JP2002304013A - Toner and image forming apparatus - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To achieve both oilless fixing and extending the life of a developing device. In a synchronous distribution curve of a synchronous external additive equivalent particle diameter to a toner mother particle equivalent particle diameter, an external additive coverage at a toner mother particle equivalent particle diameter corresponding to a developing roller surface roughness is used as a reference value. The external additive coverage at a toner base particle equivalent particle size larger than the developing roller surface roughness is equal to or greater than the virtual reference line with a constant external additive coverage obtained from the value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner and an image forming apparatus which can realize a fixing device having a simple structure and can prevent occurrence of filming in a developing device.

[0002]

2. Description of the Related Art FIG. 3 is a view for explaining a conventional image forming apparatus having an intermediate transfer member. The rotary developing device 1 is provided with developing rollers of four colors of Y, M, C, and K. Each time the photosensitive member 2 makes one rotation, the developing roller of each color is switched to a rotary type and contacts the photosensitive member. . The photoreceptor 2 is uniformly charged by the charging device 3 and is exposed to an image for each color to form an electrostatic latent image. The photoreceptor 2 is developed for each color by contacting the Y, M, C and K developing rollers. Transfer is performed in contact with the transfer member 5 (primary transfer). The residual toner on the photoconductor after the transfer is scraped off by the cleaning device 4. When the four-color images are superimposed on the intermediate transfer member 5, the sheet 8 is conveyed, the secondary transfer roller 7 is brought into contact with the sheet, and a secondary transfer bias is applied from a power source (not shown) to collectively transfer color images onto the sheet 8. (Secondary transfer). The secondary transfer roller 7 swings as shown by an arrow so as to come into contact with and separate from the intermediate transfer body 5.
They are separated during color superimposition on the intermediate transfer member, and contact during transfer. The residual toner on the intermediate transfer body after the transfer is scraped off by the cleaning device 6.

In such an image forming apparatus, as shown in FIG. 4, a sheet 8 on which a full-color image has been transferred is passed through a fixing device including a heat roller 10 and a backup roller 11 to fix toner. ing. However, in such a fixing device, high-temperature offset occurs due to wrapping of the paper or welding of the toner to the heat roller. Therefore, in order to prevent this, as shown in FIG. 5, an oil application roller 12 is provided and oil is applied to the heat roller 10.

[0004]

In a conventional image forming apparatus, oil is applied to a heat roller against paper winding and high-temperature offset, which are problems of the fixing device, so that the toner and the fixing roller are separated from each other. The problem was solved by increasing the quality. However, in this method, since the oil application is controlled, the structure is complicated, the apparatus is expensive and large, the application roller needs to be replaced, and user convenience is impaired. In order to solve these problems, the oil application roller was eliminated, and instead of the heat roller, a fluorine-based material was used for the surface layer, and the amount of wax put into the toner was increased compared to the conventional oil. Less fixation is considered.

