JPH0825663A - Multi-color thermosensible recording - Google Patents

Abstract

PURPOSE:To record clear black characters with no bleeding on color thermosensible recording paper. CONSTITUTION:A yellow image and the yellow component of black characters are first recorded. After fixing a yellow thermosensible coloring layer, Magenta of black characters, cyanogen and Magenta images are recorded. Next, after fixing a Magenta thermosensible coloring layer, cyanogen images are recorded. As a result, recording in the yellow component of black characters with small coloring thermal energy is given to a yellow thermosensible coloring layer, thus reducing yellow bleeding. Recording in black characters with thermal recording is given to a three-color thermosensible coloring layer, so it is possible to minimize bleeding due to a shift in coloring of black characters.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal recording method for recording clear black characters without color bleeding.

[0002]

2. Description of the Related Art A color thermosensitive recording paper is known in which a cyan thermosensitive coloring layer, a magenta thermosensitive coloring layer and a yellow thermosensitive coloring layer are sequentially laminated on a support. When recording a multicolor image on this color thermosensitive recording paper, a yellow image is recorded (printed) on the yellow thermosensitive coloring layer by a thermal head, and after this recording, the yellow thermosensitive coloring layer is optically fixed. Next, a magenta image is thermally recorded on the magenta thermosensitive coloring layer, and then the magenta thermosensitive coloring layer is optically fixed. Finally, a cyan image is thermally recorded on the cyan thermosensitive coloring layer.

In a postcard or the like, a full-color image and a black character are often mixed, but since this black character is represented by a subtractive color mixture of cyan, magenta, and yellow, if a color shift occurs during recording, the black character This will cause color bleeding. Therefore, for example, Japanese Unexamined Patent Publication No.
No. 2,866,87 proposes a method of recording the black character at one time by applying the maximum thermal energy for developing the cyan, magenta, and yellow colors to the maximum density to the color thermal recording paper at the same time so that the three colors are simultaneously developed. Has been done.

[0004]

In the method of recording black characters by simultaneously developing three colors, as shown in FIG. 13, the heat applied from the thermal head 2 to the color thermosensitive recording paper 3 is broken line in the figure. The temperature distribution is as shown in. The yellow thermosensitive coloring layer has the largest coloring area since it requires the smallest thermal energy for coloring, and the cyan thermosensitive coloring layer has the smallest coloring area because it requires the largest thermal energy for coloring. As a result, as shown in FIG. 14, around the black character 4 recorded with all the colors of yellow, magenta and cyan, the red portion 5 and the yellow portion 6 due to the yellow and magenta colors are colored so as to frame the black character. However, the outline of the black character 4 is blurred.

The present invention has been made to solve the above problems, and an object thereof is to provide a method for recording clear black characters without blurring.

[0006]

In order to solve the above-mentioned problems, the present invention provides a cyan thermosensitive coloring layer, a magenta thermosensitive coloring layer, and a yellow thermosensitive coloring layer, which are sequentially formed on a support.
The yellow thermosensitive coloring layer on the top and the magenta thermosensitive coloring layer in the middle have photo-fixing property by electromagnetic radiation of different wavelength range, and the lower layer is a color thermosensitive recording paper with higher coloring heat energy. First, the yellow thermosensitive coloring layer is thermally recorded with the thermal energy that develops to almost the maximum density, then the yellow thermosensitive coloring layer is optically fixed, and then the thermal recording is performed with the thermal energy that the cyan thermosensitive coloring layer develops the maximum density. By doing so, black characters are recorded.

In the present invention, the magenta thermosensitive coloring layer is first subjected to thermal recording by the thermal energy for coloring to the maximum density, and then the yellow thermosensitive coloring layer and the magenta thermosensitive coloring layer are optically fixed, and then the cyan thermosensitive coloring is performed. The black characters are recorded by thermal recording with the thermal energy at which the layer develops color almost at the maximum density.

