JP2000002876A - Reflection type liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the insufficiency of visibility by the lack of the light quantity of a reflection type liquid crystal display device without requiring the change of intricate constitution by arranging a light diffusion reflection layer having a light reflection and diffusion surface on one side of a liquid crystal cell and providing the front surface of this light diffusion reflection layer with a fluorescent brightening agent layer. SOLUTION: The light diffusion reflection layer 19 having the light reflection and diffusion surface is arranged on the one side of the liquid crystal cell having a liquid crystal layer 16 arranged between two transparent substrates 14a and 14b. The surface of this light diffusion reflection layer 19 is provided with the agent layer 18. The fluorescent brightening agent layer 18 disposed on the light diffusion reflection layer 19 is a layer consisting of a chemical material which generates fluorescence in a UV part region by irradiation with the light which is made incident from the upper side and passes through color filters 12 and the liquid crystal layer 16. The layer is usually formed by applying a coating liquid contg. a fluorescent brightening agent and a binder in a dissolved state in an org. solvent on the surface of the light diffusion reflection layer 19. The thickness of the fluorescent brightening agent layer 18 disposed on the surface of the light diffusion reflection layer 19 is set within a rang of 0.1 to 10 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a reflection type liquid crystal display device. The present invention particularly relates to a reflection type color liquid crystal display device in which the brightness of a displayed image is improved.

[0002]

2. Description of the Related Art With the development of a highly information-oriented society, liquid crystal display devices have been remarkably spread. That is, a CRT type display has been conventionally used as a computer image display device in particular, but with the development of a highly information-oriented society, it has become necessary to reduce the weight, thickness and power consumption of the image display device. As a result, various non-CRT displays including liquid crystal display devices have been developed. Among them, at present, a liquid crystal display device is most widely used as an image display device having all the features of lightness, thinness, and power saving. In the early stage of the development of the liquid crystal display device, a reflection type image display system utilizing the reflection of external light in an image pattern on a liquid crystal display screen was used. However, since the amount of reflected light is insufficient and the visibility of the displayed image is insufficient, a light source (backlight) is disposed behind the liquid crystal display surface to obtain a patterned transmission image. A display device has been developed, and this transmissive liquid crystal display device is still most widely used.

[0003] However, the transmissive liquid crystal display device needs to continue to supply power to the backlight at the time of its use, and thus there is a limit to the power saving. Therefore, recently, as a means for further improving the power saving property of the liquid crystal display device, the improvement of the reflection type liquid crystal display device has been receiving attention again.

[0004] Reflection type liquid crystal display devices include, for example, "Classification of reflection type LCD and light use efficiency" (Tatsuo Uchida, et al., "Monthly LCD Intelligence" 19977.4, 54-58).
Page), "High-quality, reflective color liquid crystal display" (Tatsuo Uchida, "Monthly Display" July 1997, 50
Pp. 54) and "Reflection-type color liquid crystal display device" (Tatsuo Uchida, "EKISHO Vol. 2, No. 1 (1998),
51 to 56), there are various types. As a typical type, a liquid crystal material is injected between two transparent substrates provided with image display electrodes. A type in which a reflective layer having a light reflecting / diffusing surface is disposed on one side (the side opposite to the image viewing side) of the formed liquid crystal cell can be given. In other words, by installing a reflective layer with a light reflection / diffusion surface on the opposite side of this liquid crystal cell, light incident on the liquid crystal display surface can be efficiently extracted while appropriately reducing the directionality of the incident light. Becomes

One of the major drawbacks of the reflection image formed by the reflection type liquid crystal display device is the darkness of the reflection image. That is, in general, this reflected image is obtained by temporarily passing light incident on a liquid crystal display device through a liquid crystal layer in a liquid crystal cell, and then using a light reflection / diffusion (or diffusion / reflection) plate provided on the back surface of the liquid crystal cell. After being reflected on the surface, it is obtained by passing through the liquid crystal layer again and taking it out. That is, since the incident light beam passes through the liquid crystal layer twice, the amount of light is greatly reduced. There is also known a reflection type liquid crystal display device in which a light diffusion reflection surface is formed on a liquid crystal driving electrode surface provided inside a liquid crystal cell, but also in this case, an incident light beam passes through a liquid crystal layer twice. The same is true in this regard. Insufficient light quantity in the reflected image becomes more remarkable when a color filter is superimposed on the liquid crystal cell for colorizing the image.

[0006] Insufficient light quantity of the reflected image taken out by the reflection type liquid crystal display device has already been considered as a problem, and various improvements have been proposed. For example, JP-A-8-248
No. 414 discloses that a light-transmitting medium layer having a high refractive index is provided on the surface of a light-reflective layer (light-diffuse reflective layer) provided on the back surface of a reflective liquid crystal cell to improve light quantity and visual characteristics. ,
There are disclosures about obtaining high contrast reflection images.

