JP3102815B2 - Liquid crystal display - Google Patents

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 comprising a liquid crystal panel having a polarizing plate.

[0002]

2. Description of the Related Art A liquid crystal display device comprises a liquid crystal panel in which liquid crystal is sealed in a pair of substrates, and the liquid crystal panel is usually used together with a pair of polarizing plates. The polarizing plate arranged on the light incident side of the liquid crystal panel is called a polarizer, and the polarizing plate arranged on the light emitting side of the liquid crystal panel is called an analyzer. The polarizing plate has a function of transmitting linearly polarized light along a predetermined transmission axis and blocking other linearly polarized light. Polarizers and analyzers are often arranged with their transmission axes orthogonal.
For example, when a twisted nematic liquid crystal panel is used, the polarizing plates are arranged in such an orthogonal relationship.

FIG. 5 is a diagram showing a part of a projection type display device using a twisted nematic liquid crystal panel. In order to perform color display, three liquid crystal display panels 1, 2, 3 are used, and a pair of polarizing plates 1a, 1b, 2a, 2b, 3a, 3b is provided for each of the liquid crystal display panels 1, 2, 3. Provided. Light from a light source (not shown) is transmitted and reflected by the first dichroic mirror 4 to be split into two (R component and
The G and B components) and the reflected light components (G and B components) are transmitted and reflected by the second dichroic mirror 5 and further divided into two components (G component and B component). The R component of the light transmitted through the first dichroic mirror 4 passes through the liquid crystal panel 3 from the reflection mirror 6 and passes through the second dichroic mirror 5.
The B component of the light reflected by passes through the liquid crystal panel 2, and the G component of the light transmitted through the second dichroic mirror 5 passes through the liquid crystal panel 1. In this way, the components of each color of the light transmitted through each of the liquid crystal panels 1, 2, 3 and the associated polarizing plates 1a, 1b, 2a, 2b, 3a, 3b are, for example, by a dichroic mirror 7 or a reflection mirror 8 for color synthesis. The images are synthesized and go to a screen (not shown).

In the projection type liquid crystal display device shown in FIG. 5, the dichroic mirror 4 is designed to have, for example, a characteristic P shown in FIG. In FIG. 6, the wavelength λ ₀ is a value at the boundary between the red region and the green region, and the dichroic mirror 4 transmits a wavelength component of light in the red region having a wavelength of λ ₀ or more, and emits green light having a wavelength of λ ₀ or less. And a wavelength component of light in the blue region. Incidentally, the source light contains P-polarized light and S-polarized light, and the P-polarized light with respect to the dichroic mirror 4 is arranged so as to coincide with the transmission axis of each of the polarizing plates (polarizers) 1a, 2a, and 3a. The characteristic P in FIG.
This is a characteristic with respect to polarized light, and the characteristic of S-polarized light generally deviates from the characteristic of P-polarized light as shown by a broken line. Therefore, not only the P-polarized light of the specified wavelength is incident on each of the polarizing plates (polarizers) 1a, 2a, 3a, but also the S-polarized light of a wavelength deviated from the wavelength of the P-polarized light.

[0005]

A polarizing plate (polarizer) disposed on the light incident side of the liquid crystal panel transmits specific linearly polarized light from the light source unit and blocks other linearly polarized light. For example, when a polarizing plate (polarizer) is arranged so as to transmit P-polarized light, the S-polarized light is placed on the polarizing plate (polarizer).
, The S-polarized light is absorbed in the polarizing plate (polarizer) and is thus blocked. Therefore, when both the P-polarized light and the S-polarized light enter the polarizing plate (polarizer), the P-polarized light is transmitted, but the S-polarized light is blocked.

A polarizing plate that functions as a polarizer absorbs light of a P-polarized component or an S-polarized component, which is converted into heat and the surrounding temperature rises. Therefore, there has been a problem that the characteristics of the liquid crystal panel adjacent thereto are deteriorated by the temperature and the display characteristics are deteriorated. In the case of the projection type display device shown in FIG. 5, the wavelength of the S-polarized light component to be absorbed differs for each of the polarizing plates (polarizers) 1a, 2a, 3a. The temperature state becomes different, and the display characteristics deteriorate.

An object of the present invention is to provide a liquid crystal display device provided with means for controlling incident polarization separately from the polarizing plate in order to prevent a temperature rise due to absorption of the polarizing plate serving as a polarizer.

[0008]

The liquid crystal display device according to the present invention SUMMARY OF THE INVENTION includes an optical source unit 10, the three polarizing plates 1a, 2a, 3a
And three liquid crystal panels 1, 2 and 3 disposed after the respective polarizing plates, and provided between the light source unit and the polarizing plate, and emits light from the light source unit into one of P-polarized light and S-polarized light. Polarization of
RGB light of one color and RGB light of the other polarization
And the other two colors of light of the other polarization
Dichroic mirror 4, between light source unit and polarizing plate
And one of the first dichroic mirrors
One color light of the polarized RGB light and the other polarized light,
Separated into RGB light of one polarization and one color light of the other polarization
Then, one color light of the other polarization is directed to one polarizing plate.
A second dichroic mirror 6a,
A first dichroic mirror provided between the polarizing plate
The remaining two colored lights of the other polarization from
And direct the light of each color to the remaining polarizers.
And a third dichroic mirror 5 .

