JP2008018701A - Printing method and image formation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for preventing creation of a negative image of a previous image even when a used thermal transfer sheet is rewound, the same energy is imparted to elements of thermal heads, and thermal transfer is performed by an appropriately adjusted intermediate color tone (gray solid). <P>SOLUTION: The used thermal transfer sheet obtained after thermal transfer has a residual image Zyr formed of a concentration-reduced yellow colorant by transfer of an image Zyt, a residual image Zmr formed of a concentration-reduced magenta colorant by a transfer of an image Zmt, and a residual image Zcr formed of a concentration-reduced cyan colorant by transfer of an image Zct. When at least two residual images selected from the group of residual images are overlapped with an identifying part for head adjustment of the colorant layers containing the selected residual images, they are misaligned with each other in printing. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a printing method and an image forming apparatus using a thermal transfer sheet.

In image formation using the thermal transfer method, a dye layer mainly composed of yellow, magenta, and cyan and, if necessary, a transparent protective layer that protects the image formed on the receiving layer with yellow, magenta, and cyan as a base material A thermal transfer sheet provided on one surface of the sheet in a surface sequential manner is used.

In this image formation, for example, in the course of conveying the thermal transfer sheet from the supply side to the winding side in an image forming apparatus such as a printer, heat corresponding to image information separated into yellow, magenta, and cyan is transferred from the thermal head to yellow, In addition to the magenta and cyan color dye layers, thermal transfer is performed to transfer the dye to the image receiving sheet.

For the purpose of increasing the use efficiency of the thermal transfer sheet, a method of performing thermal transfer by making the conveyance speed of the image receiving sheet transfer material relatively larger than the conveyance speed of the thermal transfer sheet, a so-called N-times mode method has been proposed. (For example, refer to Patent Documents 1 to 5.)

In image formation by thermal transfer method, in the transfer from each color dye layer, the dye of the density corresponding to the image information is transferred onto the image receiving sheet for each element of the thermal head, and the dye of each color dye layer after transfer is transferred Less. As a result, the used thermal transfer sheet after the thermal transfer has left an image-like trace of the image. Specifically, in each color dye layer, an inverted image of the image information separated into colors is left. It becomes.

However, in the sublimation transfer, even if high gradation (black) printing is performed, not all the dyes in the dye layer are transferred, so that the remaining reversed image can be seen slightly. Further, since the respective colors are separated, the details of the formed image cannot be easily recognized from the trace of image formation in each dye layer.
Japanese Unexamined Patent Publication No. 63-11368 JP-A 63-165169 JP-A-3-247490 Japanese Patent Laid-Open No. 3-120098 JP-A-4-39086

However, if, for example, the same image forming apparatus as the apparatus that formed the image is used and the used thermal transfer sheet is rewound from the winding side to the supply side and thermal transfer is performed again, the same energy is given to each element of the thermal head. When heat transfer is performed with a gradation of intermediate colors (gray solid) adjusted as appropriate, there is a possibility that a negative image of an image initially produced by the heat transfer sheet may be obtained.

Therefore, in order to protect personal information and improve security, an image reproduction prevention measure is required to prevent the image image from being easily taken out from the used thermal transfer sheet.

In view of the above situation, the object of the present invention is to rewind a used thermal transfer sheet to give the same energy to each element of the thermal head, and even if it is thermally transferred with an intermediate color gradation (gray solid) appropriately adjusted, The present invention provides a method for preventing negative image production.

In the present invention, a thermal transfer sheet including a yellow dye layer, a magenta dye layer, and a cyan dye layer is used as a dye layer formed on one surface of a base sheet in a surface sequential manner, and the transferred image Z is converted into yellow, magenta, and cyan. The transferred image is obtained by superimposing the image Zyt, the image Zmt, and the image Zct transferred from the yellow dye layer, the magenta dye layer, and the cyan dye layer onto the image receiving sheet by thermal transfer in accordance with image information obtained by color separation. A printing method comprising forming Zt, wherein, in a used thermal transfer sheet obtained after the thermal transfer, a residual image Zyr in which a yellow dye is reduced in concentration by transferring the image Zyt, and a magenta dye by transferring the image Zmt Is transferred to the residual image Zmr and the image Zct, and the cyan dyeing is performed. So that at least two afterimages selected from the group consisting of afterimages Zcr having a reduced density overlap each other when the identification portions for cueing each color dye layer including the selected afterimages are superimposed. A printing method characterized by printing.

