JPH07318959A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To improve an angle of visibility characteristic and to reduce an angle of visibility area where a gradation inversion phenomenon occurs. CONSTITUTION:Electrodes 3, 4 and the electrodes 5, 6 respectively making a pair are formed on a substrate 1 and the substrate 2 holding a liquid crystal layer 7 therebetween. When a voltage is impressed between the electrodes 3, 4 and between the electrodes 5, 6, electric fields occur between electrode gaps on the substrates 1, 2 respectively. By the electric field, an oriented direction of a liquid crystal molecule in the liquid crystal layer 7 is controlled, and a display is performed without using a twist structure, and the angle of visibility area where the gradation is inverted when a gradation display is performed is reduced, and the angle of visibility characteristic when a halftone is displayed is improved remarkably.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high quality liquid crystal display device, and more particularly to a liquid crystal display device having a wide viewing angle.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have been widely applied to display terminals of information equipment such as personal computers and word processors, and video equipment such as televisions and video monitors.

Although many types of liquid crystal display modes have been proposed, one of the widely used types is a twisted nematic type (TN type). In this type of liquid crystal display device, as shown in the perspective view of FIG. 13, a liquid crystal layer is arranged between a substrate 41 on which an electrode 43 is formed and a substrate 42 on which an electrode 44 is formed and which is parallel to the substrate 41. The substrate 41, 42 is sandwiched between two polarizing plates 46, 47. The lines shown on the polarizing plates 46 and 47 respectively represent the directions of the polarization axes. When the liquid crystal molecules 45 of the liquid crystal layer are in the initial alignment direction, that is, when no voltage is applied to the electrodes 43 and 44, the liquid crystal molecules 45 have a twisted arrangement as shown in the right side of FIG. The long axis of the liquid crystal molecule 45 on the substrate 41 and the long axis of the liquid crystal molecule 45 on the substrate 42 are substantially orthogonal to each other.

When no voltage is applied to the electrodes 43 and 44,
Due to the twisted structure of the liquid crystal molecules 45, the linearly polarized light passing through the polarizing plate 46 propagates in the liquid crystal layer while rotating its polarization plane by 90 °. On the other hand, when a sufficiently high voltage is applied to the electrodes 43 and 44, the liquid crystal molecules 45 have their long axes aligned in the direction of the electric field and are arranged vertically to the substrates 41 and 42 as shown on the left side of FIG. Rotation of the plane of polarization does not occur because the twisted structure is lost. Therefore, as shown in FIG. 13, when two polarizing plates 46 and 47 whose polarization axes are orthogonal to each other are arranged,
A bright display is obtained when no voltage is applied, and a dark display is obtained when a voltage is applied. Also, when two polarizing plates 46 and 47 are arranged so that the polarization axes are parallel to each other, a bright and dark display is obtained. Gives the opposite display. Further, by applying an intermediate voltage to the electrodes 43 and 44 so that the liquid crystal molecules 45 stand up to some extent with respect to the substrates 41 and 42, halftone display can be performed.
(For example, electronic display device (Ohm) 35-37
See page).

FIG. 14 shows the results of an experiment conducted to investigate the viewing angle characteristics of a TN type liquid crystal display device.
In, the circumferential direction indicates the azimuth angle, and the radial direction indicates the deflection angle. In FIG. 14, the TN is changed in the range of −180 ° to + 180 ° in the azimuth angle and 0 ° to 70 ° in the tilt angle with respect to the image display surface of the liquid crystal display device, and the TN is changed.
When a four-gradation display is performed by a liquid crystal display device of the type, a shaded area is provided in a display image in which the grayscale cannot be identified between grayscales or the grayscale is reversed.

As an attempt to improve the viewing angle characteristics based on a TN type liquid crystal display device, for example, as shown on pages 547 to 550 of Japan Display '92 (S.I.D. There is a lateral TN type liquid crystal display device in which a twist angle of liquid crystal molecules is controlled by using an electric field parallel to a plane to obtain a desired display brightness. Figure 15 shows lateral TN
FIG. 3 is a perspective view showing the configuration and operation of a mold type liquid crystal display device.

An important difference between the lateral TN type and the TN type is that a pair of parallel electrodes 53 and 54 are formed on the lower substrate 52 in order to apply an electric field to the liquid crystal layer in a direction parallel to the substrate surface. That is what is being done. When the liquid crystal layer is sandwiched between this substrate 52 and the upper substrate 51, and the liquid crystal molecules 55 of the liquid crystal layer are in the initial alignment direction, the long axis of the liquid crystal molecules 55 on the substrate 51 and the liquid crystal molecules 55 on the substrate 52 If the long axis and the long axis are made substantially orthogonal to each other as shown in the right side of FIG. 15, the liquid crystal molecules 55 are generated when no voltage is applied.
As in the TN type, a 90 ° twisted arrangement is adopted, and the linearly polarized light passing through the polarizing plate 56 propagates in the liquid crystal layer while rotating its polarization plane by 90 °. On the other hand, when a voltage is applied between the electrodes 53 and 54 of the lower substrate 52, the liquid crystal molecules 55 near the surface of the substrate 52 tend to align with their major axes in the direction of the electric field, so that the applied voltage increases. The twist angle of the liquid crystal molecules 55 gradually decreases from 90 ° to 0 °, and when the applied voltage is sufficiently high,
The parallel arrangement (homogeneous arrangement) is shown on the left side of FIG. Therefore, the two polarizing plates 5 are provided outside the substrates 51 and 52.
By arranging 6 and 57 respectively, bright and dark display can be performed according to the same principle as the TN type. In addition, liquid crystal molecules 55
The voltage is controlled by controlling the magnitude of the twist angle of the liquid crystal molecules. However, since the liquid crystal molecules 55 do not rise up with respect to the substrates 51, 52, the asymmetry of the molecular arrangement is less than that of the TN type,
Wider viewing angle in the halftone.

