JPH02822A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To produce the bright liquid crystal display element with a good black-and-white extent at high yield by specifying the product of the refractive index anisotropy of the liquid crystal in a liquid crystal layer and the thickness of the liquid crystal layer, providing a light shield film to a nondisplay part, and arranging uniaxial birefringent plates between the liquid crystal layer and a polarizing plate. CONSTITUTION:The product DELTAn1.d1 of the refractive index anisotropy DELTAn1 of the liquid crystal in the liquid crystal layer 3 and the thickness d1 of the liquid crystal 3 is set to 0.4-1.5mum and the light shield film is provided to at least part of the nondisplay part; and the uniaxial birefringent plates 4A and 4B are arranged between the liquid crystal and at least either of deflecting plates 1 and 2 and a light source is provided on the reverse side. Only one liquid crystal layer 3 is required and no 2nd liquid crystal layer which easily causes deterioration in productivity and a color irregularity is not necessary. Consequently, a black-and-white display which has a higher contrast ratio than a conventional supertwist liquid crystal display element is can be obtained and a sharp negative display of high display quality is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal display element suitable for high-density display.

[Prior art] Conventionally, by increasing the twist angle of liquid crystal molecules between both electrodes,
A super twist element (T
, J., 5chefferand J., Nehr.
ing, Appl, Phys, Lett,
45(10) 1021-1023 (1984)
) was known.

However, in this method, the value of Δn-d between the birefringence Δn of the liquid crystal of the liquid crystal display element used and the thickness d of the liquid crystal layer is substantially between 0.8 and 1.2 μm (Japanese Patent Application Laid-Open No. 60-10
No. 720), good contrast was obtained only with specific combinations of display colors, such as yellow-green and dark blue, bluish-violet and light yellow.

As described above, since this liquid crystal display element could not perform black and white display, it had the disadvantage that it could not perform multicolor or full color display when combined with a microcolor filter.

On the other hand, a method has been proposed that uses a similar method and sets the product Δn-ci of the liquid crystal's birefringence and thickness to a small value of around 0.6 μm, thereby providing a nearly white and black display. . (M, 5chadtet al,
Appl, Phys, Lett, 50(5),
1987, p. 236) However, when this method was used, the display was dark, the maximum contrast was not very high, and the display had a bluish tinge, so there was a drawback that the display lacked sharpness.

In addition, as a liquid crystal display element with black and white display and high contrast, there is a method in which two layers of liquid crystal cells with opposite spirals are stacked, a voltage is applied to only one cell, and the other cell is used simply as an optical compensation plate. Proposed. (Haka Okumura, Television Society Technical Report, 11(27), p. 7
9. (1987)) However, with this method, the 80-d matching in a 2N cell is extremely difficult, making it difficult to improve yield, and because it requires two layers of liquid crystal cells, it sacrifices the thin and light characteristics of liquid crystal cells. It had its drawbacks.

[Problem to be solved by the invention l In the conventional method, a bright liquid crystal display element with good black and white
It was difficult to produce with good yield.

Bright black-and-white display elements are not only easy to see without any distinctive coloring, but also have color filters formed inside or outside the cells, unlike conventional twisted nematic (TN) elements with a 90° twist. It is expected that the market will expand dramatically as it can realize mono-color, multi-color, or full-color display, and is thin, lightweight, and has low power consumption.

For this reason, there has been a desire for a liquid crystal display element that is a bright monochrome display element with good contrast and can be produced with high yield.

Means for Solving the Problems 1 The present invention has been made to solve the above-mentioned problems, and includes an optically active optical system sandwiched between a pair of substrates with transparent electrodes arranged substantially in parallel and having alignment control films. The twist angle of the nematic liquid crystal with positive dielectric anisotropy containing a polar substance is 160
A liquid crystal display element that has a liquid crystal layer with an angle of ~300°, a driving means that applies a voltage between transparent electrodes on a substrate under L that sandwich this liquid crystal layer, and a pair of polarizing plates installed on the outside of this liquid crystal layer. In, the product Δn,・d, of the refractive index anisotropy Δn of the liquid crystal in the liquid crystal layer and the thickness dl of the liquid crystal layer, is 0.4 to 1.5 μm
and a light-shielding film is provided on at least part of the non-display area,
A liquid crystal display element characterized in that a birefringent plate is disposed on at least one side between a liquid crystal layer and a polarizing plate, and a light source is provided on the back side, and the refractive index of liquid crystal in the liquid crystal layer. The ratio Δn1·d between the anisotropy Δn1 and the thickness dl of the liquid crystal layer is 0.
4 to 1.5 μm, a light shielding film is provided on at least part of the non-display area, a pair of birefringent plates are placed on both sides of the liquid crystal layer and inside a pair of polarizing plates, and a light source is provided on the back side. 802·d2 of the liquid crystal display element and its birefringent plate is 2 of the size of Δn1·d of the liquid crystal layer.
73 or less and 1/12 or more.

