JPH07311376A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide a liquid crystal display device which has less dependency on visual angles and executes bright display. CONSTITUTION:This liquid crystal display device is provided with a light introducing means 2 for introducing parallel light perpendicularly to a liquid crystal layer of a prescribed thickness and a light leading out means 3 for diffusing the light emitted from a liquid crystal cell 1. A luminous flux guides the light to the liquid crystal cell 1 in the range equal to or smaller or than a pixel to be impressed with an electric field. The light is collected at the pixels of the liquid crystal cell 1 and is diffused on the observer side of the liquid crystal cell 1 when the liquid crystal cell 1 is provided with a surface illuminating means on its rear surface. The liquid crystal cell 1, in the case of the liquid crystal cell having double refractive anisotropy, is provided with a lens assembly for condensing the light to an area of <=80 to >=40% of the pixel area, an optical means laminated on the liquid crystal cell 1 so as to approximately eliminate the coloration by the double refractiveness of the liquid crystal cell 1 and the light leading out means 3 which is arranged on the observer side of the liquid crystal cell 1 and diffuses the light. As a result, the light is converged to the pixel parts with respect to the liquid crystal layer 10 and has no dependency on the visual angles for the observer.

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 a high light utilization efficiency and a wide viewing angle.

[0002]

2. Description of the Related Art Conventionally, in a display device using a liquid crystal cell, the utilization efficiency of light is low, and moreover, the viewing angle, which is an observation direction in which a certain degree of contrast and brightness are obtained, is limited. That is, even if the display is observed from the front, the display tends to be dark, and in a large screen, it is observed from an oblique direction with respect to the display peripheral portion, so that there is a drawback that the contrast is lowered or the contrast is inverted. Such a large viewing angle limitation is said to have a high viewing angle dependency.

For such a liquid crystal display, particularly in a projection type display, a fiber plate is used as in JP-A-4-43481, or a microlens is disclosed in JP-A-6-75212. Has been attempted to limit the luminous flux used for display.

[0004]

However, since the projection type display device projects an image, narrowing the light flux does not limit the viewing angle on the projection surface. Since the surface is directly observed as a display screen, if the light flux is narrowed down, the displayed contents cannot be read at all when observed from an oblique direction. Therefore, in a liquid crystal display device for directly observing such a display surface, even if a lens is used, it is best to dispose one layer of magnifying lens on the surface of the liquid crystal cell. Was not preferable because the light was dissipated and the contour of the pixel was unclear. Especially in the display mode using the birefringence of the liquid crystal, the screen becomes large because it is suitable for high time division driving, but since it depends on the light of a specific wavelength, the reversal of the contrast is likely to occur depending on the direction of the light, and if a lens is used, the viewing angle is increased. It was considered inappropriate because it was subject to restrictions.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and basically guides light substantially parallel to the pixels of the liquid crystal cell and reflects the light from the liquid crystal cell by the reflection surface. And a light derivation means composed of a concave lens array for diffusing the emitted light.

Therefore, according to the present invention, in the case of directly observing the liquid crystal which is the display surface, the light introducing means for guiding the light substantially parallel to the liquid crystal layer having the predetermined thickness and the light emitted from the liquid crystal cell. And a light derivation means for diffusing light.
The present invention also provides a light introducing unit that guides light in the thickness direction of the liquid crystal cell to a range substantially equal to or smaller than the pixel to which an electric field is applied, and a light deriving unit that expands the light of the pixel portion emitted from the liquid crystal cell. And are provided. Alternatively, a liquid crystal cell having aligned pixels, a surface illuminating means arranged on the back surface of the liquid crystal cell, a light introducing means for condensing light from the surface illuminating means onto the pixels of the liquid crystal cell, and an observer of the liquid crystal cell. And a light derivation means arranged on the side for diffusing light. The present invention provides a liquid crystal cell having aligned pixels and having a predetermined birefringence anisotropy when an electric field is applied or when no electric field is applied, and an area of each pixel arranged on the back surface of the liquid crystal cell.
A light introducing means composed of a lens assembly for condensing light in an area of 0% or less and 40% or more, an optical means laminated on the liquid crystal cell so as to substantially eliminate coloring due to birefringence of the liquid crystal cell, and a liquid crystal cell Is a liquid crystal display device provided with a light deriving unit arranged on the viewer side for diffusing light.