On the other hand, as for the developing device, as shown in FIG. 6, a supply roller 21 comes into contact with a developing roller 20 by opposing rotation to rub the toner on the surface of the developing roller to cause frictional charging. After the toner on the developing roller surface is regulated to a predetermined thickness and charged at the same time, the toner is supplied to the photoreceptor 2. If the amount of wax contained in the toner is large, the toner adheres to the regulating blade 22. Filming occurs. For example, when development with a low image duty is performed, selective consumption of toner occurs, and large and small particle diameter toner remains in the developing device. After that, when the concentration of the small particle diameter toner in the developing device becomes high, the time that the toner remains in the unevenness on the surface of the developing roller becomes long, and filming to the regulating blade occurs.
In particular, when a toner having a large amount of wax is used for the purpose of oilless fixing, heat or pressure stress is applied to the toner in the developing device.
Wax adheres to the regulating blade, which triggers filming from a very early stage, causing a situation in which the life of the developing device is shorter than before.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is intended to achieve both oilless fixing and extension of the life of a developing device. Therefore, according to the first aspect of the present invention, in the synchronous distribution curve of the synchronous external additive equivalent particle diameter with respect to the toner base particle equivalent particle diameter, the external additive coverage at the toner mother particle equivalent particle diameter corresponding to the developing roller surface roughness is determined. As a reference value, with respect to a virtual reference line in which the external additive coverage obtained from the value is constant, the external additive coverage in the toner base particle equivalent particle diameter larger than the developing roller surface roughness was set to be equal to or larger than the virtual reference line. It is characterized by the following. The invention according to claim 2 is characterized in that the external additive coverage of the reference value is 80 to 120%. According to the third aspect of the present invention, the average particle diameter of the synchronous toner to which the external additive is attached is set to be equal to or larger than the average particle diameter of the entire toner, and the external additive coverage of the large particle diameter toner larger than the surface roughness of the developing roller is increased. It is characterized by the following. According to a fourth aspect of the present invention, there is provided a toner having a large particle size larger than the surface roughness of the developing roller by setting the liberation rate of the base particles at a toner particle size smaller than the surface roughness of the developing roller to at least the liberation rate of the base particles having a toner particle size larger than the surface roughness of the developing roller Is characterized in that the external additive coverage is increased. According to a fifth aspect of the present invention, at least a latent image carrier on which an electrostatic latent image is formed, developing means for developing the electrostatic latent image on the latent image carrier with toner, and transferring the toner image on the latent image carrier And a fixing unit for fixing the transferred image, wherein the toner is the toner according to claim 1.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram for explaining a synchronous distribution curve showing the ratio between the amount of toner base particles defining the synchronous toner of the present invention and the amount of an external additive attached thereto. The vertical axis is the external additive equivalent particle size. Here, the equivalent particle diameter will be described. In the analysis of toner particles by the particle analyzer method, the toner particles are introduced into plasma to excite and emit light. The toner particles are formed by mother particles made of resin (carbon) such as polyester,
It is coated with an external additive such as silica (silicon oxide) to improve fluidity and chargeability. When excited and emitted, it emits light according to the emission spectrum (frequency) specific to the element and the amount of the element. Light emission intensity is obtained. Therefore, the emission frequency and its intensity are measured, and the amounts (mass) of the elements constituting the base particles and the external additives are respectively measured from the measurement results. The equivalent particle diameter is expressed in terms of the particle diameter in terms of the particle diameter, and is calculated as the cube root voltage of the signal intensity (proportional to the mass) of the measured emission spectrum (see JP-A-12-47425).

In the particle analyzer method, when the toner base particles and the external additive are integrated, the light emission is detected at the same timing, so they are said to be synchronized (synchronous toner). When they are separated, light emission is detected at different timings, so they are called asynchronous (asynchronous toner), and those plotted on the horizontal axis and the vertical axis in FIG. 1 are asynchronous toner and asynchronous external additive. What is plotted at any other point is the synchronous toner, and the plotting position is determined by the ratio of the amount of the base particles to the amount of the external additive.

When the external additives are uniformly distributed (internally added) inside the base particles, the amount of both the base particles and the external additives is proportional to the cube of the particle size. Is linear, and when the external additive is attached only to the base particle surface,
Since the amount of the base particles is proportional to the cube of the particle size and the amount of the external additive is proportional to the surface area of the base particles, that is, the square of the particle size, the synchronous distribution curve becomes a (2/3) th power curve. . Therefore, when the coverage of the external additive on the base particle surface is constant, the synchronous distribution curve becomes a (2/3) th power curve like the virtual reference line S in FIG. Also, when the external additive is adhered to the toner at a fixed ratio, if the ratio of the free external additive increases, the ratio of the synchronous external additive decreases, so that the slope of the synchronous distribution curve decreases, and the free external additive decreases. When the ratio of the external additive decreases, the ratio of the synchronous external additive increases, and the slope of the synchronous distribution curve increases. From these facts, the state of attachment of the external additive to the toner base particles can be analyzed.

The toner according to the present invention has a reference value (80-120%) of the external additive coverage at the toner base particle equivalent particle size corresponding to the surface roughness of the developing roller. When the virtual reference line S having a constant rate is drawn, the coverage of the external additive is set to be equal to or higher than the virtual reference line S at the toner base particle equivalent particle diameter larger than the surface roughness of the developing roller. Long life is compatible.

A characteristic required of the toner to improve the durability of the developing device is to relieve stress applied to the base particles from the developing roller and the regulating blade. It is also effective to make the mother particles themselves resistant to stress.However, toner containing a large amount of wax that is compatible with oilless fixing created by the pulverization method has a certain probability that the wax is exposed on the surface. It's hard to expect. To alleviate the stress on the toner, there is a method in which an external additive attached to the surface acts as a spacer for the stress from the regulating blade.

