JPS61160257A - Control method for transfer density irregularity of thermal transfer printer - Google Patents

Abstract

PURPOSE:To eliminate the irregularity of transfer density by the effect of heat storage, by adding the applied energy less than the energy by which ink is dissolved to the element which does not participate in recording a picture or a letter for a fixed time after start of recording. CONSTITUTION:Applied energy is simultaneously given to elements other than the elements which transfer a picture or a letter for S'' seconds after state of transfer. Now, if elements 2, 8, 10, 12 are driven to form a picture or a letter for S'' seconds, the remainder elements are driven by a pulse width slightly less than the pulse width D0 when ink is dissolved. By driving thus all the elements for S'' seconds, the temperature increase of thermal head base is promoted and thereafter, even though driven by ordinary applied energy, a specific transfer density can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling transfer density unevenness in a thermal transfer printer, which makes the transfer density uniform.

In general, when a thermal printer continues to print, the base temperature of the thermal head increases and the color density becomes darker, and conversely, when no printing continues, the base temperature of the thermal head decreases and the color density becomes lighter. . For this reason, in the past, a temperature sensor was attached to the thermal head to control the base temperature to be constant, but after the temperature was detected, there was a time lag in feeding back this and changing the applied energy, resulting in a response time. In the case of rough control, the image quality became mottled, which actually caused a decline in quality. Therefore, a method has been proposed in which the power supplied to the heating element is increased to a preset amount from when the power is turned on or when the recovery operation is performed until a predetermined amount of printing is performed to prevent uneven color density. (Unexamined Japanese Patent Publication No. 58-20473, Unexamined Japanese Patent Publication No. 28-1983
20475), when performing area modulation to express shading by changing the size of the transfer dot, it is common to change the applied energy, but heat storage can also be controlled by varying the applied energy. If this were to be done, the control would be extremely complicated and the cost would be high.

Purpose The present invention was made in view of the above-mentioned circumstances.
The purpose is to eliminate unevenness in transfer density using a heat storage effect with a simple configuration.

The 11th commandment.

In order to achieve the above object, the present invention is characterized in that an applied energy smaller than that required to dissolve ink is applied to an element that does not participate in recording one image or character for a predetermined period of time after the start of recording. be. Hereinafter, the present invention will be explained based on examples.

First, FIG. 3 shows an outer curve of the temperature of the thermal head substrate. The horizontal axis is the time after energy application, and the vertical axis is the substrate temperature. Transfer rate 100%, 50%.

] 5% means the ratio of elements used for transfer in the line-shaped elmmen, that is, the transfer rate is 100%.
means that if there are 100 elements, all the elements 1- will always be used. Normally, the transfer rate for documents, etc. is 20-30% at most, and 50-30% for images.
It is about 60%. If the transfer rate is 50% and the transfer time for one screen is 87 seconds as shown in FIG. 3, the temperature of the substrate changes from the starting temperature to T''C.

Therefore, the present invention provides for a period of Su seconds after the start of transcription (Fig.
, elements other than the elements to which images or characters are actually transferred are also subjected to applied energy at the same time.

FIG. 1 and FIG. 2 are diagrams showing an embodiment according to the present invention, and the numbers indicate element numbers. Now, suppose, as shown in Figure 1, for S" seconds (Figure 3), 2-8-10-1
Assuming that element 2 is driven to form an image or character, the remaining element i is driven with a pulse width slightly smaller than the pulse width Do when the ink is dissolved, as shown in Figure 2. . In this way, by driving all the elements for S'' seconds, the temperature rise of the thermal head substrate is promoted, and even if the elements are thereafter driven with normal applied energy, a predetermined transfer density can be obtained.

Incidentally, it goes without saying that S'' seconds is not fixed and may be varied depending on conditions.

Effects As described above, according to the present invention, for a predetermined period of time after the start of transfer, elements other than the elements that actually perform transfer are driven with applied energy slightly smaller than that needed to dissolve the ink, and thereafter, normal applied energy is applied. Since it is driven by energy, it is possible to prevent uneven transfer density with an inexpensive configuration without requiring any special control.

[Brief explanation of the drawing]

1 and 2 are diagrams for explaining the present invention in detail. FIG. 1 is a diagram showing a driving element, and FIG. Figure 3 is
It is a temperature rise curve diagram of a board|substrate. 1 to 14...Printing elements. Figure 1 Figure 2

Claims (1)

[Claims] A method for controlling transfer density unevenness in a thermal transfer printer, characterized in that energy smaller than that required to dissolve ink is applied to elements that do not participate in the recording of images or characters for a predetermined period of time after the start of recording.