JP2004017572A - Thermal head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal head that can make a heating distribution uniform by suppressing warpage of a substrate 2 in the thermal head having a heating section on the surface of the substrate 2 supported by a supporting member 3. <P>SOLUTION: The thermal deformation ratios of the substrate 2 and the support member 3 are substantially the same. A thermal deformation suppressing member 4 is provided on the support member 3. The thermal deformation suppressing member 4 is in a plate shape of a material the same as that of the substrate 2. The support member 3 has a phenol resin as a main component. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a thermal head used for erasing characters printed on a rewritable card.
[0002]
[Prior art]
Japanese Patent Application Laid-Open No. H11-138881 discloses a thermal head having a heat generating portion on a substrate surface and supporting the substrate by a support member. Referring to FIG. 6, first, a thick-film resistor (heating element) is formed on the surface of the alumina ceramic substrate 11 by a method such as screen printing, and then the ceramic substrate 11 is formed by a resin base material 21 (support member). Is supported. When a current is applied to the electrode connected to the resistor through the lead wire 30 further connected to the resistor, the resistor generates heat.
[0003]
[Problems to be solved by the invention]
When the above-mentioned conventional thermal head is used for erasing characters printed on a rewritable card, the process of raising the temperature from room temperature to 90 to 100 ° C. in a few seconds and then returning to near room temperature many times is repeated many times. Will repeat. Then, the resin base material 21 serving as a support member undergoes a deformation considered to be caused by its own condensation reaction, heat shrinkage, and the like, and the substrate 11 supported by the support material increases with an increase in the number of uses and a lapse of the use period. There was a problem of warping.
[0004]
Then, in the usage state of the thermal head, the distance between the resistor, which is a heating element, and the object to be heated becomes uneven, and the resulting uneven heating distribution occurs. Such non-uniformity causes problems such as, for example, unerasing characters on the rewrite card.
Accordingly, an object of the present invention is to provide a thermal head capable of making the heating distribution uniform by suppressing the warpage of the substrate.
[0005]
[Means for Solving the Problems]
In order to solve the above problem, a first thermal head according to the present invention includes a heat generating portion 1 on a surface of a substrate 2 as shown in FIG. The thermal deformation ratio of the substrate 2 and that of the support member 3 are substantially equal.
[0006]
As in the first thermal head, if the thermal deformation rates of the substrate 2 and the support member 3 are substantially equal, both the substrate 2 and the support member 3 are similarly deformed even if heating and cooling are repeated. Therefore, one of the substrate 2 and the supporting member 3 hardly gives stress to the other, and the substrate 2 does not warp due to the stress. Accordingly, a thermal head having a uniform heating distribution can be provided, and the problem to be solved by the present invention can be solved.
[0007]
In the configuration example of the first thermal head, the substrate 2 and the support member 3 are made of the same material or a material that can be regarded as the same material. More specifically, the substrate 2 and the support member 3 may both be made of alumina, the substrate 2 may be made of alumina, and the support member 3 may be made of a composite material of phenol resin and alumina.
[0008]
Further, in order to solve the above problem, a second thermal head of the present invention has a heat generating portion 1 on the surface of a substrate 2 as shown in FIG. 1, and the substrate 2 is mounted on a supporting member 3 having a different thermal deformation rate. In the thermal head fixed in this manner, a thermal deformation suppressing member 4 is provided on the support member 3. Due to the deformation suppressing effect of the thermal deformation suppressing member 4, the thermal deformation of the support member 3 on which it is disposed is suppressed. Then, the application of stress to the substrate 2 due to the deformation of the support member 3 is reduced, the warpage of the substrate 2 can be prevented, and the heating distribution of the thermal head can be made uniform.
[0009]
The thermal deformation suppressing member 4 referred to here is one that is integrated with another thermal head constituent member, one that is a completely separate member, one that has the function of another thermal head constituent member, Includes all that have only the suppression function. For example, it includes a member in which the thermal deformation suppressing member 4 is embedded in the support member 3 and a member in which the supporting member 3 and the thermal deformation suppressing member 4 are integrally formed in a layer shape or the like.
