JP2006092831A - Ceramic heater, fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramic heater composed by further smoothing a surface of an overcoat layer covering a heating resistor. <P>SOLUTION: A relationship between the size of air bubbles generated in the overcoat layer 18 where the heating resistors 121-124 stuck to a substrate 11 are formed and that on the substrate 11 with no heating resistors 121-124 formed is made to satisfy (the size on the heating resistors) > (the size on the substrate), and a portion on the substrate 11 located in the overcoat layer 18 is mounded, whereby irregularities formed on the surface of the overcoat layer 18 are reduced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a thin ceramic heater used for information equipment, home appliances, manufacturing equipment, etc., a fixing device such as a printer, a copying machine, a facsimile, or the like mounted with the ceramic heater, an image forming apparatus using the fixing device, a ceramic heater It relates to the manufacturing method.

The overcoat glass that protects the heating resistor of the conventional ceramic heater has irregularities on the surface where the heating resistor is formed and the substrate surface where it is not formed, and heat is generated to smooth out this irregularity. A filling material is formed on the surface portion of the substrate on which the resistor is not formed so as not to overlap the heating resistor. (For example, Patent Document 1)
JP-A-5-251220 (second page, FIG. 1)

  In the technique of Patent Document 1 described above, in order to form the filling material so that it does not overlap with the resistor between the portion where the heating resistor is formed and the portion where the heating resistor is not formed, the resistor and the resistor are formed. There is a problem in that the smaller the gap between the parts, the easier the filling material overlaps with the resistor, and the concavity and convexity becomes larger.

  An object of the present invention is to provide a ceramic heater capable of making the unevenness as smooth as possible without overlapping with the heating resistor even if the interval between the heating resistor and the portion where the heating resistor is not formed is small, and fixing using this ceramic heater An apparatus, an image forming apparatus using the fixing device, and a method for manufacturing a ceramic heater are provided.

  In order to solve the above-described problems, in the ceramic heater of the present invention, a heating resistor and power for supplying power to the heating resistor in the longitudinal direction of a long flat substrate formed of a heat-resistant and insulating material are provided. An electrode is formed and an overcoat layer formed by printing and baking a glass paste on the substrate and the heating resistor is applied, and the size of bubbles generated in the overcoat layer is determined by the substrate. The surface of the overcoat layer is made uneven by making the top larger than that on the heating resistor.

  According to the present invention, since the unevenness on the surface of the ceramic heater can be reduced and smoothed, it is possible to suppress friction when the heat generating body slides the ceramic heater.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1 and 2 are diagrams for explaining an embodiment of the ceramic heater according to the present invention. FIG. 1 is a front view, and FIG. 2 is a sectional view taken along line xx ′ of FIG.
1 and 2, 11 is a heat-resistant and electrically insulating material such as aluminum oxide, aluminum nitride having a thermal conductivity of about 20 W / m · k, silicon nitride having a thermal conductivity of 100 to 180 W / m · K, or the like. It is a substrate having a high mechanical conductivity and a high thermal conductivity.

  121 to 124 are printed and formed in parallel with the longitudinal direction on the surface side of the substrate 11 using a heating resistor paste containing silver (Ag) / palladium (Pd) alloy as a main component and fired at a high temperature. This is a belt-like heating resistor having a predetermined resistance value and a film thickness of about 5 μm to 15 μm. Reference numeral 13 denotes a power feeding electrode made of a good conductor film made of, for example, Ag / Pd alloy layered on one end of the heating resistor 121, and reference numeral 14 denotes a good conductor film made of, for example, Ag / Pd layered on one end of the heating resistor 124. It is the electrode for electric power feeding which consists of.

  Reference numeral 15 denotes a connecting portion formed by printing and firing, for example, an Ag / Pd alloy conductor paste in which a part of each of the other end of the heating resistor 121 and one end of the heating resistor 122 is overlaid. Reference numeral 16 denotes a connection portion formed by printing and firing, for example, an Ag / Pd alloy conductor paste in which a part of each of the other end of the heating resistor 122 and one end of the heating resistor 123 is overlaid. 17 is formed by printing and baking, for example, an Ag / Pd alloy conductive paste in which the other end of the heating resistor 123 and one end of the other end of the heating resistor 124 having one end connected to the electrode 14 are overlaid. Connected part. Each conductor paste is printed by a thick film printing method. The electrodes 13 and 14 and the connection portions 15 to 17 may be made of Ag, Ag / Pt (platinum) alloy or the like in addition to the Ag / Pd alloy.

