JPH0519251A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To simplify the structure and to improve coloring of a display and a visual field characteristic by placing three pieces of phase plates by a specific constitution. CONSTITUTION:Between a pair of polarizing plates of a liquid crystal display device of a supertwisted nematic(STN) type in which a liquid crystal molecule is subjected to twist orientation by about 240 deg. a first and a second phase plates 22, 23 in which one leading axis intersects at about 40 deg. against the orientation processing direction of one substrate 14, and also, each leading axis is allowed to intersect at an angle of about 35 deg. to each other are placed. In such a way, a difference of a phase difference of every wavelength light generated at the time of transmitting through a liquid crystal cell is corrected roughly by two pieces of phase plates and coloring of a display color of the liquid crystal display device of the STN type is compensated. Moreover, another piece of third phase plate 24 is made adjacent to one piece 20 of the polarizing plates and placed so that its leading axis becomes roughly parallel or orthogonal to a transmission axis of the polarizing plate 20. In such a way, brightness at the time when the liquid crystal display device is looked at from the front becomes bright, and also, a visual field characteristic at the when it is observed obliquely is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a super twisted nematic type simple matrix liquid crystal display device.

[0002]

2. Description of the Related Art Liquid crystal display devices are used as display devices for office automation equipment. Since such a display device is required to have high-definition display,
The number of pixels is large, high time-division driving is required, and the display characteristics are required to have high contrast and a wide viewing angle. In order to meet such demands, as a display device such as a personal computer, a super twisted nematic type (hereinafter, referred to as ST
A simple matrix liquid crystal display device of N type) is used.

In this STN type simple matrix liquid crystal display device, a pair of substrates which are arranged to face each other with a predetermined space therebetween, and electrodes which are arranged so as to intersect the inner surfaces of the pair of substrates which face each other at right angles to each other. An alignment film formed over the electrode formation surface for aligning liquid crystal molecules in a predetermined direction, a liquid crystal material enclosed between the substrates so as to be sandwiched between the alignment films, and the pair of substrates. And a pair of polarizing plates arranged so as to sandwich the pair of substrates from the outside. Molecules in the vicinity of the alignment film of the liquid crystal material interposed between the alignment films of the pair of substrates are arranged in the alignment treatment direction by the alignment regulating force of the alignment film, and the liquid crystal molecules are aligned in accordance with a predetermined alignment treatment. Twisted at an angle of 180 ° to 270 ° from one substrate to the other substrate.

The liquid crystal molecules in the twist orientation change their orientation when an electric field is applied between the opposing electrodes by time division driving, and the pair of polarizing plates visualize the optical change accompanying this orientation change. Displays the desired display.

The above-mentioned liquid crystal display device uses the birefringence effect of the liquid crystal in order to increase the twist angle of the liquid crystal molecule arrangement in order to enable high time division driving and to increase the visual contrast. Therefore, there is a problem that the display is colored, the viewing angle is narrow, and the display color changes depending on the viewing angle.

In order to solve the above-mentioned coloring problem, a driving cell in which driving electrodes are provided on a pair of substrates facing each other as described above, and the driving cell is twisted in a direction opposite to the twisting direction of liquid crystal molecules. A two-layer STN-type liquid crystal display device in which the compensation cell and the compensation cell are arranged in two layers has been proposed. In this two-layer STN type liquid crystal display device, the difference in the phase difference for each wavelength light generated in the driving cell can be corrected by the compensation cell, and the coloration of the display can be suppressed and a display close to black and white can be performed.

Since the above-mentioned two-layer STN type liquid crystal display device uses the same liquid crystal cell as the driving cell as the compensation cell, the manufacturing process of this compensation cell is complicated and expensive, and the display device is There was a problem of becoming large.
Further, the coloring of the display has not been sufficiently removed, and the viewing angle characteristics have not been improved yet.

Further, the compensating cell of the two-layer STN type liquid crystal display device is replaced with one or two phase plates, and the phase plate is used to compensate for the difference in the phase difference of each wavelength light generated in the driving cell. The STN type liquid crystal display device has also been proposed. This liquid crystal display device is configured as shown in FIG.
That is, between the lower substrate 1 and the upper substrate 2, 240 from the alignment treatment direction 1a of the lower substrate 1 toward the alignment direction 2a of the upper substrate 2.
A liquid crystal material 3 having a twist orientation is enclosed. The lower substrate 1, the upper substrate 2 and the liquid crystal material 3 form a liquid crystal cell 4. On the lower side of the lower substrate 1 on the side where light enters the liquid crystal cell 4, a polarizer 5 having a fast axis 5a aligned in a direction rotated clockwise by 140 ° from the alignment treatment direction 1a is arranged. An analyzer 6 having a fast axis 6a aligned in a direction rotated counterclockwise by 55 ° from the alignment treatment direction 1a is arranged above the cell 4. The fast axes of the liquid crystal cell 4 and the analyzer 6 intersect each other at 35 °, and one of the phase plates adjacent to the liquid crystal cell intersects at 40 ° from the alignment treatment direction. It is arranged to.