As shown in FIG. 2, when the toner 23 is conveyed between the developing roller 20 and the contact member 22, the toner rolls along the uneven surface of the developing roller, and In such a case, the toner easily enters the concave portion of the developing roller and stays. However, in the case of a large particle size toner, the stress from the contact member is large, which causes filming. Therefore,
The external additive of a large particle diameter toner having a larger surface roughness than the developing roller has a higher coverage than the reference coverage curve S (FIG. 1), and the external additive is sufficiently adhered to the surface, thereby causing stress. Suppress the occurrence of filming. Regarding the fixing property in this case, in the case of the large particle size toner, there is a high possibility that the wax is exposed from the surface, so that the fixing property can be sufficiently secured. Therefore, it is possible to achieve both oilless fixing and a longer life of the developing device.

The addition of the external additive to the toner particles is performed, for example, by
It can be performed by a V-type blender, Henschel mixer, Loedige mixer or the like. Further, if necessary, coarse particles of the toner may be removed by using a vibration sieving machine, a wind sieving machine, or the like. As a method of selectively changing the addition amount of the external additive according to the toner particle size, the toner is divided into several stages for each particle size, and the external addition process is separately performed, and then these are blended. The coverage can be changed according to the particle size.

In the case of a toner having a small particle diameter, there is a high possibility that the toner stays in the concave portion of the developing roller. However, the stress from the contact member is small, and the probability that the wax contained in the toner is exposed on the surface is low. Therefore, filming is unlikely to occur.On the other hand, since the fixing property can be improved by reducing the external additive coverage, the external additive coverage of the toner having a small particle diameter smaller than the developing roller surface roughness can be reduced. Is desirable.

The present invention is not limited to a toner containing a wax, and is similarly applicable to a toner using a low-melting resin containing no wax. In the above, the description has been given based on the synchronous distribution curve of the external additive coverage, but the present invention is not limited to this. For example, the average particle diameter of the _total toner including the synchronous toner to which the external additive is attached and the asynchronous toner to which no external additive is attached or a small amount of the asynchronous toner is D _total , and the average particle diameter of the synchronous toner is D _doki.
Then, D _doki / D _total ≧ 1 may be satisfied. By doing so, a toner having a large particle diameter larger than the surface roughness of the developing roller slightly smaller than the average particle diameter of the toner becomes a toner having a large external additive coverage, and
A toner having a small particle diameter smaller than the surface roughness of the developing roller becomes a toner having a small external additive coverage, and can suppress filming and perform satisfactory fixing.

When the liberation rate of base particles having a toner particle diameter smaller than the surface roughness of the developing roller is αA and the liberation rate of base particles having a toner particle diameter larger than the surface roughness of the developing roller is αB, αA / αB ≧ 1 Is also good. By doing so, a toner having a large particle diameter larger than the surface roughness of the developing roller becomes a toner having a large external additive coverage, and a toner having a small particle diameter smaller than the surface roughness of the developing roller becomes a toner having a small external additive coverage. In addition, filming can be suppressed and fixing can be performed satisfactorily.

The toner used in the image forming apparatus of the present invention may be either a negative polarity toner or a positive polarity toner. The base particles are controlled by at least a base resin constituting the toner and a charge amount. Charge controlling agents, pigments, external additives, mold release agents, magnetic agents, and other additives. Further, the image forming apparatus to which the toner of the present invention is applied is not limited to an image forming apparatus having an intermediate transfer member as shown in FIG.
Applicable to image forming devices that directly transfer and fix the toner image on the photoreceptor to paper, and to devices that attempt to extend the life of the developing device while ensuring the fixability of the fixing device. It is.

Examples of the base particles include polystyrene and copolymers such as hydrogenated styrene resin, styrene / isobutylene copolymer, ABS resin, ASA resin, AS resin,
AS 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-based resin or methacrylate-based resin and its copolymer, Styrene / acrylic resin and its copolymer, for example, styrene / acrylic copolymer, styrene / diethylamino / ethyl methacrylate copolymer, styrene / butadiene / acrylic 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 / acrylate / maleate copolymer, styrene / methyl methacrylate / 2-ethylhexyl acrylate Styrene-n-butylarylate-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, polypropylene and its copolymer, fluorine resin, polyamide resin, polyvinyl alcohol resin, polyurethane resin, polyvinyl butyral resin, etc. blended one or more kinds Can be used.

As the coloring agent, carbon black, spirit black, nigrosine, rhodamine,
Triaminotriphenylmethane, cationic, dioxazine, copper phthalocyanine, berylen, azo, gold-containing azo pigment, azochrome complex, carmine, benzidine, solar pure yellow 8G, quinacridone, polytungstophosphoric acid, indasulene blue, Sulfonamide derivatives and the like can be used.

