JP3344554B2 - Reflective liquid crystal display device and pressure-sensitive input device integrated liquid crystal display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection type liquid crystal which is used in office automation (OA) equipment such as word processors and notebook personal computers, various video equipment and game equipment, and does not use a direct-view backlight. More particularly, the present invention relates to a color reflective liquid crystal display device and a reflective liquid crystal display device integrated with a pressure-sensitive input device.

[0002]

2. Description of the Related Art At present, liquid crystal display devices are frequently used as color displays having characteristics such as thinness and light weight. A particularly widely used color liquid crystal display device is a transmission type liquid crystal display device using a light source as a background, and its use is expanding in various fields.

[0003] In contrast to this transmissive liquid crystal display device, a reflective liquid crystal display device, which is another display method, does not require a backlight, so that power for a light source can be reduced.
It has features such as saving the space and weight of the backlight. That is, power consumption can be reduced as a whole of the display device, a small battery can be used, and the display device is suitable for a device intended to be lightweight and thin. Alternatively, if the devices are manufactured so as to have the same size or weight, the use of a large battery can greatly increase the operation time.

[0004] Further, from the viewpoint of the contrast characteristics of the display surface, in a CRT or the like, which is a light-emitting display device, a significant decrease in the contrast ratio can be seen outdoors in the daytime, or a transmissive type device subjected to low reflection processing. Also in the liquid crystal display device, when the ambient light such as under direct sunlight is much stronger than the display light, a significant decrease in the contrast ratio cannot be avoided. On the other hand, the reflective liquid crystal display device obtains display light proportional to the amount of ambient light, and is particularly suitable for outdoor use such as portable information terminal equipment, digital cameras, and portable video cameras.

[0005] Despite the very promising application fields as described above, the contrast ratio, the reflectance, the multi-color display, the high-definition display, and the ability to cope with moving images are insufficient. A reflective color liquid crystal display device having sufficient practicality has not been obtained.

Hereinafter, the reflection type liquid crystal display device will be described in more detail. Conventional twisted nematic (hereinafter referred to as T
The N-type) liquid crystal display device has a configuration using two polarizing plates, and is excellent in contrast ratio and viewing angle dependence characteristics, but inevitably has low reflectance. Further, since the distance between the liquid crystal modulation layer and the light reflection layer is apart by the thickness of the substrate or the like, parallax occurs due to a shift in the optical path between the time of incidence and reflection of illumination light.

[0007] In particular, in a configuration used in a normal transmissive liquid crystal display in which a color filter in which different pixels are provided for each color element is combined with a single liquid crystal modulation layer, the color element that passes through at the time of incidence and reflection is light. This is not the case when the traveling direction is inclined, and is not suitable for high-resolution, high-definition display of color. For these reasons, reflective color display using this display mode has not been put to practical use.

On the other hand, guest-host type liquid crystal devices (hereinafter abbreviated as GH) in which a dye is added to liquid crystal without using a polarizing plate or using only one polarizing plate have been developed. Therefore, there is a problem that reliability is lacking, and a high contrast ratio cannot be obtained because the dichroic ratio of the dye is low. In particular, lack of contrast significantly reduces color purity in color display using a color filter, so it is necessary to combine with a color filter having high color purity. However, there is a problem in that the advantage of high brightness of the present system due to the absence of a polarizing plate is impaired.

[0009] Against this background, a method using a single polarizing plate that can be expected to provide high resolution and high contrast display (hereinafter, referred to as a method).
A liquid crystal display element of a single polarizer type has been developed. Among them, 1/4 that can realize high contrast
Many examples in combination with a wave plate are disclosed.

As one example, a reflection type TN (45 ° twist type) liquid crystal display device using one polarizing plate and a 板 wavelength plate is disclosed in Japanese Patent Application Laid-Open No. 55-48733. I have. In this prior art, by using a liquid crystal layer twisted by 45 ° and controlling the applied electric field,
Black and white display is realized by realizing two states, that is, a state where the plane of polarization of the incident linearly polarized light is parallel to the optical axis of the quarter-wave plate and a state where the plane is twisted by 45 °. The configuration of this liquid crystal cell includes a polarizer, a 45 ° twist liquid crystal layer, a 、 wavelength plate, and a reflector from the incident light side.

Further, USP 4,701,028 (Cl
erc et al.) disclose a reflective liquid crystal display device in which one polarizing plate, a quarter-wave plate, and a vertically aligned liquid crystal cell are combined. Also, JP-A-6-337421 discloses that
A reflective liquid crystal display device combining one polarizing plate, a quarter-wave plate, and a bend vertical alignment liquid crystal cell is disclosed. Euro Display 96 (P. 464) also discloses a reflective liquid crystal display device in which one polarizing plate, a quarter-wave plate, and a vertically aligned liquid crystal cell are combined.

Also, SID96 DIGEST (P.7)
63) discloses an example in which a display mode in which a liquid crystal having a negative dielectric anisotropy and having a chiral dopant added is sandwiched between upper and lower substrates subjected to a vertical alignment process is applied to reflection projection. I have.

The display operation of the single polarizing plate system disclosed in the above-mentioned JP-A-6-337421 will be described. The polarizing plate disposed on the incident side has a function of passing only one direction of the linear components of the polarized light of the incident light and the emitted light, and absorbing the light of the other direction. The incident light that has passed through the polarizing plate is converted into circularly polarized light by an optical phase difference compensating plate such as a λ / 4 plate, enters the liquid crystal layer, passes through the vertically aligned liquid crystal layer, and reaches the reflecting plate as it is. The light arriving at the reflector is converted into the opposite circularly polarized light by the reflector, passes through the liquid crystal layer, the λ / 4 plate, and the like in the reverse order of the incidence, and becomes linearly polarized light orthogonal to the linearly polarized light at the time of incidence. , A dark state is realized.

Further, by applying a voltage, the liquid crystal layer is tilted,
When a phase difference under certain conditions is developed, the incident circularly polarized light that has passed through the polarizing plate is converted into linearly polarized light, which is then converted into linearly polarized light as it is by the reflector, and linearly polarized light parallel to the linearly polarized light at the time of incidence is obtained. Is realized.

That is, the necessary and sufficient conditions for realizing these states with respect to the light that enters and exits the liquid crystal display device perpendicularly are as follows. It is already known that the light becomes linearly polarized light of right or left circularly polarized light on the reflector in the dark state.

In a portable information device, a touch panel (pressure-sensitive input device) is an effective input means in addition to a conventionally used keyboard. In particular, in the input of a language that needs to convert the input from the keyboard, for example, Japanese, etc., with the advancement of information processing ability and the development of software, the touch panel is not merely a pointing device, but is directly input by handwriting. -It has become common to use it as an input device. In the case of such an input mode, the input device is arranged to be superposed on the front surface of the display device.

However, in the reflection type liquid crystal display device, since the reflected light is used for display, the means for low reflection processing of the touch panel must not impair the display of the reflection type liquid crystal display device provided below. JP-A-5-12782
Japanese Patent Laid-Open Publication No. 2 (1999) discloses that a low reflection process is performed by superposing a quarter-wave plate and a polarizing plate on a touch panel.

[0018]

However, in the liquid crystal display device disclosed in Japanese Patent Application Laid-Open No. 55-48733, it is necessary to provide a quarter wavelength plate between the liquid crystal layer and the reflection plate. In principle, it is difficult to form a reflective film inside the liquid crystal cell, and it is not suitable for high resolution and high definition display.

US Pat. No. 4,701,028;
-337421, EuroDisplay96
In the vertical alignment type liquid crystal display device described in (p. 464), first, the direction of vertical alignment, in particular, the tilt vertical alignment is parallel between the upper and lower substrates, and the liquid crystal falls in one direction. Second, there is a problem that the viewing angle dependence in the plane is extremely large, and secondly, there is a problem of coloring due to a large wavelength dependence of the reflectance.