Japanese Patent Application Laid-Open No. Hei 9-61854 discloses that a phosphor layer that emits red fluorescent light, a phosphor layer that emits green fluorescent light, and a blue fluorescent light are applied to each of pixel electrodes of a reflective type color liquid crystal display device. An invention has been disclosed in which a phosphor layer that emits light is arranged to facilitate full-color display of a liquid crystal display device.

[0008]

It can be understood that the improvement of the reflection type liquid crystal display device described in each of the above publications exhibits desired effects, but the structure becomes complicated.
There are problems that hinder industrial production. SUMMARY OF THE INVENTION An object of the present invention is to provide a method for solving insufficient visibility due to insufficient light quantity of a reflective liquid crystal display device without requiring a complicated configuration change. In addition, the present invention particularly provides a method for solving a reduction in visibility due to a lack of light amount of a reflective type color liquid crystal display device without requiring a complicated configuration change and without largely breaking a color balance. With the goal.

[0009]

SUMMARY OF THE INVENTION The present invention is directed to one of a liquid crystal cell having two transparent substrates having transparent electrodes for driving a liquid crystal material and a liquid crystal material layer disposed between the two substrates. A reflective liquid crystal display device comprising a light diffusion / reflection layer having a light reflection / diffusion surface on the side thereof, characterized in that a fluorescent whitening agent layer is provided on the surface of the light diffusion / reflection layer. Reflective liquid crystal display device (reflective liquid crystal display device of the first embodiment of the present invention). The reflection type liquid crystal display device according to the present invention is preferably a reflection type liquid crystal display device for displaying a color image constituted by disposing a color filter on one side of a liquid crystal cell.

The present invention also provides a transparent substrate provided with a transparent electrode for driving a liquid crystal material, a substrate provided with a light-diffuse reflective electrode for driving a liquid crystal material (which may be transparent or opaque), and A reflective liquid crystal display device comprising a liquid crystal cell having a liquid crystal material layer disposed between the two substrates, wherein a light brightening agent layer is provided on a surface of the light diffusion reflective electrode. There is also a reflective liquid crystal display device (the reflective liquid crystal display device according to the second embodiment of the present invention). The reflection type liquid crystal display device according to the present invention is a reflection type liquid crystal display device for displaying a color image constituted by disposing a color filter on the side of a transparent substrate provided with a transparent electrode for driving a liquid crystal material of a liquid crystal cell. Is preferred.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a reflection type liquid crystal display device of the present invention will be described in detail with reference to the accompanying drawings. FIG.
Shows an example of a typical configuration of the reflective liquid crystal display device of the first embodiment of the present invention, and FIG. 2 shows an example of a typical configuration of the reflective liquid crystal display device of the second embodiment of the present invention. Is shown.

Referring to FIG. 1, a reflection type liquid crystal display device 10 is shown.
Is a display-side transparent protective film 11, a color filter 12, a liquid-crystal-cell upper transparent substrate 13, from the top (light enters from the upper side, passes twice through the liquid crystal layer, and then exits as diffused reflected light). Upper transparent electrode 14a, upper alignment film 15
a, liquid crystal layer 16, lower alignment film 15b, lower transparent electrode 14
b, a liquid crystal cell lower transparent substrate 17, a fluorescent whitening agent layer 18, and a light diffusion / reflection layer 19. In this configuration, the fluorescent whitening agent layer 1 provided on the light diffusion / reflection layer 19
Reference numeral 8 denotes a characteristic component of the present invention, and the other components and materials of each layer are already known.

The fluorescent whitening agent layer provided on the light diffusion / reflection layer, which is a characteristic layer of the present invention, emits ultraviolet light by being irradiated from the upper side and passing through the color filter and the liquid crystal layer. A layer made of a chemical material that produces fluorescence in the region,
Usually, it is formed by applying a coating solution containing a fluorescent whitening agent and a binder in a dissolved state in an organic solvent to the surface of the light diffusion / reflection layer.

There is no particular limitation on the fluorescent whitening agent that can be used in the present invention. Examples of the fluorescent whitening agent that can be preferably used include 1,4-bis (2-methylstyrine) benzene and trans-4,4'-. Stilbene compounds such as diphenylstilbene and diaminostilbene, 7-hydroxy-4
And coumarin-based compounds such as methyl coumarin.

The binder that can be used for forming the optical brightener layer is not particularly limited. Examples of the binder that can be preferably used include (meth) acrylic acid and (meth) acrylic acid.
Copolymers with acrylic esters, styrene / maleic anhydride copolymers, and products of the copolymers with alcohols can be mentioned.

The organic solvent used for preparing the coating solution for forming the fluorescent brightening agent layer is not particularly limited. For example, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether Alkylene glycol monoalkyl ethers such as diethylene glycol monomethyl ether, polyalkylene glycol monoalkyl ethers, acetates of these glycol monoalkyl ethers, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate and the like. Acetates, benzene,
Aromatic hydrocarbons such as toluene and xylene, methyl ethyl ketone, acetone, methyl isobutyl ketone, ketones such as cyclohexanone, ethanol, propanol,
Alcohols such as butanol, hexanol, cyclohexanol, ethylene glycol, diethylene glycol and glycerin can be mentioned. The organic solvent is usually used in an amount in the range of 0.5 to 20 times (by weight) the total amount of the optical brightener and the binder.

