layer is set so that the transmitted light is maximized. On the other hand, in a driving state in which a driving voltage is applied to a transparent electrode (not shown), the liquid crystalline molecules 6 try to align perpendicularly to the surfaces of the substrates 5 and 7 depending on the magnitude of the applied voltage. However, near the center of the liquid crystal layer in the thickness direction between the substrates, it is almost perpendicular to the substrate surface. A continuous inclined orientation will occur. In such a state, it is difficult to obtain a complete black display. At the same time, the average orientation of the tilted liquid crystal molecules in the vicinity of the substrate interface changes depending on the observation angle, and the viewing angle dependency in which the transmittance and the brightness change depending on the viewing angle occurs.

  As means for solving such a problem, it is preferable to first arrange an optical compensation film that compensates for the residual phase difference of the liquid crystal layer in the vicinity of the substrate interface, so that a complete black display is obtained and the front contrast ratio is improved. Further, as described in the above-mentioned Patent Document 1, it is preferable to dispose an optical film that compensates for a liquid crystal layer that is continuously tilted and aligned so that viewing angle characteristics are improved. In addition, since the liquid crystal molecules 6 are tilted at the time of halftone display, the magnitude of birefringence of the liquid crystal molecules 6 when viewed from an oblique direction is different between the tilt direction and the opposite direction, and there is a difference in luminance and color tone. Arise. When a structure called multi-domain in which one pixel of a liquid crystal display device is divided into a plurality of regions, the viewing angle characteristics of luminance and color tone are averaged and improved.

  Specifically, each pixel is composed of two or more (preferably 4 or 8) regions in which the initial alignment state of the liquid crystal molecules is different from each other, and the luminance and color tone bias depending on the viewing angle are averaged. Can be reduced. Further, the same effect can be obtained even if each pixel is composed of two or more different regions where the alignment direction of the liquid crystal molecules continuously changes in a voltage application state.

As described above, one of the preferable aspects of the present invention is an aspect in which the absorption axis of the polarizing film and the horizontal direction of the screen of the display device are parallel or perpendicular. FIG. 2 shows an aspect in which the absorption axis of the polarizing film and the horizontal direction of the screen of the display device are parallel or vertical in the ECB type liquid crystal display device.
In the embodiment as shown in FIG. 2, the orientation control direction of the optical compensation film composed of the discotic structural unit preferably intersects the absorption axis of the polarizing film in the range of 40 to 50 °, more preferably 45 °. preferable. The crossing angle between the alignment control direction of the optical compensation film composed of discotic structural units and the alignment treatment direction of the liquid crystal layer is preferably in the range of −20 to 20 °.

[TN type liquid crystal display]
Next, an embodiment in which the present invention is applied to a TN mode liquid crystal display device will be described in detail with reference to FIG. FIG. 3 shows a preferred embodiment of the present invention in which the absorption axis of the polarizing film and the horizontal direction of the screen of the display device are parallel or perpendicular. Here, an example in which TFT (active) driving is performed using nematic liquid crystal having positive dielectric anisotropy as field effect liquid crystal will be described.

  The liquid crystal cells 5 to 7 include an upper substrate 5 and a lower substrate 7 and a liquid crystal layer formed of liquid crystal molecules 6 sandwiched between them. An alignment film (not shown) is formed on the surface of the substrates 5 and 7 in contact with the liquid crystal molecules 6 (hereinafter sometimes referred to as “inner surface”), and by a rubbing process or the like applied on the alignment film, The alignment of the liquid crystal molecules 6 in a state where no voltage is applied or a state where a voltage is not applied is controlled. Further, on the inner surfaces of the substrates 5 and 7, a transparent electrode (not shown) capable of applying a voltage to the liquid crystal layer made of the liquid crystal molecules 6 is formed.

  In the TN mode liquid crystal display device, in a non-driving state where no driving voltage is applied to the electrodes, the liquid crystal molecules 6 in the liquid crystal cell are aligned substantially parallel to the substrate surface, and the alignment direction is twisted by 90 ° between the upper and lower substrates. ing. In the case of a transmissive display device, the backlight light passes through the lower polarizing plate 2 and becomes linearly polarized light. The linearly polarized light propagates along the twisted structure of the liquid crystal layer, passes through the upper polarizing plate 1 as it is by rotating the polarization plane by 90 ° while maintaining the polarization state, and the display device displays white.

  On the other hand, when the applied voltage is increased, the liquid crystal molecules 6 gradually stand in the direction perpendicular to the substrate surface while eliminating the twist. In the TN mode liquid crystal display device in an ideal high voltage application state, the twist of the liquid crystal molecules 6 is almost completely eliminated, and the alignment state is almost perpendicular to the substrate surface. At this time, the linearly polarized light that has passed through the lower polarizing plate 2 propagates without rotating the polarization plane because the liquid crystal layer has no twisted structure, and is incident at an angle perpendicular to the absorption axis of the upper polarizing plate 1. It is shut off and displayed in black.

  As described above, in the TN mode, a function as a display device is achieved by blocking or transmitting polarized light. In general, as a numerical value representing display quality, a ratio between white display luminance and black display luminance is defined and used as a contrast ratio. The higher the contrast ratio, the higher the quality of the display device, and in order to increase the contrast, it is important to maintain the polarization state in the liquid crystal display device and pass through.

An example of a TN mode liquid crystal cell configuration will be described below. A liquid crystal cell in which a liquid crystal cell having a positive dielectric anisotropy between the upper and lower substrates 5 and 7 and a refractive index anisotropy, Δn = 0.0854 (589 nm, 20 ° C.) and Δε = + 8.5 is rubbed and aligned. Is made. The alignment control of the liquid crystal layer is controlled by an alignment film and rubbing. A director indicating the alignment direction of the liquid crystal molecules, that is, a so-called tilt angle is preferably set in a range of about 0.1 ° to 10 °, and is set to 3 ° here. The rubbing direction is applied in a direction perpendicular to the upper and lower substrates, and the tilt angle can be controlled by the strength and the number of rubbing times. The alignment film is formed by applying and baking a polyimide film. The magnitude of the twist angle of the liquid crystal layer is determined by the crossing angle of the upper and lower substrates in the rubbing direction and the chiral agent added to the liquid crystal material. Here, a chiral agent having a pitch of about 60 μm is added so that the twist angle is approximately 90 °. The thickness d of the liquid crystal layer is set to 5 μm.

  The liquid crystal material LC is not particularly limited as long as it is a nematic liquid crystal. As the dielectric anisotropy Δε is larger, the driving voltage can be reduced. When the refractive index anisotropy Δn is small, the thickness (gap) of the liquid crystal layer can be increased, the liquid crystal sealing time can be shortened, and the gap variation can be reduced. In addition, a larger Δn can reduce the cell gap and enable high-speed response. In general, Δn is set between 0.04 and 0.28, the cell gap is set between 1 and 10 μm, and the product of Δn and d is adjusted so as to be between 0.25 and 0.55 μm.

  The absorption axis 12D of the upper polarizing film 12 and the absorption axis 22D of the lower polarizing film 22 are laminated substantially orthogonally, and the absorption axis 12D of the upper polarizing film 12 and the rubbing direction (alignment axis) 5RD of the upper substrate 5 of the liquid crystal cell are The layers are stacked so that the absorption axis 22D of the lower polarizing film 22 and the rubbing direction (alignment axis) 7RD of the lower substrate 7 of the liquid crystal cell are approximately parallel to each other. A transparent electrode (not shown) is formed inside each alignment film of the upper substrate 5 and the lower substrate 7, but in a non-driving state where no driving voltage is applied to the electrodes, the liquid crystal molecules 6 in the liquid crystal cell As a result, the polarization state of light passing through the liquid crystal panel is propagated along the twisted structure of the liquid crystal molecules 6, and the polarization plane is rotated by 90 ° and emitted. That is, the liquid crystal display device realizes white display in the non-driven state. On the other hand, in the driving state, the liquid crystal molecules 6 are oriented in a direction that forms an angle with respect to the substrate surface, and the light that has passed through the lower polarizing plate 2 is transmitted to the letter such as the liquid crystal layer by the optical compensation layers 14 and 24. The foundation is canceled out, passes through the liquid crystal layer 6 while maintaining the polarization state, and is blocked by the polarizing film 12. In other words, an ideal black display can be obtained in the driving state in the liquid crystal display device.

A light diffusion layer (not shown) is formed on the upper side (viewing side) of the upper polarizing plate 1 from the polarizing film 12 on the outer side, or on the outer side of the lower polarizing plate 2 viewed from the polarizing film 22 of the lower protective film 21. Is arranged. The protective film 11 and the protective film 21 also serve as a support for the light diffusion layer. Further, the protective films 23 and 13 on the side of the upper and lower polarizing plates close to the liquid crystal cell may also serve as a support for the optically anisotropic layers 14 and 24, and the upper polarizing plate 1 and the lower polarizing plate 2. May be incorporated in the liquid crystal display device as an integrally laminated structure together with the optically anisotropic layers 14 and 24.
In the liquid crystal display device of the present invention, the support of the light diffusing layer can also serve as a protective film on one side of the polarizing film, and more preferably, the transparent support of the optical compensation sheet is used as the other side of the polarizing film. That is, the light diffusion layer, the transparent protective film (also used as a support), the polarizing film and the transparent protective film (preferably used as a transparent support), and more preferably an optically different film. An integral elliptically polarizing plate laminated in the order of the isotropic layers can be used. This integrated elliptical polarizing plate has the effect of expanding the contrast viewing angle, reducing the change in the tint viewing angle, reducing the gradation inversion, and reducing the display unevenness. Further, the polarizing plate preferably includes an optically anisotropic layer having optical compensation ability. When the integrated elliptical polarizing plate is used, the liquid crystal display device can be optically compensated accurately with a simple configuration. it can. In the liquid crystal display device, it is preferable that the light diffusion layer, the transparent protective film, the polarizing film and the transparent support are laminated in order of the optically anisotropic layer from the outside of the device (the side far from the liquid crystal cell). .

  Further, in a liquid crystal display device, when a structure called multi-domain in which one pixel is divided into a plurality of regions is used, the viewing angle characteristics in the vertical and horizontal directions are averaged, and the display quality is improved.

[IPS mode liquid crystal display]
Next, an embodiment in which the present invention is applied to an IPS mode liquid crystal display device will be described in detail with reference to FIG.

The liquid crystal display device shown in FIG. 4 includes liquid crystal cells 5 to 7 and an upper polarizing plate 1 and a lower polarizing plate 2 that are disposed with the liquid crystal cell interposed therebetween. The liquid crystal cells 5 to 7 include a liquid crystal cell upper substrate 5, a liquid crystal cell lower substrate 7, and a liquid crystal layer 6 sandwiched between them. The liquid crystal layer 6 is rubbed on the opposing surfaces of the substrates 5 and 7. The orientation direction is controlled by the processing directions 5RD and 7RD.

  The upper polarizing plate includes a pair of transparent protective films 11 and 13 and a polarizing film 12 sandwiched between them (assuming that the transparent protective film 13 is disposed on the side close to the liquid crystal cell). The absorption axis 12D of the polarizing film 12 is preferably substantially parallel to the roll feed direction (MD direction) 11D, 13D of the transparent protective films 11, 13. It is preferable that the MD directions 11D and 13D are parallel because an effect of improving the mechanical stability of the polarizing plate and equalizing the optical performance can be obtained. Further, when the MD direction 11D of the transparent protective film 11 disposed on the side far from the liquid crystal cell and the absorption axis 12D of the polarizing film 12 are substantially parallel, mechanical reliability such as dimensional change of the polarizing plate and prevention of curling are obtained. Improves. Even if the MD direction 13D and the absorption axis 12D are orthogonal, the same effect can be obtained, and if the transparent protective films 11 and 13 have sufficient thickness and rigidity, the absorption axis 12D and the two protective films in the MD direction Even if 11D and 13D intersect at different angles, the same effect can be obtained.

  Similarly to the upper polarizing plate, the lower polarizing plate preferably has the configuration shown in FIG. 4, and the MD direction 23 </ b> D of the polarizing film 22 and the protective film 23 on the side close to the liquid crystal cell of the polarizing film 22 is substantially different from each other. Is preferably parallel or orthogonal to. When the MD directions 23D and 21D of the transparent protective films 23 and 21 are orthogonal to each other, the optical characteristics of light perpendicularly incident on the liquid crystal display device are prevented from deteriorating by canceling out the birefringence of the respective protective films. can do. Further, in the aspect in which the MD directions 23D and 21D are parallel to each other, when the liquid crystal layer has a residual phase difference, the phase difference can be compensated by the birefringence of the protective film.

  FIG. 5 is a schematic side sectional view showing an IPS mode liquid crystal cell. Usually, a plurality of pixels are provided by matrix electrodes, but a part of one pixel is shown. A linear electrode 91 is formed inside a pair of transparent substrates 5 and 7, and an alignment control film (not shown) is formed thereon. The rod-like liquid crystal molecules 6 sandwiched between the substrates 5 and 7 are oriented so as to have a slight angle with respect to the longitudinal direction of the linear electrode 91 when no electric field is applied. In this case, the dielectric anisotropy of the liquid crystal is assumed to be positive. When the electric field 9D is applied, the direction of the liquid crystal molecules 6 changes in the electric field direction. The light transmittance can be changed by disposing the polarizing plates 1 and 2 at a predetermined angle. The angle formed by the electric field direction 9D with respect to the surface of the substrate 7 is preferably 20 ° or less, more preferably 10 ° or less, that is, substantially parallel. Hereinafter, in this invention, what is 20 degrees or less is generically expressed as a parallel electric field. In addition, the effect does not change even if the electrode 91 is formed separately on the upper and lower substrates or only on one substrate.

