JP2000108398A - Thermal printer and method for thermal recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To clearly record a small character or a thin line. SOLUTION: A frame memory 101 stores one frame of image data. A first line memory 102 stores a present line of image data transmitted from the frame memory 101. A second line memory 103 stores the previous line of image data. An adjacent judgment circuit 104 refers to the image data in the first line memory 102 and second line memory 103 and judges whether or not all of one dot data in the first line memory 102 is independent dot data. An adjacent correction circuit 105 increases a gradation level of the independent dot data in the image data transmitted from the first line memory 102 on the basis of the judgment result of the adjacent judgment circuit 104. A heating section 115 is energized for a time period corresponding to the gradation level of the image data corrected by the adjacent correction circuit 105, thereby coloring a color thermal recording paper 201.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printer and, more particularly, to a multi-color thermal printer capable of recording a full-color image.

[0002]

2. Description of the Related Art A conventional multi-color thermal printer is disclosed in Japanese Patent Application Laid-Open No. Hei 4-223178. The above-described conventional multi-color thermal printer has a configuration in which thermal energy is applied to a color thermal recording material by a thermal head having a plurality of heating elements, and the color thermal recording material is colored. The coloring material contained in the color heat-sensitive recording material changes in the density at which the coloring material is developed in accordance with the amount of applied thermal energy. By utilizing the properties of the coloring material, a full-color image is recorded on the color thermosensitive recording material.

[0003]

In a conventional multi-color thermal printer, when recording an image in which dots, such as natural images, are densely packed, a plurality of heating elements provided on the thermal head generate heat. Therefore, the temperature has risen to around the temperature required for color development. Moreover,
The plurality of heating elements can be quickly increased to a temperature required for coloring the thermosensitive recording material at a certain density under the influence of the temperature propagating from the adjacent heating elements. Therefore, since the heat-sensitive recording material develops a color at an appropriate density, a clear image is recorded.

However, when recording an image in which dots such as small characters and fine lines are sparse, the plurality of heating elements generate heat at a low frequency, and are in a temperature state lower than the temperature required for coloring. Moreover, the plurality of heating elements are
Since the influence of the temperature propagating from the adjacent heating element is also reduced, extra time is required to increase the temperature required for coloring the thermosensitive recording material at a certain density.
That is, the plurality of heating elements do not rise to an appropriate temperature within a certain time. Therefore, the color thermosensitive recording material heated by the plurality of heating elements emits a color at a density lower than the original. As a result, an unclear image is recorded.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a multi-color thermal printer capable of clearly recording even small characters and fine lines.

[0006]

According to the present invention, there is provided a recording apparatus, comprising:
The gradation number of the dot data is corrected with reference to the gradation number of an adjacent dot.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first aspect of the present invention is a storage means for storing gradation data to be recorded on a heat-sensitive recording material, and the gradation data corresponding to the gradation of the gradation data stored in the storage means. Recording control means for setting a conduction time to drive a heating element, determining means for determining whether or not each dot data included in the gradation data stored in the storage means is isolated dot data, When the determination means determines the dot data as isolated dot data, a correction means for increasing the gradation of the dot data is adopted.

According to this structure, the energization time of the dot data determined as the isolated dot data is extended, so that the heating element has a density corresponding to the number of gradations of the data stored in the storage means. The temperature rises to the temperature required when the heat-sensitive recording material develops color. Therefore, since the data stored in the storage means is recorded on the thermal recording material at an original density, it is possible to provide a thermal printer capable of clearly recording even small characters and thin lines.

A second aspect of the present invention, in the first aspect, adopts a configuration in which the determination means performs the determination in consideration of a gradation difference from peripheral dots.

According to this structure, the data stored in the storage means is determined as isolated dot data even when there is a remarkable density difference from surrounding dots, so that the energizing time is extended. Therefore, the data stored in the storage means is more clearly recorded on the thermosensitive recording material at the original density.

According to a third aspect of the present invention, in the second aspect, the correction means sets the gradation of the dot data to a temperature required when the thermal recording material develops a color at the gradation. Is increased up to the gradation corresponding to the energization time for heating.

