JP3501941B2 - Reflective liquid crystal display - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflective liquid crystal display device that uses reflected light for display, and more particularly to a reflective liquid crystal display device using a single polarizing plate system.

[0002]

2. Description of the Related Art Reflective liquid crystal display devices are widely used because they consume little power and can be realized with a simple structure. In particular, the reflective liquid crystal device can obtain display light in proportion to the amount of ambient light, and is particularly suitable for outdoor use such as a portable information terminal device.

As a reflection type liquid crystal display device, a TN (twisted nematic) system using two polarizing plates is often used. Others, no polarizing plate, or 1
A guest-host type liquid crystal element (hereinafter abbreviated as GH) in which a dichroic dye is added to a liquid crystal using only one sheet has also been developed. In addition, a liquid crystal display element of a system using one polarizing plate (hereinafter, abbreviated as a one-polarizing plate system), which can be expected to have high resolution and high contrast display, has been developed, and further technical development for practical use has been made. Progress is being made and the possibility of widespread application is opening.

As an example of using a ferroelectric liquid crystal, Yoshihara et al. Devised a construction using two polarizing plates in Japanese Patent Laid-Open No. 9-90347. Furthermore, Yoshihara et al. Are trying to apply the ferroelectric liquid crystal material to the single-polarizing plate system at the 23rd liquid crystal debate (the proceedings of the same lecture, page 452).

Since the conventional TN type liquid crystal element uses two polarizing plates, it has excellent contrast ratio and viewing angle dependence characteristics, but has low reflectance. Further, since the distance between the liquid crystal modulation layer and the light reflection layer is separated by the thickness of the substrate,
There is a parallax due to the deviation of the optical path between when the illumination light is incident and when it is reflected, and a double image occurs. In particular, in a structure in which color filters having different colors are combined in close proximity to the liquid crystal modulation layer for each pixel, it is insufficient to deal with multicolor and high-definition display.

On the other hand, there has been developed a GH type liquid crystal element in which a dichroic dye is added to a liquid crystal without using a polarizing plate or using only one polarizing plate. In this system, the reflector can be placed close to the liquid crystal layer, and there is no problem with double images, but lack of reliability due to the addition of dichroic dye,
Further, there is a problem that a high contrast ratio cannot be obtained because the dichroic dye has a low dichroic ratio. In particular, the lack of contrast significantly reduces the color purity in a color display using a color filter, so it is necessary to combine with a color filter with high color purity, and as a result, the brightness decreases and the advantage of high brightness is lost. Be done. Also, the speed for rewriting the display content is slow, and it is difficult to display a moving image.

[0007]

Therefore, a liquid crystal display device of a single-polarizing plate type has been developed, which can be expected to display moving images with high resolution and high contrast. In this configuration, good display is realized, but there is a problem that power is consumed regardless of the display content because the liquid crystal is continuously driven.

From the viewpoint of power consumption, by applying the ferroelectric liquid crystal, it is possible and effective to use a method such as rewriting only the changed portion of the display content. However, in the structure of Japanese Patent Laid-Open No. 9-90347 of Yoshihara et al., Since two polarizing plates are used, a double image similar to that of the TN system is observed, and a good display cannot be obtained. Furthermore, the second such as Yoshiwara
3rd Liquid Crystal Debate Conference (Proceedings of the same lecture, p. 452, "Liquid Debate 2"
Abbreviated as "3p452"), the ferroelectric liquid crystal system can be applied to the single-polarizing plate system, and a bright display is possible. Further, since the reflector is close to the liquid crystal layer, good display without parallax is possible. become.

The increase in display brightness is due to the fact that one polarizing plate is used as compared with the case where the polarizing plates are used in the crossed Nicols arrangement. Further, when sandwiched between two crossed Nicols polarizing plates, the wavelength that can be converted into polarized light in a favorable transmission direction is limited by the liquid crystal layer, and therefore the polarizing plate is limited to the entire visible wavelength band. I can't get the brightness,
There is no such limitation in the bright state of the single-polarizing plate mode of Yoshihara et al., And bright display can be obtained in the entire visible wavelength band, which also contributes to the improvement of brightness.

As described above, although the brightness is improved in the ferroelectric liquid crystal display of the single-polarizing plate type, on the other hand, this structure causes a problem in display characteristics that black display cannot be realized. This point will be described in more detail.

Yoshihara et al. Applied a surface-stabilized ferroelectric liquid crystal mode (SSFLC mode), which is a typical ferroelectric liquid crystal mode, by using a polarizing plate and a light reflecting layer close to the liquid crystal layer. The display is performed in a configuration in which the liquid crystal layer is sandwiched (that is, in a single-sheet polarizing plate mode). At this time,
The liquid crystal alignment is electrically switched between two orientations contained in the plane of the substrate. Further, the liquid crystal alignments oriented in the respective directions have the alignment arrangements included in the planes including the substrate normal, and do not take the twisted alignment as in the TN method using nematic liquid crystals.

