JP2004177811A - Image forming apparatus and solid release agent for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simply constituted image forming apparatus dispensing with an unnecessary rotating body, and capable of suppressing uneven coating and also, capable of attaining both of the initial coating amount and the long life, and to provide solid release agent for the image forming apparatus. <P>SOLUTION: A solid body such as zinc stearate is used as the solid release agent 7 to be applied on a photoreceptor drum 1 and a transfer belt, and also, a hardness distribution is given to the inside of the solid body. And, the softer surface layer 701 comes into contact with the photoreceptor drum 1, and the surface layer 701 is softly pushed against the drum by a pressure spring 8 from the side of the harder underlayer 702 etc. Then. the release agent is applied through the soft surface layer 701 at the initial stage of the durable use, and the release agent is applied through the hard underlayer 702 at the latter stage of the durable use. By such a constitution, both the sufficient coating with the release agent at the initial stage of the durable use and the long life over the whole durable use are attained, dispensing with the unnecessary rotating mechanism etc. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus that forms a toner image on a toner carrier and transfers the toner image onto a recording medium to form an image. More specifically, the present invention relates to an image forming apparatus in which a release agent is applied to a toner carrier to enhance the releasability of toner from the toner carrier, and a solid release agent therefor.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an image forming apparatus using toner, there is an image forming apparatus that supplies a substance having lubricity or releasability between a toner carrier (photosensitive drum, transfer belt, etc.) and a cleaning member. (For example, Patent Documents 1 and 2). This is to ensure that the toner remaining on the toner carrier after the transfer is removed by the cleaning member.
[0003]
In the image forming apparatuses disclosed in Patent Documents 1 and 2, a brush roller that comes into contact with the surface of an image carrier (toner carrier) and a solid agent that comes into contact with the brush roller while contacting the brush roller are provided. Thus, the lubricant is scraped from the solid agent by the brush roller and applied to the image carrier. Here, in the image forming apparatus of Patent Document 1, the amount of application is controlled by the pressing force pressing the solid agent against the brush roller. In the image forming apparatus of Patent Document 2, the amount of solid agent entering the brush roller or the hardness is different between the image area and the outside. Thus, the lubricant is sufficiently supplied to the non-image area.
[0004]
[Patent Document 1]
JP-A-2000-75752 (paragraphs [0028] and [0035], FIG. 3)
[Patent Document 2]
JP 2001-5359 A (paragraphs [0023] to [0025], etc., FIG. 2)
[0005]
[Problems to be solved by the invention]
However, the above-described conventional image forming apparatus has the following problems. That is, in these image forming apparatuses, a rotating body called a brush roller is provided between the toner carrier and the solid agent. This is understood to be to control the amount of lubricant applied to the toner carrier. This is because simply pressing the solid agent against the toner carrying member makes it difficult to apply the solid agent uniformly due to a one-sided contact or the like. On the other hand, however, the provision of the brush roller itself and its rotating mechanism complicates the structure, resulting in an increase in the size of the apparatus. Further, the application amount itself can be controlled by the hardness of the solid agent and the pressing force against the brush roller. However, if the required amount of coating is obtained in the early stage of durable use, the amount of coating will be excessive in the later stage of durable use. Therefore, the expected life of the solid agent cannot be achieved.
[0006]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the conventional image forming apparatus. That is, the object is to provide an image forming apparatus which has a simple structure without an extra rotating body, hardly causes coating unevenness, and achieves both an initial coating amount and a long life, and a solid release agent therefor. Is to provide.
[0007]
[Means for Solving the Problems]
An image forming apparatus according to the present invention for solving this problem has a toner carrier, and forms an image by transferring a toner image formed on the toner carrier onto a recording medium. There is a solid release agent that comes into contact with the toner carrier and applies a release agent on its surface. The solid release agent has a softer surface in contact with the toner carrier and a softer surface in the opposite surface. It has a hard hardness distribution.
[0008]
In this image forming apparatus, the solid release agent is provided so as to contact the toner carrier. Therefore, when the toner carrier rotates, the solid release agent is gradually scraped off by friction with the toner carrier. As a result, the release agent is applied to the surface of the toner carrier. The applied release agent has the effect of improving the release properties of the surface of the toner carrier. Therefore, the transferability of the toner image from the toner carrier to the recording medium or the like is good. In addition, it has good cleaning properties for toner slightly remaining on the surface of the toner carrier after transfer.
