JP2632946B2 - Color image display device and color image display method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention receives and outputs an image signal or a facsimile signal or other image signal output from a floppy disk, an optical disk, a magneto-optical memory medium, a computer or the like. Regarding an image display device and an image display method,
In particular, the present invention relates to an image display device and an image display method for outputting diversified color images.

[Conventional technology]

Conventionally, video output from TVs and VTRs and output during interactive work with computers have been CRT (CRT) and TN
(Twisted nematic) High-definition images such as documents and graphics by WP (word processor) and facsimile have been output and displayed on paper as hard copies printed on liquid crystal display monitors.

Here, the CRT outputs a beautiful image with respect to the above-described moving image output, but with respect to an image that has been stationary for a long time, flicker and scanning stripes due to insufficient resolution lower visibility. Further, although the conventional liquid crystal display such as the above-mentioned TN liquid crystal realizes flatness, there are problems such as troublesome production such as sandwiching a liquid crystal on a glass substrate and a dark screen. CRT and TN liquid crystals also have a drawback that even during the output of a still image as described above, there is no stable image memory, so that the beam or pixel voltage must always be accessed.

On the other hand, the image output on paper is high definition,
Although a stable memory image can be obtained, the use of a large amount of it requires space for organizing, and wasteful use of resources due to disposal in large quantities does not become ridiculous.

Therefore, an image display method for configuring a display device capable of expressing a high-definition image that was conventionally obtained only as a hard copy with the same sharpness as a hard copy, and displaying and erasing it repeatedly has been studied. Various display methods using a belt-shaped image carrier using methods such as electrophotographic recording and thermal recording have been proposed. For example,
57-171380 proposes a method for forming a color image by a thermal method.

[Problems to be solved by the invention]

However, in the conventional image display method, it is necessary to arrange the color paints in a staggered manner, and to precisely select the color paint portions with a thermal head, and to provide a means for keeping the temperature warm during display. Practical application has been difficult due to the disadvantages described above. In order to solve the above problem, the present inventors formed an image on the image carrier using the difference in optical scattering state, prepared a color pattern separately from the image, and combined the two as one unit. (Japanese Patent Application No. 62-336125). According to this, since the image carrier and the color pattern are separate, a high-definition color image without flicker can be easily obtained. The principle of image display is as shown in FIG. 8, in which an image is formed by a difference in optical scattering state of the image carrier 10 by the polymer liquid crystal 21, that is, a transparent state and an opaque state. When light is irradiated, light passes through the color pattern 12 in the image portion formed on the image carrier, and furthermore, a color image is displayed.

The present invention is to further improve the color display method, which can be widely applied in the color display method having the above structure, and specifically, to prevent display color crosstalk,
It is an object of the present invention to provide an apparatus and a method which enable a sharper color display.

[Means for solving the problem]

According to the present invention, a color image is converted into position information, and a transparent-opaque pattern is formed on an image carrier having a polymer liquid crystal that becomes transparent by rapid cooling after heating,
A color image display device and a color image display method for displaying an image by using the color light scattered by the opaque portion by combining the carrier and a color pattern, wherein the polymer liquid crystal is heated to an isotropic state once. After that, a means for forming the transparent-opaque pattern by controlling the transmittance or the scattering intensity according to the holding time at the liquid crystal temperature up to room temperature is provided, and the transparent-opaque pattern and the corresponding The use of a color image display device and a color image display method in which the positions of the color patterns and the color patterns are shifted in accordance with the incident angle of light that is transmitted substantially linearly, prevents crosstalk other than display colors, and provides a clear desired color. Contrast can be obtained.

Hereinafter, a basic configuration of a color image display according to the present invention will be described in detail. In the present invention, as a material for forming a transparent-opaque pattern on a sheet, a material exhibiting thermotropic liquid crystallinity is preferable. For this example,
A so-called side-chain type polymer liquid crystal in which a low-molecular liquid crystal having a methacrylic acid polymer or a siloxane polymer as a main chain is added in a pendant form, or a polyester type used in the field of high-strength high-elasticity heat-resistant fiber or resin, or It is a main chain type polymer liquid crystal of a polyamide type or the like.

As the liquid crystal phase, a liquid crystal phase having a smectic, nematic, cholesteric or other phase, or a discotic liquid crystal may be used.

