JPH07261168A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To improve the contrast of a STN liquid crystal display element. CONSTITUTION:This liquid crystal display element consists of a STN liquid crystal cell 1, phase difference plates 2, 3 laminated on the liquid crystal cell 1, and upper polarizing plate 4 and lower polarizing plate 5 which interpose the liquid crystal cell 1 and phase difference plates 2, 3 between them. The wavelength dependence of DELTAn.d of the phase difference plates 2, 3 is made to coincide with the wavelength dispersibility of the liquid crystal display cell 1.

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 using a super twisted nematic (STN) liquid crystal, which enables excellent black and white display, that is, paper white display regardless of the viewing angle, The present invention relates to a liquid crystal display device which is intended to have contrast.

[0002]

2. Description of the Related Art A conventional liquid crystal display device of this type displays black and white by a structure in which two retardation plates are superposed between a liquid crystal cell and an upper polarizing plate, and a lower deflecting plate is arranged on the back side of the liquid crystal cell. Alternatively, color display is performed by providing a color filter on the upper substrate of the liquid crystal cell. FIG. 11 is an explanatory view of a liquid crystal display device according to the prior art, (a) is a sectional view,
(B) shows the direction of the optical axis of each constituent layer.

In the figure, 01 is a liquid crystal cell in which a liquid crystal layer is injected between an upper substrate and a lower substrate, 02 is a lower retardation plate,
03 is an upper retardation plate, 04 is an upper polarizing plate, 05 is a lower polarizing plate,
Reference numeral 06 represents the light absorption axis of the upper polarizing plate (90 ° with respect to the reference line θ = 0 ° -180 °, the same applies hereinafter), 07 represents the light absorption axis of the lower polarizing plate (160 °), and 08 represents the stretching axis of the upper retardation plate (40 °), 0
9 is a lower retardation plate stretching axis (50 °).

The liquid crystal cell 01 constitutes a liquid crystal display element structure having a twisted spiral structure of a nematic liquid crystal having a positive dielectric anisotropy between two electrode plates (an upper substrate and a lower substrate), and Polarizing plates (upper polarizing plate 04 and lower polarizing plate 05) above and below both electrode plates so that the light absorption axis (240 °) is orthogonal or parallel to the liquid crystal molecules adjacent to the electrode plates.
And two phase difference plates (a lower phase difference plate 02 and an upper phase difference plate 0) between the upper polarizing plate 04 and the liquid crystal display element 01.
3) is arranged. A liquid crystal display device of this type disclosed in the prior art includes, for example, Japanese Patent Publication No. 51-1.
3666 can be mentioned.

[0005]

In the conventional liquid crystal display element, as described above, the upper retardation plate and the lower retardation plate are superposed between the liquid crystal cell and the upper polarizing plate, or the liquid crystal cell and the upper polarizing plate are arranged. The retardation plate is placed between the liquid crystal cell and the lower polarizing plate and the lower retardation plate is placed between the liquid crystal cell and the lower polarizing plate to reduce the coloring of the display light. There is a problem in that the chromatic dispersion with respect to is not the same, so that the black and white display is colored and the resolution of the color display is lowered (the chromaticity range is narrowed).

An object of the present invention is to solve the above-mentioned problems of the prior art and to solve the above-mentioned problems of the prior art, and to provide a liquid crystal display device capable of obtaining high-contrast monochrome display and color display. It is in.

[0007]

In order to achieve the above object, a first invention according to claim 1 is a liquid crystal cell comprising a super twist nematic liquid crystal layer, and a retardation plate laminated on the liquid crystal cell. In a liquid crystal display device comprising an upper polarizing plate and a lower polarizing plate laminated with the liquid crystal display cell and the retardation plate sandwiched therebetween, the wavelength dependence of the retardation plate with respect to Δn · d is determined by the wavelength dispersion of the liquid crystal display cell. Characterized by matching with sex.

