JPH04286661A - Melting type thermal transfer recording method - Google Patents

Abstract

PURPOSE:To express multiple gradation without performing finely relative intermittent feeding of an ink film and a thermal head. CONSTITUTION:An ink film and a recording paper are fed intermittently by a unit feed quantity L substantially the same as the width of a heat generating element. At every intermittent feeding, the heating value of the heat generating element is controlled to 8 stages, and ink dots are recorded on one recording picture element by feeding intermittently 4 times. Temperature distribution of the heat generating element is irregular, having the highest parts at the centers of 2 electrodes. By controlling the heating value, 8 kinds of ink dots having different sizes are recorded. With the 8 kinds of ink dots and 4 kinds of recording areas, gradations having 32 stages are expressed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a melt-type thermal transfer recording method used in video printers and the like, and more particularly to a method for easily recording gradation images.

0002

2. Description of the Related Art As an image recording method, a melting type thermal transfer recording method is known in which an ink film is heated from behind and the thermally melted ink is transferred onto recording paper. Since this melt-type thermal transfer recording method involves melting ink and transferring it, it has hitherto been considered difficult to record gradation images. In view of these problems, the present applicant intermittently feeds the ink film and recording paper in the sub-scanning direction by a unit feed amount by an amount smaller than the length (width) of the heating element in the sub-scanning direction, and In addition to recording one recording pixel with multiple intermittent feeds, a heating element is driven for each intermittent feed to generate a constant amount of heat, and the recording area of the recording pixel is changed in multiple stages to express gradation. proposed a melt-type thermal transfer recording method (Japanese Patent Application No. 124474/1999).

0003

[Problems to be Solved by the Invention] Since the above-mentioned melting type thermal transfer recording method expresses gradation by the feed amount in the sub-scanning direction, it is possible to express the gradation by the amount of feed in the sub-scanning direction.
When expressing multiple gradations of two or more gradations, the unit feed amount must be made considerably small, which requires a feed mechanism that can perform minute feeds with high precision.

0004

[Means for Solving the Problems] The above problem is solved by using a heat generating element which is elongated in the main scanning direction and has a selection electrode arranged between two common electrodes, and the unit feed amount is set by the heat generating element. This is achieved by making the width approximately equal to the width of , recording pixels in unit feeds of m times, and controlling the amount of heat generated by the heating element in n stages for each unit feed. In the present invention, the ink dot size is set in n stages and the recording area is set in m stages to express m×n gradations. Therefore, by increasing the gradation by n times without changing the unit feed amount, , eliminating the need for highly accurate intermittent feeding.

[0005]

[Embodiment] In FIG. 3 showing the configuration of a melt-type thermal transfer recording apparatus embodying the present invention, image data of each pixel input from a TV camera, scanner, etc. is stored in a frame memory 10.
once written to. When recording an image, one line of image data is read out from the frame memory 10, subjected to gradation correction in the image processing section 11, and then stored in the table memory 1.
Sent to 2. This table memory 12 converts the image data into drive data and writes this into the line buffer memory 13. Drive data for one scanning line read from the line buffer memory 13 is sent to the head driver 14. The thermal head 19 has a large number of heating elements arranged in a line, and the thermal head driver 18 controls the amount of heat generated by each heating element.

The platen drum 16 has a toothed belt 17.
It is connected to the pulse motor 18 via the pulse motor 18, and is intermittently rotated by the pulse motor 18 by a predetermined unit feed amount. A recording paper 20 and an ink film 21 are placed on the platen drum 16 in an overlapping state, and a thermal head 19 is pressed against the platen drum 16 from above. The ink film 21 is composed of a support 21a such as a plastic film and an ink layer 21b coated thereon, and when heated by the thermal head 19, the molten ink 22 is transferred to the recording paper 20. Ru. Further, the ink film 21 moves intermittently along the guide rollers 23 and 24 together with the recording paper 20. Note that reference numeral 25 is a motor driver for controlling the rotation of the pulse motor 18, and reference numeral 26 is a control circuit for controlling each part.

As shown in FIGS. 4 and 5, the thermal head 19 has a glaze layer 31 formed on a ceramic substrate 30. As shown in FIGS. On this glaze layer 31, common electrodes 32a,
32b... are formed in a comb-teeth shape, and selection electrodes 33a, 33b... are arranged between them. The common electrode is
A positive potential is applied, and a negative potential corresponding to the amount of heat generated is applied to the selection electrode. The length (width) L (for example, 20 to 30 μm) in the sub-scanning direction is set across these electrodes.
A resistor 34 is formed, and the portion of the resistor 34 between the two common electrodes constitutes one heating element. In addition, the code|symbol 35 is a protective layer.

When a negative potential is applied to the selection electrode 33a, the two common electrodes 32a, 3 located on both sides of the selection electrode 33a
2b, the current flows toward the selection electrode 33a through the resistor 34.
, and heat is generated between the common electrodes 32a and 32b. Here, since the heat generation amount of the resistor 34 is small in the portion overlapping with the electrode, the heat generation distribution is as shown in FIG.
The peak is between a and the selection electrode 33b. Furthermore, when the negative potential of the selection electrode 33a is increased to reduce the current, the amount of heat generated decreases overall as shown by the dotted line.

