JP2003109727A - Plate-shaped heater, fixing device, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide, for example, a plate-like heater which can be used for a fixing device of a copying machine to stably fix toner, a fixing device using the heater, and an image forming apparatus equipped with the fixing device. Aim. SOLUTION: A long substrate 1 made of a heat-resistant and electrically insulating material, a band-shaped resistance heating element 2 formed on the surface of the substrate 1 along the longitudinal direction, and a substrate connected to the resistance heating element 2 1
Layer is formed on the front side 1a or the back side 1b of the
Lower electrode 31d, 3 with lower resistance per unit area than 2
The 2d side is made of Ag · Pd or Ag · Pt, and the upper-layer electrodes 31u and 32u are the same as or lower than the lower-layer electrodes 31d and 32d.
The heater H1 includes power supply electrodes 31 and 32 of g, and a vitreous overcoat layer 4 formed so as to cover the surface of the resistance heating element 2 and the front surface 1a of the substrate.
A fixing device 8 using the heater H1; and an image forming device 9 equipped with the fixing device 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an O copy machine such as an electronic copying machine, a facsimile or a computer printer.
The present invention relates to a plate heater used for toner fixing of device A or household electric appliances and precision manufacturing devices, a fixing device using the plate heater, and an image forming apparatus equipped with the fixing device.

[0002]

2. Description of the Related Art In the light, thin, short and small flow of electronic equipment, miniaturization and multi-functionalization of boards and components to be formed are being promoted in order to increase the density of circuit boards.

In an electronic copying machine, for example, a toner image formed on the surface of a photosensitive drum is transferred onto a copy sheet, and then this copy sheet is nipped between a plate heater and a pressure roller provided in a fixing device. However, the copy sheet is heated by the heat of the plate-shaped heater to melt and fix the toner.

The fixing device equipped with the plate-shaped heater has a good heater starting (heating) property and can heat the toner almost directly, so that the thermal efficiency is high and the power saving is achieved, and the device can be miniaturized. There is an advantage.

This type of conventional plate heater is made of alumina A
l ₂ O ₃ , aluminum nitride AlN or silicon carbide S
On the surface of the front surface of the elongated heat-resistant and electrically insulating substrate made of ceramics such as iC having a flat surface, a mixture of conductive components such as silver Ag powder and palladium Pd powder,
A silver-Ag-palladium-Pd-based paste in which glass powder (inorganic binder) and a water-soluble organic binder are kneaded is applied by printing and firing to form an elongated strip-shaped thick resistance heating element.

The surface of the plate-shaped heater excluding both ends of the front surface of the substrate has an electrically insulating property in order to protect the resistance heating element from abrasion and shock and to increase mechanical strength and to protect it from oxidation and sulfidation. Covered with a good glassy overcoat layer.

[0007] Further, silver Ag, platinum Pt powder or the like having a lower resistance value and better conductivity than the material for forming the resistance heating element and glass are provided on the portions not covered with the overcoat layer on both ends of the resistance heating element. Two layers of thick-film power supply electrodes in the shape of a quadrangle or an oblong quadrangle by printing, coating and firing a silver Ag paste, etc. kneaded with a powder (inorganic binder) and an organic binder (organic binder). It is formed separately.

This is done by connecting the resistance heating element and the power feeding electrode by layering the respective end portions, and the power feeding electrode portion needs to have a low resistance value per unit area in order to suppress heat generation. This is because. In addition, since the overcoat layer covers up to the overlaid portion of both of them, the height (thickness) from the substrate surface to the upper surface of the overcoat layer is
The height (thickness) from the substrate surface to the upper surface of the power supply electrode is small (thin), and the height (thickness) of the upper surface of the power supply electrode on the substrate surface is almost the same as the upper surface of the overcoat layer.
Furthermore, it was necessary to form another thick-film power feeding electrode.

If the heights of the upper surface of the power supply electrode and the upper surface of the overcoat layer are not even, the socket for sandwiching and locking the substrate portion on which the power supply electrode is provided is successful. There is a possibility that a problem such as failure to establish continuity may occur.

Although it is possible to form the power supply electrode to be thicker, it is impossible to form the power supply electrode because it is overlaid with the resistance heating element and thus the multi-layer portion is too thick compared to other portions. It is necessary to form the power feeding electrode portion excluding the multi-layer portion with the two layers.

When the power supply electrode is formed by using silver Ag or platinum Pt having good conductivity and oxidation resistance, it reacts with the glass of the substrate or the overcoat layer when the thick film coated on the surface of the substrate is baked. Bubbles may be generated and swelled, or a thick film that has risen may peel off and may not function as an electrode.
This swelling affects even the surface of the glassy overcoat layer on the upper surface, and unevenness in fixing occurs due to unevenness generated, and if this unevenness is severe, the resistance heating element is completely separated from the substrate and breaks electrically. The continuity may not be obtained.