A second aspect of the present invention is to provide a super twist nematic liquid crystal layer having a positive dielectric anisotropy and to which an optical rotatory substance is added, and to give a twisted spiral structure to the liquid crystal layer. A liquid crystal cell comprising a pair of electrodes sandwiching the liquid crystal layer, and a retardation plate laminated on the liquid crystal cell, and an upper polarizing plate laminated on the liquid crystal display cell and the retardation plate. And a lower polarizing plate, the upper retardation plate and the lower retardation plate are made of polyacrylate, and the Δn · d value of the liquid crystal cell is 0.8.
2 to 0.92 μm, the gap value for inserting the liquid crystal layer is 4.5 μm to 7.0 μm, and Δ for each retardation plate is
The n · d value is 0.4 μm to 0.6 μm.

Further, a third invention according to claim 3 is
A pair of super twist nematic liquid crystal layers having a positive dielectric anisotropy and added with an optical rotatory substance, and an alignment film for imparting a twisted spiral structure of 240 ° to the liquid crystal layers, sandwiching the liquid crystal layers. A liquid crystal cell consisting of electrodes, an upper retardation plate provided on the upper surface side of the liquid crystal cell, an upper polarizing plate provided on the upper retardation plate, a lower retardation plate provided on the lower surface side of the liquid crystal cell, In a liquid crystal display element having a lower polarizing plate provided on the lower surface side of the retardation plate, the upper retardation plate and the lower retardation plate are made of polyacrylate, and the center of the vertical alignment axis of the liquid crystal cell is used as a reference. In addition, the absorption axis angle of the upper polarizing plate is 10 degrees, the stretching axis angle of the upper retardation plate is 70 degrees, the stretching axis angle of the lower retardation plate is 110 degrees, and the absorption axis angle of the lower polarizing plate is 80 degrees. And the Δn · d value of the liquid crystal cell 0.82 to 0.92 μm, the gap value for inserting the liquid crystal layer is 4.5 μm to 7.0 μm, and the Δn · d value for each retardation plate is 0.4 μm to 0.
The feature is that the thickness is 6 μm.

The fourth invention according to claim 4 is
A pair of super twist nematic liquid crystal layers having a positive dielectric anisotropy and added with an optical rotatory substance, and an alignment film for imparting a twisted spiral structure of 240 ° to the liquid crystal layers, sandwiching the liquid crystal layers. A liquid crystal cell composed of electrodes, a lower retardation plate provided on the upper surface side of the liquid crystal cell, an upper retardation plate provided on the upper surface side of the upper retardation plate, and an upper polarizing plate provided on the upper retardation plate In the liquid crystal display device having a lower polarizing plate provided on the lower surface side of the liquid crystal cell, the upper retardation plate and the lower retardation plate are made of polyacrylate, and the center of the vertical alignment axis of the liquid crystal cell is used as a reference. In this case, the absorption axis angle of the upper polarizing plate is 90 degrees, the stretching axis angle of the upper retardation plate is 35 degrees, and the stretching axis angle of the lower retardation plate is 70 degrees.
The absorption axis angle of the lower polarizing plate is 160 degrees, the Δn · d value of the liquid crystal cell is 0.82 to 0.92 μm, and the gap value of the liquid crystal layer is 4.5 μm to 7.0 μm.
m, the Δn · d value per one of the phase difference plates is 0.4 μm
˜0.6 μm.

The crossing angle of the optical axes is:
It is ± 10 degrees.

[0012]

In the structure of the first invention, the wavelength dependence of Δn · d of the retardation plate is matched with the wavelength dispersion of the liquid crystal display cell, so that the normally closed transmittance of the liquid crystal cell is improved. It becomes the minimum, the spectral transmittance at each wavelength becomes flat, and a high-contrast display is obtained.

In the structure of the second aspect of the invention, the Δn · d value of the liquid crystal cell is 0.82 to 0.92 μm, and the gap value of the liquid crystal layer is 4.5 μm to 7.0 μm.
m, the Δn · d value per one of the phase difference plates is 0.4 μm
By setting the thickness to ˜0.6 μm, the wavelength dependence of Δn · d of the retardation plate matches the wavelength dispersibility of the liquid crystal display cell, the normally closed transmittance of the liquid crystal cell is minimized, and the spectrum at each wavelength is reduced. The transmittance becomes flat and a high-contrast display can be obtained.