[0009]
Here, the following effects are exhibited by the solid release agent having the above-described hardness distribution. First, in the early stage of durability, the solid release agent having a low hardness, that is, a soft portion contacts the toner carrier. For this reason, the release agent is sufficiently applied to the surface of the toner carrier. Therefore, even when the surface of the toner carrier is relatively rough in the initial stage of durability, transferability and cleaning property of the toner are ensured. Also, the uniformity of the coating amount is high. This is because the soft part of the solid release agent quickly adapts even if it hits one side. Next, in the latter half of the durability, the solid release agent having a high hardness, that is, a hard portion comes into contact with the toner carrier. For this reason, the amount of the release agent applied to the toner carrier is reduced as compared with the initial stage of durability. However, since the surface of the toner carrier is relatively smooth in the latter stage of the durability, the amount of the release agent applied is small and sufficient. Rather, there is an advantage that the release agent is not consumed excessively. For this reason, a longer life can be obtained with a smaller volume of the solid release agent than in the case where the solid release agent is generally low.
[0010]
Here, the hardness distribution of the solid release agent may be such that the hardness changes stepwise from the contact surface side to the opposite side to the toner carrier, or the hardness changes continuously. You may. In the former case, the portion of the solid release agent that comes into contact with the toner carrier gradually becomes harder from the beginning to the end of durability. As a result, a portion of the solid release agent having an appropriate hardness is used depending on the stage of durable use. In the latter case, the portion of the solid release agent that comes into contact with the toner carrier gradually becomes harder from the beginning to the end of durability. As a result, a portion of the solid release agent having an appropriate hardness is used depending on the stage of durable use.
[0011]
In the present invention, it is more preferable that the hardness distribution of the solid release agent differs depending on the position of the toner carrier in the width direction or the direction crossing the width. In this case, an effect of suppressing a change in the attitude of the solid release agent with respect to the toner carrier and an effect of preventing chipping of the solid release agent can be obtained. For example, when a distribution is provided in which the hardness increases faster at both ends than the center in a direction intersecting the width direction of the toner carrier, a change in the attitude of the solid release agent is suppressed. Further, when the hardness is lower at both ends than the center in the width direction of the toner carrier, chipping of the solid release agent is prevented.
[0012]
The present invention also relates to a solid release agent used in the above-mentioned image forming apparatus, that is, a solid release agent which comes into contact with a toner carrier of the image forming apparatus and applies the release agent on the surface thereof. It is also intended that the contact surface side with the carrier is softer and the opposite surface side has a harder hardness distribution.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. This embodiment has an image forming unit for each color, and a type in which a toner image formed by each image forming unit is temporarily transferred onto an intermediate transfer belt, overlapped, and then re-transferred onto printing paper. The present invention is applied to a forming apparatus.
[0014]
The image forming apparatus according to the present embodiment is schematically configured as shown in FIG. That is, the image forming apparatus has the photosensitive drums 1Y, 1M, 1C, and 1K for each color. The transfer belt 2 includes a transfer belt 2 that is in contact with each of the photosensitive drums 1Y, 1M, 1C, and 1K. Further, on the opposite side of each of the photosensitive drums 1Y, 1M, 1C, 1K with the transfer belt 2 interposed therebetween, a toner image on each of the photosensitive drums 1Y, 1M, 1C, 1K is transferred onto the transfer belt 2. Transfer chargers 3Y, 3M, 3C and 3K are provided. The transfer belt 2 is stretched over rollers 4 and 5. A transfer charger 6 is provided opposite to one roller 5. When the transfer belt 2 and the printing paper S pass between the roller 5 and the transfer charger 6, the toner image on the transfer belt 2 is transferred onto the printing paper S. Although not shown in the drawings because they are well known, a charger, an exposure device, a developing device, a cleaner, and the like for forming an image are arranged around each of the photosensitive drums 1Y, 1M, 1C, and 1K.
[0015]
The image forming apparatus of the present embodiment has solid release agents 7Y, 7M, 7C, and 7K that are in contact with the respective photosensitive drums 1Y, 1M, 1C, and 1K. Each of the solid release agents 7Y, 7M, 7C, 7K is pressed against the photosensitive drums 1Y, 1M, 1C, 1K by pressing springs 8Y, 8M, 8C, 8K. Similarly, the transfer belt 2 is also provided with a solid release agent 7B and a pressing spring 8B. The pressing force of each of the pressing springs 8Y, 8M, 8C, 8K, 8B is about 0.0098 N / mm ² . If the solid release agent 7Y or the like is installed above the photosensitive drum 1Y or the like, this pressing force is very light enough to be achieved by the weight of the solid release agent 7Y or the like. The solid release agents 7Y, 7M, 7C, 7K, 7B are solid zinc stearate provided over the entire width of the photosensitive drum 1Y and the like. The details will be described later.