In addition, the SID96 DIGEST
p. In the display mode described in 763, linearly polarized light is incident using a polarizing beam splitter without using a quarter-wave plate, and is not applied to a direct-view type. Further, | d / p | when the natural pitch of the liquid crystal is p and the cell thickness is d.
There is no mention of the detailed setting of and the optimal Δn * d (birefringence difference * liquid crystal layer thickness).

Further, even when the performance that can be used as a reflection type liquid crystal display device is realized, there is a problem that the visibility is extremely deteriorated when the touch panel is arranged.
This is because, in a transmissive liquid crystal display device and other light-emitting display devices, a decrease in visibility when a touch panel is arranged is caused by a light source (for example, a ceiling light or the like) that causes reflected light from the touch panel. It can be easily solved by removing the reflected light or changing its direction. However, in the reflection type display device, the light source generates reflected light from the touch panel and serves as a display light source of the display device.

[0022] Therefore, it is important to solve the reduction in visibility as well as to realize a reflective display device and a practical and low power consumption portable information device. JP-A-5-12
The configuration of the touch panel disclosed in Japanese Patent No.
Although the quarter-wave plate has an effect of preventing reflection by the action of the quarter-wave plate, a normal quarter-wave plate inevitably decreases at a specific wavelength in the visible region.

Further, the brightness of the display is determined by the extent to which the polarization state of the display device provided below includes the transmitted light component of the circularly polarized light obtained by the combination of the １ ／ wavelength plate and the light plate. . That is, when a display device having substantially no polarization characteristics is used in the lower part (for example, a white tailor type guest-host liquid crystal device in which a dye is mixed in a 360-degree twisted liquid crystal), the reflection efficiency is determined by the transmittance of the polarizing plate in front of the touch panel. As a result, at the maximum when the touch panel is not used, it is reduced to half.

As another example, when the lower display device uses linearly polarized light for display (for example, TN type and STN in which a polarizing plate is further disposed in the gap between the touch panel and the liquid crystal cell).
In the case of a liquid crystal display device of the same type, the efficiency is similarly reduced to a maximum of １ ／ when a touch panel is not used, and the phase difference of a 波長 wavelength plate depends on the wavelength of light. The color tone changes due to the arrangement of being sandwiched between the boards.

In any case, the brightness is insufficient, and it is not suitable as a combination with a reflection type liquid crystal display device having no means for improving the brightness of background light or the like. That is, JP-A-5-12782
No. 2, there is a need to further improve the anti-reflection function of the touch panel, and there is no disclosure of a suitable configuration for utilizing external light incident on the touch panel for the reflective liquid crystal.

The present invention has been made in order to solve the above-mentioned problem of a single-polarizer type liquid crystal display device capable of high-resolution display, and is intended to provide a color display reflective type excellent in visibility. It is an object to provide a liquid crystal display device and a reflective liquid crystal display device integrated with a pressure-sensitive input device.

[0027]

In order to achieve the above object, the inventors of the present invention have conducted intensive studies. As a result, it has been found that a single polarizing plate system capable of realizing a high-resolution display with a configuration free of parallax is possible. As a means for electrically switching between different polarization states on the reflector required for realizing a bright state and a dark state, a dark state of the liquid crystal display device is realized without applying a voltage to the liquid crystal layer. It has been found that the configuration of the polarizing plate and the optical retardation compensator as described above is necessary for achieving a good dark state without requiring high precision in the manufacturing process of the liquid crystal layer. Further, the inventors have found out the configurations of a polarizing plate and an optical retardation compensator for realizing such a polarization state, and have studied the configuration of a liquid crystal layer for realizing an optimal display using the polarizing plate and the optical retardation compensating plate.

First, in the reflective liquid crystal display device according to claim 1 of the present invention, a first substrate having light reflectivity, a transparent second substrate having a transparent electrode, and the first and second substrates are provided. A nematic liquid crystal layer having a negative dielectric anisotropy sandwiched between the substrates and a circularly polarized light incident on the liquid crystal layer.
A plurality of optical phase difference compensators disposed on the second substrate;
And a single polarizing plate , the surfaces of the first and second substrates are substantially vertically aligned, the natural pitch of the liquid crystal is p, the thickness of the liquid crystal layer is d, and the birefringence of the liquid crystal is When the rate difference is Δn, 0 <| d / p | <1 and 2
So that 00 nm ≦ Δn * d ≦ 1200 nm holds,
It is characterized in that the natural pitch of the liquid crystal, the thickness of the liquid crystal layer, and the difference in the birefringence of the liquid crystal are selected.

With this configuration, it is possible to realize a good dark display in a state where no voltage is applied and a bright display by applying a voltage. That is, the liquid crystal layer can be configured so as to be vertically aligned well when no voltage is applied and to be twisted when voltage is applied.

Preferably, in the above structure, the relationship between the natural pitch p of the liquid crystal and the liquid crystal layer thickness d is 1/6 <│d
By selecting so as to satisfy / p│ <1, good display with small wavelength dependence is realized.

Furthermore, the invention described in claim 2 of the present invention, prior Symbol plurality of optical retardation compensator plate that is disposed on the second substrate is a two substrate of the optical retardation compensator plate A first optical retardation compensator having a retardation in the normal direction set to 100 nm or more and 180 nm or less, and a retardation in the normal direction to the substrate, which is disposed on the first optical retardation compensator and 200 nm or more A second optical phase difference compensator set at 360 nm or less, and a second optical phase difference compensator
1. A reflection type liquid crystal display device comprising : a single polarizing plate disposed thereon; a transmission axis (or absorption axis) of the polarizing plate and a retardation of the first and second optical phase difference compensating plates. When the angles formed by the phase axes are θ1 and θ2, respectively, 35
The polarizing plate and the optical phase difference compensating plate are arranged so that ゜ ≦ | 2 × θ2−θ1 | ≦ 55 ° is satisfied. With this configuration, a good circle is formed on the liquid crystal layer. Polarized light can be incident.

[0032]

[0033] Here, in addition to the above configuration, as in the invention of claim 3, wherein one liquid crystal molecules on the first or second substrate is an angle not in the normal direction and 0 with respect to the substrate By configuring so as to have a uniform orientation, uniform and favorable display can be realized.

In order to further achieve the above object, the inventors of the present invention have conducted intensive studies. As a result, in order not to impair the reflectivity modulation method capable of displaying high resolution, unnecessary flat scattering and a flat mirror surface are required. Similarly, a diffusive reflector having no disturbing action (depolarization action) on polarized light is much more effective than a case where a scattering plate is arranged in front of a display device using a specular reflector having no diffusivity. Was found to be a means.

Therefore, in the reflection type liquid crystal display device according to the present invention, as described in claim 4 , the surface of the light reflecting electrode has a smooth and continuously changing uneven-shaped light reflecting film, The film functions as a voltage application electrode to the liquid crystal layer using the transparent electrode of the second substrate as a counter electrode.

On the other hand, the inventors have found that the average period of the uneven shape characterizes the diffusive reflection characteristics.
That is, in order to uniformly diffuse the incident light, the average period may be set in the same manner with respect to an arbitrary direction in the plane of the reflector, but by changing this period with respect to a specific direction in the plane, the average period can be specified. It is possible to increase the reflectance when the illumination light from the azimuth is reflected in a specific azimuth.

[0037] That is, in the reflective type liquid crystal display device of the present invention to achieve good dark state as compared to the GH mode, as claimed in claim 5, wherein the uneven shape formed on the surface of the light reflective electrode, The liquid crystal display device is characterized in that the average uneven period is different depending on the orientation in the plane of the substrate, and a brighter liquid crystal display device can be realized.

Further, by setting the bright azimuth of the diffusive reflector to this good azimuth, particularly excellent visibility can be obtained. Bright orientation of this diffusive reflector, although generally depends on the orientation of the observer and the orientation of the illumination, as better placement for various illumination conditions, as claimed in claim 6, wherein said second substrate In a reflective liquid crystal display device provided with a reflective film having a concave-convex shape having a different average concave-convex period formed thereon, an observation direction viewed by an observer includes a short direction of the concave-convex period of the reflective film and a normal line of a display surface. It is characterized in that it is set in a plane.