According to this structure, the data stored in the storage means is recorded on the heat-sensitive recording material at the original density because the heating element rises to the original density.

According to a fourth aspect of the present invention, in the third aspect, the energizing time for obtaining the highest gradation of the isolated dot data after the correction is set by changing the energizing time of the normal dot data of another color which develops at a higher temperature. A configuration is adopted in which the duration is set to be longer than the bias heating time and equal to or shorter than the energization time for producing the isolated dot data of the other color.

According to this configuration, even when the highest gradation of the isolated dot data is recorded, the reproducibility of the normal dot data of other colors is not affected at all. Is recorded on the heat-sensitive recording material properly at the original density.

According to a fifth aspect of the present invention, gradation data to be recorded is stored, and it is determined whether or not each dot data included in the stored gradation data is isolated dot data.
When the dot data is determined as isolated dot data, the tone of the dot data is increased and the density of the isolated dot data is increased to print.

According to this method, the energization time of the dot data determined as isolated dot data is extended, so that the heating element has a density corresponding to the number of gradations of the data stored in the storage means. The temperature rises to the temperature required when the heat-sensitive recording material develops color. Therefore, since the data stored in the storage means is recorded on the thermal recording material at an original density, it is possible to provide a thermal printer capable of clearly recording even small characters and thin lines.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. (Embodiment) FIG. 1 is a block diagram showing a configuration of a printing unit of a thermal printer according to an embodiment of the present invention. In the following embodiments, a thermal printer that performs recording at four gradations will be described as an example.

The frame memory 101 stores one frame of image data separated for each color of yellow, magenta, and cyan, and transfers the image data to the first line memory 102 line by line. This one line of image data is
It consists of one dot data composed of two bits,
The dot data can express four gradations from the gradation number 0 to the gradation number 3.

The first line memory 102 stores image data of one line (hereinafter referred to as “current line”) to be printed at present, and sends it to the adjacent correction circuit 105.
The second line memory 103 is a memory for storing the image data of the reference line, and the image data stored in the first line memory 102 is sequentially transferred every time the recording is completed.

The adjacency determining circuit 104 converts the image data stored in the first line memory 102 into the second line memory 10.
3 by comparing with the image data stored in
It is determined whether the one line of image data stored in the line memory 102 is isolated image data such as a point or a line, and the result of the determination is sent to the adjacent correction circuit 105.
The adjacency correction circuit 105 increases the number of bits of the image data of one line transferred from the first line memory 102 from 2 bits to 3 bits so that gradation expression up to 8 gradations can be performed, and then the adjacency determination circuit 105 In accordance with the determination result of step 104, the number of gradations of the one line of image data is corrected for each dot data, and this is sequentially sent to the comparator 106.

The comparator 106 is connected to the adjacent correction circuit 10
5 is compared with the number of gradations provided from the gradation counter 107, and 1-bit print data (hereinafter, referred to as “color development”) representing color development (1) or non-color development (0). Is sent to the thermal head 108.

The tone counter 107 is provided in the print control circuit 11
By the control of 0, the number of gradations from gradation number 0 to gradation number 7 is given to the comparator 106. That is, the gradation counter 107 sets the comparator 106 to 1 for one gradation.
When the comparison of the image data for the lines is completed, the number of gradations is set to 1
And give it to the comparator 106. Therefore, the image data for one line is converted into 0 gradation by the comparator 106.
Are compared with the number of gradations from to. As will be described later, in consideration of the fact that the maximum gradation that can express one dot data is increased from 4 gradations to 8 gradations by the adjacent correction circuit 105, the gradation counter 10 is provided to the comparator 106.
7 gives the number of gradations from gradation number 0 to gradation number 7.

In the thermal head 108, a shift register 109 receives one line of color print data sent from the comparator 106 one bit at a time in synchronization with a clock signal sent from the print control circuit 110, and converts the data into parallel data. And sends it to the latch circuit 111.

The latch circuit 111 includes a print control circuit 110
From the shift register 109 by the latch signal sent from the
Holds the color print data for one line, which is output from the drive circuit 114, and outputs it to the drive circuit 114.

