JP2007212960A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device having luminous display and high contrast and nearly free from viewing angle dependency and to provide a transflective liquid crystal display device having luminous display and high contrast and nearly free from viewing angle dependency especially in a transmission mode. <P>SOLUTION: The liquid crystal display device is constituted of at least a polarizing plate, a first optically anisotropic layer having a specified retardation value, a second optically anisotropic layer having a specified retardation value and comprising a liquid crystal film whose nematic hybrid alignment structure is fixed, a liquid crystal cell where a liquid crystal layer is interposed between upper and lower substrates disposed opposite to each other, a third optically anisotropic layer whose retardation value (Re) in the plane direction, retardation value (Rth) in the thickness direction and the ratio Rth/Re are specified values, the first optically anisotropic layer and a polarizing plate in this order from a backlight side. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device used in an OA device such as a word processor or a personal computer, a portable information device such as an electronic notebook or a cellular phone, a camera-integrated VTR equipped with a liquid crystal monitor, or a reflective type and a transmissive type. And a transflective liquid crystal display device.

  There are three types of liquid crystal display devices: a transmissive type capable of displaying an image in a transmissive mode, a reflective type capable of displaying an image in a reflective mode, and a transflective type capable of displaying an image in both a transmissive mode and a reflective mode. Due to its thin and light features, it is widely used as a display device for notebook computers and televisions. In particular, the transflective liquid crystal display device employs a display method that combines a reflective type and a transmissive type. By switching to one of the display methods according to the ambient brightness, the power consumption is reduced, and However, since clear display can be performed even in a dark place, it is frequently used in various portable electronic devices.

By the way, the transmissive, reflective, and transflective liquid crystal display devices, particularly in the transmissive mode, have a lower display contrast and a different display color when viewed obliquely due to the refractive index anisotropy of the liquid crystal molecules. Or the problem of viewing angle such as inversion of gradation cannot be avoided, and improvement thereof is desired.
As a method for solving this problem, in the past, in a transmissive liquid crystal display device using a TN mode (a twist angle of a liquid crystal layer of 90 degrees), an optical compensation film has been proposed to be placed between a liquid crystal cell and an upper and lower polarizing plate and put into practical use. Has been.
For example, a configuration in which an optical compensation film in which a discotic liquid crystal is hybrid-aligned is disposed between the liquid crystal cell and the upper and lower polarizing plates, and an optical compensation film in which a liquid crystalline polymer is nematic hybrid-oriented is disposed between the liquid crystal cell and the upper and lower polarizing plates. (See Patent Document 1, Patent Document 2, and Patent Document 3).

In the transflective liquid crystal display device, in the transmission mode, it is necessary to dispose circularly polarizing plates composed of one or a plurality of uniaxial retardation films and polarizing plates above and below the liquid crystal cell in terms of display principle. is there.
In order to enlarge the viewing angle of the transmission mode of the transflective liquid crystal display device, a method of using an optical compensation film in which a nematic hybrid alignment is performed on a circularly polarizing plate disposed between a liquid crystal cell and a backlight (Patent Document 4, Patent Document) 5) has been proposed and put into practical use.

However, even if the above method is used, it is difficult to say that the viewing angle problems such as a decrease in display contrast, a change in display color, or a gradation inversion when viewed from an oblique direction have been sufficiently solved. In particular, in a transflective liquid crystal display device, since a circularly polarizing plate composed of one or more stretched films and a polarizing plate is used in principle as described above, further improvement in viewing angle is required.
Japanese Patent No. 2640083 JP-A-11-194325 Japanese Patent Laid-Open No. 11-194371 JP 2002-31717 A JP 2004-157454 A

  In view of the above problems, an object of the present invention is to provide a liquid crystal display device that has a bright display, high contrast, and little viewing angle dependency. In addition, the present invention provides a transflective liquid crystal display device having a bright display, high contrast, and little viewing angle dependency, particularly in a transmissive mode, by providing a reflective layer partially in a liquid crystal cell. With the goal.

That is, according to the first aspect of the present invention, in order from the backlight side, the polarizing plate, the first optical anisotropic layer having a retardation value of 210 to 300 nm at a wavelength of 550 nm, and the retardation value of 50 to 140 nm at a wavelength of 550 nm. A second optically anisotropic layer, a liquid crystal cell in which a liquid crystal layer is sandwiched between an upper substrate and a lower substrate disposed opposite to each other, and a third optical anisotropy having a retardation value of 50 to 140 nm at a wavelength of 550 nm Liquid crystal display device comprising at least an optical layer, a first optical anisotropic layer having a retardation value of 210 to 300 nm at a wavelength of 550 nm, and a polarizing plate, wherein the second optical anisotropic layer is a nematic hybrid A liquid characterized in that it comprises at least a liquid crystal film having a fixed alignment structure, and the third optically anisotropic layer satisfies the following formulas [1] to [3]: Display device, and more.
[1] 50 ≦ Re ≦ 140
[2] −250 ≦ Rth ≦ −50
[3] -3 <Rth / Re <-0.5
(Here, Re means an in-plane retardation value of the third optically anisotropic layer, and Rth means a thickness direction retardation value of the third optically anisotropic layer.) Re and Rth are respectively Re = (Nx−Ny) × d [nm] and Rth = {Nz− (Nx + Ny) / 2} × d [nm], where d is the third optical anisotropy. The layer thickness (nm), Nx, Ny are the in-plane main refractive index of the third optical anisotropic layer, Nz is the main refractive index in the thickness direction, and Nx>Ny> Nz.