  On the heating resistors 121 to 124 and the connection portions 15 to 17 where the electrodes 13 and 14 are left, an overcoat layer 18 is formed by printing a glass paste by a thick film method and firing the glass paste.

The overcoat layer 18 is formed by printing and baking for each layer using a borosilicate glass paste mainly composed of lead-free amorphous SiO _{2 and} B ₂ O ₃ , for example, and this is repeated three times. 3 layers.

  Bubbles are generated in the overcoat layer 18 thus formed. When three layers are formed using the same paste, the bubbles generated in the overcoat layer 18 by the first layer firing are gradually increased by the third layer firing by printing and firing each layer. . The bubbles generated in the overcoat layer 18 on the heating resistors 121 to 124 are made of metal powder such as Ag and Pd and move through the soft heating resistors 121 to 124, respectively. The surface of the overcoat layer 18 rises by combining with the bubbles generated in the overcoat layer 18.

  That is, a bubble Ba having a size of about 2 μm to 3 μm is generated on the heating resistors 121 to 124, and a bubble Bb that is larger than a bubble Ba having a size of about 5 μm to 15 μm is generated on the substrate 11. Due to the generation of bubbles of different sizes, as shown in FIG. 2, the overcoat layer 18 on the substrate 11 rises, and the concave portions 21 and the convex portions 22 of the glass on the heating resistors 121 to 124 and the substrate 11 are formed. The difference becomes smaller.

  FIG. 3 shows the result of measuring the film thickness state of the overcoat layer 18 thus formed from the substrate 11. As can be seen from FIG. 3, the difference (step) in the thickness of the upper surface portion of the overcoat layer 18 is within 9 μm, confirming that the film is in a smooth state.

  In this embodiment, since the surface of the overcoat layer 18 can be made smooth, the object to be heated can slide the overcoat layer 18 smoothly.

  In this embodiment, the step of printing / firing the overcoat layer 18 is described as three times, but it may be performed twice or four times or more.

  Next, another embodiment of the ceramic heater of the present invention will be described. In this embodiment, for example, two types of lead-free amorphous glass pastes having different softening points are used for the overcoat glass layer 18, and the first and second layers have a softening point of about 600 to 650 ° C. The third layer is formed by printing and firing using a paste of about 700 to 750 ° C. having a softening point higher than that of the first and second layers.

The glass viscosity of the third layer is higher (harder) than the glass viscosity of the first and second layers by using a glass having a higher softening point in the first layer and the third layer of the overcoat layer 18. The bubbles are in a state where they do not escape into the air. Since the softening point is determined as the temperature when the viscosity of the glass is log ₁₀ 7.5 Pa · s, considering from FIG. 5, for example, when looking at a having a softening point higher than b and b, the glass viscosity This is because a is higher (harder) than b at the current firing temperature of 850 ° C.

  In the first and second layers that have melted again, bubbles are generated and become larger. Further, since the generated bubbles cannot move in the overcoat layer 18, conversely, they are made of metal powder such as Ag and Pd and move in the soft heating resistors 121 to 124, and heat is generated. The heat generating resistor between the resistor and the heat generating resistor is accumulated on the substrate 11 and the overcoat layer 18 in this portion is raised.

  The result of measuring the film thickness state of the overcoat layer 18 formed in this way from the substrate 11 is shown in FIG. As can be seen from this figure, the difference in the film thickness of the upper surface portion of the overcoat layer 18 is within 9 μm, confirming that it is in a smooth state.

  Also in this embodiment, small bubbles formed on the heating resistors 121 to 124 of the overcoat layer 18 and large bubbles formed on the substrate 11 can be generated, and the surface of the overcoat layer 18 with small unevenness can be generated. Obtainable.

  The ceramic heater 100 having the above-described configuration is incorporated in a fixing device and is energized by, for example, a circuit configuration shown in FIG. That is, when the commercial power supply 61 is energized to the electrodes 13 and 14 of the ceramic heater 100 via the solid state relay 63 connected to the control terminal of the temperature control circuit 62, current is supplied to the heating resistors 121 to 124 connected in series. Flows and generates heat. The temperature of the substrate 11 also rises due to heat generated by the heating resistors 121-124. This heat is transmitted to the temperature sensing part of the thermistor 64 attached to the back side of the substrate 11 and changes the resistance value of the temperature sensing part. A change in the resistance value of the thermistor 64 is output via a wiring conductor formed on the back side of the substrate 11, and this is input to the temperature control circuit 62 to determine whether the temperature is at the set temperature. When the temperature is lower than the set temperature, an ON signal is output to the solid state relay 63, and when the temperature is higher than the set temperature, an OFF signal is output to the solid state relay 63.