The drive circuit 114 includes a latch circuit 111
The strobe signal sent from the print control circuit 110 based on the color print data for one line held by
A current is applied to the heating elements provided in the heating section 115 in correspondence with the total number of color print data for one line. Further, these heating elements are linearly arranged on the printing surface of the heating section 115 so as to be substantially parallel to the main scanning direction. These heating elements generate heat when a current is passed by the drive circuit 112, and the heat is applied to the color thermosensitive recording paper 201 described later to perform printing.

The print control circuit 109 also controls the above-described first line memory 102, second line memory 103, gradation counter 107, and latch counter 113.

In this embodiment, a color thermosensitive recording paper 201 shown in FIG. 2 is used as a color thermosensitive recording material.

FIG. 2 is a sectional view showing the color thermal recording paper 201 processed by the thermal printer according to the above embodiment. The color thermosensitive recording paper 201 has a support 202 on which a cyan thermosensitive coloring layer 203 is formed.
Magenta thermosensitive coloring layer 204 and yellow thermosensitive coloring layer 2
05 are sequentially stacked. Further, a protective layer 206 is formed as an uppermost layer.

The heat-sensitive coloring layers 203 to 205 are colored according to their respective heat-sensitive characteristics, and are colored at a high temperature in the order of the yellowest heat-sensitive coloring layer 205 from the uppermost layer, the magenta heat-sensitive coloring layer 204, and the cyan lowermost coloring layer 203. Will do. The yellow thermosensitive coloring layer 205 and the magenta thermosensitive coloring layer 20 that develop color at a lower temperature than the cyan thermosensitive coloring layer 203
For No. 4, after the recording, the yellow thermosensitive coloring layer 205 was irradiated with ultraviolet light having a wavelength of 420 nm on the magenta thermosensitive coloring layer 204 and irradiated with ultraviolet light having a wavelength of 365 nm. It becomes possible.

Each of the thermosensitive coloring layers 203 to 205 has a coloring density which varies depending on the amount of heat energy applied. Since colors are formed at a high temperature in the order of the yellow heat-sensitive coloring layer 205, the magenta heat-sensitive coloring layer 204, and the cyan heat-sensitive coloring layer 203, the density of each color increases in accordance with an increase in the amount of heat applied to the color heat-sensitive recording paper 201, that is, the number of gradations. . For example, in order to develop the yellow thermosensitive coloring layer 205,
The residual heat as thermal energy immediately before the yellow thermosensitive coloring layer 205 develops color is given as bias heating, and thermal energy for gradation expression is given in a form added thereto. Similarly, it is necessary to apply bias heating as residual heat to the magenta thermosensitive coloring layer 204 and the cyan thermosensitive coloring layer 203.

Next, the printing operation of the thermal printer having the above configuration will be described. The thermal printer having the above configuration performs recording in the order of the yellow thermosensitive coloring layer 205, the magenta thermosensitive coloring layer 204, and the cyan thermosensitive coloring layer 203.

First, the operation in the case where the thermal printer having the above configuration prints on the yellow thermosensitive coloring layer 205 will be described.

First, the frame memory 101 transfers the image data of the first line to the first line memory 102. After the data is transferred to the first line memory 102,
The adjacency discrimination circuit 104 stores the image data of the first line stored in the first line memory 102 and the second line memory 1
With reference to the image data of the previous line stored in the first line memory 102, it is determined whether all the 1-dot data in the image data of the first line stored in the first line memory 102 are isolated 1-dot data. Is determined.

Here, as a specific discrimination method performed by the adjacency discrimination circuit 104, a case where the image data of the m-th line is discriminated will be described as an example. FIG. 3 is a schematic diagram showing a part of the contents of the first line memory and the second line memory in the thermal printer according to the embodiment. The first line memory 102 stores the image data of the m-th line, and the second line memory 103 stores the image data of the (m-1) -th line. Here, the n-th 1-dot data in the image data of the m-th line is expressed as (m, n).

The adjacency discrimination circuit 104 refers to the image data of the m-th line stored in the first line memory 102 and the image data of the (m-1) -th line stored in the second line memory 103 to determine the first line. Regarding all the 1-dot data in the image data of the m-th line stored in the memory 102, it is either isolated 1-dot data (hereinafter referred to as “isolated dot data”) or non-isolated 1-dot data ( Hereafter, it is determined whether the data is “normal dot data”.

