KR20040104403A - Liquid crystal display device - Google Patents

Abstract

PURPOSE: An LCD(Liquid Crystal Display) is provided to obtain a good display characteristic of a moving picture by dispersing metal particles with a liquid crystal medium. CONSTITUTION: A liquid crystal layer has metal particles and liquid crystal particles. The multiplication between the thickness d of the liquid crystal layer and a refraction index of anisotropic liquid crystal particles is 0.1 to 1.0 um. At least one sheet among protective films in which a deflection film of the first polarizing plate is positioned between them is an optical compensation sheet having a double refraction characteristic. The retardation value of the optical compensation sheet is 10nm to 70nm.

Description

Liquid Crystal Display {LIQUID CRYSTAL DISPLAY DEVICE}

The present invention relates to a liquid crystal display device.

In liquid crystal display devices used for a clock, a computer, a word processor, or the like, electrodes are provided on at least one substrate as a substrate structure, an alignment film is formed on the substrate, and the alignment film is disposed inward, and the liquid crystal is interposed therebetween. It is common to take the structure that is enclosed. The transparent electrode of such a liquid crystal display element is generally formed in the form of a display pattern such as a stripe or a lattice on a substrate, and the alignment film is formed on the entire surface of the transparent electrode and the exposed substrate (other than the display pattern). Formed by application or deposition. Each of the two transparent electrode substrates is arranged with the alignment film inward, and a liquid crystal material is enclosed therebetween, whereby a liquid crystal display element is manufactured. Therefore, the enclosed liquid crystal generally contacts only the alignment film. In general, the alignment film is formed because it is necessary to orientate, or align, the liquid crystals in a predetermined direction, thereby aligning the liquid crystal molecules.

Various modes, such as TN, VA, IPS, OCB, are known for a liquid crystal display element. Liquid crystal display devices generally have problems in viewing angle characteristics, but by combining them with an optical compensation film that is optimal for each mode, the viewing angle characteristics have been greatly improved. However, these liquid crystal display devices have a drawback that the response speed is low and the limit of several milliseconds is present, which has been a major problem when used in television panels and the like requiring high-speed response. On the other hand, a completely new type of liquid crystal material using liquid crystal molecules as a protective agent for metal particles has recently been studied (Non Patent Literature 1). However, when this type of liquid crystal material is injected into the liquid crystal, there is a problem that the alignment direction of the liquid crystal is disturbed, light leakage occurs, and the viewing angle characteristic is deteriorated.

[Non-Patent Document 1] Polymer Paper Collection, Vol. 59, No. 12, pp. 753-759 (Dec., 2002)

An object of the present invention is to provide a liquid crystal display device which is excellent in high-speed response and also excellent in viewing angle characteristics.

(1) A liquid crystal display device comprising: a liquid crystal cell comprising a pair of substrates arranged at least on one side with electrodes, a liquid crystal layer sandwiched between the substrates, and a first polarizing plate disposed outside the liquid crystal cell; The metal particles are dispersed in the liquid crystal layer, and the product Δn · d of the thickness d (μm) of the liquid crystal layer and the refractive index anisotropy Δn is 0.1 to 1.0 μm, and at least one of the protective films for sandwiching the polarizing film of the first polarizing plate is birefringent. A liquid crystal display device, characterized in that the optical compensation sheet having a property.

(2) The liquid crystal display device according to (1), wherein the retardation value of the optical compensation sheet is 10 nm to 70 nm.

(3) The liquid crystal display device according to (1) or (2), wherein the optical compensation sheet is formed by laminating an optically anisotropic layer made of a liquid crystal compound on a transparent support.

(4) The liquid crystal display device according to (1) to (3), wherein the liquid crystal cell is a liquid crystal cell in TN mode, VA mode, IPS mode, or OCB mode.

