JP2913823B2 - Liquid crystal display device and driving method thereof - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device used for a display or the like and a driving method thereof.

[Conventional technology]

At present, as a display method of a liquid crystal display element most frequently used, there is a method using a twisted nematic effect. First, the liquid crystal display element used for this will be described. Two glass substrates with a transparent electrode, which have been subjected to an alignment treatment such as rubbing, are laminated so that the rubbing directions are orthogonal to each other, and a nematic liquid crystal is sandwiched therebetween. The liquid crystal has a twisted orientation in which the major axis of the molecule is parallel to the substrate and the substrate is 90 degrees between the two substrates. A polarizing plate is attached to both sides of the substrate such that the polarization directions thereof are parallel or perpendicular to each other to obtain a liquid crystal display device.

Next, the display principle will be described. It is assumed that the polarization directions of the two polarizing plates on both sides of the substrate are parallel to each other. When no voltage is applied to the liquid crystal, the linearly polarized light incident on the liquid crystal display element rotates 90 degrees along the twist of the liquid crystal molecules. Since the polarization directions of the laminated polarizing plates are parallel to each other, the rotated light cannot pass through the polarizing plate and is in a dark state. When a voltage is applied to the liquid crystal, the liquid crystal molecules rise vertically to the substrate, the molecules are untwisted, and the incident light maintains its polarization state. For this reason, it passes through the polarizing plate,
It becomes a bright state. As described above, light and dark display can be performed by the voltage applied to the liquid crystal.

[Problems to be solved by the invention]

The liquid crystal display device utilizing the twisted nematic effect requires a polarizing plate as described above. Therefore, in this liquid crystal display device, more than half of the incident light, which is usually indeterminate polarized light, is lost by the polarizing plate. This not only lowers the light utilization efficiency, but also causes the temperature of the liquid crystal display element to rise due to the loss of light being absorbed by the polarizing plate or the like, which is a distant factor that causes deterioration of the liquid crystal.

In addition, although a method of dividing incident light of irregular polarization into two polarization components orthogonal to each other, that is, p-polarized light and s-polarized light, displaying each using a panel having the same characteristics, and synthesizing the two images is also conceivable. In this case, an optical element such as a polarizing beam splitter and a space for them are required, which is not practical.

SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid crystal display element which solves the above-mentioned problems of the prior art, and a driving method for using the liquid crystal display element to obtain a display with high light use efficiency.

[Means for solving the problem]

The liquid crystal display element of the present invention has a light-shielding portion larger than a light-collecting diameter outside a glass substrate of a liquid-crystal cell having a light-condensing action in which a liquid crystal is sandwiched between two glass substrates with transparent electrodes that have been subjected to the same orientation treatment. A first liquid crystal display element having a film formed thereon and a second liquid crystal display element having the same structure as the first liquid crystal display element are combined so that liquid crystal orientation directions are orthogonal to each other.

In addition, the driving method of the liquid crystal display element is such that a liquid crystal is sandwiched between two glass substrates with a transparent electrode that have been subjected to the same orientation treatment. A liquid crystal display device in which a first liquid crystal display device having a large light-shielding film formed thereon and a second liquid crystal display device having the same structure as the first liquid crystal display device are combined so that liquid crystal orientation directions are orthogonal to each other. The same driving voltage is applied to the first liquid crystal display element and the second liquid crystal display element.

[Action]

The liquid crystal display element of the present invention has the same structure in which a light-shielding film is formed on the outside of a glass substrate of a liquid crystal cell having a light-condensing function sandwiching liquid crystal between two glass substrates with transparent electrodes that have been subjected to the same orientation treatment. It is a combination of two liquid crystal display elements such that the liquid crystal alignment directions are orthogonal to each other. The position of each light-shielding film is a position substantially corresponding to a focal point when a light-condensing action occurs, and the size of the light-shielding film is slightly larger than the light-condensing diameter.