In the second aspect of the present invention, in order from the backlight side, a polarizing plate, a first optical anisotropic layer having a retardation value of 210 to 300 nm at a wavelength of 550 nm, and a retardation value of 50 to 140 nm at a wavelength of 550 nm. 3, a liquid crystal cell in which a liquid crystal layer is sandwiched between an upper substrate and a lower substrate that are arranged opposite to each other, a second optical anisotropy having a retardation value of 50 to 140 nm at a wavelength of 550 nm Layer, a liquid crystal display device comprising at least a first optically anisotropic layer having a retardation value of 210 to 300 nm and a polarizing plate at a wavelength of 550 nm, wherein the second optically anisotropic layer is nematic hybrid alignment A liquid crystal display device comprising at least a liquid crystal film having a fixed structure, wherein the third optical anisotropic layer satisfies the following formulas [1] to [3]: It relates.
[1] 50 ≦ Re ≦ 140
[2] −250 ≦ Rth ≦ −50
[3] -3 <Rth / Re <-0.5
(Here, Re means an in-plane retardation value of the third optically anisotropic layer, and Rth means a thickness direction retardation value of the third optically anisotropic layer.) Re and Rth are respectively Re = (Nx−Ny) × d [nm] and Rth = {Nz− (Nx + Ny) / 2} × d [nm], where d is the third optical anisotropy. The layer thickness (nm), Nx, Ny are the in-plane main refractive index of the third optical anisotropic layer, Nz is the main refractive index in the thickness direction, and Nx>Ny> Nz.

  A third aspect of the present invention relates to the liquid crystal display device according to the first or second aspect of the present invention, wherein the liquid crystal layer uses a twisted nematic mode.

  A fourth aspect of the present invention relates to the liquid crystal display device according to the first or second aspect of the present invention, wherein the liquid crystal layer has a parallel orientation and a twist angle of 0 degree.

  A fifth aspect of the present invention relates to the liquid crystal display device according to the first or second aspect of the present invention, wherein the first and third optical anisotropic layers are polymer stretched films.

  According to a sixth aspect of the present invention, an angle between a tilt direction in which a hybrid direction of the liquid crystal film of the second optically anisotropic layer is projected onto a substrate plane and a rubbing direction of the liquid crystal layer is within ± 30 degrees. The present invention relates to a liquid crystal display device according to the first or second aspect of the invention.

  According to a seventh aspect of the present invention, the liquid crystal film of the second optically anisotropic layer is made of a liquid crystal material exhibiting optically positive uniaxial properties, and the nematic hybrid alignment formed in the liquid crystal state by the liquid crystal material is fixed. The liquid crystal display device according to the first or second aspect of the present invention, wherein the liquid crystal film is a liquid crystal film having an average tilt angle of 36 to 45 degrees in the nematic hybrid alignment.

  In an eighth aspect of the present invention, the lower substrate of the liquid crystal cell includes a transflective electrode in which a region having a reflective function and a region having a transmissive function are formed. The present invention relates to a liquid crystal display device described in the second item.

  According to a ninth aspect of the present invention, in the eighth aspect of the present invention, the thickness of the liquid crystal layer in the region where the liquid crystal cell has a reflection function is smaller than the thickness of the liquid crystal layer in a region where the liquid crystal cell has a transmission function. The liquid crystal display device described in 1.

  The liquid crystal display device of the present invention has features that display is bright, front contrast is high, and viewing angle dependency is small.

Hereinafter, the present invention will be described in detail.
The liquid crystal display device of the present invention has the following two configurations (A) or (B), and a member such as a light diffusion layer, a light control film, a light guide plate, and a prism sheet is added as necessary. There is no particular limitation. In terms of obtaining optical characteristics with little viewing angle dependency, either (A) or (B) may be used.
(A) Polarizing plate / first optical anisotropic layer / third optical anisotropic layer / liquid crystal cell / second optical anisotropic layer / first optical anisotropic layer / polarizing plate / backlight (B) Polarizing plate / first optical anisotropic layer / second optical anisotropic layer / liquid crystal cell / third optical anisotropic layer / first optical anisotropic layer / polarizing plate / backlight

Hereinafter, the constituent members used in the present invention will be described in order.
First, the liquid crystal cell used in the present invention will be described.
As liquid crystal cell methods, TN (Twisted Nematic) method, STN (Super Twisted Nematic) method, ECB (Electrically Controlled Birefringence) method, IPS (In-Plane Switching) method, VA (Vertical Alignment) method, OCB (Optically Compensated) Birefringence method, HAN (Hybrid Aligned Nematic) method, ASM (Axially Symmetric Aligned Microcell) method, halftone gray scale method, domain division method, display method using ferroelectric liquid crystal, anti-ferroelectric liquid crystal, etc. The method is mentioned. As a method of the liquid crystal cell, a display method using ECB (electrically controlled birefringence) in which liquid crystal molecules are homogeneously aligned is preferable. When the TN method, STN method, etc. are used, when the liquid crystal layer thickness of the transmissive display portion is set to be thick and the liquid crystal layer thickness of the reflective display portion is set to be thin, if the liquid crystal layer thickness difference between the two regions is increased, both This is because problems in manufacturing are likely to occur due to alignment defects of liquid crystal molecules occurring at the boundaries of the regions.
Also, the liquid crystal cell driving method is not particularly limited, and a passive matrix method used for STN-LCDs, etc., and an active matrix method using active electrodes such as TFT (Thin Film Transistor) electrodes and TFD (Thin Film Diode) electrodes, Any driving method such as a plasma addressing method may be used.

The liquid crystal cell has a configuration in which a liquid crystal layer is sandwiched between two transparent substrates (an observer side is an upper substrate and a backlight side is a lower substrate) arranged opposite to each other.
The material exhibiting liquid crystallinity for forming the liquid crystal layer is not particularly limited, and examples thereof include various ordinary low-molecular liquid crystal substances, polymer liquid crystal substances, and mixtures thereof that can constitute various liquid crystal cells. In addition, a dye, a chiral agent, a non-liquid crystal substance, or the like can be added to these as long as liquid crystallinity is not impaired. In addition to the electrode substrate and the liquid crystal layer, the liquid crystal cell may include various components necessary for forming various types of liquid crystal cells described later.

