JPS63202717A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To permit correction of the pretilt angle of a liquid crystal which is fluctuated by a temp. fluctuation by constituting a titled device in such a manner that the polarization directions of polarizing plates can be adjusted by varying the installation condition of the polarizing plates in accordance with the fluctuation in the pretilt angle of the liquid crystal sealed into the device. CONSTITUTION:An operator turns a driving gear 35 of the device in an arrow B direction by the fingertip to rotate a gear 31 in an arrow C direction when, for example, a temp. change arises in the liquid crystal 28 sealed in the device and the contrast of the display is deteriorated. The upper polarizing plate 29 is thereby moved in an arrow D direction with respect to the lower polarizing plate 30. The upper polarizing plate can be moved in the direction opposite from the arrow D direction with respect to the lower polarizing plate 30 when the driving gear 35 is turned in the direction opposite from the arrow B direction. The fluctuation in the molecular axis arrangement direction of the liquid crystal, i.e., pretilt angle, generated by the temp. fluctuation is easily corrected in the above-mentioned manner and, therefore, the display device having the good contrast is obtd.

Description

[Detailed Description of the Invention] [Summary] A liquid crystal display device in which a polarizing plate is disposed on the back surface of at least one of a pair of transparent substrates of a liquid crystal display panel in which a liquid crystal is sealed, wherein the installation state of the polarizing plate is By making it variable so that the polarization direction can be adjusted, it compensates for changes in the liquid crystal pretilt angle due to temperature fluctuations in the environment where the liquid crystal display device is installed, and prevents deterioration in display quality. be.

[Industrial application field]

The present invention relates to improvements in liquid crystal display devices, and particularly to a liquid crystal display device that prevents deterioration in display quality due to fluctuations in the pretilt angle of liquid crystal sealed in a display section.

A pair of transparent glass substrates, each provided with a linear transparent electrode, are arranged separated by a predetermined space, a liquid crystal is sealed in this space, and the polarization directions differ by 90 degrees from each other on the surfaces of the glass substrates. Liquid crystal display devices each provided with a polarizing plate are well known.

Such liquid crystal display devices have a flat, thin structure and low power consumption, and are therefore widely used as display devices for portable word processors, personal computers, and the like.

In addition, compared to the TN type liquid crystal display device currently in practical use, the display response speed is faster, the display contrast is superior, and the worker's viewing angle dependence (display quality varies depending on the position where the worker looks at the display panel). Liquid crystal display devices using ferroelectric liquid crystals are being developed, which have advantages such as good ferroelectric liquid crystal (no change).

[Conventional technology]

FIG. 2 is a sectional view of a conventional liquid crystal display device having a polarizing plate.

As shown in the figure, a linear transparent electrode 2 made of a transparent indium tin oxide (ITO) layer is formed on the main surface of one transparent glass substrate 1 with a predetermined pinch parallel to the plane of the paper. An alignment film 3 made of an organic thin film of polyvinyl alcohol or the like which has been subjected to a rubbing process is formed.

Note that the rubbing process refers to a process in which shallow grooves are formed in an organic thin film in a predetermined direction, and the alignment direction of liquid crystal molecules is regulated along the grooves.

Further, on the main surface of the other transparent glass substrate 4, linear transparent electrodes 5 are formed at a predetermined pitch in a direction perpendicular to the plane of the paper, and an alignment film 6 that has been subjected to a rubbing process is formed thereon. . The glass substrates 1 and 4 are opposed to each other with a predetermined space in between, and the periphery thereof is sealed with a sealant 7, and a ferroelectric liquid crystal 8, for example, is sealed in the space.

Further, on the back surfaces of each of the pair of glass substrates 1 and 4, an upper polarizing plate 9 and a lower polarizing plate 1 whose polarization directions are different by 90 degrees are provided.
0 is set for each.

When a predetermined voltage is applied between the transparent electrodes selected from among the many orthogonal transparent electrodes 2 and 5, the pretilt angle of the liquid crystal in the display cell determined by the intersection between these electrodes (the liquid crystal molecules angle of orientation at a given angle from the axis)
changes by a predetermined value.

Therefore, white light is made to enter the liquid crystal 8 from, for example, the upper polarizing plate 9 side of the liquid crystal display device along the polarization direction of the polarizing plate, and the voltage applied between the electrodes 2.5 is applied to the upper polarizing plate 9. If the voltage is set so that the alignment direction of the liquid crystal molecules is the same for the linearly polarized white light that has passed through the upper polarizing plate 9, the white light that has passed through the upper polarizing plate 9 will pass through the liquid crystal molecules, and the white light will pass through the lower polarizing plate 10. The light reaches the liquid crystal while remaining along the direction in which it was introduced. Since the lower polarizing plate IO differs in polarization direction by 90 degrees from the upper polarizing plate 9, the light that reaches the lower polarizing plate IO cannot pass through the lower polarizing plate 10, resulting in a dark display.