This switching operation is characterized by the angle at which the liquid crystal alignment direction changes within the plane of the liquid crystal display substrate depending on the direction of the applied electric field. Hereinafter, this angle is referred to as a switching angle. This switching angle is SSFL
Japanese Patent Laid-Open No. 9-90347 discloses that the C mode is equivalent to twice the tilt angle of the liquid crystal composition, and the best display is obtained when the switching angle is 45 degrees. . In the case of Japanese Patent Laid-Open No. 9-90347, two polarizing plates are used, and a liquid crystal layer is sandwiched by crossed Nicol polarizing plates having orthogonal absorption axes. At this time, by using one of the alignment arrangements in which the liquid crystal is uniformly aligned, the liquid crystal alignment direction at that time is aligned with the absorption axis of one of the two polarizing plates, thereby realizing a good dark display. Good dark display is black display due to dark display over the entire visible light range.

On the other hand, in the structure of the liquid crystal 23p452, the liquid crystal layer is sandwiched between only one polarizing plate and the light reflecting layer. At this time, the product of the refractive index difference of the liquid crystal and the liquid crystal layer thickness is 1
It is disclosed in the same report that dark display is realized when a condition of about 30 nm, that is, a quarter wavelength condition of a central wavelength in a visible region of 550 nm is substantially satisfied. Further, according to a study by the inventors of the present application, the switching angle is
It has been confirmed that 45 ° gives the best characteristics even in the case of the one-sheet polarizing plate mode configuration disclosed in Liquid Disclosure 23p452.

However, as a result of further detailed examination, in the case of the one-sheet polarization mode, even if the ideal switching angle of 45 degrees is obtained, it is good on the short wavelength side and the long wavelength side of the visible region. It was revealed that such a dark display could not be obtained and coloring was unavoidable. In other words, by changing from the two-polarizing plate method to the one-polarizing plate method, although the parallax and the brightness are improved, the black display is deteriorated and the characteristics are deteriorated. As a solution in this case, when a color filter close to the liquid crystal layer or a color reflector is used, it is easy to presume that the layer thickness of the liquid crystal layer has different values for each color pixel. However, this structure has a problem in that at least one of the substrates sandwiching the liquid crystal layer has to be stepped, which results in a complicated structure. Also, this method cannot be applied when a color filter is not used.

Further, looking at other conventional techniques, SSFL
In the case where twisted alignment is not observed in the liquid crystal layer when the liquid crystal alignment is traced by the upper and lower substrates, which is parallel to the substrate plane of C or the like, a method for obtaining good display has not been realized. In other words, a structure capable of high-definition display and high-brightness display and capable of obtaining good black and white display without requiring a complicated substrate structure is a liquid crystal substrate plane represented by a ferroelectric liquid crystal or the like. It has not been realized when the change in orientation within is used for display.

Therefore, the present invention has been made to solve the above problems, and is a liquid crystal display device of a single polarizing plate type capable of high-resolution display, in which liquid crystal moves in the plane of the liquid crystal substrate. SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned display problems found in the above, and to obtain a reflective liquid crystal display device of color display excellent in visibility.

[0017]

In order to achieve the above object, a reflection type liquid crystal display device according to claim 1 of the present application has at least a first substrate having light reflectivity and a second substrate having light transmissivity. When a liquid crystal layer having liquid crystal composition interposed between the first and second substrate, comprising a single polarizing plate disposed in an optical path for viewing the liquid crystal layer, a first substrate, A liquid crystal layer,
In a reflective liquid crystal display device in which a polarizing plate and a polarizing plate are laminated in this order, the liquid crystal alignment is electrically selectable from the first and the first.
At least a liquid crystal alignment position of the 2, the first and second liquid crystal alignment position of both liquid crystal orientation in the plane including the substrate normal is substantially contained, and the alignment arrangement substantially free The orientations of the planes including the substrate normal are different from each other, and the value obtained by integrating the refractive index difference of the liquid crystal layer with respect to the light traveling in the substrate normal direction over the liquid crystal layer thickness direction is Also any light in the visible range
It can satisfy 1/4 wavelength condition for being set from 100nm to one of the 180 nm, furthermore, between the liquid crystal layer and the polarizing plate, Li with respect to the substrate normal direction of the transmitted light
The retardation is 200 nm to 360 nm described above.
(1/2 + n (n is 0 or more
Are provided a number)) optical retardation compensator plate that is set to a value of
And the transmission axis (or absorption axis) of the polarizing plate and the liquid
Substrate with liquid crystal alignment in any liquid crystal alignment configuration of crystal layer
Angle formed by the projection on the plane and the retardation of the optical retardation compensator
If the angles formed by the axes are θ1 and θ2, respectively,
The value of | 2 × θ2-θ1 | at the first liquid crystal alignment position
Is 35 ° or more and 55 ° or less, and the second liquid crystal
The value of | 2 × θ2-θ1 | at the orientation position is 60 ° or more.
It is characterized in that it is installed at 120 ° or less .