In the reflection type liquid crystal display device according to the first aspect, the light passing through the polarizing plate and the two optical phase difference compensating plates is substantially circularly polarized light, so that the light is closer to the reflecting plate than the two. Even if there is reflection without change in polarization state, the reflected light is absorbed by the polarizing plate at the time of emission. Therefore, reflected light from a pressure-sensitive input device (touch panel) useful as an input device for a portable device does not cause deterioration in visibility. As a liquid crystal display device to be combined with the anti-reflection touch panel as described above, a reflection type liquid crystal display device according to the present invention, in which circularly polarized light passing through the touch panel can be effectively used for display without adding a retardation plate or a polarizing plate, etc. Found that it was extremely effective as a liquid crystal display device combined with a touch panel.

That is, according to the present invention, a reflective liquid crystal display device integrated with a pressure-sensitive input device according to a seventh aspect of the present invention is the reflective type liquid crystal display device according to the first aspect, wherein the reflective liquid crystal display device has a layered gap and is provided with a push from the outside of the device. A planar pressure-sensitive element having a function of sensing pressure is sandwiched between the first optical phase difference compensating plate and the second substrate.

[0041]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing the structure of a reflection type liquid crystal display device of the present invention. The liquid crystal layer 1 is sandwiched between an incident-side substrate 4 on which a rubbing-aligned vertical alignment film 2 is formed and a reflection-side substrate 5 on which a rubbing-aligned vertical alignment film 3 is formed. These substrates 4 and 5 have
Electrodes 6 and 7 for applying a voltage to the liquid crystal layer are formed respectively.

The electrode 7 may also serve as a reflector.
Furthermore, in that case, it may have a smooth uneven shape to the extent that the polarization of the reflected light is preserved. As the smooth uneven shape, one having a different uneven period on the reflecting plate depending on the direction may be used. An active element or the like may be used as a means for applying a voltage to the electrode pair having the above configuration, and it goes without saying that the present invention is not affected by the voltage applying means.

A first optical phase difference compensating plate 8 and a second optical phase difference compensating plate 9 are disposed on the observer side of the substrate 4 of the liquid crystal display device thus configured. Are located.

Hereinafter, the operation of each optical element will be described. The liquid crystal display device of the present invention is a reflection type liquid crystal display device in which illumination light such as external light is made incident on the liquid crystal layer 1 through the polarizing plate 10 and observed from the polarizing plate 10 side where the illumination light has entered.
Only the linearly polarized light component of a specific direction in the illumination light is selectively transmitted and incident by the polarizing plate 10, and the incident linearly polarized light is changed in the polarization state by a plurality of optical phase difference compensating plates to become circularly polarized light. Optically arranged as follows.

For example, in the configuration of the liquid crystal display device as shown in FIG. 1, the incident light that has passed through the optical phase difference compensating plate 8 and the optical phase difference compensating plate 9 is converted into substantially circularly polarized light in the visible light wavelength region. I do. That is, which of the left-handed and right-handed circularly polarized light depends on the arrangement of the optical elements of one polarizing plate and two optical phase difference compensating plates. Therefore, a case will be described in which the first optical phase difference compensating plate 8 and the second optical phase difference compensating plate 9 are arranged such that the phase differences thereof are 135 nm and 270 nm, respectively, as shown in FIG. However, this is a case where observation is performed from the direction of incident light of the liquid crystal display device. FIG.
Θ1 (the angle between the transmission axis direction 12 of the polarizing plate and the slow axis direction 13 of the first optical phase difference compensator) = 75 °, θ
2 (the angle between the transmission axis direction 12 of the polarizing plate and the slow axis direction 14 of the second optical phase difference compensator) = 15 °, the light incident on the liquid crystal display device is After passing through the optical phase difference compensating plate 9 and the optical phase difference compensating plate 8, the incident light becomes substantially clockwise circularly polarized light in the visible light wavelength region.

Further, in the configuration of the liquid crystal display device having three optical phase difference compensating plates shown in FIG. 3, the first optical phase difference compensating plate 8, the second optical phase difference compensating plate 9, and the third optical phase compensating plate 9 The phase difference with the phase difference compensator 11 is 135n
The case where they are arranged to be m, 270 nm, and 270 nm will be described. The installation angle is as shown in FIG.
θ1 (the angle between the transmission axis direction 12 of the polarizing plate and the slow axis direction 13 of the first optical phase difference compensator) = 100.2 °, θ2
(The angle between the transmission axis azimuth 12 of the polarizing plate and the slow axis azimuth 14 of the second optical phase difference compensator) = 34.2 °, θ3 (the angle of the transmission axis azimuth 12 of the polarizing plate and the third optical phase difference compensator) When the liquid crystal display device is arranged such that the angle formed by the slow axis direction 15) = 6.5 °, the light incident on the liquid crystal display device is polarized, the optical phase difference compensating plate 9, the optical phase difference compensating plate 8, and the optical Phase difference compensator 1
1 and becomes circularly polarized light with a wider wavelength band than in the case of using two optical phase difference compensators.

Optical phase difference compensator 8 and optical phase difference compensator 9
And the optical retardation compensator 11 are mainly made of a stretched film made of polycarbonate.
130 nm to 1 for transmitted light in the surface normal direction of 0 nm
The optical phase difference compensator 9 and the optical phase difference compensator 11 have a phase difference controlled to 40 nm,
It has a phase difference controlled from m to 275 nm. The design of these retardation compensators can be changed together with the liquid crystal layer 1 in consideration of the characteristics of the observer from the tilt direction. For example, as a design for the optical phase difference compensators 8, 9, and 11 for transmitted light in an inclined direction while establishing the set angle of the present embodiment, at least one of the optical phase difference compensators 8, 9, and 11 is designed as follows. It is possible by changing to a biaxial optical phase difference compensator.

The incident light that has entered the liquid crystal layer changes its polarization state according to the birefringence of the liquid crystal layer arranged according to the applied voltage, and reaches the reflector. The polarization state on the reflector is realized in different states depending on the liquid crystal orientation.

First, the operation in the dark state will be described. When a chiral nematic liquid crystal is sandwiched between vertically aligned substrates, under certain conditions, liquid crystal molecules are vertically aligned without twisting. Assuming that the thickness of the liquid crystal layer is d and the natural pitch of the liquid crystal is p, theoretical analysis reveals that when d and p satisfy Expression (1), the liquid crystal exhibits vertical alignment. The pitch of the liquid crystal includes left-handed and right-handed. Here, left-handed is indicated by a minus sign and right-handed is indicated by a + sign. Therefore, d /
Since the value of p can be both positive and negative, it is represented by an absolute value as follows.

| D / p | <K3 / (2 * K2) (1) where K2 and K3 are Frank's elastic constants. Judging from the physical properties of K2 and K3 of the liquid crystal material, K3 /
Since it is known that K2 generally takes a value near 2, it is necessary to satisfy | d / p | <1 after all.

When the above expression (1) is satisfied, the liquid crystal molecules are vertically aligned, and therefore do not have birefringence for light traveling in the normal direction of the device. Therefore, when circularly polarized light enters the liquid crystal layer, the incident light reaches the reflector without any change in the polarization state in the liquid crystal layer. In the reflection plate, the light becomes circularly polarized light in the opposite direction and is shielded by the polarization plate, so that a dark state is realized. When this dark state is established in the entire visible wavelength region, black display is realized.

Further, it has been found that a liquid crystal layer that is twisted by applying a voltage is required to realize a bright state.

