JPH09211452A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a bright color picture with a high degree of whiteness by averaging incidence efficiencies of each wave length made incident on each picture element corresponding to each color of the liquid crystal display element. SOLUTION: A hologram which diffracts a parallel light beams from a light source part by wavelengths of R, G, and B and focuses them on picture elements corresponding to respective colors of liquid crystal cells 7, is formed by periodically arranging unit holograms each consisting of a set of three kinds of R, G, and B hologram cells 12R, 12G, and 12B corresponding to an individual picture element of each color, and each of the hologram cells 12R, 12G, and 12B focuses the diffracted light of a specific wavelength on a picture element of a color corresponding to one of the liquid crystal cells 7, and make the light of the other wavelengths exit to the picture elements corresponding to the other colors of the liquid crystal cells 7. Thus, either one kind of the wavelengths of R, G, and B is not so much emphasized as a conventional one, but the incident efficiencies of light of each wavelength can be averaged and a color picture having a high degree whiteness can be displayed.

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 that displays a color image.

[0002]

2. Description of the Related Art Some liquid crystal display devices illuminate the back surface of a liquid crystal display panel (liquid crystal display element) with light from a light source to display a color image. In such a liquid crystal display device, red (R), green (G), which correspond to each pixel of the liquid crystal display panel,
With a structure in which a color filter composed of three colors of blue (B) is used and color display is performed by coloring the color filter when light from the light source section is transmitted, the light from the light source section causes the liquid crystal display panel to be displayed. At the time of transmission, the light of the complementary color component is absorbed by the color filter, so that the light utilization efficiency is poor and the display becomes dark.

In order to solve such a problem, conventionally, as shown in FIG. 4, the light from the light source unit 1 is diffracted by the hologram 2 at different diffraction angles for each wavelength of R, G, and B, and the liquid crystal. A liquid crystal display device has been developed which displays a color image by condensing light on pixels corresponding to each color of the display panel 3. In this case, the light source unit 1 has a structure in which the light source 5 is arranged at the focal position of the reflector 4 formed of a paraboloid, and the light generated from the light source 5 is reflected by the reflector 4 as light parallel to the optical axis 6. There is. Liquid crystal display panel 3
Is a liquid crystal cell 7 in which liquid crystal is sealed between a pair of transparent electrode substrates, an incident side polarization plate 8 arranged on the incident side of the liquid crystal cell 7, and an emission side arranged on the emission side of the liquid crystal cell 7. It is composed of a side polarizing plate 9. The liquid crystal cell 7 has a structure in which pixels corresponding to R, G, and B are arranged in a dot matrix between a pair of electrode substrates, and a black matrix 10 is formed at a position corresponding to each pixel. ing.

By the way, the hologram 2 used in such a liquid crystal display device is one which diffracts any wavelength by one diffraction grating, and diffracts at different diffraction angles depending on the wavelength. Light is arranged so as to be incident at a predetermined angle (for example, an angle of about 60 °), and the incident light is divided into R, G, and B wavelengths as shown in FIG. The structure is such that light is emitted toward the pixel corresponding to. That is, the hologram 2 has a structure in which unit holograms corresponding to unit pixels each having three pixels corresponding to three colors of R, G, and B of the liquid crystal cell 7 as one set are periodically arranged.

Therefore, in this liquid crystal display device, when the parallel light from the light source 1 is incident on the hologram 2 at a predetermined angle, the incident light is reflected by the hologram 2 at each wavelength of R, G and B as shown in FIG. Since the light is diffracted at different diffraction angles and emitted toward the pixels corresponding to each color of the liquid crystal cell 7, color display can be performed without using a color filter.

[0006]

However, in such a liquid crystal display device, the incident light is divided into R, G, and B wavelengths by the unit hologram of the hologram 2 to form pixels corresponding to each color of the liquid crystal cell 7. Since it is a structure that collects light toward,
The condensing points S _R , S _G , and S _B of the light of each wavelength differ depending on the respective wavelengths of R, G, and B. For example, as shown in FIG. When set at the position of the G pixel, the liquid crystal cell is aligned on a straight line L ₀ parallel to the light incident on the hologram 2 through which the R wavelength and B wavelength focusing points S _R and S _B pass through the G wavelength focusing point S _G. 7 will be located at the locations corresponding to the R and B pixels. Therefore, the incident efficiency of the G wavelength light incident on the G pixel of the liquid crystal cell 7 is good, but the incident efficiency of the R wavelength and B wavelength light incident on the R pixel and the B pixel is poor as compared with the G wavelength light. Therefore, there is a problem that the color of G wavelength appears strongly, the whiteness is biased in the green direction, and the whiteness decreases.