FIG. 16 shows a viewing angle region in which the gradation of a 4-gradation image in the lateral TN type liquid crystal display device cannot be identified or is reversed, as indicated by the shaded region as in FIG. As is apparent from FIG. 16, the lateral TN type liquid crystal display device can significantly improve the viewing angle characteristics as compared with the TN type liquid crystal display device.

Further, in the lateral TN type liquid crystal display device, the arrangement when no voltage is applied may be a homogeneous arrangement, and the twist angle may increase with the application of the voltage. It is almost the same as what was done.

[0010]

The conventional TN type liquid crystal display device has a problem of so-called viewing angle characteristic in which optical characteristics such as luminance, contrast and chromaticity change depending on the viewing angle of an observer. Particularly in the case of performing halftone display, in the TN type, the liquid crystal molecules stand up to a certain degree to the substrate, so that the symmetry of the molecular orientation is lost, and as a result, the viewing angle characteristics are significantly reduced, and the viewing direction is reduced. Depending on the case, a gradation inversion phenomenon such that the gradation is inverted may occur.

Further, in the lateral TN type liquid crystal display device in which the twist angle of the liquid crystal molecule array is controlled by an electric field parallel to the substrate surface, as described above, the liquid crystal molecules are provided in the vicinity of one substrate, that is, an electrode formed by an electrode pair. Although the viewing angle characteristics are improved by moving only within the gap, even in this method, the gradation inversion phenomenon is still not solved in some viewing angle areas, and completely good viewing angle characteristics cannot be obtained. .

When the liquid crystal display device has a large screen or a plurality of observers view the liquid crystal display, this viewing angle characteristic becomes an important problem, and therefore improvement thereof is strongly demanded.

An object of the present invention is to solve the problems in the conventional liquid crystal display device and to provide a liquid crystal display device having dramatically improved viewing angle characteristics.

[0014]

In order to solve the above problems, in the liquid crystal display device of the present invention, a pair of electrodes are formed on the surfaces of the two substrates sandwiching the liquid crystal layer on the liquid crystal layer side. It is characterized by

[0015]

In the liquid crystal display device of the present invention, the pair of electrodes are formed on the surfaces of the two substrates sandwiching the liquid crystal layer on the liquid crystal layer side. Since the direction is voltage controlled, it is possible to perform display without using a twisted structure, and the viewing angle characteristics are greatly improved.

[0016]

Embodiments of the liquid crystal display device of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a perspective view showing a configuration of a liquid crystal display device of a first embodiment of the present invention, and FIG. 2 is a perspective view for explaining the operation of the liquid crystal display device of the first embodiment. is there. Reference numerals 1 and 2 denote substrates, respectively, and strip-shaped electrodes 3 and 4 are formed on the surface of the substrate 1 in pairs, and strip-shaped electrodes 5 and 6 are formed on the surface of the substrate 2 in pairs. The electrodes 3 and 4 are arranged in parallel on the substrate 1, and the electrodes 5 are arranged on the substrate 2.
And the electrode 6 are arranged in parallel. For the electrodes 3 to 6, a metal material such as aluminum or chromium, or a transparent conductive material such as indium and tin oxide (ITO) can be used. The latter has slightly higher resistance, but the electrodes 3 to
Since the liquid crystal molecules 10 on 6 also contribute to the display by moving along with the movement of the liquid crystal molecules 10 around, there is an advantage that a brighter display can be obtained. These two substrates have surfaces on which the electrodes 3 to 6 are formed facing each other, and the liquid crystal layer 7 is sandwiched therebetween. Liquid crystal molecules when no voltage is applied
The inner surfaces of the two substrates 1 and 2 are subjected to an alignment treatment by using, for example, a rubbing method so that 10 is in a predetermined arrangement state. Further, polarizing plates 8 and 9 for forming polarized light or displaying polarized light are arranged on the outer surfaces of the two substrates 1 and 2.

When no voltage is applied to the pair of electrodes 3 and 4 and the pair of electrodes 5 and 6, the liquid crystal molecules 10 are arranged in parallel (homogeneous arrangement) in a predetermined direction as shown on the right side of FIG. There is. At this time, the polarizing plate 8 is arranged such that the polarization axis is parallel to the long axis L of the liquid crystal molecules 10, and the light passing through the polarizing plate 8 reaches the polarizing plate 9 without changing the polarization state. The polarizing plate 9 is arranged so that the polarization axis is orthogonal to the polarizing axis of the polarizing plate 8, and thus, light whose polarization state does not change cannot pass through the polarizing plate 9 and the polarizing plate 9 Is displayed in a dark state.