The present inventors have made intensive studies and found that the following conditions are required in order to realize the above-mentioned circular polarization state substantially in the visible wavelength region. That is, the optical phase difference compensator 8 is capable of giving a phase difference of only １ ／ wavelength to light of 400 nm to 700 nm which is a main visible light wavelength range, that is,
The retardation has a retardation of 100 nm to 180 nm, and the optical phase difference compensating plate 9 is capable of giving a phase difference of only 波長 wavelength to a visible light wavelength range of the same range, that is, , 2 in retardation
It has a thickness of from 00 nm to 360 nm, and in the arrangement of the polarizing plate and the optical retardation compensator shown in FIG. 2, if the condition of 35 ° ≦ | 2 × θ2−θ1 | ≦ 55 ゜ (2) is satisfied good. Within the range satisfying this condition, θ1,
It goes without saying that each value of θ2 can be changed,
The specific value is desirably determined by the combination of the wavelength dispersion of the birefringence of the two optical phase difference compensators used.

When no voltage is applied, the amount of birefringence of the vertically aligned liquid crystal layer is almost 0, and does not largely depend on the precision of producing the liquid crystal layer. Therefore, the production and production of the liquid crystal layer is easy.

Further, with the arrangement of the three optical phase difference compensating plates shown in FIG. 4, the transmission axis (or absorption axis) of the polarizing plate and the retardation of the first, second, and third optical phase difference compensating plates. Assuming that the angles formed by the axes are θ1, θ2, and θ3, respectively, two optical lenses are set when the condition of 35 ° ≦ | 2 × θ3-θ2 + θ1 | ≦ 55 is satisfied. It has been found that circularly polarized light can be obtained in a wider wavelength range than when a retardation compensator is used.

Next, the display operation will be described. The optical phase difference compensator set as in equation (2) or equation (3) turns the circularly polarized incident light into linearly polarized light on the reflector to realize a bright state. The direction of the optical field of the linearly polarized light is arbitrary within the plane of the reflector. That is, even if the visible wavelength light is linearly polarized in different directions depending on the wavelength, or if the light is all linearly polarized in the same direction, a bright bright state is similarly realized.

In particular, to realize the optical function of the liquid crystal layer such that the light incident on the liquid crystal layer, which is substantially circularly polarized in order to realize the dark state, is linearly polarized in an arbitrary direction in the visible wavelength range. is important. Further, in the present application, since a liquid crystal layer having a negative dielectric anisotropy is used, the liquid crystal molecules are aligned in parallel with the substrate with the application of a voltage. In this case, since the liquid crystal is provided with chirality as described above, it is possible to form a pretilt of several degrees instead of perfect vertical alignment.

Since the reflection type liquid crystal display device according to the present invention is switched by the above-described mechanism, in order to evaluate the optical arrangement of a certain liquid crystal display device, it is necessary to prevent the circularly polarized light from entering the liquid crystal layer. It was found that it was sufficient to evaluate the polarization state on the reflector. Therefore, the inventors have found the following evaluation function.

In analyzing the polarization state, two components perpendicular to the traveling direction of the optical electric field are described by a vector, and the propagation medium is described by a Jones matrix method in which the propagation medium is described by a 2 × 2 matrix. .

The linearly polarized light having an arbitrary vibration direction can be described by a linear combination of clockwise and counterclockwise circularly polarized light having the same amplitude. When the amplitude is different, the light generally becomes elliptically polarized light, and becomes circularly polarized light when only one of the right and left circularly polarized light components.
For this reason, the absolute values of the left and right circularly polarized light components (generally, complex numbers) of the light emitted from the liquid crystal are obtained, and if the values are equal on the left and right, a straight line, and if different, an ellipse (including a circle).

For this reason, the Jones matrix of the liquid crystal is selected to be M, and the incident (standardized amplitude) circularly polarized light is selected, for example, clockwise, and it is represented by a + suffix. Do), evaluation function (Figur
Suitable as e of Merit)

[0063]

(Equation 1)

Here, S3 is a function of a standardized Stokes parameter of light emitted by making circularly polarized light incident on the liquid crystal layer.

In the following description of the present invention, this is used as an evaluation function. Equation (4) shows that the polarized light (M
C +) is obtained by taking the inner product of the C + component and the C- component of C +), and the difference of the square (that is, the amplitude) of the absolute value of the complex number is evaluated, and when they are equal (that is, when linearly polarized light is emitted). , The second term on the right side becomes 0, and FOM = 1
Becomes Also, FOM = 0 is obtained when the second term on the right side is 1
This is the case where circularly polarized light is emitted.

Since the liquid crystal layer is vertically aligned without applying a voltage, in this case, when circularly polarized light enters, the reflection is inevitably circularly polarized light, and a good dark display is realized. On the other hand, in order to realize a bright display in a state where a voltage is applied, it is necessary to enter circularly polarized light, pass through the liquid crystal layer, convert to linearly polarized light, and emit the light. A liquid crystal layer satisfying these conditions has various conditions depending on the applied voltage, the twist angle of the liquid crystal layer, retardation, and the like.

The inventors of the present invention have conducted intensive studies and, as a result, have examined the correlation among the applied voltage, the twist angle, and the retardation, and have found optimum conditions. That is, in the space of the twist angle (horizontal axis) between the upper and lower substrates of the liquid crystal and Δn * d (retardation), the value of the FOM of Expression (4) is set to 0 to 1
FIGS. 5 to 8 show the results of plotting by dividing by 0.1 between. In the figure, the applied voltage is 2.5 V, 3.0
V, 3.5 V, and 4.0 V, the above evaluation function F
OM is shown as a result for light of 550 nm, which is the central wavelength of visible light.

In the range of 0 to 0.1 in FIGS. 5 to 8, the incident circularly polarized light becomes circularly polarized light after passing through the liquid crystal layer, and a bright display cannot be realized. On the other hand, in the range of 0.9 to 1.0 in FIGS. 5 to 8, the incident circularly polarized light becomes linearly polarized light after passing through the liquid crystal layer, indicating that a good bright state can be realized.

The applied voltages of 2.5 V, 3.0 V, 3.
It can also be seen that the optimum condition changes when the voltage is changed to 5 V or 4.0 V. This can be freely set in consideration of the driving voltage and driving method of the driver. For example, when steepness is required as in simple matrix driving, a lower voltage condition may be set. In the case of active matrix driving, the driving voltage can be adjusted so that the gradation characteristics become good.

However, FIGS. 5 to 8 are merely examples, and it has been confirmed that the optimum condition slightly shifts depending on the physical properties (dielectric anisotropy and elastic constant) of the liquid crystal material and the magnitude of the tilt angle. are doing. Therefore, it is necessary to set optimal conditions depending on the type of liquid crystal or alignment film used.

Here, similarly for the other colors other than the reference green (550 nm) color, the FOM is plotted as follows:
It has been confirmed that the plot obtained by expanding and contracting the axis of Δn * d can be plotted without changing the horizontal axis (twist angle) in FIG. In other words, in a region of a curved “peak” having a large FOM value (shown by hatching in the drawing), a region other than the green has a wavelength other than green in a region where a similarly large “peak” is obtained for light of another wavelength. This means that favorable conditions are also obtained for the light of. For this reason, when the “peak” of the FOM extends in the direction of the vertical axis of the figure, that is, where the dependency on Δn * d is small, a good white display without coloring is realized with little wavelength dependency of display. Yes, it turned out to be desirable. in this way,
The present inventors have found that good display is exhibited only when limited conditions are satisfied.

The present inventors have adapted the action of the bright state to a liquid crystal display device which can secure a sufficient lightness in a practically sufficient range, that is, a visible wavelength range, and which can be easily manufactured at a high yield. A range in which a liquid crystal composition can be developed has been found. Specifically, when the natural pitch of the liquid crystal is p and the thickness of the liquid crystal layer is d, | d / p | ≦ 1, and Δn * d of the liquid crystal layer is from 200 nm to 1200 nm. More preferably, the condition of 1/6 <| d / p | <1 is satisfied,
The retardation (Δn * d) value of the liquid crystal layer is 300 nm
From 800 nm.

