JPH04235066A - Gradation thermal printer - Google Patents

Abstract

PURPOSE:To eliminate the damage of recording content caused by the fading of the part recorded on thermal paper in low density during long-term preservation after recording. CONSTITUTION:A printing element 1 of one unit is divided into a plurality of elements 1a, 1b having different areas and one of both elements is selected by an element selecting means 5 so that the area thereof becomes wide as the gradation of input data becomes high and the heat value of the element is controlled by a printing density control means 6 so that the printing density due to the selected element is in direct proportion to the gradation of the input data apparently.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gradation thermal printer for printing gradation signals such as video signals onto thermal paper.

0002

2. Description of the Related Art FIG. 4 shows a colored area (hereinafter referred to as
This is a diagram showing the shape of a "coloring part" (referred to as a "coloring part"), which is a square in this example. Figure 5 is a diagram showing the relationship between the gradation of input data and the color density of recorded area 1 (hereinafter referred to as "print density"), where the horizontal axis is the gradation of input data, and the vertical axis is the printing density of the recorded area, characteristics Curve 2 is the gradation density characteristic, and level 3 indicated by a broken line is the level of discoloration due to long-term storage of thermal paper. Further, FIG. 6 is a diagram showing the apparent density, where the vertical axis is the apparent density and the part 3 is the fading level of the thermal paper.

Conventional gradation thermal printers express the gradation of the input data by keeping the print density light in the shape shown in FIG. 4 when the input data is in the low gradation area; Gradation is expressed by increasing the print density while maintaining the shape. This relationship is shown in Figure 5. By coloring the thermal paper to a density that is directly proportional to the gradation of the input data, the apparent density also increases in direct proportion to the gradation of the input data, as shown in Figure 6. In this way, the gradation of the input data matches the apparent density.

0004

[Problems to be Solved by the Invention] When recording with a conventional gradation thermal printer, the thermal paper itself develops some color due to long-term storage, so the recording of low gradation areas is impaired as shown in Figure 6. There was a problem that

The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide a gradation thermal printer in which the recording of low gradation areas is not impaired due to discoloration of the thermal paper. do.

[0006]

[Means for Solving the Problems] The gradation thermal printer according to the present invention divides one unit of printing element into a plurality of elements, and the printing area becomes wider as the gradation of input data becomes higher. Select one or more elements so that
The printing density by this selected element is the apparent density (printing density) x (printing area) that is proportional to the gradation of the input data.
The print density, that is, the amount of heat generated, is controlled so that the following is achieved.

[0007]

[Operation] According to the present invention, (print density) x (print area)
Therefore, input data from low to high gradations is recorded on the thermal paper at high density, so even if the thermal paper fades due to long-term storage, the recording of the low gradation areas will not be damaged.

[0008]

[Embodiment] FIG. 1 is a diagram showing an embodiment of the present invention, in which 1a is a first element divided into an area of 1/5 of one printing element 1;
1b is a second element divided into 4/5 areas, 4 is input data gradation discrimination means, 5 is element selection means, and 6 is print density adjustment means.

When the input data is, for example, 4-bit data, the data gradation discrimination means 4 discriminates the gradation, sends an energization time-based signal to the print density adjustment means 6, and also sends an energization time system signal to the element selection means. A selection command signal is sent to 5. The element selection means 5 selects input data from 0 to 3 as shown in Table 1.
For gradations, use element 1a; for 4 to 11 gradations, use element 1.
When b is 12th to 15th gradation, elements 1a and 1b are selected. The print density control means 6 controls the energization time so that the print density of the selected element is apparently proportional to the gradation of the input data. This relationship is shown in Table 1.

0010

[Table 1]

That is, when the input data is in the range of 0 to 3 gradations, element 1a is selected, when the input data is in the range of 4 to 11 gradations, element 1b is selected, and when the input data is in the range of 12 to 15 gradations, elements 1a and 1b are selected. do. Since the area ratio of elements 1a and 1b is 1:4, in order to record with an apparent density proportional to the gradation of input data, the time element 1 shown in the "energization time" column in Table 1 is
By energizing from a to 1b, printing can be performed with an apparent density proportional to the gradation of the input data, as shown in FIG.

FIG. 3 is a diagram showing the printing density according to Table 1. Even at the lowest printing density, gradation 1, it is not lower than fading level 3, so that the recorded content is not damaged.

[0013] In the above embodiment, the printing element 1 has a ratio of 1:4.
Although the elements 1a and 1b are divided into elements 1a and 1b having an area ratio of , this division ratio is not limited to this example, and may be divided into three or more.

[0014]

Effects of the Invention The present invention divides one unit of printing element into a plurality of elements with different areas, and selects elements with different areas according to the gradation of input data. Since printing is performed by adjusting the current application time so that the density is directly proportional to the tone, a thermal printer is obtained in which the recorded contents are not damaged due to discoloration of the thermal paper.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing the print shape of one unit according to this embodiment.

FIG. 3 is a diagram showing the energization time, print density, and apparent density with respect to the gradation of input data of the printing element according to the present embodiment.

FIG. 4 is a diagram showing the shape of one unit of a conventional printing element.

FIG. 5 is a diagram showing apparent density with respect to gradation of input data in a conventional example.

FIG. 6 is a diagram showing the influence of discoloration of thermal paper on print data.

[Explanation of symbols]

1 One unit printing element 1a, 1b element 4 Data gradation discrimination means 5 Element selection means 6 Print density adjustment means

Claims (1)

[Claims] Claim 1: A thermal head in which a unit printing element that generates heat when driven by input data is divided into a plurality of elements with different areas, and a printing area that increases as the gradation of the input data increases. 1 divided above so that it becomes wider
Alternatively, a gradation thermal printer comprising means for selecting a plurality of elements, and means for controlling print density by the selected printing elements so that the apparent print density is directly proportional to the gradation of input data.