JP2008158442A - Toner, developing device using the same, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide toner containing resin base particles having a diameter of less than 4 μm and giving a printed image of high resolution by an image forming apparatus having a line head with an exposure spot diameter of 15 to 40 μm on a photoreceptor. <P>SOLUTION: The toner containing resin base particles, silicone oil or fluorine oil, and silica and titanium oxide is prepared by controlling in such a manner that: the volume average particle diameter of the resin base particles is 2 μm to less than 4 μm; the ratio of (volume average particle diameter of the resin base particles)/(number average particle diameter of the resin base particles) is larger than 1 and less than 1.1; the content of the silicone oil or fluorine oil is 0.05 mass% to less than 2 mass% with respect to the resin base particles; and the content of titanium oxide is 0.3 mass% to 1 mass% with respect to the resin base particles. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrostatic charge image developing toner used in a copying machine, a printer, a fax machine and the like. Furthermore, the present invention relates to a developing device and an image forming apparatus in which the toner is used.

2. Description of the Related Art In recent years, an image forming apparatus having a line head (exposure apparatus) whose exposure spot diameter on a photoreceptor is 15 to 40 μm and whose resolution of printed images has been increased has been used. The diameter of the resin mother particles contained in the toner used in the image forming apparatus is less than 4 μm. A problem in handling toner containing resin mother particles having a diameter of less than 4 μm is that the toner is likely to scatter and is difficult to convey after being compressed to the developing roller. One means for solving these problems is mixing of resin base particles and oil.
In order to prevent filming on the electrostatic latent image carrier and the developing roller, a developing device that performs development by attaching a toner obtained by adding silicone oil or fluorine oil to resin base particles to the latent image has been studied (for example, Patent Document 1). The toner contains aggregates of resin base particles, and development by the developing device is not performed well.
On the other hand, a uniform image density is obtained by the toner in which hydrophobic silica having negative chargeability and fluidity and hydrophobic rutile-anatase type titanium oxide having low resistance and negative overcharge prevention property are added to the toner base particles. An image forming method that is maintained for a long period of time has been studied (see, for example, Patent Document 2). Even when hydrophobic silica, hydrophobic rutile-anatase type titanium oxide and oil are added to resin base particles having a diameter of less than 4 μm, a toner containing an aggregate of resin base particles may be obtained. Even when printing is performed by an image forming apparatus having an exposure device having an exposure spot diameter of 15 to 40 μm on a photoconductor using a toner containing an aggregate of resin base particles having a diameter of less than 4 μm, a high-resolution printed image is obtained. It is not possible.
JP 2001-166527 A Japanese Patent No. 3693106

  The problem to be solved by the present invention is a toner that contains a resin mother particle having a diameter of less than 4 μm and that can provide a high-resolution printed image by an image forming apparatus having a line head with an exposure spot diameter of 15 to 40 μm on the photoreceptor. Is an offer. Another problem to be solved by the present invention is to provide a developing device and an image forming apparatus that can obtain a high-resolution printed image using the toner.

The present invention relates to a toner containing resin mother particles, silicon oil or fluorine oil, silica and titanium oxide, and the resin mother particles have a volume average particle diameter of 2 μm or more and less than 4 μm. Diameter) / (number average particle diameter of resin base particles) is greater than 1 and less than 1.1, and the content of silicon oil or fluorine oil is 0.05 mass% or more and less than 2 mass% with respect to the resin base particles. In the toner, the content of titanium oxide is 0.3% by mass or more and 1% by mass or less based on the resin base particles.
In a preferred embodiment of the present invention, the titanium oxide contained in the toner is a rutile-anatase type.

  The present invention is a developing device including a photoconductor, a developing roller, and a gap adjusting member provided at both ends of the developing roller, and the toner is used to perform non-contact jumping development. The toner conveying surface is provided to face the photoconductor with a predetermined development gap, and conveys the toner to the photoconductor. The gap adjusting member is composed of a spacer, and contacts the photoconductor to set the development gap. The spacer is a developing device that is made of a material having higher hygroscopicity than the developing roller and is fixed to the developing roller through an elastic layer.

  The present invention is an image forming apparatus including a developing device and a line head, wherein the toner is used to form an image, the developing device is the developing device, and the line head is substantially orthogonal to the main scanning direction. A light beam is imaged on a surface to be scanned conveyed in the sub-scanning direction to form a spot, each of which corresponds to a plurality of light emitting element groups each having a plurality of light emitting elements and the plurality of light emitting element groups. And a plurality of imaging lenses that each image a light beam emitted from each of the plurality of light emitting elements belonging to the corresponding light emitting element group on the surface to be scanned. In each of the light emitting element groups, the distance Gx between the most upstream light emitting element and the most downstream light emitting element in the main scanning direction is equal to the most upstream light emitting element and the most downstream light emitting element in the sub scanning direction. A plurality of light emitting element arrays in which two or more of the light emitting elements are arranged in the main scanning direction are arranged in the sub scanning direction so that the plurality of light emitting elements are two-dimensionally arranged, A group row in which two or more light emitting element groups are arranged in the main scanning direction at the main scanning group pitch Px so that the main scanning group pitch Px is larger than the sub scanning group pitch Py is arranged in the sub scanning direction. In the image forming apparatus, the plurality of light emitting element groups are two-dimensionally arranged in a plurality at the sub-scanning group pitch Py.

A method for producing resin base particles contained in the toner of the present invention will be described in detail. The manufacturing method includes the following steps.
First step: Colored resin solution preparation step In this step, the binder resin, wax and colorant are dissolved or dispersed in an organic solvent to obtain a colored resin solution.
Second step: emulsification step In this step, a basic compound and water are sequentially added to the colored resin solution to emulsify the colored resin solution in the aqueous medium.
Third step: coalescence step At least one operation of forming colored resin fine particles by adding an aqueous electrolyte solution to the prepared emulsion suspension and coalescing the dispersoid in the emulsion suspension to form particles. It is a process to be performed.
Fourth Step: Separation / Drying Step In this step, after removing the organic solvent under reduced pressure, the resin mother particles are separated from the aqueous medium, washed and dried to obtain resin mother particles.

First, the colored resin solution preparation step, which is the first step, will be described in detail. In the colored resin solution preparation step, first, a binder resin, a wax and a colorant are introduced into an organic solvent and dissolved or dispersed.
The binder resin, wax, and colorant are preferably dissolved or dispersed in the organic solvent by a high-speed stirrer. At that time, a master kneading chip in which a colorant is predispersed can be used. A master kneading chip in which wax is pre-dispersed, or a wax master solution finely dispersed below the toner particle size by wet dispersion using media can also be used.

In the colored resin solution preparation step, Desper (manufactured by Asada Iron Works Co., Ltd.), T.M. K. A high-speed stirrer such as a homomixer (manufactured by PRIMIX Corporation) can be used. A preferred blade tip speed at this time is 4 to 30 m / s, and a more preferred blade tip speed is 8 to 25 m / s. By using the high-speed stirrer, the binder resin can be efficiently dissolved in the organic solvent, and uniform fine dispersion of the colorant in the binder resin solution can be achieved. That is, the state of the colorant finely dispersed in advance can be maintained in the binder resin solution by stirring at high speed.
When the blade tip speed is lower than 4 m / s, fine dispersion of the colorant in the binder resin solution becomes insufficient. On the other hand, when it is higher than 30 m / s, heat generation due to shearing becomes large, and it becomes difficult to uniformly stir together with volatilization of the solvent. Moreover, the preferable temperature in the case of melt | dissolving or disperse | distributing is the range of 20-60 degreeC, and a more preferable temperature is the range of 30-50 degreeC.

  A preferable range of the solubility of the organic solvent in water at 25 ° C. is 0.1 to 30% by mass, and a more preferable range is 0.1 to 25% by mass. The boiling point of organic solvents at normal pressure is lower than the boiling point of water. Specific examples of the organic solvent satisfying these conditions are ketones such as methyl ethyl ketone and methyl isopropyl ketone, and esters such as ethyl acetate and isopropyl acetate. Two or more organic solvents can be mixed and used, but from the viewpoint of solvent recovery, one kind of organic solvent is preferably used alone. In addition, a low boiling point organic solvent that dissolves the binder resin and easily removes the solvent in a subsequent process is preferably used.

An emulsifier may be added to the organic solvent together with the binder resin, the colorant and the wax.
In order for the emulsifier to function in the coalescing step, it is necessary to have a characteristic capable of maintaining dispersion stability even in the presence of an electrolyte added later. Specific examples of emulsifiers having such properties include polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene Nonionic emulsifiers such as oxyethylene sorbitan fatty acid esters and various pluronics; alkyl sulfate ester type, alkyl sulfonate type anionic emulsifiers; quaternary ammonium salt type cationic emulsifiers; alkyl benzene sulfonate type emulsifiers, direct It is a chain alkylbenzene sulfonic acid type emulsifier.
The above-mentioned emulsifiers may be used alone or in combination of two or more. That is, in the method for producing resin mother particles contained in the toner of the present invention, it is possible to prevent non-uniform coalescence by adding an electrolyte in the presence of an emulsifier. Thereby, a preferable particle size distribution is obtained.
A preferable amount of the emulsifier to be used is 0.1 to 3.0% by mass with respect to the solid content, a more preferable amount is 0.3 to 2.0% by mass, and a particularly preferable amount is 0.3 to 1.5% by mass. When the amount of the emulsifier to be used is less than 0.1% by mass with respect to the solid content, the desired effect of preventing the generation of coarse particles cannot be obtained. Further, when the amount of the emulsifier used is more than 3.0% by mass with respect to the solid content, the coalescence of the dispersoid in the emulsified suspension does not sufficiently proceed even if the amount of the electrolyte is increased, and the predetermined amount. As a result, fine particles remain and the yield decreases.

Next, in the emulsification step of the second step, a basic compound and water are sequentially added to the colored resin solution to emulsify the colored resin solution in the aqueous medium. Preferably, water is gradually added to the colored resin solution in which the carboxyl group of the binder resin is neutralized with a basic compound. By neutralizing the carboxyl group, the hydrophilicity of the binder resin is improved, and the affinity between water and the binder resin is improved.
The added water is hydrated to the carboxyl group portion of the binder resin, and the binder resin is dissolved or finely dispersed in combination with the stirring effect. On the other hand, the binder resin intervenes in the aqueous medium and the acid-base interaction becomes stronger, and the viscosity of the system containing the colored resin solution increases with the addition of water. When a certain amount of water is added, there is a point that the viscosity decreases, which is called a so-called phase inversion point. The viscosity increases until just before this, and the viscosity reaches the maximum value. The increase in viscosity correlates with the addition amount of the basic compound, and the increase in viscosity increases as the addition amount increases.

  On the other hand, the amount of the basic compound affects not only the emulsification step of the second step but also the uniformity and speed at the time of producing colored resin fine particles in the coalescence step of the third step described later. The preferred addition amount of the basic compound is in the range of 1 to 3 equivalents relative to the carboxyl group of the binder resin, and the more preferred addition amount of the basic compound is in the range of 1 to 2 equivalents. By adding the basic compound in excess of the amount required to neutralize all of the carboxyl groups of the binder resin, it is possible to prevent the formation of irregularly shaped particles in the coalescence process, and the resin The particle size distribution of the mother particles can be made narrow.

