JP2002304015A - Toner and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent selective developing. SOLUTION: As for the synchronous distribution curve of a synchronous medium resistance additive agent equivalent particle size to a toner base particle equivalent particle size, and with reference to a virtual reference line which is obtained by taking the medium resistance additive agent coating ratio for the toner base particle equivalent particle size equivalent to the surface roughness of a developing roller or a toner means particle size as a reference value and fixing the medium resistance additive agent coating ratio obtained from the reference value, the medium resistance additive agent coating ratio for the base particle equivalent particle size larger than the toner base particle equivalent particle size equivalent to the surface roughness of the developing roller or the toner mean particle size is made equal to or exceeding the virtual reference line.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a toner and an image forming apparatus in which a medium resistance external additive is added to a toner to adjust a charge amount.

[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.

[0003]

The toner used in such an image forming apparatus has a particle size distribution, and the width of the particle size distribution is narrow or the so-called particle size is uniform depending on the conditions at the time of toner production. ) Or wide (so-called non-uniform particle sizes ranging from small to large). Generally, in the case of a toner manufactured by a pulverization method, the particle size distribution is relatively wide. Classification can reduce the size to some extent, but it has technical limitations and increases costs. On the other hand, when produced by a polymerization method, the particle size distribution can be narrowed, but even this does not result in a single particle size.

When a toner having such a particle size distribution is used, a phenomenon called selective development occurs in which toner in a certain particle size range is preferentially consumed. That is, in the developing device 10 shown in FIG. 4, the toner is conveyed in the order of the toner storage unit 11 → supply roller 12 → developing roller, charged and supplied for development. Then, the toner amount is regulated. In the case of non-magnetic toner, the supply of toner from the supply roller 12 to the developing roller 13 is as follows.
The supply roller is brought into contact with the developing roller by opposing rotation, and the toner is rubbed to frictionally charge and electrostatically adhere. At this time, when the toner on the developing roller 13 is small,
For example, when toner is supplied to the developing roller for the first time,
Immediately after the solid development, the toner in the toner storage unit 11 is supplied to the developing roller 13 as it is. On the other hand, when toner is present on the developing roller, for example, after developing a white background or developing a character or line with a low print density, the toner is held on the developing roller according to the developing roller surface roughness, regulation conditions, and supply conditions. Toner having a particle diameter that is easy to remain on the developing roller, and toner having a particle diameter that is difficult to be retained is separated from the developing roller and collected in the developing device.

In general, there are many image outputs such as characters and lines with low printing density such as the latter, so that toner having a particle size that is easily held by the developing roller is preferentially consumed. The toner that is easily held by the developing roller is determined by conditions such as the surface roughness of the developing roller. Originally, these conditions are set so that the toner having an average particle diameter around the toner easily develops its ability, and thus is consumed preferentially. Is a toner having an average particle diameter or, depending on conditions, a particle diameter region near the developing roller surface roughness. This phenomenon is called selective development.

FIG. 5 is a diagram showing a particle size distribution of toner remaining in a developing device by selective development. In the figure, assuming that the original toner particle size distribution is D, the toner consumed by the selective development is in the region where the particle size is the most abundant. The ratio of the larger particle size to the other particle size, that is, the average particle size or the particle size smaller than the developing roller surface roughness increases, and when the toner is replenished, the easily developed toner is preferentially consumed again. Therefore, the concentration of the unused toner further proceeds, and the distribution becomes like D '.

[0007] Thus, the toner in the developing device is reduced,
If the amount of toner unsuitable for development increases in the developing unit due to repeated replenishment, toner having a small particle size and a large particle size unsuitable for development must be used for development. At this time, the toner having a small particle diameter has a large charge amount with respect to the weight ratio. Therefore, the toner is difficult to be developed due to the image force of the charge, and the toner stays on the surface of the developing roller. Filming, which is likely to be welded to the like. On the other hand, a large particle size toner has a small charge amount in a weight ratio, and thus is easily carried by a developing electric field and is easily developed. However, in the case of a large particle size toner, there is a problem that dust and dropout occur at the time of transfer, and the image becomes rough.

As a countermeasure for eliminating the adverse effects of such selective development, for example, there is a method of stirring the toner in a developing device. However, the selective consumption of the toner depends on the image pattern because it is caused by the image output. Continuing to use the toner with insufficient agitation may cause partial improper concentration of the toner. By agitation, the concentration can be made as uniform as possible to delay the progress. However, simply delaying concentration by selective consumption is not sufficient as a drastic measure.

There is also a method in which the toner on the developing roller is peeled off each time. The toner on the development is peeled off each time, for example, by increasing the contact depth of the supply roller. As a result, the toner on the developing roller is as after solid development every time, and the toner is consumed uniformly regardless of the particle diameter. However, this method causes a large increase in torque and toner damage, and it is necessary to take countermeasures for realization.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the charge amount of a medium resistance external additive that leaks the charge of a toner is changed according to the toner particle size. This is to make the ratio to mass constant so that selective development does not occur.

For this purpose, the invention according to claim 1 provides a synchronous distribution curve of the synchronous external resistance additive additive equivalent particle diameter with respect to the toner base particle equivalent particle diameter, wherein the toner base equivalent to the developing roller surface roughness or the toner average particle diameter. With the medium resistance external additive coverage at the particle equivalent particle diameter as a reference value, the developing roller surface roughness or the toner average particle diameter is compared with a virtual reference line obtained from the value to keep the medium resistance external additive coverage constant. The medium resistance external additive coverage at a base particle equivalent particle diameter larger than the toner base particle equivalent particle diameter corresponding to the diameter is equal to or larger than the reference line. In the invention according to claim 2, the reference value is 80 to 120%.
It is characterized by being. According to a third aspect of the present invention, there is provided a photoconductor on which an electrostatic latent image is formed, a developing unit for developing the electrostatic latent image on the photoconductor, a transfer unit for transferring an image on the photoconductor, and the transferred toner. Fixing means for fixing an image, wherein the toner is the toner according to claim 1 or 2.