As described above, the IPS mode is aligned parallel to the substrate surface when no voltage is applied or when a low voltage is applied. In general, the alignment control is performed by rubbing after the alignment film is applied, but this alignment process tends to cause alignment unevenness. Since the IPS is aligned in parallel to the substrate surface as described above, this alignment unevenness becomes a large retardation unevenness, which leads to uneven brightness unevenness particularly in light leakage during black display. On the other hand, in each of the VA, TN, and OCB modes, liquid crystal molecules are aligned perpendicular to the substrate surface during black display. Therefore, even if the alignment unevenness is large, the retardation unevenness is small and the luminance unevenness is small.
FIG. 6 is a schematic cross-sectional view of a liquid crystal cell when the IPS mode has a higher response speed and a higher transmittance. Unlike the case of FIG. 5, the electrode has a two-layer structure with an insulating layer 93 interposed therebetween. The lowermost electrode may be an unpatterned electrode or a linear electrode. The upper electrode is preferably linear, but may be any shape such as mesh, spiral, or dot as long as the electric field from the lower electrode 92 can pass through, and a floating electrode with a neutral potential may be further added. . The insulating layer 93 may be either an inorganic material such as SiO or a nitride film, or an organic material such as acrylic or epoxy.
In this method, since the contrast ratio is improved due to the high transmittance, luminance unevenness due to in-plane alignment unevenness during black display is easily observed. In addition, since the electric field strength is high, uneven brightness is likely to occur when a low voltage is applied.

  As the liquid crystal material LC, nematic liquid crystal having a positive dielectric anisotropy Δε is used. The thickness (gap) of the liquid crystal layer was more than 2.8 μm and less than 4.5 μm. As described above, when the retardation (Δn · d) is more than 0.25 μm and less than 0.32 μm, transmittance characteristics having almost no wavelength dependence within the visible light range can be obtained more easily. By the combination of an alignment film and a polarizing plate, which will be described later, the maximum transmittance can be obtained when the liquid crystal molecules are rotated 45 ° from the rubbing direction to the electric field direction. The thickness (gap) of the liquid crystal layer is controlled by polymer beads. Of course, the same gap can be obtained with glass beads, glass fibers, and resin columnar spacers. The liquid crystal material LC is not particularly limited as long as it is a nematic liquid crystal. The larger the value of the dielectric anisotropy Δε, the lower the driving voltage, and the smaller the refractive index anisotropy Δn, the thicker the liquid crystal layer (gap), and the shorter the liquid crystal sealing time. And variation in gaps can be reduced.

  The liquid crystal display device of the present invention can be obtained by applying the polarizing plate for a liquid crystal display device of the present invention to the IPS mode. As described above, the support of the light diffusing layer can also serve as the protective film on one side of the polarizing film, and more preferably, the transparent support of the optical compensation film is used on the other side of the polarizing film. Since it can also serve as a protective film, it is laminated in the order of a light diffusion layer, a protective film (also used as a support), a polarizing film and a protective film (preferably used as a transparent support), and more preferably an optical compensation film. The integrated polarizing plate is used. The polarizing plate not only has a polarizing function, but also contributes to an increase in viewing angle, in particular, an increase in contrast viewing angle, a decrease in change in tint viewing angle, a decrease in gradation inversion, and a reduction in display unevenness. Furthermore, it is preferable that the polarizing plate is provided with an optical compensation film having optical compensation ability, and the liquid crystal display device can be optically compensated accurately with a simple configuration. In the liquid crystal display device, it is preferable that the light diffusion layer, the protective film, the polarizing film, the transparent support, and more preferably the optical compensation film are laminated in this order from the outside of the device (side far from the liquid crystal cell).

  The liquid crystal display device used in the present invention is effective not only in the display mode described above but also in an aspect applied to the OCB mode, VA mode, HAN mode, and STN type.

  The liquid crystal display device of the present invention is not limited to the above-described configuration, and may include other members. For example, a color filter may be disposed between the liquid crystal cell and the polarizing film. In addition, an optical compensation film can be separately provided between the liquid crystal cell and the polarizing plate. When used as a transmissive type, a cold cathode or a hot cathode fluorescent tube, or a backlight having a light emitting diode, a field emission element, or an electroluminescent element as a light source can be disposed on the back surface. Further, the liquid crystal display device of the present invention may be of a reflective type. In that case, only one polarizing plate may be disposed on the observation side, and a reflective film is formed on the back surface of the liquid crystal cell or the inner surface of the lower substrate of the liquid crystal cell. Is installed. Of course, it is also possible to provide a front light using the light source on the liquid crystal cell observation side.

  The liquid crystal display device of the present invention includes an image direct view type, an image projection type, and a light modulation type. The present invention is particularly effective when applied to an active matrix liquid crystal display device using a three-terminal or two-terminal semiconductor element such as TFT or MIM. Of course, an embodiment applied to a passive matrix liquid crystal display device represented by STN type called time-division driving is also effective.

In the present invention, the polarizing plate having a specific light diffusion layer increases the contrast viewing angle of the liquid crystal display device, reduces the change in the tint viewing angle, reduces the gradation inversion, and reduces the display unevenness such as brightness unevenness and color unevenness. In addition, the viewing angle of the liquid crystal display device can be improved by having a predetermined relationship between the slow axis of the protective film of the polarizing plate and the absorption axis of the polarizing film. Furthermore, it is preferable to dispose an optical compensation film between the polarizing plate and the liquid crystal cell because the viewing angle is further improved.

  Hereinafter, materials used for various members usable in the liquid crystal display device of the present invention, manufacturing methods thereof, and the like will be described in detail.

〔Polarizer〕
In the present invention, a polarizing plate for a liquid crystal display device having a first protective film, a polarizing film, a second protective film, and a light diffusion layer in this order is used. The polarizing film is obtained, for example, by dyeing a polyvinyl alcohol film or the like with iodine and stretching, and laminating both surfaces with a protective film, and further forming a light diffusion layer on at least one protective film, or A polarizing plate obtained by laminating a light diffusion film having a light diffusion layer that has already been formed can be used. The polarizing plate is disposed outside the liquid crystal cell. It is preferable that a pair of polarizing plates each including a polarizing film and a pair of protective films sandwiching the polarizing film are disposed with the liquid crystal cell interposed therebetween.

[Protective film]
The polarizing plate of the present invention is obtained by laminating a pair of protective films on both sides of a polarizing film. The kind of protective film is not particularly limited, and cellulose esters such as cellulose acetate, cellulose acetate butyrate, and cellulose propionate, polycarbonate, polyolefin, polystyrene, polyester, and the like can be used. Commercially available polymers [for norbornene polymers, “Arton” {manufactured by JSR Corporation], “Zeonoa” {manufactured by Nippon Zeon Corporation}, etc.] may be used. The above optical compensation film can be used as one protective film. The protective film of the present invention is preferably a transparent protective film.

[Light diffusion layer]
A light-diffusion layer consists of translucent particle | grains and translucent resin. The light diffusing layer is preferably formed on the protective film closest to the viewer side, but may be disposed on the outer protective film close to the light source. Of course, they may be disposed in the protective film (for example, between the polarizing film and the protective film), in the optical compensation film (for example, between the optical compensation film and the protective film), or in the liquid crystal cell. The haze value and the scattered light profile are adjusted by the translucent particles and the translucent resin. In the present invention, it is preferable to use translucent fine particles having two or more types and / or materials in addition to using one type of particles.

(Translucent fine particles)
The light-transmitting fine particles have the refractive index and the refractive index of the light-transmitting resin constituting the entire light diffusion layer (when inorganic fine particles are added to the light-transmitting resin to adjust the refractive index of the layer, which will be described later) The optical average refractive index) is preferably 0.03 to 0.30. If this difference in refractive index is 0.03 or more, the difference in refractive index between the two will not be too small, and a good light diffusion effect can be obtained. If the difference in refractive index is 0.30 or less, light diffusion is achieved. This is preferable because the problem is that the property is too high and the entire light diffusion layer is whitened. The difference in refractive index is more preferably 0.06 to 0.25, and most preferably 0.09 to 0.20.

(First translucent fine particles)
In the liquid crystal display device of the present invention, the particle diameter of the translucent fine particles (first translucent fine particles) for improving the display quality (improving viewing angle characteristics) is more preferably 0.5 to 3.5 μm. More preferably, it is 0.5 to 2.0 μm. If the particle diameter is 0.5 μm or more, it is preferable because the scattering effect is great, the viewing angle characteristics are improved, the backscattering is not excessively increased, and the decrease in brightness is not increased. On the other hand, if it is 2.0 μm or less, the scattering effect is small and problems such as insufficient improvement in viewing angle characteristics do not occur. The particle diameter is more preferably 0.6 to 1.8 μm, and most preferably 0.7 to 1.6 μm. By appropriately adjusting the particle diameter, an angular distribution of light scattering can be obtained.

  In the light diffusing layer suitable for the present invention, the haze value and the light-transmitting particles are appropriately combined with the refractive index difference between the light-transmitting particles and the light-transmitting resin constituting the entire light diffusing layer, and the particle size of the light-transmitting fine particles. It is particularly preferable to adjust the scattered light profile in terms of achieving both viewing angle characteristics and whitening (blur).

  The greater the light diffusion effect of the light diffusion layer, the better the viewing angle characteristics. However, in order to maintain the front brightness in terms of display quality of the liquid crystal display device, it is also necessary to increase the transmittance as much as possible.

(Second translucent fine particles)
In the light diffusing layer in the present invention, it is also preferable to further add translucent fine particles (second translucent fine particles) that are not mainly intended to impart a diffusion effect. The second light-transmitting fine particles are used for providing irregularities on the surface of the light diffusion layer and providing a reflection preventing function. The particle diameter of the second light transmissive fine particles is preferably larger than the particle diameter of the first light transmissive particles, and more preferably 2.5 to 10.0 μm. Thereby, suitable surface scattering can be provided. If the particle diameter is 2.5 μm or more, it is preferable from the viewpoint of film hardness because it is not necessary to reduce the thickness of the layer when providing the desired surface irregularities. On the other hand, if the particle diameter is 10 μm or less, one particle per particle Therefore, the particle sedimentation stability in the coating solution is also excellent, which is preferable. The particle diameter of the second light transmissive fine particles is more preferably 2.7 to 9 μm, and most preferably 3 to 8 μm.

  In order to achieve good display quality in the liquid crystal display device of the present invention, it is also important to prevent reflection of external light. The lower the haze value on the surface, the less white-brown feeling is caused by external light and a clear display can be obtained.However, if the surface haze value is too low, the reflection increases, so the outermost layer has a light diffusing layer. It is necessary to provide a low refractive index layer having a refractive index lower than the refractive index to reduce the reflectance. In order to control the surface haze value, it is preferable to provide appropriate irregularities on the surface of the resin layer with the second light-transmitting fine particles, but this is not restrictive.

  The refractive index of the second translucent particles is preferably smaller than the first translucent particles in the difference from the refractive index of the translucent resin constituting the entire light diffusion layer.

  The surface unevenness of the light diffusion layer preferably has a surface roughness Ra of 0.5 μm or less, more preferably 0.3 μm or less, and most preferably 0.2 μm or less. The surface roughness Ra (centerline average roughness) can be measured according to JIS B-0601.

  The haze value of the light diffusion layer, particularly the internal scattering haze (internal haze) that greatly contributes to the diffusion of transmitted light has a strong correlation with the effect of improving the viewing angle characteristics. The light emitted from the backlight is diffused by the light diffusion layer installed on the surface of the polarizing plate on the viewing side, whereby the viewing angle characteristics are improved. However, since the front luminance is reduced if it is excessively diffused, the internal haze of the light diffusion layer in the present invention needs to be 45% or more and 80% or less. The internal haze is more preferably from 45% to 70%, particularly preferably from 45% to 60%. As a method of increasing noise to internal scattering, increasing the particle concentration of translucent fine particles for the purpose of imparting diffusibility, increasing the coating film thickness, and further increasing the refractive index difference between the particles and the resin, etc. There is a way.

In the present invention, in order to improve the display quality of the liquid crystal display device (improve viewing angle characteristics), the scattered light intensity of 30 ° with respect to the light intensity at the output angle of 0 ° of the scattered light profile of the goniophotometer is within a specific range. Is particularly preferred. The scattered light intensity of the goniophotometer with respect to the light intensity with an output angle of 0 ° of the scattered light profile is preferably 0.05% or more from the viewpoint of visual characteristics, and is 0.3 from the viewpoint of not greatly reducing the front luminance. % Or less is preferable. Therefore, the scattered light intensity of the light diffusion layer in the present invention is preferably 0.05 to 0.3%, more preferably 0.05 to 0.2%, and 0.05 to 0.15. % Is particularly preferred. More preferably, the light diffusion layer in the present invention satisfies the preferable range of the scattered light intensity and the preferable range of the internal haze at the same time.

  The haze due to surface scattering of the polarizing plate of the present invention (surface haze) is 0.1 to 30%, preferably 10% or less, and preferably 5% or less, from the viewpoint of achieving both reduction in reflection and reduction in white-brown feeling. Particularly preferred. If importance is attached to the reduction of white-brown feeling due to external light, it is preferably 4% or less, and more preferably 2% or less. Since the reflection increases when the surface haze is reduced, a low refractive index layer is provided, and the average value of the integrated reflectance in 5 ° incident light in the wavelength region from 450 nm to 650 nm should be 3.0% or less. Is preferably 2.0% or less, and most preferably 1.0% or less. In the present invention, with respect to improving the display quality of the liquid crystal display device (viewing angle characteristic improvement), it is necessary to adjust the above-mentioned internal noise, preferably further adjusting the internal scattering property, and more preferable. At the same time, by setting the surface haze and / or reflectivity within a suitable range, the contrast in the bright room is improved and the most preferable effect can be exhibited.

