JPH07261186A - Reflection type liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide a reflection type liquid crystal display device which prevents light reflection between pixels and is capable of making screen display of a high contrast. CONSTITUTION:This reflection type liquid crystal display device has a rear surface electrode plate 1 which has light reflective metallic electrodes 12 arranged in a stripe form, an observer side electrode plate 2 which is arranged to face this rear surface electrode plate and has transparent electrodes 22 arranged in a stripe form and a liquid crystal material 4 which is sealed between these electrode plates. The display device described above makes screen display by impressing voltage between the metallic electrodes and the transparent electrodes thereby driving the liquid crystal material. The light reflective metallic electrodes are composed of rectangular pattern parts 12a which are disposed in the parts corresponding to the pixel parts and connecting pattern parts 12b which are disposed in the parts corresponding to the inter-pixel parts and connect, are narrower than the rectangular pattern parts and connect the rectangular pattern parts to each other in one direction. Since the areas of the connecting pattern parts are smaller than the rectangular pattern parts, the light reflection of the light reflective metallic electrodes in the inter-pixel parts decreases.

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 in which light-reflective metal electrodes are arranged in stripes on a back electrode plate located on the side opposite to a screen observer, and particularly, it has a high contrast. The present invention relates to an improvement in a reflective liquid crystal display device capable of displaying a screen.

[0002]

2. Description of the Related Art Generally, a liquid crystal display device comprises a pair of electrode plates on which electrodes are arranged and a liquid crystal substance enclosed between the electrode plates, the main part of which is used to apply a voltage between the electrodes. By applying the voltage, the alignment state of the liquid crystal substance is changed to control the plane of polarization of the light transmitted through the liquid crystal substance, and at the same time, the polarizing film controls the transmission / non-transmission of the liquid crystal substance to perform screen display. As a liquid crystal display device of this type, a light source (lamp) is arranged on the back surface or the side surface of the back electrode plate, and a backlight type or light guide type transmissive type with a built-in lamp in which light rays are incident from the back electrode plate side. Liquid crystal display devices are widely used.

However, in a transmissive liquid crystal display device with a built-in lamp, the power consumption of the lamp is large and the CRT is large.
Since it consumes almost the same amount of power as other types of displays such as a plasma display and a plasma display, it has the drawbacks that the original low power consumption of the liquid crystal display device is impaired and that it becomes difficult to use it for a long time on the mobile phone. Was.

On the other hand, without incorporating such a lamp, 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, and There is also known a reflection type liquid crystal display device in which incident light is reflected by a light reflecting material provided on the 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. 4, a metal reflection plate a3 is provided on the back surface of the back electrode plate a, or as shown in FIG. It is known that the electrode a2 is made of a light-reflective metal thin film and incident light is reflected by the electrode a2 to display a screen. In the reflection type liquid crystal display device shown in FIG. The display screen constituted by the above has a drawback that it is reflected on the metal reflection plate a3 to form a virtual image and is double observed.
The reflection type liquid crystal display device shown in FIG.
4 to 5, b is a viewer-side electrode plate, c is a liquid crystal substance,
Reference numeral d denotes a polarizing film, and reference numeral e denotes a sealing material that integrates the back electrode plate a and the observer-side electrode plate b in the peripheral portion.

In a simple matrix drive type liquid crystal display device utilizing the light-reflecting metal electrode a2, the light-reflecting metal electrode a2 is arranged in a stripe pattern, while the opposite viewer-side electrode plate b is arranged. The electrodes b2 are also arranged in a stripe shape in a direction intersecting with the metal electrode a2, and a scanning voltage is sequentially applied to one of the electrodes a2 and b2 and a signal voltage is applied to the other electrode, and the scanning voltage is applied to the electrodes. And a liquid crystal substance at a portion where the two electrodes to which a signal voltage is applied intersects (this portion constitutes a rectangular pixel portion) is displayed on the screen.

[0007]

By the way, in the liquid crystal display device of the simple matrix drive system, the light reflecting metal electrodes a2 arranged in stripes are conventionally formed in a long strip-shaped pattern as shown in FIG. Therefore, the light-reflective metal electrode a2 is present at a portion corresponding to the pixel portion and also uniformly at a portion corresponding to a space between the pixel portions (referred to as an inter-pixel portion). is doing.

Since the external light incident on the inter-pixel portion is reflected by the light-reflecting metal electrode a2 in this portion, the reflected light reduces the contrast of the display screen and deteriorates the display quality. There was a problem that would end up.

In this case, with respect to the light-reflecting metal electrode, a transparent electrode is used as a base and a metal thin film is laminated on the transparent electrode to form a two-layer structure, and the metal thin film is processed into a rectangular pattern to apparently form a rectangular shape. It is considered that the above problem can be alleviated by separating the pattern so that the metal thin film is not provided at the portion corresponding to the inter-pixel portion. However, in order to obtain such a structure, it is necessary to form the transparent electrode coating film for the underlayer and the metal thin film in two steps, and moreover, it is transparent by using two kinds of photomasks having different patterns. Since it is necessary to process the electrode and the rectangular pattern separately, the manufacturing cost becomes high and the method is practically difficult to apply.

The present invention has been made by paying attention to such a problem, and a problem thereof is that a reflection type liquid crystal display capable of displaying a high contrast screen by preventing light reflection in the inter-pixel portion. To provide a device.

[0011]

That is, the invention according to claim 1 is a back electrode plate having a plurality of light-reflecting metal electrodes arranged in stripes, and a back electrode plate arranged facing the back electrode plate. An observer-side electrode plate having transparent electrodes arranged in a stripe shape and a liquid crystal substance enclosed between these electrode plates are provided, and a voltage is applied between the metal electrode and the transparent electrode to remove the liquid crystal substance. Assuming a reflective liquid crystal display device that is driven to display a screen, the light-reflective metal electrode is provided in a rectangular pattern portion provided in a portion corresponding to a pixel portion and the rectangular pattern portion provided in a portion corresponding to an inter-pixel portion. It is characterized in that it is composed of a connecting pattern part that is narrower than the shape pattern part and connects the rectangular pattern parts to each other in one direction.

According to the reflection type liquid crystal display device of the first aspect of the present invention, the light reflective metal electrode is provided in the rectangular pattern portion provided in the portion corresponding to the pixel portion and in the inter-pixel portion. The connecting pattern portion is provided at a corresponding portion and is narrower than the rectangular pattern portion, and is composed of a connecting pattern portion that connects the rectangular pattern portions in one direction, so that the connecting pattern portion is smaller than the forming area of the rectangular pattern portion. Since the area where the light is reflected is reduced, it is possible to reduce the light reflection of the light reflective metal electrode in the inter-pixel portion.

Therefore, since the light reflection in the inter-pixel portion is reduced, the contrast of the display screen is improved, so that the display quality can be improved.

The connection pattern portion of the light-reflective metal electrode provided in the portion corresponding to the inter-pixel portion has a scanning voltage applied to the rectangular pattern portion of the light-reflective metal electrode provided in the portion corresponding to the pixel portion. Alternatively, it functions as an induction wire for applying a signal voltage, and this connecting pattern portion may be configured by one linear pattern portion or may be configured by two or more linear pattern portions. is there. When the connecting pattern portion is composed of two or more linear pattern portions, even if one of these linear pattern portions is broken, the light-reflecting metal electrode is provided through the other linear pattern portion. It is possible to surely apply the voltage to the rectangular pattern portion. The invention according to claim 2 is made for such a technical reason.

That is, the invention according to claim 2 is premised on the reflection type liquid crystal display device according to the invention according to claim 1, and the connection pattern portion is constituted by two or more linear pattern portions. It is a feature.

Further, according to the reflection type liquid crystal display device of the second aspect of the invention, even if one of the linear pattern portions is broken, the light is reflected through the other linear pattern portion. Since it is possible to reliably apply a voltage to the rectangular pattern portion of the conductive metal electrode, it is possible to prevent display defects and improve reliability in screen display.

As the metal electrode according to the present invention, it is desirable to use a metal having a high light reflectance.
Aluminum (Al), magnesium (Mg), silver (A
g), nickel, (Ni), or alloys of these metals can be applied. It is also possible to add a different type of metal to these metals or alloys to improve the adhesion and hardness of the back electrode plate to the substrate and adjust the coefficient of thermal expansion. Examples of such dissimilar metals include Ti,
Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn,
Fe, Ni, Co, Cu and Zn can be applied. Further, for the same reason, it is possible to add a non-metal instead of the dissimilar metal. Such non-metals include Si, P,
Bi, Sb, etc. can be illustrated. It should be noted that since the light reflectance of the metal electrode decreases when the amount of addition of these dissimilar metals or nonmetals increases, the amount of addition should be kept extremely small.

The metal electrode can be formed into a film by a known method such as a vacuum evaporation method, a sputtering method and an ion plating method. Prior to the film formation, the substrate surface of the back electrode plate is subjected to plasma or plasma. By treating with ultraviolet rays, the adhesion between the substrate and the metal electrode can be increased. After the film formation, the metal electrode can be formed by patterning according to a well-known photolithography process.

Further, as the substrate of the back electrode plate provided with the metal electrode in the inventions described in claims 1 and 2, for example, a glass substrate can be preferably applied. Also, besides this,
Ceramic substrates, plastic films, plastic boards, etc. can be applied. This substrate is not limited to being transparent, but may be colored in black, white, or another color.
When a black substrate is used, a light-shielding film is not formed between the pixels of the liquid crystal display device to prevent reflection of light rays incident on the portion where the metal electrode does not exist, thereby improving the contrast of the display screen. Can be achieved. Further, when the liquid crystal display device is used in a bright room with a lot of room light, the above-mentioned room light is used for screen display, and a lamp is provided inside the device for use in a dark room where the room light is insufficient. In the case of a built-in transflective liquid crystal display device, it is desirable to use a transparent substrate.

Next, a transparent substrate such as a glass substrate, a ceramic substrate, a plastic film or a plastic board can be applied as the substrate of the observer side electrode plate, and a transparent conductive film such as ITO or a NESA film can be used as the transparent electrode. Can be applied. It is also possible to provide a light-scattering layer on the observer-side electrode plate to scatter the display light to expand the viewing angle of the display screen, or to provide a color filter layer to color the display light for color display. . The light-scattering layer may be provided either inside the substrate in contact with the liquid crystal substance or outside the substrate in contact with the polarizing film or the retardation plate. As such a light scattering layer, for example, a transparent resin binder in which fine particles having a different refractive index are dispersed can be applied. Examples of such fine particles include SiO ₂ , CaF ₂ , and Mg.
F ₂ , ZrO ₂ , MgO, CaO, Al ₂ O ₃ , SnO
₂ , PbO, Sb ₂ O ₅ , CeO ₂ , LiF, NaF,
Inorganic fine powder such as BaF ₂ , TiO ₂ and HfO ₂ , or fine powder of fluororesin such as PTFE (polytetrafluoroethylene), fine powder of amorphous polyolefin, beads of polydivinylbenzene, hollow beads of polystyrene, fine powder of polysulfone, Fused quartz fine powder, FK-
Fine powder of fluoride-containing silicate glass such as 6 can be used. Further, the surface of the substrate is roughened to form irregularities having a depth of the submicron order on the surface, and the irregularities are used instead of the light scattering layer to scatter the display light so that the visual field of the display screen. It is also possible to enlarge the corners.

Further, as the color filter layer,
A color filter layer formed by printing an ink containing a colorant on a pixel pattern by a printing method, a color filter layer formed by dyeing a transparent resin on a pixel pattern by a dyeing method, or a photosensitive transparent resin containing a colorant A color filter layer by a pigment dispersion method formed by exposing and developing a pixel pattern according to a photolithography process after applying the above, and a color filter layer by an electrodeposition method formed by electrodeposition of an electrodeposition coating material containing a coloring material on the pixel pattern A well-known color filter layer such as an electrophotographic color filter layer formed by adhering a toner containing a coloring material to a pixel pattern according to the electrophotography can be used.

Since the metal electrode according to the present invention has a smaller electric resistance than the transparent electrode of the observer-side electrode plate, the liquid crystal display device uses a simple matrix drive system (the liquid crystal substance or its alignment state is STN, ECB, In the case of OCB (π cell), homeotropic or antiferroelectric liquid crystal), the metal electrode is used as the scanning side electrode and the transparent electrode of the observer side electrode plate is used as a signal. It is preferably used as an electrode.

[0023]

According to the reflection type liquid crystal display device of the present invention, the light-reflecting metal electrode has a rectangular pattern portion provided in a portion corresponding to the pixel portion and a portion corresponding to the inter-pixel portion. And a connecting pattern part that is narrower than the rectangular pattern part and connects the rectangular pattern parts to each other in one direction, because the forming area of the connecting pattern part is smaller than the forming area of the rectangular pattern part. It is possible to reduce the light reflection of the light reflective metal electrode in the inter-pixel portion.

Therefore, since the light reflection in the inter-pixel portion is reduced, the contrast of the display screen is improved, so that the display quality can be improved.

According to the reflective liquid crystal display device of the second aspect of the present invention, the connection pattern portion is composed of two or more linear pattern portions, and one linear pattern portion is broken. However, since it is possible to reliably apply a voltage to the rectangular pattern portion of the light-reflecting metal electrode via the other linear pattern portion, it is possible to prevent display defects and improve reliability in screen display. Become.

[0026]

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

[Embodiment 1] In the reflection type liquid crystal display device according to this embodiment, as shown in FIG. 2, a back electrode plate 1 and an observer side electrode plate 2 arranged facing the back electrode plate 1. When,
A sealing material 3 that integrates the two electrode plates 1 and 2 at their peripheral portions and a liquid crystal substance 4 sealed between the two electrode plates 1 and 2 constitute a main part.

The back electrode plate 1 has a thickness of 0.7 μm.
m, and a light-reflecting metal electrode 12 having a thickness of 0.2 μm and arranged in a stripe pattern on the glass substrate 11, while the observer-side electrode plate 2 has a thickness of 0. The glass substrate 21 has a thickness of 7 μm, and the transparent electrodes 22 are arranged on the glass substrate 21 in stripes.

The light-reflective metal electrode 12 is formed by forming a thin film of an alloy made of aluminum by adding 2% by weight of molybdenum to a thickness of 0.2 μm on the glass substrate 11.
It is formed by patterning according to a well-known photolithography process, and the pattern is shown in FIG. That is, this light-reflecting metal electrode 12 has a thickness of 330 μm.
Rectangular pattern parts provided at a pitch of m (one side 315
12a having a rectangular shape of μm) and these rectangular pattern portions 12a are connected in one direction to form a rectangular pattern portion 1
2a (connecting pattern portion 12b (width 1
2 μm of two linear pattern portions).

[Embodiment 2] The reflective liquid crystal display device according to this embodiment is substantially the same as the reflective liquid crystal display device according to Embodiment 1 except for the material and pattern of the light reflecting metal electrode 12.

That is, as the metal electrode 12, an alloy obtained by adding 3% by weight of tungsten to aluminum was used, and the pattern shown in FIG. 3 was adopted as the pattern. As is apparent from FIG. 3, the metal electrode 12
Is a rectangular pattern portion (having a rectangular shape with a side of 285 μm) 12a provided at a pitch of 300 μm, and these rectangular pattern portions 12a are connected in one direction to apply a drive voltage to the rectangular pattern portion 12a. Connection pattern portion 12b (consisting of a single linear pattern portion having a width of 20 μm and passing through the center of the rectangular pattern portion 12a).

[0032]

According to the first aspect of the invention, since the formation area of the connecting pattern portion is smaller than the formation area of the rectangular pattern portion in the light reflecting metal electrode, the light reflecting metal electrode in the inter-pixel portion is formed. It is possible to reduce light reflection.

Therefore, since the light reflection in the inter-pixel portion is reduced, the contrast of the display screen is improved and the display quality is improved.

According to the second aspect of the invention, since the connecting pattern portion is composed of two or more linear pattern portions, one linear pattern portion may be broken. Since the voltage can be reliably applied to the rectangular pattern portion of the light-reflecting metal electrode via the other linear pattern portion, display defects can be prevented and reliability in screen display can be improved.

[Brief description of drawings]

FIG. 1 is a plan view of a light reflective metal electrode of a reflective liquid crystal display device according to a first embodiment.

FIG. 2 is a cross-sectional view of the reflective liquid crystal display device according to the first embodiment.

FIG. 3 is a plan view of a light-reflecting metal electrode of the reflective liquid crystal display device according to the second embodiment.

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

FIG. 5 is a cross-sectional view of a reflective liquid crystal display device according to a conventional example.

FIG. 6 is a plan view of a light reflective metal electrode of a reflective liquid crystal display device according to a conventional example.

[Explanation of symbols]

 1 Rear Electrode Plate 2 Observer Side Electrode Plate 3 Sealing Material 4 Liquid Crystal Substance 11 Glass Substrate 12 Light Reflective Metal Electrode 12a Rectangular Pattern Part 12b Connection Pattern Part 21 Glass Substrate 22 Transparent Electrode

Claims (2)

[Claims] 1. An observer-side electrode having a back electrode plate having a plurality of light-reflective metal electrodes arranged in stripes and transparent electrodes arranged so as to face the back electrode plate and arranged in stripes. A reflective liquid crystal display device comprising a plate and a liquid crystal substance enclosed between these electrode plates, and applying a voltage between the metal electrode and the transparent electrode to drive the liquid crystal substance to display a screen. The reflective metal electrode is provided in a portion corresponding to the pixel portion, and the rectangular pattern portion is provided in a portion corresponding to the inter-pixel portion, is narrower than the rectangular pattern portion, and the rectangular pattern portions are in one direction. A reflection type liquid crystal display device, comprising: 2. The reflective liquid crystal display device according to claim 1, wherein the connection pattern portion is composed of two or more linear pattern portions.