An object of the present invention is to average the incidence efficiency of light of each wavelength incident on each pixel corresponding to each color of a liquid crystal display device so that a bright color image with high whiteness can be obtained. .

[0008]

SUMMARY OF THE INVENTION According to the present invention, collimated light from a light source is diffracted by a hologram at different diffraction angles for each wavelength of red, green and blue, and is collected in pixels corresponding to each color of a liquid crystal display element. In a liquid crystal display device that displays a color image by illuminating light, a hologram includes one set of three types of hologram cells for red wavelength, green wavelength, and blue wavelength corresponding to each color pixel of a liquid crystal display element. The unit holograms are arranged periodically, and each of the three types of hologram cells transmits light of a specific wavelength among red, green, and blue wavelengths diffracted at different diffraction angles to the pixel of the corresponding color of the liquid crystal display element. It is characterized in that it has a structure of condensing and emitting lights of other wavelengths toward the pixels of other colors of the liquid crystal display element corresponding to the respective colors.

Therefore, according to the present invention, the unit hologram of the hologram is composed of three types of hologram cells for red wavelength, green wavelength, and blue wavelength, and each hologram cell includes red, green, and blue hologram cells. Of the wavelengths, the light of a specific wavelength is focused on the pixel of the liquid crystal display element corresponding to the color of that wavelength, so that only one of the red, green, and blue wavelengths is generated as in the conventional hologram. It does not appear strongly, and the incidence efficiency of light of each wavelength incident on each pixel corresponding to each color of the liquid crystal display element can be averaged, whereby a color image with high whiteness can be displayed, and Since each hologram cell emits light having a wavelength other than the specific wavelength toward the other pixels of the liquid crystal display element corresponding to that color, the light utilization efficiency is good and a bright color image can be obtained. That.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the liquid crystal display device of the present invention will be described below with reference to FIGS.
The same parts as those of the conventional example shown in FIGS. 4 and 5 are designated by the same reference numerals, and the description thereof will be omitted. In this liquid crystal display device, collimated light from the light source unit 1 is diffracted by the hologram 11 at different diffraction angles for each wavelength of R, G, and B, and is collected in pixels corresponding to each color of the liquid crystal display panel 3 as in the conventional case. By illuminating, a color image is displayed.
The liquid crystal display panel 3 includes a liquid crystal cell 7, an incident side polarization plate 8 and an emission side polarization plate 9 as in the conventional case.
Is R between a pair of transparent electrode substrates in which liquid crystal is sealed,
Pixels corresponding to the colors G and B are arrayed and formed in a dot matrix shape, and a black matrix 10 is formed at a position corresponding to each pixel. In this case, each pixel of the liquid crystal cell 7 and the hologram 11
Is 1.1 mm, the refractive index n of the transparent electrode substrate of the liquid crystal cell 7 is 1.52, and the pixel pitch of the liquid crystal cell 7 is 83 μm in the vertical direction and 88 μm in the horizontal direction. The size of the openings of the black matrix 10 is 43 μm in the vertical direction and 54 μm in the horizontal direction.

In addition, the hologram 11 diffracts any wavelength with one diffraction grating and diffracts with a different diffraction angle for each wavelength, and the parallel light from the light source has a predetermined angle (about 60 °). The liquid crystal cell 7 has such a structure that it is incident at an angle and is diffracted to be incident on the pixels of the liquid crystal cell 7 corresponding to the respective colors of R, G and B. In other words, the hologram 11 has a unit hologram 13 in which three types of hologram cells 12R, 12G, and 12B for R wavelength, G wavelength, and B wavelength corresponding to each color pixel of the liquid crystal cell 7 are set as a cycle. The hologram cells 12R, 12G, and 12B are arranged in a regular pattern.
Of the R, G, and B wavelengths diffracted at different diffraction angles, light having a specific wavelength is focused on a pixel of a corresponding color of the liquid crystal cell 7, and light of other wavelengths is corresponding to the liquid crystal. The cell 7 has a structure of emitting light toward the other color pixels.

