JPH02210326A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To decrease external light reflecting on the surface of a device and to improve the visibility of the display pattern by arranging a polarizing plate so as to be inclined with respect to a liquid crystal cell, and providing a light shielding plate preventing the injection of the external light proceeding toward a visual inspector after it reflects on the surface of the polarizing plate. CONSTITUTION:The polarizing plate 2 is arranged so as to be inclined with respect to the surface of the liquid crystal cell 1, and the light shielding plate is provided around the polarizing plate 2 to prevent the injection of the external light proceeding toward the visual inspector 7 after it reflects on the surface of the polarizing plate 2. Therefore, the reflecting light A on the surface of the polarizing plate 2 proceeds in the direction of the light shielding plate 4, and it is not made incident on the eyes of the visual inspector. The reflecting light B, which passed through the polarizing plate 2 and was reflected on the surface of the liquid crystal cell 1, passes through the polarizing plate 2 again and is made incident on the eyes of the visual inspector, but the incident light amount is very little because it reciprocatingly twice passes the polarizing plate 2 low in transmitting rate. The external light which proceeds toward the visual inspector after it reflects on the surface of the polarizing plate 2 is completely shielded by the light shielding plate 4. Thus, the reflecting light which made incident on the eyes of the visual inspector 7 is significantly decreased, and therefore, the visibility of the display pattern is largely improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal display device used as a display device for automobile instruments, display panels, and the like.

[Background Art] With the increasing use of electronics in automobiles, display systems for automobile instruments and the like are becoming increasingly electronic, and display devices using liquid crystals are in particular use.

The basic configuration of such a liquid crystal display device is generally a liquid crystal cell in which liquid crystal is sealed between a pair of transparent glass substrates, and a polarizing plate arranged parallel to the liquid crystal cell at least on the viewer's side. (For example, JP-A-56-16111, JP-A-57-197589, etc.). By applying a voltage to the liquid crystal, the molecular arrangement of the liquid crystal is changed and the light transmittance is changed to display a predetermined pattern such as letters and numbers.

[Problem M to be Solved by the Invention] By the way, a liquid crystal display device is a light-receiving type display in which the liquid crystal itself has no ability to emit light. However, liquid crystal display devices have a high surface reflectance, and when strong external light enters the device surface from behind or above the viewer, the reflected light enters the viewer's eyes, making it difficult to see the display pattern and reducing visibility. There's a problem.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to reduce the reflection of external light on the surface of a liquid crystal display device, which obstructs the visibility of display patterns on a liquid crystal display device, and to make the display easier to see.

[Means for Solving the Problems] The configuration of the present invention for solving the above problems is shown in FIG. 1. A liquid crystal cell 1 in which liquid crystal is sealed between a pair of transparent substrates,
In a liquid crystal display device that displays a pattern by disposing a polarizing plate 2 at least on the viewer 7 side and changing the molecular arrangement of the liquid crystal by applying a voltage, the polarizing plate 2 is tilted with respect to the surface of the liquid crystal cell 1. A light shielding plate 4 is provided around the polarizing plate 2 to prevent external light from entering the viewer 7 after being reflected on the surface of the polarizing plate 2.

[Function] In the above configuration, since the polarizing plate 2 is arranged at an angle with respect to the liquid crystal cell 1, the reflected light A (FIG. 2) on the surface of the polarizing plate 2 travels in the direction of the light shielding plate 4, and is visible to the viewer 7. It doesn't get noticed. The reflected light B that passes through the polarizing plate 2 and is reflected on the surface of the liquid crystal cell 1 passes through the polarizing plate 2 again and enters the eyes of the viewer 7.
Since the light passes through the polarizing plate 2, which has a low transmittance, twice in a round trip, the light level becomes extremely small. In addition, the light shielding plate 4 completely blocks external light that is directed toward the viewer after being reflected on the surface of the polarizing plate 2, so the amount of reflected light that enters the eyes of the viewer 7 is significantly reduced, and the visibility of the display pattern is improved. Greatly improved.

[Example code] FIG. 1 shows an embodiment of a liquid crystal display device of the present invention.