  The preferable ratio with respect to the total amount of the organic solvent and water of the organic solvent after the completion of the emulsification step is in the range of 20 to 35% by mass, and the more preferable ratio is in the range of 20 to 30% by mass. As described above, the amount of water up to the phase inversion point decreases as the amount of organic solvent in the colored resin solution preparation step decreases, and increases as the amount of basic compound increases. At the phase inversion point, the viscosity of the emulsified suspension may be high, and the colored resin solution may not be completely finely dispersed in the aqueous medium. Therefore, more water is preferably added. A preferable amount of water added is in the range of 50 to 80% by mass of the amount of water added up to the phase inversion point and the total amount of water used up to the phase inversion point.

  The binder resin used in the present invention is not particularly limited. A preferred binder resin is a polyester resin having an acid value of 3 to 30 KOHmg / g, and a more preferred binder resin is a polyester resin having an acid value of 5 to 20 KOHmg / g. If the acid value of the polyester resin is less than 3, resin mother particles cannot be produced. On the other hand, if the acid value of the polyester resin is greater than 30, the charge amount under the toner use environment is not stable. The polyester resin having an acid value of 3 to 30 KOHmg / g becomes an anionic type by neutralizing the carboxyl group with a basic compound. As a result, the hydrophilicity of the resin increases and can be dissolved or dispersed stably.

  Specific examples of the basic compound for neutralization are inorganic bases such as sodium hydroxide, potassium hydroxide and ammonia, and organic bases such as diethylamine, triethylamine and isopropylamine. An aqueous solution of an inorganic base such as sodium hydroxide, potassium hydroxide or ammonia is a particularly preferred basic compound.

  The emulsified suspension produced by the above-described method exists in a state where the colored resin solution is emulsified in an aqueous medium. The state varies depending on the type of organic solvent, the amount used, the acid value of the binder resin, the amount used of the basic compound, the stirring conditions, etc., but preferably such as resin oil droplets, wax dispersoids, colorant dispersoids, etc. The dispersoid is emulsified as oil droplets having a particle size of less than 1 μm. In such a state, the stability of the emulsified suspension, the unitary stability in the subsequent steps, the particle size distribution of the colored resin fine particles, and the like are improved.

Next, the unification process which is the 3rd process is explained. By adding the electrolyte, the colored resin fine particles are salted out or destabilized, and the colored resin fine particles are integrated with each other, so that the coalescence progresses to produce the coalesced particles.
Specific examples of the electrolyte used here are water-soluble salts such as sodium sulfate, ammonium sulfate, potassium sulfate, magnesium sulfate, sodium phosphate, sodium dihydrogen phosphate, sodium chloride, potassium chloride, ammonium chloride, calcium chloride, sodium acetate and the like. It is. The electrolyte is composed of one type of water-soluble salt or a mixture of two or more types of water-soluble salts. In particular, a monovalent cation sulfate such as sodium sulfate or ammonium sulfate is a preferable electrolyte for promoting uniform coalescence.

  In addition, since the colored resin fine particles obtained are swollen by a solvent and the hydration state of the particles is unstable due to the addition of an electrolyte, it is preferable that the colored resin fine particles are not broken up. The coalescence proceeds under a low shear force where only one proceeds.

  In order to promote uniform coalescence, the agitation conditions for coalescence are important. Specific examples of the stirring blade are an anchor blade, a turbine blade, a fiddler blade, a full zone blade, a max blend blade (registered trademark, manufactured by Sumitomo Heavy Industries, Ltd.), and a half moon blade. Particularly preferred stirring blades are large blades that are excellent in uniform mixing properties even at low rotations, such as Max Blend blades and full zone blades.

A preferable peripheral speed of the stirring blade for generating a uniform unity is 0.2 to 10 m / s, a more preferable peripheral speed is 0.2 to 8 m / s, and a more preferable peripheral speed is 0.2 to 6 m / s. If the peripheral speed of the stirring blade is higher than 10 m / s, fine particles remain. On the other hand, if the peripheral speed is less than 0.2 m / s, the stirring is not uniform and coarse particles are generated. Under the above-described conditions, coalescence proceeds only by collision between the colored resin fine particles, and the colored resin fine particles are not dissociated and dispersed. In particular, in the coalescing process, the generation of fine particles is small and a narrow particle size distribution can be obtained.
That is, in the colored resin solution preparation step and the emulsification step, stirring is preferably performed with a high-speed stirrer such as a desper, and in the coalescence step, stirring is preferably performed with a large blade that can be uniformly mixed at a low speed such as a Max blend blade. . Therefore, preferably, the emulsification suspension obtained in the emulsification step is transferred to another container attached to the large blade, and the coalescence step is performed.

Moreover, the preferable quantity of the electrolyte to be used is 0.5-15 mass% with respect to solid content, and a more preferable quantity is 1-12 mass% with respect to solid content, and a more preferable quantity is solid content. It is 1-6 mass% with respect to content. When the amount of the electrolyte is less than 0.5% by mass, coalescence does not proceed sufficiently. If the amount is more than 15% by mass, a large amount of stop water for the post-process is required, and it takes time for washing and drying, which decreases productivity.
Moreover, the preferable density | concentration of electrolyte solution is 1-15 mass%, and a more preferable density | concentration is 3-10 mass%. When the concentration is less than 1% by mass, the effect of the electrolyte is not sufficiently exhibited, and a large amount of electrolyte is required for salting out and coalescence, and colored resin fine particles may not be generated. On the other hand, when the concentration is higher than 15% by mass, unevenness is likely to occur in the system, and aggregates are generated during the production of colored resin fine particles in the initial stage of coalescence, and as a result, coarse particles are likely to be generated.

  In the coalescing step, when the aqueous electrolyte solution is added, the stirring speed is preferably increased in order to uniformly and quickly mix the electrolyte into the system. Moreover, the preferable temperature of a temporary time is the range of 10-50 degreeC, The more preferable temperature is the range of 20-40 degreeC, The especially preferable temperature is the range of 20-35 degreeC. When the temperature is lower than 10 ° C., coalescence is difficult to proceed. On the other hand, when the temperature is higher than 50 ° C., the coalescence speed is increased, and aggregates and coarse particles are easily generated. In the method for producing toner particles contained in the developer of the present invention, colored resin fine particles can be produced by coalescence under a low temperature condition of 20 to 40 ° C.

In the coalescing process, the colored resin fine particles swollen by the organic solvent collide, and the fine particles are fused to grow.
Moreover, since particle growth maintains a substantially constant growth rate under a certain condition, it can be expressed by creating a particle growth curve blotted from time and particle size. As a result, the arrival time of the target particle diameter can be estimated from the curve. Preferably, coalescence is stopped by adding water.

  In order to remove the solvent quickly under low temperature conditions, the solvent removal is preferably carried out under reduced pressure. In removing the solvent, an antifoaming agent is preferably added. A defoamer in the form of a silicone emulsion is preferably used. Specific examples of silicone-based antifoaming agents include BY22-517, SH5503, SM5572F, BY28-503 (manufactured by Toray Dow Corning Silicone), KM75, KM89, KM98, KS604, KS538 (Shin-Etsu Chemical Co., Ltd.) ))). Among these, BY22-517, which has little influence on physical properties and has a high defoaming effect, is preferably used. The preferable addition amount of an antifoamer is 30-100 ppm with respect to solid content.

  In the separation / drying step, which is the fourth step, the colored resin fine particles are separated, and then washed and dehydrated. Separation of the colored resin fine particles from the aqueous medium can be performed by a separation means such as a centrifugal separator, a filter press, or a belt filter. Next, the resin mother particles are obtained by drying the particles. Specific examples of dryers include ribocorn dryers (Okawara Seisakusho Co., Ltd.), mixed vacuum dryers such as Nauta Mixer (Hosokawa Micron Corp.), fluidized bed dryer (Okawara Seisakusho Ltd.), vibrating fluidized bed dryer It is a fluidized bed type dryer such as a machine (central processing machine).

  Resin mother particles produced by the above production method include an additive such as a colorant or wax in a binder resin. When the resin mother particles are observed with a transmission electron microscope, it can be confirmed that additives such as a colorant and wax are encapsulated in the particles and dispersed almost uniformly.

It is considered that the resin base particles are softly agglomerated by the liquid crosslinking force of silicone oil or fluorine oil to form secondary particles. The secondary particles do not have the scattering property and the difficulty of transporting to the developing roller, which are disadvantages of the resin mother particles having a diameter of less than 4 μm. Further, the secondary particles are crushed while reciprocating between a developing roller and a photosensitive member constituting a non-contact jumping developing device to be described later in which an AC bias is used. Therefore, in the image formation with the toner of the present invention, development is performed with resin mother particles having a diameter of less than 4 μm, and the resolution of the printed image is high.
The volume average particle diameter (Dv) / number average particle diameter (Dn) of the resin base particles contained in the toner of the present invention is greater than 1 and less than 1.1. When oil is added to the resin base particles having Dv / Dn of 1 or less or 1.1 or more, the small particle size toner particles enter between the large particle size toner particles, and the resin base particles are strongly aggregated by the liquid crosslinking force, The obtained secondary particles are not crushed while reciprocating between the developing roller and the photoreceptor constituting the non-contact jumping developing device.
The volume average particle size of the resin base particles contained in the toner of the present invention is 2 μm or more and less than 4 μm. In image formation using toner obtained from resin mother particles having a particle size of less than 4 μm, not only the resolution and gradation of the printed image are high, but also the thickness of the toner layer forming the printed image is thin, which is necessary for fixing. Small amount of heat and toner consumption. Resin mother particles having a diameter of less than 2 μm contain 20% by mass or more of a colorant and have a low fixability.

  Specific examples of the silicone oil contained in the toner of the present invention include hydrogen silicone oil, phenyl silicone oil, amino silicone oil, epoxy silicone oil, carboxy silicone oil, polyether silicone oil, hydrophilic silicone oil, methacrylic silicone oil, mercapto. Silicone oil, one-end reactive silicone oil, higher alkoxy silicone oil, and alkyl silicone oil. Specific examples of the fluorine oil contained in the toner of the present invention are perfluoropolyether and polytrifluoroethylene chloride. The amount of silicone oil or fluorine oil added is 0.05% by mass or more and less than 2% by mass with respect to the resin base particles. When the addition amount of silicone oil or fluorine oil is less than 0.05% by mass with respect to the resin base particles, the resin base particles are not softly aggregated, and secondary particles in which the resin base particles are aggregated cannot be obtained. When the addition amount of silicone oil or fluorine oil is 2% by mass or more with respect to the resin mother particles, the resin mother particles strongly agglomerate, and the obtained secondary particles are a developing roller constituting a non-contact jumping developing device, It is not crushed while reciprocating between the photoreceptors.

