JPH11143401A - Liquid-crystal display sheet and write-erase system therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid-crystal display sheet of simple constitution which allows the rewriting of information and a write-erasing system. SOLUTION: In a liquid-crystal display sheet 1, light impinging from one polarizing plate 3 is transmitted through a liquid-crystal element 4 and is emitted from or shut by the other polarizing plate 2, with information displayed by such transmission and shutting of the light. The liquid crystal element 4 is formed using a pair of liquid crystal sheet bases 9, 11 made from a material containing plastic liquid crystals and a liquid crystal layer 7 made of a material containing ferroelectric liquid crystals, with alignment layers 10, 12 formed on the liquid-crystal-layer sides of the liquid crystal sheet bases 9, 11. Information is written and erased by passing the liquid crystal display sheet 1 through an electric field. The information written is retained even if the electric field is removed. Therefore, the liquid crystal display sheet 1 has no electrodes, can be simplified, and is small and lightweight.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display sheet using liquid crystal used as an original, a poster, a flyer advertisement, and the like, and a writing / erasing system for the liquid crystal display sheet.

[0002]

2. Description of the Related Art For example, Japanese Patent Application Laid-Open No. 64-7018 discloses an example of a conventional information recording medium using a ferroelectric polymer liquid crystal. FIG. 10 is a sectional view showing the information recording medium 51. On one surface of the light transmitting substrate 52 of the information recording medium 51, a transparent electrode 53 is formed,
Further, a liquid crystal layer 54 is formed by applying a ferroelectric polymer liquid crystal while extending and orienting it so as to cover the transparent electrode 53. A transparent electrode 55 is formed on the liquid crystal layer 54, and a protective film 56 is formed to cover the transparent electrode 55 as necessary.

The method of writing and erasing information on the information recording medium 51 is as follows. First of all, erase all
The entire information recording medium 51 is heated until the liquid crystal layer 54 becomes a chiral smectic C (SmC *) phase, a predetermined erasing voltage is applied, and the information recording medium 51 is applied while the voltage is applied.
This is performed by cooling the whole until the liquid crystal layer 54 becomes glassy. The writing is performed by irradiating the liquid crystal layer 54 with laser light while applying a predetermined writing voltage in a glassy state, and heating the irradiated area instantaneously until the SmC * phase is reached, thereby inverting the alignment state of the liquid crystal molecules. Done by Further, partial erasing is performed in the glass state while applying a predetermined erasing voltage in the same manner as in writing. The inversion state of the orientation of the liquid crystal molecules is maintained even when the voltage application is stopped.

[0004]

As a manuscript, a poster, a flyer advertisement, and the like, a printed matter obtained by printing information on paper is often used. However, once printed information cannot be changed, the printed matter must be discarded when the content is changed. Therefore, the amount of refuse increases, but such increase of refuse is not preferable in terms of destruction of nature and environmental protection. Also,
Although paper and ink are wasted, this is not preferable in terms of effective use of resources.

The information recording medium 51 disclosed in Japanese Patent Laid-Open Publication No. Sho 64-7018 is capable of rewriting information, and can be used in place of a printed material to reduce the amount of dust and waste paper and ink. It is relatively complicated, and the recording medium 51 itself is large and heavy.

It is an object of the present invention to provide a liquid crystal display sheet having a simple structure capable of rewriting information and a system for writing and erasing the liquid crystal display sheet.

[0007]

The present invention comprises a pair of polarizers and a liquid crystal element disposed between the polarizers, wherein the liquid crystal element comprises a pair of liquid crystal sheet substrates and the liquid crystal sheet substrates. And a liquid crystal layer sandwiched by the liquid crystal layer and an alignment film formed on the liquid crystal layer side of each liquid crystal sheet substrate, wherein the liquid crystal sheet substrate is made of a material containing plastic liquid crystal, and the liquid crystal layer is made of a ferroelectric liquid crystal. A liquid crystal display sheet, comprising:

