JPH0628374B2 - Fusion thermal transfer recording device - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention is a multi-layered system in which one pixel is composed of a plurality of dot matrices and a pseudo gradation image is obtained by the area ratio of mark dots recorded in the matrix. The present invention relates to a fusion-type thermal transfer recording device using a tonal recording system.

[Technical background of the invention and its problems]

In a fusion-type thermal transfer recording apparatus that heats and melts heat-melting ink with a thermal head to transfer and record the ink to recording paper, density expression by ink transfer is
Since it is "1" or "0", gradation expression by area modulation, which is so-called binary area gradation, is generally performed.

However, in this method, the number of gradations that can be expressed when one pixel is expressed by a matrix of n × n image points is only n ² +1 including the background density level of the recording paper. Therefore, for example, only 17 gradations can be expressed with a matrix size of 4 × 4. However, in order to obtain an image that is natural to the eyes, it is generally said that the resolution of color image points is 4 dots / mm or more and the number of gradations is 64 or more. This 2
To satisfy the value area modulation method, a thermal head having an 8 × 8 matrix size and a heating element density of 32 dots / mm or more must be used. However, the limit of the currently feasible thermal head is 16 dots / mm, and it is currently difficult to realize thermal transfer recording having a resolution of 32 dots / mm. Therefore, it is extremely difficult to obtain a smooth density gradation by the binary area gradation.

Therefore, in order to solve this, ink with different densities should be
A method of obtaining multi-gradation by using a combination of image dots having different densities and image dot arrangements by using ink ribbons laminated in layers
No. 193377), or a method of sequentially superposing recording image points from low density ink to high density ink by using an ink ribbon in which inks having different densities are sequentially applied in the longitudinal direction (JP-A-59-55768). Proposed. However, all of these methods have drawbacks such as unstable ink transfer and long printing time.

[Object of the Invention]

The present invention has been made in view of the above circumstances, and an object thereof is to provide a fusion-type thermal transfer recording apparatus using a multi-gradation recording method capable of extremely smooth gradation expression without lowering the resolution. And

[Structure of Invention]

The present invention provides a plurality of types of fixed patterns set in accordance with the density level in a matrix formed of a plurality of dots, and a plurality of levels of image point forming energy given to mark dots forming each fixed pattern. Means for selecting the fixed pattern and the image forming energy for expressing a pseudo gradation according to the selected multi-tone image signal, and means for recording by the selected fixed pattern and the image forming energy. In the fusion-type thermal transfer recording apparatus including :, each of the fixed patterns uses at least one of the specific rows and columns in the matrix, and at least one of the specific rows and columns respectively. The fixed patterns are made common to each other, and the dot positions at which the vertically and horizontally extending image points constituting each fixed pattern intersect are defined in the matrix. Characterized in that disposed in the central portion.

〔The invention's effect〕

According to the present invention, since a multi-gradation image is obtained by multi-valued image formation energy of a fixed pattern, it is possible to obtain a larger number of gradations than conventional even with a small matrix size. It is possible, and the gradation characteristics are extremely smooth. Further, since the same number of gradations as the conventional one can be expressed with a smaller matrix size than the conventional one, it is possible to increase the number of gradations and at the same time, the resolution thereof.

Further, according to the present invention, since gradation expression is performed by changing the image forming energy of the mark dots forming a specific fixed pattern, the most preferable pattern for thermal transfer recording can be selected.

In this case, as each fixed pattern, the image point sequence is concentrated in at least one of a specific row and a specific column in the matrix, and the portion where the image point sequence is concentrated is fixed between the fixed patterns. Place it in a common position,
Since the intersecting positions of vertically and horizontally extending image point rows are arranged in the central portion of the matrix of each fixed pattern in the matrix that forms the fixed pattern, the image point rows are regularly arranged at substantially equal intervals even in the portions where different patterns are adjacent. To be done. For this reason, it is possible to prevent deterioration of density reproducibility (linearity) caused by noise due to irregular image point arrangement and random bridge, and obtain high quality recording. In particular, when the center positions of heat generation are matched in each fixed pattern, the center positions of the image points are regularly spaced from each other by a certain distance, so that the independence of the patterns is maintained and higher image quality recording can be performed. .

