JPH0862568A - Liquid crystal display - Google Patents

Abstract

(57) [Summary] [Purpose] An ST with excellent viewing angle characteristics and excellent uniformity.
Provide N-LCD. [Constitution] Δnd of the driving liquid crystal layer is 0.80 μm or more,
90 μm or less, transmission axis azimuth of upper polarizing plate is −20 ° or more, 20 ° or less, transmission axis azimuth of lower polarizing plate is −20 °
20 ° or less, upper phase plate slow axis azimuth angle of 90 ° or more, 120 ° or less, lower phase plate slow axis azimuth angle of 110 °
Above, 150 ° or less, Δnd of upper phase plate and lower phase plate
450 nm or more, 550 nm or less, 300 n
Liquid crystal display device with a thickness of m or more and 380 nm or less. [Effect] Display ST with good viewing angle characteristics and excellent uniformity
N-LCD is obtained.

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 liquid crystal display device (STN-LCD), especially a color display.
Regarding STN-LCD.

[0002]

2. Description of the Related Art STN-LCDs are widely used in word processors, personal computers and the like because they can display a large capacity by using a low cost simple matrix driving method.
In addition, as the sophistication of society increases, colorization of STN-LCD is also required, and color STN-LCD has been commercialized. But,
The display quality is low and has not reached a level satisfying the user's demand. Color display STN-L currently commercialized
The low display quality of the CD is due to the unevenness of the surface of the counter substrate provided with the color filter. As a result, the alignment process becomes non-uniform and the thickness of the driving liquid crystal layer also becomes non-uniform, resulting in display unevenness in the STN-LCD having a steep rising characteristic. In order to make the display unevenness inconspicuous, the contrast ratio must be lowered.

In order to reduce irregularities on the surface of the counter substrate having a color filter, attempts have been made to increase the film thickness of the flattening film and polish the surface of the counter substrate, but it is effective even if the production process is increased. Few. Further, a color filter manufacturing method (electrodeposition method) in which unevenness does not occur on the surface of the counter substrate is being developed, but cost reduction remains a future problem.

In JP-A-5-107520, the product of the layer thickness of the driving liquid crystal layer and the birefringence of the twisted nematic liquid crystal is 0.75 μm or more and 1.0 μm or less, and the twist angle of the driving liquid crystal layer is 210 °. Above, above 270 °, up and down 2
A single polarizing plate and a single phase plate are used, and the retardation of the phase plate is 200 nm or more and 450 nm or less. As a result, of the applied voltages of two or more values, normally open display in which dark display is performed on the high voltage side is realized, but it is not the optimum display condition.

The STN-LCD uses a simple matrix driving method, but has a problem that the contrast ratio is lowered due to a frame response. To solve this, AA (Active
A driving method has been proposed by TJ Scheffer et al. However, the number of driving circuits increases and the cost increases.

As described above, sufficient display quality cannot be obtained with the conventional color STN-LCD.

[0007]

SUMMARY OF THE INVENTION In view of the above problems of the prior art, the object of the present invention is to eliminate the display unevenness that has been a problem in conventional STN-LCDs, and to provide high display quality and low cost.
The purpose is to provide STN-LCD, especially color STN-LCD.

[0008]

Means for Solving the Problems As a first means, the present inventors have made a pair of substrates provided with electrodes, a driving liquid crystal layer made of nematic liquid crystal, and an upper polarization plate disposed above and below the substrate. Plate, lower polarization plate, upper phase plate arranged between upper polarization plate and substrate, lower phase plate arranged between lower polarization plate and substrate, and drive for applying a voltage of two or more values A liquid crystal display device comprising a driving liquid crystal layer having a twist angle of 200 ° or more, and a substrate sandwiching the driving liquid crystal layer. If the product of refraction is 0.80 μm or more and 0.90 μm or less and the azimuth angle is defined counterclockwise from the horizontal direction of the substrate, the azimuth angle of the transmission axis of the upper polarizing plate is −20 ° or more and 20 ° or less, The azimuth angle of the transmission axis of the lower polarizing plate is -20 ° or more, 20
If the high refractive index of the two electro-optic principal axes in the plane of the phase plate is defined as the slow axis, the azimuth angle of the slow axis of the upper phase plate is 90 ° or more and 120 ° or less. The azimuth angle of the slow axis of the lower phase plate is 110 ° or more and 150 ° or less, and the retardations of the upper phase plate and the lower phase plate at a wavelength of 550 nm are 450 nm or more and 550 n, respectively.
The present invention invented a liquid crystal display device characterized by having a thickness of m or less, 300 nm or more, and 380 nm or less.