Further, a polymer liquid crystal having a phase exhibiting SmC ^* in which asymmetric carbon is introduced into the polymer liquid crystal and exhibiting ferroelectricity can be preferably used.

Hereinafter, specific examples of the polymer liquid crystal will be described, but the present invention is not limited thereto.

In the liquid crystal as described above, the optical anisotropy changes depending on the temperature, the temperature rise and the cooling rate, and the light transmittance changes. The principle of image formation in the present invention utilizes this property of liquid crystal. Next, referring to FIG. 7, a principle process in a case where a polymer liquid crystal layer is provided on a transparent substrate will be described.

In FIG. 7, the state of light scattering is shown. This is heated above T ₂ (Tiso = isotropic state transition temperature) as shown in a by a heating means such as a thermal head or a laser or the like, and then rapidly cooled, as shown in FIG. Is fixed. In this quenched state, it is sufficient that the substrate is naturally radiated into the air without using any cooling means. This isotropic state is stable at room temperature or room temperature below T ₁ (Tg = glass transition temperature), and is also a stable state as an image memory.

Meanwhile after heating to T ₂ or more as a, liquid crystal temperature T ₁ ~
Holding toward one second to several seconds as an example between T _2,
b as described, increasing the scattering strength again in this retention time, return to the original scattering state again at room temperature, this state is stably retained in the T ₁ or less.

Further, as shown in the figure, if the liquid crystal temperature is held for about 10 ms to 1 second as an example between T _{1 and} T ₂ ,
In that part, an intermediate transmission state can be maintained at room temperature, and it can be used as a gradation expression.

That is, in this example, once heated to the isotropic state,
Before reaching the room temperature can be controlled transmittance or the scattering intensity at either time held in how much the liquid crystal temperature, and which in T ₁ or less can be held stably. Further, in the above, the temperature when returning to the scattering state,
It is more quickly close to T ₂ in the liquid crystal temperature, In addition, in the case, such as a relatively long period of time left in the liquid crystal temperature, even without heating once into isotropic state, occupies return to the scattering state of regardless of the previous state It is possible.

Using a liquid crystal having the above properties, a transparent portion and a scattering portion are formed according to a desired image by adjusting a heating state, and a color image is displayed by combining this with a color pattern and irradiating light. be able to.

Next, components for actually performing color image display will be described. First, the above-mentioned liquid crystal is applied to a substrate to form an image carrier. In this case, a liquid crystal is applied using a solvent to form a film on a transparent substrate made of glass, polyester, or the like that has been subjected to alcohol washing or the like. Coating characteristics can be adjusted, but solvents such as dichloroethane, DMF, cyclohexane, tetrahydrofuran (THF), acetone,
Ethanol or other polar or non-polar solvents or mixed solvents thereof are used, which are soluble in the polymer liquid crystal used and wettability with the material of the substrate on which it is coated or the surface layer provided on the surface of the substrate. , Depending on factors such as film formability.

In order to obtain a more beautiful image, the concentration by weight of the liquid crystal relative to the solvent is such that after addition and stirring, a clear solution or a viscous state is obtained. For example, when the polymer liquid crystals represented by the structural formulas (I) to (IV) are individually dissolved in dichloroethane, the concentration by weight of the polymer liquid crystals is 10%.
In, the solution is in the form of a cloudy micelle,
At a relatively high concentration of about 25% to 25%, a stable transparent viscous solution is obtained. This tendency is also observed in combination with several other types of polymer liquid crystals and solvents. This transparent viscous solution is thoroughly washed by means of an applicator, wire bar or dipping glass,
If the temperature is maintained at the liquid crystal temperature after coating on a base material such as polyester, an optical scattering film having very high uniformity can be obtained as compared with the case where the coating is similarly performed in the micelle state.

That is, in the process of evaporating the solvent after dissolving the liquid crystal in a solvent and applying it on a substrate, or after evaporating the solvent,
By keeping the substrate at a liquid crystal temperature (75 ° C. to 110 ° C.) for a certain period of time, a stable optical scattering film can be formed.

