JP2000338472A - Transmission type liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid changes in the background color at high temp., to maintain a high contrast ratio, and to obtain a simple structure and high production yield by holding a nematic liquid crystal layer having a specified twist angle, forming the display pattern into a non-full dot type, and forming a color controlling film according to the visible transmittance and hue of the display part. SOLUTION: The device has a nematic liquid crystal layer 4 having 180 to 270 deg. twist angle held in the space surrounded by transparent substrates 1, 1 having transparent electrodes 2, 2 and alignment films and disposed parallel to each other and the peripheral sealing material 3. As for a liquid crystal panel 8 using a positive mode supertwisted nematic method, polarizing plates 5, 5 are attached to the outside of the transparent substrates 1, 1 so that the transmittance is high when no voltage is applied and that the transmittance is low when a voltage is applied. An illuminating means 9 is disposed on the back of the polarizing plate 5, and a driving means is used to apply a voltage higher than the voltage which excites the liquid crystal layer on the transparent electrodes so as to display a display pattern. The display pattern is a non-full dot type, and a color controlling film 6 having the color controlled according to the visible transmittance and hue of the display part is formed in the part corresponding to the nondisplay part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmissive liquid crystal display device of a non-full dot display type having a backlight system on the back surface.

[0002]

2. Description of the Related Art When a non-full dot type display is performed by a transmission type liquid crystal display device, a so-called negative type display in which a display portion is bright and a non-display portion is dark is generally used. In such a display mode, a high display density, that is, an alphabet / numerical display composed of 5 × 7 dots or a kana / kanji display composed of 16 × 16 dots, which is a so-called character display, can be displayed at about 1/16 duty or more. In the case of the twisted nematic (TN) method, there is a problem that visual recognition can be performed only at a specific angle.

On the other hand, Super Twisted Nematic (ST)
The use of the N) method can avoid a decrease in visibility due to an increase in display density, but a method using a retardation plate as an optical compensator for black and white conversion has a wide operating temperature range such as in-vehicle use. When the method is applied to a non-display area, there is a problem that the background color of a non-display portion changes at high temperature and the contrast is reduced. Although a temperature compensation type retardation plate has been proposed, it is difficult in terms of availability and handling.

This problem can be avoided by using a liquid crystal cell (interference cell) having the same twist angle and cell gap as the optical compensator in the same twist angle and cell gap as the display liquid crystal cell. In such a case, not only the structure becomes complicated, but also it is necessary to control the gap between the two cells with high precision including the relative relationship, and thus there is a problem that productivity is reduced.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems. Even at a high temperature, the background color does not change, a high contrast ratio is maintained, and the structure is improved. Simple, high production yield, and 1 /
It is an object of the present invention to provide a transmissive liquid crystal display device capable of performing time-sharing driving up to about 33 duties.

[0006]

That is, the transmission type liquid crystal display device of the present invention according to claim 1 is characterized in that a pair of transparent substrates and a peripheral seal, each having a transparent electrode and an alignment film, are arranged substantially in parallel. 180-degree twist angle in the space made of wood
A 270 ° nematic liquid crystal layer is sandwiched, and a polarizer is provided on both outer sides of the pair of transparent substrates so as to have a high transmittance when no voltage is applied and a low transmittance when a voltage is applied. Twisted nematic liquid crystal panel, illuminating means provided behind the polarizing plate on the back side, and applying a voltage higher than the liquid crystal layer is excited to a desired transparent electrode in a display area to display a display pattern. In a transmission type liquid crystal display device having a driving unit,
The display pattern is a non-full dot type, a portion corresponding to a non-display portion on the inner surface of the front-side transparent substrate, the display portion of the display portion when an ON voltage higher than the excitation of the liquid crystal layer is applied to the display pattern The point is that a toning film toned according to the luminous transmittance and the hue is provided. With this configuration, even at high temperatures, the background color does not change, a high contrast ratio is maintained, the structure is simple, the manufacturing yield is high, and time-division driving up to about 1/33 duty is possible. A transmission type liquid crystal display device is realized.

A feature of the transmission type liquid crystal display device according to the present invention is that the toning film is made of a photosensitive resin material.
^It has an insulation resistance of ¹² Ω / □ or more. With such a configuration, the smoothness of the toning film is improved, and the transparent electrode can be formed directly on the toning film without using the smoothing layer. Leakage between them is prevented, and clear display without bleeding is possible.