[0018]

[0019]

The reflection type liquid crystal display device of the present second aspect, a feature the liquid crystal composition a ferroelectric liquid crystal sandwiched between the substrates, the antiferroelectric liquid crystal, to be constituted by any of nematic liquid crystal To do. Reflective type according to claim 3 of the present application
A liquid crystal display device requires a liquid crystal composition sandwiched between substrates.
Ferroelectric liquid having a chevron layer structure in the Ctic C phase
It is characterized by being composed of crystals . Claim 4 of the present application
The reflective liquid crystal display device described above is characterized in that a light scattering functional layer is disposed in the vicinity of the liquid crystal layer. Claims
In the reflective liquid crystal display device described in Item 5, the light scattering functional layer adjacent to the liquid crystal layer is a light diffusive reflective layer having an uneven shape. Reflective liquid crystal display according to claim 6 of the present application
The device is characterized in that the certain certain light is green.
It

In the reflective liquid crystal display device according to the present invention, an optical retardation compensating plate is installed between the liquid crystal layer and the polarizing plate. By doing so, excellent black display in dark display can be realized for the reasons described below.

First, the reason why the dark display is insufficient without the optical phase difference compensating plate will be described. Without the optical retardation compensator, good dark display is realized at the wavelength in the visible region where the birefringence of the liquid crystal layer is a quarter wavelength condition, and at other wavelengths, this condition is satisfied. The brightness of the dark display rises. Thus, in the dark display, good black display is not realized.

On the other hand, in the present invention, an optical phase difference compensating plate can be used in addition to the above structure. Thereby, the light incident on the liquid crystal layer can be converted into light having a polarization state different from that of normal linearly polarized light by using at least the optical phase difference compensating plate.

Further details will be described. Here, for example, with respect to green (wavelength 550 nm) light,
It is assumed that the four-wavelength condition is satisfied. From this assumption,
For green light, without using an optical phase difference compensator,
Good dark display has already been realized. Therefore, it suffices to search for a configuration of an optical phase difference compensating plate that has substantially no optical effect on green light. As a setting of such an optical phase difference compensating plate, a setting that keeps the green light linearly polarized is preferable. This condition is satisfied by an optical phase difference compensating plate showing retardation of (1/2 + n) value of green wavelength, where n is an integer of 0 or more, that is, (275 + 5)
An optical retardation compensating plate having a retardation of about 50 × n) nm is preferable.

The installation orientation of the optical phase difference compensating plate having the retardation thus determined will be described. The light passing through the polarizing plate and further passing through the optical phase difference compensating plate has a different polarization state depending on the wavelength, but the green light vibrates as linearly polarized light. The relationship between the vibrating surface of the optical field of green light and the installation direction of the liquid crystal layer should be set in the same way as the relationship between the transmission axis of the polarizing plate and the installation direction of the liquid crystal layer when the optical phase difference compensator is not used. Thus, at least the display for green light is similar when the optical phase difference compensator is not used.

Specifically, when the slow axis azimuth of the optical phase difference compensating plate measured from the transmission axis azimuth of the polarizing plate on the substrate plane is θ2, the vibrating surface of the green light after passing through the optical phase difference compensating plate. Is
Similarly, it is oriented in the 2 × θ2 azimuth direction. The alignment direction of the liquid crystal layer is determined so that the liquid crystal layer works well as a quarter wavelength plate with respect to the vibrating plane of the green linearly polarized light that has passed through the optical phase difference compensating plate.

This is a case where the orientation direction of the liquid crystal layer is 35 degrees or more and 55 degrees or less with respect to the vibration surface of light immediately before entering the liquid crystal layer. That is, when the angle when the alignment direction of this liquid crystal layer is measured from the transmission axis of the polarizing plate is θ1, | 2
This is the case where xθ2-θ1 | is 35 degrees or more and 55 degrees or less. Here, the angles θ1 and θ2 may be angles from the transmission axis or the absorption axis of the polarizing plate,
Good display can be realized under similar conditions.

Here, an example in which one optical phase difference compensating plate is used is shown, but the number is not particularly limited to one, and
It may be added in more detail according to the operation of the liquid crystal layer.
Further, in this example, the wavelength used for setting the retardation and the amount of birefringence of the optical phase difference compensator and the liquid crystal layer was green, but it is possible to use wavelengths in the visible range of 380 nm or more and 780 nm or less. Accordingly, the same effect is realized when the retardation of the optical retardation compensation plate is 200 nm or more and 360 nm or less and the birefringence amount of the liquid crystal layer is 100 nm or more and 180 nm or less. The values of θ1 and θ2 can be changed within the above range depending on the wavelength dispersion of the refractive index difference of the liquid crystal composition used and the wavelength dispersion of the optical phase difference compensating plate.

As described above, if the optical phase difference compensating plate used for improving the dark display deteriorates the bright display, good display cannot be obtained. The condition for not worsening the bright display is that the light that has passed through the optical phase difference compensating plate and the liquid crystal layer becomes linearly polarized light, as in the case where no optical phase difference compensating plate is provided.

For this purpose, it is necessary to realize this condition by using the optical phase difference compensating plate selected as described above and the setting of the liquid crystal alignment direction. This means that | 2 × θ2-θ1 | is set between 60 degrees and 120 degrees using the above angle notation. More preferably, it is desirable that this value be close to 90 degrees, but it is appropriately set within this range depending on the above-mentioned conditions realized for realizing good black display and the switching angle of the liquid crystal layer.

