JPH1049082A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device in which the display thereof does not become dark and it can be clearly observed even when it is observed by wearing polarizing spectacles. SOLUTION: The polarizing plate 10 of the display side of the liquid crystal display device 1 is arranged so that more vertical polarizing components are included in the polarization direction of display light 3 emitted from the display screen of the display device 1. Since transmitted light 4 is not cut much by the polarizing lens (whose polarization direction is almost vertical) of the polarizing spectacles 2 even when the display device 1 arranged in such a way is observed by wearing the spectacles 2, visibility is not lowered. It is preferable that the deviated angle θ of a polarizing filter 10 in the polarization direction from in the vertical direction is set to be within about ±33 deg..

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 liquid crystal display device which can be clearly observed even when polarized glasses are worn.

[0002]

2. Description of the Related Art In the current monochrome and color liquid crystal display devices, the polarization direction of display light emitted from a display screen is not particularly defined in both the transmissive display system and the reflective display system, and it depends on the manufacturer and individual products. Although it varies, the polarization direction of the display light on the display screen is mostly horizontal, and rarely occurs in the horizontal direction in a color liquid crystal display device, for reasons such as widening the viewing angle to the left and right. About 45 °
Some have polarization directions of:

FIG. 3 shows a structure of a typical TFT color liquid crystal display panel. Display light reaching an observer is linearly polarized light. That is, in the sectional view of FIG.
The FT color liquid crystal display panel 20 includes an RG corresponding to each pixel on the backlight side of the color filter side transparent substrate 21.
A color filter layer 23 having a black matrix BM provided between the B color filters, an overcoat 24 for flattening the color filter layer 23, a counter common electrode 25 made of ITO, and an alignment layer 26 made of polyimide are provided in this order. A TFT provided for each electrode made of ITO on the color filter side of the TFT-side transparent substrate 22;
Electrode 27 having an alignment layer 28 made of polyimide
Are provided in order, and a liquid crystal layer 29 such as twisted nematic is sandwiched between the two substrates 21 and 22 to be sealed.
2, a polarizing plate 30 is attached to the backlight side via an adhesive layer 31, and another polarizing plate 32 is attached to the viewer side of the color filter-side transparent substrate 21 via an adhesive layer 33. When no voltage is applied to the liquid crystal layer 29, the light from the backlight 40 becomes linearly polarized light by the polarizing plate 30, and the light whose polarization plane is rotated by the liquid crystal layer 29 is blocked (or passed) by the polarizing plate 32. When a voltage is applied to the liquid crystal layer 29, the light from the backlight 40 becomes linearly polarized light by the polarizing plate 30, and the light that has passed through the liquid crystal layer 29 without rotating the polarization plane can pass through the polarizing plate 32 (or , The directions of the polarization planes of the polarizing plates 30 and 32 are set. Therefore, the polarizing plate 32
The light passing through and reaching the observer is linearly polarized light.

The liquid crystal panel 20 shown in FIG. 3 is a TFT type active matrix liquid crystal display.
Not limited to this method, the MIM method, the STN method,
In the simple matrix method of the TN method and the reflection display method, the role of the pair of polarizing plates 30 and 32 is the same, and the light passing through the polarizing plate 32 on the observation side and reaching the eyes of the observer is It is linearly polarized light. In the case of the reflective display method,
Using ambient light instead of the backlight 40, the polarizing plate 32
A reflection layer is provided on the exit side of the device, and light passing through the polarizing plate 32 is directed in the opposite direction by the reflection layer.
, And the polarization direction of the display light coincides with the direction of the polarization plane of the polarizing plate 30.

As described above, in the current liquid crystal display device, the direction of polarization of the display light, that is, the direction of the polarization plane of the polarizing plate on the emission side of the display light is mostly set to be substantially horizontal. ing.

[0006]

However, such devices are used outdoors or under strong light, such as display devices for automobiles, navigation devices, display devices for aircraft cockpits, mobile radios, mobile phones, fish finder, and watches. When the current liquid crystal display device as described above is used as the display unit, when such a liquid crystal display device is viewed through polarized glasses which are often used in such an environment, as shown in FIG. The polarized light transmission characteristics of the device 1 and the polarized glasses 2 adversely affect each other, so that the display is dark and difficult to see, and the visibility is greatly deteriorated.