[0016]
In this image forming apparatus, each of the photosensitive drums 1Y, 1M, 1C, and 1K forms a toner image of each color of yellow, magenta, cyan, and black. Then, those toner images are transferred onto the transfer belt 2 and are superimposed. Then, the image is formed by finally transferring the superimposed toner image onto the printing paper. After that, the printing paper is discharged after receiving the fixing of the toner image.
[0017]
Here, at the time of image formation, the solid release agents 7Y, 7M, 7C, and 7K are scraped off little by little as the photosensitive drums 1Y, 1M, 1C, and 1K rotate. Thus, the release agent is applied to the surfaces of the photoconductor drums 1Y, 1M, 1C, and 1K. Thus, the transfer efficiency of the toner from each of the photosensitive drums 1Y, 1M, 1C, 1K to the transfer belt 2 is improved. In addition, the cleaning property of the toner remaining on the surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K after the transfer is improved. The same applies to the solid release agent 7B of the transfer belt 2.
[0018]
The solid release agents 7Y, 7M, 7C, 7K, 7B will be described in detail. Hereinafter, these are not distinguished and are simply referred to as solid release agent 7. Similarly, the photosensitive drums 1Y, 1M, 1C, 1K and the pressing springs 8Y, 8M, 8C, 8K, 8B are also referred to as the photosensitive drum 1 and the pressing spring 8 without particular distinction. As shown in FIG. 2, the solid release agent 7 used in the image forming apparatus of the present embodiment includes a surface layer 701 having a pencil hardness of 3B and a lower layer 702 having a pencil hardness HB. It has a layered structure. The softer surface layer 701 is in contact with the photosensitive drum 1 (the same applies to the roller 4 and the transfer belt 2), and is pressed by the pressing spring 8 from the harder lower layer 702. FIG. 2 shows an initial situation of the durable use. In this state, the release agent is applied to the photosensitive drum 1 by the surface layer 701. However, as the use proceeds, the surface layer 701 eventually disappears, and the lower layer 702 comes into contact with the photosensitive drum 1. In this state, the release agent is applied to the photosensitive drum 1 by the lower layer 702.
[0019]
As a result, a sufficient release agent application in the early stage of the durable use and a sufficiently long life of the solid release agent 7 as a whole are compatible. Hereinafter, this will be briefly described. The graph of FIG. 3 shows the results of measuring the contact angle of pure water when two types of solid zinc stearate having a pencil hardness of HB and 2B were applied by pressing against a polycarbonate transfer belt. The pressing force was the same as above. For the measurement, a contact angle measuring device CA-W150 manufactured by Kyowa Interface Science Co., Ltd. was used. From the graph of FIG. 3, it can be seen that the softer 2B coating has a larger contact angle, that is, stronger mold release, than the harder HB coating. This is considered to be because more zinc stearate is applied to the target surface when a soft material is used. In the case of the photosensitive drum 1 and the transfer belt 2, the contact angle measured as described above is desirably 90 ° or more in order to ensure the transferability and cleaning property of the toner. In addition, this is clear also in the thing of HB. If the pressing force is increased even in the case of HB, a contact angle on the order of 2B can be obtained.
[0020]
Generally, more release agent is required at the beginning of durable use. This is because the surfaces of the photosensitive drum and the transfer belt are rough. Here, in the solid release agent 7 of the present embodiment shown in FIG. 2, since the soft surface layer 701 (3B) is used in the early stage of the durable use, the surface of the photosensitive drum 1 is sufficiently released. The agent is applied. In addition, the fact that the surface of the solid release agent 7 is soft at this stage means that coating failure due to one-sided contact between the solid release agent 7 and the photosensitive drum 1 hardly occurs. This is because even if there is a collision, since the surface of the solid release agent 7 is soft, the solid release agent 7 quickly adapts to eliminate the collision. This also ensures a sufficient coating amount in the early stage of durable use.