The width of the set angle for dark display is 20 degrees (55-35 degrees) and that for bright display is 60 degrees (120-60 degrees).
This is because the non-linearity between the brightness perceived by human vision and the brightness of the display light is taken into consideration. Specifically, CIE197
6Lab (or Luv) color system or Munsell color system used "lightness" (lightness or value) width is
It is decided that the dark display and the bright display have the same level.

As an example of a liquid crystal display system satisfying such a condition, an alignment parallel to the display surface of a ferroelectric liquid crystal, an antiferroelectric liquid crystal, a nematic liquid crystal phase or the like in a liquid crystal layer, and a substantial orientation of the alignment is shown. Any device that can be controlled and used for display is suitable for the principle and can be used for the liquid crystal display device of the present invention.

When the reflected light is used efficiently for display and the reflection of the surroundings due to the specularity of the display surface is intended, the action of directing the ambient light toward the observer and the elimination of the specularity. Action is needed. As this means, a mirror surface on which a light scattering film having a scattering function when light passes is arranged is effective. This scattering function has the effect of changing the traveling direction of light in various ways and can be installed in the visible optical path. However, in order to maintain a good display without parallax, which is an advantage of the one-sheet polarizing plate, it is desirable that this scattering function is close to the liquid crystal layer. Specifically, it is desirable that the liquid crystal layer is arranged on the main surface of the substrate sandwiching the liquid crystal layer on the liquid crystal layer side.

As a light diffusing function similar to this light diffusing function and a light reflecting property, a light reflecting film having irregularities has a reflecting function and a scattering and diffusing function, and is effective as a light diffusing reflecting film. To function.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing the structure of the liquid crystal display device of the present invention. The liquid crystal layer 1 is sandwiched between a substrate 4 on which an alignment film 2 subjected to an alignment treatment is formed and a substrate 5 on which an alignment film 3 similarly aligned is formed. Electrodes 6 and 7 for applying a voltage to the liquid crystal layer are formed on the substrates 4 and 5, respectively. The electrode 7 may also serve as a reflector.

Further, when the electrode 7 is provided with reflectivity, it may have smooth irregularities to the extent that the polarization of the reflected light is preserved. The smooth unevenness may have a different unevenness period on the reflection plate depending on the direction. Further, when this unevenness cannot be used to maintain the orientation of the liquid crystal layer, a smoothing transparent layer may be arranged on this uneven surface, and a scatterer that appropriately scatters light is provided in the visible optical path. They may be arranged, and their configurations are not limited.

As the voltage applying means to the electrode pair thus constructed, an active element or a stripe-shaped electrode for driving a dot matrix may be constructed, and the liquid crystal layer in the plane of the substrate may be formed. It may have another electrode structure that induces a change in orientation. The orientation change may be induced by a method other than the electric field, and is not particularly limited and is appropriately selected according to the properties of the liquid crystal used. An optical phase difference compensating plate 8 is arranged on the viewer side of the substrate 4 of the liquid crystal cell thus configured, and a polarizing plate 10 is further arranged.

The operation of each optical element will be described below. In the reflective liquid crystal display device of the present invention, 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 on which the illumination light is incident. Therefore, at least the substrate 4, the electrode 6, and the alignment films 2 and 3 installed in the visible light path.
Is selected to have translucency. Only the linearly polarized light component of the specific direction of the illumination light is selectively transmitted by the polarizing plate 10, and the polarization state is changed by the optical phase difference compensating plate 8.

Here, examples of the plane arrangement of the liquid crystal display device are shown in FIGS. 2 (a), 2 (b) and 6 (a). These show a case where the liquid crystal alignment directions are different and the alignment change of the liquid crystal layer is changed in the plane of the substrate. here,
The retardation of the optical phase difference compensating plate 8 is selected to be 270 nm, the product of the refractive index difference and the liquid crystal layer thickness is selected to be 130 nm for the liquid crystal layer, and as shown in FIG. An example will be described where all of them are facing the same direction.

As shown in FIG. 2A, when the alignment direction 13 of the liquid crystal is deviated from the slow axis direction 12 of the optical phase difference compensating plate 8 by 60 degrees (= 45 degrees + θ2), dark display is realized. Then, when an electric field applied from there through to the liquid crystal layer acts on the liquid crystal layer to change the orientation by about 45 degrees, bright display is realized. 3A and 3B show the planar arrangement of Comparative Example 1. These are the case of performing the dark display and the case of performing the bright display in Comparative Example 1 without the optical phase difference compensating plate.

The reflectance for each wavelength when the arrangements shown in FIGS. 2 and 3 were adopted was calculated. The calculated result is shown in FIG. Curves 4-1 and 4-2 in FIG. 4 are reflection spectra of dark display in Embodiment 1 and Comparative Example 1, respectively. However, as the calculation method, the Jones matrix method is used, an ideal polarizing plate that completely transmits only one polarized light, complete reflection that is metallic reflection (electric field component in an arbitrary direction in the plane is reflected at a fixed end) A plane having a reflectance of 100%) is assumed. In addition, the display is such that the intensity of incident light is 100%, and the maximum reflectance is 50% because of an ideal polarizing plate.

