JPH08166582A - Liquid crystal display - Google Patents

Abstract

(57) [Abstract] [Purpose] To significantly improve the display quality by improving the viewing angle characteristics of a liquid crystal display device. [Structure] The backlight 1 is provided with a prism sheet 2, and the prism sheet 2 is provided with a lower polarizing plate 3. The TN liquid crystal cell 4 is sandwiched between the upper polarizing plate 5 and the lower polarizing plate 3. The microlens array 6 is disposed on the panel viewing side of the upper polarizing plate. On the TN liquid crystal cell 4 in which two types of regions having different pretilt directions are formed on the inside of both substrates, a microlens array 6 in which unit constituent elements having circular optical anisotropy are formed in a matrix is provided on the viewing side of the panel. I placed it.
The polarizing plates 3 and 5 have their absorption axes orthogonal to each other so as to be normally white.

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,
More specifically, the present invention relates to a high quality liquid crystal display device in which the viewing angle characteristics of the liquid crystal display device are improved.

[0002]

2. Description of the Related Art A liquid crystal display device is a display device that changes the orientation of liquid crystal molecules in a liquid crystal layer sandwiched between a pair of substrates and utilizes the resulting change in the optical refractive index of the liquid crystal layer for display. Therefore, it is important that the liquid crystal molecules of the liquid crystal cell are initially aligned as regularly as possible. The alignment of the liquid crystal molecules is regulated by the surface state of the substrate forming the liquid crystal cell and the interaction between the liquid crystal molecules near the substrate surface.

The most widely used method for initially aligning liquid crystal molecules in a fixed direction is to apply a liquid crystal alignment film material on the surfaces of a pair of substrates facing each other, and dry and cure the applied material. This is a method in which an alignment film is formed and the surface of the alignment film is rubbed to have alignment characteristics. Since the rubbing process is performed in a uniform direction on the substrate, the pretilt angles are all uniform in the liquid crystal cell. Therefore, the pretilt angle is uniform within each picture element.

Thin Film Transistor (TFT: Thin Film)
In a liquid crystal display device using a Transistor, a twisted nematic type (hereinafter abbreviated as TN type) liquid crystal is adopted. In this TN type liquid crystal display device, liquid crystal molecules are oriented so as to be twisted by 90 ° between both substrates. The viewing angle direction of the liquid crystal display device follows the direction of liquid crystal molecules in the liquid crystal layer.

A known document describing a conventional liquid crystal display device is, for example, JP-A-6-27454. The one disclosed in this publication is a liquid crystal display optical element in which a light shielding layer is provided on a part of the lens array surface of a lens array sheet, and the liquid crystal display optical element is provided on the observation surface side of a liquid crystal cell. As a result, the viewing angle of the liquid crystal display element is expanded, but the asymmetrical optical characteristics have not been resolved.

[0006]

In the TN type liquid crystal display device, since the liquid crystal molecules have anisotropy of refractive index, there is a phenomenon that the contrast changes depending on the angle at which the human (observer) looks at the liquid crystal display device. Occurs. Generally, in a normally white mode liquid crystal display device in which light is transmitted and white display is performed when no voltage is applied, the liquid crystal cell is directly above the liquid crystal display device (vertical direction to the substrate surface in a state where a voltage is applied). ), When the liquid crystal display screen is viewed, the light transmittance decreases as the applied voltage value increases, as indicated by the solid line L1 in FIG. The light transmittance of this liquid crystal cell becomes almost zero when reaching a certain value of the applied voltage, and remains almost zero when the applied voltage is further increased. However, when the viewing angle direction of the liquid crystal display device is changed, the applied voltage-transmittance characteristic changes. This will be described below with reference to FIGS. 10 and 11.

