JPH022514A - Image forming medium and method thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to outputting an image by receiving an image signal, facsimile signal, or other image signal output from a floppy disk, optical disk, magneto-optical memory medium, computer, etc. The present invention relates to an image forming medium and an image forming method for displaying, and particularly to an image forming medium and an image forming method for outputting diversified color images.

[Prior Art] Traditionally, video output from televisions and VTRs and output from interactions with computers have been output and displayed on CRT (cathode ray tube) and TN (twisted nematic) liquid crystal display monitors, and have been output and displayed on WP (word processors) and High-definition images such as documents 2 figures etc. by facsimile etc. have been output and displayed on paper as printed hard copies.

[Problem to be solved by the invention] However, although CRTs output beautiful images when outputting the above-mentioned moving images, flickers and scanning stripes due to insufficient resolution deteriorate visibility when it comes to static images for long periods of time. There are some drawbacks that make it worse.

In addition, although conventional liquid crystal displays such as the above-mentioned TN liquid crystal have achieved flatness, they require manufacturing time and effort such as sandwiching the liquid crystal between a pair of glass substrates.
There were also problems with the screen being dark. Also, CRT and T
N liquid crystals have drawbacks such as the fact that even while outputting the above-mentioned still image, the beam and pixel voltage must be constantly accessed because they do not have a stable image memory.

In contrast, images printed on paper are high-definition,
In addition, although stable memory images can be obtained, if a large number of them are used, it takes up space to organize them, and if they are disposed of in large numbers, resources are wasted.

In order to realize a display device that can display and erase color images repeatedly, belt-shaped image carriers using methods such as electrostatic recording, electrophotographic recording, and thermal recording have been used. Various display methods have been proposed. For example, JP-A-57-17138
As shown in Japanese Patent No. 0, a method of forming a color image by a thermal method has been proposed. however,
This method requires the color paint to be arranged in a staggered pattern, and the color paint parts must be precisely selected using a heat-sensitive head, and it also requires a means to keep warm during display, so it has not been put to practical use. There may be a problem with this.

The present invention has been made to improve the shortcomings of the prior art, and is capable of expressing high-definition images, which were conventionally only available as hard copies, with the same sharpness as hard copies, and also expressing high-density color images. The object of the present invention is to provide an image forming medium on which an image can be repeatedly displayed and erased, and an image forming method thereof.

[Means for Solving the Problems] and [Operation] That is, the first invention of the present invention comprises a first polymer layer having a chiral structure, a second polymer layer capable of obtaining a light scattering state, and a first polymer layer having a chiral structure. The image forming medium is characterized in that the image forming medium has at least a layered structure, and the image forming medium is located in the mesophase temperature range of the first polymer layer or on the relatively lower temperature side than the mesophase temperature range of the second polymer layer. It is an image forming medium.

Further, the second invention of the present invention provides a method for applying heat to an image forming medium formed by laminating at least a first polymer layer having a chiral structure and a second polymer layer capable of obtaining a light scattering state. The first step is to provide a thermal signal that determines the transparent state of the second polymer layer, and the chiral pitch of the first polymer layer is controlled. and a second step of providing a thermal signal indicating desired coloration.

The present invention will be explained below with reference to the drawings.

FIG. 1 is an explanatory diagram showing an example of the layer structure of the image forming medium of the present invention. In FIG. 1, the image forming medium of the present invention is
A first polymer layer 2 and a second polymer layer 3 are sequentially laminated on a base 1.

The substrate 1 may be a transparent or opaque material such as glass, polyester, silicone rubber, or other materials.

In addition, the first polymer layer 2 can selectively reflect or transmit visible light by changing the temperature, and can also fix this by changing the temperature, and has a cholesteric liquid crystal phase or chiral smectic phase as an intermediate phase. A so-called side chain type or main chain type polymer liquid crystal layer exhibiting a liquid crystal phase is optimal.