As a second means, the present inventors have
The product of the layer thickness of the driving liquid crystal layer and the birefringence of the nematic liquid crystal is 0.84 μm or more and 0.88 μm or less, and the azimuth angle of the transmission axis of the upper polarizing plate is −10 ° or more and 10 ° or less,
The azimuth angle of the transmission axis of the lower polarizing plate is −10 ° or more and 10 ° or less, and the azimuth angle of the slow axis of the upper phase plate is 95 ° or more,
115 ° or less, and the azimuth angle of the slow axis of the lower phase plate is 1
20 ° or more and 140 ° or less, and the upper phase plate has a wavelength of 5
Retardation at 50 nm is 470 nm or more, 5
The liquid crystal display device according to the first means is invented, in which the retardation is 30 nm or less and the retardation at the wavelength of 550 nm of the lower phase plate is 320 nm or more and 360 nm or less.

As a third means, the present inventors have
The product of the layer thickness of the driving liquid crystal layer and the birefringence of the nematic liquid crystal is 0.85 μm or more and 0.87 μm or less, and the azimuth angle of the transmission axis of the upper polarizing plate is −5 ° or more and 5 ° or less. The azimuth angle of the transmission axis of the side polarizing plate is −5 ° or more and 5 ° or less, and the azimuth angle of the slow axis of the upper phase plate is 100 ° or more, 11 ° or less.
The azimuth angle of the slow axis of the lower phase plate is 125 or less.
Is ≧ ° and ≦ 135 °, and the wavelength of the upper phase plate is 550
retardation in nm is 490 nm or more, 510
Invented is the liquid crystal display device according to the first means, wherein the retardation at the wavelength of 550 nm of the lower phase plate is 330 nm or more and 350 nm or less.

As a fourth means, the present inventors have
The inventor of the liquid crystal display device according to the first means has a substrate provided with a black matrix.

As a fifth means, the present inventors have
The liquid crystal display device according to the fourth means is invented, in which the black matrix is distributed in all the portions where the matrix electrodes do not intersect when viewed from the direction of the plane normal.

As a sixth means, the present inventors have
The liquid crystal display device according to the first means is provided with a color filter on the substrate.

As a seventh means, the present inventors have
The first in which the frame frequency of the driving means is 120 Hz or more
Invented the liquid crystal display device according to the means.

[0015]

When the thickness of the driving liquid crystal layer and the alignment treatment are not uniform, the rising characteristics of the liquid crystal layer become uneven. as a result,
This appears as variations in threshold voltage and nonuniform transmission near the threshold. In the normally closed display in which the dark display is performed on the low voltage side of the applied voltage values of two or more, the transmittance of the dark display is non-uniform. Since the human eye is sensitive to variations in the transmittance of dark display, non-uniformity of transmittance is particularly noticeable in normally closed display. On the other hand, in the case of the normally open display in which the dark display is performed on the high voltage side among the applied voltage values of two or more, the transmittance of the bright display becomes non-uniform. Since the human eye is not so sensitive to the variation in the transmittance of the bright display, the unevenness of the transmittance is not noticeable in the normally open display. Therefore, in order to obtain a uniform display in the color display STN-LCD in which the rising characteristic of the liquid crystal layer is uneven due to the unevenness of the color filter, normally open display may be performed.

Color display In STN-LCD, in addition to the conventional black and white display, color display is also performed. In order to display a good hue over each gradation display, the hue during bright display is made non-colored. In addition, the hue at the time of displaying each gradation must be uncolored. Also, the contrast ratio must be increased in order to improve the saturation of the display color.

In order to change the (applied voltage-transmittance) characteristic of STN-LCD to achieve normally open display, it is necessary to optimize the setting conditions of the phase plate and the polarizing plate. Further, it is necessary to optimize the setting conditions of the phase plate and the polarizing plate in order to make the hue in normally open display uncolored, reduce the dependency of the hue on the applied voltage, and increase the contrast ratio.

The setting condition of the polarizing plate includes the azimuth angle of the transmission axis. The setting conditions of the phase plate include the azimuth of the slow axis and the retardation at a specific wavelength. Here, the slow axis is one of the two optical principal axes in the plane of the phase plate that corresponds to the high refractive index. Further, the azimuth angle is defined as a counterclockwise direction, with the direction that divides the orientation processing direction of the upper and lower substrates into two equal to 0 ° as shown in FIG.

The product of the layer thickness of the driving liquid crystal layer and the birefringence of the twisted nematic liquid crystal is 0.80 μm or more and 0.90 μm.
The azimuth angle of the transmission axis of the upper polarizing plate is -20 ° or more and 20 ° or less, and the azimuth angle of the transmission axis of the lower polarizing plate is −20 ° or less.
20 ° or more and 20 ° or less, the azimuth angle of the slow axis of the upper phase plate is 90 ° or more and 120 ° or less, and the azimuth angle of the slow axis of the lower phase plate is 110 ° or more and 150 ° or less, The retardations of the upper phase plate and the lower phase plate at a wavelength of 550 nm are 450 nm or more, 550 nm or less, and 3 respectively.
By setting the thickness to be not less than 00 nm and not more than 380 nm, normally open display and display with high contrast ratio with no hue in bright display and each gradation display can be obtained.

