JP2839802B2 - Liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a TN (twisted nematic) mode liquid crystal display device.

[0002]

2. Description of the Related Art In a TN mode, a liquid crystal display device having characteristics such as low voltage, low power consumption and long life can be manufactured.
Most widely used. FIG. 1 shows a TN-type liquid crystal display device.
2 (1), the two opposing substrates 31, 32
An alignment formed on the surfaces of the substrates 31 and 32 so that the long axis direction of the liquid crystal molecules is substantially parallel to the substrate surface and is continuously twisted by 90 ° between the substrates. The films 31c and 32c are formed so that the orientation directions 33 and 34 are orthogonal to each other. The substrates 31, 32 are shown in FIG.
As shown in (2), transparent substrates 31a and 32 made of glass or the like are used.
a, transparent electrodes 31b, 32b and alignment film 31
c, 32c.

[0003]

In the TN mode liquid crystal display device, the liquid crystal molecules have anisotropy of the refractive index (hereinafter, referred to as birefringence), and as shown in FIG. Has an angle δ. Therefore, the liquid crystal display device has a so-called viewing angle characteristic in which the contrast changes according to the viewing angle of the liquid crystal display device. Generally, in a normally white mode in which light is transmitted and white display is performed when no voltage is applied, when viewed from directly above the liquid crystal display device (in a direction perpendicular to the substrate surface) with a voltage applied to the electrodes, As shown by the solid line K1 in FIG. 8, the transmittance of light decreases as the applied voltage value increases, and the transmittance becomes substantially zero when the voltage is saturated, and the transmittance remains zero even when the applied voltage is further increased. .

However, as shown in FIG. 12, when a display is performed on a liquid crystal display device, if the viewing angle is inclined in the direction of the viewing angle to be in front of the display (hereinafter referred to as the normal viewing angle direction 36), as shown in FIG. In FIG. 8, as indicated by the one-dot chain line K2, the transmittance decreases as the applied voltage increases, and when the applied voltage exceeds a specific voltage value, the transmittance increases again and thereafter gradually decreases again. Therefore, when the viewing angle is inclined in the direction of the normal viewing angle, the black and white of the image is inverted at a specific angle or more (hereinafter, referred to as an inversion phenomenon). This is a phenomenon that occurs because the refractive index changes depending on the viewing angle because the liquid crystal molecules are tilted.

[0005] That is, when the applied voltage is zero or a relatively low voltage, the observer 37 located in the normal viewing direction 36 sees the central molecule 35 as an ellipse as shown in FIG. When the applied voltage is gradually increased, the central molecule 35 moves in the direction of the electric field, and as shown in FIG.
The observer 37 has a moment when the central molecule 35 looks like a perfect circle. As the applied voltage is further increased, the central molecule 35 becomes substantially parallel to the direction of the electric field, and the observer 37 again sees the central molecule 35 as an ellipse.

For the same reason, the transmittance-voltage characteristics are different even in viewing angles other than the normal viewing angle direction 36.
Although the reversal phenomenon does not occur, as the viewing angle is increased, the viewing angle characteristic is such that the contrast ratio between black and white is reduced. As described above, a TN mode liquid crystal display device usually has a viewing angle characteristic. In particular, the reversal phenomenon seen in the normal viewing angle direction becomes a great obstacle for a viewer, and doubts the display performance of the liquid crystal display device itself. Results.

As a technique generally known as a technique for improving a specific phenomenon in the above-described TN mode liquid crystal display device, there is a technique disclosed by Seidenki. This is because, in an active matrix type liquid crystal display device, a display electrode constituting one pixel is divided into an inner side and an outer side, and a voltage value applied to each electrode is controlled. The viewing angle characteristics are improved by changing the state of the liquid crystal molecules corresponding to the electrodes.

[0008] However, the above technique is limited to an active matrix type liquid crystal display device, and has the disadvantage that the pattern of the electrode itself is changed, which complicates the manufacturing process and the driving method.

An object of the present invention is to provide a liquid crystal display device having improved viewing angle characteristics and improved display quality.