The binder resin of the resin mother particles is not particularly limited. A preferred binder resin is a polyester resin. The polyester resin used in the present invention is a cross-linked polyester resin or a linear polyester resin, and is obtained by reacting a compound selected from the following raw materials.
The cross-linked polyester is preferably produced by reacting a divalent basic acid or a derivative thereof, a divalent alcohol, and a polyvalent compound as a cross-linking agent. The cross-linked polyester is particularly preferably produced by reacting a divalent basic acid or a derivative thereof, a divalent aliphatic polyhydric alcohol, and a polyvalent epoxy compound as a cross-linking agent.
The linear polyester resin is produced by reacting a divalent basic acid with a dihydric alcohol.

  Specific examples of the divalent basic acids used for producing the crosslinked polyester resin and the linear polyester resin include phthalic anhydride, terephthalic acid, isophthalic acid, orthophthalic acid, adipic acid, maleic acid, maleic anhydride, Fumaric acid, itaconic acid, citraconic acid, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, cyclohexanedicarboxylic acid, succinic acid, malonic acid, glutaric acid, azelaic acid, sebacic acid, and derivatives thereof.

  Specific examples of the divalent aliphatic alcohol component include 1,4-cyclohexanedimethanol, ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, neopentyl glycol, butanediol, and pentanediol. Hexanediol, polyethylene glycol, polypropylene glycol, ethylene oxide-propylene oxide random copolymer diol, ethylene oxide-propylene oxide block copolymer diol, ethylene oxide-tetrahydrofuran copolymer diol, polycaprocactone diol .

  A polyester resin produced using an aliphatic alcohol has good compatibility with waxes, and a developer containing resin mother particles having the polyester resin as a binder resin has high offset resistance. Moreover, fixing property at low temperature is improved by softening the polyester main chain. When producing a crosslinked polyester resin, a polyvalent epoxy compound is used as a crosslinking agent. Specific examples of the polyvalent epoxy compound include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, ethylene glycol diglycidyl ether, hydroquinone diglycidyl ether, N, N-diglycidyl aniline lysine triglycidyl ester, Trimethylolpropane triglycidyl ether, trimethylolethane triglycidyl ether, pentaerythritol tetraglycidyl ether, tetrakis 1,1,2,2 (P-hydroxyphenyl) ethane tetraglycidyl ether, cresol novolac epoxy resin, phenol novolac epoxy resin A polymer of a vinyl compound having an epoxy group, an epoxidized resorcinol-acetone condensate, a partially epoxidized polybutadiene, Polymers of vinyl compounds having an alkoxy group, a semi-drying or drying fatty acid ester epoxy compound. Among the above-mentioned compounds, more preferable polyvalent epoxy compounds are bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, cresol novolac type epoxy resin, phenol novolac type epoxy resin, glycerin triglycidyl ether. , Trimethylolpropane triglycidyl ether, trimethylolethane triglycidyl ether, pentaerythritol tetraglycidyl ether.

  Specific examples of the bisphenol A type epoxy resin are Daikoku Ink Chemical Co., Ltd. Epicron 850, Epicron 1050, Epicron 2055, and Epicron 3050. Specific examples of the bisphenol F type epoxy resin are Dainippon Ink and Chemicals, Inc. ) Epicron 830 and Epicron 520. Specific examples of the orthocresol novolac type epoxy resin include Epicron N-660, N-665, N-667, N-670, N, manufactured by Dainippon Ink & Chemicals, Inc. -673, N-680, N-690, N-695 Specific examples of phenol novolac type epoxy resins include Epicron N-740, N-770, N-775 manufactured by Dainippon Ink & Chemicals, Inc. A specific example of a polymer of a vinyl compound having an epoxy group is glycidyl (meth) acrylate. Homopolymer, glycidyl (meth) acrylate / acrylic copolymer, glycidyl (meth) acrylate / styrene copolymer.

Also, two or more of the polyvalent epoxy compounds described above can be used in combination. Furthermore, the following monoepoxy compounds may be used as a resin modifier. Specific examples of monoepoxy compounds that can be used at the same time include phenyl glycidyl ether, alkylphenyl glycidyl ether, alkyl glycidyl ether, alkyl glycidyl ester, glycidyl ether of alkylphenol alkylene oxide adduct, α-olefin oxide, monoepoxy fatty acid alkyl ester It is.
By using these monoepoxy compounds in combination, the fixability of the developer of the present invention and the offset resistance at high temperatures are improved. Among these, particularly preferred epoxy compounds are alkyl glycidyl esters. A specific example of the alkyl glycidyl ester is Cardura E (neodecanoic acid glycidyl ester manufactured by Shell Chemicals Japan Co., Ltd.).

The cross-linked polyester resin and the linear polyester resin can be obtained by performing a dehydration condensation reaction or a transesterification reaction in the presence of a catalyst using the raw material components described above. Although reaction temperature and reaction time are not specifically limited, Usually, it is 2 to 24 hours at 150-300 degreeC.
Specific examples of the catalyst for carrying out the above reaction are tetrabutyl titanate, zinc oxide, stannous oxide, dibutyltin oxide, dibutyltin dilaurate, and paratoluenesulfonic acid.

  When a mixture of a cross-linked polyester resin and a linear polyester resin is used, the mixing ratio is not particularly limited. A preferable mixing ratio is (mass of cross-linked polyester resin) / (mass of linear polyester resin) = 5/95 to 60/40, and a more preferable mixing ratio is 10/90 to 40/60, A particularly preferable mixing ratio is 20/80 to 40/60. When the ratio of the cross-linked polyester resin is less than 5% by mass, the hot offset resistance of the developer of the present invention, the coalescence rate of toner particles, and the dispersibility of additives such as wax and colorant in the resin base particles are increased. descend. On the other hand, when the ratio of the cross-linked polyester resin is more than 60% by mass, the melt viscosity (T1 / 2 temperature) of the resin base particles increases and the low-temperature fixability of the resin base particles decreases.

  The glass transition temperature (Tg) of the cross-linked polyester resin is not particularly limited. Preferable Tg is 40 to 85 ° C, and particularly preferable Tg is 60 to 80 ° C. When the Tg of the cross-linked polyester resin is lower than 40 ° C., a blocking phenomenon (thermal aggregation) tends to occur when the resin mother particles are stored, transported, or exposed to a high temperature inside the developing device. On the other hand, when the Tg of the cross-linked polyester resin is higher than 85 ° C., the low-temperature fixability of the resin mother particles is lowered.

  The glass transition temperature (Tg) of the linear polyester resin is not particularly limited. Preferable Tg is 35 to 70 ° C, and particularly preferable Tg is 50 to 65 ° C. When the Tg of the linear polyester resin is lower than 35 ° C., a blocking phenomenon (thermal aggregation) tends to occur when the resin mother particles are stored, transported, or exposed to a high temperature inside the developing device. On the other hand, when the Tg of the linear polyester resin is higher than 70 ° C., the low-temperature fixability of the resin mother particles is lowered.

  The softening point of the cross-linked polyester resin is not particularly limited. A preferred softening point is 150 ° C. or higher, a more preferred softening point is 150 ° C. to 220 ° C., and a particularly preferred softening point is 170 ° C. to 190 ° C. When the softening point of the cross-linked polyester resin is less than 150 ° C., the resin mother particles tend to aggregate, and troubles are likely to occur during storage and printing. When the softening point of the cross-linked polyester resin exceeds 220 ° C., the fixability of the resin mother particles is lowered.

  The softening point of the linear polyester resin is not particularly limited. The preferred softening point is 90 ° C or higher, the more preferred softening point is 90 ° C to 130 ° C, and the particularly preferred softening point is 90 ° C to 110 ° C. When the softening point of the linear polyester resin is less than 90 ° C., the glass transition temperature of the linear polyester resin decreases, the resin mother particles tend to aggregate, and troubles occur during storage and printing. . When the softening point of the linear polyester resin exceeds 130 ° C., the fixing property of the resin base particles is lowered.

The softening point of the polyester resin is a T1 / 2 temperature measured using a constant load extrusion type capillary rheometer (Flow Tester CFT-500 manufactured by Shimadzu Corporation). The measurement is performed under the conditions of a piston cross-sectional area of 1 cm ² , a cylinder pressure of 0.98 MPa, a die length of 1 mm, a die hole diameter of 1 mm, a measurement start temperature of 50 ° C., a temperature increase rate of 6 ° C./min, and a sample mass of 1.5 g.
Moreover, the measurement of the glass transition temperature (Tg) of a polyester resin is measured using DSC (Shimadzu DSC-60A). 20 mg of sample is put in an aluminum crimp cell, heated to 180 ° C. at a heating rate of 10 ° C./min, cooled to room temperature at a cooling rate of 10 ° C./min from 180 ° C., and again to 180 ° C. at a heating rate of 10 ° C./min The temperature rise and the second run value are Tg.

The colored resin solution can be prepared by mixing a charge control agent. In the toner of the present invention, silica and titanium oxide in an amount of 0.3% by mass to 1% by mass with respect to the resin base particles are added as external additives. Silicone oil and fluorine oil tend to be negatively overcharged, but titanium oxide suppresses overcharge of silicone oil or fluorine oil and stabilizes the chargeability of the toner. Furthermore, the lubricating effect and wear reduction effect of silicone oil or fluorine oil and the charging stability effect of titanium oxide are synergistic, and image formation using the toner of the present invention has high stability and durability. In particular, rutile-anatase type titanium oxide having a spindle shape and a long axis diameter of 20 to 100 nm is difficult to be embedded in the toner, and stabilizes the charging property of the toner for a long period of time.
The toner of the present invention contains 10 to 20% by mass of pigment based on the resin base particles. Since the content of the pigment contained in the toner varies from one pigment to another, there is a concern that the difference between colors in electrical resistance becomes remarkable and it becomes difficult to control full color printing. However, since the pigment is coated on the surface of the toner of the present invention with silicone oil or fluorine oil and titanium oxide, the color difference is greatly reduced.

  Next, the developing device and the image forming apparatus of the present invention will be described. FIG. 1 shows an embodiment of an image forming apparatus according to the present invention. The image forming apparatus includes a color mode in which four color toners of black (K), cyan (C), magenta (M), and yellow (Y) are superimposed to form a color image, and black (K) toner only. And a monochrome mode for forming a monochrome image can be selectively executed. FIG. 1 is a diagram corresponding to the execution of the color mode.

  The image forming unit 2 includes four image forming stations Y (for yellow), M (for magenta), C (for cyan), and K (for black) that form a plurality of images of different colors. Each of the image forming stations Y, M, C, and K is provided with a photoreceptor 21 on which the respective color toner images are formed. Each photoconductor 21 is connected to a dedicated drive motor and is driven to rotate at a predetermined speed in the direction of the arrow in the figure. As a result, the surface of the photoreceptor 21 is conveyed in the sub-scanning direction. A charging unit 23, a line head 29, a developing unit 25, and a photoconductor cleaner 27 are disposed around the photoconductor 21 along the rotation direction. When the color mode is executed, the toner images formed at all the image forming stations Y, M, C, and K are superimposed on the transfer belt 8 to form a color image, and when the monochrome mode is executed, the image forming station K is used. A monochrome image is formed using only the formed toner image. In FIG. 1, since the image forming stations of the image forming unit 2 have the same configuration, only a part of the image forming stations is given a sign for convenience of illustration, and the sign is omitted for the other image forming stations. .