According to a third aspect of the present invention, there is provided a transmission type liquid crystal display device, wherein a portion corresponding to a display pattern on a transparent substrate provided with a toning film is made of a photosensitive resin material. A light-transmitting film having the same insulation resistance and having a luminous transmittance of 50% or more is provided in the same thickness as the toning film, and is further provided on these resin films for driving without a smoothing layer. In that the transparent electrode is provided. With such a configuration, the thickness of the liquid crystal layer is made uniform, and high-quality display without unevenness becomes possible.

According to a fourth aspect of the present invention, the transmission type liquid crystal display device is characterized in that Δnd which is a product of the birefringence anisotropy Δn of the liquid crystal layer and the cell gap d is 0.6 to 1.0 μm, and In addition, a pair of polarizing plates are arranged so as to be in a yellow mode in which yellow green can be displayed below the excitation voltage and dark blue above the excitation voltage. With such a configuration, a display having a large contrast ratio and excellent visibility can be performed.

A feature of the transmission type liquid crystal display device according to the present invention according to claim 5 is that, in the transmission type liquid crystal display device according to claim 4 of the present invention, the hue of the light source of the illumination means is blue. . With such a configuration, the display color that is a transmission color when no voltage is applied can be made blue, so that a monotone display can be realized together with the dark blue background color.

[0011]

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

As shown in FIG. 1, the liquid crystal display device of the present invention has transparent electrodes 1, 2 and transparent substrates 1, 1 each having an alignment film (not shown) and arranged substantially in parallel, and a peripheral sealing material. 3, a nematic liquid crystal layer 4 having a twist angle of 180 to 270 ° is sandwiched between the pair of transparent substrates 1 and 1.
A liquid crystal panel 8 of a positive mode super-twisted nematic type having polarizers 5 and 5 attached so that the transmittance is high when no voltage is applied and the transmittance is low when a voltage is applied. Polarizing plate 5 on the lower side in the figure)
And a driving means (not shown) for applying a voltage higher than the excitation of the liquid crystal layer to a desired transparent electrode in a display area to display a display pattern. ).

In the present invention, the display pattern is a non-full dot type, and the liquid crystal layer is provided on the display pattern in a portion corresponding to a non-display portion on the inner surface of the transparent substrate 1 on the front side (upper side in the figure). It is important to provide a toning film 6 that is toned according to the luminous transmittance and the hue of the display unit when an ON voltage higher than the excitation voltage is applied.

Examples of the non-full dot type display pattern according to the present invention include, in addition to the character display described above, a segment type pattern such as a day character pattern, or a combination of this and a character display. However, in each case, the display area is distinguished from the full dot type display pattern by having a plurality of sections of 1 mm × 0.5 mm or more as non-display portions in the display area.

The liquid crystal display device having such a non-full dot type display pattern is usually time-divisionally driven at a duty ratio of about 1/8 to 1/33, but the liquid crystal panel structure of the present invention can cope with this. It is.

In the present invention, the toning film 6 provided on a predetermined portion of the front side transparent substrate is made of a photosensitive resin material in addition to the luminous transmittance and the color tone, and has an insulation resistance of 10%. It is preferably at least ¹² Ω / □. By using a photosensitive resin material, a toning film can be easily formed smoothly, and a transparent electrode can be directly formed on the toning film without using a smoothing layer. In this case, if the insulation resistance of the toning film is 10 ¹² Ω / □ or more, leakage between adjacent electrodes is prevented, clear display without bleeding is possible, and a protective layer for insulation is not required.

It is preferable that the material of the toning film further has heat resistance to withstand the process temperature, resistance to a chemical solution during patterning of the transparent electrode, and predetermined hardness. The luminous transmittance of the toning film is adjusted to the luminous transmittance of the display unit when an on-voltage higher than the excitation of the liquid crystal layer is applied to the display pattern. About 15%.

A roll coater, a bar coater, a slit coater, or the like can be used for coating the toning film material. However, since the film thickness variation causes color variation and cell gap variation, uniformity of the film thickness is obtained. It is desirable to adopt a spin coating method which is excellent in the above. In this case, a bar coater or a slit coater may be used in combination to reduce the amount of material used. Other than this example, any method may be adopted as long as the method is excellent in uniformity of the film thickness.

