JP2006126793A - Magnetic mono-component toner for developing electrostatic latent image and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide magnetic mono-component toner for developing an electrostatic latent image which can suppress a selection development on a latent image carrier and can maintain favorable image properties for a long period by using the toner having the coarse powder distribution (S) within a given range in a jumping developing method, and to provide an image forming method which uses the toner. <P>SOLUTION: The magnetic mono-component toner for developing an electrostatic latent image is used in the jumping developing method which develops an electrostatic latent image formed on a latent image carrier using a developer carrier, and the toner includes toner particles which contain at least a binding resin and a magnetic powder, and the coarse powder distribution (S) of the toner particles satisfies a following formula (1). Coarse powder distribution (S)=(50-A)/2≥17 (volume%/μm) (1) (wherein, A is a volume% of the coarse powder having particle sizes larger than D<SB>50</SB>based on volume by 2 μm or more). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a magnetic one-component toner for developing an electrostatic latent image and an image forming method using the same.
In particular, by using a toner having a coarse powder distribution degree (S) within a predetermined range in an image forming apparatus employing a jumping development method, selective development on a latent image carrier is suppressed, and a good image can be obtained over a long period of time. The present invention relates to a magnetic one-component toner for developing an electrostatic latent image capable of maintaining characteristics and an image forming method using the same.

In general, in an electrophotographic method, an electrostatic recording method, etc., an electrostatic latent image formed by charging a latent image carrier made of a photoconductive photoreceptor, dielectric, etc. by corona charging, etc., and exposing it with a laser, LED, etc. Is visualized by using a developer such as toner, or the electrostatic latent image is visualized by reversal development to obtain a high quality image.
Usually, the toner applied to these development methods is a mixture of a thermoplastic resin (binder resin) as a binder, a dye, a pigment as a colorant and a charge control agent, a wax as a release agent, a magnetic material, and the like. Kneaded, pulverized, and classified into toner particles having an average particle diameter of 5 to 15 μm are used. An inorganic fine powder such as silica or titanium oxide or an inorganic metal fine powder is externally added to the toner for the purpose of imparting fluidity to the toner, controlling charging of the toner, or improving the cleaning property. As a developing method, a two-component developing method using a carrier such as toner and iron powder and a magnetic one-component developing method in which a magnetic substance is contained inside the toner without using a carrier are known.

More specifically, for example, a number of development methods such as the magnetic brush method described in Patent Document 1, the cascade development method, the powder cloud method, and the fur brush development method described in Patent Document 2 are known. The method using these two-component developers can provide a relatively stable and high-quality image in the initial stage. However, when used over a long period of time, carrier deterioration occurs, that is, the spent phenomenon occurs. There are the common drawbacks that the imparting ability is lowered and a good quality image cannot be obtained over a long period of time, and the long-term durability is lacking because the mixing ratio of the toner and the carrier is difficult to keep constant.
Therefore, various development methods using a one-component developer composed only of toner have been proposed, and among them, a magnetic one-component development method employing a magnetic toner is generally used. (See Patent Documents 3 to 5)
U.S. Pat. No. 2,874,063 US Pat. No. 2,618,552 U.S. Pat. No. 3,909,258 Japanese Patent Laid-Open No. 55-18656 JP 2003-162089 A

However, Patent Document 3 discloses a developing method in which a conductive magnetic toner is held on a conductive developer carrier having a magnetic material therein and developed by bringing it into contact with an electrostatic latent image. However, since the toner used in this method is conductive, it is difficult to electrostatically use an electric field when transferring the toner image on the latent image carrier onto the printing paper. It was observed.
In addition, due to the trouble phenomenon derived from the conductive toner in each step, there were problems that it was difficult to obtain high image quality over a long period of time, and that there was a problem of electrical leakage destruction to the latent image carrier.

  In addition, Patent Document 4 solves the problem of lack of long-term durability with a two-component developer by using a developing method using a magnetic one-component jumping method, but with an increase in printing speed. However, it did not sufficiently respond to changes in image characteristics and durability.