FIG. 10 and FIG. 11 are configuration diagrams of a liquid crystal cell sandwiched between a pair of substrates which are arranged to face each other.
Is a perspective view and FIG. 11 is a sectional view. In the figure, 41 and 42 are substrates, 41a and 42a are glass substrates, 41b and 42b are transparent electrodes, 42c is an alignment film, 43 is a rubbing direction of the substrate 41, 44 is a rubbing direction of the substrate 42, 45 is a liquid crystal molecule, 46. Is the normal viewing angle direction. One substrate 41 is a transparent electrode 41b formed on one surface of a glass substrate 41a.
And an alignment film 41c formed on the entire surface of the glass substrate 41a so as to cover the transparent electrode 41b. Also,
The other substrate 42 arranged to face the substrate 41 includes a glass substrate 42a, a transparent electrode 42b formed on a surface of the glass substrate 42a facing the substrate 41, and a transparent electrode 4b.
2b, and an alignment film 42c formed on the entire surface of the glass substrate 42a.

The liquid crystal molecules 45 in the liquid crystal cell are twisted by about 90 ° between the substrate 41 and the substrate 42. 10 and 11, the symbol δ indicates the tilt angle of the liquid crystal molecules 45 in contact with the alignment films 41c and 42c, that is, the pretilt angle, and the number 46 indicates the normal viewing angle direction.

When voltage is applied to such a liquid crystal cell and the viewing angle is inclined from the direction perpendicular to the substrate surface to the normal viewing angle direction 46, the applied voltage-transmittance characteristic changes from solid line L1 to solid line in FIG. The characteristics change as shown by L2. That is, the transmittance decreases as the applied voltage increases, but the black and white image (negative / positive) at a specific angle
The phenomenon in which is inverted (this is called the inversion phenomenon) occurs. This is a phenomenon that occurs because the liquid crystal molecules 45 in the liquid crystal layer are tilted at a tilt angle and the refractive index changes depending on the viewing angle. This phenomenon is a great obstacle to the viewer of the image.

12 (a) to 12 (c) are views showing a phenomenon in which the refractive index changes depending on the viewing angle. In FIG. 9 (a), when the applied voltage is zero, in FIG. 9 (b), the applied voltage is gradually changed. 9C shows the case where the applied voltage is further increased. In the figure, 47 is an observer, and other parts having the same functions as those in FIG. 11 are denoted by the same reference numerals.

As shown in FIG. 12A, when the applied voltage is zero or a relatively low voltage, the liquid crystal molecules 45 in the liquid crystal layer appear elliptical to the observer 47 positioned in the normal viewing angle direction. As the applied voltage is gradually increased, the major axis direction of the liquid crystal molecules 45 moves in the direction of the electric field (perpendicular to the substrate), and as shown in FIG. There is a moment when the molecule 45 can be seen right above. Further, when the voltage is increased, the liquid crystal molecules 45 become substantially parallel to the direction of the electric field, and the liquid crystal molecules 45 appear again to the observer 47 as an ellipse as shown in FIG.

Due to the same phenomenon, in the viewing angle directions other than the normal viewing angle direction 46, due to the difference in the applied voltage-transmittance characteristic, even if the inversion phenomenon does not occur, the black and white contrast is increased as the viewing angle is deepened. The viewing angle characteristic that the ratio becomes smaller appears. Such a reversal phenomenon in the normal viewing angle direction and a decrease in the contrast ratio in the viewing angle direction other than the normal viewing angle direction in the TN type liquid crystal display device are a great obstacle for the viewer, resulting in deterioration of the display characteristics themselves of the liquid crystal display device. Becomes

Regarding the technique for obtaining a liquid crystal display device in which such a viewing angle phenomenon is improved, see "JAPAN DISPLA".
Y "(1992, p591-p594 and p886)
Then, after rubbing the surface of the alignment film in one direction, a part of the surface is covered with a resist and then in the opposite direction to the rubbing direction previously performed, and then the resist is removed and covered with a resist. The rubbing direction is made different between the region covered with the resist and the region not covered with the resist, whereby two regions, the normal viewing angle direction and the reverse viewing angle direction, are formed in the same cell. In this case, the viewing angle characteristics in the two directions appear to be mixed, and the reversal phenomenon in the normal viewing angle direction and the sharp decrease in the contrast in the reverse viewing angle direction are alleviated and improved. However, with the above method, the viewing angle characteristics in the normal viewing angle direction and the reverse viewing angle direction are made uniform, but the viewing angle characteristics in all viewing angle directions and the effective viewing angle are not widened sufficiently. .