The transparent substrate constituting the liquid crystal cell is not particularly limited as long as the liquid crystal material constituting the liquid crystal layer is aligned in a specific alignment direction. Specifically, a transparent substrate having the property of aligning the liquid crystal itself, a substrate itself lacking alignment ability, but a transparent substrate provided with an alignment film having the property of aligning liquid crystal, etc. Can also be used. Moreover, well-known things, such as ITO, can be used for the electrode of a liquid crystal cell. The electrode can usually be provided on the surface of the transparent substrate with which the liquid crystal layer is in contact. When a substrate having an alignment film is used, it can be provided between the substrate and the alignment film.
The liquid crystal display device of the present invention is a transmissive liquid crystal display device using a backlight, but a transflective film in which a region having a reflective function and a region having a transmissive function are formed on the lower substrate of the liquid crystal cell. By installing a conductive electrode, a transflective liquid crystal display device that can use both a reflection mode and a transmission mode can be obtained.

The region having a reflection function (hereinafter also referred to as a reflection layer) included in the transflective electrode is not particularly limited, and is a metal such as aluminum, silver, gold, chromium, platinum, or an alloy containing them, magnesium oxide. Examples thereof include oxides such as dielectric layers, dielectric multilayer films, liquid crystals exhibiting selective reflection, or combinations thereof. These reflective layers may be flat or curved. Furthermore, the reflective layer is processed to have a surface shape such as an uneven shape to give diffuse reflection, to the electrode on the electrode substrate opposite to the viewer side of the liquid crystal cell, or a combination thereof It may be.
The liquid crystal cell includes a transflective layer in which a region having a reflective function and a region having a transmissive function are formed. The region having the reflective function becomes a reflective display portion for performing reflective display, and the region having the transmissive function is transmissive. It becomes a transmissive display unit for performing display.

The liquid crystal layer thickness of the reflective display portion of the liquid crystal cell is preferably smaller than the liquid crystal layer thickness of the transmissive display portion. The reason for this will be described below.
First, transmissive display in the transmissive display unit when the liquid crystal layer thickness is set to a layer thickness suitable for reflective display will be described. When the liquid crystal layer suitable for reflective display is set, the amount of change in the polarization state due to the orientation change due to the external field such as the electric field of the liquid crystal layer is determined by the light incident from the observer side through the liquid crystal layer. So that a sufficient contrast ratio can be obtained by reciprocating through the liquid crystal layer. However, in this setting, the amount of change in the polarization state of the light that has passed through the liquid crystal layer is insufficient in the transmissive display unit. For this reason, in addition to the polarizing plate installed on the viewer side of the liquid crystal cell used for reflective display, even if the polarizing plate used only for transmissive display is installed on the back side of the liquid crystal cell as viewed from the viewer side, A sufficient display cannot be obtained. In other words, when the alignment condition of the liquid crystal layer is set to the alignment condition of the liquid crystal layer suitable for the reflective display portion, the transmissive display portion has insufficient lightness or the transmittance of dark display even if the lightness is sufficient. Does not decrease, and a contrast ratio sufficient for display cannot be obtained.

  More specifically, when performing reflective display, the liquid crystal in the liquid crystal layer is applied by an applied voltage so that a phase difference of approximately ¼ wavelength is given to light that passes through the liquid crystal layer only once. The orientation state is controlled. In this way, the liquid crystal layer thickness suitable for reflective display, that is, when the transmissive display is performed by performing the voltage modulation that gives the phase modulation of ¼ wavelength, the transmittance when the transmissive display section is dark display is sufficiently reduced. When the transmissive display portion is in bright display, light having about half the luminous intensity is absorbed by the polarizing plate on the light emission side, and sufficient bright display cannot be obtained. In addition, when an optical element such as a polarizing plate or a phase difference compensation plate is arranged to increase the brightness when the transmissive display portion is in bright display, the brightness when the transmissive display portion is in dark display is the brightness at the time of bright display. Therefore, the display contrast ratio becomes insufficient.

Conversely, in order to set the thickness of the liquid crystal layer under conditions suitable for transmissive display, it is necessary to perform voltage modulation on the liquid crystal layer so that a phase difference of ½ wavelength is given to the light transmitted through the liquid crystal layer. is there. Therefore, in order to use both reflected light and transmitted light for display with high resolution and excellent visibility, it is necessary to make the liquid crystal layer thickness of the reflective display portion smaller than the liquid crystal layer thickness of the transmissive display portion. . Ideally, the liquid crystal layer thickness of the reflective display portion is preferably about ½ of the liquid crystal layer thickness of the transmissive display portion.
The retardation value of the liquid crystal cell is preferably 200 nm to 400 nm, more preferably 250 nm to 350 nm in the transmissive display portion. Moreover, in a reflective display part, 100 nm-200 nm are preferable, More preferably, they are 120 nm-180 nm. If both the transmissive display unit and the reflective display unit are out of this range, unnecessary coloring and a decrease in brightness are undesirable.

  The polarizing plate used in the present invention is not particularly limited as long as the object of the present invention can be achieved, and a normal one used in a liquid crystal display device can be appropriately used. Specifically, iodine and / or dichroic dyes are applied to hydrophilic polymer films made of PVA such as polyvinyl alcohol (PVA) or partially acetalized PVA or partially saponified ethylene-vinyl acetate copolymer. It is possible to use a polarizing film composed of a polarizing film obtained by adsorbing and stretching, a polyene oriented film such as a polyvinyl chloride dehydrochlorinated product, and the like. A reflective polarizing film can also be used.

  The polarizing plate may be used alone, or may be provided with a transparent protective layer or the like on one or both sides of the polarizing film for the purpose of improving strength, improving moisture resistance, improving heat resistance, etc. good. Examples of the transparent protective layer include those obtained by laminating a transparent plastic film such as polyester or triacetyl cellulose directly or through an adhesive layer, a transparent resin coating layer, an acrylic or epoxy photocurable resin layer, and the like. . When these transparent protective layers are coated on both sides of the polarizing film, different protective layers may be provided on both sides.

