JPH11109332A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a screen fully bright by specifying the film thickness and the like of a coloring film in three colors different in transmitting wavelength region thereby extending an expressible color range and providing the coloring film incapable of deteriorating color balance. SOLUTION: In a colors filter composed of red, green and blue color filters 14R, 14G, 14B using a pigment dispersing agent, when the film thickness of the red filter 14R transmitting the light in the long wavelength region is defined as tR, that of the green filter 14G in the intermediate wavelength is defined as tG, and that of the blue filter 14B in the short wavelength is defined as tB, these thicknesses are set to satisfy tG<tR<tB. In addition, the film thicknesses tG, tR, tB of the color filters 14R, 14G, 14B are each set in the thickness showing nearly the maximum chroma (C*) value in the coloring light that passes through the color filter.

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 having three colored films having different transmission wavelength bands.

[0002]

2. Description of the Related Art There are two types of liquid crystal display devices: a transmissive type which displays by using light from a backlight, and a reflective type which displays by using external light such as natural light or indoor illumination light. On the other hand, the reflection type liquid crystal display element has a reflection member on the rear surface side for reflecting external light incident from the front surface and emitting the light to the front surface.

As a liquid crystal display element, a TN (twisted nematic) type in which liquid crystal molecules of the liquid crystal layer are twist-oriented at a predetermined twist angle between both substrates is often used. In the element, polarizing plates are arranged on the outer surface of the one substrate and the outer surface of the other substrate, respectively, with their transmission axes oriented in predetermined directions.

There are various types of liquid crystal display elements such as an active matrix type and a simple matrix type. For example, an active matrix type liquid crystal display element has a pair of substrates opposed to each other with a liquid crystal layer interposed therebetween. A plurality of pixel electrodes arranged in a matrix and a plurality of active elements respectively connected to these pixel electrodes are provided on the inner surface of one of the substrates, and the plurality of pixel electrodes are opposed to the plurality of pixel electrodes on the inner surface of the other substrate. A counter electrode for forming a pixel region is provided by the portion to be formed.

Further, there are a liquid crystal display element for displaying a black-and-white image and a liquid crystal display element for displaying a color image. In a liquid crystal display element for displaying a color image such as a full-color image, an inner surface of one of the substrates is used. In addition, three color films having different transmission wavelength bands from each other, for example, three color filters of red, green, and blue are provided corresponding to different pixel regions.

Each of the three color filters of red, green, and blue is formed so as to cover the entire pixel region in order to increase the amount of light transmitted through the corresponding pixel region.

[0007] The color filter is formed by using a filter material in which a pigment is dispersed, or is formed by dyeing a transparent film made of casein or the like. The thickness is, for example, about 1 to 2 μm in the case of a color filter using a pigment dispersion material.

[0008]

However, in a liquid crystal display device having a conventional color filter, light in a wavelength band corresponding to the color of the color filter in the visible light band is transmitted through the color filter and colored light. Since the light in the other wavelength band is absorbed by the color filter, the intensity of the emitted colored light is extremely weak with respect to the intensity of the incident light, so that a bright screen cannot be obtained.

This problem can be alleviated to some extent by increasing the brightness of the backlight in the case of a transmissive display element. However, in the case of a reflective display element which makes display using external light, a liquid crystal display is used. Since the light incident from the front surface of the display element passes through the color filter twice before being reflected by the reflection member on the rear surface side and exiting to the front surface, the attenuation of the light is large and the screen becomes considerably dark.

Therefore, conventionally, it has been considered that the film thickness of the red, green and blue color filters is reduced to reduce the absorption of light by the color filters, and the light transmittance is increased to make the screen brighter. However, when the thickness of the color filter is reduced in this manner, the transmittance of the red, green, and blue colored lights in the absorption wavelength band also increases, and the color balance of the light of each color deteriorates.

FIG. 8 shows a change in transmittance caused by reducing the thickness of the color filter. The film thickness of the color filter (the color filter using a pigment-dispersed material) 1.3 to 1.6 μm in some cases
), Light passes through the red, green, and blue color filters at the transmittances indicated by solid lines in the figure, respectively. However, when the thickness of the color filters is reduced, the red, green, and blue colors are reduced. The transmittances of the filters shift as indicated by broken lines in the figure, and the average transmittances of the three color filters shift from the level indicated by the solid line to the level indicated by the broken line.

[0012] The red color due to the thinning of the color filter,
As shown in the figure, the change in the transmittance of the green and blue color filters is such that the red light transmitted through the red filter has a higher transmittance for light on the short wavelength side, which is the absorption wavelength band of the red filter,
The half-width of the green light and the blue light transmitted through the green filter and the blue filter changes in a tendency to increase. As a result, the average transmittance of the three color filters becomes about 500.
The characteristic has a peak with a high transmittance near the wavelength of nm.

