JP3156748B2 - Liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a so-called black face type display device, and more particularly to a liquid crystal display device using a liquid crystal element as a display element.

[0002]

2. Description of the Related Art Conventionally, various display devices using liquid crystal elements have been proposed, for example, disclosed in Japanese Utility Model Publication No. 6-26946. The liquid crystal element is a light receiving type display element that cannot emit light by itself, and in the display device disclosed in the above publication, a light source is provided behind the liquid crystal element, and the liquid crystal element is illuminated from behind, so that the liquid crystal element can be viewed well. I am trying to gain sex. Further, by covering the front side of the liquid crystal element with a transparent cover, the liquid crystal element is protected and dust is prevented from adhering to the surface of the liquid crystal element.

On the other hand, for example, Japanese Patent Application Laid-Open No. 6-221878 discloses a so-called black face type display device in which the front surface of the display device is visually recognized as black when a power switch is turned off. Such a display device is a display device using a pointer-type instrument.By covering the front side of the pointer-type instrument with a dark transparent cover having a low transmittance, the front surface of the display device is visually recognized as black when the power switch is off. When the power switch is turned on, the pointer-type instrument is visually recognized by turning on the light source.

[0004]

However, it has been difficult to use a liquid crystal element as a display element of a black face type display device. That is, as shown in FIG. 5, for example, when the transmittance of the dark transparent cover 1 is 20%, the external light A such as sunlight passes through the dark transparent cover 1 and the liquid crystal element 2
The reflected light B reflected on the surface of the liquid crystal element 2 passes through the dark transparent cover 1 again, so that the reflected light B reaching the observer has a luminance of 4%. . Therefore, as the transmittance of the dark transparent cover 1 is lower, the liquid crystal element 2 behind the dark transparent cover 1 becomes less visible.
However, as shown in FIG. 6, on the other hand, the luminance of the display light D emitted from the liquid crystal element 2 upon receiving the illumination light C from the light source 3 and reaching the observer also becomes 20%, and the observer has sufficient light. There is a problem that the display light D cannot be visually recognized at a high luminance. To solve such a problem,
The brightness of the light source 3 may be increased, but a new problem arises in that the high brightness light source 3 generates a large amount of heat and consumes a large amount of power.

The present invention has been made in view of the above-mentioned problems, and provides a black face type liquid crystal display device in which display light can be visually recognized with sufficient luminance, and a liquid crystal element is hardly recognized even when external light enters. Is what you do.

[0006]

According to the present invention, there is provided a liquid crystal element having a liquid crystal cell and a polarizing member disposed on the front side of the liquid crystal cell, and a light source for illuminating the liquid crystal element from behind. a transparent cover for protecting a disposed in front side of the liquid crystal element and the liquid crystal element, the polarization of the polarization member
Has a polarization axis substantially coincident with the optical axis and is bonded to the transparent cover
And a dark colored polarizing member .

In the present invention, the polarization axis of the dark-colored polarizing member is substantially perpendicular.

[0008]

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS By providing a transparent polarizing member having a polarizing axis substantially coincident with that of a polarizing member disposed on the front side of a liquid crystal element on a transparent cover, even if external light is incident on the transparent cover, a dark polarizing member is provided. The liquid crystal element is difficult to see, and the display light of the liquid crystal element can be transmitted efficiently.

If the polarization axis of the dark-colored polarizing member is set to be substantially vertical, the S-polarized light component (horizontal component of the reflected light) of the reflected light reflected on the surface of the liquid crystal element is blocked even when external light enters. And the liquid crystal element behind the transparent cover becomes less visible.

[0011]

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. The same parts as those in the conventional example will be described with the same reference numerals.

Reference numeral 2 denotes a liquid crystal element, which includes a liquid crystal cell 4, an interference cell 5 disposed in front of the liquid crystal cell 4, and a thin-film sheet-shaped polarizing plate 6 serving as a polarizing member disposed in front of the interference cell 5. And a polarizing plate 7 in the form of a thin film sheet, which is a polarizing member disposed behind the liquid crystal cell 4. The liquid crystal cell 4 is S
It is called TN (super twisted nematic) type,
The liquid crystal cell 4 is of a dot matrix type in which many pixels are arranged in a matrix, and can display various characters and figures. The interference cell 5 is provided in front of the liquid crystal cell 4 simply to adjust the color tone of the liquid crystal cell 4, and the interference cell 5 is not used for display. The polarization axis of the polarizing plate 6 is in the vertical direction, and the display light D emitted from the liquid crystal element 2 is polarized light having a polarization axis in the vertical direction.