Further, in this seed plate heater, recently, a nitride ceramic material such as aluminum nitride AlN having high thermal conductivity has been used for the substrate in order to improve the starting (heating) property. , This aluminum nitride AlN
This phenomenon was particularly remarkable when the power feeding electrode was formed on the substrate of No. 2 by silver Ag or platinum Pt.

This is because, for example, a substrate made of AlN contains nitrogen, so that a thick film paste such as a resistance heating element, a power feeding electrode, a wiring conductor or an overcoat layer is printed on the substrate to obtain about 850. ℃ calcined to when forming a thick film pattern, the interface from the AlN substrate and the thick film paste reacts substrate surface N ₂ gas is generated, the N ₂ gas and AlN substrate and the thick film pattern However, there is a problem that the adhesiveness between the substrate and the thick film pattern such as the heating element is deteriorated to cause peeling.

In the case of a nitriding type ceramic material, the generation of bubbles causing this is because the substrate coated with the material for forming the power feeding electrode is fired in the atmosphere, so that nitrogen, carbon dioxide gas, etc. emitted from the substrate may cause the bubbles. It is assumed that this occurs because the coating applied to the surface cannot be completely removed.

When silver Ag, platinum Pt, or the like is used alone, since the material having a high melting point is not mixed in the paste for forming the power supply electrode, for example, silver Ag is uniformly melted to form a film having a high viscosity. It is presumed that this is because the area covering the surface of the substrate becomes large and the gas from the substrate becomes difficult to be released.

[0016]

Therefore, the inventors of the present invention have made various investigations on foaming of the material for forming the electrode for feeding, and when forming the material for forming the electrode for feeding on a ceramic substrate, the known single material is used for firing. Since there is no material that suppresses the size of the crystal of particles in the process, the crystal of the material particles becomes large, so there is a problem that gas from the substrate is difficult to be released and swelling (foaming) occurs. , I found out that there is a problem.

The present invention has been made in view of the above circumstances, and by selecting the material of the power feeding electrode formed by stacking on the end portion of the resistance heating element on the surface of the substrate, the power feeding electrode, the substrate, and the resistance heat generation are selected. A plate-shaped heater that does not cause foaming with the body or glass of the overcoat layer and has no conduction failure due to peeling of electrodes, a fixing device using the plate-shaped heater, and an image forming apparatus equipped with the fixing device. The purpose is to provide.

[0018]

The plate heater according to claim 1 of the present invention comprises a long substrate made of a heat-resistant and electrically insulating material and a strip-shaped substrate formed along the longitudinal direction on the surface of the substrate. A resistance heating element and a lower layer side, which is connected to the resistance heating element and is stacked on the front side or the back side of the substrate, has a lower resistance value per unit area than the resistance heating element is Ag.Pd or A.
g ・ Pt, the upper layer side is the same as the lower layer side or Ag
And a vitreous overcoat layer formed to cover the resistance heating element and the front surface of the substrate.

In the plate heater according to the present invention, the material of the lower layer electrode formed on the front (upper) surface side of the substrate is silver Ag / palladium Pd in which palladium Pd is added from conventional silver Ag. As a result, the palladium P
d suppresses the crystal growth of silver Ag and suppresses the reaction with glass to prevent foaming, and prevents the power supply electrode from peeling off from the surface of the substrate due to temperature rise during heating by energization. It is possible to prevent poor contact with the like.

In the present invention and each of the following inventions, the definitions and technical meanings of the terms of the plate heater, the fixing device and the image forming apparatus are as follows unless otherwise specified.

Materials for forming heat resistant and electrically insulating substrates
Is alumina (aluminum oxide Al ₂O₃) Etc. oxidation
Or nitride such as aluminum nitride (AlN) or charcoal
Ceramics made of carbide such as silicon carbide (SiC)
Glass, hard glass such as quartz glass or metal plate
At least the surface of the glazing (forming a glass film) is electric
It consists of an insulating plate.

In the present invention, the front surface or the upper surface or the back surface or the lower surface of the substrate means the side on which the resistance heating element is formed in front (upper).
As the surface, the opposite surface on which the resistance heating element is not formed is the back (bottom)
It is a surface expression for the sake of convenience, and does not change even if the top and bottom are turned upside down depending on the condition of use.

