JP2898860B2 - Reflective 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 reflection type liquid crystal display, and more particularly to an improvement in a reflection type liquid crystal display capable of improving its display screen.

[0002]

2. Description of the Related Art A liquid crystal display device generally comprises a pair of electrode plates provided with electrodes and a liquid crystal material sealed between these electrode plates, and its main part is constituted by applying a voltage between the electrodes. The orientation of the liquid crystal material is changed, and the plane of polarization of linearly polarized light passing through the site is rotated according to the orientation, and transmission / non-transmission of the polarized light is controlled by a polarizing film to perform screen display.

[0003] As this type of liquid crystal display device,
A backlight or light guide type lamp in which a light source (lamp) is disposed on the back or side of an electrode plate (hereinafter referred to as a back electrode plate) located on the back side of a liquid crystal display device, and a light beam enters from the back electrode plate side. 2. Description of the Related Art Built-in transmission type liquid crystal display devices are widely used.

However, in this transmissive liquid crystal display device with a built-in lamp, power consumption by the lamp is large and C
It consumes almost the same power as other types of displays, such as RT and plasma displays, which impairs the inherent low power consumption characteristics of liquid crystal display devices, and also makes it difficult to use for long periods of time at a portable location. Had.

On the other hand, external light such as room light or natural light is made to enter 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 introduced. There is also known a reflective liquid crystal display device that reflects light on a light-reflective back electrode plate and displays a screen with the reflected light. In addition, this reflective liquid crystal display device has an advantage that power consumption is small because a lamp is not used, and the device can be driven for a long time in a portable place.

As such a reflection type liquid crystal display device,
For example, it is known that a metal reflector e is arranged on the back surface of a back electrode plate a as shown in FIG. In FIG. 4, b
Denotes an observer-side electrode plate, c denotes a liquid crystal material, and d denotes a polarizing film. The external light is converted into linearly polarized light by the polarizing film d, and the linearly polarized light is reflected by the metal reflector e and both electrode plates a , B to drive a liquid crystal material c by applying a voltage between the transparent electrodes a2 and b2, thereby controlling transmission and non-transmission of the linearly polarized light and displaying a screen.

Further, 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 screen is displayed by reflecting incident light by the electrode a2.

[0008]

By the way, in the reflection type liquid crystal display device shown in FIG. 4, the display screen constituted by the liquid crystal material c is reflected on the metal reflection plate e to form a virtual image, and the double observation is performed. There was a problem that it was done.

On the other hand, in the reflection type liquid crystal display device shown in FIG. 5, the double display does not occur because the metal electrode a2 is in close contact with the liquid crystal material. Has a problem that a light source of external light (for example, a fluorescent lamp) is reflected on the electrode a2 and a virtual image thereof is observed in the screen.

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

The present invention has been made in view of such a problem, and an object thereof is to prevent a double image of the display screen and a virtual image of a light source from being realized to enable a high quality screen display. To provide a reflective liquid crystal display device.

[0012]

That is, according to the first aspect of the present invention, there is provided an observer-side electrode plate on which a transparent electrode is disposed, and an electrode disposed opposite to the observer-side electrode plate. A light-reflective back electrode plate, a liquid crystal substance sealed between these two electrode plates, and a polarizing film disposed on the outer surface of the observer-side electrode plate and changing external light incident from the outside into linearly polarized light. A reflection type liquid crystal for reflecting the external light on the back electrode plate and applying a voltage between the electrodes of the two electrode plates to drive the liquid crystal material and controlling transmission / non-transmission of the linearly polarized light to display a screen. Assuming a display device, a transparent resin having a refractive index of 1.6 or less and a resin dispersed in the transparent resin and having a refractive index smaller than that of the transparent resin are formed on the surface of the polarizing film.
To _{MgF 2, CaF 2, LiF,} NaF, than BaF ₂
A light scattering layer comprising selected fine particles is provided.

According to the first aspect of the invention, the external light incident from the external light source is scattered by the light scattering layer provided on the surface of the polarizing film, enters the liquid crystal substance, and is reflected by the back electrode plate. Because the light is also scattered by the light scattering layer when the emitted light is emitted, it is possible to prevent both the double reflection of the display screen and the virtual image of the light source caused by the light reflectivity of the back electrode plate. Become.

