JP2000047194A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To permit a display with high contrast with respect to a display device provided with both a reflective mode and a transmission mode. SOLUTION: A reflective electrode 3 is formed on a substrate 1, a counter electrode 4 is formed on a substrate 2, and a vertical alignment liquid crystal layer 5 composed of a liquid crystal material exhibiting negative dielectric anisotropy, is held between the reflective electrode 3 and the counter electrode 4. A λ/4 plate 7 is located on a surface of the substrate 2 at the rear of the side on which the counter electrode 4 is formed and a slow axis of the λ/4 plate 7 is located being inclined 45 deg. to a direction of a long axis of liquid crystal molecules under an applied voltage to the liquid crystal layer 5. Subsequently a polarizing plate 6 is located on a surface of the λ/4 plate 7 at the rear side of the substrate 2 and a transmission axis of the polarizing plate 6 is made to coincide with the direction of the long axis of liquid crystal molecules at an applied voltage to the liquid crystal layer 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflective liquid crystal display device used for OA equipment such as a word processor or a personal computer, portable information equipment such as an electronic organizer, or a camera-integrated VTR equipped with a liquid crystal monitor. The present invention relates to a liquid crystal display device having both a reflection type and a transmission type.

[0002]

2. Description of the Related Art Unlike CRTs (CRTs) and ELs (electroluminescence), liquid crystal displays do not emit light by themselves. Therefore, a transmissive liquid crystal display device in which a backlight is installed on the back of a liquid crystal display element to illuminate it is used. ing. However, backlights typically consume 50% or more of the total power consumption of liquid crystal displays. Therefore, in portable information devices that are often used outdoors or on a regular basis, a reflector is installed instead of the backlight and ambient light is used. A reflection type liquid crystal display device which performs display only by itself has been realized.

The display modes used in the reflection type liquid crystal display device include a type using a polarizing plate such as a TN (twisted nematic) mode and an STN (super twisted nematic) mode which are widely used in a transmission type, and a polarization mode. In recent years, a phase change type guest host mode capable of realizing a bright display since no plate is used has been actively developed, and is disclosed in, for example, JP-A-4-75022 and Japanese Patent Application No. 7-228365.

[0004]

However, in the phase transition type guest-host mode, a display is performed by using light absorption of a dye in a liquid crystal layer in which liquid crystal molecules and a dye are dispersed, so that sufficient contrast cannot be obtained. The display quality is remarkably deteriorated as compared with a liquid crystal display device using a polarizing plate, such as a nematic mode or an STN (super twisted nematic) mode.

In the case of a parallel or twisted liquid crystal display device, the liquid crystal molecules near the center of the liquid crystal layer are tilted in the direction perpendicular to the substrate surface when a voltage is applied, but the liquid crystal molecules near the alignment film surface are not tilted. The birefringence of the liquid crystal layer is far from 0 because it does not become perpendicular to the substrate even when voltage is applied. In the display mode in which black display is performed when voltage is applied, sufficient black is displayed due to the birefringence of the liquid crystal layer. No sufficient contrast can be obtained.

At present, it is difficult to say that TN mode and STN mode liquid crystal display devices have sufficient display quality in terms of brightness and contrast, and further improvement in display quality such as higher brightness and higher contrast is required. ing. Also,
Reflective liquid crystal display devices have the disadvantage that when ambient light is dark, the amount of reflected light used for display is reduced and visibility is extremely reduced. There was a problem that visibility under extremely bright sunny weather was reduced.

[0007]

According to a first aspect of the present invention, there is provided one substrate having an area having a reflection function and a transmission function, and the other substrate on which a counter electrode is formed, wherein the one substrate and the other are provided. In a liquid crystal display device having a liquid crystal layer sandwiched between substrates, a first polarizing means provided on a surface of the one substrate opposite to the liquid crystal layer, and a first polarizing means provided on a surface of the other substrate opposite to the liquid crystal layer. Provided second polarizing means, a first retardation plate provided between the first polarizing means and the liquid crystal layer, and a first retardation plate provided between the second polarizing means and the liquid crystal layer. And a second retardation plate.

According to a second aspect of the present invention, when the liquid crystal molecules of the liquid crystal layer are substantially oriented in a direction perpendicular to the substrate surface, the first phase difference is hardly detected when the liquid crystal layer has little retardation. The retardation of the plate and the second retardation plate is set to a λ / 4 condition.
According to a third aspect of the present invention, when the retardation of the liquid crystal layer in the reflection region is α when the liquid crystal molecules of the liquid crystal layer are substantially oriented in a direction perpendicular to the substrate surface, the second phase difference The retardation of the plate is set to the condition of (λ / 4−α).

According to a fourth aspect of the present invention, when the liquid crystal molecules of the liquid crystal layer are substantially oriented in a direction perpendicular to the substrate surface, the retardation of the liquid crystal layer in the reflection region is α, and the liquid crystal layer in the transmission region is α. Is retardation β, the retardation of the first retardation plate is (λ / 4− (β−
α)), wherein the retardation of the second retardation plate is set to (λ / 4−α). According to a fifth aspect of the present invention, the first retardation plate and the second retardation plate are each composed of a λ / 4 plate, and the transmission axis of the first polarizing means and the first retardation plate are different from each other. 45 ° angle
And the transmission axis of the second polarizing means and the second
The angle formed with the phase difference plate is 45 °.

According to a sixth aspect of the present invention, there is provided one substrate on which a reflective electrode is formed and another substrate on which a counter electrode is formed, wherein a negative dielectric anisotropy is provided between the one substrate and the other substrate. In a liquid crystal display device in which a vertically aligned liquid crystal layer using a liquid crystal material is sandwiched, a polarizing plate provided on a surface of the other substrate opposite to the liquid crystal layer, and between the polarizing plate and the reflective electrode. The λ / 4 plate is provided, and a delay axis of the λ / 4 plate is set in a direction inclined by 45 ° with respect to a transmission axis of the polarizing plate. The invention according to claim 7 is characterized in that an optical compensation layer is provided between the reflective electrode and the polarizing plate.

The invention according to claim 8 has one substrate having a reflection region in which a reflection electrode is formed and a transmission region in which a transparent electrode is formed, and the other substrate having a counter electrode formed therein. In a liquid crystal display device in which a vertical alignment liquid crystal layer using a liquid crystal material exhibiting negative dielectric anisotropy is sandwiched between the other substrates, a second substrate provided on a surface of the one substrate opposite to the liquid crystal layer. 1 polarizer, a second polarizer provided on a surface of the other substrate opposite to the liquid crystal layer, and a first λ / provided between the first polarizer and the liquid crystal layer. 4
And a second λ / 4 plate provided between the second polarizing plate and the liquid crystal layer, and transmission axes of the first polarizing plate and the second polarizing plate are set in the same direction. And the first λ / 4
The retardation axes of the plate and the second λ / 4 plate are in the same direction and 45 ° with respect to the transmission axes of the first and second polarizers.
It is characterized by being set in an inclined direction.

According to a ninth aspect of the present invention, at least one optical compensation layer is provided between the first polarizing plate and the second polarizing plate. The invention according to claim 10 is characterized in that a chiral material is added to the liquid crystal material having the negative dielectric anisotropy. An eleventh aspect of the present invention is characterized in that the liquid crystal layer is subjected to an alignment treatment so as to have a 90 ° twist.