[0008]

When recording black characters, only the yellow thermosensitive coloring layer which requires a small amount of heat energy for coloring, or the cyan thermosensitive coloring layer which requires a large amount of coloring heat energy after recording the yellow thermosensitive coloring layer and the magenta thermosensitive coloring layer. Since thermal recording is performed, black character bleeding due to the spread of heat does not occur.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 2 showing the outline of a color thermal printer, a video signal of an analog signal is separated by a decoder 10 into three color signals of red, green and blue, and an A / D converter 1
It is converted into a digital signal by 1. The obtained red, green and blue image data are respectively written in the frame memories 12a, 12b and 12c provided for the respective colors.
When synthesizing black characters in a full-color image, the image data of the full-color image is stored in the frame memories 12a, 12b, 1
2c, the black character signal is converted into a digital signal by the A / D converter 11, and data having the same value for all three colors is written to the frame memories 12a, 12b, 12c for each color. In the case of a video signal of a full-color image containing black or characters of any color, the decoder 10 may perform color separation as in the case of only the full-color image.

At the time of recording, the frame memories 12a, 12
The image data for one line is read from each of b and 12c and sent to the gradation control unit 13. This gradation control unit 13
The red, green, and blue image data are converted into yellow, magenta, and cyan image data. Then, black character pixels (black pixels) are extracted from the converted image data. The image data of the black pixels, the yellow image data, the magenta image data, and the cyan image data are selectively taken out, converted into drive data in consideration of the color development characteristics of the color thermosensitive recording paper 15, and then passed through the head drive unit 19. And sent to the thermal head 14. This thermal head 14
As is well known, a large number of heat generating elements are arranged in the main scanning direction, and these heat generating elements generate thermal energy according to the color density of the pixel to be recorded, and the color thermosensitive recording paper 1
5 is developed by heating.

The color thermosensitive recording paper 15 is wound around the outer periphery of a platen drum 17 which is rotated in the sub-scanning direction, and is rotated in the sub-scanning direction by a motor 16 connected to a motor driver 18. The optical fixing device 20 includes two ultraviolet lamps 21a and 21b. The two ultraviolet lamps 21a and 21b each have an emission peak of 420 nm.
And 365 nm ultraviolet light to irradiate the yellow thermosensitive coloring layer 38 and the magenta thermosensitive coloring layer 37 of the color thermosensitive recording paper 15 shown in FIG. 5, respectively. The light fixing time of the optical fixing device 20 is controlled by the controller 23.

In FIG. 3 showing an example of the gradation control unit 13, the red image data, the green image data and the blue image data for one line read from the frame memories 12a, 12b and 12c are used for gradation control. It is sent to the look-up table memory 25 and converted into yellow image data, magenta image data, and cyan image data in consideration of the coloring characteristics of yellow, magenta, and cyan. These image data are as shown in FIG.
It is written in the line buffer memory 26 for three colors. Here, Y is yellow, M is magenta, C is cyan,
The subscripts indicate the position in the main scanning direction.

Further, the image data is sent to the black pixel determining section 27 and it is determined whether or not the pixel is a black character pixel. This judgment is
When all of the yellow image data, the magenta image data, and the cyan image data have the maximum value, this pixel is determined as a black pixel. As shown in FIG. 7, when the i-th pixel is a black pixel, B _i = 1, black image data of B _i = 0 is given to the pixel is not the case. This black image data is written in the black line buffer memory 28, as shown in FIG.

The selection unit 29 includes the black image data in the black line buffer memory 28 and the three color line buffer memory 2.
The black image data is preferentially taken out from the image data of No. 6, and the look-up table memory 30 for driving data conversion is used.
Send to The drive data conversion look-up table memory 30 converts the image data of each pixel into drive data for controlling heat generation of the heating element.

FIG. 5 shows an example of the color thermosensitive recording paper 15. The cyan thermosensitive coloring layer 3 is provided on the support 35.
6, magenta thermosensitive coloring layer 37, yellow thermosensitive coloring layer 38
Are sequentially layered. As the support 35, an opaque coated paper or a plastic film is used. Further, when producing an OHP sheet, a transparent plastic film is used.

The cyan thermosensitive coloring layer 36 contains an electron-donating dye precursor and an electron-accepting compound as main components, and develops a cyan color when heated. Magenta thermosensitive coloring layer 3
No. 7 contains a diazonium salt compound having a maximum absorption wavelength of about 365 nm, and a coupler that thermally reacts with this compound to develop a magenta color. When the magenta thermosensitive coloring layer 37 is irradiated with ultraviolet rays in the vicinity of 365 nm, the diazonium salt compound is photodecomposed and the coloring ability is lost. The yellow thermosensitive coloring layer 38 has a maximum absorption wavelength of about 420 nm.
And a coupler that thermally reacts with the diazonium salt compound to develop a yellow color. The yellow thermosensitive coloring layer 38 loses its coloring ability when irradiated with near-ultraviolet rays in the vicinity of 420 nm.