That is, three types of hologram cells 12
In the R wavelength hologram cell 12R among the R, 12G, and 12B, as shown in FIG. 2A, the condensing point S _R of the R wavelength light is at the substantially central position of the R color pixel of the liquid crystal cell 7. , The principal ray of R wavelength is incident on the center of the pixel of R color vertically (in the normal direction), and the condensing points S _G and S _{B of} light of _G and _B wavelengths are R wavelength. On the straight line L _R parallel to the incident light on the hologram 11 that passes through the light condensing point S _R of the light of, the position corresponding to the pixels G and B of the other color of the liquid crystal cell 7, that is, the emission side from the pixels G and B. Are set at positions separated from each other, and the principal rays of the respective wavelengths are incident on the pixels G and B at specific angles. Specifically, the hologram cell 12R for the R wavelength has a diffraction grating pitch of 7
16 nm, the R, G, and B pixels of the respective colors of the liquid crystal cell 7 are uniformly formed, and the R wavelengths of the respective wavelengths incident on the pixels of the liquid crystal cell 7 are 620 nm and G.
The wavelength of 533 nm and the wavelength of B are 448 nm, and the angle of the principal ray emitted from the hologram cell 12R is 0 ° in the normal direction of the hologram cell 12R, and the left side of this normal direction is negative, as shown in FIG. When the (−) and the right side are positive (+), the R wavelength is 0 °, the G wavelength is −4.6 °, and the B wavelength is −9.1 °.

The hologram cell 12G for G wavelength is shown in FIG.
As shown in (b), the condensing point S _G of the G-wavelength light is set substantially at the center position of the G-color pixel of the liquid crystal cell 7, and the G-wave chief ray is perpendicular to the substantially center of the R-color pixel. The light is incident in the (normal direction), and the condensing points S _R and S _{B of} the other R and B wavelengths are parallel to the incident light to the hologram 11 that passes through the condensing point S _G of the G wavelength light. On the straight line L _G , the positions corresponding to the pixels R and B of the other colors of the liquid crystal cell 7, that is, the condensing point S _R of the light of R wavelength
Is a position distant to the incident side of the pixel R, and the condensing point S _B of the light of the B wavelength is set to a position distant from the pixel B to the emitting side, and the principal ray of each wavelength is set to each pixel R, B. The structure is such that each is incident at a specific angle. Specifically, the hologram cell 12G for G wavelength has a diffraction grating pitch of 624 nm and is formed uniformly along the arrangement direction of the R, G, and B color pixels of the liquid crystal cell 7. Each wavelength incident on the pixel of each color of 7 has an R wavelength of 616
nm, the G wavelength is 540 nm, the B wavelength is 464 nm, and the angle of the principal ray emitted from the hologram cell 12G is 0 when the positive or negative is determined as shown in FIG.
The R wavelength is set to + 4.6 ° and the B wavelength is set to −4.6 °.

The hologram cell 12B for the B wavelength is shown in FIG.
As shown in (c), the condensing point S _B of the B wavelength is at the liquid crystal cell 7
Is set at approximately the center position of the B color pixel, the principal ray of the B wavelength is incident perpendicularly (normal direction) to the substantially center of the B color pixel, and the light beams of other R and G wavelengths are collected. The light points S _R and S _G correspond to the pixels R and G of each color of R and G of the liquid crystal cell 7 on a straight line parallel to the incident light on the hologram 11 that passes through the condensing point S _B of the light of B wavelength. The position is set to a position apart from the pixels R and G on the incident side, and the principal ray of each wavelength is incident on each pixel R and G at a specific angle. Specifically, the hologram cell 12B for the B wavelength has a diffraction grating pitch of 543 nm and is formed uniformly along the arrangement direction of the R, G, and B color pixels of the liquid crystal cell 7. The respective wavelengths incident on the pixels of each color of 7 are R wavelength of 600 nm, G wavelength of 536 nm,
The B wavelength is 470 nm, and the angle of the principal ray emitted from the hologram cell 12B is 0 ° for the B wavelength, + 9.1 ° for the R wavelength, and +4. It is set to be 6 °.

