Heat-Sensitive Color Transfer Recording Media

The present invention relates to a novel heat-sensitive color transfer recording media. More particularly, it relates to a heat-sensitive color transfer recording media suitable for use in thermal recording system capable of producing color images, for example, thermal printer.

In recent years, thermal printer and thermal facsimile have been used widely because of their advantages such as maintenance free and low cost. Usually, a heat-transfer ribbon or carbon paper consisting of a foundation and a heat-sensitive transfer ink layer applied thereon is used as a recording media in the thermal printer and the thermal facsimile, and various improvements on the fastness of the transferred images have been proposed.

Known thermal printer and thermal facsimile are of the type producing a duplicate of single color such as black or blue, and there is a strong desire for thermal printer and thermal facsimile capable of producing multi-color images.

In color recording system technologies, there are known an impact recording system as seen in a coventional typewriter in which a cloth ribbon, e.g. a ribbon coated with inks of two colors, is employed; and an ink-jet recording system in which inks are jetted by employing two or more ink-jet heads. The former has the disadvantages of generating much noise and slow recording speed. Also, the latter has the disadvantage that problems such as clogging of the nozzle for jetting out ink tend to occur since the ink is jetted through the nozzles having a very narrow opening, and since the amount of ink jetted must be controlled, the apparatus itself is very complicated and expensive and the operation thereof is also complicated.

Recently, to make available a color printing system which overcomes the aforementioned problems, there has been proposed a color recording system utilizing the principle of color television and color phototelegraphy. FIG. 1 is a diagrammatic view showing such a color recording system. A color original 1 is subjected to color separation by filters 2a, 2b and 2c. The respective color-separated images are then read by photoelectric tubes 3a, 3b and 3c, and are converted into yellow signal Y, cyan signal C and magenta signal M. The signals are transmitted from a transmitter 4 to a receiver 5 at which the signal separation is conducted again. The signals are transmitted to a printer 6 to reproduce a color image which closely resembles the original, on a copy sheet 7. Recording machines applicable to such a system have been proposed and developed. The application of a thermal printer to the printer 6 is advantageous from view-points of low cost, ease of operation, low noise and high printing speed.

Conventionally known color image forming processes by the thermal color recording system include a process employed in a thermal color printer which makes it possible to obtain multi-color images in a single treatment as disclosed in Japanese Patent Unexamined Publication (Tokkyo Kokai) No. 156647/1979. This process uses a recording media comprising a foundation and heat-sensitive ink spots provided thereon wherein 4-color ink spots of yellow, magenta, cyan and black colors are arranged in rhomboid cells and the rhomboid cells are disposed side by side in parallel rows which extend across the foundation. The thermal head used in this process is composed of a double row of heating elements arranged in rhomboid cells corresponding to the rhomboid cells of ink spots. Minute spots of different colors are transferred from the recording media onto a copy sheet by heating with the thermal head so that different color spots are not superimposed with each other to form a color image. The publication also discloses another process wherein there are used a recording media which has parallel stripes of heat-sensitive inks of the above four colors on a foundation, the stripes extending perpendicular to the travel direction of the recording media and being disposed in a repeating series of four colors (each stripe has a very narrow width of about 0.23 mm.), and a thermal head which has heating elements (dots) arranged in a single row, whereby each color is transferred line-to-line (width of each line: about 0.23 mm. and space between the lines: 0.025 mm.) on a copy sheet.

However, the above processes have problems that the color resolution is not satisfactory and also positions between the recording media and the copy sheet cannot easily be adjusted and, therefore, it is very difficult to obtain clear color images.

In particular, since each of the heat-sensitive ink spots or stripes disclosed in the above publication contains sublimiable dyes which are sublimated by the heating with a thermal head upon printing and deposited on a copy sheet, the use of the heat-sensitive recording media proposed therein accompanies fatal disadvantages that heat control of the thermal head is very difficult during printing and also the dyes of each color tend to be sublimated and mixed with each other during the storage of the media, whereby clear images cannot be obtained.