In the conventional liquid crystal display device provided with such a phase plate, the coloring of the display is reduced by the two phase plates and the contrast is relatively high. Further, since the film-shaped phase plate is used, there are advantages that the manufacturing process is simplified and the shape can be made thin, and the display device becomes compact.

[0010]

However, in the above-mentioned conventional liquid crystal display device, since the wavelength dependence of Δn of the phase plate is different from the wavelength dependence of Δn of the liquid crystal, each phase difference generated in the drive cell is different. The difference for each wavelength light could not be corrected sufficiently. Therefore, there is a drawback that the coloring of the display cannot be sufficiently removed, the viewing angle characteristics are poor, the contrast changes significantly depending on the viewing direction of the liquid crystal display device, and the display color is significantly changed. It had the drawback of significantly reducing it. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a liquid crystal display device having a simple structure and improved display coloring and viewing angle characteristics.

[0011]

In order to achieve the above object, the liquid crystal display device of the present invention has electrodes facing each other and an alignment treatment in a predetermined direction covering the electrodes intersecting each other. And a pair of substrates on which the aligned alignment film is formed, and sealed between the pair of substrates so as to have a twist orientation of approximately 240 ° from one substrate to the other substrate, and a refractive index anisotropy Δn and a layer are formed. The product Δnd with the thickness d is 800 nm to 900 n
A liquid crystal material having a value of m is provided outside the pair of substrates,
The polarizing plates are arranged so as to sandwich the pair of substrates, and the transmission axis of one of the polarizing plates is approximately 140 with respect to the alignment processing direction of the one substrate.
And a pair of polarizing plates arranged so that their transmission axes intersect at an angle of approximately 85 °, and between these pair of polarizing plates, one fast axis is the alignment treatment direction of one substrate. Intersect with each other at about 40 °, and the mutual fast axes are about 35.
Between a pair of phase plates arranged to intersect each other at an angle of 0 °, and between the pair of polarizing plates, one of the polarizing plates is adjacent to the fast axis of which is parallel or orthogonal to the transmission axis of the adjacent polarizing plate. It is characterized in that it is arranged with another one of the phase plates arranged in.

[0012]

According to the present invention, between the pair of polarizers of the STN type liquid crystal display device in which liquid crystal molecules are twist-aligned by approximately 240 °, one fast axis is approximately 40 with respect to the alignment processing direction of one substrate. By disposing the first and second phase plates which intersect at an angle of 90 ° and whose fast axes intersect at an angle of about 35 °, it is possible to obtain light of each wavelength generated when passing through the liquid crystal cell. The difference in phase difference is almost corrected by the two phase plates and STN
Type liquid crystal display device is compensated for display color coloring, and another third phase plate is arranged adjacent to one of the polarizing plates, and its fast axis is substantially parallel to the transmission axis of the adjacent polarizing plate. Alternatively, by arranging the liquid crystal cells so as to be orthogonal to each other, the intensity of transmitted light in the front of the liquid crystal cell is increased, and the brightness when viewed from the front of the liquid crystal display device is increased. Further, since the phase difference between the light vertically incident on these phase plates and the light obliquely incident on these phase plates is different, the phase difference between the light vertically or obliquely transmitted through the liquid crystal cell is three. Interact with each other so as to cancel out the phase difference, and as a result, the area where a high contrast can be obtained is widened and the change in display color depending on the viewing angle is reduced.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings. [First Embodiment] FIGS. 1 and 2 are a sectional view and an exploded perspective view of the first embodiment. 1 and 2, the liquid crystal cell 11 includes a lower substrate 14 on which one electrode 12 and an alignment film 13 covering the electrode 12 are formed, and the one electrode 1
An upper substrate 17 on which the other electrode 15 that intersects 2 and faces the other electrode and an alignment film 16 that covers the other electrode 15 is formed; and a sealing material 18 that joins the upper and lower substrates 14 and 17 at a predetermined interval, Also, the dielectric constant ratio Δε / ε⊥ is enclosed in a region surrounded by the upper and lower substrates 14 and 17 and the sealing material 18.
Has a value of 1.90, and the elastic constant ratio K3 / K1 has a value of 1.8.
3, a liquid crystal material 19 having a value of K3 / K2 of 2.4 and a value of the ratio d / p of the gap d and the natural pitch p of 0.5.

