JPH07261171A - Reflection type liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide a reflection type liquid crystal display device which is capable of making screen display with high quality by preventing double images on a display screen and the virtual image of a light source. CONSTITUTION:The main part of this liquid crystal display device is composed of an observer side electrode plate 3 on which transparent electrodes 31 are arranged, a rear surface electrode plate 4 which is arranged to face this observer side electrode plate 3 and on which electrodes 41 is arranged, a liquid crystal material 5 which is encapsulated between both electrode plates 3 and 4, and a polarizing film 2 which is laminated on the outer side surface of the observer side electrode plate 3. In addition, the device has a light scattering layer 1 formed by mixing and dispersing >=2 kinds of resins varying in refractive index in the state of separating their phases from each other on the surface of this polarizing film 2. The rays reflected by the rear surface electrode plate 4 and the surface of the polarizing film 2 are scattered by this light scattering layer 1 and emitted. Since the scattered light is not converged to the virtual image position, the double images on the display screen and the virtual image of the light source are prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflective liquid crystal display device, and more particularly to a reflective liquid crystal display device capable of improving its display screen.

[0002]

2. Description of the Related Art Generally, a liquid crystal display device comprises a pair of electrode plates having electrodes and a liquid crystal substance enclosed between the electrode plates, the main part of which is composed of a pair of electrode plates and a voltage applied between the electrodes. The alignment state of the liquid crystal substance is changed, and the polarization plane of the linearly polarized light that passes through the part is rotated according to the alignment state, and the transmission / non-transmission of this polarization is controlled by the polarization film to perform screen display.

As a liquid crystal display device of this type,
A back light type or light guide type lamp in which a light source (lamp) is arranged on the back surface or side surface of an electrode plate (hereinafter referred to as the back electrode plate) located on the back side of the liquid crystal display device, and light rays are incident from the back electrode plate side Built-in transmissive liquid crystal display devices have become widespread.

However, in this transmissive liquid crystal display device with a built-in lamp, the power consumed by the lamp is large.
Since it consumes almost the same amount of power as other types of displays such as RTs and plasma displays, it has the drawbacks of impairing the inherent low power consumption characteristics of liquid crystal display devices and making it difficult to use for a long time at a portable location. Had.

On the other hand, outside light such as room light or natural light is made incident from an electrode plate (referred to as an observer-side electrode plate) located on the observer side of the apparatus without incorporating such a lamp, and this incident light is incident. There is also known a reflection type liquid crystal display device in which light is reflected by a light-reflective back electrode plate and a screen is displayed by this reflected light. In addition, this reflective liquid crystal display device has advantages that it consumes less power because it does not use a lamp and can withstand long-time driving at a portable location.

As such a reflection type liquid crystal display device,
For example, as shown in FIG. 3, one in which a metal reflector a3 is arranged on the back surface of the back electrode plate a is known. In addition, in FIG.
Reference numeral b is an observer-side electrode plate, c is a liquid crystal substance, d is a polarizing film, and e is a seal member that integrates the back electrode plate a and the observer-side electrode plate b in the peripheral portion, and the external light The polarizing film d converts the linearly polarized light into the linearly polarized light, and the linearly polarized light is reflected by the metal reflection plate a3, and the transparent electrodes a of the two electrode plates a and b are used.
A voltage is applied between 2 and b2 to drive the liquid crystal substance c, and the transmission / non-transmission of the linearly polarized light is controlled to display on the screen.

The reflection type liquid crystal display device shown in FIG.
The electrode a2 of the back electrode plate a is made of a metal thin film, and the incident light is reflected by this electrode a2 to display a screen.

[0008]

By the way, in the reflection type liquid crystal display device shown in FIG. 3, the display screen formed of the liquid crystal substance c is reflected on the metal reflection plate a3 to form a virtual image, which is double observed. There was a problem that was done.

On the other hand, in the reflection type liquid crystal display device shown in FIG. 4, since the metal electrode a2 is in close contact with the liquid crystal substance, the double display does not occur, but on the other hand, the electrode a2 is used. Has a problem that the light source (for example, a fluorescent lamp) of the external light is reflected on the electrode a2 because the incident light is specularly reflected, and the virtual image is observed on the screen.