In consideration of a simple matrix drive that requires steepness in the electro-optic effect, the twist angle is from 120 to 170 degrees, and the retardation (Δn * d) of the liquid crystal layer is from 500 to 1200 nm. Is optimal. These preferable conditions can be realized by a practical liquid crystal material having a Δn of the liquid crystal of about 0.07 even when the manufacturing conditions of the liquid crystal display device in which the thickness of the liquid crystal layer is set to 4.5 μm or more are used. A highly practical liquid crystal display device can be manufactured.

Hereinafter, embodiments of the present invention under the above conditions will be described, but the scope of the present invention is not limited to these embodiments. <Embodiment 1> As Embodiment 1, between upper and lower substrates,
1 shows a reflective liquid crystal display device which has been subjected to a rubbing treatment so that an angle between liquid crystal alignment treatment directions is 110 degrees. The retardation of the liquid crystal layer was set to 350 nm, and 135 n
This is an example in which one optical phase difference compensating plate of m and 270 nm is used.

The reflection type liquid crystal display device shown in FIG. 1 was manufactured by a general manufacturing process. The electrode 7 on the substrate 5 was made of aluminum and was a light reflective electrode. The electrode 7 has both functions of a reflective film and an electrode. The liquid crystal layer thickness is 4.7 μm
The rubbing alignment direction is set so that the angle between the alignment processing directions between the upper and lower substrates is 110 degrees. Use a polyimide vertical alignment film for the alignment film,
The tilt angle was formed by rubbing. Note that the tilt angle is inclined by 2 degrees from the normal direction. In this embodiment, the rubbing process was performed on both the upper and lower substrates, but it was confirmed that uniform processing was obtained only by processing one of the substrates. Further, both substrates are aligned even when no rubbing treatment is performed, but the uniformity of the alignment is poor.

The alignment film that can be used in the present invention is a film that can vertically align the liquid crystal molecules contained in the liquid crystal layer with respect to the insulating substrate, that is, a vertical alignment film. Any known vertical alignment film can be used as long as it has the above properties. For example, a material having a structure in which a long-chain alkyl group is bonded to a polyimide skeleton is mentioned.
LS-203 (manufactured by Nippon Synthetic Rubber Co., Ltd.), SE-7511L
(Manufactured by Nissan Chemical Industries, Ltd.).

The thickness of the alignment film is about 0.05 to 0.1 μm. Examples of a method for forming the alignment film include a method in which a solution in which a polymer is dissolved is applied by a spinner coating method, a dip coating method, a screen printing method, a roll printing method, or the like, and dried. Alternatively, a method in which a polymer precursor solution is applied by the same method as described above and cured under predetermined curing conditions (heating, light irradiation, etc.) can be used. Further, it can be formed by the Langmuir-Blodgett method.

The liquid crystal usable for the liquid crystal layer is not particularly limited as long as it is a nematic liquid crystal having negative dielectric anisotropy (n type). For example, ZLI-2857, ZLI-47
88, ZLI-4788-000 (manufactured by Merck Japan) and the like. The thickness of the liquid crystal layer is
3-12 μm is preferred.

By adding a chiral dopant to the liquid crystal, the pitch of the liquid crystal layer can be adjusted to a desired value. Any known chiral dopant can be used, and examples thereof include S-811 (manufactured by Merck Japan) and cholesteryl nanoate. When the operating temperature range of the liquid crystal electro-optical device is wide, a chiral dopant whose temperature dependence of helical twisting power is opposite to that of positive and negative may be used. As such a chiral dopant, for example, S
-1011 (manufactured by Merck Japan Ltd.). In this embodiment, ZLI-2857 manufactured by Merck having negative dielectric anisotropy is used as a liquid crystal material, and S-811 manufactured by Merck is added as a chiral dopant. ZLI-
Since Δn of 2857 is 0.074, Δnd is 35
It was set to 0 nm. These specific settings were made as shown in FIG. Here, 12 is the transmission axis direction of the polarizing plate, 13 and 14 are the slow axis directions of the first and second optical phase difference compensating plates, and 16 and 17 are the substrates 4 and 5 respectively.
This is a case where the direction of the liquid crystal alignment on the vertical alignment film 2 and the vertical alignment film 3 formed thereon is observed from the direction of the incident light of the liquid crystal display device. In this embodiment, the angle between the liquid crystal molecules on the incident side and the polarizing plate is set to 30 degrees. However, since circularly polarized light is incident on the liquid crystal layer, the angle is not particularly limited, and any value may be used.

Since the value of d / p, which is the ratio of the pitch p of the liquid crystal to the thickness d of the liquid crystal layer, is set to 0.30, the liquid crystal molecules are vertically aligned without twisting in the initial state. The optical phase difference compensating plates 8 and 9 are both made of a stretched film made of polycarbonate, 8 has a phase difference controlled from 130 nm to 140 nm with respect to transmitted light in the direction of the surface normal at a wavelength of 550 nm, and 9 has the same From 265nm to 2 for light
It has a phase difference controlled to 75 nm. The arrangement of these optical retardation compensators is such that the optical characteristics of the liquid crystal display device after fabrication are good for the front direction, but the design is changed in consideration of the characteristics from the oblique direction together with the liquid crystal layer. Is also possible.

For example, the design for changing the phase difference of the optical phase compensator with respect to the transmitted light in the tilt direction while satisfying the set angle condition shown in FIG.
It is possible to change at least one of them to a biaxial optical phase difference compensating plate. Alternatively, it goes without saying that the angle setting can be changed within the range of Expression (4). Polarizing plate 10
Is a polarizing plate having an AR layer made of a dielectric multilayer film and having a single-unit internal transmittance of 45%.

FIG. 10 is a graph showing the voltage dependence of the reflectance of the liquid crystal display device manufactured under the above conditions. In order to measure the reflectance, as shown in FIG. 11, a means for applying a voltage to the reflection type liquid crystal display device of this embodiment is driven, and light from the illumination light source device is transmitted from the substrate 4 side through a half mirror. The light is incident, and the reflected light from the light reflecting film on the substrate 5 is detected by a photodetector. And in FIG.
The reflectance of 100% was determined by using the same liquid crystal display device as in the present embodiment except that only the same polarizing plate as that of the device to be measured was used without using the optical phase difference compensating plate, and the reflectance of the device without liquid crystal injection was used. is there. The luminous luminance rate (Y value) was used as the reflectance.

From the results shown in FIG. 9, it was found that good display characteristics with a brightness of 90% and a contrast of 20 can be obtained with a driving voltage of 3 V or less. Further, when the wavelength dependence of the reflectance was measured, almost flat characteristics were obtained, and good black-and-white characteristics without coloring were obtained.

In the present embodiment, the alignment direction of the liquid crystal was determined by rubbing. However, when vertical alignment without rubbing treatment was applied, it was confirmed that similar display characteristics could be obtained although the uniformity was slightly inferior. ing.

<Embodiment 2> In Embodiment 2, the angle between the alignment treatment directions of the upper and lower substrates is 120 degrees, the retardation of the liquid crystal layer is 300 nm, and the optical phase difference compensating plate is 3
A reflective liquid crystal display device using a single sheet (135 nm, 270 nm, 270 nm) will be described.

The liquid crystal display device shown in FIG. 3 was manufactured by a normal manufacturing process. The electrode 7 on the substrate 5 was a light reflective electrode using aluminum. The liquid crystal display device is adjusted so that the liquid crystal layer thickness becomes 4.5 μm after the liquid crystal is introduced, the angle between the direction processing directions of the upper and lower substrates is set to 120 degrees, and the liquid crystal is used in a normal TFT transmission type liquid crystal display. Liquid crystal properties (dielectric anisotropy, elasticity, viscosity, temperature characteristics, voltage holding characteristics) similar to those of
The product adjusted to 667 was used, and the product of the thickness of the liquid crystal layer and the amount of birefringence was set to be 300 nm.

Each of the three optical retardation compensating plates is made of a uniaxial stretched film made of polycarbonate, and the optical retardation compensating plate 8 is controlled at 130 nm to 140 nm with respect to transmitted light having a wavelength of 550 nm in the surface normal direction. The optical phase difference compensators 9 and 11 have a phase difference of 26
It has a phase difference controlled from 5 nm to 275 nm. The polarizing plate 10 is a polarizing plate having an AR layer made of a dielectric multilayer film and having a single-unit internal transmittance of 45%.

