JP2940031B2 - Liquid crystal display device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a liquid crystal electro-optical element.

[Prior Art] A conventional liquid crystal display element generally has a configuration in which two polarizing plates sandwich a liquid crystal cell. Even when a retardation plate for optical compensation is required, two polarizing plates are required. Usually, it was provided in a space sandwiched between the polarizing plates, and was not provided outside the polarizing plate. This is a matter of course, since the phase difference is not detected outside the polarizing plate and is not visible to the eyes.

[Problems to be Solved by the Invention] Conventionally, there has been known a phenomenon that when sunglasses are worn, the display on a liquid crystal display is partially darkened or, in the worst case, is completely invisible. In recent years, liquid crystal displays have also been used for displaying various meters of automobiles, so if they are not visible when wearing sunglasses, it is a safety problem.

The reason why such a phenomenon occurs is that, as described above, the conventional liquid crystal display element has a configuration in which the liquid crystal cell is sandwiched between two polarizing plates, and the emitted light is linearly polarized.

The present invention is intended to solve such a problem, and the purpose of the present invention is to make the light emitted from the liquid crystal cell circularly polarized, so that even if wearing polarized sunglasses or the like, the display is excellent. An object of the present invention is to provide a liquid crystal display element that can be viewed.

[Means for Solving the Problems] A liquid crystal display device of the present invention is a liquid crystal display device having a pair of polarizing plates, a liquid crystal cell disposed between the pair of polarizing plates, and a phase difference plate. At least one retardation plate is disposed on a side of the one of the polarizing plates different from the liquid crystal cell side, and the one of the polarizing plates is adjacent to the optical axis direction of the retardation plate. And the retardation of the retardation plate is a product of the birefringence (Δn) of the retardation plate and the thickness (d) of the retardation plate. It is characterized in that the value of the gradation (Δn · d) is approximately 0.14 μm which corresponds to 1 of the wavelength of green light. Further, the light emitted from the retardation plate is circularly polarized light in the case of green, and is elliptically polarized light close to the circularly polarized light in the case of blue and red.

[Operation] A retardation plate having a retardation of 0.14 μm is equivalent to a λ / 4 plate of green light. Therefore, if linearly polarized light is incident at an angle of about 45 degrees with respect to the optical axis direction of this retardation plate,
Linearly polarized light changes to circularly polarized light.

When viewed through polarized sunglasses, the amount of transmitted light changes in accordance with the axial relationship between the two, but does not change in the case of circularly polarized light.

Also, this retarder has the effect of converting linearly polarized light into elliptically polarized light close to circularly polarized light, even for blue and red light, so that it is possible to prevent the amount of transmitted light by polarized sunglasses from changing regardless of the color of the light. It is.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples.

Example 1 FIG. 1 is a sectional view of a liquid crystal display device of the present invention. In the figure, 1 is a liquid crystal cell, 2 is an upper polarizing plate, 3 is a lower polarizing plate,
4 is a phase difference plate, 5 is an illumination light source. 11 is an upper substrate, 12 is a lower substrate, 13 is a transparent electrode, and 14 is a liquid crystal. The illumination light source 5 may be a reflector.

The liquid crystal cell 1 is a normal twisted nematic cell having a twist angle of 90 degrees and Δn × d = 0.40 μm.
The retardation plate 4 is a uniaxially stretched polycarbonate film, and has a Δn × d = 0.14 μm.

FIG. 2 is a diagram showing the relationship between each axis of the liquid crystal display device of the present invention. 21 is the optical axis direction of the retardation plate 4 (stretching direction of the uniaxially stretched film), 22 is the polarization axis (absorption axis) direction of the upper polarizing plate 2, 23 is the rubbing direction of the upper substrate 11, and 24 is the lower substrate 12
Rubbing direction, 25 is the polarization axis (absorption axis) of the lower polarizing plate 3
Direction. 31 is an angle formed by 21 and 22. Here, the angle 31 is set to 45 degrees to the right. The directions of the polarization axes of the two polarizing plates are made to coincide with the rubbing directions of the adjacent substrates.

In the liquid crystal display device having such a configuration, since the emitted light is substantially circularly polarized light, even when viewed through polarized sunglasses,
There is no change in the amount of transmitted light according to the axial relationship between the two.

(Example 2) In this example, a uniaxially stretched film of PMMA was used as the retardation plate 4. The Δn × d was set to 0.16 μm, and the angle 31 was set to 60 degrees to the right.

Even under such conditions, the emitted light becomes substantially circularly polarized light, and thus there is an effect of preventing a change in the amount of transmitted light due to polarized sunglasses.

In the above embodiment, an example of a direct-view display is given. However, in a projection display, the same effect can be obtained by placing a retardation plate on the projection lens side of the liquid crystal cell.

[Effects of the Invention] As described above, according to the present invention, the output light from the liquid crystal cell is circularly polarized, so that even when wearing polarized sunglasses or the like, the liquid crystal display can be viewed well. A display element can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view of the liquid crystal display device of the present invention. FIG. 2 is a diagram showing the relationship between each axis of the liquid crystal display device of the present invention. DESCRIPTION OF SYMBOLS 1 ... Liquid crystal cell 2 ... Upper polarizing plate 3 ... Lower polarizing plate 4 ... Retardation plate 5 ... Illumination light source or reflection plate 11 ... Upper substrate 12 ... Lower substrate 13 ... Transparent electrode 14 ... Liquid crystal 21: Optical axis direction of retardation plate 4 (stretching direction of uniaxially stretched film) 22: Polarization axis (absorption axis) direction of upper polarizing plate 2 23: Rubbing direction of upper substrate 24: Lower substrate 12 Rubbing direction 25…… Polarization axis (absorption axis) direction of lower polarizing plate 3 31… Angle between 21 and 22

Claims (2)

(57) [Claims] 1. A liquid crystal display device comprising: a pair of polarizing plates; a liquid crystal cell disposed between the pair of polarizing plates; and a retardation plate. At least one retardation plate is disposed on a side different from the liquid crystal cell side, and an optical axis direction of the retardation plate forms an angle of approximately 45 degrees with a polarization axis direction of the adjacent one polarizing plate. The retardation (Δn · d) of the retardation plate, which is the product of the birefringence (Δn) of the retardation plate and the thickness (d) of the retardation plate, has a green wavelength. A liquid crystal display element having a thickness of about 0.14 μm, which corresponds to 1/4 of the above. 2. The liquid crystal display device according to claim 1, wherein the light emitted from the phase difference plate is circularly polarized light in the case of green and elliptically polarized light close to the circularly polarized light in the case of blue and red.