JP2000056315A - Liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display element having a good outward appearance, which is produced by putting a wiring metal in a sealed part out of sight of an observer. SOLUTION: The liquid crystal display element, which has an extremely good outward appearance and is preferable in the practical use, can be obtained by coloring a sealing agent 3 white so as to put a wiring part present under the sealing agent out of sight and to allow a border with an active area to be vague. Furthermore, the liquid crystal display element, which has an extremely good outward appearance and is quite preferable in the practical use, can be obtained by improving the light shielding property of the sealing agent and adjusting optical properties such as light reflectivity of the sealing agent to nearly same as those obtained in the operation state of the active area, that is an image display part, so as to further allow the border with the active area to be vague.

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 device, and more particularly to a reflection type liquid crystal display device whose appearance is particularly improved by preventing reflection by electrodes around an image display portion.

[0002]

2. Description of the Related Art A liquid crystal display (LCD) generally used at present has a liquid crystal sandwiched between two glass substrates having electrodes.
The periphery of one substrate is fixed with an adhesive (sealant) except for the liquid crystal sealing opening, and the liquid crystal sealing opening is sealed with a sealing agent. Usually, plastic beads having a uniform particle size are scattered between the substrates as spacers for keeping the distance between the two substrates constant. On the other hand, in the case of a liquid crystal display element for color display, a color filter having a coloring layer of three primary colors (for example, red, green, blue: RGB or yellow, cyan, magenta: YCM) is provided on one of two glass substrates. Is formed.

As a display method of a liquid crystal display element, for example, a TN (twisted nematic) type, ST (super-twisted) type
Shape, GH (guest-host) shape, or ECB (electric
An ally controlled birefringence type or a ferroelectric liquid crystal is used. As the sealant, for example, a heat- or ultraviolet-curable acrylic or epoxy adhesive is used. Further, the color type active matrix drive liquid crystal display element has a configuration in which a liquid crystal composition is sandwiched between an array substrate and a counter substrate. The array substrate is, for example,
It is an active matrix substrate on which a thin film transistor (TFT) using amorphous silicon (a-Si) as a semiconductor layer and a display electrode, a signal line electrode, and a gate electrode connected thereto are formed. The counter substrate is provided to face the TFT array substrate, and has a counter electrode and RGB color filters. A silver paste or the like as an electrode transfer material (transfer) is arranged around the screen between the array substrate and the counter substrate, and the two substrates are electrically connected by the electrode transfer material. Polarizing plates are provided on both sides of the array substrate and the opposing substrate, and by operating as an optical shutter,
Display a color image.

[0004]

In recent years, low power consumption L
As a CD, a reflection type liquid crystal display element has attracted particular attention. In the case of a reflective LCD, since ambient light incident from the outside is used as a light source, a bright screen can be obtained by displaying an image on a white background. That is, a black pattern is displayed on a white background, like drawing characters or figures on white paper,
Displaying various colors on a white background provides a bright and clear screen. Therefore, the appearance of the color of the peripheral portion of the image display area is also white, which is very advantageous in practical use.

On the other hand, in the case of an active matrix type LCD having a high display quality, various metal wirings are formed around an image display area. But,
When such metal wiring is seen around the image display area,
Actually, the display image is difficult to see because the part reflects the light and appears to shine. In the case of a conventional liquid crystal display element, the two substrates are adhered by, for example, an epoxy resin, but the resin in this case is transparent or slightly reddish depending on a mixed resin component or filler component. It has a pink color and is almost transparent. For example, its light transmittance is about 10%. As a result, the conventional reflective liquid crystal display element has a poor appearance because the wiring in the peripheral portion is visible because the sealant is almost transparent.

The present invention has been made based on the recognition of the above problem, and an object of the present invention is to provide a liquid crystal display element having a good appearance by making the wiring metal of a seal portion invisible to an observer.

[0007]

That is, the liquid crystal display device of the present invention comprises a pair of substrates arranged opposite to each other, for example, an array substrate, an opposite substrate provided opposite to the array substrate, and a periphery thereof. And a liquid crystal layer sealed in a gap between the pair of substrates, and reflects a light incident from the outside and emits the light to the outside through the counter substrate to display a predetermined image. The sealant is characterized in that the sealant is colored white, so that the peripheral electrodes are hidden to improve the display quality and the appearance.

Here, if the light transmittance of the sealant is 1% or less, the peripheral electrodes can be sufficiently hidden.

In addition, if at least one of light reflectance, color, and gloss is substantially equal to that of the image display section in a bright state, the sealant does not make the boundary with the image display section noticeable and has an excellent appearance. It will be further improved and be superior in design.

Further, if the sealant is made of fine particles of oxide dispersed therein, the above-mentioned effects can be obtained without causing a problem such as deterioration of reliability.