The reflectivity of the liquid crystal display device was measured in the arrangement shown in FIG. 11 as in the first embodiment, and 100% was the same as in the first embodiment. As described above, the voltage reflectance characteristics of the manufactured liquid crystal display device of Embodiment 2 are such that a good display characteristic with a brightness of 95% in a bright state and a contrast ratio of 25 is obtained, and a good reflection type even in visual observation. It was a liquid crystal display device. The contrast ratio was defined by dividing the reflectance in the bright state (the applied voltage was the voltage having the highest reflectance in each example) by the reflectance in the dark state. As the applied voltage in the bright state, the voltage having the highest reflectance was used for each example, and in the dark state, the voltage was applied without voltage.

As described above, when compared with the first embodiment,
It was confirmed that the contrast was improved when the circularly polarized light was produced using three retardation compensators as in the second embodiment.

<Third Embodiment> In a third embodiment, a rubbing process is performed so that the angle between the alignment process directions of the upper and lower substrates is 150 degrees, and the retardation of the liquid crystal layer is 94%.
The optical phase difference compensating plates of 135 nm and 270 nm are used one by one.

As the liquid crystal, ZLI4850 (Δn: 0.208, a nematic liquid crystal having a negative dielectric anisotropy) is used.
(Merck Japan Co., Ltd.) and CN (cholesteryl nanoate) as a chiral liquid crystal was added.
The thickness was adjusted to 0.8 μm and sandwiched as a liquid crystal layer having a cell thickness of 4.5 μm. The retardation Δnd of the liquid crystal layer is 1000
nm.

As shown in FIG. 9, the two optical phase difference compensating plates and the polarizing plate described in the second embodiment are arranged on the upper substrate of the above liquid crystal display device, and a liquid crystal display device of the present invention is manufactured. did. When this liquid crystal display device was subjected to simple matrix driving at 1/480 duty, a display with a good contrast of 10 was obtained.

The present invention is not limited to this embodiment. In the region where the retardation Δnd of the liquid crystal layer is 500 nm to 1200 nm and the angle between the orientation directions of the upper and lower substrates is 80 ° to 170 °, the steepness of the electro-optical characteristics is high, and It has been confirmed that matrix driving is possible.

<Embodiment 4> Embodiment 4 shows a driving system using an active matrix system and a device using a reflector having a smooth uneven shape. FIG. 12 is a sectional view of the configuration of the liquid crystal display device according to the present embodiment.

The liquid crystal display device 18 includes a first substrate 5 and a second substrate 4 made of transparent glass. On the first substrate 5, a TFT element 19 is formed in each pixel as an active element. An interlayer insulating film 20 is formed on the TFT element 19 and the driving wiring (not shown), and a drain terminal (not shown) of the TFT element 19 and the reflective pixel electrode 21 are electrically connected through a contact hole. You. On the pixel electrode 21, the alignment film 3 is formed with a thickness of 100 nm.

Here, the reflective pixel electrode 21 can be made of a metal material such as aluminum, nickel, chromium, silver, or an alloy using the same, and functions as a reflective metal film having light reflectivity. The shape of the reflective pixel electrode 21 has a smooth uneven shape except for the contact hole portion, and prevents the metal reflective surface from becoming a mirror surface. At this time, the vertical alignment is realized even on the uneven shape, and it has been confirmed that the unevenness does not affect the alignment.

Next, the forming method will be described in more detail. A large number of large projections 22 and a large number of small projections 23 made of a photosensitive resin material were formed on the substrate 5 on which the TFT element 19 and the driving wiring (not shown) were formed. A large number of large projections 22 and small projections 23 were formed by photolithography using circular patterns having bottom diameters D1 and D2. D1 and D2 are, for example, 5 μm and 3 μm, respectively.
Is set to The distance D3 is set to at least 2 μm. The height of these projections can be controlled by the film thickness when the photosensitive resin material was formed. For example, the height was made 1.5 μm, and the projections were formed into gentle projections by the subsequent exposure step and firing step.

A smoothing film 24 was formed of the same photosensitive resin material so as to cover the projections 22 and 23 and to fill a flat portion between the projections 22 and 23. The surface of the smoothing film 24 was formed into a smooth curved surface under the influence of the projections 22 and 23, and a desired shape was obtained. Note that the contact hole is formed so that neither the protrusion nor the smoothing film is formed.

With the TFT element substrate 25 having the above-described structure, the pixel electrode is also disposed near the liquid crystal layer also serving as a reflection plate, so that no parallax is generated. The light reflected by the pixel electrode 21 is T
It is possible to realize a bright reflective liquid crystal display device having a high aperture ratio, which is not damaged by the FT element 19 and the element driving wiring (not shown).

On the other hand, on the other substrate used together with the TFT element substrate 25, a color filter 26 having a high brightness according to the reflection system was disposed. The color filter is provided with a black matrix 27 for preventing mixing of colors between pixels and preventing leakage of reflected light in dark display due to a voltage non-applied portion between pixel electrodes and electric field disturbance. . The light incident on the black matrix 27 has already become approximately circularly polarized light here, and the reflected light from the black matrix 27 is again subjected to the action of the optical phase difference compensating plate at the time of emission and is absorbed by the polarizing plate. Even if a metal film or the like is used, the black matrix 27 does not cause reflected light to deteriorate the visibility, but it is needless to say that further low reflection processing is suitable for higher contrast display. .

On this color filter, ITO (Indium Tin Oxide) is formed as a transparent electrode 6 by sputtering, the counter electrode 6 of the pixel electrode 21 having a desired pattern having a thickness of 140 nm is formed, and the alignment film 2 is formed. And a color filter substrate 26. Even if the transparent electrode 6 has a thickness other than 140 nm,
Light reflected by the incident light without reaching the liquid crystal layer 1 due to the interference effect of the thickness of the transparent electrode 6 is absorbed by the optical phase difference compensating plates 8 and 9 and the polarizing plate 10, so that the light is not affected by the dark state. , Visibility is not impaired.

The color filter 27 is appropriately designed so as to have a brightness suitable for a high contrast display mode using a polarizing plate. When the aperture ratio of the black matrix is 90%, the transmission of the color filter substrate 28 is performed. Rate is Y
The value was 50%.

The TFT element substrate 25 thus prepared
And the color filter substrate 28 are subjected to a rubbing method to align the vertical alignment film, and are scattered with a plastic spacer (not shown) for maintaining the thickness of the liquid crystal layer, and a seal arranging process at the peripheral portion. The mixture was cured and sealed under pressure to prepare a liquid crystal cell for liquid crystal injection. Then, a liquid crystal material having a negative dielectric anisotropy Δε was introduced into the liquid crystal layer 1 by a vacuum injection method.

Next, the orientation of the liquid crystal display device will be described in detail. Hereinafter, the up, down, left, and right directions of the observer facing the device are described as the directions of the clock face, and the upward direction is described as the 12 o'clock direction. On the opposite side of the color filter substrate 28 from the liquid crystal layer 1, optical phase compensating plates 8 and 9 made of a stretched film made of polycarbonate are provided, and a polarizing plate 10 is further disposed thereon. That is, as shown in FIG.
The two optical phase difference compensating plates 13 and 14 and the polarizing plate 12 were arranged to produce a liquid crystal display device of the present invention.

The alignment direction 16 of the alignment film on the color filter substrate 28 is made to be the 3 o'clock direction of the apparatus. As the liquid crystal layer, a liquid crystal layer adjusted to have a layer thickness of 4.0 to 5.0 μm after the introduction of the liquid crystal is used.
The product of the thickness of the liquid crystal layer and the amount of birefringence is approximately 3
It was set to be 50 nm. The thickness of the liquid crystal layer has a different value depending on the position due to the uneven shape of the reflective pixel electrode 21. Further, a driving circuit was mounted around the liquid crystal display panel to obtain a liquid crystal display device.

