JPH06160834A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To perform positive/negative inversion by converting the polarizing axis on at least one side of a polarizing plate and to select display characteristic corresponding to applications in a liquid crystal display. CONSTITUTION:This device is comprised of a liquid crystal panel 1 which performs display by applying light transmission/cutoff control as applying a voltage to liquid crystal intermittently, the polarizing plate 2, at least one side of which consists of a polarizing member 2a and a frame member 2b to support the polarizing member 2a and whose polarizing axis is arranged convertibly by 0 deg./90 deg., and a control circuit 3 which applies the voltage to the liquid crystal selectively and provided with a function to perform the positive/negative inversion of the display of the liquid crystal panel 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,
The present invention relates to a liquid crystal display device in which the polarization axis of at least one of the polarizing plates is converted to 0 ° / 90 ° to perform positive / negative image inversion, and display characteristics can be optimally selected according to the application.

In recent years, as electronic devices such as semiconductor devices have been downsized, electronic devices have been downsized. Further, in the display device which is one of the element devices of the interface between the machine and the human, the liquid crystal display device has been attracting attention as a new light and thin display device.

A liquid crystal display device is becoming a display device having a display performance comparable to that of a CRT display device due to the recent development of new liquid crystal materials and driving methods and improvement of manufacturing technology of a liquid crystal display panel. However, the liquid crystal display device has a problem in manufacturing technical improvement for improving display quality centering on viewing angle characteristics.

[0004]

2. Description of the Related Art A liquid crystal display panel is intended to obtain a display device by moving a large molecule of viscous liquid crystal sandwiched between two glass plates and utilizing an optical effect such as polarized light. Is slow to respond. Therefore, it has been said that the liquid crystal display device is not suitable for a fast-moving display such as a moving image.

However, a new liquid crystal material called TN (twisted nematic) liquid crystal or STN (super twisted nematic) liquid crystal and its alignment method have been developed, or a so-called active matrix method in which TFTs (thin film transistors) are arranged in each pixel. For example, the function of the liquid crystal display device is approaching that of the CRT display device.

By the way, a basic constituent element of a liquid crystal display device is a liquid crystal display panel in which liquid crystal is sandwiched between two substrates provided with electrodes. When the voltage is intermittently applied to the liquid crystal display panel to change the alignment state of the liquid crystal molecules, an image can be displayed by transmitting or blocking light.

By the way, the liquid crystal display panel of the TN type, which is currently the mainstream, has a property that the display quality varies depending on the viewing angle characteristic, that is, the viewing angle. Therefore, various improvement means have been proposed in recent years.

FIG. 5 is a schematic sectional view of an alignment division type liquid crystal display panel. FIG. 5 (A) shows a state in which no voltage is applied, and FIG. 5 (B) shows a state in which a voltage is applied. 6 is N
6A and 6B are explanatory diagrams of a W-mode alignment division method, FIG. 6A is a layout diagram of polarizing plates, FIG.
FIG. 7 is an explanatory diagram of the alignment division method in the NB mode.
FIG. 7A is a layout view of polarizing plates, and FIG. 7B is a relationship diagram between voltage V and transmittance T. In the figure, 1 is a liquid crystal display panel,
1a is a pixel electrode, 2 is a polarizing plate, 6 is a liquid crystal, 7 is incident light, 8
Is the emitted light, and 10 is the liquid crystal display device.

The alignment division method schematically shown in FIG. 5 is a method proposed by the inventors in "Liquid Crystal Display Panel" (Japanese Patent Laid-Open No. 63-106624). That is, in FIG.
The liquid crystal 6 in the area of each pixel electrode 1a in the liquid crystal display panel 1 is divided into at least two different alignment states. Further, the polarizing plates 2 are orthogonal to each other, and the respective polarizing plates 2 are arranged so as to be parallel to the orientation direction. In this state, when no voltage is applied, the linearly polarized incident light 7 that has passed through one polarizing plate 2 is transmitted while twisting in the liquid crystal 6 and emerges from the other polarizing plate 2 as outgoing light 8. . This is a so-called white (W) state, which is a bright state where light is transmitted.

In this case, the region A and the region B are divided into two, and the orientations of the liquid crystal 6 in the respective regions are opposite to each other. In this case, the voltage V-transmittance T characteristic when the viewing angle between the respective regions is changed is averaged, so that the variation in display quality depending on the viewing angle is reduced, and the expansion of the viewing angle can be improved. For example, the viewing angle in the upward direction can be improved in the area A, and the viewing angle in the downward direction can be improved in the area B.