  Patent Document 5 discloses a magnetic toner having a weight average particle diameter within a specific range as a method of controlling the charge amount of the toner without impairing the image density. However, since this toner requires the control of the circularity of the toner and the use of a specific magnetic powder, there has been a problem that productivity is lowered. Further, it has been necessary to further improve the durability and the image quality.

In addition, as an essential problem of the developing method using the magnetic one-component jumping method, there is a phenomenon called selective development. This selective development is a phenomenon in which toner is developed by electric force, so that when the electric field acting on each toner is equal, the toner having a higher frictional charge amount is selectively transferred onto the latent image carrier. In the component development system, the carrier is not generated like the two-component development system, and therefore, it is remarkably generated. Further, there is a correlation between the charge amount of toner and the particle size, and a toner having a larger particle size, that is, a heavier weight has a smaller charge amount, and a toner having a smaller particle size is the opposite.
Accordingly, there arises a problem that a toner having a large particle size is left in the developing device every time the development is repeated. When this selective development is performed, the image after the endurance has a lower image density than the initial image, or a fogged image is generated.

Therefore, as a result of intensive investigations, the inventors of the present invention have found that, by using a magnetic one-component toner for developing an electrostatic latent image having a coarse powder distribution degree (S) within a predetermined range for a jumping development method, an appropriate charged region can be obtained. It has been found that the content of coarse powder falling off can be controlled to suppress selective development and maintain good image characteristics over a long period of time.
That is, even when image formation is repeatedly performed, the toner particle size distribution on the latent image carrier is made uniform by controlling the amount of toner coarse powder in the development process within a predetermined range. Another object of the present invention is to provide a magnetic one-component toner for developing an electrostatic latent image capable of maintaining image characteristics and an image forming method using the same.

  According to the magnetic one-component toner for developing an electrostatic latent image of the present invention, the electrostatic latent image developing toner used in the jumping development method in which the electrostatic latent image formed on the latent image carrier is developed by the developer carrier. A magnetic one-component toner comprising toner particles containing at least a binder resin and magnetic powder, and a coarse powder distribution degree (S) of the toner particles satisfying the following relational expression (1): A magnetic one-component toner for developing an electrostatic latent image is provided, and the above-described problems can be solved.

  That is, by using a toner having a coarse powder distribution within a predetermined range, it becomes possible to control the content of coarse powder that deviates from an appropriate charged area, suppress selective development, and improve the image quality over a long period of time. Characteristics can be maintained.

Further, in constituting the magnetic one-component toner for developing an electrostatic latent image of the present invention, the coarse powder distribution degree (S) is preferably set to a value in the range of 18 to 24 (volume% / μm).
With such a configuration, desired image characteristics can be maintained even when toner particles containing a predetermined amount of coarse powder are used.

In constructing the magnetic one-component toner for developing an electrostatic latent image of the present invention, it is preferable to set the volume-based D ₅₀ to a value in the range of 5 to 10 (μm).
With this configuration, the particle size distribution of the entire toner particles can be controlled, and the fine powder amount and the coarse powder amount can be contained in a balanced manner.

In constructing the magnetic one-component toner for developing an electrostatic latent image according to the present invention, the volume-based D ₅₀ before printing of toner particles is defined as D _1, and the volume-based D ₅₀ after printing 150,000 sheets of A4 size paper. When D ₂ is D ₂ , the value represented by (D ₂ -D ₁ ) is preferably 1.0 (μm) or less.
With this configuration, the particle size distribution of the toner particles can be controlled, and the volume-based D ₅₀ value can be used as a guide for preventing selective development.

In constructing the magnetic one-component toner for developing an electrostatic latent image of the present invention, the ten-point average roughness (Rz) of the sleeve surface of the developer carrying member is set to a value in the range of 2 to 8 (μm). It is preferable.
With this configuration, the toner thin layer on the developing sleeve can be more uniformly held and formed regardless of changes over time or environmental changes.

