JP2890612B2 - Heating body and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a toner fixing heater, a fixing device, and an image forming apparatus suitable for fixing toner.

(Prior Art) An image forming apparatus such as a copying machine is disclosed in, for example, JP-A-64-8357.
As described in Japanese Patent Publication No. 9, a toner image is formed by forming an image such as a character, a figure, or an image on a sheet of paper with toner, and the toner is heated using a halogen lamp or the like while conveying the sheet with rollers or the like. What fixes the toner on the paper by using it is put to practical use.

In recent years, flat heaters for fixing toner have been developed as heaters for fixing toner by being incorporated in such an image forming apparatus.

FIG. 1 is a front view showing an example of a conventional toner fixing heater. Reference numeral 1 denotes an elongated flat base made of, for example, alumina ceramics. Reference numeral 3 denotes a resistance heating element formed by applying a resistor paste containing, for example, a silver-palladium alloy or the like as a main component on one surface side of the base body by a screen printing method and firing the paste. Resistance heating element 3
Has a heat-generating portion 31 at the center, and has terminal portions 32, 32 formed wide at both ends. Silver coating layers 33, 33 are coated on the terminal portions 32, 32 by a screen printing method. 4
Is a vitreous electrically insulating protective film attached on the substrate 1 covering the resistance heating element 3.

The toner fixing heating element heats the toner while moving the sheet on which the toner image is formed on the surface of the fixing heating element in the fixing device to fix the toner image on the sheet.

(Problems to be Solved by the Invention) In a conventional heating body for fixing toner, in order to satisfactorily fix toner on a fixing body such as paper, the fixing body is heated by a roller with an optimal pressing force. At the same time, in order to reduce unevenness of the toner by reducing the unevenness of the surface of the toner fixing heater, and to smoothly move the object to be fixed on the surface of the toner fixing heater. The surface of the electrically insulating protective coating was formed smoothly to a state close to a mirror finish.

However, according to a test conducted by the inventor, when the surface of the insulating protective film is processed to be smooth to a state close to a mirror surface, an object to be fixed such as paper moving on a heating body for toner fixing is fixed by toner. It has been found that the sliding friction increases due to the close contact with the heating body, and the friction resistance further increases.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a toner fixing heater capable of smoothly moving an object to be fixed by improving the surface condition of an electrically insulating protective film.

[Configuration of the invention]

(Means for Solving the Problems) A heating body for fixing a toner according to claim 1 covers an electrically insulating base, a resistance heating element attached to the base, and at least a part of the resistance heating element. An electrical insulating protective coating which is yellowed on the substrate and has irregularities of 0.1 to 2 μm in center line average surface roughness Ra on the resistance heating element.

The heating body for toner fixing according to claim 2, wherein the heating body for covering the electric insulation, the resistance heating body attached to the base, and at least a part of the resistance heating body are covered with yellow on the base, and the surface is covered with yellow. An electrical insulating protective film formed with mesh pattern-like irregularities of the printing screen.

According to a third aspect of the present invention, there is provided a fixing device comprising: means for transporting an object to be fixed;

According to a fourth aspect of the present invention, there is provided an image forming apparatus comprising: means for adhering toner to an object to be fixed; and the fixing device according to claim 3 for fixing the toner adhering to the object to be fixed. I do.

(Function) According to the toner fixing heater according to the first aspect, the surface of the electrically insulating protective coating is formed with irregularities having a center line average surface roughness Ra of 0.1 to 2 μm on the resistance heating element. Therefore,
Even in a state where the fixing target is pressed against the toner fixing heating body with a required pressing force for fixing the toner satisfactorily,
The body to be fixed and the like are in close contact with the heating body for fixing toner, so that sliding friction is not increased, and uneven fixing of toner due to unevenness of the surface of the electrically insulating protective coating can be reduced.

According to the heating element for toner fixing according to the second aspect, the surface of the electrically insulating protective coating has mesh-pattern-shaped irregularities of the printing screen formed when printing it.
If a screen normally used for the screen printing method is used for printing the electrically insulating protective coating, the surface roughness of the mesh pattern formed on the surface of the electrically insulating protective coating is approximately 0.1 to 0.1 in the center line average surface roughness Ra. It can be set to 2 μm. Therefore, it is possible to easily obtain an appropriate surface roughness of the electrically insulating protective coating.

According to the fixing device of the present invention, the toner adhered to the fixing member is adhered by the toner fixing heating element while conveying the fixing member. In this case, the toner fixing heater has the same function as the toner fixing heater of the first or second aspect.

