JPS62282976A - Thermal transfer recording system - Google Patents

Abstract

PURPOSE:To perform high speed recording and to make gradation reproducibility excellent, by constituting the title recording system so that gradation is obtained by fixed patterns and the energy made into multivalent forming dots constituting each fixed pattern. CONSTITUTION:Because one pixel is constituted of a plurality of dot matrices and fixed patterns are formed therein, it is unnecessary to make the quantity of energy injected in each dot too strict. That is, a predetermined quantity of energy may be able to be injected in the matrices as a whole. When the fixed patterns are used, the quantity of heat energy accumulated in a thermal head 6 can be estimated in an aerea where a recording dot is formed continuously and, therefore, by positivity utilizing the accumulated heat energy, the current supply time for forming one dot and a current stop time can be shortened. Sufficient heat dissipation can be performed in an area where no dot is formed and the effect of heat accumulation does not appear. As a result, high speed recording can be realized without bringing about the lowering in image quality.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Objective of the Invention 1 (Field of Industrial Application) This invention relates to a thermal transfer recording method for obtaining gradation images using a sublimable coloring material, and particularly relates to a recording method. The present invention relates to a thermal transfer recording method that can improve speed.

(Prior Art) Conventionally, a transfer sheet comprising a coloring material layer containing a sublimable coloring material on a supporting base material and a receptor sheet having a color developing layer, etc. are overlaid, and a thermal head is used to 2. Description of the Related Art A thermal transfer recording apparatus is known that heats a transfer sheet to form a desired recording pattern and forms a transferred image on a receptor sheet. A thermal transfer recording device using a sublimable coloring material can continuously change the gradation of a single dot by changing the energy applied to the thermal head, so it is possible to record images with multiple r@ tones. is known to be extremely advantageous in obtaining

By the way, in order to realize high-speed recording with this thermal transfer recording device, it is desirable to shorten the heating time and rest time of the thermal head, that is, the driving cycle as much as possible. However, if the driving cycle of the thermal head is too short, energy injection in the high 1 degree region becomes insufficient, making it difficult to obtain a wide gradation.

Therefore, it may be possible to inject sufficient energy into the high concentration region by increasing the amplitude of the driving pulse while keeping the period of the driving pulse short. However, in this case, the heat generated during the previous dot formation is accumulated in the thermal head due to the short rest period of the thermal head. This heat accumulation phenomenon causes a change in recording density, rM tone skipping, and a change in hue in color images, resulting in a significant deterioration of image quality.

(Problems to be Solved by the Invention) As described above, in the conventional thermal transfer recording method using sublimable coloring materials, high-speed recording is impossible because shortening the dot recording period makes it difficult to control the injection energy. There was a problem that.

Therefore, an object of the present invention is to provide a thermal transfer recording system using a sublimable coloring material, which enables high-speed recording.

[Structure of the Invention (Means for Solving Problems)] The present invention relates to a thermal transfer recording device that obtains a recorded image by thermally transferring a sublimable coloring material onto a recording paper, in which one pixel is constituted by a plurality of matrices. , a fixed pattern corresponding to the density level is selected and formed within this matrix, and the gradation of each pixel is expressed by multi-leveling the recording energy of each dot constituting the selected fixed pattern. It is a feature.

(Function) When expressing one gradation by changing the injection energy of one dot, the exact energy must be applied to each dot.
must be injected. However, in the present invention, one pixel is made up of a plurality of dot matrices, and a fixed pattern is formed therein, so the amount of energy injected into each dot does not need to be so strict. In other words, it is sufficient if a predetermined energy level can be injected into the matrix as a whole. When a fixed pattern is used, it is possible to predict the amount of energy stored in the thermal head where recording dots are continuously formed, so by making productive use of this amount of stored energy, it is possible to It is possible to shorten the energization time and the down time. Furthermore, when a fixed pattern is used, there is a portion where dots are not formed, so sufficient heat can be dissipated in this portion, and the influence of heat accumulation will not appear. As a result, high-speed recording can be achieved without deteriorating image quality.

(Example) Hereinafter, the present invention will be described in detail based on the drawings.

1 to 4 are diagrams showing one embodiment of the present invention.

In FIG. 1, the output of the multi-gradation signal processing circuit 1 and the output of the matrix position i determining circuit 2 are given to a multi-value pattern table 3. The output of the multi-value pattern table 3 is sent to the thermal head drive circuit 5 via the thermal recording circuit 4.
is given to. A thermal head 6 is connected to the thermal head drive circuit 5.
is a recording medium via a transfer sheet 7.
is under pressure.