The thickness of the fluorescent whitening agent layer provided on the surface of the light diffusion / reflection layer of the present invention is preferably in the range of 0.1 to 10 μm.

In FIG. 2, a reflection type liquid crystal display device 20 is shown.
Is from above (similarly, light is incident from the upper side, passes through the liquid crystal layer twice, and then exits upward as diffuse reflection light),
Display side transparent protective film 21, color filter 22, liquid crystal cell upper transparent substrate 23, upper transparent electrode 24a, upper alignment film 25a, liquid crystal layer 26, lower alignment film 25b, fluorescent whitening agent layer 28, light diffusion reflective layer It comprises a side electrode 24b and a liquid crystal cell lower substrate 27. In this configuration, the fluorescent brightening agent layer 28 provided on the light diffusion / reflection lower electrode 24b is a characteristic component of the present invention, and the configuration and material of each of the other layers are already known. is there.

In the structure shown in FIG. 2, the fluorescent whitening agent layer provided on the light diffusion / reflection layer, which is a characteristic layer of the present invention, enters from above and passes through the color filter and the liquid crystal layer. This layer is made of a chemical material that emits fluorescent light in the ultraviolet region when irradiated with incoming light, and is usually coated with a coating solution containing a fluorescent whitening agent and a binder in a dissolved state in an organic solvent under light diffusive reflection. It is formed by coating the surface of the side electrode, and usually also the surface of the lower substrate of the liquid crystal cell.

The fluorescent whitening agent layer of the reflection type liquid crystal display device having the structure shown in FIG. 2 is not limited with respect to the fluorescent whitening agent, the binder, and the solvent used for forming the fluorescent whitening agent coating layer. Various materials described for forming the optical brightener layer having the configuration shown in FIG. 1 can be used.

The thickness of the optical brightener layer in the structure shown in FIG. 2 is usually preferably in the range of 0.1 to 10 μm.

[0022]

The reflection type liquid crystal display device having the fluorescent whitening agent layer according to the present invention has a simple structure, but significantly contributes to an increase in the amount of reflected image. Especially when used for a reflection type color liquid crystal display device having a color filter, the color balance is not affected so much.
This is particularly effective because it significantly contributes to an increase in the amount of light of the color reflection image.

[Brief description of the drawings]

FIG. 1 shows an example of a typical configuration of a reflective liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 shows an example of a typical configuration of a reflective liquid crystal display device according to a second embodiment of the present invention.

[Signs in the drawings]

 10, 20 Reflective liquid crystal display device 11, 21 Display-side transparent protective film 12, 22 Color filter 13, 23 Liquid crystal cell upper transparent substrate 14a, 24a Upper transparent electrode 14b Lower transparent electrode 15a, 25a Upper alignment film 15b, 25b Lower Side alignment film 24b Light diffusion reflective lower electrode 16, 26 Liquid crystal layer 17 Liquid crystal cell lower transparent substrate 27 Liquid crystal cell lower substrate 18, 28 Fluorescent whitening agent layer 19 Light diffusion reflective layer

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kazunori Hasebe 200 No. Onakazato, Fujinomiya-shi, Shizuoka Fuji Photo Film Co., Ltd. F-term (reference) 2H042 BA01 BA13 BA20 2H091 FA02Y FA14Y FA31Y FA43Y FB02 FB12 FD24 GA03 LA16 2H092 GA19 PA08 PA12 PA13 5C094 AA08 AA10 AA45 BA43 CA24 DA13 EA05 EA06 EB02 ED03 ED11 ED13

Claims (4)

[Claims] A light reflection / diffusion surface is provided on one side of a liquid crystal cell having two transparent substrates provided with transparent electrodes for driving a liquid crystal material, and a liquid crystal material layer disposed between the two substrates. 1. A reflective liquid crystal display device comprising a light diffusion / reflection layer having the following structure, wherein the light diffusion / reflection layer is provided with a fluorescent whitening agent layer on a surface thereof. 2. The reflection type liquid crystal display device according to claim 1, wherein a color filter is arranged on one side of the liquid crystal cell for displaying a color image. 3. A substrate having a transparent substrate provided with a transparent electrode for driving a liquid crystal material and a substrate provided with a light diffusion reflective electrode for driving a liquid crystal material.
And a liquid crystal cell having a liquid crystal material layer disposed between the two substrates, wherein the light diffusion reflective electrode has a fluorescent whitening agent layer on its surface. A reflective liquid crystal display device, characterized in that: 4. A reflection type liquid crystal display device according to claim 3, wherein a color filter is arranged on a side of a transparent substrate provided with a transparent electrode for driving a liquid crystal material of a liquid crystal cell.