According to a fourth aspect of the present invention, the toner is attached to the fixing member by the image forming means, and the toner attached to the fixing member is fixed by the fixing device. At this time, the fixing device has the function of the fixing device according to the third aspect.

(Embodiment) An embodiment of the present invention will be described with reference to FIG. 1 to FIG.

FIG. 1 is a partially cutaway front view showing one embodiment of a toner fixing heater according to the present invention, FIG. 2 is a partially cutaway sectional view along a longitudinal direction, and FIG. FIG. 3 is a cross-sectional view along the short side direction. 2 and 3 are enlarged in the thickness direction and are different from the actual shape. In addition, the irregularities on the surface of the electrically insulating protective coating in FIG. 3 are exaggerated and different from the actual appearance.

In these figures, reference numeral 1 denotes an elongated flat substrate made of alumina ceramics having a length of about 300 mm, a width of about 8 mm, and a thickness of about 1 mm. Reference numeral 2 denotes a grace layer formed on one surface of the base 1 for heat insulation, and reference numeral 3 denotes an elongated resistance heating element formed on the surface of the grace layer 2. Reference numeral 4 denotes an electrical insulating protective film that covers the surface of the resistance heating element 3 and the surface of the grace layer 2 and is adhered on the base 1. Grace layer 2
Is not a necessary configuration.

Next, the detailed structure of the heating body for fixing toner will be described through the manufacturing process. The grace layer 2 is formed in an arc shape in which the center is highest in the longitudinal cross section of the base 1,
Its height is about 100 μm from the surface of the substrate 1. The cross-sectional shape and the height of the highest point are uniform and continuous over the entire length of the base 1 in the longitudinal direction.

The resistance heating element 3 is formed by applying a resistance paste containing a silver / palladium alloy or the like as a main component to the surface of the grace layer 2 by a screen printing method and then firing the paste. The resistance heating element 3 has a band shape of about 1.5 to 2.5 mm in width and about 10 μm in thickness,
Approximately 6-7mm in width and about 15 in length at both ends of the heating part 31 of about 270mm in length
mm terminal portions 32 and 33 are integrally formed of the same material. Then, on the surfaces of the terminal portions of the terminal portions 32, silver coating layers 33, 33 for connecting an external power supply line are formed. The resistance heating element 3 is provided at the center of the grace layer 2 in the width direction, that is, at the highest part.

After forming the resistance heating element 3 on the grace layer 2, the electrically insulating protective coating 4 includes frit glass such as lead borosilicate gas so as to cover the resistance heating element 3 and the exposed grace layer 2. It is applied by a screen printing method on a glass base. At this time, a mesh pattern of the printing screen is formed on the surface of the electrically insulating protective coating 4. Thereafter, the glass base is fired to form the electrically insulating protective coating 4, and the firing temperature and the firing time at this time are set so as not to erase the shape of the mesh pattern.

Since the electrically insulating protective coating 4 is uniformly applied to the entire surface except for the silver coating layers 33 and 33 with a thickness of about 10 μm, the unevenness of the mesh pattern is the center line average roughness specified in JIS. Ra is left as a height difference of 0.1 to 2 μm. In addition,
If the surface of the electrically insulating protective film 4 has irregularities of 2 μm or more, it may be smoothed by polishing with a sandpaper of No. 800 to 5000. The value of 0.1 to 2 μm is a value measured by a surface roughness measuring device.

The heating body for fixing the toner is disclosed in, for example, JP-A-64-33579.
As described in Japanese Patent Application Laid-Open Publication No. H10-115, the paper is incorporated in a fixing device using a roller as a sheet conveying means.

FIG. 4 is a cross-sectional view of a principal part showing an embodiment of the present invention of such a fixing device. In this figure, the heating element for toner fixing is drawn in an enlarged manner in the thickness direction. In the figure, reference numeral 41 denotes a heating element for toner fixing, and reference numeral 42 denotes a roller for conveying a sheet 43 on which a toner image is formed while pressing the sheet 43 on the heating element 41 for toner fixing. Heat of the toner fixing heater 41 is applied to paper
The toner acts on the toner adhering to 43 and the toner is fixed on the paper. It is not necessary that the toner fixing heater 41 and the sheet 43 come into direct contact with each other.

FIG. 5 is a conceptual diagram showing the image forming apparatus of the present invention.
In the figure, 51 is an image forming means for forming a toner image on a sheet, and 52 is the above-mentioned fixing device for fixing the toner on the sheet. In the figure, the arrow indicates the direction in which the sheet is conveyed. In addition, as such an image forming apparatus, a copying machine,
There are devices such as a printer or facsimile.