In such a liquid crystal display device, collimated light from the light source 1 is incident on the hologram 11 at an angle of about 60 °, and the incident light is converted into R, G, and R by the hologram 11.
When the light is diffracted at different diffraction angles for each wavelength of B and focused on the pixels corresponding to each color of the liquid crystal cell 7, the unit hologram 13 of the hologram 11 is used for R wavelength, G wavelength, and B wavelength.
Three types of hologram cells for wavelengths 12R, 12G, 12
Of B, R, G, and B, light of a specific wavelength can be condensed on each pixel of the liquid crystal cell 7 corresponding to the color of the wavelength, and light of a wavelength other than the specific wavelength can be collected. Can be made incident on other pixels of the liquid crystal cell 7 corresponding to the respective colors.

That is, the hologram cell 12 for the R wavelength is used.
As shown in FIG. 2A, the light incident on R is diffracted by the R wavelength hologram cell 12R at different diffraction angles for each wavelength of R, G, and B, and among the diffracted wavelengths, The R wavelength light is condensed on the R color pixel of the liquid crystal cell 7, and G
The light of the wavelength is condensed toward the G color pixel of the liquid crystal cell 7,
The light of the wavelength is condensed toward the B-color pixel of the liquid crystal cell 7.
At this time, the principal rays of the G wavelength and the B wavelength are incident on the pixels G and B corresponding to the respective colors at an angle, but the principal ray of the R wavelength is perpendicular to the center of the R color pixel which is the condensing point S _R thereof. Since the light is incident in the (normal direction), the light of the R wavelength can be efficiently incident.

The light incident on the hologram cell 12G for G wavelength is diffracted by the hologram cell 12G for G wavelength at different diffraction angles for R, G, and B wavelengths, as shown in FIG. 2B. Of the diffracted wavelengths, the G wavelength light is condensed on the G color pixel of the liquid crystal cell 7, the R wavelength light is condensed toward the R color pixel of the liquid crystal cell 7, and the B wavelength light is condensed. The light is condensed toward the B color pixel of the liquid crystal cell 7. At this time, R
Each principal ray of wavelength and B wavelength has a pixel R corresponding to each color,
Although it is incident on B at an angle, the principal ray of the G wavelength is incident vertically (in the normal direction) to the center of the G color pixel which is the condensing point S _G , and therefore the light of the G wavelength is efficiently emitted. It can be incident well.

The light incident on the B wavelength hologram cell 12B is diffracted by the B wavelength hologram cell 12B at different diffraction angles for each of the R, G, and B wavelengths. Of the diffracted wavelengths, the B wavelength light is focused on the B color pixel of the liquid crystal cell 7, and the R wavelength light is focused toward the R color pixel of the liquid crystal cell 7, The light is condensed toward the G color pixel of the liquid crystal cell 7. At this time, R
Each principal ray of the wavelength and the G wavelength corresponds to each pixel R corresponding to each color,
Although it is incident on G at an angle, the principal ray of the B wavelength is incident vertically (in the normal direction) to the center of the B color pixel which is the condensing point S _B thereof. It can be incident well.

As described above, in this liquid crystal display device, three types of hologram cells 12R, 12G, and 12B for the R wavelength, the G wavelength, and the B wavelength of the hologram 11 are used to make incident wavelengths of R, G, and B, respectively. Since the light of the specific wavelength can be condensed on each pixel of the liquid crystal cell 7 corresponding to the color of the wavelength, the light of each of the R, G, and B wavelengths can be obtained as in the conventional hologram 2. Of these, light of any one wavelength (for example, light of G wavelength) does not strongly appear, whiteness does not deviate in the green direction, and light of each wavelength incident on each pixel corresponding to each color of the liquid crystal cell 7. The incidence efficiency can be averaged, and a color image with high whiteness can be displayed. Moreover, the focusing point S _R of the light of the specific wavelength,
S _G and S _B are set substantially at the centers of the pixels corresponding to the respective colors of the liquid crystal cell 7, and the principal ray of a specific wavelength among the respective wavelengths is vertically incident on the respective pixels of the liquid crystal cell 7 corresponding to the respective colors. Therefore, the difference in the emission direction of the light due to the R, G, and B wavelengths is smaller than that of the conventional one, and thus the color unevenness in the viewing angle direction can be reduced. In addition, since each of the hologram cells 12R, 12G, and 12B can cause light having a wavelength other than the specific wavelength to be incident on other pixels of the liquid crystal cell 7 corresponding to that color, the light utilization efficiency is high and the brightness is high. A color image can be obtained.