The operation of the present invention will be described below. According to the liquid crystal display device of the first aspect of the present invention,
In the reflection mode in which the display is performed with the reflected light in the region having the reflection function, the retardation (birefringence) of the liquid crystal layer in the viewer direction is 0 (initial alignment state in the vertical alignment mode, voltage applied state in the parallel alignment mode). Then, the linearly polarized light transmitted through the first polarizing means is transmitted through the first retardation plate and the liquid crystal layer and reflected, passes through the liquid crystal layer and the first retardation film again, and is transmitted to the first polarizing means. At the time of incidence, since there are many polarized components perpendicular to the transmission axis of the first polarizing means, dark display is possible, and
If retardation occurs in the direction of the observer, the linearly polarized light transmitted through the first polarizing means passes through the first retardation plate and the liquid crystal layer and is reflected and passes again through the liquid crystal layer and the first retardation plate. When the light enters the first polarizing means, the light has a polarization component parallel to the transmission axis of the first polarizing means, so that a bright display having a gradation corresponding to each retardation is possible.

In a transmission mode in which a display is made with transmitted light in a region having a transmission function, if the retardation of the liquid crystal layer in the viewer direction is almost 0, the linearly polarized light that has passed through the second polarizing means is changed to the second light. When passing through the phase difference plate, the liquid crystal layer and the first phase difference plate and entering the first polarizing means, there are many polarized components orthogonal to the transmission axis of the first polarizing means, so that dark display is possible, When the retardation increases in the direction of the observer, the linearly polarized light that has passed through the second polarizing means passes through the second retardation plate, the liquid crystal layer, and the first retardation plate, and passes through the first polarizing means. At the time of incidence, since it has a polarization component parallel to the transmission axis of the first polarization means, a bright display having a gradation corresponding to each retardation can be performed. Therefore, when the reflection mode and the transmission mode are used together, dark display is possible at the same time, and a display with high contrast is possible even when both are used. Further, gradation display can be performed by changing the retardation value by the voltage.

According to the liquid crystal display device of the second aspect of the present invention, in a reflection mode in which display is performed by reflected light in a region having a reflection function, when birefringence due to the liquid crystal layer in the direction of an observer is almost zero, Circularly polarized light enters, is reflected by a region having a reflection function, and becomes circularly polarized light whose rotation direction is reversed.
When the light passes through the phase difference plate, the light becomes linearly polarized light orthogonal to the transmission axis of the first polarizing means. In the reflection region of the liquid crystal display device, the device functions as an optical isolator, so that dark display with little light leakage is obtained.

In a state where there is birefringence due to the liquid crystal layer in the direction of the observer, by changing the retardation, the light incident on the first polarizing means is reflected and re-enters the first polarizing means. Then, a polarized light component parallel to the transmission axis of the first polarizing means is generated and incident, so that a bright display capable of gradation display is obtained.

Next, in a transmission mode in which a display is performed using light transmitted through a region having a transmission function, circularly polarized light is incident on the liquid crystal layer when birefringence due to the liquid crystal layer is almost zero in the viewer direction, and circularly polarized light passes through the liquid crystal layer. Is stored, and passes through the first retardation plate to become linearly polarized light orthogonal to the transmission axis of the first polarizing means, thereby providing a dark display with little light leakage. When the birefringence of the liquid crystal layer is present in the direction of the observer, the retardation changes. Therefore, when light incident from the second polarizing means enters the first polarizing means, it is transmitted through the first polarizing means. Since the light is incident as a polarized light component parallel to the axis, a bright display capable of gradation display is obtained.

Therefore, even when both the reflection mode and the transmission mode are used, the state of the liquid crystal molecules at the time of dark display is the same, and at the same time, dark display without light leakage is possible, and the state of the ambient light intensity is not limited. Also, a display with high contrast is realized as a reflection type, a transmission type or a dual use type.

According to the liquid crystal display device of the third aspect of the present invention, even when the remaining retardation cannot be neglected, such as when the display mode is subjected to the parallel alignment processing or when the pretilt angle is large even in the vertical alignment processing, the reflection type liquid crystal display apparatus can be used. Display with high contrast is realized. In the reflection mode, elliptically polarized light shifted from the circularly polarized light by the remaining retardation is incident on the liquid crystal layer. The light passes through the liquid crystal layer and becomes circularly polarized light in a region having a reflection function, and is reflected and becomes circularly polarized light whose rotation direction is reversed. When the light passes through the liquid crystal layer and exits from the liquid crystal layer, the light becomes elliptically polarized light deviated from circularly polarized light. The elliptically polarized light at this time is in a state where the phase is shifted by 90 degrees from that at the time of incidence. Therefore, when the light passes through the first retardation plate, the light becomes linearly polarized light orthogonal to the transmission axis of the first polarizing means. In the reflection region of the liquid crystal display device, the device functions as an optical isolator, so that dark display with little light leakage is obtained.

Therefore, even when the remaining retardation cannot be ignored, a high-contrast display can be realized as a reflection type. When the reflective display is mainly used, for example, when the area of the reflective electrode is larger than the area of the transmissive electrode, the phase difference plate 10 shown in the embodiment may be a λ / 4 plate.

According to the liquid crystal display device of the fourth aspect of the present invention, even when the remaining retardation cannot be ignored, such as when the display mode is parallel-aligned, or when the pre-tilt angle is large even in the vertical alignment process, the reflective liquid crystal display device can be used. A display with high contrast is realized as a transmission type or a dual use type.
In the reflection mode, elliptically polarized light shifted from the circularly polarized light by the remaining retardation is incident on the liquid crystal layer. The light passes through the liquid crystal layer and becomes circularly polarized light in a region having a reflection function, and is reflected and becomes circularly polarized light whose rotation direction is reversed. When the light passes through the liquid crystal layer and exits from the liquid crystal layer, the light becomes elliptically polarized light deviated from circularly polarized light. The elliptically polarized light at this time is in a state where the phase is shifted by 90 degrees from that at the time of incidence. Therefore, when the light passes through the first retardation plate, the light becomes linearly polarized light orthogonal to the transmission axis of the first polarizing means.
In the reflection region of the liquid crystal display device, the device functions as an optical isolator, so that dark display with little light leakage is obtained.

Next, in the transmission mode in which the display is performed by the transmitted light in the region having the transmission function, when the birefringence due to the liquid crystal layer is hardly observed in the direction of the observer, the same state as the emission light in the reflection mode when emitted from the liquid crystal layer is obtained. Second so that it becomes elliptically polarized light of
Is set, and the elliptically polarized light having the phase difference enters, so that when passing through the first retardation plate, it becomes linearly polarized light orthogonal to the transmission axis of the first polarizing means and has little light leakage. The display becomes dark. Therefore, even when the remaining retardation cannot be ignored, a high-contrast display can be realized as a reflection type, a transmission type, or a dual use type.

According to the liquid crystal display device of the present invention, when the remaining retardation can be ignored,
With the simplest configuration, circularly polarized light can be incident on the liquid crystal layer.