That is, the polarizing direction of the polarizing lens of the polarizing glasses 2 is substantially vertical. This is a polarization direction set in order to prevent glare due to reflection on the water surface, since reflected light from the water surface has more S-polarized light components than P-polarized light.

[0008] This point will be explained a little more. Among the polarization components of the light reflected on the object surface, the plane containing the incident light, the reflected light, and the normal of the object surface at the reflection position is called an entrance plane, and the component polarized parallel to this entrance plane is P-polarized light. The component polarized perpendicular to the plane of incidence is called S-polarized light. FIG. 5 shows an example of a medium (glass) having a refractive index of 1 (air) to a refractive index of 1.52 as an example.
FIG. 4 is a graph showing the amplitude reflectance when light is incident on the P-polarized light and the S-polarized light. The reflectance of the S-polarized light increases as the incident angle increases. On the other hand, when the incident angle of the P-polarized light increases, the reflectance becomes zero at an intermediate angle (this incident angle is changed to the Brewster angle (Brewer angle)).
say ster's angle) θ _B. ), The reflectance also increases as the angle of incidence further increases.

As described above, when light enters a water surface or the like having a large refractive index from air having a small refractive index, the P-polarized light component is hardly reflected near the Brewster angle. Therefore, when the transmitted polarized light direction is set to be substantially perpendicular to the polarizing lens so as to cut the S-polarized light from the water surface by the polarizing glasses 2, glare due to reflection on the water surface can be prevented, and the underwater state can be prevented. You can also see. FIG. 6 shows this state. In the figure, 2 is polarized glasses, 5 is incident light, 6 is a water surface, 7 is reflected light, 8 is light that has passed through the polarized glasses 2, and 9 is an underwater observation target. As is clear from this figure, the incident light 5 of natural light is reflected by the water surface 6 and reflected light 7
Then, for the above reason, the P-polarized light component is reduced and almost becomes S-polarized light. Therefore, polarized glasses 2 worn by the observer
Assuming that the polarization direction (the direction of the transmitting polarization plane) is substantially vertical, the reflected light 7 is almost cut off, and the P-polarized light component from the observation target 9 in water passes through the polarizing glasses 2, so that the However, the observation target 9 underwater can be seen.

Returning to FIG. 4, if the polarization direction of the polarizing plate on the observation side of the liquid crystal display device 1 of the display unit used outdoors or under strong light is substantially horizontal as described above, The polarization plane of the display light 3 emitted from the device 1 is substantially horizontal. On the other hand, as described above, the polarization direction of the polarizing lens of the polarizing glasses 2 is substantially perpendicular. Therefore, the display light 3 polarized in a substantially horizontal direction is almost blocked by the polarizing glasses 2 and only a very small amount of the light 4 passes through the polarizing glasses 2, so that the contrast is lowered and the display is dark and difficult to see. Visibility becomes worse.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems of the prior art, and has as its object to provide a liquid crystal display device in which a display can be clearly observed without darkening even when observation is performed with polarizing glasses. It is to provide.

[0012]

According to a liquid crystal display device of the present invention which achieves the above object, in a liquid crystal display device provided with a polarizing plate at least on an observation side, the polarization direction of display light emitted from a display screen is substantially perpendicular. The polarization direction of the polarizing plate on the observation side is set so that

In this case, the polarization direction of the polarizing plate on the observation side is
It is desirable that the angle is set within ± 33 ° with respect to the vertical direction.

In the present invention, by setting the polarization direction of the polarizing plate on the observation side so that the polarization direction of the display light emitted from the display screen is substantially vertical, even if the observer wears polarized glasses, This prevents a decrease in the brightness of the displayed image, maintains practical visibility, prevents danger due to deterioration of display, and contributes to work safety.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The principle and embodiments of the liquid crystal display device of the present invention will be described below. When the polarization direction of the display light emitted from the display screen of the liquid crystal display device is set so as to increase the horizontal component as shown in FIG. 4, the polarization of the polarizing glasses 2 in the normal use state of the observer Since the horizontal polarization component is blocked by the lens (the polarization direction is substantially vertical), the contrast of the display decreases,
In the present invention, as shown in FIG.
The polarizing filter 10 on the display side of the liquid crystal display device 1 (in the case of the configuration as shown in FIG. 3, the polarization direction of the display light 3 emitted from the display screen of the liquid crystal display device 1 includes many vertical polarization components). When the liquid crystal display device 1 having such an arrangement is observed with the polarizing glasses 2 on, the transmitted light 4 is transmitted through the polarizing lens of the polarizing glasses 2 (the polarization direction is substantially the same). (Vertical direction)
This utilizes the effect that the visibility does not decrease.

