JP3395579B2 - Liquid crystal display device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflective twisted nematic liquid crystal display element (hereinafter referred to as TN liquid crystal display element).

[0002]

2. Description of the Related Art A TN liquid crystal display device is a device in which a pair of polarizing plates are arranged with a liquid crystal cell in which liquid crystal molecules are twist-aligned at a twist angle of approximately 90 °. There are a transmissive type that uses light from a backlight for display and a reflective type that uses external light such as natural light or room illumination light for display.

FIG. 11 is a perspective view showing a schematic structure of a conventional reflective TN liquid crystal display element.
It comprises a liquid crystal cell 2, a pair of front and rear polarizing plates 5 and 6 which are arranged with the liquid crystal cell 2 in between, and a reflecting plate 7 which is arranged behind the rear polarizing plate 6.

Although the structure of the liquid crystal cell 2 is not shown, a transparent electrode for applying an electric field to the liquid crystal is provided on the inner surface of the liquid crystal cell 2, and a nematic liquid crystal between a pair of front and rear transparent substrates on which an alignment treatment is performed is provided. A layer is provided, and the liquid crystal molecules of the liquid crystal layer are aligned in the vicinity of both substrates along the direction of the alignment treatment applied to the inner surfaces of these substrates,
A twist orientation is formed between both substrates with a twist angle of approximately 90 °. In FIG. 11, arrows 3a and 4a indicate the alignment directions of liquid crystal molecules in the vicinity of both substrates of the liquid crystal cell 2.

The pair of front and rear polarizing plates 5 and 6 have their transmission axes 5a and 6a substantially orthogonal to each other, and the transmission axes 5a and 6a of the polarizing plates 5 and 6 are located near the front and back substrates of the liquid crystal cell 2. It is arranged in a direction substantially parallel to the orientation directions 3a and 4a or in a direction substantially orthogonal to the orientation directions (parallel direction in the drawing).

That is, in the liquid crystal display element 1, the display is bright when the electric field is not applied to the liquid crystal of the liquid crystal cell 2 (the liquid crystal molecules are aligned in the initial twist alignment state). The so-called normally white mode display is performed in which the light emission rate is lowered and the display is darkened as the liquid crystal molecules rise and align with respect to the substrate surface by the application of an electric field to the liquid crystal.

The liquid crystal display element includes a monochrome display element and a color display element. In the color display element, a color filter is provided on the inner surface of one of the substrates of the liquid crystal cell.

By the way, the TN liquid crystal display element 1 has a viewing angle (observation direction in which the display can be observed with a good contrast) determined by the twist alignment state of the liquid crystal molecules of the liquid crystal cell 2.

The display of the liquid crystal display element is generally in the front direction of the display surface (the front surface of the liquid crystal display element), and slightly tilted toward the lower edge of the display surface rather than the direction perpendicular to the display surface. Observed from the direction. Therefore, the TN liquid crystal display element 1 is designed so that its viewing angle matches the viewing direction.

That is, in the conventional liquid crystal display element 1, as shown in FIG. 11, the liquid crystal molecule alignment direction 4a in the vicinity of the rear substrate of the liquid crystal cell 2 is viewed from the front side with respect to the horizontal axis x of the display surface. And the liquid crystal molecule alignment direction 3a in the vicinity of the front substrate is set to a direction of about 45 ° counterclockwise with respect to the horizontal axis x, and the liquid crystal molecules are shown in the figure. As indicated by the broken line arrow, the twist direction is twist-oriented at a twist angle of approximately 90 ° clockwise from the rear substrate toward the front substrate with reference to the alignment direction 4a in the vicinity of the rear substrate. ing.

The viewing angle of the TN liquid crystal display element 1 in which the alignment state of the liquid crystal molecules of the liquid crystal cell 2 is set in this way is right below the display surface when viewed from the direction perpendicular to the display surface, and therefore the normal viewing direction. The display observed from is the display with the best contrast.

[0012]

However, the conventional reflective TN liquid crystal display element 1 in which the alignment state of the liquid crystal molecules of the liquid crystal cell 2 is set so that the viewing angle is right below the display surface.
Have a problem that the display viewed from the normal viewing direction is dark.

That is, since the display of the liquid crystal display element is observed from the normal viewing direction, that is, the direction slightly inclined to the lower edge direction of the display surface rather than the direction perpendicular to the display surface, the reflection type liquid crystal display In the case of the element 1, of the light that enters from the display surface, is reflected by the reflection plate 7, and is emitted to the display surface, the upper edge of the display surface is obliquely above the display surface, that is, with respect to the direction perpendicular to the display surface. The reflected light of the light incident from the direction inclined to the direction is most strongly observed.

However, in the conventional liquid crystal display element 1 whose viewing angle is right below the display surface, the transmittance of light incident from obliquely above the display surface in the front direction is low, and therefore it is observed from the normal viewing direction. The display is dark.

This problem is particularly noticeable in the color liquid crystal display element in which the color filter is provided in the liquid crystal cell 2, and in this color liquid crystal display element, the transmitted light is absorbed by the color filter in the light other than the specific wavelength band. Since only the light of a specific wavelength band is transmitted through the color filter and becomes the light colored in the color filter, the intensity of the emitted colored light becomes extremely weak with respect to the intensity of the incident light, and the normal observation direction The display seen from is even darker.