Further, in the structure of the third invention,
Based on the center of the vertical alignment axis of the liquid crystal cell,
The absorption axis angle of the upper polarizing plate is 10 degrees, the stretching axis angle of the upper retardation plate is 70 degrees, and the stretching axis angle of the lower retardation plate is 1 degree.
The absorption axis angle of the lower polarizing plate is 80 degrees, and the Δn · d value of the liquid crystal cell is 0.82 to 0.92 μ.
m, the gap value for inserting the liquid crystal layer is 4.5 μm
7.0 μm, and by setting the Δn · d value per one of the retardation plates to 0.4 μm to 0.6 μm, the wavelength dependence of Δn · d of the retardation plate on the wavelength dispersion of the liquid crystal display cell. In agreement, the normally closed transmittance of the liquid crystal cell is minimized, the spectral transmittance at each wavelength is flat, and a high-contrast display is obtained.

Further, in the configuration of the above-mentioned fourth invention,
Based on the center of the vertical alignment axis of the liquid crystal cell,
The absorption axis angle of the upper polarizing plate is 90 degrees, the stretching axis angle of the upper retardation plate is 35 degrees, and the stretching axis angle of the lower retardation plate is 7 degrees.
0 degree, the absorption axis angle of the lower polarizing plate is 160 degrees, and the Δn · d value of the liquid crystal cell is 0.82 to 0.92 μ.
m, the gap value for inserting the liquid crystal layer is 4.5 μm
7.0 μm, the Δn · d value per one of the retardation plates is 0.4 μm to 0.6 μm, and the wavelength dependence of the retardation plate on Δn · d matches the wavelength dispersion of the liquid crystal display cell, The normally closed transmittance of the liquid crystal cell is minimized, the spectral transmittance at each wavelength is flat, and high contrast display is obtained.

The upper retardation plate and the lower retardation plate are not limited to the above polyacrylate, and may be made of a material having optical characteristics equivalent to these.

[0017]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a schematic sectional view for explaining a first embodiment of a liquid crystal display device according to the present invention, in which 1 is a liquid crystal cell and 2 is a liquid crystal cell.
Is a lower retardation plate, 3 is an upper retardation plate, 4 is an upper polarizing plate, and 5 is a lower polarizing plate. The liquid crystal cell 1 is provided with electrodes on the opposing surfaces of two transparent substrates made of glass or the like, and a super twist nematic liquid crystal layer twisted by 240 ° is sandwiched between these electrodes. The lower retardation plate 2 and the upper retardation plate 3 are made of polyacrylate.

As shown in the figure, a lower retardation plate 2 and a lower polarizing plate 5 are laminated on the lower surface side of the liquid crystal cell 1, and an upper retardation plate 3 and an upper polarizing plate 4 are laminated on the upper surface side of the liquid crystal cell 1. A liquid crystal display element is configured.

In the above construction, the orientation axis of each constituent material,
The stretching axis is based on the center of the vertical alignment axis of the liquid crystal cell 1, the absorption axis angle of the upper polarizing plate is 10 degrees, the stretching axis angle of the upper retardation plate is 70 degrees, and the lower retardation plate is stretching. The axis angle is 110 degrees, the absorption axis angle of the lower polarizing plate is 80 degrees, and the Δn · d value of the liquid crystal cell is 0.82 to 0.82.
0.92 μm, the gap value for inserting the liquid crystal layer is 4.
5 μm to 7.0 μm, Δn per one of the retardation plates
The d value is 0.4 μm to 0.6 μm.

As a result, the wavelength dependence of the retardation film with respect to Δn · d matches the wavelength dispersion of the liquid crystal display cell,
The normally closed transmittance of the liquid crystal cell is minimized, the spectral transmittance at each wavelength is flat, and high contrast display is obtained.

FIG. 2 is a schematic sectional view for explaining a second embodiment of the liquid crystal display device according to the present invention, and the same reference numerals as those in FIG. 1 correspond to the same parts.

As shown in the figure, a lower polarizing plate 5 is laminated on the lower surface side of the liquid crystal cell 1, and a lower retardation plate 2, an upper retardation plate 3 and an upper polarizing plate 4 are laminated on the upper surface side of the liquid crystal cell 1. A liquid crystal display element is configured.