  The translucent fine particles may be monodispersed organic fine particles or inorganic fine particles. As the particle size does not vary, the scattering property varies less and the haze can be easily designed. As the translucent fine particles, plastic beads are preferred, and those having particularly high transparency and a difference in refractive index from the translucent resin are preferred.

As organic fine particles, polymethyl methacrylate beads (refractive index 1.49), acrylic-styrene copolymer beads (refractive index 1.54), melamine beads (refractive index 1.57), polycarbonate beads (refractive index 1.57). ), Styrene beads (refractive index 1.60), cross-linked polystyrene beads (refractive index 1.61), polyvinyl chloride beads (refractive index 1.60), benzoguanamine-melamine formaldehyde beads (refractive index 1.68), etc. It is done. As the inorganic fine particles, silica beads (refractive index 1.44 to 1.46), alumina beads (refractive index 1.63), and the like are used.
It is preferable to contain 3-30 mass parts of translucent fine particles with respect to 100 mass parts of translucent resin, More preferably, it is 5-20 mass parts. If it is less than 3 parts by mass, the scattering property is insufficient, and if it exceeds 30 parts by mass, image quality blurring and surface turbidity are likely to occur.

  In the case of the above translucent fine particles, since the translucent fine particles easily settle in the resin composition (translucent resin), an inorganic filler such as silica may be added to prevent sedimentation. Good. As the amount of the inorganic filler added increases, it is more effective in preventing the sedimentation of the translucent fine particles, but adversely affects the transparency of the coating film. Therefore, it is preferable that an inorganic filler having a particle size of 0.5 μm or less is contained in an amount of less than 0.1% by mass so as not to impair the transparency of the coating film with respect to the translucent resin.

(Translucent resin)
As the translucent resin, three types of resins that are mainly cured by ultraviolet rays and electron beams, that is, an ionizing radiation curable resin, a mixture of an ionizing radiation curable resin and a thermoplastic resin and a solvent, and a thermosetting resin are used. Is done. In order to impart hard coat properties, an ionizing radiation curable resin is preferably the main component.

The thickness of the light diffusion layer is usually 1.5 μm to 30 μm, preferably 3 μm to 20 μm. In general, the light diffusing layer also functions as a hard coat layer. However, if the thickness of the light diffusing layer is 1.5 μm or more, the hard coat property is sufficient. If the thickness is 30 μm or less, there is no problem in curling and brittleness, which is a preferable direction.

  When providing the low refractive index layer, the refractive index of the translucent resin is preferably 1.46 to 2.00, more preferably 1.48 to 1.90, and further preferably 1.50. 1.80. The refractive index of the translucent resin is an average value of the light diffusion layer measured without including the translucent fine particles. If the refractive index of the light diffusion layer is not too small, the antireflection property will not be lowered. If the refractive index is not too large, the color of the reflected light does not become strong, which is a preferable direction. From this point, the above range is preferable. The refractive index of the light diffusion layer is set to a desired value in terms of antireflection properties and reflected light color.

  The resin used for the translucent resin is preferably a polymer having a saturated hydrocarbon or polyether as a main chain, and more preferably a polymer having a saturated hydrocarbon as a main chain. The translucent resin is preferably crosslinked. The polymer having a saturated hydrocarbon as the main chain is preferably obtained by a polymerization reaction of an ethylenically unsaturated monomer. In order to obtain a crosslinked resin, it is preferable to use a monomer having two or more ethylenically unsaturated groups.

  Examples of the monomer having two or more ethylenically unsaturated groups include esters of polyhydric alcohol and (meth) acrylic acid {for example, ethylene glycol di (meth) acrylate, 1,4-cyclohexanediacrylate, pentaerythritol tetra ( (Meth) acrylate, pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolethane tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipenta Erythritol hexa (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,3,5-cyclohexanetriol trimethacrylate, polyurethane polyacrylate, poly Ester polyacrylates, etc.], vinylbenzene derivatives (for example, 1,4-divinylbenzene, 4-vinylbenzoic acid-2-acryloylethyl ester, 1,4-divinylcyclohexanone), vinyl sulfone (for example, divinyl sulfone), acrylamide ( For example, methylenebisacrylamide) and methacrylamide. Among these, an acrylate or methacrylate monomer having at least three functional groups, and further an acrylate monomer having at least five functional groups are preferable from the viewpoint of film hardness, that is, scratch resistance. A mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate is commercially available and is particularly preferably used.

  These monomers having an ethylenically unsaturated group can be cured by a polymerization reaction by ionizing radiation or heat after being dissolved in a solvent, coated and dried together with various polymerization initiators and other additives.

  Instead of or in addition to the monomer having two or more ethylenically unsaturated groups, a cross-linked structure resulting from the reaction of the cross-linkable group may be introduced into the translucent resin. Examples of the crosslinkable group include an isocyanate group, an epoxy group, an aziridine group, an oxazoline group, an aldehyde group, a carbonyl group, a hydrazine group, a carboxyl group, a methylol group, and an active methylene group. Vinylsulfonic acid, acid anhydride, cyanoacrylate derivative, melamine, etherified methylol, ester and urethane, and metal alkoxide such as tetramethoxysilane can also be used as a monomer for introducing a crosslinked structure. A functional group that exhibits crosslinkability as a result of the decomposition reaction, such as a block isocyanate group, may be used. That is, in the present invention, the crosslinkable group may not react immediately but may exhibit reactivity as a result of decomposition. These binders having a crosslinkable group can form a crosslinked structure by heating after coating.

  In addition to the polymer, the translucent resin is preferably formed from a monomer having a high refractive index and / or metal oxide ultrafine particles having a high refractive index.

  Examples of the high refractive index monomer include bis (4-methacryloylthiophenyl) sulfide, vinyl naphthalene, vinyl phenyl sulfide, 4-methacryloxyphenyl-4′-methoxyphenyl thioether and the like.

Examples of the metal oxide ultrafine particles having a high refractive index include at least one oxide selected from zirconium, titanium, aluminum, indium, zinc, tin, and antimony, and have a particle size of 100 nm or less, preferably 50 nm. The following fine particles are preferable. The metal oxide ultrafine particles having a high refractive index are preferably oxide ultrafine particles of at least one metal selected from aluminum, zirconium, zinc, titanium, indium and tin. Specific examples include ZrO ₂ and TiO _2. Al ₂ O ₃ , In ₂ O ₃ , ZnO, SnO ₂ , Sb ₂ O ₃ , ITO and the like. Among these, ZrO ₂ is particularly preferably used.

  The addition amount of the high refractive index monomer and the metal oxide ultrafine particles is preferably 10 to 90% by mass, more preferably 20 to 80% by mass, based on the total mass of the translucent resin.

  The light diffusion layer is preferably formed by coating on a transparent base film that also serves as a protective film for the polarizing film, preferably a cellulose acetate film. The solvent of the coating solution for forming the light diffusion layer is transparent to prevent excessive penetration of the diffusion layer component into the transparent base film and to ensure adhesion between the diffusion layer and the transparent base film. It is composed of at least one solvent that dissolves a base film (for example, a triacetyl cellulose film) and at least one solvent that does not dissolve a transparent base film. More preferably, at least one of the solvents that dissolve the transparent substrate film has a higher boiling point than at least one of the solvents that do not dissolve the transparent substrate film. More preferably, the boiling point temperature difference between the solvent having the highest boiling point among the solvents that dissolve the transparent substrate film and the solvent having the highest boiling point among the solvents that do not dissolve the transparent substrate film is 30 ° C. or more. Yes, most preferably 40 ° C or higher.

  As a solvent for dissolving the transparent substrate film (preferably triacetyl cellulose), ethers having 3 to 12 carbon atoms, specifically, dibutyl ether, dimethoxymethane, dimethoxyethane, diethoxyethane, propylene oxide, 1 1,4-dioxane, 1,3-dioxolane, 1,3,5-trioxane, tetrahydrofuran, anisole, phenetol, etc .; ketones having 3 to 12 carbon atoms, specifically acetone, methyl ethyl ketone, diethyl ketone, dipropyl Ketones, diisobutyl ketone, cyclopentanone, cyclohexanone, methylcyclohexanone, methylcyclohexanone, etc .; esters having 3 to 12 carbon atoms, specifically, ethyl formate, propyl formate, n-pentyl formate, methyl acetate, ethyl acetate , Methyl propionate Propion brewed ethyl, n-pentyl acetate, γ-ptyrolactone, etc .; organic solvents having two or more functional groups, specifically, methyl 2-methoxyacetate, methyl 2-ethoxyacetate, ethyl 2-ethoxyacetate, 2 -Ethyl ethoxypropionate, 2-methoxyethanol, 2-propoxyethanol, 2-butoxyethanol, 1,2-diacetoxyacetone, acetylacetone, diacetone alcohol, methyl acetoacetate, and ethyl acetoacetate. These may be used alone or in combination of two or more. The solvent for dissolving the transparent substrate is preferably a ketone solvent.

As a solvent that does not dissolve the transparent substrate film (preferably triacetyl cellulose), methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, 1-pentanol, 2-methyl- Examples include 2-butanol, cyclohexanol, isobutyl acetate, methyl isobutyl ketone, 2-octanone, 2-pentanone, 2-hexanone, 2-heptanone, 3-pentanone, 3-heptanone, 4-heptanone, and toluene. These may be used alone or in combination of two or more.

  The mass ratio (A / B) of the total amount (A) of the solvent that dissolves the transparent substrate film and the total amount (B) of the solvent that does not dissolve the transparent substrate film is preferably 5/95 to 50/50, more preferably. Is 10/90 to 40/60, more preferably 15/85 to 30/70.

  As a method for curing the ionizing radiation curable resin composition as described above, the ionizing radiation curable resin composition can be cured by a normal curing method, that is, by irradiation with electron beams or ultraviolet rays.

  For example, in the case of electron beam curing, 50 to 1000 KeV emitted from various electron beam accelerators such as a Cockrowalton type, a bandegraph type, a resonant transformation type, an insulating core transformer type, a linear type, a dynamitron type, and a high frequency type. Preferably, an electron beam having an energy of 100 to 300 KeV is used, and in the case of ultraviolet curing, ultraviolet rays emitted from light such as an ultra-high pressure mercury lamp, a high-pressure mercury lamp, a low-pressure mercury lamp, a carbon arc, a xenon arc, and a metal halide lamp are used. it can.

(Photoinitiator)
Examples of photo radical polymerization initiators include acetophenones, benzoins, benzophenones, phosphine oxides, ketals, anthraquinones, thioxanthones, azo compounds, peroxides (JP-A-2001-139663, etc.), 2, Examples include 3-dialkyldione compounds, disulfide compounds, fluoroamine compounds, aromatic sulfoniums, lophine dimers, onium salts, borate salts, active esters, active halogens, inorganic complexes, and coumarins.

  Examples of acetophenones include 2,2-dimethoxyacetophenone, 2,2-diethoxyacetophenone, p-dimethylacetophenone, 1-hydroxy-dimethylphenylketone, 1-hydroxy-dimethyl-p-isopropylphenylketone, 1-hydroxy Cyclohexyl phenyl ketone, 2-methyl-4-methylthio-2-morpholinopropiophenone, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone, 4-phenoxydichloroacetophenone, 4-t- Butyl-dichloroacetophenone and the like are included.

  Specific examples of the active halogens include Wakabayashi et al., “Bull Chem. Soc Japan”, 42, 2924 (1969), US Pat. No. 3,905,815, and JP-A-5-27830. Publication, M.M. P. The compounds described in “Jurnal of Heterocyclic Chemistry” by Hutt, Vol. 1 (No. 3) (1970) and the like, and particularly, oxazole compounds substituted with a trihalomethyl group and s-triazine compounds are exemplified. More preferred are s-triazine derivatives in which at least one mono-, di- or trihalogen-substituted methyl group is bonded to the s-triazine ring.

Specific examples include various s-triazine compounds and oxathiazole compounds, such as 2- (p-methoxyphenyl) -4,6-bis (trichloromethyl) -s-triazine, 2- (p -Methoxyphenyl) -4,6-bis (trichloromethyl) -s-triazine, 2- (p-styrylphenyl) -4,6-bis (trichloromethyl) -s-triazine, 2- (3-Br-4 -Di (ethyl acetate) amino) phenyl) -4,6-bis (trichloromethyl) -s-triazine, 2-trihalomethyl-5- (p-methoxyphenyl) -1,3,4-oxadiazole included.

  Specifically, Nos. In p14 to p30 in JP-A-58-15503, p6-p10 in JP-A-55-77742, and p287 in JP-B-60-27673. 1-No. 8, No. pp. 443 to p444 of JP-A-60-239736. 1-No. 17, U.S. Pat. No. 4,701,399. Compounds such as 1-19 are particularly preferred.

  Specific examples of the active halogens are as follows.

These initiators may be used alone or in combination.
“Latest UV Curing Technology”, Technical Information Association, 1991, p. 159 and Kiyotsugu Kato, “Ultraviolet Curing System”, published in 1989, General Technology Center, p. Various examples are also described in 65-148 and are useful in the present invention.

