JP3018651B2 - Display panel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display panel capable of displaying and erasing an image using a composite film having a resin and liquid crystal dispersed in the resin, and more particularly to a photopolymerizable resin as the resin. Display panel.

[0002]

2. Description of the Related Art In recent years, attention has been focused on a display device in which a composite film having a resin and liquid crystal dispersed in the resin is sandwiched between substrates having a pair of electrodes. For example, JP-A-63-1
Japanese Patent No. 24024 describes a light valve in which a liquid crystal exhibiting a transition from a smectic phase to a nematic phase is dispersed in a polymer binder, written by heat, and erased by an electric field.

On the other hand, Japanese Patent Application Laid-Open No. Hei 1-210929 describes a liquid crystal display element and device in which a film-like liquid crystal layer in which a pigment and a liquid crystal substance are dispersed and held in a cured product matrix is sandwiched between a pair of substrates with electrodes. .

[0004] All of the techniques described in the above publications are:
This is a display device using a composite film having a resin and liquid crystal dispersed in the resin, and has a memory function that allows writing and erasing and stores written display information for a certain period.

Next, referring to FIGS. 3 to 5, the display principle of the prior art will be described. FIG. 3 is an explanatory diagram showing the relationship between the phase transition of the liquid crystal and the light transmittance. In FIG. 3, smectic A at room temperature
The phase liquid crystal S1 is in a state of a light-scattering focal conic domain, and has a light transmittance of 1 to 2%. As the temperature of the smectic A phase liquid crystal S1 is increased,
Eventually, the liquid crystal S2 becomes a nematic phase. The liquid crystal S2 in the nematic phase is light-scattering, and has a light transmittance of 1 to 2%, similarly to the liquid crystal S1 in the smectic A phase. When the temperature of the liquid crystal S2 in the nematic phase is further increased, the liquid crystal S3 in the isotropic phase (isotropic) is obtained.

When the liquid crystal S3 in the isotropic phase is cooled, an electric field E = 0 is applied to the liquid crystal S3, that is, the liquid crystal is cooled without applying an electric field. Transition to a different state (phase). That is, when cooling in the state of E = 0, as shown in FIG. 4, the liquid crystal S2 becomes a nematic phase in a light scattering state, and further, a smectic A phase in a state of a focal conic domain having the same light scattering property as the first. It becomes the liquid crystal S1. However, when the cooling is performed in a state where a predetermined electric field E other than 0 is applied, as shown in FIG. 5, the liquid crystal S4 becomes a nematic phase in a light transmitting state, and
The liquid crystal S5 has a light-transmitting homeotropic domain phase. The light transmittance of the liquid crystal S5 is 70 to 80%.

Therefore, in a state where an electric field is applied to a display panel having a composite film having liquid crystal dispersed in a resin,
An image can be displayed by performing writing scanning on the composite film by laser light or writing by heat conduction from a thermal head moving while contacting the display panel, and cooling while applying an electric field. it can.

[0008]

The performance of the display panel of this type of display device is determined by the performance of the composite film (resin and liquid crystal dispersed in the resin) which is capable of writing and erasing and has a memory function. It depends on the characteristics (display characteristics such as the degree of change in response speed and light transmittance, memory characteristics such as how long the display period lasts, temperature characteristics, durability, etc.). Therefore, an excellent display panel can be provided by using a composite film having excellent characteristics and being easily manufactured.

In view of the above circumstances, the present invention provides a display panel using a composite film having a resin and a liquid crystal dispersed in the resin, the display panel having excellent characteristics and using a composite film which can be easily manufactured. An object of the present invention is to provide a display panel.

[0010]

Next, the configuration of the present invention devised to solve the above-mentioned problem will be described. The components of the present invention correspond to the components of the embodiments described later. For the sake of simplicity, the reference numerals of the components of the embodiment are enclosed in parentheses. The reason why the present invention is described in correspondence with the reference numerals of the embodiments described below is to facilitate understanding of the present invention, and not to limit the scope of the present invention to the embodiments. In order to solve the above-mentioned problems, a display panel according to the present invention comprises a composite film (3) in which a smectic liquid crystal is dispersed in a transparent photopolymerizable resin; A colored pixel sheet (P2) in which colored pixels are arranged on a white sheet that reflects light of a predetermined color forward when light enters, and a front side disposed on the front side and the rear side of the composite film (3), respectively. It has a transparent electrode film and a rear transparent electrode film.

Further, the display panel according to the present invention is characterized in that, in the display panel, the colored pixel sheet (P2) is made of a material having high thermal conductivity.

The display panel according to the present invention having the above-mentioned features is
A voltage is applied between the transparent electrode films to form the composite film (3).
Image writing and erasing are performed by an image writing unit having an electric field applying unit for applying an electric field to the substrate and a heating unit for selectively heating a portion corresponding to each of the colored pixels of the composite film (3) to increase the temperature. It can be carried out.