Preferably, the product of the layer thickness of the driving liquid crystal layer and the birefringence of the twisted nematic liquid crystal is 0.84 μm or more and 0.88 μm or less, and the azimuth angle of the transmission axis of the upper polarizing plate is −10 ° or more, 10 or more. And azimuth of the transmission axis of the lower polarizing plate is -10 ° or more and 10 ° or less, and the azimuth of the slow axis of the upper phase plate is 95 ° or more and 115 ° or less,
Azimuth of slow axis of lower phase plate is 120 ° or more, 140 °
The retardations of the upper phase plate and the lower phase plate at a wavelength of 550 nm are 470 nm or more and 53, respectively.
By setting the thicknesses to 0 nm or less, 320 nm or more, and 360 nm or less, normally open display, and display of high contrast ratio with no hue in bright display and each gradation display can be obtained.

More preferably, the product of the layer thickness of the driving liquid crystal layer and the birefringence of the twisted nematic liquid crystal is 0.85 μm.
m or more and 0.87 μm or less, the azimuth angle of the transmission axis of the upper polarizing plate is −5 ° or more and 5 ° or less, and the azimuth angle of the transmission axis of the lower polarizing plate is −5 ° or more and 5 ° or less, The azimuth angle of the slow axis of the upper phase plate is 100 ° or more and 110 ° or less, and the azimuth angle of the slow axis of the lower phase plate is 125 ° or more and 135 ° or less. Retardation at a wavelength of 550 nm is 490 nm or more, 510
By setting the thickness to be not more than nm, not less than 330 nm and not more than 350 nm, normally open display and display of high contrast ratio with no hue in bright display and each gradation display can be obtained.

In the normally open display, the non-electrode portion has a transmittance similar to that of the bright display, so that light leakage from the non-electrode portion becomes a problem. By providing the black matrix so as to cover the non-electrode portion, light leakage from the non-electrode portion can be suppressed, and a display with a high contrast ratio can be obtained even when a plurality of pixels are simultaneously observed.

The material of the black matrix may be a dye, a pigment, or a metal such as chromium or aluminum.

More preferably, by providing a black matrix so as to cover all the non-electrode parts, light leakage from the non-electrode parts can be completely suppressed, and a display with a high contrast ratio can be obtained even when observing a plurality of pixels at the same time. To be

Further, by providing the substrate with a color filter, color display is possible. The simple matrix drive used in STN-LCD is a drive system that enables large-capacity display at low cost. The switching of one pixel in the simple matrix drive is determined by the signal voltage value applied during the scanning time, but the signal voltage value applied during the scanning time is 10 times or more that in the non-scanning. When the response of the liquid crystal layer is sufficiently slow, its alignment state cannot follow the time change of the applied voltage, and is therefore determined by the effective value of the applied voltage. On the other hand, when the response of the liquid crystal layer is sufficiently fast, the orientation state of the liquid crystal layer follows the time change of the applied voltage (frame response), and the orientation state of the liquid crystal layer is not determined by the effective value of the applied voltage. Even if the effective value is equal to or higher than the threshold voltage, the rising state of the liquid crystal cannot be maintained for one frame time (time between scanning pulses). Therefore, the contrast ratio is lowered. In normally open display, since dark display is performed on the high voltage side, the increase in transmittance of dark display due to frame response is large, and the contrast ratio is likely to decrease.

A response time of about 300 ms is required for displaying a mouse, but in normally open display, the contrast ratio is greatly reduced by the frame response even when the response time is 300 ms.

In order to prevent this, one frame time may be shortened and the next signal voltage may be applied while the liquid crystal layer maintains the rising state. In order to quantify the effect of frame response on color display, the following evaluation parameters are introduced.

Color displaying 512 colors using 8 gradations
STN-LCD is assumed. Since B has the lowest transmittance among the three colors R, G, and B, the transmittance T (blue) of B displayed in the second gradation counted from the lower transmittance of the 8 gradations and the black The ratio T (blue) / T (black) of the display transmittance T (black) is used as an evaluation parameter. FIG. 3 shows the relationship between the frame frequency (reciprocal of one frame time) and T (blue) / T (black) measured at a bias ratio in a practical range. The white circles and black circles in FIG. 3 have bias ratios of 13: 1 and 10: 1, respectively.

The contrast ratio in FIG. 3 is obtained from the transmitted light in the area of about 10 pixels of the color STN-LCD equipped with a black matrix. The liquid crystal display element used for the measurement has 240 scanning electrodes, and the contrast ratio when it is driven by a rectangular wave of 1 kHz is 40: 1. T (bl
If ue) / T (black) is 2: 1 or more, B displayed in the second gradation and black display can be clearly distinguished. 120 Hz or more for a bias ratio of 10 and 130 Hz for a bias ratio of 13.
As a result, T (blue) / T (black) of 2: 1 or more was obtained.

