JP2001281912A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent melt sticking of a toner on a toner carrying body and to realize good low temperature fixing. SOLUTION: The toner T is controlled in such a manner that the synchronization rate of the external additive after development is smaller than that before the development. Namely, the mother particle 18 of the toner T having a low melting point is coated with an external additive 19 of first and second layers before development, and after development, a part of the external additive 19 in the second layer is separated from the mother particle 18 to deposit on an OPC 2 to form an external additive layer (A). Therefore, the particle of the toner T comprising the mother particle 18 deposits on the OPC 2 through the external additive layer (A) when the toner moves from a developing roller 16 to the OPC 2. When the toner T is transferred from the OPC 2 to a transfer paper, the external additive layer (A) on the OPC 2 is not transferred but remains on the OPC 2. By leaving a part of the external additive before development on the OPC 2, more preferable low temperature fixing can be realized while melt sticking of the toner on the developing roller 16 in the stage prior to development can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of an image forming apparatus for forming an image using a toner composed of a large number of base particles and a large number of external additives, and more particularly, to a method of applying a toner to a toner carrier. It belongs to the technical field of an image forming apparatus that prevents adhesion and performs good low-temperature fixing.

[0002]

2. Description of the Related Art In an image forming apparatus, an electrostatic latent image on a latent image carrier is developed with toner, the developed image is transferred to a transfer material such as paper, and the latent image is transferred onto the transfer material. A transfer image of the exposed electrostatic latent image is formed on a carrier, and then the transferred image is fixed to form an image.

FIG. 1 is a view schematically showing a full-color intermediate transfer type image forming apparatus which is an example of such a conventional image forming apparatus. As shown in FIG. 1, in the image forming apparatus 1, an image is exposed as an electrostatic latent image on a latent image carrier (hereinafter, also referred to as OPC) 2, and the electrostatic latent image on the OPC 2 is Each of the non-magnetic one-component developing units 3, 4, 5, and 6 of yellow, magenta, cyan, and black is developed in order (arbitrary order of each color) to be visualized. After being color-matched on the intermediate transfer belt 7a of the transfer body 7 and subjected to primary transfer, the color is secondarily transferred to a transfer material 9 such as paper on a secondary transfer roller 8a (shown in FIG. 10) of the transfer device 8, Thereafter, a desired image can be obtained on the transfer material 9 by heating and fixing in the fixing device 10. Then, after the developed image is transferred to the transfer material 9, the residual toner T ′ remaining on the OPC 2 is removed by the cleaning blade 11 and stored in the residual toner box 12.

Each of the non-magnetic one-component developing units 3, 4, 5, and 6 has substantially the same configuration. As shown in FIG. The toner T is conveyed to the toner supply roller 15 by the conveyance means 14, and further, the toner T is supplied to the developing roller 16 which is a toner carrier by the toner supply roller 15, and is carried on the surface of the developing roller 16. Further, as the developing roller 16 is rotated at a high speed, the toner T on the developing roller 16 is regulated to a uniform thin layer by the toner regulating member 17 pressed against the surface of the developing roller 16 and is uniformly charged. The paper is evenly transported to the OPC2.

[0005] Such a conventional non-magnetic one-component developing apparatus 1
In the above case, the toner T may be fused on the developing roller 16 to cause filming. For this reason, the toner T fused portion of the developing roller 16 may cause a conveyance failure, and image streaks may occur. . Therefore, conventionally, as shown in FIG. 2B, the base particles 18 of the toner T are coated with an external additive 19 to prevent the toner T from adhering to the developing roller 16. The diameter of the external additive 19 is set to be extremely smaller than the diameter of the base particles 18. In addition, in order to enable low-temperature fixing in the heat fixing by the fixing device 10, conventionally, the toner T has relatively soft base particles 18 having a low softening point even at room temperature.
Is used.

[0006]

By the way, in the base particles 18 having a low softening point, since the base particles 18 are relatively soft, the external additive 19 is easily embedded in the base particles 18. When the external additive 19 is embedded in the base particles 18 as described above, even if the external additive 19 is coated on the base particles 18, the toner T is fused to the developing roller 16 and filming easily occurs. turn into. Therefore, conventionally, the external additive 1
9 is added to increase the coverage of the external additive 19 on the base particles 18, thereby preventing the fusion of the toner T to the developing roller 16. However, since the external additive has a high melting point, if a large number of external additives 19 are simply used, not only a large amount of heat is deprived by the external additive 19 at the time of heating and fixing, but also the mother particles 18 can be removed by many external additives. 19, there is a problem that heat is hardly transmitted to the base particles 18 and the low-temperature fixability is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has as its object to prevent image fusion of a toner to a toner carrying member and realize better image fixing at a low temperature. It is to provide.

[0008]

According to a first aspect of the present invention, there is provided an image forming apparatus which carries a toner comprising a large number of base particles and a large number of external additives and exposes the toner to light. A developing device having a toner carrier that is conveyed toward the body, and the toner carrier is pressed against the developing device, and an electrostatic latent image formed on the surface of the photosensitive layer is developed with toner from the toner carrier to form a toner image. An image forming apparatus including at least a latent image carrier to be transferred, a transfer device for transferring the toner image on the latent image carrier to a transfer material, and a fixing device for heating and fixing the toner image transferred to the transfer material. The toner is characterized in that the mother particles are soft at room temperature and have a low softening point, and the external additive synchronization rate after development of the toner is set to be smaller than that before development. At this time, the external additive synchronization rate is the inclination θ of the straight line α shown in FIG.

