JP2004230582A - Thermal head and thermal printer employing it, and process for manufacturing thermal head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly reliable thermal head capable of forming a good print by stabilizing the carrying state of a recording medium. <P>SOLUTION: A plurality of heating resistors 3 and a plurality of driver ICs 6 for controlling heat generation of the heating resistors 3 are arranged substantially in parallel on the upper surface of a substrate 1 and the driver ICs 6 are coated commonly with a stripe sealing material 7. In such a thermal head, a stripe overcoat layer 8 of fluororesin is applied along the longitudinal direction of the sealing material at least on the side closer to the heating resistors 3 than the sealing material 7. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a thermal head used as a printing device such as a facsimile or a video printer, and a thermal printer using the same.
[0002]
[Prior art]
Conventionally, a thermal head has been used as a printing device such as a facsimile or a video printer.
[0003]
In such a conventional thermal head, as shown in FIG. 6, for example, a plurality of heating resistors 23 and a plurality of driver ICs 26 for controlling the heating of these heating resistors 23 are formed on an upper surface of a substrate 21 made of alumina ceramics or the like. The heating resistor 23 is covered with a protective film 25 made of silicon nitride or the like, and the driver IC 26 is covered with a sealing material 27 mainly composed of epoxy resin. A plurality of heating resistors 23 are converted into image data while a recording medium such as a thermal paper or an ink film is conveyed onto the heating resistors 23 while being in sliding contact with the surface of the protective film using a platen roller disposed directly above the heating resistors 23. Joule heat is generated selectively on the basis of each of these, and the generated heat is transmitted to the recording medium via the protective film 25 to form a print. It has become.
[0004]
The sealing material 27 covers the driver IC 26 to shield the driver IC 26 from the atmosphere, and at the time of recording operation, supports the conveyance of the recording medium on the surface on the side of the heating resistor 23 to generate heat. It functions as a guide member for guiding on the resistor 23. A liquid precursor such as an epoxy resin is applied over the arrangement region of the driver ICs 26 by a dispenser or a screen printing method, and is thermally cured at a predetermined temperature. Formed by
[0005]
[Patent Document 1]
JP-A-11-78093 [Patent Document 2]
JP-A-8-281990 [Patent Document 3]
JP-A-7-186428 [0006]
[Problems to be solved by the invention]
However, in the above-described conventional thermal head, when the sealing material 27 is formed, when a liquid precursor of the epoxy resin is applied to the array region of the driver ICs 26, the precursor is moved in the sub-scanning direction (the longitudinal direction of the sealing material). (In the direction perpendicular to the direction perpendicular to the vertical direction), and the corner of the upper surface of the driver IC 26 may be exposed from the surface of the sealing material 27. Therefore, during the recording operation, if the recording medium is conveyed while being in sliding contact with the surface of the encapsulant on the side of the heating resistor, there is a possibility that the recording medium comes into contact with the exposed portion and the recording medium is damaged.
[0007]
In addition, since the degree of spread of the precursor in the sub-scanning direction varies depending on the region, the height of the surface of the sealing material 27 may be uneven along the longitudinal direction of the sealing material 27. In such a case, the sliding contact pressure of the recording medium with respect to the sealing material 27 varies greatly depending on the region, which makes the conveyance state of the recording medium unstable and causes sticking.
[0008]
The present invention has been devised in view of the above-described drawbacks, and has as its object to stabilize the conveyance state of a recording medium and to form a high-reliability thermal head capable of forming a good print, a method of manufacturing the same, Another object of the present invention is to provide a thermal printer.
[0009]
[Means for Solving the Problems]
In the thermal head of the present invention, a plurality of heating resistors and a plurality of driver ICs for controlling heat generation of the heating resistors are arranged substantially in parallel on the upper surface of the substrate, and the driver ICs are shared by a band-shaped sealing material. A band-like overcoat layer made of a fluororesin disposed along the longitudinal direction of the sealing material at least on the side of the heating resistor relative to the sealing material. It is assumed that.