The present invention has been made in view of the above circumstances, and an object thereof is to provide a liquid crystal display device in which the display quality is significantly improved by improving the viewing angle characteristics of the liquid crystal display device.

[0015]

In order to solve the above-mentioned problems, the present invention has (1) a pair of substrates arranged to face each other, and an alignment film formed on each of the facing surfaces of the substrates. ,
At least one of the alignment films of the substrate has a plurality of alignment characteristics, and a microlens array is arranged on the panel viewing surface side in a liquid crystal cell in which liquid crystal is sealed, or (2)
In a liquid crystal cell having a pair of substrates arranged to face each other and a liquid crystal cell in which liquid crystal is sealed in the substrate, and a plurality of regions in which the directions of liquid crystal molecules are the same in the screen opening,
The microlens array is arranged on the panel viewing surface side, and (3) in (1) or (2) above, the unit component of the microlens array has circular and elliptical optical anisotropy. And (4) in (1) or (2), the unit constituent element of the microlens array has linear optical anisotropy, Arranged in a plane and three-dimensionally, and further, (5) in (1) or (2), a plurality of the microlens arrays having the same shape or different shapes are laminated and arranged on the panel viewing surface side. It is characterized by what was done.

[0016]

In the liquid crystal display device of the present invention having the above structure, the viewing angle characteristics of the liquid crystal cell can be greatly improved by disposing the microlens array on the panel viewing surface side of the liquid crystal cell.
The optical effect of the microlens array will be described with reference to FIGS. 7 and 8. In the figure, 21 and 31 are backlights and 2
2 and 32 are prism sheets, 23 and 33 are lower polarizing plates,
24 and 34 are liquid crystal cells, 25 and 35 are upper polarizing plates, and 36.
Is a microlens array optical element.

Normally, the angle of the exit angle from the liquid crystal cell is determined by the angle of the incident light to the liquid crystal cell, although it is slightly affected by refraction, reflection and scattering. That is, as shown in FIG. 7, the light from the backlight 21 condensed by the prism sheet 22 into a component perpendicular to the panel surface is emitted after passing through the liquid crystal cell 24. In the liquid crystal display device of the present invention, as shown in FIG. 8, after the light condensed by the prism sheet 32 into the component perpendicular to the panel surface passes through the liquid crystal cell 34, it is emitted by the microlens array 36 at a wide angle. It As a result, even when the liquid crystal display screen is obliquely observed, the optical component having the applied voltage-transmittance characteristic mainly in the vertical direction component of the liquid crystal cell 34 is observed. Therefore, the change in applied voltage-transmittance characteristic as described above, which occurs when the viewing angle direction for viewing the liquid crystal display screen is changed, can be significantly improved.

(1) In the invention according to claim 1, an alignment film is formed on each of the opposing surfaces of a pair of substrates arranged to face each other, and at least one alignment film of the substrate has a plurality of alignment characteristics. Since the microlens array is placed on the panel viewing surface side in the liquid crystal cell in which the liquid crystal is enclosed, the change in applied voltage-transmittance characteristic that occurs when the viewing angle direction for viewing the liquid crystal display screen is changed can be significantly improved. . (2) In the invention according to claim 2, the liquid crystal has a liquid crystal cell in which liquid crystal is sealed in a pair of substrates which are opposed to each other, and a plurality of regions in which the directions of liquid crystal molecules are the same in the screen opening are present. Since the microlens array is arranged in the cell on the side where the panel is viewed, the microlens array can widen the effective viewing angle in any direction. (3) In the invention according to claim 3, since the unit constituent elements of the microlens array have circular and elliptical optical anisotropies and are arranged in a plane and three-dimensionally, the microlens array can be arbitrarily selected. It is possible to widen the effective viewing angle in the direction. (4) In the invention according to claim 4, the unit constituent element of the microlens array has linear optical anisotropy,
Since they are arranged two-dimensionally and three-dimensionally, it is possible to widen the effective viewing angle in any direction by the microlens array. (5) In the invention according to claim 5, since a plurality of the microlens arrays having the same shape and different shapes are laminated and arranged on both sides of the panel visually recognized, the effective viewing angle can be widened in any direction by the microlens array. Is possible.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram for explaining an embodiment of a liquid crystal display device according to the present invention. In the figure, 1 is a backlight, 2 is a prism sheet, 3 is a lower polarizing plate, and 4 is TN.
(Twisted Nematic) liquid crystal cell, 5 is upper polarizing plate, 6
Is a microlens array.