It is an object of the present invention to provide a heat-sensitive color transfer recording media which can be used in a thermal printer to give clear multi-color images of high resolution at low cost.

Another object of the present invention is to provide a heat-sensitive color transfer recording media which makes it possible to use a low cost, small-size thermal color printer.

A further object of the present invention is to provide a heat-sensitive color transfer recording media suitable for high-speed color recording.

According to the present invention, there is provided a heat-sensitive color transfer recording media comprising a continuous foundation and a multiplicity of coated areas of heat-sensitive transfer inks applied onto the foundation; the multiplicity of the coated areas being disposed on the continuous foundation side by side so as to traverse the continuous foundation; the multiplicity of the coated areas being arranged sequentially in the longitudinal direction of the continuous foundation in a repeating unit which comprises a plurality of coated areas of different colors, at least yellow, magenta and cyan; each of the different color coated areas included in the repeating unit having a length in the longitudinal direction of the continuous foundation substantially equal to the length or width of a copy sheet; and each of the heat-sensitive transfer ink layers of the coated areas being a transparent ink layer comprising a transparent coloring agent and a transparent hot-melt vehicle. Thus, the present invention provides a heat-sensitive color transfer recording media capable of producing color copy by superimposing different color ink images onto the copy sheet.

FIG. 1 is a diagrammatic view showing a color recording system.

FIG. 2 is a schematic plan view of an embodiment of the heat-sensitive color transfer recording media of the present invention.

FIG. 3 is a cross-sectional view of the recording media of FIG. 2 taken along the line X--X.

FIG. 4 is a schematic plan view showing a modified embodiment of the recording media shown in FIGS. 2 and 3.

FIGS. 5A, 5B and 5C are schematic views showing a manner of forming a color image using the recording media shown in FIGS. 2 and 3.

FIG. 6 is schematic plan view showing another embodiment of the recording media according to the present invention.

FIG. 7 is a cross-sectional view of the recording media shown in FIG. 6 taken along the line Y--Y.

FIG. 8 is a schematic plan view showing a modified embodiment of the recording media shown in FIGS. 6 and 7.

FIGS. 9 and 10 are schematic views showing a manner of forming a color image using the recording media shown in FIGS. 6 and 7.

The heat-sensitive color transfer recording media of the present invention is used for forming a multi-color image on a copy sheet by successively transferring a plurality of heat-sensitive transfer ink layers of different colors, at least three primary colors, i.e. yellow, magenta and cyan, which constitute the coated areas included in each repeating unit, onto the copy sheet so that different color ink images are superimposed on the copy sheet.

That is, the formation of a color image using the recording media of the present invention can be performed by superimposing two or three color ink images of yellow, magenta and cyan on the copy sheet.

More specifically, colors other than the primary pure yellow, cyan and magenta, such as red, blue, green, black, etc. can be formed by superimposing two or three of yellow, cyan and magenta ink images. In that case, the different color ink images transferred and superimposed are present on the copy sheet in such a state that they are not substantially admixed with each other. Accordingly, each of the ink layers in the recording media of the present invention must be highly transparent, and otherwise, a clear color image with a good color reproduction cannot be obtained.

In the present invention, the visible light transmittance of each ink layer of yellow, magenta or cyan is preferably not less than 68%, more preferably not less than 80%. In order to obtain each ink layer having the above transmittance, it is necessary to use a coloring agent having a high transparency and a hot-melt vehicle (such as binders and softening agents) having a high transparency. Further, the coloring agent and hot-melt vehicle used in each ink layer preferably should have near refractive indexes from each other.

In the present invention, the term "transparent coloring agent" means a coloring agent capable of giving a transparent ink layer when the coloring agent is admixed with a transparent hot-melt vehicle composed of a binder, a softening agent, etc.

The transparent yellow coloring agents used in the yellow ink layer include pigments such as Chrome Yellow (lead chromate), Zinc Yellow (basic zinc chromate), Lemon Yellow (barium chromate), Cadmium Yellow, Naphthol Yellow S, Hansa Yellow 5G, Hansa Yellow 3G, Hansa Yellow G, Hansa Yellow GR, Hansa Yellow A, Hansa Yellow RN, Hansa Yellow R, Banzidine Yellow, Banzidine Yellow G, Benzidine Yellow GR, Permanent Yellow NCG and Quinoline Yellow Lake; and dyes such as Auramine.