According to the present invention, light incident from one polarizer as a polarizer passes through a liquid crystal element and is emitted or blocked from the other polarizer as an analyzer. Information is displayed according to the state of emission and cutoff of such light.
The liquid crystal element uses a pair of liquid crystal sheet substrates made of a material containing a plastic liquid crystal and a liquid crystal layer made of a material containing a ferroelectric liquid crystal material. A film is formed. Writing and erasing of information is performed by passing the liquid crystal display sheet through an electric field of a predetermined voltage. That is, by applying a writing voltage or an erasing voltage, two orientation states of the ferroelectric liquid crystal molecules are selectively controlled. The direction of polarization of the incident polarized light is different between the region where the write voltage is applied and the region where the erase voltage is applied, and light in one vibration direction passes through the analyzer and exits, while the other vibration direction. Is blocked by the analyzer. As described above, information can be written and erased only by passing the liquid crystal display sheet through the electric field. Further, since the orientation state of the ferroelectric liquid crystal is maintained even when the electric field is removed, it is not necessary to continuously apply a voltage in order to hold the written information. Therefore, no electrodes are required. As described above, the liquid crystal display sheet of the present invention has no electrodes, has a simple configuration, and is small and lightweight.

The present invention is characterized in that each alignment film has the same plurality of dot shapes and is arranged in a matrix.

According to the present invention, the same plurality of dot-shaped alignment films are arranged in a matrix, so that matrix display is possible. Since the alignment film formed on each liquid crystal sheet substrate is the same, it can be formed in the same process, and can be realized easily and inexpensively.

The present invention is characterized by comprising a plurality of the liquid crystal elements emitting different colors. According to the present invention, for example, three liquid crystal elements respectively corresponding to three colors of yellow, magenta, and cyan are provided to enable color display. In particular, by sharing a common member in each liquid crystal element, components are simplified, and miniaturization and weight reduction are achieved. In addition, by realizing a liquid crystal element using a material in which a colorant of each color and a ferroelectric liquid crystal are mixed, one of the polarizing plates can be omitted, the components can be simplified, and the size and weight can be reduced. Can be

The present invention is characterized in that the liquid crystal layer includes a dye, and includes a transflective reflector disposed in place of one of the pair of polarizers.

According to the present invention, the liquid crystal layer contains a dye, whereby one of the two polarizing plates can be omitted to simplify the structure. External light, such as sunlight or a fluorescent lamp, which enters through a polarizing plate as a polarizer passes through a liquid crystal element, is reflected by a semi-transmissive reflective plate, and exits through the liquid crystal element and the polarizing plate again. At this time, the polarizing plate functions as an analyzer. In addition, internal light such as a backlight that enters through the transflective reflector passes through the liquid crystal element and the polarizing plate and exits. A brighter display can be realized by using brighter light by selectively using such external light and internal light.

According to the present invention, information is written or erased by passing the above-mentioned liquid crystal display sheet between a pair of charging members to which a predetermined write voltage or erase voltage is applied. Is a write / erase system.

According to the present invention, it is possible to write and erase information by passing the liquid crystal display sheet between a pair of charging members to which a predetermined writing voltage or erasing voltage is applied.

In the present invention, the charging member is a charging roller or a charging head.

According to the present invention, a charging roller or a charging head is used as the charging member. In other words, when a charging roller is used, writing and erasing of information can be easily achieved by adding a new device that applies a predetermined voltage using the photosensitive drum and back electrode in the existing electrophotographic printing system. it can. When a charging head is used, information is written and erased by using a device that applies a predetermined voltage instead of an LED driving circuit using an LED head or a back electrode in a printer system such as an LED (light emitting diode) printer. Can be easily realized.

[0018]

FIG. 1 is a sectional view showing the structure of a liquid crystal display sheet 1 according to a first embodiment of the present invention.
FIG. 2 is a perspective view of the liquid crystal display sheet 1. The liquid crystal display sheet 1 has a liquid crystal element 4 between a pair of polarizing plates 2 and 3.
The liquid crystal element 4 is configured by sandwiching a liquid crystal layer 7 made of a material containing a ferroelectric liquid crystal between a pair of liquid crystal sheet members 5 and 6. Each liquid crystal sheet member 5, 6
An alignment film 10, 12 is formed on a liquid crystal layer 7 side surface of a liquid crystal sheet substrate 9, 11 such as a polymer film made of a material containing a plastic liquid crystal. The thickness of the liquid crystal layer 7 (hereinafter referred to as "cell thickness") ) Are adhered by a sealant 13 via a spacer (not shown) for regulating the above.