When a voltage is applied, the alignment of the liquid crystal 6 can be released as shown in FIG. 5 (B). Then, since the incident light 7 that has passed through one of the polarizing plates 2 passes through the liquid crystal 6 as it is, it is shielded by the other polarizing plate 2, and this is in a dark state in which light does not pass, that is, so-called black (B). It is in a state.

By the way, in FIG. 6 (A), the polarizing plates 2 are orthogonal to each other and light is always transmitted, and NW (normally white)
Mode. In this NW mode, as shown in FIG. 6B, the transmittance T shown by the solid line when the panel is viewed from the front changes suddenly, and the display characteristics are excellent. But,
When the viewing angle is changed, the difference in characteristics between regions is large as indicated by the broken line, and the amount of increase in the brightness of black display is too large.

On the other hand, when the polarizing plates 2 are arranged in parallel as shown in FIG. 7A, light is always shielded. This mode is an NB (normally black) mode in which light is shielded and dark black is displayed when no voltage is applied.
In this NB mode, when the viewing angle is changed, the difference in the voltage V-transmittance T characteristic between regions is small as shown in FIG. 7B, and therefore the viewing angle characteristic can be improved.

In order to improve the viewing angle characteristics, there is also a means for adding a retardation film or the like made of a sheet-like optically anisotropic member, and the inventors of the present invention referred to as "liquid crystal display device" (Japanese Patent Laid-Open No. 2659/1992).
28).

In the NB mode, the characteristics in the front direction of the panel have a drawback that the dark state where the voltage V is not applied is colored instead of black due to wavelength dispersion, and the contrast is low. This drawback can be improved by, for example, a multi-gap method in which the thickness of the liquid crystal layer corresponding to each color of RGB is changed, but it is troublesome to manufacture and is not practical.

Comparing the NW mode and the NB mode in this way, the NW mode has a good display when the panel is viewed from the front, but the viewing angle is narrow. Further, in the NB mode, the viewing angle is wide, but the contrast seen from the front is low, and it is difficult to obtain black with high purity in black display.

By the way, in a normal full-color TV display, high contrast from the front of the panel and black display with high purity are not so important. It is generally
This is because the area of the lowest luminance portion on the display screen is small and is canceled by other display portions to make it inconspicuous. Even if the voltage V-transmittance T characteristic slightly shifts, a luminance shift occurs between the gray scales. Therefore, the viewing angle characteristics are important.

On the other hand, in the case of a display screen of a personal computer (hereinafter abbreviated as a personal computer) or the like, since the voltage difference between the gray scales is large and the tolerance is large, the viewing angle characteristic does not matter so much. However, black display on the entire display surface is complicated, so I want a high-purity black display when viewed from the front of the panel.

Therefore, conventionally, the liquid crystal display panel used for the TV has been selectively used in the NB mode or the NW mode, and for the personal computer in the NW mode.

[0020]

However, in recent years, the multimedia orientation of personal computers has become stronger, and full-color display has become indispensable for liquid crystal display panels used in personal computers. However, it has become impossible to obtain sufficient required performance by properly using the mode of the liquid crystal display panel as in the past.

Therefore, in the present invention, the polarization axis of at least one of the polarizing plates can be converted by 0 ° / 90 °, positive / negative image inversion is performed in association with the conversion, and the positive / negative image inversion can be performed from the front of the display panel depending on the application. An object of the present invention is to provide a liquid crystal display device capable of appropriately selecting whether to improve display characteristics or to expand a viewing angle.

[0022]

The above-mentioned problems include a liquid crystal display panel, two polarizing plates, and a control circuit, wherein the liquid crystal display panel transmits / receives light while intermittently applying voltage to the liquid crystal. Display is performed by controlling light shielding, and the polarizing plate has a liquid crystal display panel sandwiched from both sides, at least one of which is composed of a polarizing member and a frame member supporting the polarizing member, and has a polarization axis of 0. The driving circuit is arranged so that it can be converted into ° / 90 °, and the drive circuit selectively applies a voltage to the liquid crystal and has a function of inverting the display on the liquid crystal display panel between the positive image and the negative image. Is solved by a liquid crystal display device configured as follows.

[0023]

In the conventional liquid crystal display device, since the polarizing plate is fixed, it is not possible to appropriately switch the mode between NW and NB depending on the application. However, in the present invention, at least one polarizing plate is polarized. The axis can be converted by 0 ° / 90 °. Then, the control circuit 3 can switch the display between the positive image and the negative image in conjunction with the 0 ° / 90 ° conversion of the polarization axis.

That is, at least one of the polarizing plates is supported by a polarizing plate support member so as to be rotatable by at least 0 ° / 90 ° so that mode switching between NW and NB can be performed. Then, in response to this, the control circuit can invert the positive image / negative image of the display.