The transparent magenta coloring agents used in the magenta ink layer include pigments such as Permanent Red 4R, Brillant Fast Scarlet, Brilliant Carmine BS, Permanent Carmine FB, Lithol Red, Permanent Red F5R, Brilliant Carmine 6B, Pigment Scarlet 3B, Rhodamine Lake Y and Alizarine Lake; and dyes such as Rhodamine.

The transparent cyan coloring agents used in the cyan ink layer include pigments such as Victoria Blue Lake, metal-free Phthalocyanine Blue, Phthalocyanine Blue and Fast Sky Blue; and dyes such as Victoria Blue.

The transparent coloring agent is used in an amount ranging from 1 to 20% (% by weight, hereinafter the same), preferably from 5 to 15%, based on the weight of each heat-sensitive transfer ink layer. When the content of the coloring agent is more than the above range, the transparency of the ink layer is lowered so that color reproduction becomes difficult, and when the content of the coloring agent is less than the above range, a tinting strength of the ink layer is lowered.

The heat-sensitive transfer ink layer is composed of a transparent coloring agent and a transparent hot-melt vehicle composed of binder, softening agent, etc.

The transfer ink layer is formed by coating a heat-sensitive transfer ink composition onto a foundation. Preferably, the transfer ink composition contains 1 to 20% of a coloring agent, 20 to 80% of a binder and 3 to 25% of a softening agent, based on the total dry weight of the ink composition. The coating may be carried out by hot-melt coating or solvent coating. The thickness of the transfer ink layer is usually selected from 1 to 10 .mu.m.

As a binder, it is preferable to employ solid waxes having a penetration (provided in JIS K 2530) of 10 to 30 (at 25.degree. C.) in order to improve the heat sensitivity of the resulting transfer ink layer. Examples of such waxes are carnauba wax, microcrystalline wax, haze wax, bees wax, ceresine wax and spermaceti. The solid wax may be employed in combination with an easily hot-meltable material such as low molecular weight polyethylene, oxidized wax or ester wax, as occasion demands.

As a softening agent, it is preferable to employ easily hot-meltable materials such as petroleum resins, polyvinyl acetate, polystyrene, styrene-butadiene copolymer, cellulose esters, cellulose ethers and acrylic resins, and lubricating oils such as mineral oils.

In order to provide the heat-sensitive transfer ink layer with good melt-transferability, an extender pigment may be added to the heat-sensitive transfer ink composition. Preferably the extender pigment is also transparent. Examples of the transparent extender pigment are magnesium carbonate (magnesium hydroxide carbonate), calcium carbonate (precipitated calcium carbonate), kaolin clay (aluminum silicate), sericite (basic potassium aluminum silicate), high dispersive silicic acid anhydride (commercially available under the name "Aerosil" made by Nippon Aerosil Kabushiki Kaisha) and white carbon (precipitated silica). The extender pigment is employed in an amount of not more than 10%, preferably 2 to 10%, based on the total dry weight of the heat-sensitive transfer ink composition.

Further, a finely divided heat conductive material may be added to the heat-sensitive transfer ink composition in order to provide the heat-sensitive transfer ink layer with good melt-transferability, unless the heat conductive material hinders the transparency of the ink layer. The preferred heat conductive material has a heat conductivity of 6.0.times.10.sup.-4 to 25.0.times.10.sup.-4 cal./sec.cm..degree.C. Examples of the heat conductive material are powders of metals such as aluminum, copper, tin and zinc. The heat conductive material is employed in an amount of not more than 30%, preferably 3 to 30%, based on the total dry weight of the ink composition.

From the view point of melt-transferability, it is desirable that the resulting respective heat-sensitive transfer ink layers have a melting point of 50.degree. to 150.degree. C. and a viscosity of 20 to 10,000 cP. at a temperature 30.degree. C. higher than the melting point. Also, it is desirable that the transfer ink layers are rather hard, since soft layers are easily soiled, and therefore the transfer ink layers having a penetration of 0.1 to 50 are preferred.