Specifically, it is desirable to use titanium oxide, calcium carbonate, or a mixture thereof as the oxide.

[0012]

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

FIG. 1 is a schematic plan view illustrating a liquid crystal display device of the present invention.

FIG. 2 is a schematic enlarged sectional view of a peripheral portion thereof. As shown in FIG. 2, the liquid crystal display device of the present invention has an array substrate A, a counter substrate B, and a liquid crystal layer LC sandwiched between them. In the array substrate A, switching elements (not shown) are arranged in a matrix on a substrate 4 made of a light transmitting material such as glass or quartz, and an alignment film 9 is formed on a display pixel electrode 12. A metal wiring layer 2 is provided around the image display section. Each of these wiring layers has a role of supplying a predetermined signal to a signal line or a video line of the image display unit.

On the other hand, the counter substrate B has a configuration in which a color filter 7, a counter electrode 8, and an alignment film 9 are laminated in this order on the lower surface side of a light-transmitting substrate 5 such as glass or quartz.

The array substrate A and the counter substrate B are sealed and fixed by a sealant 3 at the periphery thereof. In the present invention, the sealing agent 3 is colored white so that the surrounding metal wiring layer 2 is hidden so that it cannot be seen from the outside.

That is, the liquid crystal display device of the present invention is of a so-called "reflection type", in which external light incident from the observation surface side is reflected by the display pixel electrode 12 and its intensity is controlled for each pixel to thereby obtain a predetermined value. Display an image. Here, by coloring the sealant 3 white, reflection of light by the wiring layer 2 can be prevented, and the problem that a displayed image is difficult to see can be solved. Further, the sealant 3 is used for the image display unit 1.
The boundary between the sealant 3 and the image display unit 1 can be made almost invisible by coloring so as to have almost the same whiteness as.

Next, a method of coloring the sealant 3 will be described in detail. As the sealant, for example, an epoxy-based thermosetting resin (manufactured by Mitsui Toatsu Chemicals, Inc.) can be used. As a white pigment to be mixed with this sealant,
Oxide fine particles can be used. According to the experiment of the inventor, when the chemical stability of the added material is poor, the reliability of the seal is reduced, and impurities may be eluted into the liquid crystal, which is not preferable for the TFT-LCD. I understood that. Therefore, sufficient attention must be paid to the selection of the material of the white pigment and its purity. Further, depending on the material to be added, conductivity may be exerted, which may affect the electrical operation of the liquid crystal display element. Practically, if the leak resistance through the seal between the adjacent wirings is adjusted to be approximately 100 kΩ or more, the damage to the TFT due to static electricity can be reduced.

According to the study of the present inventor, the particle size is 0.1 to 2
It has been found that titanium oxide or calcium oxide having a size of about μm is preferably used. The fine particles of these oxides can also be used as an appropriate mixture.

Furthermore, the present inventor has found that if white fine particles are directly mixed with a sealant, the dispersibility is not good, and it is better to disperse the fine particles once in a solvent and then add them to the sealant. As the solvent, propylene glycol monomethyl ether acetate and the like are preferable. In addition, since the viscosity of the sealant decreases when a solvent is used in this manner, it is preferable to adjust the viscosity by adding a solvent in which a pigment is dispersed to the sealant and mixing the mixture, and then evaporating an excess solvent.

The light transmittance of the sealant can be adjusted by the addition amount of white fine particles as a pigment. The target light transmittance is 1% or less, and preferably 0.7% or less. However, if too much white fine particles are added, the strength of the sealant and the adhesion may decrease. According to the experiment of the present inventors, the concentration of the white fine particles in the sealant was 2% by weight.
It has been found that it is desirable to set it to 0% or less. Also,
From the viewpoint of the effect on thixotropy, it is desirable that the weight ratio is not more than three times the filler. Typically, the concentration of white fine particles can be 8% by weight.

Next, a TFT-LC using this sealing agent
The manufacturing process of D will be described. First, general TFT
Film formation and patterning are repeated in the same manner as in the process of forming a thin film transistor, a thin film transistor, an electrode wiring such as a signal line, a scanning line or a storage capacitor line, and
A source electrode of the FT and a display pixel electrode 12 also serving as an electrode of the storage capacitor are formed. Here, since the display pixel electrode 12 has a role as a reflecting mirror for reflecting external light, it is desirable to form the display pixel electrode 12 from a material having a high reflectance such as aluminum.

The image display unit has, for example, 400 pixels vertically and 6 pixels horizontally.
It can be composed of an amorphous silicon TFT array having 40 pixels and a pixel pitch of 300 μm.