[0021]
In addition, the graph of FIG. 4 shows changes in the amount of zinc stearate consumed per hour when two types of solid zinc stearate having a pencil hardness of HB and 2B are used for a long time. It can be seen from the graph of FIG. 4 that the softer 2B is always consumed more. This is because more zinc stearate is applied to the target surface when a soft material is used. Therefore, if the solid release agent as a whole has a low hardness, it is consumed at an early stage and the expected life cannot be completed.
[0022]
Generally, late use does not require a release agent as much as in the early stages. This is because the surfaces of the photosensitive drum and the transfer belt become smooth. Here, in the solid release agent 7 of the present embodiment shown in FIG. 2, since the hard lower layer 702 (HB) is used in the later stage of the durable use, the release agent is excessively applied on the surface of the photosensitive drum 1. Is not applied. That is, the solid release agent 7 will not be unnecessarily worn in the latter half of the durable use. For this reason, as shown in FIG. 5, the release agent is applied abundantly while the number of prints is small, but the amount of application decreases as the number of prints increases. Therefore, the life of the solid release agent 7 is long. As described above, in the solid release agent 7 of the present embodiment, both ample application in the early stage of durable use and a sufficient lifetime over the entire durable use are compatible.
[0023]
Needless to say, the solid release agent that can be used in the image forming apparatus of the present embodiment is not limited to the one shown in FIG. As shown in FIG. 6, it may have three layers of a surface layer 711 (3B), a middle layer 712 (B), and a lower layer (HB), or may have more layers. Further, as shown in FIG. 7, the hardness may be changed not stepwise but smoothly.
[0024]
Further, the hardness distribution of the solid release agent may be different depending on the location. FIG. 8 shows an example. The solid release agent of FIG. 8 has a two-layer structure of a surface layer 721 having a hardness of 3B and a lower layer 722 having a hardness of HB. However, in the center of the figure, the surface layer 721 is thick and the lower layer 722 is thin. On the other hand, at the left and right ends in the figure, that is, at the front and rear ends in the rotation direction of the photosensitive drum 1, the surface layer 721 is thin and the lower layer 722 is thick. The total thickness of the surface layer 721 and the lower layer 722 is the same everywhere. Thereby, there is an effect that the posture change of the solid release agent is suppressed. This is because the solid release agent may be dragged by the rotation of the photosensitive drum 1 and tilt rightward in FIG. In such a case, with the solid release agent of FIG. 8, as shown in FIG. 9, the lower layer 722 comes into contact with the photosensitive drum 1 first on the left side in the figure, that is, on the side where wear is progressing. This prevents the solid release agent from further tilting to the right. The hardness distribution may be smoothly changed between the center and the end.
[0025]
Further, the hardness distribution may be different in the width direction of the photosensitive drum 1. FIG. 10 shows an example. The solid release agent of FIG. 10 has a two-layer structure of a surface layer 731 having a hardness of 3B and a lower layer 732 having a hardness of HB. However, in the center of the figure, the surface layer 731 is thin and the lower layer 732 is thick. On the other hand, at the left and right ends in the figure, that is, at the ends in the width direction of the photosensitive drum 1, the surface layer 731 is thick and the lower layer 732 is thin. The total thickness of the surface layer 731 and the lower layer 732 is the same everywhere. This has the effect of preventing chipping of the solid release agent at the end. This is because hard solid zinc stearate is generally brittle, and if it is too large at the edges, it may lose some rhythm. In the solid release agent shown in FIG. 10, the hard lower layer 732 is reduced at the end that is easily affected by other impacts, so that it is relatively hard to chip. Note that the hardness distribution may change smoothly as shown in FIG.
[0026]
In the present embodiment, zinc stearate is used as a solid release agent. In this case, the molding method of the solid body includes a powder pressing method and a melting method. In any case, a molding having a desired hardness can be obtained by adjusting the mixing ratio of the materials, the temperature, the pressure, and other conditions. Obtainable. In addition, the layered material shown in FIG. 2 or the like may be formed by molding solid zinc stearate having different hardnesses, and combining them to perform a secondary process of heating and compressing them. In addition, a material whose hardness changes smoothly as shown in FIG. 7 can be manufactured by pouring materials having different hardnesses into a mold.