The present invention, as a reflection type TN liquid crystal display element, sufficiently satisfies a display observed in a normal viewing direction, that is, a direction slightly tilted to a lower edge direction of the display surface rather than a direction perpendicular to the display surface. The object of the present invention is to provide a product that can be sufficiently brightened while ensuring a possible contrast.

[0017]

The present invention is a reflection type T
In the N liquid crystal display device, liquid crystal molecules of a liquid crystal cell having a liquid crystal layer provided between a pair of front and rear substrates have a front surface with respect to the horizontal axis of the display surface of the display device in the vicinity of the rear substrate of the pair of substrates. 45 ° greater than 0 ° counterclockwise when viewed from the direction
It is characterized in that it is oriented in a direction within a smaller angle range, and is twist-oriented with a twist angle of approximately 90 ° clockwise when viewed from the front surface direction from the rear substrate to the front substrate with reference to the orientation direction. To do.

In this liquid crystal display element, since the liquid crystal molecules of the liquid crystal cell are aligned in the above-described alignment state, the upper edge direction of the display surface is obliquely above the display surface, that is, the direction perpendicular to the display surface. The transmittance of light incident from the direction inclined to is high,
Therefore, the amount of emitted light that is incident from the direction in which it is most strongly observed, that is, the reflected light of the light that is incident obliquely above the display surface is increased.

Therefore, according to the liquid crystal display element of the present invention, even a reflective TN liquid crystal display element is sufficiently bright for a display observed from the normal observation direction while ensuring a satisfactory contrast. can do.

Further, in this liquid crystal display element, since the alignment state of the liquid crystal molecules of the liquid crystal cell is set as described above,
The viewing angle is in the diagonally lower right direction of the display surface when viewed from the direction perpendicular to the display surface, but if the viewing angle direction is in this vicinity, it is displayed slightly more than the normal viewing direction, that is, the direction perpendicular to the display surface. The contrast of the display observed from the direction inclined to the lower edge direction of the surface is not so much as compared with the conventional liquid crystal display element in which the viewing angle is directly below the display surface.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, the liquid crystal display device of the present invention is arranged such that the alignment direction of liquid crystal molecules in the vicinity of the rear substrate of the liquid crystal cell is counterclockwise when viewed from the front direction with respect to the horizontal axis of the display surface. The angle is in the range of more than 0 ° and less than 45 °, and the liquid crystal molecules are oriented in the clockwise direction when viewed from the front side from the rear side substrate to the front side substrate with reference to the alignment direction in the vicinity of the rear side substrate. By performing twist orientation at a twist angle of °, even a reflection type TN liquid crystal display device can make a display observed from a normal observation direction sufficiently bright while ensuring a sufficiently satisfactory contrast.

In the liquid crystal display device of the present invention, the desirable orientation direction of the liquid crystal molecules in the vicinity of the rear substrate of the liquid crystal cell is 5 counterclockwise when viewed from the front direction with respect to the horizontal axis of the display surface.
It is a direction within an angle range of ° to 30 °, and more preferably a direction within an angle range of about 10 ° to about 25 °. The present invention is particularly effective for a color liquid crystal display device using a liquid crystal cell provided with a color filter.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A first embodiment of the present invention will be described below with reference to FIGS.
Will be described with reference to. FIG. 1 is a schematic configuration diagram of a liquid crystal display element of this embodiment, and FIG. 2 is a sectional view of the liquid crystal display element.
As shown in FIGS. 1 and 2, the liquid crystal display element 10 includes a liquid crystal cell 11, a pair of front and rear polarizing plates 21 and 22 arranged with the liquid crystal cell 11 in between, and a rear polarizing plate 2.
2 and a reflecting plate 23 arranged behind.

The liquid crystal cell 11 is of an active matrix type using a TFT (thin film transistor) as an active element, and is disposed on the inner surface of the rear substrate 13 of the pair of front and rear transparent substrates (eg glass substrates) 12, 13. The transparent pixel electrodes 14 are arranged in a matrix in the row direction and the column direction, and the inner surface of the front substrate 12 faces all of the pixel electrodes 14 and is formed by the portions facing the pixel electrodes 14, respectively. A transparent counter electrode 15 forming a pixel region is provided.

Although not shown in FIG. 2, TFTs (active elements) are provided on the inner surface of the rear substrate 13 so as to be connected to the respective pixel electrodes 14 and T of each row is provided.
A gate line that supplies a gate signal to the FT and a T in each column
A data line for supplying a data signal to the FT is wired.

Further, the liquid crystal cell 11 used in this embodiment.
Is a multi-color filter, such as red, green, and blue.
The color filters 16R, 16G, and 16B for colors are provided. These color filters 16R, 16G, 16B
Are provided on the inner surface of the front substrate 12 in such a manner that the pixel electrodes 14 and the counter electrodes 15 are alternately arranged corresponding to the pixel regions facing each other.
Is formed on a transparent protective film (insulating film) 17 provided so as to cover the color filters 16R, 16G and 16B.

