JP2008260216A - Molding die, elastic roll, manufacturing method thereof, electrophotographic process cartridge, and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a molding die capable of obtaining an elastic layer having an excellent form precision without cooling the molding die and using a mold releasing agent to the surface in the molding when releasing a roll from the molding mold after hardening of the elastic layer is finished in molding the roll with the mold. <P>SOLUTION: The molding mold is characterized in that it manufactures the elastic roll having the elastic layer on an axis center body and the inner surface of the molding mold contains nitrogen content of 3 mol% and more and 8 mol% or less. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a molding die used for manufacturing an elastic roll. The present invention also relates to an elastic roll manufacturing method using the molding die, an elastic roll manufactured by the manufacturing method, an electrophotographic apparatus process cartridge and an image forming apparatus equipped with the elastic roll.

  2. Description of the Related Art Conventionally, an elastic roll has been manufactured in which a multilayer elastic layer containing various materials having various functions such as elasticity and conductivity is formed on the outer periphery of a rigid shaft core body such as metal. As a method for manufacturing this elastic roll, mold forming is often used because an elastic roll having a desired shape accuracy can be obtained with relatively high reproducibility without requiring a post-process such as polishing.

  In this mold forming, a cylindrical elastic mold is arranged by supporting both ends of a shaft core with a piece with an injection port, and a liquid elastic layer material is injected from the injection port. Thereafter, the mold is heated to thermoset the liquid elastic layer material to form an elastic layer having a desired shape. Next, an elastic roll is obtained by taking out the elastic roll after the thermal curing of the elastic layer material by heating is removed from the mold (hereinafter, referred to as “demolding”).

  However, when the mold is removed, the elastic layer inside the mold is pressed against the inner surface of the mold with a strong force due to thermal expansion. For this reason, when the elastic roll is removed immediately after molding, the elastic layer may be deformed or the elastic layer may be broken.

Therefore, a method for reducing the frictional force on the contact surface between the inner surface of the mold and the elastic layer at the time of demolding has been conventionally attempted as follows.
(1) As the first method, after the elastic layer is molded, the mold and the elastic layer inside the mold are sufficiently cooled so that the elastic layer is not thermally expanded and then demolded. Can do.

(2) As the second method, a method of applying a release agent to the inner surface of the mold can be exemplified.
(3) As a third method, a method of providing a releasable film excellent in releasability on the inner surface of the mold can be exemplified. Patent Document 1 includes a releasable film composed of a fluororesin mixed with PTFE powder and having a surface ten-point average roughness (Rz) of 10 or more and a contact angle (wetting) of 80 ° or more. An OA roller molding die having a peripheral surface is disclosed.

On the other hand, in recent years, functions required for an elastic roll as a product have been diversified and advanced, and accordingly, many characteristics have been required for the elastic roll. Therefore, in order to meet these requirements, the selection range of materials that can be used in the elastic layer is narrower than in the past, and silicone rubber is increasingly used as a useful material. In general, this silicone rubber is excellent in rebound resilience, but has a low tear strength and is inferior in mold release from a mold.
JP 2006-096004 A

  However, each of the methods (1) to (3) has various problems, and this problem is more remarkable when an elastic roll having an elastic layer made of silicone rubber is formed. It was.

  That is, in the method (1), it takes time to cool the elastic roll, and the productivity is inferior. In addition, depending on the material of the mold and the mechanical properties of the elastic layer, and the degree of affinity between these two materials, there is a large gap between the inner surface of the mold and the elastic layer, even when sufficiently cooled. There were cases where contact stress was applied. In such a case, the mechanical strength of the elastic layer cannot withstand contact stress during demolding, and the elastic layer may be deformed or broken.

  In addition, the mold cooled after the elastic layer is molded is cooled down to room temperature, and when heat molding is performed using this mold, a large amount of heat is required to raise the temperature from room temperature to the curing temperature of the elastic roll material. It was. As a result, problems such as an increase in the molding cycle and an increase in power consumption have occurred. Furthermore, equipment such as a heat exchanger is required for heating the elastic roll material and cooling the elastic roll, resulting in problems such as high costs and equipment space.

In the above method (2), the release agent may have an adverse effect on the properties of the elastic layer, such as permeating into the elastic layer of the elastic roll or changing the surface properties of the elastic layer.
In the method (3), when the mold is used for a long period of time, a part where the releasable film is partially peeled is formed on the inner surface of the mold, and the releasability of the elastic layer is partially inferior. There was a case where a part occurred. As a result, at the time of demolding, an excessive contact stress due to a decrease in releasability is partially applied to the elastic layer, which may induce destruction / deformation of the elastic layer.

  As a result of intensive studies, the present inventor has found that the inner surface of the molding die may be configured so that the nitrogen content is 3 mol% or more and 8 mol% or less. That is, according to the present invention, when the inner surface of the molding die has a special nitrogen content, when the elastic roll is removed, the die is cooled or a mold release agent is applied to the inner surface of the die. Without any problem, the peelability between the inner surface of the mold and the elastic layer is improved. As a result, an object of the present invention is to propose a molding die capable of preventing the deformation and destruction of the elastic layer and forming an elastic layer with excellent shape accuracy.