The driving method of the present invention applies the same driving voltage to two liquid crystal display elements. When the incident light is made parallel to the glass substrate and an appropriate driving voltage equal to or higher than the threshold voltage of the liquid crystal is applied, the component parallel to the liquid crystal orientation of the liquid crystal display element on the incident light side, that is, the extraordinary light has a light condensing action. And converges to the focal position. Since the light shielding film is formed at the focal position, this extraordinary light is blocked and does not escape to the opposite side. The component perpendicular to the liquid crystal alignment of the liquid crystal display element, that is, ordinary light, does not receive the light condensing action, and thus escapes as it is. However, the next incident liquid crystal display element is combined so that the orientation direction of the liquid crystal molecules is orthogonal to the previous liquid crystal display element. Therefore, the component parallel to the liquid crystal alignment,
That is, the light becomes an abnormal light and receives a light condensing action, and converges to the focal position. Since the light shielding film is formed at the focal position similarly to the previous liquid crystal display element, the light is blocked. Thus, 2 of the same structure
By combining the liquid crystal display elements so that the liquid crystal orientation directions are orthogonal to each other, all incident light is blocked. That is, a dark display is obtained. On the other hand, even if an extremely low drive voltage equal to or lower than the threshold voltage of the liquid crystal is applied, no special action is produced for both abnormal light and ordinary light. Therefore, most of the incident light goes straight and transmits. That is, a bright display is obtained. At this time, the portion of the light-shielding film is shielded from light. However, since the light-shielding film is extremely small in comparison with the display area, light loss is very small.

As described above, the liquid crystal display element of the present invention does not require a polarizing plate, and a driving method thereof enables display with high light use efficiency.

〔Example〕

Next, examples of the present invention will be described. FIGS. 1A, 1B and 1C show an embodiment of the structure of a liquid crystal display element. (A) is a side view, (b), (c) is a front view. This is a combination of two liquid crystal display elements 105 and 106 having the same structure such that the liquid crystal alignment directions are orthogonal to each other. Each of the liquid crystal display elements has a light-shielding film 104 formed outside a glass substrate of a liquid crystal cell having a condensing function in which a liquid crystal 103 is sandwiched between two glass substrates 102 and 107 with transparent electrodes. When the position of the light shielding film operates as a lens,
This is a position substantially corresponding to the focal point. The size of the light-shielding film is slightly larger than the light-collecting diameter. A liquid crystal cell having a light condensing function is generally called a liquid crystal lens and has various structures. Here, a liquid crystal cell having a structure in which a liquid crystal is sandwiched between a pixel electrode having a circular window pattern and a transparent plate electrode is used.

Before describing the method of driving the liquid crystal display element of the present invention, the operation principle of the liquid crystal lens will be described with reference to FIG. The liquid crystal lens in this case has a structure in which a liquid crystal 103 is sandwiched between a pixel electrode 301 having a circular window pattern and a flat plate transparent electrode 302. When only a voltage lower than the threshold voltage of the liquid crystal is applied between the electrodes, as shown in FIG.
The liquid crystal 103 has a homogeneous orientation, that is, the major axis of the liquid crystal molecule is parallel to the substrate. At this time, there is no special effect on the incident light, that is, since the focal length of the liquid crystal display element is infinite, neither the ordinary light nor the extraordinary light of the incident light exits without being converged. Here, extraordinary light refers to a polarization component parallel to the orientation direction of the liquid crystal molecules, and ordinary light refers to a polarization component perpendicular to the orientation direction of the liquid crystal molecules.

When an appropriate voltage equal to or higher than the threshold voltage of the liquid crystal is applied between the electrodes, as shown in FIG. 3 (b), the central portion of the pattern having a small electric field intensity is oriented in parallel with the substrate with the initial orientation, and the electric field intensity is reduced. In the large pattern end, the major axis of the liquid crystal molecule is oriented perpendicular to the substrate. As the long axis of the liquid crystal molecules is oriented perpendicular to the substrate, the effective refractive index for extraordinary light decreases, so that the refractive index distribution decreases from the pattern center toward the periphery. For this reason, it has a light condensing property for an extraordinary light component of the incident light, that is, a convex lens effect. At this time, there is no effect on ordinary light because no effective refractive index distribution occurs. That is, the ordinary light exits without being collected. As described above, when a voltage equal to or higher than the threshold voltage is applied, the liquid crystal lens has a lens function for extraordinary light and has no lens function for ordinary light. Also, when a voltage lower than the threshold voltage is applied, the lens does not have a lens action for either extraordinary light or ordinary light.