  The charging unit 23 includes a charging roller whose surface is made of elastic rubber. The charging roller is configured to rotate in contact with the surface of the photosensitive member 21 at a charging position, and is driven to rotate at a peripheral speed in the driven direction with respect to the photosensitive member 21 as the photosensitive member 21 rotates. . The charging roller is connected to a charging bias generator (not shown). The charging roller is supplied with the charging bias from the charging bias generator, and the charging roller 23 and the photosensitive member 21 are brought into contact with each other at a charging position. Charge the surface.

  The line head 29 includes a plurality of light emitting elements arranged in the axial direction of the photoconductor 21 (direction perpendicular to the paper surface of FIG. 1), and is spaced from the photoconductor 21. Then, light is emitted from these light emitting elements to the surface of the photosensitive member 21 charged by the charging unit 23, and a latent image is formed on the surface of the photosensitive member 21.

  The developing unit 25 includes a developing roller 251 that conveys toner to the photoconductor 21 and a supply roller 252 that supplies toner to the developing roller 251. The developing roller 251 is at a developing position where the developing roller 251 and the photosensitive member 21 are close to each other by an AC bias applied to the developing roller 251 from a developing bias generator (not shown) electrically connected to the developing roller 251. The electrostatic latent image formed by the line head 29 is made visible by the non-contact jumping development method in which the upper charged toner is jumped to the photosensitive member 21. The non-contact jumping development method is described in JP-A-2006-163160.

  FIG. 2 is a diagram schematically showing a developing gap provided between the photosensitive member 21 and the developing roller 251. An image carrying surface 21 a is formed at the center of the photoreceptor 21. Image non-bearing surfaces 21 b and 21 c are formed at both ends of the photoreceptor 21. A toner conveyance surface 251 a is formed at the center of the developing roller 251. Toner non-transport surfaces 251b and 251c are formed at both ends of the developing roller 251. A tape-like spacer 253 is fixed to the toner non-transport surfaces 251b and 251c of the developing roller 251. The spacer 253 is pressed against the image non-carrying surfaces 21b and 21c of the photoreceptor 21, and the development gap g is between the toner carrying surface 251a of the developing roller 251 and the image carrying surface 21a of the photoreceptor 21 facing the toner carrying surface 251a. Is formed. The developing gap g is adjusted to a desired size by the thickness of the spacer 253. The material of the spacer 253 is a material having elasticity and higher hygroscopicity than the developing roller 251. The spacer 253 is fixed to the toner non-transport surfaces 251b and 251c of the developing roller 251 with an adhesive layer 254 having elasticity.

  Thus, after the toner image made visible at the developing position is conveyed in the rotation direction of the photoconductor 21, the transfer belt 8 is transferred to the transfer belt 8 at the primary transfer position where the transfer belt 8 described later and each photoconductor 21 come into contact with each other. Primary transfer.

  In this embodiment, a photoreceptor cleaner 27 is provided in contact with the surface of the photoreceptor 21 downstream of the primary transfer position in the rotational direction of the photoreceptor 21 and upstream of the charging unit 23. The photoconductor cleaner 27 is in contact with the surface of the photoconductor 21 to clean and remove toner remaining on the surface of the photoconductor 21 after the primary transfer.

  The transfer belt unit 8 includes a driving roller 82, a driven roller 83 (blade facing roller) disposed on the left side of the driving roller 82 in FIG. 1, and stretched around these rollers in the direction indicated by the arrow (conveying direction). A transfer belt 8 that is circulated and driven. In addition, on the inner side of the transfer belt 81, four primary transfer units are arranged to be opposed to each of the photoconductors 21 included in the image forming stations Y, M, C, and K when the photoconductor cartridge is mounted. Rollers 85Y, 85M, 85C, and 85K are provided. Each of these primary transfer rollers 85 is electrically connected to a primary transfer bias generator (not shown). When the color mode is executed, as shown in FIG. 1, all the primary transfer rollers 85Y, 85M, 85C, and 85K are positioned on the image forming stations Y, M, C, and K sides, so that the transfer belt 8 is moved. A primary transfer position is formed between each photoconductor 21 and the transfer belt 8 in contact with the photoconductor 21 included in each of the image forming stations Y, M, C, and K. Then, by applying a primary transfer bias from the primary transfer bias generator to the primary transfer roller 85 at an appropriate timing, the toner images formed on the surface of each photoconductor 21 are respectively associated with the corresponding one. At the next transfer position, the image is transferred to the surface of the transfer belt 8 to form a color image.

  On the other hand, when the monochrome mode is executed, among the four primary transfer rollers 85, the color primary transfer rollers 85Y, 85M, and 85C are separated from the image forming stations Y, M, and C facing each other, and the monochrome primary transfer is performed. By bringing only the roller 85K into contact with the image forming station K, only the monochrome image forming station K is brought into contact with the transfer belt 81. As a result, the primary transfer position is formed only between the monochrome primary transfer roller 85K and the image forming station K. Then, by applying a primary transfer bias from the primary transfer bias generator to the monochrome primary transfer roller 85K at an appropriate timing, the toner image formed on the surface of each photoconductor 21 is transferred to the primary transfer position. Then, the image is transferred onto the surface of the transfer belt 81 to form a monochrome image.

  The drive roller 82 circulates and drives the transfer belt 8 in the direction of the arrow in the figure, and also serves as a backup roller for the secondary transfer roller 121. A rubber layer having a thickness of about 3 mm and a volume resistivity of 1000 kΩ · cm or less is formed on the peripheral surface of the driving roller 82, and secondary transfer is omitted by grounding through a metal shaft. The conductive path of the secondary transfer bias supplied from the bias generation unit via the secondary transfer roller 121 is used. Thus, by providing the driving roller 82 with a rubber layer having high friction and shock absorption, when the sheet enters the contact portion (secondary transfer position) between the driving roller 82 and the secondary transfer roller 121. It is difficult for an impact to be transmitted to the transfer belt 8, and deterioration of image quality can be prevented.

  The sheets fed by a pair of pickup rollers 79 that feed sheets one by one from the sheet feeding cassette 77 are fed to the secondary transfer position.

  The secondary transfer roller 121 is provided so as to be able to come into contact with and separate from the transfer belt 81 and is driven to come into contact with and separate from a secondary transfer roller drive mechanism (not shown). The fixing unit 13 includes a heating roller 131 that includes a heating element such as a halogen heater and is rotatable, and a pressure roller 132 that presses and biases the heating roller 131. Then, the sheet on which the image is secondarily transferred is guided to a nip formed by the heating roller 131 and the pressure unit 132 roller, and the image is thermally fixed at a predetermined temperature in the nip. The sheet thus subjected to the fixing process is conveyed to a paper discharge tray 4 provided on the upper surface of the housing body 1.

  Further, in this apparatus, a cleaner portion 71 is disposed to face the driven roller 83. The cleaner unit 71 includes a cleaner blade 711 and a waste toner box 713. The cleaner blade 711 removes foreign matters such as toner and paper dust remaining on the transfer belt after the secondary transfer by bringing the tip of the cleaner blade 711 into contact with the driven roller 83 via the transfer belt 8. The foreign matter removed in this way is collected in a waste toner box 713. Further, the cleaner blade 711 and the waste toner box 713 are configured integrally with the driven roller 83. Therefore, when the blade facing roller 83 moves as will be described below, the cleaner blade 711 and the waste toner box 713 also move together with the blade facing roller 83.

  FIG. 3 is a perspective view schematically showing an embodiment of the line head according to the present invention. FIG. 4 is a cross-sectional view in the sub-scanning direction of one embodiment of the line head according to the present invention. The line head 29 according to the present embodiment includes a case 291 whose longitudinal direction is the main scanning direction XX, and positioning pins 2911 and screw insertion holes 2912 are provided at both ends of the case 291. Then, the positioning head 2911 is fitted into a positioning hole (not shown) provided in the photosensitive member cover (not shown) that covers the photosensitive member 21 and is positioned with respect to the photosensitive member 21, so that the line head 29. Is positioned with respect to the photoreceptor 21. Further, the line head 29 is positioned and fixed with respect to the photosensitive drum 21 by screwing and fixing a fixing screw into a screw hole (not shown) of the photosensitive member cover through the screw insertion hole 2912.

  The case 291 holds the microlens array 299 at a position facing the surface of the photoreceptor 21, and includes a light shielding member 297 and a glass substrate 293 in the order close to the microlens array 299. In addition, a plurality of light emitting element groups 295 are provided on the back surface of the glass substrate 293 (the surface opposite to the microlens array 299 among the two surfaces of the glass substrate 293). That is, the plurality of light emitting element groups 295 are two-dimensionally arranged on the back surface of the glass substrate 293 so as to be separated from each other by a predetermined distance in the main scanning direction XX and the sub scanning direction YY. Here, each of the plurality of light emitting element groups 295 is configured by two-dimensionally arranging a plurality of light emitting elements, which will be described later. In the present embodiment, organic EL (Electro-Luminescence) is used as the light emitting element. That is, in the present embodiment, the organic EL is disposed as a light emitting element on the back surface of the glass substrate 293. Then, the light beam emitted from each of the plurality of light emitting elements toward the photosensitive drum 21 is directed to the light shielding member 297 through the glass substrate 293.

  A plurality of light guide holes 2971 are formed in the light shielding member 297 on a one-to-one basis with respect to the plurality of light emitting element groups 295. Further, the light guide hole 2971 is formed as a substantially cylindrical hole that penetrates the light shielding member 297 with a line parallel to the normal line of the glass substrate 293 as a central axis. Accordingly, all the light emitted from the light emitting elements belonging to one light emitting element group 295 is directed to the microlens array 299 through the same light guide hole 2971, and interference between light beams from different light emitting element groups 295 is blocked. This is prevented by the member 297. The light beam that has passed through the light guide hole 2971 formed in the light shielding member 297 is imaged as a spot on the surface of the photoconductor 21 by the microlens array 299. The specific configuration of the microlens array 299 and the imaging state of the light beam by the microlens array 299 will be described in detail later.

  As shown in FIG. 4, the back cover 2913 is pressed against the case 291 through the glass substrate 293 by the fixing device 2914. That is, the fixing device 2914 has an elastic force that presses the back cover 2913 toward the case 291, and presses the back cover 2913 with the elastic force, so that the inside of the case 291 is light-tight (that is, inside the case 291). From the outside of the case 291 so that no light leaks from the case 291). Note that a plurality of fixing devices 2914 are provided in the longitudinal direction of the case 291. The light emitting element group 295 is covered with a sealing member 294.

  FIG. 5 is a perspective view schematically showing the microlens array. FIG. 6 is a cross-sectional view of the microlens array in the main scanning direction. The microlens array 299 includes a glass substrate 2991 and a plurality of lens pairs configured by two lenses 2993A and 2993B arranged one-on-one so as to sandwich the glass substrate 2991. These lenses 2993A and 2993B can be formed of resin.