The multi-gradation signal processing circuit 1 processes multi-gradation/halftone signals input in the form of digital signals from a scanner, an A/D converter, an image memory, or a transmission system @scale or decoding circuit according to printer specifications. This is a circuit that performs signal processing and outputs according to the characteristics.

The matrix position specifying circuit 2 is a circuit necessary for digital recording or pseudo halftone recording, and is a circuit for specifying the position of a pixel in a matrix array consisting of a plurality of pixel points. In the case of a normal line printer, it is linked with a dot counter in the main scanning direction and a line counter in the sub-scanning direction. Further, in some cases, processing is also performed to sample a signal in accordance with the matrix shape and arrangement in conjunction with the image signal input clock used in the multi-gradation signal processing circuit 1.

The multivalued pattern table 3 is the main part of this embodiment, and contains four types of fixed patterns as shown in FIGS. 2 and 3, and the amount of energy to be injected into each dot of each of these fixed patterns. It consists of a ROM that records the. In this embodiment, as shown in FIGS. 2 and 3, one pixel is composed of a matrix of 3×3=9 dots, and the entire density region from the low density region to the high density region is divided into I, II, I[
[, TV is divided into four density areas, and fixed patterns a1, a2,
a3.

I am trying to allocate a4. al is a pattern in which one recording dot is formed at the center of the matrix, and this dot is taken as a reference dot position.

A2 is a pattern consisting of four upwardly convex dots centered on the reference dot position, a3 is a cross pattern centered on the reference dot position, and a4 is a pattern with one dot added to the upper right of the cross pattern.

Further, the reference dot positions of these patterns are all located in the matrix, and by setting the positions of the photothermal centers of each of these patterns, the heat distribution within the pattern becomes uniform, and a high-quality image can be obtained. This multi-value pattern table 3
outputs dot data at a position designated by the matrix position designation circuit 2 out of the fixed pattern corresponding to the output indicating the density level from the multi-tone signal processing circuit 1.

The thermal recording circuit 4 is a circuit for controlling the pulse width and pulse height of each dot of the thermal head in conjunction with the thermal head drive circuit 5, and is controlled by the output data from the multi-line pattern table 3.

The thermal head drive circuit 5 is an IC circuit including a shift register, a latch, a gate, and a driver (not shown), and is mounted on the substrate of the thermal head 6.

In this embodiment, the movement of the thermal head drive circuit 5 and the thermal recording circuit 4 is used as an energy sub-portion for gradation expression.

The transfer sheet 7 and the receptor sheet 8 are connected to the thermal head 6
and a platen roller (not shown), and a predetermined pressure is applied thereto. The transfer sheet 7 is a base sheet 9
In the figure, a color material layer 10 made of a heat sublimable dye is formed on the lower surface. For the base sheet 9, a sheet of polyethylene terephthalate, polyethylene naphthalate, or the like having a thickness of approximately 6 mm is suitable, for example. Note that a heat-resistant layer having a thickness of approximately 0.5 to 1 mm may be provided on the surface of the base sheet 9 as the transfer sheet 7 to improve running performance with the thermal head. On the other hand, the receptor sheet 9 preferably has a receptor layer made of polyester film, polyvinyl chloride film, or the like, or treated with these resins, but may be plain paper.

In such a thermal transfer recording device, when the energy applied to the thermal head is controlled while moving the transfer sheet 7 and the receptor sheet 8 relative to the thermal head 6 in the direction of the arrow in the figure, the heat generated by the energy injected is controlled. The resistor generates heat, and this heat sublimates the heated portion of the color material layer 10 of the transfer sheet 7. Therefore, the heated portion of the coloring material @10 is released from the base sheet 9. The sublimated coloring material is received by the receptor sheet 8, and desired recording dots 11 are formed. When the energization energy of the thermal head 6 is changed, the amount of coloring material received on the receptor sheet 8 is also changed, thereby changing the gradation level of the dots.

The apparatus of this embodiment is capable of expressing not only 1-dot gradation changes but also 36 gradations using a fixed pattern of four stages.

That is, as shown in FIG. 2, in the first density region (gradation level ○ to 6), the formation energy of one recording dot constituting the fixed pattern of al is changed from 0 to 6, and the gradation level is 0. It expresses seven gradations from ~6.

In the second density region (gradation levels 7 to 1), the total implantation energy of the three recording dots constituting the fixed pattern a2 is changed from 7 to 19, and gradation levels 7 to 19 are 13.
It expresses gradation.

Third concentration region 1i! (1 degree level 20 to 30), the total implantation energy of the five recording dots constituting the fixed pattern a3 is changed from 20 to 30, and the gradation level 20 is obtained.
I try to get 11 levels of ~30.