Among the liquid crystals, polymer liquid crystals such as those represented by the structural formulas (I) to (IV) are preferable, and a solvent used for coating is a mixed solvent of a plurality of solvents or a mixture other than the polymer liquid crystal material. , A coloring material and the like can be added in a range that does not adversely affect the coating. The obtained film thickness is 20% by weight based on the solvent weight of the polymer liquid crystal of the coating agent.
In this case, it is about 10 μm, and generally 2 to 15 μm.

By scanning the thus obtained image carrier with a thermal head, a desired character or graphic pattern can be fixed as a transparent portion. If this image carrier is guided on a black background having an optical density of 1.2, a clear display of black on a white background will be obtained.

Further, the image can be deleted. That is, the entire surface of the image carrier on which the image is recorded is heated to about 120 ° C., and then kept at about 105 ° C. for several seconds, the entire surface returns to the original white scattering state, and is stable even when returned to room temperature. Yes, recording and display can be performed again. This phenomenon can be controlled by the normal change of the liquid crystal shown in FIG. On the other hand, when the image carrier on which the image is recorded is guided on a color pattern and irradiated with a backlight or a front light source, a color display image can be visually observed depending on the alignment of the color pattern and the image carrier.

As the color pattern, for example, a generally used pattern in which R (red), G (green), and B (blue) are sequentially formed at a pitch of 125 μm can be used. The principle of color display is as follows. The image portion fixed as the transparent portion of the image carrier is composed of dots having the same pitch as the pitch of the color pattern. If this dot matches the position of R of the color pattern, red light is transmitted, and G If the position is matched, green light is transmitted, but the color light that has passed through the transparent portion of these image carriers does not enter the field of view when viewed at a position deviated from the direction of the incident angle of light, and conversely, the image carriers Are scattered, and they are clearly seen as scattered light. For example, when R (red), B (blue), and G (green) color patterns are used, if R passes through the transparent portion, B and G scattered by the scattering portion are visually observed. Has a mixture of B and G because the dots are small enough.
Seen as cyan. As a result, the whole becomes one color display image. In the above description, light that is not scattered and is transmitted through the image carrier is referred to as substantially linearly transmitted light.

In the above-described structure for color display, since the color pattern and the image carrier are separate, a normal thermal printer, FAX, etc. can be used to draw an image on the image short itself. It has the advantage of being able to easily output a color image because it can be easily done if it matches, but the inevitable gap between the color pattern and the image carrier, the liquid crystal layer on the image carrier Due to the thickness and the thickness of the color pattern, the pitch of the color pattern and the dots constituting the image may not match well with the light irradiation.

That is, a color pattern, light passing through the image carrier is perpendicularly incident on both, and a beautiful color image is displayed if the dot positions of both perfectly match,
If the angle of incidence of the light deviates from the vertical line, the pitch between the image dots and the color pattern does not coincide with the light incidence due to the color pattern, the thickness of the image carrier, and the gap between the two. The scattered light overlaps on the boundary of the scattering portion of the image carrier, so that so-called crosstalk occurs, and a clear color contrast cannot be obtained.

In general, since an image is viewed from the front, it is not appropriate to make the incident angle direction of light vertical, so the above phenomenon inevitably occurs. If the degree of crosstalk is roughly calculated by setting the incident angle of light to be constant, the gap between the color pattern including the thickness and the image carrier is set to l, the incident angle of light θ, and the pitch of the pattern and the The deviation Δ from the dot is Δ =
ltanθ. If θ = 30 ° and l = 20 μm, Δ
= 11.5 μm, and a mixture of colors other than the display color occurs at about 9% of the pitch of 125 μm.

In the present invention, the above-mentioned crosstalk is solved by the positional relationship between the color pattern and the image carrier. The details will be described below with reference to the drawings.

FIG. 1 shows a color image display using an oblique incidence backlight (light source + oblique projection Fresnel lens), which is viewed directly. In this case, the color pattern is on the light source side and the image carrier is on the outside, and a mirror image is formed.
The aligned color pattern and the image carrier are irradiated using an optical system that projects light having oblique directionality onto a backlight. By doing so, the color (R in the figure, red) that has passed through the transparent portion of the image carrier substantially linearly
Does not enter the visual field, the colors (G, green and B, blue) hitting the scattering portion of the image carrier are scattered, and these scattered lights are clearly recognized as a mixed color (cyan).