The heat-sensitive color transfer recording media of the present invention may further include a heat-sensitive transfer ink layer of black color in addition to the transfer ink layers of yellow, magenta and cyan colors for the purpose of reproducing sharp black image. The black transfer ink layer is formed from a heat-sensitive transfer ink composition containing a black coloring agent such as carbon black or Nigrosine Base. The ink composition for the black transfer ink layer may have the formulation similar to the ink compositions for the transfer ink layers of yellow, magenta and cyan colors except the coloring agent. However, the black transfer ink layer may not be necessarily transparent, since usually the black image is not superimposed with the yellow, magenta or cyan image.

As a foundation, those materials having an adequate heat resistance and good heat conductivity are preferably employed. Preferable examples of the foundation employed are polymer films and papers each having a thickness of 3 to 25 .mu.m and a density of 0.8 to 1.5 g./cm..sup.3, such as cellophane, polyimide film, polyester film, polyethylene film, polystyrene film, polypropylene film, condenser paper, glassine paper, synthetic paper and laminated paper.

The transfer ink layers of yellow, magenta and cyan colors and if desired, further black color are provided on a continuous foundation in such a manner that the three or four different color ink layers are disposed side by side so as to traverse the continuous foundation without overlapping with each other in a repeating unit. The repeating unit including the three or four different color ink layers is disposed sequentially in the longitudinal direction of the continuous foundation.

The heat-sensitive color transfer recording media of the present invention can be classifed into the following two types:

The recording media of the first type comprises a continuous foundation having a width narrower than the length or width of a copy sheet, for example, a width similar to that of usual ink ribbons, and a multiplicity of coated areas of the above mentioned transparent heat-sensitive transfer inks applied onto the foundation; the multiplicity of the coated areas being disposed on the continuous foundation side by side so as to traverse the continuous foundation; the multiplicity of the coated areas being arranged sequentially in the longitudinal direction of the continuous foundation in a repeating unit which comprises a plurality of different color coated areas; and each of the different color coated areas included in the repeating unit having a length in the longitudinal direction of the continuous foundation substantially equal to the length or width of a copy sheet [the recording media of this type is hereinafter referred to as "recording media (I)"]. The recording media (I) can be suitably used for color recording system using a thermal color serial printer.

The recording media of the second type comprises a continuous foundation having a width substantially equal to the length or width of a copy sheet and a multiplicity of coated areas of the above transparent heat-sensitive transfer inks applied onto the foundation; the multiplicity of the coated areas being disposed on the continuous foundation side by side so as to traverse the continuous foundation; the multiplicity of the coated areas being arranged sequentially in the longitudinal direction of the continuous foundation in a repeating unit which comprises a plurality of different color coated areas; and each of the different color coated areas included in the repeating unit having a size substantially equal to the size of the copy sheet (for example, A4 size) [the recording media of this type is hereinafter referred to as "recording media (II)"]. The recording media (II) can be suitably used for color recording system using a thermal color line printer.

The recording media (I) according to the present invention is hereinafter described in detail with reference to the accompanying drawings.

FIG. 2 is a schematic plan view showing an embodiment of the recording media (I). FIG. 3 is a cross-sectional view of the recording media of FIG. 2 taken along the line X--X. FIG. 4 is a schematic plan view of another embodiment of the recording media (I). FIGS. 5A, 5B and 5C schematically illustrate a manner of forming a color image using the recording media (I).

As shown in FIGS. 2 and 3, the recording media (I) designated by reference number 10 comprises a continuous foundation 11 having a width narrower than the length (or width) of a copy sheet and transparent heat-sensitive transfer ink layers 12Y, 12M and 12C of yellow, magenta and cyan colors provided sequentially on the continuous foundation 11 in a repeating unit A including the three different color ink layers in the longitudinal direction of the foundation 11.