Among the descriptions in L, descriptions of the coloration properties of selective reflection by changing the chiral pitch of cholesteric liquid crystal polymers depending on temperature and materials can be found, for example, in Hanzai, Asada, Abe, "Liquid Crystal Polymers," Chapter 3, 2. Section (1988) Sigma Publishing Co., Ltd.
ules) J Vol, 20. No, 2.298
(1987), Watanabe et al.
“Thermotropic polypebutides (T.
hernotr-opic PolypepLides
) 3 J, also r Makromol.

Chell, Makroiol, Symp, J.
12, p. 203 (1987), and other documents. Similar coloring properties are also expected for chiral smectic liquid crystal polymers due to their chiral pitch.

The second polymer layer 3 that can be used in the present invention has a main chain of a methacrylic acid polymer, a siloxane polymer, a polyester polymer, a polyamide polymer, etc., and a low molecular weight liquid crystal is added in a bent or linear form. Side chain type or main chain type thermotropic polymer liquid crystals are preferred. In addition, in the second polymer layer, in the liquid crystal phase as an intermediate phase, smectic, chiral smectic,
Nematic, cholesteric or other phase liquid crystals, discotic liquid crystals, etc. can be used. Hereinafter, several specific examples of the vine polymer liquid crystal used as the second polymer layer will be shown, but the present invention is not limited thereto.

MW = 18,000 ([1) 1ass 50℃ +00 One liquid crystal phase (Sol) C l5o.

(rV) In addition, dichloroethane, DMF, cyclohexanone, tetrahydrofuran (THF), acetone, ethanol and other polar or non-polar solvents, or mixed solvents thereof are used as solvents for coating and forming these films. It is selected depending on factors such as solubility with the polymer liquid crystal used or film formability.

Next, the functional characteristics of the second polymer layer 3 according to the present invention when the polymer liquid crystal represented by formula (I) is used alone will be explained in detail.

The polymeric liquid crystal represented by formula (I) above was dissolved in dichloroethane, and this was applied using an applicator onto a transparent Bossester base substrate that had been washed with alcohol.

Thereafter, when it was left in an atmosphere at 95° C. for 10 minutes, a white scattering film was formed. This film thickness is 10 gm when the concentration of polymer liquid crystal is 20 wt% before coating.
I got something like that.

When the thus obtained white sheet was scanned with a thermal head, the transparent portion was fixed according to the 9-character graphic pattern. When this sheet was introduced into a black Huck Clarand L with an optical density of 1.2, a clear display of black on a white background was obtained. Further, when this sheet was projected using a normal over-height projector (0HP) ζ, a clear white image was obtained on the screen.

Next, all 11'11 of the sheets on which the above pattern was recorded
After heating to about +20°C and then keeping it at about tOS°C for several seconds, when it was returned to room temperature, the entire surface returned to the original white scattering state, and it remained stable at room temperature and was recorded again.
I have been thinking about displaying it.

This phenomenon occurs in the film state below the glass transition point in which the polymeric liquid crystal maintains a stable memory state, in the liquid crystal film state in which it can maintain a substantially optical scattering state, and in the film state in which the polymer liquid crystal maintains a stable memory state. This can be controlled because at least three isotropic film states can be taken.

Here, the principle process of image formation using a polymeric liquid crystal layer will be explained using FIG. 2.

In FIG. 2, the above-mentioned scattering state is the state indicated by ■ in the figure. If this is heated to T2 (T, , , = isotropic state transition temperature) or higher as shown in ■a using a heating means such as a heat-sensitive head or a laser, and then rapidly cooled, it becomes almost isotropic as shown in ■ in the figure. The light transmission state similar to the state is fixed. In this rapid cooling state, it is sufficient to naturally dissipate heat from the substrate into the air without using any particular cooling means. This isotropic state is stable at room temperature or room temperature below T+ (Tg=glass transition temperature), and is a stable state as an image memory.