The portion corresponding to the display pattern of the substrate on which the toning film is formed in this way is made of a photosensitive resin material, has the same insulation resistance as that of the toning film, and has a luminous transmittance of 50%.
% Of the light-transmitting film having the same thickness as the toning film, and a driving transparent electrode provided on these resin films without a smoothing layer.

In this case, the thickness of the liquid crystal layer is made uniform, and high-quality display without unevenness is possible, and the transparent electrode is hardly disconnected, and the degree of freedom in selecting display colors is increased. I do. Here, the preferable material of the light transmitting film and the preferable coating method of the light transmitting film material are the same as those of the toning film. The light-transmitting film may be transparent, but may be appropriately colored in comparison with the hue of the toning film from the viewpoint of design.

A transparent conductive film is formed by sputtering or the like on the substrate on which the toning film and, in some cases, the light-transmitting film have been formed. The sheet resistance of the transparent conductive film is set to a value determined by the pattern design of the element.
A range of about 0 to 100 Ω / □ is usually adopted. Less than,
A transparent electrode is formed by patterning according to a conventional method.

On the other substrate, an alkali prevention film and a transparent conductive film are sequentially formed, and a transparent electrode is similarly formed. An alignment film having a thickness of about 60 nm is formed on the substrate on which the toning film is formed. On the other substrate, an insulating film such as an inorganic film in which titania and silica are mixed is preferably printed and formed by, for example, a sol-gel method, and then an alignment film is formed and rubbing treatment is preferably performed. The inorganic film is effective for preventing a short circuit between opposing substrates.

It is preferable in terms of the process that the dispersion of the spacers for controlling the gap between the substrates and the printing of the peripheral sealing material are performed on separate substrates. In order to establish electrical continuity between the top and bottom of the substrate, a part of the peripheral sealing material mixed with conductive beads may be used.

Note that the toning film may extend below the peripheral sealing material or may extend to a portion that does not cover the seal. However, when extending to below the seal, the gap between the sealing portion and the display portion may be reduced. Since the gaps are almost the same, there is an advantage that the gap can be easily controlled in cell creation.

After the substrate provided with the toning film and the other substrate are opposed to each other, and the peripheral sealing material is cured through a thermocompression bonding process to cut out the injection port, the terminal portion, etc., the cell and the boat for liquid crystal injection are heated. After the liquid crystal is injected by a vacuum injection method, a liquid crystal cell is manufactured by a method such as sealing the injection port with a UV-curable resin.

Although the twist angle of the liquid crystal layer is in the range of 180 to 270 °, it is preferably 180 to 240 ° from the viewpoint that the generation of domains at high temperatures hardly occurs. Further, as Δnd, about 0.6 to 1.0 μm can be used. However, in a small area, the transmittance without applying a voltage is low, and in a large area, there is a tendency that the viewing angle dependence of the transmittance is large. Therefore, the thickness is preferably about 0.7 to 0.9 μm. On both sides of the cell, a polarizing plate is installed so that a so-called positive mode in which the transmittance is high when no voltage is applied and the transmittance is low when a voltage is applied, and a liquid crystal panel is assembled.

In the positive mode, the liquid crystal molecules are raised by application of a voltage, and the transmittance is reduced in a region where the birefringence is small. Therefore, even if the temperature changes, the transmittance and The transmitted color is relatively stable, and as a result, the contrast is also stable. On the other hand, since the portion having a low transmittance corresponding to the background color in the negative mode is in a light-shielding state by using the birefringence of the liquid crystal, the birefringence easily changes with temperature, and therefore the transmittance and the color tone are easy. , And the contrast changes greatly in appearance.

As described above, the positive mode has a small change in contrast and color tone due to temperature, and can be applied to a wide temperature range. However, in a transmissive display using a backlight, a bright background is always obtained. Absent. In the present invention, by providing the above-described toning film on the background portion, it is possible to perform a negative display in a positive mode having a good temperature characteristic.

The polarizing plate is set at such an angle that the transmittance is high and yellowish green when no voltage is applied, and the transmittance is low and dark blue when a voltage is applied. Is a preferred embodiment in that a high contrast ratio can be achieved.