The present invention includes (1) a thermal transfer sheet driving device that conveys a thermal transfer sheet in which a dye layer formed on one surface of a base sheet includes a yellow dye layer, a magenta dye layer, and a cyan dye layer. (2) An image receiving sheet driving device that conveys the image receiving sheet; and (3) a controller I that separates the transferred image Z into yellow, magenta, and cyan, respectively, and applies thermal energy to the thermal head according to the obtained image information. In the image forming apparatus, (1) the thermal transfer sheet driving device and / or (2) the image receiving sheet driving device is configured to respond to the image information from the yellow dye layer, the magenta dye layer, and the cyan dye layer, respectively. When the image Zyt, the image Zmt, and the image Zct are transferred onto the image receiving sheet by thermal transfer, the driving operation is determined by the control unit II. In the used thermal transfer sheet obtained after the thermal transfer, the control unit II has a residual image Zyr obtained by lowering the density of the yellow dye by transferring the image Zyt, and a lower density of the magenta dye by transferring the image Zmt. At least two afterimages selected from the group consisting of the afterimage Zmr formed and the afterimage Zcr formed by lowering the density of the cyan dye by the transfer of the image Zct are the headings of the respective color dye layers each including the selected afterimage. The image forming apparatus is characterized in that control is performed so as to cause a deviation from each other when the identification portions for overlapping are overlapped.
The present invention is described in detail below.

The thermal transfer sheet used in the printing method of the present invention is one in which a dye layer is provided on one surface of a substrate sheet, and includes at least a yellow dye layer, a magenta dye layer, and a cyan dye layer as the dye layer.

As a base material sheet in the said heat transfer sheet, the same base material sheet as what is used for the conventional heat transfer sheets, such as a plastic film, paper, and cellophane, can be used as it is. Although the said base material sheet is not specifically limited, What performed various surface treatments, such as an easily bonding process, may be sufficient.
The base sheet may be a composite film in which two or more of the plastic film, paper, and cellophane are laminated.

The dye layer in the thermal transfer sheet is provided in the surface order on one surface of the base sheet, but the order of the yellow dye layer, magenta dye layer and cyan dye layer is not particularly limited.
The dye layer is generally a layer formed by supporting a sublimable dye with an arbitrary binder. The dye layer can be formed from a known sublimable dye and a known binder resin by a conventionally known method. The sublimation dye is a dye that diffuses or sublimates by heat and can be used in the present invention as long as it is a dye that is used in a conventionally known sublimation transfer type thermal transfer sheet. The selection is made in consideration of printing sensitivity, light resistance, storage stability, solubility in a binder, and the like.
The printing method of the present invention can be applied to a wide range of thermal transfer sheets including a conventionally known thermal transfer sheet and a widely used thermal transfer sheet as long as the dye layer is provided.
In the present specification, the “image to be transferred Z” is not particularly limited as long as it is a transfer target, and includes, for example, not only drawings and photographs but also characters and symbols.

In the printing method of the present invention, the transferred image Z is transferred from the yellow dye layer, the magenta dye layer and the cyan dye layer to the image receiving sheet by thermal transfer according to image information obtained by color separation into yellow, magenta and cyan, respectively. In this printing method, the transferred image Zt is formed by superimposing the transferred image Zyt, the image Zmt, and the image Zct.

More specifically, the printing method includes a step (i) of obtaining image information obtained by color-separating at least three colors of yellow, magenta, and cyan for the transferred image Z, and according to the image information obtained by the color separation. A step (ii) of transferring an image onto the image receiving sheet by thermal transfer;

The color separation in the step (i) can be performed by a conventionally known method.
In the step (ii), generally, the thermal transfer sheet and the image receiving sheet are arranged so that the dye layer in the thermal transfer sheet can come into contact with the image receiving sheet, and the surface of the thermal transfer sheet opposite to the side on which the dye layer is provided. The thermal head arranged in the above is pressed to record an image on the image receiving sheet according to the image information obtained in the step (i).