An alignment film material such as polyimide is applied to one surface of the liquid crystal sheet substrates 9 and 11 which are made of a material containing a plastic liquid crystal and are realized by, for example, a laminated (laminated) plate. After the applied alignment film material is fired, an alignment process such as a rubbing process for aligning liquid crystal molecules is performed. Thus, the alignment films 10 and 12 are formed. In the liquid crystal display sheet 1 of the present embodiment, the alignment film material is processed into a predetermined pattern by an etching process after baking, and then the alignment process is performed. The alignment films 10 and 12 are formed by such pattern processing.
Have, for example, the same plurality of dot shapes and are arranged in a staggered matrix. The region of the alignment film is a region of the pixel 8. Thus, the liquid crystal sheet members 5 and 6 are completed.

Alignment films 10 and 12 of liquid crystal sheet members 5 and 6
The liquid crystal sheet members 5 and 6 are bonded together with the sealant 13 so that the surface is on one side. Thereafter, a material containing a ferroelectric liquid crystal is sealed in the gap between the liquid crystal sheet members 5 and 6, whereby the liquid crystal layer 7 is formed. Usable ferroelectric liquid crystals include:
Examples include naphthalene-based liquid crystals and phenylpyrimidine-based non-chiral liquid crystals. Thus, the liquid crystal element 4 is completed. Polarizing plates 2 and 3 are attached to the surfaces of the liquid crystal sheet members 5 and 6 opposite to the liquid crystal layer 7, respectively. Thus, the liquid crystal display sheet 1 is completed.

The ferroelectric liquid crystal has a multi-layer structure, and the major axis of the liquid crystal molecules is inclined by a predetermined angle from a direction perpendicular to each layer, and the inclination direction is gradually changed from one layer to the next layer. The spiral structure is arranged so as to be shifted. The cell thickness of the liquid crystal layer 7 is selected to be much smaller than the helical pitch of the ferroelectric liquid crystal. For example, the value is selected to be smaller than 2 μm, and particularly to about 1.5 μm.

FIG. 3 is an enlarged view showing the dot shape of the pixel 8. As the pixel 8 having a dot shape, specifically, a square pixel 8a as shown in FIG.
A circular pixel 8b as shown in FIG. 3B and a hexagonal pixel 8c as shown in FIG. 3C may be used. Further, other than these, it may be 3, 5 and 7 or more polygons. Further, the square may be a square, a rectangle, or a rhombus.

The pixels 8 are arranged in a staggered matrix in which the positions of the pixels 8 in the row and column directions adjacent to each other are shifted by a half pitch. However, the present invention is not limited to such an arrangement, and may be simply arranged in a matrix and arranged so that the pitch does not shift.

The relationship between the polarization axes 2a and 3a of the polarizing plates 2 and 3 and the alignment direction of the liquid crystal molecules in the liquid crystal layer 7 is such that, for example, incident light transmitted through the polarizing plate 3 transmits through the liquid crystal layer 7 in the writing state. The incident light transmitted through the polarizing plate 2 and emitted, and transmitted through the polarizing plate 3 in the erased state is transmitted through the liquid crystal layer 7 and
Selected to be blocked by.

FIG. 4 is a diagram for explaining the principle of operation of the liquid crystal display sheet 1. One of the polarizing plates 2 and 3 is used as an analyzer, and the other polarizing plate 3 is used as a polarizer;
It is assumed that light passes from the polarizer 3 toward the analyzer 2. The liquid crystal has a phase called a chiral smectic C phase, and this phase is usually used as a ferroelectric liquid crystal. As described above, the ferroelectric liquid crystal has a helical structure, but since the cell thickness is selected to be much smaller than the helical pitch of the ferroelectric liquid crystal, the helical structure is unwound and two bistable states are obtained. Can be The liquid crystal molecules 7a have spontaneous polarization in a direction perpendicular to the layer, and when a voltage is applied in that direction, the liquid crystal molecules 7a are oriented so as to align the spontaneous polarization in the direction of the electric field.
Therefore, by applying the electric fields + E and −E, the orientation direction of the liquid crystal molecules 7a changes. That is, when an electric field + E is applied, a spontaneous polarization PS2 facing the paper surface of FIG. 4 is obtained, and when an electric field -E is applied, a spontaneous polarization PS1 facing the paper surface of FIG. 4 is obtained. Due to such a change in the orientation of the liquid crystal molecules 7a, the vibration direction of the polarized light incident on the liquid crystal layer 7 becomes different.

Therefore, the light passes through the polarizer 3 and passes through the liquid crystal layer 7.
The light that has entered the pixel in the written state is emitted from the analyzer 2. On the other hand, the light incident on the erased pixel of the liquid crystal layer 7 is blocked by the analyzer 2. Information can be displayed in a matrix by such a combination of pixels.