Embodiment of the Invention

[Cell Liquid Crystal Layer]

Examples of the liquid crystal molecules include conventionally known liquid crystal molecules. Preferably, a rod-shaped molecular compound is mentioned, Specifically, azomethine, azoxy, cyano biphenyl, cyano phenyl ester, benzoic acid ester, cyclohexane carboxylic acid phenyl ester, cyano phenyl cyclohexane , Cyano substituted phenylpyrimidines, alkoxy substituted phenylpyrimidines, phenyldioxanes, tolans and alkenylcyclohexylbenzonitriles are preferably used. As liquid crystal compounds of TN, VA, IPS, and OCB, the liquid crystal compounds described in JP-A-11-302653, JP-A-9-249881, JP-A-2002-193853, and JP-A-2003-73670 are used. Can be mentioned.

[Metal Particles Dispersed in Liquid Crystal]

The metal is a divalent or higher metal compound, preferably a transition metal element such as Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Ga, In, Tl, Ge, Sn, Ti, Zr, V, Ta, Mo, W, Mn, Fe, Ce, Sm and the like can be mentioned. Preferably Pt, Cu, Ag, Au, Zn, Ga, In, Tl, Ge, Sn, Ti, Zr, V, Ta, Mo, more preferably Pt, Cu, Ag, Au, Zn, Ga, In , Tl, and the like.

The particle size is preferably 1 μm or less. Preference is given to 0.001 μm to 0.5 μm. More preferably, 0.001 µm to 0.01 µm. Although the shape may be any, spherical shape is preferable. The concentration of the metal particles is preferably less than 10 wt% based on the total composition in the liquid crystal layer. More preferably, it is 0.01 to 5% of range.

The organic compound may be coated on the metal particles. It is more preferable to coat the liquid crystal molecules on the metal particles. It is preferable that the quantity which coat | covers an organic compound or a liquid crystal molecule to metal particle is 30% or more with respect to the surface area of a metal particle. It is more preferable if it is 60%.

Dispersion and coating of metal particles are described in `` Ultrafine Handbook Fuji Techno System '', `` The Latest Trend in Technology and Applications of Ultrafine Particles 2 '', `` SBTECHNO-RESEARCH CO., LTD '', `` The Latest Trend of Inorganic Particles and Ultrafine Technology and Applications TORAY RESEARCH CENTER ”, Polymer Papers, Vol. 59, No. 12, pp. 753-759 (Dec., 2002) and the like can be used.

[Optical Compensation Sheet]

As the optical compensation sheet having the birefringence of the present invention, any one can be used as long as it has the birefringence. As such an optical compensation sheet, Unexamined-Japanese-Patent No. 6-214116, Unexamined-Japanese-Patent No. 2001-249223. 2002-82226, 2001-100039, US Pat. And WV FILM Wide View-A WV A03B and WV A12B manufactured by Film Corporation.

In the present invention, an optical compensation sheet having an optically anisotropic layer formed of rod-like liquid crystalline molecules or discotic liquid crystalline molecules on the transparent support can be preferably used. The optically anisotropic layer may be a single layer or a plurality of layers, one may be an optically anisotropic layer formed of discotic liquid crystalline molecules, the other may be an optically anisotropic layer formed of rod-like liquid crystalline molecules, and both may be rod-like liquid crystalline molecules or disco. Tick liquid crystalline molecules may be sufficient. A more preferable optically anisotropic layer is formed by orienting discotic liquid crystalline molecules and fixing the alignment state thereof. Discotic liquid crystalline molecules generally have a large birefringence. In addition, the discotic liquid crystalline molecules have various alignment forms. Therefore, by using discotic liquid crystalline molecules, it is possible to produce an optical compensation sheet having optical properties that cannot be obtained with a conventional synthetic polymer film.

In the case where optical isotropy (low retardation value) is required as the transparent support of the optical compensation sheet, a cellulose acetate film is generally used. On the contrary, when optical anisotropy (high retardation value) is required, a stretched synthetic polymer film (eg, polycarbonate film, polysulfone film) is used. In the technical field of optical materials such as optical compensation sheets, synthetic polymer films are used when optical anisotropy (high retardation value) is required for the polymer film, and cellulose acetate when optical isotropy (low retardation value) is required. It was a general principle to use cellulose esters such as butyrate and cellulose propionate, polyolefins and the like. European Patent No. 0911656A2 discloses a cellulose acetate film having a high retardation value which can be used for applications requiring optical anisotropy, inverting conventional general principles. It is preferable that the thickness of a transparent support body is 20 micrometers-200 micrometers. More preferably, it is 30 micrometers-80 micrometers.