Light is incident on the liquid crystal cell 11 from below in the drawing. Below, the lower substrate is referred to as the incident side substrate 14, and the upper substrate is referred to as the emission side substrate 17. A polarizer 20 made of a linear polarizing plate is arranged outside the incident side substrate 14 of the liquid crystal cell 11, and an analyzer 21 made of a linear polarizing plate is arranged above the emission side substrate 17. Two phase plates 22 and 23 are arranged in this order between the emission side substrate 17 of the liquid crystal cell 11 and the analyzer 21.

The alignment films 13 and 16 formed on the surfaces of the incident-side substrate 14 and the exit-side substrate 17 facing each other are subjected to an alignment treatment such as rubbing, and the incident-side substrate 14
As shown in FIG. 2, when the liquid crystal cell 11 is observed from the front, the alignment film 13 is subjected to an alignment treatment in a direction 13a having an inclination of about 30 ° from the lower left to the upper right with respect to a horizontal line. .. The alignment film 16 of the outgoing side substrate 17 facing the incident side substrate 14 is rotated clockwise (hereinafter, negative or −) with respect to the alignment treatment direction 13a of the incident side substrate 14 (hereinafter, referred to as incident side alignment treatment direction). The orientation treatment is applied in the direction 16a rotated by 60 °. By such an alignment treatment, the liquid crystal molecules of the liquid crystal material 19 are arranged with a pretilt angle of about 8 °, and are arranged as a 240 ° (φo) twist in the negative rotation direction from the incident side substrate 14 to the emitting side substrate 17. .. The gap d of the liquid crystal cell 11 and the refractive index anisotropy Δn
The value of the product Δnd with is 864 nm (measurement wavelength: 589n
m).

The transmission axis 20a of the polarizer 20 is counterclockwise with respect to the incident side alignment treatment direction 13a (hereinafter, positive or +
Is arranged in the direction of + 140 ° (α), and the analyzer 21 has its transmission axis 21a in the incident side alignment treatment direction 13
It is arranged in a direction intersecting with a at 55 ° (ε).

The first and second phase plates 22 and 23 are composed of a phase plate in which polycarbonate is uniaxially stretched and the value of Δnd is 370 nm (measurement wavelength: 589 nm). The axis 22a is the incident side alignment treatment direction 13
The second phase plate 2 is disposed at about 40 ° (γ) with respect to a.
3, the fast axis 23a is arranged in a direction of approximately 5 ° (δ) with respect to the incident side alignment treatment direction 13a. And
The third phase plate 24 is arranged such that the fast axis 24a is approximately 50 ° (β) with respect to the incident side alignment treatment direction 13a.

The first embodiment can achieve the object of the present invention even if the direction of the fast axis of the third phase plate 24 is changed. That is, as shown in FIG. 3, the fast axis 24a of the third phase plate 24 can be arranged so as to coincide with the direction of approximately 140 ° with respect to the incident side alignment treatment direction 13a. Incidentally, in FIG. 3, members other than the third phase plate 24 are the same as the structure shown in FIG.

As described above, in the first embodiment, the pair of polarizing plates have the transmission axes of one polarizing plate intersecting at approximately 140 ° with respect to the alignment treatment direction of the one substrate, and at approximately 85 ° to each other. They are arranged so as to intersect each other at an angle of 90 °, and one fast axis intersects with the alignment treatment direction of one substrate at an angle of about 40 ° between the pair of polarizing plates, and each fast axis is at about 35 °.
Further, the third phase plate is disposed between the pair of polarizing plates so as to be adjacent to any one of the polarizing plates, and the fast axis thereof is parallel or orthogonal to the transmission axis of the adjacent polarizing plate. It is arranged like this.

Therefore, the difference in the phase difference between the light beams of different wavelengths, which occurs when the light passes through the liquid crystal cell, is substantially corrected by the pair of first and second phase plates, so that the display color of the STN type liquid crystal display device is colored. By compensating, and further arranging another third phase plate adjacent to one of the polarizing plates so that its fast axis is substantially parallel or orthogonal to the transmission axis of the adjacent polarizing plate, The intensity of the transmitted light in the front of the liquid crystal cell becomes strong, and the brightness when viewed from the front of the liquid crystal display device becomes bright. Further, since the phase difference between the light vertically incident on these phase plates and the light obliquely incident on these phase plates is different, the phase difference between the light vertically or obliquely transmitted through the liquid crystal cell is three. Interact with each other so as to cancel out the phase difference, and as a result, the area where a high contrast can be obtained is widened and the change in display color depending on the viewing angle is reduced.