As described above, by changing the potential of the selection electrode 33a stepwise, the area of the heating element changes where the ink melting calorific value T or more is generated.
As shown in FIG.
The size of 0 changes. Note that the numbers represent the level of heat generation, with "1" being a state in which no heat is generated, and "8" being a state in which heat generation is maximum. Further, a rectangle 41 represents an area that can be recorded once by the heating element, and its width is the same as the width of the resistor 34 and corresponds to the unit feed amount sent by the platen drum 16.

By intermittently rotating the platen drum 16 by a unit feed amount L, the recording pixels 42 are divided into four recording areas A1, A2, A3, and A, as shown in FIG.
The recording area is divided into 4 areas, and ink dots in 8 stages shown in FIG. 1 are recorded in each recording area. (A) is recording area A
(B) shows a state in which ink dots are recorded only on 1.
shows a state in which ink dots are recorded in recording areas A1 and A2, respectively, and the length in the sub-scanning direction is 2L. As shown in (A) to (D), since the recording area changes in four stages depending on the gradation level, 32 gradations can be expressed by combining eight types of ink dots. Table 1 shows the gradation levels corresponding to the drive data and the level of heat generation when recording each recording area. This table data is stored in the table memory 12 mentioned above.

[0011]

[Table 1]

Next, the operation of the above device will be explained. The control circuit 26 rotates the pulse motor 18 via the motor driver 25 to rotate the recording paper 20 and the ink film 2.
1 is intermittently transferred in the direction of the arrow by a unit feed amount L. At the same time, as shown in FIG. 6, the image data of each pixel for one line lined up in the main scanning direction is read out from the frame memory 10, subjected to processing such as γ correction in the image processing section 11, and then transferred to the table memory 12. send to This table memory 12
converts the image data into drive data for generating the amount of heat shown in Table 1.

First, drive data for recording the recording area A1 for one line of pixels is read from the table memory 12 and sent to the head driver 14 via the line buffer memory 13. The head driver 14 drives the thermal head 19 to cause each heating element to generate heat, heats the ink film 21 from behind, and transfers melted ink dots into the recording area A1. At this time,
The potential of the selection electrode of each heating element is set according to drive data, and one ink dot is selected from the eight stages shown in FIG. 1.

After recording in the recording area A1, the platen drum 16 is intermittently rotated by a unit feed amount L by the pulse motor 18, and drive data for recording in the recording area A2 is read out and written into the line buffer memory 18. When the recording paper 20 and the ink film 21 are fed by the unit feed amount L, the head driver 14 reads drive data from the line buffer memory 18, energizes each heating element of the thermal head 19, and creates ink dots in the recording area A2. transcribe.

Thereafter, in the same manner, ink dots are transferred to the recording areas A3 and A4 while intermittently transporting the recording paper 20 and the ink film 21 by the unit feed amount L. In this way, ink dots are recorded in recording pixels for one line by four times of intermittent feeding and four times of heat generation. When one line of recording is completed, the next one line of image data is read out from the frame memory 10 and recorded on the recording paper 20 according to the procedure described above.

[0016] The above embodiment is about creating a monochrome hard copy, but yellow (Y), magenta (M)
A hard copy of a multicolor image can be created by thermally transferring the image onto the recording paper 20 three times using a color ink film coated with three color inks of , cyan (C) in order. In addition, the size of the ink dot is changed by controlling the current of each heating element, but when recording a unit recording area, multiple pulses are supplied to the heating element, and by changing the number of pulses, the amount of heat generated is Alternatively, the amount of heat generated may be controlled by controlling the current flow time of the heating element during recording of a unit recording area.

[0017]

[Effects of the Invention] As explained in detail above, the present invention has the following features:
The recording paper and the thermal head are intermittently moved relative to each other by a unit feed amount that is approximately the same as the width of the heating element, and the heat generation amount of the heating element is controlled in n steps for each intermittent feed, and the thermal head is moved intermittently by m times. Since one recording pixel is recorded, m×n gradations can be expressed. Therefore, in the conventional method of expressing gradations using only intermittent feed, in order to express multiple gradations, the unit feed amount must be much smaller than the width of the heating element.
In contrast, the present invention expresses multiple gradations without changing the amount of intermittent feed, so even if the accuracy of intermittent feed is poor, stable gradations can be expressed.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the relationship between heat generation level and ink dots.

FIG. 2 is an explanatory diagram showing four levels of recording area.

FIG. 3 is a schematic diagram of a melt-type thermal transfer recording apparatus that implements the present invention.

4(A) is an explanatory diagram showing the arrangement of electrodes, and FIG. 4(B) is an explanatory diagram showing the heating state of the heating element. FIG.

FIG. 5(A) is a cross-sectional view taken along line AA in FIG. 4(A);
(B) is a sectional view taken along line B-B.

FIG. 6 is a flowchart showing a recording procedure for recording pixels.

[Explanation of symbols]

19 Thermal head 20 Recording paper 21 Ink film 32a-32c Common electrode 33a, 33b selection electrode 40 Ink dot 42 Recording pixels A1 ~ A4 Recording area

Claims (1)

[Claims] 1. Using a thermal head in which a plurality of heating elements are arranged in the main scanning direction, the thermal head is intermittently moved in the sub-scanning direction by a unit feed amount relative to the recording paper, and each heating element is In a melt-type thermal transfer recording method in which an ink film is heated by generating heat and the molten ink is transferred to a recording paper to record an image, a selective electrode is elongated in the main scanning direction and is located between two common electrodes. Using a heating element with a structure in which A melt-type thermal transfer recording method characterized by expressing.