JPS63247724A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain high contrast by disposing polarization axes of polarizing films on both faces of a nematic liquid crystal cell in such a manner as to allow transmission of light in voltage non impressed parts, impressing an excitation voltage to electrodes of the parts except a display pattern and providing a part where the degree of light shielding is lower than in the voltage impressed part. CONSTITUTION:Light is mostly shielded in the voltage impressed part if the polarizing axes of the polarizing films 7A, 7B on the front and rear faces of the nematic liquid crystal cell having light shielding films 4 are disposed at 90 deg. with each other and the films are stuck to a positive type. The light leaks slightly from the part of the voltage non impressed part where the degree of light shielding is low if the polarization axes are disposed at 90 deg. with each other and said films are stuck to a positive type. The light of the specific color transmits only the voltage impressed part if a part of the polarizing films is stuck with color polarizing films to a positive type in place of sticking this part of the polarizing films to a negative type. The degree of freedom of display design is increased and designability is improved is improved if the polarizing films on one or both faces are selectively stuck without changing the constitution of the liquid crystal cell itself according to this constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a liquid crystal display device that performs negative type display in which a light shielding film is formed.

[Prior Art] Conventionally, liquid crystal display devices used for displaying automobile instruments or clocks, etc., often employ a negative type display in which bright characters, figures, etc. are displayed on a dark display surface.

In a negative type liquid crystal display device, no voltage is applied to the liquid crystal layer in the background area, so the liquid crystal molecules are twisted, and the plane of polarization of the light is twisted along this, making the polarization axes of the pair of polarizing films parallel. This arrangement prevents light from passing through the background portion. However, in the background area of a normal negative liquid crystal display device, the plane of polarization of the light is twisted and the light travels.
Since the refractive index differs depending on the color of light, there is a problem in that a certain amount of light of a certain color passes through. The ratio (contrast ratio) between simply placing a pair of polarizing films with their polarization axes perpendicular to that of placing them parallel is 1000.
It becomes more than that. However, with a normal negative type liquid crystal display device,
When a liquid crystal layer is sandwiched between these layers, as mentioned above, the plane of polarization of the light travels in the background area with a twist, making it impossible to obtain sufficient polarization for all colors, resulting in light leakage in the background area. , this was a problem.

For this reason, it has been proposed to form a light shielding film on this background portion to prevent light leakage from the background portion.

However, if a light-shielding film is provided simply to eliminate light leakage from the background area, the background area will become dark, but the non-display pattern area, which prevents light from passing through the display pattern area, will darken the background area. This causes the same problem as the background area described above because light leaks to some extent, and when the ratio of darkness between the background area and this non-display pattern area becomes large, light leaks through areas where no light should originally be transmitted. If the display was transparent, there was a risk of misreading the display.

For this reason, the applicant provided a light-shielding film in the background area, and also added a polarizing film so that light would pass through the areas where no voltage was applied to the liquid crystal, as in the case of positive liquid crystal display devices.
It is proposed that a voltage be applied to a portion of the liquid crystal that prevents light from passing through to drive the display pattern. As a result, in the part where voltage is applied to the liquid crystal,
Since the liquid crystal is upright, there is no effect of color, and by arranging a pair of polarizing films so that their polarization axes are orthogonal, high light-shielding properties can be obtained by fully utilizing the polarizing performance of the habo polarizing films. A high contrast of 1000 or more was obtained.

[Problems to be Solved by the Invention] A liquid crystal display device in which a light-shielding film is formed in this manner and the polarization axis of the polarizing film is set for positive display is certainly able to obtain high contrast as described above. However, if there is a display part within the same liquid crystal cell that does not require a high degree of light shielding, or if there is a display part that requires a certain amount of light to leak even when shielded,
Furthermore, there is a problem in that it is not easy to change the color locally.

[Means for Solving the Problems] The present invention has been made to solve these problems, and consists of sandwiching a nematic liquid crystal layer between substrates provided with electrodes, and shielding areas other than those corresponding to display patterns. In a liquid crystal display device equipped with a film, the polarizing axes of the pair of polarizing films on both sides of the liquid crystal cell are arranged so that light passes through the part where no voltage is applied, and the polarizing axes of the pair of polarizing films on both sides of the liquid crystal cell are arranged so that light passes through the part where no voltage is applied. a first part to which a voltage higher than the voltage that excites the nematic liquid crystal is applied; and a second part to which the degree of light shielding at the voltage application part is lower than the light shielding degree at the voltage application part of the first part. The present invention provides a liquid crystal display device characterized by providing a portion.

The present invention will be explained with reference to the drawings.

FIG. 2 shows a cross-sectional view of a basic example of a negative-tone twisted nematic liquid crystal display device of the present invention.

