JPH08297280A - Liquid crystal display device - Google Patents

Abstract

PURPOSE: To obtain a bright liquid crystal display device which is thin and light, is low in electric power consumption and is good in utilization efficiency of light. CONSTITUTION: Incident light is converted to linearly polarized light via a polarizer 40 and the linearly polarized light is made incident on a liquid crystal layer 38. A display voltage is impressed on transparent electrodes 34, 36 by a modulation control means 42 and the double refraction quantity of the liquid crystal layer 38 is controlled by changing the electric field with respect to the liquid crystal layer 38. Only the light of the specific polarization component in the specific wavelength region of the exit light from the liquid crystal layer 38 modulated in the polarization state is selectively reflected in chiral nematic liquid crystals 39. Then, the efficient conversion of the incident linear polarized light to circularly polarized light by the liquid crystal layer 3 having double refractiveness is possible, the half of external light is, therefore, utilized and bright display is obtd. The switching of all reflection or all transmission is made possible by making, for example, left circularly polarized light or right circularly polarized light. The display of extremely bright contrast is thus obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device for performing monochrome display or color display.

[0002]

2. Description of the Related Art Conventionally, a display element in a liquid crystal display device of this type has a low power consumption because it is a non-luminous element that modulates external light, and is thin and lightweight because it can be applied to a flat panel display. It is used in a wide range of fields as an information display device used for clocks, calculators, computer terminals, word processors, television receivers, and the like.

On the other hand, in the present age, as typified by the keyword of advanced information society, the amount of information distribution is increasing, and the demand for collecting and selecting information in each individual is increasing. Against this social background, the need for personal portable information terminals has been widely recognized, and its realization is expected, and development is being actively pursued.

In this portable information terminal, an information display device as a man-machine interface plays an important role and is positioned as a key device of this device.

Further, the display device of this portable information terminal is required to display a large amount of information, be lightweight and thin, have excellent visibility, and have low power consumption. It is expected as a display element that satisfies such characteristics, and its development is being actively promoted.

By the way, when the liquid crystal is used as a display element of a portable information terminal, it is desirable that color display can be performed in view of the amount of display information. When color display is performed using liquid crystal, a micro color filter method in which red, green, and blue color filters are formed for each display pixel in a liquid crystal cell is used, and the light intensity of each color is changed by various methods described later. By the modulation, color display is performed by the additive color mixing method with a plurality of pixels. Most of the color liquid crystal display systems currently in practical use use this system.

A method for performing color display by using a color polarizer in place of this color filter (Japanese Patent Laid-Open No. 17420/58 and Japanese Patent Laid-Open No. 17421/58).
Issue) is also proposed. In this method, color display is possible by patterning the color polarizer for each pixel.

An actual color liquid crystal display device can be realized by combining the above-described colorization system with various display systems for modulating light intensity.

As a typical method for modulating the light intensity, there is a TN (Twisted Nematic) method. This method uses a liquid crystal cell in which liquid crystal is arranged between two substrates and the orientation of liquid crystal molecules is twisted by 90 degrees from one substrate to the other substrate. As described above, when the liquid crystal molecules are aligned, they exhibit optical rotatory power optically, and when the alignment of the liquid crystal molecules is changed by the voltage applied between the electrodes, the optical rotatory power is eliminated. As a result, the amount of transmitted light changes, and the light intensity can be modulated, and display can be performed.

This TN system has a low voltage and a low power consumption, has a good contrast, and can display a gradation.
It is most widely used for liquid crystal displays among various operation modes.

The TN method has many excellent features as described above, but since the threshold characteristic is not steep,
That alone is not suitable for large-capacity display. Therefore, when displaying a large capacity, it is generally used in combination with an active element such as a thin film transistor (hereinafter referred to as a TFT).

On the other hand, the so-called STN (Super Twisted NeW), in which the twist angle of liquid crystal molecules is larger than 90 degrees,
matic) method has been proposed. This method uses optical rotatory power and birefringence effect, and has a steep threshold characteristic, so that it is suitable for multiplex driving, and large-capacity display can be performed without using an active element such as a TFT. .
However, in this display method, black and white display could not be performed at first because the optical rotation and the birefringence effect were utilized. After that, achromatic coloring was achieved by optically performing phase compensation, and it is now widely used as a display device of a word processor or a portable computer.

In addition, a guest-host (display) is performed by mixing a dichroic dye in the liquid crystal and changing the orientation of the liquid crystal molecules to orient the dye molecules and utilizing the absorption anisotropy. GH) method. The guest-host system includes a Heilmeier type that uses a polarizing plate and a phase transition type that does not use a polarizing plate.

The guest-host system has a feature that the viewing angle is wide in both systems. In addition, since the phase transition type display can be performed without using a polarizing plate, a bright display can be realized.

Further, a display system has been proposed in which liquid crystal is dispersed in a polymer matrix and a scattering effect due to a mismatch in refractive index between the polymer and the liquid crystal is utilized. This method also
Since the display can be performed without using a polarizing plate, a bright display can be realized and the viewing angle is wide.

Further, using a ferroelectric liquid crystal (FLC),
A method utilizing the birefringence effect has also been proposed. This system is characterized in that it has a very fast response speed and also has a memory property.

Each of the above-mentioned methods is a combination of a color separating means and a light intensity modulating means, but in addition, a color display method using a liquid crystal has been proposed.

A method of providing a color display by providing a liquid crystal layer capable of controlling the wavelength of transmitted light on the front surface of a monochrome display device and switching the wavelength of transmitted light in time sequence (Proc. Eurodispl
ay 7 page (1984)) has also been proposed. This is CR
A liquid crystal optical shutter having a color filter function is placed in front of a light emitting element such as T, and the liquid crystal shutter having a color filter function is synchronized with the formation of red, green and blue images by the light emitting element. Switch in order. By repeating this in time sequence, color display is performed.

It is well known that when a substance having a birefringent property is inserted between orthogonal polarizers, an interference color depending on the phase difference between ordinary light and extraordinary light is exhibited. Therefore, by utilizing the birefringence of liquid crystal, an electric field control birefringence (ECB) effect of controlling the birefringence amount of a liquid crystal cell by an electric field is used to
Multi-color display with pixels (Appl.Phys.Lett. Vol. 19, 391 page (1971), Electronics Lett. Vol. 7, 699 page (1971))
Is also proposed.

In addition, a method of performing color display by enclosing a guest / host liquid crystal to which a dichroic dye having a different absorption wavelength is added for each pixel (Japanese Patent Application Laid-Open Nos. 55-9515 and 55-26584). ) Or a liquid crystal cell using guest-host liquid crystals with different absorption wavelengths is stacked to display a color by subtractive color mixing (Proc.SID
22 volumes and 41 pages (1981)) are also proposed. Furthermore,
A method of displaying by utilizing the selective reflection phenomenon of cholesteric liquid crystal has also been proposed.

The phenomenon in which this cholesteric liquid crystal selectively reflects light having a wavelength corresponding to its spiral pitch is described in the literature (Appl. Opt. Vol. 7, No. 1, 1729 page (1968), Phys. Rev. Lett. 2).
It is well known for example, Volume 5 No. 9 577 Page (1970)). Specifically, the right-handed cholesteric liquid crystal has an anisotropy of incident light in the range of Δλ = 2Δn · p (1), where Δn is the refractive index anisotropy of the liquid crystal, p is the pitch, and Δλ is the reflection center wavelength. Only the right-handed circularly polarized light component is selectively reflected, and the right-handed circularly polarized light components of other wavelengths and the left-handed circularly polarized light components of all wavelengths are transmitted.

At this time, the reflection center wavelength λm is represented by λm = na · p (2). However, na is the average refractive index of the liquid crystal.

Further, the left-handed cholesteric liquid crystal operates in the opposite manner to the right-handed cholesteric liquid crystal described above.

That is, FIG. 9 schematically shows the selective reflection phenomenon of the left-handed cholesteric liquid crystal. As shown in FIG. 9, when the right-handed and left-handed circularly polarized light components are incident on the left-handed cholesteric liquid crystal, only the left-handed circularly-polarized light component of the incident light in a predetermined wavelength range is selectively reflected, and other wavelengths The left-handed circularly polarized light component and the right-handed circularly polarized light components of all wavelengths are transmitted through the cholesteric liquid crystal layer.