[0010]
The thermal head according to the present invention is characterized in that the overcoat layer and the sealing material are arranged substantially in parallel with each other.
[0011]
Further, a thermal printer according to the present invention includes the above-described thermal head and a transport unit that transports a recording medium onto the heating resistor.
[0012]
Still further, a method of manufacturing a thermal head according to the present invention is characterized in that a plurality of heating resistors and a plurality of driver ICs for controlling heat generation of the heating resistors are mounted and arranged substantially in parallel on the upper surface of the substrate, In a thermal head formed by forming a band-shaped sealing material that covers the same in common, prior to the formation of the sealing material, at least on the heating resistor side of the driver IC arrangement region along the driver IC arrangement direction. A band-shaped overcoat layer made of a fluororesin to be disposed is applied.
[0013]
According to the thermal head of the present invention, the overcoat layer made of a fluororesin disposed along the longitudinal direction of the sealing material is provided on the heating resistor side of the sealing material covering the driver IC. When the stopper is formed, even if the precursor of the resin material constituting the sealing material applied to the array region of the driver IC tries to spread to the heating resistor side, the flow of the precursor has extremely high water repellency. The overcoat layer can be favorably dammed. Therefore, the corner of the upper surface of the driver IC on the side of the heating resistor can be reliably covered with the sealing material, effectively preventing the surface of the recording medium from being scratched, and providing a good print. Becomes possible.
[0014]
In addition, since the spread of the precursor to the heating resistor side is successfully blocked by the overcoat layer, the height of the heating resistor side surface of the sealing material becomes substantially uniform, and the recording medium is sealed. Variations in the sliding contact pressure on the material for each region can be effectively prevented. Therefore, it is possible to stabilize the transport state of the recording medium and effectively prevent problems such as sticking.
[0015]
Further, since the fluororesin constituting the overcoat layer has extremely high water repellency, even if the thickness of the overcoat layer is extremely thin as 0.2 μm to 2 μm, the above-described effects can be obtained. The cost required for formation can be kept low, and the productivity of the thermal head can be kept high.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a plan view of a thermal head according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of the thermal head of FIG. 1, wherein 1 is a substrate, 2 is a partial glaze layer, 3 is a heating resistor, and 4 is an electrode. The pattern 5 is a protective film, 6 is a driver IC, 7 is a sealing material, and 8 is an overcoat layer.
[0017]
The substrate 1 is formed in a rectangular shape by an electrically insulating material such as alumina ceramics, and has a partial glaze layer 2, a heating resistor 3, a driver IC 6, and the like attached to the upper surface thereof to support them. Function as a supporting base material.
[0018]
On the upper surface of the substrate 1, a partial glaze layer 2 made of glass is attached in a strip shape in the longitudinal direction of the substrate 1, and a plurality of heating resistors 3 are provided near the top.
[0019]
The partial glaze layer 2 is formed to have, for example, an arc-shaped cross section with a radius of curvature of 1 mm to 4 mm, and the thickness of the top is set to 20 μm to 160 μm.
[0020]
Since the partial glaze layer 2 is formed of glass having low thermal conductivity (thermal conductivity: 0.7 W / m · K to 1.0 W / m · K), the heat generated by the heating resistor 3 inside the partial glaze layer 2. Of the thermal head to maintain good thermal response characteristics of the thermal head, specifically, as a heat storage layer for raising the temperature of the heating resistor 3 to a predetermined temperature required for printing in a short time. Make
[0021]
Further, the plurality of heating resistors 3 provided near the top of the partial glaze layer 2 are linearly arranged in the main scanning direction at a density of, for example, 600 dpi (dot per inch). Is formed of an electric resistance material such as TaN, TaSiO, TiSiO, etc., so that when power is applied through the electrode patterns 4 and the like electrically connected to both ends thereof, Joule heat is generated and printing is performed on a recording medium. , For example, a temperature of 130 ° C. to 350 ° C.