As the resistance heating element, a material mainly composed of silver Ag / palladium Pd, silver Ag or silver Ag / platinum Pt, or a so-called PTC semiconductor having positive temperature characteristics is used. A small amount of rare earth element such as lanthanum La or yttrium Y is added to the barium titanate BaTiO ₃ based material, and a paste material obtained by kneading glass powder (inorganic binder) and organic binder (organic binder) is formed into a strip shape. Composed of formed.

As a form of the resistance heating element formed on the substrate, one or a plurality of resistance heating elements are electrically connected linearly or a plurality of them are connected in series.

As the material for forming the power supply electrode, the lower layer electrode on the substrate side is composed of silver Ag and palladium Pd or platinum Pt, and the upper layer electrode is silver Ag alone or silver Ag and palladium Pd. It consists of a material composed of and.

Further, as a glass material for the overcoat layer
As for lead oxide PbO-boron oxide B₂O₃-Silicon oxide
SiO₂System glass, zinc oxide ZnO-silicon oxide S
iO₂-Barium oxide BaO-based glass, silicon oxide
SiO₂-Boron oxide B₂O₃-Aluminum oxide Al₂O
₃System glass, silicon oxide SiO₂-Boron oxide B₂O ₃
-Zinc oxide ZnO-based glass and silicon oxide SiO₂−
Boron oxide B₂O₃-Sodium oxide Na₂O type glass
Etc. can be used.
Silicon oxide SiO₂, Aluminum nitride AlN, boronitride
If you add filler such as elemental BN or silicon carbide SiC, heat transfer
The conductivity can be increased.

The surface of the vitreous overcoat layer may not be a smooth flat surface but may be a rough surface having fine irregularities. When a fixing film or copy paper pressed against a pressure roller arranged oppositely presses against this rough surface, the film or copy paper is sent out by abutting with a proper friction resistance without applying strong pressure. You can

Further, in the plate heater of the present invention, a temperature detecting sensor may be provided on the opposite (back) surface side of the substrate on which the resistance heating element is formed. If a temperature detection sensor such as a thermistor, thermocouple, or thermostat is provided on the board, the temperature of the heater can be accurately received, the change in resistance value can be accurately detected, and this can be fed back to the temperature control circuit. Not only can proper temperature be controlled, but accidents such as ignition due to overheating of the heater can be prevented.

The temperature detecting sensor may be installed by directly forming a thick film thermistor together with a wiring conductor on the substrate, or by mounting a separate chip thermistor, or by electrically connecting to the sensor. The wiring conductor may be formed on the substrate by a coating as in the case of the feeding electrode, or may be separately connected by an electric wire.

The plate heater according to claim 2 of the present invention is
The substrate is made of a ceramic material.

By making the substrate ceramic,
The same operation as described in claim 1 is achieved.

A plate heater according to claim 3 of the present invention is
It is characterized in that the upper layer electrode side is formed of a material having a low resistance value and a high abrasion resistance with respect to the lower layer electrode side.

The upper electrode of the power feeding electrode is made of a material such that the amount of palladium Pd added is smaller than that of the lower electrode so that the damage such as conductivity, abrasion resistance, and abrasion resistance during attachment / detachment to / from the socket is reduced. The electrical and mechanical connection with the socket can be ensured.

A fixing device according to a fourth aspect of the present invention is the fixing device according to any one of the first to third aspects, wherein the pressure roller and the resistance heating element are arranged to face the pressure roller. It is characterized by including the plate heater described above.

Since the plate-shaped heater having the above-mentioned effects according to the first to third aspects is provided, the starting (heating) is fast and there is no swelling or peeling in the power feeding electrode portion.
The toner can be fixed smoothly.

An image forming apparatus according to a fifth aspect of the present invention comprises means for adhering toner to an electrostatic latent image formed on a medium and transferring the toner to a copying medium to form a predetermined image. 5. The fixing device according to claim 4, wherein the copying object on which an image is formed by a pressure roller is pressed against a plate-shaped heater so as to fix the toner.
It is characterized by having.

It is possible to provide a copying machine, a printer, or the like equipped with the fixing device having the above-mentioned operation. It should be noted that the copy sheet in the present invention is a generic term for a sheet or film on which an original document, an actual article or the like is copied.