The retardation value is a value obtained by multiplying the thickness of the film by the in-plane birefringence. The specific value is obtained by extrapolating from the measurement result of in-plane retardation with the direction of incidence of the measurement light perpendicular to the film membrane surface, the measurement result of in-plane retardation with respect to the slow axis, and the measurement result of inclination with respect to the vertical direction with respect to the film membrane surface. . The measurement can be performed using an ellipsometer (for example, M-150: Nippon Spectrum Co., Ltd. product). As the measurement wavelength, 550 nm is adopted. The retardation value Re is calculated as follows.

Retardation value (Re) = (nx-ny) × d

In formula, nx is the refractive index of the slow-axis direction in a film plane: ny is the refractive index of the fast axis direction in a film plane, and d is the thickness (nm) of a film.

[Polarizing Plate]

A polarizing plate consists of a polarizing film and two transparent protective films arrange | positioned at both sides. The optical compensation sheet is used as one protective film. The other protective film may use a normal cellulose acetate film (e.g., Fuji-Taek TD80UF (manufactured by Fuji Photo Film Co., Ltd.), and a polarizing plate on which a functional layer (e.g., hard coat layer, anti-glare layer, anti-reflection layer, forward scattering layer, etc.) is formed. It may also be a protective film (eg, a CV film manufactured by Fuji Photo Film Co., Ltd.) As the cellulose acetate film (including the support of the optical compensation sheet and the polarizing plate protective film), a non-chlorine system described in Publication 2001-1745 (issue date 2001.3.15). The optical compensation sheet is preferably used on the liquid crystal cell side, and the polarizing film includes an iodine polarizing film and a dye polarizing film or a polyene polarizing film using a dichroic dye. The dye-based polarizing film is generally produced using a polyvinyl alcohol-based film. Roneun is described in Japanese Laid-Open Patent Publication No. 2002-86554, No. 2002-131548 copper or the like.

[LCD]

The liquid crystal display device of the present invention may be a transmissive, reflective or semi-transmissive type, and is particularly advantageously used for transmissive liquid crystal display devices. The transmissive liquid crystal display device consists of a liquid crystal cell and two polarizing plates arrange | positioned at both sides. The liquid crystal cell carries liquid crystal between two electrode substrates. One optical compensation sheet is arrange | positioned between a liquid crystal cell and one polarizing plate, or two sheets are arranged between a liquid crystal cell and both polarizing plates.

Various modes, such as TN, VA, IPS, and OCB, are known for a liquid crystal cell. In this invention, it is preferable that it is a liquid crystal cell of OCB mode, VA mode, or TN mode.

In the liquid crystal display device used for the system of this invention, a spacer is provided between two glass plates. The spacer is for keeping the gap of the liquid crystal layer constant.

The cell gap is preferably set to 10 µm or less, more preferably 2 to 8 µm, further preferably 4 to 6 µm.

Although the preferable range of refractive index anisotropy (DELTA) n of a liquid crystal layer molecule is 0.2 or less, it is more preferable to set it as 0.03-0.18, and it is still more preferable to set it as 0.07-0.15. The preferable range of (DELTA) n * d is 0.1-1 micrometer, 0.3-1 micrometer is more preferable, and 0.4-1 micrometer is still more preferable.

The liquid crystal cell of OCB mode is a liquid crystal display using a liquid crystal cell of band alignment mode that (or symmetrically) aligns rod-shaped liquid crystalline molecules in a substantially opposite direction at the top and bottom of the liquid crystal cell. US Patent 4583825, U.S. Pat. Disclosed in each specification of the call. Since the rod-shaped liquid crystal molecules are symmetrically aligned at the top and bottom of the liquid crystal cell, the liquid crystal cell in the band alignment mode has a magneto-optic compensation function. Therefore, this liquid crystal mode is also called OCB (Optically Compensatory Bend) liquid crystal mode. The liquid crystal display of the band alignment mode has an advantage that the response speed is high.