As the smectic liquid crystal, a liquid crystal which exhibits a smectic A layer at a use environment temperature and has a nematic phase showing a positive dielectric anisotropy at a use environment temperature or higher can be used.

The above-mentioned “composite film in which a smectic liquid crystal is dispersed in a transparent photopolymerizable resin” is used to prepare a mixed solution of a liquid crystal material and a photopolymerizable resin at a temperature at which the liquid crystal is stably present. By polymerizing, a microstructure having a liquid crystal phase and a photopolymerizable resin phase both interconnected three-dimensionally can be easily produced. Further, the rear transparent electrode film of the display panel can be disposed on an arbitrary front side or rear side of the colored pixel sheet.

The "heating means for selectively heating a portion corresponding to each of the colored pixels of the composite film to raise the temperature" may be a laser beam scanning device disposed apart from the display panel, or the display means. A thermal head or the like disposed in contact with the rear surface of the panel can be employed.

[0016]

Next, the operation of the display panel of the present invention having the above-described structure will be described. The composite film in which the smectic liquid crystal is dispersed in the transparent photopolymerizable resin is obtained by polymerizing the photopolymerizable resin while maintaining a mixed solution of the liquid crystal material and the photopolymerizable resin at a temperature at which the liquid crystal is stably present. , Easy to manufacture. Then, a display panel is manufactured by laminating a colored pixel sheet disposed on the rear side of the composite film, and a front transparent electrode film and a rear transparent electrode film disposed on the front side and the rear side of the composite film. be able to. In a state where a voltage is applied between the transparent electrode films of the display panel by applying an electric field and an electric field is applied to the composite film, a portion corresponding to each of the colored pixels of the composite film is heated by the heating unit. When the temperature is increased by selective heating, the heated portion becomes transparent and an image is written. When the display panel on which the image is written is cooled while an electric field is applied to the composite film, the written image is displayed as it is. The colored pixel sheet emits light from the front.
White sheet that reflects light of a given color forward when it enters
It has a configuration in which colored pixels are arranged thereon. others
Therefore, the display panel of the present invention uses color printed on white paper.
Like a picture, you can obtain a natural image when you observe it directly.
Can be. When the colored pixel sheet is made of a material having high thermal conductivity, energy efficiency can be improved when writing an image from the rear side of the display panel.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing a reflective color image display panel which is an embodiment of the display panel of the present invention. In FIG. 1, a front plastic film 1 having ITO formed on the entire rear side (lower side in FIG. 1) and a front side (in FIG. 1,
A composite film 3 is disposed between the upper plastic film 2 and the rear plastic film 2 on which the ITO is formed on the entire surface. The front plastic films 1 and 2 and the composite film 3 constitute a composite film panel P1. On the rear surface (the lower surface in FIG. 1) of the rear plastic film 2, yellow (Yellow) Y and magenta (Magenta) are provided in small fine pixel units.
M, colored pixel sheet P2 colored cyan (Cyan) C
Is arranged. A display panel P is composed of the colored pixel sheet P2 and the composite film panel P1.

In order to display on the display panel P, an electric field applying means for applying a voltage between the transparent electrode films to apply an electric field to the composite film, and corresponding to each of the colored pixels of the composite film. An image writing unit is used which comprises a heating unit for selectively heating a portion to increase the temperature. That is, the portion corresponding to the pixels Y, M, and C of the composite film 3 containing the liquid crystal which becomes the smectic A phase at room temperature is selectively heated by the heating means to make a transition to the isotropic phase. When the composite film 3 is cooled while applying an electric field, the heated portion 32 (see FIG. 1) becomes transparent. When the display panel P is viewed from the front side, a color image can be seen.

The composite membrane panel P1 was composed of 1 part of an acrylic photopolymerizable resin, 4 parts of a smectic A liquid crystal composition (4 parts of "S2" manufactured by BDH), and a polymerization initiator (0.2 part of "Darocur 1116" manufactured by Merck). Part, monoazo metal complex salt dye
After the mixture obtained by dissolving 02 parts is uniformly applied on the above-mentioned plastic film with ITO, another plastic film with ITO is superimposed, and the resin component in the mixture is polymerized and cured by irradiating UV. When the performance of the composite membrane panel P1 was tested, when a 50 V alternating current was applied in the nematic phase, the transmittance of the transparent portion 32 in the smectic phase was 72%, and the transmittance of the cloudy portion 31 was 0.7%. there were. When the cross section was observed with a scanning electron microscope, a uniform three-dimensional fine structure of 1 to 1.3 μm was recognized.