In FIG. 1, IA is a substrate, 2A is an electrode formed thereon, and an alignment film 3A is further formed thereon. On the other hand, the other substrate IB has an electrode 2B on it, and a light shield 11ii14 in a part other than the display pattern.
, an alignment film 3B is formed thereon. These two substrates are arranged so that their electrode surfaces face each other, their peripheries are sealed with a sealing material 5, and nematic liquid crystal is injected inside to form a liquid crystal layer 6 to form a liquid crystal cell.

A pair of polarizing films 7A are provided on both sides of this liquid crystal cell.

7B is disposed, and its polarization axis is such that light is basically blocked at the portion to which a voltage is applied, as in the case of a normal positive type liquid crystal display element.

Specifically, the alignment film is formed so that it is twisted at approximately 90 degrees, and the liquid crystal molecules twist at approximately 90 degrees when no voltage is applied.
° twisted state, and the polarizing axes of the polarizing films may be arranged so as to be parallel or perpendicular to the respective orientation directions, that is, the polarizing axes of the polarizing films are arranged so that they are at approximately 90° to each other.

However, even if this orientation direction is 90°, the twist of the liquid crystal may be 270° or 450° instead of 90°, or the orientation direction may not be exactly 80° but 85° or 100°.
Also, the angle between the polarization axis and the orientation direction is not limited to being parallel or orthogonal,
It may be 85° or 85°.

Furthermore, Fig. 1 shows a layout diagram of the polarizing film of the present invention.The polarization axis direction of the polarizing film on the back side is all in the direction of a.For the 0 surface, the B part is removed, and the 0 part is in the C direction. It is. Therefore, for the B section, the polarization axes of the polarizing films are at approximately 90 degrees to each other as described above, but for the 0 section, they are at approximately Oo to each other. In other words, in the 0 part, light is transmitted through the part to which a voltage is applied.

The substrate used in the present invention may be a transparent substrate made of glass, plastic, etc., and the inner surface thereof has In2O3-9
A transparent electrode is formed using a transparent conductive film such as n02(ITO) or 111203. In addition, a film of a low-resistance conductive material such as metal or conductive paste may be formed on the transparent electrode in the form of thin lines, a grid, or the like.

The alignment film is made of organic polymer such as polyimide, polyamide, polyvinyl alcohol, 5i02, Ti02, Al2O
The alignment film may be any alignment film that aligns the liquid crystal, such as rubbing a film made of an inorganic material such as No. 3, or diagonally depositing the film, and it may be one layer or two layers as required.

The light shielding film of the present invention may be provided on the inner surface of the liquid crystal cell, or
It may be provided on the outer surface, and its light transmittance is 0.02 to 1.0.
%. However, it is preferable to form the light-shielding film on the inner surface of the liquid crystal cell because it is less likely to cause misalignment between the display pattern and the light-shielding film when viewed from an oblique direction.

This light-shielding film is formed on the background part of the display, and usually only needs to be formed on one substrate. Of course, it may be formed separately on both substrates, but it is not necessary to form it on one substrate. It requires fewer steps and is more productive.

This light-shielding film is formed by depositing or plating a metallic light-shielding film such as aluminum, nickel, or chromium through a transparent electrode and an insulating film, or by printing a light-shielding ink such as carbon paste. It is sufficient if it is formed.

The sealing material may be an ordinary sealing material such as epoxy resin or silicone resin. Usually, an opening is formed in a part of the sealing material, and after forming a cell, liquid crystal is injected through the opening. Just seal it.

The liquid crystal to be injected may be an ordinary nematic liquid crystal, which usually has a twist of approximately 90 degrees, but as mentioned above, it has a twist of approximately 90 degrees.
A chiral substance may be added to give a twist of 0° or 450°.

In addition, a single layer of color filter may be formed on the inner or outer surface of the substrate, the substrate may be a polarizing film substrate, a touch switch, an ultraviolet cut filter, or a non-reflection filter may be laminated on the outer surface of the substrate. Techniques that can be applied to ordinary liquid crystal display elements may be applied within a range that does not impair the effects.

In the example shown in FIG. 1, the display is a negative type as a whole, but the voltage applied to the electrodes is similar to that of a positive type display and a negative type display.

That is, there is a negative type part where a voltage is applied to a part of the liquid crystal where it is desired to transmit light, and a positive type part where a voltage is applied to a part where it is desired to block light.

In the present invention, the background part with the light-shielding film and the polarizing axes of the front and back polarizing films are arranged so that they are approximately 90 degrees to each other, so that the positive type bonding is used, so that the part to which voltage is applied is mostly light-blocked, and no light leaks. Although it doesn't come.

The negative-tone film is arranged so that the polarization axes of the polarizing films are approximately Oo from each other, and the areas where no voltage is applied are not sufficiently light-shielded, and a small amount of light leaks out.

Furthermore, instead of partially applying a negative polarizing film, if a positive color polarizing film is applied only to this part, light of a specific color will be transmitted only to the part where a voltage is applied.