The results of measuring the electro-optical characteristics of the liquid crystal display devices having the arrangements shown in FIGS. 2 and 3 are shown in FIGS. 4 to 12. 4 to 11A and B,
The electro-optical characteristics of the liquid crystal display device having the structure shown in FIGS.

FIG. 4 shows Y-V characteristics showing the relationship of the transmittance (Y value) with respect to the driving voltage (V) when time-divisionally driven at 1/480 duty and 1/15 bias, and the contrast at that time. The solid line OFF represents the OFF waveform, the dotted line ON represents the change in the transmittance when the ON waveform is applied, and the broken line CR represents the contrast. As shown in FIG. 4, the first embodiment having the arrangement shown in FIGS. 2 and 3 has a high contrast of 66,
The transmittance is high at 73%. 5 and 6 show isoluminance curves when observed from directions tilted in respective directions from the normal direction of the liquid crystal cell. FIG. 5 shows a dark state and FIG. 6 shows a bright state. Here, the concentric circles are 10 °, 20 °, and 30 ° from the normal direction of the substrate of the liquid crystal display device, respectively, from the inside.
The black square (■) has a transmittance of 10%, the white square (□) has a transmittance of 20%, and the black triangle (▲) has a transmittance of 30%. %, White triangle (△)
Indicates a transmittance of 40%, a black star (*) indicates a transmittance of 50%, a white star (*) indicates a transmittance of 60%, and a cross mark (+) indicates a transmittance of 70%. As shown in FIGS. 5 and 6, in the first embodiment, the region where the transmittance is less than 10% is wide in the dark state, and the region where the transmittance is 10% or more appears widely in the bright state.

FIG. 7 shows isocontrast curves when observed from various directions of the liquid crystal display device. In FIG. 7, the concentric circles are 10 ° and 20 ° from the normal direction of the substrate of the liquid crystal display device, respectively, from the inside. The directions are tilted at 30 °, 40 °, and 50 °, and the black circles (●) indicate that the contrast is less than 1, that is, the light and dark are reversed, and the black squares (■) indicate the contrast is 10% and the white squares ( □) has a contrast of 20%, black triangles (▲) has a contrast of 30%, white triangles (△) has a contrast of 40%, black stars (★) have a contrast of 50%, white stars (☆) have a contrast of 60.
%, The cross mark (+) shows a contrast of 70%, the X mark shows a contrast of 80%, and the * mark shows a contrast of 90%. As shown in FIG. 7, in the first embodiment, the contrast is wide in the range of 10 or more, and the inversion region in which the light and dark appearing in the upper right direction of the liquid crystal display device is inverted is narrowed, and the viewing angle characteristics are improved. Is getting better.

FIGS. 8A and B to FIGS. 11A and 11B are voltage-transmittance characteristics representing changes in transmittance with respect to an applied voltage when the liquid crystal display device is tilted by 10 ° in each azimuth direction from the normal line.
The change in display color at that time is shown in the CIE chromaticity diagram. Figure 8
A and B are + based on the incident side alignment treatment direction 13a, respectively.
FIG. 9A and FIG. 9B respectively show the voltage-transmittance characteristics when tilted in the direction of 150 °, that is, in the left azimuth direction of the liquid crystal cell by 10 ° from the normal line of the liquid crystal cell, and the CIE chromaticity diagram of the display color at that time. The voltage-transmittance characteristic when tilted in the direction of + 330 ° with respect to the incident side alignment treatment direction 13a, that is, when the liquid crystal cell is tilted rightward by 10 ° from the normal line of the liquid crystal cell, and the CIE of the display color at that time. Chromaticity diagrams, FIGS. 10A and 10B show the voltage-transmittance in the direction of + 60 ° with respect to the incident side alignment treatment direction 13a, that is, the voltage-transmittance when the liquid crystal cell is upwardly inclined by 10 ° from the normal line of the liquid crystal cell. Characteristic and C of display color at that time
IE chromaticity diagram, FIGS. 11A and 11B show incident side alignment treatment direction 1 respectively.
FIG. 3 is a CIE chromaticity diagram of the voltage-transmittance characteristic when the liquid crystal cell is tilted in the direction of + 240 ° with respect to 3a, that is, in the downward direction of the liquid crystal cell by 10 ° in sequence, and the display color at that time. .. Here, the black squares (■) and solid lines are the normal direction of the liquid crystal cell, the white squares (□) and dotted lines are the directions inclined by 10 ° from the normal line of the liquid crystal cell, and the black triangles (▲) and the broken lines are the normal directions of the liquid crystal cell. The direction tilted 20 ° from the line, the white triangle (△) and the one-dot chain line are the directions tilted 30 ° from the normal line of the liquid crystal cell, and the black star (★)
And the two-dot chain line is a direction inclined by 40 ° from the normal line of the liquid crystal cell,
White star (☆) and thin dotted line are 50 ° from the normal line of the liquid crystal cell
It represents the tilted direction. As is clear from these figures, even when viewed from each direction of the liquid crystal cell, a steep voltage −
It exhibits transmittance characteristics, and the change in display color is relatively small.