  Thus, the temperature of the heating resistors 121 to 124 is adjusted by controlling the power applied to the heating resistors 121 to 124. Although the temperature control circuit 62 has been described with respect to the on / off control of the solid state relay 63, temperature control by a pulse width modulation control method or the like may be used.

  In the ceramic heater 100, when power is supplied to the electrodes 13 and 14, current flows through the heating resistors 121 to 124, respectively, and the heating resistors 121 to 124 exhibit a substantially uniform heating temperature distribution in the longitudinal direction. Become. In this embodiment, for example, when the resistance value of the heating resistors 121 to 124 is 25Ω and a voltage of 100 V is applied, a current of 4 A flows, and a heating value of 400 W can be obtained.

  Normally, as described above, the thermistor 64 provided on the back side of the substrate 11 detects the temperature of the ceramic heater 100 and controls the solid state relay 63 on / off through the temperature control circuit 62 to control it to a predetermined temperature. .

Next, with reference to FIG. 7, an embodiment of the fixing device of the present invention when the embodiment of the ceramic heater described above is mounted on the fixing device 200 will be described. The ceramic heater 100 in the figure is the same as that in FIGS. 1 and 2, and the same portions are denoted by the same reference numerals and description thereof is omitted.
In FIG. 7, reference numeral 201 denotes a pressure roller which is rotated by a rotating shaft 202, and a heat resistant elastic material such as a silicone rubber layer 203 is fitted on the surface thereof. The ceramic heater 100 is juxtaposed with the rotating shaft 202 of the pressure roller 201 and attached to a base (not shown).

  Around the ceramic heater 100, an endless roll-shaped fixing film 204 made of a heat-resistant sheet such as a polyimide resin is circulated so as to be circulated, and over the substrate 11 via the heating resistors 121 to 124. The surface of the coat layer 18 is in elastic contact with the silicone rubber layer 203 of the pressure roller 201 via the fixing film 204.

  In the fixing device 200, the ceramic heater 100 is energized through a connector (not shown) in which a phosphor bronze plate or the like in contact with the electrodes 13 and 14 is subjected to elasticity by silver plating, and the overcoat layer 18 of the heating resistors 121 to 124 is heated. The toner image T1 is first heated and melted by the ceramic heater 100 via the fixing film 204 between the surface of the fixing film 204 provided above and the silicone rubber layer 203, and at least the surface portion greatly exceeds the melting point and is completely softened. Melt. Thereafter, on the paper discharge side of the pressure roller 201, the copy paper P is separated from the ceramic heater 100, the toner image T2 is naturally radiated and cooled and solidified again, and the fixing film 204 is also separated from the copy paper P.

  As described above, the toner image T1 is once completely softened and melted and then cooled again on the paper discharge side of the pressure roller 201, so that the condensing force of the toner image T2 is very large.

  In this fixing device 200, the overcoat layer 18 of the ceramic heater 100 is further smoothed, so that the copy paper can be reliably heated and the movement of the copy paper on the overcoat layer 18 can be made smooth. Become.

Next, an image forming apparatus according to the present invention will be described with reference to FIG. 8, taking as an example a copying machine equipped with a ceramic heater according to the present invention and a fixing device using the ceramic heater. In the drawing, the part of the fixing device 200 is the same as described above, and the same reference numerals are given to the same parts, and the description thereof is omitted.
In FIG. 8, 301 is a casing of the copying machine 300, 302 is a document placing table made of a transparent member such as glass provided on the upper surface of the casing 301, and scans the document P1 by reciprocating in the arrow Y direction.

  An illuminating device 302 including a light irradiation lamp and a reflecting mirror is provided in the upper direction in the housing 301, and a reflected light source from the document P1 irradiated by the illuminating device 302 is a short focus small diameter imaging element. A slit exposure is performed on the photosensitive drum 304 by the array 303. The photosensitive drum 304 rotates in the direction of the arrow.

  Reference numeral 305 denotes a charger that uniformly charges, for example, a photosensitive drum 304 coated with a zinc oxide photosensitive layer or an organic semiconductor photosensitive layer. An electrostatic image subjected to image exposure by the imaging element array 303 is formed on the photosensitive drum 304 charged by the charger 305. This electrostatic image is visualized using toner made of a resin that softens and melts when heated by the developing device 306.