FIG. 6 shows the coloring characteristics of the thermosensitive coloring layers 36 to 38.
It shows sex. The horizontal axis shows the color thermosensitive recording paper 15.
Represents the thermal energy applied and is a yellow thermosensitive
The color layer 38 has a color gamut Y_TIt develops with the heat energy of
The thermosensitive coloring layer 37 has a coloring region M _TDevelops with the heat energy of
It The cyan thermosensitive coloring layer 36 has a coloring region C_TThermal energy
Develops with. Under normal storage conditions, the color thermosensitive recording
Color gamut C on recording paper 15_TGiven the heat energy of
Since there is almost no, optical fixing to the cyan thermosensitive coloring layer 36
Sex is not given. If needed, another wavelength
A diazonium salt compound and a coupler
You can use it.

Next, recording of a full-color image containing black characters will be described with reference to FIGS. 1 and 7 to 10.
The control unit 23 controls the motor 16 via the motor driver 18.
To rotate the color thermosensitive recording paper 15 to the thermal head 1.
4 is sent to the print position. At the same time, the control unit 23, as shown in FIG.
The red image data, the green image data, and the blue image data of the first pixel of the first line (L = 1) are read from 2b and 12c, respectively.

These image data are converted into yellow image data, magenta image data, and cyan image data by the gradation control look-up table memory 25, and then,
It is written in the line buffer memory 26 for three colors. Further, the black pixel determination unit 27 checks whether or not all of the three-color image data have almost the maximum values, and if so, determines that they are black pixels. In the case of this black pixel, "1" is written in the black line buffer memory 28, and otherwise, "0" data is written. Thereafter, similarly, writing is performed on the line buffer memory for three colors 26 and the line buffer memory for black 28 for the second to nth pixels.

When the head of the recording area of the color thermosensitive recording paper 15 reaches the print position, as shown in FIG. 1, the recording of the yellow component forming the yellow image and the black character is started. In this print, as shown in FIG. 8, the selection unit 29 determines whether or not the black image data of the first pixel of the black line buffer memory 28 is “1”.

If the black image data is "1",
The black image data is preferentially taken out and sent to the drive data conversion look-up table memory 30, converted into drive data for generating the thermal energy B ₁ T shown in FIG. 6, and sent to the head drive unit 19. This heat energy B ₁ T is for causing the yellow thermosensitive coloring layer 38 to develop the maximum density. On the other hand, in the case of “0”, the yellow image data is fetched from the three-color line buffer memory 26 and sent to the drive data conversion look-up table memory 30. The conversion look-up table memory 30 is
According to the color density of yellow, it is converted into drive data for generating heat energy in the color gamut Y _T , and this is sent to the head drive unit 19.

According to the procedure described above, the black image data or the yellow image data of the first pixel to the nth pixel on the first line are sequentially converted into drive data, and these drive data are head driven. After sending to the section 19, the thermal head 14 is energized to drive each heating element. Each heating element is continuously energized for a time corresponding to the yellow image data, or is intermittently driven by the number of drive pulses corresponding to the yellow image data. This allows
The heating element that should record the pixels of the yellow image is
The thermal energy in _T is applied to the color thermosensitive recording paper 15 to cause the yellow thermosensitive coloring layer 38 to develop a color at a density according to the image data, and yellow dots are recorded on the color thermosensitive recording paper 15.

When the black image data is "1", the heat generating element transfers the heat energy B ₁ T to the color thermosensitive recording paper 1.
5, the yellow thermosensitive coloring layer 38 is colored to the maximum density. As a result, the yellow component of the black dots expressed by the subtractive color mixture of three colors of yellow, magenta, and cyan is recorded on the color thermosensitive recording paper 15. The heating elements that do not record yellow dots or black dots are naturally not energized.

After recording the yellow image or the black character on the first line, the platen drum 17 rotates by one line.
During this period, the yellow image data or the black image data of the second line is read out, and the yellow component of the yellow dot or the black dot of the second line (the highest density yellow) is recorded on the color thermosensitive recording paper 15 by the procedure described above. . Less than,
Similarly, the third and subsequent lines are recorded.