According to a second aspect of the present invention, the toner before development has an external additive synchronization rate of 0.50 or more and an external additive release rate of 3.50.
0% or more. At this time, the external additive release rate is (the amount of the asynchronous external additive / the total amount of the external additive) × 1.
The non-synchronous external additives are those that are not attached to the toner base particles. Further, the invention according to claim 3 is characterized in that the mother particle and the external additive, the photosensitive layer surface of the latent image carrier, and the charging sequence on the surface of the transfer body are the mother particle and the external additive <latent image carrier. And the surface of the photosensitive layer, and the surface of the base material and the external additive <the transfer member. The image forming apparatus according to any one of claims 1 to 3, wherein a speed difference is set between the toner carrier and the latent image carrier. .

Further, the invention according to claim 5 is characterized in that the base particles have a low softening point of 105 ° C. to 115 ° C. Further, in the invention according to claim 6, the external additive release ratio is set to be 3.0% or more for the toner in the developing device, and 3.5% for the toner on the transfer material after development. It is characterized in that it is set as follows. Furthermore, the invention according to claim 7 is such that the toner image on the latent image carrier is primarily transferred to an intermediate transfer material, and the toner image primarily transferred to the intermediate transfer material is transferred to the transfer material by the transfer device. It is characterized by becoming.

[0011]

In the image forming apparatus of the present invention having the above-described structure, the toner whose base particles have a low softening point is used, and the external additive synchronization ratio of the toner after development is higher than that before development. Become smaller. For this reason, after the development, a part of the external additive adhering to the base particles having a low softening point is peeled off from the base particles without being embedded in the soft base particles and released. Therefore, before development, the toner base particles are covered with many external additives, so that even when the toner particles have a low softening point, the toner carrier Is suppressed, and filming of the toner carrier is prevented. Further, after the development, a part of the external additive is peeled off from the base particles and released, so that the amount of the external additive attached to the base particles after the development is reduced. Therefore, since the amount of the external additive adhering to the base particles is small, the amount of heat taken by the external additive during heat fixing is reduced, and heat is easily transmitted to the base particles. As a result, the base particles can be effectively melted even at a relatively low temperature, and good low-temperature fixing can be realized.

As described above, the specific operation of the image forming apparatus of the present invention which can realize satisfactory low-temperature fixing while preventing filming of the toner carrier is performed as follows.
First, before development, many external additives adhere to the toner base particles as described above, and thus, the first layer of the external additive is formed on the base particles by toner stirring in the developing device. At the same time, the second layer of the external additive adheres to the first layer of the external additive, and the mother particles are coated in two layers by the external additive. Therefore, even when the external additive of the first layer on the base particle side is embedded in the base particles during the stirring of the toner in the developing device, the external additive coated on the second layer is the same as the external additive of the first layer. Because it compensates for the embedding and covers the mother particles more reliably,
The fusion of the toner to the toner carrier is suppressed, and the filming of the toner carrier is prevented.

In particular, in the second aspect of the invention, the external additive synchronization rate of the toner before development is set to 0.5 or more. In this case, the external additive synchronization rate is 0.5, which is equivalent to two layers of the external additive covering the mother particle. Therefore, the external additive synchronization rate should be set to 0.5 or more. Thus, the external additive of the second layer more reliably covers the base particles. Thereby, the fusion of the toner to the toner carrier is more reliably suppressed, and the filming of the toner carrier is more effectively prevented. In addition, the external additive release rate of the toner before development is set to 3.0% or more. When the external additive release rate is set to 3.0% or more, the free external additive enters between the toners and the toner and the toner carrier, so that the liberation between the toners and the separation of the toner and the toner carrier are performed. As a result, adhesion between toners is prevented, and fusion of the toner to the toner carrier is more effectively prevented. Further, since the stress on the toner at the time of pressing is alleviated, the free external additive works effectively for filming, and the filming is more reliably prevented.

In the image forming apparatus of the present invention, during development, in the image portion where the toner is in contact with the toner carrier and the biased latent image carrier, the toner is caused by an electric field from the latent image carrier. As a result of friction, friction occurs. Due to this frictional force, a part of the external additive of the second layer is peeled off from the base particles and released, forming a layer of the released external additive on the latent image carrier. Part of the agent is interposed between the toner composed of the released base particles and the latent image carrier. As described above, at the time of development, a part of the external additive of the second layer is peeled off from the base particles and released, so that the external additive synchronization rate of the toner becomes smaller than before the development.

In particular, according to the third aspect of the present invention, since the charging sequence between the external additive and the latent image carrier is such that external additive <latent image carrier, the external additive layer is Due to friction with the carrier, the negative charge is further increased, and the adhesion to the latent image carrier increases. In the invention of claim 4,
Because there is a speed difference between the toner carrier and the latent image carrier, between the external additive coated with the base particles and the latent image carrier,
An even greater frictional force will occur. Due to this frictional force, a part of the external additive of the second layer is more reliably peeled off from the base particles, and the layer of the external additive liberated on the latent image carrier is surely formed.

Further, at the time of transfer of the image forming apparatus of the present invention, the external additive layer on the latent image carrier is formed by the charge of the external additive particles and the interface between the latent image carrier and the photosensitive layer. The image remains on the latent image carrier without being transferred to the transfer material by the generated mirror image force or the attraction force generated by the bias applied to the latent image carrier. As described above, by forming the external additive layer on the latent image carrier and actively transferring and remaining the external additive, the amount of the external additive attached to the surface of the base particles of the toner is reduced, As a result, the toner composed of the base particles with the reduced amount of the external additive is transferred to the transfer material with high transfer efficiency.

