JPS6153088A - Two-color thermal recording method - Google Patents

Abstract

PURPOSE:To prevent mixing of colors, lowering of contrast, fogging or the like from occurring, by maintaining the temperature of a thermal recording head to be substantially constant during application of heat. CONSTITUTION:A thermal recording medium 1 is selectively heated from the side of a base layer thereof heating elements 9 of the thermal recording head 7, and thereafter a transfer paper 6 is released from the medium 1. In this case, by setting the quantity of thermal energy supplied by the elements 9 to be large or small, the two-color recording is performed. Also, in the case where the color formed in the element 9 at a high temperature is different from that at a low temperature, two-color recording is performed on the basis of a temperature difference in the heating elements 9. The head 7 is maintained in contact with a heat source body 10, and is maintained at a substantially constant temperature by controlling the temperature of the body 10. A heater 11 provided in the heat source body 10 is connected to a temperature-controlling part 12 so as to control the temperature of the body 10.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a multicolor thermal recording method in which a thermal recording head is used to apply different levels of heat to a thermal recording medium, and in particular, a first color transfer ink layer and a first color transfer ink layer. The present invention relates to a transfer type two-color thermal recording method using a thermal recording medium having a second transfer ink layer.

[Conventional technology]

Conventionally, as a two-color recording method using heat in a facsimile or a similar device, the following method using a thermal recording medium has been proposed. For example, a two-color recording medium is a recording medium in which two types of coloring layers with different coloring temperatures and coloring hues are combined with respective dye precursors, color developers, and various additives, and coated in two layers on a base layer. use,
There is a method of performing two-color thermal recording by changing the heating temperature of a thermal recording head in which heating elements are arranged linearly. By appropriately selecting the above-mentioned materials, combinations of blue and red, black and red, etc., are possible as color hues. However, when high-temperature coloring, for example black, is developed, a low-temperature coloring, for example red, develops around the black image, making it impossible to obtain a clear image.

Furthermore, in such thermal recording media, since the thermal recording medium itself develops color, specially treated paper must be used as the recording paper, and ordinary recording paper cannot be used, and the recorded Image storage is also poor.

Therefore, a thermal recording medium in which thermal transfer ink layers having different melting temperatures and hues are laminated on a base layer has been proposed as a thermal recording medium that can use plain paper and is capable of two-color recording. Depending on the heating temperature, this thermal recording medium can transfer only one layer or both layers, and can perform two-color recording.

As another method, a transfer type thermal recording medium containing a thermosensitive coloring material has been proposed. This thermal recording medium contains a thermal coloring material in the thermal transfer ink that develops a hue different from that of the thermal transfer ink, and the transfer ink surface of this thermal recording medium is overlapped with plain paper, and thermal recording is performed from the base side of the thermal recording medium. Ink is selectively heated by a head and transferred onto transfer paper for recording. At this time, when heating at a relatively low temperature, only transfer of the transfer ink occurs, and when heating at a relatively high temperature, at the same time the ink is transferred.
The thermosensitive color forming material contained in the ink develops a different hue from that of the transfer ink. This enables two-color thermal recording by changing the heating temperature. However, even when using this thermal recording medium, for example, if only red ink transfer occurs at low temperatures, and transfer and black color development occur at high temperatures, when a black image is formed, the periphery of the image will be transferred but no color will develop. A phenomenon occurs in which a red image exists around a black image, making it impossible to obtain a clear image.

The present inventors have developed a thermosensitive two-color recording medium that is normally colorless but develops color at a relatively high temperature, as a heat-sensitive two-color recording medium that can record clear images on plain paper and has good color separation. In addition, a thermal recording medium has been proposed in which a first transfer ink layer that can be transferred and a second transfer ink layer that can be transferred at a relatively low temperature are provided on a base layer.