[0038]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a plate heater according to the present invention will be described below with reference to the drawings. FIG. 1 is a front (upper) front view showing a cutaway part of an intermediate portion of the plate-shaped heater H1,
2 is a back (lower) side view showing a part of the intermediate portion of the plate-shaped heater H1 of FIG. 1 by cutting it out, and FIG. 3 is an enlarged view showing a portion cut along the line aa in FIG. FIG. 4 is a cross-sectional view, and FIG. 4 is a cross-sectional view in which the vicinity of the power supply electrode at the end is longitudinally cut in the axial direction. (Note that
The thickness of each layer such as the resistance heating element, the feeding electrode and the overcoat layer with respect to the substrate shown in the drawing is exaggeratedly written thickly, and is not proportional. ) In the figure, 1 is alumina Al ₂ O ₃ which is a heat resistant and electrically insulating material.
And ceramics such as aluminum nitride AlN, here aluminum nitride AlN (coefficient of thermal expansion of 4 ×
^{10 -6 / ℃ ~5 × 10 -6} / consist ° C. approximately) length of about 26
0-300 mm (here about 300 mm), width about 5-1
5mm (here about 6mm), thickness about 0.4-0.8m
It is a long strip-shaped substrate of m (here, about 0.6 mm).

Reference numeral 2 denotes the front (upper) surface side 1a of the substrate 1.
The length of the surface is approximately U and the total length is about 450m.
It is a strip-shaped thick-film resistance heating element mainly composed of about 80% by weight of silver Ag and about 20% by weight of palladium Pd having a width of about 1.5 mm and a width of about 1.5 mm and a thickness of about 10 μm.

Reference numerals 31 and 32 denote electrodes for power supply, which will be described later, connected to the resistance heating element 2 at both ends of the resistance heating element 2.

Reference numeral 4 denotes silicon oxide SiO ₂ -boron oxide B ₂ O ₃ -aluminum oxide Al ₂ O ₃ formed on substantially the entire surface of the resistance heating element 2 and the substrate 1 excluding the power supply electrodes 31 and 32. It is a glassy overcoat layer formed by melting a system glass.

Since the above-mentioned power supply electrodes 31 and 32 have the same structure, one power supply electrode 31 will be described in detail with reference to FIG. 4, and the electrode 31 will be the lower layer electrode 31d on the substrate 1 side.
The lower layer electrode 31d and the upper layer electrode 31u are formed in two layers. The thickness of each of the upper layer electrode 31d and the lower layer electrode 31u is about 10 to 30 μm, the lower layer electrode 31d has a larger area than the upper layer electrode 31u, and the resistance heating element 2 is formed on one end side in layers. An upper electrode 31u is layered on the end side (also the end side of the substrate 1).

The power supply electrodes 31 and 32 have a resistance value (100 mΩ / mm) per unit area formed by the resistance heating element 2.
Resistance value (1 mΩ) lower than ^{2 to} 1000 mΩ / mm ²
/ Mm ^{2 to} about 1.5 mΩ / mm ² ), and is formed wide so as to suppress heat generation during energization.

The lower layer electrode 31d and the upper layer electrode 31u are made of different materials. For example, the lower layer electrode 31d is made of silver Ag.
The upper layer electrode 31u is composed of about 99% by weight of silver Ag and about 1% by weight of palladium Pd, while the upper layer electrode 31u is composed of about 96% by weight and about 4% by weight of palladium Pd. The content is small and the resistance value is lower than that of the lower electrode 31d, and the oxidation resistance and the abrasion resistance are high.

On the surface of the back (lower) surface 1b of the substrate 1, the power supply electrode 3 is provided along the extending direction of the resistance heating element 2.
Approximately 1 mm wide and 10-30 μm thick, made of a good conductive material mainly composed of silver Ag / palladium Pd similar to 1,32.
A pair of film-shaped wiring conductors 3a and 3b of m are formed in parallel, and wide electrode portions 33 and 34 are provided at the ends thereof.

Further, the temperature detecting element 6 such as a thermistor having a temperature sensing portion facing the back (lower) surface side 1b of the substrate 1 bridging between the other ends of the wiring conductors 3a and 3b is electrically conductive. It is bonded via an adhesive. A protective coat layer (not shown) made of an insulating resin such as an epoxy resin or a silicone resin is formed on the surface including the thermistor and the joint. The temperature detecting element 6 is installed on the lower surface 1b of the substrate 1 where the temperature can be detected stably.

When manufacturing the plate-shaped heater H1, the resistance heating element 2 is composed of, for example, a mixed powder of silver Ag and palladium Pd, a glass powder (inorganic binder) and an organic binder (organic adhesive). Kneaded Ag / P
After forming a thick film by screen-printing the d paste along the longitudinal direction of the front (upper) surface side 1a of the substrate 1, the firing peak temperature is about 850 ° C. for about 10 minutes (the firing furnace elapsed time is about It is formed by firing for 40 minutes.

