JP3051233B2 - Negative liquid crystal display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a negative type liquid crystal display device which has a countermeasure against static electricity.

[0002]

2. Description of the Related Art A liquid crystal display element has become indispensable as a display component of, for example, a word processor or a personal computer due to the development of a so-called super twisted nematic (STN) mode and a thin film transistor driven twisted nematic mode (TN). Has become. In particular,
Negative displays that do not transmit light in the background and are light-transmissive in a display portion to which a voltage is applied have been used for various purposes, including in-vehicle use and audio use, because of the sharpness of the display.

[0003]

However, the conventional liquid crystal display element has a problem in that static electricity during use causes display unevenness or short-circuit due to abnormal alignment. As a countermeasure, it is known to use a dopant liquid crystal (a liquid crystal with an increased amount of impurities added), but a relatively large current flows through the liquid crystal due to the impurities added to the liquid crystal, which causes deterioration of the liquid crystal display element. There is a problem that it is fast.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and in a negative type liquid crystal display device having a liquid crystal layer sandwiched between a pair of substrates, at least one surface of the liquid crystal display device is provided. Provided is a negative liquid crystal display device, wherein a film made of a dark colored conductive ink is formed on a polarizing plate . Further, the sheet resistance of the coating is 10 kΩ /
□ The above negative type liquid crystal display element characterized by the following:
Provide a child.

[0005] The color of the conductive film of the present invention is made dark to improve the contrast . In particular, it is preferably black .

A preferred example of the colored conductive film used in the present invention is one in which a colored ink or the like is formed on the element surface by a method such as printing. In particular, in a negative type liquid crystal display element, conventionally, it is generally practiced to print a light-shielding mask (black frame) on the element surface to prevent light from leaking from a seal portion to improve the contrast. It is preferable to make the ink conductive by dispersing and mixing the conductive particles, and the structure is also simplified, which is preferable.

As the conductive particles, metal particles may be used, but carbon particles having a particle diameter of 1 μm or less can be used. These may be used directly or dispersed in a vehicle such as a phenol resin solution, mixed with ordinary black ink, and used as conductive.

[0008] Such film formation yo if performed on at least one surface of the element surface bur, it is also possible to carry out on both sides. Further, in order to sufficiently obtain the effect of removing static electricity , a film is formed on the polarizing plate which is the surface of the element.

Although the thickness of the conductive film is not particularly limited,
The thickness is usually about 5 to 30 μm. Further, in order to sufficiently obtain an effect of removing static electricity, the sheet resistance of the coating is preferably 10 kΩ / □ or less, more preferably 1 kΩ / □ or less. For example, when a film is formed in a frame shape with a width of about 1.5 mm and a thickness of about 20 to 30 μm, the resistance is approximately 5 kΩ after formation.
/ Cm or less.

In the above, an example in which a colored conductive film patterned by printing is provided has been described. However, a method of applying another patterning means such as a spin coater, or applying a pattern after providing a mask and performing patterning, etc. Of course, it can be used.

The present invention is generally applicable to a negative type liquid crystal display device having a liquid crystal layer sandwiched between a pair of substrates. Also,
As a method of manufacturing the liquid crystal display element according to the present invention, a commonly used method can be employed.

That is, on a pair of substrates provided with electrodes, a light-shielding film other than a display portion is formed, if necessary, and then an alignment film is formed.
The alignment process is performed, the alignment film surfaces are opposed to each other, the periphery is sealed with a sealing material, liquid crystal is sealed inside to form a liquid crystal cell, polarizing plates are provided on both sides, and the liquid crystal cell is driven as a negative type liquid crystal display element. By providing a voltage applying means.

The liquid crystal layer used in the present invention is a liquid crystal layer having the same structure as that of a conventional twisted nematic liquid crystal display element, a super twisted liquid crystal display element, and other liquid crystal display elements. Specifically, a nematic liquid crystal having a positive dielectric anisotropy containing an optical rotatory substance is sandwiched between a pair of transparent electrode substrates arranged substantially in parallel, and the twist angle of liquid crystal molecules between the two electrodes is set to 160. The angle may be up to 300 °.

The basic structure of a liquid crystal cell sandwiching the above liquid crystal layer is as follows. ITO patterned with a desired pattern on the surface of a substrate such as plastic or glass
(In ₂ O ₃ -SnO ₂ ), a transparent electrode such as SnO ₂ is provided to form a substrate with electrodes. The electrode layer may be patterned corresponding to the display, or may be a solid electrode when used as a common electrode. The method for forming the electrode layer is not particularly limited, but from the viewpoint of making the layer thickness uniform, an evaporation method, a sputtering method, or the like is preferably used.

In the present invention, an insulating film such as SiO ₂ or TiO ₂ , TFT, MI
M, an active element such as a thin film diode, a retardation film, a polarizing film, and the like may be formed.

In order to improve the contrast, a light-shielding film may be formed above or below the electrode. This light-shielding film is formed on the background portion of the display, and usually only needs to be formed on one substrate. Of course, it may be formed separately on both substrates, but forming it on one substrate reduces the number of steps and improves productivity.

An alignment film is formed on the surface of the substrate with electrodes. When this light shielding film is provided on the electrode,
An alignment film is formed thereon. As the orientation film forming method, a known orientation control method such as a method of forming an organic polymer film of polyimide, polyamide, polyvinyl alcohol or the like by a printing method or a spinner method, rubbing the film, or an oblique vapor deposition method can be used. Two substrates are prepared so as to sandwich the liquid crystal layer described above.

At this time, an insulating film of TiO ₂ , SiO ₂ , Al ₂ O ₃ or the like is provided between the electrode and the orientation control film to prevent a short circuit between the substrates, or a transparent electrode of Al, Cr, Ti or the like is provided. A low-resistance lead electrode may be provided, or a color filter may be stacked above or below the electrode.

The sealing material may be an ordinary sealing material such as an epoxy resin or a silicone resin, and may be used by mixing a colored, preferably black dye or pigment. In order to enclose the liquid crystal in the seal, usually, an opening is formed in a part of the seal, the cell is formed, and then the liquid crystal is injected from the opening to seal the opening.

A pair of polarizing plates are arranged on both outer sides of the cell.
It is general that the polarizing plate itself is also arranged outside the substrate constituting the cell, but if performance permits, the substrate itself may be formed of a polarizing plate or provided as a polarizing layer between the substrate and the electrode. Is also good. In the case of a twisted nematic liquid crystal display device, the polarizing axes of a pair of polarizing plates are generally parallel to each other in order to perform a negative display. In addition, it is also possible to arrange the polarization axes so as to be orthogonal to each other, and to use a light-shielding film and perform reverse driving such that a selection voltage is applied to a portion not to be displayed.

In the present invention, the transmission type is mainly used in many cases, but the reflection type is also applicable, and its application range is wide. When the transmission type is used, a light source is arranged on the back side. Of course, a light guide and a color filter may be used in combination with the light source. Further, in the case of the transmission type, a background portion other than the pixels can be covered with a light shielding film by printing or the like.

In the present invention, a color filter can be used in combination. By forming the color filter on the inner surface of the cell, a more accurate color display can be achieved without causing a shift due to a viewing angle. In particular,
It may be formed below the electrode, or may be formed above the electrode. Further, a color filter for correcting color, a color polarizing plate may be used in combination, a dye may be added to the liquid crystal, or illumination having a specific wavelength distribution may be used.

In the present invention, driving is performed by connecting driving means for applying a voltage to the electrodes of the liquid crystal cell having such a configuration.

In the present invention, various techniques used in ordinary liquid crystal display elements can be applied as long as the effects of the present invention are not impaired.

[0025]

EXAMPLE A glass substrate with ITO was patterned to form a light-shielding film using black ink by offset printing inside the cell except for the portion corresponding to the display pattern, and a 0.7 μm-thick film was further formed thereon. Form a polyimide film,
This was rubbed to form an alignment film to produce a segment electrode substrate.