As shown in the calculation result, in the dark display in Comparative Example 1, the reflectance does not become sufficiently small on the short wavelength side and the long wavelength side of the visible wavelength, whereas in the first embodiment, It is sufficiently lowered, and good dark display is realized.

Further, FIG. 5 shows the result calculated by the same method and assumption for the bright display. Curve 5-1 in FIG.
a, 5-1b, and 5-1c show that the liquid crystal alignment direction in the first embodiment is 15 from dark display (θ1 = 75 degrees).
Change by 30 degrees, 45 degrees, θ1 = 90 degrees, 105 degrees,
It is a reflection spectrum in the case of 120 degrees. Also, curve 5
2a, 5-2b, and 5-2c are reflection spectra of θ1 = 60 degrees, 75 degrees, and 90 degrees, which showed the same orientation change in Comparative Example 1. The curves 5-1c and 5-2
c has almost the same curve.

As shown in the calculation result, the bright display in the first embodiment shows a large difference from that of the comparative example 1 having the same switching angle even when the switching angle is 45 degrees or less. As a result, there is almost no change in the characteristics of bright display. Especially, in the case of the brightest display compared by the curves 5-1c and 5-2c, no characteristic change was observed, and it was confirmed that the bright display was not deteriorated even by using the optical phase difference compensating plate.

<< Conditions Required for Liquid Crystal Layer >> Conditions for the liquid crystal layer that enable such good display will be further described. First, it is necessary to have a liquid crystal layer having an appropriate birefringence with respect to light passing through the liquid crystal layer in the direction normal to the display surface in either of the alignment arrangements for displaying bright display and dark display. is there. Further, the orientation of the liquid crystal layer needs to be controlled and changed so that the orientation is different in the plane of the substrate. Here, the amount of birefringence of the liquid crystal layer is the amount of birefringence of the liquid crystal with respect to light traveling in the direction normal to the display surface, and the orientation of the liquid crystal layer is in the plane of the substrate as shown in FIG. No need to
It may be inclined in the direction of the substrate normal. Including such a case, the birefringence amount of the liquid crystal layer can be defined by Expression 1.

[0046]

[Equation 1]

Here, n _e : the extraordinary refractive index of the liquid crystal, n _o :
Ordinary refractive index of the liquid crystal, Δn = n _e -n _o: difference in refractive index between the liquid crystal,
d: The thickness of the liquid crystal layer.

The different alignment arrangement included in the plane including the substrate normal will be further described with reference to FIG. Figure 6
(A) is a perspective view showing what kind of switching operation is required for the alignment of the liquid crystal layer. A good liquid crystal display device can be realized by controlling the arrangement between different liquid crystal orientations shown here. Further, as long as the liquid crystal is included in the plane shown here, the liquid crystal may have an inclination in the normal direction to the substrate.

The z direction in FIG. 6B is a coordinate axis taken in the normal direction to the substrate, and the tilt angle of the liquid crystal alignment measured from this direction is θ _LC . This value is determined by the alignment of the liquid crystal and is a function of the coordinate z. Light traveling in the normal direction of the display device, passing through the liquid crystal layer of the bearing is inclined by theta _LC, influenced by different birefringence according theta _LC. The birefringence, when Δn is small compared to n _o is the polar angle theta _LC, is sufficiently approximated by Equation 2 below.

[0050]

[Equation 2]

Therefore, when the product of this and the integral line element dz is integrated over the layer thickness of the liquid crystal, the birefringence amount for the light passing through the liquid crystal layer is calculated. When the liquid crystal alignment is included in the plane including the substrate normal, that is, when no twist is seen between the upper and lower substrates, the change in light is determined only by this birefringence amount. It is possible to specify the property of the liquid crystal layer necessary for the present invention by the value of.

That is, the potential liquid crystal layer candidates are
The birefringence amount defined by this equation 1 is 100 to 18
The two orientations contained at 0 nm are controllable. Various liquid crystal orientations can be used as long as they satisfy this condition. As an example, a chevron layer structure, which is found in a so-called ferroelectric liquid crystal and which is found when a smectic C phase of a liquid crystal composition is formed into a layer, can be used. Further, it may be a smectic C phase in the antiferroelectric liquid crystal, and the nematic liquid crystal may be oriented so as to meet this condition.

Particularly in the case of nematic liquid crystal, the liquid crystal has a homogeneous alignment which is not twisted and which is oriented on a substrate which has been subjected to parallel alignment treatment, and an electric field which is generated in parallel to the substrate to control the liquid crystal in different directions, so that the liquid crystal is in the plane of the substrate. To have at least two orientations, and these may be electrically selected. Also, in a hybrid orientation in which one of them has been subjected to a vertical orientation treatment, the surface including the orientation has a substrate normal line. The electric field may be controlled to rotate about the axis.