  That is, a plurality of lenses 2993A are arranged on the front surface 2991A of the glass substrate 2991, and a plurality of lenses 2993B are arranged on the back surface 2991B of the glass substrate 2991 so as to correspond to the plurality of lenses 2993A on a one-to-one basis. Further, the two lenses 2993A and 2993B constituting the lens pair share a common optical axis OA. The plurality of lens pairs are arranged one-on-one in the plurality of light emitting element groups 295. In this specification, an optical system including a pair of lenses 2993A and 2993B forming a one-to-one pair and a glass substrate 2991 sandwiched between the pair of lenses is referred to as a “microlens ML”. The plurality of lens pairs (microlenses ML) are two-dimensionally arranged at predetermined intervals in the main scanning direction XX and the sub-scanning direction YY, corresponding to the arrangement of the light emitting element groups 295.

  FIG. 7 is a diagram illustrating an arrangement of a plurality of light emitting element groups. In the present embodiment, one light emitting element group 295 is configured by arranging two light emitting element rows L2951 arranged in the main scanning direction XX at predetermined intervals and arranging two light emitting element rows L2951 in the sub scanning direction YY. Yes. That is, eight light emitting elements 2951 corresponding to the microlens ML indicated by the two-dot chain line in FIG. The plurality of light emitting element groups 295 are arranged as follows.

  That is, two light emitting element groups 295 are arranged such that three light emitting element group rows L295 (group rows) configured by arranging a predetermined number (two or more) of light emitting element groups 295 in the main scanning direction XX are arranged in the sub scanning direction YY. Dimensionally arranged. Further, all the light emitting element groups 295 are arranged at different main scanning direction positions. Further, the plurality of light emitting element groups 295 are arranged so that the sub scanning direction positions of the light emitting element groups (for example, the light emitting element group 295C1 and the light emitting element group 295B1) whose main scanning direction positions are adjacent to each other are different. Note that in this specification, the geometric center of gravity of the light emitting element 2951 is defined as the position of the light emitting element 2951. Therefore, the distance between the two light emitting elements means the distance between the geometric centers of gravity of the respective light emitting elements. Further, in this specification, the “geometric centroid of light emitting element group” means the geometric centroid of all light emitting element positions belonging to the same light emitting element group 295. In addition, the main scanning direction position and the sub scanning direction position mean the main scanning direction component and the sub scanning direction component at the position of interest, respectively.

  Corresponding to the arrangement of the light emitting element groups 295, a light guide hole 2971 is formed in the light shielding member 297, and a lens pair including lenses 2993A and 2993B is arranged. That is, in the present embodiment, the gravity center position of the light emitting element group 295, the central axis of the light guide hole 2971, and the optical axis OA of the lens pair configured by the lenses 2993A and 2993B are configured to substantially coincide. ing. The light beams emitted from the light emitting elements 2951 of the light emitting element group 295 enter the microlens array 299 through the corresponding light guide holes 2971 and are spotted on the surface of the photosensitive drum 21 by the microlens array 299. Is imaged.

  FIG. 8 is a diagram illustrating an imaging state of the microlens array in the present embodiment. Also, in the figure, in order to show the imaging characteristics of the microlens array 299, the light beams emitted from the geometric center of gravity E0 of the light emitting element group 295 and the positions E1 and E2 separated from the geometric center of gravity E0 by a predetermined interval. Represents the trajectory. As shown by the locus, the light beam emitted from each position is incident on the back surface of the glass substrate 293 and then emitted from the surface of the glass substrate 293. The light beam emitted from the surface of the glass substrate 293 reaches the surface of the photosensitive drum (scanned surface) via the microlens array 299.

  As shown in FIG. 8, the light beam emitted from the geometric gravity center position E0 of the light emitting element group forms an image at the intersection I0 between the surface of the photosensitive drum 21 and the optical axis OA of the lenses 2993A and 2993B. As described above, this is because, in this embodiment, the geometric gravity center position E0 (the position of the light emitting element group 295) of the light emitting element group 295 is on the optical axis OA of the lenses 2993A and 2993B. . The light beams emitted from the positions E1 and E2 are imaged at positions I1 and I2 on the surface of the photosensitive drum 21, respectively. That is, the light beam emitted from the position E1 is imaged at the position I1 on the opposite side across the optical axis OA of the lenses 2993A and 2993B in the main scanning direction XX, and the light beam emitted from the position E2 is In the main scanning direction XX, an image is formed at a position I2 on the opposite side across the optical axis OA of the lenses 2993A and 2993B. In other words, an imaging lens composed of a lens pair composed of lenses 2993A and 2993B having a common optical axis and a glass substrate 2991 sandwiched between the lens pairs is a so-called reversal optical system having reversal characteristics.

  Further, as shown in FIG. 8, the distance between the positions I1 and I0 where the light beam is imaged is longer than the distance between the positions E1 and E0. That is, the absolute value of the magnification (optical magnification) of the optical system in the present embodiment is greater than 1. That is, the optical system in the present embodiment is a so-called magnifying optical system having magnifying characteristics. As described above, in the present embodiment, the microlens ML that is an optical system including the lens pair including the lenses 2993A and 2993B having the same optical axis and the glass substrate 2991 sandwiched between the lens pairs is used in the present invention. It functions as an “imaging lens”.

  FIG. 9 is a diagram showing details of the arrangement of the light emitting elements in the present embodiment. In FIG. 9, reference numeral CG2951 represents the geometric center of gravity of the light emitting element 2951 (the position of the light emitting element 2951). Reference numeral CG295 represents the geometric center of gravity of each of the eight light emitting elements 2951 belonging to the light emitting element group 295 (geometric center of gravity of the light emitting element group 295). As shown in FIG. 9, in this embodiment, eight light emitting element rows L2951 configured by arranging four light emitting elements at predetermined intervals in the main scanning direction XX are arranged in two lines in the sub scanning direction YY. Light emitting elements 2951 are two-dimensionally arranged. In the same light emitting element group, the positions of the eight light emitting elements 2951 in the main scanning direction XX are different from each other, and the two light emitting elements 2951 adjacent in the main scanning direction XX are different from each other in the light emitting element row L2951. These two light emitting element rows L2951 are arranged in the sub-scanning direction YY. Thus, in the present embodiment, the eight light emitting elements 2951 belonging to the same light emitting element group correspond to “a plurality of light emitting elements” in the present invention.

  In FIG. 9, reference symbol Gx represents the distance (main scanning group width) between the most upstream light emitting element 2951 and the most downstream light emitting element 2951 in the main scanning direction XX in one light emitting element group 295. The symbol Gy represents the distance (sub scanning group width) between the position of the most upstream light emitting element 2951 and the position of the most downstream light emitting element 2951 in the sub scanning direction YY in one light emitting element group 295. As shown in FIG. 9, in this embodiment, the main scanning group width Gx is set larger than the sub-scanning group width Gy. That is, each light emitting element group 295 has a flat array structure with the main scanning direction XX as a major axis. Specifically, in this embodiment, Gx = 0.148 mm and Gy = 0.021 mm are set.

  FIG. 10 is a diagram illustrating a relationship between adjacent light emitting element groups in the present embodiment. In FIG. 10, the symbol Px represents the distance (main scanning group pitch) between the geometric centroids CG295 of the two light emitting element groups 295 adjacent in the main scanning direction XX. The symbol Py represents the distance (sub-scanning group pitch) between the geometric centroids CG295 of the two light emitting element groups 295 adjacent to each other in the sub-scanning direction YY. As shown in the figure, in this embodiment, the main scanning group pitch Px is set larger than the sub-scanning group pitch Py. Specifically, in this embodiment, Px = 1.016 mm and Py = 0.9 mm are set.

  FIG. 11 is a diagram showing a spot forming operation by the above-described line head. Hereinafter, the spot forming operation by the line head in the present embodiment will be described with reference to FIGS. In order to facilitate understanding of the invention, here, a case where a plurality of spots are formed side by side on a straight line extending in the main scanning direction XX will be described. In the present embodiment, a plurality of light emitting elements emit light at a predetermined timing while conveying the surface (scanned surface) of the photosensitive member 21 (latent image carrier) in the sub-scanning direction YY, thereby causing the light-emitting element to emit light in the main scanning direction XX. A plurality of spots are formed side by side on an extending straight line.

  That is, in the line head of this embodiment, six light emitting element rows L2951 are arranged side by side in the sub-scanning direction YY corresponding to each position of the sub-scanning direction positions Y1 to Y6 (FIG. 7). Therefore, in this embodiment, the light emitting element rows L2951 at the same sub-scanning direction position emit light at substantially the same timing, and the light emitting element rows L2951 at different sub-scanning direction positions emit light at different timings. More specifically, the light emitting element rows L2951 are caused to emit light in the order of the sub-scanning direction positions Y1 to Y6. A plurality of spots are formed side by side on a straight line extending in the main scanning direction XX of the surface by causing the light emitting element array L2951 to emit light in the order described above while transporting the surface of the photosensitive drum 21 in the sub scanning direction YY. To do.

  Such an operation will be described with reference to FIGS. First, the light emitting elements 2951 of the light emitting element row L2951 in the sub scanning direction position Y1 belonging to the most upstream light emitting element groups 295A1, 295A2, 295A3,. The plurality of light beams emitted by the light emitting operation are enlarged while being inverted by the “imaging lens” having the above-described inversion enlarging characteristics and imaged on the surface of the photosensitive drum. That is, a spot is formed at the position of the “first” hatching pattern in FIG. In FIG. 11, white circles represent spots that have not yet been formed and are to be formed in the future. In the same figure, the spots labeled with reference numerals 295C1, 295B1, 295A1, and 295C2 indicate spots formed by the light emitting element groups 295 corresponding to the reference numerals assigned thereto.

  Next, the light emitting elements 2951 of the light emitting element row L2951 in the sub-scanning direction position Y2 belonging to the same light emitting element group 295A1, 295A2, 295A3,. The plurality of light beams emitted by the light emitting operation are enlarged while being inverted by the “imaging lens” having the above-described inversion enlarging characteristics and imaged on the surface of the photosensitive drum. That is, a spot is formed at the position of the “second” hatching pattern in FIG. Here, while the conveyance direction of the surface of the photosensitive drum 21 is the sub-scanning direction YY, the light emitting element rows L2951 on the downstream side in the sub-scanning direction YY are sequentially arranged (that is, at the positions Y1, Y2 in the sub-scanning direction). The reason (in order) is that the “imaging lens” corresponds to having a reversal characteristic.

  Next, the light emitting elements 2951 of the light emitting element row L2951 in the sub scanning direction position Y3 belonging to the second light emitting element group 295B1, 295B2, 295B3,. The plurality of light beams emitted by the light emitting operation are enlarged while being inverted by the “imaging lens” having the above-described inversion enlarging characteristics and imaged on the surface of the photosensitive drum. That is, a spot is formed at the position of the “third” hatching pattern in FIG.

  Next, the light emitting elements 2951 of the light emitting element row L2951 in the sub-scanning direction position Y4 belonging to the light emitting element groups 295B1, 295B2, 295B3,. The plurality of light beams emitted by the light emitting operation are enlarged while being inverted by the “imaging lens” having the above-described inversion enlarging characteristics and imaged on the surface of the photosensitive drum. That is, a spot is formed at the position of the “fourth” hatching pattern in FIG.

