JPH09138394A - Liquid crystal display device and liquid crystal projector - Google Patents

Abstract

(57) An object of the present invention is to provide a liquid crystal display device capable of color gradation display with a simple structure. In a birefringence control type liquid crystal display element in which a plurality of sub-pixels are arranged in a matrix, each pixel is composed of two adjacent sub-pixels, one sub-pixel displays a gradation, and the other sub-pixel Display color on sub-pixels. On the back side of the birefringence control type liquid crystal display element, a reflection plate 23 having a sawtooth groove formed on its surface is arranged. The reflector 23 guides the light passing through one of the two sub-pixels forming one pixel to the other. Therefore, the incident light of each pixel passes through the two sub-pixels, undergoes both the gradation display and the color display, and is emitted to the front surface side. Therefore, color gradation display is possible.

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 a liquid crystal projector capable of multi-gradation color display.

[0002]

2. Description of the Related Art As a color liquid crystal display device capable of displaying a color image, a birefringence control type, a preoic type, a color filter type and the like are known. Among these, birefringence control (ECB: electrically controlled birefringenc)
The e) type liquid crystal display element changes the molecular alignment of the liquid crystal by applying an electric field to the liquid crystal to change the birefringence effect of the liquid crystal layer, and the birefringence effect is transmitted through the pair of polarizing plates. A desired color is displayed by changing the spectral distribution of light.

In this birefringence control type liquid crystal display element, since the display color and the gradation (brightness) change simultaneously with the change of the applied voltage, it is difficult to control the same color gradation display and the same gradation multicolor display. There is a problem.

[0004]

As a method of solving these problems, a method of forming a liquid crystal display element by stacking a birefringence control type liquid crystal display element and a black and white TN liquid crystal display element in two stages is considered. That is, it is conceivable that light (coloring light) that has passed through the pixels of the birefringence control type liquid crystal display element is controlled by the black-and-white TN liquid crystal display element to enable multi-gradation display for each color.

However, the liquid crystal display device having such a structure has a problem that the structure is complicated and the cost is doubled. Further, the reflective liquid crystal projector using this liquid crystal display element also has a problem that the configuration becomes complicated.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a liquid crystal display device and a liquid crystal projector capable of good multi-gradation display of a plurality of colors with a simple structure.

[0007]

In order to achieve the above object, the invention according to claim 1 provides a liquid crystal display device,
A display pixel including a liquid crystal enclosed between a pair of substrates and including a color pixel for setting a display color according to an applied voltage and a brightness adjusting unit for adjusting the brightness of the display color of the color pixel according to the applied voltage. And a light path means for passing the light passing through the brightness adjusting means to the color pixels.

According to the liquid crystal display device having the above structure, the display color is set in the color pixel, and even if the brightness of the color pixel is not the brightness to be displayed, it is combined with the brightness corresponding to the display color of this color pixel. The brightness is set by the light brightness adjusting means for adjusting to the brightness to be displayed, and the light passing through the brightness adjusting means is passed through the color pixels to combine the brightness, so that the color to be displayed is displayed at the brightness to be displayed. It is possible to realize a good multi-gradation display of a plurality of colors. The display pixels may be displayed using only color pixels, or may be displayed using color pixels and brightness adjusting means.

According to a fifth aspect of the present invention, in a liquid crystal projector, a first substrate in which pixel electrodes are arranged in a matrix and a common electrode is arranged on a surface of the first substrate facing the pixel electrodes. A liquid crystal display device including two substrates, a liquid crystal arranged between the first and second substrates, and a polarizing plate arranged outside at least one of the first and second substrates; and the pixel electrode. Is connected to a common electrode, and a first voltage is applied between one of two pixel electrodes adjacent to each other to set a display color and the common electrode, and two adjacent pixel electrodes are connected to adjust the brightness to be displayed. Drive means for applying a second voltage set according to the brightness of the display by the first voltage between the other of the two pixel electrodes and the common electrode; a light source for irradiating the liquid crystal display element with light; The liquid crystal display of the light emitted from the light source The projected image is emitted from the liquid crystal display device by passing between one of the two adjacent pixel electrodes of the child and the common electrode and between the other of the two adjacent pixel electrodes and the common electrode to combine the hue and brightness. And an optical path means for controlling the optical path.