On the other hand, when a sufficiently high voltage is applied between the pair of electrodes 3 and 4 of the upper substrate 1, a strong electric field is applied along the surface of the substrate 1 from the electrode 3 to the electrode 4 (or in the opposite direction). Therefore, a force is exerted on the liquid crystal molecules 10 near the surface of the substrate 1 such that the major axis L is oriented in the electric field direction (arrow E1 direction). At the same time, when a sufficiently strong voltage is applied between the pair of electrodes 5 and 6, a force is applied to the liquid crystal molecules 10 near the surface of the lower substrate 2 so that the long axis L is directed in the electric field direction (arrow E2 direction). Works. If the electrodes 3 and 4 and the electrodes 5 and 6 are arranged in parallel by applying a force to rotate the liquid crystal molecules 10 in the direction of the electric field near the surfaces of the substrates 1 and 2, it is shown on the left side of FIG. As described above, the liquid crystal molecules 10 rotate in the direction in which the major axis L coincides with the electric field direction and are arranged in parallel. In this case, since the polarization direction of the light passing through the polarizing plate 8 and the long axis L of the liquid crystal molecules 10 make an angle, the polarization state of the light changes while propagating in the liquid crystal layer 7, and the polarizing plate 9 The light arriving at becomes the elliptically polarized light, the component in the polarization axis direction of the polarizing plate 9 passes through the polarizing plate 9, and the display on the polarizing plate 9 becomes a bright state.

FIG. 3 is a characteristic diagram showing the relationship between the applied voltage to the electrodes and the relative transmittance of the liquid crystal layer. By changing the applied voltage to the electrodes 3 to 6, the liquid crystal molecules 10 are aligned in the initial alignment direction and the electric field direction. Since it is held in the intermediate position between
The relative transmittance of the liquid crystal layer 7 can be changed, and a display of intermediate brightness can be obtained.

In the above liquid crystal display device, liquid crystal molecules 10
, And the incident light has a single wavelength, the angle θ formed by the major axis L of the liquid crystal molecules 10 in the initial alignment direction and the electric field direction in FIG. When the product (Δn · d) of the refractive index anisotropy Δn and the thickness d of the liquid crystal layer 7 is half the wavelength of the incident light, the brightness of bright display becomes maximum. Practically, the angle θ may be any value within the range of 30 ° to 60 °. The actual rotation angle of the liquid crystal molecules 10 in the bright state is smaller than the angle θ because the so-called anchoring effect due to the interaction between the surfaces of the substrates 1 and 2 and the upper limit of the applied voltage is limited. Therefore, the angle θ is preferably set to any value in the range of preferably 45 ° or more and 60 ° or less, more preferably 50 ° or more and 55 ° or less.

Further, the product (Δn · d) is preferably set to an arbitrary value between 45% and 55% of its dominant wavelength in the case of color display, and in the case of white display. It is necessary to consider the display brightness and display hue, and the product (Δn · d)
Is between 220 nm and 300 nm, more preferably between 250 nm and 2 nm
It is recommended to set it to any value between 70 nm.

In the liquid crystal display device of the first embodiment, the angle θ was set to 50 °, the product (Δn · d) was set to 270 nm, and a white fluorescent lamp was used as the back light source. Further, the electrodes 3 to 6 are
A device having a width of 3 μm and a thickness of 150 nm was used. A liquid crystal material having a refractive index anisotropy Δn of 0.075 is used, the thickness d of the liquid crystal layer 7 is 3.6 μm, the distance between adjacent electrodes 3 and 4 and the electrode 5,
The intervals between 6 were set to 7 μm, respectively.

FIG. 4 is a characteristic diagram showing the results of the examination of the viewing angle characteristics in the liquid crystal display device of the first embodiment. As in the case of FIG. 14, the region in which the shade is indistinguishable or inverted when four gradations are displayed. The lines are shaded. In the liquid crystal display device of the first embodiment, if the deflection angle is within 60 °, there is no gradation reversal phenomenon and the shade can be surely identified, and TN type or lateral T
The viewing angle characteristics could be greatly improved as compared with the N-type.

FIG. 5 is a perspective view showing the shape of the electrode pattern in the liquid crystal display device of the first embodiment. Reference numerals 11 and 12 denote comb-tooth-shaped electrode patterns on the substrate 1, and reference numerals 13 and 14 denote comb-tooth-shaped electrode patterns on the substrate 2. The electrode patterns 11 and 12 are formed by conductive base portions 11a and 12a and a plurality of electrodes 3 and 4 extending from the base portions 11a and 12a, and the electrode patterns 13 and 14 are conductive base portions 13a and 12a. 14a and a plurality of electrodes 5, 6 extending from the base portions 13a, 14a. A plurality of pairs of electrodes 3, 4 and electrodes 5, 5 are formed on the substrates 1, 2 by comb-shaped electrode patterns 11, 12, 13, 14.
By providing 6, the electrodes 3 to 6 can be easily positioned even if the set interval between the pair of electrodes 3 and 4 and the set interval between the pair of electrodes 5 and 6 are as narrow as 7 μm, and a plurality of continuous electrodes can be arranged. Since the liquid crystal molecules 10 simultaneously operate in the area, the size of one pixel can be enlarged.