According to the liquid crystal display device of the present invention, the birefringence of the liquid crystal layer is substantially 0 when no voltage is applied to the liquid crystal layer, and a good black level is obtained when no voltage is applied. The contrast of the display device is improved. According to the liquid crystal display device of the present invention, when the surrounding light is dark, a transmissive liquid crystal display device that performs display using a light transmitted through the transparent electrode 8 having a high transmittance using a backlight. When the ambient light is bright, it is possible to perform display as a reflective liquid crystal display device that displays by utilizing the reflected light from the reflective electrode 3 formed of a film having a relatively high light reflectance. Even when the reflection type and the reflection type are used together, a complete black display is simultaneously performed, so that a display with high contrast can be performed. The description is given below.

In general, a transflective liquid crystal display device has a display mode of normally black (hereinafter referred to as NB) and normally white (hereinafter referred to as NW) using birefringence. In the case of NW, the applied voltage to the liquid crystal layer which becomes black in response to a change in the cell gap changes, whereas in the case of NB, the voltage applied to the liquid crystal layer which becomes white in response to the change in the cell gap changes. Therefore, in the NW, since the contrast ratio changes remarkably due to a change in the cell gap, high-precision cell gap control is required. On the other hand, in the NB, the change of the contrast ratio due to the change of the cell gap hardly occurs, and the margin for the cell gap control is increased.

Further, when a defect occurs in the TFT element and the voltage is not applied to the pixel electrode, a black spot is formed, so that the defect becomes inconspicuous. Therefore, according to the present invention, since the NB transmission / reflection type display device is efficiently manufactured in terms of production technology, a display with high contrast can be easily realized under any ambient light.

According to the liquid crystal display device according to the seventh and ninth aspects of the present invention, the influence caused by the refractive index anisotropy of the liquid crystal molecules generated in the light incident direction and the viewing angle direction of the liquid crystal layer 5 is eliminated. By providing an optical compensation layer for compensating, it is possible to compensate for the refractive index anisotropy generated in the light incident direction and the viewing angle direction of the liquid crystal layer 5, and to obtain a contrast depending on the light incident direction and the viewing angle direction. Drop can be prevented.

According to the liquid crystal display device of the tenth aspect of the present invention, a chiral material is added to a vertically aligned liquid crystal layer using a liquid crystal material exhibiting negative dielectric anisotropy, and liquid crystal molecules rotate when a voltage is applied. This makes it possible to stabilize the rotation of the liquid crystal molecules when a voltage is applied. Further, when the rubbing directions of the upper and lower substrates are set in directions other than the same direction, since the trajectory of the alignment processing is not in the same direction, the streaks become less noticeable.

According to the liquid crystal display device of the present invention, when the liquid crystal display device is oriented at an angle of several degrees with respect to the substrate in order to prevent disclination at the time of applying a voltage, retardation occurs in the tilt direction of the liquid crystal molecules. Occurs, but the directions in which the liquid crystal molecules are tilted near the substrate are mutually 90 degrees near the upper and lower substrates.
Due to the angle of °, the retardation that occurs can be canceled out, and a black display with little leakage light can be obtained.

[0030]

(Embodiment 1) Embodiment 1 of the present invention will be described with reference to FIG. Al, Ta on substrate 1
The reflective electrode 3 is formed of a material having a high reflectance, such as
An opposing electrode 4 is formed, and a liquid crystal layer 5 made of a liquid crystal material having a negative dielectric anisotropy is sandwiched between the reflecting electrode 3 and the opposing electrode 4.

On the surfaces of the reflective electrode 3 and the counter electrode 4 which are in contact with the liquid crystal layer 5, vertical alignment films (not shown) are provided.
Are formed, and after applying the alignment film, at least one alignment film is subjected to an alignment treatment such as rubbing. Liquid crystal layer 5
Liquid crystal molecules have a tilt angle of about 0.1 ° to 5 ° with respect to the vertical direction of the substrate surface by an alignment treatment such as rubbing of a vertical alignment film.

Since a liquid crystal material having a negative dielectric anisotropy is used for the liquid crystal layer 5, when a voltage is applied between the reflective electrode 3 and the counter electrode 4, the liquid crystal molecules move in a direction parallel to the substrate surface. Lean toward. Here, the reflective electrode 3 is used as an electrode for applying a voltage to the liquid crystal layer 5, but may have a laminated structure of a reflective electrode and another film, for example, an Al reflective plate and an ITO transparent electrode.

As the liquid crystal material of the liquid crystal layer 5, Ne (refractive index for extraordinary light) = 1.5546, No (refractive index for normal light) = 1.4773, ΔN (Ne−No) = 0.
A liquid crystal material having a refractive index anisotropy of 0773 was used. A λ / 4 plate 7 is arranged on the surface of the substrate 2 opposite to the side on which the counter electrode 4 is formed, and the delay axis of the λ / 4 plate 7 is the long axis of the liquid crystal molecules when a voltage is applied to the liquid crystal layer 5. It is arranged so as to be inclined at 45 ° to the direction.

The λ / 4 plate 7 changes linearly polarized light into circularly polarized light and circularly polarized light into linearly polarized light. The λ / 4 plate 7 is the substrate 2
Was formed on the surface opposite to the side on which the counter electrode 4 was formed,
It may be provided between the reflective electrode 3 and the substrate 2.

The λ / 4 plate 7 can be attached to the substrate surface or integrated with the polarizing plate 6 to reduce the manufacturing cost. Next, a polarizing plate 6 is provided on the surface of the λ / 4 plate 7 opposite to the substrate 2, and the transmission axis of the polarizing plate 6 is set to the λ / 4 plate 7.
Are arranged at an angle of 45 ° with respect to the delay axis.

FIG. 7A is a plan view of the active matrix substrate of the first embodiment, and FIG. 7B is a cross-sectional view taken along the line FF of FIG. 7A. The active matrix substrate includes a gate wiring 21, a data wiring 22, a driving element 2
3, a drain electrode 24, an auxiliary capacitance electrode 25, a gate insulating film 26, an insulating substrate 27, a contact hole 28, an interlayer insulating film 29, and a reflective electrode 30.

The auxiliary capacitance electrode 25 is electrically connected to the drain electrode 24 and overlaps with the auxiliary capacitance wiring 32 via the gate insulating film 26 to form an auxiliary capacitance. The contact hole 28 is provided in the interlayer insulating film 29 for connecting the reflection 30 and the auxiliary capacitance electrode 25.

The light transmission state of the liquid crystal display device of the first embodiment will be described with reference to FIG. FIG. 13A shows a case of black display in which no voltage is applied to the liquid crystal layer.
3 (b) shows a case of white display in which a voltage is applied to the liquid crystal layer, and the reflection electrode 3 is formed in the left area in each figure.

The black display will be described with reference to FIG.
The incident light entering from the surface of the polarizing plate 6 from above in FIG. 13A becomes linearly polarized light that matches the transmission axis of the polarizing plate after passing through the polarizing plate 6 and is incident on the λ / 4 plate 7.

The λ / 4 plate 7 is disposed between the transmission axis direction of the polarizing plate 6 and λ
The 軸 plate 7 is arranged so that the delay axis direction is 45 °, and the light passing through the λ / 4 plate 7 becomes circularly polarized light. When no electric field is applied to the liquid crystal layer 5, the liquid crystal layer 5 using a liquid crystal material exhibiting a negative dielectric anisotropy has liquid crystal molecules oriented almost perpendicularly to the substrate surface, and the liquid crystal with respect to incident light. Layer 5
Has a very small refractive index anisotropy, and the phase difference caused by light passing through the liquid crystal layer 5 is almost zero.