[0022]
The electrode pattern 4 connected to the heating resistor 3 functions as a power supply wiring for supplying power to the heating resistor 3 and the like, and is made of a metal material such as aluminum or copper. After being attached and led out over the surface of the substrate 1, the lead-out portion is electrically connected to a corresponding terminal of the driver IC 6, which will be described later.
[0023]
A protective film 5 is applied to the surfaces of the plurality of heating resistors 3 and the electrode patterns 4 described above, and the plurality of heating resistors 3 and the plurality of electrode patterns 4 are commonly covered with the protection film 5. I have.
[0024]
The protective film 5 is made of an inorganic material having excellent abrasion resistance such as silicon nitride (Si ₃ N ₄ ) or sialon (Si—Al—O—N). It protects against abrasion due to sliding contact and corrosion from contact with moisture and the like contained in the atmosphere.
[0025]
On the other hand, a plurality of driver ICs 6 are arranged on the upper surface of the substrate 1 substantially in parallel with the arrangement of the heating resistors 3.
[0026]
The driver IC 6 has electronic circuits such as a shift register, a latch circuit, and a switching transistor densely integrated on each circuit forming surface (lower surface), and selectively heats the plurality of heating resistors 3. More specifically, the switching transistor is turned on / off based on image data supplied from the outside, and functions to control the energization of each heating resistor 3.
[0027]
As the driver IC 6, for example, a flip-chip type IC having an electronic circuit and terminals on the lower surface is used, and conventionally known face-down bonding, that is, solder bonding of the terminals of the driver IC 6 to the lead-out portions of the corresponding electrode patterns 4. By doing so, the driver IC 6 is electrically connected to the electrode pattern 4.
[0028]
The plurality of driver ICs 6 are commonly covered with a sealing material 7 having a mountain-shaped cross section mainly composed of an epoxy resin, and furthermore, a protective film 5 located closer to the heating resistor 3 than the sealing material 7. Is covered with a strip-like overcoat layer 8 made of a fluororesin.
[0029]
The sealing material 7 is an epoxy resin containing an inorganic filler made of, for example, silica (SiO ₂ ) or alumina (Al ₂ O ₃ ) in an amount of about 50% by mass to 70% by mass and adjusted to a predetermined coefficient of thermal expansion and hardness. By blocking the driver IC 6 from the atmosphere, the electronic circuit of the driver IC 6 is effectively prevented from being corroded by contact with moisture or the like in the atmosphere, and the driver IC 6 is applied with an external force ( (E.g., contact with the recording medium).
[0030]
The sealing member 7 also functions as a guide member for supporting the running of the recording medium on the surface on the side of the heating resistor 3 and guiding the recording medium onto the heating resistor 3 during the recording operation.
[0031]
On the other hand, the overcoat layer 8 is disposed so that its longitudinal direction is substantially parallel to the sealing material 7, and is adjacent to the sealing material 7 on the heating resistor 3 side in the longitudinal direction. Deposited in shape.
[0032]
Since such an overcoat layer 8 itself has high water repellency, the liquid precursor applied to the arrangement region of the driver ICs 6 spreads to the heating resistor side when forming the sealing material 7. Can be satisfactorily blocked.
[0033]
For this reason, the upper corner of the heating resistor side of the driver IC 6 can be reliably covered with the sealing material 7, and the recording medium slidably contacting the heating resistor side surface of the sealing material 7 is effectively prevented from being damaged. As a result, it is possible to provide good printing.
[0034]
In addition, since the spread of the precursor to the heating resistor side can be satisfactorily blocked by the overcoat layer 8, the height of the heating resistor side surface of the sealing material 7 becomes substantially uniform in the longitudinal direction. When the running of the medium is guided by the surface of the sealing material 7 on the side of the heating resistor, it is possible to effectively prevent the sliding pressure of the recording medium against the sealing material 7 from greatly varying from region to region. Therefore, it is possible to stabilize the transport state of the recording medium and effectively prevent problems such as sticking.
