JPS63149168A - Thermal recorder - Google Patents

Abstract

PURPOSE:To obtain stable images with high quality even on rapid variations in the temperature of a head substrate, by providing a temperature table for selecting a heat generation reference for a thermal head according to variations in the temperature of the head substrate, and correcting the calorific value of the head according to the rate of change of the head substrate temperature with recording time. CONSTITUTION:When recording is started and heat generating elements 7a generate heat according to an image signal, substrate temperature information is sent, as required, from a thermistor 10 fitted to a substrate 7b to a CPU 14a, and a pulse duration of heating pulses corresponding to the substrate temperature information is selected from a temperature table stored in a ROM 14b. Simultaneously with heat generation, a platen roller 6 is rotated at a fixed speed to feed a recording sheet 1 and an ink sheet 4, whereby predetermined recording is performed. When the temperataure of the head substrate 7b is rapidly raised at least in a predetermined degree, namely, when the rate of change of the temperature of the substrate 7b reaches or exceeds a certain value (which is determined for each particular recorder radiation characteristics of the substrate 7b or the like) due to black solid recording or the like, a correction for further reducing the pulse duration of the heating pulses is performed, and after recording for a predetermined period of time or for a predetermined recording length with the pulse duration, the pulse duration is returned to the original predetermined duration, and recording is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a thermal recording device that can be used in facsimiles, printers, and the like.

<Prior Art> Recording methods commonly used in facsimiles, printers, etc. include thermal recording methods and thermal transfer recording methods.

The former conveys a heat-sensitive sheet that develops color through heat, and uses a thermal head to heat the sheet in an image pattern.The latter conveys a recording sheet and an ink sheet in close contact, and uses a thermal head to heat the ink sheet. The ink is heated in an image pattern to melt the ink, and the melted ink is transferred to the recording sheet.

In both of the above methods, the substrate temperature of the thermal head is detected by a thermistor or the like, and the amount of heat applied by the thermal head is adjusted according to the detected temperature from a preset temperature table as shown in FIG. 5, for example. .

That is, when heat is accumulated in the substrate due to heat generated by the thermal head, the amount of heat generated by the thermal head is adjusted to be reduced.

<Problems to be solved by the invention> However, in reality, it is the temperature near the heating element in the head substrate that affects the recording quality, but the thermistor is placed at a certain distance from the heating element due to the structure of the thermal head. This is provided in advance. Therefore, the temperature detected by the thermistor is detected with a time delay relative to the actual change in the substrate temperature near the heating element.

Although this time delay does not pose a problem for general recording, temperature detection using a thermistor cannot follow changes in substrate temperature for recording that involves sudden temperature changes, such as recording with a large black area. This may cause problems with recording.

For example, when the substrate temperature rises rapidly, if the thermal head is made to generate heat on the same basis as when the substrate temperature is low, the image quality will be significantly degraded due to excessive thermal energy.

Especially when using a polyethylene terephthalate film as the base of the ink sheet in the thermal transfer recording method,
There is a problem in that the film undergoes local expansion and contraction due to rapid temperature changes, which causes wrinkles in the ink sheet, resulting in uneven image waves, etc.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and provide a thermal recording device that can obtain stable high-quality images even if the temperature of the head substrate changes rapidly.

<Means for Solving the Problems> The present invention solves the above-mentioned conventional problems in a thermal recording device that records an image on a recording sheet by causing a thermal head to generate heat in accordance with an image signal. The present invention is characterized by having a temperature table for selecting a heat generation standard for the thermal head in accordance with changes in temperature of the substrate, and means for correcting the amount of heat generated by the thermal head in accordance with a rate of change in temperature of the head substrate with respect to recording time. It is something.

<Operation> According to the above means, when the substrate temperature of the thermal head changes, the heat generation reference changes according to the temperature table, and the thermal head generates heat at a temperature appropriate for image recording. In addition, when the temperature of the head substrate changes rapidly, the amount of heat generated by the thermal head is corrected according to the rate of temperature change, thereby performing more fine-grained recording control and obtaining high-quality recorded images. .

<Example> Next, an embodiment of the present invention to which the above means is applied will be described.

FIG. 1 is a schematic explanatory diagram of an embodiment in which a thermal transfer recording device is applied to a facsimile. In the figure, a recording sheet l wound into a roll is loaded into a roll holder 2,
Further, an ink sheet 4 wound between a supply roll 3a and a take-up roll 3b is removably loaded onto an ink sheet frame 5.

When the recording sheet 1 and the ink sheet 4 are closely conveyed between a platen roller 6 that rotates in the direction of the arrow and a thermal head 7 that is in pressure contact with the roller 6, a heating element 7a that generates heat in response to an image signal is heated. As a result, the melted or low-viscosity ink is transferred onto the recording sheet 1 in an image pattern.

In addition, the ink sheet 4 after image recording is taken up by a winding roll 3b.
The recording sheet 1 that has been wound up and on which an image has been recorded is separated from the ink sheet 4 by a peeling member 8, cut by a cutter 9 from the trailing edge of the image, and discharged from the apparatus.