In the step (ii), an image Zyt corresponding to image information obtained by color separation into yellow among the image information obtained by color separation in the step (i) is usually transferred by thermal transfer to the yellow dye. Step (ii) of transferring from the layer onto the image receiving sheet, among the image information obtained by color separation into each color by the step (i), an image Zmt corresponding to the image information obtained by color separation into magenta is obtained by thermal transfer. Of the image information obtained by color separation into each color by the step (im) and the step (im) of transferring from the magenta dye layer onto the image receiving sheet, the image information obtained by color separation into cyan is used. A step (ic) of transferring the image Zct from the cyan dye layer onto the image receiving sheet by thermal transfer;
The order of the step (ii), the step (im) and the step (ic) is not particularly limited. In general, the yellow dye layer, the magenta dye layer and the cyan dye layer provided on one surface of the base sheet described above Follow the order in which they are arranged in plane order.

All the images in step (ii), step (im) and step (ic) are transferred to the same location on the image receiving sheet. Therefore, usually, the position of the image receiving sheet with respect to the thermal head at the time of thermal transfer is fixed, and each color dye layer is cued so that each color dye layer faces the same transfer location on the image receiving sheet.
The cueing is usually performed by detecting an identification portion for cueing each color dye layer and conveying the thermal transfer sheet until the identification portion reaches a predetermined position for transfer.

Although it does not specifically limit as said identification site | part, For example, the detection mark provided on the base material sheet for this identification, the switching site | part of each color dye layer, etc. are mentioned.
The detection mark may be any color as long as it can be detected by the position detection mechanism of the thermal recording printer. For example, the detection mark may be a color that can be recognized by human vision, such as black or red, and is colorless and transparent. You may make it comprise with the ink which absorbs infrared rays, and an infrared detector may detect. The detection mark may be printed with magnetic ink or conductive ink and detected electromagnetically.
The detection mark is not particularly limited, and can be formed by, for example, a known ink and printing method.
The detection mark can be formed as various patterns such as a line segment, a straight line, and a register mark.
The said detection mark can be formed in the part which is not used for printing, such as the surface or back surface of a base material sheet, the surface of a transparent protective layer, for example.

The image Zyt, the image Zmt, and the image Zct are superimposed on each other by cueing the respective color dye layers and transferred to the same location on the image receiving sheet, thereby forming a transfer image Zt. It becomes.

Each color dye layer in each of the above step (iy), step (im) and step (ic) has a dye density that decreases depending on the density of the image as a result of the transfer of each color dye onto the image receiving sheet for image transfer. Usually, not all of the dye that was present in the dye layer before transfer is transferred, and the reversal image has a residual image that can be seen slightly.

In the printing method of the present invention, in the used thermal transfer sheet obtained after the thermal transfer, a residual image Zyr in which the yellow dye is reduced in density by transferring the image Zyt, and a magenta dye is reduced in density by transferring the image Zmt. At least two afterimages selected from the group consisting of the afterimage Zmr and the afterimage Zcr obtained by reducing the density of the cyan dye by the transfer of the image Zct are identified for cueing each color dye layer that includes the selected afterimage. When the portions are overlapped, the images are printed so as to be displaced from each other.

For example, in the case where the at least two afterimages selected are the afterimage Zmr and the afterimage Zcr, the above-described printing method may be an identification region for cueing the magenta dye layer containing the afterimage Zmr in the used thermal transfer sheet obtained after the thermal transfer. Are printed so that the afterimage Zmr and the afterimage Zcr are shifted from each other when the identification portion for cueing the cyan dye layer including the afterimage Zcr is superimposed.

For example, when the at least two afterimages selected are the afterimage Zmr and the afterimage Zcr, the afterimage Zyr may deviate from both the afterimage Zmr and the afterimage Zcr, or may deviate from the afterimage Zmr and be the same as the afterimage Zcr. It may be the same as the afterimage Zmr and may be shifted from the afterimage Zcr.