[0010]

According to the present invention, there is provided a liquid crystal display device having a twisted nematic liquid crystal layer interposed between a pair of transparent substrates such that the major axis direction of the molecule is spirally twisted by about 90 °. In a liquid crystal display device configured to be disposed between the polarizing plates, a uniaxially stretched retardation film is disposed between at least one of the pair of polarizing plates and the liquid crystal display element, and the retardation film is , The refractive index in the thickness direction of the film is different from the refractive index in the plane direction,
And a three-dimensional retardation film having anisotropy of the refractive index also in the plane direction, wherein the retardation value in the plane direction is 1
A liquid crystal display device having a thickness of from 100 to 300 nm, wherein an angle between the slow axis of the retardation film and the absorption axis of the polarizing plate is selected to be 10 ° or less.

[0011]

Further, the present invention provides a liquid crystal display element having a twisted nematic liquid crystal layer interposed between a pair of transparent substrates so that the major axis direction of the molecule is spirally twisted by about 90 °, between the pair of polarizing plates. In the liquid crystal display device configured to be disposed, a uniaxially stretched retardation film is disposed between at least one of the pair of polarizing plates and the liquid crystal display element, and the retardation film is in a thickness direction of the film. Is a three-dimensional retardation film having a refractive index different from the refractive index in the plane direction and having anisotropy of the refractive index also in the plane direction, wherein the ratio NZ value of the retardation value in the thickness direction to the retardation value in the plane direction of the film Is 0.4 ~
0.8, wherein the angle between the slow axis of the retardation film and the absorption axis or transmission axis of the polarizing plate is selected to be 10 ° or less.

Further, the present invention provides a liquid crystal display device having a twisted nematic liquid crystal layer interposed between a pair of transparent substrates such that the major axis direction of the molecule is spirally twisted by about 90 °, between the pair of polarizing plates. In the liquid crystal display device configured and arranged, a retardation plate formed by laminating two layers of a uniaxially stretched retardation film is disposed between at least one of the pair of polarizing plates and the liquid crystal display element, The retardation film is a three-dimensional retardation film in which the refractive index in the thickness direction of the film is different from the refractive index in the planar direction, and has anisotropy of the refractive index also in the planar direction, and the retardation value in the planar direction is 100. ５００500 nm, ratio NZ of the retardation value in the thickness direction to the retardation value in the plane direction
Value is 0.3 to 0.8, and the angle between the slow axis of the retardation film on the liquid crystal display element side and the fast axis of the retardation film on the polarizing plate side is 10 ° or less. The angle between the slow axis or fast axis of the retardation film on the element side and the orientation axis of the retardation film side substrate of the liquid crystal display element is 10 ° or less, the slow axis or the slow axis of the retardation film on the polarizing plate side. A liquid crystal display device characterized in that an angle formed between a fast axis and a transmission axis of a polarizing plate is selected to be 10 ° or less.

[0014]

According to the present invention, there is provided a liquid crystal display device comprising a liquid crystal display element having a twisted nematic liquid crystal layer interposed between a pair of transparent substrates and disposed between a pair of polarizing plates. Of the above polarizing plates, a uniaxially stretched retardation film is disposed between at least one of the polarizing plates and the liquid crystal display element. The retardation film has a refractive index in the thickness direction of the film different from that in the plane direction, and has anisotropy in the refractive index also in the plane direction. This retardation film has a retardation value in the plane direction of 100 to 300 nm.
The angle between the slow axis of the film and the absorption axis of the polarizing plate is arranged to be 10 ° or less, depending on the viewing angle with respect to the liquid crystal display surface and the voltage applied to the liquid crystal display element. It is possible to compensate for the changing anisotropy of the refractive index and improve the viewing angle characteristics. In addition, this makes it possible to adjust the retardation value in the liquid crystal display surface, adjust the variation in the wavelength of transmitted light caused by passing through the liquid crystal display element, and prevent the liquid crystal display surface from being colored.