As described above, by adopting the configuration of the present invention, it is possible to partially perform special display depending on the design of the liquid crystal cell.

Particularly in the case of the bar graph display shown in FIG. 1, relative discrimination of displayed values becomes easier if light leaks to such an extent that the entire display range of the bar graph can be recognized. For this reason,
For analog display parts such as bar graphs, polarizing films can be arranged in parallel to provide a normal negative display, or one polarizing film can be used as a color polarizing film to provide a positive display, so that a specific color is displayed at the voltage applied part. Make it.

[Example] Example 1 The configuration was as shown in FIGS. 1 and 2, the liquid crystal was ZLI-2978-000 manufactured by Merck, the polarizing film was G-1220Du manufactured by Nitto Denko, and the cell gap was 5. Full m.

The negative type polarizing film is used for the analog engine revolution meter in the first drawing section.

A light shielding film was formed on the inner surface of the cell and printed with carbon ink to a thickness of about 21 Lm. Further, the driving voltage was set to IOV. Part B in Figure 1, including the light-shielding film, hardly transmits any light when the light is blocked by voltage application, so the existence of the display segment is not known. However, it is difficult to tell how many revolutions an engine tachometer can generally display. In such a case, it is better to be able to see how far the display segment exists.In such a case, if a negative type polarizing film is attached only to the D part as shown in Figure 1 of this embodiment, even when the light is blocked with no voltage applied, Since it transmits a small amount of light, there is a difference in brightness from the light-shielding film portion, making it possible to recognize the presence of the display segment.

Example 2 As shown in FIG. 1, a red color polarizing film is pasted on one side of only the scale part of the engine tachometer in section D, aligning the polarization axis with the other parts. By doing so, light is normally transmitted in a state where no voltage is applied.

In this embodiment, when a certain number of rotations is exceeded, a voltage is applied, only red light is transmitted, and a warning is displayed.
The polarizing films on both sides of the liquid crystal cell may be color polarizing films so that light of a specific color (for example, blue) is transmitted even when no voltage is applied.

[Effects of the Invention] In the present invention, the polarizing film on both sides of the liquid crystal cell may be pasted on only part of the liquid crystal cell using a negative type film, or a color polarizing film may be pasted on one or both sides of a part of the cell, and a light-shielding film may be applied to the non-display pattern area. By forming a display pattern and driving the display pattern portion in a positive display type, it is possible to reduce the degree of light shielding or display a specific color in only one portion while maintaining high contrast in one normal portion.

In the present invention, by attaching polarizing films on one side or both sides separately without changing the structure of the liquid crystal cell itself, the degree of freedom in display design is increased and the design is improved. In addition, different types of display devices can be made using the same manufacturing process, improving reliability and productivity.

In particular, it is preferable to make the entire display segment distinguishable to some extent, such as a bar graph. By making the displayed part identifiable even when it is not displayed, it is possible to determine the ratio of the displayed part to the entire display range. The present invention also has advantages. Various configurations used in known liquid crystal display elements may be added to the present invention within a range that does not impair the effects of the present invention, and various applications will be possible in the future.

[Brief explanation of drawings]

FIG. 2 is a sectional view of a liquid crystal cell used in a basic example of the present invention. FIG. 1 is a plan view showing an example of how polarizing films of the present invention are pasted. Substrate = lA, IB Electrode: 2A, 2B Alignment film; 3A, 3B Light shielding film: 4 Seal material = 5 Liquid crystal layer: 6 Polarizing film = 7A, 7B Polarizing axis of back polarizing film: a Polarizing axis of B section surface polarizing film :b Polarization axis of part C surface polarizing film 20th Figure 1 Figure 2

Claims (5)

[Claims] (1) In a liquid crystal display device in which a nematic liquid crystal layer is sandwiched between substrates provided with electrodes and a light-shielding film is provided in areas other than those corresponding to the display pattern, the polarization axes of a pair of polarizing films on both sides of the liquid crystal cell are set by voltage. A first part is arranged so that light passes through the non-applied part, and a voltage higher than the voltage that excites the nematic liquid crystal is applied to the electrode of the display pattern part other than the desired display pattern; A liquid crystal display device comprising: a second portion having a light shielding degree lower than that of the voltage application portion of the first portion. (2) The second part is arranged so that the polarization axes of the pair of polarizing films are transmitted through the voltage application part, and a voltage higher than that which excites the nematic liquid crystal is applied to the electrode of the desired display pattern part. A liquid crystal display device according to claim 1. (3) The liquid crystal display device according to claim 1, wherein the polarizing film disposed in the second portion is a color polarizing film, and only light of a specific color is transmitted through the voltage applied portion. (4) The liquid crystal display device according to claim 1, wherein illumination means is provided behind the polarizing film on the back side. (5) The liquid crystal display device according to claim 1, which uses a liquid crystal obtained by adding a dichroic dye to a nematic liquid crystal.