[0027]
As described in detail above, in the image forming apparatus according to the present embodiment, a solid material of zinc stearate is used as a solid release agent for applying the release agent to the photosensitive drum 1 and the transfer belt 2. A hardness distribution is provided therein. That is, the softer surface layer (701 or the like) comes into contact with the photosensitive drum 1 and is lightly pressed from the harder lower layer (702 or the like) side. Thus, the release agent is applied by the soft surface layer at the beginning of the durable use, and the release agent is applied by the hard lower layer at the end of the durable use. In this way, both ample application of the release agent in the early stage of durable use and a long lifetime over the entire durable use are achieved. On the other hand, since no extra rotation mechanism or the like is required, there is no need to increase the size or complicate the device. In addition, by providing a difference in the hardness distribution of the solid release agent depending on the location, it is possible to suppress a change in the posture of the solid release agent or to prevent chipping.
[0028]
Note that the present embodiment is merely an example, and does not limit the present invention in any way. Therefore, naturally, the present invention can be variously modified and modified without departing from the gist thereof.
[0029]
For example, although the release agent used in the present embodiment is zinc stearate, the release agent is not limited to this, and another material having release properties may be used. Examples of such are calcium stearate, magnesium palmitate, manganese oleate and other various fatty acid salts. Other than fatty acid salts, silica, fluororesin (Teflon (trademark), etc.) and polyvinylidene fluoride (Kyner (trademark), etc.) can be mentioned. When a configuration in which the solid release agent 7Y or the like is installed above the photoreceptor drum 1Y or the like is employed, the pressing spring may not be provided.
[0030]
The application of the present invention is not limited to the secondary transfer method as described in the present embodiment, but may be an image forming apparatus of a type in which the image is directly transferred from a photosensitive drum onto printing paper. . Further, the invention is not limited to a tandem type full-color machine, but may be a multi-cycle type color machine or a monochrome machine. Further, any of a copier, a printer, a facsimile, and the like may be used.
[0031]
【The invention's effect】
As is apparent from the above description, according to the present invention, an image forming apparatus which has a simple configuration without an extra rotating body, is less likely to cause coating unevenness, and has an excellent balance between the initial coating amount and the life. A solid release agent for that purpose is provided.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment.
FIG. 2 is a diagram showing a solid release agent according to an embodiment.
FIG. 3 is a graph showing the difference in the contact angle of pure water depending on the hardness of a release agent.
FIG. 4 is a graph showing a difference in consumption depending on hardness of a release agent.
FIG. 5 is a graph showing a transition of an application amount according to the number of prints in the solid release agent according to the embodiment.
FIG. 6 is a view showing another solid release agent according to the embodiment.
FIG. 7 is a diagram showing another solid release agent according to the embodiment.
FIG. 8 is a view showing another solid release agent according to the embodiment.
FIG. 9 is a view showing a correcting action when the solid release agent is inclined.
FIG. 10 is a view showing another solid release agent according to the embodiment.
FIG. 11 is a view showing another solid release agent according to the embodiment.
[Explanation of symbols]
1Y, 1M, 1C, 1K Photoconductor drum (toner carrier)
2 Transfer belt (toner carrier)
7Y, 7M, 7C, 7K, 7B Solid release agents 701, 711, etc. Surface layer of solid release agent (soft)
702,713 etc. Lower layer of solid release agent (hard)

Claims (5)

An image forming apparatus having a toner carrier and forming an image by transferring a toner image formed on the toner carrier onto a recording medium,
A solid release agent for applying a release agent on the surface of the toner carrier in contact with the toner carrier;
The image forming apparatus according to claim 1, wherein the solid release agent has a softer hardness on a contact surface side with the toner carrier and a harder hardness on an opposite surface side. The image forming apparatus according to claim 1,
The image forming apparatus according to claim 1, wherein the solid release agent has a hardness distribution in which hardness changes stepwise from a contact surface side to an opposite surface side to the toner carrier. The image forming apparatus according to claim 1,
The image forming apparatus according to claim 1, wherein the solid release agent has a hardness distribution in which hardness continuously changes from a contact surface side to an opposite surface side to the toner carrier. An image forming apparatus according to any one of claims 1 to 3,
An image forming apparatus, wherein a hardness distribution of the solid release agent differs depending on a position in a width direction or a direction intersecting the width direction of the toner carrier. A solid release agent that contacts a toner carrier of an image forming apparatus and applies a release agent on its surface.
A solid release agent characterized in that the contact surface side with the toner carrier is softer and the opposite surface side has a harder hardness distribution.

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