JP3935489B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a lateral electric field type (IPS) active matrix liquid crystal display device.

  The horizontal electric field type liquid crystal display device performs pixel display by forming an electric field parallel to the liquid crystal substrate between the pixel electrode and the common electrode. Compared to a TN mode method or the like that forms an electric field perpendicular to the substrate. Thus, there is an advantage that a wide viewing angle can be obtained. However, the conventional horizontal electric field type active matrix liquid crystal display device can display almost completely black in the normal direction of the panel, but when observing the panel from a direction deviated from the normal direction, In the direction deviated from the optical axis direction of the polarizing plates arranged above and below, light leakage unavoidable due to the characteristics of the polarizing plates occurs, resulting in a problem that the viewing angle is narrowed and the contrast is lowered. Further, when observed from an oblique direction, the optical path of light becomes long, and the apparent retardation of the liquid crystal layer changes. For this reason, when the viewing angle is changed, the wavelength of transmitted light changes, and the color of the screen changes and appears, and a color shift occurs depending on the viewing direction.

Various proposals have been made to improve contrast reduction and color shift depending on the viewing angle in such a conventional horizontal electric field type liquid crystal display device. For example, a technique has been proposed in which a compensation layer having optical anisotropy is interposed between a liquid crystal layer and a pair of polarizing plates sandwiching the liquid crystal layer (Patent Document 1). Although this technique is effective for color shifting, it cannot sufficiently improve contrast. In addition, a technique has been proposed in which first and second retardation plates are interposed between a liquid crystal layer and a pair of polarizing plates sandwiching the liquid crystal layer (Patent Document 2). Although this technique is described as being effective in reducing contrast and improving color shift, a higher improvement effect is desired.
JP 11-133408 A JP 2001-242462 A

  An object of the present invention is to provide a lateral electric field type active matrix liquid crystal display device having a high contrast ratio over a wide range using an optical film in which a polarizing plate and a retardation film are laminated.

  As a result of intensive studies to solve the above problems, the present inventors have found the following liquid crystal display device and completed the present invention.

That is, the present invention provides a horizontal electric field type liquid crystal panel having a liquid crystal layer whose orientation orientation is changed by an electric field parallel to the substrate surface, the first and second polarizing plates arranged with the liquid crystal panel sandwiched therebetween, In a liquid crystal display device including a first optical film disposed between one polarizing plate and the liquid crystal panel, and a second optical film disposed between the second polarizing plate and the liquid crystal panel,
The first optical film has a retardation film A1 having a relationship of nz> nx ≧ ny, an in-plane retardation (Re) of 200 to 300 nm, a relationship of nx>nz> ny, and an Nz coefficient. Including a retardation film B having a controlled three-dimensional refractive index such that satisfies 0.3 <Nz <0.7,
The second optical film includes a retardation film A2 having a relationship of nz> nx ≧ ny,
And the slow axis of the retardation film B and the absorption axes of the first and second polarizing plates are parallel or perpendicular,
The first polarizing plate and the second polarizing plate both have protective films on both sides of the polarizer,
The thickness direction retardation (Rth ₁ ) of the protective film on the liquid crystal panel side of the first polarizing plate and the thickness direction retardation (Rth ₂ ) of the retardation film A1 are:
0 ≦ || Rth ₁ | − | Rth ₂ || ≦ 15 nm, and
The thickness direction retardation (Rth ₃ ) of the protective film on the liquid crystal panel side of the second polarizing plate and the thickness direction retardation (Rth ₄ ) of the retardation film A2 are:
Satisfying 0 ≦ || Rth ₃ | − | Rth ₄ || ≦ 15 nm ,
The thickness direction retardation (Rth ₁₎ and _{(Rth 3), + 30~ +} 100nm, a liquid crystal display device comprising der Rukoto relates.

However, the above film, the X-axis plane refractive index in the film plane is maximum, Y-axis and a direction perpendicular to the X-axis, a thickness direction and Z-axis of the film, the respective axial 590 When the refractive index at nm is nx, ny, nz and the film thickness is d (nm),
In-plane retardation (Re) = (nx−ny) × d,
Nz = (nx−nz) / (nx−ny),
Thickness direction retardation (Rth) = (nx−nz) × d .

  In the liquid crystal display device of the present invention, the first optical film including the retardation film A1 and the retardation film B is disposed on one side of the liquid crystal panel, and the optical film including the retardation film A2 is disposed on the other side. As a result, light leakage during black display, which has conventionally occurred in active matrix liquid crystal display devices, can be reduced. Such a liquid crystal display device can suppress a decrease in contrast due to a change in the axis of the polarizer caused by a change in viewing angle between polarizers arranged in crossed Nicols, has a high contrast ratio in all directions, and has a wide viewing angle. Easy-to-see display can be realized. In addition, color shift can be suppressed.

  The retardation film A1 and the retardation film A2 both have a relationship of nz> nx ≧ ny. The retardation film A1 and the retardation film A2 can control the retardation in the thickness direction, and can suppress a decrease in contrast when viewed obliquely.

  When the polarizing film is disposed in a crossed Nicol state, the retardation film B can eliminate light leakage in a direction shifted from the optical axis by the specific retardation film, and is an IPS mode liquid crystal display device. Is preferably used. In particular, it has a function of compensating for a decrease in contrast in an oblique direction of the liquid crystal layer. The retardation film B is laminated so that the absorption axis of the polarizing plate and the slow axis of the retardation film are orthogonal or parallel.

  The retardation film B has an in-plane retardation (Re) of 200 to 300 nm, and the Nz value is 0.3 <Nz <0.7. The in-plane retardation (Re) is preferably 240 nm or more, more preferably 260 nm or more from the viewpoint of enhancing the compensation function, while it is preferably 290 nm or less, more preferably 280 nm or less. The Nz value is preferably 0.4 or more, more preferably 0.45 or more from the viewpoint of enhancing the compensation function. On the other hand, the Nz value is preferably 0.6 or less, more preferably 0.55 or less.

When the protective film for the polarizing plate, particularly the protective film on the liquid crystal panel side, has a positive thickness direction retardation (Rth), the viewing angle becomes narrow due to birefringence. On the other hand, since the retardation film A1 and the retardation film A2 have a relationship of nz> nx ≧ ny, the respective thickness direction retardations (Rth ₂ ) and (Rth ₄ ) have negative values. The birefringence due to the positive thickness direction retardation possessed by the protective film of the polarizing plate can be compensated by the negative thickness retardation possessed by the retardation film A1 and the retardation film A2. Therefore, the thickness direction retardations (Rth ₁ ) and (Rth ₃ ) of the protective films on the liquid crystal panel side of the first and second polarizing plates, and the thickness direction retardations (Rth ₂ ) of the retardation films A 1 and A _2. ) And a difference in absolute value of (Rth ₄ ) of 10 nm or less makes it possible to obtain a viewing angle with better contrast. The difference in absolute value is preferably as small as possible, preferably 5 nm or less, and most preferably 0 nm.