  As a commercially available photo radical polymerization initiator, “Kayacure (DETX-S, BP-100, BDDK, CTX, BMS, 2-EAQ, ABQ, CPTX, EPD, ITX, QTX, BTC” manufactured by Nippon Kayaku Co., Ltd. , MCA, etc.), “Irgacure (651, 184, 500, 907, 369, 1173, 2959, 4265, 4263, etc.)” manufactured by Ciba Specialty Chemicals Co., Ltd., “Esacure (KIP100F, KB1) manufactured by Sartomer, Inc. , EB3, BP, X33, KT046, KT37, KIP150, TZT) "and the like, and combinations thereof are preferable examples.

  It is preferable to use a photoinitiator in the range of 0.1-15 mass parts with respect to 100 mass parts of polyfunctional monomers, More preferably, it is the range of 1-10 mass parts.

[Low refractive index layer]
In the present invention, the object of the present invention can be achieved by providing at least one light diffusing layer in the range described above, but the refractive index lower than the refractive index of the layer adjacent to the outermost layer. By coating the layer with an appropriate film thickness, antireflection performance can be obtained, reflection of outside light can be suppressed, and contrast in a bright room environment can be increased. This is preferable.

  Next, the material for forming the low refractive index layer will be described below.

(Curable composition)
The low refractive index layer of the present invention is formed by applying and curing a curable composition containing a fluorine-containing compound as a main component or a monomer having a plurality of bonding groups in the molecule and low refractive index particles. Thus, the refractive index is adjusted in the range of 1.20 to 1.50. 1.25 to 1.45 are preferable, and 1.30 to 1.40 are more preferable.

Preferred embodiments of the cured product composition include:
(1) A composition containing a fluorine-containing polymer having a crosslinkable or polymerizable functional group,
(2) a composition comprising as a main component a hydrolysis-condensation product of a fluorine-containing organosilane compound;
(3) A composition containing a monomer having two or more ethylenically unsaturated groups and inorganic fine particles having a hollow structure.

  Thereby, compared with the low refractive index layer using magnesium fluoride or calcium fluoride, an optical film excellent in scratch resistance can be obtained even when used as the outermost layer. The dynamic friction coefficient of the cured low refractive index layer surface is preferably 0.03 to 0.15, and the contact angle with water is preferably 90 to 120 °.

(1) Composition containing a fluorine-containing polymer having a crosslinkable or polymerizable functional group As the fluorine-containing polymer having a crosslinkable or polymerizable functional group, a fluorine-containing monomer and a crosslinkable or polymerizable functional group And a copolymer with a monomer having. Examples of the fluorine-containing monomer include fluoroolefins (for example, fluoroethylene, vinylidene fluoride, tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoro-2,2-dimethyl-1,3-dioxole, etc.), (meth) Partial or fully fluorinated alkyl ester derivatives of acrylic acid [for example, “Biscoat 6FM” {manufactured by Osaka Organic Chemical Industry Co., Ltd.}, “M-2020” {manufactured by Daikin Industries, Ltd.}, etc.], complete or partially fluorinated And vinyl ethers.

  As one example of the monomer for imparting a crosslinkable group, a (meth) acrylate monomer having a crosslinkable functional group in the molecule in advance, such as glycidyl methacrylate, can be mentioned. In another embodiment, a monomer having a functional group such as a hydroxyl group is used, and after synthesizing the fluorine-containing copolymer, a monomer that further introduces a crosslinkable or polymerizable functional group by modifying these substituents is used. Is the method. These monomers include (meth) acrylate monomers having a carboxyl group, a hydroxyl group, an amino group, a sulfonic acid group, etc. {for example, (meth) acrylic acid, methylol (meth) acrylate, hydroxyalkyl (meth) acrylate, allyl acrylate, etc.} Is mentioned. The latter embodiment is disclosed in JP-A-10-25388 and JP-A-10-147739.

  From the viewpoints of solubility, dispersibility, coatability, antifouling property, antistatic property and the like, the above-mentioned fluoropolymer can contain components that can be suitably copolymerized. In particular, for imparting antifouling properties and slipperiness, it is preferable to introduce a silicone component, which can be introduced into both the main chain and the side chain.

  The polysiloxane partial structure introduction method to the fluorine-containing polymer main chain is, for example, an azo group-containing polysiloxane amide described in JP-A-6-93100 [commercially available "VPS-0501", "VPS-1001" {product Name; manufactured by Wako Pure Chemical Industries, Ltd.}] and the like. The method of introducing into the side chain of the fluoropolymer is, for example, “J. Appl. Polym. Sci.”, 2000, p. 78, 1955, as disclosed in JP-A-56-28219 and the like, polysiloxanes having a reactive group at one end [for example, “Silaplane” series {manufactured by Chisso Corporation}, etc.] are polymerized. It can be synthesized by a method of introducing or a method of polymerizing a polysiloxane-containing silicon macromer, and both methods can be preferably used.

  As described in JP 2000-17028 A, a curing agent having a polymerizable unsaturated group may be used in combination with the fluorine-containing polymer. Further, as described in JP-A-2002-145952, combined use with a compound having a fluorine-containing polyfunctional polymerizable unsaturated group is also preferable. Examples of the compound having a polyfunctional polymerizable unsaturated group include the above-described monomers having two or more ethylenically unsaturated groups. Moreover, the hydrolysis-condensation product of the organolane described in Unexamined-Japanese-Patent No. 2004-170901 is also preferable, and the hydrolysis-condensation product of the organosilane containing a (meth) acryloyl group is especially preferable.

  These compounds are particularly preferred because they have a large combined effect for improving scratch resistance, particularly when a compound having a polymerizable unsaturated group is used in the fluoropolymer main body.

  When the fluorine-containing polymer itself does not have sufficient curability, necessary curability can be imparted by blending a crosslinkable compound. For example, when the fluoropolymer main body contains a hydroxyl group, it is preferable to use various amino compounds as curing agents. The amino compound used as the crosslinkable compound is, for example, a compound containing one or both of a hydroxyalkylamino group and an alkoxyalkylamino group in total, specifically, for example, a melamine compound, Examples include urea compounds, benzoguanamine compounds, glycoluril compounds, and the like. For curing these compounds, an organic acid or a salt thereof is preferably used.

  Specific examples of these fluoropolymers are described in JP2003-222702A, JP2003-183322A, and the like.

(2) Composition mainly composed of hydrolyzed condensate of fluorine-containing organosilane compound The composition mainly composed of hydrolyzed condensate of fluorine-containing organosilane compound also has a low refractive index and hardness of the coating film surface. Is preferable. A condensate of a tetraalkoxysilane with a hydrolyzable silanol-containing compound at one or both ends with respect to the fluorinated alkyl group is preferred. Specific compositions are described in JP-A Nos. 2002-265866 and 2002-317152.

(3) A composition containing a monomer having two or more ethylenically unsaturated groups and inorganic fine particles having a hollow structure As yet another preferred embodiment, a low refractive index layer comprising low refractive index particles and a binder can be mentioned. . The low refractive index particles may be organic or inorganic, but particles having pores inside are preferable. Specific examples of the hollow particles are described in the silica-based particles described in JP-A-2002-79616. The particle refractive index is preferably 1.15 to 1.40, more preferably 1.20 to 1.30. Examples of the binder include monomers having two or more ethylenically unsaturated groups described in the section of the light diffusion layer.

  In the low refractive index layer of the present invention, it is preferable to add the polymerization initiator described in the above section of the light diffusion layer. When a radically polymerizable compound is contained, 1 to 10 parts by mass, preferably 1 to 5 parts by mass of a polymerization initiator can be used with respect to the compound.

(Inorganic particles)
In the low refractive layer of the present invention, inorganic particles can be used in combination. In order to impart scratch resistance, fine particles having a particle size of 15% to 150%, preferably 30% to 100%, more preferably 45% to 60% of the thickness of the low refractive index layer can be used. .

(Other additives)
For the purpose of imparting antifouling properties, water resistance, chemical resistance, slipping properties, etc., a known polysiloxane-based or fluorine-based antifouling agent, slipping agent, etc. are appropriately used for the low refractive index layer of the present invention. Can be added.

In the present invention, the film having a light diffusing layer has a vertical peeling charge of −200 pc (picocoulomb) / cm ² to +200 pc measured at room temperature and normal humidity with respect to either triacetyl cellulose (TAC) or polyethylene terephthalate (PET). / Cm ² is preferable. More preferably, it is −100 pc / cm to +100 pc / cm ² , further preferably −50 pc / cm ² to +50 pc / cm ² , and most preferably 0 pc / cm ² . Here, the unit pc is 10 ⁻¹² coulomb. More preferably, the vertical peel charge measured at room temperature of 10% RH is −200 pc / cm ² to +200 pc / cm ² , more preferably −50 pc / cm ² to +50 pc / cm ² , most preferably 0 pc / cm ^{2. 2} .

The measuring method of the vertical peeling charge is as follows.
The measurement sample is left in advance for 2 hours or more in an environment of measurement temperature and humidity. The measuring device is composed of a table on which a measurement sample is placed and a head that can hold a counterpart film and can repeatedly press and peel the measurement sample from above, and an electrometer for measuring the charge amount is connected to the head. A film having antiglare and antireflection performance to be measured is placed on a table, and TAC or PET is attached to the head. After neutralizing the measurement portion, the head is pressure-bonded to the measurement sample and peeled off repeatedly, and the charge values at the first peeling and the fifth peeling are read and averaged. This is repeated for three samples by changing the sample, and the average of all the samples is defined as vertical peeling charge.

Surface resistivity of a film having a diffusion layer of the present invention is preferably 1 × 10 ⁷ Ω / □ or more 1 × 10 ¹⁵ Ω / □ or less, 1 × 10 ⁷ Ω / □ or more 1 × 10 ¹⁴ Ω / □ or less More preferably, it is 1 × 10 ⁷ Ω / □ or more and 1 × 10 ¹³ Ω / □ or less.

  The measuring method of the surface resistance value is a circular electrode method described in JIS. That is, the current value one minute after voltage application is read to determine the surface resistance value (SR).

In order to reduce the surface resistance value, it is preferable to provide an antistatic layer. A preferred layer structure is shown below. In the following layer configuration, the base film also serves as the second protective film.
• Base film / light diffusion layer / antistatic layer / low refractive index layer • Base film / antistatic layer / light diffusion layer / low refractive index layer • Base film / light diffusion layer (antistatic layer) / low refraction Index layer-Base film / light diffusion layer / medium refractive index layer (antistatic layer) / high refractive index layer / low refractive index layer-Base film / light diffusion layer (antistatic layer) / medium refractive index layer / high Refractive index layer / low refractive index layer-base film / antistatic layer / light diffusion layer / medium refractive index layer / high refractive index layer / low refractive index layer-base film / light diffusion layer / medium refractive index layer / high Refractive index layer (antistatic layer) / low refractive index layer

  Note that the low refractive index layer may not be provided, and is not limited to the above configuration. The antistatic layer is preferably a layer containing conductive polymer particles or metal oxide fine particles (for example, ATO, ITO), and can be provided by coating or atmospheric pressure plasma treatment. In the case of providing an antifouling layer, it can be provided in the uppermost layer of the above configuration.

Further, in order to increase the film hardness (for imparting scratch resistance), in addition to thickening the light diffusion layer having hard coat properties described in the present invention, a hard coat layer (in the present invention) It is also preferable to provide at least one layer with or without light diffusibility. The preferred layer structure is as follows. In the following layer configuration, the base film also serves as the second protective film.
-Base film / hard coat layer / light diffusion layer / low refractive index layer- Base film / light diffusion layer / hard coat layer / low refractive index layer It is not limited to the configuration. Furthermore, it is also preferable to combine the antistatic layer.

  The average value in the wavelength region from 450 nm to 650 nm of the integrated reflectance at 5 ° incidence of the film having a light diffusion layer in the present invention is preferably 3.0% or less, more preferably 2.0% or less, and most preferably. Is 1.0% or less.

[Transparent substrate film]
As a material for the transparent substrate film, a transparent resin film, a transparent resin plate, a transparent resin sheet, and the like can be used, but a transparent glass substrate can also be used instead of the transparent substrate film. As transparent resin films, triacetyl cellulose (TAC) film (refractive index 1.48), diacetylene cellulose film, acetate butyrate cellulose film, polyethylene terephthalate (PET) film, polyethersulfone film, polyacrylic resin film Polyurethane resin film, polyester film, polycarbonate film, polysulfone film, polyether film, polymethylpentene film, polyether ketone film, (meth) acrylonitrile film and the like can be used. The thickness is usually about 25 to 200 μm. Preferably, it is 30-100 micrometers, More preferably, it is 40-80 micrometers. Since the transparent substrate film is also used on the outermost surface of the polarizing plate, it is preferable to use a cellulose acetate film generally used as a protective film for the polarizing plate. As the transparent substrate film of the light diffusion layer, a cellulose acetate film having high transparency and a smooth surface is preferable.

(Cellulose acetate film)
In the present invention, it is particularly preferable to use cellulose acetate having an acetylation degree of 59.0 to 61.5% for the transparent substrate film. 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 polymerization degree (DP) of the cellulose ester is preferably 250 or more, and more preferably 290 or more.

  The cellulose acetate used in the present invention preferably has a narrow molecular weight distribution of Mw / Mn (Mw is a mass average molecular weight, Mn is a number average molecular weight) by gel permeation chromatography (GPC). The specific value of Mw / Mn is preferably 1.0 to 1.7, more preferably 1.3 to 1.65, and most preferably 1.4 to 1.6. preferable.