For example, at the time of determining (m, n), the adjacent determination circuit 104 determines whether (m, n-) is adjacent to (m, n).
The data contents of (1), (m, n + 1), and (m-1, n) are referred to. At this time, when one dot data having a gradation number of 1 or more exists in the one dot data to be referred to, the adjacency determination circuit 104 determines that (m, n) is normal dot data, Conversely, when there is no 1-dot data having a tone number of 1 or more, that is, when the tone numbers of all 1-dot data are 0, (m, n)
Is determined to be isolated dot data.

The adjacency discrimination circuit 104 calculates the 1-dot data stored in the first line memory 102
The determination is performed as described above.

When determining the image of the first line, the image data stored in the second line memory 103 is not stored in the second line memory 103. Every one
The determination is performed as described above, with the number of gradations of the dot data being 0. The above is the determination method of the adjacent determination circuit 104.

After the determination of the image data of the first line is completed, the adjacentness determination circuit 104 sends the determination result to the adjacentness correction circuit 105.

First, the adjacent correction circuit 105 increases the number of bits of the image data of the first line transferred from the first line memory 102 from 2 bits to 3 bits. As a result, the highest gradation that can express each one dot data in the image data of the first line is 4 from the gradation number 0 to the gradation number 3 but from the gradation number 0 to the gradation number 7 Is increased to 8.

Next, the adjacent correction circuit 105 receives the determination result from the adjacent determination circuit 104, and assigns 3 to the number of tones of one dot data determined as isolated dot data in the image data of the first line. Add. More specifically, since the number of gradations of one dot data is 0, 1, 2, and 3, the adjacent correction circuit 104 adds 3 to the number of gradations and adds 3, 4, 5,. 6 is assumed. Further, the number of gradations to be added to the isolated dot data is within a range where, when recording the isolated dot data having the increased number of gradations by this correction, the thermosensitive coloring layer which is colored at a higher temperature than the thermosensitive coloring layer to be recorded is not formed. It is necessary to determine it appropriately. Here, the yellow thermosensitive coloring layer 2
Since recording is performed at 05, the number of gradations to be added to the isolated dot data is determined within a range in which the magenta thermosensitive coloring layer 204 is not colored.

As described above, the adjacent correction circuit 104 corrects the number of tones for all the isolated dot data in the image data of the first line.

As described above, this gradation correction method may be performed by adding a constant value to the original number of gradations represented by the isolated dot data, or by multiplying the constant value by a constant value. May go.

After the above correction is completed, the adjacent correction circuit 10
5 sequentially transfers the corrected first-line image data to the comparator 106 one dot data at a time. At the same time, the tone counter 107 outputs the tone number 0 to the comparator 106 as tone data according to the control signal of the print control circuit 110.

The comparator 106 is connected to the adjacent correction circuit 10
5 is compared with the number of gradations 0, and when the number of gradations is 0 or more, the color print data 1 (color development) is transferred to the shift register 109, and conversely, the number of gradations 0
If smaller, the color print data 0 (non-color) is transferred to the shift register 109. Here, since one dot data has the number of tones of 0 or more, the color print data 1 is always output from the comparator 106.

As described above, the comparator 106 compares all the one-dot data sequentially transferred from the adjacent correction circuit 105, that is, the image data for one line, with the gradation number 0 as described above. The resulting color print data is sequentially transferred to the shift register 109 in the thermal head 108.

The internal operation of the thermal head 108 will be further described with reference to FIG. FIG. 3 shows control signals in a printing unit of the thermal printer according to the present embodiment,
FIG. 4 is a timing chart showing a state of energization time for a heating element.

The color print data D 1 sequentially output by the comparator 106 is input to the shift register 109 in synchronization with the clock signal CL sent from the print control circuit 110. After the input of the color print data D1 for one line is completed, the color print data for one line is
When S changes from the HI state to the LOW state, it is transferred to the latch circuit 111 and further transferred to the drive circuit 114.