Here, a cholesteric liquid crystal is first mentioned as one having a selective reflection effect, but a chiral nematic liquid crystal in which a chiral agent is added to a normal nematic liquid crystal and a chiral smectic liquid crystal are optically equivalent to the cholesteric liquid crystal. The selective reflection effect is shown. Cholesteric liquid crystals are generally unstable and unreliable in a chemical atmosphere or ultraviolet rays. On the other hand, the chiral nematic liquid crystal is excellent in light resistance and stable,
A chiral nematic liquid crystal is generally used in practice because the pitch is relatively easy to adjust, the reflection wavelength width is easy to adjust, and the material selection range is wide. Therefore, in the following description, a chiral nematic liquid crystal will be used unless otherwise specified. However, even if the chiral nematic liquid crystal is a cholesteric liquid crystal or a chiral smectic liquid crystal, there is no particular difference in the following description.

Conventionally, various optical elements have been proposed by utilizing the unique optical characteristics of this chiral nematic liquid crystal.

Specifically, a right-handed chiral nematic liquid crystal cell and a left-handed chiral nematic liquid crystal cell are stacked, or a half wavelength is provided between two right-handed or left-handed chiral nematic liquid crystal cells. There is an optical notch filter (J. Appl. Phys. 42, Vol. 10, 4096 pages (1971)) with a plate inserted.

Further, by selecting a material, a chiral nematic liquid crystal whose spiral pitch is sensitive to temperature can be produced,
This is used for thermometers, accessories, etc., and color display is performed by changing the temperature (Japanese Patent Application Laid-Open No. 55-55).
No. 45022) is also proposed.

Further, this chiral nematic liquid crystal is used as a reflector, and the DSM using the dynamic scattering effect of the liquid crystal.
A system and a system in which display is performed in combination with a liquid crystal valve of a phase transition system (JP-A-59-116680 and JP-A-60-133426) have also been proposed.

Similarly, a projection type display device is realized by combining the chiral nematic liquid crystal and a light valve utilizing the scattering effect of the polymer dispersion type liquid crystal display system.
Documents (JP-A-4-188111 and JP-A-4-188111)
No. 188112).

Further, the selective reflection by the cholesteric liquid crystal polymer and the TN display system are combined, and further ¼
A method of displaying by combining a wave plate (Japanese Patent Laid-Open No. 6-23
No. 0362) has been proposed. This utilizes the optical rotatory power of the TN liquid crystal cell, and by rotating the polarization direction by 90 ° with and without voltage application,
The display is performed by switching the polarization direction incident on the / 4 wavelength plate and switching the left and right circularly polarized light. The structure of this display element is shown in FIG.

In FIG. 10, the transparent substrate 2 and the alignment film 3 are sequentially provided on the upper substrate 1 to form an electrode substrate, and the transparent electrode 5 and the alignment film 6 are sequentially provided on the lower substrate 4. An electrode substrate is constructed. These electrode substrates are arranged so that the alignment films 3 and 6 face each other, and the liquid crystal 7 is sandwiched between them to form a liquid crystal cell. A polarizing plate 8 is provided on the light incident side of the upper substrate 1 of this liquid crystal cell, and a quarter wavelength plate 9, a cholesteric liquid crystal polymer film 10 and a light absorbing plate 11 are provided on the lower substrate 4 side.

Considering the action of the quarter-wave plate 9 in this configuration, the TN layer of the liquid crystal 7 is used as an element for switching the polarization direction of light, and therefore the TN layer is used.
When no electric field is applied to the layer (OFF), linearly polarized light of −45 ° with respect to the optical axis of the quarter wavelength plate 9 enters the quarter wavelength plate 9 as shown in FIG. Quarter wave plate 9
After passing through, it becomes right circularly polarized light. On the other hand, T
When a sufficient electric field is applied to the N layer (ON), the opposite phenomenon occurs. That is, with respect to the optical axis of the quarter wavelength plate 9,
Linearly polarized light incident in the direction of 45 ° (−45 ° or + 45 °) is converted into right circularly polarized light or left circularly polarized light depending on the polarization direction. In this way, by rotating the polarization direction by 90 ° with and without applying a voltage, the quarter wavelength plate 9
Display is performed by switching the direction of polarization incident on the TN layer and switching the left and right circularly polarized light.

Next, selective reflection by a cholesteric liquid crystal polymer is combined with a display system such as TN, ECB, STN, FLC, phase transition type guest-host, polymer dispersed type guest-host, and a quarter wave plate is further added. A method in which the output light is circularly polarized in combination and the amplitude intensity thereof is modulated by the above-mentioned display method to perform display (JP-A-6-23).
No. 0371) is also proposed. FIG. 11 shows the structure of this display element in the case of using the TN method.

In FIG. 11, an electrode substrate is constructed by sequentially providing a transparent electrode 22 and an alignment film 23 on an upper transparent substrate 21, and a transparent electrode 25 and an alignment film 26 on a lower transparent substrate 24. The electrode substrates are sequentially provided to form an electrode substrate. These electrode substrates are arranged so that the alignment films 23 and 26 face each other, and the liquid crystal 27 is sandwiched between them to form a liquid crystal cell. A polarizing plate 28 is provided on the light incident side of the transparent substrate 21 of this liquid crystal cell, and a polarizing plate 29, an adhesive layer 30, and a quarter wavelength plate 3 are provided on the light emitting side of the transparent substrate 24.
1, adhesive layer 32, cholesteric liquid crystal polymer reflector 3
3 Further, a light absorbing plate 34 is sequentially provided.

Further, there is also a document (Japanese Patent Laid-Open No. 35478/1988) in which a head-up display is constructed by synthesizing an image formed by CRT or LCD and an image of the outside world by using a chiral nematic liquid crystal element as a half mirror. .

As another example, a structure in which a nematic liquid crystal cell is inserted between two right-handed or left-handed chiral nematic liquid crystal cells is laminated to form a three-layer structure, and the amount of transmitted light in a specific wavelength range is A liquid crystal with three different kinds of chiral nematic liquid crystals with different helical pitches is controlled to control different wavelength ranges by a total of nine liquid crystal layers, and the spectrum of transmitted light is arbitrarily changed. Color light valve (IEEE Tran.Elect.De
v.ED-21 volume 171 pages (1974)). This is to apply a voltage to the above-mentioned nematic liquid crystal cell to change its retardation and modulate the amount of transmitted light.

By directly applying a voltage to the chiral nematic liquid crystal layer, the spiral pitch of the chiral nematic liquid crystal is changed to perform color display (Mol. Cryst. 1).
Volume 325 Page (1966), Phys.rev. Lett. 24 Volume 209 Page (1970)
Year)) is also proposed. This is a system in which the selective reflection wavelength is varied by applying an electric field parallel or perpendicular to the spiral axis of the chiral nematic liquid crystal and changing the spiral pitch.

In addition, a color display system which utilizes selective reflection of a chiral nematic liquid crystal dispersed in a polymer matrix to perform display in a scattering state when no voltage is applied and a selective reflection state when a voltage is applied (JP-A-3- 209425) is also proposed.

[0040]

However, the above-mentioned conventional liquid crystal display device will first be described as having the following problems when applied to color display.

That is, in the method of forming a micro color filter for each pixel, only one color of light passes through the color filters of three colors such as red, green and blue, and the light of other colors is absorbed. Therefore, even if any of the liquid crystal display methods described above is combined, the light utilization efficiency is theoretically 1/3 or less of the total light amount, and there is a problem in light utilization efficiency.

Further, since the display system used conventionally is mainly the TN system or STN system using a polarizer, more half of the external light is absorbed and the light utilization efficiency is further deteriorated. That is, when the micro color filter is combined with the TN method or the STN method, there is a problem that in principle, only 1/6 of the external light can be used.

Further, in the TN system, it is necessary to form an active element for each pixel in order to display a large capacity.
Since this blocks light, there is a problem that the light utilization efficiency is further deteriorated. Further, for the purpose of improving the contrast, a light-shielding layer called a black matrix is provided in a portion other than the display pixels, which further deteriorates the light use efficiency.