In the present invention, a uniaxial birefringent plate is disposed at least on one side between the liquid crystal layer and the polarizing plate.

Therefore, only one liquid crystal layer is required, and a liquid crystal display element with bright black and white display can be easily obtained without reducing productivity or providing a second liquid crystal layer that tends to cause color unevenness.

This liquid crystal layer has the same structure as the liquid crystal layer of a conventional super twist liquid crystal display element, and has electrode groups facing each other, thereby making it possible to control on/off for each dot. The twist angle of this liquid crystal layer is about 160 to 300@. In particular, about 200 to 260 degrees is preferable in terms of contrast, domain, etc.

Specifically, a dielectric anisotropic or positive nematic liquid crystal containing an optically active substance is sandwiched between a pair of transparent electrode substrates arranged almost in parallel, and the twist angle of the liquid crystal molecules between the two electrodes is set to 1.
The angle should be between 60 and 300 degrees. This is because if it is less than 160 degrees, there will be little improvement in contrast during time-division driving at high duty, which requires a steep change in transmittance, and if it exceeds 300 degrees, it will be difficult to improve the contrast. This is because hysteresis and domains that scatter light are likely to occur.

Also, the product Δn,·d of the refractive index anisotropy (Δn,) of the liquid crystal of the liquid crystal layer and the J7 value (dl) of the liquid crystal layer is 0.4 to 1.
It is assumed to be 5 μm.

This is because when the thickness is less than 0.4 μm, the transmittance when on is low;
The display color tends to be bluish, and the thickness of 1.5 μm
If the value exceeds , the hue when turned on changes from yellow to red, making it difficult to display black and white.

In particular, in applications where achromatic display colors are strictly required,
It is preferable that Δn,·dl of the liquid crystal layer be 0.5 to 1.0 μm.

Note that this range of Δn1·do is preferably satisfied within the operating temperature range of the liquid crystal display element, and a beautiful display can be obtained within the operating temperature range. Due to extreme performance requirements, only in a portion of the operating temperature range,
It is possible that this relationship may be satisfied. In this case, in a temperature range in which the range of Δn,·dl deviates from the above range, the display may become colored or the viewing angle characteristics may deteriorate.

ITO (In*O) patterned into the desired pattern
A film of polyimide, polyamide, etc. is provided on the surface of a substrate made of plastic, glass, etc. on which a transparent electrode such as 101-3no, 5nu2, etc. is provided, and this surface is rubbed or SiO
A substrate with transparent electrodes on which an alignment control film is formed by obliquely vapor-depositing the above-mentioned nematic liquid crystal with positive dielectric anisotropy is prepared between the substrates with transparent electrodes.
A liquid crystal layer with a twist of 60 to 300° is sandwiched between them. A typical example of this is a dot matrix liquid crystal display element in which many electrodes are formed in rows and columns, with 640 striped electrodes formed on one substrate and perpendicular to these on the other substrate. 400 stripe-shaped electrodes are formed on the screen, resulting in a display of 640 x 400 dots. Further, each of these 640 striped electrodes can be arranged in groups of 3 to form 1920 striped electrodes, and RGB color filters can be arranged to provide a full-color display of 640 x 400 dots.

Note that an insulating film such as NiTio2.5in2 or A1.03 may be provided between the electrode and the alignment control film to prevent short circuits between the substrates, or a lead electrode of low resistance such as AI, Cr, 'ri, etc. may be provided on the transparent electrode. Alternatively, a color filter may be placed above or below the electrode.

In the present invention, a light shielding film is formed on at least a portion of the non-display portion of this element.

There are various methods for forming this light-shielding film, including printing with black ink, dyeing, vapor deposition of thin metal films such as chromium and nickel, plating, etc., black photoresist, and electrodeposition. Can be used.

Furthermore, when a light-shielding film is provided on the inner surface of a cell, an insulating film may be formed on or under the light-shielding film as necessary.

