JPH03292162A - Heating element drive method in thermal recorder - Google Patents

Abstract

PURPOSE:To perform a uniform temperature control with high reproducibility by a method wherein a plurality of blocks are driven in a time sharing system at a timing in which an electric current demand state within a conduction pulse applying time to a heating element belonging to an arbitrary block has a different part from an electric current demand state within a conduction pulse applying time to a heating element belonging to another block to which a pulse is applied with a delay therefrom. CONSTITUTION:A plurality of heating elements are divided into a plurality of blocks. A shift time in a time sharing drive for applying a conduction pulse per block is (dt). A peak current part 44 of the N-th block is overlapped with a small current part 43 of the (N-1)-th block. A peak current part of the (N+1)-th block is also overlapped with small current parts of the other blocks. A time from (ton) to (tp) as a peak current part varies more or less in accordance with an initial temp. of a related heating element so as to extend with a lower initial temp.. Therefore, it is desirable for a power source efficiency to prevent even the momentary overlap of the times from (ton) to (tp) in the respective blocks. Thus, the time sharing drive of the blocks may be conducted at a timing in which a (dt) is set slightly longer than a (ton) - (tp) time at a minimum action guarantee temp. of a recorder.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to thermal recording, thermal transfer recording, electrically conductive thermosensitive recording, electrically conductive transfer recording, thermal inkjet, etc. The present invention relates to a method for driving a heating resistor in a device.

[Summary of the invention]

The present invention provides the above-mentioned heat generating resistors such as thermal heads for heat-sensitive recording and thermal inkjet heads (both referred to as thermal inkjet heads) or heat generating resistive layers of current-carrying recording paper. Thermal recording or thermal transfer recording in which a heating resistor (both the heating resistor and the energized heating resistor layer are referred to as a heating resistor) is energized to cause the heating resistor to generate heat, and recording is performed on a recording medium by the temperature rise of the heating resistor due to the heat generation. , in thermal recording methods such as thermal ink transfer recording, electrically conductive thermosensitive recording, and 1i electrically conductive transfer recording, the heat-generating resistor has a resistance value that is lower in a lower temperature region than that in a specific temperature region, and a lower resistance value in a high temperature region, with a specific temperature region as a boundary. The heating resistor is provided with a characteristic of changing almost stepwise to a higher resistance value, and when the temperature of the portion of the heating resistor before voltage application is below the specific temperature range, one voltage pulse is applied to the heating resistor. By energizing, the temperature of the heating resistor is steeply increased from the temperature of the heating resistor before voltage application to the specific temperature range by greater power consumption. After reaching the area, until the voltage application is completed, the temperature of the heat generating resistor is gradually increased by lower power consumption, and recording is performed. If the temperature is higher than the specific temperature range, by maintaining the gradual temperature rise state during the pulse energization, the temperature rise of the heat generating resistor is reduced according to the temperature of the heat generating resistor before the voltage pulse is applied. A thermal recording device in which the heat generating resistor itself has a kind of heat generating temperature control function of changing the speed and generating heat so that the temperature rise peak temperature of the heat generating resistor approaches a constant temperature by applying a voltage with a constant pulse width. In a driving method of dividing a plurality of heat generating resistors into a plurality of blocks and applying an energizing pulse for generating heat to each of the heat generating resistors included in each block in a time division manner, A first current consumption state corresponding to the steep temperature rise in which the current consumption value in each heat generating resistor within the energization pulse application time is larger; and a smaller current consumption state that is significantly different from this first current consumption state. With respect to at least two states including the second current consumption state corresponding to the gradual temperature increase state, the first current consumption state within the time period of applying the energization pulse to the heating resistor included in the arbitrary block is , further applying an energizing pulse to the heating resistor included in the arbitrary block at a timing that does not overlap with the first current consumption state within the application time of the energizing pulse to the heating resistor included in another arbitrary block; A portion where the second current consumption state within the time period overlaps with the first current consumption state within the time period during which the energization pulse is applied to the heating resistor included in another block to which the energization pulse is applied later than this block. By time-divisionally driving the plurality of blocks at a timing with , excellent performance such as a reduction in drive peak current in the thermal recording device is achieved.

[Conventional technology]

In conventional thermal recording methods, for example, there is a thermal recording method in which heat generated by a heating resistor of a thermal head is directly transmitted to thermal paper etc., and a method in which air bubbles are generated in liquid ink by heat generated by a heating resistor in a thermal head. The thermal inkjet method uses the pressure created by these bubbles to blow away the plate ink.
Ruthenium oxide,
Metal compound resistors such as tantalum nitride, and cermet resistors in which an insulator such as silicon oxide is dispersed in a high melting point metal such as tantalum, have been used.

When an appropriate voltage is applied to the heat generating resistor of the conventional thermal head described above, a current flows through the heat generating resistor, generating Joule heat, and this state is maintained for a certain period of time to transfer the thermal energy necessary for recording to thermal recording paper, etc. give to The Joule thermal energy generated by the heating resistor is determined by the resistance value of the heating resistor, the applied voltage, and the time for which this voltage is applied. Optimal recording quality can be achieved by adjusting the applied voltage or voltage application time depending on the characteristics, heat transfer characteristics from the heating resistor to the thermal paper, the background temperature around the heating resistor, the temperature of the recording medium itself, etc.
Alternatively, the thermal energy generated by the heating resistor is adjusted to an optimum value so as to achieve the desired recording density in gradation recording.

For example, in a current transfer recording method using an ink donor sheet or the like having a current-carrying heat-generating resistive layer and a current-carrying head, carbon paint or the like is used as the current-carrying heat-generating resistive layer, and the current-carrying head conducts current to the current-carrying heat-generating resistive layer. In this method, the ink donor sheet itself generates heat to melt or sublimate the ink and transfer the ink to the recording medium.Similar to the above-mentioned thermal recording method, the sheet resistance of the energized heating resistance layer, the temperature of the ink donor sheet itself, Depending on the conditions such as the electrode temperature of the current-carrying head, the applied voltage or voltage application time is adjusted to achieve the optimum recording quality or the desired recording density in gradation recording by controlling the heat energy generated in the current-carrying heat-generating resistive layer. Adjustment was made to the optimum value.

[The invention attempts to solve i! ! ! I] In the conventional thermal recording method, adjustment of the thermal energy involved in recording by adjusting the pressure applied to the heating resistor and the pulse width of the voltage application is extremely complicated, and the recording equipment is large and expensive due to the following reasons. I was making it a thing.