A prism sheet 2 is provided on the backlight 1, and a lower polarizing plate 3 is provided on the prism sheet 2. The TN liquid crystal cell 4 is sandwiched between the upper polarizing plate 5 and the lower polarizing plate 3. The microlens array 6 is disposed on the panel viewing side of the upper polarizing plate. That is, in the liquid crystal display device of Example 1, in the TN liquid crystal cell 4 in which two types of regions having different pretilt directions are formed inside both substrates, unit constituent elements having a circular optical anisotropy are arranged in a matrix. The formed microlens array 6 was arranged on the viewing side of the panel. In FIG. 1, the absorption axes of the polarizing plates 3 and 5 are orthogonal to each other so as to be normally white.

FIG. 2 is a schematic diagram showing changes in the transmitted light component of the microlens array. In the microlens array 6 of Example 1, the incident light component is refracted as shown,
A transmitted light component having an angle near the vertical direction is circularly changed to a wide angle and emitted. FIG. 3 is a diagram schematically showing a part of a cross section for showing the alignment state of liquid crystal molecules of a TN type liquid crystal cell, in which 7 is a base substrate, 8 is a transparent electrode, 9 is an alignment film, and 10 is an alignment film. A counter substrate, 11 is a transparent electrode, 12 is an alignment film, 13 is a liquid crystal layer, and 13a is a liquid crystal molecule. Elements such as various switching elements and electric wiring are not shown because they are not directly related to the gist of the present invention.

The combined area of the ranges shown by A and B in FIG. 3 is one picture element area. In this liquid crystal cell, as shown in FIG. 3, a transparent electrode 8 is formed on the entire surface of a base substrate 7. An alignment film 9 is formed on the surface of the transparent electrode 8. A transparent electrode 11 is formed on the entire facing surface of a transparent counter substrate 10 arranged to face the base substrate 7, and the alignment film 12 is formed over the entire surface of the counter substrate 10 so as to cover the transparent electrode 11. Are formed. Both boards 7,
A liquid crystal layer 13 is sandwiched between the layers 10. Alignment film 9,1
Each of the liquid crystal molecules 2 is subjected to an alignment treatment, and the pretilt angle δ of the liquid crystal molecules 13a is formed as shown in FIG. In the first embodiment, the pitch of one picture element is 150 μm, and the pitch of the microlens array 6 is 70 μm.

FIG. 4 is a diagram showing the optical characteristics of the liquid crystal display device of the first embodiment. The solid line A shows the angle at which the black and white reversal of the image of Example 1 starts, and the broken line B shows the angle at which the black and white reversal of the image starts when the microlens array is not used.

In the liquid crystal display device of Example 2, unit components having linear optical anisotropy are formed in stripes in a liquid crystal cell in which two types of regions having different pretilt directions are formed inside both substrates. The microlens array 6 was placed on the viewing side of the panel. The schematic view of the liquid crystal display device according to the second embodiment is similar to that of the first embodiment, and the microlens array 6 is arranged so that the stripe-shaped arrangement is in the horizontal direction.

FIG. 5 is a schematic diagram of changes in the transmitted light component of the microlens array. In the microlens array 6 of this embodiment, the incident light component is refracted as shown in the figure, and the component having an angle in the vicinity of the vertical direction is linearly changed to a wide angle and emitted. The alignment state of the liquid crystal molecules of the liquid crystal cell is the same as that in the second embodiment. In the second embodiment, the pitch of the microlens array 6 is set to 70 μm while the pitch of one picture element is 150 μm.