[0010]
Further, the support member 3 includes a member mainly containing a conventionally used phenolic resin. Similarly, a substrate 2 made of a ceramic material such as alumina conventionally used can be used. By disposing the thermal deformation suppressing member 4 on the support member 3, it is possible to suppress the warpage of the substrate 2 due to the warpage of the support member 3 itself due to the thermal deformation of the support member 3.
[0011]
The use of a material mainly composed of a phenolic resin as the support member 3 has the advantage that the strength of the entire thermal head can be ensured high due to its rigidity. In addition, when a phenolic resin is used as a constituent material of a material exposed to a high-temperature environment such as a thermal head, it is advantageous in that it is not necessary to consider its deterioration due to its high heat resistance.
[0012]
The thermal deformation suppressing member 4 has, for example, a plate shape. It is fixed to the support member 3 with an adhesive or the like. As the adhesive, it is preferable to use a silicone adhesive from the viewpoint of excellent heat resistance. This point is an important factor when selecting a material that constitutes an object exposed to a high-temperature environment such as a thermal head. Further, by making the thermal deformation suppressing member 4 in a plate shape, the handleability is improved, which is advantageous in manufacturing a thermal head. An advantage of the handling property here is that, for example, stacking is possible, so that an excessive storage space is not required. Further, since the thermal deformation suppressing member 4 has a plate shape, there is an advantage that the outer dimensions are not largely changed when the thermal deformation suppressing member 4 is arranged on the outer surface of the supporting member 3. The thermal deformation suppressing member 4 is a member which has not been conventionally provided, and in many cases, a thermal head manufacturing process must be newly added. In this case, if the support member 3 has a flat portion, it is easy to attach the support member 3 to the flat portion, and there is an advantage that the work load can be reduced.
[0013]
Further, it is preferable that the thermal deformation suppressing member 4 is made of substantially the same raw material as the material of the substrate 2. For example, when alumina is used for the substrate 2, alumina is also used for the thermal deformation suppressing member 4. This is advantageous in terms of convenience of sorting work when disposing of the used thermal head. From the viewpoint of obtaining this advantageous effect, the above-mentioned “substantially the same raw material” is used even when different aluminas having different types and amounts of additives are used. In addition, if the shape is the same as that of the raw material or if the shape can be easily processed from the same shape, it is advantageous in that the number of manufactured parts is not increased. Here, the simple processing is, for example, processing of dividing and grinding a part of the shape, drilling, chamfering, or the like.
[0014]
Further, it is preferable that the thermal deformation suppressing member 4 is disposed at a position facing the substrate 2 with the supporting member 3 interposed therebetween (FIGS. 1 and 3). When the thermal deformation suppressing member 4 is brought into contact with or near the substrate 2, the heating element 1 such as a resistor is disposed on the substrate 2. This is because it may be caused. Further, in order to suppress the warpage of the substrate 2, it is considered preferable to dispose the thermal deformation suppressing member 4 in a position and a direction that can be regarded as increasing the thickness of the substrate 2. Further, in order to suppress the deformation of the bottom surface of the support member 3 as shown in FIG. 2B, it is considered that fixing the bottom surface with the thermal deformation suppressing member 4 is more effective.
[0015]
Of course, even if the thermal deformation suppressing member 4 is disposed on the side surface of the support member 3, the present invention can solve the problem. By suppressing the warpage of the substrate 2, uniform heating distribution of the thermal head can be realized. . However, in order to make the effect equivalent to the case where the thermal deformation suppressing member 4 is arranged at a position facing the substrate 2 with the supporting member 3 interposed therebetween, it is considered preferable to arrange at least two thermal deformation suppressing members 4. .
[0016]
That is, as shown in FIGS. 1 and 3, the side surface of the support member 3 has two sets of long sides and two sets of short sides. Needless to say, even if the thermal deformation suppressing member 4 is arranged only on one long side, the problem to be solved by the present invention can be solved. However, in this case, a very slight deformation will occur on the long side of the support member 3 on the side where the heat deformation member 4 is not disposed, and will cause a very slight disturbance in the shape balance of the entire thermal head. Therefore, in order to further prevent the disturbance and the deformation of the support member 3 and the substrate 2, it is preferable to dispose the thermal deformation suppressing member 4 on each of the two long sides. As shown in FIGS. 1 and 3, when one thermal deformation suppressing member 4 is provided on the bottom surface of the support member 3, the present invention can be realized without causing a very slight disturbance in the shape balance of the entire thermal head. It is advantageous in that the problem to be solved can be solved and the number of parts is not increased.