On the other hand, after heating to 12 or more as shown in Figure 1 (■a), if the liquid crystal temperature is held between T and -T2 for 1 second to several seconds, the scattering intensity increases again during this holding time as shown in ■b. , it returns to the original scattering state (2) again at room temperature, and this state is stably maintained below T1.

Also, as shown by ■ in Figure 1, if the liquid crystal temperature is held between 11 and 12 for about 10 milliseconds to 1 second, for example, the intermediate transmission state will be maintained at room temperature. It can also be used as a gradation expression.

That is, in the above case, the transmittance or scattering intensity can be controlled by how long the liquid crystal temperature is maintained at room temperature after being heated to an isotropic state.
Further, this can be stably maintained below T. Furthermore, in the above case, the temperature for returning to the scattering state should be the one closer to T2 within the liquid crystal temperature or faster, and if the liquid crystal temperature is left for a relatively long time, it may be necessary to return to the isotropic state. , it is possible to return to the scattering state (■) regardless of the previous state.

By the method described above, the polymer liquid crystal exhibiting a light scattering state and a transparent state is most suitable as the second polymer layer. In addition, polymers that exhibit light scattering effects by other known methods, such as phase-separated polymers and other phase-change type polymers, can also be used as the second polymer layer.

In the present invention, it is preferable that the mesophase temperature range of the first polymer layer is on a relatively lower temperature side than the mesophase temperature range of the second polymer layer.

The image forming method of the present invention thermally controls an image forming medium formed by laminating at least a first polymer layer having a chiral structure and a second polymer layer capable of obtaining a light scattering state. There is a control method that gives image information that has been
The first step is to change the thermal signal that determines the transparent state of the polymer layer.
and a second step of controlling the chiral pitch of the first polymer layer and changing the thermal signal that exhibits the desired coloration. In this case, it is preferable that the first step of generating a thermal signal that determines the transparent state of the second polymer layer includes a gradation signal.

[Example] Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 The image forming medium shown in FIG. 1 was used as the first polymer layer 2,
A thermotropic polymer liquid crystal represented by the following formula (V) shown in the above literature is laminated on top of the thermotropic polymer liquid crystal represented by the following formula (IT), for example, as the second polymer layer 3. It was made by

(IV) By adjusting the amount of the unit having a dodecyl group in the thermotropic liquid crystal having the structure represented by the above formula (V), and by selecting the temperature within the range of approximately 110°C to 135°C. , it can be used as a cholesteric liquid crystal that exhibits selective scattering/reflection/transmission with a dynamic range in the visible range.

That is, here, as shown in FIG. 5, the mesophase or cholesteric liquid crystal temperature range of the first polymer layer is equal to the mesophase (liquid crystal) temperature range of the second polymer layer (Tgz =
1.40°C to T112=196°C) is used.

The second polymer layer (polymer liquid crystal shown in formula (■)) exhibiting light scattering is in a transparent phase at a temperature of approximately 200° C. or higher. Therefore, for the layer, -200°C
After heating to the above temperature, the second polymer layer 3 is fixed in a transparent state when it is cooled relatively rapidly to a temperature below the glass transition point of the layer.

Alternatively, by appropriately selecting the heating temperature above the liquid crystal temperature of the second polymer layer (formula (■)) or the cooling process to below the glass transition point, an intermediate transparent state can be achieved as described above. It is possible to perform gradation expression.

On the other hand, the first polymer layer exhibits a coloring property that has a dynamic range in the visible region below the glass transition point of the second polymer layer. Therefore, after approximately determining the transparency of the second polymer layer, the color of the first polymer layer can be determined by providing temperature control to the cooling process until the temperature reaches room temperature.

That is, thermal control is performed by a first step of providing a temperature distribution that determines the transparency of the second polymer layer, and a second step of providing a temperature distribution that determines the color development of the first polymer layer. Thus, the imaging medium of the present invention can express and fix color images.