Alternatively, as shown in FIG. 4, the recording media (I) designated by reference number 10 may have the heat-sensitive transfer ink layers 12Y, 12M and 12C and an additional heat-sensitive transfer ink layer 12B of black color. The four different color ink layers are arranged on the continuous foundation 11 in the same manner as above.

These heat-sensitive transfer ink layers are arranged repeatedly in the longitudinal direction of the foundation 11 in the repeating unit A including the yellow, magenta, cyan ink layers and, if desired, black ink layer, and each of the heat-sensitive transfer ink layers included in each repeating unit A has a length in the longitudinal direction of the foundation 11 substantially equal to the width (or length) of a copy sheet such as plain paper.

FIGS. 5A, 5B and 5C schematically illustrate a manner of forming a color image using the recording media (I) shown in FIGS. 2 and 3. As illustrated in FIG. 5A, the yellow heat-sensitive transfer ink layer 12Y of the recording media 10 is first laid on top of the copy sheet 7 in such a manner that the ink layer 12Y is facing to the copy sheet 7 over its entire width. The yellow ink layer 12Y is then melt-transferred imagewise onto the copy sheet 7 activated by a yellow signal Y with the heat from a serial thermal head 30 which moves from one end of the copy sheet 7 to the other end along the back surface of the recording media 10. As shown in FIG. 5B, when the thermal head 30 reaches the other end of the copy sheet 7, the thermal head 30 is then returned to the original position and, at the same time, the recording media 10 is moved in the same direction as the returning thermal head (right to left in FIG. 5B), whereby the subsequent magenta ink layer 12M is laid on top of the copy sheet in such a manner that the magenta ink layer 12M is facing to the copy sheet at the same position as the imprinted yellow image. The magenta ink layer 12M is then melt-transferred imagewise onto the yellow image of the copy sheet activated by a magenta signal M in the same manner as in the case of the formation of the yellow image as shown in FIG. 5A to give a magenta image on the yellow image. Then, the cyan ink layer 12C is laid on top of the copy sheet 7 in the same manner as above and the cyan ink layer is melt-transferred imagewise onto the magenta image of the copy sheet activated by a cyan signal C in the same manner as above to give a cyan image on the magenta image.

After completion of the color image formation on the copy sheet 7 in an area corresponding to the width of the recording media 10, the copy sheet 7 is shifted perpendicularly to the travel direction of the recording media 10 by a distance corresponding to the width of the recording media 10 as shown in FIG. 5C, and the same image forming operation as above is repeated. In this manner, partial color images are formed successively on the copy sheet 7 along the longitudinal direction (or transverse direction) of the copy sheet 7, whereby a complete image identical to the original can be reproduced on the copy sheet 7.

As described above, the recording media (I) makes it possible to reproduce any desired color image by successively forming yellow, magenta, cyan color images and, if desired, black color image on copy sheet 7, from one end to the other of the copy sheet 7 in section-wise (one section approximately corresponding to the width of the recording media 10 or the length of the serial thermal head 30) and superimposing the color images in each section. Thus, the recording media (I) can be used in color transfer recording according to a so-called "serial flame scanning recording system".

Since the recording media (I) has a small size, i.e. a width of 3 to 35 mm., and the thermal head used therefor is a serial thermal head, the recording media (I) is very advantageous in that the printing apparatus can be reduced in its size and can be manufactured at low cost.

The recording media (II) according to the present invention is hereinafter described in detail with reference to the accompanying drawings.

FIG. 6 is a schematic plan view showing an embodiment of the recording media (II), FIG. 7 is a schematic cross-sectional view of the recording media of FIG. 6 taken along the line Y--Y, FIG. 8 is a schematic plan view showing another embodiment of the recording media (II), FIGS. 9 and 10 illustrate a manner of forming a color image using the recording media (II).