[Problem to be Solved by the Invention 3] No matter which of the above thermal recording media is used for two-color thermal recording, the recording characteristics will change if the environmental temperature changes. Normally, when the environmental temperature is low, the recorded image temperature, that is, the temperature applied to the thermal recording medium from the heating element, decreases, resulting in lower image density in areas recorded at relatively high temperatures and poor color separation. be. Furthermore, if the image density of a portion recorded at a relatively low temperature also decreases, the overall contrast may be low. Particularly when using the thermal recording medium proposed by the present inventors, the decrease in color separation due to changes in environmental temperature is easily noticeable.

It is an object of the present invention to eliminate the above-described drawbacks when using a two-color thermal recording medium and to provide a thermal recording method with good color separation.

[Means and solutions for solving the problems] In order to solve the above-mentioned problems, the present invention provides a two-color thermal recording method that uses a thermal recording head to apply different levels of heat to a thermal recording medium. The method is characterized in that the temperature of the thermal recording head is maintained substantially constant during the application of heat. If the temperature of the thermal recording head is maintained constant in this way, the image temperature is not affected by the environmental temperature.

〔Example〕

Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 1 shows the basic principle of the two-color thermal recording method of the present invention. The thermal recording medium 1 shown in FIG. 1 is composed of an ink layer 2 and a base layer 3, and the ink layer 2 is further divided into a first transfer ink layer 4 and a second transfer ink layer 5 as shown in FIG. ing. The ink layer 2 passes between the thermal recording head 7 and the pressure roll 8 in contact with the transfer paper 6 . The pressure roll 8 rotates in the direction of the arrow to advance the thermal recording medium 1 forward together with the transfer paper 6. At this time, the thermal recording medium 1 is selectively heated from the base layer side by the heating element 9 of the thermal recording head 7, and then the transfer paper 6 is peeled off from the thermal recording medium 1.

At this time, two-color recording is performed depending on the magnitude of the thermal energy applied by the heating element 9. Even when the thermal recording medium 1 produces different colors at high and low temperatures, two-color recording is similarly performed depending on the difference in temperature of the heating element 9. The thermal recording head 7 is in contact with a heating element 10, and is maintained at a nearly constant temperature by controlling the temperature of the heating element IO. Heating body 1
A heater 11 is provided inside the 0, and a temperature control section 12
is connected to the heating element 10 to control the temperature of the heating element 10.

Although the thermal recording head is heated and maintained at a constant temperature in this way, the recording characteristics vary depending on the temperature.

For example, when recording red under relatively low temperature printing conditions and recording black under relatively high temperature printing conditions, the temperature of the thermal recording head will affect the environmental temperature dependence of image reproduction, as shown in the table below. different. If the thermal recording head temperature is too low,
When the environmental temperature is low, the overall contrast decreases,
Red is mixed into the part that should originally be a black image. On the other hand, if the temperature of the thermal recording head is too high, fogging will occur when the environmental temperature is high, and black will be mixed into the portion that should originally be a red image, resulting in poor color separation. therefore,
The temperature of the thermal recording head, which is least affected by the environmental temperature, is preferably 30 to 50°C.

The recording characteristics of thermal recording head and environmental temperature are as follows:
A thermal recording head that is kept at a nearly constant temperature in advance,
By performing two-color recording by applying a signal so that the heat generation temperature differs depending on the color of the printed image, two-color thermal recording that is hardly affected by changes in environmental conditions can be realized. In particular, by using the thermal recording medium described below, good images without bleeding can be stably obtained.

FIG. 2 shows a thermal recording medium that is particularly useful in the two-color thermal recording method of the present invention. The thermal recording medium 1 has a base layer 3 formed with a first transfer ink layer 4 which is transferred at a relatively high temperature and a second transfer ink layer 5 which is transferred at a relatively low temperature. The base layer 3 has appropriate heat resistance strength and appropriate thermal conductivity (usually 3,
sec-cw+), there is no particular restriction on the material, and for example, paper such as capacitor paper or glassine paper, or plastic film such as polyester film or polycarbonate film may be used. When thermal recording is performed from the base layer side of the thermal recording medium using a thermal recording head or the like, it is better to reduce the loss of thermal energy in the base layer, so the thickness of the base layer is usually preferably 60 μm or less. is a binder such as carnauba wax, ester wax, polyethylene, beeswax, ceresin wax, polystyrene, styrene, butyral resin, polyvinyl acetate, butylene copolymer, cellulose-esters, cellulose-ethers, acrylic resins, This layer is made of softeners such as petroleum resins, stearic acid, lanolin, and vaseline, and is made by mixing these in appropriate proportions. The first transfer ink layer contains a dye precursor 13 and a color developer 14. These dye precursors and color developer react during transfer at a relatively high temperature to develop color.