Further, FIG. 12 is a Y-V characteristic diagram showing the change of the transmittance with respect to the driving voltage of the time division driving in the embodiment of the configuration shown in FIG. Also in the embodiment of FIG. 3, the transmittance in the bright state is high and the contrast is also high.

For comparison, the same electro-optical characteristics as those of the first embodiment were measured with respect to the liquid crystal display device having the structure in which only the third phase plate is removed from the structure of the liquid crystal display device shown in the first embodiment. 19 and 26A and 26B. 19 is different from the YV characteristic diagram of FIG. 4 of the first embodiment in FIGS.
5A and 5B of the first embodiment correspond to the isocontrast curves of FIG. 5, FIG. 22 corresponds to the isocontrast curves of FIG. 7 of the first embodiment, and FIGS. 23A and 23B to FIGS. This corresponds to FIGS. 8A, B to 11A, B of the first embodiment, respectively.

The electro-optical characteristics of the first embodiment of the present invention shown in FIGS. 4 to 11A and B and FIGS. 19 to 26A and B.
As is clear from comparison with the electro-optical characteristics of the comparative example shown in FIG. 1, the electro-optical characteristics of the first embodiment are superior to those of the comparative example. That is, in the first embodiment, as is clear from comparing FIGS. 4 and 12 with FIG. 19, the brightness and contrast in the normal direction of the liquid crystal cell have Y values of 73 in the case of the phase plate arrangement of FIG. %, The contrast is 66, the Y value is 71% and the contrast is 75 in the case of the phase plate arrangement in FIG. 3, respectively, which are higher than the Y value of 62% and the contrast of 55 in the comparative example, respectively. Also, FIGS. 5 and 6 and FIGS.
Comparing with, in the first embodiment, the region where the transmittance is low in the dark state is wide, and the region where the transmittance is high in the bright state is wide. Then, comparing FIG. 7 and FIG. 22, in the first embodiment, the high contrast region is wide and the inversion region is narrow. Moreover, FIGS. 8A, B to 11A, B and FIGS. 23A, B to 26
Comparing A and B, the display colors of the first embodiment and the comparative example are the same. Therefore, in the first embodiment of the present invention, the change in the display color is equal to that in the comparative example, but the transmittance in the front direction of the liquid crystal display device is high and the viewing angle characteristics are improved.

[Second Embodiment] The present invention is not limited to the arrangement of the phase plate of the first embodiment, but the third phase plate may be arranged adjacent to the polarizing plate on the light emitting side. Concrete second
Examples will be described in detail with reference to FIGS. 13 to 15. The same members as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. In FIGS. 13 and 14, a polarizer 20 is arranged below the entrance side substrate 14 of the liquid crystal cell 11, and an analyzer 21 is arranged above the exit side substrate 17. Two phase plates 22 and 23 are arranged in this order between the emission side substrate 17 of the liquid crystal cell 11 and the analyzer 21.

The alignment films 13 and 16 formed on the surfaces of the incident-side substrate 14 and the outgoing-side substrate 17 facing each other are subjected to an alignment treatment such as rubbing.
As shown in FIG. 14, when the liquid crystal cell 11 is observed from the front, the alignment film 13 is subjected to the alignment treatment in the direction 13a having a horizontal direction with an inclination of about 30 ° from the lower left to the upper right. .. The alignment film 16 of the outgoing side substrate 17 facing the incident side substrate 14 is subjected to the alignment treatment in the direction 16a rotated by 60 ° in the clockwise direction with respect to the alignment treatment direction 13a of the incident side substrate 14. By such an alignment treatment, the liquid crystal molecules of the liquid crystal material 19 are aligned with a pretilt angle of about 8 °, and the liquid crystal molecules are moved in the negative rotation direction from the incident side substrate 14 toward the emission side substrate 17 by 240.
Arrange as a ° (φo) twist. The product Δnd of the gap d of the liquid crystal cell 11 and the refractive index anisotropy Δn is 864 nm (measurement wavelength: 589 nm).

