JP3814080B2 - Centrifugal mold - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a centrifugal mold for producing an endless belt used as an intermediate toner image carrier in an electrostatic copying process such as a copying machine or a printer.
[0002]
[Prior art]
FIG. 5 is a sectional view showing a conventional method for producing an endless belt by centrifugal molding. In the conventional centrifugal molding method, a solution is poured into the inner surface of a cylindrical coating mold 10 'which is a rotating coating mold by spray coating or the like, and then the centrifugal molding mold 10' is rotated at high speed around the axis a of the cylinder. Then, the solution applied by the centrifugal force is spread in the axial direction to form a film 2 having a uniform thickness, and then the uniform film 2 is heated by a heater 3 to be dried and solidified (in some cases, further cured) After treatment) it is peeled off. This membrane 2 becomes an endless belt.
[0003]
Since this heat treatment must be performed while rotating the mold 10 'so that the coating liquid inside the mold does not dripping, generally, the mold 10' is moved from the heater 3 outside the rotating mold. Heat through.
[0004]
The heater 3 generally uses visible light such as a halogen lamp or far infrared light such as a far infrared lamp. When the applied film 2 becomes a certain uniform film, the heater is turned on and dried. Then, the heater 3 is turned off in a dry state where the coating film does not adhere even when touched with a finger, and the rotation of the mold 10 ′ is stopped to peel off.
[0005]
When the film 2 is cured, when the heater 3 is turned off, the heater 2 is not turned off. Conversely, the input to the heater is further increased, and the temperature of the mold 10 'is increased to cure the film 2. When the film 2 reaches a desired hardness, the heater 3 is turned off, the rotation of the mold 10 'is stopped, and the film 2 is peeled off.
[0006]
By the way, if the coating film applied by centrifugation is not sufficiently dried by the solvent, the film 2 is soft and tears when it is peeled off, and if it is too dry or solidified, the film 2 is used for centrifugal molding. There is a problem that the mold 10 ′ is too close to the mold and is torn, and the heating conditions must be carefully controlled.
[0007]
Therefore, it is desirable to be able to freely control the rate of temperature rise and the ultimate holding temperature during heating during drying or curing of the applied film.
[0008]
In addition, as a material of the mold body 1 in the centrifugal mold 10 ′, a metal mold is generally used for performing heat treatment during drying or curing treatment of the applied film 2, but because of film releasability. In addition, surface roughness processing close to a mirror surface is required. Moreover, prevention of internal stress due to thermal expansion and contraction during heating and cooling and heat resistance against heating temperature are also required. Aluminum or an aluminum alloy is used to meet all of these requirements.
[0009]
However, if aluminum or aluminum alloy is used as it is, it can be seen from the fact that it has surface gloss, so the heat absorption rate is poor and the temperature rise is very slow. Therefore, in order to speed up the temperature rise, attempts have been made to improve such as reducing the thickness of the mold or forming the heat absorption film 4 by applying a black body material having a good heat absorption rate.
[Problems to be solved by the invention]
[0010]
However, in this centrifugal molding method, since the mold must be rotated at a high speed, the mold must be firmly fixed by chucking from both sides. For this reason, even if the temperature is raised by heating, chucking is performed from both ends of the mold 10 '. Through this, heat flowed out, the temperature at both ends decreased, and the temperature in the axial direction of the mold 10 'did not become uniform.
[0011]
When such a temperature distribution occurs, the solvent removal of the coating film becomes non-uniform, and the film curing time also becomes non-uniform, resulting in variations in film thickness and non-uniform internal stress during curing. There was a problem that wrinkles occurred when the image was taken out and a good image could not be formed even if an image was formed.
[0012]
An object of the present invention is to solve such a problem and to provide a centrifugal mold that can form a good endless belt without causing an axial temperature distribution (temperature difference).
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a centrifugal coating mold for forming an endless belt by centrifugal molding, wherein the heat absorption rate of the centrifugal molding mold is different along the axial direction of the cylinder. It is characterized by that.
[0014]
Decreasing the heat absorption rate at the center of the mold for centrifugal molding, increasing the heat absorption rate at both ends, or forming a heat absorption film on the outside of the mold for centrifugal molding, and changing the density of the heat absorption film The heat absorption rate is made different, or the density of the heat absorption film is increased at both ends and decreased at the center, or the heat absorption film is formed in a mesh shape at the center of the centrifugal mold. Can be.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[Example 1]
1 and 2 are sectional views showing an embodiment of a centrifugal mold according to the present invention. The mold body 1 of the centrifugal mold 10 is formed of the same aluminum or aluminum alloy as the conventional one and has a cylindrical shape. The present invention is characterized by the heat absorption film 14 formed outside the mold body 1.
[0016]
The heat absorbing film 14 of the present invention is formed by spraying a heat absorbing material. Therefore, prior to spray application, about one-sixth was left from both ends of the mold body 1 having an aluminum cylindrical shape, and a 1 mm mesh net 5 made of SUS was wound around, and a black body paint was applied from above by spraying. After drying, the net was removed to obtain a centrifugal mold 10 on which a heat absorbing film 14 as shown in FIG. 1 was formed.
[0017]
That is, in the central portion, the place where the heat absorption film 14 is formed and the place where it is not formed are distributed. Therefore, the heat absorption rate is different between the mesh portion of the heat absorption film 14 and the portions formed on the entire surface of both ends, and the temperature at both ends of the centrifugal mold 10 is higher than the temperature at the center. Even if heat flows out from both ends through the chuck, the temperature distribution of the centrifugal mold 10 can be kept constant by appropriately setting the mesh size of the mesh 5, the length of the mesh 5, and the like. .