In particular, in the invention of claim 7, the toner image on the latent image carrier is primarily transferred to the intermediate transfer member, and then secondarily transferred from the intermediate transfer member to the transfer material. Therefore, also at the time of the primary transfer, the external additive layer on the latent image carrier is interposed by the mirror image force or the attraction force with the latent image carrier as in the case of directly transferring the latent image carrier onto the transfer material. The toner remains on the latent image carrier without being transferred to the transfer member. And
In the same manner as described above, the external additive layer is formed on the latent image carrier, and the external additive is positively transferred, so that the amount of the external additive adhered to the surface of the base particles of the toner is reduced. As a result, the toner composed of the base particles having the reduced amount of the external additive is primarily transferred to the intermediate transfer body with high transfer efficiency. Also at the time of the primary transfer, friction occurs because the toner receives a force due to the electric field from the intermediate transfer member at the contact portion between the toner and the intermediate transfer member to which the bias is applied.
Due to this frictional force, a part of the external additive in the second layer is further peeled off from the base particles and released, forming a layer of the released external additive on the intermediate transfer member. A part of the agent is interposed between the toner composed of the released base particles and the intermediate transfer member. Thus, even during the primary transfer, the second
A part of the external additive in the layer is further peeled off from the base particles and released, thereby further reducing the external additive synchronization rate of the toner.

In particular, if a speed difference is provided between the latent image carrier and the intermediate transfer member, friction occurs between the toner and the intermediate transfer member. In this case, if the charging sequence is set such that the mother particles and the external additive <the intermediate transfer member between the base particles and the external additive and the intermediate transfer member, the frictional force is generated by the electric field from the intermediate transfer member. Together with the force, it becomes a large frictional force. Therefore, as in the case of the frictional force between the toner carrier and the latent image carrier, the external additive is peeled off from the toner base particles and released, and is released between the toner and the intermediate transfer member. An external additive layer is formed. The external additive layer is further negatively charged due to friction with the intermediate transfer member.

Also during the secondary transfer, the external additive layer on the intermediate transfer member is affected by the image force and primary transfer bias generated by the charge of the external additive particles and the interface of the base material of the intermediate transfer member. The toner remains on the intermediate transfer member without being transferred to the transfer material by the applied suction force of the intermediate transfer member. In this way, by forming the external additive layer on the intermediate transfer member and positively transferring the external additive to the transfer, the amount of the external additive adhered to the surface of the base particles of the toner is reduced as described above. As a result, the toner composed of the base particles having the reduced external additive amount is transferred to the transfer material with high transfer efficiency.

Finally, at the time of fixing of the image forming apparatus of the present invention, many external additives are first adhered to the base particles of the toner in the developing device. In the toner thus obtained, a predetermined amount of the external additive is released from the base particles, and the amount of the external additive attached to the base particles is reduced. Therefore, the amount of heat deprived by the external additives attached to the base particles during heating and fixing is reduced, and the external additives of the first layer attached to the base particles are embedded in the base particles. Since the two layers of the external additive are peeled off and the amount thereof is reduced, heat is more easily transmitted to the base particles. As a result, the base particles can be effectively melted even at a relatively low temperature, and good low-temperature fixing can be achieved.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. An image forming apparatus according to an embodiment of the present invention has the same configuration as that shown in FIGS. 1 and 2A and 2B. Therefore, the operation of the image forming apparatus of this example at the time of image formation is the same as that of the above-described conventional example. In that case, in the image forming apparatus 1 of this example, a predetermined speed difference is set between the developing roller 16 and the OPC 2 and between the OPC 2 and the intermediate transfer body 7, respectively.

In the image forming apparatus 1 of this embodiment, the toner T used is a toner having a low softening point in which the base particles 18 are soft at room temperature, and the external additive synchronization rate after the development of the toner T is equal to the developing ratio. It is set to be smaller than the previous one. In that case, as is clear from the experimental results described below,
This value is preferably set to 0.5 or more for the toner T in the developing device, that is, the toner T before development, and is preferably set to 0.4 or less for the toner T after development.

It is preferable that the toner before development has an external additive synchronization rate of 0.5 or more and an external additive release rate of 3.0% or more. This makes it difficult for free external additives to enter between the toners and between the toner and the toner carrier. For this reason, since the toner is a low softening point toner, the toner easily adheres to each other and the toner easily fuses to the developing roller 16. Therefore, even if it is lower to some extent, there is no problem in practical use, but it is not preferable to lower it further. Further, the low softening point of the base particles 18 of the toner T is preferably 105 ° C. to 115 ° C. This is because if the softening point of the base particles 18 is lower than 105 ° C., the toner T gradually becomes easier to fuse to the developing roller 16. Is not preferred. If the low softening point of the base particles 18 is higher than 115 ° C., the low-temperature fixing becomes gradually poor. However, even if the softening point is increased to some extent, there is no problem in practical use.

Further, the toner T (the base particles 18 and the external additive 19) is negatively charged, and the photosensitive member substrate and the photosensitive layer of the OPC 2 are grounded or given a predetermined bias. The intermediate transfer member 7 is also biased. The charge trains are set so that the base particles 18 and the external additives 19 <the surface of the photosensitive layer of the OPC2 and the base particles 18 and the external additives 19 <the surface of the intermediate transfer member 7. Further, the external additive release rate of the toner T is set to be 3.0% or more for the toner T in the developing device, and 3.5 for the toner T after development.
%.