FIG. 6 is a diagram showing the optical characteristics of the liquid crystal display device of the second embodiment. The solid line C indicates the angle at which the black-and-white reversal of the image of Example 2 starts, and the broken line D indicates the angle at which the black-and-white reversal of the image starts when the microlens array is not used.

Although the above-mentioned embodiment is applied to the liquid crystal display device of the TN type active matrix drive system, the present invention is not limited to this and can be applied to liquid crystal display devices of other modes. Further, the present invention can be applied not only to the active matrix driving type but also to a duty driving type liquid crystal display device and the like. Further, the pitch, shape, arrangement, etc. of the microlens array 6 are not limited to this, and can be set according to the purpose of the liquid crystal display device and the optical design.

As described above, in the liquid crystal display device of the present invention,
Light condensed into a component perpendicular to the panel surface by the prism sheet 2 passes through the TN liquid crystal cell 4, and then is emitted by the microlens array 6 at a wide angle. As a result, even when observing the liquid crystal display screen from an angle,
An optical component having an applied voltage-transmittance characteristic mainly in the vertical direction component of the TN liquid crystal cell 4 is observed. Therefore, the change in applied voltage-transmittance characteristic as described above, which occurs when the viewing angle direction for viewing the liquid crystal display screen is changed, can be significantly improved.

As described above, the liquid crystal display device of the present invention has a pair of substrates arranged to face each other, and an alignment film formed on each of the facing surfaces of the pair of substrates, and at least the pair of substrates. In a liquid crystal display panel in which one alignment film has a plurality of alignment characteristics, and between the pair of substrates, there are areas where different alignment characteristics face each other and areas where the same alignment characteristics face each other, the microlens array is placed on the panel viewing surface side. In the arranged liquid crystal display device, (1) a unit constituent element of the microlens array has a circular optical anisotropy.
(2) Each unit element of the microlens array has an elliptical optical anisotropy. (3) The unit constituent elements of the microlens array have linear optical anisotropy.

Further, the liquid crystal display device of the present invention comprises a pair of substrates arranged to face each other, and a liquid crystal cell in which liquid crystal is sealed in a gap between the facing surfaces of the pair of substrates. A liquid crystal display panel in which a microlens array is disposed on the panel viewing surface side of a liquid crystal display panel having a plurality of similar regions, and (4) the unit constituent element of the microlens array is a circular optical anisotropic element. Have sex. (5) The unit constituent element of the microlens array has an elliptical optical anisotropy. (6) Each unit constituent element of the microlens array has a linear optical anisotropy.

[0031]

As is apparent from the above description, the present invention has the following effects. (1) Effects corresponding to claims 1 to 5: (1) After making the rising direction of the liquid crystal molecules in a plurality of different directions within one picture element,
Furthermore, the microlens array makes it possible to widen the effective viewing angle in any direction. Therefore,
The inversion phenomenon and the change in contrast caused by the viewing angle of the liquid crystal display device, which are serious problems in the display characteristics of the liquid crystal display device, can be almost eliminated, and excellent display characteristics can be provided. (2) Effect corresponding to claim 1: A pair of substrates arranged to face each other and an alignment film formed on each of the facing surfaces of the substrates, at least one of the alignment films having a plurality of alignments. Since a microlens array is placed on the panel viewing surface side in a liquid crystal cell that has characteristics and in which liquid crystal is sealed, the applied voltage that occurs when the viewing angle direction for viewing the liquid crystal display screen is changed.
It is possible to significantly improve the change in the transmittance characteristics, and it is possible to make the viewing angle characteristics uniform in all viewing angle directions and widen the effective viewing angle. (3) Effect corresponding to claim 2: Having a pair of substrates arranged to face each other, and a liquid crystal cell in which liquid crystal is sealed in the substrates,
Since the microlens array is placed on the panel viewing surface side in the liquid crystal cell in which there are multiple regions where the liquid crystal molecules are in the same direction in the screen opening, the reversal phenomenon and the change in contrast caused by the viewing angle of the liquid crystal display device. Therefore, the viewing angle characteristics and display quality of the liquid crystal display device can be significantly improved. (4) Effect corresponding to claim 3: Since the unit constituent elements of the microlens array have circular and elliptical optical anisotropies and are arranged in a plane and three-dimensionally, any microlens array can be used. It is possible to widen the effective viewing angle in the direction. (5) Effect corresponding to claim 4: Since the unit constituent elements of the microlens array have linear optical anisotropy and are arranged in a plane and three-dimensionally, the microlens array can be arranged in any direction. It is possible to widen the effective viewing angle. (6) Effect corresponding to claim 5: Since the plurality of microlens arrays having the same shape and different shapes are laminated and arranged on the panel viewing surface side, the effective viewing angle in any direction by the microlens array Can be extended.