Therefore, a liquid crystal display device in which the thickness of the color filter is reduced has a low color purity because the transmittance in the absorption wavelength band of each of the red, green, and blue colored lights is increased, and the color of each color light is also low. Since the balance is poor and the display color by the additive color mixture of red, green and blue light is close to cyan (bluish green), good white display cannot be obtained. SUMMARY OF THE INVENTION An object of the present invention is to provide a color liquid crystal display device which can display many unclear colors, has a high transmittance, and has an excellent color balance.

[0014]

A liquid crystal display device according to the present invention comprises a plurality of first electrodes provided on one of inner surfaces of a pair of front and rear substrates opposed to each other with a liquid crystal layer interposed therebetween;
At least one second electrode provided on the other inner surface, the region facing the plurality of first electrodes forming a plurality of pixel regions, and an inner surface of one of the substrates corresponding to each of the pixel regions. 3 with different transmission wavelength bands provided
The three colored films meet the conditions of the intermediate wavelength band transmitted colored film <the long wavelength band transmitted colored film <the short wavelength band transmitted colored film, and have passed through each colored film. The color range defined by the three color coordinates defined by the color system representing the color of the colored light is set to a film thickness showing a maximum value.

According to the liquid crystal display device of the present invention, the aforementioned 3
Since the thickness of the color film is set as described above, the color range that can be expressed is expanded, and by providing the color film without deteriorating the color balance, the screen can be made sufficiently bright. it can.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the liquid crystal display device of the present invention, as described above, the thickness of the three colored films is longer than that of the intermediate wavelength band transparent colored film in the visible light band. The thickness of the film is thicker, the thickness of the short-wavelength band transmission colored film is set to be thicker than that of the long-wavelength band transmission colored film, and the color defined by the color system representing the color of the colored light transmitted through each of the colored films. By setting the film thickness that maximizes the color range surrounded by the color coordinates of the colors, the range of colors that can be expressed is expanded, and the screen is brightened sufficiently without deteriorating the color balance. It is like that. It is desirable that the color coordinates of the colored light transmitted through the colored film be defined by a CIE1976L * a * b * color system.

When the three color films are, for example, red, green, and blue color filters using a pigment dispersion material, the thickness of the red filter is 0.9 to 1.2 μm, and the thickness of the green filter is The film thickness may be set in the range of 0.8 to 1.1 μm, and the film thickness of the blue filter may be set in the range of 1.1 to 1.4 μm. The range of colors that can be expressed by the red, green, and blue colored lights transmitted through these color filters can be expanded.

Further, in the liquid crystal display device according to the present invention, the colored films of the three colors are each formed in an area smaller than the area of the pixel region, and a region of the pixel region which does not correspond to the colored film is formed of non-colored light. In this case, it is preferable that only the light transmitted through the region corresponding to the colored film among the light transmitted through the pixel region is absorbed by the colored film in the absorption wavelength band. The light transmitted as colored light and transmitted through the non-colored light emitting area is transmitted without being absorbed by the colored film and is transmitted as high-luminance non-colored light. As a result, color pixels with high luminance are displayed, so that the screen can be made brighter.

According to the present invention, a transmissive liquid crystal display element for displaying by utilizing light from a backlight is provided with a reflecting member on the rear surface side, and a reflective for displaying by utilizing external light such as natural light or indoor illumination light. Type liquid crystal display element,
Even with a reflective liquid crystal display element, the screen can be made sufficiently bright.

[0020]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a front view of a part of the liquid crystal display device, and FIG.
FIG. 2 is a sectional view taken along the line II-II in FIG. The liquid crystal display element of this embodiment is of an active matrix type using a TFT (thin film transistor) as an active element, and a pair of front and rear substrates (a transparent substrate made of glass or the like) facing each other with a liquid crystal layer 18 interposed therebetween. A plurality of transparent pixel electrodes 3 are arranged in a matrix on the inner surface of the rear substrate 2 and active elements (hereinafter, referred to as TFTs) 4 corresponding to the pixel electrodes 3 are provided. Has been established.

In FIG. 1, the electrode (R) is a pixel electrode for displaying a red pixel, the electrode (G) is a pixel electrode for displaying a green pixel, and the electrode (B) is a blue pixel. These pixel electrodes 3 are alternately arranged in a row direction (the horizontal direction of the screen) and arranged in a straight line, and display pixels of the same color in a column direction (the vertical direction of the screen). Pixel electrodes 3 are alternately shifted in the row direction by about 1.5 pitches and arranged in a zigzag manner.