Therefore, the circularly polarized light that has passed through the λ / 4 plate 7 passes through the liquid crystal layer 5 without breaking the circularly polarized light, and
The light is reflected by the upper reflective electrode 3. The reflected circularly polarized light passes through the liquid crystal layer 5 in the direction of the substrate 2 and is again incident on the λ / 4 plate 7 as circularly polarized light.

After passing through the λ / 4 plate 7, the circularly polarized light incident on the λ / 4 plate 7 becomes linearly polarized light in a direction orthogonal to the transmission axis direction of the polarizing plate 6, and is incident on the polarizing plate 6. . λ / 4
The linearly polarized light that has passed through the plate 7 is linearly polarized light in a direction orthogonal to the transmission axis of the polarizing plate 6, and is absorbed by the polarizing plate 6 and is not transmitted. As described above, when no voltage is applied to the liquid crystal layer 5, black display is performed.

Next, the white display will be described with reference to FIG. FIG. 3B shows a case in which a voltage is applied to the liquid crystal layer 5, which is the same as FIG. 3A until it passes through the λ / 4 plate 7, and a description thereof will be omitted.

When a voltage is applied to the liquid crystal layer 5, the liquid crystal molecules oriented vertically from the substrate surface tilt in the horizontal direction with respect to the substrate surface, and the circularly polarized light from the λ / 4 plate 7 incident on the liquid crystal layer 5 becomes
The light becomes elliptically polarized light due to the birefringence of the liquid crystal molecules, and after being reflected by the reflective electrode 3, the polarization changes further in the liquid crystal layer 5. Even after passing through the λ / 4 plate 7, linearly polarized light is orthogonal to the transmission axis of the polarizing plate 6. And the light is transmitted through the polarizing plate 6.

By adjusting the voltage applied to the liquid crystal layer at this time, the amount of light that can be transmitted through the polarizing plate 6 after being reflected can be adjusted, and gradation display can be performed. When a voltage is applied from the reflective electrode 3 and the counter electrode 4 to the liquid crystal layer 5 to change the alignment state of the liquid crystal molecules so that the phase difference of the liquid crystal layer 5 becomes a 波長 wavelength condition, the λ / 4 plate 7 After passing through the liquid crystal layer 5, the circularly polarized light passes through the liquid crystal layer 5 and becomes linearly polarized light orthogonal to the transmission axis of the polarizing plate 6 when reaching the reflective electrode 3, and then passes through the liquid crystal layer 5 again to become circularly polarized light. Later, the light passes through the λ / 4 plate 7, becomes linearly polarized light parallel to the transmission axis of the polarizing plate 6, and the reflected light transmitted through the polarizing plate 6 is maximized.

Therefore, when no voltage is applied to the liquid crystal layer 5, a black display is obtained without birefringence in the liquid crystal layer 5, and when a voltage is applied to the liquid crystal layer 5, the light transmittance varies depending on the applied voltage. The gradation display becomes possible.

FIG. 4 shows the vertical direction of the reflection type liquid crystal display device when the cell gap of the liquid crystal layer is d = 3.56 μm and the phase difference of the liquid crystal layer is dΔN = 0.2752 in the liquid crystal display device of the first embodiment. 5 shows the spectral reflectance characteristics at the time of incident vertical light reception. Here, in FIG. 4, the spectral reflection at the time of vertical incidence and vertical light reception with respect to the reflector alone is set to 100.

As shown in FIG. 4, in the dark display where no voltage is applied to the liquid crystal layer 5 and in the bright display where a voltage of 3.25 V is applied, a sufficient contrast ratio of 50 or more in the entire wavelength range from 400 nm to 700 nm is obtained. Is obtained. When the voltage applied to the liquid crystal layer 5 is 3.25 V, a reflectance of about 40% is obtained, which is almost the same as the transmittance of the polarizing plate 6 used, and has a high light use efficiency and a high reflection type. Suitable for liquid crystal display devices.

FIG. 5 shows that the cell gap of the liquid crystal layer is d = 4.5 μm and the phase difference of the liquid crystal layer is dΔN =
The spectral reflectance characteristics at the time of vertical incidence and vertical light reception of the reflection type liquid crystal display device at 0.3479 are shown. Therefore, the cell gap of the liquid crystal having the spectral reflectance characteristic shown in FIG.
In the reflection type liquid crystal display device with m, a sufficient contrast ratio of 50 or more was obtained in the entire range of wavelengths from 400 nm to 700 nm in dark display where no voltage was applied to the liquid crystal layer 5 and in bright display where a voltage of 3 V was applied. Can be When the voltage applied to the liquid crystal layer 5 is 3 V, the cell gap d = 3.
A reflectance of about 40% can be obtained as in the case of a 56 μm reflective liquid crystal display device.

FIG. 6 shows the relationship between the cell gap at a wavelength of 550 nm and the contrast ratio at the time of vertical incidence and vertical light reception of the reflection type liquid crystal display device of the first embodiment. In FIG. 6, the measurement is performed by applying a voltage in which the phase difference dΔn of the liquid crystal satisfies the 波長 wavelength condition. As shown in FIG. 6, in the reflective display device of Embodiment 1, the contrast ratio is maintained at 500 or more regardless of the cell gap of the liquid crystal layer.

Therefore, when a voltage is applied to the liquid crystal layer 5, display can be performed without lowering the contrast ratio as long as the phase difference dΔn satisfies the 波長 wavelength condition, and the cell gap d can be set arbitrarily. .

FIG. 12 shows that the delay axis of the λ / 4 plate 7 is
When the angle of 45 ° to the transmission axis is 0 °, λ /
The relationship between the angle shift of the delay axis of the four plates 7 and the contrast ratio is shown. Here, the deviation of the angle of the delay axis of the λ / 4 plate 7 is 3 °.
Within this range, a contrast ratio of 50 or more can be obtained, and a reflective liquid crystal display device having good display characteristics can be manufactured.

Accordingly, a display device having a high contrast can be obtained even when the angle between the delay axis of the λ / 4 plate 7 and the transmission axis of the polarizing plate 6 slightly deviates from the set value in laminating the polarizing plate and the λ / 4 plate. Although FIGS. 6 and 7 remove the influence of the surface reflection of the panel, the effect of the surface reflection of the panel cannot be neglected in actual use, and the contrast ratio in that case is about 20. Is a good value as the contrast of the reflective liquid crystal display device.

In the liquid crystal display device using the vertically aligned liquid crystal material used in the present embodiment, the retardation of the liquid crystal layer can be reduced to almost 0 when no voltage is applied, so that in the case of normally black display, the dark state becomes darker. Can increase the contrast.

(Embodiment 2) Embodiment 2 of the present invention will be described with reference to FIG. The same components as those in the first embodiment are denoted by the same reference numerals. A on one substrate 1
Reflective electrode 3 formed of a material having a high reflectivity such as 1 or Ta
And transparent electrode 8 formed of a material having high transmittance such as ITO
A counter electrode 4 is provided on the substrate 2, and a liquid crystal layer 5 made of a liquid crystal material having a negative dielectric anisotropy is sandwiched between the reflection electrode 3 and the transparent electrode 8 and the counter electrode 4. I have.

