JP3044906B2 - Liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display, and more particularly to a twisted nematic liquid crystal display having improved viewing angle characteristics due to birefringence characteristics of liquid crystal.

[0002]

2. Description of the Related Art A liquid crystal display device is characterized by its light weight, thinness, low power consumption, etc., and is therefore suitable for a clock type, a calculator, a laptop type word processor, a personal computer, etc. requiring a large display capacity. Used. In particular, in recent years, a color liquid crystal television using a twisted nematic liquid crystal display device formed with a thin film transistor and a color filter has been manufactured, and the demand for the twisted nematic liquid crystal display device has been increased. However, the viewing angle characteristics of the liquid crystal display device are not always satisfactory as the viewing angle deviates from the vertical direction of the liquid crystal display device, that is, the contrast decreases and the hue changes as the viewing angle increases.

As a technique for improving this, in order to compensate for the viewing angle dependence of the birefringence characteristics of the twisted nematic liquid crystal,
A liquid crystal display device using a uniform uniaxial polymer film having negative optical anisotropy in the thickness direction has been proposed for the liquid crystal display device, and the polymer film presses the thermoplastic polymer in the thickness direction and applies pressure. It is disclosed that it can be obtained by heating and cooling (JP-A-2-15239). However, it is difficult to obtain the polymer film with uniform quality and to apply the polymer film to a large-area liquid crystal display device, and its mass productivity is not satisfactory.

The inventors of the present invention have conducted intensive studies on a twisted nematic liquid crystal display device and have found that an inorganic layered compound is used.
By applying a retardation film in which Δn _XY × d, n _XY , n _Z , and (n _XY −n _z ) × d are controlled to the liquid crystal display device, the conventional problem can be solved and the viewing angle characteristics can be improved. The present inventors have found that a twisted nematic liquid crystal display device can be stably obtained industrially advantageously and have led to the present invention.

[0005]

That is, the present invention provides a liquid crystal display device comprising a liquid crystal layer comprising nematic liquid crystal molecules having a positive dielectric anisotropy and having a pair of electrodes having electrodes and being kept in parallel with the electrodes facing each other. Twisted nematic liquid crystal having a structure in which the major axis of the liquid crystal molecules is parallel to the transparent substrate and the major axis of the liquid crystal molecules is twisted by 80 to 100 degrees in the vertical direction of the transparent substrate in a state where no voltage is applied. Cell, a liquid crystal display device comprising a pair of linearly polarizing films disposed outside the twisted nematic liquid crystal cell, a retardation film using an inorganic layered compound, the thickness of the film is d,
When the retardation in the film plane is Δn _XY × d, the average refractive index in the film plane is n _XY , and the refractive index in the thickness direction is n _Z , Δn _XY × d is 50 nm or less;
_XY is greater than n _Z, and (n _XY -n _Z) × d is 20n
The present invention relates to a liquid crystal display device comprising at least one retardation film having a thickness of not less than m and not more than 1000 nm between at least one twisted nematic liquid crystal cell and a linearly polarizing film. Hereinafter, the present invention will be described in detail.

In the present invention, for example, when the inorganic layered compound is swelled and dispersed in a medium, laminated on a substrate and dried, the orientation is parallel to the substrate surface and random in the plane due to its planar structure. The inorganic layered compound layer thus deposited has an in-plane retardation of almost 0 as a whole and a refractive index structure in which the average refractive index in the plane of the layer is larger than the refractive index in the thickness direction. It becomes what has. Examples of the inorganic layer compound include clay minerals. Clay-based minerals are of a two-layer structure having an octahedral layer with aluminum or magnesium as the central metal on top of a silica tetrahedral layer, and a silica tetrahedral layer with aluminum or magnesium as the central metal. Octahedral layers are classified into a three-layer structure sandwiched from both sides. Examples of the former include kaolinites and antigolites, and examples of the latter include smectites, vermiculites and micas depending on the number of ion exchange cations. Specifically, kaolinite, dickite, nacrite, halloysite, antigorite,
Chrysotile, pyrophyllite, montmorillonite,
Hectorite, sodium 4 silicon mica, sodium teniolite, muscovite, margarite, talc, vermiculite, phlogopite, zansophyllite, chlorite and the like can be mentioned.

As a retardation film using the inorganic layered compound, the inorganic layered compound layer may be used alone,
It may be used as a mixture layer with another resin. Examples of the method of forming the inorganic layered compound layer alone into a retardation film include, for example, a method of laminating a dispersion of the inorganic layered compound on a substrate by a casting method, a coating method and the like, followed by drying and peeling from the substrate. This makes it possible to easily and continuously obtain a uniform quality retardation film. Specifically, after forming an inorganic layered compound layer on a film having release properties such as a polyester film subjected to a release treatment on the surface,
It can be obtained by peeling from the film.

When the mixture layer of the inorganic layered compound and the other resin is used as a retardation film, a resin having solubility in a medium of a dispersion of the inorganic layered compound is usually used. Cellulose-based resins, polyvinyl alcohol-based resins, and the like are preferably used because they are excellent in optical properties. As a method for forming a retardation film from a mixture layer of the inorganic layered compound and another resin, after dissolving a resin having solubility in a medium of a dispersion liquid of the inorganic layered compound, the liquid is added to the inorganic layered compound layer alone. And a method of performing the same processing as in the case of (1).

The inorganic layered compound layer alone or the mixture layer of the inorganic layered compound and another resin has no birefringence or a transparent layer having a very small birefringence from the viewpoint of handling. It may be laminated on a substrate to form a retardation film. Here, the transparent substrate is not particularly limited as long as it does not have birefringence or has a very low birefringence and can uniformly laminate a dispersion of an inorganic layered compound. A cellulosic film, a clean glass substrate, or the like, which has been subjected to a chemical treatment, is preferably used. If the birefringence of the transparent substrate increases and the Δn _XY × d of the retardation film exceeds 50 nm, the contrast of the liquid crystal display device decreases. Therefore, the retardation of the transparent substrate needs to be 50 nm or less, and is set to 30 nm. Is preferred.