Further, the external light is specularly reflected on the surface of the polarizing film d, and its reflectance is generally as high as several% to 10%. Therefore, the virtual image of the light source is observed due to the polarizing film d. There was also.

The present invention has been made by paying attention to such a problem, and its problem is to prevent double display of the display screen and virtual image of the light source to enable high quality screen display. Another object of the present invention is to provide a reflective liquid crystal display device.

[0012]

That is, the invention according to claim 1 is directed to an observer-side electrode plate provided with a transparent electrode and an observer-side electrode plate disposed so as to face the observer-side electrode plate. A light-reflective back electrode plate, a liquid crystal material enclosed between the two electrode plates, and a polarizing film arranged on the outer surface of the viewer-side electrode plate to convert external light incident from the outside into linearly polarized light. A reflection-type liquid crystal that displays the screen by controlling the transmission / non-transmission of the linearly polarized light by reflecting the external light on the back electrode plate and applying a voltage between the electrodes of both electrode plates to drive the liquid crystal substance. Assuming that a display device is used, the surface of the polarizing film is provided with a light scattering layer formed by mixing and dispersing two or more kinds of resins having different refractive indexes in a phase-separated state.

According to the reflection type liquid crystal display device of the first aspect of the present invention, the light rays incident on the light scattering layer are reflected or refracted in random directions at the interfaces between the resins mixed and dispersed in the phase separation state. Then, the reflection and refraction are repeated many times to be scattered.

Therefore, the external light incident from the external light source is scattered by the light scattering layer and enters the liquid crystal substance, and the light beam reflected by the back electrode plate is also scattered by the light scattering layer at the time of its emission. To be done. Then, the light rays reflected by the back electrode plate or the polarizing film surface are scattered and emitted by the light scattering layer, and the scattered light is not focused on the virtual image position. It is possible to prevent both the double copy of the display screen and the virtual image of the light source that are caused.

In the present invention, the two or more kinds of resins constituting the light scattering layer may have any refractive index, but the difference in the refractive index between them is 0 in order to improve the light scattering performance of the light scattering layer. It is preferable to use a resin having a refractive index of 0.05 or more, and it is preferable to use a resin having a low refractive index in order to prevent the surface reflection of the light scattering layer and reliably prevent the virtual image of the light source.

As the resin having a low refractive index among these resins, for example, a fluorine resin or a silicon resin can be used. As the resin having a high refractive index, a resin having a refractive index of 1.6 or more can be used, and examples thereof include epoxy resin, acrylic resin, polyester resin, amino resin and polyurethane resin. Further, as these low-refractive-index resins and high-refractive-index resins, solvent-drying type resins, heat-curing or polymerizing type resins, electron-beam or ultraviolet ray-curing or curable type resins, or It is also possible to use an oxidative curing type resin or the like.

The light scattering layer can be formed by mixing two or more kinds of these resins in a solvent and coating or printing on the surface of the polarizing film. Immediately before applying or printing these resins, it is desirable to irradiate the resin liquid with ultrasonic waves to sufficiently disperse these resins. As a coating method or a printing method, bar coating, roll coating, gravure coating, curtain coating, spin coating, flexographic printing, screen printing or the like can be applied.

Further, by appropriately adjusting the drying conditions or by utilizing the internal relaxation phenomenon at the time of curing the resin, unevenness having a depth of about 0.05 to 5 μm is formed on the surface of the light scattering layer, and light scattering is performed. It is also possible to improve the contrast of the display screen by scattering the light reflected by the layer surface.

When the polarizing film having the light-scattering layer thus formed is adhered to the viewer-side electrode plate, static electricity may be generated, and the static electricity may damage the liquid crystal substance. In such a case, generation of static electricity can be avoided by interposing a conductive transparent thin film (transparent conductive film) between the polarizing film and the light scattering layer. Claim 2
The invention according to (1) is made for such technical reasons.

That is, the invention according to claim 2 is premised on the reflective liquid crystal display device according to claim 1, and a transparent conductive film is provided between the polarizing film and the light scattering layer. It is characterized by.