The present invention for solving the above problems has the following configuration.
1. A molding die for producing an elastic roll having an elastic layer on a shaft core,
The molding die according to claim 1, wherein the inner surface of the molding die has a nitrogen content of 3 mol% or more and 8 mol% or less.

2. 2. The molding die according to 1 above, wherein the inner surface of the mold is formed by nitriding the inner surface of the mold made of metal, so that the nitrogen content is 3 mol% or more and 8 mol% or less. Molding mold.
3. (1) a step of inserting a shaft core into the molding die according to 1 or 2 above;
(2) forming an elastic layer on the outer peripheral surface of the shaft core body by heating and curing the elastic layer material after the elastic layer material is filled in the molding die;
(3) a step of removing the shaft body on which the elastic layer is formed from the molding die;
(4) forming a resin layer on the outer peripheral surface of the elastic layer;
A method for producing an elastic roll, comprising:

4). An elastic roll produced by the method for producing an elastic roll described in 3 above.
5. 5. The elastic roll as described in 4 above, wherein the elastic layer contains an addition reaction cross-linked silicone rubber.

6). 6. The elastic roll as described in 4 or 5 above, wherein the resin layer contains a resin having a urethane bond.
7). The elastic roll according to any one of 4 to 6, wherein the elastic roll is a developer carrying roll.

8). An image forming body;
8. The elastic roll according to 7 above, wherein the elastic roll is provided in contact with the image forming body, and a thin layer of developer formed on the surface of the elastic roll is supplied to the surface of the image forming body. An elastic roll for developing the electrostatic latent image on the image forming body;
An electrophotographic process cartridge.

9. An image forming body;
8. The elastic roll according to 7 above, wherein the elastic roll is provided in contact with the image forming body, and a thin layer of developer formed on the surface of the elastic roll is supplied to the surface of the image forming body. An elastic roll for developing the electrostatic latent image on the image forming body;
A transfer roll for transferring the developer on the image forming body to a recording material;
A fixing roll; and a pressure roll that forms a nip portion with the fixing roll and conveys the recording material in pressure contact with the nip portion;
An image forming apparatus.

  According to the present invention, in mold molding, after the elastic layer material is cured, when the elastic roll is removed, the mold is cooled or a mold release agent is applied to the inner surface of the mold. In addition, the peelability between the inner surface of the molding die and the elastic layer can be improved. As a result, it is possible to manufacture an elastic roll having an elastic layer with excellent shape accuracy by preventing deformation and destruction of the elastic layer.

[Molding mold]
The molding die of the present invention is for producing a shaft core and an elastic roll having an elastic layer on the shaft core. In this elastic roll, a resin layer may be further formed on the outer periphery of the elastic layer after the elastic layer is formed. The inner surface of this molding die is characterized in that the nitrogen content is 3 mol% or more and 8 mol% or less.

  Here, when the nitrogen content on the inner surface of the molding die is less than 3 mol%, the peelability between the inner surface of the die and the molded elastic layer is lowered, and the elastic layer is likely to be deformed or broken. On the other hand, when the nitrogen content on the inner surface of the mold is larger than 8 mol%, the heat conduction from the molding mold heated during the curing of the elastic layer to the elastic layer material becomes non-uniform or the curing of the elastic layer is excessively hindered. It is considered to be done. As a result, the elastic layer is deformed and the forming process accuracy of the molding die is inferior.

  The nitrogen content on the inner surface of the molding die is preferably 4 mol% or more and 8 mol% or less, more preferably 5 mol% or more and 8 mol% or less, and further preferably 6 mol% or more and 8 mol% or less. When the nitrogen content on the inner surface of the molding die is within these ranges, the elastic layer has excellent releasability from the inner surface of the die and can form the elastic layer with excellent processing accuracy. .

  The inner surface of the molding die of the present invention is preferably made to have a nitrogen content of 3 mol% to 8 mol% by nitriding the inner surface of a metal mold. In this case, a nitriding method that can be used includes a gas nitriding method, a salt bath nitriding method, and a gas soft nitriding method.

The gas nitriding method is a method of treating an object to be treated in an ammonia decomposition gas at 500 ° C. to 550 ° C. for 50 hours or more.
In addition, the salt bath nitriding method is a method of processing for about 4 hours while feeding air into a processing bath at about 550 ° C. containing KCN, K ₂ CO ₃ or the like.

  Among these methods, the gas soft nitriding method is preferable because the dimensional change on the inner surface of the mold is small and the processing time is relatively short. In this gas soft nitriding method, after putting a metal mold into an electric furnace, ammonia gas is blown and the furnace temperature is set to 500 to 600 ° C., whereby a part of the ammonia gas is decomposed to generate nitrogen. The nitrogen is combined with a metal element in the vicinity of the inner surface of the mold to form a nitride.