[0012]

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 the medium-resistance external additive adhered to the toner. The vertical axis indicates the external additive equivalent particle diameter. 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. Toner particles are formed on a base particle made of a resin (carbon) such as polyester by using titanium oxide (T) for improving fluidity and chargeability.
iO ₂ ) or titanium oxide and silica (silicon oxide) coated as an external additive. When excited and emitted, the emission spectrum (frequency) peculiar to the element and the emission intensity according to the amount of the element are reduced. can get. 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 additive is uniformly distributed (internally added) inside the base particle, the amount of both the base particle and the external additive is proportional to the cube of the particle size, so that the synchronous distribution curve is obtained. 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.

According to the present invention, in FIG. 1, the coverage of the medium resistance external additive in the developing roller surface roughness or the toner base particle equivalent particle size corresponding to the toner average particle size is set to a reference value (80 to 80).
120%), and draws a virtual reference line S passing through the reference point P and having a constant coverage. The resistance external additive coverage is set to be equal to or higher than the reference line S.

[0016] As in the resistor external additive, for example, titanium oxide (TiO _2), a mixture of titanium oxide and silicon oxide with a (TiO ₂ + SiO ₂₎ or the like, resistance of 10 ^8-1
Use the one with 0 ¹² Ω · cm. The medium-resistance external additive is used as a measure for fogging and for controlling the toner charge distribution for improving the developability. When the resistance value is less than 10 ⁸ Ωcm, the toner chargeability is remarkably reduced and fog and toner scattering are caused. When the density exceeds 10 ¹² Ωcm, the charge distribution of the toner is widened, and fogging or the like by the opposite polarity toner occurs.

In the present invention, a medium-resistance external additive such as titanium oxide is added to the toner base particle equivalent particle diameter d1 larger than the developing roller surface roughness or the toner average particle diameter d1 shown in FIG. By setting the coverage of the medium resistance external additive in the region of the diameter dx to be equal to or higher than the reference line, the toner charge in the small particle size region is leaked, and the mass ratio of the charge to the other particle size region is set to the same level. Developability is improved.

The addition of the medium-resistance external additive to the toner particles can be performed by, for example, a V-type blender, a Henschel mixer, a 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.

FIG. 2 shows the same particle size distribution as that of the toner shown in FIG. 5, but in the present invention, dx>
In the region d1, the toner is easily developed because the mass ratio of the charged charges is improved, and the toner in this region has an average particle diameter that is preferentially consumed or the surface of the developing roller as indicated by a distribution D ″ indicated by a broken line. The toner can be consumed in the same manner as the toner in the particle size region near the roughness, and it is possible to avoid that this region remains without being consumed by the selective development.

The toner used in the image forming apparatus of the present invention may be either a negative polarity toner or a positive polarity toner, and the base particles are at least a resin of a base material 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.
The present invention is also applicable to an image forming apparatus or the like that directly transfers and fixes a toner image on a photoconductor to a sheet.

As the base particles, polystyrene and copolymers such as hydrogenated styrene resin, styrene / isobutylene copolymer, ABS resin, ASA resin, AS resin, A
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, examples of the charge controlling agent include 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.

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.

[0027]

As described above, according to the present invention, the surface resistance of the developing roller or the coverage ratio of the medium resistance external additive in the toner base particle equivalent particle diameter corresponding to the average particle diameter of the toner is set as the reference value. With respect to an imaginary reference line having a constant coverage of the medium resistance external additive obtained from the above, the surface roughness of the developing roller or the toner having a base particle equivalent particle size larger than the toner base particle equivalent particle size corresponding to the toner average particle size. By setting the resistance external additive coverage to be equal to or higher than the above-mentioned reference line, it is possible to improve the charge-to-mass ratio in the large particle size region and to avoid selective development.

[Brief description of the drawings]

FIG. 1 is a diagram showing a synchronous distribution curve for explaining a toner of the present invention.

FIG. 2 is a diagram illustrating avoidance of selective development in a small particle size region.

FIG. 3 is a diagram illustrating an image forming apparatus.

FIG. 4 is a diagram illustrating a developing device.

FIG. 5 is a diagram illustrating selective development.

[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
Developing device, 11: toner storage unit, 12: supply roller, 13
... developing roller, 14 ... regulating blade.

Claims (3)

[Claims] In the synchronous distribution curve of the synchronous medium resistance external additive equivalent particle diameter to the toner base particle equivalent particle diameter, the medium resistance at the toner base particle equivalent particle diameter corresponding to the developing roller surface roughness or the toner average particle diameter. Using the external additive coverage as a reference value,
With respect to an imaginary reference line obtained from the value and keeping the coverage ratio of the medium resistance external additive constant, a base particle equivalent particle size larger than the developing roller surface roughness or a toner base particle equivalent particle size corresponding to the toner average particle size. 3. The toner according to claim 1, wherein the coating ratio of the medium-resistance external additive is not less than the reference line. 2. The toner according to claim 1, wherein the reference value is 80 to 120%. 3. A photoreceptor on which an electrostatic latent image is formed, a developing unit for developing the electrostatic latent image on the photoreceptor, a transfer unit for transferring an image on the photoreceptor, 3. An image forming apparatus comprising: a fixing unit for fixing, wherein the toner is the toner according to claim 1 or 2.