Further, as the charge control agent, an electron-accepting organic complex, chlorinated polyester, nitrophenic acid,
Secondary ammonium salts, pyridinyl salts and the like can be used. Further, as the release agent, polypropylene wax, polyethylene wax, or the like can be used. Further, 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.

Further, as the magnetic agent, Fe, Co, N
i, Cr, Mn, Zn or other metal powder, Fe ₃ O ₄ , Fe ₂
Metal oxides such as O ₃ , Cr ₂ O ₃ , and ferrite, and alloys that exhibit ferromagnetism by heat treatment, such as alloys containing manganese and acid, may be used, and may be preliminarily treated with a coupling agent or the like. Absent. Then, these are mixed by using a general kneading and pulverizing method, a spray-dry method, a polymerization method or the like, thereby producing mother particles.

On the other hand, various external additives can be used, for example, inorganic fine particles such as metal oxides such as silica, alumina and titanium oxide, and composite oxides thereof;
Organic fine particles such as acrylic fine particles can be used.
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 it is less than this, in high temperature and high humidity,
It is not preferable because the chargeability and the fluidity tend to decrease due to the adsorption of moisture. The particle size of the external additive is preferably from 0.001 to 1 μm from the viewpoint of transportability and chargeability. The amount of the external additive to be added is 0.1 to the toner base particles.
It is preferably 1 to 5 wt%. If the amount is further increased, the probability that the external additive becomes asynchronous with the toner increases,
Secondary agglomeration and the like of the external additives frequently occur, which leads to a decrease in chargeability and an increase in transport streaks.

Further, the external additive is not limited to one type, and a mixture of two or more types can be used. Then, the toner T of the present example is formed by dry-mixing the above-described base particles and the external additive with a high-speed fluid mixer such as a Henschel mixer or a Papen-Meier, or a mixer such as a mechanochemical method, and adhering them together. Is done.

[0024]

As described above, according to the present invention, the external additive coverage obtained from the equivalent particle size of the base particles corresponding to the surface roughness of the developing roller is used as the reference value, and the external additive obtained from the value is used as the reference value. By setting the external additive coverage at a base particle equivalent particle diameter larger than the developing roller surface roughness to a reference line at which the coverage is constant, the filming in the developing device is suppressed, and the fixing is excellent. Can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a synchronous distribution curve defining a toner of the present invention.

FIG. 2 is a diagram illustrating occurrence of filming in a developing roller.

FIG. 3 is a diagram illustrating an image forming apparatus provided with an intermediate transfer member.

FIG. 4 is a diagram illustrating a two-roller fixing device.

FIG. 5 is a diagram illustrating a fixing device including an oil application roller.

FIG. 6 is a diagram illustrating a developing device.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 rotary developing device 2 photoreceptor 3 charging device 4 cleaning device 5 intermediate transfer member 6 cleaning device 7 secondary transfer roller 8 paper 10
Heat roller, 11 backup roller, 12 oil application roller, 20 developing roller, 21 supply roller,
22 ... Regulation blade.

Claims (5)

[Claims] In a synchronous distribution curve of a synchronous external additive equivalent particle diameter to a toner mother particle equivalent particle diameter, an external additive coverage at a toner mother particle equivalent particle diameter corresponding to a developing roller surface roughness is used as a reference value, With respect to a virtual reference line that keeps the external additive coverage obtained from the value, the external additive coverage at a toner base particle equivalent particle diameter larger than the developing roller surface roughness is set to be equal to or greater than the virtual reference line. Toner. 2. The external additive coverage of the reference value is 80-1.
2. The toner according to claim 1, wherein the toner content is 20%. 3. The method according to claim 1, wherein the average particle size of the synchronous toner to which the external additive is attached is equal to or larger than the average particle size of the entire toner, and the external additive coverage of the toner having a large particle size larger than the surface roughness of the developing roller is increased. Characterized toner. 4. The method according to claim 1, wherein the release rate of the base particles having a toner particle size smaller than the surface roughness of the developing roller is not less than the release rate of the base particles having the toner particle size larger than the surface roughness of the developing roller. A toner having a high additive coverage. 5. A latent image carrier on which at least an electrostatic latent image is formed, developing means for developing the electrostatic latent image on the latent image carrier with toner, and transfer for transferring a toner image on the latent image carrier 5. An image forming apparatus comprising: means for fixing a transferred image; and the toner is the toner according to claim 1.