[0015]

According to a second aspect of the present invention, in the liquid crystal display device, the retardation film has a retardation value in the thickness direction of the film having a ratio NZ value of 0.4 to 0.3 in the thickness direction with respect to the retardation value in the plane direction of the film. 8 and arranged so that the angle between the slow axis of the film and the absorption axis or transmission axis of the polarizing plate is 10 ° or less. As a result, it changes depending on the viewing angle with respect to the liquid crystal display surface,
In addition, it is possible to compensate for anisotropy of the refractive index that changes according to the voltage applied to the liquid crystal display element, improve the viewing angle characteristics, and make the inversion phenomenon less likely to occur.

According to a third aspect of the present invention, in the liquid crystal display device, the retardation film has a retardation value of 100 to 500 nm, and a retardation value in a thickness direction with respect to a retardation value in a plane direction of the film. It is selected from those having a specific NZ value in the range of 0.3 to 0.8, and two of them are stacked and arranged. At this time, the angle between the slow axis of the retardation film on the liquid crystal display element side and the fast axis of the retardation film on the polarizing plate side is 10 ° or less, the slow axis of the retardation film on the liquid crystal display element side or A fast axis,
The angle between the retardation film-side substrate of the liquid crystal display element and the orientation axis of the substrate is 10 ° or less, and the angle between the slow axis or fast axis of the polarizing plate-side retardation film and the transmission axis of the polarizing plate is 1 °.
Arrange so that it is 0 ° or less. Thereby, it is possible to compensate for the anisotropy of the refractive index that changes depending on the viewing angle with respect to the liquid crystal display surface and the voltage applied to the liquid crystal display element, and prevent the asymmetry of the contrast in the left-right direction with respect to the normal viewing angle direction and the decrease in the contrast.

[0018]

FIG. 1 is a perspective view showing the structure of a liquid crystal display device 1a according to one embodiment of the present invention. Liquid crystal display device 1a
Interposes a liquid crystal display element 4 between a pair of polarizing plates 2 and 3,
Further, a retardation plate 5 is arranged between the polarizing plate 2 and the liquid crystal display element 4. The light enters the liquid crystal display device 1a from the direction of the arrow 15 (from the polarizing plate 3 side) and exits from the polarizing plate 2. Therefore, the retardation plate 5 is arranged on the light emission side of the liquid crystal display element 4.

The liquid crystal display element 4 has ITO on the opposing surfaces of a pair of transparent substrates 6 and 7 made of glass or the like.
(Indium tin oxide) and other transparent electrodes 8 and 9 are formed, and further, alignment films 10 and 11 are formed on the surfaces thereof.
The substrates are bonded together with a spacer 12 interposed therebetween to keep the distance between the substrates constant, and a twisted nematic liquid crystal layer 13 is injected and sealed with a sealing material 14. Transparent electrode 8,
Reference numeral 9 may be any of a segment type, a simple matrix type, and an active matrix type.

The twisted nematic liquid crystal layer 13 is made of a liquid crystal material manufactured by Merck Japan Co., Ltd., and is subjected to an alignment treatment between the substrates 6 and 7 so that the major axis direction of the molecules is spirally twisted by about 90 °.

The twist direction of the liquid crystal molecules is the light incident direction 1
5, ie, counterclockwise as seen from the emission side, as shown by arrow 16. That is, the alignment direction of the alignment film 11 on the transparent substrate 7 is indicated by an arrow 23, and is rotated by 45 ° from the reference direction 21. The alignment direction of the alignment film 10 on the transparent substrate 6 is indicated by an arrow 22, and is rotated clockwise by 45 ° from the reference direction 21. Here, the reference direction 21 indicates a direction from 3 o'clock to 9 o'clock when the observer of the liquid crystal display device 1a is located on the near side of FIG. 1, that is, the so-called 6 o'clock direction. As a result, the molecules of the twisted nematic liquid crystal layer 13 are twisted 90 ° in the counterclockwise direction as described above.

The alignment films 10 and 11 were made of polyimide resin manufactured by Japan Synthetic Rubber Co., Ltd., and rubbed using a cloth woven with nylon fibers as the alignment treatment. The distance between the substrates 6 and 7 was set to 4.5 μm by using the spacer 12 made of the above-described plastic beads or the like.