[0035]
Further, since the fluororesin constituting the overcoat layer 8 has extremely high water repellency, even if the thickness of the overcoat layer 8 is extremely thin as 0.2 μm to 2 μm, the above-described effects can be obtained. The cost required for forming the layer 8 can be reduced, and the productivity of the thermal head can be kept high.
[0036]
The fluororesin constituting the overcoat layer 8 is preferably set to have a contact angle with water of 105 ° to 160 °. In this case, the thickness of the overcoat layer 8 is set to 0.2 μm to 2 μm. Even if the thickness is set very thin, the overcoat layer 8 can effectively prevent the encapsulant 7 from spreading, so that the cost required for forming the overcoat layer 8 can be reduced and the thermal head High productivity can be maintained. Here, when the contact angle of the fluororesin is set smaller than 105 °, the force of the overcoat layer 8 to repel the precursor of the sealing material 7 tends to be insufficient, and the thickness of the overcoat layer 8 is set to 2 μm or less. In this case, there is a tendency that it is difficult to effectively prevent the encapsulant 7 from spreading. On the other hand, it is difficult to manufacture a fluororesin having a contact angle larger than 160 °, and to maintain high productivity of the thermal head. Tends to be difficult. Therefore, it is preferable that the fluororesin constituting the overcoat layer 8 be set so that the contact angle with water is 105 ° to 160 °.
[0037]
As shown in FIG. 3, the thermal printer incorporating the above-described thermal head includes a platen roller 9 and transport rollers 10a and 10b as transport means for transporting the recording medium onto the heating resistor 3 of the thermal head T. , 10c, 10d, etc. are provided.
[0038]
The platen roller 9 is a cylindrical member in which butadiene rubber or the like is wound around a shaft core made of a metal such as SUS to a thickness of about 3 mm to 15 mm, and is rotatable on the heating resistor 3 of the thermal head T. And presses the recording medium against the surface of the protective film on the heating resistor 3 to convey the recording medium in a direction perpendicular to the arrangement of the heating resistors 3 (the direction of the arrow in the figure).
[0039]
The transport rollers 10a, 10b, 10c, and 10d have their outer peripheral portions formed of metal, rubber, or the like. The transport rollers 10a, 10b, 10c, and 10d are formed of metal, rubber, or the like. The conveyance roller 10a, 10b, 10c, 10d and the platen roller 9 support the running of the recording medium.
[0040]
As described above, the recording medium conveyed by these conveying means 9, 10a, 10b, 10c, and 10d is slidably contacted with the heat generating resistor 3 on the heat generating resistor side surface of the sealing material 7 on the upstream side in the conveying direction. As a result, the recording medium is sequentially guided on the heating resistor 3 by the sealing material 7 and comes into sliding contact with the surface of the protective film on the heating resistor 3.
[0041]
At the same time, the plurality of heating resistors 3 are caused to generate Joule heat selectively in accordance with the driving of the driver IC 6, and the heat is transmitted to the recording medium via the protective film 5, thereby forming a predetermined print.
[0042]
Next, a method for manufacturing the above-described thermal head will be described in detail with reference to FIG. FIG. 4 is a sectional view of each step for explaining the method of manufacturing the thermal head of FIG.
(1) First, a substrate 1 on which the above-described partial glaze layer 2, heating resistor 3, electrode pattern 4, and protective film 5 are sequentially deposited and formed on the upper surface is prepared (FIG. 4A).
[0043]
When the substrate 1 is made of, for example, alumina ceramics, a ceramic material powder of alumina, silica, magnesia or the like is mixed with an appropriate organic solvent and a solvent to form a slurry, which is formed by a conventionally known doctor blade method or the like. Then, a ceramic green sheet is formed, punched into a predetermined shape, and fired at a high temperature (about 1600 ° C.).
[0044]
Further, the partial glaze layer 2 is formed by printing and applying a predetermined glass paste obtained by adding and mixing an appropriate organic solvent to glass powder on the upper surface of the substrate 1 by a conventionally known screen printing or the like. (900 ° C. to 1200 ° C.).