Furthermore, the front and rear substrates 12, 1 are
On the inner surface of 3, that is, on each pixel electrode 14 and the counter electrode 15, alignment films 18 and 19 made of polyimide or the like are provided over the entire display area.
8 and 19 are each subjected to an alignment treatment of rubbing the film surface in a predetermined direction.

The front substrate 12 and the rear substrate 13 are joined together via a frame-shaped sealing material 20 surrounding the display area, and a display surrounded by the sealing material 20 between the two substrates 12 and 13. A nematic liquid crystal layer LC is provided in the area.

The molecules of the liquid crystal of this liquid crystal layer LC are
The alignment films 18 and 19 provided on the inner surface of 2,13 is restricted orientation direction in the vicinity of each of the substrates 12 and 13, are twisted in torsion angle of approximately 90 ° in between the substrates 12 and 13. In FIG. 1, an arrow 12
Reference numerals a and 13a indicate the alignment directions of liquid crystal molecules in the vicinity of both substrates 12 and 13.

In the liquid crystal display device 10, the liquid crystal molecules of the liquid crystal cell 11 are arranged in a pair of substrates 1.
In the vicinity of the rear side substrate 13 of the reference numerals 2 and 13, the orientation is made counterclockwise with respect to the horizontal axis x of the display surface in an angle range of more than 0 ° and less than 45 °, and the rear side Twisted at a twist angle of approximately 90 ° clockwise when viewed from the front surface direction from the substrate 13 to the front substrate 12.

The orientation direction 13a of the liquid crystal molecules near the rear substrate 13 is observed among the light that is incident from the display surface of the liquid crystal display element 10, is reflected by the reflection plate 23 and is emitted to the display surface. It is set according to the incident angle of the incident light (effective incident light) most strongly reflected on the person side.

That is, as described in the sections of [Prior Art] and [Problems to be Solved by the Invention], the display of the liquid crystal display element is usually in a substantially front direction of the display surface, and Since the light is observed from a direction slightly inclined to the lower edge direction of the display surface rather than the direction perpendicular to the display surface, the incident light effective for observation is diagonally above the display surface, that is, the direction perpendicular to the display surface. The light is incident from a direction inclined to the upper edge direction.

According to the observation direction of the observer, the effective incident light is within an angle range of about 20 ° to about 30 ° in the upper edge direction of the display surface with respect to the direction perpendicular to the display surface. The light is incident at an inclination angle of.

Therefore, in this embodiment, the effective incident angle of the incident light (angle with respect to the direction perpendicular to the display surface) is set to 30.
When the angle is set to 0, the alignment direction 13a of the liquid crystal molecules near the rear substrate 13 of the liquid crystal cell 11 is set to the following direction.

That is, as shown in FIG. 1, the liquid crystal cell 1
Alignment direction 1 of liquid crystal molecules in the vicinity of the rear substrate 1
3a is in a direction deviated from the horizontal axis x of the display surface by approximately 25 ° counterclockwise when viewed from the front direction.

Then, in this embodiment, the alignment direction 12a of the liquid crystal molecules in the vicinity of the front substrate 12 of the liquid crystal cell 11 is determined.
Depending on the alignment direction 13a of the liquid crystal molecules in the vicinity of the rear substrate 13, a direction deviated from the alignment direction 13a by 90 ° counterclockwise as viewed from the front direction, that is, on the horizontal axis x of the display surface. On the other hand, when viewed from the front direction, it is approximately 115 counterclockwise
The liquid crystal molecules are twisted by about 90 ° clockwise when viewed from the front side from the rear side substrate 13 toward the front side substrate 12 with reference to the alignment direction 13a in the vicinity of the rear side substrate 13 as a reference. It is twisted at the corners.

In the liquid crystal display element 10, the display is bright when the electric field is not applied to the liquid crystal of the liquid crystal cell 11 (the liquid crystal molecules are aligned in the initial twist alignment state). When the electric field is applied to the liquid crystal, liquid crystal molecules rise and align with respect to the substrate surface, the light emission rate decreases and the display darkens. This is what is called a normally white mode display. As shown in FIG. 1, the polarizing plates 21 and 22 of the polarizing plates 21 and 22 have their transmission axes 21a and 22a substantially orthogonal to each other, and the transmission axes 21a and 22a are located near the front substrate 12 and the back substrate 13 of the liquid crystal cell 11. The liquid crystal molecules are arranged in a direction substantially parallel to the liquid crystal molecule alignment directions 12a and 13a or in a direction substantially orthogonal thereto (parallel direction in the figure).

Further, the reflection plate 23 is made of a metal plate having a high reflectance such as aluminum or silver. The reflection plate 23 has a reflection characteristic in which the reflectance in the vertical direction varies depending on the incident direction of light, and the incident direction from which a high reflectance in the vertical direction is obtained is displayed on the display surface of the liquid crystal display element 10. Are arranged substantially parallel to the vertical axis y.

FIG. 3 shows a method of measuring the reflection characteristic of the reflection plate 23. In this measuring method, while rotating the reflection plate 23 in the circumferential direction, light from the spot light source 30 arranged at a fixed position at the rotation center of the reflection plate 23 is incident at a predetermined incident angle and is perpendicular to the reflection plate surface. By continuously measuring the amount of reflected light in different directions, the change in vertical reflectance (ratio of the amount of light received by the light receiving unit 31 to the amount of light emitted from the spot light source 30) with respect to the change in the incident direction of light. The angle of incidence of light on the reflection plate 23 (angle with respect to the direction perpendicular to the surface of the reflection plate) is set to be 30 °, which is the incident angle of incident light effective in the liquid crystal display element 10.
Is set to the same angle as.