Similarly to the resistance heating element 2, the electrode portions 31 to 34 and the wiring conductors 3a and 3b are powders made of a material having good conductivity mainly composed of Ag / palladium Pd (the resistance heating element 2 is formed). It is a material with better conductivity than the material.)
And an Ag / Pd paste in which glass powder (inorganic binder) and organic binder (organic adhesive) are kneaded, the resistance heating element 2 at the end of the upper surface side 1a of the substrate 1 front (upper) surface and back (lower) It can be formed by forming a thick film on the surface of the surface side 1b by screen printing and then firing.

The electrode portions 31 and 32 are the lower layer electrode 31.
Using materials in which the mixing ratio of Ag and Pd for d and the upper layer electrode 31u are changed as described above, the respective layers are formed and fired.

Further, the temperature detecting element 6 such as a thermistor is provided with the wiring conductors 3a and 3b through a conductive adhesive in which a mixed powder of silver Ag or silver Ag / palladium is mixed with an inorganic binder or an organic binder. It is joined to the end.

The resistance heating element 2 and the electrode portions 31 to 31 are
The formation of the coating film forming 34 and the wiring conductors 3a and 3b may be performed separately before or after each, or simultaneously.

After this, both of the front (upper) surface side 1a of the substrate 1
The surface portion except the upper electrode 31u, 32u at the end and the resistance
For example, silicon oxide S is applied to the surface of the anti-heating element 2.
iO ₂SiO containing as a main component₂-B₂O₃-Al₂O₃System Gala
Soot powder and ethyl cellulose (organic binder)
Screen glass paste made by kneading with organic solvent
Print to form a coating.

After this coating film is dried, it is baked in a baking furnace at a baking peak temperature of about 850 ° C. for about 10 minutes (the baking furnace elapsed time is about 40 minutes) to obtain a thickness of 15 μm to 100 μm.
m as a glassy coat layer 4.

This glass has a softening point of about 750 ° C. and is lower than the firing temperature of the pasty coating material constituting the resistance heating element 2. As the firing temperature is raised, the glass paste melts and the resistance heating element 2 is heated. When the surface of the glass flows on the substrate 1 and becomes substantially flat, the heating is stopped and the glass is cooled to form the vitreous overcoat layer 4.

The plate-shaped heater H1 having such a structure
Is SSR (Solid State Relay) or PWM
(Pulse Width Modulation) or the like and a temperature control circuit are connected, and when current is applied between the terminal portions 31 and 32, a current flows through the resistance heating element 2 and the resistance heating element 2 heats up. In No. 2, a substantially uniform temperature distribution is obtained over the entire length.

In this heater H1, the silver Ag / palladium Pd contained in the metal alloy serves as an electric resistance element, and the resistance value of the heating element 2 depends on the ratio of silver Ag / palladium Pd contained in the resistance paste and the glass powder. Adjusted. In the present embodiment, the resistance value is about 25 ohm [Ω],
Applying a voltage of 100V causes a current of about 4A to flow,
The heating value is 0 W.

Then, the thermistor 6 usually provided on the back (lower) surface side of the substrate 1 detects the temperature of the heater H1 and turns on / off the SSR or the like through a temperature control circuit to control the temperature to a predetermined temperature. This has the effect of preventing accidents such as ignition due to overheating of the heater H1.

The plate-shaped heater H1 has a lower electrode 31d (3) formed on the front (upper) surface side 1a of the ceramic substrate 1.
By making the material of 2d) a material composed of silver Ag / palladium Pd in which palladium Pd is added from conventional silver Ag, the palladium Pd suppresses crystal growth and reacts with glass at the time of electrode formation. Suppresses and prevents foaming, prevents swelling and swelling, prevents the power supply electrodes 31 and 32 from peeling off from the surface of the substrate 1 due to a temperature rise during energization heating, and prevents contact failure with a power supply terminal of a socket or the like. Can be prevented.

The upper electrode 31u (32u) of the power supply electrodes 31, 32 has a smaller amount of palladium Pd added than the lower electrode 31d (32d) to improve conductivity, oxidation resistance and abrasion resistance. By using the material, it is possible to provide the plate-shaped heater H1 capable of surely performing electrical and mechanical connection with the socket. Therefore,
The upper electrode 31u (32u) may be made of silver Ag alone without addition of palladium Pd.

FIG. 5 is a sectional view of another embodiment near the power supply electrodes 31 and 32 at the end of the plate-shaped heater according to the present invention, which is longitudinally cut in the axial direction. Figure 3
The same parts as those in FIG.