[0045]
Further, after the formation of the partial glaze layer 2, the heating resistor 3 and the electrode pattern 4 are formed in a predetermined pattern by employing a conventionally known thin film forming technique. Specifically, when the heating resistor 3 is made of TaSiO and the electrode pattern is made of Al, a resistive thin film made of TaSiO and a metal thin film made of Al are sequentially laminated on the upper surface of the substrate 1 and the partial glaze layer 2 by conventionally known sputtering. At the same time, the heat generating resistor 3 and the electrode pattern 4 are simultaneously formed by processing the laminate into a predetermined pattern by employing a conventionally known photolithography technique and etching technique.
[0046]
On the other hand, the protective film 5 covering the heating resistor 3 and the electrode pattern 4 is formed by applying a conventionally known thin film forming technique, for example, sputtering, and applying the above-mentioned inorganic material to the upper surface of the heating resistor 3 or the electrode pattern 4 by 2 μm. It is formed by being applied to a thickness of ２０20 μm.
(2) Next, prior to the formation of the sealing material 7 and the mounting of the driver IC 6, the overcoat layer 8 is formed on the substrate 1 in a belt-like shape on the side of the heating resistor rather than the area in which the driver ICs 6 are to be arranged (area to be formed). (FIG. 4B).
[0047]
The overcoat layer 8 is formed, for example, by applying a liquid fluorocarbon resin precursor on the protective film 5 located closer to the heating resistor 3 than the sealing material 7 by using a dispenser or the like, and coating the precursor with a liquid. It is formed into a thickness of 0.2 μm to 2 μm by curing and polymerizing at a temperature of from 200 ° C. to 200 ° C.
(3) Subsequently, a driver IC 6 for controlling heat generation of the heat generating resistor 3 is mounted on the substrate (FIG. 4C).
[0048]
The driver IC 6 forms an ingot (chunk) made of single-crystal silicon, for example, by employing a conventionally-known Czochralski method (pulling method), and slices this into a plate shape using a diamond cutter or the like. Thereafter, by adopting a conventionally well-known semiconductor manufacturing technique on one main surface of the plate body, it is manufactured by integrating electronic circuits such as shift registers and latch circuits at a high density.
[0049]
When the driver IC 6 is formed of a flip-chip type IC, the driver IC 6 is mounted on the substrate 1 by face-down bonding which is conventionally known, that is, a terminal provided on the circuit forming surface of the driver IC 6 is mounted on the electrode pattern 4. This is performed by electrically connecting the driver IC 6 and the electrode pattern 4 by soldering to the provided electrodes.
(4) Finally, the thermal head is completed by forming the sealing material 7 so as to cover the array region of the driver ICs 6 (FIGS. 4D and 4E).
[0050]
The sealing material 7 is formed by applying a liquid precursor of an epoxy resin to which a predetermined amount of an inorganic filler is added and mixed, for example, using a dispenser or the like to the mounting area of the driver IC 6, and applying a temperature of 80 ° C. to 200 ° C. And a polymer having a thickness of 0.4 mm to 2 mm.
[0051]
At this time, even if the liquid precursor serving as the base of the sealing material 7 tries to flow out to the heating resistor side, such outflow is satisfactorily blocked by the water-repellent action of the overcoat layer 8, and therefore the driver IC 6 It is possible to reliably cover the corners of the upper surface of the heating resistor side with the sealing material 7, and it is possible to effectively prevent the surface of the recording medium from being scratched and to provide a good print.
[0052]
In addition, the height of the surface of the sealing material 7 on the side of the heating resistor can be made substantially uniform over the longitudinal direction of the sealing material 7, so that the running of the recording medium is guided by the surface of the sealing material 7 on the side of the heating resistor. In addition, it is possible to effectively prevent the sliding contact pressure of the recording medium with respect to the sealing material 7 from greatly varying in each region. Therefore, it is possible to stabilize the transport state of the recording medium and effectively prevent problems such as sticking.
[0053]
Further, since the fluororesin constituting the overcoat layer 8 has extremely high water repellency, even if the thickness of the overcoat layer 8 is extremely thin as 0.2 μm to 2 μm, the above-described effects can be obtained. The cost required for forming the layer 8 can be reduced, and the productivity of the thermal head can be kept high.