FIG. 4 is a reflection characteristic diagram of the reflection plate 23 measured by the above method. In the drawing, the incident direction is the reflection plate 23.
0 ° is an incident direction at the start of measurement, which is arbitrarily determined.

As shown in this reflection characteristic diagram, the reflection plate 23
Has a reflection characteristic that the vertical reflectance alternately increases or decreases every 90 ° of the incident direction of light, and therefore, the incidence direction in which the high vertical reflectance is obtained and the vertical reflectance The incident directions in which the rate becomes low are in a relationship orthogonal to each other.

Therefore, in this embodiment, the reflection plate 23 is used.
Is arranged such that the incident direction for obtaining a high vertical reflectance is substantially parallel to the vertical axis y of the display surface of the liquid crystal display element 10, and the above-mentioned effective incident light incident direction is obliquely above the display surface. The incident light is efficiently reflected and emitted in the front direction of the display surface.

In the liquid crystal display element 10, incident light (external light) from the front surface, that is, the display surface, is a polarization component in a direction (absorption axis direction) orthogonal to the transmission axis 21a by the front polarizing plate 21. Of the light which is absorbed by the liquid crystal cell 11 and enters the rear polarizing plate 22, the light of the polarization component in the direction of the transmission axis 22a of the polarizing plate 22 is absorbed by the rear polarizing plate 22. And the light is reflected by the reflecting plate 23, and then sequentially passes through the rear polarizing plate 22, the liquid crystal cell 11, and the front polarizing plate 21 and is emitted to the display surface (front surface).

The liquid crystal cell 11 has red, green and blue color filters 16 corresponding to the respective pixel regions.
Since the R, 16G, and 16B are provided, the light transmitted through each pixel region of the liquid crystal cell 11 is converted into the color filters 16R and 1R.
Lights other than the specific wavelength band are absorbed by 6G and 16B,
Only light in a specific wavelength band is transmitted through the color filter to become light colored in the color of the color filter, and a multicolor color image is displayed by the red, green, and blue colored light emitted from each pixel area.

In the liquid crystal display element 10, the molecules of the liquid crystal of the liquid crystal cell 11 are formed in the vicinity of the rear substrate 13 at an angle of approximately 25 ° counterclockwise with respect to the horizontal axis x of the display surface when viewed from the front direction. Orientation, and the orientation direction 13
Since the liquid crystal molecules are twisted from the rear substrate 13 toward the front substrate 12 in a clockwise direction when viewed from the front side with a twist angle of approximately 90 ° with reference to a, the reflective TN.
Even in the case of a liquid crystal display device, it is possible to make the display observed from the normal observation direction sufficiently bright while ensuring a sufficiently satisfactory contrast.

That is, in the liquid crystal display element 10, since the alignment state of the liquid crystal molecules of the liquid crystal cell 11 is set as described above, the viewing angle is diagonally right of the display surface when viewed from the direction perpendicular to the display surface. Although it is in the downward direction, if the viewing angle direction is near this, the display contrast observed from the normal viewing direction, that is, the direction slightly tilted to the lower edge direction of the display surface rather than the direction perpendicular to the display surface, Compared with the conventional liquid crystal display element in which the viewing angle is directly below the display surface, it is not so different.

Further, in the liquid crystal display element 10, since the liquid crystal molecules of the liquid crystal cell 11 are aligned in the above-described alignment state, the display surface is obliquely above the display surface, that is, perpendicular to the display surface. The transmittance of the light incident from the direction inclined to the upper edge direction is high, and therefore the intensity of the effective incident light, that is, the light emitted by reflecting the light incident from diagonally above the display surface is increased.

The transmittance of light incident from diagonally above the display surface of the liquid crystal display element 10 of the above embodiment will be described below in comparison with the conventional liquid crystal display element 1 shown in FIG.

FIG. 5 shows the incident angle of the above-mentioned effective incident light of the reflected light of the light incident from obliquely above the display surface at 30.
The incident direction of the light transmitted with high transmittance when
The liquid crystal display element 10 of the above embodiment and the conventional liquid crystal display device 1
And each are shown.

As shown in FIG. 5A, the liquid crystal cell 2 of the conventional liquid crystal display element 1 designed so that the viewing angle is directly below the display surface has a liquid crystal molecule alignment direction in the vicinity of the rear substrate. 4a is a direction that is approximately 45 ° clockwise when viewed from the front direction with respect to the horizontal axis x of the display surface, and liquid crystal molecule alignment direction 3a in the vicinity of the front substrate is substantially counterclockwise when viewed from the front direction with respect to the horizontal axis x. The direction is 45 °, and the liquid crystal molecules are viewed from the front side from the rear side substrate to the front side substrate with reference to the alignment direction 4a in the vicinity of the rear side substrate, as shown in the figure by the broken line arrow. And twisted clockwise with a twist angle of about 90 °.