A vertical alignment film (not shown) is formed on each of the surfaces of the reflective electrode 3, the transparent electrode 8 and the counter electrode 4 which are in contact with the liquid crystal layer 5, and after the alignment film is applied, at least one of the alignment films is formed. An alignment treatment such as rubbing is performed on the alignment film. The liquid crystal molecules of the liquid crystal layer 5 have a tilt angle of about 0.1 ° to 5 ° with respect to the vertical direction of the substrate surface by an alignment treatment such as rubbing of the vertical alignment film.

Here, although the reflective electrode 3 is used as an electrode for applying a voltage to the liquid crystal layer, the transparent electrode 8 is extended above the reflective electrode without using the reflective electrode as an electrode, and the liquid crystal layer in the reflective region is formed. 5 may be used as an electrode for applying a voltage. As the liquid crystal material of the liquid crystal layer 5, Ne = 1.
A liquid crystal material having a refractive index anisotropy of 5546, No = 1.4773 was used.

A λ / 4 plate 7 is arranged on the surface of the substrate 2 opposite to the side on which the counter electrode 4 is formed, and the retardation axis of the λ / 4 plate 7 It is arranged so as to be inclined 45 ° with respect to the long axis direction. The surface of the substrate 1 opposite to the side where the reflective electrode 3 and the transparent electrode 8 are formed has a λ / 4
The plate 10 is arranged, and the delay axis of the λ / 4 plate 10 is set in the same direction as the delay axis of the λ / 4 plate 7.

A polarizing plate 6 is provided on a surface of the λ / 4 plate 7 opposite to the substrate 2, and a polarizing plate 9 is provided on a surface of the λ / 4 plate 10 opposite to the substrate 1. The transmission axis of the polarizing plate 9 is set to be inclined by 45 ° with respect to the delay axes of the λ / 4 plate 7 and the λ / 4 plate 10.

FIG. 8A is a plan view of an active matrix substrate according to the second embodiment of the present invention, and FIG.
(A) is a cross-sectional view taken along the line AA. The active matrix substrate includes a gate wiring 21, a data wiring 22, a driving element 23, a drain electrode 24, an auxiliary capacitance electrode 25, a gate insulating film 26, an insulating substrate 27, a contact hole 28,
It has an interlayer insulating film 29, a pixel electrode 30 for reflection and a pixel electrode 31 for transmission.

The auxiliary capacitance electrode 25 is electrically connected to the drain electrode 24 and overlaps with the gate wiring 21 via the gate insulating film 26 to form an auxiliary capacitance. The contact hole 28 is provided in the interlayer insulating film 29 to connect the transmission picture element electrode 31 and the auxiliary capacitance electrode 25.

This active matrix substrate has a reflection picture element electrode 30 and a transmission picture element electrode 31 in one picture element, and a reflection picture element for reflecting light from the outside in one picture element. The pixel electrode 30 and the transmissive picture element electrode 31 that transmits light of the backlight are formed.

The light transmission state in the liquid crystal display device according to the second embodiment will be described with reference to FIG.

FIG. 13A shows a case of a black display in which no voltage is applied to the liquid crystal layer 5, and FIG. 13B shows a case of a white display in which a voltage is applied to the liquid crystal layer 5.

In FIG. 13, the region having the reflective electrode 3 has the same structure as the reflective liquid crystal display device of the first embodiment, and when used as a reflective display device, the same principle as that of the first reflective liquid crystal display device. , And the description is omitted. The state of light in the region where the transparent electrode 8 is formed, which is the right region in FIGS. 13A and 13B, will be described. The light emitted from the lower side of FIG. 13A by a light source (not shown) is converted into linearly polarized light by the polarizing plate 9 so as to coincide with the transmission axis of the polarizing plate 9.

The λ / 4 plate 10 is composed of the λ / 4 plate 10 and the polarizing plate 9.
Are arranged so that the delay axis direction of the transmission axis direction is 45 °, and the light that has passed through the λ / 4 plate 10 becomes circularly polarized light.
When no electric field is generated in the liquid crystal layer 5, the liquid crystal layer 5 using a liquid crystal material having a negative dielectric anisotropy has liquid crystal molecules oriented almost perpendicularly to the substrate surface, and the liquid crystal with respect to the incident light. The refractive index anisotropy of the layer 5 is very small,
Is substantially zero.

Therefore, the circularly polarized light emitted from the λ / 4 plate 10 passes through the liquid crystal layer 5 without breaking the circularly polarized light, and
Incident on. The direction of the delay axis of the λ / 4 plate 10 coincides with the direction of the delay axis of the λ / 4 plate 7, and the circularly polarized light incident on the λ / 4 plate 7 is a straight line in a direction orthogonal to the transmission axis direction of the polarizing plate 9. It becomes polarized light and enters the polarizing plate 6.

The linearly polarized light emitted from the λ / 4 plate 7 is a linearly polarized light in a direction orthogonal to the transmission axis of the polarizing plate 6, and is absorbed by the polarizing plate 6 and does not transmit light. As described above, when no voltage is applied to the liquid crystal layer 5, black display is performed.

Next, the white display will be described with reference to FIG. FIG. 13B shows a case in which a voltage is applied to the liquid crystal layer. This is the same as FIG. 13A until the light passes through the λ / 4 plate 10, and a description thereof will be omitted.

When a voltage is applied to the liquid crystal layer 5, the liquid crystal molecules of the liquid crystal layer 5 oriented vertically from the substrate surface are tilted in the horizontal direction with respect to the substrate surface, and the circularly polarized light from the λ / 4 plate 10 is incident on the liquid crystal layer. Becomes elliptically polarized light due to the birefringence of the liquid crystal layer 5, and λ
Even after passing through the / 4 plate 7, the light does not become linearly polarized light orthogonal to the transmission axis of the polarizing plate 6, and light is transmitted through the polarizing plate 6.
By adjusting the voltage applied to the liquid crystal layer 5 at this time,
The polarization state of light incident on the polarizing plate 6 can be changed,
By adjusting the amount of light transmitted through the polarizing plate 6, gradation display becomes possible.

When a voltage is applied to the liquid crystal layer 5 so that the phase difference of the liquid crystal layer 5 is １ ／ wavelength condition, the circularly polarized light after passing through the λ / 4 plate 10 is converted to the cell thickness of the liquid crystal layer 5. Becomes a linearly polarized light that is orthogonal to the transmission axis of the polarizing plate 9 at half the point, and becomes a circularly polarized light when passing through the remaining liquid crystal layer 5. When the circularly polarized light emitted from the liquid crystal layer 5 passes through the λ / 4 plate 7, it becomes linearly polarized light parallel to the transmission axis of the polarizing plate 6, so that most of the light incident on the polarizing plate 6 passes through the polarizing plate 6. Therefore, the transmitted light of the polarizing plate 6 becomes maximum.

Therefore, in the second embodiment, when no voltage is applied to the liquid crystal layer 5 in both the area of the reflective electrode 3 and the area of the transparent electrode 8, the liquid crystal layer 5 has no birefringence and black display is obtained. By applying a voltage to the liquid crystal layer 5, the amount of transmitted light is adjusted, and gradation display is possible. FIG. 9 shows the spectral transmission at the time of vertical incidence and vertical light reception in the transmission region of the transmission / reflection dual-mode liquid crystal display device having the liquid crystal layer cell gap d = 3.56 μm and the liquid crystal layer phase difference dΔN = 0.2752 in Embodiment 2. The rate characteristics are shown. Here, the spectral reflectance characteristics in the region where the reflective electrode 3 is present are the same as in FIG.