The first optically anisotropic layer used in the present invention is not particularly limited as long as it has excellent transparency and uniformity, but a polymer stretched film or an optical compensation film made of liquid crystal can be preferably used. Examples of the stretched polymer film include a uniaxial or biaxial retardation film composed of a cellulose-based, polycarbonate-based, polyarylate-based, polysulfone-based, polyacryl-based, polyethersulfone-based, cyclic olefin-based polymer, or the like. Can do. The first and third optical anisotropic layers exemplified here may be composed only of a polymer stretched film, may be composed only of an optical compensation film made of liquid crystal, Both optical compensation films made of liquid crystals can be used in combination. Among them, a cyclic olefin polymer is preferable in terms of cost, high film uniformity, and low birefringence wavelength dispersion characteristics, which can suppress color modulation of image quality. In addition, as an optical compensation film made of liquid crystal, various liquid crystalline polymers exhibiting main chain type and / or side chain type liquid crystal properties such as liquid crystalline polyester, liquid crystalline polycarbonate, liquid crystalline polyacrylate, etc. Examples thereof include an optical compensation film obtained from a low molecular weight liquid crystal having a reactivity that can be increased in molecular weight, and the like. These films may be a self-supporting single film or formed on a transparent support substrate.
In the present invention, the retardation value of the first optically anisotropic layer at a wavelength of 550 nm is adjusted to 210 to 300 nm. The retardation value is more preferably 250 to 275 nm.

  The second optically anisotropic layer used in the present invention is an optically positive uniaxial liquid crystalline polymer, specifically, an optically positive uniaxial liquid crystalline polymer compound or at least one. An optically positive uniaxial liquid crystal polymer composition containing the liquid crystal polymer compound, and an average of the liquid crystal polymer compound or the liquid crystal polymer composition formed in a liquid crystal state It is a layer including at least a liquid crystal film in which a nematic hybrid alignment structure having a tilt angle of 5 to 45 degrees is fixed.

Here, the nematic hybrid alignment referred to in the present invention refers to an alignment form in which liquid crystal molecules are nematically aligned, and the angle between the director of the liquid crystal molecules and the film plane at this time is different between the upper surface and the lower surface of the film. Therefore, since the angle formed by the director and the film plane is different between the vicinity of the upper surface interface and the vicinity of the lower surface interface, the angle continuously changes between the upper surface and the lower surface of the film. I can say that.
In the film in which the nematic hybrid alignment state is fixed, the directors of the liquid crystal molecules are oriented at different angles at all positions in the film thickness direction. Therefore, the film no longer has an optical axis when viewed as a film structure.

  The average tilt angle as used in the present invention means the average value of the angle formed by the director of the liquid crystal molecules and the film plane in the film thickness direction of the liquid crystal film. In the liquid crystal film to be used in the present invention, the angle formed by the director and the film plane in the vicinity of one interface of the film is usually 20 to 90 degrees as an absolute value, preferably 40 to 85 degrees, and more preferably 70 to 80 degrees. In the opposite side of the surface, the angle is usually 0 to 20 degrees, preferably 0 to 10 degrees, and the average tilt angle is usually 5 to 5 degrees as an absolute value. It is 45 degrees, preferably 20 to 45 degrees, more preferably 25 to 43 degrees, and most preferably 36 to 40 degrees. When the average tilt angle is out of the above range, it is not desirable because there is a risk of a decrease in contrast when viewed from an oblique direction. The average tilt angle can be obtained by applying a crystal rotation method.

  The liquid crystal film constituting the second optically anisotropic layer used in the present invention can be any liquid crystal as long as the nematic hybrid alignment state as described above is fixed and has a specific average tilt angle. It may be formed from. For example, a liquid crystal film obtained by forming a low molecular liquid crystal in a nematic hybrid alignment in a liquid crystal state and then fixing by photocrosslinking or thermal crosslinking, or a liquid crystal film formed in a nematic hybrid alignment in a liquid crystal state and then cooling the alignment. A liquid crystal film obtained by fixing can be used. In addition, the liquid crystal film as used in the field of this invention does not ask | require whether the film itself exhibits liquid crystallinity, but means what is obtained by film-forming liquid crystal substances, such as a low molecular liquid crystal and a polymer liquid crystal.

  In addition, the film thickness for the liquid crystal film to exhibit a better viewing angle improving effect on the liquid crystal display device depends on the type of the target liquid crystal display element and various optical parameters. Although it cannot be said, it is usually in the range of 0.2 μm to 10 μm, preferably 0.3 μm to 5 μm, particularly preferably 0.5 μm to 2 μm. When the film thickness is less than 0.2 μm, a sufficient compensation effect may not be obtained. Further, if the film thickness exceeds 10 μm, the display may be unnecessarily colored.

  In addition, as the apparent retardation value in the plane when viewed from the normal direction of the liquid crystal film, in a film with nematic hybrid orientation, the refractive index in the direction parallel to the director (hereinafter referred to as ne) is perpendicular to the direction. When the refractive index (hereinafter referred to as “no”) is different and the value obtained by subtracting “no” from “ne” is the apparent birefringence, the apparent retardation value is the apparent birefringence and the absolute film thickness. Is given by the product of This phase difference value can be easily obtained by polarization optical measurement such as ellipsometry. The retardation value of the liquid crystal film is usually in the range of 10 nm to 400 nm, preferably 30 nm to 200 nm, particularly preferably 50 nm to 140 nm with respect to monochromatic light having a wavelength of 550 nm. When the phase difference value is less than 10 nm, a sufficient viewing angle expansion effect may not be obtained. On the other hand, if it is larger than 400 nm, the liquid crystal display device may be unnecessarily colored when viewed from an oblique direction.