[0007]

As a result, the light concentrated in the pixel portion to which the electric field is applied is more preferably guided to the substantially parallel light in the region where the liquid crystal is moved by the electric field along the electro-optical change direction with respect to the display of the liquid crystal molecules. Since the light that has passed through the liquid crystal layer is expanded, the light is converged on the liquid crystal layer to the pixel portion that contributes to the display, and the light has a small viewing angle dependence on the observer.

[0008]

1 is a sectional view of a liquid crystal display device according to an embodiment of the present invention, in which 1 is a liquid crystal cell having a liquid crystal layer 10 having a predetermined thickness, and 2 is substantially perpendicular to the liquid crystal layer 10 of the liquid crystal cell 1. Reference numeral 3 is a light introducing means for guiding light parallel to each other, and 3 is a light guiding means for diffusing the light emitted from the liquid crystal cell 1.

In the liquid crystal display device according to the present invention,
Basically, when the light is guided to the pixel portion of the liquid crystal and is observed, the light is enlarged or diffused. Therefore, in a reflection type display device, a liquid crystal cell having aligned pixels and a liquid crystal layer of a predetermined thickness, a reflection surface arranged on the back surface of the liquid crystal cell, and a liquid crystal cell substantially parallel to the pixels of the liquid crystal cell. And a light derivation means including a concave lens array for guiding light and diffusing the light reflected by the reflecting surface and emitted from the liquid crystal cell. Based on the configuration common to such a reflective display device and the transmissive display as shown in FIG. 1, a more detailed description will be given below with reference to FIG.

The liquid crystal cell 1 has, for example, 90 to 2 liquid crystal molecules.
A so-called twisted nematic liquid crystal layer 10 arranged in a spiral form of 70 degrees is supported by a substrate 11 provided with electrodes 12 for applying an electric field for each pixel so as to be orthogonal to the inner surface. When the liquid crystal cell 1 needs the polarizing plate 13,
It is simple and preferable to be attached on the front and rear sides of the substrate 11, but if the light scattering of the polarizing plate has a significant influence when focusing the light introducing means 2 and the light deriving means 3, as will be described later, It is preferable to dispose a polarizing plate outside the light introducing means 2 and the light deriving means 3.

The light introducing means 2 comprises a convex lens array 20 arranged for each pixel, and if necessary, a transparent flat plate 21 such as acrylic resin or optical glass as shown in FIG. The microlens 22 may be formed of a transparent material having a different refractive index such as silver.
When the light flux cannot be sufficiently reduced by the convex lens array, the light introducing unit 2 may be configured by a flat convex lens array, a laminated body of the convex lens array and the concave lens array, or a laminated body of a plurality of the convex lens array and the concave lens array. Further, when the pixels are composed of the three primary colors of RGB, each of such lenses may be associated with each of the pixels for each color.
One lens may be associated with one RGB set. When using such a convex lens array 20, it is most desirable to arrange the liquid crystal layer 10 so as to be substantially at the focal position.

The light deriving means 3 comprises a concave lens array 30 arranged for each pixel, and if necessary, like the light introducing means 2, a transparent flat plate such as acrylic resin or optical glass is provided with silicon or epoxy resin. The microlenses may be formed of transparent materials having different refractive indexes such as silver chloride. Further, in the case where the pixel has a structure of three primary colors of RGB, each of such lenses may correspond to each pixel of each color, or one lens may be provided for one set of RGB. It may be associated. When using such a concave lens array 30, it is most desirable to arrange the liquid crystal layer 10 so as to be substantially at the focal position thereof.