In the figure, reference numeral 11 denotes a device main body having an opening 12 on the front side, and a TN (twisted nematic) liquid crystal cell 1 is arranged and fixed within the opening 12. The TN liquid crystal cell 1 has a known configuration, and the liquid crystal molecules sealed between a pair of transparent glass substrates have their alignment direction twisted by 90 degrees between the transparent glass substrates, and have the property of twisting the light passing through the TN liquid crystal cell 1 by 90 degrees. has. Transparent electrodes are arranged between the glass substrate and the liquid crystal according to the display pattern.

A front polarizing plate 2 is disposed on the front side of the liquid crystal cell 1, that is, on the viewer 7 side, so as to be inclined upward with respect to the liquid crystal cell 1. A transparent cover 6 covers the surface of the front polarizing plate 2, and the transparent cover 6 is supported around the inner wall of the opening 12.

Further, on the back side of the liquid crystal cell 1, a rear polarizing plate 3 is assembled parallel to the liquid crystal cell 1, and further on the back side thereof.

A backlight 5 is arranged parallel to the liquid crystal cell 1 on the surface.

The front polarizing plate 2 and the rear polarizing plate 3 are arranged so that their absorption axes are parallel to each other, and when no voltage is applied, the rear polarizing plate 3
The linearly polarized light that has passed through is rotated by 90 degrees by the TN liquid crystal cell 1 and cannot pass through the front polarizing plate 2. When a voltage is applied, the twisting of the liquid crystal molecules disappears, and the light from the back illumination 5 passes through the front polarizing plate 2 to produce arbitrary characters,
It is visually recognized as a pattern of numbers, etc.

The device main body 11 has the upper edge of the opening 12 projected forward to serve as a light shielding plate 4. Here, when viewing the display from the position of the viewer 7, the transparent cover 6 and the front polarizing plate 2 are arranged so that only the lower surface of the light shielding plate 4 appears to be reflected on the surfaces of the transparent cover 6 and the front polarizing plate 2. Set the position, block external light entering from the top of the transparent cover 6,
The reflected light on the surfaces of the front polarizing plate 2 and the transparent cover 6 of external light coming from behind the viewer 7 is prevented from entering the eyes of the viewer 7. Further, in order to suppress re-reflection on the lower surface of the light shielding plate 4, it is desirable to use a dark-colored material for the lower surface of the light shielding plate 4.

Next, the effects of the liquid crystal display device of the present invention will be explained with reference to FIG.

Reflection of light coming from behind the viewer 7 on the surface of the display device includes reflected light A on the surface of the front polarizing plate 2, reflected light B on the entire system of the liquid crystal cell 1, the rear polarizing plate 3, and the back illumination 5, The reflected light C on the surface of the transparent cover 6 can be considered separately. In the conventional configuration (Fig. 3) in which the front polarizing plate 2 is provided parallel to the liquid crystal cell 1, both the reflected light A and the reflected light B enter the eyes of the viewer 7 and significantly impede the visibility of the display. In the configuration of the invention (FIG. 2), since the front polarizing plate 2 is inclined, the reflected light A on the surface of the front polarizing plate 2 travels in the direction of the light shielding plate 4, and only the reflected light B reaches the eyes of the viewer 7. to go into. Here, the reflected light B passes through the front polarizing plate 2 twice before entering the eyes of the viewer 7, and since the polarizing plate has a low light transmittance due to its nature, compared to the reflected light A. The light amount level becomes sufficiently small. Therefore, by removing reflected light A, reflection in the entire display device can be reduced by a considerable amount.

In order to confirm the effects of the present invention, a light source 8 was installed in front of the display device as shown in FIG. 4, and the reflected light at the viewing position was measured using a luminance meter 9 to determine the reflectance. For comparison, a similar test was also conducted on a display device with a conventional configuration (FIG. 5).

The polarizing plate 2.3 used has a natural light transmittance of 41°7%,
The reflectance is 4.15%, and the reflectance of the entire system including the TN liquid crystal cell 1, rear polarizing plate 3, and backlight 5 is 6.15%.
It was 33%. The polarizing plates 2.3 were placed with their light absorption axes parallel to each other, and the measurement was performed with no voltage applied to the liquid crystal cell 1, that is, with black display. Note that a transparent cover and light shielding plate were not used during the measurement.