The specific arrangement conditions of the optically anisotropic layer in the liquid crystal display device of the present invention will be described. In describing the more specific arrangement conditions, the optically anisotropic layer made of a liquid crystal film will be described with reference to FIGS. , The tilt direction of the optically anisotropic layer and the pretilt direction of the liquid crystal cell layer are respectively defined below.
First, the upper and lower sides of the optically anisotropic layer made of a liquid crystal film are respectively defined by the angle formed between the liquid crystal molecule director and the film plane in the vicinity of the film interface of the liquid crystal film constituting the optically anisotropic layer. The surface where the angle formed by the rectifier and the film plane forms an angle of 20 to 90 degrees on the acute angle side is defined as b surface, and the surface which forms the angle of 0 to 20 degrees on the acute angle side is defined as c surface. And
When the c-plane is viewed from the b-plane of this optical anisotropic element through the liquid crystal film layer, the angle formed by the liquid crystal molecule director and the projection component on the c-plane of the director is an acute angle and parallel to the projection component. The direction is defined as the tilt direction of the optical anisotropic element (FIGS. 1 and 2).
Next, usually, at the cell interface of the liquid crystal cell layer, the driving low-molecular liquid crystal is not parallel to the cell interface but is inclined at a certain angle, and this angle is generally referred to as a pretilt angle. A direction in which the angle formed by the projection component on the director interface is an acute angle and parallel to the projection component of the director is defined as the pretilt direction of the liquid crystal cell layer (FIG. 3).

The third optically anisotropic layer used in the present invention has negative refractive index anisotropy, that is, satisfies Nx>Ny> Nz (the meaning of symbols will be described later). In the third optically anisotropic layer, Re (in-plane retardation value) represented by the following formula [1] is preferably 50 to 140 nm, and more preferably 70 to 120 nm. preferable.
The third optically anisotropic layer preferably has an Rth (a retardation value in the thickness direction) represented by the following formula [2] of −250 to −50 nm, and −200 to −80 nm. Is more preferable.
The third optically anisotropic layer has an Rth / Re value (ratio of thickness direction retardation value to in-plane retardation value) represented by the following formula [3] larger than −3 to −0. Is preferably less than 0.5, more preferably in the range of -2 to -1.
[1] Re = (Nx−Ny) × d
[2] Rth = {Nz− (Nx + Ny) / 2} × d
[3] Rth / Re
In the above formula, Nx and Ny are in-plane main refractive indexes of the optically anisotropic layer, Nz is a main refractive index in the thickness direction, and d is the thickness (nm) of the optically anisotropic layer.

  In the present invention, the third optically anisotropic layer may be formed of a single layer or a multilayer as long as the above relationship is satisfied. The third optically anisotropic layer may be a polymer film that exhibits optical anisotropy, or may be one that exhibits optical anisotropy by aligning liquid crystalline molecules. When the third optical anisotropic layer is a polymer film, examples of the material for the polymer film include norbornene polymers, triacetyl cellulose, polyimide, polyamide, polyester, polyester imide, polyether ketone, and modified polycarbonate. However, in addition to these materials, if the orientation state of the polymer molecular chain when expressing negative optical anisotropy can take the same orientation state of the molecular chain as the above material, the material of the polymer film Is not limited to the above materials. Among these, a polymer film made of a norbornene polymer is preferable. In addition, a desired Rth may be expressed by biaxially stretching a polymer film, and a technique for biaxially stretching a norbornene polymer is described in JP-A-2005-43740. In addition, an additive may be added to the polymer to adjust Rth, and techniques for adjusting Rth of triacetyl cellulose are described in JP-A Nos. 2000-1111914 and 2001-166144.

The first, second, and third optically anisotropic layers can be produced by bonding each other through an adhesive layer or a pressure-sensitive adhesive layer.
The adhesive forming the adhesive layer is not particularly limited as long as it has sufficient adhesion to the optically anisotropic layer and does not impair the optical properties of the optically anisotropic layer. For example, acrylic resin, methacrylic resin, epoxy resin, ethylene-vinyl acetate copolymer, rubber, urethane, polyvinyl ether, and mixtures thereof, thermosetting and / or photocuring, electron beam Various reactive types such as a curable type can be mentioned. These adhesives include those having the function of a transparent protective layer for protecting the optically anisotropic layer.

  The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited. For example, an acrylic polymer, a silicone-based polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine-based or rubber-based polymer is appropriately used as a base polymer. It can be selected and 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.

  The pressure-sensitive adhesive layer can be formed by an appropriate method. For example, a pressure sensitive adhesive solution of about 10 to 40% by weight in which a base polymer or a composition thereof is dissolved or dispersed in a solvent composed of a suitable solvent alone or a mixture such as toluene and ethyl acetate is prepared. A method in which it is directly attached on the optically anisotropic layer by an appropriate development method such as a casting method or a coating method, or an adhesive layer is formed on a separator in accordance with the above, and this is applied to the optically anisotropic layer. For example, a method of transferring onto the anisotropic layer. The pressure-sensitive adhesive layer includes, for example, natural and synthetic resins, in particular, tackifier resins, fillers and pigments made of glass fibers, glass beads, metal powders, other inorganic powders, colorants, You may contain the additive added to adhesion layers, such as antioxidant. Moreover, the adhesive layer etc. which contain microparticles | fine-particles and show light diffusibility may be sufficient.

  When bonding optically anisotropic layers to each other via an adhesive layer or an adhesive layer, the surface of the optically anisotropic layer is surface treated to improve adhesion to the adhesive layer or adhesive layer. can do. The surface treatment means is not particularly limited, and a surface treatment method such as corona discharge treatment, sputtering treatment, low-pressure UV irradiation, or plasma treatment that can maintain the transparency of the optically anisotropic layer surface can be suitably employed. Among these surface treatment methods, corona discharge treatment is good.

