JPH0631970A - Thermal recording device - Google Patents

Abstract

PURPOSE:To improve image quality by providing a temperature detector means for detecting the temperature of an intermediate transfer medium opposite to a plurality of record blocks and a record energy control means for controlling application energy of the record blocks with the temperature obtained by the temperature detector means. CONSTITUTION:On a face opposite to an intermediate transfer medium 1 of a thermal head 2, a large number of heat generating elements 2 arranged in a row are arranged. Further, a string of the heat generating element 2A is divided, for example, into five record blocks 2A1-5. On respective positions on the intermediate transfer medium 1 opposite to the record blocks 2A1-5, five thermistors 10A-E are provided. A record energy control circuit 11 calculates recording energy to be applied to the record blocks 2A1-5 on the basis of the temperature detected by the thermistors 10A-E. That is, the surface temperature of the intermediate transfer medium 1 works as an offset of the recording energy to be applied to the thermal head 2 at forming an ink image, so that calculation is made such that a summation of the heat energy indicated by the surface temperature of the intermediate transfer medium 1 and the thermal energy of applying record energy becomes constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal recording apparatus for recording desired images or characters on recording paper in accordance with an electric signal applied to a thermal recording head.

[0002]

2. Description of the Related Art In recent years, a thermal recording device is easy to handle because it does not require development and fixing and is completely dry recording, and it does not require mechanical operation during printing and has low noise. Yes, as a highly reliable recording device, a printer,
It is widely used in digital copiers, facsimiles, etc. However, in any case, there is a disadvantage that clear recording cannot be performed unless a dedicated recording paper is used. Therefore, a thermal recording apparatus using an intermediate transfer medium has been devised so that clear recording can be performed on plain paper without using a dedicated recording paper.

An example of this type of thermal recording apparatus will be described below with reference to the drawings. FIG. 5 is a front view showing the basic construction of a thermal recording apparatus using an intermediate transfer medium, and FIG. 6 is a side view seen from the direction of arrow A.
5 and 6, reference numeral 1 denotes a roller-shaped intermediate transfer medium (also referred to as an intermediate transfer roller), and the outer periphery of the metal tube 1B is covered with a silicone rubber layer 1A.
Reference numeral 2 is a thermal head, 2A is its heating element, 3 is an ink sheet, 4 is a heater, and energization is controlled by a thermistor 5 and a temperature control circuit 6 which are provided in sliding contact with the metal tube 1B, and the intermediate transfer medium 1 is transferred. It is heated and kept at a predetermined temperature. Further, 7 is a recording sheet, and 8 is a pressure roller.

The operation of the thermal recording apparatus configured as described above is as follows. First, when a recording command signal is input to the thermal head 2, the thermal head 2 is pressed against the intermediate transfer medium 1 via the ink sheet 3. continue,
The thermal head 2 operates the heating element 2A according to the input recording signal to melt the ink applied on the ink sheet 3. As a result, the ink image 3A is formed on the surface of the silicone rubber layer 1A. On the other hand, the pressure roller 8
Is pressed against the intermediate transfer medium 1, and the recording paper 7 is carried between the pressure roller 8 and the intermediate transfer medium 1. Then, the ink image 3A is moved in the direction of the arrow X by the rotation of the intermediate transfer medium 1, and the press roller 8 and the intermediate transfer medium 1 are moved.
And is transferred onto the recording paper 7 between. At this time,
Silicone rubber layer 1 coated on the surface of the intermediate transfer medium 1
A has flexibility, and the ink image 3A is well copied and faithfully transferred onto the paper surface of the recording paper 7, and as a result, clear recording can be performed. Incidentally, such a thermal recording apparatus is introduced in, for example, Japanese Patent Laid-Open No. 3-227254.

