JPH0338988B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a printing method for a thermal color image printer that forms color images or color patterns such as color television.

First, the outline of the conventional basic configuration of a thermal color image printer will be explained. As shown in FIG. 1, a thermal head 1 is mounted and spaced on a carriage (not shown), and as shown in FIG. Many dot-shaped heating elements X ₁ , X ₂ on the tip surface...
At least three sets of Xn are provided. The heating elements X ₁ , X ₂ . . . positioned. A thermal ink ribbon 2 is provided in front of the thermal head 1, and this ribbon 2 is connected to the heating element of the thermal head 1 as shown in FIG.
Thermal inks 3a, 3b, 3c of different colors are applied and formed into films corresponding to the sets A, B, C of X 1 , X ₂ . . _. Xn. A recording medium 4 (plain paper) is provided in front of the thermal ink ribbon 2, and a line feed mechanism (not shown) moves the recording medium 4 (plain paper) in a direction perpendicular to the spacing direction of the head 1, that is, a heating element X ₁ ,
X ₂ . . . is line fed in the arrangement direction of Xn at a pitch corresponding to the above-mentioned interval l. During the spacing of the head 1, the heat-sensitive ink 3 is selectively driven by the heating elements X ₁ , X ₂ . . .
a, 3b, and 3c are melted into dots to form a recording medium 4.
This spacing movement and the recording medium 4
The line feed operation is performed multiple times. In other words, in addition to single color dots of magenta, cyan, and yellow, there are blue dots due to the overlap of magenta and cyan, red dots due to the overlap of magenta and yellow, green dots due to the overlap of cyan and yellow, and black dots due to the overlap of magenta, cyan, and yellow. , and the white of the recording medium 4 itself, a total of eight color dots are appropriately combined to form a color image.

By the way, in such a heat-sensitive head, _the heating elements X ₁ , X ₂ . . . are other heating elements X ₂ , X ₃
...The temperature tends to be lower than that of Xn _-1 , and for this reason, the dots formed by the heating element _X1 and Xn are formed smaller. Therefore, as shown in FIG. 4, the width of the printing area 5 formed by the heating elements X ₁ , X ₂ . . . As a result, even if the recording medium 4 is line-fed with an accurate pitch l, slight white stripes are generated at the upper and lower sides of each print area, which significantly deteriorates the print quality.
In order to solve these problems,
In Publication No. 55644, the first and m-th columns of a group of heating elements arranged in m rows and n columns at the tip of the print head are enlarged in the sub-scanning direction, and the sizes of the tots in the first and m-th columns are increased. is made to be the same size as the other dots. However, since the paper feeding device used in this type of printer is generally constructed of a gear train, errors occur in the paper feeding pitch due to backlash or eccentricity of the gears, uneven rotation of the drive motor, etc. Therefore, even if the size of the dots is uniform, it is inevitable that white lines will be formed on the upper and lower sides of the printing area due to this paper feeding error.

Furthermore, in Japanese Patent Application Laid-Open No. 53-140934, by making the paper feed amount smaller than the printing width of the print head, some of the upper and lower printing lines are made heavier; The disadvantage is that the structure is complicated, resulting in high costs.

In addition, especially with thermal color printers, there is a restriction that paper must be fed at a pitch that corresponds to the width of the color band of the ink ribbon.
It is impossible to make the paper feed pitch smaller than the print width of the print head.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a thermal color printer that does not cause white streaks between printing areas and has high print quality at a low cost.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

As shown in FIG. 5, the thermal head 1 is similar to the conventional one in that it is equipped with a large number of heating elements X ₁ , X ₂ . . . An auxiliary heating element X ₀ is provided above and close to the uppermost heating element X ₁ of each of the groups A, B, and C.
The heating elements X ₁ , X _{2 .} . .