On the surface of the array substrate thus formed, for example, AL-1051 (manufactured by Nippon Synthetic Rubber Co., Ltd.) is applied to a thickness of about 500 angstroms and rubbed to form an alignment film 9. can do.

Next, a red, green, and blue color filter 7 and an IT
The common electrode 8 using O (indium tin oxide) is formed. Further, an alignment film 9 is formed by applying and rubbing AL-1051. Next, around the counter substrate, a sealant added with a pigment is printed as described above,
Further, 5 μm diameter plastic beads (trade name: Micropearl, manufactured by Sekisui Fine Chemical) are sprayed on the substrate surface as spacers. At this time, the thickness of the sealant is 5μ.
With m, the transmittance can be about 0.5%. Next, the alignment films 9 face each other, and the direction of each rubbing is 90 degrees.
The opposing substrate and the array substrate are arranged so as to be in order, and the opposing substrate and the array substrate are bonded by heating to cure the sealant 3.

Next, the liquid crystal composition 1 is injected by a vacuum injection method from an injection port provided in a part of the sealant 3, and thereafter the injection port is sealed with an ultraviolet curing resin. Examples of the liquid crystal composition include ZLI-4792 (manufactured by E. Merck) and S
811 to which 0.1 wt% is added can be used.

LLC2-9218S (manufactured by Sanritz Co., Ltd.) is attached as a polarizing plate 6 to the front surface of the counter substrate of the liquid crystal cell thus manufactured, and a drive circuit is connected to the electrode terminals.

In the color display type active matrix reflection type liquid crystal display element thus formed, the wiring 2 under the seal is inconspicuous because the sealant is white, and the disturbance of the display screen due to the reflection is eliminated, and a good appearance is obtained. Was done.
Further, in the display mode in which the base is white, the boundary between the display portion and the sealant 3 can be made almost inconspicuous. That is, by making the optical characteristics of the bright state in the image display unit and the optical characteristics of the sealant 3 uniform, these boundaries can be made inconspicuous. For example, it is desirable that the light reflectance, color, gloss, and the like of the sealant 3 be substantially the same as the image display unit in the bright state. In this case, the display screen can be clearly emphasized, the recognition can be easily performed, and the design can be improved. The embodiments of the invention have been described with reference to examples. However, the present invention is not limited to these specific examples. For example, in the illustrated specific example, a color filter is provided on the counter substrate, but a color filter may be provided on the array substrate. Further, the present invention is not limited to a liquid crystal display element capable of color display, but can be similarly applied to a liquid crystal display element for monochrome display to obtain similar effects.

Further, the present invention is not limited to the active matrix type liquid crystal display device, but is equally applicable to various reflection type liquid crystal display devices such as segment type, bar graph type and simple matrix type. Thus, a similar effect can be obtained.

[0030]

According to the present invention, by coloring the sealant white, the wiring portion below the sealant cannot be seen.
A boundary between the active area and the active area is not conspicuous, and a liquid crystal display element having a very good appearance in practical use can be obtained. Furthermore, the light shielding property of the sealant is high, and the optical characteristics such as light reflectivity are substantially equal to those of the active area, that is, the bright state of the image display unit, so that the boundary with the active area is further inconspicuous, A liquid crystal display element with a very good appearance in practical use is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic plan view of a liquid crystal display device of the present invention.

FIG. 2 is a schematic sectional view of a peripheral portion of the liquid crystal display device of the present invention.

[Explanation of symbols]

 Reference Signs List 1 display area 2 wiring layer 3 sealant 4 substrate 5 substrate 6 polarizing plate 7 color filter 8 counter electrode 9 alignment film 12 pixel electrode A array substrate B counter substrate LC liquid crystal layer

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Takeshi Yamamoto 1-9-2, Hara-cho, Fukaya-shi, Saitama F-term in Toshiba Fukaya Electronics Factory (reference) 2H089 LA07 MA04Y MA05Y NA09 NA25 NA45 PA18 QA16 TA09 TA12 TA15

Claims (5)

[Claims] A pair of substrates disposed opposite to each other, a sealant adhered to peripheral portions thereof, and a liquid crystal layer sealed in a gap between the pair of substrates; A liquid crystal display device of a reflection type for displaying a predetermined image by being emitted to the outside, wherein the sealant is colored white. 2. The liquid crystal display device according to claim 1, wherein the light transmittance of the sealant is 1% or less. 3. The liquid crystal display device according to claim 1, wherein the sealant has at least one of light reflectance, color, and gloss substantially equal to an image display portion in a bright state. 4. The liquid crystal display device according to claim 1, wherein the sealant is formed by dispersing fine particles made of an oxide. 5. The liquid crystal display device according to claim 4, wherein said oxide is made of titanium oxide, calcium carbonate, or a mixture thereof.