Next, the configuration of the liquid crystal display device of the present invention composed of the above members will be described.
The configuration of the liquid crystal display device of the present invention must be selected from the following two types as shown in FIGS.
(A) Polarizing plate / first optical anisotropic layer / third optical anisotropic layer / liquid crystal cell / second optical anisotropic layer / first optical anisotropic layer / polarizing plate / backlight (B) Polarizing plate / first optical anisotropic layer / second optical anisotropic layer / liquid crystal cell / third optical anisotropic layer / first optical anisotropic layer / polarizing plate / backlight

The angle formed by the pretilt direction of the liquid crystal layer in the liquid crystal cell and the tilt direction of the second optically anisotropic layer made of the liquid crystal film in which the nematic hybrid alignment structure is fixed is preferably in the range of 0 to 30 degrees, more preferably It is in the range of 0 to 20 degrees, and particularly preferably in the range of 0 to 10 degrees. If the angle between the two is 30 degrees or more, a sufficient viewing angle compensation effect may not be obtained.
In addition, the angle formed by the slow axis of the first optical anisotropic layer and the tilt direction of the second optical anisotropic layer is preferably 50 degrees or more and less than 80 degrees. More preferably, it is 55 degrees or more and less than 75 degrees. If the angle is 80 degrees or more, or less than 55 degrees, the front contrast may be lowered, which is not preferable.
Similarly, the angle formed by the slow axis of the first optically anisotropic layer and the slow axis of the third optically anisotropic layer is preferably 50 degrees or more and less than 80 degrees. More preferably, it is 55 degrees or more and less than 75 degrees. If the angle is 80 degrees or more, or less than 55 degrees, the front contrast may be lowered, which is not preferable.
The light diffusion layer, the backlight, the light control film, the light guide plate, and the prism sheet are not particularly limited, and known ones can be used.
The liquid crystal display device of the present invention can be provided with other constituent members in addition to the constituent members described above. For example, by attaching a color filter to the liquid crystal display device of the present invention, a color liquid crystal display device capable of performing multicolor or full color display with high color purity can be manufactured.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited to these. Note that the phase difference value (Δnd) in this example is a value at a wavelength of 550 nm unless otherwise specified.
The phase difference values in the front and oblique directions were measured using an automatic birefringence meter (manufactured by Oji Scientific Instruments, KOBRA12-ADH). The in-plane retardation value (Re), thickness direction retardation value (Rth), and tilt angle were determined according to Japanese Patent Laid-Open No. 10-332933.

Example 1
The conceptual diagram of the liquid crystal display device according to the first embodiment will be described with reference to FIG. 4, and the shaft configuration according to the first embodiment will be described with reference to FIG.
The substrate 1 is provided with a transparent electrode 3 formed of a material having high transmittance such as ITO, and the substrate 2 is provided with a counter electrode 4 formed of a material having high transmittance such as ITO, and the transparent electrode 3 and the counter electrode 4, a liquid crystal layer 5 made of a liquid crystal material exhibiting positive dielectric anisotropy is sandwiched between them. A third optical anisotropic layer 9, a first optical anisotropic layer 10, and a polarizing plate 7 are provided on the opposite surface of the substrate 2 on the side on which the counter electrode 4 is formed, and the transparent electrode 3 of the substrate 1. The second optically anisotropic layer 11, the first optically anisotropic layer 12, and the polarizing plate 8 are provided on the opposite side of the surface on which is formed. A backlight 13 is provided on the back side of the polarizing plate 8.

According to Japanese Patent Laid-Open No. 6-347742, a second optically anisotropic layer 11 made of a liquid crystal film having a thickness of 0.76 μm and a nematic hybrid alignment having an average tilt angle of 37 degrees in the thickness direction was fixed. .
Further, according to JP-A-2005-43740, a third stretched polymer stretched film comprising a norbornene polymer film having a Re value of 110 nm, an Rth value of −110 nm, and an Rth / Re value of −1.0. The optically anisotropic layer 9 was produced, and a liquid crystal display device was produced with the arrangement as shown in FIG.
The liquid crystal cell 6 used was ZLI-1695 (manufactured by Merck) as a liquid crystal material, and the liquid crystal layer thickness was 4.9 μm. The pretilt angle at both interfaces of the substrate of the liquid crystal layer was 2 degrees, and Δnd of the liquid crystal cell was approximately 320 nm.

A polarizing plate 7 (thickness: about 100 μm; SQW-062 manufactured by Sumitomo Chemical Co., Ltd.) is disposed on the viewer side (upper side of the drawing) of the liquid crystal cell 6, and the first polarizing plate 7 is disposed between the polarizing plate 7 and the liquid crystal cell 6. A stretched polymer film 10 made of a uniaxially stretched norbornene polymer film is disposed as the optically anisotropic layer 10, and a stretched polymer film 9 composed of a norbornene polymer film is disposed as the third optically anisotropic layer 9. did. Δnd of the stretched polymer film 10 was approximately 270 nm.
Further, behind the liquid crystal cell 6 as viewed from the observer, the second optically anisotropic layer 11 is a liquid crystal film 11 and the first optically anisotropic layer 12 is a uniaxially stretched norbornene polymer film. A molecular stretched film 12 was disposed, and a polarizing plate 8 was disposed on the back surface. The Δnd of the liquid crystal film 11 having the hybrid nematic alignment structure fixed was 105 nm, and the Δnd of the polymer stretched film 12 was 265 nm.
The absorption axes of the polarizing plates 7 and 8, the slow axes of the polymer stretched films 9, 10 and 12, the pretilt direction of both interfaces of the liquid crystal cell 6, and the tilt direction of the liquid crystal film 11 were arranged under the conditions described in FIG.
FIG. 6 shows the contrast ratio from all directions, with the ratio of transmittance (white display) / (black display) of white display 0V and black display 5V when the backlight is lit (transmission mode). Yes. Concentric circles represent the same viewing angle and are drawn at intervals of 20 degrees. Therefore, the viewing angle of the outermost circle represents 80 degrees.
FIG. 6 shows that it has a favorable viewing angle characteristic.