For example, to explain one of groups A, B, and C as an example, in FIG. 7, heating elements X ₁ , X ₂ , . . .
...A pattern P ₁ is formed by selectively driving Xn,
Next, the recording medium 4 (see Fig. 1) is line fed, and the current head spacing heating element X ₁ ,
A case where pattern P ₂ is formed by selectively driving X ₂ ...Xn will be described. At the same column address of the previous printing line and the current printing line, there is a part where the previous pattern P ₁ was formed by the lowest heating element Xn, and the current pattern P ₂ was formed by the top heating element X. If there is a part formed by ₁ , both patterns P ₁ and P ₂ in this part (column address) are nothing but continuous patterns. In such a case, pattern _P3 is formed by driving the auxiliary heating element _X0 , and pattern P3 is overlapped with both pattern P1 and pattern P2, so that pattern P1 and pattern P2 are continuous. This auxiliary heating element _X0 is driven and controlled by a central processing unit CPU (not shown) using line counters and address counters commonly used in the art according to the flowchart of FIG. can do. The line counter counts the number of printed lines, and counts the output signal of a well-known home position sensor provided at the home position of head 1, and the address counter counts the number of lines to be printed. It counts the timing pulses that specify the

Both counters are initially cleared to 0, but then head 1 leaves the home position and the count value L of the line counter is incremented by _f1 . When a print timing pulse arrives there, the address counter counts this pulse and increments the count value by +1. Here, it is determined whether or not to drive the highest heating element _X1 at the column address k specified by the address counter in the current printing line. When driving heating element X ₁ , the auxiliary heating element Drive ₀ . The heating element is located at the corresponding column address k of the current printing line.
When X ₁ is not driven or when heating element Xn is not driven at the corresponding column address k of the previous printing line, auxiliary heating element X ₀ is not driven. At this point, it is determined whether the count value of the address counter has reached the final column address or not, and the routine returns to the address counter counting operation until the count value reaches the final column address, and the same operation is performed at the head. Repeated during spacing. When the count value of the address counter reaches the final column address and printing of one line is completed, the address counter is cleared and the recording medium 4 is line fed. The above operations are repeatedly executed until the end signal arrives, and after the end signal arrives, the line counter is cleared and the series of printing operations ends.

As described above, according to the present invention, an auxiliary heating element is disposed near and above the uppermost heating element of each set of heating elements, and the pattern formed by this auxiliary heating element is set one line before. Since both the lower side of the print line and the upper side of the current print line overlap to make both print lines continuous, no white stripes will occur between each print line. Further, according to the present invention, the upper and lower sides of each printing line can be made continuous without changing the paper feed pitch, so there is no need to use a paper feed device with a complicated configuration, and the cost is low. A printer with high printing quality can be obtained.

[Brief explanation of drawings]

FIG. 1 is a side view showing the basic configuration of a conventional device;
FIG. 2 is an enlarged front view of a conventional thermal head, FIG. 3 is an enlarged front view of a thermal ink ribbon, FIG. 6 is an enlarged front view of the thermal head according to the present invention, FIG. 6 is a flowchart of driving the auxiliary heating element, and FIG. 7 is an explanatory diagram for explaining the printing operation. 1...Thermal head, 2...Thermal ink ribbon,
3a, 3b, 3c...thermal ink, 4...recording medium, X1 to _Xn ...heating element, _X0 ...auxiliary heating element,
A, B, C...Pair of heating elements, _P1 , _P2 ...Heating elements
Pattern formed by X ₁ to Xn, P ₃ ... Complementary pattern formed by auxiliary heating element X ₀ .

Claims (1)

[Scope of Claims] 1. A plurality of sets of a plurality of heating elements arranged in a direction perpendicular to the spacing direction of the print head are arranged on the front end surface of the print head facing the recording medium via a thermal ink ribbon. The thermal ink ribbons are arranged in groups, each of the groups being positioned at intervals corresponding to the line feed amount of the recording medium, and the thermal ink ribbon having a different color of thermal ink at a position facing each of the groups. In a thermal color image printer in which an auxiliary heating element is disposed near and above each of the uppermost heating elements of each set and on the tip surface of the printing head, during spacing of the printing head. selectively drive the heating elements of each of the sets, and at this time, when driving the highest heating element of any of the sets at a certain column address of the current printing line, and one line before that. When the lowest heating element of the group is being driven in the printing line at the column address, the auxiliary heating element is driven to connect the lower side of the previous printing line and the current line at the column address. Dots are formed that overlap with the upper side of the print line, and the spacing of the print head and the line feed of the recording medium are performed multiple times to form a color image, pattern, etc. on the recording medium. Printing method for thermal color image printers.