Since the light shielding film apparently improves the contrast of the element, the light transmittance is preferably lower, and the light transmittance of the light shielding film is preferably 10% or less, particularly 5% or less. This is because the contrast of the display portion of the liquid crystal display element of the present invention is about 10 to 50.

This light-shielding film may be provided on the inner surface of the cell or on the outer surface of the cell, but it is preferable to provide it on the inner surface of the cell from the viewpoint of pattern misalignment.

When providing a light-shielding film on the inner surface of the cell by printing or dyeing, trying to increase the degree of light-shielding at the end of the cell will result in a thicker film, which may cause short circuits between the substrates or worsen the uniformity of the cell gap. There is a risk of causing Therefore, when forming a light shielding film using such a method, the light transmittance of the light shielding film should be 115 or more, particularly 1/2, of the light transmittance of the black part of the display area.
It is preferable that the amount is above 1%, specifically about 1 to 5%.

In this case, since the liquid crystal display element of the present invention performs high-duty driving, the contrast is lower than that of a liquid crystal display element with a light-shielding film used in conventional audio equipment and the like. This eliminates the need to increase the thickness of the light-shielding film in order to obtain a high degree of light-shielding, unlike the light-shielding films of liquid crystal display elements with light-shielding films conventionally used in audio equipment. , problems such as decreased uniformity of cell gaps and short circuits are less likely to occur.

Furthermore, although this light-shielding film is provided on at least part of the non-display area, it is usually used by providing a light-shielding film on all non-display areas except for the display area corresponding to the pixel electrode. .

This light-shielding film is provided in a non-display portion that is not a display pixel, but a portion without a light-shielding film may be provided even in the non-display portion.

For example, in the case of a dot matrix display, the light shielding film may be provided in a stripe or grid pattern between the dots, and may be provided on one substrate or separately on both substrates. You can.

As a result, even with a positive type cell configuration in which the display portion becomes black when a voltage is applied to the arrangement of the polarizing film of the liquid crystal display element, negative type display is possible.

A pair of polarizing plates is placed on the consumer side of this liquid crystal layer. This polarizing plate itself is generally placed outside the substrate that makes up the cell, but if performance permits, the substrate itself may be made up of a polarizing plate, or it may be provided as a polarizing layer between the substrate and the electrode. Good too.

In the present invention, a birefringent plate is laminated adjacent to the liquid crystal layer. This birefringent plate may be provided between the liquid crystal layer and the polarizing plate, and may be provided on only one side of the liquid crystal layer or on both sides.

Further, this birefringent plate may be provided between the liquid crystal layer and the polarizing plate; for example, it may be provided in a layer between the liquid crystal layer and the electrode, or it may be provided in a layer between the electrode and the substrate, or the substrate itself may be provided as a layer. It may be provided as a refractive plate, as a layer between a substrate and a polarizing plate, or as a combination of these.

As this birefringent plate, any transparent plate that exhibits -axial birefringence can be used, and plastic films, inorganic crystal plates, etc. can be used. In order to obtain the desired birefringence effect, Δn2・d2 is adjusted and used, but with one plate, TA
If it is not possible to adjust the birefringence, the same birefringence plate or a combination of a plurality of different birefringence plates may be used.

In order to perform a good black and white display, for a liquid crystal layer with a certain twist angle and Δn1・dl, the magnitude of Δn2・d2 of the −axial birefringent plate and the direction of their optical axes, and It is important to optimize the direction of the polarization axes of the pair of polarizing plates.

The size of Δn2・d2 of the birefringent plate (or the sum of the birefringent plates when multiple plates are used) should be set to approximately 273 or less and 1/12 or more of the size of Δn1・d of the liquid crystal layer. Easy to obtain black and white display. Specifically, about 0.05 to 0.7 μm
It is preferable that

Even if the magnitude of Δn2·d2 of the birefringent plate is larger than this, that is, even if it is approximately equal to the magnitude of Δn,*d of the liquid crystal layer, a black and white display can be obtained, but Δn
The larger 2·d2 is, the narrower the viewing angle tends to be. Therefore, in order to obtain a display with high contrast and a wide viewing angle, it is preferable to set Δn2·d2 to 273 or less of the magnitude of Δn1·dl of the liquid crystal layer.

Further, if Δn,·d2 is set smaller than 1/12 of the magnitude of Δn1·dl of the liquid crystal layer, the contrast will decrease and the deviation from black and white display will increase, so it is set to 1/12 or more.