Further, the light scattering layer, the resin and its refractive index than the resin having a refractive index of 1.6 or lower refractive index lower
Both _{MgF 2, CaF 2, LiF,} NaF, BaF 2
It is composed of selected fine particles and has an extremely low refractive index as a whole, so that surface reflection of external light from the light source can be prevented and a virtual image of the light source caused by this surface reflection can be prevented. .

As described above, it is possible to prevent both the double reflection of the display screen and the virtual image of the light source caused by the light reflectivity of the back electrode plate and the surface of the polarizing film, so that the display screen can be improved.

Here, in the invention according to claim 1, the transparent resin constituting a part of the light scattering layer includes, for example,
Resins usually applied to paints can be used. Non-aqueous resin can be used as such a resin for coating, for example,
Polyester resins, amino resins, polyurethane resins and the like can be used. In addition, an emulsion resin can be used as the transparent resin. Examples of such an emulsion resin include an aqueous synthetic latex, a non-aqueous emulsion resin, and an aqueous emulsion resin. It is also possible to apply a water-soluble resin. As such a water-soluble resin, for example, polyvinyl alcohol, a water-soluble polyester resin, a water-soluble acrylic resin, and the like can be used. Further, an ultraviolet curable acrylic resin or an electron beam curable acrylic resin may be used. In addition, a vinyl chloride resin, a fluorine resin, a silicone resin, a cellulose resin, a phenol resin, a xylene resin, a toluene resin, a polyimide resin, or the like can also be used. Further, a resin obtained by adding an ultraviolet absorber such as a benzophenone-based ultraviolet absorber or an imidazole-based ultraviolet absorber to these resins may be used.

Further, an adhesive can be used as the transparent resin. As such an adhesive, for example,
Synthetic resin adhesives, emulsion adhesives, hot melt adhesives, and synthetic rubber adhesives can be used. And
As the synthetic resin adhesive, a urea resin adhesive,
Melamine resin adhesive, phenol resin adhesive, epoxy resin adhesive, vinyl acetate resin solvent adhesive, cyanoacrylate resin adhesive, urethane resin adhesive, α-olefin-maleic anhydride resin Two-part adhesives of molecules and isocyanate compounds, reactive acrylic resin adhesives, ultraviolet curable acrylic resin adhesives,
An electron beam-curable acrylic resin adhesive, an anaerobic modified acrylic resin adhesive, or the like can be used. Examples of the emulsion adhesive include a vinyl acetate resin emulsion adhesive, a vinyl acetate copolymer resin emulsion adhesive, an ethylene-vinyl acetate copolymer resin emulsion adhesive, and an acrylic resin emulsion adhesive. Available. In addition, a heat-resistant adhesive such as a polyimide resin-based adhesive, a polyamide-imide resin-based adhesive, and a silicone resin-based adhesive, and a water-soluble adhesive such as polyvinyl alcohol can also be used. Further, an adhesive obtained by adding an ultraviolet absorber such as a benzophenone-based ultraviolet absorber or an imidazole-based ultraviolet absorber to these adhesives may be used.

Next, as the fine particles to be dispersed in such a transparent inside resin, is desirable to have a refractive index 0.05 or more different refractive index of the transparent resin to improve the light scattering property, MgF _2, CaF ₂ , LiF, NaF, Ba
Fine powder selected from F ₂ can be used. These fine particles may have any shape.

Here, the light scattering layer desirably has an uneven surface in order to prevent specular reflection on the surface and more reliably prevent generation of a virtual image of the light source.

The invention according to claim 2 has been made based on such technical reasons.

That is, a second aspect of the present invention is based on the reflection type liquid crystal display device according to the first aspect of the present invention, wherein the surface of the light scattering layer has irregularities having a depth of 0.05 to 10 μm. It is a feature.

The reason why the depth is set to 0.05 to 10 μm is that, in the case of an uneven surface having a depth of less than 0.05 μm, the scattering effect of reflected light is insufficient and specular reflection on the surface is large. On the other hand, when the thickness exceeds 10 μm, the light scattering layer needs to be formed to a thickness exceeding 10 μm, which is inefficient. Preferably, the depth is 0.05 to 1
μm unevenness.