Further, a thermistor 10 is attached to the substrate 7b of the thermal head 7, and a temperature table is provided for selecting a heat generation standard for the heating element 7a of the thermal head 70 in accordance with the substrate temperature detected by the thermistor 10.

In the figure, reference numeral 11 denotes a document conveyance system that conveys the document 12 using a separation roller 11a and a conveyance roller llb, and 13 denotes a reading system that reads the conveyed document 12 using a light source 13a, a mirror 13b, a lens 13c, and a photoelectric conversion element 13d. 14 is a control unit that controls the drive of the device.

Next, regarding the drive control of the control section 14 in the above device,
This will be explained using the block diagram of FIG. 2 and the flowchart of FIG. 3.

When recording is started and the heating element 7a generates heat in accordance with the image signal, substrate temperature information is sent to the CPU 14a from time to time by the thermistor 10 attached to the substrate 7b, and the RO
A heat application pulse width corresponding to the substrate temperature information is selected from a temperature table as shown in FIG. 5, for example, stored in M1Jb.

Simultaneously with the heat generation, the platen roller 6 rotates at a constant speed to convey the recording sheet 1 and the ink sheet 4, thereby performing predetermined recording.

Also, the board 7b sent from the thermistor 10 at any time.
Based on the temperature information, the CPU 14a calculates the temperature change rate T per unit time as follows.

T: Time rate of change of thermistor detection temperature T: Thermistor detection temperature t: Time Δt: Sampling time interval ΔT of thermistor detection temperature: Amount of change in thermistor detection temperature within sampling time Δ T1: Thermistor detection temperature T2 at the start of sampling
: Temperature detected by the thermistor after the sampling time Δ has elapsed The heat application pulse width is corrected according to the temperature change rate T, and the heating element 7a is driven with the finally determined pulse width via the head driver 14c.

For example, when recording with a predetermined pulse width selected in the temperature table, if the temperature of the head substrate 7b suddenly rises above a certain level due to black solid recording, etc., that is, the temperature change rate T of the substrate 7b reaches a certain value. If the temperature exceeds T0 (To is determined for each device based on the heat dissipation characteristics of the substrate 7b, etc.),
After adding a correction to further reduce the heat application pulse width and recording for a certain period of time or a certain recording length with that pulse width,
Recording is performed again by returning the pulse width to the predetermined pulse width.

By repeating the above operation until the end of recording, high quality recording that is not affected by temperature changes on the head substrate 7b can be obtained. In the case of solid black recording, etc., the temperature of the head substrate 7b rises rapidly, and the natural heat dissipation of the substrate 7b is not enough just by adjusting the heat application pulse width using the temperature table, and the substrate will overheat if left as it is. By further reducing the applied pulse width according to the temperature change rate, the substrate 7b
This prevents overheating.

This makes it possible to absorb the time delay in substrate temperature detection and obtain high-quality images.

Further, since the temperature of the ink sheet 4 does not change more than a certain level, the ink sheet 4 does not expand or contract, the incidence of wrinkles can be kept low, and it is possible to prevent image waves and the like.

<Other Embodiments> In the above-mentioned embodiments, an example of a thermal transfer recording device using an ink sheet 4 was explained, but as shown in FIG. It goes without saying that the present invention can also be similarly applied to a heat-sensitive recording device that performs recording by heating at step 7.

<Effects of the Invention> As described above, the present invention not only controls the applied heat energy according to the temperature change of the head substrate, but also corrects the applied energy according to the rate of change of the substrate temperature. It is possible to always obtain stable, high-quality recorded images without being affected.

[Brief explanation of the drawing]

Fig. 1 is a schematic explanatory diagram of a thermal transfer recording device, Fig. 2 is a block diagram of a control section, Fig. 3 is a flowchart, Fig. 4 is an explanatory diagram of a configuration of a thermal recording device, and Fig. 5 is an explanatory diagram of a temperature table. be. 2 is a recording sheet, 2 is a roll holder, 3a is a supply roll, 3b is a take-up roll, 4 is an ink sheet, 5 is an ink sheet frame, 6 is a platen roller, 7 is a thermal head,
7b is a substrate, 7a is a heating element, 8 is a peeling member, 9 is a cutter, 10 is a thermistor, 11 is an original conveyance system, lla is a separation roller, llb is a conveyance roller, 12 is an original, 13 is a reading system, 13a is a light source , 13b is a mirror, 13c is a lens, 13d is a photoelectric conversion element, 14 is a control section, 14a is a CPU, and 14b is a ROM. 14c is a head driver, and 15 is a heat-sensitive sheet.

Claims (1)

[Claims] A thermal recording device that records an image on a recording sheet by causing a thermal head to generate heat in accordance with an image signal has a temperature table that selects a heat generation standard for the thermal head according to a temperature change of the head substrate, and the recording time 1. A thermal recording device comprising means for correcting the amount of heat generated by a thermal head in accordance with a rate of temperature change of a head substrate relative to a temperature of a head substrate.