In addition, in the TN type large capacity display device to which the active element is added, there is a problem that the disclination occurs due to the lateral electric field between the adjacent pixels and the contrast is lowered, which is solved. In order to achieve this, a technique of covering the disclination portion with a light shielding layer to improve the contrast is used. This is also a factor that deteriorates the light use efficiency.

Due to the various reasons described above, in the large-capacity display color display using the TFT which is generally used at present, the typical utilization efficiency of the external light is only 1 to 5%.

Therefore, the display using the conventional color display system requires an external light source such as a backlight in order to obtain a bright display. This makes it possible to obtain an easy-to-read display, but on the other hand, the backlight consumes more power than the liquid crystal consumes, and the backlight and its optical system become thicker than the liquid crystal display. is what happened.

In this case, it cannot be said that the excellent characteristics inherent in the liquid crystal display such as thinness, light weight and low power consumption are sufficiently exhibited.

Further, in the conventional color display system in which the guest-host system is laminated, the light utilization efficiency is higher than that in the above-described system, and a bright display is obtained. However, since the threshold characteristic is not steep, it is necessary to form an active element such as a TFT for each pixel in order to perform large-capacity display, and if this is multilayered, manufacturing becomes difficult and the manufacturing cost increases. was there. Therefore, the stacked guest-host method is not applied to large-capacity display.

Furthermore, the method using different color polarizers for each pixel is difficult to manufacture and has not yet been put to practical use.

Further, a system in which a liquid crystal layer capable of controlling the wavelength of transmitted light is provided on the front surface of a monochrome display device and the wavelength of transmitted light is switched in time sequence has a feature that a high resolution display can be realized. When displaying in red, green, and blue for switching, the brightness becomes 1/3 of the incident light, and there is a problem in terms of light utilization efficiency.
Furthermore, since it is the light emitting display element that forms the image,
There was also a problem that the reflection type could not be realized.

Further, in the color display utilizing the electric field control birefringence effect, multicolor display is possible with one pixel, but the purity of the displayable color is not good, the display color is sensitive to temperature, and There was a problem that the color changed depending on the viewing direction.

An example in which color display is performed by changing the temperature of the chiral nematic liquid crystal is not excellent in controllability and the response speed is slow, so that it has not been put to practical use.

In the conventional structure in which the chiral nematic liquid crystal layer is used as the reflection plate and various liquid crystal display systems are combined with the quarter-wave plate, the combination with the scattering type liquid crystal display element does not have sufficient contrast and is driven. There were problems such as high voltage. Also, TN, ECB,
FIG. 11 shows the combination of STN and FLC to modulate the light intensity.
In the case as shown in (2), it is necessary to use two polarizers, and there is a problem that the display is dark. Further, the combination with the phase transition type guest-host system has a problem that the contrast is not sufficient, it is not suitable for a large capacity, and the response speed is slow. In addition, it is necessary to combine a quarter-wave plate in each case, and the presence of the quarter-wave plate makes the display darker, increases the number of constituent elements, and complicates the structure and increases the manufacturing cost. was there.

The method of inserting a nematic liquid crystal cell between two chiral nematic liquid crystal cells and stacking them to perform color display requires a backlight because it is a transmissive type, and nine liquid crystal cells. There is a problem that a cell becomes necessary, the display portion becomes thick, and the weight increases. The method of directly applying a voltage to the chiral nematic liquid crystal layer has a problem that it is difficult to perform multicolor display because the change in the selective reflection wavelength is small, the driving voltage is high, and the intensity cannot be modulated.

The method utilizing selective reflection of the chiral nematic liquid crystal dispersed in the polymer matrix has the same drawbacks as the method using the scattering state in which the liquid crystal is dispersed in the polymer. That is, the contrast cannot be sufficiently obtained and the driving voltage is high.

As described above, the conventional display system cannot be said to fully exhibit the excellent features of the liquid crystal display element, such as thinness, light weight, and low power consumption, and is insufficient as a display device for a portable information terminal. Therefore, there is a demand for a display system for a new information display terminal which is bright, has excellent visibility, and is capable of color display.

An object of the present invention is to solve the above conventional problems, and to provide a liquid crystal display device which is thin, lightweight, has low power consumption, and has good light utilization efficiency and is bright.

[0058]

The liquid crystal display device of the present invention comprises a polarizer for converting incident light into linearly polarized light, a selective reflection layer for selectively reflecting only light of a specific polarization component in a specific wavelength region, By controlling the birefringence amount of the liquid crystal layer provided between the polarizer and the selective reflection layer and exhibiting optical birefringence and the liquid crystal layer on which the linearly polarized light from the polarizer is incident, by controlling the electric field. A modulation control unit that modulates the polarization state of the light emitted from the liquid crystal layer to modulate the intensity of the reflected light from the selective reflection layer is provided, thereby achieving the above object.

In addition, the liquid crystal display device of the present invention includes a first color polarizer that converts only light in the first wavelength range into linearly polarized light, and a first color polarizer that selectively reflects only light of a specific polarization component in the first wavelength range.
A selective reflection layer, and a first element section having a first liquid crystal layer provided between the first color polarizer and the first selective reflection layer and exhibiting birefringence in light in the first wavelength range, A second color polarizer that converts only light in a second wavelength range different from the first wavelength range into linearly polarized light, a second selective reflection layer that selectively reflects only light of a specific polarization component in the second wavelength range, and Provided between the second color polarizer and the second selective reflection layer,
A second element part having a second liquid crystal layer exhibiting birefringence in light of a wavelength range, and a third color for converting only light of a third wavelength range different from the first and second wavelength ranges into linearly polarized light. A polarizer, a third selective reflection layer that selectively reflects only light of a specific polarization component in the third wavelength region, and a third selective reflection layer that is provided between the third color polarizer and the third selective reflection layer. By controlling the birefringence amount of the third element part having the third liquid crystal layer exhibiting birefringence in the light of the three wavelength regions and the first, second and third liquid crystal layers on which the linearly polarized light is incident, by the electric field, respectively. Modulation control means for respectively modulating the polarization states of the light emitted from the first, second and third liquid crystal layers and respectively modulating the reflected light intensities from the first, second and third selective reflection layers. There, the above object is achieved thereby.

Further, the liquid crystal display device of the present invention comprises the first
A polarizer capable of converting light in the wavelength range, the second wavelength range, and the third wavelength range into linearly polarized light, a first selective reflection layer that selectively reflects light of a specific polarization component in the first wavelength range, and a second wavelength range A selective reflection layer having a second selective reflection layer that selectively reflects light of a specific polarization component and a third selective reflection layer that selectively reflects light of a specific polarization component in a third wavelength region; A liquid crystal layer which is provided between the child and the selective reflection layer and which optically exhibits birefringence in the light of the first wavelength band, the second wavelength band and the third wavelength band, and the linearly polarized light from the polarizer. Modulation control means for modulating the polarization state of the light emitted from the liquid crystal layer by controlling the amount of birefringence of the incident liquid crystal layer by an electric field and respectively modulating the intensity of reflected light from the selective reflection layer. It is provided, and the above-mentioned object is achieved thereby.

Further, preferably, a cholesteric liquid crystal, a chiral nematic liquid crystal, a chiral smectic liquid crystal, the above film-formed liquid crystal, or the above-mentioned microencapsulated liquid crystal is used as the selective reflection layer in the liquid crystal display device of the present invention.

Further, the liquid crystal display device of the present invention comprises a polarizer for converting light in the first wavelength band, the second wavelength band and the third wavelength band into linearly polarized light, and a light having a specific polarization component in the first wavelength band. A first cholesteric liquid crystal or a chiral nematic liquid crystal or a chiral smectic liquid crystal that selectively reflects
A second cholesteric liquid crystal, a chiral nematic liquid crystal, or a chiral smectic liquid crystal that selectively reflects light of a specific polarization component in the second wavelength region, and a second cholesteric liquid crystal that selectively reflects light of a specific polarization component in the third wavelength region. A cholesteric liquid crystal, a chiral nematic liquid crystal, or a chiral smectic liquid crystal is encapsulated and mixed, and the selective reflection layer is provided between the polarizer and the selective reflection layer, and the first wavelength region, the second wavelength region, and the third wavelength region. By controlling the amount of birefringence of the liquid crystal layer optically exhibiting birefringence in the wavelength range and the liquid crystal layer on which the linearly polarized light from the polarizer is incident by an electric field, A modulation control means for modulating the polarization state and respectively modulating the reflected light intensity from the selective reflection layer,
Thereby, the above object is achieved.