Roughly speaking, in the fourth density region (gradation levels 31 to 36), the total amount of implanted energy of the six recording dots constituting the fixed pattern a4 is varied from 31 to 36, and the total amount of energy injected into the six recording dots constituting the fixed pattern a4 is varied from 31 to 36. It represents six stages.

As a result of the above, 36 levels of gradation can be obtained in a 3×3 matrix as a whole.

By the way, the amount of energy injected into the thermal head 6 is
It is determined by the pulse island of the energizing pulse to the thermal head 6, the energizing time, etc. Figure 4 shows the method of energy injection. FIG. 2C shows a conventional drive pulse. Conventionally, it was necessary to inject a precise amount of energy into each dot, so the next energization could not be carried out until the surface temperature of the thermal head reached ○, which resulted in a shorter energization cycle (3 dots). could not be made shorter. On the other hand, since a fixed pattern is used in this embodiment, when dots within the fixed pattern are formed continuously in the sub-scanning direction, the influence of heat accumulation when the dots are formed first can be expected. Therefore, the next energization can be performed before the heat is completely dissipated. In other words, the energization cycle can be shortened by actively utilizing heat storage. Moreover, if heat storage is actively utilized in this way, the energization pulse width (energization time) can be made shorter than before, as shown in Figure (a), and the energization pulse height can be reduced, as shown in Figure (b). can be lowered. Furthermore, in portions that are not continuous in the sub-scanning direction, a sufficiently long pause period for one dot can be ensured, so the drive cycle can be equivalently lengthened, and problems such as density changes due to heat accumulation are alleviated.

FIGS. 5 to 7 are diagrams showing other embodiments of the present invention.

This device obtains density gradations by the dithering method in the low density region, and superimposes iW by the fixed pattern method of the present invention on the gradation obtained by the dithering in the medium 1 degree region and the high density region. It is something.

That is, in FIG. 5, the output of the multi-gradation signal processing circuit 1 is input to the dithering logic circuit 12 in addition to the multi-value pattern table 3. If the output value of the multi-tone signal processing circuit 1 is tone data expressing low density, processing is performed in the dithering processing circuit 12, and the output value of the tone data expressing intermediate density and high a degree is processed by the dithering processing circuit 12. In this case, a predetermined multi-value pattern is selected from the multi-value pattern table 3. In addition,
The dithering processing circuit 12 and the multi-value pattern table 3 are
Since similar processing is actually performed, it is also possible to compile these into the multi-value pattern table 3.

FIG. 6 shows the relationship between gradation levels and multi-value patterns. Here, an example is shown in which 66 gradations are expressed by changing a 4×4 dither pattern, a fixed pattern, and an injection energy pattern of a thermal head.

The areas assigned to the dither matrix and the fixed pattern are shown in FIG.

In the low 1 degree region α, gradation levels O to 3 are obtained by performing multi-value dithering using threshold patterns T1 and T2.
Expresses 33 gradations up to 2. In the range of gradation levels O to 16, the threshold pattern T1 is selected, and in the range of gradation levels 17 to 32, the direct threshold pattern T2 is selected. The multivalue level set at this time corresponds to the amount of energy to be injected into the thermal head. therefore,
To express lid level "32", level "2" energy is injected into all dots of 4x4. With this amount of energy, the influence of heat accumulation can be almost ignored even when each heating resistor element of the thermal head is driven continuously.

In the high 1 degree region β, there are five fixed patterns b! -b5 are used, and the density pattern obtained with these fixed patterns b1-b5 is superimposed on the dithered pattern expressing the gradation level of "32".

As a result, as shown in FIG. 6, the a-degree pattern of the high concentration region β becomes a pattern in which particularly high energy is concentrated in the positions represented by the fixed patterns b, to b5.

In this example, each dot expresses a low density level, but this is done because the peak of energy injected into each heating element is small, and the thermal head accumulates little heat even if continuous dots are recorded. ing.

On the other hand, in the high 1 degree region where fixed patterns are superimposed, the heat storage of the thermal head is used for the dot rows in which the fixed pattern is formed in the sub-scanning direction, and the heat storage is used for the other dot rows. Energy is distributed in such a way that the amount of energy does not increase.

In addition, the threshold device for dithering in the low concentration region is
Adopting a dot dispersion type such as a Bayer type has the advantage of improving resolution characteristics, but depending on the case, a dot concentration type such as a spiral type may be used to improve gradation characteristics. When the dot concentration type is adopted, by matching the dot concentration point of the dither pattern with the reference dot position serving as the thermal center, an effect such as not causing visual discomfort can be obtained.