The light incident on the liquid crystal display element from the light source is
The liquid crystal display element is passed between one of the two adjacent pixel electrodes that set the display color and the common electrode, and between the other of the two adjacent pixel electrodes that adjust the brightness between them and the common electrode. It is possible to emit a projected image in which the hue and the luminance are combined, and it is possible to perform a good multi-gradation display of a plurality of colors.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of the present invention.
FIG. 3 is a cross-sectional view showing the configuration of the birefringence control type liquid crystal display device according to the embodiment of the present invention.

As shown in FIG. 1, the birefringence control type liquid crystal display element includes a pair of transparent substrates 11 and 12, and a liquid crystal 13 sealed between the pair of transparent substrates 11 and 12 with a sealing material SC.
A pair of polarizing plates 21 and 22 sandwiching the pair of transparent substrates 11 and 12, and arranged outside the polarizing plate 21.
A reflection plate 23 having a sawtooth groove formed on the surface thereof, and a polarizing plate 2
2 and a strip-shaped oblique light absorbing plate 24 arranged outside the light source 2.

The pair of transparent substrates 11 and 12 are made of glass, transparent resin or the like. As shown in FIG. 2, TFTs 14 and transparent pixel electrodes 15 are arranged in a matrix on the lower transparent substrate (TFT substrate) 11.

As shown in FIG. 2, the gate electrode of each TFT 14 is connected to the gate line GL arranged in the row direction, and the drain electrode is arranged in the data line D arranged in the column direction.
It is connected to L and the source electrode is connected to each pixel electrode 15.

On each TFT 14 and pixel electrode 15,
An alignment film 16 is arranged on the entire surface. The surface of the alignment film 16 has a predetermined direction (direction of 0 °) 16 shown in FIG.
Alignment treatment such as rubbing is applied to a.

On the other hand, on the upper transparent substrate (counter substrate) 12, a common electrode 17 facing each pixel electrode 15 is arranged. A common voltage is applied to the common electrode 17. An alignment film 18 is formed on the entire surface of the common electrode 17.
Is arranged. The alignment film 18 has a surface shown in FIG.
18a (direction 16 of the alignment treatment of the alignment film 16)
Orientation treatment such as rubbing is performed in a counterclockwise direction of 90 °).

The liquid crystal 13 is composed of a nematic liquid crystal or the like to which a chiral material is added, and the TFT substrate 11 to the counter substrate 12 are subjected to the alignment treatment applied to the alignment films 16 and 18.
It is oriented by twisting 90 ° toward.

As shown in FIG. 3A, the transmission axis 22a of the upper polarizing plate 22 is 1 with respect to the alignment treatment direction 16a.
It is set at 30 °. The lower polarizing plate 21 is shown in FIG.
As shown in (C), the transmission axis 21a is set to 150 ° with respect to the alignment treatment direction 16a.

The reflection plate 23 is made of a metal plate or the like, and has a groove portion having a sawtooth cross section on its surface as shown in the enlarged cross-sectional view of FIG. The groove is formed so as to extend in the direction perpendicular to the plane of the drawing, two adjacent surfaces are formed so as to contact each other at an angle of approximately 90 °, and the adjacent slopes of the groove correspond to the upper pixel electrode 15, respectively. Is formed. The reflection plate 23 receives the light 35 incident on one pixel.
The function of guiding a and 35b to one pixel adjacent to each other is fulfilled.

The oblique light absorbing plate 24 is made of a material in which carbon or the like is added to a transparent resin and has a strip-like elongated shape. The oblique light absorbing plate 24 is arranged between the respective pixels, and is arranged in the same direction as the groove of the reflecting plate 23 extends. The oblique light absorbing plate 24 absorbs light obliquely directed to the display surface, of the light incident from the polarizing plate 22 side.