The thermal energy generated by applying a voltage pulse to the heating resistor can be determined by the voltage or pulse width of the applied pulse as described above, but the temperature of the heating resistor depends on the application period of the pulse, the number of consecutive applications, etc. The pulse application history of the heating resistor in the vicinity of the heating resistor of interest, that is, the heating history of the heating resistor, the temperature of the support substrate of the thermal head, the temperature of the ink donor sheet and liquid ink, the environmental temperature, etc.

Thermal recording mechanism does not directly depend on the amount of thermal energy generated by the heating resistor, but rather depends on the temperature of the coloring layer of thermal recording paper and the temperature of the ink layer, in other words, the temperature of the heating resistor. do. Therefore, if you want to make the temperature of the heating resistor uniform when it generates heat in order to obtain a uniform thermal record, the information about the thermal environment where the heating resistor is placed at the moment when it is about to generate heat as described above is necessary. Collect or predict thermal N-layer information, adjust and determine the applied voltage or voltage application pulse width so that the temperature of the heating resistor rises to a specific temperature, and then heat the heating resistor. I have to let it happen.

The information collection means, prediction means, and recording condition determination means described above include various temperature sensors that detect the temperature of the thermal head board and environmental temperature, a memory that stores past recorded data to understand the recording history, and a thermal The load on hardware such as a simulator such as a thermal equivalent circuit that predicts the physical state, and a CPU and gate circuit that performs arithmetic processing is extremely large. The software that supports these nodes is also extremely complex. Especially in large, high-definition thermal recording equipment that has many heating resistors, and equipment that performs gradation recording.
The amount of information to be processed becomes enormous, making it inevitable that the device becomes larger and more expensive, and recording quality may be sacrificed.

Furthermore, the processing time for collecting information, predicting, and determining recording conditions is also limited by the CPU, etc., and this becomes an obstacle to high-speed recording.

Furthermore, thermal heads generally have a glaze layer as a heat insulating layer to increase thermal efficiency, but since this glaze layer is made using a thick film process, the variation in thickness is ±20% of the average thickness. % or more, and the heat retention effect of this glaze layer varies widely randomly among individual thermal heads. Therefore, as mentioned above, no matter how accurately the information on the thermal environment of the heating resistor is captured and processed and the recording conditions are determined each time, it is difficult to control the heating temperature with high precision due to variations in the thermal characteristics of the thermal head. I can't. If we were to control the heat generation temperature with higher precision, it would be necessary to incorporate variations in the thermal characteristics of individual thermal heads as control parameters, which would require adjustment for each recording device one by one, resulting in a great sacrifice in mass productivity. have to pay.

In addition, when considering the case where the thermal head in a recording device needs to be replaced due to a malfunction or end of life of the thermal head, it is virtually impossible to adjust the settings of the recording device to suit the characteristics of each thermal head. It's extremely difficult. Variations in heat capacity and thermal resistance also exist in the periphery of the heat generating resistor layer in electrical thermal recording, and there is a problem similar to that of the above-mentioned thermal head.

Means for Solving CRAM] The present invention was made in order to solve the various problems mentioned above for uniformizing the temperature of the heat generating resistor. By providing a control function, the conventional method eliminates the complexity of controlling the temperature of the heating resistor, and furthermore aims to realize its excellent performance with a lower peak current.

The present invention provides a heating resistor with a specific temperature range as a boundary.
It has a characteristic that the resistance value changes in an almost step-like manner from this temperature range to a lower resistance value in the lower temperature part and a higher resistance value in the high temperature part.
When the temperature of the part of the heat generating resistor before voltage application is equal to or higher than the specific temperature, by applying one voltage pulse to the heat generating resistor and energizing it, the temperature of the heat generating resistor before voltage application is reduced to the above specified temperature. Up to a specific temperature range, the temperature of the heating resistor is steeply increased in a short time by larger power consumption, and after the specific temperature range is reached within the - voltage pulse until the voltage application is completed. Recording is performed by slowly raising the temperature of the heat generating resistor with smaller power consumption, and if the heat generating resistor is at a higher temperature than the specific temperature range at the time when the voltage application is started, the pulse energization is performed. A plurality of heat generating resistors in a thermal recording device that performs recording while maintaining the temperature rising state slowly during a period of time are divided into a plurality of blocks, and each of the heat generating resistors included in each block is divided into blocks for generating heat. In determining the timing of driving a block in which energizing pulses are applied in a time-division manner, the current consumption value in each heating resistor within the energizing pulse application time in the heating resistor is larger, and the first one corresponds to the steep temperature rise. and a second current consumption state corresponding to the gradual temperature increase state that consumes a smaller current value that is significantly different from the first current consumption state. The first current consumption state within the application time of the energization pulse to the heating resistor included in the block is the first current consumption state within the application time of the 1lii pulse to the heating resistor included in another arbitrary block.
In addition, with a tie that does not overlap with the current consumption state of the second current consumption state within the time period for applying the energization pulse to the heating resistor included in the arbitrary block, apply the energization pulse later than this block. The plurality of blocks are time-divisionally driven using a tie ring having a portion where the first current consumption state overlaps with the first current consumption state during the application time of the current pulse to the heating resistor included in another block.

[Effect]

If the heating resistor is used as a first heater when the heating resistor is at a temperature higher than the specific temperature range, then when the heating resistor is at a temperature lower than the specific temperature range, a second heater is connected to the first heater. A heater is assembled in parallel to the circuit of the heating resistor.

Therefore, when a constant voltage is applied when the temperature of the heating resistor is lower than the specific temperature range, the first heater and the second heater are simultaneously energized, and the consumption in the heating resistor is reduced. The current rises steeply. When the specific temperature range is reached or at a higher temperature, the second heater either stops energizing due to an increase in resistance value or becomes energized with a small amount of current, and the current flowing to the first heater almost always decreases. Only. That is, the current consumption in the heating resistor changes from a high current state to a lower current state across the specific temperature range.

Therefore, when trying to drive multiple heating resistors, each heating resistor starts to be energized with the same tie selection.
, the time required for the temperature of the heating resistor to reach the specific temperature range is extremely large, but if the plurality of heating resistors are divided into a plurality of blocks, the current will be In addition, only the first current consumption state is made non-overlapping by energizing each block, and the second current consumption state is set to the first and second current consumption states of another block. If you turn on the power in a manner that does not matter if it is in a current consumption state, the total effective current will increase, but the second heater of any one block is always energized, and at least one of the blocks is always energized. It is possible to create a state in which one of the first heaters is energized, and as a result, the total current value at any given time does not undergo large step-like fluctuations, and unevenness in power supply current output is eliminated.

Furthermore, since the energization times of the blocks are partially overlapped, the time required to pass through and finish energizing all the blocks is short.

〔Example〕

The details of the present invention will be explained with reference to examples.

First Example of Device Related to the Present Invention FIG. 1 is a plan view of a thermal head used for heat-sensitive recording, etc. related to the driving method of the present invention, and FIG. 2 is a cross-sectional view of the heating resistor portion of this thermal head. It is. On a glazed substrate (6) of alumina ceramic or the like,
A thin film heating resistor (
1) and one end of this heating resistor is connected to an individual electrode (2).
and the other end is connected to the first common electrode (3).

The individual electrodes are connected to a current switching element (4) such as a transistor. (5> is a second common electrode connected to the switching element (4>). The thermal head does not include the switching element (4) and the second common electrode (5), and is used separately as a recording device. You can set it up.

A positive potential is applied to the first common electrode, a negative potential is applied to the second common electrode, and the switching element (
By opening and closing 4), a voltage pulse is applied to the heating resistor (1).If a voltage pulse is applied to the heating resistor (1), an appropriate voltage is applied depending on the applied voltage and the resistance value of the heating resistor (1). Power consumption occurs, generating Joule heat, and the temperature of the heating resistor (1) begins to rise.In this case, assuming that the heating resistor is in the low temperature phase of the metal-semiconductor phase transition, that is, the metal phase, The resistance value becomes lower, resulting in higher power consumption under a constant voltage, resulting in a steep temperature rise.

FIG. 1O shows the heating resistor (1) accompanying the pulse application.
) is a diagram showing the change in surface temperature (71) over time. In this figure, Tc represents the temperature of the metal-semiconductor phase transition in the electrical conductivity of the heating resistor, ton is the time at which the pulse application starts, and tp is the time when the surface temperature of the heating resistor reaches the phase transition temperature (Tc). The time at which the pulse reaches, toff, represents the time at which the application of the pulse ends. During the period from tp to toff, the heating resistor (4) has become a heating resistor with a higher resistance value due to metal-semiconductor phase transition, and this heating The surface temperature of the resistor increases gradually from around the phase transition temperature Tc.The actual temperature of the heating resistor depends on the thermal inertia due to the heat capacity and thermal resistance of the heating resistor itself and surrounding structural members. may be slightly higher than the above Tc.The rise in surface temperature of the heating resistor from ton to tp is as follows:
The area of 1) is 0.015mrrr which corresponds to the heating resistor density of 8 tons l-7mm, the resistance value on the low temperature side of the heating resistor is approximately 500Ω, the resistance value on the high temperature side is approximately 2000Ω, and the applied voltage is 20V. In this case, unless a heat absorbing material such as thermal paper is brought into contact with the surface of the heating resistor, the base temperature of the heating resistor will rise to about 150°C, which can be called the base temperature, in about 0.2 milliseconds or less from ton at room temperature. reaches Tc of , and then 1
The temperature reaches about 300°C or more, which is sufficient for thermosensitive recording, in about ξ seconds.

During this time, the thermal characteristics of the thermal resistance and heat capacity around the heating resistor change depending on the thickness of the glaze on the glazing substrate of the thermal head and the thickness of the protective layer coated on the surface of the heating resistor, so the structure of the thermal head It varies from person to person. However, the heath temperature of the heating resistor is determined by the phase transition temperature Tc of the material constituting the heating resistor, and does not depend on the above-mentioned thermal characteristics of the thermal head or the structure of the thermal head. The temperature of the heating resistor is raised to the temperature level of Tc in a short time.

As explained in the problem of the prior art, thermal heads have variations in thermal characteristics such as heat dissipation properties for the heat generating resistor, but these variations occur when the temperature rises and cools beyond the above Tc, that is, after the above tp. and the time constant from ton to t
Although this appears as some variation in the temperature increase gradient up to p, ie, some variation in the time of tp, it does not cause any variation in the TcO value itself.

By the way, the color development mechanism in thermal recording is a chemical reaction caused by the heat of the coloring agent in the direct thermal method, and the reaction rate depends on the temperature, and in the thermal transfer method and thermal inkjet, it is a physical reaction such as physical melting, sublimation, and evaporation of the ink. It is a type of phase change, and recording is controlled by the temperature of the ink. Therefore, in the thermal recording device according to the present invention, which is controlled to a constant temperature Tc at the midpoint of temperature rise, the thermal characteristics of the thermal head etc. The influence of variations on recording characteristics is much smaller.

In addition, variations in the resistance value of the heating resistor may exist depending on the resistance film thickness, etc., regardless of whether the thermal head is used in conventional thermal recording or the thermal recording head related to the thermal recording of the present invention. In the thermal recording device, the to
This appears in the variation in the time from the temperature of n to Tc and the temperature increase gradient from tp to toff, but the Tc is inherent to the material and is unrelated to the resistance value itself, similar to the case of the variation in thermal characteristics described above. The influence of resistance value variations on recording characteristics is extremely small.

In order to make the temperature increase gradient due to the resistance value variation of the heat generating resistor and the peak temperature variation at time tof smaller and uniform, it is necessary to make the temperature rise gradient due to the resistance value variation of the heat generating resistor smaller and uniform. The applied voltage or current may be adjusted to make the power uniform according to the resistance value of the heating resistor, or the value from tp to toff (actually, from ton to toff) may be adjusted.

If even stricter uniformity is required, the applied voltage can be adjusted according to the resistance value of the heating resistor in the phase of metallic electrical conductivity on the low temperature side.
The purpose is to make the temperature gradient from on to tp uniform, that is, to the above-mentioned Tc, and the time itself from ton to tp cannot be directly adjusted, but only by voltage adjustment or current adjustment.

- The time from tOn to tp in the thermal recording device related to the present invention is much shorter than the time from ton to tof, and since the time from ton to tp is self-controlled by the temperature Tc, it is difficult to record. The adjustment effect on the characteristics is from tp to to when adjusting the voltage and current.
It exerts its strength more strongly on the high temperature side up to ff. Therefore, in the case of adjusting the applied voltage or current so that the power is uniform according to the magnitude of the resistance value of the heating resistor in the phase of semiconducting electrical conductivity on the high temperature side of the heating resistor described above, t
The influence of the adjustment settings from on to tp can be ignored. Conversely, the applied voltage and
If the current is adjusted, the effect of this adjustment is tp to t.
It is necessary to pay attention to the influence on temperature behavior up to off.

As mentioned above, the influence on the recording characteristics due to variations in thermal characteristics and resistance values of the thermal head is extremely small in the case of the thermal recording device according to the present invention. The higher the temperature Tc is and the closer it is to the peak temperature Tp required for sufficient recording, the more uniform recording becomes possible. Also, the smaller the power consumption on the high temperature side is compared to the power consumption on the low temperature side of Tc, or
When considering constant voltage driving, the higher the resistance value is on the high temperature side than on the low temperature side and the larger the difference, the more uniform recording becomes possible.

Especially when the above-mentioned conditions for more uniform recording are both satisfied with a high degree of sufficiency! ! ! In controlling the density gradation in thermal recording, etc., high-definition gradation can be easily achieved by controlling the pulse application time from ton to toff.

In the above-mentioned device example, the metal-semiconductor transition temperature of the heating resistor was set at approximately 150°C. The S3 equipment uses thermal inkjet that records with short pulses at temperatures of 200°C or 250°C.
If you use a heating resistor with a high phase transition temperature such as ℃, and increase the power by lowering the resistance value of the heating resistor (or increasing the applied voltage), you can rapidly increase the temperature to a high peak temperature, and color the thermal paper. Reactions etc. occur sufficiently in a short time due to high temperature, and the above t
A short applied pulse width (tof
f-ton), the exothermic peak temperature can be ensured, and uniform recording becomes possible. On the other hand, in low-speed, low-power-consumption thermal heads, etc., the resistance value on the low temperature side and the resistance value on the high temperature side of the heating resistor are set higher (or the applied voltage is lowered).
What is necessary is to slowly raise the temperature to TC and then slowly reach the peak temperature. In this case, since the peak temperature does not need to be very high, it is preferable to lower the phase transition temperature Tc to 120°C or the like.

Second Example of Device Related to the Present Invention FIG. 3 is a diagram illustrating a second example of the device related to the driving method of the present invention. A resistor (7) and a second resistor (8) consisting of a film pattern that undergoes a metal-nonmetal (insulator) phase transition at a specific temperature Tc2 are laminated, and this second resistor (8) is Individual electrode (2) in parallel with resistor (7)
FIG. 2 is a plan view of a main part of a thermal head including a heat generating resistor connected between a common electrode (3) and a common electrode (3). FIG. 4 is a cross-sectional view taken along line AA' of this heating resistor section, and FIG. 5 is a cross-sectional view taken along line B-B.
'This is a cross-sectional view. Together with the individual electrode (2), i1 is connected to the pole (3).
), the temperature at that time is the second temperature.
When the temperature is lower than the phase transition temperature Tc2 of the resistor (8), heat that contributes to recording is generated in the first resistor (7) and the second resistor (8), and this heat causes the heating resistor to When the temperature (that is, the temperature of the second resistor) reaches the Tc2,
The second resistor is made non-metallic (or made into an insulator) and the first
It generates only a negligible amount of heat compared to the heat generated by the resistor. Therefore, in this state, only a small amount of heat is generated compared to the state where heat is generated at a temperature lower than Tc2, and the temperature rise on the surface of the heating resistor changes in the same manner as in the diagram showing temperature changes in FIG. 10. The surface temperature rise of the heating resistor from ton to tp is 0.015 m, which is equivalent to the heating resistor density of 8 tons)/mm.
rrf, the resistance value of the first resistor is 2200Ω, the resistance value of the second resistor at a temperature lower than the Tc is about 650Ω,
If the resistance value on the high temperature side is about 20Ω, the parallel resistance value as a heating resistor is about 50Ω below the temperature of Tc2.
0Ω, and about 2000Ω at Tc2 or more, and the resistance value characteristics are the same as those of the first device example described above, and therefore the heat generation characteristics are also almost the same. In the above resistance example, the second resistor is T
Although the resistance value changed approximately 30 times after c2, it is possible to change the resistance value by more than two orders of magnitude depending on the selection of materials.

The first device example uses a single resistive material with 2 resistors before and after Tc2.
However, in the second device example, parallel resistance is used to realize the desired resistance value, so there is a high degree of freedom in selecting materials to achieve the required resistance value.

Third device example related to the present invention Utilizing the structure of the second device example described above, which has a high degree of freedom in material selection, the resistance value is designed so that the power consumption per area is reduced to a certain extent at temperatures above Tc2. Then, as shown in the change curve (72) of the heating element surface temperature shown in Fig. 11, even if a DC voltage is applied and steady power consumption is performed, the heating element surface temperature will fall within the temperature range in which the heating resistor does not burn out. An equilibrium temperature Te is reached at which heat generation and heat radiation are equal, and the equilibrium temperature Te can be maintained approximately as long as the voltage application is not terminated. Although it is possible to maintain a state of equilibrium temperature using a normal resistor alone such as the first resistor, in the case of the thermal recording device according to the present invention, the temperature is slightly lower than the equilibrium temperature Te. Since temperature control such as bias temperature is performed at TC2, the equilibrium temperature Te is not easily affected by surrounding temperature conditions, and the heat generation in the second resistor supports the temperature rise to Tc2. Therefore, there is an advantage that the equilibrium temperature Te can be reached in a shorter time and with slight time variations. When such a stable equilibrium temperature Te is achieved, the reproducibility of gradation recording control by toff timing control can be increased, and gradation printing of excellent quality can be provided.

Fourth device example related to the present invention In the second device example, the first resistor (7) is made of a metal/nonmetal (insulator or semiconductor) with Tel different from the phase transition temperature Tc2 of the second resistor. It is also possible to construct it from a material that transfers.

For example, if the phase transition temperature Tel of the first resistor is 200°C and the phase transition temperature of the second resistor is 150°C, and a constant voltage is applied to the heating resistor with such a configuration, the surface temperature of the heating resistor will change. is the change song of the heating element surface temperature in Figure 12! II (7
3). There is a steep temperature rise from ton, when voltage application is started, to temperature TC2, then a gradual temperature rise until Tel, and thereafter the temperature rises more slowly or remains in a stable state that does not vary beyond Te1. The condition that the temperature does not rise above this temperature Te1 is the above-mentioned T
The parallel resistance value of the first and second resistors is high at a temperature of e1 or more, and generates only an insufficient amount of heat to raise the temperature to a temperature of Te1 or more; The purpose is to realize a state in which the phase transition continues to occur from the metal phase to the non-metal phase and from the non-metal phase to the metal phase while the voltage continues to be applied to the second resistor. If such a state is achieved, gradation recording can be easily performed as in the case of achieving the equilibrium temperature Te described above, and the temperature gradient in the high temperature region, that is, from GoC2 to Tcl, is somewhat gentle. This reduces the thermal shock to the vicinity of the heating resistor in the high-temperature area, resulting in a highly reliable heating structure.

FIG. 13 shows how the temperature changes on the surface of the heating resistor when the heating resistor structures of the first and second device examples shown in FIGS. 1 and 3 are driven with continuous pulses. FIG. 14 shows how the temperature changes on the surface of the heating resistor when the heating resistor structures of the third and fourth device examples are driven by continuous pulses. From the first pulse to the nth pulse, the intermediate temperature Tc that rises steeply and reaches is constant;
The time taken to raise the temperature to Tc by the pulse is longer because the initial background temperature of the heating resistor is low, but
After the pulse, the heat generation curve is almost the same. In this way, the heat generation temperature can be self-controlled to a constant level without any control over the -cut drive. The long heat generation time in the first pulse is not a particular problem, even in sublimation type gradation printers, but if strict recording density management is required, the first pulse, i.e., the bank ground Only when the temperature is low, the applied pulse width may be extended by the length of the heating time to uniformly control the peak temperature holding time.

In a recording device that performs gradation recording, regardless of whether it is a direct thermal method, a sublimation transfer method, or an energized recording method, it is common to control the gradation by changing the length of the applied pulse width.

In conventional thermal recording methods, gradation control was difficult because the peak temperature of the heating resistor changes greatly with the length of the pulse width, but with the thermal recording device according to the present invention, at least Since the intermediate temperature of the ink is self-controlled to a constant value, it is possible to perform gradation control with good reproducibility of the exothermic peak temperature and the total thermal energy given to the ink, etc., using only the time parameter of the pulse width.
In the fourth example of the apparatus, it is possible to achieve a more uniform peak temperature and to achieve precise gradations. In the conventional example, 6
Relative density control of about 4 gradations is sometimes performed,
In absolute density control, at most 16 gradations are the original skin. However, as is clear from the above explanation, absolute density control is easy with the thermal head in the thermal recording apparatus according to the present invention, and 128 gradations and 256 gradations are also possible. FIG. 15 is a diagram showing the temperature waveform of the heating resistor surface temperature with respect to the pulse width applied to the heating resistor in the thermal recording method of the first and second apparatus examples related to the present invention for gradation control. , FIG. 16 is a diagram showing the temperature waveform of the surface temperature of the heating resistor in the third and fourth device examples. In each figure, the heating resistor temperature waveform (18-1, 2O-1) due to the first gradation pulse (19-1, 2l-1) begins to cool down in the middle of the temperature rising process. Even with such gradation pulse settings, the P: end of most pulses up to the Nth gradation is the self-controlled intermediate temperature T of the heating resistor.
If it is after the time when c (or Tc2) is reached, the gradation accuracy will be high.

Fifth Device Example In the second device example shown in FIGS. 3, 4, and 5, the first resistor and the second resistor have the same planar shape. , the first resistor (10) and the second resistor (11) may be arranged in parallel with different planar shapes as shown in FIG. Figure 7 shows the heating resistor c- in Figure 6.
It is a c' sectional view. The shape of this first resistor (10) matches the external shape of the heating resistor, and the shape of the second resistor (11
) is formed in part a with a slit b opening in the center of the heating resistor. The first resistor (10) is laminated on the second resistor (11).

When a voltage pulse is applied to the heating resistor of this fifth device example to generate heat, the change in the temperature distribution on the surface of the heating resistor in the cross section cc' in FIG. The distribution of body surface temperature is m(77). The part a where the first resistor and the second resistor are laminated has a temperature Tc.
The temperature rises rapidly until it reaches , and the temperature reaches a valley at part b.

When part a exceeds the temperature Tc, the entire area a, b of the heating resistor body
Then, only the heat generated by the first resistor is generated, and the gradual heat generation is made uniform. When the temperature is higher than Tc, the heat from the surrounding part a diffuses into part b, which is the temperature valley, and the surface temperature distribution of the cross section of the heating resistor approaches a trapezoidal shape, which is different from that of the conventional heating resistor. While the temperature peaks at the center of the heating resistor, the heat generation temperature distribution is faithful to the shape of the heating resistor.

6th Device Example As shown in FIG. 8 is a plan view of the heat generating resistor, and FIG. 9 is a sectional view taken along line DD' of this heat generating resistor, the second resistor ( 11) is provided in part b and not in part a, as shown in the distribution curve (76) of the heating element surface temperature shown in FIG. 17, especially near the temperature Tc, b
In other words, the temperature peak at the center of the heating resistor becomes sharper than before, and at high temperatures of 70 or above, the sharpness of the temperature peak tends to approach the conventional sharpness. The use of this example device in the gradation method is possible with low density (small area) floors, which was previously difficult! Improves reproducibility in region II. It is also suitable for generating bubbles in liquid ink, such as thermal inkjet, which requires instantaneous high temperatures locally.

Seventh Device Example The above examples are devices for uniformly controlling the heating temperature of a heating resistor that applies heat to a recording medium such as thermal recording paper, an ink donor sheet transferred to the recording medium, or a heating resistor that applies heat to liquid ink. However, when a voltage pulse is applied to a thermal recording paper or an ink donor sheet having a heating resistance layer by a current-carrying head having a current-carrying electrode, the thermal recording paper or ink donor sheet having a heating resistance layer itself generates and records the energized heat. In the recording method, the heating resistor layer is a laminated heat generating layer including a first resistive layer made of a normal heat generating resistive material such as carbon paint, and a second resistive layer made of a material that undergoes a metal-nonmetal phase transition at a temperature Tc5, for example. Even when using this method, uniform recording can be achieved by uniform self-control of the intermediate temperature of heat generation.

An example of the apparatus of the present invention for this electrical thermal recording will be described below.

FIG. 19 is a sectional view of the current-carrying heat-sensitive recording device, in which the current-carrying heat-sensitive recording paper (50) includes a coloring recording layer (51), the second
phase change resistance layer (52), the first normal resistance layer (53)
), this second resistance layer (52) is made by uniformly coating a material whose main component is a material whose electrical conductivity changes from metallic at the low temperature side to non-metallic at the high temperature side of a specific temperature range. It is a layer or a layer formed by vapor deposition. The specific temperature range Tc5 that causes the change in electrical conductivity should be different depending on the recording device, such as high-speed recording type, low power consumption type, gradation recording type, etc., but for example, about 100°C to 150°C is preferable. be. With the electrically conductive thermal recording paper (50) sandwiched between the platen (66) and the electrically conductive head (60),
A voltage pulse is applied between the pass electrode (61) and the return electrode (62) to generate heat in the first and second resistance layers (52, 53). When the laminated heat generating layer reaches the heat generating temperature Tc5, the resistance value of the second resistive layer (53) increases rapidly and hardly contributes to heat generation, and the second resistive layer (53) hardly contributes to heat generation.
The heat generated by 2) causes a gradual temperature rise in the coloring layer (51), and coloring is performed.

The eighth device example, FIG. 20, shows a heat-melting ink layer (56) and a conductive layer (56).
4>, second resistive particles (58) made of a material whose electrical conductivity changes from metallic at the low temperature side to non-metallic at the high temperature side of a specific temperature Tc6, and carbon particles, etc. FIG. 2 is a cross-sectional view of an ink donor sheet for electrical transfer provided with a mixed heating resistance layer (55) in which first resistance particles (57) having a normal resistance characteristic of 1 are dispersed. FIG. 21 is a cross-sectional view of a current recording device using this ink donor sheet,
The current between the current-carrying electrode (61) of the current-carrying head and the return path electrode (65) provided at a location some distance from the current-carrying head flows through the mixed heating resistance layer (55) of the ink donor sheet.
, it mainly flows in the depth direction of this layer. The second resistive particle (58) undergoing a phase transition and the first resistive particle (58)
7) constitutes a parallel circuit between the current-carrying electrode (61) and the conductive layer (54), and below the specific temperature Tc6, both contribute to heat generation, and above Tc6, the second resistive particles hardly It no longer contributes to heat generation.

The mixed heating resistance layer (55) and the conductive layer (54) do not have to be provided on the ink donor sheet, but may be a separate sheet from the ink donor sheet as a heating sheet.

In the device examples using the material layer (or particles) that undergoes metal-nonmetal transition and the normal resistance layer (or particles) in the heating resistance layer shown in FIGS. 19 and 21, the first , as in the case of thermal recording using a thermal head equipped with a second resistor, the heat-generating resistive layer is controlled by the voltage, the current-carrying time, the temperature of the current-carrying head, and the current-carrying thermal paper including the heat-generating resistor layer. Regardless of the previous temperature, platen or environmental temperature, etc., the specified temperature (Tc5 or Tc5) when energized is
The temperature is quickly raised to c6), and the temperature is gradually raised. Therefore, the exothermic peak temperature can be easily maintained at a stable temperature based on the specific temperature (Tc5 or Tc6), and uniform thermal recording can be achieved without the need for conventional heat control.

Embodiments of the Invention Next, the heat generation driving method of the present invention in all of the above-mentioned apparatus examples will be explained by way of embodiments.

FIG. 23 shows each heat generating resistor and heat generating resistor layer (42
) shows the waveform (41) of the current flowing through the heat generating resistor and the heat generating resistor layer when a voltage pulse as shown in FIG. The heating resistor temperature before energization is Tc (or Tc2)
In the following case, for example, the resistance value of the second resistor in the above-mentioned second device example is low, and the resistance value as a heating resistor is
The resistance value of the first resistor and the resistance value in the second low state are parallel, and more current flows. This state is
This continues until time tp when the second resistor reaches the temperature range Tc2 where it transitions to a high temperature phase, and after this time, the current value decreases as the resistance value of the second resistor increases, and the current is turned on. This state persists until the end of the pulse. If driven at a constant voltage, the heating element resistance value is approximately 500Ω before tp, tp
If it is 2000Ω thereafter, the current value will decrease by 1/4 after tp.

Strictly speaking, the resistance value of the first resistor has a slight temperature dependence.
/°C, and the second resistor also has a slight temperature dependence of its resistance value even in a temperature range far from the phase transition temperature region where the resistance value changes greatly. , the current value slightly fluctuates in the pulse application time period before time tp and in the pulse application time period after tp. Further, the current value is also influenced by the heat generating resistor circuit and C acid content. However, the influence of these on the flow value is
The change in current value is very small compared to the change in the current value near the time tp.

Incidentally, in each type of thermal recording device, a recorded image is generally expressed by a plurality of dots, and for example, in the case of a thermal head, a large number of minute heat generating resistors are provided, and each heat generating resistor expresses the dot.

Since the tal device provided in the recording device cannot be made unnecessarily large, -a, when the plurality of heating resistors are divided into a plurality of blocks and an energizing pulse is applied to each of these blocks. Divided driving is performed to reduce the maximum power in recording, that is, the maximum current. In the recording apparatus according to the present invention, - dot il'l
Since a large current change occurs within the pulse, even if the second
Even if divided driving is performed in which the driving times of each block do not overlap as shown in FIG. 2, the current capacity is wasted. but,
As shown in FIG. 24, if the time shift amount for driving each block is set by the time from ton to tp in FIG. 23, and the number of heating resistors in one block is set to a small number, the power source Fluctuations in the supplied current are reduced, and the current can also be suppressed.

FIG. 24 is an example of a timing chart showing the pulse (461) application timing to each block and the current waveform (45-i) of the corresponding block in block division drive based on the above-mentioned concept. It is. The shift time of the divided drive is dt. The peak current part of the Nth block (the part corresponding to (44) in Fig. 23) is the N-1th block.
It overlaps with the small current portion of the block (the portion corresponding to (43) in Fig. 23), and the peak current portion of the N+1 block also overlaps with the small current portion of the other blocks. The time from ton to tp, which is the peak current portion, varies somewhat depending on the initial temperature of the heat generating resistor involved, and the lower the initial temperature, the longer it becomes.

This is because it takes longer for the heating resistor to heat up to the temperature Tc as the temperature rises from a lower temperature. In terms of power efficiency, it is desirable that the time from ton to tp does not overlap between the blocks even momentarily. The blocks can be divided and driven at longer timings. It also senses the temperature around the heating resistor or heating resistor layer, and
may be changed depending on this temperature. When driven as shown in Fig. 24, the result is 1! When using a power source with a high capacity, compared to driving at the timing shown in Figure 22,
All blocks can be driven in a short time,
Helps speed up recording.

The applied pulse width (ton to t.

When split driving is performed with a time shift of dt, which is a sufficiently short time compared to be.

Taking a thermal head as an example, a plurality of heating resistors are arranged in a straight line, and recording is performed by continuously moving a thermal recording paper relative to the heating resistor row in a direction perpendicular to the heating resistor row. When trying to record a straight line with a line width of 1 door), the shift time dt for block division is so long that it cannot be ignored compared to the time it takes for the thermal recording paper to move the distance of the line width of 1 dot. , the straight line becomes a stepped line corresponding to the block position. However,
In the above-mentioned driving method in which dt is shortened and the number of divisions is increased, the step-like difference becomes small corresponding to the shortness of dt.
It can be expressed as a straight line with no noticeable difference. Therefore,
This is a very useful method when used as a drawing profiler.

By the way, vanadium oxide compounds are examples of the above-mentioned substances that undergo metal-non-gold (or insulator, semiconductor) transitions. By doping vanadium oxide with a small amount of Cr, the electrical conductivity changes like a metal/nonmetal (or an insulator or a semiconductor) in a temperature range higher than room temperature. Nonmetallic (or insulating, semiconducting) at higher temperatures
Both vanadium and vanadium oxide are high melting point substances that have metallic electrical conductivity at lower temperatures and can be used as heating resistors. As a heat-generating resistive film, a bottom film can be formed by a thin film process such as sputtering, or it can be made into a powder and mixed with a binder to form a paste, or it can be made into an organic metal and manufactured by a thick film process such as coating. In the eighth device example (device example for energization thermal recording), particles are used that have uniform particle diameters that are approximately the same thickness as the heat generating resistor layer. In either case, Ifi, M, and the sized vanadium oxide component require at least a polycrystalline structure. In the case of spackling, sputtering is performed using an alloy target of metal vanadium and chromium, or a metal hanadium target embedded with chromium using argon and oxygen gas, or a target made of sintered vanadium oxide powder and chromium oxide powder is used. There are methods such as argon gas or a method of mixing a small amount of oxygen with argon gas and performing high frequency sputtering.

In any spackling, it is desirable that the temperature of the deposited film is several hundred degrees Celsius or higher to ensure a more crystalline state, but it is also possible to increase the crystallinity by performing laser irradiation or vacuum 7 annealing heat treatment after the acid film. be.

When an appropriate amount of Cr is doped, the electrical conductivity changes by 2 to 3 orders of magnitude at the above transition temperature, so when used as a heating resistor layer of a heating resistor or current-carrying thermal paper, the electrical conductivity changes above and below the above transition temperature under a constant voltage application state. 2-3 as power consumption value
This is accompanied by a substantial exothermic and non-exothermic change from the thermal recording point of view.

Therefore, by incorporating ordinary resistors such as tantalum nitride or cermet in parallel, the heat generating resistor of the series of device examples described above can be realized. By changing the proportion of Cr doped into the vanadium oxide, it is possible to change the transition temperature, and it is possible to set the series of intermediate temperatures Tc. With vanadium oxide that is not doped with Cr, the rate of resistance change is small and changes gradually with temperature, but there is a nearly one-digit increase in resistance from the low temperature side to the high temperature side after about 400 degrees Celsius. It can be used for a heating resistor composed of a single material like the first example of the device related to the present invention, or it can be used as a heating resistor material in combination with a normal resistor material. For example, in the second device example described above, the first resistor and the second resistor were provided as separate layers as the resistive film, but
If a phase change material such as vanadium oxide can maintain its phase change characteristics even in a film having a mixed structure with another metal (for example, tantalum), a heating resistor can be formed as a mixed film. In this case, a single heating resistor film similar to the first example of the device described above is obtained, and processing such as the bottom film and patterning of the heating resistor can be simplified.

FIG. 25 is a diagram showing a temperature change in the linear resistance of the heating resistor that undergoes metal-nonmetal transition in the first device example described above. The line resistance itself changes depending on the film thickness and line width, so it is a reference value, but for vanadium oxide doped with about 0.5% Cr to vanadium, the line resistance characteristic curve (
31), there is a three-digit change in resistance value at about 150°C. The temperature range in which the resistance value changes changes depending on the amount of Cr doped, and as the Cr doping amount increases, the temperature range in which the resistance value changes gradually shifts to the lower temperature side. C
If the amount of doping r with respect to vanadium exceeds several percent, the change in resistance value increase from the low temperature side to the high temperature side disappears, making it difficult to achieve the purpose of the device function related to the present invention. As mentioned above, since the amount of Cr doped changes the temperature characteristics of the resistance change, the change in the linear resistance is affected by the microscopic non-uniformity within the sample of the amount of Cr doped with respect to vanadium oxide, for example, as shown in FIG. It may also be a gentle curve with a certain temperature range, such as the curve (32).

Even with such a gradual change, the purpose of the device function related to the present invention can be achieved.

Also, for example - side 0. When an attempt is made to raise the temperature of a heating resistor several millimeters in length by applying current, the temperature does not rise spatially uniformly within the heating resistor. The change in resistance value as a heating resistor appears to be gradual as shown in FIG. A gradual increase in temperature is occurring.

Therefore, in order to keep the temperature rising slowly in areas where the temperature rises more quickly, and in order to quickly transition to a more gradual temperature rise in the areas where the temperature rises quickly, a function is required to correct the temperature distribution within the heating resistor to make it more uniform. It also has the advantage of being able to realize recording with higher fidelity of recording dots than conventional thermal recording methods.

In all of the above-mentioned device examples, the intermediate temperature (TC) at which the heating rate of the heat generating resistor changes during the heating process of the heat generating resistor is determined even if a recording medium such as thermal paper, which is a heat absorption source, is in contact with the heat generating resistor. The temperature does not change even when the temperature changes or even when there is no contact, and the temperature changes more slowly above the intermediate temperature.
Deterioration and destruction of the heating resistor in the thermal head in conventional thermal recording due to an abnormal rise in the heat generation peak temperature in a non-sheet feeding state are less likely to occur in the heating resistor in the recording apparatus according to the present invention, and noise etc. It exhibits high reliability even in situations such as malfunctions and runaways of the drive control circuit and CPLJ.

The above is also common in energized thermal recording, as there is less risk of abnormal heating of the energized thermal recording paper due to circuit runaway, ignition, destruction of equipment parts such as platens, etc., and increases the reliability and safety of the equipment. It is an effect.

In addition, in all of the above device examples, the resistance characteristics of the heating resistor, heating resistance layer, etc. do not necessarily require that the electrical conductivity changes discontinuously at a specific temperature, but rather that they have a specific range. The temperature may change continuously within a temperature range. A sufficient effect can be achieved if the resistance value of the heating resistor changes by about 1.5 to 10 times. This amount of change is under the condition of constant voltage application.
A resistance value that provides power consumption (energy) that allows temperature rise due to heat generation to reach the temperature required for recording, and a resistance value that provides power consumption (energy) that at least exceeds the temperature of the heating resistor or heating resistor layer at the temperature level involved in recording. This means a realistic ratio of resistance values that is about the size that should be maintained.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to perform temperature control more uniformly and reproducibly than conventionally in any temperature environment in which a heating resistor, etc. is placed. High quality recording is possible. It is possible to suppress variations in recording characteristics even with variations in thermal properties of recording elements. It is also possible to suppress variations in recording characteristics due to variations in the resistance value of the heating resistor and the sheet resistance value of the heating resistor layer. Highly accurate density gradation control and halftone gradation control are easy. Temperature information collection circuits such as temperature detection in recording equipment and recording density correction circuits are simple, making it possible to provide equipment that is small and inexpensive.Highly reliable and safer with respect to runaway resistance of heating resistors, etc. The heat generation temperature distribution is faithful to the shape of the heating element, resulting in excellent recording quality.

In thermal recording devices with excellent performance such as ■
The power supply capacity can be made smaller.

■ High-speed recording is possible.

■ Straight lines can be recorded faithfully using heating resistor arrays or current-carrying electrode arrays.

It exhibits excellent effects such as.

[Brief explanation of drawings]

FIG. 1 is a plan view of a thermal head according to the present invention, FIG. 2 is a cross-sectional view of a heating resistor of the thermal head of FIG. 1, and FIG. 3 is a plan view of a heating resistor according to the present invention. Fourth
5 is a sectional view of the heating resistor of FIG. 3, FIG. 6 is a plan view of the heating resistor according to the present invention, and FIG. 7 is a sectional view of the heating resistor of FIG.
8 is a plan view of the heating resistor according to the present invention; FIG. 9 is a sectional view of the heating resistor shown in FIG. 8; FIGS. FIG. 12 is a diagram showing a change in surface temperature of a heating resistor in an example of a device related to the present invention;
Figures 13 and 14 are diagrams showing changes in surface salinity of the heating resistor due to continuous heat generation in an example of the device related to the present invention, and Figures 15 and 16 are diagrams showing heat generation in the example of the device related to the present invention. A diagram showing the temperature change in gradation control of the surface temperature of the resistor.
17 and 18 are diagrams showing the surface temperature distribution of the heating resistor in an example of a device related to the present invention, FIG. 19 is a cross-sectional view of a main part of the current-carrying thermosensitive recording device related to the present invention, and FIG. 20 21 is a cross-sectional view of an ink donor sheet for electric thermal transfer according to the present invention, FIG. 21 is a cross-sectional view of a main part of an electric thermal transfer recording apparatus according to the present invention, and FIGS. 22 and 24 are cross-sectional views of an ink donor sheet for electric thermal transfer according to the present invention. 23 is a diagram showing the drive current waveform of the heat generating resistor in an embodiment of the present invention; FIG. 25 is a timing chart showing the drive timing of the heat generating resistor and the current waveform of the heat generating resistor according to the embodiment of the present invention; FIG. FIG. 2 is a diagram showing resistance value characteristics of a resistor. l...Heating resistor 7.10...First resistor 8.11...Second resistor 2...Individual electrode 3.5...Common electrode 4...Switching element 1B -N, 20-N...Heating resistor surface temperature 19-N
, 21-N... Gradation energization pulse 31.32... Resistance value characteristic of resistor 41.45.47... Current waveform 42.46.48... Energization pano Ps ε0... Energization Thermal paper 51...color recording layer 52...first resistance layer 53...second resistance layer 54...conductive layer 55...mixed heating resistance layer 56...ink layer 57...・First resistance particle 58 ・ ・ 60 ・ ・ 61 ・ ・ Tc T Te ・ t On ・ off tp ・ ・ dt ・ ・ FIG. 4 ・ Second resistance particle ・ Current-carrying head ・ Current-carrying electrode cl, Tc2 ・・Phase transition temperature of resistor, equilibrium temperature of heating resistor, energization pulse application time...i! Electric pulse application end time, Tc arrival time, drive shift time or more

Claims (2)

[Claims] (1) A method of dividing a plurality of heating resistors into a plurality of blocks, and applying an energization pulse for generating heat to each of the heating resistors included in each block in a time-sharing manner, the method comprising: a first current consumption state in which each heating resistor consumes a larger current value during the energization pulse application time; and a second current consumption state in which a smaller current value is consumed which is significantly different from the first current consumption state. and a current consumption characteristic that transitions between at least two states from the first current consumption state to the second current consumption state, and within the time of applying a current pulse to the heating resistor included in the arbitrary block. drive the plurality of blocks in a time-division manner at a timing when the first current consumption state of the first current consumption state does not overlap with the first current consumption state within the application time of the energization pulse to the heating resistor included in another arbitrary block. A method for driving a heating resistor in a thermal recording device, characterized in that: (2) The second current consumption state during the application time of the energization pulse to the heat generating resistor included in the arbitrary block and the heat generating resistor included in another block to which the energization pulse is applied later than this block. 2. The heating resistor in the thermal recording device according to claim 1, wherein the plurality of blocks are time-divisionally driven at a timing in which the first current consumption state overlaps with the current consumption state within the energization pulse application time. driving method.