  The nitrogen content on the inner surface of the mold can be controlled by adjusting the temperature, the treatment time in the furnace, and the ammonia gas content in the atmosphere gas in the furnace. The temperature and the treatment time in the furnace can be appropriately selected according to the desired nitrogen content, but the treatment temperature is preferably 480 ° C. or more and 520 ° C. or less, and the treatment time is preferably 3 hours or more and 6 hours or less.

[Elastic roll and manufacturing method thereof]
In the present invention, an elastic roll can be produced by the following steps using the above-described molding die.
(1) A step of inserting the shaft core into the molding die.
(2) A step of forming an elastic layer on the outer peripheral surface of the shaft core body by filling the elastic layer material in the molding die and then heat-curing the elastic layer material.
(3) A step of removing the shaft body on which the elastic layer is formed from the molding die.
(4) A step of forming a resin layer on the outer peripheral surface of the elastic layer.

Here, in the step (1), a hollow cylindrical molding die is used, and the shaft core body is inserted into the molding die so that the center axis of the molding die coincides with the central axis of the shaft core body. Then, the position of the shaft core body is fixed in the molding die by a fixing jig existing in the molding die.
Next, in the step (2), a liquid elastic layer material is injected into the molding die from the inlet in the molding die. Thereafter, the elastic layer material is heated and cured under a predetermined condition to form an elastic layer on the outer peripheral surface of the shaft core body.

  Thereafter, in the step (3), the shaft core body on which the elastic layer is formed is removed from the molding die. Typically, the molding die of the present invention can be divided into two on a plane parallel to the central axis. For this reason, after heat-curing, it can be demolded by dividing the molding die into two parts and removing the divided pieces from the shaft core body on which the elastic layer is formed. Note that the molding die is not limited to the two-divided type, and a part of the molding die can be removed, and the shaft core body on which the heat-cured elastic layer is formed can be taken out from the removed portion. What is necessary is just to enter.

  Next, in step (4), a resin layer is formed on the outer peripheral surface of the elastic layer. As a method for forming this resin layer, for example, after preparing a coating solution for the resin layer, the resin layer is coated on the outer peripheral surface of the elastic layer by a spray coating method, a dipping method, or the like. The method of heat-drying a process liquid can be mentioned.

In the present invention, by using the molding die, the peelability between the inner surface of the mold and the elastic layer is enhanced even when the elastic roll having the elastic layer formed on the shaft core is removed from the mold. (The frictional force applied to the elastic layer is reduced). For this reason, the elastic roll can be easily removed from the mold without deforming or destroying the elastic layer. As a result, an elastic roll with excellent dimensional accuracy can be manufactured.
Moreover, the elastic roll manufactured by said manufacturing method has an elastic layer on the outer periphery of a shaft core body, and a resin layer on the outer periphery of an elastic layer, respectively.
Hereinafter, each member used with the manufacturing method of this invention is demonstrated.

(Shaft core)
The shaft core used in the present invention is, for example, a cylinder having a carbon steel alloy surface subjected to industrial nickel plating having a thickness of 5 μm. In addition to this, examples of the material constituting the shaft core include the following materials.
-Alloys such as iron, aluminum, titanium, copper and nickel, and alloys such as stainless steel, duralumin, brass and bronze containing these metals.
・ Composite materials such as carbon black or carbon fiber hardened with plastics ・ Other known materials that are rigid and conductive.
Further, as the shape of the shaft core body, in addition to the columnar shape, a cylindrical shape having a central portion as a cavity can also be used.

[Elastic layer]
The elastic layer is provided on the outer periphery of the shaft core body. The elastic layer material is not particularly limited as long as it is a liquid that satisfies desired characteristics. As the elastic layer material, for example, a material containing a polymer, a conductive agent and fine particles in an appropriate ratio can be used, and the elastic layer material can be molded by being injected into a molding die.
Hereinafter, each material contained in the elastic layer material will be described.

<Polymer>
As the polymer, it is preferable to use addition reaction cross-linked silicone rubber. Hereinafter, the addition reaction crosslinked silicone rubber will be described in detail.

The addition reaction cross-linked silicone rubber has the following advantages.
・ Excellent workability.
・ Since no by-product is generated due to the curing reaction, the dimensional stability is good.
-The physical properties after curing are stable.

  Further, when an addition reaction cross-linked silicone rubber is used as the elastic layer material and the nitrogen content on the inner surface of the molding die is 3 mol% or more and 8 mol% or less, the curing reaction of the silicone rubber near the inner surface of the die is partially It is thought that it is inhibited. As a result, in the addition reaction crosslinked silicone rubber in the molding die, a completely cured portion and a portion having a small degree of curing are mixed and distributed at an appropriate ratio. The elastic layer after molding exhibits different amounts of curing shrinkage depending on the degree of curing depending on the location. Due to the difference in curing shrinkage depending on the location, the inner surface of the molding die and the elastic layer surface are not completely in close contact with each other, and a part that is not in partial or local contact is generated. As a result, the contact area between the inner surface of the molding die and the elastic layer surface can be reduced, and the contact stress applied to the elastic layer at the time of demolding can be reduced.