Incidentally, in order to determine the above-mentioned external additive synchronization rate and external additive release rate, the amount of the external additive not attached to the base particles 18 (also referred to as asynchronous toner as will be described later),
The amount of the toner composed of the base particles 18 to which the external additive 19 does not adhere (also referred to as asynchronous toner as described later) and the amount of the toner to which the external additive 19 adheres (also referred to as synchronous toner as described later) It is necessary to analyze the state of adhesion between the base particles 18 and the external additive 19 in order to know the toner particle size. Toner analysis methods have heretofore been performed in several ways. The image forming apparatus 1 of this example employs, for example, the following particle analyzer method.

That is, in the image forming apparatus 1 of this example,
As a method of analyzing the adhesion state between the base particles 18 of the toner T and the external additive 19, an annual meeting of the Electrophotographic Society of Japan (total 95
Times), "Japan Hardcopy '97", Collection of Papers, "New Evaluation Method of External Addition-Toner Analysis by Particle Analyzer-", Toshiyuki Suzuki, Toshio Takahara, Electrophotographic Society, 199
The toner analysis method disclosed on July 9-11, 2007 is employed.

In this toner analysis method, particles of toner T formed by adhering an external additive 19 made of silica (SiO ₂ ) to the surface of base particles 18 made of resin (C) are introduced into plasma. Excites the toner T particles,
This is a method of performing elemental analysis by obtaining emission spectra as shown in FIGS. 3A and 3B accompanying this excitation.

In FIG. 3, the horizontal axis of the emission spectrum indicates the time axis. First, as shown in FIG. 3A, when the toner T particles obtained by adhering the external additive (SiO ₂ ) to the resin base particles (C) of the toner T are introduced into the plasma, the mother particles (C) and the outer particles are formed. The additive (SiO ₂ ) emits light. At this time,
Since the base particles (C) and the external additive (SiO ₂ ) are simultaneously introduced into the plasma, the base particles (C) and the external additive (SiO ₂ ) are introduced.
₂ ) and emit light simultaneously. Thus, when the base particles (C) and the external additive (SiO ₂ ) emit light simultaneously, it is said that the base particles (C) and the external additive (SiO ₂ ) are synchronized. In other words, the state where the base particles (C) and the external additive (SiO ₂ ) are synchronized indicates a state where the external additive (SiO ₂ ) is attached to the base particles (C).

Further, as shown in FIG.
Base particles (C) or base particles (C) to which iO ₂ ) does not adhere.
When the external additive (SiO ₂ ) released from the gas is introduced into the plasma, the mother particles (C) and the external additive (S
iO ₂ ) emits light, but at this time, the base particles (C) and the external additive (SiO ₂ ) are introduced into the plasma at different times.
Light emission occurs at a time different from ₂ ) (for example, when the base particles are introduced into the plasma before the external additives, the base particles emit light first, and thereafter the external additives emit light after a delay).

Thus, the base particles (C) and the external additives (Si
O ₂ ) emits light at different times from each other,
It is said that the base particles (C) and the external additive (SiO ₂ ) are not synchronized (that is, asynchronous). In other words, the state in which the base particles (C) and the external additive (SiO ₂ ) are asynchronous is as follows:
This means that the external additive (SiO ₂ ) is not attached to the base particles (C).

Further, in FIGS. 3 (a) and 3 (b), the height of the light emission signal indicates the intensity of the light emission. The intensity of the light emission is not the size or shape of the particle, but the intensity within the particle. It is proportional to the number of atoms of the element (C, SiO ₂ ) contained. Therefore, in order to express the emission intensity of the element as the size of the particles, when light emission of the base particles (C) and the external additive (SiO ₂ ) is obtained as shown in FIG. 4, these base particles (C) And spherical particles made only of the external additive (SiO ₂ ), the base particles (C) and the external additive (Si
O ₂ ). The spherical particles at this time are called equivalent particles, and the particle size is called an equivalent particle size. Since the external additive is very small, the particles cannot be detected one by one. Therefore, the emission signal of the detected external additive is added to be converted into one equivalent particle and analyzed. . The equivalent particle size of the equivalent particles obtained from the respective emission spectra of the base particles and the external additive is calculated by
Is plotted for each particle, the equivalent particle size distribution diagram of the toner particles as shown in FIG. 5 is obtained.

In FIG. 5, the horizontal axis represents the equivalent of the base particle (C).
The vertical axis represents the external additive (SiO 2). _TwoTable) Equivalent particle size
are doing. The equivalent particles on the horizontal axis represent the external additive (Si
O_Two) Represents an asynchronous parent particle (C) without attachment
ing. In that case, the external additive less than the specified external additive concentration
Are also shown on this horizontal axis, and the non-
Synchronous mother particles (C). Also, the equivalent on the vertical axis
The particles are made of an asynchronous external additive (S) released from the base particles (C).
iO_Two). In addition, not on the horizontal and vertical axes
The equivalent particles are obtained by adding an external additive (SiO 2) to the base particles (C)._Two) Adheres
Represents the synchronized toner T. Like this
The external additive (Si) to the base particles (C) of the toner T
O_Two) Is analyzed. The toner analysis method
Is any other than this particle analyzer method.
It goes without saying that an analysis method can be adopted.