[0018]
In the above embodiment, the 1 mm mesh net 5 made of SUS is used. However, the mesh roughness and the net material are not limited thereto. Further, it is not necessary to be made of metal, and other materials such as a resin can be used. Furthermore, it is not necessary to be a net, and various forms such as those in which thread-like materials are arranged in parallel can be used.
[0019]
While the mold is fixed on one side to a rotating device and rotated slowly, a dispersion prepared by diluting a polyimide precursor solution (Toray Nice # 3000 manufactured by Toray Industries, Inc.) prepared in advance in a solvent DMAC is added to the inside of the mold. It was applied to.
[0020]
Thereafter, the centrifugal mold was fixed at both ends and rotated at a high speed to form a coating film to a uniform thickness, and then the external heater was turned on and heated to 100 ° C. to dry the solvent.
[0021]
When the temperature of the mold for centrifugal molding is measured with a radiation thermometer, the conventional mold 10 'shown in FIG. 5 has a lower end portion and a higher central portion as shown by the dotted line (1) in the graph of FIG. However, in this example, as shown by the solid line (1) in FIG. 3, no temperature fluctuation was observed at both ends and the center of the mold, and it was found that a constant temperature was maintained.
[0022]
The heater was turned off and the rotation was stopped. After cooling, the film was peeled off. When the film thickness of this film was measured, the coating film thickness was uniform at both ends and the center, and there was no abnormality in appearance such as wrinkles.
[0023]
[Example 2]
In the same manner as in Example 1, a centrifugal mold having a heat absorbing film formed thereon was coated and dried with the same diluted dispersion, and then the input of an external heater was raised to raise the mold temperature to 280 ° C. Cured.
[0024]
The temperature of the centrifugal mold was measured with a radiation thermometer. As shown by the solid line (2) in the graph of FIG. 3, the temperature at both ends and the central part was uniform, and the conventional mold as shown by the dotted line (2) No temperature distribution was observed as in 10 '.
[0025]
[Comparative Example 1]
As shown in FIG. 5, a heat absorption film 4 formed on the entire outer surface of the mold body 1 is used on the same mold body 1 as in Example 1, and a coating film is formed in the same manner as in Example 1. Heated. And the temperature distribution at that time was measured, and the film thickness and external appearance of the dry cured film were observed.
[0026]
As shown by the dotted lines (1) and (2) in the graph of FIG. 3, even at 100 ° C. (dotted line (1)), the temperature at both ends is lower than that of the example (solid line (1)). The dotted line (2)) shows that the temperature difference is further increased.
[0027]
The film thickness distribution was hardly observed during drying, but the vicinity of the edge was thicker, and irregular appearance of irregularities was observed.
At 280 ° C., almost no film thickness distribution was observed, but after a while after peeling, wrinkles that wavy in the circumferential direction occurred at both ends.
[0028]
[Comparative Example 2]
As shown in FIG. 4, the heat absorbing film 24 was formed on the same mold body 1 as in Example 1 only at both ends of the outer surface of the mold. A coating film was formed on this centrifugal mold 10 ″ in the same manner as in Examples 1 and 2 and heated by the heater 3. Then, the temperature distribution was measured, and the film thickness and appearance of the dried cured film were observed. The temperature was measured with a radiation thermometer, but the central part could not be measured correctly, and the coating film had a bumpy shape.
[0029]
Therefore, the temperature was measured with a contact thermometer while rotating at a low speed, and after taking correspondence with the input, the measurement was performed in the same manner as in Example 2 with a predetermined input.
[0030]
【The invention's effect】
As described above, according to the present invention, in the centrifugal molding method for creating an endless belt, the axial heat absorption coefficient of the cylindrical centrifugal mold is made different. Even if heat escapes due to heat, the temperature difference between both ends and the center can be reduced.
[0031]
If the heat absorption rate at the center of the mold for centrifugal molding is reduced and the heat absorption rate at both ends is increased, even if heat escapes from both ends of the die, it is possible to maintain a substantially constant temperature throughout the die. Thus, the film thickness of the endless belt can be made constant, and abnormality in the external shape can be reduced.
[0032]
If the heat absorption film is formed outside the centrifugal mold and the density of the heat absorption film is changed, a desired distribution can be obtained with a simple structure.
If the heat absorption film is formed in a mesh shape at the center of the centrifugal mold, it is easier than controlling the film thickness.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a centrifugal mold according to an embodiment of the present invention.
2 is a perspective view for explaining a method of forming a heat absorption film of the centrifugal mold of FIG. 1. FIG.
3 is a graph showing the temperature distribution of a centrifugal mold in Examples 1 and 2, in which solid lines are Examples 1 and 2 and dotted lines are Comparative Example 1. FIG.
FIG. 4 is a cross-sectional view of a centrifugal mold used in Comparative Example 2 of the present invention.
FIG. 5 is a cross-sectional view of a conventional centrifugal molding die (Comparative Example 1).
[Explanation of symbols]
10 Centrifugal mold 1 Mold body 2 Endless belt (membrane)
3 Heater 5 Net 14 Heat absorption film

Claims (5)

A centrifugal mold for forming an endless belt by centrifugal molding, wherein the heat absorption rate of the centrifugal mold is different along the axial direction of the cylinder. The centrifugal mold according to claim 1, wherein the heat absorption rate at the center of the centrifugal mold is reduced and the heat absorption rate at both ends is increased. The centrifugal mold according to claim 1 or 2, wherein a heat absorption film is formed outside the centrifugal mold, and the heat absorption rate is varied by changing the density of the heat absorption film. 4. The centrifugal mold according to claim 3, wherein the density of the heat absorption film is large at both ends and small at the center. 5. The centrifugal mold according to claim 4, wherein the heat absorbing film is formed in a mesh shape at the center of the centrifugal mold.

Images