  Further, it is considered that the curing of the addition reaction cross-linked silicone rubber is locally inhibited by the coordination of a catalyst such as a platinum catalyst in the silicone rubber to the nitrogen atom present in the inner surface of the mold. . The degree of inhibition of this curing is greatly affected by the amount of nitrogen atoms present in the inner surface of the mold.

  Here, when the nitrogen content in the inner surface of the molding die is smaller than 3 mol%, the curing of the addition reaction cross-linked silicone rubber in the vicinity of the inner surface of the die is not inhibited and proceeds at a uniform high rate. For this reason, the adhesion between the elastic layer surface and the inner surface of the molding die is increased in the same manner as a die having a chemical nickel plating or iron inner surface, and the release property of the cured elastic layer to the molding die is increased. Becomes lower. In addition, when the elastic roll is removed after the elastic layer is formed, the stress applied to the surface of the elastic layer is increased, and the elastic roll cannot be removed while maintaining high shape accuracy.

  Conversely, if the nitrogen content on the inner surface of the molding die is greater than 8 mol%, curing of the addition reaction cross-linked silicone rubber in the vicinity of the inner surface of the die will be significantly hindered. As a result, the curing of the silicone rubber in the vicinity of the inner surface of the mold is not sufficiently completed, and the shape accuracy of the molded product becomes insufficient.

  This addition reaction crosslinking type silicone rubber contains, for example, an organopolysiloxane represented by the following formula (1) and an organohydrogenpolysiloxane represented by the following formula (2). Further, a crosslinking catalyst is added to the addition reaction crosslinked silicone rubber.

(In the formula, R is an alkenyl group, and x is a positive integer.)
This organopolysiloxane is a base polymer of addition reaction crosslinking type silicone rubber, and its weight average molecular weight is not particularly limited, but is preferably 100,000 or more and 1,000,000 or less, more preferably 400,000 or more and 700,000 or less. Furthermore, the viscosity of the organopolysiloxane is preferably 10 Pa · s or more and 250 Pa · s or less from the viewpoint of processing characteristics and the characteristics of the obtained elastic layer.

  The alkenyl group of the organopolysiloxane is a site that reacts with the active hydrogen of the organohydrogenpolysiloxane to form a crosslinking point, and the type thereof is not particularly limited. For reasons such as high reactivity with active hydrogen, at least one of a vinyl group and an allyl group is preferable, and a vinyl group is more preferable.

(In the formula, y is a positive integer of 2 or more, and z is a positive integer.)
The organohydrogenpolysiloxane functions as a crosslinking agent for addition reaction in the curing process, and the number of hydrogen atoms bonded to silicon atoms in one molecule is 2 or more. In order to appropriately perform the curing reaction, a relatively low molecular weight weight average molecular weight of 1,000 to 5,000 is preferable.

<Crosslinking catalyst>
As a crosslinking catalyst for the reaction of organopolysiloxane and organohydrogenpolysiloxane, for example, chloroplatinic acid hexahydrate can be used. In addition, transition metal compounds that exhibit a catalytic action in the hydrosilylation reaction can also be used. The following can be used as the crosslinking catalyst.
_{· Fe (CO) 5, Co} (CO) 8, RuCl 3, IrCl 3, [(olefin) PtCl _{2] 2,} a vinyl group-containing polysiloxane -Pt complex, L ₂ Ni (olefin), L ₄ Pd, L ₄ Pt.
・ L ₂ NiCl ₂
(However, L is PPh ₃ or PR ′ ₃ , where P is phosphorus, Ph is a phenyl group, and R ′ is an alkyl group).

Among these, preferred crosslinking catalysts are platinum, palladium, and rhodium-based transition metal compound catalysts.
When the cross-linking catalyst is a platinum-based metal compound catalyst, the amount is preferably 1 ppm to 100 ppm as platinum in the addition reaction cross-linked silicone rubber, but is not limited to this range. Absent. What is necessary is just to select the compounding quantity of a crosslinking catalyst suitably with target hardening time, product shape, etc. FIG.

<Conductive agent>
A conductive agent can be blended in the elastic layer as necessary. Examples of the conductive agent include the following.
・ Metallic powders and fibers such as aluminum, palladium, iron, copper and silver.
-Metal oxides such as titanium oxide, tin oxide, and zinc oxide.
-Metal compound powders such as copper sulfide and zinc sulfide.
-Particles with tin oxide, antimony oxide, indium oxide, molybdenum oxide attached to the surface. Powder with zinc, aluminum, gold, silver, copper, chromium, cobalt, iron, lead, platinum or rhodium attached to the surface by electrolytic treatment, spray coating or mixed shaking.
-Carbon powders such as acetylene black, ketjen black, PAN-based carbon black, and pitch-based carbon black.
Ionic conductive materials such as KSCN, LiClO ₄ , NaClO ₄ and quaternary ammonium salts.