[0017]
In the thermal head shown in FIGS. 1 and 3, the thermal deformation suppressing member 4 is provided on at least one surface of the support member 3 (whether external or internal) other than the substrate 2. If so, the problem to be solved by the present invention can be solved.
[0018]
The reason why the second thermal head of the present invention can suppress the warpage of the substrate 2 will be described with a specific example with reference to the drawings. The support member 3 shown in FIG. 2 is a phenolic resin having an outer shape in the form of a boat, and its opening edge and the outer peripheral end of the substrate 2 are fixed to each other by, for example, an adhesive as shown in FIG. Is configured. Here, when the support member 3 is exposed to a high-temperature environment, which is the environment in which the thermal head is used, the support member 3 undergoes deformation considered to be caused by heat shrinkage, condensation reaction, and the like. For example, FIG. 2A shows a state before exposing the support member 3 to a high-temperature environment, and FIG. 2B shows a state after exposing the support member 3 to a high-temperature environment. Therefore, the substrate 2 fixed to the support member 3 is deformed, that is, warped under the influence of the deformation of the support member 3. Therefore, as shown in FIG. 1, the deformation of the support member 3 is suppressed by disposing the thermal deformation suppressing member 4 on the support member 3, in other words, the support member 3 is corrected, and as a result, the warpage of the substrate 2 is reduced. It can be suppressed.
[0019]
Here, how to fix the thermal deformation suppressing member 4 and the support member 3 will be described. As the fixing member, an adhesive is preferable. This is because, when the thermal deformation suppressing member 4 and the support member 3 are bound, engaged, or fitted together, there is a possibility that they leave room for mutual movement and the correction is insufficient. This is because in order to correct the deformation of the substrate 2 or the support member 3, it is considered that strong mutual contact may be required. Since the adhesive is a member constituting the thermal head, it is needless to say that the adhesive has higher temperature resistance. In this regard, it is preferable to use a silicone-based adhesive that has been conventionally fixed to the substrate 2 and the support member 3 and has a high temperature resistance. However, an epoxy adhesive, a phenol adhesive, and the like are also suitable. Most preferably, the adhesive is provided over the entire contact surface between the thermal deformation suppressing member 4 and the support member 3. This is because the adhesion becomes higher. However, when a certain adhesion strength is sufficient, the amount of the adhesive required to maintain the sufficient strength and the arrangement state thereof are sufficient.
[0020]
In the case illustrated in FIG. 2, the thermal deformation suppressing member 4 is, for example, an alumina plate made of the same material as the substrate 2. Alumina is less likely to be thermally deformed than phenolic resins. Therefore, as shown in FIG. 3, the thermal deformation suppressing member 4 made of an alumina plate is fixed to the support member 3 made of phenolic resin, and the substrate 2 is further fixed to the surface of the heat deformation suppressing member 4 on the opposite side. Then, the alumina plate suppresses the phenolic resin from trying to thermally expand, and the thermal expansion is hindered. Therefore, the deformation of the phenolic resin serving as the support member 3 is suppressed, and as a result, the warpage of the substrate 2 made of alumina can be suppressed.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
An example of an embodiment of the present invention will be described below with reference to the drawings.
As shown in FIG. 4, a large alumina plate having a thickness of 0.8 mm and having a large number of vertical and horizontal dividing grooves 15 is prepared. A conductive paste containing an Ag-Pd alloy powder and a glass frit is screen-printed and fired on the surface of each of the alumina plate through-holes near the periphery of the through-holes 14 to form the electrodes 9 (film thickness: 10 to 12 μm). Next, the conductive paste is screen-printed and fired so as to extend in the vicinity of the periphery of the back side of the through hole 14 on the back surface of the large-sized alumina plate and toward the center of the alumina plate surface, thereby forming the land 6. Thus, the electrodes 9 formed on the surface of the large alumina plate and the lands 6 formed on the back surface of the alumina plate are connected via the through holes 14. At this time, a land 6 'is formed simultaneously with the electrode 9 (land 6) on the back surface of the large alumina plate.