Further, preferably, in addition to the above-mentioned constitution, the reflection type liquid crystal display device of the present invention further comprises a light absorption layer provided on the back side for absorbing the light transmitted through the selective reflection layer.

Further, specifically, the light absorption layer according to claim 1 is provided on the back surface side of the selective reflection layer and absorbs at least light in a specific wavelength range transmitted through the selective reflection layer. More specifically, the light absorption layer according to claim 2 is the first,
It absorbs at least the first wavelength band, the second wavelength band, and the second wavelength band light that has passed through the two or three element parts. Claim 3
The light absorption layer added to is provided on the back surface side of the selective reflection layer,
At least the first wavelength region and the second wavelength region that have passed through the selective reflection layer.
It absorbs light in the wavelength range and the third wavelength range. Further, the light absorption layer according to claim 5 is provided on the back surface side of the selective reflection layer, and transmits at least the first wavelength region and the second wavelength region that pass through the selective reflection layer.
It absorbs light in the wavelength range and the third wavelength range.

[0065]

According to the present invention, a bright liquid crystal display device is realized by efficiently utilizing the selective reflection effect, which is thin and lightweight, has low power consumption, and improves light utilization efficiency. Cholesteric liquid crystals, chiral nematic liquid crystals, chiral smectic liquid crystals, substances in which these liquid crystals are made into a film and the molecular orientation is fixed, and polymer liquid crystals are controlled to have a molecular orientation so as to show vitrification. There are things I did, but here,
The following description will be given using a chiral nematic liquid crystal.

In the present invention, a polarizing plate, a liquid crystal cell enclosing a liquid crystal having birefringence, and a selective reflection layer which selectively reflects light of a specific polarization component in a specific wavelength range, for example, a visible light range are laminated. This liquid crystal cell is a light modulation element, and the retardation R can be changed by the control of the electric field by the modulation control means to make the light emitted from the liquid crystal layer into an arbitrary polarization state.

By the way, the outgoing light in this arbitrary polarization state can be described by combining left and right circularly polarized light. That is, all elliptically polarized light including linearly polarized light is represented by the combination of left and right polarized light components.

The chiral nematic liquid crystal as the selective reflection layer on which the emitted light in this arbitrary polarization state enters is
Since only the light of the circularly polarized light component corresponding to the pitch of the incident polarized light is selectively reflected, the reflectivity greatly differs depending on the ellipticity and the polarity of the incident polarized light.

As described above, by combining the above-mentioned liquid crystal layer with the chiral nematic liquid crystal layer, it is possible to change the ellipticity of the polarized light incident on the chiral nematic liquid crystal layer and control the reflected light intensity. That is, for example, by controlling the retardation R of the liquid crystal layer in the right-handed chiral nematic liquid crystal layer, for example, when the right circularly polarized light enters the chiral nematic liquid crystal layer, the reflected light intensity becomes maximum, and, for example, the left circularly polarized light is changed. When the light enters the chiral nematic liquid crystal layer, the intensity of reflected light becomes minimum. Also, when any elliptically polarized light in the intermediate state of the left and right polarized light is incident, only the right circularly polarized light component of this incident light is reflected and the left circularly polarized light component is transmitted, so the intensity according to the ellipticity of the incident light. Will be reflected light. Here, as the reflected light intensity changes, the transmitted light intensity also changes.

Therefore, by combining a chiral nematic liquid crystal cell and a liquid crystal cell whose birefringence can be changed by an electric field, an optical element for modulating the reflected light intensity and the transmitted light intensity can be realized.

The present invention applies this principle, and includes a chiral nematic liquid crystal cell which selectively reflects light of red, green and blue wavelengths and a liquid crystal cell whose birefringence amount can be changed by an electric field. By combining,
A liquid crystal display capable of color display can be realized.

On the other hand, in the conventional method using the selective reflection of the chiral nematic liquid crystal, TN, ECB, STN, F
Since the light intensity was modulated in combination with the LC and the amplitude of the circularly polarized light was modulated by the 1/4 wavelength plate, it was necessary to use two polarizers, and there was a problem that the display became dark. Even with the conventional method that does not use two sheets, 1 /
Since the four-wave plate is used, there is a problem that the display becomes darker due to the existence of the quarter-wave plate, the structure and the manufacturing process are complicated, and the manufacturing cost is increased. However, the present inventors have found that when an electric field is applied to the liquid crystal layer, the optical rotatory power of light also changes, but at the same time, the polarization state changes and all states from linearly polarized light to circularly polarized light can be realized.

According to the structure of the present invention, only one polarizer is used, no quarter wave plate is used, and the incident linearly polarized light is efficiently circularly polarized by the liquid crystal layer having birefringence. Because it can be converted, half of the external light is available, resulting in a bright full-color display. Further, by inputting left-handed circularly polarized light and right-handed circularly polarized light, all reflection or all transmission can be switched, and a display with very good contrast can be obtained.
Further, since the polarization state of the light incident on the selective reflection layer can be arbitrarily changed, halftone display is possible. Furthermore, 1
It also has a feature that it can be manufactured at a low cost with a simple configuration that does not use a / 4 wavelength plate.

[0074]

Embodiments of the present invention will be described below.

(Embodiment 1) This embodiment 1 is a liquid crystal display device in the case of performing monochromatic display.

FIG. 1 is a sectional view showing the structure of a liquid crystal display device according to the first embodiment of the present invention.

In FIG. 1, there are provided transparent substrates 31, 32 and 33 arranged at predetermined intervals. On this transparent substrate 31, a transparent electrode 34 and an alignment film 35 of liquid crystal molecules are sequentially provided. In addition, a transparent electrode 36 is provided on the transparent substrate 32.
Further, an alignment film 37 of liquid crystal molecules is sequentially provided. A liquid crystal layer 38 having optical birefringence is provided between the alignment films 35 and 37 to form a liquid crystal cell. Further, between the transparent substrates 32 and 33, a chiral nematic liquid crystal layer 39 as a selective reflection layer that selectively reflects only light in a specific wavelength range is provided to form a chiral nematic liquid crystal cell. Further, a polarizer 40 that converts incident light into linearly polarized light is provided on the incident side of the transparent substrate 31, and a light absorption layer 41 that absorbs light in a specific wavelength range is provided on the exit side of the transparent substrate 33. It is provided. Further, the modulation control means 42 connected to these transparent electrodes 34, 36
Is the liquid crystal layer 38 on which the linearly polarized light from the polarizer 40 is incident.
The amount of birefringence of the liquid crystal layer 3 is controlled by the electric field which is an external field due to the display voltage applied to the transparent electrodes 34 and 36.
The polarization state of the emitted light from 8 is modulated to control the intensity of the reflected light from the chiral nematic liquid crystal layer 39. As described above, by combining the chiral nematic liquid crystal cell with the liquid crystal cell capable of changing the amount of birefringence by the external field and the modulation control means 42, an optical element capable of modulating the reflected light intensity and the transmitted light intensity can be obtained. The reflective liquid crystal display device 43 is constructed.

Here, an example of a method of manufacturing the reflection type liquid crystal display device 43 will be described.

First, a 1.1 mm-thick glass substrate (7059; manufactured by Corning Glass Works) was used as the transparent substrates 31 to 33, and ITO films were used as the transparent electrodes 34 and 36 on the glass substrate by the sputtering method. To form each. Alignment films 35 and 37 are formed on these ITO films, respectively. These alignment films 35,
37 is a polyimide (RN-1024; Nissan Chemical Co., Ltd.)
Are uniformly formed by spin coating, and after baking, rubbing treatment is performed on the upper and lower substrates so that the rubbing directions are opposite.

After that, in order to keep the distance between the transparent substrates 31 and 32 constant, a fiber glass spacer (not shown) of 8 μm is sprinkled, and 9 μ as a liquid crystal sealing layer (not shown).
The adhesive sealing material mixed with the m. fiberglass spacer was formed by screen printing and bonded. After that, liquid crystal was injected by vacuum deaeration between the two substrates to prepare an ECB type liquid crystal cell.