  Among these conductive agents, carbon black is preferable because the electrical resistivity can be reduced by adding a relatively small amount, and conductivity can be imparted without increasing the hardness of the rubber composition.

<Fine particles>
In the elastic layer material of the present invention, fine particles can be added as a reinforcing filler and a bulking agent. Examples of the fine particles include the following.
-Fumed silica, wet silica, quartz fine powder, diatomaceous earth, carbon black, zinc oxide, basic magnesium carbonate, activated calcium carbonate, magnesium silicate.
-Aluminum silicate, titanium dioxide, talc, mica powder, aluminum sulfate, calcium sulfate, barium sulfate, glass fiber, carbon black for rubber, organic reinforcing agent, organic filler.

<Additives>
In addition to the above materials, various additives can be added to the elastic layer material. As the plasticizer, for example, polydimethylsiloxane oil, diphenylsilanediol, trimethylsilanol, phthalic acid derivatives, adipic acid derivatives, and the like can be used.
As the softening agent, for example, lubricating oil, process oil, coal tar, castor oil and the like can be used.

As the anti-aging agent, for example, phenylenediamines, phosphates, quinolines, cresols, phenols, dithiocarbamate metal salts and the like can be used.
As the heat-resistant agent, for example, iron oxide, cerium oxide, potassium hydroxide, iron naphthenate, potassium naphthenate, or the like can be used.
In addition, processing aids, colorants, ultraviolet absorbers, flame retardants, oil resistance improvers, foaming agents, scorch inhibitors, tackifiers, lubricants, and the like can be added.

[Resin layer]
A resin layer can be further formed as a surface layer on the elastic layer.
The resin layer can contain, for example, various polyamides, fluorine resins, hydrogenated styrene-butylene resins, urethane resins, silicone resins, polyester resins, phenol resins, imide resins, olefin resins, and the like. Among these, it is preferable that the resin layer contains a resin material (urethane resin or the like) having a urethane bond. By containing the resin material having a urethane bond in the resin layer, it is possible to prevent the elastic layer material from seeping out on the surface of the elastic roll and to impart excellent surface characteristics to the elastic roll.

  Further, these materials can be dispersed in an appropriate solvent using a conventionally known dispersion apparatus using beads such as a sand mill, a paint shaker, a dyno mill, and a pearl mill. As this solvent, methyl ethyl ketone, toluene, methyl isobutyl ketone and the like can be used. By performing this dispersion treatment, a coating liquid capable of forming a resin layer with few surface defects can be obtained. The obtained coating liquid can be applied onto the elastic layer by spray coating, dipping, or the like.

  In the case of an elastic roll used in the electrophotographic process, the thickness of the resin layer is preferably 5 μm or more in order to prevent contamination of the image forming body due to exudation of elastic layer components. In addition, from the viewpoint of increasing the hardness of the elastic roll surface and preventing fusion of the developer, the thickness of the resin layer is preferably 500 μm or less, and more preferably 10 μm or more and 30 μm or less.

(Developer carrying roll)
The elastic roll of the present invention is preferably used in an image forming apparatus as a developer carrying roll. By using the elastic roll as the developer carrying roll in the image forming apparatus in this manner, a uniform amount of developer can be stably supplied onto the image forming body.

When used as a developer-carrying roll as described above, it is preferable to use a developing roll having an elastic layer and a resin layer, and to disperse fine particles having an average particle diameter of 1 μm to 20 μm in the resin layer. As a result, the developer on the surface of the developer carrying roll can be easily transported, and a sufficient amount of developer can be transported to the development region. Examples of the fine particles used for such purposes include the following.
-Plastic pigments such as polymethyl methacrylate fine particles, silicone rubber fine particles, polyurethane fine particles, polystyrene fine particles, amino resin fine particles, and phenol resin fine particles.

  Among these fine particles, polymethyl methacrylate fine particles and polyurethane fine particles are particularly preferable. The fine particles listed above are preferably added to the resin layer in the range of 3% by mass to 200% by mass with respect to the total mass of the constituent components of the resin layer excluding the fine particles.

[Electrophotographic process cartridge and image forming apparatus]
Next, an electrophotographic process cartridge and an image forming apparatus incorporating the developer carrying roll of the present invention will be described with reference to FIG.
The image forming body 501 in FIG. 3 is charged by a charging roll 502 so that the surface has a predetermined polarity and a uniform potential. Thereafter, exposure 503 of target image information is received, and an electrostatic latent image corresponding to the target image is formed on the surface of the image forming body 501.

  Further, a developer carrying roll 504 is provided so as to contact the image forming body, and a thin layer of developer formed on the surface thereof can be supplied to the surface of the image forming body. The electrostatic latent image is visualized by the developer 505 supplied by the developer carrying roll 504. The visualized image is transferred to the recording material 507 by applying a voltage from the back surface of the recording material 507 conveyed by the paper supply roll 506 by the transfer roll 508.