That is, in FIG. 2, the polarizing direction of the polarizing lens of the polarizing glasses 2 worn by the observer is set to the vertical direction as usual, and the polarizing direction of the polarizing filter 10 on the display side of the liquid crystal display device 1 is changed from the vertical direction. The screen brightness is represented by c, as shown by the relative brightness change of the screen when the angle is θ.
os ² θ. This change in brightness is the maximum value of 70
%, It has been found that a liquid crystal display device that can withstand practical use is obtained. From FIG. 2, it can be seen that the deviation angle θ of the polarization direction of the polarization filter 10 from the vertical direction is within ± 33 ° to provide a liquid crystal display device that can endure such practical use. In addition, when the decrease in brightness is less than 50%, the deviation angle θ of the polarization direction of the polarization filter 10 from the vertical direction needs to be within ± 45 °.

Next, specifically, a TFT as shown in FIG.
In the color liquid crystal display panel, by adjusting the rubbing direction of the alignment layers 26 and 28 made of polyimide,
The polarization direction of the polarizing plate 32 is set to be inclined at 6 ° from the upper right to the lower left with respect to a vertical line in the display surface (θ = + 6 °).
The polarizing plate 32 was mounted.

Since the display light emitted from the screen of the TFT color liquid crystal display panel contains a large amount of vertical polarization components, even if the liquid crystal display panel is observed with polarized glasses, the visibility hardly decreases.

When this display device is used for a navigation system mounted on an automobile, there were some models which could not be visually recognized at all by using polarized glasses, but there was no practical problem in the embodiment of the present invention.

Although the liquid crystal display device of the present invention has been described based on the embodiments, the present invention is not limited to these embodiments, and various modifications are possible.

[0021]

As is apparent from the above description, according to the liquid crystal display device of the present invention, even a viewer wearing polarized glasses can prevent a decrease in brightness of a displayed image and maintain practical visibility. However, there is a remarkable effect of preventing danger due to deterioration of display and contributing to work safety.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the configuration and operation of a liquid crystal display device according to the present invention.

FIG. 2 is a diagram illustrating a change in relative brightness of a screen with respect to a change in an angle of a polarization direction of a polarization filter on a display side of a liquid crystal display device.

FIG. 3 is a cross-sectional view illustrating a configuration of a liquid crystal panel.

FIG. 4 is a diagram for explaining a problem of a conventional liquid crystal display device.

FIG. 5 is a diagram illustrating the amplitude reflectance of P-polarized light and S-polarized light at an interface.

FIG. 6 is a diagram for explaining the principle and operation of polarized glasses.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display device 2 ... Polarized glasses 3 ... Display light 4 ... Transmitted light 5 ... Incident light 6 ... Water surface 7 ... Reflected light 8 ... Transmitted light 9 ... Observation target 10 ... Polarizing filter (polarizing plate) 20 ... TFT color liquid crystal display Panel 21 ... Transparent substrate on the color filter side 22 ... Transparent substrate on the TFT side 23 ... Color filter layer 24 ... Overcoat 25 ... Common electrode 26 ... Alignment layer 27 ... Pixel electrode 28 ... Alignment layer 29 ... Liquid crystal layer 30 ... Backlight side polarization Plate 31 ... Adhesive layer 32 ... Observer side polarizing plate 33 ... Adhesive layer 40 ... Backlight

Claims (2)

[Claims] In a liquid crystal display device provided with a polarizing plate at least on a viewing side, a polarizing direction of a polarizing plate on a viewing side is set so that a polarizing direction of display light emitted from a display screen is substantially vertical. A liquid crystal display device. 2. The liquid crystal display device according to claim 1, wherein a polarization direction of the observation-side polarizing plate is set within ± 33 ° with respect to a vertical direction.