JP2000015866A - Image recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recorder capable of writing an image into a reversible thermal recording medium including a liquid crystal component in a high speed without deteriorating the recording medium. SOLUTION: This reversible thermal recording medium 1 includes a liquid crystal component wherein an indication color is changed in accordance with a heating temperature and the indication color is fixed when it is cooled. This recorder comprises an erasing roller 52, a preheating plate 54 and an optical modulating unit 60. The optical modulating unit 60 is so constituted that optical shutter elements each being made from a PLZT are arranged in a line in the direction perpendicular to the conveying direction of the recording medium 1. A light passing through an optical shutter element which is turned on emits the recording medium 1 to heat it so that an image can be written thereinto.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image recording apparatus, and more particularly to an apparatus for recording a predetermined image on a reversible thermosensitive recording medium having a liquid crystal compound exhibiting a cholesteric phase.

[0002]

BACKGROUND OF THE INVENTION In recent years, from the viewpoint of energy saving and environmental protection, development of rewritable sheets capable of rewriting information has been promoted for the purpose of paperless and paper saving. Also, various recording materials capable of rewriting information have been developed with the development of IC cards and prepaid cards. However, rewritable recording materials currently in practical use are black and white or monocolor, and materials capable of full color display are desired.

As a rewritable material capable of full color display, a polymer cholesteric liquid crystal compound is known, but the response speed at the time of recording is low, and it has not been put to practical use. A low-molecular-weight cholesteric liquid crystal compound has been proposed as a material that improves this. This liquid crystalline compound shows a cholesteric phase in a temperature range higher than room temperature, and shows a reflection color according to the temperature. Further, when the temperature is rapidly cooled from these temperatures, the reflection color before the rapid cooling is maintained. That is, the sheet on which the liquid crystal is uniformly applied is heated to various temperatures and cooled to obtain full-color information (image), and the image is erased by reheating to a certain temperature and cooling. Is also possible. The present inventors have studied the practical use of a recording medium having such a low-molecular-weight cholesteric liquid crystal compound.

[0004]

As described above, an organic low-molecular-weight cholesteric liquid crystal compound, which is a recording material capable of full-color display in a rewritable manner, determines a display color (reflection color or transmission color) in accordance with the heating temperature, as described above. The display color is fixed by rapidly cooling from that temperature. Therefore, by controlling the heating temperature, the display color can be freely selected and multi-color or full-color display can be performed. However, for that purpose, it is necessary to control the heating temperature with high accuracy for the two-dimensional recording area.

Conventionally, a thermal head has been widely used as a heating type recording means. The thermal head has a unique hysteresis effect that the temperature characteristic of the head changes due to accumulation of heat, and it is difficult to control the temperature with high accuracy. Writing at a slow speed can neglect the history effect, but is not practical. In addition, the thermal head performs writing while rubbing against the recording medium.However, in the case of a recording medium that can be written many times by rewritable, there is also a problem that the surface is deteriorated by multiple times of printing. ing.

Accordingly, an object of the present invention is to provide a recording medium in which the display color changes in accordance with the heating temperature and which rapidly cools from that temperature to fix the display color, at a high speed and with a deterioration of the recording medium. It is an object of the present invention to provide a recording apparatus capable of writing an image without causing the image to be written.

[0007]

In order to achieve the above object, an image recording apparatus according to the present invention comprises a light modulator in which a plurality of optical shutter elements are arranged in a line as heating means for recording an image. Means for controlling the heating temperature of the recording medium by modulating the light energy with each optical shutter element.

As a recording medium, a sheet having a recording layer made of a low-molecular cholesteric liquid crystal compound is used. This liquid crystal compound has a characteristic that the display color changes in accordance with the heating temperature, and the display color is fixed by rapidly cooling from that temperature. Therefore, by controlling the heating temperature, it is possible to freely select a display color and perform black-and-white display, mono-color display, or full-color display. When heated to a certain temperature and cooled, it shows a transparent or scattering state, and the recorded information is erased.

As the optical shutter element, an element such as PLZT or liquid crystal capable of modulating light on / off or multi-level transmittance is used. The temperature of the recording medium rises due to the energy of light transmitted through the optical shutter element, and a desired color is displayed. In particular, full-color images can be recorded by modulating the transmittance to multiple values. The recording medium is conveyed in a direction perpendicular to the direction in which the optical shutter elements are arranged, thereby recording a two-dimensional image.

According to the present invention, since a low-molecular-weight cholesteric liquid crystal compound having good heat-responsiveness is used as a recording medium and the heating temperature is controlled by a light modulating means, high-speed recording can be achieved, and full-color display can be achieved. Is also possible. Moreover, since the recording medium does not rub against the recording head or the like, the recording medium does not deteriorate even if the number of times of rewriting increases.

On the other hand, the image recording apparatus according to the present invention preferably has an erasing means for erasing an image already recorded on a recording medium. The quality of a newly recorded image can be improved. Furthermore, if there is a pre-heating unit for pre-heating the recording medium prior to the recording of the image, the recording process can be performed efficiently.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image recording apparatus according to the present invention will be described below with reference to the accompanying drawings.