The light scattering layer having such an uneven surface is
The particles can be formed by selecting fine particles having an appropriate particle size, mixing the fine particles with a transparent resin, coating and drying. Further, these fine particles can be used after being subjected to an appropriate surface treatment. Examples of such a surface treatment include a coating treatment with a transparent resin or a coupling agent, and a treatment for causing a surface reaction with an alcohol, an amine, or an organic acid. And, for example, a particle size of 0.2
An acrylic resin (refractive index: 1.5) in which 9 μm of MgF ₂ (refractive index: 1.38) dispersed in 9 μm was applied to a thickness of 10 μm and dried to obtain a surface having a depth of 0.3 μm. 1 to
It has irregularities of 0.5 μm. The epoxy resin (refractive index 1.57) in which MgF ₂ was dispersed at 15% by weight was applied to a thickness of 4 μm on the aluminum thin film of a glass plate on which a 200 nm-thick aluminum thin film was formed, and dried and dried. A light scattering layer is obtained by applying a light beam from a direction perpendicular to the light scattering layer, and the luminance (cd) of the reflected light at various positions.
/ M ² ) is shown in FIG. In FIG. 3, the horizontal axis indicates the viewing angle (the angle between the measurement position and the incident light beam) θ. FIG. 3 also shows the results of the same measurement using CaF ₂ (refractive index: 1.43) instead of MgF ₂ .

From the results shown in FIG. 3, it can be seen that the light-scattering layer has a very high scattering effect on the whole of the light transmitted through the light-scattering layer and the light reflected on the surface of the light-scattering layer, so that a virtual image of the light source does not occur. Can be confirmed.

Next, the reflection type liquid crystal display device is applied to STN (Supe
r Twisted Nematic) In the case of a liquid crystal display device, a retardation film for compensating the refractive index anisotropy of the liquid crystal is provided on the polarizing film in order to prevent coloring of the screen due to the refractive index anisotropy of the liquid crystal. It is desirable to provide.

The invention according to claim 3 has been made based on such technical reasons.

That is, the invention according to claim 3 is based on the reflection type liquid crystal display device according to claim 1 or 2, wherein the polarizing film comprises a protective film and a protective film.
It is characterized by including a retardation film adhered to the lum via an adhesive layer .

As the retardation film, a film obtained by uniaxially or biaxially stretching a plastic film and imparting a refractive index anisotropy to the film can be used, and the stretched axes of these stretched films cross each other. It is also possible to use a multilayer film laminated in a direction. For example, triacetyl cellulose film, polycarbonate film,
It is obtained by uniaxially or biaxially stretching a film such as a polyethylene terephthalate film, a polystyrene film, a polyethylene film, a polymethacrylmethyl film, a polyethersulfone film, a polyetherketone film, and a polyaryl film.

This retardation film can be bonded to the polarizing film by using an adhesive prepared separately.

Next, as a polarizing film applicable to the invention according to the first to third aspects, a dichroic dye such as iodine or a dichroic dye is adsorbed on a uniaxially stretched film, and these dyes are oriented in a stretching direction. You can use what you let. Further, as the polarizing film, a film provided with a protective film on both surfaces of the dye-adsorbing film, and further provided on both surfaces thereof an adhesive layer for bonding an observer-side electrode plate and an abrasion-resistant hard coat layer, respectively. Things can also be used. 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, and the like can be used. As, for example, a triacetyl cellulose film,
A polycarbonate film, a polyethylene terephthalate film, a polystyrene film, a polyethylene film, a polymethacrylmethyl film, a polyethersulfone film, a polyetherketone film, a polyaryl film, or a multilayer film obtained by laminating these films can be used.

In the invention according to claims 1 to 3, the light-scattering layer is formed by bar coating, roll coating,
It can be formed by applying or printing by a method such as curtain coating, gravure coating, spin coating, flexographic printing, and screen printing.

[0032]

According to the first to third aspects of the present invention, since a light scattering layer is provided on the surface of the polarizing film disposed on the outer surface of the observer side electrode plate, external light incident from an external light source is not subjected to the light scattering. The light is scattered by the layer and is incident on the liquid crystal material, and is also scattered by the light scattering layer when the light reflected by the light-reflective back electrode plate is emitted. It is possible to prevent both of the double reflection of the display screen and the virtual image of the light source due to this.

Furthermore, the light scattering layer with a resin and which from its refractive index 1.6 or lower refractive index lower
Selected from MgF ₂ , CaF ₂ , LiF, NaF, BaF ₂
Since it is composed of selected fine particles and has an extremely low refractive index as a whole, surface reflection of external light from the light source can be prevented, and a virtual image of the light source caused by this surface reflection can also be prevented. Becomes

[0034]

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

The reflection type liquid crystal display device according to this embodiment is
As shown in FIG. 1, an observer-side electrode plate 3 having a 0.7 μm thick glass plate as a base material and having a transparent electrode 31 disposed thereon, and an electrode 41 formed of a light-reflective aluminum thin film in a pixel pattern, and A back electrode plate 4 having a light absorbing film pattern 42 provided in a gap portion between the equal electrodes 41, a liquid crystal material 5 sealed between these two electrode plates 3, 4; The main part is constituted by the polarizing film 2 and the light scattering layer 1 sequentially laminated on the outer surface. As shown in FIG. 2, the polarizing film 2 comprises a uniaxially stretched film 22 on which iodine is adsorbed, triacetyl cellulose protective films 21 and 23 laminated on the front and back sides, and an adhesive layer 24 on the back side. And an adhesive layer 26 applied on the retardation film 25 and adhered to the observer-side electrode plate. The light-scattering layer 1 contains 9% by weight of M
An acrylic resin (refractive index: 1.5) in which gF ₂ (average particle size: 0.2 μm, refractive index: 1.38) is dispersed is applied on the protective film 21 to a thickness of 10 μm. And its surface has irregularities with a depth of 0.1 to 0.5 μm.

When the reflective liquid crystal display device is driven under illumination of a 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. Was.

[0037]

According to the first to third aspects of the present invention, it is possible to prevent both the double reflection of the display screen and the virtual image of the light source due to the light reflectivity of the back electrode plate, and to prevent the surface of the polarizing film from being damaged. Since a virtual image of the light source due to reflection can be prevented, the display screen of the reflection type liquid crystal display device can be improved.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view of a polarizing film on which a light scattering layer according to an example is laminated.

FIG. 3 is a graph showing a scattering effect of a light scattering layer.

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

FIG. 5 is a sectional view of a reflection type 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 21 Protective film 22 Uniaxially stretched film which adsorbed iodine 23 Protective film 24 Adhesive layer 25 Retardation film 26 Adhesive layer 31 Transparent electrode 41 Light reflective electrode

Continuation of front page (72) Inventor Osamu Koga 1-5-1, Taito, Taito-ku, Tokyo Toppan Printing Co., Ltd. (72) Inventor Kenichi Nishiwaki 6-6 Akemi no Satomachi, Daito City, Osaka Prefecture (72) Inventor Koichiro Murahashi 1-3-3 Hyakurakuso, Minoh-shi, Osaka (72) Inventor Masahiro Morikawa 4-7-21, Tatsuminami, Ikuno-ku, Osaka-shi, Osaka (56) References JP-A-58-173717 (JP, A) Sho 61-143791 (JP, A) JP-A-2-173701 (JP, A) Japanese Utility Model Sho 60-191001 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02F 1 / 1335 G02B 5/02

Claims (3)

(57) [Claims] 1. An observer-side electrode plate provided with a transparent electrode,
A light-reflective rear electrode plate disposed opposite to the observer-side electrode plate and having electrodes disposed thereon, a liquid crystal material sealed between these two electrode plates, and an outer surface of the observer-side electrode plate A polarizing film that changes the external light incident from the outside into linearly polarized light, and reflects the external light on the back electrode plate and applies a voltage between the electrodes of the two electrode plates to drive the liquid crystal material, In a reflective liquid crystal display device for displaying a screen by controlling transmission and non-transmission of linearly polarized light, a transparent resin having a refractive index of 1.6 or less and a transparent resin dispersed in the transparent resin are provided on the surface of the polarizing film. Its refractive index is small and MgF ₂ , CaF ₂ , LiF, N
aF, reflective liquid crystal display device, characterized in that it comprises a light scattering layer made of the fine particles selected from the BaF _2. 2. The light scattering layer has a surface having a depth of 0.05 to 10
2. The reflection type liquid crystal display device according to claim 1, wherein the reflection type liquid crystal display device has irregularities of μm. 3. The polarizing film comprises a protective film and
3. The reflective liquid crystal display device according to claim 1, further comprising a retardation film bonded to the protective film via an adhesive layer .