In constituting the magnetic one-component toner for developing an electrostatic latent image of the present invention, the toner particles contain toner particles having a particle size of 4.0 (μm) or less in a range of 30 (number%) or less. Is preferred.
By comprising in this way, the amount of fine powder can be controlled within a predetermined range, and selective development can be effectively suppressed.

In constituting the magnetic one-component toner for developing an electrostatic latent image of the present invention, it is preferable to set the average circularity of the toner particles to a value in the range of 0.92 to 0.96.
By comprising in this way, favorable fluidity | liquidity can be obtained, and charging adjustment can be performed easily.

In constructing the magnetic one-component toner for developing an electrostatic latent image of the present invention, the latent image carrier is an amorphous silicon photosensitive member, and the Vickers hardness of the outermost surface of the amorphous silicon photosensitive member is 300 or less. It is preferable.
With this configuration, the toner adhesion amount on the latent image carrier can be accurately defined, and the image quality can be stably maintained.

Another aspect of the present invention is an image forming method in which any one of the above-described magnetic one-component toners for developing an electrostatic latent image is applied to an image forming apparatus having a jumping development system.
That is, by applying a toner having a coarse powder distribution degree within a predetermined range to a specific image forming apparatus, selective development on the latent image carrier is suppressed, and stable image quality can be obtained over a long period of time. Obtainable.

[First Embodiment]
The first embodiment of the present invention is a magnetic one-component toner for electrostatic latent image development used in a jumping development system in which an electrostatic latent image formed on a latent image carrier is developed with a developer carrier. Thus, the toner is composed of toner particles containing at least a binder resin and magnetic powder, and the toner particle has a coarse powder distribution degree (S) satisfying the relational expression (1).

(1) Magnetic one-component toner The magnetic one-component toner for developing an electrostatic latent image of the present invention is composed of toner particles containing at least a binder resin and magnetic powder. Various additives such as a colorant and a charge control agent can be contained.

(1) -1 Binder Resin (1) -1-1 Type The type of the binder resin used in the toner of the present invention is not particularly limited. For example, styrene resin, acrylic resin, styrene- Acrylic copolymer, polyethylene resin, polypropylene resin, vinyl chloride resin, polyester resin, polyamide resin, polyurethane resin, polyvinyl alcohol resin, vinyl ether resin, N-vinyl resin, styrene-butadiene resin It is preferable to use a thermoplastic resin such as

More specifically, the polystyrene resin may be a homopolymer of styrene or a copolymer with another copolymerizable monomer copolymerizable with styrene.
As copolymerizable monomers, p-chlorostyrene; vinyl naphthalene; ethylene unsaturated monoolefins such as ethylene, propylene, butylene, and isobutylene; vinyl halides such as vinyl chloride, vinyl bromide, and vinyl fluoride; vinyl acetate, propion Vinyl esters such as vinyl acrylate, vinyl benzoate, vinyl butyrate; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, n-octyl acrylate, 2-chloroethyl acrylate, acrylic (Meth) acrylic esters such as phenyl acid, methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate; other acrylic acid derivatives such as acrylonitrile, methacrylonitrile, acrylamide; Vinyl ethers such as methyl ether and vinyl isobutyl ether; Vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone and methyl isopropenyl ketone; N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrolidene and the like Examples thereof include N-vinyl compounds. These may be used alone or in combination of two or more with a styrene monomer.

Moreover, as the polyester resin, any resin obtained by condensation polymerization or co-condensation polymerization of an alcohol component and a carboxylic acid component can be used.
The following are mentioned as a component used when synthesize | combining a polyester-type resin.
First, as a divalent or trivalent or higher alcohol component, ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1, Diols such as 4-butenediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol; bisphenol A, hydrogen Bisphenols such as added bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylenated bisphenol A; sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, Antaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4- Examples thereof include trivalent or higher alcohols such as butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxymethylbenzene.