[0005]

However, in the thermal recording apparatus having the above-mentioned structure, the surface temperature of the metal tube 1B is detected by the thermistor 5 and the heater 4 is energized to control the surface of the intermediate transfer medium 1. Although it is intended to keep the temperature constant, in reality, the partial temperature variation of the heater 4 itself, the individual thermal conductivity of the metal tube 1B and the intermediate transfer medium 1, and the supporting member of the intermediate transfer medium 1 Due to the outflow of heat and the like, the intermediate transfer medium 1 has a temperature distribution as shown in FIG. 7 in the longitudinal direction thereof. That is, FIG.
3 is a graph showing a temperature distribution on the surface of the intermediate transfer medium 1 in the longitudinal direction. The temperature distribution depends on the influence of the environmental temperature as shown in the graph of (A) and the influence of the elapsed time after the heating of the intermediate transfer medium 1 is started by the heater 4 as shown in the graph of (B). Change. Specifically, the temperature of the central portion of the intermediate transfer medium 1 in the longitudinal direction is higher than the temperatures of both end portions thereof, and the tendency is that the environmental temperature is low and the elapsed time from the start of heating. The shorter the time, the more prominent. As a result, the temperature distribution of the intermediate transfer medium 1 causes a problem that the density of the ink image 3A formed on the surface of the medium greatly changes.

The present invention has been made in order to solve such a problem, and corrects the temperature distribution on the surface of the intermediate transfer medium to always perform recording with a uniform density regardless of the position of the surface of the intermediate transfer medium. It is an object of the present invention to provide a thermal recording device capable of

[0007]

In order to achieve the above object, the present invention provides a recording head which is divided into a plurality of recording blocks and is driven separately for each block, an intermediate transfer medium, and the recording head. An ink sheet that is inserted between the intermediate transfer medium and transfers the ink image onto the intermediate transfer medium by heat generated by the recording head, and a recording paper is pressed against the intermediate transfer medium to transfer and record the ink image onto the recording paper. And a temperature recognizing unit that directly or indirectly determines the temperature on the intermediate transfer medium facing the recording blocks, and a temperature on the intermediate transfer medium facing the recording blocks, which is determined by the temperature recognizing unit. In addition, a recording energy control means for controlling the applied energy of the corresponding recording block in the direction of eliminating the unevenness of the recording density is provided.

Further, according to the present invention, the temperature recognizing means is disposed at a predetermined position on the intermediate transfer medium in a slidable contact state, and the detected temperature value at each corresponding position is sequentially output to the recording energy control means. The feature is that it is a thermistor. Further, in the present invention, the temperature recognition means measures a temperature detected value at a predetermined position on the intermediate transfer medium which is measured in advance for each environmental temperature, and / or is measured in advance every predetermined time after the heating of the intermediate transfer medium is started. The temperature distribution table holds temperature detection values at predetermined positions on the intermediate transfer medium, and recognizes the temperature on the intermediate transfer medium according to the input environmental temperature or the elapsed time from the start of heating of the intermediate transfer medium. It is characterized by that.

[0009]

According to the above construction, the recording head and the ink sheet form an ink image to be recorded on the intermediate transfer medium. Then, the ink image is further transferred to a recording sheet by the recording unit and recorded as a permanent image. Here, when the ink image to be recorded is formed on the intermediate transfer medium, the temperature recognition means determines and recognizes the temperature at a predetermined position on the intermediate transfer medium. Regarding such a predetermined position, the recording head is handled by being divided into a plurality of recording blocks, and each recording block is a corresponding position on the intermediate transfer medium facing each other.

The recording energy control means determines the recording energy to be applied to each recording block based on the temperature value obtained by the temperature recognizing means so as to eliminate the recording density unevenness, and controls the application. The temperature recognizing means is a thermistor, which is arranged in a slidable contact with a predetermined position on the intermediate transfer medium, and directly detects the temperature of the position. Then, the temperature detection value at each predetermined position is sequentially output to the recording energy control means.

Further, the temperature recognizing means preliminarily obtains the respective temperature detection values measured at a predetermined position on the intermediate transfer medium for each environmental temperature or each time a predetermined time elapses after the heating of the intermediate transfer medium is started. Hold the temperature table held,
It is also possible to indirectly recognize the temperature on the intermediate transfer medium according to the input environmental temperature or elapsed time. Then, it is also possible to select a corresponding one from the temperature detection values held in the table and output it to the recording energy control means.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the thermal recording apparatus according to the present invention will be specifically described below with reference to the drawings. FIG. 1 is a front view showing the configuration of a first embodiment of a thermal recording apparatus according to the present invention, and FIG. 2 is a side view seen from the direction of arrow A. 1 and 2,
Reference numeral 1 denotes an intermediate transfer medium formed in the shape of a roller, which is obtained by coating the outer circumference of a metal tube 1B with a silicone rubber layer 1A. In addition, the intermediate transfer medium 1 is energized by a thermistor 5 and a temperature control circuit 6 provided in a slidable contact with the surface of the metal tube 1B to energize a heater 4 arranged in the longitudinal direction in the hollow part of the metal tube 1B. By controlling the temperature, it is heated and kept warm at a predetermined temperature. Reference numeral 2 denotes a thermal head, which is pressed against the intermediate transfer medium 1 via the ink sheet 3 and then operates the heating element 2A to apply recording energy to the intermediate transfer medium 1 (that is, the silicone rubber layer 1A).
And an ink image 3A is formed on it. The ink image 3A is moved in the direction of arrow X by the rotation of the intermediate transfer medium 1, and is further transferred onto the recording paper 7 carried in between the intermediate transfer medium 1 and the pressure roller 8.