  Next, the sheet is conveyed to a nip portion constituted by a fixing roll 509 and a pressure roll 510, and is subjected to image fixing by pressure contact and output as an image formed product. The image forming body 501 is cleaned by a cleaning unit 511 in order to remove the developer, dust, and the like remaining on the image forming body 501, is neutralized by a neutralizing member (not shown), and proceeds to the charging process again. The developer removed by the cleaning unit 511 is collected in a waste developer container 512. A cleaning roll can also be used as a member of the cleaning unit 511.

  On the other hand, the developer carrying roll 504 is supplied with the developer from the developer storage tank 514 by the developer supply roll 513 on the surface thereof, and the developer supply roll 513 and the developing blade 515 so that the developing blade 515 has a uniform thickness. Are in contact. The developer that has not been used when developing the electrostatic latent image with the image forming body on the developer carrying roll 504 is once scraped off from the developer carrying roll 504 by the developer supply roll 513. The charging roll 502, the developer carrying roll 504, and the transfer roll 508 are applied with a necessary voltage by a bias application power source.

  The electrophotographic process cartridge is a unit in which members such as those described here, excluding the transfer roll and the fixing unit, are integrated. In addition, it is possible to output a color image formed product by arranging four color electrophotographic process cartridges of black, magenta, cyan, and yellow, transferring each developer to a recording material, and performing image fixing. Developer.

Hereinafter, the present invention will be described in detail by way of examples, but this does not limit the present invention. Hereinafter, unless otherwise specified, commercially available high purity products were used as chemicals.
In Examples 1 and 2 and Comparative Examples 1 and 2, production of molds and elastic rolls and evaluation thereof were performed as follows.

[Molding mold]
First, as shown in FIG. 1, a cylindrical steel mold having an inner diameter of φ16 and an outer diameter of φ26 was prepared. Next, after processing the inner diameter of the molding die into a desired shape, a gas soft nitriding treatment was performed on the inner surface thereof to form a nitride having a desired nitrogen content. At this time, in the nitriding treatment, 30 mol% of ammonia gas is added to nitrogen gas, and the molding die is inserted into a furnace in an atmosphere set to a temperature in the range of 450 ° C. or higher and 550 ° C. or lower. For 2 to 8 hours. Then, a nitride layer having a desired nitrogen content was formed in the vicinity of the inner surface of the molding die. In each example and comparative example, the nitrogen content in the nitride layer was controlled by changing the furnace temperature and the furnace treatment time within the above ranges.

[Method of measuring the nitrogen content of the inner surface of the molding die]
The nitrogen content on the inner surface of the molding die produced as described above was measured with an electron beam microanalyzer (JXA-8500F (trade name) manufactured by JEOL Ltd.). As a test piece for measurement, a central portion of the molding die was cut into a 1 cm square, and a portion corresponding to the inner surface thereof was prepared for analysis.

[Method of forming elastic layer]
In the said shaping | molding metal mold | die, it distribute | arranged by supporting the both ends of the shaft core body which gave the chemical nickel plating of thickness 5micrometer to the iron round bar of outer diameter 8mm and length 280mm. Next, the elastic layer material was injected into the molding die through an injection port provided in a member of the molding die that supports the shaft core. The elastic layer material is a mixture of addition reaction cross-linked silicone rubber and conductive carbon black. The elastic layer material has a viscosity before curing of 150 Pa · s and an Asker C hardness of 40 ° after curing. It had physical properties.

  Also, the elastic layer material is injected into the molding die by bringing the injection nozzle into contact with the material injection port of the support member of the molding die and at a constant flow rate for about 10 seconds until the elastic layer material overflows from the material injection port. This was done by injection. Thereafter, the molding die was heated to cure the elastic layer material in the molding die. After curing, the roll core having an outer diameter of about 16 mm and an elastic layer length of 240 mm was obtained by removing the shaft core provided with the elastic layer from the mold without cooling the mold. .

[Measurement of roundness of roll with elastic layer on shaft core]
Below, the measuring method of the roundness of the roll obtained as mentioned above is demonstrated. As shown in FIG. 2, the roll was inserted between laser beams of a laser length measuring device (manufactured by Keyence Corporation, LS-5040 (trade name)), and the roll was rotated at a rotation speed of 120 ° / s. And about one outer diameter measurement point, the outer diameter was measured in the outer peripheral direction at intervals of 0.33 ms (rotation angle every 3.6 °; total 100 points). The outer diameter measurement points were measured at intervals of 5 mm from L1 to the other end of the elastic layer, with L1 being a position 5 mm in the roll longitudinal direction from one end of the elastic layer.