Further, it is also possible to use an orientation twist and an electroclinic effect of a nematic liquid crystal due to a chiral additive or the like. It suffices that the alignment arrangement of the liquid crystal is substantially included in the plane perpendicular to the substrate. In other words, strictly speaking, even when there is a component that is not included in this plane, the thickness of the liquid crystal layer at that portion is so small that the component does not significantly contribute to the birefringence action of the liquid crystal layer, or the substrate normal line of the liquid crystal orientation. It is sufficient if the direction component is large. For example, in nematic liquid crystals, even if the liquid crystal alignment in the vicinity of the alignment layer placed on the substrate is deviated from this plane due to being constrained in the alignment treatment direction, it does not have a significant optical effect. It goes without saying that it is good. A reflective liquid crystal display device using a surface-stabilized ferroelectric liquid crystal for the liquid crystal layer was manufactured, and it was confirmed that the same result as the above calculation result was obtained. Therefore, a specific example will be described below.

[0055]

EXAMPLES Example 1 As a first example, an example in which a ferroelectric liquid crystal is used for a liquid crystal layer will be shown. A reflective liquid crystal display device similar to that shown in FIG. 1 was produced. On smooth substrates 4 and 6 made of borosilicate glass, ITO with a thickness of 150 nm was formed on 4 by sputtering, and aluminum on 6 was formed by vacuum evaporation on 100. Both of them were formed into a predetermined pattern by photolithography and etching to form a transparent electrode for display 7 and a reflective metal electrode 8, respectively. Further, a polyimide film was applied onto each electrode by a spin coating method, baked, and formed into alignment films 2 and 3. The alignment film thus formed is subjected to an alignment treatment by a rubbing treatment, sprayed with plastic spacers having an average particle diameter of 1.0 micron, and arranged in opposition to each other. It was cured and fixed under pressure.

Furthermore, a liquid crystal material exhibiting a smectic C phase at room temperature and a switching angle of 45 degrees (refractive index difference 0.145) is introduced between the substrates by a vacuum injection method, and a liquid crystal driving power source is further supplied. Connected The actual amount of birefringence of the liquid crystal layer thus produced was about 130 nm. This is slightly smaller than the product of the refractive index difference of the liquid crystal material and the diameter of the plastic spacer, which is 145 nm, but because the liquid crystal layer has a chevron structure having an elevation angle from the direction of the substrate surface, and due to the elasticity of the plastic spacer. . On the substrate 4 of this liquid crystal display device, an optical retardation compensation plate made of polycarbonate (having a retardation adjusted to 270 nm for light having a wavelength of 550 nm) and a polarizing plate (having a polarization degree of 99.9%) were arranged. . This installation orientation is set so as to realize FIGS. 2 (a) and 2 (b). In this way, Example 1 of the liquid crystal display device
Was produced.

A reflection type liquid crystal display device manufactured in substantially the same manner as in Example 1 without using an optical phase difference compensating plate, the polarization was changed so that the arrangements shown in FIGS. 3 (a) and 3 (b) were obtained. The plates were arranged to prepare Comparative Example 1. Table 1 shows the display evaluation results by visual observation of the liquid crystal display device thus manufactured.

[0058]

[Table 1]

As described above, it is shown that the dark display of the liquid crystal display device predicted by the calculation can be improved by adding the optical phase difference compensating plate. Furthermore, with this method, the brightness display did not change in both brightness and hue, and a good display was obtained even if the brightness display was combined.

Example 2 An example in which a concave-convex diffuse reflector is used in the reflective liquid crystal display system of Example 1 will be shown. Example 2 of the liquid crystal display device having the structure shown in FIG. 7 was produced. An insulating organic film 14 having an uneven shape is formed on a substrate 5, aluminum is formed as a light-reflecting metal film 15 on the substrate 5 by a vacuum vapor deposition method, and a transparent flattening insulating layer 16 for flattening the unevenness is formed. Is formed by spin coating of an organic film and a thermosetting process, and an electrode 17 having a thickness of 140 nm is formed thereon.
A thick ITO film was formed and formed by a sputtering method. The method of forming the uneven shape of the insulating organic film 14 is as follows.
A layer for covering these is formed, and a curved uneven shape having a good diffusion property is produced. In the shape of the unevenness thus produced, the difference between the peak and the valley was 1 μm.

The planarization insulating layer 16 on this has a layer thickness of 2-3.
In μm, a sufficiently flat surface was prepared. Also, the electrode 17
Was manufactured by dividing the electrode 17-1 and the electrode 17-2 with a distance of 5 μm by photolithography and etching so that the black and white display boundary could be observed. The light-reflecting substrate manufactured in this manner was processed in the same manner as in Example 1 by the same steps and materials as those used in Example 1.
Using a light-transmissive substrate similar to
Example 2 of a reflective liquid crystal display device was produced by introducing a liquid crystal composition, adhering an optical retardation compensating plate and a polarizing plate, and connecting a drive test voltage applying means. As the polarizing plate 10, an observer side is provided with an AR coating of an optical thin film.

The reflection type liquid crystal display device of Example 2 manufactured in this way has a sufficiently good image quality when the same voltage is applied to the liquid crystal on the electrode 17-1 and the electrode 17-2. It was confirmed that a good black-and-white display with no clutter was obtained, and that a display with a good scattering function was given.