The thickness direction retardation (Rth ₂ ) of the retardation film A1 and the thickness direction retardation (Rth ₄ ) of the retardation film A2 are preferably −30 to −100 nm.

From the viewpoint of a wide viewing angle contrast, the thickness direction retardation (Rth ₂ ) and the thickness direction retardation (Rth ₄ ) are preferably −30 to −100 nm, and more preferably −30 to −70 nm. preferable. In addition, it is preferable that the retardation film A1 and the retardation film A2 have the same thickness direction retardation (Rth) from the viewpoint of obtaining a good contrast with a wide viewing angle.

In addition, when a film having a thickness direction retardation (Rth ₁ ) and (Rth ₃ ) of +30 to +100 nm, and further +30 to +70 nm is used as the protective film on the liquid crystal panel side of the polarizing plate, the protective film and the retardation are used. In order to reduce the difference in the absolute value of the thickness direction retardation (Rth) from the films A1 and A2, the retardation film A1 and the retardation film A2 having the thickness direction retardation (Rth ₂ ) and (Rth ₄ ) are used. Are preferably used.

  The in-plane retardation (Re) of the protective film is not particularly limited, but is 10 nm or less, more preferably 6 nm or less. The thickness d of the protective film is not particularly limited, but is generally 500 μm or less, and preferably 1 to 300 μm. In particular, the thickness is preferably 5 to 200 μm.

  As said retardation film A1 and / or retardation film A2, what was formed with the layer containing the liquid crystal polymer fixed to homeotropic orientation can be used suitably.

In the liquid crystal display device, each of the first polarizing plate and the second polarizing plate has a protective film on both sides of the polarizer,
The slow axis of the protective film on the liquid crystal panel side of the first polarizing plate and the absorption axis of the first polarizing plate are parallel or perpendicular,
The slow axis of the protective film on the liquid crystal panel side of the second polarizing plate and the absorption axis of the second polarizing plate are preferably parallel or perpendicular.

  In the liquid crystal display device, the first optical film is preferably laminated from the first polarizing plate side in the order of the retardation film A1 and the retardation film B from the viewpoint of a wide viewing angle contrast.

  Hereinafter, a lateral electric field type (IPS) active matrix liquid crystal display device of the present invention will be described with reference to the drawings. Fig.1 (a) is an example of sectional drawing of the liquid crystal display device of this invention, FIG.1 (b) is a conceptual diagram which shows the axial direction of each film.

  As shown in FIGS. 1A and 1B, a horizontal electric field type liquid crystal panel LC and a first polarizing plate P1 and a second polarizing plate P2 are arranged with the liquid crystal panel LC interposed therebetween. As shown in FIG. 1B, the polarizing plate P1 and the polarizing plate P2 are arranged so that their absorption axes are vertical. Between the polarizing plate P1 and the liquid crystal panel LC, there are a retardation film A1 having a relationship of nz> nx ≧ ny and a retardation film B having a controlled three-dimensional refractive index having a relationship of nx> nz> ny. In this order from the polarizing plate P1 side. On the other hand, a retardation film A2 having a relationship of nz> nx ≧ ny is disposed between the polarizing plate P2 and the liquid crystal panel LC.

  In FIGS. 1A and 1B, the retardation film A1 and the retardation film B are arranged in this order from the polarizing plate P1 side, but from the polarizing plate P1 side, the retardation film B and the retardation film A1. It is also possible to arrange them in this order. Since good contrast is obtained at a wide viewing angle, it is preferable to dispose the retardation film A1 and the retardation film B in this order from the polarizing plate P1 side.

  Moreover, in FIG.1 (b), the phase difference film B is arrange | positioned so that the slow axis and the absorption axis of polarizing plate P1 may become perpendicular | vertical, and the absorption axis of polarizing plate P2 may become parallel. However, the retardation axis of the retardation film B and the absorption axis of the polarizing plate P1 may be parallel to each other and the absorption axis of the polarizing plate P2 may be perpendicular. Since good contrast can be obtained at a wide viewing angle, the retardation film B is preferably arranged as shown in FIG.

  As shown in FIG. 1A, the polarizing plate P1 and the polarizing plate P2 usually have protective films b and b ′ on both surfaces of the polarizer a.

  The slow axis of the protective film b on the liquid crystal panel side of the polarizing plate P1 is parallel or perpendicular to the absorption axis of the polarizing plate P1, and the slow axis of the protective film b on the liquid crystal panel side of the polarizing plate P2 is the polarizing plate P2. It is preferable to be parallel or perpendicular to the absorption axis because a good contrast can be obtained at a wide viewing angle.

  As the polarizing plate, one having protective films on both sides of the polarizer is usually used. The polarizer is not particularly limited, and various types can be used. Examples of the polarizer include hydrophilic polymer films such as polyvinyl alcohol film, partially formalized polyvinyl alcohol film, and ethylene / vinyl acetate copolymer partially saponified film, and two colors such as iodine and dichroic dye. Examples thereof include polyene-based oriented films such as those obtained by adsorbing volatile substances and uniaxially stretched, polyvinyl alcohol dehydrated products and polyvinyl chloride dehydrochlorinated products. Among these, a polarizer composed of a polyvinyl alcohol film and a dichroic material such as iodine is preferable. The thickness of these polarizers is not particularly limited, but is generally about 5 to 80 μm.

  A polarizer obtained by dyeing a polyvinyl alcohol film with iodine and uniaxially stretching it can be produced, for example, by dyeing polyvinyl alcohol in an aqueous solution of iodine and stretching it 3 to 7 times the original length. If necessary, it can be immersed in an aqueous solution such as potassium iodide which may contain boric acid, zinc sulfate, zinc chloride or the like. Further, if necessary, the polyvinyl alcohol film may be immersed in water and washed before dyeing. In addition to washing the polyvinyl alcohol film surface with dirt and anti-blocking agents by washing the polyvinyl alcohol film with water, it also has the effect of preventing unevenness such as uneven coloring by swelling the polyvinyl alcohol film. is there. Stretching may be performed after dyeing with iodine, or may be performed while dyeing, or may be performed with dyeing after iodine. The film can be stretched in an aqueous solution of boric acid or potassium iodide or in a water bath.