On the other hand, a colored pixel layer composed of yellow Y, magenta M, and cyan C is colored by a pigment in a toner using an electrophotographic process by digital recording, and each color has a high whiteness at a recording density of 400 lines / inch. Written on smooth paper. As shown in FIG. 2A, the pattern of the colored pixels is such that the transmission control portion using the stripe shape and the colored pixel portion are overlapped to form a color image display panel. Exposure was performed with the -model ("Model 2004" manufactured by Uniphase Corporation) so as to correspond to the color-developed pixels, and the transmittance was selectively changed by heat generation due to light absorption in the composite film. as a result,
As shown in FIG. 1, an image could be displayed between the unexposed composite film portion 31 and the composite film portion 32 corresponding to the exposed pixels. That is, in the non-exposed portion 31 of FIG. 1, a white turbid state is displayed, and in the exposed portion 32 where the image is written by the laser, the color image of yellow Y, magenta M, and cyan C is opposite to the colored pixel through the composite film. It could be observed from the side (front side). Also written in this way,
The displayed color image is maintained at a temperature at which the liquid crystal of the composite film 3 becomes a smectic A phase. When the sample was left for two months, almost the same image as the image at the time of writing was retained, and the memory property could be confirmed. afterwards,
When the entire sample was re-exposed, it was confirmed that the entire sample became cloudy.

Further, in the colored pixel sheet P2 of the display panel P shown in FIG. 1, a structure is provided in which a white portion is provided between each pixel as shown in FIGS. 2A, 2B and 2C. Let S be the unit area of the pixel, and let m be the area of the white portion in the area corresponding to the unit area when the white portion is provided. When the following equation is satisfied, the crosstalk is satisfied. Does not occur (the color of the non-display pixel adjacent to the display pixel is not displayed), and an image with high contrast was obtained.

In addition, in the colored pixel layer of the colored pixel sheet P2, when each of the colored pixels of yellow Y, magenta M, and cyan C contains a monoazo metal complex salt dye that absorbs an Ar laser, it is visually observed. An image could be written from the side of the colored pixel on the side (front side) and the side opposite (rear side), and the transparency of the composite film 3 could be improved.

The embodiments of the display panel according to the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiments, and does not depart from the present invention described in the claims. Various small design changes can be made. For example, it is possible to use a semiconductor laser light source or another laser light source in a laser scanning device used for a heating unit that selectively heats a portion corresponding to each of the colored pixels of the composite film to increase the temperature. . Further, instead of the laser beam scanning device, it is also possible to use a thermal head disposed in contact with the rear surface of the display panel. Various patterns other than the pattern shown in FIG. 2 can be adopted as the arrangement pattern of the colored pixels. The colored pixels can be formed by using a conventionally known printing process.

[0024]

The display panel of the present invention has a structure in which the composite film for controlling the light transmittance has a structure in which a smectic liquid crystal is dispersed in a transparent photopolymerizable resin. A composite film having such a structure is formed by polymerizing a photopolymerizable resin while maintaining a mixed solution of a liquid crystal material and a photopolymerizable resin at a temperature at which the liquid crystal is stably present, thereby forming a liquid crystal phase and a photopolymerizable resin phase. It is possible to easily manufacture a microstructure in which both are three-dimensionally interconnected. Further, the composite membrane having the above structure,
It has sufficient practicality in display characteristics, such as the degree of change in light transmittance, and memory characteristics, such as how long a display period lasts. In the colored pixel layer of the colored pixel sheet P2, yellow Y, magenta M, cyan C
When each of the color-developed pixels contains a monoazo metal complex dye that absorbs an Ar laser, an image can be written from the colored pixel side opposite to the viewing side (front side) and the opposite side (rear side). The transparency of the film 3 was also improved. Ma
In addition, when the colored pixel sheet receives light from the front,
Colored pixels on a white sheet that reflects light of a given color forward
Are arranged. Therefore, the table of the present invention
The display panel looks like a color image printed on white paper,
Natural images can be obtained when observed directly.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the configuration of an embodiment of a display panel according to the present invention.

FIG. 2 is an explanatory diagram of a colored pixel sheet of a display panel according to the present invention.

FIG. 3 is an explanatory diagram showing the relationship between the phase transition of the liquid crystal and the light transmittance.

FIG. 4 is an explanatory diagram of the light transmittance of a liquid crystal in a nematic phase when the liquid crystal is cooled in a state of an electric field E = 0.

FIG. 5 is an explanatory diagram of a light transmittance of a liquid crystal in a nematic phase when the liquid crystal is cooled in a state where a non-zero electric field E is applied.

[Explanation of symbols]

 P2: colored pixel sheet 3: composite film,

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuo Terao 2274 Hongo, Ebina-shi, Ebina-shi, Kanagawa Prefecture Inside the Fuji Xerox Co., Ltd. In-house (56) References JP-A-2-4215 (JP, A) JP-A-2-200828 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/1333 G02F 1 / 133 565 G02F 1/1335 505

Claims (2)

(57) [Claims] 1. A composite film in which a smectic liquid crystal is dispersed in a transparent photopolymerizable resin, and a white color laminated on the rear side of the composite film and reflecting light of a predetermined color forward when light enters from the front. a display panel having a color pixel sheets colored pixels are arranged on the sheet, and each arranged front transparent electrode film and the rear side transparent electrode film on the front side and the rear side of the composite membrane. 2. The display panel according to claim 1, wherein the colored pixel sheet is made of a material having high thermal conductivity.