The transmission axis 20a of the polarizer 20 is + 140 ° (α) counterclockwise with respect to the incident side alignment treatment direction 13a.
Of the transmission axis 21a of the analyzer 21.
Is arranged in a direction intersecting with the incident side alignment treatment direction 13a at 55 ° (ε).

22 and 23 of the first and second phase plates are Δn
The value of d is composed of a phase plate having a wavelength of 370 nm (measurement wavelength: 589 nm), and the fast axis 22a of the first phase plate 22 is arranged at approximately 40 ° (γ) with respect to the incident side alignment treatment direction 13a, The fast axis 23a of the second phase plate 23 is arranged in a direction of approximately 5 ° (δ) with respect to the incident side alignment treatment direction 13a.

The third phase plate 24 is the second phase plate 23.
Is arranged between the analyzer 21 and the analyzer 21, and its fast axis 24a is arranged in a direction of approximately 55 ° (β) with respect to the incident side alignment treatment direction 13a.

In the second embodiment, the object of the present invention can be achieved even if the direction of the fast axis of the third phase plate 24 is changed. That is, as shown in FIG. 15, the fast axis of the third phase plate 24 is approximately 14 with respect to the incident side alignment treatment direction 13a.
You may make it arrange | position so that it may correspond to the direction of 5 degrees.

As described above, in this second embodiment, the pair of polarizing plates have their transmission axes intersecting at approximately 140 ° with respect to the alignment treatment direction of one substrate, and are substantially parallel to each other. They are arranged so as to intersect with each other at an angle of 85 °, and one fast axis intersects with the alignment treatment direction of one substrate at about 40 ° between the pair of polarizing plates, and each fast axis is at about 3 °.
They are arranged so as to intersect each other at 5 °, and further, between the pair of polarizing plates, another third phase plate is adjacent to one of the polarizing plates, and its fast axis is parallel or orthogonal to the transmission axis of the adjacent polarizing plate. It is arranged to do.

Therefore, the difference in the phase difference for each wavelength light generated when the light is transmitted through the liquid crystal cell is substantially corrected by the pair of first and second phase plates, and the display color of the STN type liquid crystal display device is colored. By being compensated, and by arranging another third phase plate adjacent to one of the polarizing plates so that its fast axis is substantially parallel or orthogonal to the transmission axis of the adjacent polarizing plate, The intensity of transmitted light in the front of the liquid crystal cell is increased, and the brightness when viewed from the front of the liquid crystal display device is increased. Further, since the phase difference between the light vertically incident on these phase plates and the light obliquely incident on these phase plates is different, the phase difference between the light vertically or obliquely transmitted through the liquid crystal cell is three. Interact with each other so as to cancel out the phase difference, and as a result, the area where high contrast can be obtained becomes wider, and the change in display color depending on the viewing angle is reduced.

FIGS. 16 and 17 show the results of measuring the electro-optical characteristics of the liquid crystal display devices arranged as shown in FIGS. 14 and 15, respectively. FIGS. 16 and 17 show YV characteristics showing the relationship of the transmittance (Y value) with respect to the drive voltage (V) when time-divisionally driven at 1/480 duty and 1/15 bias, and the contrast at that time. The solid line OFF indicates the OFF waveform, and the dotted line ON indicates O.
Representing the change in transmittance when N waveforms are applied,
The broken line CR represents the contrast. As shown in FIG. 16, the second embodiment having the arrangement shown in FIG. 14 has a high contrast of 63 and a high transmittance of 72%. Further, as shown in FIG. 17, in the second embodiment having the arrangement shown in FIG. 15, the contrast is slightly low at 39, but the transmittance is high at 72%. In the second embodiment, the area of high contrast is wide even when the viewing angle is changed, and the change in display color is small.

As described above, the second embodiment has an extremely high transmittance in the bright state as compared with the YV characteristic shown in FIG. 19 of the comparative example having the structure shown in FIG. Viewing angle characteristics are significantly improved.

As described above, according to the liquid crystal display device of the present invention, the transmittance in the front direction of the liquid crystal display device is extremely high, and the contrast is high in each direction,
Moreover, the change in hue of the transmitted light depending on the viewing angle is small, and the viewing angle characteristics are improved.

[0039]

According to the present invention, one fast axis between a pair of polarizing plates of an STN type liquid crystal display device in which liquid crystal molecules are twist-aligned by approximately 240 ° is approximately 40 ° with respect to the alignment treatment direction of one substrate. And cross each other's fast axes about 35
By arranging the first and second phase plates intersecting each other at an angle of °, the difference in the phase difference for each wavelength light generated when passing through the liquid crystal cell is substantially corrected by the two phase plates and the STN Type of liquid crystal display device, while compensating for display color coloring, another third phase plate is arranged adjacent to one of the polarizing plates, and its fast axis is substantially equal to the transmission axis of the adjacent polarizing plate. Since they are arranged so as to be parallel or orthogonal to each other, the transmitted light intensity in the front of the liquid crystal display device is strong and the brightness when viewed from the front of the liquid crystal display device becomes brighter. The viewing angle characteristics of are improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is an exploded perspective view showing a schematic configuration of a first embodiment of the present invention.