The distance between the transparent substrates 31 and 32 is set to 8 μm in the case of the first embodiment, but when the incident light is linearly polarized light, if the retardation R = Δn · d is 3/4 or more of the wavelength, Since all polarization states between left and right circularly polarized light can be realized, the relationship of Δn · d> λm · (3/4) (3) holds between the refractive index anisotropy Δn of the liquid crystal and the substrate spacing d. Good. However, if it is too thick, the response speed becomes slower, so that it is usually 1 μm to 50 μm.
μm is desirable, and more desirably 4 μm to 10 μm. Here, λm is the chiral nematic liquid crystal layer 39.
Is the selective reflection wavelength, and is represented by the above-mentioned formula (2).

The polarizer 40 is attached to the liquid crystal cell manufactured by the above procedure so that the polarization axis forms an angle of 45 ° with the rubbing direction.

Next, a chiral nematic liquid crystal cell is manufactured by the same procedure as described above except that the transparent electrode is not formed. At this time, the distance between the chiral nematic liquid crystal layers 39 is 8 μm as in the above case.
Although the thickness is set to 1, the thickness is not particularly limited as long as the thickness shows selective reflection, but it is preferably 1 μm or more and 100 μm or more.
m or less, and more preferably 4 μm or more and 10 μm or less.

In the first embodiment, the chiral nematic liquid crystal cell is formed by forming an alignment film (not shown) and rubbing the chiral nematic liquid crystal cell so that the rubbing directions are opposite to each other in the upper and lower substrates. However, the rubbing direction may be any direction, and the rubbing direction may not be applied. In that case, it is not necessary to form the alignment film, and the manufacturing procedure can be simplified.

Further, when the rubbing directions are antiparallel, it is desirable to adjust the thickness of the chiral nematic liquid crystal layer 39 so that the cell thickness becomes an integral multiple of the pitch of the chiral nematic liquid crystal. That is, corresponding to each pitch,
That is, it is desirable to change the cell thickness according to the selective reflection wavelength of the chiral nematic liquid crystal. This is because a good alignment state of liquid crystal molecules can be obtained by adjusting the cell thickness according to the spontaneous pitch of the chiral nematic liquid crystal. The chiral nematic liquid crystal is adjusted as follows.

An appropriate amount of a chiral material (S-811; manufactured by Merck) is mixed with a liquid crystal material (ZLI-5087; manufactured by Merck) and adjusted so that the selective reflection wavelength range overlaps the visible light range. As an example, a reflection spectrum when a chiral agent is mixed in an amount of 18% by weight and a cell thickness is 8 μm is shown in FIG.
Shown in In this case, the selective reflection center wavelength was 570 nm, the reflection wavelength width was 40 nm, and the reflected light had a green color. The selective reflection wavelength width is, as shown in the above equation (1),
Depending on the magnitude of the refractive index anisotropy of the liquid crystal used, it can be varied by arbitrarily selecting the liquid crystal. As an example, a chiral agent (CB) is added to a liquid crystal material (BL001; manufactured by BDH).
15; manufactured by Merck & Co., Inc.) was mixed in an amount of 39% by weight, and the reflection wavelength width was 80 nm.

As the light absorption layer 41, carbon fine particles added to a binder was formed on the back surface of the transparent substrate 33 by a printing method. The light absorption layer 41 is prepared by adjusting an organic dye or a pigment dye so that the absorption wavelength range includes at least the selective reflection wavelength range, and adding the binder to the binder to form it on the transparent substrate 33 by printing. May be.

In addition, a light absorbing sheet such as black paper may be attached to the back surface of the transparent substrate 33 with an adhesive.

Further, the transparent substrate 33 and the light absorption layer 41.
Substrate having light absorbency in place of, for example, polycarbonate, polyethylene terephthalate, polyether sulfone, acrylic and epoxy polymers, crosslinkable polymers such as acrylic, carbon or black pigment-based or organic dye You may use what added. In this case, since the light absorption layer 41 also serves as the substrate,
It also has the excellent feature of simplifying manufacturing. As described above, the reflective liquid crystal display device 43 of the first embodiment is manufactured.

The operation of the above arrangement will be described below.

First, the polarizer 40 converts incident light into linearly polarized light. Thus, the incident light converted into the linearly polarized light causes a phase difference between the ordinary light and the extraordinary light due to the birefringence effect of the liquid crystal layer 38, and is converted into the elliptically polarized light having an arbitrary ellipticity. At this time, the optical phase difference δ between the ordinary ray and the extraordinary ray passing through the liquid crystal layer 38 changes in accordance with the relation of δ = 2π / λ · R (4), where λ is the wavelength and R is the retardation.

Generally, when linearly polarized light obtained through the polarizer 40 is incident on the liquid crystal layer 38 which is a birefringent medium,
The emitted light becomes various elliptically polarized lights due to the optical phase difference of the medium. For example, in the case of linearly polarized light that is incident at 45 degrees with respect to the optical axis of the birefringent medium, if the optical phase difference is π / 2 radians, the emitted light is circularly polarized light, and the optical phase difference is π radians. In this case, the light is emitted as linearly polarized light whose azimuth is rotated 90 degrees with respect to the incident linearly polarized light. That is, by changing the retardation R of the liquid crystal cell depending on the external field, the outgoing linearly polarized light can be converted into arbitrary elliptically polarized light.

FIG. 3 schematically shows how the polarization state changes due to this phase difference δ.

Incident light converted into elliptically polarized light having an arbitrary ellipticity in the liquid crystal layer 38 is incident on the chiral nematic liquid crystal layer 39, and the ellipticity and the polarity of the light having the wavelength corresponding to the spiral pitch are changed. It is reflected with the corresponding light intensity. For example, when the chiral nematic liquid crystal is, for example, right-handed, all right-handed circularly polarized light is reflected, and when it is left-handed circularly polarized light, all is transmitted. A part of the polarized light in the intermediate state between the two polarized lights is reflected and the other polarized light is transmitted. Further, the transmitted light is absorbed by the light absorption layer 41 provided behind the chiral nematic liquid crystal layer 39 and is not reflected.

As described above, in the liquid crystal display element of Example 1, the ellipticity of the polarized light incident on the chiral nematic liquid crystal layer 39 is controlled by controlling the birefringence amount of the liquid crystal layer 4 by the external field. The intensity of light reflected from the chiral nematic liquid crystal layer 39 can be controlled.
That is, the reflected light having the intensity corresponding to the ellipticity of the incident light on the chiral nematic liquid crystal layer 39 is obtained.

In the first embodiment, the liquid crystal layer 38 employs an ECB system in which liquid crystal molecules are aligned parallel to the substrate as a liquid crystal element for modulating the polarization state of incident light, but the birefringence amount is Any method can be used as long as it can be controlled by the field, for example, an ECB method in which liquid crystal molecules are aligned perpendicular to a substrate, a TN method using twisted molecular orientation of liquid crystals, or The STN method and the like can be used, and the method using the birefringence of FLC can also be used, so that the degree of freedom in design is increased.

Further, for example, when the chiral nematic liquid crystal is left-handed, for example, right-handed circularly polarized light, left-handed circularly polarized light, or reflected light when linearly polarized light having an intermediate polarization state is incident on the chiral nematic liquid crystal cell. The measurement result of the wavelength dependence of the intensity is shown in FIG. As shown in FIG. 4, the intensity of the reflected light can be changed by changing the phase of the incident light, all the left circularly polarized light is reflected, and in the case of right circularly polarized light, all is transmitted. It can be seen that in the case of a certain linearly polarized light, since a part of the light is reflected, the reflectances are different and gradation display can be performed. In the case of the first embodiment, the display by the reflected light is black and green.

When the light absorption layer 41 is not formed in the reflective liquid crystal display element of the first embodiment, a transmissive liquid crystal display element can be realized, and in that case, white and magenta display can be realized. Measurement of wavelength dependence of transmitted light intensity when right-handed circularly polarized light, left-handed circularly polarized light, and linearly polarized light having an intermediate polarization state are incident on the liquid crystal display device of Example 1 thus produced Results are shown in FIG. As shown in FIG. 5, it is understood that the transmitted light intensity can be changed by changing the phase of the incident light, and gradation display can be performed.