  Next, the light emitting elements 2951 of the light emitting element row L2951 in the sub scanning direction position Y5 belonging to the light emitting element groups 295C1, 295C2, 295C3,. The plurality of light beams emitted by the light emitting operation are enlarged while being inverted by the “imaging lens” having the above-described inversion enlarging characteristics and imaged on the surface of the photosensitive drum. That is, a spot is formed at the position of the “fifth” hatching pattern in FIG.

  Finally, the light emitting elements 2951 of the light emitting element row L2951 in the sub-scanning direction position Y6 belonging to the light emitting element groups 295C1, 295C2, 295C3,. The plurality of light beams emitted by the light emitting operation are enlarged while being inverted by the “imaging lens” having the above-described inversion enlarging characteristics and imaged on the surface of the photosensitive drum. That is, a spot is formed at the position of the “sixth” hatching pattern in FIG. In this way, by performing the first to sixth light emitting operations, a plurality of spots are formed side by side on a straight line extending in the main scanning direction XX.

  As described above, in the line head in the present embodiment, a plurality of light emitting element groups 295 each having a plurality of light emitting elements 2951 are arranged in one-to-one correspondence with the plurality of light emitting element groups 295, and And a plurality of microlenses ML (imaging lenses) that image the light beams emitted from the plurality of light emitting elements 2951 belonging to the corresponding light emitting element group 295 on the surface of the photosensitive drum (scanned surface). The plurality of light emitting element groups 295 and the plurality of light emitting elements 2951 are arranged as follows. That is, the plurality of light emitting element groups 295 are two-dimensionally arranged such that a plurality of group rows L295 in which two or more light emitting element groups 295 are arranged in the main scanning direction XX are arranged in the sub scanning direction YY. The plurality of light emitting elements 2951 belonging to the same light emitting element group 295 is two-dimensional so that a plurality of light emitting element arrays L2951 configured by arranging two or more light emitting elements 2951 in the main scanning direction XX are arranged in the sub scanning direction YY. Are arranged.

  The line head 29 is configured such that the main scanning group width Gx is larger than the sub-scanning group width Gy. In such a line head 29, since the light emitting element group 295 has a flat arrangement structure having the major axis in the main scanning direction XX, crosstalk in the main scanning direction may occur. In other words, when the light emitting element group 295 is configured in this way, the light emitting element 2951 located at the end of the light emitting element group 295 in the main scanning direction XX and the imaging lens corresponding to the light emitting element 2951 in the main scanning direction. The distance Δ between adjacent imaging lenses tends to be small. Therefore, the light beam emitted from the light emitting element 2951 positioned at the end of the light emitting element group 295 is incident on the imaging lens adjacent to the imaging lens corresponding to the light emitting element 2951 in the main scanning direction. There is a possibility of crosstalk in the main scanning direction XX. When such crosstalk occurs, there is a possibility that good spot formation cannot be realized. Next, the problem and the means for solving the problem will be described with reference to the drawings.

  FIG. 12 is a schematic diagram showing the principle of the present invention. In FIG. 12, solid line circles 2993B and 2993BT represent a lens 2993B which is one of constituent members of the microlens ML (imaging lens). As described above, the lens 2993B is disposed corresponding to the light emitting element group 295. In the case where the light emitting element group 295 has a flat array structure with the main scanning direction XX as the major axis, as in the line head of the present embodiment, crosstalk in the main scanning direction XX may occur. In other words, the light beam emitted from the light emitting element 2951T located at the end of the light emitting element group 295 passes through the lens 2993BT to the imaging lens adjacent to the imaging lens corresponding to the light emitting element 2951T in the main scanning direction XX. May be incident. On the other hand, the line head is configured as follows. That is, the distance between the geometric centroids CG295 of the two light emitting element groups 295 adjacent in the main scanning direction XX is the main scanning group pitch Px and the two light emitting element groups adjacent in the sub scanning direction YY. When the distance between the geometric centers of gravity of 295 is defined as the sub-scanning group pitch Py, the main scanning group pitch Px is configured to be larger than the sub-scanning group pitch Py. Therefore, a sufficient distance Px between the two light emitting element groups adjacent in the main scanning direction is ensured. As a result, the distance Δ between the light emitting element 2951T located at the end of the light emitting element group 295 in the main scanning direction XX and the imaging lens adjacent to the imaging lens corresponding to the light emitting element 2951T in the main scanning direction XX is also sufficient. Will be secured. Therefore, the light beam emitted from the light emitting element 2951T located at the end of the light emitting element group 295 is incident on the imaging lens adjacent to the imaging lens corresponding to the light emitting element 2951T in the main scanning direction XX. Crosstalk in the main scanning direction XX can be suppressed, and favorable spot formation can be realized.

  By the way, the line head 29 forms a spot on the surface to be scanned by forming an image of the light beam emitted from the light emitting element 2951 of the light emitting element group 295 by the micro lens ML (imaging lens). At this time, the line head 29 forms a spot on the surface to be scanned so as to realize a predetermined resolution. In other words, the distance between adjacent spots on the surface to be scanned is set so as to realize a preset resolution. Therefore, the imaging lens forms an image of the light beams emitted from the plurality of light emitting elements 2951 included in the light emitting element group 295 as spots on the surface to be scanned at a predetermined magnification (optical magnification) in order to realize such a distance between spots. To do. In the line head 29 according to the above-described embodiment, a magnifying optical system having an absolute value of magnification greater than 1 is used as the imaging lens. Therefore, crosstalk in the main scanning direction XX can be more effectively suppressed, and better spot formation can be realized. The reason for this will be described.

  First, in explaining the above reason, the imaging lens is an enlargement optical system (imaging lens having an absolute value of magnification greater than 1) and a reduction optical system (imaging lens having an absolute value of magnification of less than 1). Consider the configuration of the light emitting element group 295 required to realize the resolution as described above. When the imaging lens is a magnifying optical system, the light beams emitted from two light emitting elements 2951 adjacent in the main scanning direction XX are formed as two spots on the surface of the photoreceptor (scanned surface) while being magnified. The That is, the distance between the two spots on the surface of the photoconductor is larger than the distance between the two light emitting elements. On the other hand, the relationship between the distance between the light emitting elements and the distance between spots when the imaging lens is a reduction optical system is opposite to that in the case of an enlargement optical system. That is, the distance between the two spots on the surface of the photoreceptor is smaller than the distance between the two light emitting elements. Therefore, when realizing the same resolution (that is, realizing the same spot-to-spot distance), when the magnifying optical system is used, the distance between the light emitting elements adjacent to each other in the main scanning direction XX is required to be small. When the reduction optical system is used, the distance between adjacent light emitting elements in the main scanning direction XX is required to be large. As a result, when the enlargement optical system is used, a light emitting element group 295 having a small main scanning group width Gx is required, whereas when the reduction optical system is used, a light emitting element group having a large main scanning group width Px. Will be required.

  Therefore, in the line head in the above embodiment, the absolute value of the magnification of the imaging lens is set to a value larger than 1. If this is the case, the light beam emitted from the light emitting element 2951T positioned at the end of the light emitting element group 295 as described above is mainly applied to the imaging lens corresponding to the light emitting element 2951T. This is because crosstalk in the main scanning direction XX, which is incident on an imaging lens adjacent in the scanning direction XX, can be more effectively suppressed, and better spot formation can be realized. That is, as the above discussion shows, when the magnifying optical system is used as the imaging lens, the main scanning group width Gx of the light emitting element group 295 can be reduced. Therefore, the distance Δ between the light emitting element 2951T located at the end of the light emitting element group 295 in the main scanning direction XX and the imaging lens adjacent to the light emitting element 2951T in the main scanning direction XX is increased. It becomes possible. Therefore, the main effect is that the light beam emitted from the light emitting element 2951 located at the end of the light emitting element group 295 is incident on the imaging lens adjacent to the imaging lens corresponding to the light emitting element 2951 in the main scanning direction XX. Crosstalk in the scanning direction XX can be more effectively suppressed, and better spot formation can be realized.

  In the above embodiment, in one light emitting element group 295, a plurality of light emitting elements 2951 belonging to the light emitting element group 295 are arranged symmetrically with respect to the geometric center of gravity CG295 of the light emitting element group 295. And in the said embodiment, it is comprised so that the position of the light emitting element group 295 may exist on the optical axis OA of a corresponding imaging lens. In this case, the light beam emitted from the light emitting element 2951 located at the end of the light emitting element group 295 enters the imaging lens adjacent to the imaging lens corresponding to the light emitting element 2951 in the main scanning direction XX. This is because crosstalk in the main scanning direction XX can be more effectively suppressed, and better spot formation can be realized. The reason for this will be described.

  FIG. 13 is a diagram showing a case where the position of the light emitting element group is coincident with the optical axis of the imaging lens, and FIG. 14 is a case where the position of the light emitting element group is not coincident with the optical axis of the imaging lens. FIG. The light emitting element group 295 includes light emitting elements 2951 at both ends in the main scanning direction XX. In the line head 29 configured as described above, a plurality of light emitting elements 2951 are symmetrically arranged with the position of the light emitting element group 295 as the axis of symmetry, and the optical axis OA of the imaging lens (the optical axis of the lens 2993B) and the The symmetry axis is matched. In FIGS. 13 and 14, the optical axis OA of the imaging lens is located substantially at the center of each lens 2993B, and is located at the intersection of two alternate long and short dashed lines. Therefore, in the line head 29 configured as in the above embodiment, the distances from the optical axis OA of the imaging lens to the light emitting elements 2951TD and 2951TU at both ends in the main scanning direction are equal to each other (FIG. 13). Therefore, the distance ΔU from the light emitting element 2951TU at the other end in the main scanning direction to the lens 2993BU is equal to the distance ΔD from the light emitting element 2951TD at the one end in the main scanning direction to the lens 2993BD.

  On the other hand, when the symmetry axis of the light emitting element group 295 and the optical axis of the imaging lens do not coincide with each other, the symmetry axis is shifted in any of the main scanning directions with respect to the optical axis, that is, in FIG. In such a case, the distance relationship is different. In FIG. 14, the geometric center of gravity CG295 of the light emitting element group is shifted to the upstream side in the main scanning direction XX with respect to the optical axis OA of the imaging lens (the optical axis of the lens 2993). Therefore, the distance ΔU from the light emitting element 2951TU at the other end in the main scanning direction to the lens 2993BU is smaller than the distance ΔD from the light emitting element 2951TD at the one end in the main scanning direction to the lens 2993BD. That is, the distance between the light emitting element 2951TU and the imaging lens is shortened. As a result, there is a high possibility that the light beam emitted from the light emitting element 2951TU enters the lens 2993BU. That is, the possibility of occurrence of crosstalk in the main scanning direction XX is increased.

  As described above, when the geometric center of gravity CG295 of the light emitting element group does not coincide with the optical axis OA of the corresponding imaging lens, there is a high possibility that crosstalk occurs in the main scanning direction XX. On the other hand, in the above embodiment, the light emitting element group 295 is configured such that the position thereof is on the optical axis OA of the corresponding imaging lens. Therefore, the main effect is that the light beam emitted from the light emitting element 2951 located at the end of the light emitting element group 295 is incident on the imaging lens adjacent to the imaging lens corresponding to the light emitting element 2951 in the main scanning direction XX. Crosstalk in the scanning direction XX can be more effectively suppressed, and better spot formation can be realized.