FIG. 3 is an exploded perspective view showing another arrangement example of the phase plate in the first embodiment.

FIG. 4 is a liquid crystal display device having the arrangement of the phase plate shown in FIG. 2 of the first embodiment, showing a change in transmittance with respect to a drive voltage in time division driving, and Y representing contrast at that time.
-V characteristic diagram.

FIG. 5 is an equal transmittance curve diagram showing a transmittance distribution when observed from each direction in a dark state in the liquid crystal display device having the arrangement of the phase plate shown in FIG. 2 of the first embodiment.

6 is an equal transmittance curve diagram showing a transmittance distribution when observed from each direction in a bright state in the liquid crystal display device having the arrangement of the phase plate shown in FIG. 2 of the first embodiment.

FIG. 7 is an isocontrast curve diagram when the liquid crystal display device having the arrangement of the phase plate shown in FIG. 2 of the first embodiment is observed from each direction.

8A is a diagram showing a liquid crystal display device having the arrangement of the phase plate shown in FIG. 2 of the first embodiment, with respect to an applied voltage when the liquid crystal display device is tilted to the left azimuth direction by 10 ° from the normal line of the liquid crystal cell. FIG. 4 is a Y-V characteristic diagram showing transmittance.

FIG. 8B shows a display color when the liquid crystal display device having the arrangement of the phase plate shown in FIG. 2 of the first embodiment is tilted in the left azimuth direction of the liquid crystal display device by 10 ° in sequence from the normal line of the liquid crystal cell. The CIE chromaticity diagram showing a change.

9A is a diagram showing the liquid crystal display device having the arrangement of the phase plate shown in FIG. 2 of the first embodiment, with respect to the applied voltage when the liquid crystal display device is tilted in the right direction by 10 ° from the normal line of the liquid crystal cell in sequence. FIG. 6 is a YV characteristic diagram showing the transmittance.

9B is a liquid crystal display device having the arrangement of the phase plate shown in FIG. 2 of the first embodiment, showing a display color when the liquid crystal display device is tilted to the right direction of the liquid crystal cell by 10 ° from the normal line of the liquid crystal cell in order. The CIE chromaticity diagram showing a change.

10A is a liquid crystal display device having the arrangement of the phase plate shown in FIG. 2 of the first embodiment, in the upper direction of the liquid crystal display device,
FIG. 7 is a YV characteristic diagram showing the transmittance with respect to an applied voltage when the liquid crystal cell is sequentially inclined by 10 ° from the normal line.

10B is a liquid crystal display device having the arrangement of the phase plate shown in FIG. 2 of the first embodiment, in the upper direction of the liquid crystal display device,
FIG. 6 is a CIE chromaticity diagram showing a change in display color when sequentially tilted by 10 ° from the normal line of the liquid crystal cell.

11A is a liquid crystal display device having the arrangement of the phase plate shown in FIG. 2 of the first embodiment, in the lower direction of the liquid crystal display device,
FIG. 7 is a YV characteristic diagram showing the transmittance with respect to an applied voltage when the liquid crystal cell is sequentially inclined by 10 ° from the normal line.

11B is a liquid crystal display device having the arrangement of the phase plate shown in FIG. 2 of the first embodiment, in the lower direction of the liquid crystal display device,
FIG. 6 is a CIE chromaticity diagram showing a change in display color when sequentially tilted by 10 ° from the normal line of the liquid crystal cell.

FIG. 12 is a YV characteristic diagram showing a change in transmittance with respect to a drive voltage in time-division driving and a contrast at that time in the liquid crystal display device having the arrangement of the phase plate shown in FIG. 3 of the first embodiment.

FIG. 13 is a sectional view showing a second embodiment of the present invention.

FIG. 14 is an exploded perspective view showing a schematic configuration of a second embodiment of the present invention.

FIG. 15 is an exploded perspective view showing another arrangement example of the phase plate in the second embodiment.

16 is a YV characteristic diagram showing a change in transmittance with respect to a driving voltage in time division driving and a contrast at that time in the liquid crystal display device having the arrangement of the phase plate shown in FIG. 14 of the second embodiment.