Reference numeral 3 denotes a light source, which illuminates the liquid crystal element 2 from behind with illumination light C emitted from the light source 3. The light source 3 is provided with a diffusion plate 8, which can illuminate the liquid crystal element 2 substantially uniformly. Reference numeral 9 denotes a transparent cover, which is disposed in front of the liquid crystal element 2. The transparent cover 9 protects the liquid crystal element and prevents dust from adhering to the surface of the liquid crystal element 2. Reference numeral 10 denotes a thin-film sheet-shaped dark polarizing plate serving as a dark polarizing member. The dark polarizing plate 10 is bonded to the front side of the transparent cover 9. The dark polarizing plate 10 has a low transmittance, and has a transmittance of 20% for natural light (light oscillating in all directions). The polarization axis of the dark polarizing plate 11 is in the vertical direction.

As shown in FIG. 1, the illuminating light C emitted from the light source 3 is natural light, but the display light D of the liquid crystal element 2 emitted through the polarizing plate 6 of the liquid crystal element 2 is polarized vertically. The polarized light has an axis. Further, the polarization axis of the dark polarizer 10 attached to the transparent cover 9 is in the vertical direction, and the polarization axis of the display light D and the polarization axis of the dark polarizer 10 are coincident with each other, as shown in FIG. The display light D can pass through the transparent cover 9 and the dark polarizer 10 at a luminance of 45%.

As shown in FIG. 3, the external light A has a luminance of 20% when passing through the dark polarizing plate 10. The reflected light B reflected on the surface of the liquid crystal element 2 is again transmitted to the dark polarizing plate 10.
And a luminance of about 4%. Therefore, even if the external light A enters, the liquid crystal element 2 behind the transparent cover 9 is difficult to see.

As described above, according to the first embodiment, the reflected light B is visually recognized at about 4% with respect to the external light A like the black face type display device shown in the conventional example. However, the display light D is transmitted with a high efficiency of 45%, and the display light D can be transmitted at twice or more efficiency as compared with the transmittance of the display device of 20% shown in the conventional example. The user can observe the display light D with high luminance.

The polarizing axes of the polarizing plate 6 and the dark-color polarizing plate 10 need only be substantially coincident with each other, and the polarizing axis of the dark-color polarizing plate 10 may be set in a horizontal direction. The reflected light is S when the incident angle is about 20 degrees or more.
Since the polarization component (the horizontal component of the reflected light) is larger than the P polarization component (the vertical component of the reflected light), especially when the incident angle is the Brewster angle, the reflected light is only the S-polarized component, If the polarization axis of the dark color polarizing plate 10 is set to the vertical direction as in the first embodiment, the S-polarized light component of the reflected light B can be blocked, and the liquid crystal element 2 behind the transparent cover 9 becomes difficult to see.

Further, as in the comparative example shown in FIG. 4, a dark polarizing film 11 which is a dark polarizing member may be provided by being formed integrally with the transparent cover 12, but as in the above embodiment,
If the dark polarizing plate 10 is attached to the transparent cover 9 and provided,
The device can be provided at low cost.

[0020]

The present invention provides a liquid crystal element having a liquid crystal cell and a polarizing member disposed on the front side of the liquid crystal cell, a light source for illuminating the liquid crystal element from behind, and a liquid crystal element disposed on the front side of the liquid crystal element. A transparent cover that protects the liquid crystal element,
Having a polarization axis substantially coinciding with the polarization axis of the polarizing member;
A dark polarization member to be bonded to the light cover, it is also <br/> has a liquid crystal element of the rear of the transparent cover even the incident external light is difficult to see, and efficiently transmitted through the display light of the liquid crystal element Can be done.

Further, in the present invention, the polarization axis of the dark-colored polarizing member is substantially vertical, and it is possible to block S waves of reflected light which is incident on the liquid crystal element and reflected by the surface of the liquid crystal element, Further, the liquid crystal element behind the transparent cover becomes difficult to see.

[0022]

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram of display light showing the embodiment.

FIG. 3 is an explanatory diagram of external light and reflected light showing the embodiment.

FIG. 4 is a sectional view showing a comparative example.

FIG. 5 is an explanatory diagram of external light and reflected light showing a conventional example.

FIG. 6 is an explanatory diagram of display light showing a conventional example.

[Explanation of symbols]

 4 Liquid crystal cell 6 Polarizing plate (polarizing member) 9 Transparent cover 10 Dark polarizing plate (Dark polarizing member)

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-242435 (JP, A) JP-A-6-301025 (JP, A) JP-A-62-178925 (JP, A) 75912 (JP, U) Japanese Utility Model Showa 62-38622 (JP, U) Special Table 60-500923 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/1335 G02F 1 / 13 505 G09F 9/00 G02B 5/30

Claims (2)

(57) [Claims] A liquid crystal element having a liquid crystal cell and a polarizing member disposed in front of the liquid crystal cell; a light source for illuminating the liquid crystal element from behind; and the liquid crystal element disposed in front of the liquid crystal element. a transparent cover that protects the polarizing unit
The transparent cover has a polarization axis substantially coincident with the polarization axis of the material.
A liquid crystal display device comprising: a dark polarizing member to be attached . 2. The liquid crystal display device according to claim 1, wherein the polarization axis of the dark polarization member is substantially perpendicular.