FIG. 5 shows the relationship between the voltage applied to each pixel (between the pixel electrode 15 and the common electrode 17) of the liquid crystal display element having such a structure, the reflectance and the display color. As shown in the figure, this liquid crystal display device has a certain voltage value (about 2.4
In the voltage range of V) or less, the hue changes, and in the voltage range exceeding this voltage value, only the brightness changes with achromatic color.
Therefore, the color display color can be controlled by applying an arbitrary voltage of 2.4 V or less to each pixel.
Further, the luminance gradation can be controlled by applying an arbitrary voltage in the range exceeding 2.4 V to each pixel.

Therefore, in this liquid crystal display device, as shown in FIG. 4, an odd number column, that is, the 2n-1th column (n is a natural number).
Pixel (hereinafter, first sub-pixel) and an even column adjacent to one of the pixels, that is, the pixel in the second n-th column (hereinafter, second sub-pixel) form one pixel. As shown in FIG. 5, data designating a display color from colors having different reflectances is applied to the first sub-pixel. Therefore, the display color of the first sub-pixel itself is displayed with the brightness according to the display color. The second sub-pixel is supplied with the data of the gradation of the luminance to be synthesized and displayed on the first sub-pixel and the second sub-pixel by synthesizing with the luminance of the first sub-pixel according to the display color.

In order to enable such color gradation display, as shown in FIG. 2, each gate line GL is connected to the row driver 31 via the terminal portion T1. The row driver 31 supplies a gate signal (scanning signal) to each gate line GL. Among the data lines DL, the odd-numbered data lines DL are connected to the first column driver 32 via the terminal portion T2. First column driver 32
Supplies the color data indicating the color supplied from the converter 34 to the data lines DL in the odd columns.

The data lines DL in the even columns are connected to the second column driver 33 via the terminal portion T3. The second column driver 33 combines the luminance with the luminance of the first sub-pixel (2n-1th column) corresponding to the color data supplied from the first column driver 32 to the odd-numbered column (2n-1th column). Grayscale data for setting the display brightness to be displayed in the first sub-pixel (2n-1th column) and the second sub-pixel (2n-th column) is connected to the second sub-pixel (2n-th column). And to the data lines DL in even columns.

The converter 34 is provided with a conversion table 34T, and the image data supplied from outside is supplied with color data (color voltage signal) for instructing a color in order to realize a display instructed by the image data. It is converted into gradation data (brightness adjustment voltage signal) that indicates the gradation to be displayed by combining with the brightness of the color data. The converter 34 supplies the color data to the first column driver 32 and the gradation data to the second column driver 33.

FIG. 6 shows an example of the conversion table 34T. The conversion table 34T converts, for example, image data indicating "black" into 2.5V gradation data and 2.5V color data, respectively. According to the display characteristics of FIG. 5, when the applied voltage is 2.5 V, the display is almost black (dark). Therefore, black is displayed on both sub-pixels, and the combined display color is also black. Similarly, the conversion table 34T converts the image data indicating “white” into 5V gradation data and 5V color data, respectively. The conversion table 34T also converts image data indicating “dark red (red 0)” into 3V gradation data and 0.5V color data. According to the display characteristics of FIG. 5, the display is dark when the applied voltage is 3 V, and
At 5V the display is red. Therefore, the combined display color is dark red. The converter 34 D / A converts the output data of the conversion table 34T, for example, and outputs it.

As described above, the conversion table 34T shown in FIG.
Converts the color and brightness instructed by the image data into data instructing the brightness and color necessary for composite display based on the display characteristics shown in FIG. That is, the color displayed by combining the first sub-pixel and the second sub-pixel is the first
The brightness determined by the color data supplied to the sub-pixels and the brightness obtained by combining the first sub-pixel and the second sub-pixel is the brightness determined by the brightness of the color data of the first sub-pixel and the brightness of the color data. And the luminance of the second sub-pixel can be combined and obtained.