Note that in the above example, a fixed pattern is superimposed on the gradation expression by dithering in the low density area, and in addition to the gradation expression by dithering in the medium and high density areas, but the dithering is used in the low density area. The gradation is expressed by chisel, and the medium and
In a high density region, gradation expression may be performed using only a fixed pattern.

Further, the present invention is not limited to the case where a 3×3 or 4×4 square matrix is used, but for example, the fixed patterns C1 to C1 consisting of a diamond-shaped matrix as shown in FIG.
C4 may also be used. This matrix is arranged as shown in FIG. 9(a) in the low concentration region and as shown in FIG. 9(1) in the high concentration region.

Therefore, the columns that are continuous in the a1 scanning direction can be efficiently energized using heat storage, and the other columns can have sufficient energization suspension periods, so high-speed recording is possible and gradation reproducibility is also good.

Furthermore, the present invention is applicable to color thermal transfer recording devices. In this case, for example, yellow,
It is sufficient to prepare magenta and cyan colors and perform transfer recording of these colors by a plane sequential or line sequential recording method.

[Effects of the Invention] As explained above, according to the present invention, gradations are obtained by multi-leveling the formation energy of the fixed patterns and the dots constituting each fixed pattern, so that the dots are not continuous. The effect of heat accumulation can be expected where the formation of Therefore, by effectively utilizing this heat storage, it is possible to efficiently utilize energy and achieve the effect of enabling high-speed recording.

Furthermore, since a sufficient pause w4 can be ensured where the dots are not continuous, the influence of heat accumulation can be eliminated. Therefore, it is possible to obtain a recorded image with good image quality and excellent gradation reproducibility.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a thermal transfer recording device according to an embodiment of the present invention, FIG. 2 is a diagram showing the contents of a multi-value pattern table of the same device, and FIG. 3 is a diagram showing the amount of energy injected in the same device. A relationship diagram showing the relationship between the recording density and the fixed pattern used; FIG. 4 is a waveform diagram for explaining the influence of energization pulses and heat storage in the same device in comparison with a conventional example; and FIG. FIG. 6 is a block diagram showing the configuration of a thermal transfer recording device according to an embodiment of the present invention, FIG. 6 is a diagram showing the relationship between gradation levels and multivalue patterns in the same device, and FIG. 7 is a diagram showing the relationship between the amount of energy injected and the recording density in the same device. FIG. 8 is a diagram showing the relationship between the dither matrix used and the fixed pattern. FIG. 8 is a diagram showing a fixed pattern according to still another embodiment of the present invention. FIG. 9 is a diagram showing the relationship between the dither matrix used and the fixed pattern. FIG. 3 is a diagram showing an example of expressing a density region. 1... Multi-width signal processing circuit, 2... Matrix position designation circuit, 3... Multi-value pattern table, 4...
Thermal recording circuit, 5... thermal head drive circuit,
6...Thermal head, 7...Transfer sheet, 8.
. . . Receiver sheet, 9 . . . Base sheet, 10 . . . Color material layer, 11 . Applicant's representative Patent attorney Takehiko Suzue M2 Figure 3 Figure 5

Claims (5)

[Claims] (1) A transfer sheet containing a sublimable coloring material is brought into contact with a recording paper and the transfer sheet is heated to transfer the sublimation coloring material onto the recording paper to form a recorded image. In the thermal transfer recording method, one pixel is made up of a matrix of multiple dots, and a fixed pattern selected according to the density level is formed within the matrix, and the formation energy of each recording dot constituting the selected fixed pattern is A thermal transfer recording method that expresses the gradation of each pixel by converting it into multiple values. (2) The thermal transfer recording method according to claim 1, wherein gradation is expressed by dithering in low density areas, and gradation is expressed by a fixed pattern in medium and high density areas. (3) In low density areas, gradation is expressed by dithering, and in medium and high density areas, in addition to the gradation expression by dithering, a fixed pattern corresponding to the density level is superimposed. A thermal transfer recording method according to claim 1. (4) The fixed pattern representing at least a medium-density area or a high-density area has an L-shape or a cross-shape in which recording dots are consecutively arranged in a sub-scanning direction row and a main-scanning direction row based on a predetermined position in the matrix. 4. The thermal transfer recording method according to claim 1, wherein the thermal transfer recording method has a shape consisting of a shape or a combination thereof. (5) The thermal transfer recording method according to any one of claims 1 to 4, wherein the recording paper is a receptor sheet provided with a color developing layer.