As described above, according to the configuration of the first embodiment,
Since the incident linearly polarized light can be efficiently converted into circularly polarized light by the liquid crystal layer 38 having birefringence, half of the external light can be used and a bright display can be obtained. Further, by inputting left-handed circularly polarized light and right-handed circularly polarized light, it is possible to switch to all reflection or all transmission, and a display with good contrast can be obtained. Furthermore, since the polarization state can be arbitrarily changed, halftone display is possible. Furthermore, the present Example 1 has an excellent feature that it can be manufactured at low cost because only one polarizer is used.

Example 2 Example 2 is a liquid crystal display device for color display.

FIG. 6 is a sectional view showing the structure of a liquid crystal display element according to the second embodiment of the present invention.

In FIG. 6, the transparent substrates 51, 52, 53
Are provided at predetermined intervals, and the transparent electrode 54 is provided on the transparent substrate 51.
Further, an alignment film 55 is provided to form an electrode substrate, and a transparent electrode 56 and an alignment film 57 are provided on the transparent substrate 52 to form an electrode substrate. These alignment films 5
The electrode substrates are arranged so that the electrodes 5 and 57 face each other, and the liquid crystal layer 58 that exhibits birefringence in the light in the red wavelength region is disposed between
Is provided to form a liquid crystal cell. In addition, a chiral nematic liquid crystal cell 59 is provided between the transparent substrates 52 and 53 as a chiral nematic liquid crystal layer 59 as a red selective reflection layer that selectively reflects only the light of a specific polarization component in the red wavelength range. There is. Furthermore, the transparent substrate 51
On the incident side of, a polarizer 60 that converts light in the wavelength range of red light into linearly polarized light is provided. Further, the modulation control means 62 connected to these transparent electrodes 54, 56 determines the amount of birefringence of the liquid crystal layer 58 on which the linearly polarized light from the polarizer 60 is incident, according to the display voltage applied to the transparent electrodes 54, 56. The polarization state of the light emitted from the liquid crystal layer 58 is modulated by controlling with an electric field which is an external field, and the intensity of reflected light from the chiral nematic liquid crystal layer 59 is modulated and controlled. This constitutes the red liquid crystal device 63.

Similar to the red liquid crystal device 63, a green liquid crystal device 63a and a blue liquid crystal device 63b are sequentially provided, and a light absorption layer 61 is provided on the back surface side of the blue liquid crystal device 63b.

In the second embodiment, the chiral nematic liquid crystal layer 5 in which the pitches are adjusted so that the selective reflection wavelengths are red, green and blue, respectively, by the same method as in the first embodiment.
Three kinds of 9, 59a and 59b are prepared, and each constitutes a selective reflection layer. As the red selective reflection layer 59, a color polarizer 60 that converts only red light into linearly polarized light is used. Similarly, for the green and blue selective reflection layers, a color polarizer 6 that converts only light in the selective reflection wavelength range into linearly polarized light
0a and 60b are used. The reflective liquid crystal display device 64 of the second embodiment capable of full-color display can be realized by stacking three elements of each color and further providing the light absorption layer 61. At this time, the color polarizers 60, 60a, 60b of the respective colors ideally convert only the light in the selective reflection wavelength region of the respective colors of the chiral nematic liquid crystal layers 59, 59a, 59b into linearly polarized light, and the light in the other wavelength regions. It is desirable to select it so that it is transparent without any influence.

In this liquid crystal display element manufacturing method, the constituent elements of each color can be manufactured by the same method as in the first embodiment. However, each color polarizer 60, 6
0a and 60b are cyan and polarizer (CC2B-1
8SL; manufactured by Saint-Ritz, a magenta polarizer (UC2)
-MO1-18SL; manufactured by Saint-Ritz), and a polarizer (KCC2Y-18SL; manufactured by Saint-Ritz) for yellow was used.

The operation of the above arrangement will be described below.

First, the incident light is a cyan color polarizer 60.
Only the red light is converted to linearly polarized light, and the other light is transmitted without any influence. The red light converted into linearly polarized light by the cyan color polarizer 60 is the liquid crystal layer 5
The birefringence effect of 8 causes a phase difference between the ordinary light and the extraordinary light, which is converted into elliptically polarized light according to the birefringence amount and enters the chiral nematic liquid crystal layer 59. The elliptically polarized light incident on the chiral nematic liquid crystal layer 59 is reflected with a light intensity corresponding to its ellipticity, and the other light is transmitted.

Of the transmitted light, the green color is converted into linearly polarized light by the magenta color polarizer 60a, and the other light is transmitted without any influence. The green light converted into linearly polarized light by the magenta color polarizer 60a causes a phase difference between the ordinary light and the extraordinary light due to the birefringence effect of the liquid crystal layer 58a, and is converted into elliptically polarized light according to the birefringence amount to be chiral nematic. It is incident on the liquid crystal 59a. The elliptically polarized light incident on the chiral nematic liquid crystal layer 59a is reflected with a light intensity corresponding to its ellipticity, and the other light is transmitted.

Further, of the transmitted light, blue light is converted into linearly polarized light by the yellow color polarizer 60b, and the other light is transmitted without any influence. The blue light converted into the linearly polarized light by the yellow color polarizer 60b causes a phase difference between the ordinary light and the extraordinary light due to the birefringence effect of the liquid crystal layer 58b, and is converted into the elliptically polarized light according to the birefringence amount to be a chiral nematic. It is incident on the liquid crystal layer 59b. The elliptically polarized light incident on the chiral nematic liquid crystal layer 59b is reflected with a light intensity corresponding to its ellipticity, and the other light is transmitted.

The light thus transmitted through all the layers is finally absorbed by the light absorption layer 61.

That is, the chiral nematic liquid crystal layers 59, 59a, 5 exhibiting selective reflection with a specific polarization component in a specific wavelength range.
9b and color polarizers 60, 60a, 60b for converting only light in the wavelength range corresponding to the selective reflection wavelength of each color into linearly polarized light
And liquid crystal layers 58, 58a, 58b capable of controlling the amount of birefringence
By stacking the elements configured by, it is possible to control the reflected light or transmitted light of red, green, and blue in each layer independently, so that full color display is realized by additive color mixing for reflected light and subtractive color mixing for transmitted light. can do.

As described above, in the case of the second embodiment in which three layers of liquid crystal display elements having different selective reflection wavelengths are laminated to manufacture a full-color reflection type liquid crystal display device 64, ideally, 50% of the incident light is Available, resulting in a brighter full-color display.

In the second embodiment, the elements of the respective colors are provided in the order of red, green and blue. However, since the elements of the respective colors of red, green and blue can be controlled independently, the order of stacking is particularly Two
It is obvious that the same effect can be obtained by stacking in any order without being limited to the above order.

(Embodiment 3) The present embodiment 3 is a liquid crystal display device for performing color display, and is a simplified configuration of the embodiment 2.

FIG. 7 is a sectional view showing the structure of a liquid crystal display element according to the third embodiment of the present invention.

In FIG. 7, the liquid crystal display element of the third embodiment is provided with a polarizer 70 capable of converting light in the wavelength regions of red, green and blue into linearly polarized light on the incident side, and a transparent substrate 71,
Transparent electrodes 74 and 76, and alignment films 75 and 77 of liquid crystal molecules are formed on the alignment film 72, respectively, and the polarization state of the linearly polarized light incident through the polarizer 70 is converted between these alignment films 75 and 77. In order to achieve this, a liquid crystal cell is configured by providing a liquid crystal layer 78 that exhibits optical birefringence with respect to light in the wavelength bands of red, green, and blue.

The selective reflection layer is made of the transparent substrates 72, 73.
The chiral nematic liquid crystal layer 79 that selectively reflects the red color sandwiched by and the chiral nematic liquid crystal layer 7 that selectively reflects the green color sandwiched by the transparent substrates 73 and 73a.
9a, and a chiral nematic liquid crystal layer 79b sandwiched between the transparent substrates 73a and 73b that selectively reflects blue light. Further, the light absorption layer 81 is provided on the back surface side of the transparent substrate 73b.

Further, the modulation control means 82 is the transparent electrode 7
By controlling the amount of birefringence of the liquid crystal layer on which the linearly polarized light from the polarizer is incident on 4, 76 by the electric field that is an external field due to the display voltage applied to the transparent electrodes 74, 76, The polarization state of the emitted light is modulated to modulate the intensity of the reflected light from the selective reflection layer. The reflective liquid crystal display device 83 is configured as described above.