Since at least two afterimages selected from the group consisting of the afterimage Zyr, the afterimage Zmr, and the afterimage Zcr are darker than the afterimage Zyr in terms of preventing negative image production, it is preferable to include the afterimage Zmr and the afterimage Zcr, More preferably, the afterimage Zyr, the afterimage Zmr, and the afterimage Zcr are shifted from each other. When the selected at least two afterimages are dark, it is difficult to identify the original image, and thus it is easy to prevent negative image production.

In the present invention, the displacement is caused by, for example, (A) an afterimage Zyr, an afterimage Zmr, and an afterimage Zyr, and (B) an afterimage Zyr. , And the like, which are caused by different print lengths of at least two afterimages selected from the group consisting of the afterimage Zmr and the afterimage Zcr.

For example, when the selected at least two afterimages are an afterimage Zmr and an afterimage Zcr, the deviation in the above (A) is between the identification portion for cueing the magenta dye layer and the print start position of the image Zmt. This can be caused by making the length different between the identification portion for cueing the cyan dye layer and the printing start position of the image Zct. The yellow, magenta, and cyan color dye layers are generally provided in a size that includes the size of the transferred image. The identification site is usually always detected for cueing each color dye layer.

Conventionally, in the thermal transfer sheet, between the position of the identification site for each color dye layer and the position where transfer or printing according to image information formed by color separation into each color is a fixed length, usually, Only by detecting the identification site for each color dye layer, the printing start position from each color dye layer was determined. Therefore, when the used thermal transfer sheet thermally transferred by the conventional printing method is rewound from the winding side to the supply side in the image forming apparatus and then thermally transferred again by the conventional method, the image transferred from each color dye layer is transferred onto the image receiving sheet. In this case, printing is started from the same position, and images based on the respective colors are overlapped, so that a negative image that is clear enough to distinguish the transferred image may be obtained.

In the printing method of the present invention, as the deviation, for example, the deviation (A) described above is caused, so that the used thermal transfer sheet is rewound from the winding side to the supply side and thermally transferred again by a conventional method. However, since the transfer from the at least two dye layers causing the shift is started from different positions on the image receiving sheet, the image images do not overlap each other, and the transferred image is discriminated from the obtained image. I can't.

The deviation in (B) can be caused, for example, by making the print length of the afterimage Zmr different from the print length of the afterimage Zcr when the at least two selected afterimages are the afterimage Zmr and the afterimage Zcr.
The printing length is the length of the printing area in the conveyance direction of the thermal transfer sheet or the image receiving sheet.

Conventionally, the print length is usually constant during transfer from each color dye layer. Therefore, conventionally, when an identification site for each color dye layer is detected, as described above, printing from each color dye layer is started from a position at a distance from the identification site, and the print length of any color dye layer is It was the same. Therefore, when the used thermal transfer sheet thermally transferred by the conventional printing method is rewound from the winding side to the supply side in the image forming apparatus and then thermally transferred again by the conventional method, the image transferred from each color dye layer is transferred onto the image receiving sheet. Since the print lengths are the same, the images based on the colors overlap each other, and a negative image that is clear enough to distinguish the transferred image may be obtained.

In the printing method of the present invention, the used thermal transfer sheet obtained by causing the shift of (B) described above has an afterimage in which at least two dyed layers have different shapes due to the difference in printing length. Will have. Therefore, even when the used thermal transfer sheet is rewound from the winding side to the supply side and thermal transfer is started again from the same position on the image receiving sheet by the conventional method, it can be obtained from the at least two dyed layers. The image images do not overlap each other, and the transferred image cannot be determined from the obtained image.

The deviation (B) is, for example, the transfer speed of the thermal transfer sheet to the image receiving sheet at the time of transfer in each transfer from at least two dye layers selected from the group consisting of a yellow dye layer, a magenta dye layer, and a cyan dye layer. For example, at the time of transfer, the conveying speed of the image receiving sheet may be changed. In this case, however, the printing speed also needs to be changed and the control tends to be complicated. Therefore, a method in which the printing speed is constant and the conveyance speed of the thermal transfer sheet is changed is preferable in terms of simplicity.

Even if the deviation in the present invention is any of the above-mentioned (A) or (B), it is possible to prevent the negative production only by causing a slight deviation. Thus, both (A) and (B) may be displaced.