On the other hand, in the liquid crystal cell 11 of the liquid crystal display element 10 of the above embodiment, as shown in FIG. 5B, the liquid crystal molecule alignment direction 13a near the rear substrate is the horizontal axis of the display surface. The liquid crystal molecule alignment direction 12a in the vicinity of the front substrate is approximately 25 ° counterclockwise with respect to x, when viewed from the front direction.
Is about 11 to the left when viewed from the front with respect to the horizontal axis x.
The direction is 5 °, and the liquid crystal molecules are seen from the front side from the rear side substrate to the front side substrate with reference to the alignment direction 13a in the vicinity of the rear side substrate, as shown by the broken line arrow in the figure. And twisted clockwise with a twist angle of about 90 °.

FIG. 6 shows a method for measuring the transmittance of the liquid crystal display element 1. In this transmittance measuring method, the conventional liquid crystal display element 1 is rotated in the circumferential direction while the reflection plate is not provided on the rear surface thereof, that is, the liquid crystal cell 2 is only sandwiched between the pair of polarizing plates 5 and 6, and Light from a spot light source 32 arranged at a fixed position is incident on the front side of the liquid crystal display element 1 at a predetermined position at a predetermined incident angle, and the amount of light transmitted to the rear side of the liquid crystal display element 1 is received by a light receiving section 33. This is a method of investigating the change of the transmittance with respect to the change of the incident direction of light by continuously measuring. Here, the incident angle of the light to the liquid crystal display element 1 (the angle with respect to the direction perpendicular to the front surface of the liquid crystal display element is ) Is set to the same angle as 30 ° which is the incident angle of the effective incident light described above in the liquid crystal display element 10 of the above-described embodiment.

In this way, the conventional liquid crystal display device 1
The transmittance of incident light from each direction in the angle range of 0 ° to 90 ° is set to 1.5 V in the non-electric field state in which the molecules of the liquid crystal in the entire display region of the liquid crystal cell 2 are in the initial twist alignment state. When an electric field is applied to measure the liquid crystal molecules in two states, that is, in an alignment state in which a halftone display is obtained, as shown in FIG. 7, in the case of the liquid crystal display element 1,
The transmittance is low for the effective incident light described above.

That is, as shown in FIG. 5, the direction on the horizontal axis x on the right side of the display surface of the liquid crystal display device is 0 °, and the direction on the vertical axis y on the upper edge side of the display surface is 90 °. Direction, 180 ° on the horizontal axis x on the left side of the display surface
, The direction on the vertical axis y on the lower edge side of the display surface is 27
If the direction is 0 °, in the conventional liquid crystal display element 1, 90 °
The transmittance of light incident from the direction of 30 ° with respect to the perpendicular of the liquid crystal cell 2 is low.

As can be seen from the incident direction-transmittance characteristic of FIG. 7, in the conventional liquid crystal display element 1 having the viewing angle right below the display surface, the incident direction of the light transmitted with the highest transmittance is the liquid crystal display. When the angle is 30 ° with respect to the vertical line of the element 1, the direction is approximately 20 ° from the horizontal axis x as shown in FIG.

The liquid crystal display element 1 used for the above-mentioned transmittance measurement is for monochrome display in which the liquid crystal cell 2 is not provided with a color filter, and a color liquid crystal display in which the liquid crystal cell 2 is provided with a color filter. In the case of an element, its transmittance is lower than the incident direction-transmittance characteristic of FIG.

In contrast to such a conventional liquid crystal display element 1, the liquid crystal display element 10 of the above-mentioned embodiment has its liquid crystal cell 1 as can be seen by comparing (a) and (b) of FIG.
The alignment state of the liquid crystal molecules of No. 1 is approximately 7 in the counterclockwise direction when viewed from the front direction as compared with the liquid crystal cell 2 of the conventional liquid crystal display element 1.
0 ° different.

Therefore, the liquid crystal display element 10 of the above-mentioned embodiment.
Indicates that the incident direction of the light transmitted with the highest transmittance is when the incident angle of the light on the liquid crystal display element 1 is 30 °, and is substantially 90 ° as shown in FIG. 5B. .

Therefore, when the display is viewed from the normal viewing direction, the transmittance of the effective incident light incident obliquely from above the display surface is the highest, and therefore the light is reflected and emitted to the viewer side more strongly. Since the intensity of the emitted light to the observer side becomes strong, the display observed from the normal observation direction can be made sufficiently bright.

FIG. 8 is two kinds of comparisons performed to compare the brightness of the display observed from the normal observation direction between the liquid crystal display element 10 of the above-mentioned embodiment and the conventional liquid crystal display element 1 shown in FIG. 2 shows a front luminance measuring method of.

The measurement of the front luminance was carried out by setting the incident angle of light on both liquid crystal display elements 1 and 10 to 30 ° which is the effective incident light incident angle of the above-mentioned embodiment. In the measuring method shown in FIG. 8A, the ring-shaped light source 3 is provided on the display surface of the liquid crystal display element 1 or 10 for measuring the display brightness.
4 are opposed to each other, and light is made incident on a predetermined portion (center portion in the figure) of the display surface of the liquid crystal display elements 1 and 10 at an incident angle of 30 ° from the entire circumferential direction, in a direction perpendicular to the display surface. This is a method of measuring the intensity of the emitted light of the light receiving section 35.