Therefore, when the response time is about 300 ms, a practically sufficient color display can be obtained if the frame frequency is 120 Hz or higher.

[0031]

EXAMPLES Specific examples of the present invention are shown below.

Example 1 FIG. 1 shows the structure of the liquid crystal display device of the present invention. The upper and lower substrates 12, 22 are XY electrodes 14,
24 and the alignment films 11 and 21, and the liquid crystal layer 10 is sandwiched therebetween. The XY electrodes 14 and 24 on the upper and lower substrates are connected to the drive circuits 15 and 25. An upper phase plate 19, a lower phase plate 29, an upper polarization plate 13, and a lower polarization plate 23 are placed outside the upper and lower substrates. Below the lower substrate, there are a light source 31, a light guide plate 32, and a reflector 33.

The upper and lower substrates 12 and 22 are made of glass,
The XY electrodes 14 and 24 are made of ITO. Alignment films 11 and 2
Reference numeral 1 is made of a polyimide-based polymer, and is oriented by a rubbing method. The condition of the orientation treatment is the cutting depth 0.4 mm
The rotation speed was 1000 rpm and the feed speed was 33 m / s, and the pretilt angle was 4 °. The twist angle was 240 °. The liquid crystal layer 10 is composed of a nematic liquid crystal and a chiral agent, has a layer thickness d of 6.2 μm, and the liquid crystal material is a mixture of HR2038, HR2047 made by Roddick and S811 made by Merck. 75.59
%, 23.55%, 0.86%, and Δn is 0.13.
8, Δnd is 0.855 μm. Sekisui Fine Chemical's spherical polymer beads were dispersed between the substrates to make the liquid crystal layer thickness uniform. The polarizing plate is G1220DU manufactured by Nitto Denko, and the phase plate is also NRF (made of polycarbonate) manufactured by Nitto Denko.

The azimuth angle of the transmission axis of the lower polarizing plate is −5 °, the transmission axis angle of the upper polarizing plate is 5 °, the slow axis angle of the lower phase plate is 125 °, and Δnd at a wavelength of 550 nm is 0.32.
μm, slow layer axis angle of upper phase plate 100 °, wavelength 550
Δnd in nm was 0.51 μm.

The display characteristics of the liquid crystal display element section (the liquid crystal display device excluding the drive circuit) of the liquid crystal display device manufactured as described above were measured. The measurement region was a region where no beads were present in one pixel, and a rectangular wave of 1 kHz was used. The applied voltages for bright display and dark display were 2.20 V and 2.35 V, respectively, and normally open display was obtained in which bright display was performed on the low voltage side. The contrast ratio was 96: 1, and the transmittances of bright display and dark display were 25% and 0.26%, respectively.

Next, when a display state was observed by connecting to a driving circuit, the bright display, the dark display, and each gradation display were uniform over the entire surface, and were observed from an oblique direction with respect to the direction normal to the substrate plane. Even so, the brightness of the bright display was not significantly reduced, and neither the bright display nor the dark display was inverted.

As described above, a normally open display was obtained under the above-mentioned phase plate and polarizing plate conditions, and a liquid crystal display device excellent in uniformity and viewing angle characteristics was obtained.

Example 2 In the liquid crystal display device of Example 1, the azimuth angle of the transmission axis of the lower polarizing plate is 0 °, the transmission axis angle of the upper polarizing plate is 0 °, and the slow axis of the lower phase plate is Angle 130
, Δnd at a wavelength of 550 nm was 0.36 μm, the slow layer axis angle of the upper phase plate was 105 °, and Δnd at a wavelength of 550 nm was 0.55 μm.

The display characteristics of the liquid crystal display element section (the liquid crystal display device excluding the drive circuit) of the liquid crystal display device manufactured as described above were measured. The measurement region was a region where no beads were present in one pixel, and a rectangular wave of 1 kHz was used. The applied voltages for the bright display and the dark display were 2.19 V and 2.34 V, respectively, and a normally open display in which the bright display was performed on the low voltage side was obtained. The contrast ratio is 106: 1, bright display,
The transmittances of dark display were 25% and 0.24%, respectively.

Next, when a display state was observed by connecting to a driving circuit, it was observed that the bright display, the dark display, and each gradation display were uniform over the entire surface, and were observed from an oblique direction with respect to the normal direction to the substrate plane. Even so, the brightness of the bright display was not significantly reduced, and neither the bright display nor the dark display was inverted.

As described above, normally open display was obtained under the above-mentioned conditions of the phase plate and the polarizing plate, and a liquid crystal display device excellent in uniformity and viewing angle characteristics was obtained.

(Example 3) In the liquid crystal display device of Example 1, the azimuth angle of the transmission axis of the lower polarizing plate is 0 °, the transmission axis angle of the upper polarizing plate is 0 °, and the retardation layer of the lower phase plate is Axis angle is 1
Δnd at 30 °, wavelength 550 nm is 0.34 μm,
The slow layer axis angle of the upper phase plate was 105 °, and Δnd at a wavelength of 550 nm was 0.50 μm.