In the above embodiment, it is desirable that the three types of hologram cells 12R, 12G, and 12B are set so that the diffraction efficiency is maximized at the wavelengths of the corresponding colors, but it is not always the case that the respective colors are different. The diffraction efficiency need not be maximum at the wavelength of. Further, in the above-described embodiment, the case where the color image displayed on the liquid crystal display panel 3 is directly observed has been described. However, a projection lens is arranged on the exit side of the liquid crystal display panel 3, and the projection lens is used for the liquid crystal display panel 3. It can also be applied to a liquid crystal projector that observes a displayed color image by enlarging and projecting it on a screen.

[0021]

As described above, according to the present invention, the unit hologram of the hologram is composed of three kinds of hologram cells for red wavelength, green wavelength and blue wavelength, and each hologram cell is red. , Of the wavelengths of green, blue, and light of a specific wavelength are focused on the pixels of the liquid crystal display element corresponding to the color of that wavelength, so that the wavelength of red, green, or blue is the same as in conventional holograms. Only one type of wavelength does not appear strongly, and the incidence efficiency of light of each wavelength incident on each pixel corresponding to each color of the liquid crystal display element can be averaged, thereby displaying a color image with high whiteness. In addition, since each hologram cell emits light of wavelengths other than the specific wavelength toward the other pixels of the liquid crystal display element corresponding to that color, the light utilization efficiency is good and a bright color image is obtained. Got It is possible.

[Brief description of drawings]

FIG. 1 is a schematic view showing diffraction states of specific wavelengths of R, G, and B by unit holograms of holograms in an embodiment of a liquid crystal display device of the present invention.

2A and 2B show a diffraction state by each hologram cell of the unit hologram of FIG. 1, FIG. 2A is a principle diagram showing a diffraction state by a hologram cell for R wavelength, and FIG. 2B is a diffraction diagram by a hologram cell for G wavelength. A principle diagram showing a state, (c) is a principle diagram showing a diffraction state by a hologram cell for B wavelength.

FIG. 3 is a diagram showing the positive / negative of the angle of the emission direction of light diffracted by the hologram cell of FIG.

FIG. 4 is an overall configuration diagram showing an example of a liquid crystal display device.

FIG. 5 is a diagram showing a diffraction state of light by a conventional hologram.

[Explanation of symbols]

The straight line passing through first light source unit 3 liquid crystal display panel 7 crystal cell 11 hologram 12R, 12G, 12B hologram cells 13 units hologram S _R, S _G, S _B condensing point L _R, L _G, the L _B each focusing point

Claims (3)

[Claims] 1. A color image is obtained by diffracting parallel light from a light source unit by a hologram at different diffraction angles for respective wavelengths of red, green and blue, and condensing the parallel light on pixels corresponding to respective colors of a liquid crystal display element. In the liquid crystal display device for displaying, the hologram is a unit hologram in which one set of three kinds of hologram cells for red wavelength, green wavelength and blue wavelength corresponding to each color pixel of the liquid crystal display element is periodic. The three types of hologram cells each condense light of a specific wavelength among red, green, and blue wavelengths diffracted at different diffraction angles to a pixel of a corresponding color of the liquid crystal display element, A liquid crystal display device having a structure in which light of other wavelengths is emitted toward pixels of other colors of the liquid crystal display element corresponding to the respective colors. 2. Each of the three types of hologram cells comprises:
Of the red, green, and blue wavelengths diffracted at different diffraction angles, the condensing point of the light of a specific wavelength is set at substantially the center position of the pixel of the corresponding color of the liquid crystal display element, and other than the specific wavelength. Is set at a position corresponding to a pixel of another color of the liquid crystal display element on a straight line parallel to the incident light on the hologram passing through the condensing point of the light of the specific wavelength. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is provided. 3. Each of the three types of hologram cells comprises:
Of red, green, and blue wavelengths diffracted at different diffraction angles, a principal ray of a specific wavelength is incident substantially vertically to the center of a pixel of a corresponding color of the liquid crystal display element. The liquid crystal display device according to claim 1.