Next, the operation of the birefringence control type liquid crystal display device having the above structure will be described. The image data supplied from the outside is sent to the converter 34. The converter 34 converts the image data into
In accordance with the conversion table 34T of FIG. 6, the gradation data (luminance adjustment voltage data) for instructing the display gradation and the color data (color voltage data) for instructing the color are converted.

The converter 34 supplies the gradation data to the second column driver and the color data to the first column driver, respectively. The second column driver supplies the grayscale data to the data lines DL of the even columns, and the first column driver supplies the color data to the data lines DL of the odd columns. The gradation data and the color data are applied to the pixel electrode 15 of the corresponding row via the turned-on TFT 14 at the timing when the scanning signal (gate signal) is supplied from the row driver 31. The gradation data is applied to the liquid crystal 13 of the second sub pixel via the pixel electrodes 15 of the even columns, and the color data is applied to the liquid crystal 13 of the first sub pixel via the pixel electrodes 15 of the odd columns. It

Therefore, the first sub-pixel displays the color corresponding to the color data, and the second sub-pixel displays the gradation for setting the brightness obtained by combining with the brightness corresponding to the color data. Data is input to the first sub-pixel and the second
The gradation is set by combining the sub-pixels.

As shown in FIG. 4, the light 35a incident on the first sub-pixel from the front side has a color and a brightness corresponding to this color due to the first sub-pixel. The light emitted from the first sub-pixel is guided to the second sub-pixel by the reflecting plate 23, is subjected to the brightness adjusting action of the second sub-pixel, and is emitted to the front surface side. Further, the light 35b incident on the second sub-pixel from the front surface side is subjected to the brightness adjusting action of the second sub-pixel. The light emitted from the second sub-pixel is guided to the first sub-pixel by the reflection plate 23, and the color exhibited by the first sub-pixel and the brightness corresponding to this color and the brightness due to the brightness adjusting action of the second sub-pixel are displayed. The light is combined and emitted to the surface side.

As described above, in this liquid crystal display device, the light incident on each pixel passes through the first and second sub-pixels and is subjected to both color display and gradation display. Therefore, by controlling the color of the first sub-pixel and the brightness corresponding to this color and the brightness of the second sub-pixel in association with each other,
Color gradation display is possible. Further, since the output voltage of the second column driver 33 is a relatively low voltage, the power supply voltage of the second column driver 33 can be reduced and the power consumption of the first column driver 32 can be reduced.

(Second Embodiment) Next, a second embodiment of the reflection type liquid crystal projector using the birefringence control type liquid crystal display device of the first embodiment will be described with reference to the drawings. explain.

As shown in FIG. 7, the reflection type liquid crystal projector 41 of this embodiment has a light source 42, a first condenser lens 43, a birefringence control type liquid crystal display element 44, a mirror 45 and a second condenser lens 46. Composed of.

The light source 42 emits light toward the first condenser lens 43. The first lens 43 collimates the incident light and irradiates the birefringence control type liquid crystal display element 44. The birefringence control type liquid crystal display element 44 is arranged such that the extending direction of the groove portion of the reflection plate 23 is parallel to the incident direction of light, and the color of the incident light is controlled by the first sub-pixel. The gradation is controlled by the second sub-pixel and the light is emitted toward the mirror 45. Mirror 45
Reflects the colored light toward the second lens 46, and the second lens 46 collects the reflected light and projects it on a projection screen (not shown).

Thus, the birefringence control type liquid crystal display element 4
By setting the extending direction of the groove portion of the reflection plate 23 of No. 4 to be substantially parallel to the direction of the light emitted from the light source 42, a reflective liquid crystal projector capable of full-color display with a simple configuration can be realized.