Further, the measuring method shown in FIG.
A spot light source 36 is arranged diagonally above the display surface of the liquid crystal display element 1 or 10 for measuring the display brightness (direction of 90 °), and a spot light source 30 is provided at a predetermined position (center portion in the figure) on the display surface.
This is a method in which light is incident at an incident angle of 0 ° and the intensity of emitted light in a direction perpendicular to the display surface is measured by the light receiving section 37.

The reflectance measured by the method of FIG. 8A, that is, the reflectance of the omnidirectional reflector made of barium sulfate is 1
When it is set to 00%, the reflected light intensity with respect to the irradiation light from the ring-shaped light source 34 is 66.74 in the conventional liquid crystal display element 1.
% And 68.34% in the liquid crystal display element 10 of the example.

Further, when the reflectance measured by the method of FIG. 8B, that is, the barium sulfate reflectance is 100%,
The ratio of the reflected light intensity to the irradiation light from the spot light source 36 was 26.64% in the conventional liquid crystal display element 1 and 30.04% in the liquid crystal display element 10 of the example.

When the display brightness of the liquid crystal display element 10 of the above-mentioned embodiment is evaluated from the measurement results, the front luminance when light is evenly incident from the entire circumferential direction of the display surface is the same as that of the conventional liquid crystal display element 1. Although it is about 1.02 times, the front luminance when the incident direction of light is obliquely above the display surface is 1.13 times as high as that of the conventional liquid crystal display element 1.

That is, the liquid crystal display element 10 of the above embodiment.
In comparison with the conventional liquid crystal display element 1, when the display is observed from the normal observation direction, the reflected light intensity is 13% higher than the effective incident light incident from diagonally above the display surface.

The normal viewing direction is a direction slightly inclined to the lower edge direction of the display surface rather than the direction perpendicular to the display surface. The brightness of the display observed from the normal observation direction is
It may be considered that the front luminance is almost the same as that measured by the above method.

Therefore, the liquid crystal display element 1 of the above embodiment
0 means that the display brightness is at least 1 when the display is viewed from the normal viewing direction, as compared with the conventional liquid crystal display element 1.
It is higher than 0%.

Then, the liquid crystal display device 10 of the above embodiment.
Are the color filters 16R, 16G, and 1 in the liquid crystal cell 11.
Since it is a color liquid crystal display device including 6B, the transmitted light absorbs light other than the specific wavelength band by the color filter, and only the light in the specific wavelength band passes through the color filter and is colored in the color filter. Since the intensity of the colored light emitted is extremely weaker than the intensity of the incident light, the intensity of the emitted light of the reflected light of the light incident from diagonally above the display surface can be increased as described above. If possible, the color display observed from the normal observation direction can be made sufficiently bright.

Further, the viewing angle of the liquid crystal display element 10 of the above-mentioned embodiment is the left when viewed from the front direction with respect to the direction of the viewing angle of the conventional liquid crystal display element 1, that is, the direction directly below the display surface (direction of 270 °). There is a direction shifted by about 70 ° around this direction, but this direction is the diagonally lower right direction of the display surface when viewed from the direction perpendicular to the display surface, and if the viewing angle direction is in this direction, the normal viewing direction, that is, The display contrast observed from a direction slightly inclined to the lower edge direction of the display surface rather than the direction perpendicular to the display surface is not so much as compared with the conventional liquid crystal display element whose viewing angle is directly below the display surface. Therefore, it is possible to secure a sufficiently satisfactory contrast.

In the first embodiment, the incident angle of the effective incident light of the reflected light of the light incident obliquely above the display surface was set to 30 °. As described above, it depends on the position of the observer, and in most cases, the light incident on the upper edge direction of the display surface at a tilt angle within an angle range of approximately 20 ° to approximately 30 ° with respect to the direction perpendicular to the display surface. The reflected light is observed by the observer.

Therefore, the alignment state of the liquid crystal molecules of the liquid crystal cell 11 of the liquid crystal display element 10 is such that the incident angle of effective incident light incident from obliquely above the display surface is an arbitrary angle within the range of 20 ° to 30 °. It may be designed according to.

FIG. 9 is a schematic constitutional view of a liquid crystal display element showing a second embodiment of the present invention. This embodiment shows effective incidence of reflected light of light incident obliquely above the display surface. This is an example in which the incident angle of light is 20 °.

The liquid crystal display element 10 of this example is different from the first embodiment in the alignment state of the liquid crystal molecules of the liquid crystal cell 11 and the orientation of the transmission axes 21, 22 of the polarizing plates 21, 22. Since the configuration is the same as that of the first embodiment, the duplicated description will be omitted by giving the same reference numerals to the drawings.

In the liquid crystal display element 20 of this embodiment in which the incident angle of the effective incident light observed by the observer is 20 °, the alignment direction 13a of liquid crystal molecules in the vicinity of the rear substrate 13 of the liquid crystal cell 11 is It is set in the direction like.

That is, as shown in FIG. 9, the liquid crystal cell 1
Alignment direction 1 of liquid crystal molecules in the vicinity of the rear substrate 1
3a is in a direction deviated from the horizontal axis x of the display surface by 10 ° counterclockwise when viewed from the front direction.