For this reason, it is preferable to set Δn,·d2 to 273 or less of the size of Δn0·d of the liquid crystal layer, and to 1/12 or more, specifically, approximately 0.05 to 0.7 μm. .

When set in this way, it is difficult to obtain a high-contrast negative display, but a high-contrast positive display is obtained. Therefore, by combining this high-contrast, positive-display liquid crystal display element and a light shielding layer, a high-contrast, negative-display liquid crystal display element can be obtained.

The present invention will be described in more detail below with reference to the drawings.

FIG. 1 is a perspective view schematically showing a liquid crystal display element according to the present invention. Figures 2 (A) and (B) show the polarization axis direction of the upper polarizing plate in Figure 1, the optical axis direction of the birefringent plate, the long axis direction of the liquid crystal molecules above the liquid crystal layer, and , is a plan view showing the relative positions of the polarization axis direction of the lower polarizing plate, the optical axis direction of the birefringent plate, and the long sleeve direction of the liquid crystal molecules under the liquid crystal layer.

In FIG. 1, 1.2 is a pair of polarizing plates, 3 is Δn, *d, or 0.4 to 1.2 for displaying characters and figures.
48, 4B is a liquid crystal layer with a torsion angle of 160 to 300' made of Nemadig liquid crystal with a positive dielectric anisotropy of 5 μm.
Birefringent plate laminated below, 5 is the polarization axis of the upper polarizing plate,
6 is the polarization axis of the lower polarizing plate, 7 is the liquid crystal molecule above the liquid crystal layer, 8 is the liquid crystal molecule below the liquid crystal layer, 9A is the optical axis direction of the upper birefringent plate, and 9B is the lower birefringent plate. It shows the optical axis direction of the refracting plate. A light source (not shown) is provided below this lower polarizing plate.

In FIG. 2, 01 is the direction of the polarization axis 5 of the upper polarizing plate when viewed from the long axis direction of the liquid crystal molecules 7 above the liquid crystal layer, and 01 is the long axis of the liquid crystal molecules 7 above the liquid crystal layer. 02 is the optical axis direction 9A of the upper birefringent plate measured clockwise when viewed from the direction, and 02 is the direction of the polarization axis 6 of the lower polarizing plate when viewed from the long axis direction of the liquid crystal molecules 8 below the liquid crystal layer. 03 is measured clockwise, and 04 is measured clockwise in the optical axis direction 9B of the lower birefringent plate viewed from the long sleeve direction of the liquid crystal molecules 8 below the liquid crystal layer.

In the present invention, these θ8, θ2, θ3, and θ4 may be optimized so that black and white display is achieved.

When using the pixel portion of the liquid crystal display element of the present invention in a negative drive mode, for example, the twist angle of the liquid crystal layer is set to be about 240''', its Δn,·d is set to be about 0.8 μm, and the liquid crystal layer is placed above and below it. If Δn2·d2 of the pair of uniaxial birefringent plates is about 0.4 μm, it is preferable that the polarizing axes of the pair of polarizing plates intersect at an angle of about 60 to 120@.

In addition, when using the same liquid crystal layer and a uniaxial birefringent plate and using the pixel part with positive drive, it is necessary to make the polarization axes of the pair of polarizing plates intersect at an angle of approximately ±30 degrees. 6 In the present invention, since a light-shielding film is provided in the non-display area, even if the drive of the pixel part is a positive drive in which the part to which voltage is applied becomes black, negative display is possible. Become.

That is, in a positive type display, in a pixel portion, a voltage is applied to the pixels to be identified and the pixels become black, and to pixels not to be identified, no voltage is applied and the pixels become white, resulting in a black display on a white background. On the other hand, in this negative type display using positive type drive, the non-display area without electrodes is blackened with a light shielding film, and in the pixel area, no voltage is applied to the pixel that you want to identify, so it becomes white and you do not want to identify it. A voltage is applied to the pixel and the pixel turns black, resulting in a white display on a black background.

In the present invention, by this negative type display by positive type drive,
Compared to a simple negative type display as described above, a high-contrast black-and-white display with excellent viewing angle characteristics is possible.

In this case, for 02.04, 51≦02≦14
By setting 0@, 40'''≦04≦170'', it is possible to realize a high-contrast positive display with high off-state transmittance and low on-state transmittance, which is preferable.

As a result, this liquid crystal display element is capable of black-and-white display with excellent viewing angle characteristics and a high contrast ratio.