  In general, in cellulose acylate, the substitution degree of the 2,3,6-position hydroxyl groups of the cellulose unit is not evenly distributed by 1/3 each, and the substitution degree of the 6-position hydroxyl group tends to be small. . In the present invention, the degree of substitution of the 6-position hydroxyl group of the cellulose unit of cellulose acylate is preferably 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 32% or more of an acyl group, more preferably 33% or more, and particularly preferably 34% or more. Further, the substitution degree of the 6-position acyl group of the cellulose unit is preferably 0.88 or more. The 6-position hydroxyl group of the cellulose unit may be 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 in addition to the acetyl group. The degree of substitution at each position can be determined by NMR. Examples of the cellulose acylate in the present invention include “0043” to “0044”, “Example” (Synthesis Example 1), “0048” to “0049” (Synthesis Example 2) described in JP-A No. 11-5851, “ The cellulose acetate obtained by the method of “0051” to “0052” (Synthesis Example 3) can be used.

(Organic solvent used in the solvent cast method)
The cellulose acetate film is preferably produced 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 replaced 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 most preferable that it is 40-60 mol%. Methylene chloride is a representative halogenated hydrocarbon. Two or more organic solvents may be mixed and used.

(Plasticizer)
A plasticizer can be added to the cellulose acetate film in order to improve mechanical properties or increase the drying speed. 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 diethylhexyl 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 of the amount of cellulose ester, more preferably 1 to 20% by mass, and most preferably 3 to 15% by mass.

Degradation inhibitors (for example, antioxidants, peroxide decomposers, radical inhibitors, metal deactivators, acid scavengers, amines, etc.) 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 0.01% by mass or more, the effect of a good deterioration preventing agent is exhibited. If the addition amount is 1% by mass or less, problems such as bleeding out (bleeding out) of the deterioration preventing agent to the film surface hardly occur. Examples of particularly preferred deterioration inhibitors include butylated hydroxytoluene (BHT) and tribenzylamine (TBA).

(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. In addition, as described in JP-A-7-333433, it is preferable to provide an undercoat layer. From the viewpoint of maintaining the flatness of the film, the temperature of the cellulose acetate film in these treatments is preferably Tg or lower, specifically 150 ° C. or lower. When using as a transparent protective film of a polarizing plate, it is particularly preferable to carry out acid treatment or alkali treatment, that is, saponification treatment on cellulose acetate, from the viewpoint of adhesiveness to the polarizing film. The surface energy of the obtained cellulose acetate film is preferably 55 mN / m or more, and more preferably 60 mN / m or more and 75 mN / m or less. Moreover, in order to apply | coat uniformly on a cellulose acetate film, it is also preferable to heat-process before coating and to improve the planarity of a cellulose acetate film.

(Saponification treatment)
When producing the polarizing plate of this invention, it is preferable to improve the adhesiveness in an adhesive surface by hydrophilizing the surface of the protective film on the side bonded to the polarizing film.

a. Method of immersing in alkaline solution This is a method of saponifying all surfaces that are reactive with alkali on the entire surface of the film by immersing the film in an alkaline solution under appropriate conditions, and no special equipment is required. From the viewpoint of cost. The alkaline liquid is preferably a sodium hydroxide aqueous solution. A preferred concentration is 0.5 to 3 mol / L, particularly preferably 1 to 2 mol / L. The liquid temperature of a preferable alkali liquid is 30-75 degreeC, Most preferably, it is 40-60 degreeC. The combination of these saponification conditions is preferably a combination of relatively mild conditions, but can be set according to the material and composition of the film and the target contact angle. After being immersed in the alkali solution, it is preferable to neutralize the alkali component by thoroughly washing with water or immersing in a dilute acid so that the alkali component does not remain in the film.

  By saponification treatment, the surface opposite to the surface having the coating layer is hydrophilized. The protective film for polarizing plate is used by adhering the hydrophilic surface of the transparent support to the polarizing film. The hydrophilized surface is effective for improving the adhesiveness with the adhesive layer mainly composed of polyvinyl alcohol.

In the saponification treatment, the lower the contact angle with respect to the surface of the transparent support opposite to the side having the coating layer, the better from the viewpoint of adhesion to the polarizing film, while the dipping method simultaneously has the coating layer. Since it is damaged by alkali from the surface to the inside, it is important to set the minimum reaction conditions. When the contact angle to water of the transparent support on the opposite surface is used as an index of damage to each layer due to alkali, particularly when the transparent support is triacetylcellulose, preferably 10 ° to 50 °, more preferably Is 30 ° to 50 °, more preferably 40 ° to 50 °. If it is 50 degrees or less, since a problem does not arise in adhesiveness with a polarizing film, it is preferable. On the other hand, if it is 10 ° or more, the film is not damaged too much, and the physical strength is maintained, which is preferable.

b. Method for applying alkaline solution As a means for avoiding damage to each film in the above-described immersion method, an alkaline solution is applied only to the surface opposite to the surface having the coating layer under appropriate conditions, heating, washing with water, A drying alkaline solution coating method is preferably used. The application in this case means that an alkaline liquid or the like is brought into contact only with the surface to be saponified, and means that the application is performed by coating, spraying, contact with a belt containing the liquid, or the like. By adopting these methods, a separate facility and process for applying an alkaline solution are required, so that the immersion method (a) is superior from the viewpoint of cost, but the alkaline solution and only the surface to be saponified In order to make contact, a layer using a material weak against an alkaline solution can be used on the opposite surface. For example, a vapor deposition film such as aluminum or a sol-gel film has various effects such as corrosion, dissolution, peeling, etc. caused by an alkali solution. It can be used without problems.

  In any of the saponification methods (a) and (b) above, since each layer can be formed after being unwound from a roll-shaped base film, it can be performed by a series of operations in addition to the film manufacturing process. Good. Furthermore, the polarizing plate can be produced more efficiently than when the same operation is performed on a single wafer by continuously performing the bonding process with the unwound polarizing film.

c. Method of saponification by protecting with a laminate film As in the case (b) above, when the coating layer is insufficient in resistance to an alkaline solution, the laminate film is formed on the surface on which the final layer is formed after the final layer is formed. By dipping in an alkaline solution after bonding, only the surface of the triacetyl cellulose opposite to the surface on which the final layer is formed can be hydrophilized, and then the laminate film can be peeled off. Even in this method, the hydrophilic treatment necessary for the polarizing plate protective film can be applied only to the surface opposite to the surface on which the final layer of the triacetyl cellulose film is formed without damaging the coating layer. Compared with the method (b) above, there is an advantage that a laminate film is generated as a waste, but an apparatus for applying a special alkaline solution is unnecessary.

d. Method of immersing in alkaline solution after forming up to middle layer If the lower layer is resistant to alkaline solution, but the upper layer is insufficiently resistant to alkaline solution, both sides are hydrolyzed by immersing in alkaline solution after forming up to the lower layer However, the upper layer can be formed thereafter. Although the manufacturing process becomes complicated, for example, in the case of a film having a hard coat layer and a low refractive index layer of a fluorine-containing sol-gel film, when having a hydrophilic group, the layer between the hard coat layer and the low refractive index layer There is an advantage that adhesion is improved.

e. Method for forming a coating layer on a previously saponified triacetyl cellulose film Triacetyl cellulose film is saponified by, for example, preliminarily dipping in an alkali solution, and either one of the surfaces is applied directly or via another layer. May be formed. In the case of saponification by dipping in an alkaline solution, the interlayer adhesion with the triacetyl cellulose surface hydrophilized by saponification may deteriorate. In such a case, after saponification, only the surface on which the coating layer is to be formed is treated by corona discharge, glow discharge or the like to remove the hydrophilic surface and then form the coating layer. Further, when the coating layer has a hydrophilic group, the interlayer adhesion may be good.

[Preparation of polarizing plate]
In the present invention, a transparent substrate film such as a cellulose acetate film is disposed on both sides of the polarizing film as a protective film, and a light diffusion layer is formed on at least one of the protective films, or the light diffusion already formed The polarizing plate for a liquid crystal display device of the present invention can be produced by laminating a light diffusion film having a layer on a polarizing film. The transparent substrate film used may be a commercially available cellulose acetate film, but is produced by the above-mentioned solution casting method, and cellulose stretched in the width direction in the form of a roll film at a stretch ratio of 10 to 100%. It is preferable to use an acetate film. Furthermore, in the polarizing plate of the present invention, an optical compensation film having an optically anisotropic layer containing a liquid crystalline compound can be laminated on one protective film, and the protective film can be used as an optical compensation film. It can also be combined.

  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.

  The moisture permeability of the protective film is important for the productivity of the polarizing plate. The polarizing film and the protective film are bonded together with an aqueous adhesive, and the adhesive solvent is dried by diffusing in the protective film. The higher the moisture permeability of the protective film, the faster the drying and the higher the productivity. However, if the protective film is too high, moisture will enter the polarizing film depending on the usage environment (high humidity) of the liquid crystal display device. Polarization ability decreases. The moisture permeability of the protective film is determined by the type and thickness of the transparent substrate film (thickness including a liquid crystal compound when the protective film is an optical compensation film), free volume, hydrophilicity / hydrophobicity, and the like.

Moisture permeability of the protective film in the polarizing plate of the present invention is preferably 100~1000g / m ² · 24hrs, and more preferably a 300~700g / m ² · 24hrs.

  In the case of film formation, the thickness of the transparent substrate film can be adjusted by lip flow rate and line speed, or stretching and compression. Since the moisture permeability varies depending on the main material to be used, it is possible to make a preferable range by adjusting the thickness. In the case of film formation, the free volume of the transparent substrate film can be adjusted by the drying temperature and time. Also in this case, moisture permeability varies depending on the main material to be used, so that a preferable range can be obtained by adjusting the free volume. The hydrophilicity / hydrophobicity of the transparent substrate film can be adjusted by an additive. The moisture permeability can be increased by adding a hydrophilic additive to the free volume, and conversely, the moisture permeability can be lowered by adding a hydrophobic additive. By independently controlling the moisture permeability, a polarizing plate having optical compensation ability can be manufactured at low cost with high productivity.

The slow axis of the transparent substrate film of the optical film or the cellulose acetate film and the transmission axis of the polarizing film can be arranged so as to be substantially parallel.
As the polarizing film, a known polarizing film or a polarizing film cut out from a long polarizing film whose absorption axis is neither parallel nor perpendicular to the longitudinal direction may be used.

  The protective film is usually supplied in a roll form, and it is preferable that the protective film is continuously bonded to the long polarizing film so that the longitudinal directions thereof coincide. Here, the orientation axis (slow axis) of the protective film may be any direction, and the orientation axis of the protective film is preferably parallel to or perpendicular to the longitudinal direction for ease of operation.

  When laminating the protective film and the polarizing film, the slow axis (alignment axis) of at least one protective film (the protective film disposed on the side close to the liquid crystal cell when incorporated in a liquid crystal display device), Although it is possible for the absorption axis (stretching axis) of the polarizing film to intersect, if the slow axis of the protective film and the absorption axis of the polarizing film are parallel to each other, the polarizing plate can prevent dimensional change and curl prevention. The mechanical stability of can be improved. At least two axes of a total of three films of the polarizing film and the pair of protective films, a slow axis of one protective film and an absorption axis of the polarizing film, or a slow axis of the two protective films are substantially parallel. The same effect can be obtained.

(adhesive)
The adhesive between the polarizing film and the protective film is not particularly limited, and examples thereof include PVA resin (including modified PVA such as acetoacetyl group, sulfonic acid group, carboxyl group, oxyalkylene group) and boron compound aqueous solution, Of these, PVA resins are preferred. The thickness of the adhesive layer is preferably 0.01 to 10 μm, particularly preferably 0.05 to 5 μm after drying.

(Integrated manufacturing process of polarizing film and protective film)
The polarizing plate for a liquid crystal display device of the present invention has a drying step for reducing the volatile content rate after stretching the film for polarizing film, and has a protective film bonded to at least one side after drying or during drying. Thereafter, it is preferable to provide a post-heating step. In an aspect in which the protective film also serves as an optical compensation film functioning as an optical compensation layer or a base film of a light diffusion layer, a transparent base material having a protective film having a light diffusion layer on one side and an optical compensation film on the opposite side It is preferable to post-heat after laminating the films.

  As a specific attaching method, during the drying process of the polarizing film film, the protective film is attached to the polarizing film using an adhesive while holding both ends, and then both ends are cut off or both ends after drying. There is a method of releasing the polarizing film from the holding part, cutting off both ends of the film, and then attaching a protective film. As a method for cutting the ears, a general technique such as a method of cutting with a cutter such as a blade or a method of using a laser can be used. After bonding, it is preferable to heat in order to dry the adhesive and improve the polarization performance. The heating condition varies depending on the adhesive, but in the case of an aqueous system, it is preferably 30 ° C. or higher, more preferably 40 ° C. or higher and 100 ° C. or lower, and further preferably 50 ° C. or higher and 90 ° C. or lower. It is more preferable in terms of performance and production efficiency that these processes are manufactured in a consistent line.

(Performance of polarizing plate)
The optical properties and durability (short-term and long-term storage stability) of a polarizing plate for a liquid crystal display device comprising a protective film, a polarizing film and a light diffusion layer related to the present invention are commercially available super high contrast products {for example, It is preferable to have performance equivalent to or better than “HLC2-5618” manufactured by Sanritz). Specifically, the visible light transmittance is 42.5% or more, and the degree of polarization {(Tp−Tc) / (Tp + Tc)} ^1/2 ≧ 0.9995 (where Tp is parallel transmittance and Tc is orthogonal transmission) The absolute value of the change rate (%) of the light transmittance before and after being left at 60 ° C. and 90% RH for 500 hours and 80 ° C. for 500 hours in a dry atmosphere is 3 or less, Furthermore, the absolute value of the change rate (%) of the polarization degree is preferably 1 or less, more preferably 0.1 or less.

(Optical compensation film)
The optical compensation film is used for eliminating image coloring or expanding the viewing angle in a liquid crystal display device. In the present invention, as described above, the optical compensation film is not an essential member. For example, in an aspect in which birefringence is added to one or both of the pair of protective films of the polarizing plate to function as the optical compensation film. It is unnecessary.

  The in-plane retardation value (Re) of the entire optical compensation film is preferably 20 to 200 nm. The retardation value (Rth) in the thickness direction of the entire optical compensation film is preferably 50 to 500 nm.

  Examples of the optical compensation film include an optical compensation film made of a stretched birefringent polymer film and an optical compensation film having an optical compensation film formed from a low-molecular or high-molecular liquid crystalline compound on a transparent substrate film. Any can be used in the invention. In addition to a laminate of two optical compensation films, an optical compensation film having a laminated structure can also be used. Regarding the optical compensation film having a laminated structure, in consideration of the thickness, an optical compensation film made of a coating-type laminate is preferable to an optical compensation film made of a laminate of stretched polymer films.

  The polymer film used for the optical compensation film may be a stretched polymer film or a combination of a coating type polymer layer and a polymer film. As a material for the polymer film, a synthetic polymer (for example, polycarbonate, polysulfone, polyethersulfone, polyacrylate, polymethacrylate, norbornene resin, triacetyl cellulose) is generally used.

(Optical compensation film made of liquid crystalline compound)
Next, an optical compensation film having an optical compensation film made of a liquid crystalline compound will be described in detail.
Since the liquid crystalline compound has various alignment forms, the optical compensation film made of the liquid crystalline compound exhibits a desired optical property by a single layer or a laminate of a plurality of layers. That is, the optical compensation film may be an embodiment composed of a base film and one or more optical compensation films formed on the base film. The retardation value of the optical compensation film as a whole can be adjusted by the optical anisotropy of the optical compensation film. Moreover, there are a low molecular weight type and a high molecular weight type used in the present invention, and both can be used.

(Optical compensation film made of discotic liquid crystalline compound)
As the liquid crystalline compound for forming the optical compensation film, a discotic liquid crystalline compound can be used. The discotic liquid crystalline compound is preferably aligned substantially perpendicular to the polymer film surface (average inclination angle in the range of 50 to 90 °).

  Discotic liquid crystalline compounds are described in various documents {C.I. Destrade et al., “Mol. Crysr. Liq. Cryst.”, 71, p. 111 (1981); No. of “Chemical Review” published by the Chemical Society of Japan. 22, “Liquid Crystal Chemistry”, Chapter 5, Chapter 10, Section 2 (1994); Kohne et al., “Angew. Chem. Soc. Chem. Comm.”, P. 1794 (1985); Zhang et al., “J. Am. Chem. Soc.”, 116, p. 2655 (1994)} can be employed. Regarding the polymerization of the discotic liquid crystalline compound, those described in JP-A-8-27284 can be employed.

The discotic liquid crystalline compound preferably has a polymerizable group so that it can be fixed by polymerization. For example, a structure in which a polymerizable group is bonded as a substituent to the discotic core of a discotic liquid crystalline compound can be considered. However, when the polymerizable group is directly connected to the discotic core, the alignment state is maintained in the polymerization reaction. It becomes difficult. Therefore, a structure having a linking group between the discotic core and the polymerizable group is preferable. That is, the discotic liquid crystalline compound having a polymerizable group is preferably a compound represented by the following general formula (1).
General formula (1): D (-LP) n
In the formula, 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.

  Preferred specific examples of the discotic core (D), the divalent linking group (L) and the polymerizable group (P) in the general formula (1) are (D1 described in JP-A-2001-4837, respectively). ) To (D15), (L1) to (L25), and (P1) to (P18), and the contents described in the publication can be preferably used.

These liquid crystalline compounds are preferably substantially uniformly oriented in the optical compensation film, more preferably fixed in a substantially uniformly oriented state, and liquid crystals are obtained by a polymerization reaction. Most preferably, the active compound is immobilized. In the case of a discotic liquid crystalline compound having a polymerizable group, it is preferable to substantially align vertically. Substantially perpendicular means that the average angle (average tilt angle) between the disc surface of the discotic liquid crystalline compound and the surface of the optical compensation film is in the range of 50 ° to 90 °. The discotic liquid crystalline compound may be obliquely aligned or may be gradually changed (hybrid alignment). Even in the case of oblique orientation or hybrid orientation, the average inclination angle is preferably 50 ° to 90 °.

  The optical compensation film is preferably formed by applying a coating liquid containing a liquid crystalline compound and the following polymerization initiator and other additives onto the alignment film.

  As a solvent used for preparing 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 etc.), alkyl halides (eg chloroform, dichloromethane). Etc.), esters (eg methyl acetate, butyl acetate etc.), ketones (eg acetone, methyl ethyl ketone etc.), ethers (eg tetrahydrofuran, 1,2-dimethoxyethane etc.). 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 (for example, extrusion coating method, direct gravure coating method, reverse gravure coating method, die coating method, etc.).

(Fixation of alignment state of liquid crystalline compounds)
The aligned liquid crystalline compound is preferably fixed while maintaining the alignment state. The immobilization is preferably carried out by a polymerization reaction of a polymerizable group introduced into the liquid crystal compound. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator, and a photopolymerization reaction is more preferable. Examples of the photopolymerization initiator include α-carbonyl compounds (for example, those described in US Pat. Nos. 2,367,661 and 2,367,670) and acyloin ethers (for example, those described in US Pat. No. 2,448,828). ), Α-hydrocarbon-substituted aromatic acyloin compounds (for example, those described in US Pat. No. 2,722,512), polynuclear quinone compounds (for example, those described in US Pat. Nos. 3,046,127 and 2,951,758), Combinations of triarylimidazole dimer and p-aminophenyl ketone (for example, those described in US Pat. No. 3,549,367), acridine and phenazine compounds (for example, those described in JP-A-60-105667, US Pat. 4239850) and oxadiazole compounds (examples) For example, those described in US Pat. No. 4,212,970).

It is preferable that the usage-amount of a photoinitiator is 0.01-20 mass% of solid content of a coating liquid, and it is more preferable that it is 0.5-5 mass%. Light irradiation for the polymerization of the liquid crystalline compound is preferably performed using ultraviolet rays. The irradiation energy is preferably ^{20mJ / cm 2 ~50J / cm 2} , further preferably 100 to 800 mJ / cm ^2. In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions. The thickness of the optical compensation film is preferably 0.1 to 10 μm, and more preferably 0.5 to 5 μm.

(Alignment film)
In forming the optical compensation film, it is preferable to use an alignment film in order to align the liquid crystalline compound. The alignment film is an organic compound (for example, ω-triconic acid) formed by rubbing treatment of an organic compound (preferably polymer), oblique deposition of an inorganic compound, formation of a layer having a microgroup, or Langmuir-Blodgett method (LB film). , Dioctadecyldimethylammonium chloride, methyl stearylate, etc.). 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. An alignment film formed by a polymer rubbing treatment is particularly preferable.

  The rubbing process is carried out by rubbing the surface of the polymer layer several times in a certain direction with paper or cloth. The type of polymer used for the alignment film can be determined according to the alignment (particularly the average tilt angle) of the liquid crystal compound. For example, in order to align the liquid crystalline compound horizontally, a polymer that does not decrease the surface energy of the alignment film (ordinary alignment polymer) is used. Specific types of polymers are described in various documents about liquid crystal cells or optical compensation films. Any of the alignment films preferably has a polymerizable group for the purpose of improving the adhesion between the liquid crystal compound and the transparent support. The polymerizable group can be introduced by introducing a repeating unit having a polymerizable group in the side chain or as a substituent of a cyclic group. It is more preferable to use an alignment film that forms a chemical bond with the liquid crystal compound at the interface. Such an alignment film is described in JP-A-9-152509.

  The thickness of the alignment film is preferably 0.01 to 5 μm, and more preferably 0.05 to 1 μm.

  In addition, after aligning the liquid crystalline compound using the alignment film, the liquid crystalline compound is fixed in the alignment state to form an optical compensation film, and only the optical compensation film is transferred onto the transparent substrate film. Good.

  The base film that supports the optical compensation film is not particularly limited, and various polymer films can be used. For example, a triacetyl cellulose, norbornene resin, etc. are mentioned. Further, as described above, the protective film of the polarizing plate may also serve as the support for the optical compensation film. About the specific example of the material of the base film in this aspect, it is the same as the specific example of the material of the protective film of a polarizing plate, and is as above-mentioned.

[Example 1]
A liquid crystal display device having the configuration shown in FIG. 1 was produced. That is, from the observation direction (above), the upper polarizing plate 1, the upper optical compensation film 14, the liquid crystal cell (upper substrate 5, liquid crystalline molecules 6 included in the liquid crystal layer, lower substrate 7), lower optical compensation film 24, lower side A polarizing plate 2 was laminated, and a backlight (not shown) using a cold cathode fluorescent lamp was disposed below the lower polarizing plate.

  Below, the manufacturing method of each used member is demonstrated.

(Production of ECB mode liquid crystal cell)
The liquid crystal cell had a cell gap of 3.5 μm, a liquid crystal material having a positive dielectric constant anisotropic layer was sealed between the substrates by drop injection, and Δn · d of the liquid crystal layer 7 was 300 nm. The liquid crystal material has a positive dielectric anisotropy, a refractive index anisotropy, and a liquid crystal having Δn = 0.0854 (589 nm, 20 ° C.) and Δε = + 8.5 (for example, MLC-9100 manufactured by Merck) is used. did. In addition, the crossing angle of the liquid crystal cell is 0 °, and the upper and lower substrate rubbing directions (orientation control direction) of the liquid crystal cell are later aligned with the slow axis of the support (the direction parallel to the casting direction). ) And 45 °. The polarizing plate absorption axis intersected the liquid crystal cell alignment direction (rubbing direction) approximately 45 °, and the crossing angle of the upper and lower polarizing plate absorption axes was approximately 90 ° crossed Nicol.

(Production of cellulose acetate film)
The following composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose acetate solution.

(Cellulose acetate solution composition)
Cellulose acetate having an acetylation degree of 60.7 to 61.1% 100 parts by weight Triphenyl phosphate (plasticizer) 7.8 parts by weight Biphenyl diphenyl phosphate (plasticizer) 3.9 parts by weight Methylene chloride (first solvent) 336 parts by weight Methanol (second solvent) 29 parts by mass 1-butanol (third solvent) 11 parts by mass

The obtained dope was cast using a band stretching machine. After the film surface temperature on the band reached 40 ° C., the film was dried with warm air of 70 ° C. for 1 minute, and the film from the band was dried with 140 ° C. drying air for 10 minutes, and the residual solvent amount was 0.3% by mass. A cellulose acetate film (thickness: 80 μm) was prepared. About the produced cellulose acetate film (transparent support body, protective film), Re value and Rth value in wavelength 546nm were measured by the above-mentioned method. Re was 3 nm and Rth was 8 nm.
The produced cellulose acetate film was immersed in a 2.0 mol / L potassium hydroxide solution (25 ° C.) for 2 minutes, neutralized with sulfuric acid, washed with pure water, and then dried. The surface energy of the cellulose acetate film was determined by a contact method and found to be 63 mN / m. Thus, the cellulose acetate film for protective films was produced.

(Preparation of alignment film for optical compensation film)
On this cellulose acetate film, a coating solution having the following composition was applied at 28 mL / m ² with a # 16 wire bar coater. Drying was performed with warm air of 60 ° C. for 60 seconds and further with warm air of 90 ° C. for 150 seconds. Next, the formed film was rubbed in the same direction with respect to the in-plane slow axis (parallel to the casting direction) of the cellulose acetate film.

(Orientation film coating solution composition)
The following modified polyvinyl alcohol 20 parts by mass Water 360 parts by mass Methanol 120 parts by mass Glutaraldehyde (crosslinking agent) 1.0 part by mass

(Preparation of optical compensation film)
On the above alignment film, 91.0 g of the following discotic liquid crystalline compound, 9.0 g of ethylene oxide modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.), cellulose acetate butyrate (CAB551- 0.2, Eastman Chemical Co., Ltd.) 2.0 g, Cellulose Acetate Butyrate (CAB531-1, Eastman Chemical Co., Ltd.) 0.5 g, Photopolymerization Initiator (Irgacure 907, Ciba Geigy Corp.) 3.0 g, increase A coating solution prepared by dissolving 1.0 g of a sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) in 414 g of methyl ethyl ketone was applied to 6.2 ml / m ² (6.2 cc / m ²⁾ with a wire bar of # 3.6. ) Applied. This was heated in a constant temperature zone of 130 ° C. for 2 minutes to align the discotic liquid crystalline compound. Next, UV irradiation was performed for 1 minute using a 120 W / cm high pressure mercury lamp in an atmosphere of 60 ° C. to polymerize the discotic liquid crystalline compound. Thereafter, it was allowed to cool to room temperature to form an optical compensation film.

In the prepared optical compensation film, the discotic liquid crystalline compound has a hybrid orientation in which the angle (tilt angle) formed by the disk surface and the protective film increases from the protective film toward the air interface and is 11 ° to 66 °. It was. The inclination angle was measured using an ellipsometer (M-150, manufactured by JASCO Corporation), the retardation value was measured while changing the observation angle, and assumed to be a refractive index ellipsoid model, and “Design Concepts of the Electronic Negative”.
It was calculated by the method described in “Birefringence Compensation Films SID98 DIGEST”.