Next, the display principle of the liquid crystal display element driving method of the present invention will be described with reference to FIG. Two liquid crystal display elements
The same voltage is applied to 105 and 106 from the drive power supply 203.
The incident light is parallel to the glass substrate. Second
FIG. 7A shows a case where an appropriate voltage higher than the threshold voltage of the liquid crystal is applied. At this time, the component parallel to the liquid crystal orientation of the liquid crystal display element A105 on the incident light side, that is, the extraordinary light 201 with respect to the liquid crystal display element A is subjected to the light condensing action according to the principle described above and converges on the focal position. Since the light shielding film 104 is formed at the focal position, this extraordinary light is blocked and does not escape to the opposite side. Since the component perpendicular to the liquid crystal orientation of the liquid crystal display element 105, that is, ordinary light, does not receive the light condensing action as described above,
Get out as it is. However, the next incident liquid crystal display element 106 is combined with the previous liquid crystal display element 105 such that the orientation direction of the liquid crystal molecules is orthogonal. Therefore,
The light becomes the extraordinary light 202 with respect to the liquid crystal display element B, receives the light condensing action, and converges to the focal position. Since the light shielding film 104 is formed at the focal position as in the case of the liquid crystal display element, the light is blocked. Thus, by combining two liquid crystal display elements having the same structure in which the liquid crystal orientation directions are orthogonal to each other, all incident light is blocked. That is, a dark display is obtained.

On the other hand, FIG. 2B shows a case where a voltage lower than the threshold voltage of the liquid crystal is applied. At this time, the two liquid crystal display elements 105, 10
6 has no special effect on either extraordinary light or ordinary light. Therefore, most of the incident light goes straight and transmits. That is, a bright display is obtained. At this time, the light blocking film 104 is shielded from light, but the light blocking film 104 is extremely small in comparison with the display area. Since the condensing diameter of the liquid crystal lens can be about 10 microns in diameter, assuming a display area of 100 to 200 squares, which is one pixel of a normal liquid crystal panel, the area of the light shielding film 104 is 1% or less of the pixel area. is there. Therefore, light loss is also negligible.

As described above, the liquid crystal display element of the present invention does not require a polarizing plate, and enables display with high light use efficiency.

〔The invention's effect〕

As described above, the liquid crystal display element and the driving method of the present invention enable display with high light use efficiency without the need for a polarizing plate, and are very useful in industry.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of the structure of a liquid crystal display device of the present invention,
FIG. 2 is a diagram showing an example of a display principle according to a method of driving a liquid crystal display element of the present invention, and FIG. 3 is a diagram showing a principle of operation of a liquid crystal lens. 101: Transparent electrode, 102, 107: Glass substrate, 103: Liquid crystal, 104: Light shielding film, 105: Liquid crystal display element A, 106 ...
Liquid crystal display elements B, 201: extraordinary light for liquid crystal display element A, 202: extraordinary light for liquid crystal display element B, 203: drive power supply, 301: circular window electrode, 302: flat plate transparent electrode.

Claims (2)

(57) [Claims] 1. A liquid crystal cell having a condensing function in which a liquid crystal is sandwiched between two glass substrates with a transparent electrode which have been subjected to the same orientation treatment, and a light-shielding film having a diameter larger than the converging diameter is formed outside the glass substrate. A liquid crystal display device comprising: a first liquid crystal display device as described above; and a second liquid crystal display device having the same structure as the first liquid crystal display device, so that liquid crystal orientation directions are orthogonal to each other. 2. A light-shielding film having a diameter larger than a light-collecting diameter is formed outside a glass substrate of a liquid-crystal cell having a light-condensing action, in which a liquid crystal is sandwiched between two glass substrates with a transparent electrode that have been subjected to an orientation treatment in the same direction. A first liquid crystal display element and a second liquid crystal display element having the same structure as that of the first liquid crystal display element are combined so that liquid crystal orientation directions are orthogonal to each other. A method for driving a liquid crystal display element, wherein the same driving voltage is applied to a liquid crystal display element and the second liquid crystal display element.