In the method of manufacturing the reflection type liquid crystal display device 83, each constituent element can be manufactured by the same method as in the first embodiment.

In the third embodiment, the chiral nematic liquid crystal layers 79, 79a and 79b were laminated as the selective reflection layer in the order of the selective reflection wavelengths of red, green and blue. However, since the layers are independent, the order of lamination is Obviously, the same effect can be obtained optically even if changed.

The operation of the above arrangement will be described below.

First, the incident light is converted into linearly polarized light by the polarizer 70 and is incident on the liquid crystal layer 78. The linearly polarized light incident on the liquid crystal layer 78 has a phase difference between ordinary light and extraordinary light due to the birefringence effect of the liquid crystal, and is converted into elliptically polarized light according to the birefringence amount. At this time, since the phase difference generated in the light of each wavelength of red, green, and blue is different, the light is converted into elliptically polarized light of different ellipticity. That is, the intensity of light selectively reflected by the chiral nematic liquid crystal layer varies depending on the wavelength. Therefore, by modulating the amount of birefringence of the liquid crystal layer with an electric field, the spectrum of the reflected light can be changed,
Multi-color display can be performed.

In the liquid crystal display element produced in this Example 3, since the reflection wavelength width can be changed by changing the refractive index anisotropy of the liquid crystal as described above, the conventional color due to the interference color of the ordinary light and the extraordinary light of the ECB effect. It has an excellent feature that the purity of the displayed color is better than that of the display method.

Further, the liquid crystal display element produced according to the third embodiment has an excellent feature that multi-color display can be performed at a low cost with a simpler structure than the second embodiment.

(Embodiment 4) The present embodiment 4 is a liquid crystal display device in the case of performing color display, which is a further simplification of the structure of the embodiment 3.

FIG. 8 is a sectional view showing the structure of a liquid crystal display element according to the fourth embodiment of the present invention.

In FIG. 8, the liquid crystal display element of the present Example 4 is provided with a neutral polarizer 90 for converting light in each wavelength region of red, green and blue into linearly polarized light on the incident side, and selectively reflecting light on the emitting side. A support substrate 92 is provided on the back surface side of the layer, which also serves as a light absorption layer that absorbs light in the wavelength bands of red, green, and blue transmitted through the selective reflection layer. A transparent electrode 94 and an alignment film 95 of liquid crystal molecules are formed on the transparent substrate 91, and light of a specific polarization component in the selective reflection wavelength range of each color of red, green and blue is formed on the supporting substrate 92. Chiral nematic liquid crystal layer 9 as a selective reflection layer that selectively reflects
9, a transparent electrode 96, and an alignment film 97 of liquid crystal molecules are formed. The alignment films 95 and 97 are adjusted to have a predetermined interval, and a liquid crystal layer 98 that exhibits optical birefringence in light of respective color wavelength ranges of red, green, and blue is provided between them to form a liquid crystal cell. .

The chiral nematic liquid crystal layer 99 is
It is composed of liquid crystal microcapsules 99a, 99b, 99c in which chiral nematic liquid crystals having selective reflection wavelength bands in different wavelength bands of red, green and blue are enclosed.

The modulation control means 92a is the transparent electrode 9
By controlling the amount of birefringence of the liquid crystal layer 98 connected to the transparent electrodes 94 and 96 and receiving the linearly polarized light from the polarizer 91 by the electric field which is an external field due to the display voltage applied to the transparent electrodes 94 and 96, the liquid crystal The polarization state of the light emitted from the layer 98 is modulated, and the intensity of the reflected light from the selective reflection layer is modulated. The reflective liquid crystal display device 93 is configured as described above.

In this method of manufacturing the reflection type liquid crystal display device 93, each constituent element can be manufactured by the same procedure as in the first embodiment.

The operation of the above arrangement will be described below.

First, the incident light is converted into linearly polarized light by the polarizer 90 and is incident on the liquid crystal layer 98. This liquid crystal layer 9
The linearly polarized light entering 8 is converted into elliptically polarized light according to the birefringence amount due to a phase difference between ordinary light and extraordinary light due to the birefringence effect of the liquid crystal. At this time, since the phase differences received by the lights of the red, green, and blue wavelengths are different from each other, they are converted into elliptically polarized lights having different ellipticities. That is, the intensity of light selectively reflected by the chiral nematic liquid crystal layer 99 differs for each wavelength. Therefore, by modulating the amount of birefringence of the liquid crystal layer 98 with an electric field, the spectrum of reflected light can be varied, and multicolor display can be performed.

The liquid crystal display element manufactured according to the fourth embodiment is excellent in that, in addition to the excellent characteristics described in the third embodiment, the manufacturing process is further simplified by the simpler structure and the multi-color display can be performed at low cost. It has different characteristics.

In Examples 1 to 3 described above, the chiral nematic liquid crystal cell was used for the selective reflection layer, but by forming a film, a liquid crystal cell having a simpler structure can be realized.

For example, it is known from the literature (Japanese Unexamined Patent Publication No. 6-186534) that the orientation of liquid crystal molecules in a liquid crystal state can be frozen by controlling the orientation of liquid crystalline polyester on a glass substrate and then performing heat treatment to cure it. Has been. Therefore, a chiral nematic liquid crystal layer 99 is prepared by forming a cholesteric film from this polymer liquid crystal and adjusting the pitch so that the selective reflection wavelength region is in the visible light region.
Can be used instead of, with the same effect.

In addition, the fact that a chiral nematic liquid crystal can be microencapsulated can be found in the literature (eg, Japan Society for the Promotion of Science, 142nd Committee, Polarized Liquid Crystal Device Handbook, Chapter 9, 9.
5, and JP-A-5-66391).

The following method can be given as an example of the method for producing the liquid crystal microcapsules. That is, first, the liquid crystal and the gum arabic solution are emulsified and mixed at room temperature or higher, and a gelatin solution having an equal concentration is added thereto. Next, when distilled water is added to adjust the pH (hydrogen ion concentration), gelatin and gum arabic react to produce a thick liquid polymer. Then, when the temperature is lowered, coacervation starts, and the gelatin / arabic gum film adheres to the periphery of the liquid crystal particles to form a capsule film. Further, a curing agent such as aldehyde is added to age the capsule film.

A selective reflection layer can be formed by printing a transparent ink on the transparent substrate 3 by adding a binder to this and making it ink.

Even if the microencapsulated chiral nematic liquid crystal prepared by the above method is used as the selective reflection layer, the same effect can be obtained.

In any of Examples 1 to 4, parallel-aligned E was used as a liquid crystal display system in which the amount of birefringence can be controlled by an external field.
A CB type liquid crystal cell was adopted, but as a liquid crystal display type having the same effect, an inclined vertical alignment ECB type or ST
Even if the N method is used, the same effect can be obtained, and an excellent effect that a large capacity display can be achieved by simple matrix driving is exhibited.

Further, as long as it exhibits birefringence and the amount of birefringence can be controlled by an external field, it is not limited to liquid crystal, and for example, P
The same effect can be obtained by forming a transparent electrode on an optical crystal such as LZT or lithium niobate and applying a voltage to change the amount of birefringence. Further, in this case, it is possible to operate at high speed, and the excellent characteristics of having a memory property are also exhibited.

[0142]

As described above, according to the liquid crystal display device of the first aspect, since the display is performed by changing the polarization state by the electric field by utilizing the birefringence of the liquid crystal, the display modes of various systems can be used. Not only can it be used and design flexibility increased,
Since the intensity of reflected light can be modulated by controlling the polarization state incident on, for example, a chiral nematic layer as a selective reflection layer, a quarter wave plate is not required, and
Only one polarizer is needed and a bright display is obtained.
In addition, large capacity display can be performed by simple matrix driving, and an element can be manufactured at low cost. Furthermore, by utilizing the selective reflection of the chiral nematic liquid crystal, it was conventionally necessary to separately form the colored layer and the reflective layer, but one layer can serve as the colored layer and the reflective layer.