The printing method of the present invention transfers at least one time from the yellow dye layer, the magenta dye layer, and the cyan dye layer to the image receiving sheet by thermal transfer in accordance with image information obtained by color separation into yellow, magenta, and cyan, respectively. A series of processes including the above can be regarded as one cycle.
The printing method of the present invention can prevent the production of a negative only by causing the above-described deviation in the one cycle.

However, the shift in the present invention is preferably generated irregularly.
In the present invention, the phrase “irregularly causing deviation” includes, for example, the case where the deviation is irregularly generated over a plurality of cycles as well as the one cycle.
In the present invention, if the deviation occurs irregularly, the same apparatus as the image forming apparatus that has previously performed thermal transfer is used, and the used thermal transfer sheet after the previous thermal transfer is transferred from the winding side to the supply side. Even when rewinding and performing thermal transfer again with the same print start position and print length, negative production can be sufficiently prevented.

In the present invention, the mechanism for irregularly generating the deviation is not particularly limited, but it is preferable to determine the deviation pattern based on a random number, for example, because it can be easily performed.
The method of determining the deviation pattern based on random numbers is not particularly limited. For example, a control unit having a mechanism for generating random numbers is provided in the image forming apparatus, and the print start position and / or print length is determined based on the random numbers. And a method of determining and performing the transfer.
Examples of the mechanism for generating the random number include conventionally known mechanisms such as a mechanism for generating a random number based on a physical random number generation function.

In the printing method of the present invention, a used thermal transfer sheet obtained after the thermal transfer is obtained by performing thermal transfer so as to cause the above-described deviation (A) and / or (B) with a commercial printer that is not generally sold. Even if printing is performed again using a commercially available printer, a clear negative image cannot be obtained.

The image forming apparatus according to the present invention includes (1) a thermal transfer sheet driving device that conveys a thermal transfer sheet in which a dye layer provided on one surface of a base sheet includes a yellow dye layer, a magenta dye layer, and a cyan dye layer. (2) Image receiving sheet driving device for conveying the image receiving sheet, and (3) Control for separating the transferred image Z into yellow, magenta and cyan, respectively, and applying thermal energy to the thermal head according to the obtained image information Part I is included.

In the image forming apparatus according to the present invention, the (1) thermal transfer sheet driving device and / or the (2) image receiving sheet driving device may correspond to the image information from the yellow dye layer, the magenta dye layer, and the cyan dye layer, respectively. When the image Zyt, the image Zmt, and the image Zct are transferred onto the image receiving sheet by thermal transfer, the driving operation is determined by the control unit II.

FIG. 1 shows an example of the image forming apparatus of the present invention.
In the figure, 1 is a thermal transfer sheet supply roll, 2 is a thermal transfer sheet take-up roll, 3 is a friction roller, 4 is a thermal head, 5 is a platen roller, 6 is a paper feed roller, 7 is a grip roller, 8 is a control unit, Reference numeral 9 denotes a driver, 10 denotes a power source, 11 denotes a multi-control motor, 12 denotes a recording head moving motor, 13 denotes a torque limiter, 14 denotes a thermal transfer sheet driving device, and 15 denotes an image receiving sheet driving device.
The control unit 8 includes a control unit I and a control unit II.
The control unit I controls the recording head moving motor 12 via a control signal.

In the image forming apparatus according to the aspect of the invention, the control unit II may use the used thermal transfer sheet obtained after the thermal transfer to obtain a residual image Zyr obtained by reducing the density of the yellow dye by transferring the image Zyt, and magenta by transferring the image Zmt. Each color dye layer in which at least two afterimages selected from the group consisting of an afterimage Zmr formed by reducing the density of the dye and an afterimage Zcr formed by transferring the image Zct and reduced in density by the cyan dye each include the selected afterimage When the identification parts for cueing are superimposed, control is performed so that they are shifted from each other.

The control unit II controls the paper feed roller 6, the multi-control motor 11, the image receiving sheet driving device 15, and the thermal transfer sheet driving device 14 via the control signal, and the driving force from the thermal transfer sheet driving device 14 is torqued. By transferring the heat transfer sheet to the heat transfer sheet take-up roll 2 via the limiter 13, the heat transfer sheet is unwound from the heat transfer sheet supply roll 1 and then taken up on the heat transfer sheet take-up roll 2.
The thermal transfer sheet is disposed between the thermal head 4 and the platen roller 5, and the thermal head 4 is in contact with the surface opposite to the dye layer.