On the other hand, in this thermal recording apparatus, in addition to the thermistor 5 described above as the thermistor for detecting the temperature of the intermediate transfer medium 1, five thermistors 10A to 10E (see FIG. 2) are formed in the silicon rubber layer 1A. It is slidably arranged at a predetermined position on the surface. A recording energy control circuit 11 for controlling the applied recording energy is connected to the heating element 2A of the thermal head 2. Then, the recording energy is controlled based on the detection results of the thermistors 10A to 10E.

Next, the method of controlling the recording energy applied to the heating element 2A of the thermal head 2 of this thermal recording apparatus will be described with reference to FIG. On the surface of the thermal head 2 facing the intermediate transfer medium 1, a large number of heating elements 2A arranged in a line are arranged. Further, the row of the heating elements 2A is divided into five recording blocks 2A1 to 2A5, and five thermistors 10A to 10E are provided at respective positions on the intermediate transfer medium 1 facing the respective recording blocks 2A1 to 2A5. It is provided. The temperature distribution in the longitudinal direction of the surface of the intermediate transfer medium 1 is detected by these thermistors 10A to 10E. It should be noted that the optimum position for mounting the thermistors 10A to 10E is the part of the surface of the intermediate transfer medium 1 on which the thermal head 2 is in pressure contact. However, because that part is structurally unmountable, the thermal head 2 It is provided at a position before coming into contact with the intermediate transfer medium 1 (that is, on the side opposite to the direction in which the ink image 3A is moved).

The temperature distribution on the surface of the intermediate transfer medium 1 detected by the thermistors 10A to 10E is, of course, the same as the temperature distribution described above (see FIG. 7). However, the detected temperature in each of the recording blocks 2A1 to 2A5 is represented by the temperature result at one point measured by each of the thermistors 10A to 10E.
On the other hand, the recording energy control circuit 11 controls each thermistor 1
Each recording block 2 based on the detected temperature value from 0A to 10E
The recording energy to be applied to A1 to 2A5 (specifically, the time and voltage value of the applied pulse) is calculated. That is, the surface temperature of the intermediate transfer medium 1 is equal to the ink image 3
It acts as an offset for the recording energy applied to the thermal head 2 when forming A, so that the sum of the thermal energy indicated by the surface temperature of the intermediate transfer medium 1 and the thermal energy due to the applied recording energy becomes constant. Calculate the recording energy.

FIG. 8 is a flowchart showing a method of controlling application of recording energy to the thermal head 2. First, the thermistors 10A to 10E detect the temperatures at the five surfaces of the intermediate transfer medium 1 (S1). Then, the detected temperature value is input to the recording energy control circuit 11 (S2). Subsequently, the recording energy control circuit 11 determines the recording energy to be applied to each of the recording blocks 2A1 to 2A5 of the thermal head 2 based on the input detected temperature value (S3).

In this case, in the recording energy control circuit 11, each data of the surface temperature of the intermediate transfer medium 1 and the recording density corresponding thereto is held in a table in advance, and by referring to this table, the detected temperature The applied recording energy required to obtain the reference recording density (arbitrarily set) is calculated below. That is, as described above, based on the basic formula of [required applied recording energy] = [thermal energy for making reference recording density] − [thermal energy at detection temperature], the applied recording energy is applied to a specific applied voltage value. Or applied pulse time, etc. Then, the recording energy control circuit 11 controls the application of the obtained applied recording energy for each recording block to each recording block (S4).