In this embodiment, the liquid crystal display device 1a performs a so-called normally white display in which light is transmitted and white display is performed when no voltage is applied. Therefore, the polarizing plates 2 and 3
Are arranged such that their transmission axis directions 24 and 25 are orthogonal to the alignment directions 22 and 23 of the alignment films 10 and 11 of the transparent substrates 6 and 7, respectively.

Further, in the liquid crystal display device 1a, a retardation plate 5 is disposed between the liquid crystal display element 4 and the polarizing plate 2. The retardation plate 5 is formed by uniaxially stretching a polymer compound, and is installed such that its slow axis direction 26 coincides with the absorption axis direction 27 of the polarizing plate 2. As the retardation plate 5, an NZ plate (retardation plate) manufactured by Nitto Denko Corporation was used. The NZ plate used had a retardation value Re of 217 nm in the plane direction and NZ (ratio of the retardation value in the thickness direction to the retardation value in the plane direction of the film) = 0.56.

When a voltage is applied to the liquid crystal layer 13, the liquid crystal molecules move in a direction parallel to the direction of the electric field as shown in FIG. Once the anisotropy (Δn) of the refractive index in the thickness direction decreases, the anisotropy of the refractive index becomes “0” at a specific voltage, and the anisotropy of the refractive index increases again when a further voltage is applied. I do.

Therefore, by disposing a retardation plate 5 having anisotropy of the refractive index in the thickness direction to compensate for the anisotropy of the refractive index on the liquid crystal display element 4, the refractive index of the liquid crystal can be reduced. It is possible to compensate for the change in anisotropy, increase the viewing angle at which the inversion phenomenon occurs, and improve the viewing angle.

FIG. 2 is a contrast radar chart of the display surface of the liquid crystal display device 1a, and FIG. 3 is a contrast radar chart of the liquid crystal display device 1a of this embodiment when the retardation plate 5 is not provided. When the measurement point on the liquid crystal display surface is set as the origin O, and the X axis, the Y axis, and the X axis, which are orthogonal to each other at the origin O, are set on the liquid crystal display surface, the contrast radar chart becomes the observation point. The angle between the line connecting the measurement point and the Z axis and θ is θ, and this angle θ is represented by a circle of a concentric circle centered on the origin O of the chart every 10 °.
Further, a line segment connecting the observation point and the origin O is projected on the XY plane, an angle formed between the projected line segment and the Y axis is φ, and this angle φ is set to the origin O on the contrast radar chart every 15 °. Is represented by a radial half line. Where φ = 0
The direction of ° indicates the normal viewing angle direction, and the direction of φ = 180 ° indicates the opposite viewing angle direction.

The measured values plotted in FIGS. 2 and 3 are:
It is determined as follows. The applied voltage when the transmittance is 50% is V (T50%) with respect to the transmittance when no voltage is applied.
Then

[0029]

V1 = V (T50%) + 2.0

[0030]

V2 = V (T50%)-1.5 When the measured value is obtained by setting the transmittance of light at the measurement point when the applied voltage is V1 to T1 and the transmittance of light when the applied voltage is V2 to T2, the contrast CR becomes

[0031]

(Equation 3)

Is given by the following equation. FIGS. 2 and 3 show that, of the CR values of the measurement points obtained by the above equations, the CR value is CR = 1.
Points indicating 0, 20, 30, 40, 50, and 60 are plotted on a contrast radar chart. A point having a large CR value indicates a point having a high contrast.

When FIG. 2 is compared with FIG. 3, as shown in FIG. 2, the phase difference plate 5 (Re = 217 nm, NZ
= 0.56), it is in the range of 0 ° ≦ φ ≦ 105 ° or 285 ° ≦ φ ≦ 360 °, that is, 105 ° left and right when viewed from the normal viewing angle direction (φ = 0 °). In the range of 0 ° ≦ θ ≦ 30 °, that is, from the Z-axis direction (vertical direction) with respect to the measurement point on the liquid crystal display surface.
The contrast value CR obtained by the above equation shows a uniformly high value in the range up to an angle of 30 ° with the axis.
In addition, the high contrast region extends in the direction of φ = 0 °, that is, in the normal viewing direction, to the range of 0 ° ≦ θ <60 °, and the viewing angle characteristic is improved by installing the retardation plate 5. Is shown.