As shown in FIGS. 6 and 7, the recording media (II) designated by reference number 20 comprises a continuous foundation 21 having a width substantially equal to the width (or length) of a copy sheet and transparent heat-sensitive transfer ink layers 22Y, 22M and 22C of yellow, magenta and cyan colors provided sequentially on the continuous foundation 21 in a repeating unit B including the three different color ink layers in the longitudinal direction of the foundation 21. Alternatively, as shown in FIG. 8, the recording media (II) may have the transfer ink layers 22Y, 22M and 22C and additionally a heat-sensitive transfer ink layer of black color. The four different color layers are arranged on the foundation 21 in the same manner as above.

These heat-sensitive transfer ink layers are arranged repeatedly in the repeating unit B including the yellow, magenta and cyan ink layers and, optionally, black ink layer, and each of the heat-sensitive transfer ink layers included in each repeating unit B has a size substantially equal to that of a copy sheet 7 such as plain paper, for example, A4 size, B5 size, etc.

FIG. 9 schematically illustrates a manner of forming a color image using the recording media (II) shown in FIGS. 6 and 7. As shown in FIG. 9, the recording media 20 is carried in one direction over a line thermal head 40. The thermal head 40 comes in contact with the uncoated surface of the recording media 20 and the surface having the heat-sensitive transfer ink layers 22Y, 22M and 22C comes in contact with the copy sheet 7. The recording media 20 and the copy sheet 7 are brought into contact on the line thermal head 40 while they are being moved in one direction at a constant rate and the heat-sensitive transfer ink layers are melt-transferred imagewise on the copy sheet 7 with the heat from the line thermal head 40.

More specifically, the yellow ink layer 22Y in one repeating unit B of the recording media is transferred imagewise onto the copy sheet 7 activated by a yellow signal Y to give a yellow image on the copy sheet 7 and thereafter the copy sheet 7 is returned to the line thermal head 40 and brought into contact with the magenta ink layer 22M on the line thermal head 40, whereby the magenta ink layer 22M is imagewise transferred onto the copy sheet 7 activated by a magenta signal M to give a magenta image on the yellow image. After the formation of the magenta image, the copy sheet 7 is again returned to the line thermal head 40 and the cyan ink layer 22C is imagewise transferred onto the copy sheet 7 activated by a cyan signal C in the same manner as above to give a cyan image on the magenta image.

In this manner, the yellow, magenta and cyan images are successively formed over a whole area of one copy sheet 7. As a result, any desired color image can be reproduced on the copy sheet by superimposing an appropriate combination of yellow, magenta and cyan color images over a whole area of the copy sheet 7. For example, a black image can be reproduced on an area of the copy sheet 7 corresponding to black color of the original by superimposing the yellow, magenta and cyan colors.

As described above, the recording media (II) makes it possible to reproduce any desired color image by successively forming yellow, magenta and cyan color images on a copy sheet 7. Thus, the recording media (II) can be used in color transfer recording according to serial flame scanning recording system.

FIG. 10 shows a preferred embodiment for practising the color image forming process shown in FIG. 9. In this embodiment, the copy sheet 7 is wound around a drum 50 so that the both ends of the copy sheet are brought into contact with each other, and the copy sheet 7 faces the line thermal head 40 interposing the recording media 20. The recording media 20 is supplied from a feed roll 60 to the line thermal head 40 at a constant rate and is taken up at a wind roll 70. Each of the heat-sensitive transfer ink layers 22Y, 22M and 22C has the same size as that of the copy sheet 7 and the drum 50 on which the copy sheet 7 has been wound is rotated at the same linear velocity with the recording media 20, whereby any print shear among the yellow, magenta and cyan color images formed on the copy sheet 7 can be prevented. Thus, the process is very advantageous since the mechanism of the thermal printer used can be simplified and the printer can be operated easily.

The above line thermal head 40 is facing to the recording media 20 over the entire width of the recording media 20 and is a line head similar to that used in a conventional line printer. The thermal head 40 is preferably those having more than 6 heating elements, more preferably 8 to 16 heating elements, per 1 mm. in order to obtain a color image with a high resolution.

The recording media (II) has an advantage that it can be used in a line printer which enables high speed printing.

The recording media (I) and (II) have been described with reference to the color image formation on the copy sheet 7 in the order of the yellow, magenta and cyan colors, but it is to be understood that the order is not limited thereto.