In addition, in order to achieve a bright display, there is a theoretical angle of 45 degrees between the light that has passed through the upper polarizing plate 9 and the direction of the liquid crystal molecules, so the white light that passes through the liquid crystal and is emitted to the lower polarizing plate 10. A voltage for controlling the alignment of the molecular axes of the liquid crystal may be applied between the electrodes 2 and 5 so that the direction of the light matches the polarization direction of the upper polarizing plate 9.

In this way, dark and bright display states of the display device were realized.

[Problem that the invention seeks to solve]

However, in such a liquid crystal display device, even if a predetermined voltage is applied, the molecular axes of the liquid crystal cannot be aligned to a predetermined position due to temperature fluctuations in the liquid crystal sealed between the substrates. In other words, the preset alignment direction of liquid crystal molecules, that is, the pretilt angle, fluctuates under the influence of temperature fluctuations, which affects the display, resulting in a display with poor contrast and a problem of deterioration in display quality.

FIG. 3 shows such an inconvenient situation in a conventional liquid crystal display device.

Straight line 11 in the figure is the rubbing direction of the alignment film of the conventional device, straight lines 12A and 12B are the alignment direction of liquid crystal molecules when the temperature is 13°C and voltage is applied, and dotted lines 13^ and 13B are the temperature Tt°C.
and shows the alignment direction of liquid crystal molecules when voltage is applied.

As the temperature of the liquid crystal changes from 11°C to 12°C, the pretilt angle of the liquid crystal changes from θ to 02°C, and accordingly, the angle θ between the straight lines 14 and 15 of the upper polarizing plate 9 changes. The angle formed between the polarization direction and the polarization direction of the lower polarizing plate 10 changes to the angle formed between the polarization direction of the upper polarizing plate 9 and the polarizing direction of the lower polarizing plate 10, as shown by the angle θ4 between dotted lines 16 and 17. cause inconvenience.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a liquid crystal display device capable of correcting fluctuations in the pretilt angle of the liquid crystal due to temperature fluctuations.

[Means for solving problems]

To achieve the above object, the liquid crystal display device of the present invention includes a pair of transparent insulating substrates each having a transparent electrode on its main surface, which are arranged opposite to each other with a predetermined space therebetween, a liquid crystal is sealed in the space, and at least In a display device configuration in which a polarizing plate is provided on the back side of one transparent insulating substrate, the installation state of the polarizing plate can be varied to adjust the polarization direction in response to fluctuations in the pretilt angle of the enclosed liquid crystal. This is what I did.

[Effect]

The liquid crystal display device of the present invention is such that the installation state of the polarizing plate provided on at least one of the display panels is variable in response to fluctuations in the pretilt angle of the liquid crystal sealed between the transparent insulating substrates of the liquid crystal display panel. This makes it possible to compensate for fluctuations in the pretilt angle of the liquid crystal due to temperature fluctuations, thereby providing high-quality display.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a perspective view of an embodiment of a liquid crystal display device of the present invention.

As shown in the figure, on the main surface of one transparent glass substrate 21,
A transparent electrode 2 with a linear pattern formed by vapor-depositing a metal film made of a linear ITO layer in a direction parallel to the plane of the paper and spaced at a predetermined interval.
2 is formed, and an alignment film 23 made of polyvinyl alcohol that has been subjected to a predetermined rubbing process is formed thereon.

In addition, on the main surface of the other transparent glass substrate 24, as described above, the linear transparent electrodes 25 are formed at a predetermined pitch in the direction perpendicular to the plane of the paper, and on the main surface are made of polyvinyl alcohol that has been subjected to a rubbing process. The alignment films 26 are formed in layers.

These pair of glass substrates 21 and 24 are opposed to each other with a predetermined space in between, and their peripheral parts are sealed with a sealant 27.
A ferroelectric liquid crystal 28 is sealed in the space.

Further, an upper polarizing plate 29 and a lower polarizing plate 30, each having a polarization direction different by 90 degrees, are installed on the back surfaces of the pair of glass substrates, and the structure up to this point is the same as that of a conventional liquid crystal display device.

Here, according to the feature of the present invention, one of the four corners of the upper polarizing plate 29 and the lower polarizing plate 30 is connected by a gear 31 as shown in the figure, and the other corner located on the diagonal of the corner where the gear 31 is installed. Notches 32 and 33 are provided at each corner, and the support shaft 3 is inserted between these notches 32 and 33.
It is movably supported by 4. In addition, the gear 31
A drive gear 35 is separately provided which meshes with the drive gear 35.