Here, as an effective method for providing the above-mentioned temperature distribution, there is a method such as modulating the pulse duty of the heating head or the voltage level applied to the heating head according to each color. Since the image formed as described in L has shading in color, it is theoretically possible to provide a full-color image.

FIG. 6 shows a schematic representation of the energy level given to the heating head in the form of a pulse in order to carry out the image forming method of this embodiment. In addition, in FIG. 6, although there may be some overlap in the mesophase temperature ranges of the first polymer layer and the second polymer layer, )≦Tg2 (glass transition temperature of the second polymer layer), it is easier to control image formation.

In order to erase the image formed by the above method, the image forming medium is heated to at least the isobathic phase transition temperature of the second polymer layer or higher, and then slowly cooled to cause a white scattering state on the surface. is obtained.

The above-mentioned effect of color development on the image forming medium of the present invention is achieved by using the first polymer layer as the lower layer, the second polymer layer as the soil layer, and applying thermal means from the second polymer layer side. The second polymer layer is the lower layer, the first polymer layer is the upper layer, and the thermal means is driven from the first polymer layer side. In the case of a heating head, the upper layer surface is coated with silicone resin, fluorine resin,
A thin layer of polyimide or other material may be provided as a protective layer.

In addition, when the first polymer layer is provided as a lower layer, an alignment film of polyimide, PVA, or the like may be provided on the surface of the substrate l, and an upward alignment process such as rubbing or a vertical alignment process using other methods may be performed. This layer is effective for increasing the color purity of the coloring property, and is also effective in increasing the color purity of the color development in this layer. Further improving the orientation of the first polymer layer by providing an alignment layer similar to the above alignment film between the second polymer layers on the first polymer layer by shearing coating or other method. It's coming.

If the image forming medium and the image forming method of the present invention as explained above are used, FIGS. 3(a), (b) and 4
With a display device as shown in the figure, it is possible to obtain a direct view type or projection type display.

In the display devices shown in FIGS. 3(a) and 3(b), a color image can be viewed directly against a white background, and the fourth
If projected onto a white screen using the display device shown in the figure,
Projection color that provides color brightness on a dark background colorant. This is due to the effect of providing the second polymer layer as an optical scattering layer.

[Effects of the Invention] As explained above, according to the present invention, for example, a desired color can be selected and obtained for one dot of the heating head, and high-density color images can be repeatedly produced. Can be displayed and deleted.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of the layer structure of the image forming medium of the present invention, and FIG. 2 is a diagram showing the relationship between temperature, transmittance, and scattering intensity of the polymer liquid crystal used in the second polymer layer. 7. FIGS. 3(a), 4(b) and 4 are explanatory diagrams showing a display device using a final IJI image forming medium, and FIG. Second
An explanatory diagram showing the relationship between the mesophase liquid crystal temperature range of the polymer layer in Embodiment 1 and FIG. Second
FIG. 3 is a schematic diagram showing the energy given to the heat generating head of the step in the form of pulses. 1... Base 2... First polymer layer 3
...Second polymer layer

Claims (4)

[Claims] (1) An image forming medium in which at least a first polymer layer having a chiral structure and a second polymer layer capable of obtaining a light scattering state are laminated, wherein the intermediate phase of the first polymer layer An image forming medium characterized in that the temperature range is on a relatively lower temperature side than the mesophase temperature range of the second polymer layer. (2) The image forming medium according to claim 1, wherein the first polymer layer exhibits a cholesteric liquid crystal phase or a chiral smectic liquid crystal phase as its intermediate phase. (3) Provide thermally controlled image information to an image forming medium formed by laminating at least a first polymer layer having a chiral structure and a second polymer layer capable of obtaining a light scattering state. a first step of providing a thermal signal that determines the transparent state of the second polymer layer;
and a second step of controlling the chiral pitch of the polymer layer and providing a thermal signal indicating desired coloration. (4) The image forming method according to claim 3, wherein the first step of providing a thermal signal that determines the transparent state of the second polymer layer includes a gradation signal.