The image receiving sheet is fed between the thermal head 4 and the platen roller 5 by the rotation of the paper feed roller 6, the image is transferred by the thermal head, and the grip roller 7 receives the driving force from the image receiving sheet driving device 15. The paper is discharged by the rotation of. At this time, until the image receiving sheet is sent between the thermal head 4 and the platen roller 5, the thermal head 4 is separated from the platen roller 5, and the image receiving sheet is sent between the thermal head 4 and the platen roller 5. After that, the thermal head 4 presses the platen roller 5 through the thermal transfer sheet and the image receiving sheet by the action of the recording movement motor 12.

While being transferred to the thermal head 4, the thermal transfer sheet fed from the thermal transfer sheet supply roll 1 is in contact with the friction roller 3 on the side opposite to the side in contact with the thermal head 4, that is, on the dye layer side.
The friction roller 3 is given a driving force from a multi-control motor 11.
The multi-control motor 11 adjusts the conveyance speed of the thermal transfer sheet and the conveyance speed of the image receiving sheet by the control unit II. Here, the control unit II determines the print start position and / or print length so that the above-described deviation occurs, and adjusts each conveyance speed according to the print start position and the print length.

Since the image forming apparatus of the present invention has the control unit II and can easily cause a shift in the image forming position in each dye layer, it can be suitably used in the above-described printing method of the present invention.

Since the printing method of the present invention has the above-described configuration, the used thermal transfer sheet is rewound to give the same energy to each element of the thermal head, and even when the thermal transfer is performed with an appropriately adjusted intermediate color gradation (gray solid), Production of a negative image of the initial image can be prevented.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples and Comparative Examples.
In the text, “part” or “%” is based on mass unless otherwise specified.

Examples 1-24
(1) Image 1 was formed by printer A using a thermal transfer sheet having a yellow dye layer, a magenta dye layer, and a cyan dye layer having the following composition provided in the surface order.
In the thermal transfer sheet, the size of each dye layer is 180 mm in length (printing direction) × 110 mm in width, and a detection mark is provided at the head of each dye layer. Printer A detects the detection mark. Thus, cueing of each of the above dye layers is performed.

<Yellow dye layer composition>
5.5 parts of yellow dye (Macrolex Yellow 6G manufactured by Bayer)
4.5 parts of polyvinyl butyral resin (S-REC BX-1 manufactured by Sekisui Chemical Co., Ltd.)
Methyl ethyl ketone 45 parts Toluene 45 parts

<Magenta dye layer composition>
Magenta dye 5.5 parts (CI Disperse Red 60)
4.5 parts of polyvinyl butyral resin (S-REC BX-1 manufactured by Sekisui Chemical Co., Ltd.)
Methyl ethyl ketone 45 parts Toluene 45 parts

<Cyan dye layer composition>
Cyan dye 5.5 parts (CI Solvent Blue 63)
4.5 parts of polyvinyl butyral resin (S-REC BX-1 manufactured by Sekisui Chemical Co., Ltd.)
Methyl ethyl ketone 45 parts Toluene 45 parts

(2) Using the same type of thermal transfer sheet as in (1) above, printing is performed in the same manner as in (1) above except that the printing start position of each dye layer is advanced by 1 mm from (1) in the same direction as the image forming direction. The conditions were set and the image 2 was separately formed using the printer A.

(3) Using the same type of thermal transfer sheet as in (1) above, the printing conditions are set in the same manner as in (1) above except that the printing start position of each dye layer is delayed by 1 mm in the same direction as the image forming direction. Then, the image 3 was separately formed using the printer A.

The thermal transfer sheet after formation of each image 1 to 3 is divided into a yellow dye layer, a magenta dye layer, and a cyan dye layer. For example, as shown in Table 1, the yellow dye layer of image 1, the magenta dye layer of image 2, and the image Pseudo-image-formed thermal transfer sheets of Examples 1 to 24 were produced by combining dye layers that formed different images, such as a combination with one cyan dye layer.
The image-formed thermal transfer sheet was wound around the core on the supply side, and the printer A was used to print 145 gray solids under the same conditions as in (1) above.