FIG. 17 is a YV characteristic diagram showing a change in transmittance with respect to a driving voltage in time division driving and a contrast at that time in the liquid crystal display device having the arrangement of the phase plate shown in FIG. 15 of the second embodiment.

FIG. 18 is an exploded perspective view showing a schematic configuration of a liquid crystal display device having a conventional phase plate arrangement and illustrated for comparison with the present invention.

FIG. 19 is a YV characteristic diagram showing a change in transmittance with respect to a driving voltage in time division driving and a contrast at that time in a comparative example having the arrangement of the phase plate shown in FIG. 18.

20 is an equal transmittance curve diagram showing a transmittance distribution when observed from each direction in a dark state in the comparative example having the arrangement of the phase plate shown in FIG.

FIG. 21 is an equal transmittance curve diagram showing the transmittance distribution when observed from each direction in the bright state in the comparative example having the arrangement of the phase plate shown in FIG.

22 is an isocontrast curve diagram when the liquid crystal display device is observed from each direction in the comparative example having the arrangement of the phase plate shown in FIG.

23A is a YV diagram showing the transmittance with respect to the applied voltage when the liquid crystal display device is tilted in the left azimuth direction by 10 ° from the normal line of the liquid crystal cell in the comparative example having the arrangement of the phase plates shown in FIG. Characteristic diagram.

23B is a CI showing a change in display color when the liquid crystal display device is tilted to the left azimuth direction by 10 ° from the normal line of the liquid crystal cell in the comparative example having the phase plate arrangement shown in FIG.
E chromaticity diagram.

24A is a YV diagram showing the transmittance with respect to the applied voltage when the liquid crystal display device is tilted in the right direction of the liquid crystal display device by 10 degrees in sequence from the normal line in the comparative example having the phase plate arrangement shown in FIG. Characteristic diagram.

FIG. 24B is a CI showing a change in display color when the liquid crystal display device is tilted to the right direction of the liquid crystal display device by 10 ° from the normal line in the comparative example having the phase plate arrangement shown in FIG.
E chromaticity diagram.

25A is a YV diagram showing the transmittance with respect to the applied voltage when the liquid crystal display device is tilted upward by 10 ° from the normal line of the liquid crystal cell in the comparative example having the phase plate arrangement shown in FIG. Characteristic diagram.

25B is a CI showing the change in display color when the liquid crystal display device is tilted upward by 10 ° from the normal line of the liquid crystal cell in the comparative example having the arrangement of the phase plates shown in FIG.
E chromaticity diagram.

26A is a YV diagram showing the transmittance with respect to an applied voltage when the liquid crystal display device is tilted downward by 10 degrees from the normal line of the liquid crystal cell in the comparative example having the phase plate arrangement shown in FIG. Characteristic diagram.

26B is a graph showing a change in display color when the liquid crystal display device is tilted downward by 10 ° from the normal line of the liquid crystal cell in the comparative example having the arrangement of the phase plates shown in FIG.
E chromaticity diagram.

[Explanation of symbols]

 11 Liquid Crystal Cell 12, 15 Electrode 13, 16 Alignment Film 14 Incident Side Substrate 17 Emission Side Substrate 18 Sealing Material 19 Liquid Crystal Material 20 Polarizer 21 Analyzer 22 First Phase Plate 23 Second Phase Plate 24 Third Phase Plate 13a Incident Side Orientation treatment direction 20a Transmission axis of polarizer 21a Transmission axis of analyzer 22a, 23a, 24a Fast axis of phase plate

Claims (1)

Claim: What is claimed is: 1. A pair of substrates each having an electrode crossing each other and an alignment film that covers the electrodes and is subjected to an alignment treatment in a predetermined direction on each of the facing surfaces, Sealed between the pair of substrates so as to have a twist orientation of approximately 240 ° from one substrate to the other substrate, and the product Δnd of the refractive index anisotropy Δn and the layer thickness d has a value of 800 nm to 900 nm. The liquid crystal material is arranged outside the pair of substrates so as to sandwich the pair of substrates, the transmission axis of one of the polarizing plates intersects with the alignment treatment direction of the one substrate at approximately 140 °, and Between the pair of polarizing plates arranged such that their transmission axes intersect at an angle of approximately 85 °, one fast axis between the pair of polarizing plates is approximately 40 ° with respect to the alignment treatment direction of one substrate.
And a pair of phase plates arranged so that their mutual fast axes intersect at approximately 35 °, and between the pair of polarizing plates, any one of the polarizing plates is adjacent to the fast axis. A liquid crystal display device comprising: another phase plate arranged in parallel or orthogonal to a transmission axis of an adjacent polarizing plate.