As such a transparent conductive film, it is possible to use a material in which indium oxide, tin oxide or zinc oxide is used as a base material and another metal oxide is added thereto to exhibit conductivity. Specific examples thereof include ITO formed by adding indium oxide as a base material and tin oxide, or metal oxide formed by adding indium oxide as a base material and aluminum oxide.

Next, as the polarizing film applicable to the present invention, a uniaxially stretched film in which a dichroic dye such as iodine or a dichroic dye is adsorbed and these dyes are oriented in the stretching direction can be used. . Further, as the above polarizing film, those provided with protective films on both sides of the dye adsorption film,
Further, an adhesive layer for adhering the electrode plate on the observer side may be provided on one surface thereof. In addition, as the uniaxially stretched film, for example, a uniaxially stretched polyvinyl alcohol film, or a uniaxially stretched polyethylene terephthalate film, a uniaxially stretched cellulose acetate film, a uniaxially stretched polycarbonate film, a uniaxially stretched polyvinyl chloride film, or the like can be used, and a protective film. As, for example, triacetyl cellulose film, polycarbonate film, polyethylene terephthalate film, polystyrene film, polyethylene film,
A polymethylmethacrylate film, a polyethersulfone film, a polyetherketone film, a polyaryl film, or a multilayer film in which these films are laminated can be used.

Further, the liquid crystal display device is an STN (Super Twis
ted nematic) In the case of a liquid crystal display device, in order to prevent screen coloring due to the refractive index anisotropy of the liquid crystal, a retardation film for compensating the refractive index anisotropy of the liquid crystal is provided on the polarizing film. Is desirable. As such a retardation film, a plastic film that is uniaxially stretched or biaxially stretched to impart refractive index anisotropy to the film can be used. For example, a film such as a triacetyl cellulose film, a polycarbonate film, a polyethylene terephthalate film, a polystyrene film, a polyethylene film, a polymethylmethacrylate film, a polyethersulfone film, a polyetherketone film, or a polyaryl film is uniaxially or biaxially stretched. It was done. It is also possible to use a multilayer film in which these stretched films are laminated in the direction in which the stretch axes intersect.

[0024]

According to the first aspect of the present invention, the surface of the polarizing film is provided with a light-scattering layer formed by mixing and dispersing two or more kinds of resins having different refractive indexes in a phase-separated state, and the light-scattering layer is incident on the light-scattering layer. The light rays are reflected or refracted in random directions at the interface between the resins, and scattered by repeating the reflection and refraction many times. Therefore, the external light incident from the external light source is scattered by the light scattering layer and enters the liquid crystal substance, and the light beam reflected by the back electrode plate is also scattered by the light scattering layer at the time of its emission. Then, the light rays reflected by the back electrode plate or the polarizing film surface are scattered by the light scattering layer and are emitted, and the scattered light is not focused on the virtual image position, and therefore, due to the light reflectivity of the back electrode plate or the polarizing film surface. It is possible to prevent both the double copy of the display screen and the virtual image of the light source.

Further, according to the invention of claim 2, since the transparent conductive film is provided between the polarizing film and the light scattering layer, the polarizing film provided with the light scattering layer is used as the observer side electrode plate. It is possible to prevent the generation of static electricity when bonding to.

[0026]

Embodiments of the present invention will now be described in detail with reference to the drawings.

[Embodiment 1] As shown in FIG. 1, the reflection type liquid crystal display device according to this embodiment comprises a glass plate having a thickness of 0.7 μm as a base material and a transparent electrode 31 disposed on the observer side. The electrode plate 3, the back electrode plate 4 having the electrode 41 made of a light-reflective aluminum thin film in a pixel pattern, the liquid crystal substance 5 enclosed between the two electrode plates 3 and 4, and the observer-side electrode plate. The polarizing film 2 and the light-scattering layer 1, which are sequentially laminated on the outer surface of the optical disc 3, constitute a main part thereof.

As shown in FIG. 2, the polarizing film 2 has a uniaxially stretched film 22 having iodine adsorbed thereon, protective films 21 and 23 of triacetyl cellulose laminated on the front and back surfaces thereof, and adhered to the back surface side thereof. The polycarbonate retardation film 25 is laminated via the agent layer 24, and an adhesive layer 26 applied on the retardation film 25 and adhered to the observer-side electrode plate 3.