Further, in FIG. 1, with respect to the light beam obliquely incident substantially linearly, each dot of the color pattern and the position of forming the transparent portion of the image carrier are relatively shifted from the viewpoint, and the light transmitted through the color pattern is So that it does not enter the body scattering area,
By successfully transmitting the incident light beam in a direction deviating from the viewpoint, crosstalk of transmitted color can be prevented. On the other hand, when there is no such shift, a part of the light transmitted through the color pattern is incident on the image carrier scattering part, and a part of the scattered light is mixed.

The same applies to the case where the image carrier and the color pattern are arranged in reverse as shown in FIG. 2 in addition to the configuration shown in FIG. That is, in FIG. 2, crosstalk is prevented by preventing the scattered light from hitting the dots of the color pattern that should be transmitted substantially linearly. When the transparent portion is not formed on the image carrier and the entire surface is a scattering portion, the color becomes white. It should be noted that, even when the backlight optical system is not the light having the directivity in the oblique direction, but is an optical system that is substantially perpendicularly incident, the same color as described above can be visually observed by placing the viewpoint away from the front. .

It is more preferable that the dots of the transparent portion are slightly larger than the dots of the corresponding color patterns.

A mirror image is formed in FIG. 1 and a normal image is formed in FIG. 2, because the surface of the liquid crystal layer of the image carrier is just reversed.

As described above, in order to prevent light that transmits substantially linearly through the color pattern from hitting the scattering portion of the image carrier, or to prevent the scattered light from hitting the dots of the color pattern that should be transmitted substantially linearly, color The deviation between the pattern and the image carrier must be adequate. The degree of crosstalk is affected by the unevenness of the gap between the color pattern and the image carrier, the thickness of both, the incident angle of light, and the like.

First, the unevenness in the gap between the color pattern and the image carrier is preferably about 50 μm or less, and if it is larger than 100 μm, it is inevitable that light other than the display color enters the scattering portion. When the image carrier faces the light source and the color pattern is on the outside, scattered light enters the color pattern. Therefore, it is desirable that the gap be slightly narrower than in the case of the opposite positional relationship. Although the gap can be adjusted to some extent by the thickness of the protective layer of the liquid crystal layer on the image carrier, the gap can be adjusted appropriately according to the structure of the color display device.

On the other hand, the thickness of the color pattern and the thickness of the image carrier liquid crystal layer are usually about 0.1 to 5 μm and about 3 to 15 μm, respectively.

As the light source, both a backlight and a front light can be used, but in any case, a light source having a light directivity is preferable, and omnidirectional light from the light source is directional using a Fresnel lens or the like. Is desirable. The incident angle is preferably about 10 ° to 60 ° with respect to the color pattern or the image carrier, and within this range, it is effective for preventing crosstalk. When the light is incident at an angle larger than 80 °, it is difficult to prevent the occurrence of crosstalk even by adjusting the shift between the color pattern and the image carrier.

Within the range satisfying the above conditions, the positional deviation between the color pattern and the image carrier is further adjusted within the range of about 1 to 100 μm. If the thickness of the color pattern and the image carrier liquid crystal layer and the gap between them are set, the degree of crosstalk can be adjusted by the incident angle of light and the positional deviation between the two. That is, the positional relationship between the color pattern and the image carrier is shifted in accordance with the angle of incidence of the light that passes through the color pattern and the image carrier substantially linearly. The thickness is set in the above-described range, and the position between the color pattern and the image carrier is calculated from the incident angle of light that is transmitted linearly (see Δ above).
(= Ltan θ) is made slightly larger in consideration of refraction at the interface and the like, whereby crosstalk can be prevented and a clear image can be obtained.

In the above configuration, light is appropriately refracted at the interface between the air layer, which is a layer having a low refractive index, and the image carrier or the color pattern, particularly when a front light is used, and as a result, the image carrier is scattered. In the portion, an appropriate scattering intensity is obtained, and the substantially linearly transmitted light successfully passes through a predetermined position.

Incidentally, as a method of forming an image on the image carrier, a usual thermal printer, fax or the like can be used. For example, when an image carrier is passed through a thermal printer having a thermal head having a density of 8 dots per millimeter to form an image, the thermal head is separated from the thermal head by two image dots by another image processor. Prints a stripe turn so that one dot is continuously turned on.
R (red), G (green), B
If (blue) is combined with a stripe color pattern sequentially formed and R is transmitted, G and B light enter the scattering portion and the G and B scattered light can be visually observed as cyan. .