In the present invention, the heat-sensitive transfer ink layers 12Y, 12M, 12C and 12B, or 22Y, 22M, 22C and 22B may be provided on the foundation with a space between the adjacent different color ink layers, but it is preferable that these ink layers are provided on the foundation in close contact with each other from the standpoint of ease of printing operation. In order to provide the ink layers in close contact with each other, any coating method which is conventionally used in the field of color printing can be used, including letterpress, gravure, flexograph, silk screen, and the like.

As described above, the recording media of the present invention can be employed suitably in a novel thermal color recording system wherein the heat-sensitive transfer ink layers of at least three colors of yellow, magenta and cyan 12Y, 12M and 12C (or 22Y, 22M and 22C) are successively melt-transferred imagewise onto the copy sheet 7 with the heat from thermal head 30 (or 40), thereby superimposing the different color images to reproduce a clear multi-color image on the copy sheet 7. Accordingly, the thermal color recording system using the recording media of the present invention does not require color printers and color facsimile equipments of complicated mechanism, but permits the use of simple, low cost equipment which is reliable and easy to operate.

Thus, the recording media of the present invention can greatly contribute to practical use of color printer and color facsimile equipment in thermal transfer recording.

Further, since the recording media of the present invention has an excellent melt-transferability, the amount of the ink layer to be transferred on the copy sheet 7 can be easily adjusted by varying input strength of pulse signals to the thermal head 30 or 40, whereby a color image having various color tones including medium tone faithful to the original can be reproduced. In addition, the recording media of the present invention has excellent effects that the reproduced image is color fast and, moreover, since plain papers can be used as the copy sheet, the running cost of color recording can be markedly reduced.

The recording media of the present invention greatly contributes to practical use of color printer, color facsimile, color video printer, color copy machine, etc. which employ a thermal printer and, therefore, are greatly valuable.

The present invention is more particularly described and explained by means of the following Examples. These Examples are intended to illustrate the invention and not be construed to limit the scope of the invention. It is to be understood that various changes and modifications may be made in the invention without departing from the spirit and scope thereof.

Yellow, magenta and cyan color heat-sensitive transfer ink compositions shown in Table 1 were applied by hot-melt coating onto a continuous polyester film having a thickness of 9 .mu.m., a width of 8 mm. and a density of 1.4 g./cm..sup.3 as a foundation so that each of resulting ink layers had a length of 210 mm., which corresponded to the width of A4 size, in the longitudinal direction of the foundation to give a recording media having repeating three different color heat-sensitive transfer ink layers as illustrated in FIGS. 2 and 3. Each of the three different color heat-sensitive transfer ink layers had a thickness of 5 .mu.m., a melting point of 90.degree. C., a viscosity of 250 cP. (at 120.degree. C.) and a penetration of 2. The visible light transmittances of the yellow ink layer, the magenta ink layer and the cyan ink layer were 85%, 80% and 81%, respectively.

The recording media thus obtained was used to form color images of yellow, magenta and cyan colors successively on an A4 size plain paper as a copy sheet using a monochromatic serial thermal printer (Canoword 55 made by Canon Inc.).

First, the yellow ink layer of the recording media was placed on a plain paper and a yellow image was melt-transferred onto the plain paper by heating with the thermal head of the printer. The recording media was then shifted so as to place the magenta ink layer on the same place of the paper and a magenta image was formed on the yellow image of the paper in the same manner as above. Finally, a cyan image was formed on the magenta image on the paper in the same manner as above. Thus, there was obtained a superimposed image of yellow, magenta and cyan colors on the paper. The image was clear and had a high resolution.

A recording media as illustrated in FIG. 4 was prepared in the same manner as described in Example 1, except that a black heat-sensitive transfer ink layer having the following composition was formed on the foundation in addition to the yellow, magenta and cyan ink layers.

The recording media thus prepared was used to form a color image on a plain paper in the same manner as in Example 1. The resulting color image was clear and, in particular, had a black color clearer than that of the color image obtained in Example 1.