The display characteristics of the liquid crystal display element section (the liquid crystal display device excluding the drive circuit) of the liquid crystal display device manufactured as described above were measured. The measurement region was a region where no beads were present in one pixel, and a rectangular wave of 1 kHz was used. The applied voltages for bright display and dark display were 2.21 V and 2.36 V, respectively, and normally open display was obtained in which bright display was performed on the low voltage side. The contrast ratio is 186: 1, bright display,
The transmittance of dark display was 24% and 0.13%, respectively.

Next, when the display state was observed by connecting to a driving circuit, it was observed that the bright display, the dark display, and each gradation display were uniform over the entire surface, and were observed from an oblique direction with respect to the normal direction to the substrate plane. Even so, the brightness of the bright display was not significantly reduced, and neither the bright display nor the dark display was inverted.

As described above, normally open display was obtained by the above-mentioned conditions of the phase plate and the polarizing plate, and a liquid crystal display device excellent in uniformity and viewing angle characteristics was obtained.

(Embodiment 4) In the liquid crystal display device of Embodiment 1, the substrate is replaced with one having a black matrix. The black matrix is made of pigment and is distributed so as to cover all non-electrode portions where a pair of matrix electrodes do not intersect. A black matrix having a layer thickness of about 1 μm is formed on the substrate by a pigment dispersion method, and a flattening film is formed thereon.
The unevenness due to the black matrix is reduced. The XY electrode was formed on the flattening film.

Display characteristics were measured by connecting to a driving circuit.
Frame frequency of drive circuit is 60Hz, bias ratio is 1
It was set to 3: 1. The measurement area was about 10 pixels. The contrast ratio was 10: 1, and the transmittances of bright display and dark display were 24% and 2.4%, respectively. As a result of observing the display state, bright display, dark display, and each gradation display are uniform over the entire surface, and there is little decrease in the brightness of bright display even when observed from an oblique direction with respect to the normal direction of the substrate plane. Moreover, neither the bright display nor the dark display was reversed.

As described above, a normally open display liquid crystal display device having excellent uniformity and viewing angle characteristics was obtained.

(Example 5) In the liquid crystal display device of Example 4, the material of the black matrix was chromium.

Display characteristics were measured by connecting to a driving circuit.
Frame frequency of drive circuit is 60Hz, bias ratio is 1
It was set to 3: 1. The measurement area was about 10 pixels. The contrast ratio was 11: 1, and the transmittances of bright display and dark display were 24% and 2.2%, respectively. As a result of observing the display state, bright display, dark display, and each gradation display are uniform over the entire surface, and there is little decrease in the brightness of bright display even when observed from an oblique direction with respect to the normal direction of the substrate plane. Moreover, neither the bright display nor the dark display was reversed.

As described above, the use of chromium as the black matrix improves the contrast ratio of the normally open liquid crystal display device.

(Embodiment 6) In the liquid crystal display device of Embodiment 1, a substrate provided with a black matrix made of chromium was used.

Display characteristics were measured by connecting to a driving circuit.
The frame frequency of the drive circuit was 150 Hz and the bias ratio was 13: 1. The measurement area was about 10 pixels. The contrast ratio was 21: 1, and the transmittances of bright display and dark display were 24% and 1.1%, respectively. As a result of observing the display state, bright display, dark display, and each gradation display are uniform over the entire surface, and there is little decrease in the brightness of bright display even when observed from an oblique direction with respect to the normal direction of the substrate plane. Moreover, neither the bright display nor the dark display was reversed.

As described above, by using the black matrix made of chrome, the light leakage from the non-electrode part is shielded, and by setting the frame frequency to 150 Hz, the frame response is suppressed and the contrast ratio is practically sufficient. It improved to a certain value.

(Embodiment 7) In the liquid crystal display device of Embodiment 2, a substrate provided with a black matrix made of chromium was used.

Display characteristics were measured by connecting to a drive circuit.
The frame frequency of the drive circuit was 150 Hz and the bias ratio was 13: 1. The measurement area was about 10 pixels. The contrast ratio was 24: 1, and the transmittances of bright display and dark display were 24% and 1.1%, respectively. As a result of observing the display state, bright display, dark display, and each gradation display are uniform over the entire surface, and there is little decrease in the brightness of bright display even when observed from an oblique direction with respect to the normal direction of the substrate plane. Moreover, neither the bright display nor the dark display was reversed.

As described above, by using the black matrix made of chrome, the light leakage from the non-electrode part is shielded, and by setting the frame frequency to 150 Hz, the frame response is suppressed and the contrast ratio is practically sufficient. It improved to a certain value.

(Embodiment 8) In the liquid crystal display device of Embodiment 3, a counter substrate provided with a black matrix made of chromium was used.