FIG. 5 is a side view showing an information writing and erasing system using the charging rollers 15 and 16, and FIG. 5B is a perspective view. For writing and erasing of information, charging rollers 15 and 16 are provided as a pair of charging members, and a voltage applying device 17 for applying a predetermined voltage between the charging rollers 15 and 16 is provided. Information is written by passing the liquid crystal display sheet 1 through an electric field of a predetermined voltage, that is, by passing between a pair of charging rollers 15 and 16 to which a predetermined writing voltage or erasing voltage is applied. , Will be erased again.

FIG. 6 is a perspective view showing an information writing and erasing system using the charging heads 18 and 19. For writing and erasing information, charging heads 18 and 19 are provided as a pair of charging members instead of charging rollers 15 and 16, and a voltage application device 17 for applying a predetermined voltage between the charging heads 18 and 19. Is provided. As in the case of the charging rollers 15 and 16, information is stored in a pair of charging heads 18 and 1 to which a predetermined writing voltage or erasing voltage is applied.
By passing the liquid crystal display sheet body 1 between 9
Written and erased.

By applying a writing voltage or an erasing voltage, two orientation states of the ferroelectric liquid crystal molecules are selectively controlled, and writing and erasing of information can be performed only by passing the liquid crystal display sheet 1 through an electric field. It is possible. Also, due to the characteristics of the ferroelectric liquid crystal, the written information is retained even when the electric field is removed.

FIG. 7 is a waveform diagram showing the applied voltage. For example, a plurality of scanning electrodes are formed on the surface of the charging roller 15, and a plurality of signal electrodes are formed on the surface of the charging roller 16. Similarly, a plurality of scanning electrodes are formed on the surface of the charging head 18, and a plurality of signal electrodes are formed on the surface of the charging head 19. While one scan electrode is selected and the voltage Vs is applied, the signal electrodes are sequentially selected and the voltage Vd is applied.

In the liquid crystal display sheet 1, for example,
Line information is written at a time. For this reason, for example, the selection period of the n-th scanning electrode corresponding to the pixels P1 and P2 of (n, m) and (n, m + 1) is 0 in one slot.
It is composed of (zero) V and Vs of 3 slots, that is, 4 slots. Two of these slots are n corresponding to the pixels P3 and P4 of (n + 1, m) and (n + 1, m + 1).
This overlaps with the selection period of the (+1) th scanning electrode. Therefore 1
The line address time, which is the drive time per scan electrode, can be defined by two slots. On the other hand, the voltage + Vd or -Vd is applied to the signal electrode depending on the display state.

Here, when information is rewritten, that is, at the time of writing or erasing, a pre-pulse Vd is applied, and then a rewriting pulse Vs-Vd of the same polarity is applied. When rewriting is not performed, that is, when the writing or erasing state is maintained, after applying the pre-pulse Vd, the rewriting pulse V having the opposite polarity is applied.
s + Vd is applied. The pulses in the third and fourth slots do not affect rewriting. For example, the voltage Vs is selected to be 30V and the voltage Vd is selected to be 10V.

As described above, according to the liquid crystal display sheet 1 of this embodiment, information can be written and erased only by passing the liquid crystal display sheet 1 through an electric field. Also,
The written information is retained even if the electric field is removed. Therefore, writing and erasing of information and holding of written information are possible even without an electrode. As described above, since the liquid crystal display sheet 1 of the present embodiment does not have electrodes,
It is simple, compact and lightweight.

The same plurality of dot-shaped alignment films 1
Since 0 and 12 are arranged in a matrix, matrix display is possible. Since the alignment films 10 and 12 formed on the liquid crystal sheet substrates 9 and 11 have the same shape, they can be formed in the same process and can be easily realized.

As charging members, charging rollers 15 and 1 are used.
6 or charging heads 18, 19 are used. That is, the charging rollers 15 and 16 are a photosensitive drum and a back electrode in an existing electrophotographic printing system, and writing and erasing of information can be easily realized by using these and adding a voltage applying device 17. it can. Alternatively, the charging heads 18 and 19 are an LED head and a back electrode in a printing system such as an existing LED printer, and by using these and using the voltage applying device 17 instead of the LED driving circuit, writing and erasing of information can be performed. Can be easily realized. In addition to the electrophotographic system and the LED printer, an inkjet printing system may be applied.