In FIG. 9, the spectral transmission at the time of vertical incidence and vertical light reception with respect to air is set to 100. As shown in FIG. 9, in the black display where no voltage is applied to the liquid crystal layer 5 and in the bright display where a voltage of 5 V is applied, a sufficient contrast ratio can be obtained in the entire wavelength range from 400 nm to 700 nm. When the voltage applied to the liquid crystal layer 5 is 5 V, a reflectance of about 30% is obtained, which is about 80% of the transmittance of the polarizing plate 6 used. For this reason, this display method has high light use efficiency and is suitable for a transflective liquid crystal display device.

FIG. 10 shows a transflective liquid crystal display when the cell gap of the liquid crystal layer 5 is d = 4.5 μm and the phase difference of the liquid crystal layer 5 is dΔN = 0.3479 in the liquid crystal display device of the second embodiment. 5 shows spectral transmittance characteristics at the time of vertical incidence and vertical light reception in a transmission region of the device. The cell gap d =
As with the 3.56-μm transflective liquid crystal display device,
In black display where no voltage is applied to the liquid crystal layer 5 and in bright display where a voltage of 5 V is applied, a sufficient contrast ratio can be obtained in the entire wavelength range of 400 nm to 700 nm, and when the voltage applied to the liquid crystal layer is 5 V In this case, a transmission of about 40% is obtained.

FIG. 11 shows a wavelength 55 at the time of vertical incidence and vertical light reception in the transmission region of the transflective liquid crystal display device according to the second embodiment.
The relationship between the cell gap at 0 nm and the contrast ratio is shown. In FIG. 11, the measurement is performed by applying a voltage in which the phase difference dΔn of the liquid crystal satisfies the 波長 wavelength condition.

As described above, the contrast ratio is 800 or more when used as a transmissive liquid crystal display in the area of the transparent electrode 8 irrespective of the cell gap, and 500 or more when used as a reflective liquid crystal display in the area of the reflective electrode 3. Have maintained. Therefore, when a voltage is applied to the liquid crystal layer 5, display can be performed without lowering the contrast ratio as long as the phase difference dΔn satisfies the 波長 wavelength condition, and the cell gap d can be set arbitrarily.

FIG. 12 shows the shift of the angle of the delay axis of the λ / 4 plate 7 and the contrast ratio when the delay axis of the λ / 4 plate 7 is inclined by 45 ° with respect to the transmission axis of the polarizing plate 6 to 0 °. Show the relationship. Here, if the deviation of the angle of the delay axis of the λ / 4 plate 7 is within 3 °, the case where the λ / 4 plate 7 is used as a transmissive liquid crystal display device in the transmissive region where the transparent electrode 8 is formed, or where the reflective electrode 3 is formed When used as a reflection type liquid crystal display device in the reflection region, a contrast ratio of 50 or more is obtained in both cases, and a reflection type transmissive type liquid crystal display device having good display characteristics is obtained.

Therefore, when the ambient light is dark, it is used as a transmissive liquid crystal display device for displaying by utilizing the light transmitted through the transparent electrode 8 using a backlight, and when the ambient light is bright, the light reflectance is increased. The display can be performed as a reflection type liquid crystal display device that performs display using light reflected by the reflection electrode 3 formed of a film having a relatively high film thickness. Therefore, if the ambient light is dark on one panel, use the backlight. If the ambient light is bright, use the ambient light without using the backlight, or use both the backlight and the reflected light. It can also be used as a transflective liquid crystal display device capable of displaying images.

Therefore, when the ambient light is brighter than in the conventional transmissive liquid crystal display device, the power consumption is lower because the backlight is not used, and when the ambient light is dark, the backlight is used. It is possible to overcome the drawback that sufficient display cannot be obtained if the surrounding light is dark as in the liquid crystal display device of the type.

In the liquid crystal display device using the vertically aligned liquid crystal material used in the present embodiment, the retardation of the liquid crystal layer can be reduced to almost zero when no voltage is applied. The dark state can be made darker, and the contrast can be increased.

(Embodiment 3) Embodiment 3 of the present invention will be described with reference to the schematic sectional view of FIG. The description of the configuration common to the first and second embodiments will be omitted. In the liquid crystal display device of the third embodiment, the distance between the substrate 1 and the polarizing plate 9 is λ.
/ 4 plate 10 and optical compensator 12, substrate 2 and polarizer 6
And a λ / 4 plate 7 and an optical compensator 11 therebetween.

When no voltage is applied to the liquid crystal layer 5, the liquid crystal layer 5 using a liquid crystal material having a negative dielectric anisotropy is used.
Are oriented almost perpendicularly from the substrate surface, and there is no refractive index anisotropy due to the liquid crystal layer 5 from the front surface of the substrate. However, when used as a reflective liquid crystal display device, light is used not only in a direction perpendicular to the substrate surface but also in light from other directions for display. When light enters the liquid crystal layer 5, it is affected by the refractive index anisotropy.

Also, since the viewing angle direction is not always perpendicular to the substrate surface, as the viewing angle direction deviates from the vertical direction of the substrate surface, the liquid crystal layer 5 is affected by the refractive index anisotropy of the liquid crystal molecules, and the contrast is increased. Is reduced. Therefore,
By providing the optical compensation layers 11 and 12 for compensating for the influence of the refractive index anisotropy of the liquid crystal molecules generated in the light incident direction and the viewing angle direction of the liquid crystal layer 5, the light incident direction of the liquid crystal layer 5 is provided. And the anisotropy of the refractive index generated in the visual angle direction can be compensated, and the decrease in contrast depending on the light incident direction and the visual angle direction can be prevented.

In the case where the pretilt of the liquid crystal molecules is slightly inclined from the direction perpendicular to the surface of the substrate so that the liquid crystal molecules tilt in one direction when a voltage is applied to the vertical alignment liquid crystal layer 5, no voltage is applied to the vertical alignment liquid crystal layer 5. Even during the addition, slight refractive index anisotropy occurs in the direction perpendicular to the substrate. Therefore, by designing the optical compensation layer so as to compensate for this refractive index anisotropy, The contrast ratio viewed from the direction is further improved.

In the third embodiment, the λ / 4 plate and the optical compensation layer have been described as separate layers. However, similar effects can be obtained by forming them in the same layer. In the third embodiment, two optical compensation layers, the optical compensation layer 11 and the optical compensation layer 12, are used, but only the optical compensation layer 11 may be used.

Although the transmission / reflection type display device has been described in Embodiment 3, in the reflection type liquid crystal display device of Embodiment 1, the refractive index anisotropy of the liquid crystal molecules of the liquid crystal layer 5 is provided between the polarizing plate 6 and the reflection electrode 3. By providing an optical compensation layer so as to compensate for the property, a decrease in contrast ratio can be prevented. In the first to third embodiments, the case of white display and black display has been described. However, a color display can be performed by providing a color filter of each color at a position corresponding to a reflection area or a transmission area.