The value of the recording energy calculated in this way is as shown in FIG.
The lower the surface temperature of the recording block is (the blocks at both ends), the larger. That is, FIG. 3 is a graph relatively showing the value of the recording energy applied to the thermal head 2 of this thermal recording apparatus. Then, by applying the value of the recording energy obtained for each recording block to each recording block 2A1 to 2A5, in the longitudinal direction of the intermediate transfer medium 1, regardless of its position, it is thermally uniform throughout. The ink image 3A can be formed with sufficient energy. That is, the temperature of the intermediate transfer medium 1 is detected for each of the recording blocks 2A1 to 2A5 of the thermal head 2, and the recording blocks 2A1 to 2A1 are detected.
By controlling the energy applied to 2A5, it is possible to always perform recording with a uniform density regardless of the actual temperature distribution of the intermediate transfer medium 1.

Incidentally, as shown in FIG. 3B, if the representative value of the recording energy obtained for each recording block is subjected to the curve interpolation calculation to obtain a finer recording energy value,
It becomes possible to perform more accurate temperature control. Next, a second embodiment of the thermal recording apparatus according to the present invention will be specifically described with reference to the drawings. FIG. 4 is a side view showing the configuration of the second embodiment of the thermal recording apparatus according to the present invention. In FIG. 4, 1 is an intermediate transfer medium, 2 is a thermal head, 3 is an ink sheet, 4 is a heater, 7 is a recording sheet, and 8 is a pressure roller, and the above is the same configuration as in the first embodiment. The difference from the first embodiment is that instead of directly detecting the temperature of the intermediate transfer medium 1 at a position facing the thermal head 2 by a thermistor, a temperature distribution table 12 of the intermediate transfer medium 1 is provided and the recording energy control circuit 11 is provided. The point is that the recording energy to be applied to the thermal head 2 is obtained by referring to the temperature distribution table 12 (described later).

With respect to the thermal recording apparatus configured as described above, the method of controlling the application of the recording energy to be applied to the thermal head 2 will be described below with reference to FIG. That is, FIG. 9 is a flowchart showing a method of controlling application of recording energy to the thermal head 2 using the temperature distribution table 12. The rows of the heating elements 2A of the thermal head 2 are 5A of 2A1 to 2A5 as in the first embodiment.
It is divided into two recording blocks. The recording blocks 2A1 to 2A2 are preset for each environmental temperature and each time a predetermined time elapses after the energization of the heater 4 is started.
The temperature of the intermediate transfer medium 1 at the position facing A5 is measured by a thermistor or thermocouple, and the detected values are stored in the temperature distribution table 12.

First, when the current environmental temperature and then the elapsed time from the start of energization of the heater 4 to the present are input to the temperature distribution table 12 (S11 and S12), the temperature detection values stored in the table are displayed. Each recording block 2A from the inside
The detection value estimated to be the surface temperature of the intermediate transfer medium 1 facing 1 to 2A5 is selected, and the recording energy control circuit 11 is selected.
Is output to (S13). Subsequently, the recording energy control circuit 11 determines the recording energy to be applied to each of the recording blocks 2A1 to 2A5 based on the detected temperature value output from the temperature distribution table 12 (S14). The method of obtaining the recording energy is the same as that shown in the description of FIG. Then, the recording energy control circuit 11 controls the application of the determined recording energy to the respective recording blocks 2A1 to 2A5 of the thermal head 2 (S15). As a result, in the longitudinal direction of the intermediate transfer medium 1, it is possible to form the ink image 3A with thermally uniform energy over the whole regardless of its position.

According to the second embodiment, the current temperature of the intermediate transfer medium 1 is estimated from the temperature of the intermediate transfer medium 1 measured in advance for each of the recording blocks 2A1 to 2A5 of the thermal head 2, and each recording block 2A1 is estimated. Therefore, by controlling the recording energy to be applied to 2A5, it is possible to always perform recording with a uniform density regardless of the temperature distribution in the longitudinal direction of the intermediate transfer medium 1. Further, in this case, it is not necessary to provide a temperature detecting means such as a thermistor for directly measuring the surface temperature of the intermediate transfer medium 1. Therefore, by providing the temperature detecting means in a sliding contact state with the intermediate transfer medium 1, There is no risk of scratching the surface of 1. Therefore, the print quality does not deteriorate. Further, the intermediate transfer medium 1 which could not be detected during the recording operation
Since the temperature of the surface contacting the thermal head 2 can be estimated at all times, more accurate application control can be performed.