(Explanation of Recording Medium) (First Example, see FIGS. 3 and 4) In FIG. 3, a reversible thermosensitive recording medium 1 as a first example includes a base layer 2, an intermediate layer 3, and a recording layer from below. 4. It is composed of a protective layer 5. The base layer 2 is made of paper or a flexible sheet material such as polycarbonate and PET (polyethylene terephthalate). The intermediate layer 3 includes a component having a function of absorbing visible light, and a surface in contact with the recording layer 4 is formed smoothly. Specifically, carbon black was dispersed in a silicon resin, and an isopropyl alcohol solution mixed with a catalyst was applied on the base layer 2 and dried and heat-cured.

When the intermediate layer 3 is colored and translucent, the base layer 2 may become light-absorbing or light-absorbing in combination with the intermediate layer 3 in order to reproduce a good full-color image. desirable. It is also possible to use a transparent material as the intermediate layer 3, but in that case, the base layer 2
It is desirable that the material has a light absorbing property.

The recording layer 4 is a liquid crystal layer containing a low-molecular-weight cholesteric liquid crystal compound.
The cholesteryl 0,12-docosadiindionate was mixed and dissolved, and this solution was coated on the intermediate layer 3 with a blade and dried by heating to obtain a reversible thermosensitive recording layer 4. The thickness of the recording layer 4 is preferably in the range of 3 to 50 μm, more preferably in the range of 6 to 30 μm. An infrared absorber may be added to the liquid crystal compound in order to increase heat generation due to light irradiation.

In the recording medium 1 as the first example, 87
When heated to ~ 115 [deg.] C, the cholesteric liquid crystalline compound exhibits a cholesteric phase in which the helical axis is oriented perpendicular to the intermediate layer 3, and reflects light having a specific wavelength according to the temperature. It shows a red color at about 87 ° C., a green color at about 95 ° C., and a blue color at about 115 ° C., and solidifies in its reflection state by quenching from those temperatures.

Further, if the mixture is heated to about 119 ° C. or more and then rapidly cooled, it becomes transparent. That is, the entire surface of the recording medium 1 is set to 119 ° C.
When the recording layer 4 is rapidly cooled after being heated as described above, the entire surface of the recording layer 4 becomes transparent. At this time, a black image is displayed for an observer who is viewed from the direction of arrow A because visible light is absorbed by the intermediate layer 3.

When the recording medium 1 is partially heated and quenched according to image information, the heated portion shows a reflection color according to the heating temperature. In FIG. 3, reference numeral 4a indicates a portion in a transparent state, and reference numeral 4b indicates a portion left as a cholesteric phase. Therefore, when writing is performed at 95 ° C., when viewed from the direction of arrow A, green display can be observed on a black background. 87 ° C, 95 ° C, 115 ° C
When writing is performed by using, full-color display is possible.
In a portion where a low reflectance is desired to be displayed, the reflectance can be reduced by mixing the black display portion.

In the recording medium 1, the display color of the liquid crystal is observed with black background. In the middle layer 3,
When a colorant that reflects visible light in a specific wavelength range is added, the display color of the liquid crystal is observed with a certain color as the background. If a display with a white background is to be performed, a small area of each of blue, green, and red is displayed in a mosaic shape in a portion having no display information, and a white background can be obtained by performing macroscopic white display. It is possible.

On the other hand, if the mixture is heated to about 119 ° C. or more and then gradually cooled, it becomes a scattering state and becomes cloudy. That is, when the entire surface of the recording medium 1 is heated to 119 ° C. or more and then gradually cooled, the entire recording layer 4 is in a scattering state. At this time, a white display is provided to the observer viewing from the direction of arrow A.

When the recording medium 1 is partially heated and quenched according to image information, the heated portion shows a reflection color according to the heating temperature. In FIG. 4, reference numeral 4a indicates a heat reflection portion. Accordingly, when writing is performed at 95 ° C., when viewed from the direction of arrow A, a green display can be observed in white.

The portion indicated by reference numeral 4b indicates that the portion is heated to a temperature of 119 ° C. or higher, then rapidly cooled, and is in a transparent state. This part appears to be the color of the intermediate layer 3, that is, black when viewed from the observation side (the direction of arrow A). Therefore, 119 ° C
When writing is performed as described above, black display can be performed on a white background. The portion indicated by reference numeral 4c is a portion that is gradually cooled after heating and is in a scattering state, and is a margin region where writing is not normally performed. When writing is performed at 87 ° C., 95 ° C., 115 ° C., or 119 ° C. or more, full-color display can be performed. In the first example, in a portion where a low reflectance is desired to be displayed, the reflectance can be reduced as a result by mixing black display portions.

(Second example, see FIG. 5) In FIG.
The reversible thermosensitive recording medium 11 as an example includes a base layer 12, an intermediate layer 13, a recording layer 14, and a protective layer 15 from below. Except for the recording layer 14, it is the same as the first example. The recording layer 14 is composed of a composite film of a low-molecular cholesteric liquid crystal compound and a polymer resin, is separated into a liquid crystal composition 14a and a resin film 14b, and further contains a spherical spacer 16 composed of a resin, an inorganic oxide, or the like. Have been. The recording mode of the image on the recording layer 14 is the same as in the first example.