Further, different voltage waveforms were applied to the electrode 17-1 and the electrode 17-2, white display was performed on the electrode 17-1 and black display was performed on the electrode 17-2, and visual observation was performed. As a result, good display division was realized at the boundary of each electrode. In particular, it was observed whether or not there was bright display bleeding at this boundary, but this was not observed.

As described above, it was confirmed by the concave-convex reflective substrate that the light-scattering functional layer close to the substrate provided a display with good resolution. The same effect is obtained with the uneven reflector,
It can be realized even if the reflecting plate 15 has no unevenness and the insulating layer 16 has a light scattering property. Further, such a light scattering layer is provided on the substrate 4
It is effective to form a light scattering film on the liquid crystal layer side of
Needless to say.

Example 3 Further, in order to confirm that the configuration of the present invention is effective even when the orientation which realizes such an orientation change is used in the nematic liquid crystal,
Comparative Example 2 and Example 3 having comb-shaped electrodes were produced.
FIG. 8 shows the structure of the reflective liquid crystal display device manufactured as Example 3. The comb-shaped electrode 18 is formed on the substrate 5 and changes the liquid crystal alignment by an electric field generated by applying different voltages to the adjacent electrodes 18-1 and 18-2.

The reflective film 7 is made of a metal having a light reflectivity, and is electrically insulated from the electrodes 18-1 and 18-2 through the insulating film 19. The first purpose of the thus-insulated metallic reflective film 7 is to reflect light, but it may also serve other purposes. That is, for example, the electrodes 18-1 or 18
When any one of -2 is driven by active matrix, it may also serve as an auxiliary capacitance line for assisting the liquid crystal holding operation. Further, it may have a shielding effect for preventing the influence of an electric field such as a bus line on the liquid crystal, and further, as shown in FIG. 8, a stray capacitance formed between 18-1 and the reflection film 7 The stray capacitance formed on the reflective film 7 and the electrode 18-2 may be used as the auxiliary capacitance.

The change in the liquid crystal orientation changes the orientation so that the liquid crystal orientation changes in the plane of the substrate, as in the other embodiments of the present invention. At this time, the birefringence amount of the liquid crystal defined by Expression 1 is set in a predetermined range suitable for reflective display, but this has different optical parameters from the values used for transmissive display. A liquid crystal material having Δn of 0.065 was used, and the liquid crystal layer thickness was set to 2.5 μm.

The liquid crystal orientation of the reflection type liquid crystal display device thus manufactured will be described. As shown in FIG. 8, the voltage between the comb electrodes 18-1 and 18-2 is changed from 0V to 5V.
When changed over the above, the optical action of the liquid crystal layer is the change of the birefringence amount shown in FIG. 9 (a) and the direction of the slow axis shown in FIG. 9 (b) (the direction of the plane including the orientation of the liquid crystal). It was confirmed that the change of). Here, the method for confirming the birefringence amount and the slow axis azimuth is a part in which a part of the reflection plate of the reflection type liquid crystal display device of Example 3 shown in FIG. (Not shown) by polarization analysis of transmitted light.

When no voltage was applied, the amount of birefringence was large and around 160 nm, and when the voltage was high (5 V), it was around 130 nm. That is, in both cases, it was included in the range of 100 nm to 180 nm. The amount of birefringence when voltage is applied is the same as that in which the liquid crystal is aligned substantially uniformly, but more specifically, there is a component in the direction normal to the liquid crystal substrate. It is considered that there is a component in the vicinity of the substrate interface, which is oriented in the direction of the alignment treatment applied to the substrate.

First, in order to examine whether or not good display is possible without using an optical phase difference compensating plate in a liquid crystal portion having such a liquid crystal orientation, a polarizing plate is provided as shown in FIG. 10 (b). It was arranged and made into Comparative Example 2. This comparative example realizes the same planar arrangement as that of the comparative example 1 in a liquid crystal display device using comb-shaped electrodes.

At this time, a normally black display was realized in which the orientation when no voltage was applied was used for black display, and the reflectance increased with the application of voltage, resulting in a good display.

In Comparative Example 2, the display changed from dark display to bright display as the voltage increased, but good dark display was not obtained. That is, in the case of the dark display, the display is blue, and the black display is not realized.

Therefore, the polarizing plate of Comparative Example 2 was removed, and the optical retardation compensating plate 8 made of polycarbonate and having a retardation of 300 nm and the polarizing plate 10 were arranged. In addition to the polarizing plate and liquid crystal alignment when no voltage is applied, FIG.
It is manufactured so as to have the orientation described in 0 (a). Similarly, the liquid crystal display device according to Example 3 also displayed a normally black display, and the dark display was a good black display. In addition, the brightness display does not deteriorate in brightness and hue.

The conductive material used for the comb electrodes 18 is not particularly specified. In the case of a light-reflecting metal electrode, this has the effect that the reflectivity of this metal increases the utilization efficiency of light for reflective display. Further, even with a light transmissive electrode, there is an advantage that the lightness is not lowered by disposing the light reflecting film 7 thereunder.