As shown in FIG. 6, in the present invention, FIG.
Using the equivalent particle size distribution diagram of the toner particles shown in FIG.
The adhesion state between carbon (C) in the base particles and the external additive (SiO ₂ ) is determined using a single approximate straight line α passing through the origin obtained by using the least squares method. The slope θ of this approximate line α
(External additive synchronization rate) indicates the concentration of the external additive (SiO ₂ ) adhering (synchronizing) to the base particles (C). That is, the external additive (Si
The smaller the amount of O ₂ ) and the larger the inclination θ, the larger the amount of synchronized external additives (SiO ₂ ).

By the way, the toner T used in the image forming apparatus of this embodiment may be either negative polarity or positive polarity toner. The base particles 18 are at least composed of a colorant, a charge control agent, and a resin, and may further include a dispersant, a release agent (WAX), a magnetic material, and other additives.

As the base particles 18, a base particle material having a relatively low softening point at room temperature is used, and polystyrene and a copolymer such as a hydrogenated styrene resin, a styrene / isobutylene copolymer, an ABS resin, an ASA resin, AS resin, AAS resin, ACS resin, AES resin, styrene
P-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene cross-linked polymer, styrene
Butadiene / chlorinated paraffin copolymer, styrene / allyl / alcohol copolymer, styrene / butadiene rubber emulsion, styrene / maleic ester copolymer, styrene / isobutylene copolymer, styrene / maleic anhydride copolymer, acrylate Resin or methacrylate resin and its copolymer, styrene / acrylic resin and its copolymer such as styrene / acrylic copolymer, styrene / diethylamino / ethyl methacrylate copolymer, styrene / butadiene / acrylic acid Ester copolymer, styrene / methyl methacrylate copolymer, styrene / n-butyl methacrylate copolymer, styrene / methyl methacrylate / n-
Butyl acrylate copolymer, styrene / methyl methacrylate / butyl acrylate / N- (ethoxymethyl) acrylamide copolymer, styrene / glycidyl methacrylate copolymer, styrene / butadiene / dimethyl / aminoethyl methacrylate copolymer, styrene・ Acrylic acid ester ・ maleic acid ester copolymer, styrene ・ methyl methacrylate ・ acrylic acid 2-
Ethylhexyl copolymer, styrene / n-butyl acrylate / ethyl glycol methacrylate copolymer, styrene / n-butyl methacrylate / acrylic acid copolymer, styrene / n-butyl methacrylate / maleic anhydride copolymer, styrene Butyl acrylate, isobutyl maleic acid half ester, divinylbenzene copolymer, polyester and its copolymer, polyethylene and its copolymer, epoxy resin, silicone resin,
One or a mixture of two or more of polypropylene and its copolymer, a fluorine resin, a polyamide resin, a polyvinyl alcohol resin, a polyurethane resin, and a polyvinyl butyral resin can be used.
Colorants include carbon black, spirit black, nigrosine, rhodamine, triaminotriphenylmethane, cation, dioxazine, copper phthalocyanine, berylen, azo, gold-containing azo pigment, azochrome complex, carmine, benzidine, Solar Pure Yellow 8G, quinacridone, polytungstophosphoric acid,
Indaslen blue, a sulfonamide derivative and the like can be used.

The charge control agent is not particularly limited as long as it can obtain a negative charge by frictional charging, and various organic or inorganic charge control agents can be used. For example, an electron-accepting organic complex, chlorinated polyester, nitrophenic acid, or the like is used. As the release agent, polypropylene wax, polyethylene wax or the like can be used. As a dispersant, metal soap, polyethylene glycol, and the like can be used. As other additives, zinc stearate, zinc oxide, cerium oxide and the like can be used. Examples of the magnetic agent include metal powders such as Fe, Co, Ni, Cr, Mn, and Zn; metal oxides such as Fe ₃ O ₄ , Fe ₂ O ₃ , Cr ₂ O ₃ , and ferrite; and alloys containing manganese and acid. An alloy or the like exhibiting ferromagnetism can be used by the above heat treatment, and a preliminary treatment such as a coupling agent may be performed in advance. Then, the base particles 18 are produced by using these materials by a general kneading and pulverizing method, a spray-dry method, a polymerization method and the like.

As the external additive 19, various additives having relatively high hardness and having a surface subjected to a hydrophobic treatment are used.
For example, fine particles of metal oxides such as silica, aluminum oxide, titanium oxide, strontium titanate, cerium oxide, magnesium oxide, and chromium oxide, fine particles of nitride such as silicon nitride, fine particles of carbide such as silicon carbide, calcium sulfate, and barium sulfate And inorganic fine particles such as fine particles of metal salts such as calcium carbonate and composites thereof, and organic fine particles such as acrylic fine particles. Further, as these surface treatment agents, silane coupling agents, titanate coupling agents, fluorine-containing silane coupling agents, silicone oils, and the like can be used. The hydrophobicity of the external additive treated with these treating agents is preferably 60% or more by a conventional methanol method. If the temperature is lower than this, the chargeability and the fluidity are likely to be reduced due to the adsorption of moisture during the high temperature and high humidity, which is not preferable. The particle size of the external additive is preferably from 0.001 to 1 μm from the viewpoint of transportability and chargeability. The external additive is not limited to one type, and a mixture of two or more types can be used. The base particles 18 and the external additives 19 are dry-mixed with a high-speed fluid mixer such as a Henschel mixer or a Papen-Meyer or a mixer such as a mechanochemical method and adhered.