Display characteristics were measured by connecting to a driving circuit.
The frame frequency of the drive circuit was 150 Hz and the bias ratio was 13: 1. The measurement area was about 10 pixels. The contrast ratio was 30: 1, and the transmittances of bright display and dark display were 24% and 0.8%, respectively. As a result of observing the display state, bright display, dark display, and each gradation display are uniform over the entire surface, and there is little decrease in the brightness of bright display even when observed from an oblique direction with respect to the normal direction of the substrate plane. Moreover, neither the bright display nor the dark display was reversed.

As described above, by using the black matrix made of chromium, the light leakage from the non-electrode portion is shielded, and the frame frequency is set to 150 Hz, so that the frame response is suppressed and the contrast ratio is practically sufficient. It improved to a certain value.

(Embodiment 9) In the liquid crystal display device of Embodiment 1, a substrate provided with a color filter and a black matrix made of chromium was used. The color filter is manufactured by the pigment dispersion method and corresponds to the display colors of red, blue and green, and the average liquid crystal layer thickness of the display pixel portion of each color is 6.25 μm and 6.25 μm for red, blue and green, respectively. 30 μm and 6.20 μm.

Display characteristics were measured by connecting to a driving circuit.
The frame frequency of the drive circuit was 150 Hz and the bias ratio was 13: 1. The measurement area was about 10 pixels. The contrast ratio was 22: 1, and the transmittances of bright display and dark display were 5.1% and 0.23%, respectively. When the display state was observed, bright display and each color were uniform over the entire surface, and even though there was a difference of about 0.1 μm in the liquid crystal layer thickness of the display pixel portion for each color, the dark display was over the entire surface. It was uniform. Further, even when observed from an oblique direction with respect to the normal to the substrate plane, the brightness of the bright display was not significantly reduced, and the bright display and the dark display were not inverted.

As described above, by using the black matrix made of chromium, light leakage from the non-electrode portion is shielded, and by setting the frame frequency to 150 Hz, the frame response is suppressed and the normally open display is realized. As a result, a uniform display was obtained despite the difference in the liquid crystal layer thickness of the display pixel portion of each color.

(Embodiment 10) In the liquid crystal display device of Embodiment 2, a substrate provided with a color filter and a black matrix made of chromium was used. The color filter is manufactured by the pigment dispersion method, and corresponds to the display colors of red, blue, and green, and the average liquid crystal layer thickness of the display pixel portion of each color is red, blue,
6.25μm, 6.30μm, 6.20μm in green respectively
Is.

Display characteristics were measured by connecting to a driving circuit.
The frame frequency of the drive circuit was 150 Hz and the bias ratio was 13: 1. The measurement area was about 10 pixels. The contrast ratio was 26: 1, and the transmittances of bright display and dark display were 5.2% and 0.20%, respectively. When the display state was observed, bright display and each color were uniform over the entire surface, and even though there was a difference of about 0.1 μm in the liquid crystal layer thickness of the display pixel portion for each color, the dark display was over the entire surface. It was uniform. Further, even when observed from an oblique direction with respect to the normal to the substrate plane, the brightness of the bright display was not significantly reduced, and the bright display and the dark display were not inverted.

As described above, by using the black matrix made of chromium, light leakage from the non-electrode portion is shielded, and by setting the frame frequency to 150 Hz, the frame response is suppressed and the normally open display is realized. As a result, a uniform display was obtained despite the difference in the liquid crystal layer thickness of the display pixel portion of each color.

(Embodiment 11) In the liquid crystal display device of Embodiment 3, a substrate provided with a color filter and a black matrix made of chromium was used. The color filter is manufactured by the pigment dispersion method, and corresponds to the display colors of red, blue, and green, and the average liquid crystal layer thickness of the display pixel portion of each color is red, blue,
6.25μm, 6.30μm, 6.20μm in green respectively
Is.

Display characteristics were measured by connecting to a driving circuit.
The frame frequency of the drive circuit was 150 Hz and the bias ratio was 13: 1. The measurement area was about 10 pixels. The contrast ratio was 30: 1, and the transmittances of bright display and dark display were 5.1% and 0.17%, respectively. When the display state was observed, bright display and each color were uniform over the entire surface, and even though there was a difference of about 0.1 μm in the liquid crystal layer thickness of the display pixel portion for each color, the dark display was over the entire surface. It was uniform. Further, even when observed from an oblique direction with respect to the normal to the substrate plane, the brightness of the bright display was not significantly reduced, and the bright display and the dark display were not inverted.

As described above, by using the black matrix made of chromium, light leakage from the non-electrode portion is shielded, and by setting the frame frequency to 150 Hz, the frame response is suppressed and the normally open display is realized. As a result, a uniform display was obtained despite the difference in the liquid crystal layer thickness of the display pixel portion of each color.