  The protective film provided on the polarizer preferably has excellent transparency, mechanical strength, thermal stability, moisture shielding properties, isotropic properties, and the like. As described above, it is suitable when the thickness direction retardation (Rth) is +30 to +100 nm.

  Examples of the material for forming the protective film include polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, acrylic polymers such as polymethyl methacrylate, polystyrene, acrylonitrile and styrene. Examples thereof include styrene polymers such as polymers (AS resins), polycarbonate polymers, and the like. In addition, polyethylene, polypropylene, polyolefins having a cyclo or norbornene structure, polyolefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfone polymers , Polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, epoxy polymer, or the above Polymer blends and the like are also examples of polymers that form the protective film. The protective film can also be formed as a cured layer of an acrylic, urethane, acrylic urethane, epoxy, silicone, or other thermosetting or ultraviolet curable resin. As a material for the protective film, triacetyl cellulose which is generally used as a protective film for a polarizer is suitable.

  The surface of the protective film to which the polarizer is not adhered may be subjected to a treatment for the purpose of hard coat layer, antireflection treatment, antisticking, diffusion or antiglare.

  Hard coat treatment is performed for the purpose of preventing scratches on the surface of the polarizing plate. For example, a cured film having excellent hardness and slipping properties with an appropriate ultraviolet curable resin such as acrylic or silicone is applied to the protective film. It can be formed by a method of adding to the surface. The antireflection treatment is performed for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be achieved by forming an antireflection film or the like according to the conventional art. Further, the anti-sticking treatment is performed for the purpose of preventing adhesion with an adjacent layer.

  The anti-glare treatment is applied for the purpose of preventing the outside light from being reflected on the surface of the polarizing plate and obstructing the visibility of the light transmitted through the polarizing plate. For example, the surface is roughened by a sandblasting method or an embossing method. It can be formed by imparting a fine concavo-convex structure to the surface of the protective film by an appropriate method such as a blending method of transparent fine particles. The fine particles to be included in the formation of the surface fine concavo-convex structure are, for example, conductive materials made of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide or the like having an average particle size of 0.5 to 50 μm. In some cases, transparent fine particles such as inorganic fine particles, organic fine particles made of a crosslinked or uncrosslinked polymer, etc. are used. When forming a surface fine uneven structure, the amount of fine particles used is generally about 2 to 50 parts by weight, preferably 5 to 25 parts by weight, based on 100 parts by weight of the transparent resin forming the surface fine uneven structure. The antiglare layer may also serve as a diffusion layer (viewing angle expanding function or the like) for diffusing the light transmitted through the polarizing plate to expand the viewing angle.

  The antireflection layer, antisticking layer, diffusion layer, antiglare layer, and the like can be provided on the protective film itself, or can be provided separately from the protective film as an optical layer.

  For the adhesive treatment between the polarizer and the protective film, an isocyanate adhesive, a polyvinyl alcohol adhesive, a gelatin adhesive, a vinyl latex, an aqueous polyester, or the like is used.

  As the retardation films A1 and A2, those having a relationship of nz> nx ≧ ny can be used without particular limitation, but a homeotropic alignment liquid crystal layer in which a liquid crystal polymer is fixed in homeotropic alignment is preferably used.

  The homeotropic alignment liquid crystal layer is obtained by aligning a liquid crystal material with, for example, a vertical alignment agent. As a liquid crystal compound that can be homeotropically aligned, for example, a nematic liquid crystal compound is known. An outline of the liquid crystal compound alignment technique is described in, for example, Chemical Review 44 (Surface Modification, Edited by The Chemical Society of Japan, pages 156 to 163).

  As the liquid crystal material of the homeotropic alignment liquid crystal layer, for example, it can be formed by a side chain type liquid crystal polymer having a positive refractive index anisotropy and containing a monomer unit (a) containing a liquid crystalline fragment side chain. . Moreover, it can form with the side chain type liquid crystal polymer containing the monomer unit (b) containing the said monomer unit (a) and a non-liquid crystalline fragment side chain. The side chain type liquid crystal polymer can realize homeotropic alignment of the liquid crystal polymer without using a vertical alignment film. Hereinafter, the liquid crystal polymer and the like will be described.

  The monomer unit (a) has a side chain having nematic liquid crystallinity, for example, the general formula (a):

（ただし、Ｒ¹は水素原子またはメチル基を、ａは１〜６の正の整数を、Ｘ¹は−ＣＯ₂−基または−ＯＣＯ−基を、Ｒ²はシアノ基、炭素数１〜６のアルコキシ基、フルオロ基または炭素数１〜６のアルキル基を、ｂおよびｃは１または２の整数を示す。）で表されるモノマーユニットがあげられる。

(Wherein R ¹ represents a hydrogen atom or a methyl group, a represents a positive integer of 1 to 6, X ¹ represents a —CO ₂ — group or —OCO— group, R ² represents a cyano group, and has 1 to 6 carbon atoms. An alkoxy group, a fluoro group, or an alkyl group having 1 to 6 carbon atoms, and b and c each represent an integer of 1 or 2.).

  The monomer unit (b) has a linear side chain. For example, the monomer unit (b) has the general formula (b):

（ただし、Ｒ³は水素原子またはメチル基を、Ｒ⁴は炭素数１〜２２のアルキル基、炭素数１〜２２のフルオロアルキル基、または一般式（ｂ１）：

(However, the R ³ is a hydrogen atom or a methyl group, R ⁴ is an alkyl group having 1 to 22 carbon atoms, fluoroalkyl group having 1 to 22 carbon atoms, or the general formula, (b1):

ただし、ｄは１〜６の正の整数を、Ｒ⁵は炭素数１〜６のアルキル基を示す。）で表されるモノマーユニットがあげられる。

However, d is a positive integer from 1 to 6, R ⁵ represents an alkyl group having 1 to 6 carbon atoms. ) Monomer units.

  Further, the ratio of the monomer unit (a) to the monomer unit (b) is not particularly limited and varies depending on the type of the monomer unit. However, when the ratio of the monomer unit (b) is increased, the side chain type liquid crystal polymer is changed. In order to stop showing liquid crystal monodomain orientation, it is preferable to set it as (b) / {(a) + (b)} = 0.01-0.8 (molar ratio). In particular, 0.1 to 0.5 is more preferable.

  The liquid crystal polymer capable of forming a homeotropic alignment liquid crystal film includes a monomer unit (a) containing the liquid crystalline fragment side chain and a monomer unit (c) containing a liquid crystalline fragment side chain having an alicyclic ring structure. And a side chain type liquid crystal polymer.

  The monomer unit (c) has a side chain having nematic liquid crystallinity, for example, the general formula (c):

（ただし、Ｒ⁶水素原子またはメチル基を、ｈは１〜６の正の整数を、Ｘ²は−ＣＯ₂−基または−ＯＣＯ−基を、ｅとｇは１または２の整数を、ｆは０〜２の整数を、Ｒ⁷はシアノ基、炭素数１〜１２のアルキル基を示す。）で表されるモノマーユニットがあげられる。

(Provided that the R ⁶ hydrogen atom or a methyl group, h is 1 to 6 positive integer, X ² is -CO ₂ - group or -OCO- group, e and g is 1 or 2 an integer, f Represents an integer of 0 to 2, and R ⁷ represents a cyano group and an alkyl group having 1 to 12 carbon atoms.).

  Further, the ratio of the monomer unit (a) to the monomer unit (c) is not particularly limited and varies depending on the type of the monomer unit. However, when the ratio of the monomer unit (c) is increased, the side chain type liquid crystal polymer is changed. Since the liquid crystal monodomain orientation is not exhibited, it is preferable that (c) / {(a) + (c)} = 0.01 to 0.8 (molar ratio). In particular, 0.1 to 0.6 is more preferable.

  The liquid crystal polymer that can form the homeotropic alignment liquid crystal layer (1) is not limited to those having the above-described monomer units, and the above-mentioned monomer units can be appropriately combined.

  The side chain type liquid crystal polymer preferably has a weight average molecular weight (GPC) of 2,000 to 100,000. By adjusting the weight average molecular weight to such a range, performance as a liquid crystal polymer is exhibited. When the weight average molecular weight of the side chain type liquid crystal polymer is too small, the film forming property of the alignment layer tends to be poor. Therefore, the weight average molecular weight is more preferably 2.5000 or more. On the other hand, if the weight average molecular weight is excessive, the orientation as a liquid crystal tends to be poor and it becomes difficult to form a uniform alignment state. Therefore, the weight average molecular weight is more preferably 50,000 or less.

  The illustrated side chain type liquid crystal polymer can be prepared by copolymerizing an acrylic monomer or a methacrylic monomer corresponding to the monomer unit (a), the monomer unit (b), and the monomer unit (c). The monomers corresponding to the monomer unit (a), the monomer unit (b), and the monomer unit (c) can be synthesized by a known method. The copolymer can be prepared, for example, according to a polymerization method such as a conventional acrylic monomer such as a radical polymerization method, a cationic polymerization method, and an anionic polymerization method. When applying the radical polymerization method, various polymerization initiators can be used. Among them, decomposition temperatures such as azobisisobutyronitrile and benzoyl peroxide are not high and are not low. Those are preferably used.

  The side-chain liquid crystal polymer can be used as a liquid crystal composition by blending a photopolymerizable liquid crystal compound. The photopolymerizable liquid crystal compound is a liquid crystal compound having at least one unsaturated double bond such as an acryloyl group or a methacryloyl group as a photopolymerizable functional group, and a nematic liquid crystal compound is awarded. Examples of such photopolymerizable liquid crystal compounds include acrylates and methacrylates that serve as the monomer unit (a). As the photopolymerizable liquid crystal compound, those having two or more photopolymerizable functional groups are preferable for improving durability. As such a photopolymerizable liquid crystal compound, for example,

（式中、Ｒは水素原子またはメチル基を、ＡおよびＤはそれぞれ独立して１，４−フェニレン基または１，４−シクロヘキシレン基を、Ｘはそれぞれ独立して−ＣＯＯ−基、−ＯＣＯ−基または−Ｏ−基を、Ｂは１，４−フェニレン基、１，４−シクロヘキシレン基、４，４’−ビフェニレン基または４，４’−ビシクロヘキシレン基を、ｍおよびｎはそれぞれ独立して２〜６の整数を示す。）で表される架橋型ネマチック性液晶モノマー等を例示できる。また、光重合性液晶化合物としては、前記化５における末端の「Ｈ₂Ｃ＝ＣＲ−ＣＯ₂−」を、ビニルエーテル基またはエポキシ基に置換した化合物や、「−（ＣＨ₂）_m−」および／または「−（ＣＨ₂）_n−」を「−（ＣＨ₂）₃−Ｃ^*Ｈ（ＣＨ₃）−（ＣＨ₂）₂−」または「−（ＣＨ₂）₂−Ｃ^*Ｈ（ＣＨ₃）−（ＣＨ₂）₃−」に置換した化合物を例示できる。

(In the formula, R is a hydrogen atom or a methyl group, A and D are each independently 1,4-phenylene group or 1,4-cyclohexylene group, and X is each independently a —COO— group or —OCO group. -Group or -O- group, B is 1,4-phenylene group, 1,4-cyclohexylene group, 4,4'-biphenylene group or 4,4'-bicyclohexylene group, and m and n are each And a cross-linked nematic liquid crystal monomer represented by the following formula: Examples of the photopolymerizable liquid crystal compound include compounds in which the terminal “H ₂ C═CR—CO ₂ —” in Chemical Formula 5 is substituted with a vinyl ether group or an epoxy group, “— (CH ₂ ) _m —” and / Or “— (CH ₂ ) _n —” is replaced with “— (CH ₂ ) ₃ —C ^* H (CH ₃ ) — (CH ₂ ) ₂ —” or “— (CH ₂ ) ₂ —C ^* H (CH ₃ )-(CH ₂ ) ₃ — ”.

  The photopolymerizable liquid crystal compound can be converted into a liquid crystal state by heat treatment, for example, by developing a nematic liquid crystal layer and homeotropically aligning with the side chain type liquid crystal polymer, and then polymerizing or crosslinking the photopolymerizable liquid crystal compound. As a result, the durability of the homeotropic alignment liquid crystal film can be improved.

  The ratio of the photopolymerizable liquid crystal compound and the side chain type liquid crystal polymer in the liquid crystal composition is not particularly limited and is appropriately determined in consideration of the durability of the obtained homeotropic alignment liquid crystal film. Photopolymerizable liquid crystal compound: side chain type liquid crystal polymer (weight ratio) = about 0.1: 1 to 30: 1 is preferable, 0.5: 1 to 20: 1 is particularly preferable, and 1: 1 to 10: is more preferable. 1 is preferred.

  The liquid crystalline composition usually contains a photopolymerization initiator. Various photopolymerization initiators can be used without particular limitation. Examples of the photopolymerization initiator include Irgacure 907, 184, 651, and 369 manufactured by Ciba Specialty Chemicals. The addition amount of the photopolymerization initiator is added to such an extent that the homeotropic orientation of the liquid crystalline composition is not disturbed in consideration of the type of the photopolymerized liquid crystal compound, the blending ratio of the liquid crystalline composition, and the like. Usually, about 0.5-30 weight part is preferable with respect to 100 weight part of photopolymerizable liquid crystal compounds. Particularly preferred is 3 parts by weight or more.

  The homeotropic alignment liquid crystal layer is produced by applying a homeotropic alignment side chain type liquid crystal polymer on a substrate and then aligning the side chain type liquid crystal polymer in a liquid crystal state and maintaining the alignment state. This is done by immobilizing with. When a homeotropic alignment liquid crystalline composition comprising the side chain liquid crystal polymer and the photopolymerizable liquid crystal compound is used, this is applied to a substrate, and then the liquid crystalline composition is homeomorphized in a liquid crystal state. A tropic alignment is performed, and light irradiation is performed while maintaining the alignment state.

  The substrate on which the side chain type liquid crystal polymer or liquid crystalline composition is applied may have any shape of a glass substrate, a metal foil, a plastic sheet, or a plastic film. The plastic film is not particularly limited as long as it does not change depending on the orientation temperature. For example, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, polycarbonate polymers, Examples thereof include a film made of a transparent polymer such as an acrylic polymer such as polymethyl methacrylate. The vertical alignment film may not be provided on the substrate. The thickness of the substrate is usually about 10 to 1000 μm.

  The side chain type liquid crystal polymer or liquid crystal composition is applied to the substrate by a solution coating method using a solution obtained by dissolving the side chain type liquid crystal polymer or liquid crystal composition in a solvent, or the liquid crystal polymer or liquid crystal property. Although the method of melt | dissolving and melt-coating a composition is mentioned, Among these, the method of coating the solution of a side chain type liquid crystal polymer or a liquid crystalline composition on a support substrate by a solution coating method is preferable.

  Examples of the method for applying a solution of a side chain type liquid crystal polymer or liquid crystal composition adjusted to a desired concentration using the above-mentioned solvent on a substrate include a roll coating method, a gravure coating method, a spin coating method, A bar coat method or the like can be employed. After coating, the solvent is removed, and a liquid crystal polymer layer or a liquid crystal composition layer is formed on the substrate. The conditions for removing the solvent are not particularly limited, as long as the solvent can be generally removed and the liquid crystal polymer layer or the liquid crystal composition layer does not flow or even flow down. Usually, the solvent is removed by drying at room temperature, drying in a drying furnace, heating on a hot plate, or the like. Among these coating methods, the gravure coating method is preferably used in the present invention because it is easy to uniformly coat a large area.

  Next, the side chain type liquid crystal polymer layer or liquid crystal composition layer formed on the supporting substrate is brought into a liquid crystal state and homeotropically aligned. For example, heat treatment is performed so that the side chain type liquid crystal polymer or the liquid crystalline composition is in the liquid crystal temperature range, and homeotropic alignment is performed in the liquid crystal state. The heat treatment can be performed by the same method as the above drying method. The heat treatment temperature varies depending on the type of the side chain type liquid crystal polymer or liquid crystalline composition to be used and the support substrate, and cannot be generally stated, but is usually in the range of 60 to 300 ° C, preferably 70 to 200 ° C. The heat treatment time varies depending on the heat treatment temperature and the type of the side chain type liquid crystal polymer or liquid crystal composition or substrate used, but cannot be generally stated, but is usually in the range of 10 seconds to 2 hours, preferably 20 seconds to 30 minutes. Selected. If it is shorter than 10 seconds, homeotropic alignment formation may not proceed sufficiently. Among these orientation temperatures and treatment times, in the present invention, it is preferable from the viewpoint of workability and mass productivity that the treatment time is about 30 seconds to 10 minutes at an orientation temperature of 80 to 150 ° C.

  After the heat treatment is completed, a cooling operation is performed. As the cooling operation, the homeotropic alignment liquid crystal film after the heat treatment can be performed by taking it out from the heating atmosphere in the heat treatment operation to room temperature. Moreover, you may perform forced cooling, such as air cooling and water cooling. The orientation of the homeotropic alignment layer of the side chain type liquid crystal polymer is fixed by cooling to the glass transition temperature or lower of the side chain type liquid crystal polymer.

In the case of a liquid crystalline composition, the homeotropic liquid crystal alignment layer thus fixed is irradiated with light to polymerize or crosslink the photopolymerizable liquid crystal compound to fix the photopolymerizable liquid crystal compound, A homeotropic alignment liquid crystal layer with improved durability is obtained. Light irradiation is performed by, for example, ultraviolet irradiation. The ultraviolet irradiation conditions are preferably in an inert gas atmosphere in order to sufficiently promote the reaction. Usually, a high-pressure mercury ultraviolet lamp having an illuminance of about 80 to 160 mW / cm ² is typically used. Different types of lamps such as metahalide UV lamps and incandescent tubes can also be used. It should be noted that the liquid crystal layer surface temperature at the time of ultraviolet irradiation is appropriately adjusted by, for example, a cold mirror, water cooling or other cooling treatment, or by increasing the line speed.

  In this way, a thin film of a side chain type liquid crystal polymer or a liquid crystalline composition is produced, and a homeotropic alignment liquid crystal layer is obtained by fixing while maintaining the alignment property.

  The thickness of the homeotropic alignment liquid crystal film is not particularly limited, but the thickness of the homeotropic alignment liquid crystal film layer made of the coated side chain liquid crystal polymer is preferably about 0.5 to 200 μm. The homeotropic alignment liquid crystal layer can be used with or without peeling from the substrate.

  As the retardation film B, a film having an Nz coefficient of 0.3 <Nz <0.7 and an in-plane retardation (Re) of 200 to 300 nm is used. Examples of the retardation film include a birefringent film of a polymer film and an alignment film of a liquid crystal polymer.

  Examples of the polymer include polyolefins such as polystyrene, polycarbonate, and polypropylene, polyesters such as polyethylene terephthalate and polyethylene naphthalate, alicyclic polyolefins such as polynorbornene, polyvinyl alcohol, polyvinyl butyral, polymethyl vinyl ether, and polyhydroxyethyl acrylate. , Hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, polyarylate, polysulfone, polyethersulfone, polyphenylene sulfide, polyphenylene oxide, polyallylsulfone, polyvinyl alcohol, polyamide, polyimide, polyvinyl chloride, cellulosic polymer, or two of these Ternary and ternary copolymers, graft copolymers, and bren Things and the like. The retardation film controls the refractive index in the thickness direction by a method of stretching a polymer film biaxially in the plane direction, a method of stretching uniaxially or biaxially in the plane direction, and stretching in the thickness direction, etc. Can be obtained. Further, it can be obtained by, for example, a method in which a heat-shrinkable film is adhered to a polymer film and the polymer film is stretched or / and contracted by tilting under the action of the shrinkage force by heating.

  Examples of the liquid crystalline polymer include various main chain types and side chain types in which a conjugated linear atomic group (mesogen) imparting liquid crystal alignment is introduced into the main chain or side chain of the polymer. It is done. Specific examples of the main chain type liquid crystalline polymer include, for example, a nematic alignment polyester liquid crystalline polymer, a discotic polymer, and a cholesteric polymer having a structure in which a mesogen group is bonded to a spacer portion that imparts flexibility. . Specific examples of the side chain type liquid crystalline polymer include polysiloxane, polyacrylate, polymethacrylate, or polymalonate as a main chain skeleton, and a nematic alignment imparting paraffin through a spacer portion composed of a conjugated atomic group as a side chain. Examples thereof include those having a mesogen moiety composed of a substituted cyclic compound unit. The alignment film of these liquid crystalline polymers is, for example, a liquid crystalline polymer on an alignment-treated surface such as a surface of a thin film such as polyimide or polyvinyl alcohol formed on a glass plate, or an oblique deposition of silicon oxide. A solution in which the liquid crystal polymer is oriented by developing and heat-treating the above solution, and particularly in a tilted orientation, is preferred.

  The lamination of the retardation film and the polarizing plate, and further the lamination to the liquid crystal panel may be simply arranged, and can be performed by an adhesive layer or the like. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited. For example, an acrylic polymer, silicone-based polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer is appropriately selected. Can be used. In particular, those having excellent optical transparency such as an acrylic pressure-sensitive adhesive, exhibiting appropriate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties, and being excellent in weather resistance, heat resistance and the like can be preferably used.

  For each layer such as an optical film and an adhesive layer, for example, a method of treating with an ultraviolet absorber such as a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, a cyanoacrylate compound, or a nickel complex compound Those having an ultraviolet absorbing ability may be used.

  As shown in FIG. 1, the horizontal electric field type active matrix liquid crystal display device of the present invention has a horizontal electric field type liquid crystal panel LC having a liquid crystal layer whose orientation orientation is changed by an electric field parallel to the substrate surface. One side has a backlight. Although the backlight is provided on the incident side, it is omitted in the drawing. In FIG. 1, the backlight can be arranged on either the side where the polarizing plate P1 is arranged or on the side where the polarizing plate P2 is arranged, but the backlight is arranged on the side where the polarizing plate P2 in FIG. 1 is arranged. Is preferred.

  The liquid crystal panel includes a pair of substrates sandwiching a liquid crystal layer, an electrode group formed on one of the pair of substrates, a liquid crystal composition material layer having dielectric anisotropy sandwiched between the substrates, and the pair of substrates. An alignment control layer formed on the opposite side of the substrate for aligning the molecular arrangement of the liquid crystal composition material in a predetermined direction, and a driving means for applying a driving voltage to the electrode group. The electrode group has an arrangement structure arranged so as to apply an electric field mainly parallel to the interface between the alignment control layer and the liquid crystal composition material layer.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

  In-plane retardation (Re) and thickness direction retardation (Rth) were measured at a wavelength of 590 nm by an automatic birefringence measuring apparatus (manufactured by Oji Scientific Instruments Co., Ltd., automatic birefringence meter KOBRA21ADH). For the retardation film B, the Nz coefficient was calculated. In measuring the optical phase difference, measurement light was incident on the sample surface vertically or obliquely. The homeotropic orientation can be confirmed from the fact that the phase difference increases with the increase in the incident angle of the measuring light.

Example 1
(Retardation films A1, A2)

上記の化６（式中の数字はモノマーユニットのモル％を示し、便宜的にブロックポリマー体で示している、重量平均分子量５０００）で示される側鎖型液晶ポリマー５重量部、ネマチック液晶相を示す重合性液晶（Ｐａｌｉｏｃｏｌｏｒ ＬＣ２４２，ＢＡＳＦ製）２０重量部および光開始剤（イルガキュア９０７，チバスペシャルティケミカルズ社製）を前記重合性液晶に対して３重量部を、シクロへキサノン７５重量部に溶解した溶液を調製した。当該溶液を、延伸基材フィルム（日本ゼオン社製，ゼオノアフィルム）上に、バーコーターで、厚み０．６μｍで塗工し、１００℃で１０分間乾燥、ＵＶ照射し硬化させることによりホメオトロピック配向液晶層を得た。ホメオトロピック配向液晶層は、面内位相差（Ｒｅ）は略ゼロ、厚み方向位相差（Ｒｔｈ_2,4）＝−６０ｎｍであった。

5 parts by weight of a side chain type liquid crystal polymer represented by the above chemical formula 6 (the number in the formula represents mol% of the monomer unit, and is represented by a block polymer for convenience), and a nematic liquid crystal phase. 20 parts by weight of a polymerizable liquid crystal (Paliocolor LC242, manufactured by BASF) and 3 parts by weight of a photoinitiator (Irgacure 907, manufactured by Ciba Specialty Chemicals) were dissolved in 75 parts by weight of cyclohexanone. A solution was prepared. The solution is coated on a stretched substrate film (Zeon Corporation, ZEONOR film) with a thickness of 0.6 μm using a bar coater, dried at 100 ° C. for 10 minutes, and cured by UV irradiation for homeotropic alignment. A liquid crystal layer was obtained. The homeotropic alignment liquid crystal layer had an in-plane retardation (Re) of substantially zero and a thickness direction retardation (Rth _2,4 ) = − 60 nm.

(Phase difference film B)
A heat-shrinkable film was adhered to both sides of the polycarbonate film via an adhesive layer, and then uniaxially stretched 1.3 times at 152 ° C. to obtain a stretched film. The obtained stretched film had an in-plane retardation (Re) of 270 nm and an Nz coefficient = 0.50.

(Polarizing plate with retardation film / viewing side)
The retardation film A1 and the retardation film B were bonded together by a roll-to-roll through a 21 μm thick adhesive, and then the ZEONOR film was peeled off. Furthermore, on the side of the retardation film A, a polarizing plate (manufactured by Nitto Denko Corporation, SEG1224DU) was bonded through an adhesive having a thickness of 21 μm to obtain a laminated polarizing plate with a retardation film. The said polarizing plate with a phase difference film was used for the visual recognition side.

The polarizing plate is obtained by laminating a protective film with an adhesive on both surfaces of a film (polarizer: 20 μm) stretched by adsorbing iodine on a polyvinyl alcohol film. As the protective film, a triacetyl cellulose film having an in-plane retardation (Re) of 4 nm and a thickness direction retardation (Rth _1,3 ) of +60 nm was used. The absorption axis of the polarizer and the slow axis of the protective film are laminated so as to be parallel. The difference between the absolute value of a thickness direction retardation of the protective film and (Rth _1), the thickness direction retardation of the retardation film A1 (homeotropic liquid crystal layer) (Rth ₃₎ is 0 nm. The absorption axis of the polarizing plate and the slow axis of the retardation film B were arranged to be perpendicular.

(Polarizing plate with retardation film / backlight side)
The retardation film A2 (the retardation film A1 and the retardation film A2 are the same in Example 1) and a polarizing plate (manufactured by Nitto Denko Corporation, SEG1224DU) are bonded together with a 21 μm-thick adhesive and laminated and integrated. A polarizing plate with a retardation film was obtained. The polarizing plate with a retardation film was used on the backlight side.

The absorption axis of the polarizer and the slow axis of the protective film are laminated so as to be parallel. The difference between the absolute value of a thickness direction retardation of the protective film and (Rth _3), the thickness direction retardation of the retardation film A2 (homeotropic liquid crystal layer) (Rth ₄₎ is 0 nm.

(Liquid crystal display device)
As shown in FIG. 1, the polarizing plate of the polarizing film with the retardation film is arranged on both sides of the IPS mode liquid crystal panel, with the upper side as the viewing side and the lower side as the backlight side, as shown in FIG. Thus, a liquid crystal display device was obtained. The slow axis of the retardation film B and the absorption axis of the upper polarizing plate were perpendicular to each other, and the absorption axes of the upper and lower polarizing plates were perpendicular to each other.

Example 2
(Phase difference film A1)
In Example 1, a homeotropic alignment liquid crystal layer was obtained in the same manner as in Example 1 except that coating was performed with a thickness of 0.5 μm. The homeotropic alignment liquid crystal layer had an in-plane retardation (Re) of substantially zero and a thickness direction retardation (Rth ₂ ) = − 50 nm.

(Phase difference film B)
A stretched film was obtained in the same manner as in Example 1 except that the stretch ratio was changed to 1.28 times in Example 1. The obtained stretched film had an in-plane retardation (Re) of 255 nm and an Nz coefficient = 0.54.

(Polarizing plate with retardation film / viewing side)
In Example 1, the polarizing plate with retardation film was obtained like Example 1 except having used what was obtained above as retardation film A1 and retardation film B. The said polarizing plate with a phase difference film was used for the visual recognition side. The thickness direction retardation of the protective film and (Rth _1), the difference between the absolute value of a thickness direction retardation of the retardation film A1 (homeotropic liquid crystal layer) (Rth ₂₎ is 10 nm.

(Phase difference film A2)
In Example 1, a homeotropic alignment liquid crystal layer was obtained in the same manner as in Example 1 except that coating was performed with a thickness of 0.7 μm. The homeotropic alignment liquid crystal layer had an in-plane retardation (Re) of substantially zero and a thickness direction retardation (Rth ₄ ) = − 70 nm.

(Polarizing plate with retardation film / backlight side)
In Example 1, the polarizing plate with retardation film was obtained like Example 1 except having used what was obtained above as retardation film A2. The polarizing plate with a retardation film was used on the backlight side. The difference between the absolute value of a thickness direction retardation of the protective film and (Rth _3), the thickness direction retardation of the retardation film A2 (homeotropic liquid crystal layer) (Rth ₄₎ is 10 nm.

(Liquid crystal display device)
In Example 1, a liquid crystal display device was obtained in the same manner as in Example 1 except that the polarizing plate with retardation film on the viewing side and the backlight side was used as described above.

Example 3
(Phase difference film A1)
In Example 1, a homeotropic alignment liquid crystal layer was obtained in the same manner as in Example 1 except that coating was performed with a thickness of 0.7 μm. The homeotropic alignment liquid crystal layer had an in-plane retardation (Re) of substantially zero and a thickness direction retardation (Rth ₂ ) = − 70 nm.

(Phase difference film B)
A stretched film was obtained in the same manner as in Example 1 except that the stretch ratio was changed to 1.32 in Example 1. The obtained stretched film had an in-plane retardation (Re) of 290 nm and an Nz coefficient = 0.45.

(Polarizing plate with retardation film / viewing side)
In Example 1, the polarizing plate with retardation film was obtained like Example 1 except having used what was obtained above as retardation film A1 and retardation film B. The said polarizing plate with a phase difference film was used for the visual recognition side. The thickness direction retardation of the protective film and (Rth _1), the difference between the absolute value of a thickness direction retardation of the retardation film A (homeotropic liquid crystal layer) (Rth ₂₎ is 10 nm.

(Phase difference film A2)
In Example 1, a homeotropic alignment liquid crystal layer was obtained in the same manner as in Example 1 except that coating was performed with a thickness of 0.5 μm. The homeotropic alignment liquid crystal layer had an in-plane retardation (Re) of substantially zero and a thickness direction retardation (Rth ₄ ) = − 50 nm.

(Polarizing plate with retardation film / backlight side)
In Example 1, the polarizing plate with retardation film was obtained like Example 1 except having used what was obtained above as retardation film A2. The polarizing plate with a retardation film was used on the backlight side. The difference between the absolute value of a thickness direction retardation of the protective film and (Rth _3), the thickness direction retardation of the retardation film A2 (homeotropic liquid crystal layer) (Rth ₄₎ is 10 nm.

(Liquid crystal display device)
In Example 1, a liquid crystal display device was obtained in the same manner as in Example 1 except that the polarizing plate with retardation film on the viewing side and the backlight side was used as described above.