Example of Invention

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1A is a diagram showing an example using a pattern based on an L-shape as an embodiment of the present invention. That is, the fixed patterns a ₁ , a ₂ , a ₃ , and a ₄ are fixed patterns capable of expressing the density regions I, II, III, and IV, respectively, as shown in FIG. In each of the density regions I to IV, continuous density gradation is obtained by controlling the mark dot forming energy of the corresponding fixed patterns a _{1 to} a ₄ .
The fixed patterns a _{1 to} a ₄ are centered at a point P (hereinafter referred to as “heat generation center position”) located in the third row (third in the sub-scanning direction) and the second column (second in the main scanning direction) in the matrix. The pattern is mainly L-shaped, which extends vertically and horizontally. L
When the characters are mainly used, it is possible to obtain gradation characteristics having a wide dynamic range and excellent linearity by effectively utilizing the heat storage of the image points. In FIG. 6B, for comparison, a fixed pattern b ₁ , in which the heat generation center position P ′ is randomly set,
b ₂ , b ₃ and b ₄ are shown.

With the fixed patterns a _{1 to} a _{4 according} to the present embodiment, even when different patterns are adjacent to each other as shown in FIG. 3A, the heat generation center positions P thereof are regularly arranged in a grid pattern. Therefore, as shown in FIG. 7B, even if the implantation energy amount is increased, the independence of each pattern is maintained and the concentration reproducibility is not deteriorated due to the irregular bridge. In addition, the fixed patterns a _{1 to} a _{4 of} this embodiment
In this case, since the image point sequence is formed in the third row and the second column in the matrix, the recorded portion and the blank portion are regularly arranged. Therefore, noise due to uneven density is extremely small, and a high quality recorded image can be obtained.

On the other hand, in the fixed pattern of the comparative example shown in FIG. 1 (b), as shown in FIG. 4 (a), when different fixed patterns b _{1 to} b ₄ are adjacent to each other, heat is generated between the adjacent patterns. The injection center position P'points contact with each other or are too far apart. Therefore, with such a pattern,
As shown in FIG. 7B, the recording portion and the blank portion are irregularly arranged, or a random bridge occurs.
Therefore, the image quality is significantly deteriorated due to the uneven density. Also,
When such a random bridge occurs, the ink transfer area specifically and sharply increases at that portion according to the image forming energy. Therefore, the linearity of the pixel density is hindered as the image forming energy increases. In this respect, the fixed patterns a _{1 to} a _{4 according} to the present embodiment do not cause such a problem.

FIG. 5 is a block diagram showing the arrangement of an apparatus for realizing the thermal recording method according to the above embodiment. That is, the multi-gray scale image signal input in the form of a digital signal from a scanner, an A / D converter, an image memory, a demodulation circuit of a transmission system, a decoding circuit, etc. (not shown)
Thus, a signal having a form matching the specifications and characteristics of the printer is subjected to signal processing and output. The signal processed by the multi-gradation signal processing circuit 1 is input to the multi-valued pattern table 2.

The multi-valued pattern table 2 is for determining a fixed pattern and an implantation energy amount according to the concentration information held by the signal, and is specifically a ROM and is a main part of this embodiment. This multi-valued pattern table 2
Is a ROM that generates a binary dither pattern of a table look-up type in the past, and sometimes includes a calculation for compensating for the thermal storage phenomenon of the thermal head.
However, in this embodiment, this portion stores fixed pattern information and formation energy information of each mark dot as described later.

The matrix position designating circuit 3 is a circuit for designating the position on the matrix of the pattern in the matrix consisting of a plurality of image points required for digital recording or pseudo intermediate recording. Normally, in the case of a line printer, it is in the main scanning direction. It works in conjunction with the dot counter and line counter in the sub-scanning direction. In some cases, the multi-gradation signal processing circuit 1
It may be linked with the clock for image signal input used in.

The fixed pattern information and the energization energy information from the multi-valued pattern table 2 are given to the thermal recording circuit 4. The thermal recording circuit 4 controls the energizing pulse width for each heating element of the thermal head. The energizing pulse output from the thermal recording circuit 4 is output to the thermal head drive circuit 5.

The thermal head drive circuit 5 is an IC circuit including a shift register, a latch, and a gate driver, and is mounted on the thermal head substrate.