When the color develops to be black or blue, the dye precursor is 3-diethylamino-6-methyl-7-anilinofluorane, crystal violet lactone, 3.
7-bisdiethylaminofluorane, 4,4'-bisdimethylaminopiperazine hydrol, etc. can be used.

Furthermore, as a color developer, depending on the dye precursor used, 4
．． 4-Impropylidenediphenol, 2,2-bis(
4-Hydoxyphenyl) n-hebutane, 1,1-bis(
4-Hydoxyphenyl)cyclohexane, benzoic acid, salicylic acid, stearic acid, etc. can be used.

These dye precursors and color developers are microencapsulated as necessary. In this case, the microcapsules are
It is desirable to use a material that melts at about the same temperature as or higher than the temperature at which the first transfer ink layer melts.

A second transfer ink layer 5 is formed on the first transfer ink layer 4.
is formed.

As the material for the second transfer ink layer, the same material as the first transfer ink layer can be used, but the second transfer ink layer has a material and composition that can be transferred at a lower temperature than the first transfer ink layer. need to be selected. The second transfer ink layer needs to be colored so that it takes on a different color when the first transfer ink layer develops color. When the hue of the second transfer ink layer is reddish, lake red, rhodamine-based red color, etc. can be used. Other additives may be added to the first and second transfer ink layers as necessary.

For example, to improve thermal conductivity, aluminum, copper,
It is effective to add fine powder of metal such as tin or zinc. The first and second transfer ink layers are each formed by hot melt coating or by solvent coating a coating liquid in which a transfer ink composition is dispersed in a solvent.

The coating amount of each transfer ink layer is preferably 3 to 20 g/m'. - By using this thermal recording medium and using the recording method described in FIG.
If only the red colored second transfer ink layer is dissolved, a red image will be formed on the transfer paper 6. On the other hand, the temperature is such that the heat applied by the heating element 9 dissolves the first transfer ink layer and causes a reaction between the dye precursor and the color developer contained therein, so that the developed hue is, for example, black. If so, a black image is formed on the transfer paper 6. In such recording, the first transfer ink layer only develops a black color at a relatively high temperature, so when only the second ink layer is transferred at a relatively low temperature, even if the first transfer ink layer is Even if it is transferred, it will not contaminate the red color.

Furthermore, when transferring and coloring the first transfer ink layer, the area to be transferred and the area to be colored are approximately the same size, so red images are less likely to exist around black images, resulting in clearer images. An image is obtained.

Moreover, since the thermal recording head is maintained at a constant temperature, such good two-color thermal recording can be achieved without being affected by changes in environmental conditions.

The present inventors conducted two experiments to prove the effectiveness of the two-color thermal recording method according to the present invention. An experimental example will be described below.

First, in the first experimental example, the following materials were used as the first transfer ink layer and the second transfer ink layer.
A thermal recording medium was prepared by laminating a first transfer ink layer and a second transfer ink layer in this order on a thick capacitor paper.

First transfer ink layer paraffin wax 40 l Carnauba wax 25 〃 Vaseline 57 / Pigment (Shikilerado) 20 〃 Second transfer ink layer Paraffin wax 40 weight 11 Carnauba wax 25 〃 Petroleum resin 10 〃 Carbon black 20 〃 ° Overlap the ink surface of the thermal recording medium and the transfer paper, and
The pace side of the thermal recording medium was brought into close contact with the heating element of the thermal recording head maintained at 0° C., and selectively heated in an imagewise manner. At this time, when the heating conditions were changed, red recording was performed under relatively low temperature conditions, and black recording was performed under relatively high temperature conditions. Moreover, even when the environmental temperature changed from 5° C. to 30° C., there was no significant change in the recording state for both black recording and red recording.