The contrast radar chart of FIG. 3 shows the viewing angle characteristics of the liquid crystal display surface when the retardation plate 5 of the liquid crystal display device 1a of the present embodiment is not used, where 0 ° ≦ φ ≦ 105.
° or 285 ° ≦ φ ≦ 360 °, and φ =
It has a width of 0 ° ≦ θ ≦ 20 ° in the direction of 0 °, and φ = 90
0 ° ≦ θ ≦ 40 in each direction of ° and φ = 270 °
At a width of °, a semi-elliptical area is seen in which no CR values are plotted. This region is a high contrast region in which the CR value shows a value of 60 or more. When θ increases from this region, the points where the CR values show CR60, CR50, and CR40 are densely plotted. In this region, This shows that the viewing angle characteristics of the liquid crystal display surface suddenly deteriorate. When the retardation plate 5 is not used, the range of the high contrast region in the normal viewing angle direction is 0 ° ≦ θ ≦ 20 °.

The uniaxially stretched film of the polymer compound used as the retardation plate 5 usually has anisotropy of the refractive index also in the plane direction of the film, and its stretching axis (optical axis) is directed to the polarizing plate. If they are not installed in accordance with the transmission axis direction or the absorption axis direction, a phase difference occurs due to each wavelength of light, and the light transmitted through the polarizing plate 2 arranged on the light emission side will vary depending on the wavelength. Thus, the liquid crystal display device 1a is colored. In the liquid crystal display device 1a of the present embodiment, the retardation value is controlled to adjust the phase difference of the emitted light, thereby preventing coloring.

FIG. 4 is a chromaticity diagram in which the chromaticity of the display surface of the liquid crystal display device 1a of this embodiment is measured from a direction in which the viewing angle is inclined by 40 ° in the normal viewing direction. A polarizing plate with a Re of 217 nm and an NZ value of 0.56 is set so that the slow axis coincides with the transmission axis of the polarizing plate 2. The four points plotted in the figure are measured values when voltages of 0 V, 2.1 V, 2.8 V, and 3.5 V are applied to the liquid crystal display element 4, respectively. FIG. 5 is a chromaticity diagram obtained by installing a retardation plate having a retardation value Re of 347 nm and an NZ value of 0.44 and measuring chromaticity by the same installation method as in FIG. 4. FIG. 6 is a chromaticity diagram of the retardation value Re of 437 nm and NZ. FIG. 5 is a chromaticity diagram in which a chromaticity is measured by installing a retardation plate having a value of 0.54. In FIG. 4, in the liquid crystal display device 1a, when no voltage is applied and when any voltage is applied, the deviation from the white point indicated by W is small, and coloring of the display surface is suppressed.

In FIG. 5, when no voltage is applied and when 2.1
V, the white point W of the chromaticity of the display surface
Is kept low, but the applied voltage is 2.8.
A considerable deviation from the white point W is seen as V and 3.5 V are increased, and the color is colored blue-violet.

In FIG. 6, this tendency becomes more remarkable. As the applied voltage is increased to 2.8 V and 3.5 V,
In each of FIGS. 5A and 5B, a stronger coloring is observed than the value indicated by the chromaticity point. As described above, in the three-dimensional retardation film, by optimally selecting the in-plane retardation value, the light causes a phase difference at each wavelength, and the light transmitted through the exit-side polarizing plate 2 has a variation due to the wavelength. And the coloring of the liquid crystal display surface can be suppressed.

As described above, according to the present embodiment, it is possible to provide the liquid crystal display device 1a in which the viewing angle characteristics are improved, the viewing angle is enlarged, and the coloring of the display surface is suppressed. In this embodiment, the retardation plate 5 is installed so that the slow axis direction 26 of the retardation plate 5 coincides with the absorption axis direction 27 of the polarizing plate 2, but the angle formed by the slow axis direction 26 and the absorption axis direction 27 is 1
0 ° or less, the retardation value Re of the retarder 5 is 10
It has been confirmed that a similar effect can be obtained within the range of 0 to 300 nm.