[0075]

According to the present invention, in the one-sheet polarizing plate system capable of high-brightness and high-resolution display, when the liquid crystal changes its orientation in the plane of the substrate, a good black color which has not been realized so far is obtained. The display is realized. By this method, it is possible to realize a reflection type liquid crystal display device having a good display without a decrease in brightness of bright display and a hue change.

[Brief description of drawings]

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

FIG. 2 is a plan view showing setting directions of a polarizing plate and an optical phase difference compensating plate of the liquid crystal display device of Embodiment 1.

3 is a plan view showing setting directions of a polarizing plate and an optical phase difference compensating plate of the liquid crystal display device of Comparative Example 1. FIG.

FIG. 4 is a diagram showing calculation results of a reflection spectrum of dark display in the configurations of the liquid crystal display devices of Embodiment 1 and Comparative Example 1.

FIG. 5 is a diagram showing calculation results of a reflection spectrum of bright display in the configurations of the liquid crystal display devices of Embodiment 1 and Comparative Example 1.

6A and 6B are conceptual views for explaining liquid crystal alignment of a liquid crystal display device, FIG. 6A is a cross-sectional perspective view showing the concept of two states of alignment alignment of liquid crystal, and FIG. It is explanatory drawing for demonstrating the variable of a formula.

FIG. 7 is a structural cross-sectional view of a reflective liquid crystal display device according to a second example.

FIG. 8 is a structural cross-sectional view of a reflective liquid crystal display device according to a third embodiment.

9A and 9B are characteristic diagrams showing an optical action of a liquid crystal layer of the liquid crystal display device described in Example 3, respectively.

FIG. 10 is a plan layout view showing setting directions of optical elements of a liquid crystal layer of a liquid crystal display device according to Example 3, (a) is a setting view of optical elements of Example 3, and (b) is a comparison. 6 is a setting diagram of the optical element of Example 2. FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Liquid crystal layer 2, 3 Alignment film 4, 5 Substrate 6 Electrode 7 Reflective electrode 8 First optical phase compensation plate 10 Polarizing plate 11 Polarizing plate transmission direction 12 Slow axis direction 13 of first optical phase compensation plate 13 Liquid crystal layer Orientation of a straight line formed by intersecting the plane including the orientation arrangement of the display plane and the display plane 14 Organic insulating film 15 having an uneven shape Metal reflection film 16 Smoothing film 17-1, 17-2 Transparent display electrode 18-1, 18- 2 Metal display comb-shaped electrode

Claims (6)

(57) [Claims] 1. A first substrate having at least light reflectivity, a second substrate having light transparency, a liquid crystal layer having a liquid crystal composition sandwiched between the first and second substrates, and the liquid crystal layer. It comprises a single polarizing plate disposed in an optical path for viewing the first
In the reflective liquid crystal display device in which the substrate, the liquid crystal layer, and the polarizing plate are laminated in this order, the liquid crystal alignment has at least first and second liquid crystal alignment positions that are electrically selectable, first and second liquid crystal alignment position of both liquid crystal orientation in the plane including the substrate normal is substantially contained, and the orientation of the plane containing the substrate normal to the orientation arrangement is substantially free from each other A value obtained by integrating the refractive index difference of the liquid crystal layer with respect to light traveling in the direction normal to the substrate over the thickness direction of the liquid crystal layer is different for any given light in the visible range in any alignment arrangement.
/ 4 wavelength condition , 100 nm to 180 nm
It is set to one of the, further, between the liquid crystal layer and the polarizing plate, the moisture of the substrate normal direction
Retardation against overlight is 200 nm to 360
(1/2 + n (n
Is an integer greater than or equal to 0))
Is provided , and the transmission axis (or absorption axis) of the polarizing plate and the liquid crystal layer
Liquid crystal alignment in either liquid crystal alignment
The angle formed by the projection and the slow axis of the optical retardation compensator
When the angles formed are θ1 and θ2, respectively, | 2 × θ2−θ1 | at the first liquid crystal alignment position
The value is 35 ° or more and 55 ° or less, and the second liquid
The value of | 2 × θ2-θ1 | at the crystal orientation position is 60 ° or less.
A reflective liquid crystal display device, characterized in that the reflective liquid crystal display device is installed at an angle of 120 ° or less . 2. The reflective liquid crystal display device according to claim 1, wherein the liquid crystal composition is a ferroelectric liquid crystal, an antiferroelectric liquid crystal, or a nematic liquid crystal.
A reflective liquid crystal display device characterized by being formed of any one of matic liquid crystals . 3. The reflective liquid crystal display device according to claim 1, wherein the liquid crystal composition is a smectic C phase and a chevron layer.
A reflective liquid crystal display device characterized by being composed of a ferroelectric liquid crystal having a structure . 4. The reflective liquid crystal display device according to claim 1 , wherein light scattering is close to the liquid crystal layer.
A reflective liquid crystal display device characterized in that a functional layer is disposed . 5. The reflection type liquid crystal display device according to claim 4 , wherein the light scattering functional layer adjacent to the liquid crystal layer has an uneven shape.
A reflection type liquid crystal display device, which is a light diffusive reflection layer having . 6. A reflective liquid crystal display device according to claims 1 to 5, the reflection type liquid crystal display device wherein the any given light is green.