A case where a dark state is displayed using such a liquid crystal display device of the present invention will be described.

First, white light is irradiated from above the upper polarizing plate 29 along the direction of arrow A, and the transparent electrodes 22 and 25 described above are
A predetermined voltage is applied between the two. Then, the white light incident along the direction of arrow A passes through the liquid crystal 28 as described above, and enters the lower polarizing plate 30 in the same polarization direction as that of the upper polarizing plate 29.

Since the lower polarizing plate 30 has a polarization direction different from the upper polarizing plate 29 by 90 degrees, the light introduced into the lower polarizing plate 30 cannot be transmitted therethrough, so that a dark state display can be realized.

Assume now that a temperature change has occurred in the liquid crystal 28 sealed therein. When a predetermined voltage is applied between the electrodes, the alignment direction of the molecular axes of the liquid crystal does not match the polarization direction of the upper polarizing plate 29, so that the light transmitted through the liquid crystal and introduced into the lower polarizing plate 30 is Since the polarization direction does not differ by 90 degrees from the polarization direction of the polarizing plate 30, light passes through the lower polarizing plate 30, and as a result, accurate dark state display cannot be achieved, and therefore the contrast of the display is reduced. Deteriorate.

In such a case, the device of the present invention rotates the gear 31 in the direction of the arrow C by rotating the drive gear 35 with your fingers in the direction of the arrow B.
direction, thereby moving the upper polarizing plate 29 in the direction of the arrow with respect to the lower polarizing plate 30. Further, when the driving gear 35 is rotated in the direction opposite to the direction of arrow B, the upper polarizing plate 29 can be moved in the direction opposite to the direction of the arrow with respect to the lower polarizing plate 30.

In this way, it is possible to easily correct the alignment direction of the molecular axes of the liquid crystal, that is, the pretilt angle, caused by temperature fluctuations, so that a liquid crystal display device with good contrast can be obtained.

In this example, a polarizing plate was provided on the back of each of the pair of glass substrates, but the liquid crystal (host) contained a dichroic dye (which has a different light absorption spectrum (hue) depending on the direction of the molecular axis of the liquid crystal).
In a guest-host type liquid crystal display device with added guest),
Only the upper polarizing plate 29 needs to be installed. That is, in this device, the light from the upper polarizing plate 29 hits the dye molecules constituting the dichroic dye, and the light colored depending on the light absorption rate of the dye molecules is emitted downward from the lower glass substrate 21 of the display device. ,
When the angle of incidence of the light introduced into the dye molecules differs, the light emitted from the dye molecules has a different shade of color, and the light and shade can be used to display a bright state and a dark state. For this purpose, only the upper polarizing plate 29 is required, and a transparent glass substrate may be used instead of the lower polarizing plate 30.

Further, by using a ferroelectric liquid crystal as in this embodiment, since this liquid crystal has a memory property, it is possible to display a large screen without using a large number of electrodes.

Furthermore, although the liquid crystal display device of this embodiment has been described using an example of a two-color display device of white and black, it can also be applied to a color display device by using a color filter.

〔Effect of the invention〕

As described above, according to the liquid crystal display device of the present invention, even if the pretilt angle of the liquid crystal fluctuates due to environmental temperature changes, the polarizing plate can be moved to correct the fluctuation in the pretilt angle. This has the effect of providing a high-quality display with good contrast.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of the liquid crystal display device of the present invention, and FIG. 2 is a sectional view of a conventional liquid crystal display device. FIG. 3 is an explanatory diagram showing an inconvenient state of a conventional liquid crystal display device. In the figure, 21.24 is a transparent glass substrate, 22.25 is a transparent electrode,
23, 26 is an alignment film, 27 is a sealant, 28 is a ferroelectric liquid crystal, 29 is an upper polarizing plate, 30 is a lower polarizing plate, 31 is a gear, 32°33 is a notch, 34 is a support shaft, 35 is a driving gear, A is an arrow showing the direction of incidence of white light, B and C are arrows showing the direction of movement of the driving gear, D is how the polarizing plate moves. Figure 2

Claims (2)

[Claims] (1) A pair of transparent insulating substrates (21, 24) each having transparent electrodes (22, 25) on their main surfaces are arranged facing each other with a predetermined space in between, and a liquid crystal (28) is sealed in the space, and In a display device configuration in which a polarizing plate (29, 30) is provided on the back surface of at least one transparent insulating substrate (21, 24),
A liquid crystal display device characterized in that the installation state of the polarizing plates (29, 30) can be varied to adjust the polarization direction in response to variations in the pretilt angle of the sealed liquid crystal (28). (2) The liquid crystal display device according to claim 1, wherein the liquid crystal (28) is a ferroelectric liquid crystal.