[0040]

[0041]

[0042]

FIG. 7 is a diagram showing the overall configuration of a liquid crystal display device 1c according to another embodiment of the present invention. In this embodiment, the configuration and the arrangement are the same as those of the liquid crystal display device 1a shown in FIG. 1, and therefore, the components denoted by the same reference numerals as those in FIG. 1 indicate the same components as those shown in FIG.

The liquid crystal display device 1c shown in FIG. 7 uses, as the retardation plate 5, an NZ plate manufactured by Nitto Denko Corporation having a retardation value Re = 217 nm and an NZ value NZ = 0.56. The polarizer 2 is installed such that the phase axis direction 26 coincides with the absorption axis direction 27 of the polarizing plate 2.

FIG. 8 is a graph showing the relationship between the applied voltage and the light transmittance when a voltage is applied to the electrode of the normally white mode TN type liquid crystal display device. The relationship between the applied voltage and the light transmittance when the liquid crystal display surface is viewed from a direction perpendicular to the display surface is shown by a solid line K1, and the voltage applied when the viewing angle is inclined by 40 ° in the normal viewing angle direction by the conventional liquid crystal display element. The relationship between the voltage and the light transmittance is indicated by a dashed-dotted line K2. The liquid crystal display device 1c of the present embodiment has a retardation value Re = 217 nm between the liquid crystal display element 4 and the polarizing plate 2 as indicated by a broken line K3,
By installing a retardation plate 5 having an NZ value NZ = 0.56 and compensating for a change in the refractive index due to a viewing angle in the thickness direction of the liquid crystal display element 4, the characteristics of the liquid crystal display device when the viewing angle is inclined by 40 ° in the normal viewing angle direction are reduced. The increase in transmittance again by the applied voltage is suppressed to a low level. Further, it is confirmed that the actual display is performed by the liquid crystal display device 1c, and the angle at which the reversal phenomenon occurs is larger than when the retardation plate 5 is not installed.
Therefore, it is understood that the inversion phenomenon is less likely to occur.

The viewing angle characteristic of the liquid crystal display device 1c is substantially the same as that of the contrast radar chart shown in FIG.
It can be seen that by installing the retardation plate 5, the contrast in the high contrast region is uniform, the high contrast region is large in the normal viewing direction, and the viewing angle characteristics are improved.

The slow axis direction 26 of the retardation plate 5 may be set so as to coincide with the transmission axis direction 24 of the polarizing plate 2, and further, the angle formed by the slow axis direction 26 and the absorption axis direction 27. ,
Alternatively, it has been confirmed that similar effects can be obtained if the angle between the slow axis direction 26 and the transmission axis direction 24 is within 10 ° or less. Furthermore, the N of the retarder 5
If the Z value NZ is in the range of 0.4 to 0.8, it is considered that the same effect as described above can be obtained.

FIG. 9 is a diagram showing the overall configuration of still another embodiment of the present invention. Liquid crystal display device 1d of the present embodiment
Is similar in configuration and arrangement to the liquid crystal display device 1a shown in FIG. 1, and therefore, the components denoted by the same reference numerals as those in FIG.
Refers to the same thing as FIG.

The liquid crystal display device 1d shown in FIG. 9 has an NZ plate 5a manufactured by Nitto Denko Corporation having retardation values Re = 217 nm and NZ values NZ = 0.56 as retardation plates 5a and 5b (5 as a whole). 5b are laminated, and the slow axis direction 26a of the retardation plate 5a on one polarizing plate 2 is made to coincide with the transmission axis direction 24 of the polarizing plate 2; The slow axis direction 26 b of the phase difference plate 5 b is set in a direction perpendicular to the transmission axis direction 24 of the polarizing plate 2. Therefore, the transmission axis direction 24 of the polarizing plate 2 of the liquid crystal display device 1d, the slow axis direction 26a of the phase difference plate 5a, and the alignment direction 23 on the substrate 7 of the liquid crystal display element 4 match, and the phase difference The polarizing plate 3 is installed such that the slow axis direction 26 b of the plate 5 b, the alignment direction 22 of the liquid crystal display element 4 on the substrate 6, and the transmission axis direction 25 of the polarizing plate 3 match.