  And the difference between the maximum value and the minimum value of the outer diameter data of one roll (100 pieces) at each outer diameter measurement point (the point measured in the outer circumferential direction with the position of the elastic layer in the longitudinal direction fixed) The roundness at the outer diameter measurement point was used. In addition, among the roundness of each outer diameter measurement point obtained as described above for one roll, the maximum roundness was defined as the roundness of the roll.

[Measurement of surface hardness of roll with elastic layer on shaft core]
Below, the measuring method of the surface hardness of the roll obtained as mentioned above is demonstrated. First, the roll was placed on a measurement table of a micro hardness meter (manufactured by Kobunshi Keiki Co., Ltd., MD1-Type A (trade name); stylus diameter: 0.1 mm), and measured with a swing-down length of 8 mm. Further, the measurement point is L1 (0 °) at a position 5 mm in the roll longitudinal direction from one end of the elastic layer, L2 (0 °) at a position 5 mm in the roll longitudinal direction from the other end of the elastic layer, LC (0 °) is an intermediate position between L1 (0 °) and L2 (0 °). Then, L1, L2, and LC rotated by 120 ° respectively are L1 (120 °), L1 (240 °), L2 (120 °), L2 (240 °), LC (120 °), LC ( 240 °) and measured. Thus, a total of nine places were measured in one roll, and the average value was defined as the roll surface hardness.

[Method of forming resin layer]
Further, on the outer periphery of the elastic layer formed on the shaft core as described above, a coating liquid containing polyurethane resin, polyurethane particles (average particle size 15 μm) and conductive carbon black is disposed by dip coating. did.
Then, the elastic roll which arranged the resin layer on the outer periphery of the elastic layer was obtained by hardening a coating liquid for 4 hours with 150 degreeC oven.

(Image evaluation method)
Hereinafter, an image evaluation method when the elastic roll manufactured as described above is used as a developer carrying roll will be described. The electrophotographic laser beam printer (LBP2510 (trade name), manufactured by Canon Inc.) used in this image evaluation is a machine for A4 size output, the output speed of the recording medium is A4 vertical 16 sheets / minute, and the image resolution is 600 dpi. The image forming body incorporated in the printer is a reversal developing type image forming body in which an aluminum cylinder is coated with an OPC (organic photoconductor) layer, and the outermost layer is a charge transport layer using a modified polycarbonate as a binder resin. It has become.

During the operation of the printer, the image developed on the image forming body is transferred to a recording material by a transfer roll and thermally fixed by a fixing unit. The developer that has not been transferred by the transfer roll is scraped off from the image forming body by the cleaning blade. Further, the developing portion is formed into a cartridge, and a developing blade, which is a developer layer thickness regulating member, contacts the developer carrying roll in the counter direction to regulate the developer layer thickness. Image evaluation of recorded images recorded using this printer was performed according to the following criteria for solid images and halftone images.
Level where the image density is sufficiently dark and there is no density unevenness over the entire print surface: ○,
A level where fine density unevenness occurs but there is no practical problem: Δ,
Density unevenness occurs over the entire printing surface: x.

Example 1
By the above method, a cylindrical mold having a nitrogen content of 3 mol% in the nitride layer on the inner surface was obtained. Using this molding die, an elastic layer having a length of 230 mm and a thickness of 4 mm was disposed on the outer periphery of the shaft core body according to the above method. At this time, the curing condition of the silicone rubber layer is 100 ° C. for 30 minutes, and when the molded roll is removed from the mold, the conventional application of the release agent to the mold inner surface and the mold Mold cooling was not performed. Next, the roll thus obtained was subjected to secondary curing in an oven at 200 ° C. for 4 hours. Then, the roundness and surface hardness of the elastic layer after the secondary curing were measured by the above methods. The results are shown in Table 1.

  Next, as described above, a resin layer was disposed on the outer periphery of the elastic layer by a dipping method. The elastic roll thus obtained was used as a developer carrying roll in the image forming apparatus, and image evaluation was performed. The results are shown in Table 1.

(Example 2)
An elastic roll was prepared in the same manner as in Example 1 except that the nitrogen content in the nitride layer on the inner surface of the molding die was 8 mol%. In addition, roundness measurement, surface hardness measurement, and image evaluation were performed by the above methods. The results are shown in Table 1.

(Comparative Example 1)
An elastic roll was produced in the same manner as in Example 1 except that the nitrogen content in the nitride layer on the inner surface of the molding die was 1.5 mol%. Except for this, an elastic roll was prepared in the same manner as in Example 1. In addition, roundness measurement, surface hardness measurement, and image evaluation were performed by the above methods. The results are shown in Table 1.

(Comparative Example 2)
An elastic roll was prepared in the same manner as in Example 1 except that the nitrogen content in the nitride layer on the inner surface of the molding die was 10 mol%. In addition, roundness measurement, surface hardness measurement, and image evaluation were performed by the above methods. The results are shown in Table 1.