In the reflection type liquid crystal display device of the present embodiment, since the reflective pixel electrode 21 is arranged near the liquid crystal layer, there is no parallax and a good high resolution display is realized. The reflected light has an uneven shape given to the reflective electrode, so that the face of the observer is not reflected, and a good white display is realized.Those having scattering properties are not arranged on the front surface of the liquid crystal display device. They exhibited good darkness, which resulted in a display with a high contrast ratio. It is confirmed that the brightness in the bright state with respect to the standard white plate is 30% and the contrast is 15. The viewing angle characteristics were excellent, and no inversion of the display was observed.

Further, since a high brightness color filter is used, sufficient brightness can be ensured even in a display using a polarizing plate, and since the reflectance in the dark state is low, the color element selected in the dark state is used. The reflected light of the color filter 26 does not affect the reflected light of the color element selected in the bright state, thereby deteriorating the color purity. Excellent color reproducibility without impairing the reproduction range.

Further, since the voltage applied to each pixel is set to an intermediate state between the dark state and the bright state, there is no problem in reproducing halftones, and therefore, the representation of intermediate colors of each color of the color filter. There was no problem. In addition, it was confirmed that the response speed did not cause any problem in moving image reproduction in actual driving. Furthermore, even when the temperature of the surrounding environment changed, the reflectance in the dark state did not change, and good temperature characteristics were exhibited.

As described above, a reflection type liquid crystal display device capable of displaying multiple gradations and displaying a moving image and having a good color reproduction range was manufactured by a practical method.

In this embodiment, a thin film transistor (TF
T) The driving by the method has been described, but is not particularly limited.
IM (Metal Insulator Metal)
For example, an active matrix system utilizing the above method can be used. The TFT is made of amorphous silicon TF
Any of T, polysilicon TFT, and single crystal silicon TFT can be used.

Further, when the retardation of the liquid crystal is set to a large value as in the third embodiment, simple matrix driving was possible even when an uneven reflector was used. The vertical alignment is good even on such smooth irregularities, and uniform alignment has been confirmed even after rubbing. Also, good orientation was confirmed on the uneven substrate side without particularly performing rubbing treatment.

<Embodiment 5> As Embodiment 5, the lightness is improved by producing an uneven reflector having in-plane anisotropy, and further, the tilt viewing angle of the liquid crystal modulation layer is set in the direction with the higher lightness. The figure shows the one in which a good azimuth is oriented. The unevenness produced in the liquid crystal display device of Embodiment 4 was produced in different patterns and differently depending on the orientation in the plane where the reflective electrode was formed. For example, FIG.
As shown in the figure, the uneven shape was not circular but oval.

Then, the reflection characteristic of only the concave / convex reflector is measured in an optical measurement arrangement as shown in FIG.
The incident light was incident from a tilt direction, the reflected light intensity directed toward the normal direction of the reflector surface was measured, and the light source was rotated to measure the anisotropy of reflection.

As a result, reflection characteristics as shown in FIG. 15 were obtained. That is, it was confirmed that light from a specific direction was efficiently directed to the front of the liquid crystal display device. However, in consideration of the fact that the refractive index of the liquid crystal material is greatly different from that of air, at the time of measurement, a immersion oil (matching oil) having a refractive index of 1.53 is dropped on the reflection plate surface, and a transparent glass The measurement is performed with a plate attached. Also,
The measured value was converted so that 100% of the measured value was a value obtained when a standard diffusion plate (standard white plate) of MgO was similarly measured. Curve 1 is a measured converted value of the anisotropic diffuse reflector of this embodiment, and curve 2 is a similar measured value of the diffuse reflector used in the fourth embodiment.

As a result, it has been found that there is a difference in brightness between the direction of X having a long average period and the direction of Y having a short average period in the uneven shape shown in FIG. As a result of a similar study on shapes other than the elliptical shape, the relationship that the reflected light brightness increases when illuminated from a direction in which the average period of the uneven shape is short is not changed.

A liquid crystal display device was manufactured so that the orientation direction and the sticking directions of the polarizing plate and the optical retardation compensating plate were the same as those in FIG. A reflection-type liquid crystal display device having such a concave-convex reflector was produced in the same manner as in Embodiment 3 except for the concave-convex pattern production process for producing the reflector. And
When this liquid crystal display device was visually observed, a display with high brightness was realized for a viewer in the front direction, and the effect of improving the brightness of the anisotropic unevenness was exhibited. At this time, the reflection lightness was high when the illumination light was incident from the 12 o'clock direction and the 6 o'clock direction. Furthermore, in the case of illuminating from the front direction and observing from the tilt direction, the brightness was similarly high at the 12 o'clock direction and the 6 o'clock direction.

The orientation of the anisotropic uneven shape used in the present embodiment can be set to another orientation in accordance with the main use environment of the liquid crystal display device of the present invention.

<Embodiment 6> As Embodiment 6, an embodiment in which a touch panel (pressure-sensitive input device) is used as information input means in a portable device which is a main application field of the reflection type liquid crystal display device of the present invention. Will be described. FIG.
FIG. 6 shows a schematic configuration diagram of the touch panel 33. As the touch panel 33, both the movable substrate 29 and the support substrate 30 having no birefringence are used. Where 31 and 32 are
This is a transparent electrode for detecting a pressed position.

As a first configuration example using a touch panel (hereinafter, referred to as configuration example 61), a touch panel 33 having a cross-sectional structure shown in FIG. 16 is arranged on the front surface of the liquid crystal display device of the third embodiment. 17 is shown.

As a second configuration example using a touch panel (hereinafter, referred to as a configuration example 62), optical phase difference compensators 8 and 9 and a polarizing plate are provided on a movable substrate 27 of a touch panel 33 having a sectional structure shown in FIG. FIG. 18 shows a liquid crystal display device having No. 10 attached thereto and arranged on the front surface of the same liquid crystal display device as in the third embodiment in which the polarizing plate and the optical phase difference compensating plate are not attached.

At this time, the orientation of the liquid crystal layer and the arrangement of the polarizing plate and the optical retardation compensating plate were arranged as shown in FIG. 9, and the configuration other than the touch panel was the same. In addition, a gap 34 is provided so as to have a pressing force transmission preventing effect by maintaining a constant gap between the support substrate 30 of the touch panel and the substrate 4 of the liquid crystal display device, and the touch panel can be lightened without using a pressing buffer member. The pressing force was not transmitted to the substrate 4.

The touch panel has a configuration example 61 and a configuration example 62.
As a result, in the configuration example 61, the reflected light component on the touch panel was directly observed and greatly deteriorated the visibility.
The reflected light was generated not only by the gap held by the pressed position detecting transparent electrodes 29 and 30 but also by the gap held by the touch panel support substrate 30 and the polarizing plate 10.

On the other hand, in Structural Example 62, the reflected light component was not observed at all, and very good display similar to the case where the touch panel was not used was displayed. Nothing was observed due to the gaps held between the transparent electrodes 31 and 32 for detecting the touched position of the touch panel, and the gaps 34 for preventing the transmission of the pressing force, the touch panel support substrate 30, and the substrate 4 of the liquid crystal display device.
Reflection by the interface of the input device is not observed, the pressing force buffer member is not required, the weight is light, and the display device can effectively utilize the circularly polarized state by the antireflection means of the input device for display. A liquid crystal display device was manufactured.

Further, although not shown, the configuration example 62
By omitting the movable substrate 29 of the touch panel and directly disposing the transparent electrode 31 on the liquid crystal layer side of the optical phase difference compensating plate 8, a simpler and lighter configuration was possible.

In the embodiments described above, a uniaxial stretched film is used as the optical retardation compensating plate. However, a biaxial film, that is, a retardation film or a liquid crystal polymer which can control the refractive index three-dimensionally, is used. Phase difference film can be applied,
In this case, it has been confirmed that the viewing angle can be increased.