Incidentally, the polymer liquid crystal as described above has sufficient heat resistance,
Since the film strength is high, even if the polymer layer is directly rubbed and scanned with a thermal head, there is basically no problem with repeated image formation by image writing and erasing, but the strength is further increased as necessary. For this purpose, a protective layer of polyimide, aramid, or the like may be provided on the surface by lamination or the like, or a fluorine-based resin coating may be provided.

In addition, since a polymer liquid crystal has a large contrast between a transparent portion and an opaque portion (scattering portion) and a rapid change in liquid crystal state due to temperature, a clear image can be formed when this is used for an image carrier. The effect of preventing crosstalk by shifting the position of the image carrier and the color pattern is further enhanced, and a desired excellent color contrast can be obtained. Further, it is also possible to obtain a gradation display by changing the intensity of the voltage applied to each dot by a thermal head or the like at the time of drawing and changing the applied voltage pulse width.

As described above, various display modes can be obtained by using the difference between the transparent portion and the scattering portion. Therefore, if various color images corresponding to a desired color are recorded on the image carrier using a thermal head or laser heat or the like as a difference between the transparent portion and the scattering portion in which the color has been converted, this can be achieved. And a color pattern, a clear full-color image can be formed.

(Examples) Hereinafter, the present invention will be described in further detail with examples.

FIG. 3 is a configuration diagram of a display device for implementing the color image display method according to the present invention. The display device includes a recording unit including a thermal head 11, a scattering plate image carrier belt, a color filter (color pattern), a display unit including a Fresnel lens and a backlight, an image erasing unit including a surface heater and a temperature sensor, a roller, and an image. It is composed of a transport section composed of a carrier belt.

The image carrier belt 10 is composed of a polymer liquid crystal represented by the following structural formula on a transparent polyethylene terephthalate substrate having a thickness of 50 μm. Was dissolved in dichloroethane to form a 20% solution, which was applied with a wire bar, and left in an oven at 90 ° C. for 15 minutes to form a white scattering layer in an endless form. The thickness of the obtained liquid crystal layer was 8 μm.

The drive roller 17 is driven by a motor (not shown),
All other means can be operated by mechanical components, not shown, or electrical and electronic components.

First, at the time of image writing, the driving roller 17 is driven in the direction of the arrow, and an image signal is output to the thermal head (multi-head) 11 by a facsimile signal from another facsimile. An image-like transparent portion pattern is formed in the heated portion of the above. With this operation, the image-form transparent portion pattern for one page of the A4 size is sequentially formed, and then the display portion 20 stops.

FIGS. 4 to 6 show an example of an alignment detection method and a configuration for better matching each color of the formed transparent portion pattern and the color filter with the direction of the backlight light beam. In the present embodiment, the photocoupler 23 provided on the color filter 12 is used to match the transparent portion pattern formed on the image bearing belt 10 with the color pattern of the color filter 12. As an example, as shown in FIG. 4, a notch 24 is formed at the position of the blue end portion (B) of the color pattern of the color background 12 so that the light-emitting element 25 and the light-receiving element 26 face each other. 23 will be provided. This is seen from the side as shown in FIG. On the other hand, with respect to the image carrier belt 10, the blue (B)
The transparent portion 27 is always formed at the timing when 28 comes (see FIG. 6). Then, the desired transparent portion pattern is shifted by the thermal head 11 to each filter with respect to each filter as shown in FIG.
μm is written and guided to the display section 20, and the transparent section 27 formed corresponding to the top blue (B) is
When it comes to the position of the photocoupler 23, at this time, the detection amount of the light beam by the light emitting element 25 in the light receiving unit becomes maximum,
This is fed back to a belt drive motor (not shown) so that it can be stopped at a predetermined position.

In the present embodiment, as the protective layer of the liquid crystal layer, 3.5
A μm aramid sheet was provided by lamination, the average gap between the color filter and the image carrier was 10 μm, and the average incident angle of light was 45 °.

In the display section, by scanning the image carrier in the scattered transparent state, a beautiful color image was displayed in combination with the color filter provided in the display section as shown in FIG. 2 and the description thereof.

This image was left unchanged for 100 days.