In this embodiment, the alignment direction 12a of the liquid crystal molecules near the front substrate 12 of the liquid crystal cell 11 is set.
Depending on the alignment direction 13a of the liquid crystal molecules in the vicinity of the rear substrate 13, a direction deviated from the alignment direction 13a by 90 ° counterclockwise as viewed from the front direction, that is, on the horizontal axis x of the display surface. On the other hand, when viewed from the front direction, it is almost 100 counterclockwise.
The liquid crystal molecules are twisted by about 90 ° clockwise when viewed from the front side from the rear side substrate 13 toward the front side substrate 12 with reference to the alignment direction 13a in the vicinity of the rear side substrate 13 as a reference. It is twisted at the corners.

Further, this liquid crystal display element 10 is for displaying in a normally white mode, and the pair of front and rear polarizing plates 21 and 22 have their transmission axes 21a and 22a as shown in FIG. The transmission axes 21a and 22a are substantially orthogonal to each other, and the transmission axes 21a and 22a thereof are substantially parallel to or orthogonal to the liquid crystal molecule alignment directions 12a and 13a in the vicinity of the front substrate 12 and the back substrate 13 of the liquid crystal cell 11 (parallel directions in the figure). It is arranged toward.

FIG. 10 shows the effective incident angle of the reflected light of the light incident obliquely above the display surface between the liquid crystal display element 10 of the second embodiment and the conventional liquid crystal display device 1. Shows the incident direction of the light transmitted with high transmittance when is 20 °.

First, the conventional liquid crystal display element 1 shown in FIG. 10A will be described. When light is incident on the liquid crystal display element 1 at an incident angle of 20 °, the liquid crystal display element 1 transmits with high transmittance. The incident direction of light is approximately 20 °. It should be noted that this incident direction is a direction determined by the measurement method shown in FIG. 6 with the incident angle of light on the liquid crystal display element 1 being 20 °.

On the other hand, in the liquid crystal display element 10 of the second embodiment, as can be seen by comparing (a) and (b) of FIG. The state differs from the liquid crystal cell 2 of the conventional liquid crystal display element 1 by approximately 55 ° counterclockwise when viewed from the front direction.

Therefore, in the liquid crystal display element 10, the incident direction of the light transmitted with the highest transmittance is the liquid crystal display element 1.
(B) of FIG. 10 when the angle of incidence of light on is 20 °.
As shown in FIG.

Therefore, the liquid crystal display element 10 of the second embodiment has the highest transmittance of incident light, which is light from obliquely above the display surface, when the display is observed from the normal observation direction. Since the intensity of the effective incident light, that is, the emitted light of the reflected light of the light incident obliquely above the display surface is increased, the display observed from the normal observation direction can be made sufficiently bright.

Further, the viewing angle of the liquid crystal display element 10 of this embodiment is the left when viewed from the front side with respect to the direction of the viewing angle of the conventional liquid crystal display element 1, that is, the direction directly below the display surface (direction of 270 °). There is a direction shifted by approximately 55 °, but this direction is the diagonally lower right direction of the display surface when viewed from the direction perpendicular to the display surface. If the viewing angle direction is in this direction, the normal viewing direction, that is, The display contrast observed from a direction slightly inclined to the lower edge direction of the display surface rather than the direction perpendicular to the display surface is not so much as compared with the conventional liquid crystal display element whose viewing angle is directly below the display surface. Therefore, it is possible to secure a sufficiently satisfactory contrast.

The second embodiment is an example in which the effective incident angle of the incident light observed by the observer of the reflected light of the light incident obliquely above the display surface is 20 °. As described above, in most cases, effective incident light is almost 2 in the upper edge direction of the display surface with respect to the direction perpendicular to the display surface.
Since the light is incident at an inclination angle within an angle range of 0 ° to approximately 30 °, the alignment state of the liquid crystal molecules of the liquid crystal cell 11 of the liquid crystal display element 10 is changed from the alignment state of the first embodiment to the second alignment state. It may be arbitrarily selected within the range up to the alignment state of the embodiment.

The alignment state is such that the alignment direction 13a of the liquid crystal molecules in the vicinity of the rear substrate 13 is within an angle range of approximately 10 ° to approximately 25 ° counterclockwise with respect to the horizontal axis x of the display surface when viewed from the front direction. In this state, the liquid crystal molecules are twisted from the rear substrate 13 toward the front substrate 12 in a clockwise direction when viewed from the front direction with a twist angle of about 90 ° with reference to the alignment direction 13a.

This alignment state is a more desirable example, and the alignment direction 13 in the vicinity of both substrates 12 and 13 is the same.
Even if there is a deviation of about 5 ° between a and 13b, the above-mentioned first
Since the same effect as in the second embodiment can be obtained, the alignment state of the liquid crystal molecules is such that the alignment direction 13a in the vicinity of the rear substrate 13 is counterclockwise when viewed from the front direction with respect to the horizontal axis x of the display surface. It is a direction within an angle range of 5 ° to 30 °, and the liquid crystal molecules are directed from the rear substrate 13 to the front substrate 12 in the clockwise direction when viewed from the front face direction with reference to the alignment direction 13a.
It may be in a twisted orientation with a twist angle of 0 °.

