JP2003084489A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a stable transfer characteristic regardless of the use history of toner. SOLUTION: In the image forming device of a cleaner-less system using the toner obtained by covering a resin base particle surface with an external additive, sticking force between a first transfer body (19) and the toner is made larger than sticking force between image carriers (10M, 10C, 10Y and 10Bk) and the toner, and also sticking force between the first transfer body and resin base particles is made larger than sticking force between the image carriers and the resin base particles.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleanerless system image forming apparatus using a toner in which the surface of a resin mother particle is coated with an external additive.

[0002]

2. Description of the Related Art In color electrophotography, an intermediate transfer member is used to prevent abrasion of a photoconductor and facilitate superposition of color images. Further, resolution is improved by using a toner having a small particle diameter of 20 μm or less, or 10 μm or less. However, the toner having a small particle size has poor transferability as compared with the toner having a large particle size, and if the transfer electric field is strengthened to improve the transfer property, dielectric breakdown occurs and an image defect occurs. This transfer property depends on the adhesive force (van der Worth force, image force) between the toner and the photoconductor and between the toner and the intermediate transfer body.

Therefore, in order to improve transferability, the adhesive force between the intermediate transfer member and the toner is made larger than the adhesive force between the photosensitive member and the toner, and further, the toner and the transfer sheet are separated from each other than the adhesive force between the intermediate transfer member and the toner. It has been proposed to increase the adhesive force to paper (Japanese Patent Publication No. 5-50337).

[0004]

By the way, in the one-component non-magnetic toner, the surface of the resin mother particles is coated with an external additive to weaken the adhesive force of the toner and improve the charging performance. In the developing device using such toner, the toner is supplied to the developing roller by the supply roller while stirring, and the toner layer on the developing roller is friction-charged while the toner layer on the developing roller is made to have a constant thickness by the regulating blade, and the nip portion with the photoconductor is formed. Although the toner is being conveyed, the toner consumed in the transfer from the developing roller to the photosensitive member is about a few percent at most in the general use state, and the rest is returned to the developing device again to be stirred and frictionally charged. The process is repeated. In such a process, the toner, which is sufficiently coated with the external additive and has good charging performance, is preferentially consumed (selective development).

As a result of such selective development, in the toner whose durability in the developing device is deteriorated, the external additive on the surface is partly embedded in the resin mother particles and partly peeled off from the surface to expose the resin surface. . In addition, even in the new toner, the surface of all the toner particles is not sufficiently covered with the external additive, and a few percent of the free mother particles in which the coating of the external additive is insufficient are present. As a result, the adhesive force of the toner sufficiently covered with the external additive is greatly influenced by the external additive, and the toner has a small amount of the external additive on the surface of the toner as the durability of use is reduced, or the adhesive force of the free mother particles is small. The influence of the resin mother particles becomes large.

[0006] However, the above-mentioned proposed special table No. 5-50337.
In No. 6, the change in the amount of the external additive on the toner surface due to such use durability and the free mother particles are not taken into consideration, and as a result, the transfer efficiency cannot be sufficiently increased and the transfer efficiency is lowered. With a cleaner, cleaning the residual toner does not cause a problem with the decrease in transfer efficiency.However, when using a cleanerless process, the decrease in transfer efficiency is due to ghosting or color mixing due to reverse transfer in addition to color difference. Will occur.

[0007]

SUMMARY OF THE INVENTION The present invention is intended to solve the above problems, and an object thereof is to provide stable transfer characteristics regardless of the history of toner usage. Therefore, in the present invention, in the image forming apparatus of the cleanerless system using the toner in which the surface of the resin mother particle is coated with the external additive, the adhesive force between the first transfer body and the toner is larger than the adhesive force between the image carrier and the toner. In addition, the adhesive force between the first transfer member and the resin mother particles is larger than that between the image carrier and the resin mother particles. Further, according to the present invention, the adhesive force between the second transfer body and the toner is larger than the adhesive force between the first transfer body and the toner, and the adhesive force between the second transfer body and the resin base particles is between the first transfer body and the resin base particles. It is characterized by being larger than the adhesive force. Further, the present invention is characterized in that the image forming apparatus has a tandem structure including a plurality of image forming units each having an image carrier. Further, the present invention is characterized in that the sphericity of the toner is 0.95 or more.
Further, the present invention is characterized by using a polymerized toner.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration example of a cleanerless image forming apparatus having a tandem configuration to which the present invention is applied. Needless to say, the present invention is not limited to the tandem configuration and can be applied to any image forming apparatus.