In the image forming apparatus 1 of this example having the above-described configuration, the base particles 18 have a low softening point.
Is used, and the external additive synchronization rate of the toner T is smaller after development than before development. From this, after development, the external additive 1 adhering to the base particles 18 having a low softening point was
Part of 9 is not embedded in the soft base particles,
It comes off and separates from the mother particles 18. Therefore, before development, the mother particles 18 of the toner T contain many external additives 1
9. That is, by the toner stirring in the developing units 3, 4, 5, and 6, the first layer of the external additive 19 is formed on the base particles 18 as shown in FIG. The second layer of the external additive 19 comes to adhere to the agent 19, and the mother particles 18 are coated in two layers by the external additive 19 (in the example shown in FIG. The external additive 19 of the layer adheres to the entire surface of the first layer, but may partially adhere to the first layer.) Therefore, when the toner is stirred in the developing units 3, 4, 5, and 6, the base particles 18
Even if the external additive 19 of the first layer on the side is embedded in the base particles 18, the external additive 19 coated on the second layer becomes the external additive 19 of the first layer.
Of the external additive 19 of the first layer, that is, the base particles 1
8.

Thus, the fusion of the toner T to the developing roller 16 is suppressed, and the filming of the developing roller 16 is prevented. In this case, when the external additive synchronization rate is set to 0.5 or more and the external additive release rate is set to 3.0% or more, the external additive 19 of the second layer more reliably covers the base particles 18. . Therefore, the fusion of the toner T to the developing roller 16 is more reliably suppressed, and the filming of the developing roller 16 is further effectively prevented.

During development, the developing roller 16
Since there is a speed difference between the OPC 2 and the OPC 2, friction occurs between the external additive 19 covering the base particles 18 and the OPC 2. In particular, in an image portion where the toner T contacts the OPC2, the bias is applied to the toner T in the OP.
Since the force is received by the electric field from C2, a larger frictional force is generated. By the stirring, the external additive 19 of the first layer is embedded in the base particles 18, but the external additive 19 of the second layer is
As shown in FIG. 8A, a part of the external additive 19 of the second layer is removed from the base particles 18 by the frictional force because the external additive 19 adheres to the layer and is not embedded in the base particles 18. The exfoliated layer 19 of the external additive 19 is formed on the OPC 2. Then, as the OPC 2 and the developing roller 16 rotate, the toner T comes to adhere to the external additive layer A formed on the OPC 2 as shown in FIG. That is, the external additive layer A is interposed between the toner and the OPC 2. In addition, the charging sequence between the external additive 19 and the OPC 2 is such that the external additive 19 <O
Because of the relationship of PC2, this external additive layer A
Due to the friction with No. 2, the negative charge is further increased.
Then, as shown in FIG. 8B, the toner T adheres to the external additive layer A, so that the toner T moves onto the OPC 2. As described above, after the development, a part of the external additive 19 of the second layer is peeled off from the base particles 18 and released, whereby the developed base particles 1 are removed.
The amount of the external additive adhering to 8 is reduced.

Further, at the time of the primary transfer, the external additive layer A on the OPC 2 is formed by the charge of the external additive particles 19 and the interface of the OPC 2 with the photosensitive layer as shown in FIGS. 9 (a) to 9 (c). Due to the generated mirror image force F ₁ , the toner remains on the OPC 2 without being transferred to the intermediate transfer member 7, and is cleaned and OP
Removed from C2. This very distance between the external additive layer A OPC surface small, Equation 1 image force F ₁ to be described later
The denominator at is dramatically reduced, so that a large image force F
_This is because ₁ occurs. The image force F ₁ does not work almost the toner T. This is because the distance between the toner T and the OPC surface is large and the denominator of the image force F ₁ in Equation 1 is large, so that the image force F ₁ for the toner T is small. On the other hand, the toner T by the suction force F ₂ of the primary transfer bias is applied to the intermediate transfer belt 7a, is transferred to the intermediate transfer body 7. This small toner T is the distance between the intermediate transfer member 7 surface, small denominator in Equation 2 adsorption force F ₂ to be described later, a large attraction force F ₂ is to work against the toner T. The suction force F ₂ does not work almost the external additive layer A. This large distance between the external additive layer A and the intermediate transfer member 7 surface, since denominator is greater in Equation 2 adsorption force F _2, the image force attraction force F ₂ against the external additive layer A is smaller . Thus, these two image forces F ₁
And by the suction force F _2, so that the external additive layer A and the toner T is separated from each other. Now, along with the photoconductor substrate and the photosensitive layer is grounded the OPC2, the primary transfer bias of the intermediate transfer belt 7a V _t1, the dielectric constant of the charge of the external additive 19 q, PC2 photosensitive layer of epsilon, OPC2 When the gap between the surface of the intermediate transfer belt 7a and the surface of the intermediate transfer belt 7a is d, and the thickness of the photosensitive layer of the OPC 2 and the thickness of the intermediate transfer belt 7a are both t, the mirror image force F ₁ and the attraction force F ₂ are respectively ,

(Equation 1)

(Equation 2) Given by Then, the external additive layer A is formed on the OPC 2, and the external additive 19 is positively transferred and remaining, so that the amount of the external additive adhered to the surface of the base particles 18 of the toner T is further reduced. Further, since the external additive layer A is largely negatively charged due to friction with the OPC 2 and the toner T is negatively charged from the beginning, both the external additive layer A and the toner T are negatively charged. A repulsive force is generated between the additive layer A and the toner T.
Due to the repulsion between the external additive layer A and the toner T, the external additive layer A
Moves to the OPC2 side with a greater force, and the toner T moves to the OPC2 side with a greater force, so that the primary transfer is performed with high transfer efficiency.