[0054]
Note that the present invention is not limited to the above-described embodiment, and various changes, improvements, and the like can be made without departing from the gist of the present invention.
[0055]
For example, in the above-described embodiment, the overcoat layer 8 is formed only on the heat generating resistor 3 side of the sealing material 7, but instead, the overcoat layer 8 ′ is formed on both sides of the sealing material 7. Since the sealing material 7 can be prevented from spreading in the sub-scanning direction (a direction orthogonal to the longitudinal direction of the sealing material 7), the formation region of the sealing material 7 can be formed in the sub-scanning direction. It is possible to make the thermal head smaller by making it narrower.
[0056]
【The invention's effect】
According to the thermal head of the present invention, the overcoat layer made of a fluororesin disposed along the longitudinal direction of the sealing material is provided on the heating resistor side of the sealing material covering the driver IC. When the stopper is formed, even if the precursor of the resin material constituting the sealing material applied to the array region of the driver IC tries to spread to the heating resistor side, the flow of the precursor has extremely high water repellency. The overcoat layer can be favorably dammed. Therefore, the corner of the upper surface of the driver IC on the side of the heating resistor can be reliably covered with the sealing material, effectively preventing the surface of the recording medium from being scratched, and providing a good print. Becomes possible.
[0057]
In addition, since the spread of the precursor to the heating resistor side is successfully blocked by the overcoat layer, the height of the heating resistor side surface of the sealing material becomes substantially uniform, and the recording medium is sealed. Variations in the sliding contact pressure on the material for each region can be effectively prevented. Therefore, it is possible to stabilize the transport state of the recording medium and effectively prevent problems such as sticking.
[0058]
Further, since the fluororesin constituting the overcoat layer has extremely high water repellency, even if the thickness of the overcoat layer is extremely thin as 0.2 μm to 2 μm, the above-described effects can be obtained. The cost required for formation can be kept low, and the productivity of the thermal head can be kept high.
[Brief description of the drawings]
FIG. 1 is a plan view of a thermal head according to an embodiment of the present invention.
FIG. 2 is a sectional view of the thermal head of FIG.
FIG. 3 is a diagram illustrating a configuration of a thermal printer using the thermal head of FIG. 1;
FIG. 4 is a cross-sectional view of each step for explaining a method of manufacturing the thermal head of FIG.
FIG. 5 is a plan view of a thermal head according to another embodiment of the present invention.
FIG. 6 is a sectional view of a conventional thermal head.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Partial glaze layer 3 ... Heating resistor 4 ... Electrode pattern 5 ... Protective film 6 ... Driver IC
7 sealing material 8, 8 '... overcoat layer 9 ... platen rollers 10a, 10b, 10c, 10d transport rollers

Claims (4)

A thermal head in which a plurality of heating resistors and a plurality of driver ICs for controlling heat generation of the heating resistors are arranged substantially in parallel on an upper surface of a substrate, and the driver ICs are commonly covered with a band-shaped sealing material. At
A thermal head, wherein a strip-shaped overcoat layer made of a fluororesin, which is disposed along a longitudinal direction of the sealing material, is provided on at least a heating resistor side of the sealing material. 2. The thermal head according to claim 1, wherein the overcoat layer and the sealing material are arranged substantially in parallel with each other. A thermal printer, comprising: the thermal head according to claim 1; and a transport unit configured to transport a recording medium onto the heating resistor. A plurality of heating resistors and a plurality of driver ICs for controlling heat generation of the heating resistors are attached and arranged substantially parallel to each other on the upper surface of the substrate, and a band-shaped sealing material is formed to cover the driver ICs in common. Thermal head
Prior to the formation of the sealing material, a band-like overcoat layer made of a fluororesin disposed along the driver IC arrangement direction was applied at least to the heating resistor side of the driver IC arrangement region. Characteristic method of manufacturing a thermal head.

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