When the yellow mode is used, the color tone of the toning film may be adjusted to dark blue so that the transmission color of the non-display portion becomes dark blue. In this case, as the light source of the lighting means,
A light source such as CCT or LED having a specific hue such as white, red, green, or blue may be used. For example, if a light source of a blue hue is used, a transmission color without voltage application, that is, a display color can be changed to a blue color, so that a monotone display can be realized together with a dark blue background color. .

As described above, when the hue of the light source is adjusted, or when the contrast ratio may be relatively low, the light-transmitting film is colored or the transmission color of the polarizing plate is adjusted. Thus, the combination of the display color and the background color can be variously changed, and the design can be utilized.

[0032]

[Example 1] A case where a white CCT light source was applied by using a mother substrate in which a silica alkali prevention film was formed to a thickness of about 20 nm on a glass substrate by a sputtering method and applied to a thickness of 1 μm. A negative photosensitive resin material toned so that the hue of the transmitted light is dark blue and the luminous transmittance is 2% is applied to a thickness of about 1 μm, and from the outer edge of the seal provided around the liquid crystal cell. Using a photomask that shields light from the area corresponding to 1/4 to the edge of the substrate and the area corresponding to the display section, exposure is performed at 300 mJ, and development,
Drying and baking were performed. The insulation resistance value of the toning film thus formed was 3 × 10 ¹⁴ Ω / □.

The substrate on which the toning film has been formed as described above has 23
A transparent conductive film of about 100 nm was formed at a temperature of 0 ° C. by a sputtering method. The sheet resistance was about 30Ω / □. After a photoresist is applied to this substrate, exposure and development are performed using a photomask in which an electrode formation portion is shielded from light, unnecessary portions of the transparent conductive film are removed with an etchant, and N
The resist was peeled off with an aOH aqueous solution to form a transparent electrode having a pattern of displaying 2 lines of 16 characters per character of 5 × 7 dots. An alkali prevention film and a transparent conductive film were sequentially formed on the opposing substrate, and a transparent electrode was formed in the same manner. At this time, the dot size is 650 μm in height and 550 in width.
μm, the dot interval was set to 50 μm both vertically and horizontally, and the character interval was set to 0.6 mm wide and 1.1 mm long.

On the substrate on which the toning film was formed, a polyimide-based alignment film material having a pretilt angle of about 5 ° was used, and an alignment film having a thickness of about 60 nm was formed by transfer printing. On the other substrate, a printed film was formed by a sol-gel method in order to form an inorganic insulating film in which titania and silica were mixed. After that, similarly, an alignment film was formed and baked, and both substrates were rubbed so that the twist angle was 240 °.

The substrate on one side has a diameter of 6 μm as a spacer material.
Micropearls manufactured by Sekisui Fine Chemical Co., Ltd., which are resin beads of m, were sprayed, and Structural Bond manufactured by Mitsui Chemicals, Inc. was printed on the opposing substrate as a peripheral sealing material by screen printing. A seal material mixed with conductive beads was printed on a portion provided with an electrode for establishing conduction between the opposing substrates.

After these substrates are opposed to each other and cured through a thermocompression bonding process, and an injection port, a terminal portion and the like are cut out, the nematic-isotropic phase transition temperature is 100 ° C., Δ
Nematic liquid crystal to which n was 0.14 and a chiral material was added so as to have a predetermined pitch was injected by a vacuum injection method, and a UV-curable epoxy resin was applied to the injection port and sealed.

When the gap at each part of the display section was measured, the average was 6.0 μm and the variation was 1.0 μm at the maximum.
The deviation was within the order of magnitude, and cells with good uniformity were formed. Δnd of the liquid crystal layer of this cell is 0.84 μm
It is. After that, a pair of polarizing plates are attached to both outsides of the liquid crystal cell by setting the angle of the polarization axis so that the yellow mode is yellowish green below the excitation voltage and dark blue above the excitation voltage. Was completed.

The panel manufactured in this manner is 1/16
Driving at duty, installing lighting means using white CCT as a light source on the back side, and observing the display state in the temperature range from room temperature to 80 ° C, the hue of the display changed from yellow green to pale yellow green at high temperature Other than that, it was confirmed that there was no problem in visibility.