In the above description, in order to guide the light passing through the first sub-pixel to the second sub-pixel and form the optical path for guiding the light passing through the second sub-pixel to the first sub-pixel,
Although the reflection plate 23 in which the groove having a sawtooth cross section is formed is used, any other configuration can be used as long as a similar optical path can be formed. For example, the back surface of the first sub-pixel and the back surface of the corresponding second sub-pixel are connected by an optical fiber, and the light passing through the first sub-pixel is guided to the second sub-pixel through the optical fiber, and the second sub-pixel is The passed light may be guided to the first sub-pixel through the same optical fiber.

In the above description, in order to facilitate understanding, the range of applied voltage for setting the hue and
We used a birefringence control type liquid crystal display element that has a different range of applied voltage to set the gradation by combining with the brightness generated by the voltage to set the hue. It is also possible to use a birefringence control type liquid crystal display element of a type in which the range of the applied voltage to be changed and the range of the applied voltage for changing the gradation are not divided.

Also, in the first embodiment, TF
Although the present invention is applied to the birefringence control type liquid crystal display element using T as an active element, the present invention is also applicable to the birefringence control type liquid crystal display element using MIM as an active element. Further, it is also applicable to a passive matrix type birefringence control type liquid crystal display element which does not use an active element.

Although the converter 34 has been described as a structure for converting the image data into the gradation data and the color data by using the table 34T, any other structure can be adopted. For example, the configuration of the table 34T in FIG. 6 is an example in which each pixel of the birefringence control type liquid crystal display element displays white, black, and three primary colors (red, green, blue), and the liquid crystal display element is different. When the colors can be displayed, the configuration of the table can be arbitrarily changed according to the display color.

In the first embodiment, the oblique light absorbing plate 24 is arranged on the polarizing plate 22, but it may be arranged between the counter substrate 12 and the common electrode 17, as shown in FIG. . In this case, for example, the space between the oblique light absorbing plates 24 is filled with resin or the like. Further, an oblique light absorbing plate may be arranged between the counter substrate 12 and the polarizing plate 22. In addition, the location may be changed as appropriate.

Further, in the first embodiment, in the pixels of a predetermined row, the display color of the sub-pixels in the even-numbered columns (the 2n-th column) is achromatic, and the sub-pixels in the odd-numbered columns (the 2n-1th column) are set. The display color of one pixel as a whole is determined by only the above, and the brightness of this display color and the brightness of the sub-pixels in the even columns are combined to set the brightness of the entire one pixel. However, the color data may be supplied to the sub-pixels in the even-numbered columns and the gradation data may be supplied to the sub-pixels in the odd-numbered columns. Alternatively, two adjacent sub-pixels in the same row and two columns may be regarded as one pixel to supply color data to one sub-pixel and gradation data to the other sub-pixel for display.

In the first embodiment, the first sub-pixel and the second sub-pixel are regarded as one pixel as the display pixel, and substantially a single color is displayed in both the first sub-pixel and the second sub-pixel. It is possible that the sub-pixel for which the display color is set is made to pass the light of the brightness of the brightness adjusting means and only this sub-pixel is displayed, and the sub-pixel for which the brightness is adjusted does not display the display color. Furthermore, in the first embodiment, the liquid crystal display element is a birefringence control type liquid crystal display element, but the invention is not limited to this, and a twisted nematic effect type such as TN or STN using a color filter, a guest host type, It may be a liquid crystal display element of a ferroelectric or antiferroelectric liquid crystal type.

In the reflection type liquid crystal projector 41 of the second embodiment, the mirror 45 and the second condenser lens 46 are omitted, and the light from the birefringence control type liquid crystal display element 44 is
It may be configured to directly project on the projection screen. Besides, the present invention is not limited to the above description, and various modifications and applications are possible.

[0045]

As described above, according to the present invention, it is possible to provide a liquid crystal display device and a liquid crystal projector which are capable of color display with good gradation with a simple structure.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a birefringence control type liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a plan view showing a configuration and a drive circuit of a TFT substrate of the birefringence control type liquid crystal display device according to the first embodiment.