In the plate-shaped heater H2 of FIG. 5, the lower electrode of the power feeding electrode 31 (32) is of two types, and the portion 31d connected to the resistance heating element 2 has the same silver Ag as in the above embodiment. -Although it is made of a material composed of palladium Pd,
The portion 31c on the end side of the substrate 1 is made of, for example, silver Ag,
An upper layer electrode 31u made of the same material as silver Ag / palladium Pd as in the above embodiment is formed on the upper surfaces of both 31d and 31c.

The portion 31c made of silver Ag which constitutes the lower layer electrode of the plate-shaped heater H2 is the endmost side of the substrate 1, and the thermal influence from the resistance heating element 2 is small at the time of energization heating, and the power feeding is performed. The electrodes 31 and 32 are less likely to be peeled off from the surface of the substrate 1 and have the same operational effects as those of the above-described embodiment.

FIG. 6 is a perspective view of the holder 7 of the plate-shaped heater H1 provided in the fixing device or the like.
Reference numeral 0 denotes a long and slender dish-shaped holder main body formed of a heat-resistant resin, and has a concave portion 71 on the upper surface side in which the substrate 1 of the plate-shaped heater H1 is accommodated. Further, 72 is a protrusion for preventing the plate-shaped heater H1 from coming off, which is provided at an edge portion of the holder body 70.
Denoted at 3 and 73 are mounting flange portions that are continuously provided on the lower surfaces of both ends.

Further, 74 is a socket portion, and by inserting the central cutout portion 75 into the right end portion of the holder main body 70, the phosphor bronze plate in the cutout portion 75 is given the elasticity of silver plating. The connectors 76, 76 are plate-shaped heaters H
1. Terminal portions 31, 32 provided at the end of the upper surface side 1a of the substrate 1 of FIG.
An electrical connection is made in contact with. In the figure, reference numeral 77 is a power supply line connected to the connectors 76, 76, 78 is a convex portion provided on the holder main body 70 side, 79 is a concave portion provided in the cutout portion 75, and this socket portion 74 is used as the power feeding electrode 31 , 32
Accurate positioning can be achieved by mounting on.

When the socket portion 74 is mounted on the plate-shaped heater H1, the surfaces of the upper-layer electrodes 31u and 32u are rubbed by the connectors 76 and 76 in order to make a strong electrical connection. Since it is formed of a high-quality material, it is possible to maintain reliable contact without damaging the power supply electrodes 31 and 32 such as being scraped.

In the holder 7 having such a configuration, one end of the plate-shaped heater H1 on the substrate 1 is sandwiched by the projection 72 and the other end is sandwiched by the notch 75 of the socket portion 74, so that the substrate of the plate-shaped heater H1 is sandwiched. The 1 can be firmly supported so as not to be displaced or bent, and reliable electrical connection can be made.

FIG. 7 is an enlarged vertical sectional view showing an example of a fixing device 8 such as a copying machine or a printer equipped with the plate heater H1. FIG. 8 is an image forming apparatus using the fixing device 8, for example, a copying machine. 9 is a vertical cross-sectional view showing a schematic configuration of a heater 9. In the figure, a heater H1 portion is the same as that of the above-mentioned embodiment, and therefore its explanation is omitted.

In FIG. 7, reference numeral 81 denotes a pressure roller, and a rotary shaft 82 pivotally supported by a drive portion (not shown) is projectingly provided on both end faces, and a cylindrical roller body formed on the outer periphery of the rotary shaft 82. A heat resistant elastic material such as a silicone rubber layer 84 is fitted on the surface of 83.

Reference numeral 85 denotes a cylindrical heater support base which is disposed so as to face the rotary shaft 82 of the pressure roller 81, and the plate heater H1 is provided on the support 85 with the pressure roller 8 attached thereto.
It is attached and fixed in a state of being juxtaposed with 1. Further, an endless roll-shaped fixing film 86 made of a heat-resistant sheet of polyimide resin or the like is wound around the substrate 85 including the heater H1 in a circulatory manner.

The flat surface of the vitreous overcoat layer 4 formed above the heater H1 is in elastic contact with the silicone rubber layer 84 of the pressure roller 81 via the fixing film 86. In FIG. 7, P is a recording medium such as a copy sheet, T1 on the copy sheet P is a printed unfixed toner image, and T2 is a fixed toner image.

The fixing device 8 having the above-mentioned structure is used as a part of the image forming apparatus as described later, and fixes the unfixed toner image T1 transferred onto the recording medium such as the copy paper P.