FIG. 6 is a circuit diagram showing a switching element for applying a voltage to the electrodes in the first embodiment. In a liquid crystal display device that performs display by arranging a large number of pixels on a plane such as a matrix display, it is possible to improve image quality by connecting a switching element to each pixel. FIG. 6 schematically shows an example of a circuit configuration on the substrate 1. Reference numeral 15 is a thin film transistor which is a switching element, VG1, VG2, V
G3 is a gate line, and VS1, VS2, VS3, VS4 are source lines.

The electrode 4 is connected to the ground wire, and the electrode 3 is connected to the drain of the thin film transistor 15. Also,
Also in the substrate 2 (not shown), the electrode 6 is connected to the ground line and the electrode 5 is connected to the drain of the thin film transistor 15. By the switching action of the thin film transistor 15 connected to the electrodes 3 and 5, respectively, the voltage applied between the electrodes 3 and 4 and between the electrodes 5 and 6 is kept constant, so that a better display can be obtained.

In the liquid crystal display device of the first embodiment described above, the electrodes 3 to 6 are arranged so that the electrodes 3 and 5 face each other and the electrodes 4 and 6 face each other. It is preferable to set the applied voltage so that the potentials of the electrodes 3 and 5 and the potentials of the electrodes 4 and 6 become the same when the voltage is applied. By setting the applied voltage in this manner, equipotential surfaces perpendicular to the liquid crystal layer 7 are formed in the electrode gaps of the electrodes 3 and 4 and the electrode gaps of the electrodes 5 and 6, and the electric field perpendicular to the substrates 1 and 2 is generated. Occurrence is suppressed. Therefore, the effective electric field component related to the operation of the liquid crystal molecule 10 increases and the rising of the liquid crystal molecule 10 with respect to the substrates 1 and 2 is prevented, so that the distance between the electrodes 3 and 4 and the electrodes 5 and 6 is wide. The liquid crystal display device works well, and the ratio of effective display area can be increased. If such a measure is not taken, the distance between the adjacent electrodes can be increased only to 2 to 3 times the thickness of the liquid crystal layer 7. However, with the above configuration, the electrodes 3, 4 and 5, Good display can be performed even if the interval of 6 is increased from 5 times to 10 times the thickness of the liquid crystal layer 7.

In the liquid crystal display device of the first embodiment, the liquid crystal has been described as being a P-type nematic liquid crystal having a positive dielectric anisotropy. However, this is an N-type liquid crystal having a negative dielectric anisotropy. It is also possible to use nematic liquid crystal, and when N-type nematic liquid crystal is used, the short axis of the liquid crystal molecule is oriented in the direction of the electric field when a voltage is applied. Liquid crystal molecule 10
By performing the initial orientation in the direction orthogonal to, it is possible to display according to the same principle. Further, in the N-type nematic liquid crystal, even when an electric field component in a direction perpendicular to the substrates 1 and 2 is generated, the liquid crystal molecules 10 are hard to rise on the substrates 1 and 2, and the deterioration of the viewing angle characteristics due to this is suppressed. There is also the advantage that

Further, in the liquid crystal display device of the first embodiment, the liquid crystal molecules 10 are arranged in parallel in the initial alignment direction when no voltage is applied, and the electrodes 3, 4 of the substrate 1 and the electrodes 5, 6 of the substrate 2 are arranged.
By arranging and in parallel with each other, the liquid crystal molecules 10 are arranged in parallel in an electric field direction different from the initial alignment direction when a voltage is applied. However, it is not necessary that these liquid crystal molecules 10 are perfectly aligned in parallel, and if the liquid crystal molecules 10 have a twisted structure, the above effects can be sufficiently obtained as long as they are 10 ° or less, more preferably 3 ° or less. be able to. Therefore, the twist angle of the liquid crystal molecules 10 on both substrates 1 or 2 or the intersection angle between the electric field direction E1 of the electrodes 3 and 4 and the electric field direction E2 of the electrodes 5 and 6 is 10 ° or less, more preferably 3 ° or less. Can be an angle of In this case, the direction of the polarization axis of one of the polarizing plates 8 and 9 is
The contrast characteristics can be improved by shifting the liquid crystal molecules 10 in the parallel arrangement by several degrees.

(Embodiment 2) The liquid crystal display device of the second embodiment is different from the liquid crystal display device of the first embodiment in that the polarization axes of the polarizing plates 8 and 9 are different.
In the liquid crystal display device of the second embodiment, one polarizing plate 8
The polarizing axis of the polarizing plate 9 was made substantially parallel to the electrodes 3 and 4 of the substrate 1, and the polarizing axis of the other polarizing plate 9 was orthogonal to the polarizing axis of the polarizing plate 8. In this case, the display is in a bright state when no voltage is applied, and the display is in a dark state when a voltage is applied, and the bright and dark states have characteristics opposite to those of the liquid crystal display device of the first embodiment. Also in the liquid crystal display device of the second embodiment, good viewing angle characteristics can be obtained almost similarly to the liquid crystal display device of the first embodiment.