  Further, the image forming apparatus of the present embodiment using the above-described line head forms spots on the surface of the photosensitive drum (latent image carrier surface) using the line head. That is, it is possible to form a latent image on the surface of the photosensitive drum while suppressing crosstalk.

  The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. That is, in the above embodiment, the light emitting element group 295 is configured as shown in FIG. 7, but the configuration of the light emitting element group 295 is not limited thereto. In short, in a line head in which the main scanning group width Gx is set larger than the sub-scanning group width Gy, the main scanning group pitch Px is configured to be larger than the sub-scanning group pitch Py, so that the main scanning group width Gx is set in the main scanning direction XX. It is possible to realize good spot formation while suppressing crosstalk.

  In the above embodiment, the organic EL is used as the light emitting element 2951. However, the specific configuration of the light emitting element 2951 is not limited thereto, and for example, an LED (Light Emitting Diode) may be used as the light emitting element 2951. .

In the above-described embodiment, the present invention is applied to a color image forming apparatus. However, the application target of the present invention is not limited to this, and it is also applicable to a monochrome image forming apparatus that forms a so-called monochromatic image. The present invention can be applied.
EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

(Synthesis of cross-linked polyester resin)
Raw materials such as an acid, an alcohol component, and a catalyst having the following composition were put into a 50 liter reaction kettle and reacted at 240 ° C. for 12 hours under a normal pressure nitrogen stream. Thereafter, the pressure was reduced successively and the reaction was continued at 10 mmHg. The reaction was followed by the softening point based on ASTM E28-517, and the reaction was terminated when the softening point reached 160 ° C.
Terephthalic acid 3.9 parts by mass Isophthalic acid 9.06 parts by mass Ethylene glycol 2.54 parts by mass Neopentyl glycol 4.26 parts by mass Tetrabutyl titanate 0.1 parts by mass Epicron 830 0.3 parts by mass (Dainippon Ink and Chemicals, Inc. Bisphenol F type epoxy resin, epoxy equivalent 170 (g / eq)
Cardura E 0.1 parts by mass (Shell Japan alkyl glycidyl ester) epoxy equivalent 250 (g / eq)

The obtained cross-linked polyester resin was a colorless solid having an acid value of 11.0, a glass transition temperature (Tg) of 60 ° C, and a softening point (T1 / 2) of 178 ° C.
In addition, the weight average molecular weight of the cross-linked polyester resin was used by using a GPC measuring apparatus (HLC-8120GPC manufactured by Tosoh Corporation) as a separation column in combination with TSK-GEL G5000HXL / G4000HXL / G3000HXL / G2000HXL manufactured by Tosoh Corporation, column temperature: 40 ° C., Solvent: Tetrahydrofuran, solvent concentration: 0.5 mass%, filter: 0.2 μm, flow rate: 1 ml / min. Conversion was performed using standard polystyrene, and the molecular weight was determined. The weight average molecular weight was 250,000.

(Synthesis of linear polyester resin)
Raw materials such as an acid, an alcohol component, and a catalyst having the following composition were put into a 50 liter reaction kettle and reacted at 210 ° C. for 12 hours under a normal pressure nitrogen stream. Thereafter, the pressure was reduced successively and the reaction was continued at 10 mmHg. The reaction was followed by the softening point according to ASTM E28-517 and terminated when the softening point reached 87 ° C.
Terephthalic acid 5.31 parts by mass Isophthalic acid 7.97 parts by mass Ethylene glycol 2.6 parts by mass Neopentyl glycol 4.37 parts by mass Tetrabutyl titanate 0.1 parts by mass

The obtained linear polyester resin was a colorless solid having an acid value of 10.0, a glass transition temperature (Tg) of 46 ° C, and a softening point (T1 / 2) of 95 ° C.
Further, when the molecular weight of the linear polyester resin was measured in the same manner as the measurement of the molecular weight of the cross-linked polyester resin, the weight average molecular weight was 5200.

(Preparation of resin mother particle 1)
Preparation of Wax Master Dispersion 30 parts by mass of Carnauba Wax (Carnauba Wax No. 1 manufactured by Kato Yoko Co., Ltd.), 70 parts by mass of the previously produced linear polyester resin and 150 parts by mass of methyl ethyl ketone were premixed with a desper. Then, it refined | miniaturized by Starmill LMZ-10 (made by Ashizawa Finetech), and prepared the wax master dispersion liquid whose solid content is 40 mass%. This composition is linear polyester resin / wax / methyl ethyl ketone = 28/12/60.

Preparation of colorant master chip 20 L Henschel mixer with ST / AO stirring blade (2000 parts by mass of cyan pigment (Ket Blue 104 manufactured by Dainippon Ink and Chemicals, Inc.) and 2000 parts by mass of linear polyester resin) The mixture was stirred for 2 minutes at 698 min ⁻¹ to obtain a mixture. The mixture was melt-kneaded using an open roll continuous extrusion kneader (Kidex MOS140-800 manufactured by Mitsui Mining Co., Ltd.) to prepare a colorant master chip.
Moreover, when the obtained master chip was diluted with a linear polyester resin and methyl ethyl ketone, and observed with a 400 times optical microscope for the finely dispersed state of the colorant and the presence or absence of coarse particles, there was no coarse particles and the fine dispersion was uniform. Was. The composition of the master chip was colorant / linear polyester resin = 50/50 by mass ratio.

Preparation of colored resin solution Add 10.8 parts by weight of wax master dispersion, 10.4 parts by weight of colorant master chip, 12 parts by weight of cross-linked polyester resin, 10 parts by weight of linear polyester resin, and 8.65 parts by weight of methyl ethyl ketone. The temperature was kept at 40 to 45 ° C., and the mixture was mixed for 2 hours at a stirring speed of 777 min ⁻¹ with a stirrer (Desper blade diameter 230 mm manufactured by Asada Iron Works), and dissolved and dispersed.
Methyl ethyl ketone is further added to the resulting mixture to adjust the solid content to 65% by mass, and as an emulsifier, dodecylbenzenesulfonic acid-based emulsifier (Daigen Kogyo Seiyaku Co., Ltd. Neogen SC-F) 0.22 mass. A colored resin solution containing a cyan pigment was prepared by adding, dissolving and dispersing parts.

Transfer emulsification step 46.37 parts by mass (30 parts by mass of the solid content) of the colored resin solution is charged into a cylindrical container equipped with a stirrer (Desper made by Asada Iron Works) having a stirring blade with a blade diameter of 230 mm, and then basic. As a compound, 5 parts by mass of 1N aqueous ammonia was added, and after sufficiently stirring at 777 min ⁻¹ , the temperature was adjusted to 35 ° C.
Subsequently, the stirring speed was changed to 1100 min ⁻¹ and 37.25 parts by mass of water was added dropwise at a rate of 1.0 parts by mass / min. The peripheral speed of the stirring blade at this time was 13.2 m / s. As water was added, the viscosity of the system increased, but water was taken into the system at the same time as dropping, and stirring and mixing could be performed uniformly.

  In addition, a phase inversion point at which the viscosity rapidly decreased when 26 parts by mass of water was added was observed. Furthermore, after adding water, when the slurry was observed with an optical microscope, the resin was dissolved, and a state where the colorant dispersoid and the wax dispersoid were dispersed was observed, but the non-emulsified material was not observed. It was. Since the colorant dispersoid and the wax dispersoid are stably dispersed in the aqueous medium, it is considered that the resin is adsorbed on the surface of the dispersoid. At this time, the state in the system was uniform, and generation of coarse particles due to the addition was not observed.

Combined process After the emulsion suspension obtained in the phase inversion emulsification process was transferred to a cylindrical container provided with a Max Blend blade (registered trademark) having a blade diameter of 340 mm, the stirring speed was maintained at 85 min ^-1. The temperature was adjusted to 25 ° C. Thereafter, the stirring speed was increased to 120 min ⁻¹ , and 12 parts by mass of a 3.5% by mass sodium sulfate aqueous solution was dropped at a rate of 1 kg / min as the first-stage electrolyte aqueous solution. Five minutes after the completion of the dropping, the stirring speed was lowered to 85 min ⁻¹ and stirring was performed for 5 minutes, and then the stirring speed was lowered to 65 min ⁻¹ and stirring was performed for 5 minutes. Subsequently, the stirring speed was reduced to 47 min ⁻¹ and stirring was continued for 30 minutes, whereby resin mother particles 1 having a Dv of 2.9 μm and a Dv / Dn of 1.09 were produced.

(Preparation of resin mother particle 2)
Except that 12 parts by mass of a 3.5% by mass aqueous sodium sulfate solution was dropped at a rate of 3 kg / min in the coalescing step when producing the resin mother particles 1, the same conditions as the preparation conditions of the resin mother particles 1 Thus, resin mother particles 2 having a Dv of 3.1 μm and a Dv / Dn of 1.15 were produced.

(Preparation of resin mother particle 3)
Except for dropping 12 parts by mass of a 3.5 mass% aqueous sodium sulfate solution at a rate of 6 kg / min in the coalescing step when producing the resin mother particles 1, the same conditions as the conditions for producing the resin mother particles 1 Thus, resin mother particles 3 having a Dv of 3.2 μm and a Dv / Dn of 1.25 were produced.

(Preparation of resin mother particle 4)
Dv is the same as the preparation conditions of the resin mother particle 1 except that the last stirring (stirring speed is 47 min ⁻¹ ) is 10 minutes in the coalescing step when the resin mother particle 1 is produced. Resin mother particles 4 having 1.9 μm and Dv / Dn of 1.09 were produced.

(Preparation of resin mother particles 5)
After the coalescence process in producing the resin mother particles 1, the second-stage coalescence process shown below was performed.
The stirring speed was adjusted to 120 min ⁻¹ , and 2 parts by mass of a sodium sulfate aqueous solution having a concentration of 5% by mass was dropped at a rate of 1 kg / min as the second stage electrolyte. After 5 minutes from the end of dropping, the stirring speed was adjusted to 85 min ⁻¹ and stirring was continued for 5 minutes, and then the stirring speed was reduced to 65 min ⁻¹ and stirring was performed for 5 minutes. Next, the stirring speed was adjusted to 47 min ⁻¹ and stirring was continued for 20 minutes. Thus, resin mother particles 5 having a Dv of 4.1 μm and a Dv / Dn of 1.09 were produced.

(Preparation of resin mother particle 6)
Dv is the same as the preparation conditions of the resin mother particle 1 except that the last stirring (stirring speed is 47 min ⁻¹ ) is 60 minutes in the coalescing step when the resin mother particle 1 is produced. Resin mother particles 6 having a diameter of 7 μm and a Dv / Dn of 1.09 were produced.