[0009]

In the above configuration, the optical element 11 is configured to allow substantially only a predetermined linearly polarized light to enter the polarizing plates 1a, 2a, and 3a. The light of substantially predetermined linearly polarized light is linearly polarized light that coincides with the direction of the transmission axis of the polarizing plate 1a, 2a, 3a, and other linearly polarized light does not reach the polarizer 1a, 2a, the 3a. Therefore, the polarizing plates 1a, 2
There is no need to block other linearly polarized light as in the prior art at a and 3a, so that a temperature rise due to absorption does not occur. Therefore, the temperature rise around the liquid crystal panels 1, 2, 3 is reduced, and as a result, the display characteristics can be improved.

[0010]

DETAILED DESCRIPTION FIG. 1 is a diagram showing the principle of the present invention, FIG. 5
FIG. 4 is a diagram showing a projection display device using the same twisted nematic liquid crystal panel as that of FIG. In FIG. 1, the same members as those in FIG. 5 are denoted by the same reference numerals. In FIG. 1, 3
A pair of polarizing plates 1a, 1b, 2a, 2b, 3a, 3b are provided for each of the liquid crystal display panels 1, 2, 3, respectively. The polarizing plates 1a, 2a, 3a are polarizers for the respective liquid crystal display panels 1, 2, 3, and the polarizing plates 1b, 2
b and 3b are analyzers. The first and second dichroic mirrors 4 and 5 and the total reflection mirror 6 are arranged closer to the light source section 10 than the polarizing plates 1a, 2a and 3a. Further, a total reflection mirror 8 and a dichroic mirror 9 are arranged on the screen 13 side of the polarizing plates 1b, 2b, 3b.

Between the light source unit 10 and the first dichroic mirror 4, there is arranged an optical element 11 for causing substantially only a predetermined linearly polarized light to enter the polarizing plates 1a, 2a, 3a. In addition, a filter 12 that cuts infrared rays and ultraviolet rays is disposed between the light source unit 10 and the optical element 11. The optical element 11 converts the light of the polarization component other than the light of the polarization component passing through the polarizing plates 1a, 2a, 3a into the polarizing plate 1a.
The beam splitter has transmission and reflection characteristics that do not reach a, 2a and 3a.

FIG. 2 is a diagram showing transmission and reflection characteristics of the optical element 11. The dashed line Y indicates the characteristics of P-polarized light, and the solid line
X indicates the characteristics of S-polarized light. In the optical element 11, about 3
P-polarized light in the visible light range from 80 to 780 nm is reflected,
Other wavelength components are transmitted. Also, about 380 to 78
S-polarized light in the visible light region of 0 nm is transmitted, and other wavelength components are transmitted. When the filter 12 is provided, the reflection region of the P-polarized light and the transmission region of the S-polarized light of the optical element 11 may be wider.

Accordingly, the light that reaches the first dichroic mirror 4 from the light source unit 10 through the optical element 11 is only P-polarized light. The transmission axes of the polarizing plates 1a, 2a, and 3a are all arranged so as to transmit P-polarized light. Therefore, the P-polarized light passing through the optical element 11 is transmitted and reflected by the first dichroic mirror 4 and divided into two (R component, G and B components), and the reflected light components (G and B). The component is transmitted and reflected by the second dichroic mirror 5 and is further divided into two components (G component and B component). The R component of the light transmitted through the first dichroic mirror 4 passes from the reflection mirror 6 through the liquid crystal panel 3 to the dichroic mirrors 7 and 9 for color synthesis. The B component of the light reflected by the second dichroic mirror 5 passes through the liquid crystal panel 2 and goes to the dichroic mirrors 7 and 9 for color synthesis. The G component of the light transmitted through the second dichroic mirror 5 passes through the liquid crystal panel 1 and travels from the reflection mirror 8 to the dichroic mirror 9 for color synthesis. Thus, each of the liquid crystal panels 1, 2, 3
And associated polarizing plates 1a, 1b, 2a, 2b, 3a, 3
The components of each color of the light transmitted through b are combined by the dichroic mirrors 7 and 9 for color combination, and then an image is formed on the screen 13.

Therefore, even if the first dichroic mirror 4 is designed to have the characteristic P shown in FIG. 6, for example, the characteristic for P-polarized light is exhibited as it is, but the S-polarized light is already cut by the optical element 11. Therefore, the light does not reach the polarizing plates 1a, 2a and 3a. Therefore, although the P-polarized light of the specified wavelength enters the polarizing plates (polarizers) 1a, 2a, and 3a, the S-polarized light does not enter. Therefore, the polarizing plates 1a,
There is no need to block other linearly polarized light in 2a and 3a as in the prior art, and therefore, a temperature rise due to absorption does not occur.