(Embodiment 3) FIG. 7 is a perspective view showing the structure of a third embodiment of the liquid crystal display device of the present invention, and FIG. 8 is a perspective view for explaining the operation of the liquid crystal display device of the third embodiment. Yes, Figure 1
Through the members corresponding to the members described with reference to FIG. 2, the same reference numerals are given and the description thereof will be omitted. 25 and 26 are
A pair of electrodes formed on the lower substrate 2, which are electrodes 25 and 26.
Are not arranged parallel to the electrodes 3 and 4, but are arranged such that their electric field direction E2 forms an angle φ with the electric field direction E1 of the electrodes 3 and 4.

By applying a sufficiently high voltage to the pair of electrodes 25 and 26 on the substrate 2 to generate an electric field between the electrodes 25 and 26, the liquid crystal molecules 10 have a long axis L on the substrate 2 in the electric field direction. Rotate to match E2. Liquid crystal molecules on the upper substrate 1
The initial orientation direction of 10 is made to coincide with this direction, and the substrate 1
By setting the voltage applied between the upper pair of electrodes 3 and 4 to be substantially zero, the liquid crystal molecules as shown on the right side of FIG.
10 are arranged in parallel with the electric field direction E2. Further, the polarizing plate 28 is arranged so that the polarizing axis is parallel to the electric field direction E2, and the polarizing plate 29 is arranged so that the polarizing axis is orthogonal to the polarizing axis of the polarizing plate 28. In this case, the light that has passed through the polarizing plate 28 reaches the polarizing plate 29 without changing the polarization state, so this light cannot pass through the polarizing plate 29, and the display is in a dark state.

On the other hand, by applying a sufficiently high voltage to the pair of electrodes 3, 4 on the substrate 1, the liquid crystal molecules 10 on the substrate 1 rotate so that the major axis L coincides with the electric field direction E1. By making the initial alignment direction of the liquid crystal molecules 10 on the lower substrate 2 coincident with this direction and setting the voltage applied between the pair of electrodes 25 and 26 on the substrate 2 to almost zero, As shown on the left side of FIG. 8, the entire liquid crystal molecules 10 are aligned parallel to the electric field direction E1. In this case, the light passing through the polarizing plate 28 makes an angle φ between the polarization direction and the long axis L of the liquid crystal molecules 10, and therefore the polarization state changes while propagating in the liquid crystal layer 7 to become elliptically polarized light. Since the component in the polarization axis direction of the plate 29 passes through the polarizing plate 29, the display is in a bright state.

Further, by applying an intermediate level voltage to each of the electrodes 3 and 4 of the substrate 1 and the electrodes 25 and 26 of the substrate 2 and controlling each voltage level, the liquid crystal molecules 10
Can be arranged in parallel in the intermediate direction between the above two states, so that it is possible to perform display with intermediate brightness.

Also in the above liquid crystal display device, assuming that the operation of the liquid crystal molecules 10 is ideal and the incident light has a single wavelength, the angle φ formed by the electric field direction E1 and the electric field direction E2 is φ.
Is 45 °, and the product of the refractive index anisotropy Δn of the liquid crystal molecules and the thickness d of the liquid crystal layer 7 (Δn · d) is half the wavelength, the brightness of the bright display becomes maximum. Practically, the angle φ may be any value in the range of 30 ° to 60 °, but the actual rotation angle of the liquid crystal molecule 10 is the anchoring effect of the interface with the substrates 1 and 2 and the upper limit of the applied voltage. Since the angle φ is slightly smaller than the angle φ, it is preferable to set the angle φ to an arbitrary value within the range of preferably 45 ° to 60 °, more preferably 50 ° to 55 °.

Further, when the anchoring effect is taken into consideration, the initial alignment direction of the liquid crystal molecules 10 on one of the substrates 1 and 2 is changed from the electric field direction on the other substrates 1 and 2 to the actual liquid crystal molecules 10.
By slightly shifting in the direction of the electric field on one of the substrates 1 and 2 in accordance with the rotation angle of the liquid crystal molecules 10 when voltage is applied.
Becomes closer to the ideal homogeneous sequence, and a better display can be obtained.

The value of the product (Δnd) is preferably set between 45% and 55% of the main wavelength of the color display,
In the case of displaying white, it is preferable to set it between 220 nm and 300 nm, more preferably between 250 nm and 270 nm.

In the liquid crystal display device of the third embodiment, the angle φ was set to 50 °, the product (Δn · d) was set to 270 nm, and display was performed using a white fluorescent lamp as the back light source. Also electrodes
The width of 25 and 26 is 3 μm, the thickness is 150 nm, the liquid crystal has a refractive index anisotropy Δn of 0.075, and the thickness d of the liquid crystal layer 7 is 3.6.
The distance between the adjacent electrodes 25 and 26 was 7 μm. Also in the liquid crystal display device of the third embodiment, the viewing angle characteristic is the first
This is almost the same as the liquid crystal display device of the above example, and the gradation inversion phenomenon hardly occurs during image display.

Further, also in the liquid crystal display device of the third embodiment, when display is performed by a large number of pixels such as matrix display, the electrodes 3, 25 of the respective pixels are the same as in the first embodiment.
If a switching element is connected to, better display quality can be obtained.