(Example 2)
The conceptual diagram of the liquid crystal display device according to the second embodiment will be described with reference to FIG. 7, and the shaft configuration according to the second embodiment will be described with reference to FIG.
In the liquid crystal cell 6 used in Example 1, the second optically anisotropic layer 11, the first optically anisotropic layer 14, and the polarizing plate 7 are provided on the opposite surface of the substrate 2 on the side where the counter electrode 4 is formed. The third optically anisotropic layer 15, the first optically anisotropic layer 16, and the polarizing plate 8 are provided on the opposite side of the surface of the substrate 1 on which the transmissive electrode 3 is formed. . A backlight 13 is provided on the back side of the polarizing plate 8.
As the polarizing plate 7, the polarizing plate 8, the second optical anisotropic layer 11, and the third optical anisotropic layer 15, the same ones as in Example 1 were used.
A polarizing plate 7 is disposed on the viewer side (the upper side in the figure) of the liquid crystal cell 6, and a uniaxially stretched norbornene polymer is formed as the first optical anisotropic layer 14 between the polarizing plate 7 and the liquid crystal cell 6. A liquid crystal film 11 was disposed as the stretched polymer film 14 made of a film and the second optically anisotropic layer 11. Δnd of the polymer stretched film 14 was approximately 265 nm, and Δnd of the liquid crystal film 11 having the hybrid nematic alignment structure fixed thereto was approximately 105 nm.
Further, as viewed from the viewer, behind the liquid crystal cell 6, as the third optical anisotropic layer 15, a polymer stretched film 15 made of a norbornene polymer film and a first optical anisotropic layer 16 are uniaxially stretched. A stretched polymer film 16 made of the norbornene-based polymer film was disposed, and a polarizing plate 8 was disposed on the back surface. Δnd of the polymer stretched film 16 was 270 nm, the Re value of the third optical anisotropic layer 15 was approximately 110 nm, the Rth value was −110 nm, and the Rth / Re value was −1.0.
The absorption axes of the polarizing plates 7 and 8, the slow axes of the polymer stretched films 14, 15 and 16, the pretilt direction of both interfaces of the liquid crystal cell 6, and the tilt direction of the liquid crystal film 11 were arranged under the conditions described in FIG.
FIG. 9 shows the contrast ratio from all directions, with the ratio of transmittance (white display) / (black display) of white display 0V and black display 5V when the backlight is lit (transmission mode). Yes. Concentric circles represent the same viewing angle and are drawn at intervals of 20 degrees. Therefore, the viewing angle of the outermost circle represents 80 degrees.
FIG. 9 shows that the viewing angle characteristic is good.

(Comparative Example 1)
In Example 1, a liquid crystal display device similar to that in Example 1 was produced except that a uniaxially stretched polymer film of norbornene-based polymer was used instead of the third optically anisotropic layer 9.
FIG. 10 shows the contrast ratio from all directions, with the ratio of transmittance (white display) / (black display) of white display 0V and black display 5V when the backlight is lit (transmission mode). Yes. Concentric circles represent the same viewing angle and are drawn at intervals of 20 degrees. Therefore, the viewing angle of the outermost circle represents 80 degrees.
Example 1 and Comparative Example 1 are compared with respect to viewing angle characteristics.
Comparing the omnidirectional isocontrast curves between FIG. 6 and FIG. 10, the viewing angle characteristics are greatly improved by using a film satisfying the desired Re value and Rth value as the third optical anisotropic layer. I understand that.

(Comparative Example 2)
In Example 2, a liquid crystal display device similar to that in Example 1 was produced except that a uniaxially stretched polymer film of norbornene polymer was used instead of the third optically anisotropic layer 15.
FIG. 11 shows the contrast ratio from all directions, with the ratio of transmittance (white display) / (black display) of white display 0V and black display 5V when the backlight is lit (transmission mode). Yes. Concentric circles represent the same viewing angle and are drawn at intervals of 20 degrees. Therefore, the viewing angle of the outermost circle represents 80 degrees.
Example 2 and Comparative Example 2 are compared with respect to viewing angle characteristics.
Comparing the omnidirectional isocontrast curves in FIG. 9 and FIG. 11, the viewing angle characteristics are greatly improved by using a film satisfying the desired Re value and Rth value as the third optical anisotropic layer. I understand that.

(Example 3)
An outline of the transflective liquid crystal display device of Example 3 will be described with reference to FIG.
A liquid crystal display device similar to that of Example 1 was produced except that the liquid crystal cell 17 was used.
A reflective electrode 18 formed of a material with high reflectivity such as Al and a transparent electrode 19 formed of a material with high transmittance such as ITO are provided on the substrate 1 in the liquid crystal cell 17, and the reflective electrode 18 and the transparent electrode 19 are provided. And a counter electrode 4, a liquid crystal layer 5 made of a liquid crystal material exhibiting positive dielectric anisotropy is sandwiched.
The liquid crystal layer thickness of the liquid crystal cell 17 used was 2.4 μm in the reflective electrode region 18 (reflective display portion) and 4.9 μm in the transparent electrode region 19 (transmissive display portion). The pretilt angle at the both interfaces of the liquid crystal layer was 2 degrees, the pretilt angle at the both interfaces of the liquid crystal layer was 2 degrees, and Δnd of the liquid crystal cell was approximately 150 nm in the reflective display portion and approximately 320 nm in the transmissive display portion. .
As for the omnidirectional isocontrast curve, the same results as in Example 1 were confirmed, and it was found that a transflective liquid crystal display device with a wide viewing angle was obtained.
In this embodiment, the experiment was performed without a color filter. Needless to say, however, if a color filter is provided in the liquid crystal cell, a good multi-color or full-color display can be achieved.