FIG. 8 is a sectional view showing a color liquid crystal display sheet 21 according to a second embodiment of the present invention. The liquid crystal display sheet body 21 of the second embodiment is different from the liquid crystal display sheet body 1 of the first embodiment in that color display is performed.
Basically, a plurality of liquid crystal elements similar to the liquid crystal element 4, here, three liquid crystal elements 23Y and 23 corresponding to yellow (Y), magenta (M) and cyan (C), respectively.
M, 23C (hereinafter, the reference numeral 23 is used when controlling), and each of the liquid crystal elements 23Y, 23M, 23C is laminated.

More specifically, the color liquid crystal display sheet 21
Is a polarizing plate 22 and three liquid crystal elements 23Y, 23M, 2
3C and a transflective reflector 24. Between the polarizing plate 22 and the transflective reflector 24, three liquid crystal elements 23Y, 2
3M and 23C are stacked and arranged. The yellow liquid crystal element 23Y includes a liquid crystal sheet member 35 formed by forming an alignment film 26 on one surface of a liquid crystal sheet base material 25 made of a material containing plastic liquid crystal, and a liquid crystal sheet base material made of a material containing plastic liquid crystal. 27 has an alignment film 2 on one surface.
And a liquid crystal layer 36 made of a ferroelectric liquid crystal material to which a yellow dye is added.
9.

The magenta liquid crystal element 23M includes a liquid crystal sheet member 36 formed by forming an alignment film 29 on the other surface of a liquid crystal sheet base 27, and one surface of a liquid crystal sheet base 30 made of a material containing a plastic liquid crystal. And a liquid crystal sheet member 37 formed by forming an alignment film 31 on a liquid crystal layer 40 made of a ferroelectric liquid crystal material to which a magenta dye is added.
Is configured. The cyan liquid crystal element 23C includes a liquid crystal sheet member 37 formed by forming an alignment film 32 on the other surface of a liquid crystal sheet substrate 30, and an alignment film formed on one surface of a liquid crystal sheet substrate 33 made of a material containing plastic liquid crystal. A liquid crystal sheet member 38 formed with 34 is sandwiched between a liquid crystal layer 41 made of a ferroelectric liquid crystal material to which a cyan dye is added. The polarizing plate 22 is bonded to the other surface of the liquid crystal sheet substrate 25 with high positional accuracy.

By writing information only to the yellow liquid crystal element 23Y, only the yellow component is displayed. By writing information only to the magenta liquid crystal element 23M, only the magenta component is displayed, and only the cyan liquid crystal element 23C is displayed. By writing the information, only the cyan component can be displayed. Here, each dye molecule aligns following the liquid crystal molecule, and therefore, the degree of absorption of incident polarized light changes depending on the angle of the alignment direction of the dye molecule. Therefore, color display is possible.

According to the second embodiment, three color displays of yellow, magenta and cyan can be displayed. Especially,
The common components of the liquid crystal elements 23Y, 23M, and 23C, that is, the common use of the liquid crystal sheet base materials 27 and 30, simplify the components and reduce the size and weight.

Also, by using a ferroelectric liquid crystal material in which dyes of each color are mixed, only one polarizing plate is required,
The components are simplified, and miniaturization and weight reduction are achieved. Such effects can be obtained not only in the color liquid crystal display sheet 21 having a plurality of liquid crystal elements, but also in a single liquid crystal element.

As another method of colorization, red (R), green (G), and blue (G) pixels are arranged in a plane using a color filter to control writing of information to each pixel. You may adopt the method of doing.

In the color liquid crystal display sheet 21 using the semi-transmissive reflection plate 24, as shown in FIG. 9, light from an external light source 43 such as sunlight or a fluorescent lamp incident through the polarizing plate 22 is used. The light passes through the liquid crystal element 23, is reflected by the semi-transmissive reflection plate 24, and passes through the liquid crystal element 23 and the polarizing plate 22 again to be emitted. Light from an internal light source 42 such as a backlight, which has entered through the transflective reflector 24, passes through the liquid crystal element 23 and the polarizing plate 22 and exits.
In this way, a brighter display can be realized by selectively using the external light and the internal light and employing the brighter one. Note that the transflective reflector 24 may be applied to the liquid crystal display sheet 1 of the first embodiment.

The liquid crystal display sheet members 1 and 21 are suitably used for displaying a large number of print information items or print information items that need to be frequently rewritten. It can be used for applications.