As the divalent or trivalent or higher carboxylic acid component, a divalent or trivalent carboxylic acid, an acid anhydride or a lower alkyl ester thereof is used. Maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid Phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, or n-butyl succinic acid, n-butenyl succinic acid, isobutyl succinic acid, isobutenyl succinic acid, Divalent carboxylic acids such as alkyl or alkenyl succinic acid such as n-octyl succinic acid, n-octenyl succinic acid, n-dodecyl succinic acid, n-dodecenyl succinic acid, isododecyl succinic acid, isododecenyl succinic acid; 4-benzenetricarboxylic acid (trimellitic acid), 1, 2, 5- Zentricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl -2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, empole trimer acid Examples thereof include trivalent or higher carboxylic acids and the like.
Moreover, it is preferable that the softening point of a polyester-type resin is 80-150 degreeC, More preferably, it is 90-140 degreeC.

  Further, the binder resin may be a thermosetting resin. By introducing a partially crosslinked structure in this way, it is possible to further improve the storage stability, form retention, and durability of the toner without deteriorating the fixability. Therefore, it is not necessary to use 100 parts by weight of the thermoplastic resin as the binder resin for the toner, and it is also preferable to add a cross-linking agent or partially use a thermosetting resin.

  Therefore, an epoxy resin, a cyanate resin, or the like can be used as the thermosetting resin. More specifically, one or more of bisphenol A type epoxy resin, hydrogenated bisphenol A type epoxy resin, novolac type epoxy resin, polyalkylene ether type epoxy resin, cycloaliphatic type epoxy resin, cyanate resin, etc. Combinations are listed.

(1) -1-2 Glass transition point In this invention, it is preferable that the glass transition point (Tg) of binder resin is 50-65 degreeC, More preferably, it is 50-60 degreeC.
When the glass transition point is lower than the above range, the obtained toners are fused with each other in the developing device, and the storage stability is lowered. Further, since the resin strength is low, there is a tendency that toner adheres to the photoreceptor. Further, when the glass transition point is higher than the above range, the low-temperature fixability of the toner is lowered.
In addition, the glass transition point of binder resin can be calculated | required from the change point of specific heat using a differential scanning calorimeter (DSC). More specifically, it can be determined by measuring an endothermic curve using a differential scanning calorimeter DSC-6200 manufactured by Seiko Instruments Inc. as a measuring device. More specifically, 10 mg of a measurement sample is put in an aluminum pan, an empty aluminum pan is used as a reference, and measurement is performed at normal temperature and humidity at a measurement temperature range of 25 to 200 ° C. and a temperature increase rate of 10 ° C./min. The glass transition point can be determined from the endothermic curve obtained.

(1) -2 Magnetic powder The magnetic one-component toner for developing an electrostatic latent image of the present invention contains magnetic powder in the binder resin. Examples of such magnetic powder include those known per se, for example, ferrite, magnetite and other iron, cobalt, nickel and other metals exhibiting ferromagnetism, alloys or compounds containing these elements, or ferromagnetism. An alloy that does not contain an element but becomes ferromagnetic when subjected to an appropriate heat treatment, chromium dioxide, or the like can be given.

These magnetic powders are uniformly dispersed in the above-described binder resin in the form of fine powder having an average particle diameter of 0.1 to 1.0 μm, particularly 0.1 to 0.5 μm. The magnetic powder can also be used after being subjected to a surface treatment with a surface treatment agent such as a titanium coupling agent or a silane coupling agent.
The magnetic powder is contained in the toner in a proportion of 30 to 60 parts by weight, preferably 40 to 50 parts by weight. When the magnetic powder is used in a larger amount than the above range, the durability of the image density is deteriorated, and the fixability tends to be extremely lowered. When the amount is smaller than the above range, the fog in the image density durability is deteriorated. End up.