In the liquid crystal display device of the third embodiment, the liquid crystal has been described as being a P-type nematic liquid crystal having a positive dielectric anisotropy, but an N-type nematic liquid crystal having a negative dielectric anisotropy has been described. It is also possible to use, and when the N-type nematic liquid crystal is used, the short axis of the liquid crystal molecule faces the direction of the electric field when a voltage is applied, so that the N-type nematic liquid crystal molecule is used as the P-type nematic liquid crystal in the above description. Molecule 10
By performing the initial orientation in the direction orthogonal to, it is possible to display according to the same principle. Further, in the N-type nematic liquid crystal, even when an electric field component in the direction perpendicular to the substrates 1 and 2 is generated, it is difficult for liquid crystal molecules to stand up on the substrates 1 and 2, and deterioration of viewing angle characteristics due to this is suppressed. There is also an advantage.

FIG. 9 is a block diagram showing an example of an electrode pattern and a voltage circuit in the liquid crystal display device of the third embodiment.

Reference numerals 31 and 32 are electrode patterns formed in a comb-teeth shape on the substrate 1, and 33 and 34 are electrode patterns formed in a comb-teeth shape on the substrate 2. The electrode patterns 31, 32 are formed by conductive base portions 31a, 32a and a plurality of electrodes 3, 4 extending from the base portions 31a, 32a, and the electrode patterns 33, 34 are conductive base portions.
33a, 34a and a plurality of electrodes 25, 26 extending from the base portions 33a, 34a. By providing a plurality of pairs of electrodes 3, 4, 25, 26 on the substrates 1, 2 with the comb-teeth-shaped electrode patterns 31, 32, 33, 34, the set spacing between the electrodes 3, 4 and the electrodes 25, 26 Even if the set interval between them is as narrow as 7 μm, the positioning of the electrodes 3, 4, 25, 26 becomes easy, and the liquid crystal molecules 10 operate simultaneously in a plurality of consecutive areas. Therefore, the size of one pixel should be enlarged. Will be possible.

Reference numeral 16 is a resistance dividing element for dividing the voltage applied to the electrode 3 of the upper substrate 1 and the electrode 25 of the lower substrate 2. On the substrates 1 and 2, the electrode pattern 32 and the electrode pattern 34 are grounded. Further, the resistance division element 16 is configured so that the division ratio of the resistance is variably set by a signal from the outside.

The voltage supplied from the power supply 17 is the resistance dividing element 16
And is applied to the electrode 3 and the electrode 25. At this time, the voltage applied between the pair of electrodes 3 and 4 and between the pair of electrodes 25 and 26 can be changed by changing the resistance division ratio by the resistance dividing element 16.

FIG. 10 is a characteristic diagram showing a change in applied voltage between a pair of electrodes by the resistance division element shown in FIG. 9, and FIG. 11 shows a change in relative transmittance of the liquid crystal layer by the resistance division element shown in FIG. It is a characteristic diagram.

In FIG. 10, the horizontal axis represents the ratio of the upper resistance Ra to the total resistance. As the ratio of the upper resistance Ra increases, the applied voltage between the electrodes 3 and 4 decreases and the applied voltage between the electrodes 25 and 26 increases. Resistive divider
By continuously changing the applied voltage between the electrodes 3 and 4 and the applied voltage between the electrodes 25 and 26 by 16, the relative transmittance of the liquid crystal layer 7 can be made to correspond to the resistance division ratio as shown in FIG. Since the liquid crystal display device continuously changes, the bright and dark states of the liquid crystal display device can be continuously changed.

Further, in a liquid crystal display device in which a large number of pixels such as a matrix display are arranged on a plane for display, a common voltage is supplied to all the pixels and the resistance division arranged for each pixel is performed. Since the luminance of each pixel can be controlled by changing the resistance division ratio by the element 16, it is possible to suppress unevenness in display due to less voltage interference between wirings as compared with the case where a thin film transistor is used. Further, it is possible to obtain an advantage that the voltage level of the power supply can be reduced. The same effect can be obtained by using a capacitor instead of the resistance dividing element 16 and controlling the division ratio of the capacitors arranged in series.

(Embodiment 4) FIG. 12 is a perspective view showing the configuration of a fourth embodiment of the liquid crystal display device of the present invention, and the same reference numerals are given to the members corresponding to the members described with reference to FIGS. 1 and 2. Is attached and the description is omitted.

Reference numeral 18 denotes an insulating substance protruding from the surface of each of the substrates 1 and 2 on the liquid crystal layer 7 side. In the substrate 1, the electrodes 3 and 4 are formed on the pair of insulating substances 18, respectively. An electrode 5 and an electrode 6 are formed on the pair of insulating materials 18, respectively.

In the liquid crystal display device of the fourth embodiment, the anchoring effect at the interface between the liquid crystal molecules in the liquid crystal layer 7 and the substrates 1 and 2 is suppressed, and occurs between the electrodes 3 and 4 and between the electrodes 5 and 6. In order to use the electric field more effectively, the electrodes 3 to 6 were formed on the insulating material 18 and projected from the substrates 1 and 2 into the liquid crystal layer 7. As the insulating material 18, for example, silicon dioxide is used. Further, the electrodes 3 to 6 are formed of ITO or the like,
If transparent, the insulating material 18 is also preferably transparent.