In this fixing device 8, the plate heater H1
Is energized through a connector (not shown) which is made of a phosphor bronze plate which is in contact with the terminal portions 31, 32 (not shown) and which is plated with silver to give elasticity, and the resistance heating element 2 generates heat at a predetermined temperature. In this state, the pressure roller 81 is rotated by the driving unit, and the fixing film 86 that is vertically moved and pressed against the driving roller 81 is also slidably in contact with the surface of the overcoat layer 4 covering the plate-shaped heater H1 and around the heater supporting base 85. Circulate.

When the copy sheet P onto which the unfixed toner image T1 is transferred is conveyed to the fixing device 8, the copy sheet P is transferred.
While the upper and lower surfaces of both the silicone rubber layer 84 of the pressure roller 81 and the surface of the fixing film 86 are rotating, the upper and lower surfaces are passed while being pressed in the upper and lower surfaces in the direction of the arrow in the figure. At that time, the unfixed toner image T1 is printed on the copy paper P by the above-mentioned pressurization and heating of the resistance heating element 2, and the toner image T2 can be fixedly formed on the copy paper P.

That is, on the paper input side of the pressure roller 81, the unfixed toner image T1 on the copy paper P is first heated and melted by the heater H1 via the fixing film 86, and at least the surface portion thereof is largely above the melting point and completely melted. It softens and melts. Thereafter, on the sheet discharge side of the pressure roller 81, the copy sheet P separates from the heater H1, the toner image T2 radiates heat naturally, and is cooled and solidified again.
Be separated from.

In the plate heater H1 mounted on the fixing device 8 via the holder 7, the temperature of the resistance heating element 2, the substrate 1, the glass-like overcoat layer 4 and the like is increased by energizing the resistance heating element 2. To rise.

Then, in this state, the overcoat layer 4 on the upper surface side 1a of the substrate 1 and the surface of the pressure roller 81 are elastically contacted with each other via the fixing film 86, so that the space between the fixing film 86 and the pressure roller 81 is increased. The copy sheet P can pass through smoothly.

Therefore, in the fixing device 8 using the plate-shaped heater H1 of the present invention, the temperature of the plate-shaped heater H1 rises quickly and the startability is good, and the power supply electrodes 31, 31 of the plate-shaped heater H1 are provided.
Even with the problem of No. 32, uniform toner fixing is performed and a copy having a beautiful image quality without fixing unevenness can be obtained.

Next, an explanation will be given with reference to a copying machine 9 shown in FIG. 8 as an image forming apparatus equipped with the plate heater H1 and the fixing device 8 according to the present invention.

In FIG. 8, the fixing device 8 part is the same as that of the above-mentioned embodiment, and therefore, the same parts are designated by the same reference numerals and the description thereof will be omitted.

In FIG. 8, reference numeral 90 denotes a casing of the copying machine 9, and 91.
Scans the document P1 by reciprocating in the direction of arrow Y on a document placing table made of a transparent member such as glass provided on the upper surface of the housing 90.

An illumination device 9L consisting of a lamp for illuminating light and a reflecting mirror is provided above the inside of the housing 90, and the reflected light beam from the document P1 emitted by this illumination device 9L is formed into a short-focus small-diameter beam. The photosensitive drum 9 by the image element array 9A
Slit exposure is performed on D. In addition, this photosensitive drum 9D
Rotates in the direction of the arrow.

Reference numeral 92 denotes a charger, which uniformly charges the photosensitive drum 9D coated with, for example, a zinc oxide photosensitive layer or an organic semiconductor photosensitive layer. On the drum 9D charged by the charger 92, an electrostatic image subjected to image exposure by the imaging element array 9A is formed. This electrostatic image is visualized using a toner made of a resin that is softened and melted by heating by the developing device 93.

On the other hand, the copy sheet P stored in the cassette 9C is paired with a pair of conveying rollers 95 which are pressed and rotated in the vertical direction at a timing so as to be synchronized with the image on the feeding roller 94 and the photosensitive drum 9D. Is sent onto the drum 9D. Then, the toner image formed on the photosensitive drum 9D by the transfer discharger 96 is transferred onto the copy paper P.

After that, the paper P separated from the drum 9D
The sheet is guided to the fixing device 8 by the conveyance guide 97, heated and fixed, and then discharged into the tray 98. After the toner image is transferred, the residual toner on the drum 9D is removed by the cleaner 99.

The fixing device 8 has an effective length corresponding to the width (length) of the maximum-size sheet that can be copied by the copying machine 9 in the direction perpendicular to the moving direction of the copy sheet P, that is, the width (length of the maximum-size sheet). The longer the resistance heating element 2 is extended, the plate-shaped heater H1 is disposed, and the pressure roller 81 for feeding is provided in opposition to the resistance heating element 2 so as to make a light elastic contact in the extending direction of the heater H1. Is provided.