With such a structure, the light flux is converged on the region of the liquid crystal layer in which the liquid crystal molecules are driven, and the light flux emitted from the liquid crystal layer is expanded and diffused. The light guided to the liquid crystal is
In the liquid crystal molecule region that is not driven, that is, in the gap between pixels, conventionally, light is simply shielded, but in the present invention, the light is also guided to the pixel portion and contributes to the display. Therefore, although the light utilization efficiency can be improved, this is almost equal to the liquid crystal portion sandwiched between the electrodes for applying an electric field, that is, the pixel of the liquid crystal by the light introducing means 2 or is substantially equal to the pixel. It is most efficient to guide the light in the thickness direction of the liquid crystal cell in the range smaller than the pixel.

Next, as shown in FIG. 3, when the surface illuminating means 4 is provided on the back surface of the liquid crystal cell 15, the light of the surface illuminating means 4 is turned on / off independently by the pixel 15a of the liquid crystal cell 15 (the electrodes are opposed to each other. Light introducing means 25 for condensing light in a region (turned off)
And a light derivation means 35 arranged on the viewer side of the liquid crystal cell 15 for diffusing light. The surface illuminating means 4 includes, for example, a light guide plate 41 such as an acrylic resin flat plate, a linear light source 42 formed on a side surface of the light guide plate 41 and including a cold cathode tube, and the like.
It comprises a surface light diffusing sheet, a light diffusing lens or a back surface reflecting sheet provided on the light guide plate as required, or a tubular reflecting sheet for covering the linear light source (neither is shown). The light introducing means 25 needs a light collecting means adapted to emit the light of the surface illuminating means 4 in order to collect the light of the light guide plate 41 on the pixel 15a of the liquid crystal cell 15, and the light introducing means 25 substantially covers the entire surface from the light guide plate 41. If uniform light is emitted, a convex lens array may be used so that the liquid crystal layer 10 is at its focal position. On the other hand, a light guide plate laminated type or sawtooth light guide plate type illuminating means or liquid crystal cell 1 for gradually dispersing light.
In the direct type illumination in which the light source is arranged directly below 5, a concave lens is arranged for the light source or the pseudo light source,
It may be a compound lens array in which a convex lens is used for a place where there is no light source or pseudo light source. The light deriving means 35 may be composed of a concave lens array as in the previous embodiment. As a result, a display device having a brightness of 1.5 to 5 times and a viewing angle of 1.1 to 10 times that of the related art was obtained.

If the liquid crystal utilizes birefringence anisotropy, the convex lens array and the concave lens array may be used as they are as in the above example, but light of a specific wavelength is used for display. And that the contrast is inverted depending on the viewing angle. Therefore, as shown in FIG. 4, a liquid crystal cell 1 having aligned pixels and having a predetermined birefringence anisotropy when an electric field is applied or when no electric field is applied.
For 6, the light introducing means 26, which is arranged on the back surface of the liquid crystal cell 16 and includes a lens assembly for collecting light in an area of 80% or less and 40% or more of the area of each pixel, and the liquid crystal cell 1
6, a uniaxially stretched film laminated on the liquid crystal cell so as to substantially eliminate the coloring due to the birefringence of No. 6, a phase film, or an optical means 17 such as an nλ wavelength plate, and the liquid crystal cell 1.
Light deriving means 3 arranged on the observer side of 6 for diffusing light
6 and 6 are used.

Although the convex lens array described in the previous embodiment can be used as the light introducing means 26, in this embodiment, a light guide assembly having different end faces is provided, for example, a fiber array having a wide entrance side and a narrow liquid crystal cell side. Is shown.
When such a light introducing means 26 is used in this embodiment and the previous embodiments, the light beam becomes a substantially parallel light beam depending on the length of the fiber, or if the light beam is far from the liquid crystal layer only by narrowing the light beam, Since the light flux spreads, the light deriving means 3, 35, 36 may use a concave lens, a convex lens, or a Fresnel light diffusing lens sheet or the like according to the spread of the light flux.