Also, during the primary transfer, the OPC2
Since the speed difference is set between the intermediate transfer member 7 and
Friction occurs between the toner T and the intermediate transfer member 7. In this case, the frictional force is set between the base particles 18 and the external additives 19 and the intermediate transfer body 17 so that the charging sequence is such that the base particles 18 and the external additives 19 <the intermediate transfer body 7. Becomes a large frictional force together with the force by the electric field from the intermediate transfer member 7. For this reason, the external additive 19 is peeled off from the toner base particles 18 and released as in the case of the frictional force between the developing roller 16 and the OPC 2, and released between the toner T and the intermediate transfer member 7. A layer B (shown in FIG. 10A) of the external additive 19 is formed. The external additive layer B is further negatively charged by friction with the intermediate transfer member 7.

Further, at the time of the secondary transfer, the primary transfer
The external additive layer B on the intermediate transfer member 7 is
As shown in FIGS. 10 (a) to 10 (c), the external additive particles 19
Generated by the electric charge and the interface of the intermediate transfer member 7
Image power F_ThreeTransfer to the secondary transfer roller 8a of the transfer device 8
And remains on the intermediate transfer member 7 without being cleaned.
From the intermediate transfer member 7 after being cleaned by the cleaning device
Removed. The toner T is applied to the secondary transfer roll 8a
Is transferred to the transfer material 9 by the bias. Now,
The primary transfer bias of the intermediate transfer belt 7a is
V_t1And the secondary transfer bias of the secondary transfer roller 8a is set to V_t2,
The dielectric constant of the intermediate transfer belt 7a is ε ',
a of the paper as the transfer material 9 on the secondary transfer roller 8a
Let d be the gap between the surface and the thickness of the intermediate transfer belt 7a.
t, then these mirror image forces F_ThreeAnd sucking
Strength F_FourIs the secondary transfer of the secondary transfer roller 8a, respectively.
Bias V _t2Assuming that the thickness up to the application position is r,

(Equation 3)

(Equation 4) Given by As described above, the external additive layer B is formed on the intermediate transfer member 7 and the external additive 19 is positively transferred and left, so that the external additive adhered to the surface of the base particles of the toner T is similarly exposed. Since the amount of the additive is reduced and the external additive layer B and the toner T repel each other, high transfer efficiency can be realized.

At the time of fixing, many external additives 19 were first adhered to the base particles 18 of the toner T in the developing units 3, 4, 5, and 6; A predetermined amount of the external additive 19 is released from the base particles 18 of the toner T transferred to the base particles 18, and the amount of the external additives attached to the base particles 18 is reduced. Therefore, the amount of heat taken by the external additives 19 attached to the base particles 18 during heat fixing is reduced. Moreover, since the external additive 19 of the first layer adhering to the base particles 18 is embedded in the base particles 18, the external additives 19 of the second layer are peeled off and the amount thereof is reduced. This makes it easier to conduct heat. As a result, the base particles 18 can be effectively melted and fixed even at a relatively low temperature, and good low-temperature fixing can be achieved.

Actually, in the examples of the present invention and the comparative examples for comparison with these examples and the like, the external additive synchronizing ratio of the toner between before and after development (shown in FIG. 6) (Corresponding to the inclination θ of the straight line α), a filming experiment and a fixing strength experiment of the developing roller 16 were performed. The experimental method is as follows.

Configuration of Developing Unit Developing roller: aluminum roller φ = 18 mm, surface roughness R _z
= 7.2 μm, linear velocity 360 mm / s. Supply roller: urethane sponge φ = 14.6 mm, contact depth 0.3 mm, peripheral speed ratio of counter rotation (relative to rotation of developing roller) 0.65 Control blade: Control edge on trail by rubber blade edge R = 50 μm, control spring Load 1.5 kg Stirring method 100 g of the toner was charged into the developing device, and idling was performed.

Fixing device: Fixing device for engine KL2010 made by Konica Speed: 90 mm / s Fixing temperature: 140 ° C. Evaluation method The presence or absence of toner fusion to the developing roller was examined by idle rotation corresponding to a maximum of 5,000 sheets. The fixing rate was measured, and it was checked whether the fixing rate was equal to or more than a judgment reference value (70%). In that case, the fixing rate is given as follows. Fixing rate = (OD value after rubbing the fixing portion with sand eraser / OD value before rubbing) × 100 (%) Toner T The mother particles are polyester resin (softening point 109 ° C.), and the external additive is silica (SiO _2). ). Toner Analysis and Measurement Method Particle Analyzer Method, PT1000 (manufactured by Yokogawa Electric Corporation) In each example, a toner having a gradient (external additive synchronization rate) and an external additive release rate shown in Table 1 below was used. The experimental results are also shown in Table 1.

[0048]

[Table 1]

As is clear from Table 1, the inclination is large at 0.55 before development, and is 0.35 and 0.4 after development.
In the case of the toner or the toner which is reduced to 0 in the embodiment or the toner, that is, in the case of a toner in which a large amount of the external additive adheres to the mother particles before the development and a small amount of the external additive adheres to the mother particles after the development,
While filming of the developing roller 16 does not occur,
The fixing strength was satisfactory. It is considered that the reason why the fixing rate of the toner of the comparative example is poor is that other factors such as the rate of release of the external additive influence. The filming of the toner of the comparative example was caused by the external additive release rate of 2.0.
%, It seems that the film does not work effectively against filming.