In the above structure, when the center of the vertical alignment axis of the liquid crystal cell is used as a reference, the absorption axis angle of the upper polarizing plate is 90 degrees, and the stretching axis angle of the upper retardation plate is 35 degrees.
The stretching axis angle of the lower retardation plate is 70 degrees, the absorption axis angle of the lower polarizing plate is 160 degrees, and Δ of the liquid crystal cell is
The n · d value is 0.82 to 0.92 μm, the gap value for inserting the liquid crystal layer is 4.5 μm to 7.0 μm, and the Δn · d value per one retardation plate is 0.4 μm to 0. 6 μm, the wavelength dependence of Δn · d of the retardation plate matches the wavelength dispersibility of the liquid crystal display cell, the normally closed transmittance of the liquid crystal cell is minimized, and the spectral transmittance at each wavelength is flat, A high contrast display is obtained.

FIG. 3 is an explanatory view of the optical axes (absorption axis, stretching axis) of the constituent materials in the liquid crystal display element of each of the above-mentioned embodiments, 6 being the absorption axis of the upper polarizing plate and 7 being the absorption axis of the lower polarizing plate. Axis, 8
Is the stretching axis of the upper retardation plate, and 9 is the stretching axis of the lower retardation plate.

In the embodiment shown in FIG. 1, the liquid crystal cell 1
When the vertical alignment axis of (90 ° -180 °) is used as a reference,
The angle of the absorption axis 6 of the upper polarizing plate is 10 degrees, the angle of the absorption axis 7 of the lower polarizing plate is 80 degrees, and the angle of the stretching axis 8 of the upper retardation plate is 70 degrees.
The angle of the stretching axis 9 of the lower retardation plate is 110 degrees.

In the embodiment shown in FIG. 2, the absorption axis 6 of the upper polarizing plate has an angle of 90 degrees with respect to the vertical alignment axis (90 ° -180 °) of the liquid crystal cell 1. The absorption axis 7 has an angle of 165 degrees, the upper retardation plate has a stretching axis 8 of 35 degrees, and the lower retardation plate has a stretching axis 9 of 70 degrees.

FIG. 4 is an explanatory view of wavelength dispersion with respect to the Δn · d value of the liquid crystal and the retardation film in the liquid crystal display device, wherein the horizontal axis shows the wavelength (nm) and the vertical axis shows the change ratio of the Δn · d value ( Δn · d / Δn · d, λ = 550 nm) is shown.

In the figure, is a characteristic curve of wavelength dispersion of liquid crystal, is a wavelength dispersion when polyacrylate is used as a retardation plate, and is a wavelength dispersion of a conventional retardation plate using polycarbonate.

As shown in the figure, according to the liquid crystal display device of the present invention in which the retardation plate is made of polyacrylate, the wavelength dispersion of the liquid crystal and the wavelength dispersion of the retardation plate are the same in all wavelength regions. .

FIG. 5 is an explanatory view of the contrast corresponding to the Δn · d value of the liquid crystal in the liquid crystal display device according to the present invention, wherein the horizontal axis represents the Δn · d value of the liquid crystal (LCD) and the vertical axis represents the contrast. Indicate.

In the figure, the curve a is (Δn of the retardation plate
-D value- [Delta] n-d value of LCD) = 0.02 [mu] m. As described above, if the Δn · d values of the liquid crystal cell and the retardation film are substantially equal to each other, the change in contrast does not substantially change.

FIG. 6 is an explanatory diagram of contrast with respect to the optical axis angle in the liquid crystal display device, in which the horizontal axis represents the optical axis angle and the vertical axis represents the contrast.

In the present invention, the intersection angle of the optical axes is ± 1.
Since it is 0 degree, the contrast in this range is extremely good.

Specific application examples of the present invention will be described below.

FIG. 7 is a developed perspective view illustrating a structural example of a liquid crystal display device using the liquid crystal display element according to the present invention.
Reference numeral 1 is a liquid crystal cell, 2 is an upper polarizing plate, 3 is a retardation plate, and 4 is a lower polarizing plate.