According to the liquid crystal display element of claim 2,
Since a color polarizer is used in each of the three laminated layers, the reflected light intensity can be controlled independently, and full color display is possible. Further, ideally, 50% of external light can be used, so that a bright reflective full-color liquid crystal display device can be realized.

Further, according to the liquid crystal display element of the third aspect, it is possible to perform multicolor display with a simpler configuration. Further, as described above, since the reflection wavelength width can be changed by changing the refractive index anisotropy of the liquid crystal, the purity of the displayed color is better than the display by the interference color of the ordinary light and the extraordinary light of the ECB effect.

Further, according to the liquid crystal display element of claim 4, when the selective reflection layer is a cholesteric liquid crystal or a chiral nematic liquid crystal, the material selection range is widened,
It is possible to select a material whose temperature dependence of the selective reflection wavelength is small. It has excellent features such as the ability to adjust the reflection wavelength range. When the selective reflection layer uses a cholesteric liquid crystal in the form of a film or a cholesteric liquid crystal in the form of a microcapsule, in addition to the excellent characteristics described above,
By replacing the chiral nematic liquid crystal layer sandwiched between a pair of transparent substrates with a film or microencapsulated chiral nematic liquid crystal, further thinning and weight reduction are possible, and the device configuration is simple, so the manufacturing process is also simplified. And can be manufactured at a lower cost.

Further, according to the liquid crystal display element of the fifth aspect, it is possible to perform multicolor display with a simpler configuration.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration of a liquid crystal display element in Example 1 of the present invention.

FIG. 2 is a diagram showing wavelength dependence of selective reflection in the liquid crystal display element of FIG.

FIG. 3 is a diagram schematically showing how the polarization state changes depending on the phase difference δ.

FIG. 4 is a diagram showing the wavelength dependence of the intensity of selectively reflected light when the phase of incident polarized light is changed.

FIG. 5 is a diagram showing wavelength dependence of transmitted light intensity when the phase of incident polarized light is changed.

FIG. 6 is a cross-sectional view showing a configuration of a liquid crystal display element according to Example 2 of the present invention.

FIG. 7 is a cross-sectional view showing a configuration of a liquid crystal display element in Example 3 of the present invention.

FIG. 8 is a cross-sectional view showing a configuration of a liquid crystal display element in Example 4 of the present invention.

FIG. 9 is a diagram schematically showing a selective reflection effect of a chiral nematic liquid crystal.

FIG. 10 is a cross-sectional view showing a configuration example of a conventional liquid crystal display element.

FIG. 11 is a cross-sectional view showing another configuration example of a conventional liquid crystal display element.

12 is a diagram showing the relationship between the optical axis of the quarter-wave plate 9 and the direction of linearly polarized light in the liquid crystal display element of FIG.

[Explanation of symbols]

31, 32, 33, 51, 52, 53, 51a, 52
a, 53a, 51b, 52b, 53b, 71, 72, 7
3, 73a, 73b, 91 Transparent substrate 34, 36, 54, 56, 54a, 56a, 54b, 5
6b, 74, 76, 94, 96 transparent electrodes 35, 37, 55, 57, 55a, 57a, 55b, 5
7b, 75, 77, 95, 97 Alignment film 38, 58, 58a, 58b, 78, 98 Liquid crystal layer 39, 59, 59a, 59b, 79, 79a, 79b,
99 chiral nematic liquid crystal layer 40, 60, 60a, 60b, 70, 90 Polarizer 41, 61, 81 Light absorption layer 42, 62, 62a, 62b, 82, 92a Modulation control means 43, 64, 83, 93 Reflective liquid crystal Display device 63, 63a, 63b Liquid crystal display element 92 Support substrate 99a, 99b, 99c Microcapsule

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G02F 1/1347 G02F 1/1347

Claims (6)

[Claims] 1. A polarizer that converts incident light into linearly polarized light, a selective reflection layer that selectively reflects only light of a specific polarization component in a specific wavelength region, and a polarizer provided between the polarizer and the selective reflection layer. , The polarization state of light emitted from the liquid crystal layer is controlled by controlling the amount of birefringence of the liquid crystal layer exhibiting optical birefringence and the linearly polarized light from the polarizer by the electric field. And a modulation control means for modulating the intensity of the reflected light from the selective reflection layer. 2. A first color polarizer that converts only light in a first wavelength range into linearly polarized light, a first selective reflection layer that selectively reflects only light of a specific polarization component in the first wavelength range, and the first color reflection layer. The first color polarizer and the first selective reflection layer are provided between the first color polarizer and the first selective reflection layer.
A first element part having a first liquid crystal layer exhibiting birefringence in light of a wavelength range; a second color polarizer for converting only light of a second wavelength range different from the first wavelength range into linearly polarized light; A second selective reflection layer that selectively reflects only light of a specific polarization component in two wavelength ranges, and
A second element section provided between the second color polarizer and the second selective reflection layer, the second element section having a second liquid crystal layer exhibiting birefringence in light in the second wavelength range; A third color polarizer that converts only light in a third wavelength range different from the second wavelength range into linearly polarized light, a third selective reflection layer that selectively reflects only light of a specific polarization component in the third wavelength range, and A third element part provided between the third color polarizer and the third selective reflection layer, the third element part having a third liquid crystal layer exhibiting birefringence in light in the third wavelength region; A light absorption layer that absorbs at least the light in the first wavelength band, the second wavelength band, and the third wavelength band that has passed through the three-element portion; By controlling the refraction amount by an electric field, the first,
A liquid crystal display device, comprising: modulation control means for respectively modulating the polarization states of light emitted from the second and third liquid crystal layers to respectively modulate the reflected light intensities from the first, second and third selective reflection layers. 3. A polarizer capable of converting the light in the first wavelength band, the second wavelength band and the third wavelength band into linearly polarized light, and a first reflector selectively reflecting light of a specific polarization component in the first wavelength band.
A selective reflection layer, a second selective reflection layer that selectively reflects light of a specific polarization component in the second wavelength range, and a third selective reflection layer that selectively reflects light of a specific polarization component in the third wavelength range. A selective reflection layer having: a light absorption layer provided on the back surface side of the selective reflection layer and absorbing at least light in the first wavelength region, the second wavelength region and the third wavelength region transmitted through the selective reflection layer; A liquid crystal layer that is provided between the polarizer and the selective reflection layer and exhibits optical birefringence in the light of the first wavelength band, the second wavelength band, and the third wavelength band, and a straight line from the polarizer. Modulation control means that modulates the polarization state of the light emitted from the liquid crystal layer by controlling the amount of birefringence of the liquid crystal layer into which polarized light is incident by an electric field to modulate the intensity of reflected light from the selective reflection layer. And a liquid crystal display device. 4. The liquid crystal display according to claim 1, wherein a cholesteric liquid crystal, a chiral nematic liquid crystal, a chiral smectic liquid crystal, the filmed liquid crystal, or the microencapsulated liquid crystal is used as the selective reflection layer. apparatus. 5. A polarizer for converting light in a first wavelength band, a second wavelength band and a third wavelength band into linearly polarized light, and a first polarizer for selectively reflecting light of a specific polarization component in the first wavelength band. Cholesteric liquid crystal or chiral nematic liquid crystal or chiral smectic liquid crystal, second cholesteric liquid crystal or chiral nematic liquid crystal or chiral smectic liquid crystal that selectively reflects light of a specific polarization component in the second wavelength range, and specific in the third wavelength range A selective reflection layer in which a third cholesteric liquid crystal, a chiral nematic liquid crystal, or a chiral smectic liquid crystal that selectively reflects light of a polarized component is mixed and encapsulated, and a selective reflection layer provided on the back surface side of the selective reflection layer, A light absorption layer that absorbs at least the transmitted light in the first wavelength band, the second wavelength band, and the third wavelength band. A liquid crystal layer which is provided between the polarizer and the selective reflection layer and which optically exhibits birefringence in the light of the first wavelength band, the second wavelength band and the third wavelength band; Modulation control that modulates the polarization state of the light emitted from the liquid crystal layer by controlling the amount of birefringence of the liquid crystal layer on which linearly polarized light is incident by an electric field to modulate the intensity of light reflected from the selective reflection layer, respectively. And a liquid crystal display device. 6. The liquid crystal display device according to claim 1, further comprising a light absorption layer provided on the back surface side to absorb light transmitted through the selective reflection layer.