  The copy paper P stored in the cassette 307 is rotated by a pair of conveying rollers 309 that are rotated in pressure contact with each other in synchronization with the feeding roller 308 and the image on the photosensitive drum 304. Sent to the top. The toner image formed on the photosensitive drum 304 is transferred onto the copy paper P by the transfer discharger 310.

  Thereafter, the paper P that is separated from the photosensitive drum 304 is guided to the fixing device 200 by the conveyance guide 311 and subjected to a heat fixing process, and then is discharged into the tray 312. After the toner image is transferred, residual toner on the photosensitive drum 304 is removed using a cleaner 313.

  The fixing device 200 is longer in the direction orthogonal to the moving direction of the copy paper P than the effective length corresponding to the width (length) of the maximum format paper that can be copied by the copier 300, that is, longer than the width (length) of the maximum format paper. A pressure roller 201 of the ceramic heater 100 is provided by extending the heating resistors 121 to 124.

  Then, the unfixed toner image T1 on the paper P sent between the ceramic heater 100 and the pressure roller 201 is melted by receiving heat from the heating resistors 121 to 124, and characters and alphanumeric characters are printed on the copy paper P surface. A copy image such as a symbol or a drawing is displayed.

  In such a copying machine 300, the surface on which the copy paper of the ceramic heater 100 for fixing in a copying machine or the like is rubbed can be made smoother, and therefore, the dirt is attached to the ceramic heater 100. Surface temperature change can also be prevented.

  The present invention is not limited to the embodiment described above. For example, the overcoat layer material cannot be specified because it needs to be changed depending on the material of the opposing fixing film and other conditions. However, when the fixing film is a resin, the overcoat layer is an overcoat layer when glass or the fixing film is a metal. It is desirable to combine resins. As this resin, polyamide (PA), polyacetal (POM), polytetrafluoroethylene (PTFE), polyphenylene sulfide, elastomer, polyolefin, fluorine, etc., which are generally considered to be excellent in slidability, are used. Conceivable. Basically, any of them may be used, but imides such as PI (polyimide) and PAI (polyamideimide), which are heat-resistant and elastic, are preferable, but if the hardness is too low, the resin coating will be scraped off. Therefore, for example, a hardness of 3H or more is necessary.

  Ceramic heaters are used for fixing image forming devices such as copiers, but are not limited to this, and are not limited to electrical appliances for home use, precision devices for business use and experiments, and devices for chemical reactions. It can also be used as a heat source for heating and heat retention.

The block diagram for demonstrating one Embodiment regarding the ceramic heater of this invention. X-x 'sectional drawing of FIG. Explanatory drawing for demonstrating the effect of one Embodiment of this invention. Explanatory drawing for demonstrating the effect of other embodiment of this invention. Explanatory drawing for demonstrating the viscosity change of glass with temperature. The circuit block diagram for demonstrating the temperature adjustment used for FIG. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram for explaining an embodiment of a fixing device according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram for explaining an embodiment of an image forming apparatus according to the present invention;

Explanation of symbols

11 Substrate 121-124 Heating resistor 13, 14 Electrode 15-17 Connection 18 Overcoat layer 100 Ceramic heater 200 Fixing device 300 Copying machine

Claims (5)

A heating resistor and an electrode for supplying power to the heating resistor are formed in the longitudinal direction of a long flat substrate formed of a heat-resistant and insulating material, and a glass paste is formed on the substrate and the heating resistor. In a ceramic heater with an overcoat layer formed by printing and firing
The ceramic heater according to claim 1, wherein the size of bubbles generated in the overcoat layer is made larger on the substrate than on the heating resistor, thereby reducing irregularities on the surface of the overcoat layer.   The ceramic heater according to claim 1, wherein the overcoat layer is formed in multiple layers by printing and baking glass paste several times.   The overcoat layer is multilayered, the lower layer is formed by printing and baking a glass paste having a lower softening point, and the upper layer is formed by printing and baking using a glass paste having a higher softening point than the lower layer. The ceramic heater according to claim 1. A heating roller;
The fixing heater according to any one of claims 1 to 3, wherein a resistance heating element disposed opposite to the heating roller is pressed against the heating roller.
A fixing device comprising: a fixing film movably provided between the fixing heater and the heating roller. Forming means for attaching a toner to an electrostatic latent image formed on a medium and transferring the toner to a sheet to form a predetermined image;
5. A fixing device according to claim 4, wherein the toner is fixed by passing a sheet on which an image is formed through a fixing film through a fixing film while being pressed against the fixing heater. Image forming apparatus.

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