In FIG. 1, UM is an image forming unit for forming a magenta image, UC is an image forming unit for forming a cyan image, UY is an image forming unit for forming a yellow image, and UBk is an image forming unit for forming a black image. And each photoconductor drum (image bearing member)
It has 10M, 10C, 10Y and 10Bk. Chargers 12M and 12 are provided around the photosensitive drums, respectively.
C, 12Y, 12Bk, static elimination light unit 13M, 13
C, 13Y, 13Bk, exposure units 14M, 14C,
14Y, 14Bk, developing units 16M, 16C, 16Y, 1
6Bk are arranged, and M, and
Images of C, Y and Bk are formed. Each photoconductor drum is in contact with the intermediate transfer body 19 driven by the belt drive rollers 21 and 22, and the transfer blades 20M, 20C, 20Y, 20Bk are arranged to face the photoconductor drums with the intermediate transfer body interposed therebetween.
Then, a transfer electric field is applied, and the images on the respective photoconductor drums are sequentially transferred onto the intermediate transfer member 19 to be color-superposed. In addition,
The transfer blade may be a transfer roller.

The color-superimposed images on the intermediate transfer member 19 are transferred onto the transfer material 24 supplied by the paper feed roller 25 by the transfer electric field applied by the secondary transfer roller 26 facing the backup roller 23, It is fixed by the fixing device 30. Transfer residual toner on the intermediate transfer member is removed by the belt cleaner 31.

In the image forming apparatus having the tandem structure, the transfer efficiency from the photosensitive drum to the intermediate transfer member is almost 1.
A value close to 00% is achieved, which is cleaner-less with respect to the photoconductor drum, and as a result, the space between the image forming units is narrowed and the size of the entire apparatus is reduced.

FIG. 2 is a diagram schematically showing the toner used in the present invention. Toner 40 is 1 for high resolution
The toner is a small particle diameter of 0 μm or less, and the surface of the resin mother particle 40a is coated with an external additive 40b for improving the charging property and weakening the adhesive force.

FIG. 3 is a view for explaining an example of a one-component non-magnetic developing type developing device. The toner 40 shown in FIG. 2 is agitated by an agitating rod 41, supplied to a developing roller 44 by a supply roller 42, rubbed against the surface thereof and frictionally charged, and further regulated to a certain thickness by a regulation blade 43. And is triboelectrically charged and conveyed to the nip portion with the photoconductor. The toner that has not been used for the development returns to the inside of the developing device, and the stirring and the triboelectric charging by the supply roller and the regulating blade are repeated again. In the development, selective development is performed in which new toner having good charging performance and uniform charge distribution is preferentially consumed. Comparing the amount of toner consumed up to the life of the developing device and the number of printed sheets, about 95% of each development is repeatedly consumed and returned to the inside of the developing device. As a result of such usage durability, the external additive on the toner surface is embedded or peeled in the mother particles, and the amount of the external additive on the toner surface is reduced. In addition, even in a new toner, there is a few percent of free mother particles which are not sufficiently covered with the external additive. In a toner that is sufficiently coated with an external additive, the transfer efficiency is good because the charging performance is good and the adhesive force is weak, but the toner whose amount of the external additive on the surface has decreased with use durability and the free mother particles have an adhesive force. As a result, the charging performance also decreases, and the transfer efficiency decreases.

Therefore, in the present invention, sufficient transfer efficiency can be obtained even in the toner in the initial state where the external additive is sufficiently covered and in the state where the durability is deteriorated and the free mother particles. This will be described with reference to FIG. FIG. 4 is a diagram schematically showing the relationship of the adhesive force between the toner and the photoconductor and between the toners. In FIGS. 4A and 4C, the surface is sufficiently covered with an external additive. Figure 4 for toner
FIG. 4B and FIG. 4D show the case where the toner is deteriorated in durability or the external additive on the surface is reduced by the free mother particles. Here, from the photoconductor 50 to the first transfer body 51 and the second transfer body. It is assumed that images are sequentially transferred to 52.

In FIG. 4A, when the adhesive force between the toner 60 and the photoconductor 50 which are sufficiently covered with the external additive is F1, and the adhesive force between the toner 60 and the first transfer body 51 is F2, F1 <F2 (1) The relationship is established. Further, in FIG. 4B, the adhesive force between the resin mother particles 61 and the photoconductor 50 after endurance deterioration or when the outer mother particles are not sufficiently covered with the free mother particles is f1, and the resin mother particles 61 and the first transfer member 51 are shown. When the adhesive force with and is f2, the relationship of f1 <f2 (2) is established. If the relationships (1) and (2) are established, theoretically 100% transfer efficiency can be achieved even for a toner that is sufficiently coated with an external additive, a toner that has deteriorated in durability, or free mother particles. To be done.