The electric field when a voltage is applied to the electrodes 3 to 6 has a substantially uniform intensity distribution in the electrode gap between the electrodes 3 and 4 and the electrode gap between the electrodes 5 and 6, but in the present embodiment, the electrodes 3 to 6 are distributed.
Since 6 is separated from the interface between the substrates 1 and 2 by the insulating material 18, the influence of the anchoring effect is suppressed, and the electrodes 3 and
The electric fields of 4 and the electrodes 5 and 6 effectively act on the liquid crystal layer 7. As a result, a good visual field characteristic can be obtained as in the liquid crystal display device of the first embodiment, and in addition, the voltage applied to the electrodes 3 to 6 for operating the device is reduced to 1/2 to 3 minutes. It is also possible to obtain the advantage that it can be reduced to about 1.

Here, when the thickness of the insulating material 18 is extremely thin, the anchoring effect cannot be sufficiently suppressed, and when the thickness of the insulating material 18 is extremely thick, the substrates 1 and 2 are connected to the electrodes 3 to 3. The optical influence of the liquid crystal layer 7 existing between 6 and to which the electric field is not applied is increased. Therefore, the insulating material 18 preferably has a thickness in the height direction from the surface of the substrates 1 and 2 to the central position of the electrodes 3 to 6 to be 0.5 μm or more and 1.5 μm or less, and further 0.5 μm. More preferably, the thickness is set to 1 μm or less.

Next, the setting of the product (Δn · d) will be described. The liquid crystal layer 7 is held between the surface of the substrate 1 and the central positions of the electrodes 3 and 4 in the height direction, the portion from the surface of the substrate 2 to the central positions of the electrodes 5 and 6, and both parts. Consider the remaining three layers. Board 1,
Since the liquid crystal molecules between the surface of 2 and the central positions of the electrodes 3 to 6 do not move much even when an electric field is applied, the upper and lower two layers of the liquid crystal layer 7 hardly affect the display. Therefore, the thickness of the central portion of the liquid crystal layer 7 is considered as the effective cell thickness d1 that contributes to the display, and the product (Δn · d1) of this central portion is set in the same manner as in the first embodiment. Good. For color display, it is preferable to set the product (Δn · d1) between 45% and 55% of the main wavelength, and for white display, the product (Δn · d1)
1) is preferably between 220 nm and 300 nm, but 250 nm to 270 nm
Is more preferred.

The angle θ formed by the direction of the electric field and the liquid crystal molecules
Regarding the value of, the same characteristics as in the first embodiment were shown in the range of 30 ° to 60 °. However, in the fourth embodiment, the influence of the anchoring effect can be suppressed, so that the electrode 3
The range of 40 ° to 50 ° is more preferable because the liquid crystal molecules can rotate sufficiently in the direction of the electric field when a voltage is applied to ˜6.

Further, by forming the insulating material 18 and the electrode pattern in a comb shape on the substrates 1 and 2, it is possible to increase the display area per pixel as in the liquid crystal display device of the first embodiment. Further, when the number of pixels is large, a thin film transistor can be used to obtain a better display. Furthermore, the electrodes 3, 4 of the substrate 1 and the electrodes 5, 4 of the substrate 2
6 and drive so that the potentials of the electrodes 3 and 5 and the potentials of the electrodes 4 and 6 become equal, the electric field between the electrodes 3 and 4 and the electrodes 5 and 6 is changed. As in the case of the first embodiment, the liquid crystal molecules can be efficiently acted on. The insulating material 18 exerts its effect even when it is used only on one of the substrates 1 and 2.

Here, as in the first embodiment, the polarizing plates 8 whose initial alignment directions of liquid crystal molecules on the substrates 1 and 2 are adjacent to each other,
When it is parallel or orthogonal to the polarization axis of 9, the height of the electrodes 3 to 6 from the surfaces of the substrates 1 and 2 is preferably within the above range. However, when the initial alignment direction of the liquid crystal molecules on the substrates 1 and 2 is not parallel or orthogonal to the polarization axes of the adjacent polarizing plates 8 and 9, the electrodes 3 to 3 are arranged from the surfaces of the substrates 1 and 2.
Since the birefringence effect up to 6 remains when an electric field is applied, when this angle is in the range of 30 ° to 60 °, the product (Δn · d1)
It is desirable to set the height of the insulating material 18 so that is less than 50 nm, in the range of 10 ° to 30 °, or from 60 °
When it is in the range of 80 °, it is desirable that the product (Δn · d) is 75 nm or less, and the angle between the initial alignment direction of the liquid crystal molecules and the polarization axes of the polarizing plates 8 and 9 is outside the above range. Sometimes, the polarizing plates 8 adjacent to the alignment direction of the liquid crystal molecules,
There is no problem even if the height of the insulating material 18 is set by considering the same as when the polarization axis of 9 is approximately parallel or orthogonal.

Also, in the liquid crystal display devices of the first to third embodiments, the electrodes 3, 4, 5, 5 are formed by the insulating material 18.
It is possible to project 6, 25, and 26 from the substrates 1 and 2 into the liquid crystal layer 7, and by applying this configuration,
The same effect as that of the embodiment can be obtained.

Although the first to fourth embodiments of the present invention have been described above, the structure of the present invention is not limited to these embodiments, and the arrangement angle of the electrodes and the polarization axis of the polarizing plate are not limited to these. Regarding the arrangement angle, many configurations other than this are possible. Needless to say, the usefulness of the configuration of each embodiment of the present invention applied to a direct-viewing type liquid crystal display device, even when applied to a projection type liquid crystal display device,
Since the light capturing angle can be widened without deteriorating the display characteristics, the effect of improving the display brightness can be obtained. When applied to a projection type liquid crystal display device, a light control element such as a polarization beam splitter may be used as a means for forming / displaying polarized light, in addition to the polarizing plate.