(Production of elliptically polarizing plate)
A polarizing film was prepared by adsorbing iodine to the stretched polyvinyl alcohol film, and the prepared optical compensation film was attached to one side of the polarizing film on the support surface using a polyvinyl alcohol-based adhesive. In addition, a cellulose triacetate film (TD-80U, manufactured by Fuji Film Co., Ltd.) having a thickness of 80 μm was subjected to saponification treatment, and attached to the side opposite to the liquid crystal cell of the polarizing film using a polyvinyl alcohol-based adhesive. The absorption axis of the polarizing film and the slow axis (parallel to the casting direction) of the support of the optical compensation film were arranged in parallel. In this way, a polarizing plate was produced.
Also, the axis angle of the absorption axis of the polarizing film of the upper polarizing plate is 45 ° with respect to the horizontal direction of the display device, the orientation control direction (rubbing direction) of the upper optical compensation film is 45 °, and the orientation of the substrate on the liquid crystal cell Similarly, the control direction (rubbing direction) is 90 °, the axis angle of the lower polarizing plate is 135 °, the orientation control direction of the lower optical compensation film is 135 °, and the orientation control direction (rubbing direction) of the lower substrate of the liquid crystal cell. The angle was 270 °.

(Coating of light diffusion layer)
(Light diffusion layer HC-01A)
The light-transmitting resin constituting the light diffusion layer is composed of 100 parts of a hard coat coating solution containing a dispersion of ultrafine zirconium oxide particles (Desolite Z7404 JSR Co., Ltd.) and a light-transmitting resin DPHA (manufactured by Nippon Kayaku; dipentaerythritol). 57 parts by mass of a mixture of hexaacrylate and dipentaerythritol pentaacrylate) was stirred and dissolved in a methyl ethyl ketone / methyl isobutyl ketone (20/80 mass ratio) solution, and then applied and UV cured. The refractive index was 1.61. In this solution, 17 parts by mass of cross-linked polymethyl methacrylate beads (MX150, particle size 1.5 μm, refractive index 1.49), and cross-linked polymethyl methacrylate beads (manufactured by Soken Chemical, MX300 particle size 3.0 μm, refractive index 1.49) 7 parts by mass, these were mixed and adjusted to a solid content of 50% with methyl ethyl ketone / methyl isobutyl ketone (20/80 mass ratio), Application amount of 1.5 μm polymethylmethacrylate beads on a triacetylcellulose film (manufactured by FUJIFILM Corporation, TD-80U) opposite to the side having the optical compensation film of the elliptically polarizing plate Is 0.42 g / m ² , dried at 30 ° C. for 15 seconds and 90 ° C. for 20 seconds, and further purged with nitrogen (oxygen concentration 10 A polarizing plate having a light diffusion layer HC-01A by curing an application layer by irradiating an ultraviolet ray with an irradiation amount of 50 mJ / cm ² using an air-cooled metal halide lamp (manufactured by Eye Graphics Co., Ltd.) of 160 W / cm at 0 ppm) Was made. The dry thickness of the light diffusion layer was 3.0 μm.

(Light diffusion layer HC-02A to 11A)
Light diffusion layers HC-02A to HC-11A were prepared in the same manner as the light diffusion layer HC-01A, except that the coating amount of 1.5 μm crosslinked polymethylmethacrylate beads on the light diffusion layer HC-01A was changed. The coating amount of 1.5 μm polymethylmethacrylate beads is as shown in the table below.

(Light diffusion layer HC-01B)
The translucent resin constituting the light diffusion layer is 14.79 parts by mass of DPHA (manufactured by Nippon Kayaku) and 133. PET-30 (manufactured by Nippon Kayaku; a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate). 11 parts by weight (After diluting these two resins with a solvent, the refractive index of the coating film obtained by coating and UV curing was 1.53). A bead dispersion prepared by adding highly crosslinked polystyrene beads (SBX-8 manufactured by Sekisui Kasei Co., Ltd., particle size 8 μm, refractive index 1.62) to these resins as translucent fine particles so that the solid content of beads is 30% with cyclohexanone. 7.7 parts by mass and cross-linked polystyrene beads (SX13, manufactured by Soken Chemical)
17.97 parts by mass of bead dispersion prepared by adjusting the bead solid content to 30% with cyclohexanone at 0H, particle size 1.3 μm, refractive index 1.61), Irgacure 184 (polymerization initiator; Ciba Specialty Chemicals) 6) parts by mass, Irgacure 907 (polymerization initiator; manufactured by Ciba Specialty Chemicals) 1.06 parts by mass, FZ 2191 (silicone leveling agent, manufactured by Nihon Unicar), 0.22 parts by mass, and toluene 133.5 parts by mass Part, 39.2 parts by mass of cyclohexanone, and adjusted so as to have a solid content of 46%, the triacetylcellulose film on the opposite side of the elliptical polarizing plate with the polarizing film interposed therebetween (Fuji Film Co., Ltd., TD-80U) was applied so that the layer thickness was 20 μm, and 30 ° C. for 15 seconds, 90 ° C. After drying for 20 seconds, further with a nitrogen purge under (oxygen concentration 100 ppm) at 160 W / cm air-cooled metal halide lamp (manufactured by Eye Graphics Co.), coated layer and an irradiation dose of 50 mJ / cm ² Was cured to prepare a polarizing plate having a light diffusion layer HC-01B. The coating amount of 1.3 μm cross-linked polystyrene beads was 1.1 g / m ² .

(Light diffusion layer HC-01C)
The translucent resin constituting the light diffusion layer is 100 parts by mass of hard coat liquid containing silica ultrafine particle dispersion (Desolite Z7526, manufactured by JSR Co., Ltd., refractive index 1.51), and crosslinked polystyrene-based beads as translucent microparticles ( 25 parts by mass of SX130H manufactured by Soken Chemical Co., Ltd., particle size 1.3 μm, refractive index 1.61), 6 parts by mass of crosslinked polystyrene beads (SX350H manufactured by Soken Chemical Co., Ltd., particle size 3.5 μm, refractive index 1.61) Is mixed with methyl ethyl ketone / methyl isobutyl ketone (20/80 mass ratio) so as to have a solid content of 45%, and the side having the optical compensation film of the elliptically polarizing plate is opposite to the polarizing film. triacetyl cellulose film (produced by Fujifilm Corp., TD-80U) on the coating amount of 1.3μm crosslinked polystyrene beads to 0.9 g / m ² And after drying at 30 ° C. for 15 seconds and 90 ° C. for 20 seconds, using a 160 W / cm air-cooled metal halide lamp (made by Eye Graphics Co., Ltd.) under a nitrogen purge (oxygen concentration 100 ppm). A polarizing plate having a light diffusion layer HC-01C was produced by irradiating an ultraviolet ray with an irradiation amount of 50 mJ / cm ² to cure the coating layer. The dry thickness of the light diffusion layer was 3.0 μm.

(Light diffusion layer HC-01D)
In the light diffusion layer HC-01B, (1) highly cross-linked polystyrene beads (SBX-8 manufactured by Sekisui Chemical Co., Ltd., particle size 8 μm, refractive index 1.62) are converted to high-crosslinked polystyrene beads (SBX-6 manufactured by Sekisui Chemical Co., Ltd., particle size). 6 μm, refractive index 1.62), and (2) a light diffusion layer HC prepared in exactly the same manner as the light diffusion layer HC-01B except that the dry thickness of the light diffusion layer is changed from 20 μm to 5.5 μm. It was set to −01D.
Further, (3) the light diffusion layers HC-02D to 04D were prepared by applying 1.3 μm crosslinked polystyrene-based beads as shown in the table below.

(Coating of low refractive index layer)
(Preparation of sol solution (a))
In a reactor equipped with a stirrer and a reflux condenser, 119 parts by mass of methyl ethyl ketone, 3-acryloyloxypropyltrimethoxysilane “KBM-5103” {manufactured by Shin-Etsu Chemical Co., Ltd.} 101 parts by mass, diisopropoxyaluminum ethylacetate After adding 3 parts by mass of acetate and mixing, 30 parts by mass of ion-exchanged water was added and reacted at 60 ° C. for 4 hours, and then cooled to room temperature to obtain a sol solution (a). The mass average molecular weight of the sol liquid (a) was 1600, and among the components higher than the oligomer component, the component having a molecular weight of 1000 to 20000 was 100% by mass. Further, from the gas chromatography analysis, the raw material acryloyloxypropyltrimethoxysilane did not remain at all. Finally, it was prepared with a methyl ethyl ketone solution, and the solid content concentration was 29% by weight.

(Preparation of coating solution for low refractive index layer)
The low refractive index layer coating liquids LN-1 to LN-3 were adjusted according to the following table. The numbers in the table are parts of mass.

  Each of the above coating liquids was filtered through a polypropylene filter having a pore diameter of 1 μm to complete low refractive index layer coating liquids (LN-1 to LN-3).

The compounds used for the preparation of each of the above coating solutions are shown below.
“JTA-113”: a thermally crosslinkable silicone-containing fluoropolymer solution, a refractive index of 1.44, a solid content concentration of 6% by mass,
Solvent methyl ethyl ketone, manufactured by JSR Corporation,
“P-3”: fluorine-containing copolymer (P-3) described in JP-A No. 2004-45462, mass average molecular weight of about 50,000, solid content concentration of 23.8% by mass, solvent methyl ethyl ketone,
“MEK-ST-L”: Silica particle dispersion, average particle size 45 nm, solid content concentration 30% by mass, dispersion solvent methyl ethyl ketone, manufactured by Nissan Chemical Co., Ltd.
“PM980M solution”: a solution obtained by diluting a polymerization initiator PM980M, manufactured by Wako Pure Chemical Industries, Ltd. with a solvent methyl ethyl ketone so that the solid content concentration becomes 2% by mass,
“MP-triazine”: photopolymerization initiator, manufactured by Sanwa Chemical Co., Ltd.
“RMS-033”: Reactive silicone resin, made by Gelest, 6% by mass with methyl ethyl ketone,
“Hollow silica dispersion”: CS-60, dispersion solvent isopropyl alcohol, catalyst chemical industry (manufactured), refractive index 1.31, average particle size 60 nm, shell thickness 10 nm, hollow silica particles “KBM-5103 (Shin-Etsu Chemical) This is a hollow silica particle dispersion (surface modification rate: 30% by mass of hollow silica) with a surface modification of “Silane Coupling Agent, Inc.” and a dispersion having a solid content concentration of 18.2% by mass.

(Coating of low refractive index layer-1)
After coating the various light diffusion layers of the present invention, the low refractive index layer coating liquid LN-1 and 2 are further coated with a bar coater so that the dry thickness of the low refractive index layer is 95 nm. After wet coating, followed by drying at 120 ° C. for 150 seconds and further drying at 100 ° C. for 8 minutes, a nitrogen purge was performed in an air-cooled metal halide lamp (eye graphics Was used, and a low refractive index layer was formed and wound up by irradiating with an ultraviolet ray having an irradiation amount of 110 mJ / cm ² . The refractive index of the low refractive index layer was 1.45 for LN-1 and 1.41 for LN-2.

(Coating of low refractive index layer-2)
After coating the various light diffusion layers of the present invention, the low refractive index layer coating solution LN-3 is further wet-coated with a die coater so that the dry film thickness of the low refractive index layer is 95 nm. Subsequently, after drying at 120 ° C. for 70 seconds, further using a nitrogen purge, a 240 W / cm air-cooled metal halide lamp (manufactured by Eye Graphics Co., Ltd.) in an atmosphere with an oxygen concentration of 100 ppm is used. The sample was irradiated with ultraviolet rays of cm ² to form a low refractive index layer and wound up. The refractive index of the low refractive index layer was 1.38.

  Inventive samples 1-1 to 20 and comparative samples 1 to 5 were coated according to the following table to complete a film with a light diffusion layer. In addition, the inventive sample 1-19 was obtained by not applying the low refractive index layer of the inventive sample 1-9, and the inventive sample 1-20 was applied by the low refractive index layer of the inventive sample 1-18. It was not set up.

(Evaluation of light diffusion film)
About the obtained light-diffusion film, the following items were evaluated.

(1) Integral reflectance Integral reflectance is measured by attaching an adapter “ILV-471” to a spectrophotometer “V-550” (manufactured by JASCO Corporation) and entering in the wavelength region of 380 to 780 nm. The integrated reflectance at an angle of 5 ° was measured, and an average integrated reflectance of 450 to 650 nm was calculated.

(2) Internal haze (1) The total haze value (H) of the obtained optical film is measured according to JIS-K7136.
(2) Add a few drops of silicone oil to the front and back surfaces of the optical film, and use two glass plates (micro slide glass product number S9111, manufactured by MATSANAMI) between the front and back of the glass to completely separate the two glasses. The plate was adhered to the obtained optical film, the haze was measured in a state where the surface haze was removed, and the value obtained by subtracting the haze measured by sandwiching only silicone oil between two separately measured glass plates was measured. Calculated as internal haze (Hi).
(3) A value obtained by subtracting the internal haze (Hi) calculated in (2) from the total haze (H) measured in (1) above is calculated as the surface haze (Hs) of the film.

(3) Evaluation of scattered light profile Using an automatic goniophotometer GP-5 (manufactured by Murakami Color Research Laboratory Co., Ltd.), a light diffusing film is arranged perpendicular to the incident light, and it extends in all directions. The scattered light profile was measured. The scattered light intensity of 30 ° with respect to the light intensity at the emission angle of 0 ° was determined.