If the relationships (1) and (2) are established and the following relationship is further established, theoretically 100% transfer from the first transfer member to the second transfer member is achieved. That is, FIG.
Toner 6 in (c), which is sufficiently coated with an external additive
When the adhesive force between 0 and the first transfer body 51 is F2 and the adhesive force between the toner 60 and the second transfer body 52 is F3, the relationship of F2 <F3 (3) is established.

Further, in FIG. 4 (d), resin mother particles 61 which have not been sufficiently coated with the external additive after deterioration of durability or after the mother particles are loose.
When the adhesive force between the first transfer body 51 and the first transfer body 51 is f2, and the adhesive force between the resin mother particles 61 and the second transfer body is f3, the relationship of f2 <f3 (4) is established. If the relationships (3) and (4) are established, theoretically 100% of the first transfer member can be used even if the toner is sufficiently coated with the external additive, the toner is deteriorated in durability, or the free mother particles are present. It is transferred to the second transfer member. By maintaining the above relationship, a sufficient transfer efficiency can always be obtained, and at least a cleanerless photoconductor can be achieved.

Next, an example of the structure of the photosensitive member and the intermediate transfer member which satisfy the above conditions will be described. Examples of the photoconductor for satisfying the above conditions include the following. Select a resin with low surface energy for the outermost resin of the photoconductor itself. A surfactant that imparts water repellency and lipophilicity is added to the outermost layer of the photoreceptor. A material having high releasability is dispersed in the outermost surface layer of the photoreceptor.

As an example of the above, a fluorine-containing group and a silicon-containing group are introduced into the structure of the resin.

As examples of the above, ex polyoxyalkene alkyl ether, polyoxyalkene alkylphenyl ether, polyoxyalkene sorbitan fatty acid ester, fatty acid monoglyceride polyethylene glycol fatty acid ester and the like are added. Calcium stearate, potassium stearate, zinc stearate, iron stearate, barium stearate, nickel stearate, cobalt stearate, copper stearate, strontium stearate, cadmium stearate, magnesium stearate, cobalt oleate, zinc oleate. , Manganese oleate, iron oleate, zinc palmitate, cobalt palmitate, copper palmitate, magnesium palmitate, aluminum palmitate,
Calcium palmitate, lead caprylate, copper caprylate, zinc linolenate, cobalt linolenate, calcium linolenate, etc. are applied (JP 2000-267303 A, JP 6-332324 A).

In the above example, fine particles of fluorine are dispersed. Polytetrafluoroethylene powder (particle size: 0.1 to 0.3 μm) obtained by dissolving a hole-transporting triphenoramine compound in a polycarbonate resin in a weight ratio of 10: 8.
Is dispersed in an amount of 5 to 50 parts by weight based on the total solid content. ex tetrafluoroethylene resin, trifluoroethylene chloride resin, hexafluoroethylene propylene resin, vinyl fluoride resin, vinylidene fluoride resin, ethylene difluoride dichloride resin, and one of these copolymers Alternatively, two or more kinds are appropriately selected.

Any one of the above is used as the photoconductor, and urethane is used as the belt material of the intermediate transfer member.
Fluorine on polyester, polycarbonate, PET, etc.
The surface roughness of the photoconductor (Ra = 0.07 μm) <the surface roughness of the intermediate transfer member (Ra = 0.3 μm) was used, and a new toner, after use, was used. An example in which the adhesive force of each toner is obtained by compressing the toner to form a tablet, which is obtained from the torque when the toner is pressed against the photoconductor or the intermediate transfer member and driven, will be described.

[Embodiment] Initial state of toner X (state α)
The product was compressed at 100 to 500 kgf / cm ² and made into a tablet, and 20 gf / cm ^{2 to} 400 gf /
a difference (A) between the image carrier driving torque when the image carrier is pressed at cm ² and the torque when only the image carrier is driven,
The difference (B) between the first intermediate transfer member driving torque when the tablet is pressed against the first intermediate transfer member by the load and the torque (B) when only the first intermediate transfer member is driven, and the tablet is the second intermediate transfer member. In the difference (C) between the second intermediate transfer member (transfer material) drive torque when the body (transfer material) is pressed by the load and the torque when only the second intermediate transfer member (transfer material) is driven, A < After the relationship of B <C is established and the toner X is idled for 50 minutes at a developing roller peripheral speed of 350 mm / sec (equivalent to 2000 sheets of solid white continuous printing (A4)) (state β), the tablet is prepared in the same manner as above. The transfer efficiency was measured by using the toner X satisfying the relationship of A '<B'<C', where A', B ', and C'are the driving torque differences measured in the same manner. Initial (state α), 99.8-100%, durable It was (state β) also can be secured from 99.4 to 99.8 percent.
The toner X is a polymerized toner having a sphericity of 0.96.