[0060]

As described above, according to the liquid crystal display device of the present invention described in each of the claims,
By forming a pair of electrodes on the surfaces of the two substrates sandwiching the liquid crystal layer on the liquid crystal layer side, the directions of the liquid crystal molecules are voltage-controlled on the two substrates, respectively, and the viewing angle characteristics are greatly improved.

[Brief description of drawings]

FIG. 1 is a perspective view showing the configuration of a first embodiment of a liquid crystal display device of the present invention.

FIG. 2 is a perspective view for explaining the operation of the liquid crystal display device of the first embodiment.

FIG. 3 is a characteristic diagram showing a relationship between a voltage applied to an electrode and a relative transmittance.

FIG. 4 is a characteristic diagram showing an examination result of viewing angle characteristics in the liquid crystal display device of the first embodiment.

FIG. 5 is a perspective view showing the shape of an electrode pattern in the liquid crystal display device of the first embodiment.

FIG. 6 is a circuit diagram showing a switching element for applying a voltage to the electrodes in the first embodiment.

FIG. 7 is a perspective view showing a configuration of a third embodiment of the liquid crystal display device of the present invention.

FIG. 8 is a perspective view for explaining the operation of the liquid crystal display device of the third embodiment.

FIG. 9 is a configuration diagram showing an example of an electrode pattern and a voltage circuit in the liquid crystal display device of the third embodiment.

10 is a characteristic diagram showing a change in applied voltage between electrodes by the resistance division element shown in FIG.

11 is a characteristic diagram showing a change in relative transmittance of the liquid crystal display device by the resistance division element shown in FIG.

FIG. 12 is a perspective view showing the configuration of a fourth embodiment of the liquid crystal display device of the present invention.

FIG. 13 is a conventional twisted nematic type (TN
FIG. 3 is a perspective view showing the configuration of a liquid crystal display device of (type).

FIG. 14 is a characteristic diagram showing the results of an experiment conducted to investigate the viewing angle characteristics of a TN type liquid crystal display device.

FIG. 15 is a perspective view showing a configuration of a conventional lateral TN type liquid crystal display device.

FIG. 16 is a characteristic diagram showing the results of an experiment conducted to investigate the viewing angle characteristics of a lateral TN type liquid crystal display device.

[Explanation of symbols]

1, 2 ... Substrate, 3, 4, 5, 6, 25, 26 ... Electrode, 7
... Liquid crystal layer, 8, 9, 28, 29 ... Polarizing plate, 10 ... Liquid crystal molecule, 11, 12, 13, 14, 31, 32, 33, 34 ... Electrode pattern, 15 ... Thin film transistor, 16 ... Resistor dividing element,
18 ... Insulating material.

Claims (9)

[Claims] 1. A liquid crystal comprising a liquid crystal layer and two substrates sandwiching the liquid crystal layer, and a pair of electrodes formed on the surfaces of the two substrates on the liquid crystal layer side. Display device. 2. When the liquid crystal molecules in the liquid crystal layer are in the initial alignment direction, the twist angle formed by the major axis of the liquid crystal molecules on one of the substrates and the major axis of the liquid crystal molecules on the other substrate is 10. The liquid crystal display device according to claim 1, wherein the liquid crystal display device has a temperature of less than 100 degrees. 3. An intersection angle formed by a direction of an electric field formed by the pair of electrodes on one substrate and a direction of an electric field formed by the pair of electrodes on the other substrate is set to 10 degrees or less. The liquid crystal display device according to claim 1 or 2. 4. The crossing angle formed by the direction of the electric field formed by the pair of electrodes on one of the substrates and the direction of the electric field formed by the pair of electrodes on the other substrate is 30 degrees or more,
The liquid crystal display device according to claim 1, wherein the liquid crystal display device is set to 60 degrees or less. 5. When the liquid crystal molecules in the liquid crystal layer are in the initial alignment direction, the twist angle formed by the long axis of the liquid crystal molecules on one of the substrates and the long axis of the liquid crystal molecules on the other substrate is 30. 5. The liquid crystal display device according to claim 4, wherein the liquid crystal display device is set at not less than 60 degrees and not more than 60 degrees. 6. When the liquid crystal molecules in the liquid crystal layer are in the initial alignment direction, the major axis of the liquid crystal molecules on at least one of the substrates and the electric field formed by the pair of electrodes on the substrate. The angle of intersection with the direction
The liquid crystal display device according to claim 1, wherein the liquid crystal display device is set at 30 degrees or more and 60 degrees or less. 7. A pair of comb-teeth-shaped electrode patterns are formed on the substrate, and a plurality of the electrodes of the pair are formed on the substrate by the paired electrode patterns. The liquid crystal display device according to claim 6. 8. The liquid crystal display according to claim 1, further comprising a polarized light forming means for forming polarized light and a polarized light display means for selectively transmitting or reflecting the polarized light. apparatus. 9. The liquid crystal display device according to claim 8, wherein the polarized light forming means and the polarized light display means are constituted by polarizing plates.