FIG. 3A is a diagram showing a direction of a transmission axis of an upper polarizing plate. (B) is a figure which shows the orientation process direction of an orientation film. (C) is a figure which shows the direction of the transmission axis of a lower polarizing plate.

FIG. 4 is an enlarged cross-sectional view of the birefringence control type liquid crystal display element according to the first embodiment.

FIG. 5 is a diagram showing a relationship between an applied voltage, a reflectance and a display color of the birefringence control type liquid crystal display element according to the first embodiment.

FIG. 6 is a diagram showing contents of a conversion table of a converter.

FIG. 7 is a diagram showing a configuration of a reflective liquid crystal projector according to a second embodiment of the present invention.

FIG. 8 is a cross-sectional view showing a modified example of the birefringence control type liquid crystal display element according to the first embodiment.

[Explanation of symbols]

11 ... TFT substrate, 12 ... counter substrate, 13 ... liquid crystal,
14 ... TFT, 15 ... Pixel electrode, 16 ... Alignment film, 1
7 ... Common electrode, 18 ... Alignment film, 21 ... Polarizing plate, 22 ...
..Polarizing plate, 23 ... Reflecting plate, 24 ... Oblique light absorbing plate, 31 ...
.Row driver, 32 ... first column driver, 33 ... second
Column driver, 34 ... Converter, 35a, 35b ... Light,
41 ... Reflective liquid crystal projector, 42 ... Light source, 43
... First condensing lens, 44 ... Birefringence control type liquid crystal display element, 45 ... Mirror, 46 ... Second condensing lens

Claims (5)

[Claims] 1. A liquid crystal is enclosed between a pair of substrates, and comprises a color pixel for setting a display color according to an applied voltage and a brightness adjusting means for adjusting the brightness of a display color of the color pixel according to an applied voltage. A liquid crystal display device comprising: a liquid crystal display element in which the configured display pixels are arranged; and an optical path means for passing the light passing through the brightness adjusting means to the color pixels. 2. The light path means passes the light passing through one of the color pixel and the brightness adjusting means to the other of the color pixel and the brightness adjusting means, respectively, and the display pixel includes the color pixel and the brightness adjusting means. The liquid crystal display device according to claim 1, wherein the display is performed by the display of. 3. The light path means synthesizes a display color of the color pixel and a brightness corresponding to the display color with a brightness of the brightness adjusting means adjusted according to the brightness of the color pixel to obtain a predetermined value. The liquid crystal display device according to claim 1, wherein a display color of luminance is displayed on the display pixel. 4. The liquid crystal display element is a birefringence control type liquid crystal display element in which the color pixels to which switching elements are respectively connected and the luminance adjusting means are arranged adjacent to each other, and the optical path means comprises: Equipped with a saw-shaped groove,
4. The liquid crystal display device according to claim 1, wherein the two surfaces forming the groove are arranged so as to correspond to the color pixel and the brightness adjusting means of the liquid crystal display element, respectively. . 5. A first pixel electrode arranged in a matrix.
A substrate, a second substrate in which a common electrode is disposed on the surface of the first substrate facing the pixel electrode, a liquid crystal disposed between the first and second substrates, and at least one of the first and second substrates A liquid crystal display element including a polarizing plate disposed outside the pixel electrode, and between one of the two pixel electrodes and the common electrode which are connected to the pixel electrode and the common electrode and are adjacent to each other in order to set a display color. In order to adjust the brightness to be displayed by applying the first voltage to the common electrode, the second pixel is set between the other of the two adjacent pixel electrodes and the common electrode according to the brightness of the display by the first voltage. Driving means for applying a voltage, a light source for irradiating light to the liquid crystal display element, and light emitted from the light source between and adjacent to one of two adjacent pixel electrodes of the liquid crystal display element and a common electrode. It passes between the other of the two pixel electrodes and the common electrode. The hue and brightness were synthesized Te, a liquid crystal projector characterized by comprising a optical path means for emitting a projection image from the liquid crystal display device.