A recording media was prepared in the same manner as in Example 1 except that the ink compositions shown in Table 2 were used instead of those shown in Table 1. Each of the three different color ink layers had a thickness of 4.5 .mu.m., a melting point of 85.degree. C. a viscosity of 210 cP. (at 115.degree. C.) and a penetration of 3. The visible light transmittances of the yellow ink layer, the magenta ink layer and the cyan ink layer were 90%, 88% and 87%, respectively.

The obtained recording media was used to form a color image on a plain paper in the same manner as in Example 1. The resulting color image was clear and had a high resolution.

A recording media was prepared in the same manner as in Example 1 except that a condenser paper having a thickness of 10 .mu.m., a width of 8 mm. and a density of 1.2 g./cm..sup.3 was used as a foundation.

A recording media was prepared in the same manner as in Example 1 except that 10 parts by weight of Auramine base, 10 parts by weight of Rhodamine B base and 10 parts by weight of Victoria Blue B base were used as transparent coloring agents for the yellow, magenta and cyan inks, respectively, per 100 parts by weight of the total ink composition.

Each of the heat-sensitive transfer ink layers thus obtained had a thickness of 5 .mu.m., a melting point of 90.degree. C., a viscosity of 300 cP. (at 120.degree. C.) and a penetration of 4. The visible light transmittances of the yellow, magenta and cyan ink layers was 91%, 87% and 84%, respectively.

Each of the recording media obtained in Examples 4 and 5 was used to form a color image in the same manner as in Example 1. The resulting color image in each instance was clear and had a high resolution.

The yellow, magenta and cyan color heat-sensitive transfer ink compositions as shown in Table 1 were applied by hot-melt coating onto a continuous polyester film having a thickness of 9 .mu.m., a width of 297 mm. and a density of 1.4 g./cm..sup.3 as a foundation. The coatings were applied so that each of the three different color ink layers had a length of 210 mm. in the longitudinal direction of the foundation and a thickness of 5 .mu.m. to give a recording media having repeating three different color heat-sensitive transfer ink layers of A4 size as shown in FIGS. 6 and 7.

The recording media thus obtained was used to form a color image by superimposing yellow, magenta and cyan images on an A4 size plain paper using a thermal facsimile apparatus having a monochromic line head (MELFAS made by Mitsubishi Electric Corp.).

The experiment was conducted as follows: The yellow ink layer of the recording media was laid on top of a plain paper and melt-transferred by heating with the line head to give a yellow image on the paper. Then, the magenta ink layer was laid on top of the paper and melt-transferred to give a magenta image on the yellow image of the paper in the same manner as above, and finally a cyan image was formed on the magenta image of the paper in the same manner as above. The resulting color image formed by superimposing the yellow, magenta and cyan images was clear and had a high resolution.

A recording media as shown in FIG. 8 was prepared in the same manner as in Example 6, except that a black heat-sensitive transfer ink layer was added by using the same black ink used in Example 2.

The recording media thus obtained was used to form a color image on paper in the same manner as in Example 6. The resulting color image was clear and, in particular, had a black color clearer than that of the color image obtained in Example 6.

A recording media was prepared in the same manner as in Example 6 except that the ink compositions shown in Table 2 were used instead of those shown in Table 1.

A recording media was prepared in the same manner as in Example 6 except that a condenser paper having a thickness of 10 .mu.m., a width of 297 mm. and a density of 1.2 g./cm..sup.3 was used as a foundation.

A recording media was prepared in the same manner as in Example 6 except that 10 parts by weight of Auramine base, 10 parts by weight of Rhodamine B base and 10 parts by weight of Victoria Blue B base were used as transparent coloring agents for yellow, magenta and cyan inks, respectively, per 100 parts by weight of the total ink composition.

Each of the heat-sensitive transfer ink layers thus obtained had a thickness of 5 .mu.m., a melting point of 90.degree. C., a viscosity of 300 cP. (at 120.degree. C.) and a penetration of 4.

Each of the recording media obtained in Examples 8, 9 and 10 was used to form a color image in the same manner as in Example 6. The resulting color image in each instance was clear and had a high resolution.