The TFT 4 is formed on the rear substrate 2, a gate electrode 5, a gate insulating film 6 covering the gate electrode 5, and formed on the gate insulating film 6 so as to face the gate electrode 5. And a source electrode 8 and a drain electrode 9 formed on both sides of the i-type semiconductor film 7 via an n-type semiconductor film (not shown).

On the rear substrate 2, a gate line 10 for supplying a gate signal to the TFT 4 in each row is wired along one side of each pixel electrode row.
The gate electrodes 5 of the TFTs 4 in each row are formed integrally with a gate line 10 corresponding to the row.

The gate insulating film (transparent film) 6 of the TFT 4 is formed over substantially the entire surface of the substrate 2, and the gate line 10 is covered with the gate insulating film 6 except for its terminal. .

On the gate insulating film 6, each TFT 4 of each column is arranged along one side of each pixel electrode column.
A data line 11 for supplying a data signal is connected to the data line 11, and a drain electrode 9 of the TFT 4 in each column is connected to the data line 11 corresponding to the column.

The data lines 11 are arranged in a meandering manner along each pixel electrode column (a zigzag pixel electrode column) for displaying pixels of the same color, and are arranged vertically along the side edges of the pixel electrodes 3 in each row. The horizontal wiring section connecting the wiring sections is wired in parallel with the gate line 10 between adjacent pixel electrode rows.

In this embodiment, the data line 11 is wired on the gate insulating film 6, and the drain electrodes 9 of the TFTs 4 in each column are respectively connected to the data line 1 corresponding to the column.
1, but the data line 11 is
The TFT 4 may be covered with an insulating film and wired thereon, and may be connected to the drain electrode 9 of the TFT 4 at a contact hole provided in the insulating film.

The pixel electrode 3 is formed on the gate insulating film 6, and the pixel electrode 3 is connected to the source electrode 9 of the corresponding TFT 4 at one side edge.

Further, on the rear substrate 2, a compensation capacitance forming electrode (hereinafter, referred to as a pixel electrode 3) opposed to each pixel electrode 3 in that row with the gate insulating film 6 interposed therebetween corresponding to each pixel electrode row. 12 is provided.
The capacitance forming electrode 12, the pixel electrode 3, and the gate insulating film 6 between them constitute a compensation capacitor (storage capacitor) for compensating the fluctuation of the potential of the pixel electrode 3 during the non-selection period.
Are formed. The capacitance forming electrode 12 is formed in parallel with the gate line 10 so as to face a portion slightly inward of the pixel electrode 3 from the edge of the pixel electrode 3 opposite to the TFT connection side.

The gate line 10 and the capacitance forming electrode 12
Is formed of a metal film having a low resistance and a high light reflectance (for example, an aluminum-based alloy), and the data line 11 is also formed of a metal film having a low resistance and a high reflectance. The gate line 10 and the capacitance forming electrode 12 are connected to the pixel electrode 3 and the data line 1 formed on the gate insulating film 6.
In order to increase the withstand voltage between the first electrode and the first electrode, the surface is anodized.

On the inner surface of the rear substrate 2, that is, on the surface on which the pixel electrodes 3 and the TFTs 4 and the data lines 11 are formed, an alignment film 13 is provided over the entire region where the pixel electrodes 3 are arranged.

On the other hand, on the inner surface of the front substrate 1, red, green,
The three blue color filters 14R, 14G, 14B
Similarly to the arrangement of the pixel electrodes 3, the pixel electrodes 3 are provided alternately in the row direction and the column direction, and are provided on a transparent protective film (insulating film) 15 formed so as to cover these color filters 14R, 14G, and 14B. A transparent opposing electrode 16 in the form of a single film is provided, which opposes all of the pixel electrodes 3 and the regions opposing the pixel electrodes 3 each form a pixel region A, and an alignment film 17 is formed thereon. Have been. The protective film (insulating film) 15 is formed of the color filters 14R, 14R.
G and 14B can be omitted by appropriately selecting the material.

The front substrate 1 and the rear substrate 2 are
The peripheral portion is joined via a frame-shaped sealing material (not shown), and a liquid crystal layer 18 is provided between the two substrates 1 and 2 in a region surrounded by the sealing material.

The alignment films 13 and 17 provided on the inner surfaces of the pair of substrates 1 and 2 are each subjected to an alignment process by rubbing the film surfaces in a predetermined direction. The alignment direction of the liquid crystal molecules of the liquid crystal layer 18 in the vicinity of the respective substrates 1 and 2 is regulated by the alignment film 13 of the rear substrate 2 and the alignment film 17 of the front substrate 1. Twist angle (eg, approximately 90
°) twist orientation.

Further, polarizing plates 21 and 22 are disposed on the outer surfaces of the pair of substrates 1 and 2, respectively, and these polarizing plates 21 and 22 have their transmission axes oriented in predetermined directions. It is provided in.

The liquid crystal display device of this embodiment has a liquid crystal layer 18
When no electric field is applied to the substrate (the liquid crystal molecules are
The display is a bright display in a state where the liquid crystal layer 18 is oriented in the initial twist alignment state in which the liquid crystal molecules are most inclined with respect to the surface. This is a TN type liquid crystal display element that performs so-called normally white mode display in which the transmittance of light is lowered and the display becomes darker, for example, when the twist angle of liquid crystal molecules is approximately 90 °, Polarizing plate 2
The reference numerals 1 and 22 are provided with their transmission axes substantially orthogonal to each other.

Further, behind the rear polarizing plate 22,
A scattering reflector 23 is arranged as a reflecting member for reflecting light that has entered the liquid crystal display element from the front side and transmitted through the liquid crystal layer 18.

The red, green, and blue color filters 14R, 14 provided on the inner surface of the front substrate 1 of the liquid crystal display element.
G and 14B will be further described. Of these color filters 14R, 14G and 14B, the red filter 14R is a pixel region A where the (R) pixel electrode 3 for displaying red pixels and the counter electrode 16 face each other. Provided in
The green filter 14G is for displaying a green pixel (G).
Is provided in a pixel region A where the pixel electrode 3 and the counter electrode 16 are opposed to each other, and the blue filter 14B is provided in a pixel region A where the pixel electrode 3 and the counter electrode 16 are (B) for displaying a blue pixel. Have been.

The red, green and blue color filters 14R,
Reference numerals 14G and 14B denote color filters using a pigment dispersion material, and the red, green and blue color filters 14R and 14B.
Of the 4G and 14B, the thickness of the red filter 14R that transmits light in the long wavelength band is tR, the thickness of the green filter 14G that transmits light in the intermediate wavelength band is tG, and the blue filter that transmits light in the short wavelength band. Assuming that the thickness of 14B is tB, the thickness tR of the red filter, the thickness tG of the green filter, and the thickness tB of the blue filter are set so as to satisfy tG <tR <tB.

That is, the color of the colored light generated by passing through each of the color filters changes as shown in FIG. 4 according to the change in the film thickness of these color filters. FIG. 4 shows red, green, and blue color filters 14 when the film thicknesses tR, tG, and tB are respectively changed.
The change of chroma C * in the L * a * b * color system of the colored light transmitted through R, 14G and 14B is shown. The above-mentioned chroma C * is colored light of red, green and blue from a C light source (achromatic point of a * = 0, b * = 0) on the a * b * surface in the CIE1976L * a * b * color system. Represents the distance (chroma) to the color coordinate point. As shown in this figure, the chroma (C *) of each colored light has a maximum value with respect to a change in the film thickness of the color filter to be transmitted, and the film thicknesses of the color filters exhibiting these maximum values are mutually different. There is a relationship of tG <tR <tB, and the film thicknesses of the color filters of each color showing their maximum values are respectively red filter film thickness tR = 0.9 to 1.2 μm green filter film thickness tG = 0.8 to 1. 1 μm Blue filter film thickness tB = 1.1 to 1.4 μm.

Accordingly, these color filters 14R,
By setting the film thicknesses tR, tG, and tB of the 14G and 14B to the film thicknesses at which the chroma (C *) value of the colored light transmitted through the color filter substantially reaches a maximum, L * a
The area surrounded by the color coordinate points of the three colored lights on the a * b * plane in the * b * color system, that is, the color range can be increased.

As in the above embodiment, the red filter 14R
Film thickness tR of 0.9 to 1.2 μm, green filter 14G
Film thickness tG of 0.8 to 1.1 μm, blue filter 14B
Is set to 1.1 to 1.4 μm, the chroma (C *) of the red, green, and blue colored light transmitted through these color filters 14R, 14G, and 14B is almost maximized. That is, the color range connecting the color coordinate points of red, green, and blue can be widened, and a large number of colors can be displayed.

FIG. 5 shows the pixels of each color displayed by the colored light emitted from the filter corresponding area a of the pixel area A and the non-colored light emitted from the uncolored light emitting area b. L * a * b * of the display color due to the mixed light of the light transmitted through the region with respect to the change in the film thickness of each color filter
9 shows a change characteristic of a color range in a color system. here,
The graph shows the characteristics when the area of each color filter 14R, 14G, 14B is 80% of the area of the pixel region A.

In FIG. 5, the solid lines indicate that the thicknesses tG and tB of the two color filters 14G and 14B of green and blue are fixed at 1.5 μm, respectively, and the thickness tR of the red filter 14R.
When only the thickness tG of the green filter 14G is changed while the thickness tR and tB of the red and blue color filters 14R and 14B are fixed at 1.5 μm, respectively. The broken lines indicate the film thicknesses tR and tG of the two color filters 14R and 14G of red and green, respectively.
The characteristics are shown when the thickness is fixed at 5 μm and only the thickness tB of the blue filter 14B is changed.

As shown in the filter film thickness-color range characteristics of FIG. 5, each color filter has a red filter film thickness tR = 0.9 to 1.2 μm and a green filter film thickness tG = When the blue filter thickness tB is in the range of 0.8 to 1.1 μm and the blue filter film thickness tB is in the range of 1.1 to 1.4 μm, the color range substantially shows the maximum.

FIG. 6 shows the red, green, and blue colored light, which is the light emitted from the filter corresponding area a of the pixel area A of each color, and the non-colored light that is the light emitted from the uncolored light emitting area b. The chroma (in the L * a * b * color system) of the mixed light transmitted through the liquid crystal display element and displayed by the light emitted from the bright display area c between the matching pixel areas with respect to the change in the film thickness of each color filter. C *). here,
Area s of color filter 14R, 14G, 14B of each color
The characteristics when R, sG, and sB are all 80% of the area of the pixel region A are shown.

In FIG. 6, the solid lines indicate that the thicknesses tG and tB of the two color filters 14G and 14B of green and blue are fixed at 1.5 μm, respectively, and the thickness tR of the red filter 14R.
In the case where only the thickness is changed, the dashed line indicates that the thicknesses tR and tB of the two color filters 14R and 14B of red and blue are fixed at 1.5 μm, respectively, and the thickness t of the green filter 14G is
The characteristic when only G is changed, the broken line indicates that the film thicknesses tR and tG of the red and green color filters 14R and 14G are each fixed at 1.5 μm, and only the film thickness tB of the blue filter 14B is changed. This is the characteristic when it is performed.

As shown in the filter film thickness-chroma characteristic of FIG.
= 0.9-1.2 μm, green filter film thickness tG = 0.8
１．１1.1 μm, blue filter film thickness tB = 1.1-1.4.
When it is in the range of μm, the chroma C * of the mixed light has a small value.

The small value of the chroma of the mixed light means that the color of the mixed light is close to the C light source on the a * b * plane of the L * a * b * color system. Therefore, the color of the mixed light becomes more achromatic and excellent white light.

FIG. 7 shows red, green, and blue colored light, which is light emitted from the filter corresponding region a of the pixel region A of each color, and uncolored light, which is light emitted from the uncolored light emitting region b. The lightness (L *) of the mixed light transmitted through the liquid crystal display element displayed by the bright display area c between adjacent pixel areas in the L * a * b * color system with respect to the change in the film thickness of each color filter. ) Shows the change characteristics. Here, the areas sR, s of the color filters 14R, 14G, 14B of each color are shown.
The graph shows the characteristics when G and sB are both 80% of the area of the pixel region A.

In FIG. 7, the solid line indicates that the thicknesses tG and tB of the two color filters 14G and 14B of green and blue are fixed to 1.5 μm, respectively, and the thickness tR of the red filter 14R is
In the case where only the thickness is changed, the dashed line indicates that the thicknesses tR and tB of the two color filters 14R and 14B of red and blue are fixed at 1.5 μm, respectively, and the thickness t of the green filter 14G is
The characteristic when only G is changed, the broken line indicates that the film thicknesses tR and tG of the red and green color filters 14R and 14G are each fixed at 1.5 μm, and only the film thickness tB of the blue filter 14B is changed. This is the characteristic when it is performed.

As shown in the filter thickness-brightness characteristic of FIG. 7, the red, green, and blue color filters 14R, 14G, 14
B has a thickness tR, tG, tB within the above range (tR
= 0.9-1.2 μm, tG = 0.8-1.1 μm, t
B = 1.1-1.4 μm), the brightness (L) of the mixed light
*) Is in the range of about 51 to 53, and with this level of brightness (L *), the display brightness is sufficient.

The brightness (L *) of the mixed light increases as the thickness of the filter decreases, but when the thickness of the filter decreases, the chroma of the colored light decreases.
Therefore, since the color range is narrowed, the film thicknesses tR, tG, and tB of the red, green, and blue color filters 14R, 14G, and 14B.
The above range is appropriate.

As described above, in this liquid crystal display element, the thickness tR of the red filter, the thickness tG of the green filter, and the thickness tB of the blue filter are respectively tG <t.
Since the film thickness is set so as to satisfy the condition of tR <tB and to substantially maximize the chroma in the color system of the colored light transmitted through the color filter, the color area is increased and the color balance is deteriorated. In addition, the screen of the liquid crystal display element can be made sufficiently bright.

In this embodiment, the screen can be further brightened by making each of the red, green and blue color filters 14R, 14G and 14B smaller in area than the pixel area A.

For example, 60 to 95% of the area of the pixel region A
And thus each pixel region A
Only the areas a (hereinafter, referred to as filter corresponding areas) corresponding to the color filters 14R, 14G, and 14B are the emission areas of the colored light.
An area b not corresponding to 4B is a non-colored light emitting area for transmitting light, which is incident on the liquid crystal display element from its front surface, reflected by the rear reflector 23 and emitted to the front surface of the liquid crystal display element without coloring. Has become.

In this embodiment, the color filter 1 of each color is used.
4R, 14G, and 14B are provided inside the pixel region A except for the peripheral portion, and are opposed to the region on the TFT connection side with respect to the above-described compensation capacitance unit. The peripheral portion is a non-colored light emission region b over the entire circumference.

Of the light incident on each pixel region A from the front surface of the liquid crystal display element, the light incident on the compensation capacitance section is transmitted because the capacitance forming electrode 12 is formed of a metal film having a high reflectance. Reflected without.

Further, a region between adjacent pixel regions A,
In other words, the region where there is no electric field (the region where the liquid crystal molecules are always oriented in the initial twisted state) always enters the scattering reflector 23, the gate line 10, the data line 11 or the capacitance forming electrode 12. This is a bright display area c that is reflected and emitted to the front. That is, the gate lines 10 and the data lines 11 provided on the inner surface of the rear substrate 2 pass through the bright display area c, and the capacitance forming electrodes 12 also cross the bright display area c. Of the light incident on the bright display area c from the front surface of the display element, the light incident on a portion where the gate line 10 and the data line 11 pass through the capacitance forming electrode 12 is formed of a metal film having a high reflectance. Is reflected instead of transmitting.

This liquid crystal display element performs reflection type display by using external light. Light incident from the front surface of the liquid crystal display element is absorbed by the front polarizing plate 21 into light of a polarization component along its absorption axis. As a result, the light becomes linearly polarized light having a polarization component along the transmission axis, enters the liquid crystal layer 18, and is rotated by the birefringence in the process of transmitting through the liquid crystal layer 18.

The light transmitted through the liquid crystal layer 18 is
The light incident on the rear polarizing plate 22 and, of the light, a light having a polarization component along the transmission axis of the rear polarizing plate 22
Is transmitted to form image light, and the image light is transmitted to the scattering reflector 2.
The light is reflected by 3 and sequentially passes through the rear polarizer 22, the liquid crystal layer 18, and the front polarizer 21, and is emitted to the front.

At this time, of the light incident on each pixel region A from the front surface, the light transmitted through the filter corresponding region a of the pixel region A is absorbed by the color filters 14R, 14G, and 14B in the absorption wavelength band. Then, the light is colored to the color of the color filter, and the colored light is reflected and emitted to the front surface of the element. The intensity of the colored emitted light changes according to the rising alignment state of the liquid crystal molecules according to the electric field applied between the electrodes 3 and 17.

Further, of the light incident on each of the pixel regions A, the light incident on the non-colored light emission region b at the peripheral portion of the pixel region A does not pass through the color filters 14R, 14G, and 14B. The light is reflected as it is and emitted to the front of the element. The intensity of the uncolored outgoing light also changes according to the rising alignment state of the liquid crystal molecules according to the electric field applied between the electrodes 3 and 17.

That is, in this liquid crystal display device, in all the pixel regions A, of the light incident from the front surface of the liquid crystal display device, reflected by the scattering reflector 23 on the rear surface side, and emitted to the front surface, the filter corresponding region a Only the light transmitted through the color filter 14R, 14G, 14B is colored in the color of the color filters 14R, 14G, and 14B, and the light transmitted through the non-colored light emission area b is transmitted without being absorbed by the color filter. The color pixel is displayed by the colored light that is the light emitted from the non-colored light emitting region b and the non-colored light that is the light emitted from the uncolored light emitting region b.

FIG. 3 is a diagram showing a pixel arrangement of the liquid crystal display element. Each pixel A 'has one of the red (R), green (G), and blue (B) colored lights (emitted light from the filter corresponding area a). FIG.
, And non-colored light (light outside the hatched area in FIG. 3) which is light emitted from the non-colored light emission area b.
To the human eye, the entire pixel A 'appears to be colored in the color of the colored light, and a color image is displayed by the additive mixture of the red, green, and blue pixels A'. Note that the pixel A ′ is a high-luminance pixel in which the color of the colored light is slightly lightened, and the color density and brightness correspond to the light amount ratio between the colored light and the non-colored light.

Further, the light incident on the bright display area c between the adjacent pixel areas A is reflected by the gate line 10, the data line 11, or the capacitance forming electrode 12, and is reflected as non-colored light to form the front surface of the element. Out. The uncolored light emitted from the bright display area c is such that the bright display area c is always in an electric field-free state, and the liquid crystal molecules are always aligned in the initial twist alignment state. Because it does not reach, it is always high intensity light.

As described above, the area of the red, green, and blue color filters 14R, 14G, and 14B is made smaller than the area of the pixel region A, and
The film thicknesses tR, tG, tB of 4R, 14G, 14B are represented by tR
= 0.9-1.2 μm, tG = 0.8-1.1 μm, t
In the liquid crystal display device of the above embodiment in which B is set in the range of 1.1 to 1.4 μm, the red, green, and blue light has high chroma, and therefore, the color range is wide, and the mixture of these colors is high. Since the color of the light is closer to white and the brightness of the mixed light is sufficient, a full-color image with good image quality can be displayed.

Although the red, green, and blue color filters 14R, 14G, and 14B are formed in the same area in the above embodiment, these color filters 14R, 14G, and 1B are formed.
4B, the green filter 14G and the blue filter 14B
Is slightly smaller than the area of the red filter 14R (for example, about 93 to 95% of the area of the red filter 14R), the color of the mixed light can be made closer to white.

Further, the liquid crystal display device of the above embodiment has red,
The pixel electrodes 3 for displaying green and blue pixels are alternately arranged in a row direction and arranged linearly, and the pixel electrodes 3 for displaying pixels of the same color are arranged in a column direction at about 1.5 pitches. It is a so-called mosaic array type, which is arranged in a zigzag manner by shifting them alternately in the row direction.
The present invention can also be applied to a so-called grid-type liquid crystal display element in which pixel electrodes 3 for displaying green and blue pixels are linearly arranged in both the row direction and the column direction.

Further, in the above embodiment, the color filter is used as the color film, but the color film is not limited to the color filter. Further, the liquid crystal display device of the above embodiment is
Although a full-color image is displayed by additive color mixture of red, green, and blue light, the present invention provides magenta, yellow,
The present invention can also be applied to a liquid crystal display element that includes a cyan colored film (for example, a color filter) and displays a color image by subtractive color mixture. In addition to the relationship of band-transmitting colored film <intermediate-wavelength-band transmitting colored film <short-wavelength-band transmitting colored film,
By setting the thickness of the colored film of each color to a value at which the chroma of the colored light transmitted through the colored film is almost maximal,
By providing the color film having a wide color range and not causing deterioration of color balance, the screen can be made sufficiently bright.

Further, the present invention is not limited to the active matrix type, and a plurality of scanning electrodes extending in one direction are provided on an inner surface of one substrate in parallel with each other, and a direction intersecting the scanning electrodes is provided on an inner surface of the other substrate. The present invention can also be applied to a simple matrix type liquid crystal display device or the like in which a plurality of signal electrodes are provided in parallel with each other.

Further, in the liquid crystal display device of the above embodiment, the polarizing plates 21 and 22 are arranged on the front and rear surfaces thereof, and the reflecting plate 23 is arranged behind the back polarizing plate 22. For example, an electrode (the pixel electrode 3 in the above embodiment) provided on the inner surface of the back substrate 2 may be formed of a metal film, and this electrode may also serve as a reflection member. In this case, the polarizing plate is only the front polarizing plate 21. Good.

Also, as in the above embodiment, the front polarizing plate 21
And the rear polarizing plate 22, the rear polarizing plate 2
2 may be a semi-transmissive reflector, and a backlight may be provided behind the reflector 23. In this case, the reflective display using external light and the light from the backlight can be used. Both of the transmission type display to be used can be performed. In addition, the present invention can be applied to a transmission type liquid crystal display element that performs only display using light from a backlight.

[0074]

According to the liquid crystal display device of the present invention, the thicknesses of the three colored films are set as "intermediate wavelength band transmitted colored film"<"long wavelength band transmitted colored film"<"short wavelength band transmitted colored film". Since the relationship is satisfied, and the chroma of the colored light transmitted through the respective colored films is set to a value that is almost maximal, it has a wide color range, does not deteriorate the color balance, and makes the screen of the liquid crystal display element sufficiently bright. can do.