[0045]

As described above, according to the present invention, the liquid crystal element constituting the liquid crystal display sheet is composed of a pair of liquid crystal sheet substrates made of a material containing a plastic liquid crystal and a material containing a ferroelectric liquid crystal. A liquid crystal layer is used, and an alignment film is formed on the liquid crystal layer side of each liquid crystal sheet substrate. Writing and erasing of information can be performed only by passing the liquid crystal display sheet through an electric field, and the written information is retained even when the electric field is removed. Therefore, writing and erasing of information and holding of written information are possible even without an electrode. Since there is no electrode in this way, the configuration is simple, small, and lightweight.

Further, according to the present invention, since the same plurality of dot-shaped alignment films are arranged in a matrix, matrix display is possible. Since the shape of the alignment film formed on each liquid crystal sheet substrate is the same, it can be easily formed in the same process.

According to the present invention, color display is possible. In particular, by sharing a common member in each liquid crystal element, components are simplified, and miniaturization and weight reduction are achieved. In addition, by using a ferroelectric liquid crystal material in which dyes of each color are mixed, one of the polarizing plates can be omitted, the components can be simplified, and the size and weight can be reduced.

According to the present invention, since the liquid crystal layer contains a dye, the structure can be simplified by using only one polarizing plate. Further, since the transflective reflector is used, a bright display can be realized by using external light such as sunlight or fluorescent light and internal light such as a backlight.

According to the present invention, information can be written or erased by passing the liquid crystal display sheet between a pair of charging members to which a predetermined write voltage or erase voltage is applied.

According to the present invention, by using a charging roller or a charging head as the charging member, writing and erasing of information can be easily realized by using an existing electrophotographic system or a printing system such as an LED printer.

[Brief description of the drawings]

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

FIG. 2 is a perspective view of the liquid crystal display sheet 1. FIG.

FIG. 3 is an enlarged view showing a dot shape of a pixel 8;

FIG. 4 is a diagram for explaining the operation principle of the liquid crystal display sheet body 1;

FIG. 5 is a diagram for explaining an information writing and erasing system using charging rollers 15 and 16;

FIG. 6 is a perspective view for explaining an information writing and erasing system using the charging heads 18 and 19.

FIG. 7 is a waveform diagram showing an applied voltage.

FIG. 8 is a sectional view of a color liquid crystal display sheet body 21 according to a second embodiment of the present invention.

FIG. 9 is a diagram for explaining a method of using light of a color liquid crystal display sheet body 21 using a transflective reflector 24.

FIG. 10 is a sectional view showing a conventional information recording medium 51 disclosed in Japanese Patent Application Laid-Open No. 64-7018.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Liquid crystal display sheet body 2,3,22 Polarizer 4,23,23Y, 23M, 23C Liquid crystal element 5,6,35-38 Liquid crystal sheet member 7,39-41 Liquid crystal layer 8,8a-8c Pixel 9,11, 25, 27, 30, 33 Liquid crystal sheet base material 10, 12, 26, 28, 29, 31, 32, 34 Alignment film 15, 16 Charging roller 17 Voltage applying device 18, 19 Charging head 21 Color liquid crystal display sheet 24 Half Transmissive reflector 42 Internal light source 43 External light source

Claims (6)

[Claims] 1. A liquid crystal device comprising: a pair of polarizers; and a liquid crystal element disposed between the polarizers. The liquid crystal element includes a pair of liquid crystal sheet substrates, and a liquid crystal layer sandwiched between the liquid crystal sheet substrates. An alignment film formed on the liquid crystal layer side of each liquid crystal sheet substrate, wherein the liquid crystal sheet substrate is made of a material containing plastic liquid crystal, and the liquid crystal layer is made of a material containing ferroelectric liquid crystal. Liquid crystal display sheet. 2. The liquid crystal display sheet according to claim 1, wherein each alignment film has the same plurality of dot shapes and is arranged in a matrix. 3. The liquid crystal display sheet according to claim 1, further comprising a plurality of the liquid crystal elements emitting different colors. 4. The liquid crystal layer according to claim 1, wherein the liquid crystal layer includes a dye, and includes a transflective reflector disposed in place of one of the pair of polarizers. Liquid crystal display sheet. 5. A method for writing or writing information by passing the liquid crystal display sheet according to any one of claims 1 to 4 between a pair of charging members to which a predetermined write voltage or erase voltage is applied. A writing / erasing system for a liquid crystal display sheet, wherein erasing is performed. 6. The system according to claim 5, wherein the charging member is a charging roller or a charging head.