[Brief description of drawings]

FIG. 1 is a configuration diagram for explaining an embodiment of a liquid crystal display device according to the present invention.

FIG. 2 is a schematic diagram showing changes in transmitted light components of a microlens array according to the present invention.

FIG. 3 is a partial cross-sectional view showing an alignment state of liquid crystal molecules of a TN type liquid crystal cell in the present invention.

FIG. 4 is a diagram showing optical characteristics of the liquid crystal display device according to the present invention.

FIG. 5 is a schematic diagram showing changes in transmitted light components of the microlens array in the present invention.

FIG. 6 is a diagram showing optical characteristics of the liquid crystal display device according to the present invention.

FIG. 7 is a diagram showing a conventional example for explaining an optical effect of the microlens array in the present invention.

FIG. 8 is a diagram for explaining an optical effect of the microlens array in the present invention.

FIG. 9 is a graph showing a transmittance characteristic of an applied voltage in a conventional liquid crystal display device.

FIG. 10 is a perspective view for explaining viewing angle characteristics in a conventional liquid crystal display device.

FIG. 11 is a cross-sectional view for explaining viewing angle characteristics in a conventional liquid crystal display device.

FIG. 12 is a diagram showing a phenomenon in which the refractive index changes according to the conventional viewing angle.

[Explanation of symbols]

1 ... Backlight, 2 ... Prism sheet, 3 ... Lower polarizing plate, 4 ... TN liquid crystal cell, 5 ... Upper polarizing plate, 6 ... Microlens array, 7 ... Base substrate, 8 ... Transparent electrode, 9 ... Alignment film, 10 ... Counter substrate, 11 ... Transparent electrode, 12 ... Alignment film, 13 ... Liquid crystal layer 21, 31 ... Backlight, 22,
32 ... Prism sheet, 23, 33 ... Lower polarizing plate, 2
4, 34 ... Liquid crystal cell, 25, 35 ... Upper polarizing plate, 36 ...
Microlens array optical element, 41, 42 ... Substrate, 4
1a, 42a ... Glass substrate, 41b, 42b ... Transparent electrode, 42c ... Alignment film, 43, 44 ... Rubbing direction, 45
... liquid crystal molecule, 46 ... normal viewing angle direction, δ ... pretilt angle.

Claims (5)

[Claims] 1. A pair of substrates arranged to face each other, and an alignment film formed on each of the facing surfaces of the substrate, at least one alignment film of the substrate having a plurality of alignment characteristics,
A liquid crystal display device characterized in that a microlens array is disposed on the panel viewing surface side in a liquid crystal cell in which liquid crystal is sealed. 2. A liquid crystal cell having a pair of substrates arranged to face each other and a liquid crystal cell in which liquid crystals are sealed in the substrates, and a plurality of regions having the same direction of liquid crystal molecules in a screen opening. In addition, a liquid crystal display device characterized in that a microlens array is arranged on the panel viewing surface side. 3. The liquid crystal according to claim 1, wherein the unit constituent elements of the microlens array have circular and elliptical optical anisotropies, and are arranged in a planar shape and a three-dimensional shape. Display device. 4. The liquid crystal display device according to claim 1, wherein the unit constituent elements of the microlens array have linear optical anisotropy and are arranged in a plane and in a three-dimensional manner. . 5. The liquid crystal display device according to claim 1, wherein a plurality of the microlens arrays having the same shape or different shapes are laminated and arranged on the panel viewing surface side.