The drive circuit 114 includes the print control circuit 11
0 from the HI state to the L level
From the point in time when the state changes to the OW state, a current starts to flow to the heating element corresponding to the color print data whose data content is 1 among the color print data for one line held by the latch circuit 111. In the 0 gradation process, since the content of all the color print data is 1, power is supplied to all the heating elements. This energization period is bias heating.

Thereafter, the drive circuit 114 supplies current to the heating element as described above until the strobe signal returns to the HI state.

Next, the tone counter 107 outputs, to the comparator 106, the tone number 1 having a higher density than the tone number 0 as tone data according to the control signal of the print control circuit 110. In response to this, as described above, the comparator 106 compares the image data of the first line with the number of gradations of one dot data at a time, and transfers the color print data to the shift register 109. Outputs the color print data D1 output from the comparator 106 to the latch circuit 111.

The latch counter 113 outputs the latch signal LS
Is changed from the HI state to the LOW state, the latch circuit 111 newly applies the color print data D1 output from the shift register 109, that is, the color print data D1 for one line obtained by comparing with the gradation number 1. And transfers it to the drive circuit 114. Therefore, the drive circuit 114 starts to supply a current to the heating element based on the coloring print data D1 held by the latch circuit 111.

As described above, the time during which the drive circuit 114 applies a current to the heating element based on the color print data D1 for one line obtained by comparison with a certain number of gradations is determined by the latch signal sent from the latch counter 113. LS is determined by a time (hereinafter, referred to as “one gradation energizing time”) from the time when the LS changes from the HI state to the LOW state to the time when the LS changes from the HI state to the LOW state again.

Thereafter, the gradation counter 107 sequentially outputs the gradation data from the gradation number 2 to the gradation number 7 to the comparator 106.
, The image data of the first line is compared with these gradation data by the comparator 106. As described above, the drive circuit 114 causes a current to flow through the heating element provided in the heating unit 115 based on the color print data obtained by comparison with each gradation data.

Thereafter, when the strobe signal SS returns from the LOW state to the HI state, the drive circuit 114
Since the energization of the heating element is stopped, the printing of the image data of the first line is completed.

As described above, while the gradation data is sequentially updated from the low gradation to the high gradation, the bias heating energy and the gradation expression energy are given to each dot for one line of the image data, so that one line is obtained. Printing is completed for the image data of. In the one-line image data, one dot data determined as isolated dot data by the adjacent determination circuit 104 is output to the adjacent correction circuit 10.
5, the number of gradations is doubled.

When the printing of the image data of the first line is completed, the print control circuit 110 transfers the image data of the first line stored in the first line memory 102 to the second line memory 103, 101
Transfers the image data of the second line to the first line memory 102.

At this time, the first line memory 102 has
The image data of the second line to be printed at present is stored, and the second line memory 103 stores the image data of the previous line, that is, the image data of the first line. As a result, the adjacent determination circuit 104 can determine whether or not isolated dot data exists in the image data of the second line with reference to the image data of the first line and the image data of the second line. .

Thereafter, the same operation as the printing of the image data of the first line is performed, and the image data of the second line is printed.

When the printing of the image data of the second line is completed, the image data of all the lines written in the frame memory 101 are printed similarly.

Next, the thermal printer according to the present embodiment comprises a magenta thermosensitive coloring layer 204 and a cyan thermosensitive coloring layer 20.
Printing is performed in the order of 3. The basic operation is the same as the case of printing on the yellow thermosensitive coloring layer 205 described above. The difference is that since the coloring energy of each thermosensitive coloring layer in the color thermosensitive recording paper 201 is different, the one gradation energizing time for the heating element is changed according to the thermosensitive coloring layer to be printed. That is, since the coloring energy increases in the order of the yellow thermosensitive coloring layer 205, the magenta thermosensitive coloring layer 204, and the cyan thermosensitive coloring layer 203, the one gradation energizing time becomes longer in this order.

By the above operation, a full-color image is recorded on the color thermosensitive recording paper 201.

Next, the effect of correction by the adjacent correction circuit in the thermal printer according to the above embodiment will be described.