(Image recording apparatus, see FIGS. 1 and 2)
FIG. 2 shows an image recording apparatus according to the first embodiment of the present invention. This apparatus is generally composed of a conveying roller pair 51, an image erasing roller 52 and a supporting roller 53, a preheating plate 54,
Light modulation unit 60, transport roller pair 55, slow cooling member 58
It is composed of

The light modulation unit 60 comprises a light source section 61, an optical fiber array 62, an optical shutter module 63, and a converging lens array 64. The light source unit 61
The light emitted from the lamp is composed of a metal halide lamp, a reflecting mirror, and a condenser lens.
2 is incident on one end 62a. The optical fiber array 62 is a bundle of a large number of single fibers, and emits light incident from one end 62a in a linear manner from the other end 62b. The optical shutter module 63 has a transparent ceramic chip made of PLZT on which a large number of minute optical shutter elements are formed and a driver for supplying a voltage to each optical shutter element are arranged side by side on a substrate. An analyzer is provided for each. Each of the optical shutter elements is turned on in response to an electric signal supplied from a driver, corresponding to a predetermined pixel, and transmits light. The transmitted light is focused on the recording medium by the condenser lens array 64.

In the above image recording apparatus, the recording medium 1
Are inserted into the apparatus from the direction of arrow B, and rollers 51, 52,
53, and 12 by the erasing roller 52.
Heat to 0 ° C. At this time, when performing image writing on a white background, the slow cooling member 58 is operated to activate the recording medium 1.
Is gradually cooled to bring the recording layer 4 into a scattering state, that is, a cloudy state. When writing on a black background, the recording medium 1 is rapidly cooled by natural cooling without operating the slow cooling member 58 to make the recording layer 4 transparent. The operator may be able to select which of the above writings is to be performed. Thus, by making the recording layer 4 white or transparent, the previously recorded image is erased. After that, the recording medium 1 is conveyed onto the preheating plate 54. The preheating plate 54 is controlled at a constant temperature, and preheats the recording medium 1 to a constant temperature (for example, 40 ° C.) regardless of room temperature or the like.

The pre-heated recording medium 1 is a plate 54
When the light passes above, the light is selectively irradiated from the light modulation unit 60, the temperature of the light irradiation part rises, and an image is recorded. Since the heating is performed instantaneously, the recording medium 1 is immediately cooled, and the display color is fixed. If the optical shutter element is of a binary drive of ON and OFF, a mono-color image is written, and if the light transmittance is multi-valued, a full-color image can be written. The optical information emitted from the optical shutter module 63 is one-dimensional in a direction orthogonal to the transport direction B, and a two-dimensional image is written by turning on and off one line at a time in synchronization with the transport of the recording medium 1. .

(Other Embodiments) The image recording apparatus according to the present invention is not limited to the above embodiment, but can be variously modified within the scope of the invention. For example,
A cooling means for rapidly cooling the recording medium immediately after the image exposure may be provided. Further, as the light modulating means, other materials such as liquid crystal can be used in addition to PLZT as long as the light ON / OFF or the transmittance can be modulated in multiple values. Further, as the reversible thermosensitive recording medium, the first example,
It goes without saying that various types can be used other than the second example.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an image recording apparatus according to the present invention.

FIG. 2 is a plan view showing the embodiment.

FIG. 3 is a sectional view showing a first example of a recording medium.

FIG. 4 is a sectional view showing a display state different from that of FIG. 3 in the recording medium of the first example.

FIG. 5 is a sectional view showing a second example of the recording medium.

[Explanation of symbols]

 Reference numerals 1, 11: Recording medium 52: Image erasing roller 54: Preheating plate 60: Light modulation unit 63: Optical shutter module

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Hideaki Ueda 2-3-13 Azuchicho, Chuo-ku, Osaka-shi, Osaka F-term in Osaka International Building Minolta Co., Ltd. 2C162 AE12 AE25 AE28 AE33 AE34 AE47 AE52 AE77 FA05 2H088 EA44 EA62 EA68 GA03 GA10 HA21 HA24 HA28 MA20 2H093 NC76 ND47 ND48 NE06 NF11 NG16 2H111 FB59 HA07 HA35

Claims (5)

[Claims] 1. An apparatus for recording an image on a recording medium in which a display color changes according to a heating temperature and the display color is fixed by cooling, wherein a plurality of optical shutters are used as heating means for recording the image. An image recording apparatus, comprising: a light modulating means in which elements are arranged in a line, and controlling a heating temperature of the recording medium by modulating light energy by each optical shutter element. 2. The image recording apparatus according to claim 1, wherein each of the optical shutter elements modulates on / off of transmission / blocking of light. 3. The image recording apparatus according to claim 1, wherein each of the optical shutter elements modulates a light transmittance to a multi-value. 4. The image recording apparatus according to claim 1, further comprising an erasing means for erasing an image already recorded on said recording medium. 5. The image recording apparatus according to claim 1, further comprising a pre-heating means for pre-heating the recording medium before recording the image.