When the three colored films are, for example, red, green and blue color filters using a pigment dispersion material, the red filter has a thickness of 0.9 to 1.2 μm and the green filter has a thickness of 0.9 to 1.2 μm. By setting the thickness in the range of 0.8 to 1.1 μm and the thickness of the blue filter in the range of 1.1 to 1.4 μm,
The chroma of the red, green, and blue colored light transmitted through these color filters can be substantially maximized.

Further, in the liquid crystal display element of the present invention, the three colored films are formed in areas smaller than the area of the pixel region, and regions of the pixel region which do not correspond to the colored film are made of non-colored light. If it is an emission region, only the light transmitted through the region corresponding to the colored film out of the light transmitted through the pixel region is colored by absorbing the light in the absorption wavelength band by the colored film, and the uncolored light emission region is formed. The transmitted light is transmitted without being absorbed by the colored film, and the transmitted light is a colored light emitted from a region corresponding to the colored film, and a high-luminance non-colored light emitted from the uncolored light emitting region. Since a high-luminance color pixel is displayed by light, the screen can be made brighter.

The present invention also relates to a transmission type liquid crystal display element for displaying by using light from a backlight, which is provided with a reflecting member on the rear surface side to display by utilizing external light such as natural light or indoor illumination light. The present invention can also be applied to a reflective liquid crystal display element, and even if it is a reflective liquid crystal display element, its screen can be made sufficiently bright.

[Brief description of the drawings]

FIG. 1 is a front view of a part of a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line II-II in FIG.

FIG. 3 is a diagram showing a pixel arrangement of the liquid crystal display element.

FIG. 4 shows film thicknesses of red, green, and blue color filters and CIE.
The figure which shows the relationship with the chroma of each colored light of red, green, and blue on the a * b * surface of the 1976L * a * b * color system.

FIG. 5 illustrates a case where red, green, and blue color pixels are displayed by colored light that is emitted from a filter corresponding region of each pixel region and non-colored light that is emitted from an uncolored light emitting region. , CIE1976L * a * b * for filter thickness
FIG. 9 is a diagram illustrating a change characteristic of a color range on an a * b * surface of a color system.

FIG. 6 shows red, green, and blue colored light, which is light emitted from a filter corresponding region in each pixel region, and uncolored light, which is light emitted from a non-colored light emitting region, and a bright display between adjacent pixel regions. FIG. 9 is a diagram illustrating a change characteristic of chroma with respect to a filter film thickness of mixed light including uncolored light that is light emitted from a region c.

FIG. 7 is a diagram showing a change characteristic of brightness of the mixed light with respect to a filter film thickness.

FIG. 8 is a diagram showing a change in transmittance due to thinning of a color filter.

[Explanation of symbols]

 1, 2, substrate 3, pixel electrode 4, TFT (active element) 14R, 14G, 14B, color filter 17, counter electrode 21, 22, polarizing plate 23, reflector A, pixel area a, filter corresponding area b, non Colored light emission area c: Bright display area

Claims (4)

[Claims] 1. A plurality of first electrodes provided on one of inner surfaces of a pair of front and rear substrates opposed to each other with a liquid crystal layer interposed therebetween, and the plurality of first electrodes provided on another inner surface. And at least one second electrode having a plurality of pixel regions facing each other, and three colored films having different transmission wavelength bands provided on the inner surface of any of the substrates so as to correspond to the respective pixel regions. Wherein the thickness of the three colored films satisfies the condition of intermediate wavelength band transmitted colored film <long wavelength band transmitted colored film <short wavelength band transmitted colored film, and coloring transmitted through each colored film. A liquid crystal display device characterized in that the film thickness is set so as to maximize a color range surrounded by the three color coordinates defined by the color system representing the color of light. 2. The three-colored film is a red, green and blue color filter using a pigment dispersion material, wherein the red filter has a thickness of 0.9 to 1.2 μm and the green filter has a thickness of 0.9 to 1.2 μm. 0.
8 to 1.1 μm, and the thickness of the blue filter is 1.1 to 1.4.
2. The liquid crystal display device according to claim 1, wherein the thickness is μm. 3. The method according to claim 1, wherein the areas of the three colored films are smaller than the areas of the pixel regions, and a region of the pixel region that does not correspond to the colored film is a non-colored light emission region. The liquid crystal display device according to claim 1, wherein: 4. The liquid crystal display device according to claim 1, further comprising a reflection member on a rear surface side.