A particle analyzer (PT-
1000 (manufactured by Yokogawa Denki Seisakusho Co., Ltd.), the toner surface of the new toner and the toner after endurance is coated with an external additive (synchronous external additive), or the external additive is released from the toner surface. It was measured whether there is (free external additive), The toner surface data was obtained. In addition, when the cross section of the toner was observed by an electron micrograph, it was observed that the external additive on the surface of the toner after running was embedded in the mother particles as compared with the new toner.

If the toner has a spherical shape, the surface energy is small and the contact area with the member is small, so that the physical adhesive force between the toner and the member in contact with the toner is reduced. Therefore, the sphericity of the toner is set to 0.
When it is 95 or more, the transfer efficiency can be increased and the cleaner can be contributed. The sphericity of the toner here is the average sphericity measured by a FPIA-2100 measuring instrument manufactured by Sysmex Corporation, and the circularity of the two-dimensional projected image of the toner (perimeter of a circle having the same area as the projected image / projected image Perimeter).

Further, in the case of the polymerized toner, the particle size distribution becomes sharper than that of the pulverized toner, so that in the step of frictionally charging the toner, all the toner comes into contact with the uniform charging member, and a uniform charge amount is secured. Cheap. As a result, it is possible to further improve the transfer efficiency and contribute to cleanerlessness.

When transferring between the photosensitive member and the first transfer member or between the first transfer member and the second transfer member (or recording material), shearing of the toner is caused by providing a speed difference between them. It is possible to apply a force to improve the transfer efficiency.

[0028]

EFFECTS OF THE INVENTION In a developing system for carrying out one-component development, the toner must be uniformly charged by a regulating blade to form a uniform thin layer surface. Therefore, the external additive coating the surface of the toner is peeled off or embedded. Before and after the endurance, the toner characteristics change from a state where the contribution ratio of the external additive is large to a state where the contribution ratio of the mother particles is large, so that the magnitude relationship of the adhesive force as in the present invention is satisfied. This makes it possible to realize stable transfer characteristics regardless of the usage history (durability) of the apparatus.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a configuration example of a tandem cleanerless image forming apparatus to which the present invention is applied.

FIG. 2 is a diagram schematically showing a toner used in the present invention.

FIG. 3 is a diagram illustrating an example of a one-component non-magnetic developing type developing device.

FIG. 4 is a diagram schematically showing the relationship of the adhesive force between the toner and the photoconductor and between the toners.

[Explanation of symbols]

10M, 10C, 10Y, 10Bk ... Photosensitive drum (image bearing member), 12M, 12C, 12Y, 12Bk ... Charger, 13M, 13C, 13Y, 13Bk ... Static elimination unit, 14M, 14C, 14Y, 14Bk ... Exposure unit, 16M, 16C, 16Y, 16Bk ... Developing device, 19
... intermediate transfer body, 20M, 20C, 20Y, 20Bk ... transfer blades 21, 22 ... drive roller, 23 ... backup roller, 24 ... transfer material, 25 ... paper feed roller, 26 ...
Secondary transfer roller, 30 ... Fixing device, 31 ... Belt cleaner, 40 ... Toner, 40a ... Resin mother particles, 40b ... External additive, 41 ... Stir bar 41, 42 ... Supply roller, 43 ... Regulating blade, 44 ... Development Roller, 50 ... Photoconductor, 51 ... First transfer body, 52 ... Second transfer body, 60 ... Toner, 61 ... Resin mother particles.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 15/08 507 G03G 9/08 384 15/16 15/08 507B 507L F term (reference) 2H005 AA08 AA15 DA07 2H030 AA05 AB02 AD01 BB42 2H077 AA37 EA15 GA03 GA13 2H200 FA02 FA16 GA09 GA12 GA16 GA23 GA47 HA12 JA02 JA09 JC04 JC15 JC17 MA04 MA20 MC06 MC08 MC09

Claims (5)

[Claims] 1. An image forming apparatus of a cleanerless system using a toner having a resin mother particle surface coated with an external additive, wherein the adhesive force between the first transfer body and the toner is larger than the adhesive force between the image carrier and the toner. An image forming apparatus characterized in that the adhesive force between the first transfer member and the resin mother particles is larger than that between the image carrier and the resin mother particles. 2. The adhesive force between the second transfer member and the toner is larger than the adhesive force between the first transfer member and the toner, and the adhesive force between the second transfer member and the resin mother particles is the same as that between the first transfer member and the resin mother particles. The image forming apparatus according to claim 1, wherein the image forming apparatus has a force larger than the force applied. 3. The image forming apparatus according to claim 1, wherein the image forming apparatus has a tandem configuration including a plurality of image forming units each having an image carrier. 4. The image forming apparatus according to claim 1, wherein the sphericity of the toner is 0.95 or more. 5. The image forming apparatus according to claim 1, wherein a polymerized toner is used.