FIG. 10 shows the phase difference plates 5a and 5b of this embodiment.
FIG. 11 is an equal contrast radar chart showing CR10 points of the liquid crystal display device 1d provided with the phase difference plate 5;
3 is an equal-contrast radar chart showing points of CR10 when no is installed. Since the liquid crystal display devices 1a to 1d differ only in the configuration of the phase difference plate 5, FIG. 11 shows the same positions as the points of the CR 10 shown in FIG. As shown in FIG. 10, when the phase difference plates 5a and 5b are used, the point indicating CR10 is in the normal viewing angle direction (φ = 0).
(°) is plotted at an almost symmetric position. Compared with the contrast radar chart of FIG. 11, the point indicating CR10 in FIG. 10 is shown at a position where it is entirely widened. Is shown.

In the liquid crystal display device 1d of this embodiment, the slow axis direction 26a of the phase plate 5a is set to the transmission axis direction 24 of the polarizing plate 2, and the slow axis direction 26b of the phase plate 5b is set to the phase plate. 5
The liquid crystal display element 4 is set so that the slow axis direction 26b of the retardation plate 5b coincides with the alignment direction 22 on the substrate 6 of the liquid crystal display element 4 in the fast axis direction 27a (direction perpendicular to the slow axis direction 26a). The angle between the slow axis direction 26a and the transmission axis direction 24,
It is confirmed that similar effects can be obtained if the angle between the slow axis direction 26b and the fast axis direction 27a and the angle between the slow axis direction 26b and the orientation direction 22 are each 10 degrees or less. ing. The retardation plates 5a and 5b have retardation values Re of 100 to 500 nm and NZ, respectively.
If the value NZ is in the range of 0.3 to 0.8, the present embodiment 1d
It is considered that the same effect as described above can be obtained.

[0052]

According to the first aspect of the present invention, it is possible to improve the viewing angle characteristics by compensating for the viewing angle with respect to the liquid crystal display surface and the anisotropy of the refractive index that changes depending on the voltage value applied to the liquid crystal display element. it can. In addition, this makes it possible to adjust the retardation value in the liquid crystal display surface, adjust the variation in the wavelength of transmitted light caused by transmission through the liquid crystal display element, and prevent the liquid crystal display surface from being colored.

[0053]

According to the second aspect of the present invention, the anisotropy of the refractive index which changes according to the viewing angle with respect to the liquid crystal display surface and which changes according to the voltage applied to the liquid crystal display element is compensated, and the viewing angle characteristics are improved. However, the reversal phenomenon can be suppressed.

According to the third aspect of the present invention, the anisotropy of the refractive index, which varies depending on the viewing angle with respect to the liquid crystal display surface and the voltage applied to the liquid crystal display element, is compensated, and the right and left directions with respect to the normal viewing angle direction are compensated. It is possible to prevent the asymmetry of the contrast and the decrease in the contrast.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a configuration of a liquid crystal display device 1a according to an embodiment of the present invention.

FIG. 2 is a contrast radar chart of a display surface of the liquid crystal display device 1a.

FIG. 3 is a contrast radar chart on the display surface of the liquid crystal display device 1a when no retardation plate 5 is provided.

FIG. 4 is a chromaticity diagram in which the chromaticity of the display surface of the liquid crystal display device 1a of the present embodiment is measured from a direction inclined by 40 ° in the normal viewing angle direction.

FIG. 5 shows a phase difference plate 5 from a direction inclined by 40 ° in the normal viewing angle direction.
FIG. 9 is a chromaticity diagram showing the measured chromaticity of the display surface of the liquid crystal display device 1a in which Re = 347 nm and NZ = 0.44.

FIG. 6 shows a phase difference plate 5 from a direction inclined by 40 ° in the normal viewing angle direction.
FIG. 6 is a chromaticity diagram showing the measured chromaticity of the display surface of the liquid crystal display device 1a in which Re = 437 nm and NZ = 0.54.

FIG. 7 is a diagram showing an overall configuration of a liquid crystal display device 1c according to still another embodiment of the present invention.