In the liquid crystal cell of VA mode, rod-shaped liquid crystalline molecules are orientated substantially vertically when voltage is not applied. In the VA mode liquid crystal cell, (1) a narrow VA mode liquid crystal cell in which rod-shaped liquid crystalline molecules are aligned substantially vertically when no voltage is applied and is substantially horizontal when voltage is applied (Japanese Patent Laid-Open No. 2). (2) a liquid crystal cell (of MVA mode) (described in SID97, Digest of tech. Papers (Preliminary) 28 (1997) 845), in which the VA mode is multi-domained to enlarge the viewing angle. (3) A liquid crystal cell (n-ASM mode) of the liquid crystal cell (n-ASM mode) in which the rod-shaped liquid crystalline molecules are substantially vertically aligned when no voltage is applied and torsional multi-domain orientation when voltage is applied (described in Japanese Laid-Open Liquid Crystal Discussion Nos. 58-59 (1998)). ) And (4) liquid crystal cells in SURVAIVAL mode (presented by LCD International 98).

In the liquefied cell of the TN mode, when no voltage is applied, the rod-like liquid crystal molecules are substantially horizontally aligned, and are twisted to 60 to 120 ° again. TN mode liquid crystal cells are most commonly used as color TFT liquid crystal display devices, and are described in a number of documents.

EXAMPLE

Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited thereto.

Example 1

[Creation of TN type liquid crystal cell]

A polyimide alignment film was installed on the glass substrate on which the ITO transparent electrode was formed and subjected to rubbing treatment. Two board | substrates were overlapped so that an orientation film may face through the spacer of 5 micrometers. The direction of the substrate was adjusted so that the rubbing direction of the alignment film was orthogonal. Rod-shaped liquid crystalline molecules (ZL4792, manufactured by Merck Co., Ltd.) in which Ag particles having a particle diameter of 5 nm were dispersed were injected into a gap between the substrates to form a liquid crystal layer. The concentration of Ag particles was approximately 1% of the total composition in the liquid crystal layer. Δn of the liquid crystal molecules was 0.0969. The elliptically polarizing plate with the optical compensation sheet used in Example 1 of Japanese Patent Application Laid-Open No. 2001-100039 was bonded to both sides of the TN liquid crystal cell prepared as described above, so that the optically anisotropic layer faced the substrate, thereby manufacturing a liquid crystal display device. The slow axis of the laminate of the optically anisotropic layer and the transparent support and the rubbing direction of the liquid crystal cell were arranged to be perpendicular to each other. As a result of irradiating a display image by applying a voltage to a liquid crystal cell of a liquid crystal display device, image degradation such as afterimages and blurring of contours in a moving image display is reduced, and a polarizing plate having both sides of a polarizing film sandwiched by Fuji-Taek TD80U (optical compensation sheet) Display characteristics with a wide viewing angle were obtained.

Example 2

[Creation of Band Alignment Film Liquid Crystal Cell]

A polyimide film was formed as an alignment film on a glass substrate with an ITO electrode, and rubbing treatment was performed on the alignment film. The obtained two glass substrates were faced with the arrangement | positioning which a rubbing direction becomes parallel, and the cell gap was set to 5 micrometers. A liquid crystal compound (ZL1132, manufactured by Merck Co., Ltd.) having a Δn of 0.1396 in which Ag particles having a particle diameter of 5 nm were dispersed between the substrates was injected to prepare a band-aligned liquid crystal cell. The concentration of Ag particles was approximately 1% of the total composition in the liquid crystal layer. As the produced band alignment cell was sandwiched, two polarizing plates used in JP-A-2002-82226 Example 12 were bonded together. The optically anisotropic layer of the polarizing plate faced the cell substrate, and the rubbing direction of the liquid crystal cell and the rubbing direction of the optically anisotropic layer facing it were arranged to be antiparallel. As a result of irradiating a display image by applying a voltage to a liquid crystal cell of a liquid crystal display device, image degradation such as afterimages and blurring of outlines in a moving image display is reduced, and a polarizing plate having both sides of a polarizing film sandwiched by Fuji-Taek TD80U (without optical compensation sheet Display characteristics with a wide viewing angle were obtained as compared with).