[0126]

As described above, in the liquid crystal display device according to the present invention, a reflection type liquid crystal display device having high reflectivity and high contrast can be obtained. Further, the reflection film forming surface of the reflection plate can be provided on the liquid crystal layer side of the transparent substrate, and a good dark state can be realized. Therefore, a moving image can be displayed with high resolution and high contrast without parallax.
Since the liquid crystal layer is twisted, the viewing angle characteristics are excellent.

Further, if a color filter adjusted to high brightness is used in this device, a color reflection type liquid crystal display device having good color reproducibility and high display quality can be realized. In addition, when a touch panel is added to the reflective liquid crystal display device of the present invention, a high-quality input device capable of effectively utilizing the polarization state of a touch panel provided with antireflection means using a polarizing plate and a retardation plate. A body type liquid crystal display device can be realized.

[Brief description of the drawings]

FIG. 1 is a structural cross-sectional view of a reflective liquid crystal display device according to a first embodiment.

FIG. 2 is a plan view showing a setting direction of a polarizing plate and an optical phase difference compensator of the reflective liquid crystal display device of the first embodiment.

FIG. 3 is a structural cross-sectional view of a reflective liquid crystal display device using three optical phase difference compensators according to a second embodiment.

FIG. 4 is a cross-sectional view of a polarizing plate and a reflective liquid crystal display device according to the second embodiment.
It is a top view which shows the setting direction of one optical phase difference compensator.

FIG. 5 is a diagram showing a relationship between retardation and a twist angle at a voltage of 2.5 V according to an evaluation function (FOM).

FIG. 6 is a diagram illustrating a relationship between retardation and a twist angle at a voltage of 3.0 V according to an evaluation function (FOM).

FIG. 7 is a diagram showing a relationship between retardation and a twist angle at a voltage of 3.5 V, based on an evaluation function (FOM).

FIG. 8 is a diagram illustrating a relationship between retardation and a twist angle at a voltage of 4.0 V according to an evaluation function (FOM).

FIG. 9 is a plan view showing setting directions of a polarizing plate and an optical phase difference compensator when two optical phase difference compensators are used.

FIG. 10 is a diagram illustrating the relationship between the reflectance and the applied voltage in the reflective liquid crystal display devices according to the first and second embodiments.

FIG. 11 is an arrangement diagram of an optical system for measuring reflectance in the reflection type liquid crystal display devices of the first and second embodiments.

FIG. 12 is a structural sectional view of a reflective liquid crystal display device in which an active matrix according to a fourth embodiment is combined.

FIG. 13 is a plan view illustrating a structure of an anisotropic uneven reflection plate according to a fifth embodiment.

FIG. 14 is an optical system layout diagram for measuring the reflection characteristics of only the anisotropic uneven reflection plate of the fifth embodiment.

FIG. 15 is a relationship diagram showing the reflection characteristics of only the reflector of the third embodiment and the fifth embodiment using the anisotropic uneven reflector by the reflected light intensity and the azimuth Ф of the illumination light source.

FIG. 16 is a structural sectional view of a touch panel in a touch panel-integrated liquid crystal display device according to a sixth embodiment.

FIG. 17 is a structural cross-sectional view of a configuration example 61 in which the touch panel is arranged on the front surface of the liquid crystal display device in the touch panel-integrated liquid crystal display device of the sixth embodiment.

FIG. 18 is a structural sectional view of a configuration example 62 in which the touch panel is embedded in the liquid crystal display device in the touch panel integrated liquid crystal display device of the sixth embodiment.

[Explanation of symbols]

 Reference Signs List 1 liquid crystal layer 2, 3 vertical alignment film 4 second substrate 5 first substrate 6 electrode 7 reflective electrode 8 first optical phase difference compensator 9 second optical phase difference compensator 10 polarizing plate 11 third Optical phase difference compensating plate 12 Polarizing plate transmission axis direction 13 Slow axis direction of first optical phase difference compensating plate 14 Slow axis direction of second optical phase difference compensating plate 15 Delay of third optical phase difference compensating plate Phase axis direction 16 Liquid crystal alignment direction on second substrate (alignment processing direction) 17 Liquid crystal alignment direction on first substrate (alignment processing direction) 18 Reflective liquid crystal display device described in Embodiment 3 19 TFT element Reference Signs List 20 interlayer insulating film 21 reflective pixel electrode 22 large protrusion 23 small protrusion 24 smoothing film 25 TFT element substrate 26 color filter 27 black matrix 28 color filter substrate 29 movable substrate of touch panel 30 support of touch panel Plate 31 pressing position detection transparent electrode 33 touch sensor input device (touch panel) 34 pressure transmitting prevent void

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-337421 (JP, A) JP-A-63-292111 (JP, A) JP-A-1-270024 (JP, A) JP-A 8- 6025 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G02F 1/1335 G02F 1/137

Claims (7)

(57) [Claims] 1. A first substrate having light reflectivity, a transparent second substrate having a transparent electrode, and a nematic liquid crystal having a negative dielectric anisotropy sandwiched between the first and second substrates. Layer, and the second group for the circularly polarized light to enter the liquid crystal layer.
A plurality of optical phase difference compensators arranged on a plate and one
In the reflection type liquid crystal display device provided with a light plate , the surfaces of the first and second substrates are substantially vertically aligned, the natural pitch of the liquid crystal is p, the liquid crystal layer thickness is d, and the birefringence difference of the liquid crystal is Δn. 0 <│d / p│ <1 and 200 nm ≦
A reflective liquid crystal display device, wherein a natural pitch of a liquid crystal, a liquid crystal layer thickness, and a difference in birefringence of a liquid crystal are selected so that Δn * d ≦ 1200 nm is satisfied. Wherein a pre-Symbol 2 sheets plurality of optical retardation compensator plate that is disposed on the second substrate, the retardation of the substrate normal direction of the optical retardation compensator plate is 100nm or more 18
A first optical phase difference compensating plate set to 0 nm or less, and a second optical phase difference compensating plate arranged on the first optical phase difference compensating plate and having a retardation in the normal direction of the substrate set to 200 nm or more and 360 nm or less. Optical phase difference compensator and second optical position
A reflection type liquid crystal display device comprising : one polarizing plate disposed on a phase difference compensating plate , wherein the transmission axis (or absorption axis) of the polarizing plate and the first and second optical phase difference compensations are provided. The polarizing plate and the optical phase difference compensating plate are arranged such that when the angles formed by the slow axes of the plates are θ1 and θ2, respectively, 35 ° ≦ | 2 × θ2-θ1 | ≦ 55 ° is satisfied. The reflective liquid crystal display device according to claim 1, wherein: 3. A liquid crystal on one of the first and second substrates.
Uniform molecules make a non-zero angle with the normal to the substrate
3. An orientation according to claim 1, wherein
The reflective liquid crystal display device as described in the above. 4. The light-reflective electrode has a smooth and continuous surface.
A light reflecting film having an uneven shape which changes gradually, and the light reflecting film is
The transparent electrode on the second substrate is used as a counter electrode to charge the liquid crystal layer.
2. The method according to claim 1, wherein the electrode also functions as a pressure application electrode.
4. The reflection-type liquid crystal display device according to any one of items 1 to 3. 5. An unevenness formed on a surface of the light-reflective electrode.
The average irregularity period differs depending on the orientation in the substrate plane.
5. The reflection type according to claim 4, wherein
Liquid crystal display. 6. An average irregularity formed on the first substrate.
Reflective liquid crystal display with reflective film of irregular shape with different periods
In the apparatus, an observation direction viewed by an observer is adjusted by the reflection film.
Determined in the plane containing the short azimuth of the uneven period and the normal of the display surface
6. The reflection type liquid crystal display device according to claim 5, wherein
Place. 7. The reflection type liquid crystal display device according to claim 1,
With a layered gap to detect the pressing force from outside the device.
The first optical phase difference
A compensating plate and the second substrate.
A reflective liquid crystal display device with a pressure-sensitive input device.