The light scattering layer 1 has a refractive index of 1.57.
UV curable epoxy resin 90% by weight and refractive index 1.4
The coating composition is composed of a coating film having a thickness of 4 μm in which 10% by weight of the fluorine-based acrylic resin of 1 is mixed and dispersed in a phase-separated state with each other, and this coating film is formed by the following method. That is, a fluorine-based acrylic monomer is mixed in the UV-curable epoxy resin, and the mixture is applied onto the protective film 21 immediately after being ultrasonically irradiated and uniformly dispersed.
Then, it is formed by irradiating with ultraviolet light in a nitrogen atmosphere to cure the ultraviolet curable epoxy resin, and at the same time, polymerize a fluorinated acrylic monomer to generate a fluorinated acrylic resin.

When the reflection type liquid crystal display device is driven under the illumination of the fluorescent lamp, no virtual image of the fluorescent lamp is observed in the display screen, and a clear display screen with high contrast can be observed. did it.

[Embodiment 2] The reflective liquid crystal display device according to this embodiment is different from Embodiment 1 except that a transparent conductive film made of ITO is provided between the polarizing film 2 and the light scattering layer 1. It was almost the same as the reflection type liquid crystal display device according to the present invention, and a clear display screen with high contrast could be observed.

Further, in this embodiment, the light scattering layer 1
When assembling the reflective liquid crystal display device by adhering the polarizing film 2 provided with to the observer side electrode plate 3, the transparent conductive film provided between the polarizing film 2 and the light scattering layer 1 acts. It was possible to avoid the generation of static electricity.

[0033]

According to the invention of claim 1, the surface of the polarizing film is provided with a light scattering layer formed by mixing and dispersing two or more kinds of resins having different refractive indexes in a phase-separated state.
The light rays incident on the light scattering layer are reflected or refracted in random directions at the interfaces between the resins, and scattered by repeating the reflection and refraction many times. Therefore, the external light incident from the external light source is scattered by the light scattering layer and enters the liquid crystal substance,
Further, the light beam reflected by the back electrode plate is also scattered by the light scattering layer when it is emitted.

The light rays reflected by the surface of the back electrode plate or the polarizing film are scattered by the light scattering layer and emitted, and since the scattered light is not focused on the virtual image position, the light reflectivity of the surface of the back electrode plate or the polarizing film is reduced. It is possible to prevent both a double image of the display screen and a virtual image of the light source due to the above, and it is possible to improve the display screen in the reflective liquid crystal display device.

Further, according to the invention of claim 2, since the transparent conductive film is provided between the polarizing film and the light scattering layer, the polarizing film provided with the light scattering layer is used as the observer side electrode plate. It is possible to prevent the generation of static electricity at the time of bonding, and it is possible to prevent damage to the liquid crystal substance due to the generation of static electricity.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a reflective liquid crystal display device according to a first embodiment.

FIG. 2 is a cross-sectional view of a light scattering layer according to Example 1.

FIG. 3 is a cross-sectional view of a reflective liquid crystal display device according to a conventional example.

FIG. 4 is a cross-sectional view of a reflective liquid crystal display device according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light-scattering layer 2 Polarizing film 3 Observer side electrode plate 4 Back electrode plate 5 Liquid crystal substance 22 Iodine-adsorbed uniaxially stretched film 31 Transparent electrode 41 Electrode

Claims (2)

[Claims] 1. An observer-side electrode plate provided with a transparent electrode,
A light-reflective back electrode plate, which is arranged opposite to the observer-side electrode plate and has electrodes, a liquid crystal substance enclosed between the two electrode plates, and an outer surface of the observer-side electrode plate. And a polarizing film for converting external light incident from the outside into linearly polarized light, reflecting the external light on the back electrode plate, and applying a voltage between the electrodes of both electrode plates to drive the liquid crystal substance, In a reflection type liquid crystal display device for controlling the transmission / non-transmission of linearly polarized light, a light scattering layer formed by mixing and dispersing two or more kinds of resins having different refractive indexes on the surface of the polarizing film in a phase-separated state. A reflective liquid crystal display device comprising: 2. A reflective liquid crystal display device according to claim 1, wherein a transparent conductive film is provided between the polarizing film and the light scattering layer.