By adding a chiral material to the vertical alignment liquid crystal layer 5 using the liquid crystal material having a negative dielectric anisotropy according to the first to third embodiments, the liquid crystal molecules are swirled when a voltage is applied to apply the voltage. The rotation of the liquid crystal molecules at the time can be stabilized. At this time, the liquid crystal layer is subjected to an alignment treatment so that the liquid crystal layer is twisted by 90 °. In order to prevent disclination at the time of applying a voltage, the liquid crystal molecules are aligned at an angle of several degrees with respect to the normal direction of the substrate surface. Retardation occurs in the tilt direction, but the tilt directions of the liquid crystal molecules near the substrate are at an angle of 90 ° to each other near the upper and lower substrates, so that the generated retardation can be canceled out and leakage light can be reduced. A small black display is obtained.

Although the first to third embodiments use the vertical alignment liquid crystal having the negative dielectric anisotropy, the same display can be performed by using the parallel alignment liquid crystal. That is, when a parallel alignment liquid crystal is used instead of the vertical alignment liquid crystal, the liquid crystal molecules are arranged parallel to the substrate surface when no voltage is applied, and the liquid crystal molecules are tilted in the normal direction of the substrate surface when the voltage is applied. Thus, a liquid crystal display device which displays white when applied and black when applied with a voltage is obtained. In the case of black display using the parallel alignment liquid crystal, the remaining retardation becomes larger than in the case of the vertical alignment liquid crystal due to liquid crystal molecules near the substrate. Therefore, in order to perform a more complete black display, a phase difference plate for compensating for this may be used together.

When the retardation of α remains in the reflection mode in the liquid crystal layer in which the liquid crystal molecules are oriented substantially in the direction perpendicular to the substrate surface, instead of the λ / 4 plate 7,
A retardation plate having a retardation of (λ / 4−α) may be provided.

In the reflection mode, elliptically polarized light that is shifted from the circularly polarized light by the amount of the remaining retardation of the liquid crystal layer enters the liquid crystal layer. The light passes through the liquid crystal layer and becomes circularly polarized light in a region having a reflection function, and is reflected and becomes circularly polarized light whose rotation direction is reversed. When the light passes through the liquid crystal layer and exits from the liquid crystal layer, the light becomes elliptically polarized light deviated from circularly polarized light. The elliptically polarized light at this time is
At the time of incidence, the phase is shifted by 90 degrees. After passing through the phase difference plate, the light becomes linearly polarized light orthogonal to the transmission axis of the polarizing plate 6.

Therefore, even if the retardation remaining in the liquid crystal layer in a state where the liquid crystal molecules are oriented in the direction perpendicular to the substrate surface cannot be neglected, the contrast in the reflection mode can be obtained by arranging the retardation plate in consideration of the retardation. Display can be realized. Further, when the retardation of α in the reflection mode and the retardation of β in the transmission mode remains in the liquid crystal layer, a retardation plate having a retardation of (λ / 4−α) instead of the λ / 4 plate 7 is used. A phase difference plate having a retardation of (λ / 4− (β−α)) may be provided instead of the four plates 10.

In the transmission mode in which the display is performed using the transmitted light in the region having the transmission function, when the liquid crystal molecules are oriented in the direction perpendicular to the substrate surface, the ellipse is in the same state as the emitted light in the reflection mode when emitted from the liquid crystal layer. (Λ / 4-
A retardation plate having retardation of (β−α)) is set, and the elliptically polarized light having the retardation is set to the above (λ / 4−).
α), the light enters the retardation plate having the retardation of (α), and when passing through the retardation plate having the retardation of (λ / 4−α), the light becomes linearly polarized light orthogonal to the transmission axis of the polarizing plate 6 and light leakage occurs. And a dark display with less noise.

Therefore, even if the retardation remaining in the liquid crystal layer in a state where the liquid crystal molecules are oriented in the direction perpendicular to the substrate surface cannot be ignored, by providing a retardation plate in consideration of the retardation, the contrast in the reflection mode can be improved. Display can be realized.

[0094]

According to the first aspect of the present invention, a display device having a reflection mode and a transmission mode can display images with high contrast. Further, when the reflection mode and the transmission mode are used together, dark display is possible at the same time, and even when both are used, a display with high contrast is possible. Further, gradation display can be performed by changing the retardation value by the voltage. According to the invention of claim 2 of the present invention, when the liquid crystal molecules of the liquid crystal layer are substantially oriented in the direction perpendicular to the substrate surface, when there is almost no retardation of the liquid crystal layer, in the reflection region and the transmission region, Light passing through the liquid crystal layer and the phase difference plate and entering the first polarizing plate is:
Since the light is linearly polarized light orthogonal to the transmission axis of the polarizing plate, a dark display with less light leakage can be obtained.

According to the invention of claim 3 of the present invention, when the liquid crystal molecules of the liquid crystal layer are substantially oriented in the direction perpendicular to the substrate surface, even if the retardation of the liquid crystal layer in the reflection region remains by α. In the reflection region, light passing through the liquid crystal layer and the phase difference plate and entering the first polarizing plate becomes linearly polarized light orthogonal to the transmission axis of the polarizing plate, so that a dark display with little light leakage can be obtained.

According to the fourth aspect of the present invention, when the liquid crystal molecules of the liquid crystal layer are oriented substantially in the direction perpendicular to the substrate surface, the retardation of the liquid crystal layer in the reflection region is α, and the retardation in the transmission region is α. Even if the retardation of the liquid crystal layer remains by β, light passing through the liquid crystal layer and the retardation plate and entering the first polarizing plate in the reflection region and the transmission region is orthogonal to the transmission axis of the polarizing plate. Since the light is linearly polarized, a dark display with little light leakage can be obtained.

According to the invention of claim 5 of the present invention, even when the reflection mode and the transmission mode are used together, the state of the liquid crystal molecules at the time of dark display is the same, and at the same time dark display without light leakage becomes possible. Regardless of the state of the light intensity, a display with high contrast is realized as a reflection type, a transmission type, or a dual use type.

According to the invention of claim 6 of the present invention, little light leaks from the polarizing plate at the time of black display when no voltage is applied, and light at the time of white display at the time of voltage application and color display by the color filter. A reflective liquid crystal display device having high utilization efficiency and excellent display quality can be realized. According to the seventh aspect of the present invention, it is possible to prevent a decrease in contrast depending on a light incident direction and a viewing angle direction.

According to the invention of claim 8 of the present invention, when a backlight is used, display is performed with light transmitted through the transmissive region, and when ambient light is used, light is reflected on a pixel electrode formed by a reflective electrode. Display can be performed by light. Therefore, it is possible to realize a display device that can be used as a reflective type that does not require a backlight in a place where ambient light is sufficiently bright and as a transmissive type using a backlight in a dark place.

According to the ninth aspect of the present invention, it is possible to prevent a decrease in contrast depending on a light incident direction and a viewing angle direction. According to the tenth aspect of the present invention, it is possible to stabilize the rotation of the liquid crystal molecules when a voltage is applied,
When the rubbing directions of the upper and lower substrates are set in directions other than the same direction, since the trajectory of the alignment processing is not in the same direction, the streaks become less noticeable.

According to the eleventh aspect of the present invention, in order to prevent disclination at the time of applying a voltage, when the liquid crystal molecules are oriented at an angle of several degrees with respect to the normal direction of the substrate, retardation occurs in the direction of inclination of the liquid crystal molecules. However, since the inclined directions of the liquid crystal molecules near the substrate are at an angle of 90 ° to each other near the upper and lower substrates, the generated retardation can be canceled out and a black display with less leakage light can be obtained. .