(4) Viewing angle Using the measuring instrument (EZ-Contrast 160D, manufactured by ELDIM), the viewing angle in the upward direction is measured in eight stages from black display (L1) to white display (L8). did.
A viewing angle was defined as a range where the contrast ratio was 10 or more and there was no gradation inversion.
Evaluation was performed in the following four stages.
○: 76 ° or more △: 73 ° or more and less than 76 ° △ ×: 70 ° or more and less than 73 ° ×: less than 70 °

(5) Blur The image was displayed on the manufactured liquid crystal display device, and the blur of the image was evaluated in the following four stages.
○: Image blur is not known at all.
○ ': There is very little blur in the image, so I don't care.
Δ: Slight blurring of the image is observed.
×: Image blur can be recognized.

In the inventive samples 1-1 to 20, the improvement of the viewing angle characteristic and the reduction of the blur are compatible.
Furthermore, compared with Inventive Samples 1-1 to 20, Inventive Samples 1-1 to 18 have an integrated reflectivity reduced by applying a low refractive index layer, which improves viewing angle characteristics / decreases blur. In addition to the compatibility, it was particularly preferable in that an image display apparatus capable of suppressing the reflection of external light and increasing the contrast in a bright room environment can be provided.

[Example 2]
(Comparative Example 2-1)
A liquid crystal display device was produced in the same manner as in the inventive sample 1-1 of Example 1, except that the light diffusion layer HC-01A was not laminated.

(Example 2-2)
(Production of liquid crystal display device)
A liquid crystal display device was produced in the same manner as in the inventive sample 1-1 of Example 1, except that the configuration of the liquid crystal cell was changed as follows.
2, the absorption axis 12D of the upper polarizing plate polarizing film 12, the slow axis 11D of the upper polarizing plate protective film 11 is 90 °, the slow axis 13D of the upper polarizing plate protective film 13 is 0 °, and the lower polarizing plate polarizing film. 22, the slow axis 21D of the lower polarizing plate protective film 21 is 0 °, the orientation control direction 14RD of the upper optical anisotropic layer 14 is 45 °, and the orientation of the lower optical anisotropic layer 24 is The control direction 24RD was set to be 225 °.
The rubbing direction (alignment axis) 5RD of the upper (observer side) substrate 5 of the liquid crystal cell is 45 °, the rubbing direction (alignment axis) 7RD of the lower (backlight side) substrate 7 is 225 °, and the twist angle is 0. °. In this way, a normally white mode ECB type liquid crystal cell was produced. The light diffusion layer HC-01A of Sample 1-1 of the present invention was laminated on the outermost surface of this liquid crystal display device.

(Comparative Example Sample 2-2)
A liquid crystal display device was produced in the same manner as in the inventive sample 1-2 except that the light diffusion layer HC-01A was not laminated.

(Example 2-3)
A liquid crystal display device was produced in the same manner as in the inventive sample 1-1 of Example 1, except that the configuration of the liquid crystal cell was changed to the following TN liquid crystal display device.
In FIG. 3, the absorption axis 12D of the upper polarizing plate polarizing film 12 and the slow axes 11D and 13D of the upper polarizing plate protection films 11 and 13 are 45 °, the absorption axis 22D of the lower polarizing plate polarizing film 22, and the lower polarizing plate protection. The slow axes 21D and 23D of the films 21 and 23 are 135 °, the orientation control direction 14RD of the upper optical anisotropic layer 14 is 225 °, and the orientation control direction 24RD of the lower optical anisotropic layer 24 is 315 °. Was set to be.

(Production of liquid crystal cell)
The liquid crystal cell has a cell gap (d) of 4 μm, a liquid crystal material having a positive dielectric constant anisotropic layer is enclosed between the substrates by drop injection, and Δn · d of the liquid crystal layer 6 is 410 nm (Δn is a value of the liquid crystal material). Refractive index anisotropy). The rubbing direction (alignment axis) 5RD of the upper (observer side) substrate 5 of the liquid crystal cell is 45 °, the rubbing direction (alignment axis) 7RD of the lower (backlight side) substrate 7 is 315 °, and the twist angle is The angle was 90 °. In this way, a TN type liquid crystal cell was produced. The light diffusion layer HC-01A of Sample 1-1 of the present invention was laminated on the outermost surface.

(Comparative Example 2-3)
A liquid crystal display device was produced in the same manner as in Example 2-3 except that the light diffusion layer HC-01A of Sample 1-1 of the present invention was not laminated.

(Example 2-4)
In Example 2-3, the orientation direction of the liquid crystal cell and the angle of the polarizing plate absorption axis were changed to produce a TN liquid crystal display device.
The absorption axis 12D of the upper polarizing plate polarizing film 12, the slow axes 11D and 13D of the upper polarizing plate protective films 11 and 13 are 90 °, the absorption axis 22D of the lower polarizing plate polarizing film 22, the lower polarizing plate protective film 21, The slow axes 21D and 23D of 23 are set to 0 °, and the orientation control direction 14RD of the upper optical anisotropic layer 14 is set to 2
The orientation control direction 24RD of the lower optically anisotropic layer 24 was set to 70 ° and 180 °.
The liquid crystal cell has a cell gap (d) of 4 μm, a liquid crystal material having a positive dielectric constant anisotropic layer is sealed between the substrates by dropping, and Δn · d of the liquid crystal layer 6 is 410 nm (Δn is a liquid crystal material) Refractive index anisotropy). The rubbing direction (alignment axis) 5RD of the upper (observer side) substrate 5 of the liquid crystal cell is 45 °, the rubbing direction (alignment axis) 7RD of the lower (backlight side) substrate 7 is 315 °, and the twist angle is The angle was 90 °. In this way, a TN type liquid crystal cell was produced. The light diffusion layer HC-01A of Sample 1-1 of the present invention was laminated on the outermost surface.

(Comparative Example 2-4)
A liquid crystal display device was produced in the same manner as in Example 2-4 except that the light diffusion layer HC-01A of Sample 1-1 of the present invention was not laminated.

(Example 2-5)
In the inventive sample 1-1 of Example 1, the configuration of the liquid crystal cell was changed to the following IPS type liquid crystal display device, and the optically anisotropic layer was changed to a commercially available cellulose acetate film (Fujitac TD80UF, manufactured by Fuji Film Co., Ltd.). A liquid crystal display device was produced in the same manner except for the above.
In FIG. 4, the absorption axis 12D of the upper polarizing plate polarizing film 12 and the slow axes 11D and 13D of the upper polarizing plate protection films 11 and 13 are 0 °, the absorption axis 22D of the lower polarizing plate polarizing film 22, and the lower polarizing plate protection. The slow axis 21D of the film 21 is set to 90 °, the slow axis 23D of the lower polarizing plate protective film 23 is set to 0 °, and the orientation control direction 14RD of the upper optical anisotropic layer 14 is set to 0 °. did.
The optically anisotropic layer has the same optical performance as that of a protective film usually used for a polarizing plate, and corresponds to the absence of an optically anisotropic layer.
In addition, the liquid crystal cell has a cell gap (d) of 3 μm, a liquid crystal material having a positive dielectric constant anisotropic layer is sealed between the substrates by drop injection, and Δn · d of the liquid crystal layer 6 is set to 300 nm (Δn is a liquid crystal material) Refractive index anisotropy). Further, the rubbing direction (alignment axis) 5RD of the upper (observer side) substrate 5 of the liquid crystal cell is 270 °, the rubbing direction (alignment axis) 7RD of the lower (backlight side) substrate 7 is 90 °, and the twist angle is The angle was 0 °. In this way, an IPS type liquid crystal cell was produced. The light diffusion layer HC-01A of Sample 1-1 of the present invention was laminated on the outermost surface.

(Comparative Example 2-5)
A liquid crystal display device was prepared in the same manner as in Example 2-5, except that the light diffusion layer HC-01A of Sample 1-1 of the present invention was not laminated.

(Optical measurement of the manufactured liquid crystal display device)
A rectangular wave voltage of 60 Hz was applied to the liquid crystal display device thus manufactured. The apparatus for measuring optical performance is (EZ-Contrast 160D, manufactured by ELDIM). The ratio of transmittance (white display / black display), contrast ratio, black display (L1), white display (L8), etc. The transmittance viewing angle at 8 gradations cut at intervals was measured. Table 3 shows an angle range in which the transmittance of gradations adjacent in the downward direction is not inverted, and a ratio of a range angle in which the left-right contrast ratio is 10: 1 or more.
Table 3 also shows the results of color change (color unevenness) depending on the viewing angle of black display by visual observation, and luminance unevenness (light leakage) in the peripheral portion.

The color unevenness was evaluated as follows.
The color difference between the front and the viewing angle of 45 ° polar angle and 60 ° direction in the panel black display character was evaluated. When the color difference is measured with a luminance meter, in the Luv chromaticity coordinate system, if the color difference Δu′v ′ is 0.02 or less, no color unevenness is observed by visual observation (◯ in the two-step evaluation). If it is 0.02 or more, color unevenness is recognized (Δ in a two-step evaluation).

Evaluation of luminance unevenness in the peripheral portion was performed as follows.
After being stored in an environmental test room at 40 ° C. and 80% RH for 24 hours and allowed to stand at room temperature for 1 hour, the luminance difference during black display at the center of the panel and the center of the long side edge of the polarizing plate was measured. Visually, light leakage is observed on the arc on the long and short sides of the peripheral part of the polarizing plate. If the luminance difference is 0.4 cd / m ² or more, it is recognized as luminance unevenness on the screen (Δ in a three-step evaluation). If the luminance difference is 0.2 to 0.4 cd / m ² , light leakage is observed, but it is not recognized as luminance unevenness on the screen (◯ in three-step evaluation). If the luminance difference is 0.1 cd / m ² or less, neither light leakage nor luminance unevenness on the screen is recognized (◎ in the three-step evaluation). The panel had a white display of 400 cd / m ² and a contrast ratio of 700: 1.

It is the schematic which shows the example of the ECB type | mold liquid crystal display device of this invention. It is the schematic which shows the example of the ECB type | mold liquid crystal display device of this invention. It is the schematic which shows the example of the TN type | mold liquid crystal display device of this invention. It is the schematic which shows the example of the IPS type | mold liquid crystal display device of this invention. It is a schematic sectional drawing which shows the example of the IPS type | mold liquid crystal display device of this invention. It is a schematic sectional drawing which shows the example of the IPS type | mold liquid crystal display device of this invention.

Explanation of symbols

1: Upper polarizing plate 11: Upper polarizing plate protective film 11D: Slow axis of upper polarizing plate protective film 12: Upper polarizing plate polarizing film 12D: Absorption axis of upper polarizing plate polarizing film 13: Upper polarizing plate protective film 13D: Upper side Slow axis of polarizing plate protective film 14: upper optical compensation film 14RD: orientation direction of upper optical compensation film 5: upper substrate of liquid crystal cell 5RD: rubbing direction for upper substrate liquid crystal orientation 6: liquid crystal molecule, liquid crystal layer 7: liquid crystal cell Lower substrate 7RD: Lower substrate liquid crystal alignment rubbing direction 24: Lower optical compensation film 24RD: Lower optical anisotropic film alignment direction 2: Lower polarizing plate 23: Lower polarizing plate protective film 23D: Lower side Slow axis of polarizing plate protective film 22: Lower polarizing plate polarizing film 22D: Absorption axis of lower polarizing plate polarizing film 21: Lower polarizing plate protective film 21D: Slow axis of lower polarizing plate protective film 9D: Electric field Direction 91: Linear electrode 9 3: Insulating film 92: Electrode 80: Light source

Claims (9)

  A polarizing plate for a liquid crystal display device having a first protective film, a polarizing film, a second protective film, and a light diffusion layer in this order, the light diffusion layer being a translucent resin and a refraction of the translucent resin A polarizing plate for a liquid crystal display device, which is a layer containing translucent fine particles having a refractive index different from the refractive index, and wherein the internal haze of the light diffusion layer is 45% or more and 80% or less.   A polarizing plate for a liquid crystal display device, wherein the polarizing plate according to claim 1 further has an optical compensation layer.   3. The liquid crystal according to claim 1, wherein the light diffusion layer has a scattered light intensity of 30 ° with respect to a light intensity of an output angle of 0 ° of a scattered light profile of a goniophotometer in a range of 0.05 to 0.3%. Polarizing plate for display device.   A liquid crystal comprising a liquid crystal layer comprising a pair of opposed substrates having electrodes on one side and a nematic liquid crystal material sandwiched between the substrates and oriented substantially parallel to the surfaces of the pair of substrates when no voltage is applied A liquid crystal display device having a cell and a polarizing plate disposed on at least one surface outside the liquid crystal cell, wherein the polarizing plate includes a first protective film, a polarizing film, a second protective film, and a light diffusion layer in this order. The diffusion layer is a layer containing a translucent resin and translucent fine particles having a refractive index different from the refractive index of the translucent resin, and the internal haze of the light diffusion layer is 45% or more. A liquid crystal display device of 80% or less.   The liquid crystal display device in which the polarizing plate according to claim 4 further has an optical compensation layer.   6. The liquid crystal display device according to claim 4, wherein the absorption axis of the polarizing film and the horizontal direction of the screen of the display device are parallel or vertical.   The liquid crystal display device according to claim 4, wherein the liquid crystal display device is an ECB type liquid crystal display device.   The liquid crystal display device according to any one of claims 4 to 6, wherein the liquid crystal display device is a TN type liquid crystal display device.   The liquid crystal display device according to claim 4, wherein the liquid crystal display device is an IPS liquid crystal display device.

Images