Further, the alignment state of the liquid crystal molecules is such that the alignment direction 13a in the vicinity of the rear substrate 13 is in an angle range larger than 0 ° and smaller than 45 ° counterclockwise with respect to the horizontal axis x of the display surface when viewed from the front direction. And the orientation direction 13a
Liquid crystal molecules from the rear substrate 13 to the front substrate 12 with reference to
It may be in a twisted orientation with a twist angle of about 90 ° clockwise when viewed from the front side toward the front side. If the orientation state of the liquid crystal molecules is set within this range, the display observed from the normal viewing direction is displayed. While ensuring a sufficiently satisfactory contrast, it can be made sufficiently bright as compared with the conventional liquid crystal display device.

The reflecting plate 23 used in the liquid crystal display element 10 of the first and second embodiments described above has a reflecting characteristic having directivity as shown in FIG. It may be omnidirectional.

Furthermore, the liquid crystal display element 10 of the above embodiment.
Is a color liquid crystal display device in which the liquid crystal cell 11 is provided with a color filter, but the present invention can also be applied to a reflective TN liquid crystal display device for displaying black and white.

Further, the present invention is not limited to the one using the active matrix type liquid crystal cell, but a plurality of scanning electrodes along one direction are provided in parallel to each other on the inner surface of one substrate, and the scanning electrodes are formed on the inner surface of the other substrate. A simple matrix system in which a plurality of signal electrodes are provided in parallel with each other in a direction intersecting with the scanning electrodes, or a plurality of segment electrodes having a shape corresponding to a display pattern is provided on the inner surface of one substrate and a common electrode is provided on the inner surface of the other substrate. It can also be applied to a liquid crystal display element using a segment type liquid crystal cell provided with electrodes.

[0092]

According to the liquid crystal display device of the present invention, the liquid crystal molecules of the liquid crystal cell having the liquid crystal layer between the front and rear substrates are:
Near the rear substrate of the pair of substrates, 0 ° counterclockwise with respect to the horizontal axis of the display surface of the display element when viewed from the front direction.
It is oriented in an angle range larger than 45 ° and smaller than 45 °, and with the orientation direction as a reference, it extends from the rear side substrate to the front side substrate in a clockwise direction when viewed from the front side and is approximately 90 °.
Since it is twisted with a twist angle of °,
Even with a reflective TN liquid crystal display device, a display viewed from a normal viewing direction can be sufficiently brightened while ensuring a sufficiently satisfactory contrast.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a liquid crystal display element showing a first embodiment of the present invention.

FIG. 2 is a sectional view of the liquid crystal display element.

FIG. 3 is a diagram showing a method for measuring a reflection characteristic of a reflection plate.

FIG. 4 is a reflection characteristic diagram of a reflection plate measured by the method shown in FIG.

FIG. 5 is a diagram showing incident directions of light transmitted with high transmittance for the liquid crystal display element of the first embodiment and the conventional liquid crystal display device, respectively.

FIG. 6 is a diagram showing a method for measuring the transmittance of a liquid crystal display element.

7 is an incident direction-transmittance characteristic diagram of a conventional liquid crystal display element measured by the method of FIG.

FIG. 8 is a diagram showing two front luminance measurement methods performed to compare the brightness of the display observed from the normal observation direction with the liquid crystal display element of the first embodiment and the conventional liquid crystal display element.

FIG. 9 is a schematic configuration diagram of a liquid crystal display element showing a second embodiment of the present invention.

FIG. 10 is a diagram showing incident directions of light transmitted with high transmittance for the liquid crystal display element of the second embodiment and the conventional liquid crystal display device.

FIG. 11 is a schematic configuration diagram of a conventional liquid crystal display element.

[Explanation of symbols]

10 ... Liquid crystal display element 11 ... Liquid crystal cell 12a ... Orientation direction of liquid crystal molecules near the front substrate 13a ... Alignment direction of liquid crystal molecules near the rear substrate 21, 22 ... Polarizing plate 21a, 22b ... Transmission axis 23 ... Reflector

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Claims (4)

(57) [Claims] 1. A reflective twisted nematic liquid crystal display device, wherein liquid crystal molecules of a liquid crystal cell having a liquid crystal layer provided between a pair of front and rear substrates have display molecules near the rear substrate of the pair of substrates. Is oriented counterclockwise with respect to the horizontal axis of the display surface in a direction within an angle range of more than 0 ° and less than 45 ° when viewed from the front side, and the front side is directed from the rear substrate to the front substrate with reference to the orientation direction. A liquid crystal display element, which is twist-oriented at a twist angle of approximately 90 ° clockwise when viewed from the direction. 2. The alignment direction of liquid crystal molecules in the vicinity of the rear substrate is 5 ° counterclockwise with respect to the horizontal axis when viewed from the front direction.
The liquid crystal display element according to claim 1, wherein the liquid crystal display element has a direction within an angle range of -30 °. 3. The alignment direction of the liquid crystal molecules near the rear substrate is a direction within an angle range of approximately 10 ° to approximately 25 ° counterclockwise with respect to the horizontal axis when viewed from the front direction. The liquid crystal display element according to claim 1. 4. The liquid crystal display element according to claim 1, wherein the liquid crystal cell includes a color filter.