By doing so, the positive image / negative image inversion can be appropriately performed depending on the application, and the liquid crystal display panel can always be used in an optimum display state.

[0026]

1 is an exploded perspective view showing the structure of a first embodiment of the present invention, FIG. 2 is a perspective view of a second embodiment of the present invention, and FIG. 2 (A) is a perspective view showing the structure. 2B is a partially cutaway enlarged perspective view of a main part, FIG. 3 is a partially cutaway perspective view of a third embodiment of the present invention, and FIG. 4 is a main cutout of a fourth embodiment of the present invention. It is a partially notched perspective view of a part. In the figure, 1 is a liquid crystal display panel, 2 is a polarizing plate, 2a is a polarizing member, 2b is a frame member, 2c is a notch, 2d is an arcuate notch, 3 is a control circuit, 4 is a polarizing plate holder, and 4a is a polarizing plate. A detector, 4b is a stop pin, 5 is an optically anisotropic member, and 10 is a liquid crystal display device.

Embodiment 1 In FIG. 1, a liquid crystal display device 10 is a liquid crystal display panel 1.
And two polarizing plates 2 sandwiching both sides of the liquid crystal display panel 1, and a control circuit 3 for controlling the liquid crystal display panel 1.

The liquid crystal display panel 1 uses a TN type liquid crystal as a TFT.
This is an active matrix type panel driven by, but is not shown here, but has an alignment division type in which each pixel electrode is divided into at least two as shown in FIG.

At least one of the polarizing plates 2 is a polarizing member.
2a is supported by the frame member 2b. By the way, although not shown, the polarization axis of the polarizing plate 2 is selected to be parallel (0 °) or orthogonal (90 °) to the direction in which the liquid crystal is aligned. Therefore, the polarizing plate holder 4 can be inserted and removed so that the polarization axis is converted by 0 ° / 90 °. Here, the polarizing plate 2 provided on the rear surface of the liquid crystal display panel 1 on the incident side is fixed so as to be parallel to the direction in which the liquid crystal is aligned. The polarizing plate support 4 is arranged on the front surface on the emission side.

The control circuit 3 is provided between a drive circuit 3a which drives respective pixel electrodes (not shown) in series with terminals led out from the periphery of the liquid crystal display panel 1, and is interposed between the drive circuit 3a and a personal computer or the like. Interface circuit 3b. The polarizing plate 2 is the polarizing plate support 4
The positive / negative image inverting circuit 3c for inverting the display of the liquid crystal display panel 1 to the positive / negative image can be operated depending on whether the polarization axis is inserted in the direction of 0 ° / 90 °.

That is, depending on the purpose and preference of the operator,
Whether to set the NW mode to emphasize the display characteristics when viewed from the front of the panel, or to set the NB mode to emphasize the viewing angle of the panel,
Can be arbitrarily selected at any time.

Further, when the positive / negative image is reversed, the gradation of the display is reversed. Therefore, particularly in the case of color display or the like, the order of gradation is reversed as necessary in the NB mode, for example. In this case, the positive / negative image reversing circuit 3c can be provided with the function of reversing / reversing the gradation order.

Example 2 In FIG. 2, a notch 2c is formed at the corner end of the frame member 2b of the polarizing plate 2.
Is provided. In addition, as shown in FIG. 2B, a polarizing plate detector 4a including, for example, a micro switch is provided at the corner of the polarizing plate support 4. If the polarizing plate detector 4a detects the presence or absence of the notch 2c of the polarizing plate 2 that is inserted into the polarizing plate support 4, the polarization axis of the polarizing plate 2 is 0 ° / 90 °.
You can automatically know which direction the

The output signal of the polarizing plate detector 4a is adapted to enter the positive / negative image inverting circuit 3c, and 0 ° of the polarizing plate 2 is detected.
The positive image / negative image can be automatically inverted according to the angle of / 90 °.

The polarizing plate detector 4a is not limited to the mechanical switch exemplified here, but may be variously deformed such as optically detected by using a photo interrupter or magnetically detected by using a Hall element. It is possible.

Example 3 In FIG. 3, the frame member 2b of the polarizing plate 2 has a circular shape. The circular frame member 2b is inserted and attached to the polarizing plate support tool 4,
The polarizing plate 2 can be rotated from the outside of the polarizing plate support 4.

The frame member 2b of the polarizing plate 2 is provided with an arcuate cutout 2d, and the polarizing plate support 4 is provided with a stop pin 4b. When the polarizing plate 2 is rotated, the arcuate notch 2d hits the stop pin 4b and can be rotated at an angle of 0 ° / 90 °.