Next, the image was erased by using the halogen roller 32 including the halogen lamp 14 and the roller 15 and the surface heater 13, and after displaying a predetermined image, the driving of the driving roller 17 was started again in the arrow direction. At this time, the halogen roller 32
Is controlled to approximately 115 ° C., and the surface heater 13 is controlled to approximately 95 ° C. from the detection output of the temperature sensor 16. When the state of the image carrier belt 10 was observed in this manner, when passing through the halogen roller 32, this portion became almost entirely transparent, and when passing through the surface heater 13, the entire surface again scattered white. By this operation, the entire display image was erased, and a white scattering state was obtained again. Here, the width of the surface heater 13 used in the above configuration in the belt moving direction was approximately 40 mm, and the entire surface was set to at least 74 ° C. or higher.

[Effects of the Invention] As described above, by appropriately shifting the positions of the image carrier and the color pattern in accordance with the incident angle of light, crosstalk other than display colors is prevented, and a clear and bright color contrast is obtained. be able to. In addition, according to this method, even when a high-contrast image is clearly viewed directly from the front, the above-mentioned crosstalk does not occur and excellent color display can be achieved. Note that the method of the present invention can be applied to a conventional sheet in which a color filter and an image carrier are integrated.

[Brief description of the drawings]

FIG. 1 is a schematic view of a color display unit for explaining a color display method of the present invention, and FIG. 2 is a color display unit for explaining a color display method of the present invention. FIG. 3 is a schematic diagram of a color display device having a positional relationship opposite to that of FIG. 1, FIG. 3 is a configuration diagram of a color display device used in an embodiment of the present invention, FIG. 4 to FIG.
FIG. 4 is a view showing a color pattern, FIG. 5 is a sectional view,
FIG. 6 is a diagram showing an image carrier, FIG. 7 is a diagram showing a relationship between temperature and light transmittance of the liquid crystal according to the present invention, FIG. 8 is a diagram showing a principle of a color display method, It is. 10 Image carrier 11 Thermal head 12 Color pattern (color filter) 13 Surface heater 14 Halogen lamp 15 Roller 16 Temperature sensor 17 Drive roller 18 Fresnel lens ( (Oblique direction) 19 background substrate 20 display unit 21 liquid crystal layer 22 transparent substrate 23 photocoupler 24 cutout 25 light emitting element 26 light receiving element 27 transparent part 28 …… Image part 29 …… Backlight 30 …… Incident light 32 …… Halogen roller

Claims (4)

(57) [Claims] 1. A color image is converted into positional information to form a transparent-opaque pattern on an image carrier having a polymer liquid crystal which is made transparent by heating and then rapidly cooled, and the carrier and the color pattern are formed. A color image display device for displaying an image using color light scattered by the opaque portion in combination, wherein the polymer liquid crystal is heated to an isotropic state once, and then maintained at a liquid crystal temperature until room temperature. Means for forming the transparent-opaque pattern by controlling transmittance or scattering intensity with time,
And a color image display device wherein the positions of the transparent-opaque pattern and the corresponding color pattern are shifted in accordance with the incident angle of light transmitted substantially linearly. 2. The image bearing member according to claim 1, wherein said image bearing member is transparent by a color image.
2. A color image display according to claim 1, further comprising: means for forming an opaque portion together with an opaque pattern; and means for aligning the image carrier with the color pattern by detecting the opaque portion. apparatus. 3. A color image is converted into positional information to form a transparent-opaque pattern on an image carrier having a polymer liquid crystal which is made transparent by heating and then rapidly cooled, and the carrier and the color pattern are formed. A color image display method for displaying an image using color light scattered by the opaque portion in combination, wherein the polymer liquid crystal is heated to an isotropic state once, and then maintained at a liquid crystal temperature until room temperature. The transparent-opaque pattern is formed by controlling the transmittance or the scattered intensity according to time, and the positions of the transparent-opaque pattern and the corresponding color pattern are respectively adjusted according to the incident angle of light transmitted substantially linearly. A color image display method characterized by displaying a color image by shifting. 4. The method according to claim 1, wherein said image bearing member is provided with a transparent color image.
4. The color image display method according to claim 3, wherein an opaque portion is formed together with the opaque pattern, and the position of the image carrier is aligned with the color pattern by detecting the opaque portion.