On the other hand, for comparison, when recording was performed without keeping the thermal recording head at a constant temperature, at low temperatures, the proportion of red color mixed into what should have been a black image was higher than when using the method of the present invention. Ta.

Dispersion A in which the following ASBs were each dispersed in a ball mill,
A solution in which B was mixed at a ratio of 1:5 was coated on a capacitor paper having a thickness of about 15 μm in a coating amount of about 10 g/m′ in a dry state, and dried to obtain a first color transfer ink layer. A second transfer ink layer having composition C was provided thereon to form a thermal recording medium.

Fluorane leuco dye 20 parts by weight Rosin modified phenolic resin 10” Mineral spirit
90" 4.4-Isopropylidene diphenyl 2 (l heavy ff 1 part stearic acid bisamide 10 〃Mike's Frisuf Wax 5 〃Paraffin wax
5 〃Rosin modified phenolic resin 10 〃
Mineral Spirit 240 Paraffin wax 45-layer carnauba wax
35 〃Vaseline
5 Pigment (Lake Red) 20
〃Place the ink surface of the thermal recording medium and the transfer paper at about 40°C.
The base side of the thermal recording medium was brought into close contact with the heating element of the thermal recording head held in the substrate, and selectively heated in an imagewise manner. At this time, when the heating conditions were changed, red recording was performed under relatively low temperature conditions, and black recording was performed under relatively high temperature conditions. Moreover, even when the environmental temperature changed from 5° C. to 30° C., there was no significant change in the recording state for both black and red recordings. On the other hand, for comparison, when recording was performed without keeping the thermal recording head at a constant temperature, at low temperatures, the proportion of red color mixed into what should have been a black image was higher than when using the method of the present invention. Ta.

Furthermore, in this experimental example, the ratio of color mixture was smaller than in the first experimental example, and the image was good.

Although the present invention has been described above as a two-color thermal recording method, it goes without saying that it can be applied to three or more color thermal recording methods.

〔Effect of the invention〕

According to the present invention, since the thermal recording head is maintained at a constant temperature, the image temperature is not affected by changes in the environmental temperature. Therefore, problems such as color mixing, reduction in contrast, and fogging can be solved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a two-color thermal recording method according to the present invention, and FIG. 2 is a schematic cross-sectional view of a thermal recording medium used in the two-color thermal recording method of the present invention. ■... Thermal recording medium, 2... Ink layer, 3... Base layer, 4... First ink transfer layer, 5... Second ink transfer layer, 6... Transfer paper, 7 ...thermal recording head, 8.
...pressure roll, 9...heating element, 10...heating element, 11...heater, 12...temperature control section, 13.
... Dye precursor, 14... Color developer. 1-111 thermal recording medium 2-111 ink layer 3-111 base layer 4-111 first ink transfer layer 5-111 second ink transfer layer 6--transfer paper 7 --- Thermal recording head 8 --- Pressure roll 9--111 Fully ripened element 10 ---1 Completed heating element 11 --- Heater 12 ---1 Temperature control section 13-111 Dye precursor Body 14-1--Color developer

Claims (3)

[Claims] (1) In a two-color thermal recording method in which different levels of heat are applied to a thermal recording medium using a thermal recording head, during heat application,
A two-color thermal recording method characterized in that the temperature of the thermal recording head is maintained substantially constant. (2) As the thermal recording medium, a first ink layer that can be colored and transferred at a relatively high temperature and a second ink layer that can be transferred at a relatively low temperature are laminated in this order on a base layer. A two-color thermal recording method according to claim (1), characterized in that: (3) The first ink layer of the thermal recording medium transfers a color different from that of the second ink layer at a relatively high temperature, and does not substantially develop color at a relatively low temperature where the second ink layer can be transferred. A two-color thermal recording method according to claim (2), characterized in that: