JP2934748B2 - Thermal recording method - Google Patents

Description

The present invention relates to a thermal recording method such as thermal recording, thermal transfer recording, energized thermal recording, energized transfer recording, and thermal inkjet.

[Summary of the Invention]

The present invention relates to a heating resistor such as a thermal head for thermal recording or a thermal inkjet head (both are referred to as a thermal head) or a heating resistor such as a heating resistor layer of energized recording paper (hereinafter referred to as the heating resistor to avoid complexity). And both the energized heating resistor layers are referred to as heating resistors) to cause the heating resistors to generate heat, and to perform recording on a recording medium by increasing the temperature of the heating resistors due to the heat generation. In a thermal recording method such as recording, energized heat-sensitive recording, and energized transfer recording, the heating resistor has a specific temperature region as a boundary, a lower resistance value in a lower temperature region than this temperature region, and a higher resistance value in a higher temperature region. When the temperature of the portion of the heating resistor before voltage application is equal to or lower than the specific temperature range, the heating resistor is provided. By applying one voltage pulse to the body and energizing, from the temperature before the voltage application of the heating resistor to the specific temperature region, the temperature of the heating resistor is sharply increased by larger power consumption, After the temperature reaches the specific temperature range within one voltage pulse, until the voltage application is completed, recording is performed by causing the temperature of the heating resistor to rise gently with less power consumption, and When the temperature of the body is higher than the specific temperature region at the time of the start of the voltage application, the gradual temperature rising state is maintained during the pulse energization, whereby the heating resistor is heated according to the temperature before the voltage pulse application. When the speed of the temperature rise of the heating resistor is changed and heat is generated so that the peak temperature rise of the heating resistor by application of a voltage having a constant pulse width approaches a certain temperature. Cormorant give a kind of heating temperature control function to the heating resistor itself, thus realizes the excellent recording in the recording quality or the like.

[Conventional technology]

In the conventional thermal recording method, for example, a heat-sensitive recording method in which heat is generated by directly transmitting heat from a heating resistor of a thermal head to a thermal paper or the like, or bubbles are generated in liquid ink by heat generated by a heating resistor of a thermal head, In the thermal ink jet method, in which the liquid ink is blown off by the pressure generated by these bubbles, a metal compound resistor such as ruthenium oxide or tantalum nitride or an insulator such as silicon oxide is dispersed in a high melting point metal such as tantalum as a heating resistor of the thermal head. A cermet resistor or the like was used.

When an appropriate voltage is applied to the heating resistor of the above-described conventional thermal head, a current flows through the heating resistor to generate Joule heat, and this state is maintained for a certain period of time to transfer the heat energy required for recording to a thermosensitive recording paper or the like. give. The Joule heat energy generated by the heating resistor is determined by the resistance value of the heating resistor, the voltage to be applied, and the time for applying this voltage. In general thermal recording equipment, the thermal sensitivity characteristics of the thermal paper used Depending on the 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, or the like, the applied voltage or the voltage application time is adjusted to optimize the recording quality or the recording quality. Conventionally, the heat energy generated in the heating resistor is adjusted to an optimum value so as to obtain a target recording density in tone recording.

Further, for example, in an energization transfer recording method using an ink donor sheet or the like having an energization heating resistance layer and an energization head, a carbon paint or the like is used as the energization heating resistance layer. Heating the ink donor sheet itself, melting or sublimating the ink and transferring the ink to the recording medium,
As in the above-described thermal recording method, the optimum recording quality is adjusted by adjusting the applied voltage or the voltage application time according to conditions such as the sheet resistance of the energized heating resistance layer, the temperature of the ink donor sheet itself, and the electrode temperature of the energized head. Alternatively, the thermal energy generated in the current-carrying resistance layer is adjusted to an optimum value so as to obtain a target recording density in gradation recording.

[Problems to be solved by the invention]

In the conventional thermal recording method, the adjustment of the thermal energy involved in recording by adjusting the voltage applied to the heating resistor and the pulse width of the voltage applied to the heating resistor is extremely complicated for the following reasons, and makes the recording apparatus large and expensive. I was

The heat 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. However, the temperature of the heating resistor depends on the application cycle of the pulse, the number of continuous applications, and the like. It tends to fluctuate depending on the pulse application history, the pulse application history of the heating resistor around the heating resistor of interest, that is, the heating history, the temperature of the support substrate of the thermal head, the temperature of the ink donor sheet and liquid ink, the environmental temperature, and the like.

The thermal recording mechanism does not directly affect the magnitude of the heat energy generated by the heating resistor, but rather depends on the temperature of the coloring layer and ink layer of the thermal recording paper, in other words, the temperature of the heating resistor. I do. Therefore, if the temperature at the time of heat generation of the heating resistor is to be made uniform in order to obtain uniform recording heat recording, the thermal environment information where the heating resistor is placed at the moment when the heat is to be generated as described above. Or by collecting or predicting thermal history information, adjusting the applied voltage or voltage application pulse width so that the temperature of the heating resistor rises to a specific temperature, and then causing the heating resistor to generate heat. There must be.

The information collecting means, the predicting means, and the recording condition determining means as described above include various temperature sensors for detecting the temperature of the thermal head substrate and the environmental temperature, a memory for storing past recording data for grasping the recording history, The load on hardware such as a simulator such as a thermal equivalent circuit for predicting a dynamic state, a CPU for processing, and a gate circuit is extremely large. The software supporting these hardware is also very complicated. In particular, large-scale, high-definition thermal recording equipment having a large number of heating resistors, and equipment that performs gradation recording,
The amount of processing information is enormous, and an increase in the size and cost of the apparatus is unavoidable, and the recording quality may be sacrificed.
In addition, the processing time for information collection, prediction, and determination of recording conditions is also restricted by the CPU and the like, which is an obstacle to high-speed recording.

Further, in the thermal head, a glaze layer is generally provided as a heat insulating layer in order to increase thermal efficiency.Since the glaze layer is made by a thick film process, the thickness variation is ± 20 of the average value of the thickness. % Or more, and the thermal insulation effect of this glaze layer varies greatly in individual thermal heads at random. Therefore, even if information on the thermal environment of the heating resistor is accurately captured and processed as described above, and the recording conditions are determined each time, even if the thermal characteristics of the thermal head vary, highly accurate heating temperature control can be performed. Can not. If a more accurate control of the heat generation temperature is to be performed, the variation in the thermal characteristics of the thermal head must be incorporated as a control parameter, and there is a great sacrifice in mass productivity, such as adjusting each recording device one by one. I have to pay. Also, due to failure or life of the thermal head,
Considering the case where the thermal head in the recording device is replaced, it is practically difficult to adjust the setting of the recording device to the characteristics of the individual thermal head.
Variations in heat capacity and thermal resistance also exist in the peripheral portion of the heat-generating resistive layer in energized thermal recording, and have the same problems as in the above-described thermal head.

[Means for solving the problem]

The present invention has been made in order to solve the various problems for uniformizing the temperature of the heating resistor, and has a self-temperature control function of preventing the temperature of the heating resistor from being raised to a specific temperature or higher. This eliminates the complexity of controlling the temperature of the heating resistor.

The present invention provides a heating resistor having a characteristic in which a specific temperature region is a boundary and a resistance value is changed in a stepwise manner to a lower resistance value in a lower temperature portion and a higher resistance value in a high temperature portion below this temperature region. When the temperature of the portion of the body before application of the voltage is equal to or lower than the specific temperature region, a voltage pulse is applied to the heating resistor to energize the heating resistor. Up to the region, the temperature of the heating resistor is increased sharply in a short time by a larger power consumption, and after reaching the specific temperature region within the one voltage pulse, it is more until the voltage application is completed. The recording is performed by causing the temperature of the heating resistor to rise gently with low power consumption, and when the heating resistor is higher than the specific temperature region at the time of starting the voltage application, the pulse transmission is performed. Wherein to maintain the moderate Atsushi Nobori during the recording is performed.

[Action]

Assuming that the heating resistor when the heating resistor is at a temperature higher than the specific temperature region is a first heater, when the heating resistor is at a temperature lower than the specific temperature region, another second heater is connected to the first heater. A heater is assembled in parallel with 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, heat is generated by the first heater and the second heater, and the temperature of the heating resistor is increased. Make it steep. When the temperature reaches the specific temperature range or is higher, the second heater stops generating heat, and the first heater gradually increases the temperature.
That is, the second heater serves as an auxiliary heater until the temperature of the heating resistor rises to the specific temperature range.

Therefore, according to the temperature of the heating resistor immediately before the voltage pulse is applied, the heating time of the auxiliary heater is changed to control the amount of heat generation, that is, the function of controlling the peak temperature of the heating resistor is controlled by the heating resistor. You will have yourself. As a result, it is possible to realize recording with a more uniform temperature under any thermal environment of the heating resistor, for example, under any environmental temperature and heat generation history, and it is necessary to finely control the driving of the heating resistor from outside. Disappears.

〔Example〕

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

First Embodiment FIG. 1 is a plan view of a thermal head used for thermal recording or the like in the thermal recording method of the present invention, and FIG. 2 is a cross-sectional view of a heating resistor portion of the thermal head. On a substrate 6 of glazed alumina ceramic or the like,
A heating resistor 1 of a thin film made of a material having an electrical conductivity characteristic of a metal on a low temperature side and a semiconductor property on a high temperature side at about 150 ° C. is connected, and one end of the heating resistor is connected to the individual electrode 2. 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. Reference numeral 5 denotes a second common electrode connected to the switching element 4. The switching element 4 and the second common electrode 5 may not be provided as a thermal head, but may be provided separately as a recording device.

A positive potential is applied to the first common electrode and a negative potential is applied to the second common electrode, and a voltage pulse is applied to the heating resistor 1 by opening and closing the switching element 4. When a voltage pulse is applied to the heating resistor 1, appropriate power consumption occurs depending on the applied voltage and the resistance value of the heating resistor 1 to generate Joule heat, and the temperature of the heating resistor 1 starts to rise. In this case, assuming that the heating resistor is in the low-temperature phase of the metal-semiconductor phase transition, that is, in the metal phase, the resistance value becomes lower and the power consumption becomes larger under a constant voltage, resulting in a steep state. A temperature rise results.

FIG. 10 is a diagram showing a temporal change of the surface temperature 71 of the heating resistor 1 due to the pulse application. In this figure, Tc represents the temperature of the metal-semiconductor phase transition in the electrical conductivity of the heating resistor, ton is the start time of application of the pulse, and tp is the time at which the surface temperature of the heating resistor reaches the phase transition temperature Tc. , Toff represent the application end time of the pulse. tp to to
Until ff, the heating resistor 4 is a heating resistor having a higher resistance value due to the metal-semiconductor phase transition, and the surface temperature of the heating resistor is almost equal to the phase transition temperature Tc.
Make a gradual rise from near. The actual temperature of the heating resistor may be slightly higher than the above Tc due to thermal inertia due to the heat capacity of the heating resistor itself and surrounding structural members and thermal resistance.
The rise in the surface temperature of the heating resistor from ton to tp increases the area of the heating resistor 1 by 0.08 corresponding to the heating resistor density of 8 dots / mm.
15 mm ^2, 500 [Omega about the resistance of the low temperature side of the heat-generating resistor, of about 2000Ω resistance value at the high temperature side, if the applied voltage is 20V, contacting the heat absorber of the heat-sensitive paper or the like to the heating resistor surface If not, a temperature of about 150 ° C., which is also referred to as a base temperature of the heating resistor, in a time of about 0.2 milliseconds or less from the room temperature ton
approx. 300 ° C, which is enough for thermal recording in about 1 millisecond
Reach more. This time depends on the glaze thickness of the glazing substrate of the thermal head, the thickness of the protective layer coated on the surface of the heating resistor, and the like. With each other. However, the base 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-described thermal characteristics of the thermal head and the structure of the thermal head, and is extremely high. The temperature of the heating resistor is raised to the temperature level of Tc within a short time.

As described in the related art, the thermal head has variations in thermal characteristics such as thermal radiation characteristics for the heating resistor, and this variation is caused by the temperature rise cooling above the Tc, that is, after the tp. And the variation of the temperature rising gradient from the ton to tp, that is, a slight variation in the time of tp, but the value of Tc itself does not vary.
By the way, the coloring mechanism in thermal recording is a chemical reaction due to the heat of a coloring agent in the direct thermal method, and the reaction speed depends on the temperature.In the thermal transfer method and thermal inkjet, the physical properties such as physical melting, sublimation, and evaporation of the ink are used. This is a kind of phase change, and recording is controlled by the temperature of the ink. Therefore, in the method of the present invention in which the temperature is controlled to a constant temperature Tc at the intermediate point of the temperature increase, compared to the conventional case where the temperature cannot be directly controlled, the recording of the variation in the thermal characteristics of the thermal head or the like is performed. The effect on the properties will be much smaller.

Also, the resistance value variation of the heating resistor may be present regardless of the thermal head in the thermal recording of the present invention, such as the thermal head in the conventional thermal recording due to the resistance film thickness, etc.
In the present invention, this variation also appears in the variation of the time from the temperature of ton to Tc and the temperature rise gradient from tp to toff, but the Tc is unique to the substance and has nothing to do with the resistance itself. As in the case of the thermal characteristic variation described above, the variation of the resistance value has very little effect on the recording characteristics.

If the temperature rise gradient due to the resistance value variation of the heating resistor and the peak temperature variation at time toff are to be made smaller and uniform, if the heating resistor has a semiconductor-like electrical conductivity phase on the high temperature side, Adjust the applied voltage or current according to the magnitude of the resistance of the heating resistor so that it becomes uniform with power, or set tp to toff (actually ton to tof
f) should be adjusted and set.

If stricter uniformity is required, the applied voltage may be adjusted and set according to the magnitude of the resistance value of the heating resistor in the phase of metallic electrical conductivity on the low temperature side. in this case,
The temperature gradient from ton to tp, that is, the temperature gradient from Tc to Tc is made uniform. The time itself from ton to tp cannot be directly adjusted, but only voltage adjustment or current adjustment.

The time from ton to tp in the general recording method of the present invention is much shorter than the time from ton to toff, and since the time from ton to tp is self-controlled by the temperature Tc, adjustment to the recording characteristics When the voltage and current are adjusted, the effect is more pronounced on the high temperature side between tp and toff. Therefore, according to the magnitude of the resistance of the heating resistor in the phase of semiconductor electric conductivity on the high-temperature side of the heating resistor described above, in the case of adjusting the applied voltage or current so as to be uniform with electric power, from ton The effect of the adjustment setting up to tp can be ignored. Conversely, if the applied voltage and current are adjusted according to the magnitude of the resistance of the heating resistor in the metallic conductivity phase on the low-temperature side described above, the temperature behavior from tp to toff affected by this adjustment We need to be aware of the effects of

As described above, the influence on the recording characteristics due to the variation in the thermal characteristics of the thermal head and the variation in the resistance value is extremely small in the case of the present invention, but the phase transition temperature, that is, the intermediate control temperature Tc shown in FIG. The closer to the peak temperature Tp required for sufficient recording, the more uniform recording becomes possible. In addition, as the power consumption on the high temperature side is smaller than the power consumption on the lower temperature side of Tc, or when the resistance value is higher at the higher temperature side than at the lower temperature side and the difference is larger when considering constant voltage driving, more uniform recording is possible. It becomes possible.

In particular, when the above-mentioned conditions for performing more uniform recording are both satisfied with a high degree of satisfaction, the control of density gradation in thermal recording and the like can be performed simply by controlling the pulse application time from ton to toff, thereby achieving high definition. Gradation can be realized.

In the above-described embodiment, the temperature of the metal-to-semiconductor transition of the heating resistor is set to about 150 ° C., but a high-speed thermal recording device that requires a higher peak temperature, or a vehicle using a high-temperature coloring thermal paper or the like In thermal ink-jet recording equipment, thermal ink jet recording with short pulses, heat generating resistors with a high phase transition temperature of 200 ° C or 250 ° C, etc., and lowering the resistance value of the heating resistor (or increasing the applied voltage) to power When the temperature is increased, the color developing reaction of the thermal paper occurs sufficiently in a short time due to the rapid temperature rise and the high peak temperature due to the high temperature, and the exothermic peak temperature is secured even with the short applied pulse width (toff-ton) from tp to toff. And uniform recording becomes possible. Conversely, in a low-speed and low-power-consumption type thermal head, the resistance of the low-temperature side and the high-temperature side of the heating resistor are increased (or the applied voltage is reduced), and the temperature is slowly raised to Tc. What is necessary is just to reach a 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 Embodiment FIG. 3 is a view for explaining a second embodiment of the present invention, in which a first resistor 7 made of a normal heating resistor material such as tantalum nitride or cermet and a specific temperature Tc2 are used. A second resistor 8 composed of a film pattern that undergoes a metal-non-metal (insulator) phase transition is formed in a laminated manner, and this second resistor 8 is disposed between the individual electrode 2 and the common electrode 3 in parallel with the resistor 7. FIG. 3 is a plan view of a main part of a thermal head including a heating resistor having a connected configuration. 4th
The drawing is a cross-sectional view of the heating resistor section taken along the line AA ', and FIG. 5 is a cross-sectional view taken along the line BB'. When a voltage is applied between the individual electrode 2 and the common electrode 3, the temperature at that time is the second temperature.
When the temperature of the resistor 8 is lower than the phase transition temperature Tc2, heat that contributes to recording is generated in the first resistor 7 and the second resistor 8, and this heat generates a temperature of the heating resistor (that is, the second resistor 8). When the temperature of the resistor reaches Tc2, the second resistor is made non-metallic (or made into an insulator) and generates almost negligible heat as compared with the heat generated by the first resistor. Accordingly, in this state, heat is generated only slightly compared to the heat generation state at a temperature lower than Tc2, and the temperature rise on the surface of the heating resistor changes in the same manner as the temperature change in FIG.
The surface temperature rise of the heating resistor from ton to tp increases the area of the heating resistors 7, 8 to 8 dots / mm, which is equivalent to the heating resistor density of 0.
015mm ^2, 2200Ω the resistance of the first resistor, 650Omu about the resistance of the low temperature side than the Tc of the second resistor, the resistance value in the high temperature side when about 20 k [Omega, as a heat generating resistor The parallel resistance value is about 500Ω below the temperature of Tc2, and about 2000Ω above Tc2. The resistance value characteristics are the same as those of the first embodiment, and the heat generation characteristics are almost the same. In the above-described example of the resistance value, the resistance value of the second resistor changes about 30 times from Tc2 as a boundary. However, the resistance value can be changed by two digits or more depending on the material selection.

In the first embodiment, a single resistance material is used.
Although the same resistance value is realized, in the second embodiment, since the resistance is realized by the parallel resistance, the degree of freedom of material selection for realizing the required resistance value is high.

Third Embodiment If the resistance value is designed so that the power consumption per area is reduced to some extent at a temperature equal to or higher than Tc2 by using the structure of the second embodiment having a high degree of freedom in material selection, As shown in the graph of the heating element surface temperature change curve 72, even if a DC voltage is applied and steady power consumption is performed, the heating element surface temperature is equal to heat generation and heat dissipation within a temperature range in which the heating resistor does not burn out. If the temperature reaches a certain equilibrium temperature Te, the equilibrium temperature Te can be maintained substantially as long as the voltage application is not terminated. Although it is possible to form a state in which an ordinary resistor such as the first resistor alone maintains the equilibrium temperature, in the case of the present invention, the bias temperature is set at Tc2 which is a temperature slightly lower than the equilibrium temperature Te. Because such temperature control is performed, the equilibrium temperature
Advantageously, Te is hardly fluctuated by the surrounding temperature conditions, and the temperature rise up to Tc2 is assisted by the heat generated by the second resistor. There is. If such a stable equilibrium temperature Te is realized, the reproducibility of the gradation recording control by the timing control of toff can be improved, and gradation printing with excellent quality can be provided.

Fourth Embodiment The first resistor 7 in the second embodiment is made of a material that undergoes a metal-to-metal (insulator or semiconductor) transition at Tc1 different from the phase transition temperature Tc2 of the second resistor. It is also possible.

For example, when the phase transition temperature Tc1 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 having such a configuration, the surface temperature of the heating resistor becomes Shows a behavior like a change curve 73 of the heating element surface temperature in FIG. The temperature rises sharply from ton when voltage is applied to temperature Tc2, then rises slowly up to Tc1, then the temperature rises more slowly or becomes a stable state that does not rise above Tc1 . The condition that the temperature is not raised to the temperature Tc1 or more is that the parallel resistance value of the first and second resistors is high at the temperature of the temperature Tc1 or more, and only enough heat is generated to raise the temperature to the temperature Tc1 or more. So,
It is to realize a state in which the phase transition continues to occur from a metal phase to a non-metal phase and from a non-metal phase to a metal phase while a voltage is continuously applied to the second resistor at a temperature near Tc1. If such a state is realized, similarly to the case of the above-described equilibrium temperature Te, gradation recording can be easily performed, and a high temperature region, that is, from Tc2 to Tc1, has a slightly gentle temperature gradient, The thermal shock to the periphery of the heating resistor in the high-temperature portion is relieved, so that a highly reliable heating structure is obtained.

FIGS. 13 and 13 show how the temperature of the heating resistor surface changes when the heating resistor structures of the first and second embodiments shown in FIGS. 1 and 3 are driven by continuous pulses. FIG. 14 shows how the temperature of the heating resistor surface changes when the heating resistor structures of the third and fourth embodiments are driven by continuous pulses. From the first pulse to the n-th pulse, the intermediate temperature Tc at which the temperature rises steeply is constant, and the temperature rise time up to Tc by the first pulse corresponds to the low initial background temperature of the heating resistor. Although it becomes longer, the heat generation curve becomes almost the same after the second pulse. In this way, self-control to a constant heat generation temperature can be performed without performing any drive control. The long heat-up time of the first pulse does not cause any particular problem even in a sublimation type gradation printer, but when strict recording density control is required, the first pulse, that is, the background Only when the temperature is low, the applied pulse width may be extended by the longer heating time to uniformly control the peak temperature holding time.

For recording devices that perform gradation recording, the direct thermal method,
Regardless of the sublimation transfer method or the energization recording, it is general to control the gradation by the length of the applied pulse width. In the conventional thermal recording method, the gradation control was difficult because the peak temperature of the heating resistor greatly changed with the length of the pulse width. However, in the thermal recording method of the present invention, at least during the heating and heating process, Since the intermediate temperature is self-controlled to a constant value, it is possible to perform gradation control in which the heat generation peak temperature and the total heat energy applied to the ink and the like are controlled with good reproducibility by using only the time parameter called the pulse width. In the fourth embodiment, a state where the peak temperature is more uniform can be realized, and strict gradation can be realized. In the conventional example, the relative density control of about 64 gradations may be performed, but the absolute density control has a limit of 16 gradations at most. However, with the thermal head in the thermal recording method of the present invention, as is clear from the above description, the absolute density control is easy, and 128 gradations and 256 gradations are possible. FIG. 15 is a diagram showing a temperature waveform of a heating resistor surface temperature with respect to a pulse width applied to the heating resistor in the thermal recording method of the first and second embodiments of the present invention for gradation control. FIG. 16 is a diagram showing a similar temperature waveform of the surface temperature of the heating resistor of the third and fourth embodiments. In each figure, the heating resistor temperature waveforms 18-1 and 20-1 caused by the first gradation pulses 19-1 and 21-1 start cooling down in the middle of the heating process. Even if the adjustment pulse is set, if the end of most of the pulses up to the Nth gradation is after the time when the self-controlled intermediate temperature Tc (or Tc2) of the heating resistor is reached, the gradation accuracy is high. It will be.

Fifth Embodiment In the above-described second embodiment shown in FIGS. 3, 4, and 5, the first resistor and the second resistor have the same planar shape. , As shown in FIG.
The resistor 10 and the second resistor 11 may be arranged in parallel.
FIG. 7 is a cross-sectional view of the heating resistor taken along the line CC 'in FIG. The shape of the first resistor 10 matches the outer shape of the heating resistor, and the second resistor 11 is formed in the a portion with a slit b opened at 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 the fifth embodiment to generate heat, the change in the temperature distribution of the heating resistor surface temperature distribution in the sectional view taken along the line CC ′ in FIG. A distribution curve 77 of the heating element surface temperature is obtained. The portion a where the first resistor and the second resistor are stacked rises quickly until the temperature reaches Tc, and the portion b becomes a valley of temperature. a
When the temperature exceeds the temperature Tc, only the heat generated by the first resistor is generated in all the regions a and b of the heat generating resistor, and the gentle heat is uniform. In the state above Tc, the heat of the surrounding part a is diffused into the part b which has become the above-mentioned valley, the surface temperature distribution of the cross section of the heating resistor approaches a trapezoidal shape, and the temperature distribution in the conventional heating resistor is reduced. While the center of the heating resistor has a temperature peak, the heating temperature distribution is faithful to the shape of the heating resistor.

Sixth Embodiment FIG. 8 is a plan view of a heating resistor, and FIG. 9 is a cross-sectional view of the heating resistor taken along the line DD ′. As shown in FIG. Conversely, if it is provided in the part b and not provided in the part a, as shown in the distribution curve 76 of the heating element surface temperature shown in FIG. 17, especially in the vicinity of the temperature Tc, the part b, that is, the central part of the heating resistor is formed. The temperature peak becomes sharper than before, and the temperature peak has a tendency to approach the conventional sharpness as the temperature becomes higher than Tc. The use of the method brings about improvement in reproducibility of a low-density (small-area) gradation region which has been difficult in the past. It is also suitable for the generation of bubbles of liquid ink that requires an instantaneous high temperature locally like thermal ink jet.

Seventh Embodiment The above is an embodiment in which the heating temperature of the recording medium such as the thermosensitive recording paper, the ink donor sheet transferred to the recording medium, and the heating temperature of the heating resistor for applying heat to the liquid ink are uniformly controlled. However, 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. In the recording method, a laminated heat generating layer including a first resistive layer made of a normal heat generating resistive material such as a carbon paint and a second resistive layer made of a material that undergoes a phase transition between a metal and a non-metal at a temperature Tc5 is formed. The recording can be made uniform by the uniform self-control of the intermediate heating temperature even if the method is used. An embodiment of the present invention in this energization heat recording will be described below.

FIG. 19 is a cross-sectional view of the energized thermosensitive recording apparatus. The energized thermosensitive recording paper 50 includes a color recording layer 51, the second phase change resistance layer 52, and the first normal resistance layer 53. The second resistance layer 52 has a metallic conductivity on the low temperature side of the specific temperature region,
This is a layer uniformly coated with a material mainly composed of a material that changes nonmetallicly on the high temperature side, or a layer formed by vapor deposition or the like. Specific temperature range causing the above-mentioned change in electric conductivity
Tc5 should give a difference depending on the recording device such as high-speed recording type, low power consumption type, gradation recording type, etc.
The temperature is preferably from about 150C to about 150C. Above thermal recording paper 50
However, while being sandwiched between the platen 66 and the current supply head 60, a voltage pulse is applied between the current supply electrode 61 and the return electrode 62 to cause the first and second resistance layers 52 and 53 to generate heat. When the laminated heating layer reaches the temperature Tc5, the resistance value of the second resistance layer 53 rises rapidly and hardly contributes to heat generation, and the second resistance layer 53 gradually develops color due to heat generation by the first resistance layer 52. Layer 51
And the color is developed.

Eighth Embodiment FIG. 20 mainly shows a heat-fusible ink layer 56, a conductive layer 54, and a material whose electric conductivity changes metallically on the low temperature side of the specific temperature Tc6 and non-metallicly on the high temperature side. The second made of the ingredient material
FIG. 5 is a cross-sectional view of an energization transfer ink donor sheet provided with a mixed heat generation resistance layer 55 in which resistance particles 58 having a normal resistance characteristic such as carbon particles are dispersed.
FIG. 21 is a cross-sectional view of an energization recording apparatus using this ink donor sheet.The current between the energization electrode 61 of the energization head and the return electrode 65 provided at a location separated from the energization head is the same as that described above. In the mixed heating resistance layer 55 of the ink donor sheet, the flow mainly flows in the depth direction of this layer. The second resistance particles 58 and the first resistance particles 57 that undergo the phase transition form a parallel circuit between the current-carrying electrode 61 and the conductive layer 54, and both contribute to heat generation at or below the specific temperature Tc6. However, above Tc6, the second resistance particles hardly contribute to heat generation.

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

In the embodiment using a material layer (or particles) and a normal resistance layer (or particles) that make a metal-to-metal transition in the heat-generating resistance layers in FIGS. 19 and 21, the first embodiment in the second embodiment described above is used. As in the case of thermal recording using a thermal head provided with a second resistor, the heating resistor layer is provided with an energizing voltage, an energizing time, a temperature of the energizing head, and an energizing thermal paper including the heating resistor layer before energization. Temperature (Tc5 or Tc6) when power is supplied, regardless of the temperature of the platen, the environmental temperature, etc.
The temperature rises quickly, followed by a gradual rise in temperature. Therefore, the exothermic peak temperature depends on the specific temperature (Tc5 or Tc5).
It is easy to realize stable temperature based on 6), and it is possible to realize uniform thermal recording with almost no need for conventional thermal control.

Next, examples of the method of driving heat generation in all the above-described embodiments will be described.

FIG. 23 shows a waveform 41 of a current flowing through the heating resistor and the heating resistor layer when a voltage pulse such as 52 is applied to the heating resistor and the heating resistor layer. When the temperature of the heating resistor before energization is equal to or lower than Tc (or Tc2), for example, the resistance value of the second resistor in the second embodiment is low, and the resistance value of the heating resistor is the first resistor. The resistance is the parallel resistance of the body and the resistance in the second low state, and more current flows. This state continues until time tp when the second resistor reaches the temperature region of Tc2 at which the second resistor transitions to the high-temperature phase. After this time, the current value decreases as the resistance value of the second resistor increases. State, and this state continues until the end of the energizing pulse. With constant voltage drive, if the heating element resistance is about 500Ω before tp and 2000Ω after tp, the current value is t
It decreases to 1/4 after p. Strictly speaking, the resistance value of the first resistor has some temperature dependence, and a general cermet resistor has a resistance temperature coefficient of −hundreds ppm / ° C.,
In addition, the second resistor also has a slight temperature dependence of the resistance value even in a temperature range away from the phase transition temperature range in which the resistance value greatly changes. Even in the subsequent pulse application time period, there is a slight change in the current value. The current value is also affected by the L and C components of the heating resistor circuit. However, these effects on the current value are compared with the current value change near the time tp,
Very little.

By the way, in each type of thermal recording apparatus, a recorded image is generally expressed by a plurality of dots. For example, in the case of a thermal head, a large number of minute heating resistors are provided, and each heating resistor expresses the dots. Since the power supply device provided in the recording device cannot be unnecessarily increased,
Generally, the plurality of heating resistors are divided into a plurality of blocks, and a time-sharing drive of applying an energizing pulse to each of the blocks is performed to reduce the maximum power in recording, that is, the maximum current. . In the recording method of the present invention, since a large current change occurs within a one-dot energizing pulse, the current capacity is reduced even if the divided driving without overlapping the driving times of the respective blocks as shown in FIG. 22 is performed. Waste occurs. However, as shown in FIG. 24, when the time shift amount of the driving of each block is taken from the time of ton to tp in FIG. 23 and the number of heating resistors in one block is set to be small, Fluctuations in the current supplied by the power supply are reduced, and the total current can be suppressed.

FIG. 24 is an example of a timing chart showing the application timing of the pulse 46-i to each block and the current waveform 45-i of the corresponding block in the block division drive based on the above concept. The shift time of the division drive is dt. The peak current portion of the Nth block (see FIG. 23)
The portion corresponding to 44) overlaps the small current portion of the (N-1) th block (the portion corresponding to 43 in FIG. 23),
The peak current portion of one block also overlaps with the small current portion of another block. As described above, the time from ton, which is the peak current portion, to tp slightly varies depending on the initial temperature of the heating resistor concerned, and becomes longer as the initial temperature becomes lower. This is because it takes time for the heating resistor to rise to the temperature Tc as the temperature rises from a low temperature. Momentarily, the ton between the blocks
It is desirable from the viewpoint of power efficiency that the time from to tp does not overlap.
That is, the divided drive of the block may be performed at a timing when dt is set slightly longer than the time from to tp. Further, the temperature around the heating resistor or the heating resistor layer may be sensed, and the dt may be changed according to this temperature. 24th
Driving as shown in the figure, when using a power supply of the same power supply capacity, compared to driving at the timing as shown in FIG. 22,
Driving of all blocks can be completed in a short time,
Useful for faster recording.

As described above, when the division driving is performed by the time shift of dt which is sufficiently shorter than the applied pulse width (time from ton to toff), besides the efficiency of the power supply, as described below, There is an advantage in the fidelity of the record.

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 the thermosensitive recording paper in a direction perpendicular to the heating resistor array. In the case of recording a straight line having a line width of one dot, if the shift time dt of the block division is not so long that the distance of the line width of one dot is not negligible compared to the relative movement time of the thermal recording paper, The straight line becomes a step-like line corresponding to the block position. However,
In the above-described driving method in which dt is shortened and the number of divisions is increased, the step-like step becomes small corresponding to the short dt, and can be expressed as a straight line with no noticeable step. Therefore, this is a very useful method for use as a plotter in drawings.

By the way, the above series of non-metals (or insulators,
(Semiconductor) As a substance that undergoes a transition, there is a vanadium oxide-based compound. By doping a small amount of Cr into vanadium oxide, a nonmetallic (or insulator, semiconducting) change in electrical conductivity occurs in a region above room temperature. It has non-metallic (or insulating, semiconducting) conductivity at higher temperatures and metallic conductivity at lower temperatures. Both vanadium and vanadium oxide are high-melting substances and can be used as heating resistors. The heat-generating resistive film can be formed by a thin film process such as sputtering or the like, and can be formed into a paste by forming a powder and mixing a binder or the like, or can be formed by a thick film process such as coating by forming an organic metal. In the eighth embodiment (embodiment in energization thermal recording), particles having a uniform particle size approximately equal to the thickness of the heat generating resistance layer are used. In any case, the vanadium oxide component formed and sized must have at least a polycrystalline structure. In the case of sputtering, an alloy target of metal vanadium and chromium, or a metal vanadium target in which chromium is embedded is sputtered using argon and oxygen gas, and a target obtained by sintering vanadium oxide powder and chromium oxide powder is treated with argon gas. Alternatively, there is a method in which a small amount of oxygen is mixed with argon gas to perform high-frequency sputtering. In any of the sputtering methods, the temperature of the deposited portion is preferably several hundred degrees Celsius or more to ensure a more crystalline state. However, there is a method of increasing the crystallinity by laser irradiation or vacuum annealing heat treatment after film formation.

When doped with a suitable amount of Cr, the electrical conductivity changes by two to three orders of magnitude at the above transition temperature. Therefore, when used as a heating resistor or a heating resistor layer of a current-carrying thermosensitive paper, when a constant voltage is applied, the electrical conductivity changes above and below the transition temperature. 2-3 power consumption values
It changes by an order of magnitude and is accompanied by a substantial change in heat generation and non-heat generation from the viewpoint of thermal recording. Therefore, if ordinary resistors such as tantalum nitride and cermet are incorporated in parallel, the heating resistors of the above-described series of embodiments can be realized. By changing the proportion of Cr doped in the vanadium oxide, the transition temperature can be changed, and the temperature of the series of intermediate temperatures Tc can be set. In the case of vanadium oxide not doped with Cr, the rate of change in the resistance value is small and changes gradually with temperature, but the resistance value increases by almost one digit from the low temperature side to the high temperature side at about 400 ° C. It can be used for a heating resistor having a single material configuration as in the first embodiment of the present invention, or can be used as a heating resistor material combined with a normal resistor material. For example, in the above-described second embodiment, the first resistor and the second resistor are provided as separate layers as the resistive film.
If a phase change material such as vanadium oxide can maintain the 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 that of the above-described first embodiment is obtained, and processing simplification such as film formation and patterning of the heating resistor can be achieved.

FIG. 25 is a diagram showing the temperature change of the line resistance of the heating resistor having the metal-to-metal transition in the first embodiment. The line resistance itself is a reference value because it changes depending on the film thickness and the line width. However, in the case of vanadium oxide doped with about 0.5% of Cr with respect to vanadium, as shown in the line resistance characteristic curve 31, about three digits at about 150 ° C. There is a change in the resistance value. The temperature range where the resistance value changes depending on the doping amount of Cr changes,
As the Cr doping amount is increased, the temperature range of the change in the resistance value gradually shifts to a lower temperature side. If the doping amount of Cr with respect to vanadium exceeds several percent, the change in the increase in the resistance value from the low-temperature side to the high-temperature side disappears, so that the object of the present invention is hardly achieved. As described above, since the doping amount of Cr changes the temperature characteristic of the resistance change, the change in the line resistance is caused by, for example, FIG. 25 due to the microscopic nonuniformity of the doping amount of Cr with respect to vanadium oxide in the sample. It can be gentle with a certain temperature range, like the curve of 32. The object of the present invention can be achieved even with such a gentle change. In addition, for example, when trying to raise the temperature by energizing a heating resistor having a side of 0.1 mm, since the temperature does not uniformly increase in the heating resistor, the above-described heating resistor of the thermal head may be used. When a substance is used, the change in the resistance value as the heating resistor is apparently gentle as shown in FIG. 25, but in this case, the temperature rises quickly up to the intermediate temperature Tc in microscopic terms. At temperatures above Tc, a gradual temperature rise occurs. Therefore, the slow-rising portion continues to heat more quickly, and the fast-heating portion quickly transitions to a gentle heating state,
It has a function of correcting the temperature distribution in the heating resistor in a more uniform direction, and has an advantage of realizing recording with higher recording dot fidelity as compared with a conventional thermal recording method or the like.

In all the above-described embodiments, the intermediate temperature (Tc) at which the heating rate changes during the heating and heating process of the heating resistor is such that the recording medium such as thermal paper, which is a heat absorbing source, is in contact with the heating resistor. It does not change even if it is not in contact, or because it changes more slowly above the intermediate temperature,
Deterioration and destruction of the heating resistor due to an abnormal rise in the peak heating temperature of the heating resistor in the thermal head in the conventional thermal recording in the non-feeding state are unlikely to occur in the heating resistor in the recording method of the present invention. It demonstrates high reliability against malfunctions and runaway of the drive control circuit and CPU.

The above is common to energization heat recording, because there is little danger of abnormal heat generation, ignition, or destruction of equipment parts such as a platen due to circuit runaway, etc., and the reliability and safety of the equipment are increased. The effect is.

In all the above-described embodiments, the resistance characteristics of the heating resistor, the heating resistor layer, and the like do not necessarily require that the electrical conductivity change discontinuously at a particular temperature, and have a particular width. The temperature may be changed continuously in the temperature range. The effect of the present invention is sufficient if the change in the resistance value of the heating resistor is about 1.5 to 10 times. The amount of change is determined by a resistance value at which a temperature rise due to heat generation reaches a temperature required for recording under the condition of applying a constant voltage, and a power consumption (energy) at a temperature level related to recording. )) Means a realistic ratio of resistance values of at least a magnitude that maintains the temperature of the heating resistor or the heating resistor layer.

〔The invention's effect〕

As described above, according to the present invention, it is possible to control the temperature more uniformly and with higher reproducibility than before, and to achieve uniform High-quality recording with high recording performance Variations in recording characteristics can be suppressed even with variations in the thermal characteristics of the recording elements. Recording characteristics can also be achieved with variations in the resistance of the heating resistor and the sheet resistance of the heating resistor layer. High-precision density gradation control and halftone gradation control are easy. Temperature information collection circuit such as temperature detection in recording equipment and recording density correction circuit are simple, and equipment is provided in small size and low cost. Highly reliable and safer with respect to runaway resistance of the heating resistor, etc.Excellent effects such as the fact that the heating temperature distribution is faithful to the shape of the heating element and the recording quality is excellent. Demonstrate .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a thermal head according to a first embodiment of the present invention, FIG. 2 is a sectional view of a heating resistor of the thermal head of FIG. 1, and FIG. FIG. 4 is a plan view of a heating resistor according to a second embodiment of the present invention, and FIGS. 4 and 5 are sectional views taken along lines AA 'and BB' of FIG. FIG. 7 is a plan view of a heating resistor according to a fifth embodiment of the present invention, and FIG. 7 is a cross-sectional view of the heating resistor CC 'of FIG.
FIG. 8 is a plan view of a heating resistor according to a sixth embodiment of the present invention, and FIG.
FIG. 10 is a sectional view showing a change in the surface temperature of the heating resistor according to the embodiment of the present invention.
FIG. 14 is a diagram showing a change in the surface temperature of the heating resistor in the embodiment of the present invention with continuous heat generation. FIGS. 15 and 16 are diagrams showing the surface temperature of the heating resistor in the embodiment of the present invention. FIG. 17 and FIG. 18 are diagrams showing the distribution of the surface temperature of the heating resistor according to the embodiment of the present invention, and FIG. 19 is a diagram showing the seventh embodiment of the present invention. FIG. 20 is a cross-sectional view of an ink donor sheet for energized thermal transfer according to an eighth embodiment of the present invention.
FIG. 21 is a sectional view of a main part of an energization thermal transfer recording apparatus according to an eighth embodiment of the present invention, and FIGS. 22 and 24 show drive timings and current waveforms of the heating resistors in the embodiment of the present invention. FIG. 23 is a timing chart showing a driving current waveform of the heating resistor according to the embodiment of the present invention, and FIG. 25 shows a resistance value characteristic of the resistor constituting the heating resistor according to the embodiment of the present invention. FIG. 1. Heating resistor 7,10 First resistor 8,11 Second resistor 2. Individual electrode 3,5 Common electrode 4. Switching element 18-N, 20-N ...... Heating resistor surface temperature 19-N, 21-N ... gradation energizing pulse 31, 32 ... resistor resistance value characteristic 41, 45, 47 ... current waveform 42, 46, 48 ... energizing pulse 50 ... energized 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 Resistive particles 58… Second resistive particles 60… Current-carrying head 61… Current-carrying electrodes Tc, Tc1, Tc2… Phase transition temperature of resistor Te… Equilibrium temperature of heat-generating resistor ton… Time of current pulse application toff …… Electrification pulse application end time tp …… Tc arrival time dt …… Drive shift time

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-2-117854 (JP, A) JP-A-2-34361 (JP, A) JP-A-59-167278 (JP, A) JP-A-62- 105645 (JP, A) JP-A-3-130162 (JP, A) JP-A-3-218857 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B41J 2/355 B41J 2 / 335 B41J 2/345

Claims (3)

(57) [Claims] 1. A thermal recording method in which a voltage pulse is applied to a heating resistor (1) to generate heat, and recording is performed on a recording medium by directly or indirectly utilizing a temperature rise of the heating resistor due to the heat generation. The heating resistor includes a first resistor (7) made of a normal heating resistor material such as tantalum nitride or cermet, and a second resistor (7) made of a film pattern that undergoes a metal-metal phase transition at a specific temperature (Tc2). 8), and the second resistor (8) is connected to the individual electrode (2) in parallel with the first resistor (7).
And a common electrode (3), and the heating resistor has a lower resistance value in a lower temperature region than the temperature region and a higher resistance value in a high temperature region with a specific temperature region (Tc) as a boundary. A portion having a characteristic that changes substantially in a stepwise manner, when the temperature of the portion of the heating resistor before voltage application is equal to or lower than the specific temperature region (Tc), a one-voltage pulse is applied to the heating resistor. By applying a current and applying a current, the temperature of the portion of the heating resistor is sharply increased by a larger power consumption from the temperature of the heating resistor before voltage application to the specific temperature region (Tc), After the temperature reaches the specific temperature region (Tc) within one voltage pulse, until the voltage application is completed, the temperature of the portion of the heating resistor is gradually increased or maintained by lower power consumption, and recording is performed. Row Thermal recording method characterized by. 2. A thermal recording method in which a voltage pulse is applied to a heating resistor (1) to generate heat, and recording is performed on a recording medium by directly or indirectly utilizing a temperature rise of the heating resistor due to the heat generation. The heating resistor is composed of a first resistor (10) made of a normal heating resistor material such as tantalum nitride or cermet, and a second resistor made of a film pattern that undergoes a metal-metal phase transition at a specific temperature (Tc2). (11), the planar shape of the first resistor (10) matches the outer shape of the heating resistor (1), and the second resistor (11) is located at the center of the heating resistor (1). The second resistor (11) is formed at both ends (a) in such a manner that a slit (b) is opened in the portion and laminated on the first resistor (10).
Is connected between the individual electrode (2) and the common electrode (3) in parallel with the first resistor (10), and this heating resistor is connected to a specific temperature region (Tc). By providing a portion having a characteristic that changes in a step-like manner to a lower resistance value in a lower temperature region than a temperature region and a higher resistance value in a high temperature region, the temperature of the portion of the heating resistor before voltage application is specified. When the temperature is equal to or lower than the temperature range (Tc), one voltage pulse is applied to the heating resistor to energize the heating resistor, so that a larger power is applied from the temperature of the heating resistor before voltage application to the specific temperature range (Tc). The consumption causes the temperature of the portion of the heating resistor to rise steeply. After the temperature reaches the specific temperature range (Tc) within the one voltage pulse, heat is generated by lower power consumption until the voltage application is completed. Of said part of the resistor Thermal recording method and performing recording by Ya Kana temperature increase or to perform the temperature maintained. 3. A thermal recording method in which a voltage pulse is applied to a heating resistor (1) to generate heat, and recording is performed on a recording medium by directly or indirectly utilizing a temperature rise of the heating resistor due to the heat generation. The heating resistor is composed of a first resistor (10) made of a normal heating resistor material such as tantalum nitride or cermet, and a second resistor made of a film pattern that undergoes a metal-metal phase transition at a specific temperature (Tc2). (11), the planar shape of the first resistor (10) matches the outer shape of the heating resistor (1), and the second resistor (11) is located at the center of the heating resistor (1). Part (b)
The second resistor (11) is formed in parallel with the first resistor (10) in parallel with the individual electrode (2) and the common electrode (3). ), And the heating resistor has a specific temperature region (Tc) as a boundary, and has a lower resistance value in a lower temperature region and a higher resistance value in a high temperature region in a stepwise manner. By providing a portion having a changing characteristic, when the temperature of the portion of the heating resistor before voltage application is equal to or lower than the specific temperature region (Tc), one voltage pulse is applied to the heating resistor to energize. Thereby, from the temperature before the voltage application of the heating resistor to the specific temperature region (Tc), the temperature of the portion of the heating resistor is sharply increased by larger power consumption, and the temperature is increased within the one voltage pulse. After the temperature reaches the specific temperature range (Tc), voltage application is completed. A thermal recording method characterized in that the recording is performed by gradually increasing or maintaining the temperature of the portion of the heating resistor with less power consumption until the recording is completed.