By the rotation of the platen drum 17, the portion on which the yellow image or the black character is recorded reaches the optical fixing device 20. The ultraviolet lamp 21a in the optical fixing device 20 is turned on and the 420 nm ultraviolet light is applied to the color thermosensitive recording paper 15. As a result, the diazonium salt compound remaining in the yellow thermosensitive coloring layer 38 is decomposed and the yellow coloring ability is lost.

When the platen drum 17 enters the second rotation,
When the head of the recording area reaches the print position again, this time, recording of magenta and cyan components, which are the remaining constituent colors of black characters, and recording of a magenta image are started.
In this print, as shown in FIG.
It is determined whether the black image data of the first pixel of the black line buffer memory 28 is "1". If the black image data is “1”, the black image data is sent to the drive data conversion lookup table memory 30 and converted into drive data for generating thermal energy B ₂ T,
This is sent to the head drive unit 19.

On the other hand, in the case of "0", the magenta image data is taken out from the line buffer memory 26 for three colors,
This is a look-up table memory 3 for driving data conversion.
Send to 0. This conversion look-up table memory 30
Converts into drive data for generating heat energy in the color gamut M _T according to magenta image data, and sends this to the head drive unit 19.

As described above, after the drive data is sent to the head drive section 19, the thermal head 14 is energized to drive each heating element. As a result, the heating element for recording the pixels of the magenta image gives the thermal energy within the coloring area M _T to the color thermosensitive recording paper 15 and the magenta thermosensitive coloring layer 3
9 is colored to a density corresponding to the image data, and magenta dots are recorded on the color thermosensitive recording paper 15.

When the black image data is "1", the heat generating element transfers the heat energy B ₂ T to the color thermosensitive recording paper 1.
Give 5 This thermal energy B ₂ T is equivalent to the thermal energy corresponding to the highest density cyan color development shown in FIG. 6, and the magenta heat sensitive color development layer 37 and the cyan heat sensitive color development layer 3
6 develops at almost the maximum density. At this time, since the yellow thermosensitive coloring layer 38 is already fixed by the ultraviolet lamp 21a, even if the thermal energy B ₂ T is applied, the periphery of the already recorded black character does not develop yellow.

In this way, the first line is recorded for the magenta image and the magenta and cyan components of black characters. Similarly, the second and subsequent lines are sequentially recorded while the color thermosensitive recording paper 15 is intermittently transferred in predetermined steps.

The portion on which the magenta image is recorded is the optical fixing device 2.
When the temperature reaches 0, the ultraviolet rays in the wavelength range of 365 nm emitted from the ultraviolet lamp 21b are detected.
It is irradiated to 5. As a result, the magenta thermosensitive coloring layer 37
Is light-fixed. At this time, together with the magenta image, the magenta component (maximum density magenta) forming the black character is also fixed.

Thus, when the black image data is "1", the heating element gives the heat energy B ₂ T to the color thermosensitive recording paper 15 so that the magenta thermosensitive coloring layer 37 and the cyan thermosensitive coloring layer 36 have almost the maximum density at the same time. Then, the magenta and cyan components of the black dots are recorded on the color thermosensitive recording paper 15. As a result, all three colors of yellow, magenta, and cyan that make up a black character are recorded, and a black color is obtained by subtractive color mixing. Here, since the yellow heat-sensitive coloring layer 38 has already been recorded with a small heat energy,
The yellow coloring area is smaller than that in the conventional single-time recording. Therefore, bleeding due to the color mixture of magenta and cyan, and yellow, which is extra colored around the black character, is reliably prevented. Further, since the three colors of yellow, magenta, and cyan that form a black character are recorded in two steps, bleeding due to color misregistration can be minimized as compared with the case of recording a black character in three steps.

When the platen drum 17 enters the rotation eye, a cyan image is recorded on the cyan thermosensitive coloring layer 36 line by line in the same procedure as the recording of the magenta image. As a result, an image in which a full-color image and black characters are mixed is printed.

FIG. 11 shows an embodiment in which recording of magenta and cyan components of black characters and recording of a magenta image are performed separately. In this embodiment, the platen drum 1
With four rotations of 7, black characters and full-color images are recorded.

FIG. 12 shows an embodiment in which first the black character yellow and the magenta component are simultaneously recorded, and then the cyan component is recorded. First, the recording of a yellow image and the heat energy for coloring magenta in the black character portion to give magenta at a maximum density is applied to the color thermosensitive recording paper to cause yellow and magenta of the three color components of black characters to be simultaneously developed to a maximum density. Then, after fixing the yellow thermosensitive coloring layer, recording and fixing the magenta image, heat energy for recording the cyan image and generating cyan of almost the maximum density in the black character portion is applied to the color thermosensitive recording paper.