Comparative Examples 1-3
Each image-formed thermal transfer sheet obtained by separately forming the above-described images 1 to 3 is rewound by one screen, and using the printer A, the same conditions as in Examples 1 to 24 (1), and 145 gradations The gray solid was printed.

Test example 1
About each printed matter obtained from each image-formed thermal transfer sheet of Examples 1 to 24 and Comparative Examples 1 to 3, the ease of recognizing the negative image was visually evaluated based on the following evaluation criteria.

Evaluation criteria ○: The original image can be recognized.
Δ: The original image can be slightly recognized.
X: It is difficult to recognize the original image.

Table 1 summarizes the combinations of the image-formed thermal transfer sheets of Examples 1 to 24 and the test results.

Of the image-formed thermal transfer sheets of Examples 1 to 24, Examples 5, 7, 11, 14, 18, and 20 combined with dye layers that formed different images were particularly difficult to recognize negative images. The formation of images in which the print start positions of the yellow, cyan, and magenta dye layers are all different is most effective in making it difficult to recognize the negative image. Therefore, it has been found that it is preferable to form images with different print start positions for magenta and cyan.

Examples 25-48
(1) In the same manner as in Examples 1 to 24, using a thermal transfer sheet in which a yellow dye layer, a magenta dye layer and a cyan dye layer are provided in the surface order, the print length is adjusted to 140 mm, and an image 4 is printed by the printer A Formed.
In the thermal transfer sheet, the size of each dye layer is vertical (printing direction) 190 mm × width 110 mm, and a detection mark is provided at the head of each dye layer. Printer A detects the detection mark. Thus, cueing of each of the above dye layers is performed.

(2) Using the same type of thermal transfer sheet as (1) above, the printing range of each dye layer was extended by 1 mm from the above (1) by adjusting the thermal transfer sheet feed speed in the same direction as the image forming direction. Except for the above, printing conditions were set in the same manner as in (1) above, and the image 5 was separately formed using the printer A.

(3) Using the same type of thermal transfer sheet as (1) above, the print range of each dye layer was reduced by 1 mm from the above (1) by adjusting the thermal transfer sheet feed speed in the same direction as the image forming direction. Except for the above, printing conditions were set in the same manner as in (1) above, and the image 6 was separately formed using the printer A.

The thermal transfer sheet after formation of each image 4 to 6 is divided into a yellow dye layer, a magenta dye layer, and a cyan dye layer. For example, as shown in Table 2, the yellow dye layer of image 4, the magenta dye layer of image 5, and the image 4 A pseudo image-formed thermal transfer sheet of Examples 25 to 48 was produced by combining dye layers having different images such as a combination with the cyan dye layer.
The image-formed thermal transfer sheet was wound around the core on the supply side, and the printer A was used to print 145 gray solids under the same conditions as in (1) above.

Comparative Examples 4-6
Each of the image-formed thermal transfer sheets obtained by separately forming the above-described images 4 to 6 is rewound by one screen, and using the printer A, the same conditions as in Examples 25 to 48 (1), and 145 gradations The gray solid was printed.

Test example 2
About each printed matter obtained from each image-formed thermal transfer sheet of Examples 25 to 48 and Comparative Examples 4 to 6, the ease of recognizing the negative image was visually evaluated based on the same evaluation criteria as in Test Example 1. .
Table 2 summarizes the combinations of the image-formed thermal transfer sheets of Examples 25 to 48 and the test results.

Of the image-formed thermal transfer sheets of Examples 25 to 48, Examples 29, 31, 35, 38, 42, and 44, which combined dye layers that formed different images, were particularly difficult to recognize negative images. Further, when images having different print lengths for the respective dye layers of yellow, cyan, and magenta are formed, the effect of making it difficult to recognize the negative image is most noticeable. , 32 and the like are easily recognized, it was found that magenta and cyan preferably form images with different print lengths for each dye layer.
On the other hand, the image-formed thermal transfer sheets of Comparative Examples 4 to 6 easily recognized the negative image.