FIG. 8 is a graph showing a relationship between an applied voltage and a light transmittance of a TN type liquid crystal display element in a normally white mode.

FIG. 9 is a diagram showing an overall configuration of a liquid crystal display device 1d according to still another embodiment of the present invention.

FIG. 10 is a contrast radar chart showing points of CR10 of the liquid crystal display device 1d of the present embodiment.

FIG. 11 is a contrast radar chart showing points CR10 of the liquid crystal display device 1d in which the retardation plate 5 is not provided.

FIG. 12 is a diagram illustrating alignment of liquid crystal molecules in a liquid crystal display element.

FIG. 13 is a diagram illustrating a change in refractive index anisotropy according to an applied voltage of a liquid crystal display element.

DESCRIPTION OF SYMBOLS 1a to 1d Liquid crystal display device 2,3 Polarizer 4 Liquid crystal display device 5 Phase difference plate 22,23 Alignment axis direction of liquid crystal display device 24,25 Transmission axis direction of polarizer 2,3 26 Phase difference The slow axis direction of the plate 5 27 The absorption axis direction of the polarizing plate 2 28 The fast axis direction of the retardation plate 5

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shigemitsu Mizushima 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (56) References JP-A-6-88962 (JP, A) JP-A-5-88 313159 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) G02F 1/1335 510

Claims (3)

(57) [Claims] 1. A liquid crystal display device having a twisted nematic liquid crystal layer interposed between a pair of transparent substrates so that the major axis direction of the molecule is spirally twisted by about 90 ° is disposed between the pair of polarizing plates. In the liquid crystal display device configured, a uniaxially stretched retardation film is disposed between at least one of the pair of polarizing plates and the liquid crystal display element, and the retardation film has a refractive index in a thickness direction of the film. Is a three-dimensional retardation film having a refractive index different from the refractive index in the plane direction and having anisotropy of the refractive index also in the plane direction, wherein the retardation value in the plane direction is 100 to 300 nm, and the slow axis of the retardation film is A liquid crystal display device wherein the angle between the polarizer and the absorption axis of the polarizing plate is selected to be 10 ° or less. 2. A liquid crystal display device having a twisted nematic liquid crystal layer interposed between a pair of transparent substrates such that the major axis direction of the molecule is spirally twisted by about 90 ° is disposed between the pair of polarizing plates. In the liquid crystal display device configured, a uniaxially stretched retardation film is disposed between at least one of the pair of polarizing plates and the liquid crystal display element, and the retardation film has a refractive index in a thickness direction of the film. Is a three-dimensional retardation film having a refractive index different from the refractive index in the plane direction and having anisotropy of the refractive index also in the plane direction, and NZ which is a ratio of the retardation value in the thickness direction of the film to the retardation value in the plane direction of the film. Value 0.4
A liquid crystal display device wherein the angle between the slow axis of the retardation film and the absorption axis or transmission axis of the polarizing plate is selected to be 10 ° or less. 3. A liquid crystal display element having a twisted nematic liquid crystal layer interposed between a pair of transparent substrates so that the major axis direction of the molecule is spirally twisted by about 90 ° is disposed between the pair of polarizing plates. In the liquid crystal display device configured, a retardation plate formed by laminating two layers of a uniaxially stretched retardation film is disposed between at least one of the pair of polarizing plates and the liquid crystal display element, The film is a three-dimensional retardation film in which the refractive index in the thickness direction of the film is different from the refractive index in the plane direction, and also has anisotropy of the refractive index in the plane direction, and the retardation value in the plane direction is 100 to 500 nm. The ratio NZ value of the retardation value in the thickness direction to the retardation value in the plane direction is 0.3 to 0.8, and the slow axis of the retardation film on the liquid crystal display element side and the polarizing plate side The angle between the retardation film and the fast axis is 10 ° or less, and the angle between the slow axis or fast axis of the retardation film on the liquid crystal display element side and the orientation axis of the retardation film side substrate of the liquid crystal display element is formed. The angle to 10 ° or less, the slow axis or the fast axis of the retardation film on the polarizing plate side,
A liquid crystal display device characterized in that the angle between the polarizing plate and the transmission axis is selected to be 10 ° or less.