Comparative Example 1
(Phase difference film A1)
In Example 1, a homeotropic alignment liquid crystal layer was obtained in the same manner as in Example 1 except that coating was performed with a thickness of 3.0 μm. The homeotropic alignment liquid crystal layer had an in-plane retardation (Re) of substantially zero and a thickness direction retardation (Rth ₂ ) = − 300 nm.

(Phase difference film B)
In Example 1, a stretched film was obtained in the same manner as in Example 1 except that the stretch ratio was 1.45 times and the stretch temperature was changed to 45 ° C. The obtained stretched film had an in-plane retardation (Re) of 440 nm and an Nz coefficient = 0.78.

(Polarizing plate with retardation film / viewing side)
In Example 1, the polarizing plate with retardation film was obtained like Example 1 except having used what was obtained above as retardation film A1 and retardation film B. The said polarizing plate with a phase difference film was used for the visual recognition side. The thickness direction retardation of the protective film and (Rth _1), the difference between the absolute value of a thickness direction retardation of the retardation film A1 (homeotropic liquid crystal layer) (Rth ₂₎ is 240 nm.

(Phase difference film A2)
In Example 1, a homeotropic alignment liquid crystal layer was obtained in the same manner as in Example 1 except that coating was performed with a thickness of 3.0 μm. The homeotropic alignment liquid crystal layer had an in-plane retardation (Re) of substantially zero and a thickness direction retardation (Rth ₄ ) = − 300 nm.

(Polarizing plate with retardation film / backlight side)
In Example 1, the polarizing plate with retardation film was obtained like Example 1 except having used what was obtained above as retardation film A2. The polarizing plate with a retardation film was used on the backlight side. The difference between the absolute value of a thickness direction retardation of the protective film and (Rth _3), the thickness direction retardation of the retardation film A2 (homeotropic liquid crystal layer) (Rth ₄₎ is 240 nm.

(Liquid crystal display device)
In Example 1, a liquid crystal display device was obtained in the same manner as in Example 1 except that the polarizing plate with retardation film on the viewing side and the backlight side was used as described above.

Comparative Example 2
(Liquid crystal display device)
A polarizing plate used in Example 1 was placed on both surfaces of the IPS mode liquid crystal panel used in Example 1 so that their absorption axes were perpendicular to obtain a liquid crystal display device.

(Evaluation)
The liquid crystal display devices obtained in Examples and Comparative Examples were contrast ratios (Co) ≧ 10 in the vertical and horizontal directions, diagonal 45 ° -225 °, and diagonal 135 ° -315 ° in the EZcontrast 160D manufactured by ELDIM. The viewing angle was measured. The results are shown in Table 1.

It is an example of sectional drawing of the IPS mode liquid crystal display device of this invention. It is an example of the conceptual diagram which shows the axial direction of each film used for the IPS mode liquid crystal display device of this invention.

Explanation of symbols

P1 polarizing plate P2 polarizing plate a polarizer b, b ′ protective film A1 retardation film having a relationship of nz> nx ≧ ny A2 retardation film having a relationship of nz> nx ≧ ny B Three-dimensional refractive index was controlled Retardation film LC IPS mode liquid crystal cell

Claims (7)

A transverse electric field type liquid crystal panel having a liquid crystal layer whose orientation orientation is changed by an electric field parallel to the substrate surface; first and second polarizing plates disposed with the liquid crystal panel sandwiched therebetween; and the first polarizing plate; In a liquid crystal display device including a first optical film disposed between the liquid crystal panels, and a second optical film disposed between the second polarizing plate and the liquid crystal panel,
The first optical film has a retardation film A1 having a relationship of nz> nx ≧ ny, an in-plane retardation (Re) of 200 to 300 nm, a relationship of nx>nz> ny, and an Nz coefficient. Including a retardation film B having a controlled three-dimensional refractive index such that satisfies 0.3 <Nz <0.7,
The second optical film includes a retardation film A2 having a relationship of nz> nx ≧ ny,
And the slow axis of the retardation film B and the absorption axes of the first and second polarizing plates are parallel or perpendicular,
The first polarizing plate and the second polarizing plate both have protective films on both sides of the polarizer,
The thickness direction retardation (Rth ₁ ) of the protective film on the liquid crystal panel side of the first polarizing plate and the thickness direction retardation (Rth ₂ ) of the retardation film A1 are:
0 ≦ || Rth ₁ | − | Rth ₂ || ≦ 15 nm, and
The thickness direction retardation (Rth ₃ ) of the protective film on the liquid crystal panel side of the second polarizing plate and the thickness direction retardation (Rth ₄ ) of the retardation film A2 are:
Satisfying 0 ≦ || Rth ₃ | − | Rth ₄ || ≦ 15 nm ,
The thickness direction retardation (Rth ₁₎ and (Rth ₃₎ is, + 30~ + 100nm, a liquid crystal display device comprising der Rukoto.
However, in each of the above films, the direction in which the in-plane refractive index in the film plane is the maximum is the X axis, the direction perpendicular to the X axis is the Y axis, and the thickness direction of the film is the Z axis. When the refractive index at nx, ny, and nz is the film thickness d (nm),
In-plane retardation (Re) = (nx−ny) × d,
Nz = (nx−nz) / (nx−ny),
Thickness direction retardation (Rth) = (nx−nz) × d.
The thickness direction retardation of the retardation film A1 (Rth ₂₎ and the thickness direction retardation of the retardation film A2 is (Rth _4), a liquid crystal display device according to claim 1, characterized in that the -30 to-100 nm .   3. The liquid crystal display device according to claim 1, wherein the retardation film A1 and / or the retardation film A2 includes a liquid crystal polymer fixed in homeotropic alignment. The first polarizing plate and the second polarizing plate both have protective films on both sides of the polarizer,
The slow axis of the protective film on the liquid crystal panel side of the first polarizing plate and the absorption axis of the first polarizing plate are parallel or perpendicular,
4. The liquid crystal display according to claim 1, wherein the slow axis of the protective film on the liquid crystal panel side of the second polarizing plate and the absorption axis of the second polarizing plate are parallel or perpendicular. apparatus.   5. The liquid crystal display device according to claim 1, wherein the first optical film is laminated in the order of the retardation film A <b> 1 and the retardation film B from the first polarizing plate side. The material of the protective film on the liquid crystal panel side of the first polarizing plate and the material of the protective film on the liquid crystal panel side of the second polarizing plate are triacetyl cellulose. The liquid crystal display device described. The retardation film A1 and / or the retardation film A2 are formed of a liquid crystal polymer and a photopolymerizable liquid crystal compound fixed in homeotropic alignment. Liquid crystal display device.

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