(Examples 1-7, Comparative Examples 1-11)
Each of the resin base particles 1 to 6 is described in 100 g of silica fine particles (RX200) manufactured by Nippon Aerosil Co., Ltd., 1.5 g of silica fine particles manufactured by Nippon Aerosil Co., Ltd. (RX50), and JP-A-2000-128534. Hydrophobic rutile-anatase type titanium oxide prepared by the method according to Example 1 was added in the amount shown in Table 1 and stirred with a 1 liter juicer at 1000 min ⁻¹ for 3 minutes. Next, dimethyl silicone oil (KF-96-200CS, manufactured by Shin-Etsu Chemical Co., Ltd.) in the amount shown in Table 1 was added to the juicer and stirred for 3 minutes at 10,000 min ⁻¹ to prepare a toner.
On the other hand, in the image forming apparatus of FIG. 1, a developing apparatus in which an acetate tape having a thickness of 50 μm is wound as a spacer on both ends of a developing roller having a diameter of 18 mm, and a developing gap of 50 μm is provided between the photosensitive member having a diameter of 40 mm and the developing roller. And an image forming apparatus having the above-described line head.
100 g of the produced toner was put in the developing cartridge of the image forming apparatus, and a printing test was performed. The results after printing 6000 sheets are shown in Table 1. The printing test was performed under the same conditions as LP9000C manufactured by Seiko Epson Corporation except for the following conditions.
Toner transport amount; (toner diameter μm) × 0.08 mg / cm ²
Development conditions: Vdc-300V, Vpp-1000V AC bias applied at 6000 Hz Exposure power: 0.5 μJ / cm ²
Average exposure spot diameter: 30 μm at 1 / e2
The particle size of the resin mother particles was measured by PFIA-2000 manufactured by Hosokawa Micron Corporation.
The bulk density of the toner was measured according to JIS Z 7302-9.
Adhesive tape was affixed to the photosensitive member and the developing roller, and the amount of toner adhered to the adhesive tape was measured, and development efficiency = (toner amount on the photosensitive member) / (toner amount on the developing roller) was obtained.
Half printing of A3 solid 30% density was performed, OD values at 20 locations were measured at random, and the maximum OD value difference was measured as development unevenness.

The toners of Examples 1 to 7 had wettability, and scattering of the resin mother particles from these toners was difficult to occur. The development efficiency of printing by the image forming apparatus using these toners is as high as 65% or more, the development unevenness is 0.2 or less, and uniform development has been performed.
Note that the developing efficiency of printing by the image forming apparatus using the toner of Example 3 and having a developing device for applying a DC bias is as low as 13%, the development unevenness is 0.4, and uniform development is performed. There wasn't. It was confirmed that the developing device to which no AC bias was applied did not crush the secondary particles in which the resin base particles were agglomerated.
The toner of Comparative Example 1 to which no silicone oil was added was easily scattered. The development efficiency of printing by the image forming apparatus using the toner of Comparative Example 1 was relatively high at 63%, but the development unevenness was 0.3, and uniform development was not performed.
The development efficiency of printing by the image forming apparatus using the toner of Comparative Example 2 to which no titanium oxide was added was low, and the development unevenness was large.
The toners of Comparative Examples 3 and 4 in which the amount of silicone oil added was too large contained large aggregates in which the resin base particles were strongly aggregated. The development efficiency of printing by the image forming apparatus using the toners of Comparative Examples 3 and 4 was low, and the development unevenness was large.
In the toners of Comparative Examples 5 and 6 in which the resin base particles having a too large particle size distribution were used, the resin base particles were agglomerated with the resin base particles strongly agglomerated in the gaps formed by the large particle base resin particles. It is thought to contain a collection. The development efficiency of printing by the image forming apparatus using the toners of Comparative Examples 5 and 6 was low, and the development unevenness was large.
The development efficiency of printing by the image forming apparatus using the toner of Comparative Example 7 in which the resin mother particles having a volume average particle size that is too small was used, and the development unevenness was large.
The development efficiency of printing by the image forming apparatus using the toners of Comparative Examples 8 to 11 in which the resin mother particles having a volume average particle size that is too large is used, the development unevenness is 0.2 or less, and uniform development is performed. It was broken. It was confirmed that the toner containing resin mother particles having a volume average particle diameter of 4 μm or more enables stable development regardless of the presence or absence of silicone oil. The resolution of an image obtained using a toner containing resin mother particles having a volume average particle size of 4 μm or more is an image obtained using a toner containing resin mother particles having a volume average particle size of less than 4 μm. Lower than the resolution.

In preparation of the colorant master chip, 2500 parts by mass of magenta pigment (ECR-101 manufactured by Dainichi Seika Kogyo Co., Ltd.), 3000 parts by mass of yellow pigment (TonerYellowHG VP2155 manufactured by Clariant Japan Co., Ltd.), black pigment (MORGUL- manufactured by Cabot) L) Magenta resin mother particles, yellow resin mother particles, and black resin mother particles were produced under the same conditions as those for producing the resin mother particles 1 except that 2500 parts by mass were used. 2 g of silica fine particles (RX200) manufactured by Nippon Aerosil Co., Ltd. and 1.5 g of silica fine particles (RX50) manufactured by Nippon Aerosil Co., Ltd. were added to 100 g of each resin base particle, and 3 for 1000 min ⁻¹ with a 1 liter juicer. Stir for minutes. Next, 0.5 part by mass of dimethyl silicone oil (KF-96-200CS, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to each juicer, and stirred for 3 minutes at 10000 min ⁻¹ to obtain magenta toner, yellow toner and black toner. Three color toners were prepared. The color densities of the three color toners and the cyan toner were the same. When the four-color toner was put in the developing cartridge of the image forming apparatus and a printing test was performed, black fog and yellow density light (development failure) occurred.

To 100 g of each of the magenta resin mother particles, yellow resin mother particles, and black resin mother particles, 2 g of silica fine particles (RX200) manufactured by Nippon Aerosil Co., Ltd., and silica fine particles (RX50) manufactured by Nippon Aerosil Co., Ltd. 5 g and 0.5 g of the above-mentioned hydrophobic rutile-anatase type titanium oxide were added, and the mixture was stirred with a 1 liter juicer at 1000 min ⁻¹ for 3 minutes. Next, 0.5 part by mass of dimethyl silicone oil (KF-96-200CS, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to each juicer, and stirred for 3 minutes at 10000 min ⁻¹ to obtain magenta toner, yellow toner and black toner. Three color toners were prepared. When the three color toners and the cyan toner were put in the developing cartridge of the image forming apparatus and a print test was performed, the four colors were printed almost equally. Therefore, it is considered that the toner surface is coated with silicone oil and titanium oxide, and the difference in charging due to the pigment contained in the toner is suppressed.

  Next, a toner was prepared using perfluoropolyether (BARRIERTA J 25 V manufactured by NOK Co., Ltd.) which is a fluorine oil instead of silicone oil, and a printing test was performed. As a result, the same results as in Examples 1 to 7 and Comparative Examples 1 to 11 were obtained.

1 is a diagram showing an embodiment of an image forming apparatus according to the present invention. The figure which shows a developing gap typically. 1 is a perspective view schematically showing an embodiment of a line head according to the present invention. FIG. 3 is a sub-scan sectional view of an embodiment of the line head according to the invention. The perspective view which shows the outline of a microlens array. The main scanning sectional view of a micro lens array. The figure which shows arrangement | positioning of a several light emitting element group. The figure which shows the image formation state of a micro lens array. The figure which shows the detail of arrangement | positioning of a light emitting element. The figure which shows the relationship between adjacent light emitting element groups. The figure which shows the spot formation operation | movement by a line head. The schematic diagram which shows the principle of this invention. The figure which shows the case where the position of a light emitting element group corresponds with the optical axis of an imaging lens. The figure which shows the case where the position of a light emitting element group does not correspond with the optical axis of an imaging lens.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Housing main body, 2 ... Image forming unit, 4 ... Paper feed tray, 21 ... Photoconductor, 23 ... Charging part, 251 ... Developing roller, 252 ... Supply roller, 29 ... Line head, 71 ... Cleaner part, 711 ... Cleaner Blade 713 ... Waste toner box 77 ... Paper feed cassette 79 79 Pickup roller pair 8 Transfer belt 82 Drive roller 83 Drive roller 85 Primary transfer roller 121 Secondary transfer roller 13 Fixing unit 131... Heating roller 132. Pressure roller 295. Light emitting element group L295. Group row, CG295. Light emitting element group position 2951. Light emitting element L2951 Light emitting element row CG2951 Light emitting element position 293 ... Glass substrate, 299 ... Microlens array, 2991 ... Glass substrate, 2993A, 2 93B ... Lens, ML ... Micro lens, OA ... Optical axis, Gx ... Main scan group width, Gy ... Sub scan group width, Px ... Main scan group pitch, Py ... Sub scan group pitch, XX ... Main scan direction, YY ... Sub-scan direction

Claims (4)

A toner containing resin mother particles, silicon oil or fluorine oil, silica and titanium oxide,
The volume average particle diameter of the resin mother particles is 2 μm or more and less than 4 μm,
(Volume average particle diameter of resin mother particles) / (Number average particle diameter of resin mother particles) is greater than 1 and less than 1.1,
The content of silicon oil or fluorine oil is 0.05% by mass or more and less than 2% by mass with respect to the resin base particles.
A toner in which the content of titanium oxide is 0.3% by mass or more and 1% by mass or less based on the resin base particles.   The toner according to claim 1, wherein the titanium oxide is a rutile-anatase type. A developing device comprising a photoreceptor, a developing roller, and a gap adjusting member provided at both ends of the developing roller,
Non-contact jumping development is performed using the toner according to claim 1 or 2,
The developing roller is provided so that the toner conveying surface faces the photosensitive member with a predetermined developing gap, and conveys the toner to the photosensitive member,
The gap adjusting member is composed of a spacer, and a developing gap is set in contact with the photosensitive member.
The developing device, wherein the spacer is made of a material having higher hygroscopicity than the developing roller and is fixed to the developing roller via an elastic layer. An image forming apparatus including a developing device and a line head,
The toner according to claim 1 or 2 is used to form an image,
The developing device is the developing device according to claim 3,
The line head forms a spot by forming an image of a light beam on the surface to be scanned that is conveyed in the sub-scanning direction substantially orthogonal to the main scanning direction,
A plurality of light emitting element groups each having a plurality of light emitting elements;
The plurality of light emitting element groups are arranged in a one-to-one correspondence, and each of the light beams emitted from each of the plurality of light emitting elements belonging to the corresponding light emitting element group forms an image on the scanned surface. A plurality of imaging lenses,
In each of the plurality of light emitting element groups, the distance Gx between the most upstream light emitting element and the most downstream light emitting element in the main scanning direction is the distance between the most upstream light emitting element and the most downstream light emitting element in the sub scanning direction. A plurality of light emitting element arrays in which the two or more light emitting elements are arranged in the main scanning direction are arranged in the sub scanning direction so as to be larger than Gy, and the plurality of light emitting elements are arranged two-dimensionally,
A group row in which two or more light emitting element groups are arranged in the main scanning direction at the main scanning group pitch Px so that the main scanning group pitch Px is larger than the sub scanning group pitch Py is formed in the sub scanning direction. An image forming apparatus in which a plurality of the light emitting element groups are arranged two-dimensionally at a sub-scanning group pitch Py.

Images