(Embodiment 12) A liquid crystal display device of Embodiment 11 is used in which a substrate is provided with a color filter and a black matrix made of chromium. The color filter is manufactured by the pigment dispersion method and corresponds to the display colors of red, blue and green, and the average liquid crystal layer thickness of the display pixel portion of each color is red,
6.25μm, 6.30μm, 6.20 for blue and green respectively
μm.

Display characteristics were measured by connecting to a driving circuit.
The frame frequency of the drive circuit was 150 Hz and the bias ratio was 10: 1. The measurement area was about 10 pixels. The contrast ratio was 34: 1, and the transmittances of bright display and dark display were 5.1% and 0.15%, respectively. T (blue) / T
(black) was 2.5, and each color was clearly distinguishable. Fig. 4 shows the applied voltage dependency of the display color between bright display and dark display evaluated on the chromaticity coordinate system. The change in display color between the bright display and the dark display is small and it is a cold color system. When combined with a warm color backlight, an uncolored white display was obtained over each gradation. When the display state was observed, bright display and each color were uniform over the entire surface, and even though there was a difference of about 0.1 μm in the liquid crystal layer thickness of the display pixel portion for each color, the dark display was over the entire surface. It was uniform. Further, even when observed from an oblique direction with respect to the normal to the substrate plane, the brightness of the bright display was not significantly reduced, and the bright display and the dark display were not inverted.

As described above, by using the black matrix made of chromium, light leakage from the non-electrode portion is shielded, the frame frequency is 150 Hz, and the bias ratio is 1.
By setting the value to 0, the frame response was suppressed, and by setting the normally open display, a uniform display was obtained despite the difference in the liquid crystal layer thickness in the display pixel portion of each color. Note that FIG. 5 shows a state in which the liquid crystal display device of the present invention is mounted on a notebook personal computer. 51 is a display unit, 5
Reference numeral 2 is a pointer operation unit, 53 is a keyboard unit, 54 is a disk drive unit, and 55 is an applied voltage adjusting unit.

(Comparative Example 1) In the liquid crystal display device of Example 11, the condition of the phase plate and the polarizing plate was changed, and normally open display was performed in which dark display was performed on the low voltage side of the applied voltages of two or more values. .

The phase plate was not placed on the lower side of the counter substrate but was placed only on the upper side. Set the azimuth of the transmission axis of the lower polarizing plate to 75
°, the transmission axis angle of the upper polarizer is 90 °, the slow axis angle of the lower phase plate is 35 °, Δnd at the wavelength of 550 nm is 0.38 μm, the slow axis angle of the upper phase plate is 65 °, and the wavelength at 550 nm. Δnd was 0.38 μm.

The display characteristics of the liquid crystal display element section (the liquid crystal display device excluding the drive circuit) of the liquid crystal display device manufactured as described above were measured. The measurement region was a region where no beads were present in one pixel, and a rectangular wave of 1 kHz was used. The applied voltages for the dark display and the bright display were 2.19 V and 2.34 V, respectively, and a normally closed display in which the dark display was performed on the low voltage side was obtained. The contrast ratio is 119: 1, bright display,
The transmittances of dark display were 25% and 0.21%, respectively.

Display characteristics were measured by connecting to a driving circuit.
Frame frequency of drive circuit is 60Hz, bias ratio is 1
It was set to 3: 1. The measurement area was about 10 pixels. The contrast ratio was 36: 1, and the transmittances of bright display and dark display were 5.1% and 0.14%, respectively. When bright display and each color were displayed on the entire surface and the display state was observed, unevenness was noticeable. In particular, when the dark display was displayed on the entire surface, display unevenness was noticeable. Further, when observed from an oblique direction with respect to the normal to the substrate plane, the brightness of the bright display was rapidly reduced, and the bright display and the dark display were inverted.

As described above, although the normally closed display can obtain the contrast ratio, the display uniformity is poor, and particularly in the case of the dark display, the variation in the rising characteristics of the liquid crystal layer due to the unevenness of the color filter becomes apparent. Uniformity was significantly deteriorated. In addition, the viewing angle characteristics were poor, and when observed from an oblique direction, the bright display and the dark display were reversed.

Comparative Example 2 In the liquid crystal display device of Comparative Example 1, the frame frequency of the drive circuit was 160 Hz and the bias ratio was 10: 1. The display characteristics were measured with a measurement area of about 10 pixels. The contrast ratio is 42: 1,
Bright display and dark display have transmittances of 5.0% and 0.12%, respectively.
Met. When bright display and each color were displayed on the entire surface and the display state was observed, unevenness was noticeable. In particular, when the dark display was displayed on the entire surface, display unevenness was noticeable. Further, when observed from an oblique direction with respect to the normal to the substrate plane, the brightness of the bright display was rapidly reduced, and the bright display and the dark display were inverted.

As described above, in normally closed display, even if the frame frequency and bias ratio of the drive circuit are changed, the display uniformity and viewing angle characteristics are not improved.