In the first and second embodiments described above, if the temperature detection points on the intermediate transfer medium 1 are made more dense, the temperature distribution of the entire intermediate transfer medium 1 in the longitudinal direction can be detected in more detail. Therefore, the recording energy can be controlled for each element (bit) of the heating element 2A. As the control of the recording energy in this case, one line recording can be performed by using the print signals a plurality of times, as in the case of the resistance value correction for each bit of the heating element 2A that is normally performed. And if it does in this way, it becomes also possible to perform delicate application control of recording energy.

Further, in the first and second embodiments, as means for forming the ink image 3A on the intermediate transfer medium 1,
Although the thermal head 2 and the ink sheet 3 are used, the ink image 3A may be formed by using an electrically conductive recording head and an electrically conductive recording sheet.

[0025]

According to the present invention described above, in the thermal recording apparatus, the thermal head is divided into a plurality of recording blocks,
The temperature distribution of the intermediate transfer medium is determined in order to directly or indirectly obtain the surface temperature of the intermediate transfer medium at the position where each recording block faces and to control the recording energy to be applied to each recording block based on the obtained temperature. It becomes possible to always record an image with a uniform density while correcting the. Therefore, it is possible to significantly improve the image quality.

[Brief description of drawings]

FIG. 1 is a front view showing the configuration of a first embodiment of a thermal recording apparatus according to the present invention.

2 is a side view of the thermosensitive recording apparatus shown in FIG. 1 in the direction of arrow A. FIG.

3 is a graph relatively showing a value of recording energy applied to a thermal head of the thermal recording apparatus shown in FIG.

FIG. 4 is a side view showing the configuration of a second embodiment of the thermal recording apparatus according to the present invention.

FIG. 5 is a front view showing the basic configuration of a thermal recording apparatus using an intermediate transfer medium.

6 is a side view of the heat-sensitive recording apparatus shown in FIG. 5 in the direction of arrow A. FIG.

7 is a graph showing the temperature distribution in the longitudinal direction of the surface of the intermediate transfer medium of the thermal recording apparatus shown in FIG.

FIG. 8 is a flowchart showing a method of controlling application of recording energy to a thermal head.

FIG. 9 is a flowchart showing a method of controlling application of recording energy to a thermal head using a temperature distribution table.

[Explanation of symbols]

 1 Intermediate Transfer Medium 1A Silicone Rubber Layer 1B Metal Tube 2 Thermal Head 2A1 to 2A5 Recording Block 3 Ink Sheet 4 Heater 5 Thermistor 6 Temperature Control Circuit 7 Recording Paper 8 Pressing Roller 10A to E Thermistor 11 Recording Energy Control Circuit

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical display location B41J 3/20 115 C (72) Inventor Koji Ikeda 1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. In-house (72) Inventor Nobuyoshi Taguchi 1006 Kadoma, Kadoma-shi, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. A recording head, which is divided into a plurality of recording blocks and is driven separately for each block, an intermediate transfer medium, and the recording head and the intermediate transfer medium. An ink sheet that transfers an ink image onto a transfer medium, a recording unit that presses a recording sheet onto the intermediate transfer medium to transfer the ink image onto the recording sheet, and a temperature on the intermediate transfer medium that faces each recording block. Based on the temperature on the intermediate transfer medium facing each recording block obtained by the temperature recognizing unit and the temperature recognizing unit for directly or indirectly determining the applied energy of the corresponding recording block, the unevenness of the recording density is eliminated. A thermal recording device comprising: a recording energy control means for controlling the direction. 2. The thermistor is a thermistor which is disposed in a predetermined position on the intermediate transfer medium in a slidable contact state and which sequentially outputs a temperature detection value at each corresponding position to the recording energy control means. Claim 1 characterized by the above.
The heat-sensitive recording device described. 3. The temperature recognizing means measures a temperature detection value at a predetermined position on the intermediate transfer medium, which is measured in advance for each environmental temperature, and / or measures a predetermined time after starting heating of the intermediate transfer medium. The temperature distribution table holds the temperature detection value at a predetermined position on the intermediate transfer medium, and recognizes the temperature on the intermediate transfer medium according to the input environmental temperature or the elapsed time from the start of heating of the intermediate transfer medium. The heat-sensitive recording apparatus according to claim 1, wherein