[0010] A protective film for improving durability and handleability on one or both sides of the inorganic layered compound layer alone or a mixture layer of the inorganic layered compound and another resin, or a laminate of these on a transparent substrate. To form a retardation film. The protective film is not particularly limited as long as it is a film having a small birefringence. For example, a cellulose-based film subjected to a surface saponification treatment is preferably used. Where Δn _XY × d of the retardation film
Exceeds 50 nm, the contrast of the liquid crystal display device is reduced. Therefore, the protective film is formed when the Δn _XY × d of the retardation film is 50 nm or less, preferably 30 nm or less. As a method of laminating the protective film, for example, a method of laminating with an adhesive, a method of laminating with a low concentration aqueous solution of polyvinyl alcohol by a wet laminating method, or the like can be used.

Using the inorganic layered compound obtained above,
The thickness of the retardation film used is the twisted nematic type
Birefringence of liquid crystal used for liquid crystal cell and facing
It depends on the distance between the glass substrates (cell gap).
(N) of the retardation film_XY-N _Z) × d used liquid crystal cell
The film thickness d is set to be optimal for
(N_XY-N_Z) A phase difference filter having a value of xd of less than 20 nm;
When a retardation film exceeding 1000 nm is used
Can obtain a liquid crystal display device with excellent viewing angle characteristics.
Because (n_XY-N_Z) × d is 20 nm or more, 1
000 nm or less.

A method of laminating a retardation film using an inorganic layered compound on a twisted nematic liquid crystal cell is not particularly limited, and a method such as lamination to a liquid crystal display device via an adhesive may be used. In addition, the lamination position may be bonded between the liquid crystal cell and the upper polarizing film or between the liquid crystal cell and the lower polarizing film, or may be bonded to both. Furthermore, it is also possible to adopt a method of pasting together with the polarizing film to the liquid crystal cell as a laminated integrated product which has been pasted to the liquid crystal cell side of the polarizing film in advance.

[0013]

According to the present invention, it is possible to obtain a twisted nematic liquid crystal display device having excellent viewing angle characteristics with more stable quality and industrially advantageous than conventional ones.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the examples. Example 1 A synthetic hectorite (trade name: Laponite XLS), which is a clay mineral, was formed on a substrate film using a film obtained by saponifying a surface of a triacetyl cellulose film (Fujitac Fuji Photo Film Co., Ltd.) having a thickness of 80 μm. The aqueous dispersion containing 1.5% of Nippon Silica Kogyo Co., Ltd. and 1.7% of polyvinyl alcohol (trade name of Poval 103 Kuraray Co., Ltd.) has a film thickness of 1 after drying.
After laminating so as to have a thickness of 5 μm and drying, a film obtained by saponifying a surface of a triacetyl cellulose film having the same thickness of 80 μm as the substrate film is treated with a 1% aqueous solution of polyvinyl alcohol (trade name, Poval 117, manufactured by Kuraray Co., Ltd.) as an adhesive. After wet lamination on the layer side using synthetic hectorite, it was dried at 80 ° C. for 1 hour to obtain a retardation film composed of an inorganic layered compound. Δn _XY · d of this retardation film was almost 0 nm as measured by a polarizing microscope.
And the value of (n _XY −n _z ) · d was about 400 nm. When this retardation film is laminated between a top polarizing film and a liquid crystal cell of a 3 inch TFT color liquid crystal television (Panacrystal TR-3LT1 manufactured by Matsushita Electric Industrial Co., Ltd.), it is compared with a case where no retardation film is laminated. As a result, a change in contrast and hue depending on the viewing angle was small and good viewing angle characteristics were exhibited.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Aiko Shimizu 2-10-1, Tsukahara, Takatsuki-shi, Osaka Sumitomo Chemical Co., Ltd. (72) Inventor Tadashi Shindo 2-10-1, Tsukahara, Takatsuki-shi, Osaka Sumitomo (56) References JP-A-5-196819 (JP, A) JP-A-5-188367 (JP, A) JP-A-5-66401 (JP, A) JP-A-4-153621 ( JP, A) JP-A-3-233502 (JP, A) JP-A-3-155522 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/13363

Claims (2)

(57) [Claims] 1. A liquid crystal layer comprising nematic liquid crystal molecules having a positive dielectric anisotropy is sandwiched between a pair of transparent substrates having electrodes and kept in parallel with the electrodes facing each other, and applying a voltage. In a state in which the long axis of the liquid crystal molecules is parallel to the transparent substrate and the long axis of the liquid crystal molecules is twisted by 80 to 100 degrees in the vertical direction of the transparent substrate, the twisted nematic liquid crystal cell and the outside of the twisted nematic liquid crystal cell. In a liquid crystal display device comprising a pair of linear polarizing films arranged,
A retardation film using an inorganic layered compound, wherein the thickness of the film is d, the retardation in the film plane is Δn _XY × d, the average refractive index in the film plane is n _XY ,
When the refractive index in the thickness direction is n _Z , Δn _XY × d is 50
nm or less, n _XY is larger than n _Z , and (n _XY −
n _Z) liquid crystal display device × d is the at least one phase difference film is 20nm or more 1000nm or less, and having between at least one of the twisted nematic liquid crystal cell and the linear polarizing film. 2. The method according to claim 1, wherein the retardation film comprises an inorganic layer compound and at least one resin.
3. The liquid crystal display device according to 1.