Then, the unfixed toner image T1 on the sheet P fed between the heater H1 and the pressure roller 81 is melted by receiving heat from the resistance heating element 2 and characters, alphanumeric characters on the surface of the sheet P. Make a duplicated image of a symbol, drawing, etc. appear.

The copying machine 9 has the same function and effect as those described in the fixing device 8, that is, the effect of improving (speeding up) the copy processing capacity (number of copies / time).

The present invention is not limited to the above-described embodiment. For example, in the above-described embodiment, the plate heater is used for fixing an image forming apparatus such as a copying machine, but it is not limited to fixing. It can be used by attaching it to household electric appliances, precision equipment for business or industry, or equipment for chemical reaction.

[0089]

According to the invention described in claim 1, it is possible to prevent foaming of the power supply electrode formed on the substrate, prevent the electrode from bulging and rising or peeling from the surface of the substrate, and be good as a power supply terminal of a socket. It is possible to provide a plate-shaped heater with improved quality, in which various electrical connections are made.

According to the second aspect of the present invention, the same effect as that of the first aspect is obtained by making the substrate ceramic.

According to the third aspect of the present invention, it is possible to provide a plate-shaped heater in which the electrical conductivity and abrasion resistance of the power feeding electrode are enhanced, and the electrical and mechanical connection with the socket connector is ensured.

According to the invention of claim 4, claim 1
Since the plate heater having the effects described in 1 to 3 is provided, it is possible to provide a highly productive fixing device that is quick in starting (heating) and easy in maintenance.

According to the invention described in claim 5, the fixing device having the effect described in claim 4 is provided, that is, the copy processing capacity (the number of copies / time) is improved and maintenance is performed. It is possible to provide an image forming apparatus such as a copying machine or a printer which is easy to produce and has high productivity.

[Brief description of drawings]

FIG. 1 is a partially cutaway front (upper) view showing an embodiment of a plate heater according to the present invention.

FIG. 2 is a back (lower) side view in which a part of the plate-shaped heater of FIG. 1 is cut away.

FIG. 3 is an enlarged cross-sectional view showing a portion cut along line aa in FIG.

FIG. 4 is a vertical cross-sectional view of an end portion of the plate heater shown in FIG.

FIG. 5 is a vertical cross-sectional view of an end portion of a heater showing another embodiment of the plate heater according to the present invention.

FIG. 6 is a perspective view of a holder for a plate-shaped heater mounted on the fixing device of the present invention.

FIG. 7 is an enlarged vertical sectional view showing an embodiment of the internal structure of the fixing device according to the present invention.

FIG. 8 is a vertical sectional view showing a schematic configuration of an image forming apparatus according to the present invention, for example, a copying machine.

[Explanation of symbols]

H1, H2: Plate heater 1: substrate 1a: front (upper) surface side 1b: Back (lower) side 2: Resistance heating element 31, 32: Power supply electrodes 31d (32d), 31c: lower layer electrode 31u (32u): upper layer electrode 4: Glassy overcoat layer 8: Fixing device 81: Pressure roller 9: Copier

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H033 BA08 BA10 BA11 BA25 BA26                       BA27 BB18 BB21 BB22 BB28                       BB34                 3K034 AA02 AA10 AA12 AA34 AA37                       BA08 BB05 BC04 BC12 CA02                       CA27 FA22                 3K058 AA01 AA82 BA18 DA01

Claims (5)

[Claims] 1. A long substrate made of a heat-resistant and electrically insulating material; a strip-shaped resistance heating element formed along the longitudinal direction on the surface of the substrate; a front side of the substrate connected to the resistance heating element. Alternatively, the lower layer electrode side having a lower resistance value per unit area than the resistance heating element is made of Ag.Pd or Ag.Pt, and the upper layer electrode side is the same as the lower layer electrode side or made of Ag. A plate-shaped heater comprising: a power supply electrode; and a glassy overcoat layer formed so as to cover the resistance heating element and the front surface of the substrate. 2. The plate heater according to claim 1, wherein the substrate is made of a ceramic material. 3. The plate heater according to claim 1, wherein the upper layer electrode side is formed of a material having a lower resistance value and a higher abrasion resistance than the lower layer electrode side. 4. A pressure roller; and a resistance heating element facing the pressure roller.
And a plate-shaped heater according to any one of the above. 5. A means for adhering toner to an electrostatic latent image formed on a medium and transferring the toner to a copying object to form a predetermined image; a copying object on which an image is formed by a pressure roller. An image forming apparatus comprising: the fixing device according to claim 4, wherein the fixing device fixes the toner by passing the toner while pressing it against a plate heater.