In the above example, the liquid crystal layer is left spiral, but even if it is spiral or reverse, the direction of the long axis of the liquid crystal molecules in the liquid crystal layer, the direction of the polarization axis of the polarizing plate, and the optical axis direction of the birefringent plate may be different. Relationship θ1, θ
2.01 and θ4, a black and white display can be easily obtained as in the above example.

Note that in the present invention, since a display close to a black and white display can be obtained, a colorful display can be achieved by using a color filter in combination. In particular, even with high-duty driving, a high contrast ratio can be achieved, so full-color gradation display is possible, and it can also be used in LCD televisions.

By forming this color filter on the inner surface of the cell, more precise color display is possible without causing deviations due to viewing angles. Specifically, it may be formed below the electrode or above the electrode.

Also, if you need to make the colors completely black and white,
A color filter for color correction or a color polarizing plate may also be used, a dye may be added to the liquid crystal, or illumination having a specific wavelength distribution may be used.

In the present invention, a driving means for applying a voltage is connected to the electrodes of the liquid crystal cell having such a configuration, and the liquid crystal cell is driven.

Note that in the present invention, since a light-shielding film is also used, even if the display method is a positive type, a negative type display can be realized in terms of appearance. A negative type display has a feature of extremely good visibility when used as a transmission type, or in this case, a light source is placed on the back side. Of course, a light guide, a color filter, etc. may be used in combination with this.

In addition to this, the present invention includes, within the scope that does not impair the effects of the present invention,
Various techniques used in ordinary liquid crystal display elements can be applied.

In the present invention, the time division characteristics are on the same level as super twist liquid crystal display elements, and as mentioned above, bright and clear black and white display is possible. Therefore, fine color filters of the three primary colors of red, green, and blue are used as a shade inside the cell. By arranging them, it is possible to obtain a high-density multi-color liquid crystal display element.

The liquid crystal display element of the present invention can be used for personal computers,
Suitable as a display element for word processors, workstations, etc., LCD TVs, fish finders, etc.
It can be used for a variety of purposes, including radars, oscilloscopes, and various consumer dot matrix display devices, regardless of black and white display or color display.

[Operation 1] Although the principle of operation of the present invention is not necessarily clear, it can be estimated as follows.

FIG. 3(A) is a schematic side view showing the structure of a super-twist liquid crystal display element that does not use only a birefringent plate in comparison with the liquid crystal display element of the present invention, and shows a twist angle of 160 to 300. °, Δn, * d, is 0.4 to 1
．． A liquid crystal layer 13 made of nematic liquid crystal having a positive dielectric anisotropy of 5 μm, and a pair of polarizing plates 1 disposed above and below the liquid crystal layer 13.
1.12. In this example, the intersecting angle of the polarization axes of the pair of polarizing plates 11 and 12 arranged below 1 is 90°.

In the case of a liquid crystal display element having such a configuration, when no voltage is applied to the liquid crystal layer or when a low voltage such as a non-selection voltage is applied, the lower polarizing plate 1 on the incident side
When almost completely linearly polarized light passes through the liquid crystal layer 13, it becomes elliptically polarized. The shape and direction of this elliptical polarization differ depending on the wavelength of the light, and it divides light into three colors: red, green, and blue.
If we consider the primary colors separately, we get the result as shown in Figure 3 (B). When these circularly polarized lights with different shapes and directions pass through the upper polarizing plate 11 on the output side, the intensity of the passing light differs depending on the red, green, and blue light, so it appears colored in a specific color. . In addition, in Fig. 3 (B), 15.16
indicate the polarization axes of the polarizing plates 11 and 12, respectively.

On the other hand, in the present invention, the torsion angle is 160 to 300, as shown in FIG.
'', a liquid crystal layer 23 made of a nematic liquid crystal having a positive dielectric anisotropy of Δnl' dl or 0.4 to 1.5 μm, two uniaxial birefringent plates 24A and 2 disposed on the
4B, and a pair of polarizing plates 21 disposed above and below it.
22.

In this example, the twist angle of the liquid crystal layer is 240°Δn,・d,
is 0.82 μm, and the crossing angle of the polarization axes of the pair of polarizing plates 21 and 22 arranged above and below is 90°. Note that in this example, two uniaxial birefringent plates are stacked on one side to simplify the explanation, but it is also possible to use one or three or more uniaxial birefringent plates on one side. Alternatively, as described above, a pair of one or more uniaxial birefringent plates may be provided above and below the liquid crystal layer.

When this -axial birefringent plate is sandwiched between polarizing plates, it can convert incident linearly polarized light into arbitrary elliptical polarization or circularly polarized light depending on the value of Δn2・d2 of the -axial birefringence plate. , or it has the property of being able to return to linearly polarized light. Therefore, by superimposing a birefringent plate with an appropriate value of Δn2·d2 on the liquid crystal layer, the structure shown in FIG. 4 ([3)] can be obtained.

That is, in a state where no voltage is applied to the liquid crystal layer or a low voltage such as a non-selective voltage is applied, either the light is almost completely linearly polarized through the lower polarizing plate 22 on the incident side, or the light is almost completely linearly polarized through the lower polarizing plate 22 on the incident side. When transmitted through liquid crystal M2:1, the light becomes circularly polarized. By further passing this elliptically polarized light through the birefringent plates 24A and 24B, the elliptical polarized light may be returned to a state close to linearly polarized light depending on the conditions.

If we consider that light is divided into the three primary colors of red, green, and blue, it becomes as shown in Figure 4 (B). As in this example, when the directions of the red, green, and blue polarization axes are almost the same and the polarization returns to almost linear polarization, the wavelength dependence of the intensity of the passing light can be eliminated regardless of the direction of the polarization axis on the output side. I can do it. In other words, it is possible to make it achromatic.

As in this example, a polarizing plate is installed so that the polarization axes intersect by 90 degrees, and 02·d2 of the -axial birefringent plate is 2/3 to 1/2 of Δn, ·d, of the liquid crystal layer. If it is as low as about 12 and the polarization on the output side matches the polarization axis of the upper polarizing plate on the output side, the transmitted light intensity is close to achromatic,
It becomes the highest and appears white. By combining this with the light-shielding film in the non-display area, negative display is achieved. In FIG. 4(B), 25 and 26 indicate the polarization axes of the polarizing plates 21 and 22, respectively.

- Δn, d of the axial birefringent plate is Δn dl of the liquid crystal layer
If the polarization on the output side matches the absorption axis of the upper polarizing plate on the output side, the transmitted light intensity will be the lowest and it will appear black, resulting in a negative display. . In this case, as described above, it tends to be difficult to simultaneously obtain good contrast and a wide viewing angle.

Note that negative and positive display values are determined by the twist angle of the liquid crystal layer and its Δ
n, e, d, -80, d2 of the axial birefringent plate, angles θ0, θ2, o3.04 between them and the polarizing plate, etc., can be changed by changing the structural conditions.

On the other hand, if a sufficient voltage is applied to the liquid crystal layer with this configuration, the shape and direction of the elliptical polarized light transmitted through the liquid crystal layer will be different from before the voltage was applied.

Therefore, the elliptical polarization state after passing through the birefringent plate is also y4
This changes the transmittance and makes display possible.

However, although the insertion of a birefringent plate successfully aligns the shape and direction of the elliptical polarized light and creates a black or white state when no voltage is applied, this does not necessarily mean that the state becomes white or black when a voltage is applied. is not limited. For this reason, it is preferable to experimentally optimize Δn2·d2 of the birefringent plate, its front axis direction, the polarization axis direction of the polarizing plate, etc. using parameters such as the twist angle of the liquid crystal layer and Δn1·dl.

This effect of the birefringent plate works similarly even if the birefringent plate is placed on the incident side of the liquid crystal layer.

In the liquid crystal display element of the present invention, at least a portion of the non-display portion other than the opposed portions of the transparent electrodes, that is, the non-display portion other than the display element, is covered with a light-shielding film. Normally, a light-shielding film is made to cover all non-display areas other than display pixels, but in order to display a positive tone on some of the non-display areas, it is recommended not to provide a light-shielding film on some of the non-display areas. You may also do so.

By providing a light-shielding film in the non-display portion in this way and creating a negative type display, the display contrast is apparently significantly improved. Note that by using a positive type display liquid crystal cell and this light shielding film in combination to create a pseudo negative type display, there is also the advantage that the viewing angle becomes wider.

This apparent improvement in display contrast may be due to the following reasons.

That is, a large-scale dot matrix type liquid crystal display element such as 640 x 400 dots is used in a transmission type, and
When displaying "black", the dots are so minute that the naked eye simultaneously perceives the black dots and the light leaking between the dots, and perceives "black" as the amount of light that is a mixture of both. Therefore, compared to the contrast caused by turning on and off only one pixel, the apparent contrast is lowered due to light leaking from the dot gaps.

However, in the present invention, the non-display portions such as the dot gaps are covered with a light shielding film. Therefore, if the light-shielding film sufficiently blocks light between the dots, the black perceived by the naked eye at each dot will be at the same level as the black at a cell with only one pixel. Therefore, if the brightness of the light source is set to a sufficient level, a bright display with the same contrast as the original one-pixel cell can be easily obtained.

In particular, as described above, by using a positive type display liquid crystal cell in combination with this light shielding film to create a pseudo negative type display, a liquid crystal display element with a wide viewing angle and high contrast can be obtained.

[Example] Example 1 As a first substrate, an ITO transparent electrode provided on a glass substrate was patterned into a stripe shape, and an insulating film made of SiO□ for short-circuit prevention was formed by vapor deposition, and an insulating film was formed in the gap between the electrodes. A black light-shielding film with a transmittance of approximately 3% was formed in stripes using a dyeing method, a polyimide overcoat was spin-coded, and this was rubbed to form a self-regulating #M film to create a substrate.

As a second substrate, an ITO transparent electrode provided on a glass substrate is patterned into a stripe shape perpendicular to the first substrate, an insulating film of SiO□ is formed, and the electrode is A black light-shielding film with a transmittance of about 3% is formed in stripes in the gap using a dyeing method, overcoated with polyimide, and rubbed at an intersection angle of 60'' with the rubbing direction of the first substrate. A substrate on which an alignment control film was formed was prepared.

The periphery of these two substrates is sealed with a sealing material to form a liquid crystal cell, and dielectric anisotropy or positive nematic liquid crystal is injected into this liquid crystal cell to form a liquid crystal layer twisted at 240 degrees. The injection port was sealed. In this liquid crystal layer, Δn,・d,
was 0.82 μm.

Uniaxial birefringent plates of Δn,·d, or 0.14 μm were laminated on both sides of this liquid crystal cell, and a pair of polarizing plates were further laminated above and below the birefringent plates.

The relative relationship between the long axis direction of the liquid crystal molecules of this liquid crystal display element, the polarization axis direction of the polarizing plate, and the optical axis direction of the birefringent plate is 0.
+=115@θ,=95°O:1=130@,θ,
= 110''.

As a result of applying a voltage to this liquid crystal display element and examining its transmittance change, as shown in Figure 5, good threshold voltage characteristics were obtained, and a good contrast ratio was obtained when multiplex driving was performed. I found out that I can get it.

A backlight of a C light source was arranged on the back side of this liquid crystal display element, and the element was driven at a duty of 1/200 and a bias of 1/15, and the hue in the on and off states was observed. The results are shown in Figure 6.As is clear from the results, a good self-level is obtained when the camera is off, and a positive black-and-white with a slightly bluish tinge when it is on, but because the transmittance is low, it looks sufficiently black. Display or obtained.

When we measured the apparent contrast ratio of this liquid crystal display element, we found that it was approximately 30, and the contrast ratio of only one pixel should be substantially the same, but that of a positive type display with the same configuration except for the absence of a light-shielding film. An apparent contrast ratio four times higher than that of a liquid crystal display element was obtained.

Furthermore, the viewing angle characteristics were also good.

Example 2 Δn2・d was 0 on both sides of the liquid crystal cell prepared in Example 1.
．． Uniaxial birefringent plates of 40 μm were laminated, and a pair of polarizing plates were further laminated above and below the plates.

The relative relationship between the long axis direction of the liquid crystal molecules of this liquid crystal display element, the polarization axis direction of the polarizing plate, and the optical axis direction of the birefringent plate is 0.
．． = 150", 02=8560, = 120'
,O,=95@closed.

When this liquid crystal display element was placed on the backside with a C light source backlight and driven at 1/200 duty and 1/15 bias, the hue in the on and off states was observed, and a good white level was obtained when it was on. When off, the light was slightly yellowish or the transmittance was low, so a negative black-and-white display that appeared sufficiently black was obtained.

Although this liquid crystal display element had a high contrast ratio when viewed from the front, as in Example 1, the contrast ratio when viewed from a direction tilted 30'' from the vertical was about half that of Example 1; The viewing angle was narrower than the previous one.

Example 3 A liquid crystal display element was created by changing only the relative relationship between the long axis direction of the liquid crystal molecules, the polarization axis direction of the polarizing plate, and the optical axis direction of the birefringent plate in the liquid crystal display element of Example 1. . That is, 0, = 100″'02 = 70@, Ox = 6
5', Q < = 85''.

When this liquid crystal display element was driven at 1/200 duty and 1/15 bias in the same manner as in Example 1, Example 1
Almost the same black and white display was obtained, and the apparent contrast ratio was about 30.

Example 4 When three color filter layers were formed in stripes on the electrodes of the liquid crystal display element of Example 1 and the device was driven, full color gradation driving was possible.

[Effects of the Invention] As explained above, the present invention enables a black and white display with a better contrast ratio than the conventional super twist liquid crystal display element, and enables a negative type display with clear and high display quality. can get.

In addition, it has excellent effects such as time division display characteristics and viewing angle characteristics comparable to those of conventional super twist liquid crystal display elements.

In addition, since the display is close to black and white, by combining color filters with Ml, colorful displays are possible.In particular, by arranging red, green, and blue color filters for each pixel, multi-color and full-color It has also been recognized that it is effective in displaying images, opening up more diverse applications.

Furthermore, in the present invention, by simply arranging the birefringent plate,
Bright black and white display is possible without providing a second liquid crystal layer, and the liquid crystal display element has the advantage of extremely high productivity.

In particular, as mentioned above, by using a positive type display liquid crystal cell in combination with this light-shielding film to create a negative type display, it is possible to obtain a liquid crystal display element with a wide viewing angle and high contrast. .

The present invention can be applied in various ways in the future without detracting from the effects of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a perspective view schematically showing a liquid crystal display element according to the present invention. Figure 2 (A) ([3) is a plane showing the relative positions of the long axis direction of the upper and lower liquid crystal molecules, the polarization axis direction of the polarizing plate, and the optical axis direction of the birefringent plate, respectively, when viewed from above. It is a diagram. FIGS. 3A and 3B are schematic diagrams showing the structure of a simple super-twist liquid crystal display element, and a plan view illustrating the state of polarization thereof. FIGS. 4(A) and 4(B) are schematic diagrams showing the structure of the liquid crystal display element of the present invention and plan views illustrating the state of polarization thereof. FIG. 5 is a graph showing the threshold voltage characteristics of Example 1. FIG. 6 is a hue diagram showing hues in the on and off states of Example 1. 1.2.11.12.21.22 is a polarizing plate, 3.13.
23 is a liquid crystal layer, 4A, 4B, 24A, 24B are birefringent plates, 5.6.15
．． 16.25.26 is the polarization axis, 7.8 is the long axis direction of liquid crystal molecules, 9^, 9B is the optical axis direction of the birefringent plate.

Claims (3)

[Claims] (1) A nematic liquid crystal with positive dielectric anisotropy containing an optically active substance sandwiched between a pair of substrates with transparent electrodes arranged almost in parallel and having an alignment control film has a twist angle of 16
It has a liquid crystal layer of 0 to 300° and a driving means for applying a voltage between transparent electrodes of upper and lower substrates sandwiching this liquid crystal layer,
In a liquid crystal display element in which a pair of polarizing plates is installed outside the liquid crystal layer, the product Δn_1·d_1 of the refractive index anisotropy Δn_1 of the liquid crystal in the liquid crystal layer and the thickness d_1 of the liquid crystal layer is 0.4 to
1.5 μm, a light shielding film is provided on at least a part of the non-display area, a uniaxial birefringent plate is arranged on at least one side between the liquid crystal layer and the polarizing plate, and a light source is provided on the back side. A liquid crystal display element. (2) A twist angle of 16 by a nematic liquid crystal with positive dielectric anisotropy containing an optically active substance and sandwiched between a pair of substrates with transparent electrodes arranged almost in parallel and having alignment control films.
It has a liquid crystal layer of 0 to 300° and a driving means for applying a voltage between transparent electrodes of upper and lower substrates sandwiching this liquid crystal layer,
In a liquid crystal display element in which a pair of polarizing plates is installed outside the liquid crystal layer, the product Δn_1·d_1 of the refractive index anisotropy Δn_1 of the liquid crystal in the liquid crystal layer and the thickness d_1 of the liquid crystal layer is 0.4 to
1.5 μm, a light shielding film is provided on at least part of the non-display area, a pair of birefringent plates are placed on both sides of the liquid crystal layer and inside a pair of polarizing plates, and a light source is provided on the back side. A liquid crystal display element featuring: (3) The liquid crystal display element according to claim 1 or 2, wherein Δn_2·d_2 of the birefringent plate is 2/3 or less and 1/12 or more of the magnitude of Δn_1·d_1 of the liquid crystal layer. display element.