[0022]
Next, a resistor paste mainly composed of an Ag-Pd alloy powder is formed by screen printing and firing on the surface of a large alumina plate. At this time, the resistor 7 is formed such that both ends of the resistor 7 partially overlap the electrode 9 formed earlier. This resistor 7 becomes the heat generating portion 1.
[0023]
Thereafter, a paste containing lead borosilicate glass as a main component is screen-printed and fired on almost the entire surface of the resistor 9 except for the entire surface of the resistor 7 and a part of the electrode 9, thereby forming the resistor 7 film and the electrode 9 film. Protect with glass 8 film. Then, a thermistor (not shown) is mounted on the land 6 '.
[0024]
Thereafter, a stress is applied to the large alumina plate so as to open a division groove 15 formed in advance, and the alumina plate is divided into units that become the components of each thermal head. The length of the alumina plate after division, that is, the substrate 2 is 61 mm and the width is 6 mm.
[0025]
Next, the thermistor lead wire 5 and the land 6 'and the energizing lead wire 5 and the land 6 are connected. The connection is made by known spot welding.
[0026]
Next, as shown in FIGS. 1 and 3, the end of the substrate 2 and the support member 3 are fixed. A phenolic resin molding was used for the support member 3. Further, the whole shape of the supporting member 3 was a boat shape, and the end of the opening and the end of the substrate 2 were fixed (FIG. 1). A hole is formed in the center of the support member 3 at a portion corresponding to the bottom of the boat (FIG. 1), and the thermistor lead wire 5 and the energization lead wire 5 are provided outside the support member 3 as shown in FIG. Is derived. A silicone adhesive was used for the fixing.
[0027]
Further, a thermal deformation suppressing member 4 shown in FIG. 1 is fixed to the outside of the supporting member 3 corresponding to the bottom surface of the boat. Here, a hole is formed at the center of the thermal deformation suppressing member 4 like the bottom surface of the supporting member 3 (FIGS. 1 and 3), and the thermistor lead wire 5 and the conducting lead wire 5 are supported as shown in FIG. It is led out of the member 3. A silicone adhesive was also used for the fixing. An alumina plate having the same material and the same thickness as the substrate 2 was used for the thermal deformation suppressing member 4. However, in consideration of the convenience of attachment to the electronic / electric device, the length is slightly shortened (about 90%), and the thermal deformation suppressing members 4 are not arranged at both ends in the long side direction of the supporting member 3. Thus, the thermal head of the present invention was completed.
[0028]
The thermal head of the present invention is used for printing / erasing information on a thermoreversible information recording / display sheet (rewrite card) in which a low molecular composition as a thermoreversible recording layer is disposed on a polyethylene terephthalate film layer or the like. Used as a thermal head. Specifically, the temperature of the thermal head is raised from room temperature to 90 to 170 ° C. in several seconds, the temperature is maintained for several seconds, and then the temperature is lowered to room temperature in about one minute by natural cooling. Used in a mode that is repeated several times. The thermistor measures the heat generation temperature of the thermal head and sends the information to an external control device via the thermistor lead wire 5. The current-carrying lead wire 5 is for sending a current from an external power supply to the thermal head. The information is used to determine the timing of stopping current transmission from an external power supply via the control device.
[0029]
(Experiment)
When a heating experiment was conducted in which the thermal head of the present invention was kept at 150 ° C. for 100 hours from an unused state, almost no deflection of the substrate 2 was observed. However, when the same heating experiment was performed under the condition that the thermal deformation suppressing member 4 was removed, the bending amount of the substrate 2 was 50 to 60 μm (n = 20). In the former character erase experiment of the rewrite card using the thermal head of the present invention, no unerased characters were observed.On the other hand, the same character erase experiment was performed using the latter thermal head. Many were observed for the rest. This has confirmed the effectiveness of the present invention.