As a result of the measurement, a reflectance of 5.65% was obtained with the conventional configuration, and a reflectance of 1.68% with the configuration of the present invention.By providing the front polarizing plate 2 at an angle, the reflectance was lower than that of the conventional configuration. Approximately 3
It was found that it could be reduced to 0%.

FIG. 6 shows a second embodiment of the invention. In this embodiment, the front polarizing plate 2 is tilted downward, and the light shielding plate 4 is provided at the lower edge of the opening 12 of the main body 11 of the apparatus. With this configuration, there is no space above the device,
This is effective when it is difficult to attach the light shielding plate 4.

FIG. 7 shows a third embodiment of the invention. In this embodiment, the front polarizing plate 2 and the transparent cover 6 have a concavely curved shape when viewed from the viewer side.

With such a configuration, the length of the light shielding plate 4 can be shortened, and the depth of the display device can be reduced, which is effective when installation space is limited.

FIG. 8 shows a fourth embodiment of the present invention. In this embodiment, the polarizing plate 10 is provided in a region of the viewer 7f, such as a rear window, where external light enters where light reflected from the surface of the liquid crystal cell 1 enters the viewer's 7 eyes. The other configurations are the same as in the first embodiment.

At this time, the polarizing plate 10 is arranged so that its light absorption axis is perpendicular to the front polarizing plate 2. Therefore, most of the external light that passes through the polarizing plate 10 and enters the display device passes through the front polarizing plate 2. Can not do it. As a result, the reflected light B directed toward the viewer 7 can be further reduced, making it possible to almost completely suppress reflection in the display device as a whole.

In the above embodiments, the front polarizing plate was provided to be inclined upward or downward with respect to the liquid crystal cell, but the direction of inclination is not limited to this. May be installed.

In addition, as a method for fixing the front polarizing plate, in addition to attaching or fixing the front polarizing plate to a transparent cover, a structure in which the periphery or a part of the front polarizing plate is directly supported on the device may also be used. In this case, a transparent cover is not necessarily required for the configuration.

The light absorption axes of the front polarizing plate and the rear polarizing plate may form any angle, and do not necessarily need to be parallel.

Furthermore, the liquid crystal cell is not limited to a TN liquid crystal cell, but can be applied to any type of liquid crystal cell, such as an ECB liquid crystal cell or a DTN liquid crystal cell, as long as it has a configuration in which a polarizing plate is disposed at least on the viewer side.

Note that the light shielding plate may be provided at least in part around the polarizing plate, and does not necessarily need to be provided all around the polarizing plate.

[Effects of the Invention] As described above, according to the present invention, a polarizing plate is arranged to be inclined with respect to a liquid crystal cell, and a light shielding plate is provided that prevents external light from entering toward the viewer after being reflected on the surface of the polarizing plate. This feature significantly reduces the reflection of external light on the device surface.
The visibility of the display pattern can be greatly improved.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a liquid crystal display device showing an embodiment of the present invention, FIGS. 2 and 3 are views showing the state of reflection of external light in the present invention and a conventional liquid crystal display device, respectively. FIG. 5 is a diagram for explaining a test method in an embodiment of the present invention, and FIGS. 6 to 8 are cross-sectional views of liquid crystal display devices showing second to fourth embodiments of the present invention. 1...Liquid crystal cell 2...Front polarizing plate (polarizing plate) 4...Shading plate 7...Viewer diagram Figure 5: Pack illumination

Claims (1)

[Claims] In a liquid crystal display device in which a polarizing plate is disposed at least on the viewer side of a liquid crystal cell in which liquid crystal is sealed between a pair of transparent substrates, and a pattern is displayed by changing the molecular arrangement of the liquid crystal by applying a voltage, the polarizing plate is A liquid crystal display, characterized in that the plates are arranged to be inclined with respect to the surface of the liquid crystal cell, and a light-shielding plate is provided around the polarizing plate to prevent external light from entering the viewer after being reflected on the surface of the polarizing plate. Display device.