The liquid crystal cell 1 has the alignment films 21 and 22 and the electrodes 31 and 32 on the opposing surfaces of the upper substrate 11 and the lower substrate 22 made of a transparent substrate such as glass. A super twisted nematic liquid crystal layer is sealed with a seal 10 between them. The orientation axes of the orientation films 21 and 22 are set to θ = 240 ° as shown by the solid and dotted arrows shown in the figure.

A reflective layer 4'is coated on the back surface of the lower polarizing plate 4. A single reflection plate may be provided instead of the reflection layer 41.

FIG. 8 is a partially cutaway perspective view for explaining an example of the main configuration around the liquid crystal display element when a color liquid crystal display device is constructed using the liquid crystal display element according to the present invention. , Green and blue color filters R, G,
B and a light-shielding film D between each color filter, and a smoothing layer 20 made of an insulating material for reducing unevenness on the surface due to the provision of the color filters R, G, B and the light-shielding film D is provided. . Then, the upper alignment film 21 is formed on the smooth layer 20.
Are formed to give a light absorption axis (optically anisotropic axis) to the liquid crystal layer.

The structure of the polarizing plate and the retardation plate of the liquid crystal display device using the liquid crystal display element shown in FIG. 8 is the same as that in FIG.

FIG. 9 is an external view showing an example of an electronic apparatus using the liquid crystal display device according to the present invention, and shows a so-called laptop personal computer.

In the figure, 50 is a liquid crystal display device according to the present invention, 51 is a mounting portion, 52, 53 and 54 are luminance, contrast and other display state adjusting portions, 55 is a main body portion, 5
Reference numeral 6 is an operation unit.

FIG. 10 is a block diagram showing the system configuration of the laptop personal computer shown in FIG. 9, in which the liquid crystal display device 70 constituting the liquid crystal display unit 60 is the driving IC 6
Driven by 0 '. The drive IC 60 'is a control LSI managed by the microprocessor unit 61.
Under the control of 62, characters, figures, etc. stored in the ROM, RAM, or input from the operation unit such as the keyboard,
Other data is displayed on the liquid crystal display device 70.

According to the above-described embodiments and specific examples, a large-capacity information display performance capable of achieving a wide viewing angle, high contrast, and bright, complete white display (paper white display) is provided. A liquid crystal display device can be realized. Further, by combining with a color filter, it is possible to provide a bright, high-contrast color liquid crystal display device having high definition and good color purity.

[0045]

As described above, according to the present invention,
By matching the wavelength dispersion of the retardation plate and the liquid crystal cell, it becomes possible to perform high-contrast black-and-white or color display, eliminating the above-mentioned problems in the prior art and providing a liquid crystal display device with excellent functions. Can be provided.

[Brief description of drawings]

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

FIG. 2 is a schematic sectional view illustrating a second embodiment of the liquid crystal display element according to the present invention.

FIG. 3 is an explanatory diagram of optical axes (absorption axis, stretching axis) of constituent materials in the liquid crystal display element of each of the examples.

FIG. 4 Δ of the liquid crystal and the retardation plate in the liquid crystal display element
It is explanatory drawing of chromatic dispersion with respect to n * d value.

FIG. 5 is the Δn of the liquid crystal in the liquid crystal display device according to the present invention.
It is an explanatory view of the contrast corresponding to the d value.

FIG. 6 is an explanatory diagram of contrast with respect to an optical axis angle in a liquid crystal display element.

FIG. 7 is a developed perspective view illustrating a structure of a liquid crystal display device according to the present invention.

FIG. 8 is a partially cutaway perspective view for explaining a configuration example of a main part around a liquid crystal display element when a color liquid crystal display device is configured using the liquid crystal display element according to the present invention.

FIG. 9 is an external view showing an example of an electronic device using the liquid crystal display element according to the present invention.

10 is a block diagram showing a system configuration of the laptop personal computer shown in FIG.

11A and 11B are explanatory views of a liquid crystal display element according to a conventional technique, in which FIG. 11A is a sectional view and FIG. 11B shows the direction of the optical axis of each constituent layer.