FIG. 5 is a characteristic diagram showing the color development characteristics of the color thermosensitive recording paper at the time of printing normal dot data and isolated dot data by the thermal printer according to the above embodiment. The abscissa represents the energization time for the heating elements provided in the heating section 115, and the ordinate represents the coloring density of each thermosensitive coloring layer.

Curves drawn by solid lines with Y, M, and C represent the color development when printing the normal dot data of the yellow thermosensitive coloring layer 205, the magenta thermosensitive coloring layer 204, and the cyan thermosensitive coloring layer 203, respectively. Characteristics, YN, M
Curves drawn by broken lines with N and CN indicate the coloring characteristics when printing the isolated dot data of the yellow thermosensitive coloring layer 205, the magenta thermosensitive coloring layer 204, and the cyan thermosensitive coloring layer 203, respectively.

Further, the Y bias, the M bias, and the C bias indicate bias heating times for applying bias energy to the yellow thermosensitive coloring layer 205, the magenta thermosensitive coloring layer 204, and the cyan thermosensitive coloring layer 203, respectively.

Here, in order to simplify the description, the yellow thermosensitive coloring layer 205 will be described as an example.

The densities D ₀ to D ₃ indicate the densities at which each one-dot data in the image data stored in the first line memory 102 is to be recorded corresponding to the gradation number 0 to gradation number 3. Show. Time T ₀ from the time T _7, when one dot data of gradation level of 7 is printed from the gray-scale level of 0 is the time for energizing the heating elements corresponding to each of one dot data. Time T ₀ is the above-described bias heating time,
Time T is one gradation energizing time.

First, before printing, bias heating is always performed regardless of whether one dot data to be printed is normal dot data or isolated dot data.
At this time, the yellow thermosensitive coloring layer 205 must reach the density D ₀ immediately before coloring. When this one dot data is usually one dot data, the heating element
Since current is supplied only for the time T ₀ , the yellow thermosensitive coloring layer 20
5 reaches the density D ₀ immediately before coloring.

On the other hand, when the one-dot data is isolated one-dot data, the gradation number of the one-dot data is corrected to 3 by the adjacent correction circuit 105. Thus, heating elements, because they are energized by a time T _3,
The yellow thermosensitive coloring layer 205 reaches the density D ₀ immediately before coloring.

Next, when the number of gradations of one dot data to be recorded is 1, the yellow thermosensitive coloring layer 205 must produce a color at a density D ₁ corresponding to the number of gradations 1.
When the one dot data is normal dot data, the heating element is energized for the time T _1, so that the yellow thermosensitive coloring layer 205 develops a color with the density D ₁ corresponding to the number of gradations of one.

On the other hand, when the one dot data is isolated dot data, the number of gradations of the one dot data is corrected to 4 by the adjacent correction circuit 105. Thus, heating elements, because they are energized by a time T _4,
Yellow coloring layer 205 developed with a concentration D ₁ corresponding to gray scale level 1. Here, in the normal dot data recording, in the case of performing the energization for a time T ₄ to the recording paper 201, that is, when performing the energization time exceeding the time T3 required for the color of the highest gray level D ₃ Develops not only the yellow thermosensitive coloring layer 205 but also the magenta thermosensitive coloring layer 204. However, at the time of isolated dots data recording, the energization by the time T _4, because the heat generating element does not rise to a proper temperature, the magenta coloring layer 204 does not reach the concentration D ₀ of the immediately preceding color.

Further, even when the number of gradations of one dot data to be recorded is two or three, regardless of whether the one dot data is normal dot data or isolated dot data, the yellow thermosensitive coloring layer Reference numeral 205 denotes color development at densities D ₂ and D ₃ corresponding to tone numbers 2 and 3, respectively. Also in this case, when recording isolated dots data increases the number of gradations by the correction is the time exceeding the time T ₃ required for color development of the maximum gradation D ₃ energization is performed, the magenta coloring layer 204 Does not reach the density D ₀ immediately before coloring.

The color thermosensitive coloring layer 201 has 7 gradations.
When performing energization to time T ₇ corresponds to, since the yellow coloring layer 205 at the same time as the magenta coloring layer 204 also color, gray-scale level of 7 for the correction of isolated dots data is not used.