As described above, in recording a black character, since the yellow and magenta components having small coloring energy are first recorded and then the cyan component having high coloring energy is recorded, it is possible to record black characters with less bleeding as compared with the conventional case. You can In addition, since the three colors of yellow, magenta, and cyan that form black characters are recorded in two steps, bleeding due to color misregistration can be minimized.

Although all of the above embodiments have described recording of black characters, the present invention can be similarly applied to recording of black images other than characters, for example, line drawings.

[0038]

As described in detail above, according to the present invention, when recording a black character, only the yellow thermosensitive recording layer or the yellow thermosensitive recording layer and the magenta thermosensitive recording layer having a small coloring energy are recorded. Since the cyan heat-sensitive recording layer that requires a large amount of heat energy is recorded, the blurring of black characters can be reduced as compared with the conventional method. That is, since black characters are made to color by two thermal recordings on the three color thermosensitive coloring layers, it is possible to minimize the bleeding of black characters.

[Brief description of drawings]

FIG. 1 is a flowchart showing an embodiment of the present invention.

FIG. 2 is a schematic diagram of an apparatus for practicing the present invention.

FIG. 3 is a block diagram showing an example of a gradation control unit.

FIG. 4 is an explanatory diagram showing data storage states of a black line buffer memory and a three color line buffer memory, respectively.

FIG. 5 is an explanatory diagram showing a layer structure of color thermosensitive recording paper.

FIG. 6 is a graph showing coloring characteristics of each thermosensitive coloring layer.

FIG. 7 is a flowchart showing data writing to a line buffer memory.

FIG. 8 is a flowchart showing a recording procedure of a yellow component of a yellow image and a black character.

FIG. 9 is a flowchart showing a recording procedure of magenta and cyan components of black characters and a magenta image.

FIG. 10 is a flowchart showing a procedure for recording a cyan image.

FIG. 11 is a flowchart showing an example of recording black characters and a full-color image by rotating the platen drum four times.

FIG. 12 is a flowchart showing an example in which the yellow and magenta components of black characters are first recorded, and then the cyan component is recorded.

FIG. 13 is an explanatory diagram showing heat transfer to a color thermosensitive recording paper in a conventional black character recording method.

FIG. 14 is an explanatory diagram showing black characters recorded by a conventional method.

[Explanation of reference numerals] 14 thermal head 15 color thermosensitive recording paper 28 line buffer memory for black 26 line buffer memory for 3 colors 36 cyan thermosensitive coloring layer 37 magenta thermosensitive coloring layer 38 yellow thermosensitive coloring layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B41M 5/18 T

Claims (2)

[Claims] 1. A cyan thermosensitive coloring layer, a magenta thermosensitive coloring layer, and a yellow thermosensitive coloring layer are sequentially formed on a support, and the yellow thermosensitive coloring layer at the top and the magenta thermosensitive coloring layer in the middle are different from each other. In the method of recording black characters on a color thermosensitive recording paper that has the property of fixing light by electromagnetic radiation in a different wavelength range and has a higher coloring heat energy in the lower layer Black recording is performed by thermally recording with the thermal energy that the coloring layer develops to almost the maximum density, then fixing the yellow thermosensitive coloring layer optically, and then thermally recording with the thermal energy that the cyan thermosensitive coloring layer develops the maximum density. A thermal recording method characterized in that the recording is performed. 2. A cyan thermosensitive coloring layer, a magenta thermosensitive coloring layer, and a yellow thermosensitive coloring layer are sequentially laminated on a support, and the yellow thermosensitive coloring layer on the top and the magenta thermosensitive coloring layer in the middle are different from each other. In the method of recording black characters on a color thermosensitive recording paper that has the property of fixing light by electromagnetic radiation in a different wavelength range and has a higher coloring heat energy in the lower layer, the magenta Thermal recording is performed with the thermal energy at which the coloring layer develops to almost the maximum density, and then the yellow thermosensitive coloring layer and the magenta thermosensitive coloring layer are optically fixed, and then the thermal recording is performed with the thermal energy at which the cyan thermosensitive coloring layer develops the maximum density. The thermal recording method is characterized in that a black character is recorded by doing so.