Since the printing method of the present invention has the above-described configuration, the used thermal transfer sheet is rewound to give the same energy to each element of the thermal head, and even when the thermal transfer is performed with an appropriately adjusted intermediate color gradation (gray solid), Production of a negative image of the initial image can be prevented.

1 is a diagram illustrating an example of an image forming apparatus of the present invention. It is a schematic diagram of the printing method in Examples 1-24. It is a schematic diagram of the printing method in Examples 25-48.

Explanation of symbols

1. 1. Thermal transfer sheet supply roll 2. Heat transfer sheet take-up roll 3. Friction roller 4. Thermal head 5. Platen roller 6. Paper feed roller Grip roller8. Control unit 9. Driver 10. Power supply 11. Multi-control motor 12. Recording head moving motor 13. Torque limiter 14. Thermal transfer sheet driving device 15. Image receiving sheet driving device 21. Yellow dye layer 22. Magenta dye layer 23. Cyan dye layer 24. Detection mark 31. Yellow dye layer 32. Magenta dye layer 33. Cyan dye layer 34. Detection mark

Claims (7)

Using a thermal transfer sheet that includes a yellow dye layer, a magenta dye layer, and a cyan dye layer as a dye layer that is provided on one side of the base sheet in a surface sequence, the transferred image Z is separated into yellow, magenta, and cyan, respectively. The transferred image Zt is formed by superimposing the image Zyt, the image Zmt, and the image Zct transferred from the yellow dye layer, the magenta dye layer, and the cyan dye layer onto the image receiving sheet by thermal transfer in accordance with the image information. A printing method comprising:
In the used thermal transfer sheet obtained after the thermal transfer, a residual image Zyr in which the density of the yellow dye is reduced by transferring the image Zyt, a residual image Zmr in which the density of magenta dye is reduced by transferring the image Zmt, and the image When at least two afterimages selected from the group consisting of afterimages Zcr formed by lowering the density of the cyan dye by transfer of Zct are overlapped with identification portions for cueing each color dye layer each containing the selected afterimages, A printing method, wherein printing is performed so as to cause a shift from each other. The printing method according to claim 1, wherein the shift is caused by a shift in a printing start position for each of at least two afterimages selected from the group consisting of the afterimage Zyr, the afterimage Zmr, and the afterimage Zcr. The printing method according to claim 1 or 2, wherein the shift is caused by a difference in print length between at least two afterimages selected from the group consisting of the afterimage Zyr, the afterimage Zmr, and the afterimage Zcr. The printing method according to claim 1, wherein at least two afterimages selected from the group consisting of the afterimage Zyr, the afterimage Zmr, and the afterimage Zcr include the afterimage Zmr and the afterimage Zcr. The printing method according to claim 1, wherein the shift is generated irregularly. The printing method according to claim 1, wherein the deviation pattern is determined based on a random number. (1) A thermal transfer sheet driving device that transports a thermal transfer sheet in which a dye layer formed on one surface of a base sheet includes a yellow dye layer, a magenta dye layer, and a cyan dye layer, and (2) transports an image receiving sheet. And (3) an image forming apparatus having a control unit I that separates the transferred image Z into yellow, magenta, and cyan, and applies thermal energy to the thermal head according to the obtained image information. There,
The (1) thermal transfer sheet driving device and / or the (2) image receiving sheet driving device is provided on the image receiving sheet by thermal transfer according to the image information from the yellow dye layer, the magenta dye layer, and the cyan dye layer, respectively. When transferring the image Zyt, the image Zmt, and the image Zct, the driving operation is determined by the control unit II.
In the used thermal transfer sheet obtained after the thermal transfer, the control unit II has an afterimage Zyr in which the yellow dye is reduced in density by the transfer of the image Zyt, and an afterimage in which the magenta dye is reduced in density by the transfer of the image Zmt. Zmr and at least two afterimages selected from the group consisting of afterimages Zcr formed by lowering the density of the cyan dye by transfer of the image Zct are identification sites for cueing each color dye layer each including the selected afterimages An image forming apparatus, wherein the image forming apparatuses are controlled so as to be displaced from each other when they are superimposed.

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