Further, a glass substrate with ITO was patterned to form a 0.7 μm-thick polyimide film thereon, and this was rubbed to form an alignment film, thereby producing a common electrode substrate.

The segment electrode substrate and the common electrode substrate are arranged so that the electrode surfaces face each other, the periphery is sealed with an epoxy-based sealing material, and a 90 ° twisted nematic liquid crystal is injected into the inside to manufacture a liquid crystal cell. did. Further, a pair of polarizing films was disposed on both sides of the liquid crystal cell to obtain a liquid crystal display device.

At this time, one polarizing film is set so that its polarization axis is orthogonal to the alignment processing direction of the adjacent substrate, and the other polarizing film is set so that its polarization axis is parallel to the alignment processing direction of the adjacent substrate. That is, a pair of polarizing films were arranged such that their polarization axes were parallel.

Pigment-dispersed ink in which conductive particles are dispersed on the surface of this liquid crystal display element (a 1: 1 mixture of Sericol 5 Matt 091 Black manufactured by Teikoku Ink Manufacturing Co., Ltd. and Everyohm 101P manufactured by Nippon Graphite Co., Ltd.). ), A black frame was printed by a screen printing method. 1 and 2 show perspective views of the two types of embodiments. In the figure, 1 is a black frame printing as a conductive film, and 2 is a liquid crystal cell. FIG. 1 shows a print on the front surface of the liquid crystal cell 2, and FIG. 2 shows a print on the rear surface of the liquid crystal cell 2. The printing width is about 3mm , the coating thickness is 18μm,
In the printed state, the sheet resistance was 500 Ω / □ , and the resistance of the black frame was about 3 kΩ / cm.

This was driven in the same manner as that for driving a normal negative type liquid crystal display element. A liquid crystal display element free from display unevenness and short circuit due to static electricity was obtained.

As a comparative example, the ink was formed in the same manner except that an ink (Sericol 5 mat 091 black, manufactured by Teikoku Ink Mfg. Co., Ltd.) conventionally used as a pigment-dispersed ink in the examples was used. In the printed state, the sheet resistance was 7 MΩ / □ or more and was almost an insulator. Can not be obtained sufficiently suppressed generation of static electricity by the display device was achieved, with much the display unevenness compared to Example.

[0032]

According to the present invention, the provision of the colored conductive film not only improves the contrast of the negative-type liquid crystal display device, but at the same time, the adhesive applied to the front and back surfaces of the display device to prevent scratches and dirt. Static electricity generated between the film and the display element, such as when the conductive film is peeled off, can be removed and made the same potential.

Further, there is also an effect that static electricity applied from the outside is diffused and discharged in the conductive film portion.

That is, by applying a colored conductive film to a liquid crystal display element according to the present invention, a liquid crystal display element having not only an effect of improving contrast but also an excellent antistatic property and a long life of the display element can be obtained. There is an effect that it can be obtained.

Further, since generation of static electricity is suppressed, there is also an effect that adsorption of dust and foreign matter is reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention.

FIG. 2 is a perspective view showing another embodiment of the present invention.

[Explanation of symbols]

 1 Black frame printing 2 Liquid crystal cell

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-231480 (JP, A) JP-A-2-130526 (JP, A) JP-A-57-142685 (JP, A) 111180 (JP, U) Japanese Utility Model Hei 5-4128 (JP, U) Japanese Utility Model Application 57-57,785 (JP, U) Japanese Utility Model Application 50-68679 (JP, U) (58) Fields surveyed (Int. Cl. ^7, DB name) G02F 1/1333 G02F 1/1345 G02F 1/1335

Claims (2)

(57) [Claims] In a negative type liquid crystal display device having a liquid crystal layer sandwiched between a pair of substrates, a film of a dark colored conductive ink is formed on a polarizing plate on at least one surface of the liquid crystal display device. A negative-type liquid crystal display device characterized by the above-mentioned. 2. The negative type liquid crystal display device according to claim 1 , wherein the film has a sheet resistance of 10 kΩ / □ or less.