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of a reflective liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a sectional configuration diagram of a transflective liquid crystal display device according to a second embodiment of the present invention.

FIG. 3 is a cross-sectional configuration diagram of a transflective liquid crystal display device according to a third embodiment of the present invention.

FIG. 4 is a spectral reflectance characteristic diagram of the reflective liquid crystal display device according to Embodiment 1 of the present invention at the time of vertical incidence and vertical light reception with a cell gap d of 3.56 μm.

FIG. 5 is a spectral reflectance characteristic diagram of the reflective liquid crystal display device according to the first embodiment of the present invention at the time of vertical incidence and vertical light reception with a cell gap d of 4.5 μm.

FIG. 6 is a diagram illustrating a relationship between a cell gap and a contrast ratio at a wavelength of 550 nm at the time of vertical incidence and vertical light reception of the reflective liquid crystal display device according to the first embodiment of the present invention.

FIG. 7 is a diagram showing an electrode configuration of the reflective liquid crystal display device according to the first embodiment of the present invention.

FIG. 8 is a diagram illustrating an electrode configuration of a reflective liquid crystal display device according to a second embodiment of the present invention.

FIG. 9 shows a cell gap d = in Embodiment 2 of the present invention.
FIG. 10 is a spectral reflectance characteristic diagram at the time of normal incidence and vertical light reception in the transmission region of the 3.56 μm transflective liquid crystal display device.

FIG. 10 shows a cell gap d in Embodiment 2 of the present invention.
FIG. 11 is a spectral reflectance characteristic diagram at the time of normal incidence and vertical light reception in the transmission region of the dual-use transflective liquid crystal display device of = 4.5 μm.

FIG. 11 is a diagram showing a relationship between a cell gap and a contrast ratio at a wavelength of 550 nm at the time of vertical incidence and vertical light reception in a transmission region of a transflective liquid crystal display device according to Embodiment 2 of the present invention.

FIG. 12 shows a case where the case where the delay axis of the λ / 4 plate is inclined by 45 ° with respect to the transmission axis of the polarizing plate in the transmission region of the transflective liquid crystal display device in Embodiment 2 of the present invention is set to 0 °.
FIG. 6 is a diagram illustrating a relationship between a shift in the angle of the delay axis of the λ / 4 plate and a contrast ratio.

FIG. 13 is a diagram illustrating a light transmission state in the liquid crystal display devices according to the first and second embodiments of the present invention.

[Explanation of symbols]

 1, 2 substrate 3 reflective electrode 4 counter electrode 5 liquid crystal layer (vertical alignment) 6, 9 polarizing plate 7, 10 λ / 4 plate 8 transparent electrode 11, 12 optical compensation layer

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Shogo Fujioka 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Yuko Maruyama 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside (72) Inventor Naoyuki Shimada 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Sharp Corporation (72) Inventor Yoji Yoshimura 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Sharp Corporation ( 72) Inventor Mikio Katayama 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka, Japan (72) Inventor Hiroshi Ishii 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka F-term (reference) 2H049 BA02 BA07 BB03 BC22 2H089 TA09 TA14 TA18 2H091 FA08X FA08Z FA11X FA11Z FA14Y GA02 GA06 GA13 KA02 KA05 LA17 5C094 AA03 AA06 AA16 BA03 BA47 CA 19 CA23 CA25 DA13 EA04 EA05 EA06 ED03 ED11 ED14 ED20 FA03

Claims (11)

[Claims] A first substrate having a region having a reflection function and a transmission function, and a second substrate on which a counter electrode is formed;
In a liquid crystal display device in which a liquid crystal layer is sandwiched between the one substrate and the other substrate, a first polarizing means provided on a surface of the other substrate opposite to the liquid crystal layer; Is a second polarizing means provided on the opposite surface; a first retardation plate provided between the first polarizing means and the liquid crystal layer; a second polarizing means and the liquid crystal layer And a second retardation plate provided between the liquid crystal display device and the liquid crystal display device. 2. When the liquid crystal molecules of the liquid crystal layer are substantially oriented in the direction perpendicular to the substrate surface and the liquid crystal layer has little retardation, the first retardation plate and the second 2. The liquid crystal display device according to claim 1, wherein the retardation of the retardation plate is set to a λ / 4 condition. 3. When the retardation of the liquid crystal layer in the reflection area is α when the liquid crystal molecules of the liquid crystal layer are oriented substantially in the direction perpendicular to the substrate surface, the retardation of the first retardation plate is set. The liquid crystal display device according to claim 1, wherein is set in a condition of (λ / 4-α). 4. When the retardation of the liquid crystal layer in the reflective region is α and the retardation of the liquid crystal layer in the transmissive region is β when the liquid crystal molecules of the liquid crystal layer are oriented substantially in the direction perpendicular to the substrate surface. Is that the retardation of the first retardation plate is set to (λ / 4−α) condition and the retardation of the second retardation plate is set to (λ / 4− (β−α)) condition. The liquid crystal display device according to claim 1, wherein: 5. The first and second retardation plates comprise a λ / 4 plate, and the angle between the transmission axis of the first polarizing means and the first retardation plate is 45. ° and
5. The liquid crystal display device according to claim 1, wherein an angle between a transmission axis of the second polarizing unit and the second retardation plate is 45 °. 6. 6. A liquid crystal material having one substrate on which a reflective electrode is formed and another substrate on which a counter electrode is formed, wherein a liquid crystal material having a negative dielectric anisotropy is used between the one substrate and the other substrate. In a liquid crystal display device having a vertically aligned liquid crystal layer sandwiched therebetween, a polarizing plate provided on a surface of the other substrate opposite to the liquid crystal layer, and a λ / 4 plate provided between the polarizing plate and the reflective electrode A delay axis of the λ / 4 plate is set in a direction inclined by 45 ° with respect to a transmission axis of the polarizing plate. 7. The liquid crystal display device according to claim 6, further comprising an optical compensation layer between the reflection electrode and the polarizing plate. 8. One substrate having a reflection region in which a reflection electrode is formed and a transmission region in which a transparent electrode is formed, and another substrate having a counter electrode formed thereon, and a negative electrode is provided between the one substrate and the other substrate. In a liquid crystal display device having a vertically aligned liquid crystal layer using a liquid crystal material exhibiting a dielectric anisotropy of: sandwiched, a first polarizing plate provided on a surface of the other substrate opposite to the liquid crystal layer; A second polarizing plate provided on a surface of the substrate opposite to the liquid crystal layer; a first λ / 4 plate provided between the first polarizing plate and the liquid crystal layer; And a second λ / 4 plate provided between the first polarizing plate and the liquid crystal layer, the transmission axes of the first polarizing plate and the second polarizing plate are set in the same direction, The delay axes of the λ / 4 plate and the second λ / 4 plate are in the same direction, and the transmission axes of the first polarizing plate and the second polarizing plate The liquid crystal display device characterized in that it is set in the direction inclined each 45 ° against. 9. The liquid crystal display device according to claim 8, wherein at least one optical compensation layer is provided between said first polarizing plate and said second polarizing plate. 10. The liquid crystal display device according to claim 6, wherein a chiral material is added to the liquid crystal material having the negative dielectric anisotropy. 11. The liquid crystal display device according to claim 10, wherein the liquid crystal layer is subjected to an alignment treatment so as to form a 90 ° twist.