[Explanation of symbols]

 1 liquid crystal cell 2 upper retardation plate 3 upper retardation plate 4 upper polarizing plate 5 lower polarizing plate. 6 Absorption axis of upper polarizing plate 7 Absorption axis of lower polarizing plate 8 Stretching axis of upper retardation plate 9 Stretching axis of lower retardation plate.

Claims (4)

[Claims] 1. A liquid crystal cell comprising a super twisted nematic liquid crystal layer, a retardation plate laminated on the liquid crystal cell, an upper polarizing plate and a lower polarizing plate laminated with the liquid crystal display cell and the retardation plate sandwiched therebetween. In the liquid crystal display element, the liquid crystal display element is characterized in that the wavelength dependence of Δn · d of the retardation plate is matched with the wavelength dispersibility of the liquid crystal display cell. 2. A liquid crystal layer is sandwiched by a super twist nematic liquid crystal layer having a positive dielectric anisotropy and added with an optical rotatory substance, and an alignment film for imparting a twisted spiral structure to the liquid crystal layer. In a liquid crystal display device consisting of a liquid crystal cell consisting of a pair of electrodes, a retardation plate laminated on the liquid crystal cell, an upper polarizing plate and a lower polarizing plate laminated by sandwiching the liquid crystal display cell and the retardation plate, The upper retardation plate and the lower retardation plate are made of polyacrylate, and the Δn · d value of the liquid crystal cell is 0.82 to 0.92μ.
m, the gap value for inserting the liquid crystal layer is 4.5 μm
A liquid crystal display device having a thickness of 7.0 μm and a Δn · d value per one of the retardation plates of 0.4 μm to 0.6 μm. 3. A liquid crystal layer comprising a super twist nematic liquid crystal layer having a positive dielectric anisotropy and added with an optical rotatory substance, and an alignment film for imparting a twisted spiral structure of 240 ° to the liquid crystal layer. A liquid crystal cell consisting of a pair of electrodes sandwiching, and an upper retardation plate provided on the upper surface side of the liquid crystal cell,
A liquid crystal display device having an upper polarizing plate provided on the upper retardation plate, a lower retardation plate provided on the lower surface side of the liquid crystal cell, and a lower polarizing plate provided on the lower surface side of the retardation plate, wherein the upper layer When the retardation plate and the lower retardation plate are made of polyacrylate and the center of the vertical alignment axis of the liquid crystal cell is used as a reference, the absorption axis angle of the upper polarizing plate is 10 degrees, and the stretching axis angle of the upper retardation plate is 70 degrees, the stretching axis angle of the lower retardation plate is 110 degrees, the absorption axis angle of the lower polarizing plate is 80 degrees, and the Δn · d value of the liquid crystal cell is 0.82 to 0.9.
2 μm, the gap value for inserting the liquid crystal layer is 4.5 μm
˜7.0 μm, and the Δn · d value per one of the retardation plates is 0.4 μm to 0.6 μm. 4. A liquid crystal layer comprising a super twist nematic liquid crystal layer having a positive dielectric anisotropy and added with an optical rotatory substance, and an alignment film for imparting a twisted spiral structure of 240 ° to the liquid crystal layer. A liquid crystal cell consisting of a pair of electrodes sandwiching, and a lower retardation plate provided on the upper surface side of the liquid crystal cell,
In a liquid crystal display device having an upper retardation plate provided on the upper surface side of the upper retardation plate, an upper polarizing plate provided on the upper retardation plate, and a lower polarizing plate provided on the lower surface side of the liquid crystal cell, When the upper retardation plate and the lower retardation plate are made of polyacrylate and the center of the vertical alignment axis of the liquid crystal cell is used as a reference, the absorption axis angle of the upper polarizing plate is 90 degrees, and the stretching axis angle of the upper retardation plate. Is 35 degrees, the stretching axis angle of the lower retardation plate is 70 degrees, the absorption axis angle of the lower polarizing plate is 160 degrees, and the Δn · d value of the liquid crystal cell is 0.82 to 0.9.
2 μm, the gap value for inserting the liquid crystal layer is 4.5 μm
˜7.0 μm, and the Δn · d value per one of the retardation plates is 0.4 μm to 0.6 μm.