The interlocking operation of the thermal recording circuit 4 and the thermal head drive circuit 5 is the same as the operation performed to compensate for the heat storage phenomenon in the conventional fusion thermal transfer recording, and is disclosed in, for example, JP-A-57-208283 and 59-59. As described in -98878, etc., the energizing pulse width is changed, the voltage level of the energizing pulse is changed,
Alternatively, they may be used in combination.

By the way, the following information is stored in the multi-valued pattern table 2 which is the main part of the apparatus according to the above-mentioned embodiment. That is, for example, the density region is I to IV as described above.
, And fixed patterns a _{1 to} a ₄ are assigned to these density regions I to IV. Then, each of these density regions I to IV further includes the fixed pattern a ₁
The implantation energy amount control ~a _4, is divided into about 12 gradations. That is, fixed pattern information and fixed pattern formation energy information are stored inside the multi-valued pattern table 2.

Therefore, it is possible to represent 49 gradations as a whole by combining these fixed patterns a _{1 to} a ₄ and the implantation energy information.

In such a configuration, by aligning the positions of the image point rows of the fixed patterns a _{1 to} a ₄ with a specific position, it is possible to obtain a recorded image with good image quality and excellent density reproducibility.

As described above, according to the present embodiment, it is possible to increase the number of gradations from the conventional 17 gradations to 49 gradations even in a 4 × 4 matrix, and it is possible to suppress the deterioration of resolution due to this.

The present invention is not limited to the above embodiment. For example, the fixed patterns shown in FIGS. 6 to 8 are all patterns included in the basic idea of the present invention. FIG. 6 shows an example in which the positions of the image points in the sub-scanning direction are made to coincide, FIG. 7 shows an example in which the positions of the image points in the main scanning direction are made to coincide, and FIG. 8 shows the example in the main scanning direction. In this example, the positions in both the vertical direction and the sub-scanning direction are matched.

As described above, according to the present invention, it is possible to obtain a desired effect by aligning the image point rows in at least one direction.

Further, the present invention is not particularly limited to the 4 × 4, 3 × 3 matrix and can be applied to the case of using another matrix size, but in order to further enhance the effect of the present invention, n × n A matrix size of (2 <n ≦ 6) is desirable.

Further, the heat generation center position P does not need to be fixed at the same position between the respective fixed patterns, but it is preferably arranged in the central regions S ₁ and S ₂ of the matrix as shown in FIG.

As described above, the present invention can be variously modified and implemented without departing from the scope of the invention.

[Brief description of drawings]

FIG. 1 (a) is a schematic diagram showing a fixed pattern according to an embodiment of the present invention, FIG. 1 (b) is a schematic diagram showing a fixed pattern of a comparative example, and FIG. FIG. 3 is a relationship diagram showing the relationship with the recording density, FIG. 3 is a diagram for explaining the effect of the embodiment, FIG. 4 is a diagram for explaining the operation of the comparative example, and FIG. FIG. 6 is a block diagram showing an example of the configuration of an apparatus for carrying out the invention, and FIGS. 6 to 9 are schematic diagrams for respectively explaining a fixed pattern according to still another embodiment of the present invention. 1 ...... multitone signal processing circuit, 2 ...... multilevel pattern table, 3 ...... matrix location specified circuit, 4 ...... thermal recording circuit, 5 ...... thermal head drive circuit, a ₁ ~a _4,
b ₁ ~b ₄ ...... fixed pattern, P, P '...... heating center position.

Claims (2)

[Claims] 1. A plurality of types of fixed patterns set according to a density level in a matrix composed of a plurality of dots, and a plurality of levels of image point forming energy given to mark dots forming each fixed pattern, Means for selecting the fixed pattern and the image forming energy for expressing a pseudo gradation according to a given multi-tone image signal, and recording by the selected fixed pattern and the image forming energy In the fusion type thermal transfer recording apparatus, the fixed pattern uses at least one of specific rows and columns in the matrix, and at least one of the specific rows and columns. The fixed pattern is common to each fixed pattern, and the dot position where the vertically and horizontally extending image point rows that form each fixed pattern intersect is determined by the matrix. The fusion type thermal transfer recording device is characterized in that it is arranged in the center of the sheet. 2. The fusion type thermal transfer recording apparatus according to claim 1, wherein the fixed dot pattern has a common dot position where the vertically and horizontally extending image point rows intersect.