[0080]

According to the present invention, the STN-L color display and black-and-white display with high contrast ratio and excellent uniformity and low cost are provided.
You get a CD.

[Brief description of drawings]

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

FIG. 2 is a definition of azimuth in the present invention.

FIG. 3 shows frame frequency dependence of T (blue) / T (black).

FIG. 4 is a change in display color of white display between bright display and dark display of the liquid crystal display device of the present invention.

FIG. 5 shows a state in which the liquid crystal display device of the present invention is mounted on a notebook personal computer.

[Explanation of symbols]

10 ... Liquid crystal layer, 11 ... Upper alignment film, 12 ... Upper substrate, 1
3 ... Upper polarizing plate, 14 ... Upper XY electrode, 15 ... Upper driving circuit, 19 ... Upper phase plate, 21 ... Lower alignment film, 22 ... Lower substrate, 23 ... Lower polarizing plate, 24 ... Lower XY electrode , 25
... Lower drive circuit, 29 ... Lower phase plate, 31 ... Light source, 32
... light guide plate, 33 ... reflector, 51 ... display section, 52 ... pointer operating section, 53 ... keyboard section, 54 ... disk drive section, 55 ... applied voltage adjusting section.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junichi Shiro, 7-1, 1-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Yuka Utsumi 7-chome, Omika-cho, Hitachi-shi, Ibaraki No. 1 Incorporated company Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Naoki Kikuchi 3300 Hayano, Mobara-shi, Chiba Hitachi Ltd. Electronic Device Division (72) Inventor Yoshiaki Nakamura 3681 Hayano, Mobara-shi, Chiba Hitachi Device Engineering Within the corporation

Claims (7)

[Claims] 1. A pair of substrates having electrodes, a driving liquid crystal layer made of nematic liquid crystal, an upper polarizing plate and a lower polarizing plate disposed above and below the substrate, the upper polarizing plate and the substrate. And a lower phase plate disposed between the lower polarizing plate and the substrate, and driving means for applying a voltage of two or more values, and the driving liquid crystal layer is A liquid crystal display device having a twist angle of 200 ° or more and the substrate sandwiching the driving liquid crystal layer, wherein the product of the layer thickness of the driving liquid crystal layer and the birefringence of the nematic liquid crystal is 0. 80 μm or more and 0.90 μm or less, and the azimuth angle of the transmission axis of the upper polarizing plate is −20 ° or more and 20 °.
And the azimuth angle of the transmission axis of the lower polarizing plate is −20 °
Azimuth angle of the slow axis of the upper phase plate is 90 ° or more and 120 ° or less.
And the azimuth angle of the slow axis of the lower phase plate is 110 °
The liquid crystal display device is characterized in that the retardation at the wavelength of 550 nm of the upper phase plate is 450 nm or more and 550 nm or less, and the retardation of the lower phase plate at the wavelength of 550 nm is 300 nm or more and 380 nm or less. . 2. The product of the layer thickness of the driving liquid crystal layer and the birefringence of the nematic liquid crystal is 0.84 μm or more and 0.88 μm or less, and the azimuth angle of the transmission axis of the upper polarizing plate is −10 ° or more and 10 ° or less. The azimuth angle of the transmission axis of the lower polarizing plate is −10 ° or more and 10 ° or less, and the azimuth angle of the slow axis of the upper phase plate is 95 ° or more and 115 ° or less, and the lower phase plate is The azimuth of the slow axis is 120 ° or more and 140 ° or less, the retardation of the upper phase plate at a wavelength of 550 nm is 470 nm or more and 530 nm or less, and the retardation of the lower phase plate at a wavelength of 550 nm is 320 nm or more and 360 nm or less. The liquid crystal display device according to claim 1, wherein: 3. The product of the thickness of the driving liquid crystal layer and the birefringence of the nematic liquid crystal is 0.85 μm or more and 0.87 μm or less, and the azimuth angle of the transmission axis of the upper polarizing plate is −5 ° or more and 5 ° or less. And the azimuth angle of the transmission axis of the lower polarizing plate is -5 ° or more, 5 °
The azimuth angle of the slow axis of the upper phase plate is 100 ° or more and 110 ° or less.
The azimuth angle of the slow axis of the lower phase plate is 125 ° or more and 135 ° or less, the retardation of the upper phase plate at a wavelength of 550 nm is 490 nm or more and 510 nm or less, and the retardation of the lower phase plate at a wavelength of 550 nm is Is 330 nm or more and 350 nm or less, The liquid crystal display device according to claim 1. 4. The liquid crystal display device according to claim 1, wherein the substrate is provided with a black matrix. 5. The liquid crystal display device according to claim 4, wherein the black matrix is distributed in all the portions where the matrix electrodes do not intersect when viewed from the plane normal direction. 6. The liquid crystal display device according to claim 1, wherein the substrate is provided with a color filter. 7. The liquid crystal display device according to claim 1, wherein the frame frequency of the driving means is 120 Hz or higher.