[0030]
(Other Embodiment 1)
The support member 3 is previously subjected to a heat treatment to modify at least its surface so that a condensation / polymerization reaction hardly occurs. Otherwise, a thermal head is manufactured under the same conditions as in the above embodiment. As a result, thermal deformation is less likely to occur as in the case of the substrate 2 made of alumina, and as a result, it is possible to provide the thermal head of the present invention that can suppress the warpage of the substrate 2. The thermal head corresponds to the above-described first thermal head of the present invention.
[0031]
(Other Embodiment 2)
The thermal deformation suppressing member 4 shown in FIG. 1 was arranged on the inner bottom surface of the support member. Otherwise, a thermal head is manufactured under the same conditions as in the above embodiment. This has the advantage that the external dimensions of the thermal head can be maintained at the conventional level.
[0032]
(Other Embodiment 3)
The thermal deformation suppressing member 4 shown in FIG. 1 is disposed on a side surface of the support member 3 (regardless of whether the member is inside or outside the support member 3). Otherwise, a thermal head is manufactured under the same conditions as in the above embodiment. If necessary, as shown in FIG. 1, the thermal deformation suppressing member 4 is also arranged on the bottom surface of the support member 3 (regardless of whether it is inside or outside the support member 3).
[0033]
(Other Embodiment 4)
The support member 3 shown in FIG. 1 is formed in a boat shape from which a bottom portion is omitted. Further, the thermal deformation suppressing member 4 is disposed on the bottom surface of the supporting member as in FIG. Otherwise, a thermal head is manufactured under the same conditions as in the above embodiment (FIG. 5). This has the advantage that the external dimensions of the thermal head can be kept below the conventional level, and that the shape of the support member 3 is simple, so that its formability is good and that the bottom surface of the support member 3 does not shrink thermally. Therefore, there is an advantage that suppression of deformation of the substrate 2 and the support member 3 can be expected as a whole.
[0034]
(Other Embodiment 5)
In the fourth embodiment, the thermal deformation suppressing member 4 is omitted. As described above, by forming the support member 3 in a frame shape, the entire amount of thermal deformation is reduced, and this embodiment corresponds to the first thermal head of the present invention.
[0035]
【The invention's effect】
According to the present invention, it is possible to provide a thermal head capable of making the heating distribution uniform by suppressing the warpage of the substrate 2.
[Brief description of the drawings]
FIG. 1 is a sectional view showing an outline of a thermal head according to an embodiment of the present invention.
FIG. 2 is a diagram for explaining how a support member according to the present invention is deformed.
FIG. 3 is a perspective view showing an outline of a thermal head according to the embodiment of the present invention.
FIG. 4 is a diagram illustrating an outline of manufacturing the thermal head according to the embodiment of the present invention.
FIG. 5 is a diagram illustrating an outline of a manufacturing process of a thermal head according to another embodiment of the present invention.
FIG. 6 is a sectional view showing an outline of a thermal head according to a conventional embodiment.
[Explanation of symbols]
1. Heating part 2. Substrate 3. Support member 4. Thermal deformation suppressing member5. Lead wire6. Land 6 '. Land 7. Resistor 8. Glass 9. Electrode 11. Ceramic substrate 14. Through hole 15. Groove for division 20. Ceramic substrate 21. Substrate 30. Lead

Claims (7)

In a thermal head having a heat generating portion on the substrate surface and the substrate being supported by a support member,
A thermal head, wherein the substrate and the support member have substantially equal thermal deformation rates. In a thermal head having a heat generating portion on the substrate surface and the substrate being fixed by a support member having a different thermal deformation rate,
A thermal head, wherein a thermal deformation suppressing member is provided on the support member. 3. The thermal head according to claim 2, wherein the substrate is made of a ceramic material, and the support member is mainly composed of a phenolic resin. 4. The thermal head according to claim 2, wherein the thermal deformation suppressing member has a plate shape. The thermal head according to any one of claims 2 to 4, wherein the thermal deformation suppressing member is fixed to the supporting member with an adhesive. The thermal head according to any one of claims 2 to 5, wherein the thermal deformation suppressing member is made of substantially the same material as the substrate material. 7. The thermal head according to claim 2, wherein the thermal deformation suppressing member is disposed at a position facing the substrate with the supporting member interposed therebetween.

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