It is a conceptual diagram for demonstrating the tilt angle and twist angle of a liquid crystal molecule. It is a conceptual diagram of the orientation structure of the liquid crystal film which comprises a 2nd optically anisotropic element. It is a conceptual diagram explaining the pretilt direction of a liquid crystal cell. 1 is a cross-sectional view schematically showing a liquid crystal display device of Example 1. FIG. 4 is a plan view showing an angular relationship among an absorption axis of a polarizing plate, a pretilt direction of a liquid crystal cell, a slow axis of a polymer stretched film, and a tilt direction of a liquid crystal film in Example 1. FIG. It is a figure which shows the contrast ratio when the liquid crystal display device in Example 1 is seen from all directions. 6 is a cross-sectional view schematically showing a liquid crystal display device of Example 2. FIG. 6 is a plan view showing an angular relationship among an absorption axis of a polarizing plate, a pretilt direction of a liquid crystal cell, a slow axis of a polymer stretched film, and a tilt direction of a liquid crystal film in Example 2. FIG. It is a figure which shows the contrast ratio when the liquid crystal display device in Example 2 is seen from all directions. It is a figure which shows the contrast ratio when the liquid crystal display device in the comparative example 1 is seen from all directions. It is a figure which shows the contrast ratio when the liquid crystal display device in the comparative example 2 is seen from all directions. 6 is a cross-sectional view schematically showing a transflective liquid crystal display device of Example 3. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2: Substrate 3, 19: Transparent electrode 4: Counter electrode 5: Liquid crystal layer 6, 17: Liquid crystal cell 7, 8: Polarizing plate 9, 15: Third optical anisotropic layer 10, 12, 14, 16 : First optical anisotropic layer 11: Second optical anisotropic layer 13: Backlight 18: Reflective electrode

Claims (9)

In order from the backlight side, a polarizing plate, a first optical anisotropic layer having a retardation value of 210 to 300 nm at a wavelength of 550 nm, and a second optical anisotropic layer having a retardation value of 50 to 140 nm at a wavelength of 550 nm A liquid crystal cell in which a liquid crystal layer is sandwiched between an upper substrate and a lower substrate that are arranged opposite to each other, a third optical anisotropic layer having a retardation value of 50 to 140 nm at a wavelength of 550 nm, and a retardation at a wavelength of 550 nm A liquid crystal display device comprising at least a first optical anisotropic layer having a value of 210 to 300 nm and a polarizing plate, wherein the second optical anisotropic layer has a nematic hybrid alignment structure fixed A liquid crystal display device, wherein the third optically anisotropic layer satisfies the following formulas [1] to [3].
[1] 50 ≦ Re ≦ 140
[2] −250 ≦ Rth ≦ −50
[3] -3 <Rth / Re <-0.5
(Here, Re means an in-plane retardation value of the third optically anisotropic layer, and Rth means a thickness direction retardation value of the third optically anisotropic layer.) Re and Rth are respectively Re = (Nx−Ny) × d [nm] and Rth = {Nz− (Nx + Ny) / 2} × d [nm], where d is the third optical anisotropy. The layer thickness (nm), Nx, Ny are the in-plane main refractive index of the third optical anisotropic layer, Nz is the main refractive index in the thickness direction, and Nx>Ny> Nz. In order from the backlight side, a polarizing plate, a first optical anisotropic layer having a retardation value of 210 to 300 nm at a wavelength of 550 nm, and a third optical anisotropic layer having a retardation value of 50 to 140 nm at a wavelength of 550 nm A liquid crystal cell in which a liquid crystal layer is sandwiched between an upper substrate and a lower substrate which are arranged opposite to each other, a second optical anisotropic layer having a retardation value of 50 to 140 nm at a wavelength of 550 nm, and a retardation at a wavelength of 550 nm A liquid crystal display device comprising at least a first optical anisotropic layer having a value of 210 to 300 nm and a polarizing plate, wherein the second optical anisotropic layer has a nematic hybrid alignment structure fixed A liquid crystal display device, wherein the third optically anisotropic layer satisfies the following formulas [1] to [3].
[1] 50 ≦ Re ≦ 140
[2] −250 ≦ Rth ≦ −50
[3] -3 <Rth / Re <-0.5
(Here, Re means an in-plane retardation value of the third optically anisotropic layer, and Rth means a thickness direction retardation value of the third optically anisotropic layer.) Re and Rth are respectively Re = (Nx−Ny) × d [nm] and Rth = {Nz− (Nx + Ny) / 2} × d [nm], where d is the third optical anisotropy. The layer thickness (nm), Nx, Ny are the in-plane main refractive index of the third optical anisotropic layer, Nz is the main refractive index in the thickness direction, and Nx>Ny> Nz.   The liquid crystal display device according to claim 1, wherein the liquid crystal layer uses a twisted nematic mode.   The liquid crystal display device according to claim 1, wherein the liquid crystal layer has parallel orientation and a twist angle of 0 degree. The liquid crystal display device according to claim 1, wherein the first and third optically anisotropic layers are polymer stretched films.   2. The angle between a tilt direction in which a hybrid direction of a liquid crystal film of the second optically anisotropic layer is projected onto a substrate plane and a rubbing direction of the liquid crystal layer is within a range of ± 30 degrees. Or a liquid crystal display device according to 2;   The liquid crystal film of the second optically anisotropic layer is a liquid crystal film made of a liquid crystal material exhibiting optically positive uniaxiality, and fixing the nematic hybrid alignment formed in the liquid crystal state by the liquid crystal material, 3. The liquid crystal display device according to claim 1, wherein the liquid crystal film has an average tilt angle of 36 to 45 degrees in nematic hybrid alignment.   3. The liquid crystal display device according to claim 1, wherein the lower substrate of the liquid crystal cell has a transflective electrode in which a region having a reflection function and a region having a transmission function are formed.   9. The liquid crystal display device according to claim 8, wherein a layer thickness of the liquid crystal layer in a region where the liquid crystal cell has a reflection function is smaller than a layer thickness of the liquid crystal layer in a region which has a transmission function.

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