Even in the case of the rotary circular polarizing plate 2, the polarizing plate 2 is made to be 0 by mechanical or optical means.
It is possible to automatically detect which direction of ° / 90 °, and various modifications are possible.

Embodiment 4 As described above, as one method for enlarging the viewing angle of the liquid crystal display panel, the sheet-like optically anisotropic member 5 is used as the polarizing member 2a.
It is effective to combine with. Therefore, in FIG. 4, the polarizing member of the polarizing plate 2 for converting the polarization axis by 0 ° / 90 °.
2a and the optically anisotropic member 5 are integrated.

Then, the expansion of the viewing angle of the panel in the NB mode can be further increased.

[0041]

According to the present invention, particularly in an alignment division type liquid crystal display device, the polarization axis of at least one of the polarizing plates is converted by 0 ° / 90 °, and accordingly, the positive image of the display screen /
Negative image inversion can be performed. Then, it becomes possible to use the conventional liquid crystal display device having a difficulty in the viewing angle and a defect in the color purity of white / black in an optimum display state.

As a result, in particular, the present invention can be applied to various applications of liquid crystal display devices by substituting for CRT display devices including color display TVs, and the present invention is directed to the further development of liquid crystal display devices. It has a great contribution.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing a configuration of a first embodiment of the present invention.

2A and 2B are perspective views of a second embodiment of the present invention, in which FIG. 2A is a perspective view showing a configuration, and FIG.

FIG. 3 is a partially cutaway perspective view of a third embodiment of the present invention.

FIG. 4 is a partially cutaway perspective view of a main part of a fourth embodiment of the present invention.

5A and 5B are schematic cross-sectional views of an alignment division type liquid crystal display panel, where FIG. 5A is a state in which no voltage is applied, and FIG. 5B is a state in which voltage is applied.

FIG. 6 is an explanatory diagram of an NW mode alignment division method,
(A) is a layout diagram of a polarizing plate, and (B) is a relationship diagram of the voltage V and the transmittance T.

7 is an explanatory diagram of an NB mode alignment division method, and FIG.
FIG. 7A is a layout view of polarizing plates, and FIG. 7B is a relationship diagram between voltage V and transmittance T.

[Explanation of symbols]

1 Liquid crystal display panel 2 Polarizing plate 2a Polarizing member 2b
Frame member 2c Cutout 2d Circular cutout 3 Control circuit 3a Drive circuit 3b
Interface circuit 3c Positive / negative inversion circuit 4 Polarizing plate support 4a Polarizing plate detector 4b
Stop pin 5 Optical display panel 10 Liquid crystal display device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shun Roki 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited

Claims (8)

[Claims] 1. A liquid crystal display panel (1) and two polarizing plates
(2) and a control circuit (3), wherein the liquid crystal display panel (1) is for performing display by controlling light transmission / light blocking while intermittently applying a voltage to the liquid crystal. ) Is composed of a polarizing member (2a) and a frame member (2b) supporting the polarizing member (2a), at least one of which sandwiches the liquid crystal display panel (1) from both sides, and has a polarization axis of 0.
The drive circuit (3) selectively applies a voltage to the liquid crystal, and the display of the liquid crystal display panel (1) is positive / negative. A liquid crystal display device having a function of inverting a negative image. 2. The liquid crystal display device according to claim 1, wherein the liquid crystal display panel (1) is an alignment division type in which each pixel electrode is divided into at least two. 3. A polarizing plate supporting member (4) is provided, wherein the polarizing plate supporting member (4) is capable of converting the polarizing axis of the polarizing plate (2) by 0 ° / 90 °. The liquid crystal display device according to claim 1, which supports the presence or absence of the / 90 ° conversion in a detectable manner. 4. The polarizing plate (2), comprising a rectangular frame member (2b), is removably inserted into the polarizing plate support (4) at an angle of 0 ° / 90 °. Item 3. The liquid crystal display device according to item 3. 5. The polarizing plate (2) comprises a circular frame member (2b) and is attached to the polarizing plate support (4) at least 0 ° / 90 °.
The liquid crystal display device according to claim 4, which is rotatably supported. 6. The polarizing plate supporting device wherein the control circuit (3) is provided.
(4) is for inversion of the positive / negative image of the liquid crystal display panel (1) according to a command from the polarizing plate (2).
The liquid crystal display device according to claim 1, wherein the positive image / negative image inversion is performed when the polarization axis of the image is converted by 0 ° / 90 °. 7. The control circuit (3), when performing positive / negative image reversal of the display of the liquid crystal display panel (1), reverses / reverses the gradation order of the display. Liquid crystal display device. 8. The liquid crystal display device according to claim 1, wherein the polarizing member (2a) is integrated with at least one sheet-shaped optically anisotropic member (5).