[Example 2] In Example 1, after forming a toning film, it was applied to a thickness of 1 µm and the hue of the transmitted light when using a white CCT light source was light blue-violet, and the luminous transmittance was 70%. A negative-type photosensitive resin material toned so as to have a thickness of about 1 μm is applied, and using a photomask having an opening slightly larger than the display portion, the same exposure as in the formation of the toning film, Developing, drying and baking, forming a light-transmitting film so that the outer edge slightly overlaps with the surrounding toning film, and then providing both the transparent electrode and the toning film. Was prepared. The size of one opening corresponding to one display dot is 700 μm in length and 600 μm in width.
m.

When this panel was used to observe a display state from room temperature to 80 ° C. under the same illumination means and driving conditions as in Example 1, no problem was caused in visibility in this temperature range. Although the luminance of the display portion was slightly lower than that of Example 1, it was confirmed that the display portion exhibited a display color close to an achromatic color without yellowish color.

[0041]

According to the present invention, even at high temperatures, the background color does not change, a high contrast ratio is maintained, the structure is simple, the manufacturing yield is high, and time-division driving up to about 1/33 duty is possible. A transmission type liquid crystal display device is provided.

When the contrast ratio may be relatively low, the transmission color of the polarizing plate or the hue of the light source is adjusted, or the light-transmitting film is colored to combine the display color with the background color. Can be variously changed, and the design can be utilized.

Further, since the transparent electrode is provided on the back side of the toning film having a low transmittance, not only the pattern appearance which has been a problem when a transparent conductive film having a conventional low resistance is used under external light is not observed. In addition, since the liquid crystal performs display based on the principle of an optical shutter, washout, which is a drawback of light emitting elements such as light emitting diodes, EL, VF, etc., does not occur, and visibility suitable for in-vehicle use is improved. An excellent transmissive liquid crystal display device is realized.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a basic configuration of a liquid crystal display device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Transparent electrode 3 Peripheral sealing material 4 Liquid crystal layer 5 Polarizer 6 Toning film 7 Translucent film 8 Liquid crystal panel 9 Lighting means

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H089 QA16 RA10 SA03 SA04 SA07 TA04 TA05 TA11 2H091 FA08X FA08Z FA42Z FA45Z FC12 FD24 GA06 GA07 GA16 HA10 KA02 KA03 LA12 LA17

Claims (5)

[Claims] 1. A nematic liquid crystal layer having a twist angle of 180 to 270 ° is sandwiched in a space formed by a pair of substantially transparent substrates each having a transparent electrode and an alignment film and arranged substantially in parallel, and a peripheral sealing material. A positive-mode super-twisted nematic liquid crystal panel with a polarizing plate attached to both sides of the transparent substrate so that the transmittance is high when no voltage is applied and the transmittance is low when voltage is applied, and the polarization on the back side In a transmissive liquid crystal display device having illumination means provided behind the plate and driving means for applying a voltage higher than the liquid crystal layer is excited to a desired transparent electrode in a display area to display a display pattern, The display pattern is a non-full dot type, and a portion corresponding to a non-display portion on the inner surface of the front-side transparent substrate has an ON voltage higher than the excitation of the liquid crystal layer in the display pattern Transmissive liquid crystal display device in which the display unit of luminous transmittance and combined toned toning film hue when applied is characterized in that is provided. 2. The toning film is made of a photosensitive resin material.
^2. The transmission type liquid crystal display device according to claim 1, which has an insulation resistance of ¹² Ω / □ or more. 3. A portion corresponding to a display pattern on a transparent substrate provided with a toning film is made of a photosensitive resin material, has the same insulation resistance as the toning film, and has a luminous transmittance of 50%. 3. The transmission type according to claim 2, wherein the light-transmitting film is provided with the same thickness as that of the toning film, and further, a transparent electrode for driving is provided on the resin film without interposing a smoothing layer. Liquid crystal display. 4. The product of the birefringence anisotropy Δn of the liquid crystal layer and the cell gap d is Δnd of 0.6 to 1.0 μm, and is yellow-green below the excitation voltage and dark blue above the excitation voltage. 4. The transmissive liquid crystal display device according to claim 1, wherein a pair of polarizing plates are arranged so as to be capable of displaying a yellow mode. 5. The transmission type liquid crystal display device according to claim 4, wherein the hue of the light source of the illumination means is blue.