  As shown in Table 1, in Example 1, since the treatment time was as short as 3 hours at 500 ° C., the nitrogen content near the surface was as low as 3 mol%. In addition, even when an elastic roll is manufactured without applying a mold release agent to the inner surface of the molding die and without cooling the die at the time of demolding, the image evaluation result is `` Δ ”, roll roundness was 5 μm. For this reason, the elastic roll of the level which does not have a problem in use was able to be obtained.

  Further, in the molding die of Example 2 subjected to nitriding treatment at 500 ° C. for 5 hours, the nitrogen content on the inner surface of the molding die was 8 mol%. With this elastic roll, the stress between the molding die and the elastic layer can be sufficiently relieved during demolding after forming the elastic layer, and an elastic roll having a small roll roundness of 3 μm can be obtained. . Further, when this elastic roll was used as a developer carrying roll, the image evaluation result was “◯”, and there was no density unevenness on the printed surface, which was very good.

  On the other hand, the nitrogen content on the inner surface of the molding die became 1.5 mol% in the molding die of Comparative Example 1 by nitriding at a low temperature. Further, in the case where the mold release agent was not applied to the inner surface of the molding die and the mold was not cooled at the time of demolding, the stress applied to the elastic layer during the roll demolding after forming the elastic layer increased. For this reason, in Comparative Example 1, the roundness of the elastic roll is 10 μm, and when this elastic roll is used as a developer carrying roll, the image evaluation result is “x”, and density unevenness occurs over the entire printing surface. It became a level that could not be used. Therefore, in order to obtain an elastic roll having a shape accuracy that can withstand use as a developer-carrying roll using the molding die of Comparative Example 1, application of a release agent to the mold surface and demolding during molding It can be seen that time cooling is necessary.

  Furthermore, in the molding die of Comparative Example 2 in which the nitrogen content on the inner surface of the molding die is 10 mol% by nitriding at high temperature, the elastic layer material and the inner surface of the die are subjected to thermal curing of the elastic layer material. The action of suppressing the hardening became stronger due to the interaction. That is, the nitride on the inner surface of the mold becomes a catalyst poison of the curing catalyst, the elastic layer is not completely cured, and the elastic layer material remains liquid. For this reason, an elastic roll that can withstand the image performance could not be obtained.

  The elastic roll of the present invention can be suitably used as a developer carrying roll for an electrophotographic process cartridge and an image forming apparatus.

It is sectional drawing showing the shaping die of this invention. It is a conceptual diagram showing the measurement process of the roundness of a roll. 1 is a conceptual diagram illustrating an electrophotographic process cartridge and an image forming apparatus of the present invention.

Explanation of symbols

2: molding die 11: core metal 21: cylindrical portion 22 of molding die, 23: piece 24, 24 ': core metal holding recess 25: hollow inside of molding die 26: inlet 27: runner portions 28, 29 : Overflow portion 501: Image forming body 502: Charging roll 503: Exposure 504: Developer carrying roll 505: Developer 506: Paper feed roll 507: Recording material 508: Transfer roll 509: Fixing roll 510: Pressure roll 511: Cleaning Unit 512: Waste developer container 513: Developer supply roll 514: Developer storage tank 515: Developer blade

Claims (9)

A molding die for producing an elastic roll having an elastic layer on a shaft core,
The molding die according to claim 1, wherein the inner surface of the molding die has a nitrogen content of 3 mol% or more and 8 mol% or less.   The inner surface of the molding die is formed by nitriding the inner surface of a metal mold, so that the nitrogen content is 3 mol% or more and 8 mol% or less. The described mold. (1) inserting the shaft core into the molding die according to claim 1 or 2,
(2) forming an elastic layer on the outer peripheral surface of the shaft core body by heating and curing the elastic layer material after the elastic layer material is filled in the molding die;
(3) a step of removing the shaft body on which the elastic layer is formed from the molding die;
(4) forming a resin layer on the outer peripheral surface of the elastic layer;
A method for producing an elastic roll, comprising:   The elastic roll manufactured by the manufacturing method of the elastic roll of Claim 3.   The elastic roll according to claim 4, wherein the elastic layer contains an addition reaction cross-linked silicone rubber.   The elastic roll according to claim 4 or 5, wherein the resin layer contains a resin having a urethane bond.   The elastic roll according to claim 4, wherein the elastic roll is a developer carrying roll. An image forming body;
The elastic roll according to claim 7, wherein the elastic roll is provided in contact with the image forming body, and a thin layer of developer formed on the surface of the elastic roll is supplied to the surface of the image forming body. An elastic roll for developing an electrostatic latent image on the image forming body;
An electrophotographic process cartridge. An image forming body;
The elastic roll according to claim 7, wherein the elastic roll is provided in contact with the image forming body, and a thin layer of developer formed on the surface of the elastic roll is supplied to the surface of the image forming body. An elastic roll for developing an electrostatic latent image on the image forming body;
A transfer roll for transferring the developer on the image forming body to a recording material;
A fixing roll; and a pressure roll that forms a nip portion with the fixing roll and conveys the recording material in pressure contact with the nip portion;
An image forming apparatus.

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