Further, in the case of the embodiment or the toner having a relatively high external additive release rate before development and a relatively low external additive release rate after development, filming of the developing roller 16 does not occur, and The fixing strength was satisfied. In particular, it is desirable that the external additive release rate before development is 3.0% or more and the external additive release rate after development is 3.5% or less. More preferably, the inclination before development is 0.
It is desirable that the release ratio of the external additive is 3.0% or more when the ratio is 50 or more, the inclination after development is 0.40 or less, and the release ratio of the external additive is 3.5% or less. From the experimental results in Table 1, it was also found that it is preferable to set both the inclination before development and the external additive release rate to be large, and the inclination after development and the external additive release rate to be both small.

[0051]

As is apparent from the above description, according to the image forming apparatus of the present invention, the mother particles of the toner are coated with a large number of external additives before the development, and the external additives are coated after the development. Part is positively peeled off from the base particles and released, preventing fusion of the toner to the developing roller before development,
Fixability during low-temperature fixation can be improved. Therefore, good low-temperature fixing can be realized while preventing filming of the developing roller. In addition, since a part of the external additive of the toner is positively transferred to the latent image carrier or the intermediate transfer member during the transfer, the amount of the external additive adhered to the surface of the base particles of the toner to be transferred is reduced. , And as a result, high transfer efficiency can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating a full-color intermediate transfer type image forming apparatus which is an example of a conventional image forming apparatus used as an example of an embodiment of the image forming apparatus according to the present invention.

FIGS. 2A and 2B schematically show an example of a conventional developing device used in the image forming apparatus shown in FIG. 1, wherein FIG. 2A is a cross-sectional view thereof, and FIG. Of 1
FIG. 3 is a diagram showing two particles.

FIG. 3 is a view for explaining an example of a conventional toner analysis method for use in analyzing the state of adhesion between toner base particles and external additives.

FIG. 4 is a diagram illustrating equivalent particles and equivalent particle sizes used in the toner analysis method shown in FIG.

5 is a diagram showing an analysis result by the toner analysis method shown in FIG.

6 is a diagram showing, based on the analysis result shown in FIG. 5, the state of adhesion between the mother particles of the toner and the external additive by using a single approximate straight line α passing through the origin using the least squares method.

FIG. 7 is a diagram schematically illustrating toner particles used in an example of the image forming apparatus of the present invention.

FIG. 8 is a diagram for explaining the behavior of the toner shown in FIG. 7 during development.

9 is a view for explaining the behavior of the toner shown in FIG. 7 at the time of primary transfer.

FIG. 10 is a view for explaining the behavior of the toner shown in FIG. 7 during secondary transfer.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Latent image carrier (OPC), 3, 4,
5, 6: developing device, 7: intermediate transfer body, 16: developing roller,
8 transfer device, 9 transfer material, 10 fixing device, 17 toner control member, 18 base particles, 19 external additives, T toner

[Procedure amendment]

[Submission date] June 12, 2001 (2001.6.1)
2)

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Figure 2

[Correction method] Change

[Correction contents]

FIG. 2

[Procedure amendment 2]

[Document name to be amended] Drawing

[Correction target item name] Fig. 7

[Correction method] Change

[Correction contents]

FIG. 7

[Procedure amendment 3]

[Document name to be amended] Drawing

[Correction target item name] Fig. 8

[Correction method] Change

[Correction contents]

FIG. 8

[Procedure amendment 4]

[Document name to be amended] Drawing

[Correction target item name] Fig. 9

[Correction method] Change

[Correction contents]

FIG. 9

Claims (7)

[Claims] A developing device having a toner carrying member for carrying a toner composed of a large number of base particles and a large number of external additives and transporting the toner toward a photoreceptor; The electrostatic latent image formed on the surface of the photosensitive layer is developed with toner from the toner carrier to form a toner image, and the toner image on the latent image carrier is transferred to a transfer material. In an image forming apparatus including at least a transfer device and a fixing device that heats and fixes a toner image transferred to a transfer material, the base particles are a soft toner having a low softening point at room temperature, and An image forming apparatus, wherein an additive synchronization rate is set to be smaller than that before development. 2. The toner before development has an external additive synchronization rate of 0.1.
2. The image forming apparatus according to claim 1, wherein the external additive release rate is 50% or more and 3.0% or more. 3. The photosensitive member according to claim 1, wherein said mother particles and said external additive, said photosensitive layer surface of said latent image carrier, and said charge train on said transfer member surface are: mother particle and external additive <photosensitive layer surface of latent image carrier. 3. The image forming apparatus according to claim 1, wherein the image forming apparatus satisfies a condition of (a), (b) and external particles <the surface of the transfer member. 4. A speed difference is set between the toner carrier and the latent image carrier and between the latent image carrier and the transfer material, respectively.
4. The image forming apparatus according to any one of claims 1 to 3. 5. The low softening point of the base particles is from 105 ° C. to 11 ° C.
The image forming apparatus according to any one of claims 1 to 4, wherein the temperature is 5 ° C. 6. The external additive release rate is set so as to be 3.0% or more for the toner in the developing device, and to 3.5% or less for the toner on the transfer material after development. The image forming apparatus according to claim 1, wherein the image forming apparatus is set to: 7. The toner image on the latent image carrier is primarily transferred to an intermediate transfer material, and the toner image primarily transferred to the intermediate transfer material is transferred to the transfer material by the transfer device. 7. The method according to claim 1, wherein:
The image forming apparatus as described in the above.