[0015] FIG. 3 is a diagram showing the real施例of the present invention. Also in this embodiment, a pair of polarizers 1a, 1b, 2a, 2b, 3 are provided for three liquid crystal display panels 1, 2, 3, respectively.
a, 3b are provided. Next to the light source unit 10, the filter 1
2, and a total reflection mirror 12a is arranged instead of the optical element 11 of FIG. Then, there are first and second dichroic mirrors 4 and 5, and a third dichroic mirror 6a is provided instead of the total reflection mirror 6 of FIG.

In this embodiment, the first and third dichroic mirrors 4 and 6a respectively transmit and reflect a predetermined wavelength component of the P-polarized light, and the polarizing plate substantially includes only a predetermined linearly-polarized light. Is to be an optical element for making incident light. The first dichroic mirror 4 is designed to have a characteristic shown in FIG. That is,
For P-polarized light, about 600 corresponding to the wavelength λ ₀ in FIG.
It transmits wavelength components of light in the red region of nm or more and reflects wavelength components of light in the green and blue regions below that. Also,
For S polarized light, almost all S polarized light is transmitted. Therefore, only the P-polarized light in the green and blue regions is reflected toward the second dichroic mirror 5 and travels.
After being reflected and transmitted by the second dichroic mirror 5, these lights are transmitted through the respective polarizing plates (polarizers) 1a and 2a, and are modulated by the liquid crystal panels 1 and 2, respectively.

The third dichroic mirror 6a is similar to the one shown in FIG.
(B). In other words, for P-polarized light, it reflects the wavelength component of light in the red region of about 600 nm or more, and transmits the wavelength component of light less than that. In addition, almost all S-polarized light is transmitted with respect to S-polarized light. Therefore, only the light in the red region of the P-polarized light that is reflected by the third dichroic mirror 6a and travels therethrough is transmitted through the polarizing plate (polarizer) 3a, and undergoes light modulation by the liquid crystal panel 3. . All the S-polarized light passes through the third dichroic mirror 6a and is polarized by a polarizing plate (polarizer) 3a.
And it does not go to the liquid crystal panel 3. Therefore, the polarizing plates (polarizers) 1a, 2a, and 3a transmit the P-polarized light component according to the arrangement of the transmission axes, but the other S-polarized light components do not reach the polarizing plate. No temperature rise due to absorption of polarized light. The S-polarized light transmitted through the third dichroic mirror 6a may collide somewhere and cause a rise in temperature. However, such a rise in temperature does not occur near the liquid crystal panels 1, 2, and 3. The liquid crystal panels 1, 2, 3 are not deteriorated.

Therefore, according to the present invention, only the cooling in the vicinity of the light source unit 10 is sufficiently performed, and the cooling in the vicinity of the liquid crystal panels 1, 2, and 3 does not need to be performed as in the conventional configuration. In the embodiment, the polarizing beam splitter and the dichroic mirror are used as the optical element that allows substantially only a predetermined linearly polarized light to enter the polarizing plate. However, a glass plate or a polarizing plate may be used instead. And the transmission axis of the liquid crystal panel with respect to the polarizing plate is set perpendicular to the transmission axis).

[0019]

As described above, according to the present invention,
Since the temperature rise around the LCD panel can be suppressed,
It is possible to obtain a liquid crystal display device with high display quality while suppressing the characteristic deterioration of the liquid crystal panel.

[Brief description of the drawings]

FIG. 1 is a diagram showing a principle diagram of the present invention.

FIG. 2 is a diagram showing characteristics of the optical element of FIG.

3 is a diagram showing the real施例of the present invention.

4A and 4B are diagrams illustrating characteristics of the dichroic mirror in FIG. 3; FIG. 4A is a diagram illustrating characteristics of a first dichroic mirror; FIG. 4B is a diagram illustrating characteristics of a third dichroic mirror;

FIG. 5 is a diagram showing a conventional technique.

FIG. 6 is a diagram showing characteristics of the dichroic mirror of FIG.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshihiro Suzuki 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Limited (56) References JP-A-3-10218 (JP, A) JP-A-3-53219 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/13 505 G02F 1/1335 G03B 33/12

Claims (1)

(57) [Claims] 1. A light source unit (10), three polarizing plates (1a, 2a, 3a), three liquid crystal panels (1, 2, 3) disposed after each polarizing plate, and the light source unit Between the light source unit and the
Is the RGB light of one of the P-polarized light and the S-polarized light and the other.
One color of RGB light of one polarization and the rest of the other polarization
Dichroic mirror that separates two color lights
And (4) a first dichroic device provided between the light source unit and the polarizing plate.
RGB light of one polarization from the Ick mirror and the other
One color of polarized light is divided into RGB light of one polarization and RGB light of the other polarization.
One color of polarized light and one color of the other polarized light
A second dichroic lens that directs light to one polarizing plate
(6a), and a first dichroic device provided between the light source unit and the polarizing plate.
The remaining two colored lights of the other polarization from the
Separate each color light and separate each color light into the remaining polarization
A projection type display device comprising: a third dichroic mirror (5) directed to a plate .