In the liquid crystal cell 16, the pixel 16a has a portion having no electrode 18 between the pixel 16a and the adjacent pixel 16b, as shown in FIG. And for such a pixel 16a,
The pixel portion to which an electric field is actually applied is usually 90% or less, but there is a point that must be taken into consideration when guiding a light beam, unlike when guiding natural light. The reason for this is that if there is a lot of light in the area where the pixels are adjacent to each other, the contours of the pixels become unclear, and if it is attempted to concentrate the light flux only on the central part of the pixels, the lens is arranged in the vicinity of the liquid crystal layer 10, so that the lens shown in FIG. Since a large amount of light is obliquely guided like the light a, the influence of birefringence of the liquid crystal layer becomes large, and the predetermined hue, and further, the drive voltage for transmitting and blocking light deviates from the predetermined value.
Therefore, the light introducing means 26 is not more than 80% of the area of each pixel rather than guiding the light parallel to the liquid crystal layer of the pixel.
% Or more, and more preferably 78% or less and 60% or more in order to perform bright and clear display.
As a result, the present invention has a viewing angle of 15 ° to 50 ° with respect to a liquid crystal display device having a vertical viewing angle of 5 ° with respect to a contrast of 1: 2 or more, and a wide viewing field with a contrast of 1: 5. I got the horn.

[0018]

As described above, according to the present invention, light can be effectively used and the viewing angle dependency can be reduced.

[Brief description of drawings]

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

FIG. 2 is a sectional view of another light introducing means applicable to the present invention.

FIG. 3 is a cross-sectional view of a liquid crystal display device according to another embodiment of the present invention.

FIG. 4 is a sectional view of a liquid crystal display according to another embodiment of the present invention.

FIG. 5 is an explanatory diagram of pixels of a liquid crystal cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid crystal cell 2 Light introducing means 3 Light deriving means 15 Liquid crystal cell 25 Light introducing means 35 Light deriving means 16 Liquid crystal cell 17 Optical means 26 Light introducing means 36 Light deriving means

Claims (5)

[Claims] 1. A liquid crystal cell having a liquid crystal layer of a predetermined thickness, a light introducing means for guiding light substantially parallel to a liquid crystal layer of the liquid crystal cell, and a light diffused from the liquid crystal cell. A liquid crystal display device comprising: 2. A liquid crystal cell having an electrode for applying an electric field for each pixel, and a light introducing means for guiding light in a thickness direction of the liquid crystal cell in a range substantially equal to or smaller than the pixel of the liquid crystal cell, A liquid crystal display device, comprising: a light derivation unit that expands light of a pixel portion emitted from the liquid crystal cell. 3. A liquid crystal cell having aligned pixels, a surface illuminating means arranged on the back surface of the liquid crystal cell, a light introducing means for condensing light of the surface illuminating means onto a pixel of the liquid crystal cell, and a liquid crystal cell. And a light derivation means for diffusing light, which is disposed on the observer side of the liquid crystal display device. 4. A liquid crystal cell having aligned pixels and having a predetermined birefringence anisotropy when an electric field is applied or when no electric field is applied,
A light-introducing means, which is arranged on the back surface of the liquid crystal cell and includes a lens assembly that collects light in an area of 80% or less and 40% or more of the area of each pixel, and substantially eliminates coloring due to birefringence of the liquid crystal cell. 2. A liquid crystal display device comprising: an optical unit laminated on the liquid crystal cell; and a light derivation unit disposed on the viewer side of the liquid crystal cell for diffusing light. 5. A liquid crystal cell having aligned pixels and a liquid crystal layer having a predetermined thickness, a reflecting surface arranged on the back surface of the liquid crystal cell, and a reflecting surface for guiding light substantially parallel to the pixels of the liquid crystal cell. 2. A liquid crystal display device, comprising: a light deriving unit including a concave lens array for diffusing light emitted from the liquid crystal cell and reflected by the liquid crystal cell.