As described above, the adjacent correction circuit 105 sets the number of tones of one dot data determined as isolated dot data to 3
Is added, the heating element that prints the isolated dot data has a longer energization time, and thus the temperature rises to an appropriate temperature. Moreover, the energization time extended by the adjacent correction circuit 105 is within a range in which the magenta thermosensitive coloring layer is not colored, so that the isolated dot data is properly recorded on the color thermosensitive recording paper 201 at the original density.

In the above embodiment, the adjacent discrimination circuit 104 refers to three adjacent one-dot data to determine whether or not one dot data is isolated one-dot data. However, in the above-described example, in the above-described example, (m-1, n-1) and (m-1, n + 1)
In addition, the present invention can also be applied to a case where five 1-dot data adjacent to the periphery are referred to.

In the above-described embodiment, the adjacent discrimination circuit 104 determines whether one dot data is an isolated one dot data by using the current line image data and the previous line image data. Has been described, but the present invention can also be applied to a case where the number of lines of image data to be referred to is three or more to perform a wider range of determination.

In the above-described embodiment, the adjacency determination circuit 104 determines whether or not one dot data is an isolated one dot data by determining the image data of the neighboring one dot data. Although a case has been described in which whether the number of gradations is 0 or 1 or more has been described, the present invention considers the magnitude of the number of gradations of the image data of one dot data adjacent to the periphery in the above-described determination. Also applicable to cases. Thereby, a more subtle dot expression can be made at the time of recording.

[0079]

As described above, according to the present invention,
A thermal printer capable of clearly recording even small characters and thin lines can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a printing unit of a thermal printer according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a color thermal recording sheet processed by the thermal printer according to the embodiment.

FIG. 3 is an explanatory diagram of an algorithm for determining isolated dot data in the thermal printer according to the embodiment.

FIG. 4 is a timing chart showing a state of print control of the thermal printer according to the embodiment.

FIG. 5 is a characteristic diagram showing color development characteristics of a color thermosensitive recording paper by the thermal printer according to the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Frame memory 102 1st line memory 103 2nd line memory 104 Adjacency discrimination circuit 105 Adjacency correction circuit 110 Print control circuit 115 Heating part

 ────────────────────────────────────────────────── ─── Continuing the front page (72) Inventor Akira Takeoka 2-3-8 Shimomeguro, Meguro-ku, Tokyo Matsushita Electric Transmission System Co., Ltd. F-term (reference) 2C066 AA03 AD01 AD03 CC05 CC06 CD01 CD04 CD07 CD11 CD14 CD27 CE01 CE02 CF01 CF02 CF04 5C077 LL08 MP06 MP08 NN03 NN17 NP08 PP15 PP33 PP42 PP43 PQ22 PQ23 TT04 TT06 5C079 HB03 LA01 LA11 LA12 LC20 MA04 NA05 PA02 PA03

Claims (5)

[Claims] A storage means for storing gradation data to be recorded on a thermosensitive recording material, and a heating element is driven by setting an energizing time according to a gradation of the gradation data stored in the storage means. Recording control means, determining means for determining whether or not each dot data included in the gradation data stored in the storage means is isolated dot data, and wherein the determining means uses the dot data as isolated dot data. And a correcting means for increasing the gradation of the dot data when the determination is made. 2. The thermal printer according to claim 1, wherein the determination unit performs the determination in consideration of a gradation difference from peripheral dots. 3. The method according to claim 1, wherein the correcting unit changes the gradation of the dot data to a gradation corresponding to an energizing time for heating the heating element to a temperature required when the thermal recording material develops a color at the gradation. 3. The method according to claim 2, wherein the number is increased.
Thermal printer as described. 4. An energization time for obtaining the highest gradation of isolated dot data after correction is longer than a bias heating time of normal dot data of another color which develops at a higher temperature, and the other color is used. 4. The thermal printer according to claim 3, wherein the power supply time is set to be equal to or less than an energizing time for coloring the isolated dot data. 5. A method for storing gradation data to be recorded, determining whether each dot data included in the stored gradation data is isolated dot data, and determining the dot data as isolated dot data. A thermal recording method comprising: increasing the tone of the dot data to increase the density of the isolated dot data in the recording.