By the way, according to the fixing device and the image forming apparatus provided with the above-mentioned heating element for toner fixing, the portion of the surface of the electrically insulating protective film 4 of the heating element for toner fixing in which the heating portion 31 is covered is another portion. Since the sheet is formed higher and its height is uniform and continuous, the sheet is pressed uniformly over the entire length of the heat generating portion 31 and is uniformly heated. Therefore, local blurring and unclear portions are unlikely to occur in the image.

Here, using the above-mentioned heating body for toner fixing, a simple paper feeder was used to examine the passing condition by passing a piece of paper between the heating body for toner fixing and the platen roller. The unevenness of the surface of the electrically insulating protective coating of the used heating element for fixing has a center line average surface roughness Ra of about 1 μm. Also, for comparison,
A toner fixing heater having the same shape and the same dimensions as the above-mentioned toner fixing heater, having no irregularities (less than 0.1 μm) on the surface of the electrically insulating protective coating and having a substantially mirror-finished surface was prepared, and the same test was performed. The results are shown in the following table.

From this test result, it can be seen that the heating body for fixing the toner of this embodiment is significantly superior in paper-through.

In addition, since the unevenness of the surface in the above embodiment uses a mesh pattern by a printing screen, a step of forming unevenness is not particularly required, and the unevenness of 0.1 to 2 μm is controlled by controlling the temperature at the time of firing the electric insulating wire protective coating. Can be formed.

Further, in the above-described embodiment, the resistance heating element is provided at the center in the width direction of the base or the grace layer. However, the present invention is not limited to this. It may be provided on the edge side.

Further, the insulating protective film is not limited to one coated by the screen printing method, and need not be glassy.

〔The invention's effect〕

According to the toner fixing heater according to claim 1, since the surface state of the electrically insulating protective coating is appropriate, the member to be fixed and the toner fixing heater are not in close contact with each other, and the sliding friction is not increased. Sliding friction does not increase due to unevenness of the surface of the electrically insulating protective film. Therefore, it is possible to smoothly move the fixing member on the surface of the heating member for fixing toner. Further, since the surface of the electrically insulating protective film has few irregularities, it is possible to reduce toner fixing unevenness.

According to the heating element for toner fixing of the second aspect, the mesh pattern of the printing screen formed when the electrically insulating protective coating is printed on the surface of the electrical insulating protective coating is present.
Since the surface state of the electrically insulating protective film is made appropriate by this mesh pattern, the toner fixing heater according to claim 1 can be formed relatively easily.

The effects of the fixing device according to the third aspect and the heating body for toner fixing according to the first or second aspect are achieved.

The effects of the image forming apparatus according to the fourth aspect and the fixing apparatus according to the third aspect are achieved.

[Brief description of the drawings]

FIG. 1 is a partially cutaway front view showing an embodiment of the present invention and a conventional heating element for toner fixing, and FIG. 2 is a cross-sectional view along a longitudinal direction, also partially enlarged and cut away in the thickness direction. FIG. 3 is a cross-sectional view taken along a short side direction, which is also partially enlarged and cut away in the thickness direction, FIG. 4 is a cross-sectional view of a main part showing the fixing device of the present invention, and FIG. FIG. 2 is a conceptual diagram illustrating an image forming apparatus. DESCRIPTION OF SYMBOLS 1 ... Base, 2 ... Grace layer, 3 ... Resistance heating element, 31 ... Heating part, 32 ... Terminal part, 4 ... Electric insulating protective coating.

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H05B 3/00-3/82

Claims (4)

(57) [Claims] An electrically insulating substrate; a resistance heating element provided on the substrate; and a center line average surface on the resistance heating element, the resistance heating element covering at least a portion of the resistance heating element. 0.1 to 2μ in roughness Ra
and an electrically insulating protective film having m irregularities formed thereon. 2. An electrically insulating substrate; a resistive heating element provided on the substrate; a resistive heating element covering at least a part of the resistive heating element and attached to the substrate, and having a mesh pattern of a printing screen on the surface. And an electrical insulating protective film having irregularities formed thereon. 3. A fixing device, comprising: means for transporting an object to be fixed; and the heating element for fixing toner according to claim 1 or 2, which fixes toner on the object to be fixed. 4. An image forming apparatus comprising: means for adhering toner to an object to be fixed; and the fixing device according to claim 3, which fixes the toner adhering to the object to be fixed. .