Example 3

[Creation of VA liquid crystal cell]

The glass substrate with ITO electrode was made to face in parallel arrangement, and the cell gap was set to 5.5 micrometers. Δn in which Ag particles having a particle diameter of 5 nm were dispersed between substrates was injected with a liquid crystal compound of 0.0804 (MLC6680, manufactured by Merck Co., Ltd.) to prepare a VA liquid crystal cell. The concentration of Ag particles was approximately 1% of the total composition in the liquid crystal layer. Like the band alignment cell thus produced, two polarizing plates (with an optical compensation sheet of Re = 40 nm) used in Japanese Patent Application Laid-Open No. 2002-82226 Example 10 were bonded together. A voltage was applied to the liquid crystal cell of the liquid crystal display device. As a result of investigating the display image, image deterioration such as afterimages and blurring of outlines in moving picture display is reduced, and a wider viewing angle is displayed compared to a polarizing plate (without optical compensation sheet) in which both surfaces of the polarizing film are sandwiched by FujiTac TD80U. The characteristic was obtained.

Example 4

[Creation of IPS Liquid Crystal Cell]

The glass substrates were faced in a parallel arrangement, and the cell gap was set at 5 μm and the comb-shaped electrode gap was set at 10 μm. Δn in which Ag particles having a particle diameter of 4.5 nm were dispersed between substrates was injected with 0.0969 rod-shaped liquid crystal molecules (ZL4792, manufactured by Merck Co., Ltd.) to prepare an IPS liquid crystal cell. The concentration of Ag particles was approximately 1% of the total composition in the liquid crystal layer. Two sheets of the polarizing plate (with an optical compensation sheet of Re = 40 nm) produced in Example 10 of Japanese Unexamined Patent Publication No. 2002-82226 were bonded together as if the produced IPS liquid crystal cell was inserted. As a result of irradiating the display image with voltage applied to the liquid crystal cell of the liquid crystal display device, image deterioration such as afterimage or contour blur in moving picture display is reduced, and a polarizing plate having both sides of the polarizing film sandwiched by Fuji-Taek TD80U (without optical compensation sheet) Compared with this, display characteristics with a wider viewing angle were obtained.

Example 5

[Creation of TN type liquid crystal cell]

Instead of the injected liquid crystal molecules of Example 1, a rod-shaped liquid crystal component (ZL4792, manufactured by Merck Co., Ltd.), in which Ag particles having a particle diameter of 5 nm coated with liquid crystal molecules, were mixed so as to be approximately 1% of the total composition in the liquid crystal layer. It was. The coating amount in the liquid crystal molecules was set to 70% with respect to the surface area of the Ag particles. As a result of irradiating the display image by applying voltage to the liquid crystal cell of the liquid crystal display device, the slack in the moving image display is reduced, and the display angle is wider than the polarizing plate (without the optical compensation sheet) in which both sides of the polarizing film are sandwiched by the Fuji-Tak TD80U. Was obtained.

According to the present invention, a liquid crystal display device having good moving picture display characteristics can be obtained by dispersing metal particles in a liquid crystal medium, and a liquid crystal display device having very high moving picture properties and viewing angle characteristics can be obtained by combining with an optical compensation film having birefringence. have.

Claims (4)

A liquid crystal display device having a pair of substrates disposed opposite each other having at least one electrode, a liquid crystal cell comprising a liquid crystal layer interposed between the substrates, and a first polarizing plate disposed outside the liquid crystal cell, The liquid crystal layer contains metal particles and liquid crystalline molecules, The product (DELTA) n * d of the thickness d (micrometer) of the said liquid crystal layer and the refractive index anisotropy (DELTA) n of a liquid crystalline molecule is 0.1-1.0 micrometer, And at least one of the protective films between the polarizing films of the first polarizing plate is an optical compensation sheet having birefringence. The method of claim 1, And a retardation value of the optical compensation sheet is 10 nm to 70 nm. The method of claim 1, The optical compensation sheet is a liquid crystal display device in which an optically anisotropic layer made of a liquid crystal compound is laminated on a transparent support. The method of claim 1, Wherein the liquid crystal cell is a liquid crystal cell of TN mode, VA mode, IPS mode or OCB mode.