(1) -3 Wax The waxes used for improving the fixing property and the offset property are not particularly limited. For example, polyethylene wax, polypropylene wax, fluororesin wax, Fischer-Tropsch wax, Paraffin wax, ester wax, montan wax, rice wax and the like are preferably used. Two or more of these waxes may be used in combination. By adding such wax, offset property and image smearing (dirt around the image when the image is rubbed) can be more efficiently prevented.

  Further, the addition amount of the wax is preferably 1 to 5 parts by weight in the toner (the total amount of the toner is 100 parts by weight). If the addition amount is less than 1 part by weight, there is a tendency that offset properties and image smearing cannot be effectively prevented. On the other hand, if the addition amount exceeds 5 parts by weight, the toners are fused together, and storage stability This is because there is a tendency to decrease.

(1) -4 Colorant In the toner of the present invention, a pigment such as carbon black or a dye such as acid violet can be dispersed in the binder resin as a colorant in order to adjust the color tone.
Such a colorant is usually blended at a ratio of 1 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

(1) -5 Charge Control Agent The charge control agent used in the present invention remarkably improves the charge level and the charge rising property (an indicator of whether or not the charge is charged to a constant charge level in a short time). It is blended in order to obtain excellent properties and the like. That is, when the toner is positively charged for development, a positively chargeable charge control agent is added. When the toner is negatively charged for development, a negatively chargeable charge control agent can be added. .

(1) -5-1 Positive charge control agent Specific examples of the positive charge control agent include pyridazine, pyrimidine, pyrazine, orthooxazine, metaoxazine, paraoxazine, orthothiazine, metathiazine, parathiazine, 1, 2 , 3-triazine, 1,2,4-triazine, 1,3,5-triazine, 1,2,4-oxadiazine, 1,3,4-oxadiazine, 1,2,6-oxadiazine, 1,3,4 -Thiadiazine, 1,3,5-thiadiazine, 1,2,3,4-tetrazine, 1,2,4,5-tetrazine, 1,2,3,4-tetrazine, 1,2,4,6-oxa Azine compounds such as triazine, 1, 3, 4, 5-oxatriazine, phthalazine, quinazoline, quinoxaline; azine fast red FC, azine fast red 12 Direct dyes composed of azine compounds such as K, azine violet BO, azine brown 3G, azine light brown GR, azine dark green BH / C, azine deep black EW, and azine black 3RL; nigrosine such as nigrosine, nigrosine salt, nigrosine derivative Compound; Acid dye comprising nigrosine compound such as nigrosine BK, nigrosine NB, nigrosine Z; metal salt of naphthenic acid or higher fatty acid; alkoxylated amine; alkylamide; quaternary ammonium such as benzylmethylhexyldecylammonium chloride, decyltrimethylammonium chloride It can be a salt.
These may be used alone or in combination of two or more.
In particular, the nigrosine compound is optimal for use as a positively chargeable toner from the viewpoint of obtaining a quicker start-up property.

Also, a quaternary ammonium salt, a carboxylate, or a resin or oligomer having a carboxyl group as a functional group can be used as the positively chargeable charge control agent.
More specifically, a styrene resin having a quaternary ammonium salt, an acrylic resin having a quaternary ammonium salt, a styrene-acrylic resin having a quaternary ammonium salt, a polyester resin having a quaternary ammonium salt, a carboxylic acid Styrene resin with salt, acrylic resin with carboxylate, styrene-acrylic resin with carboxylate, polyester resin with carboxylate, polystyrene resin with carboxyl group, acrylic with carboxyl group Examples thereof include one or more resins such as a resin, a styrene-acrylic resin having a carboxyl group, and a polyester resin having a carboxyl group.

In particular, a styrene-acrylic copolymer resin having a quaternary ammonium salt as a functional group is optimal from the viewpoint that the charge amount can be easily adjusted to a value within a desired range.
In this case, preferred acrylic comonomers to be copolymerized with the styrene units include methyl acrylate, ethyl acrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, iso-butyl acrylate, Examples include (meth) acrylic acid alkyl esters such as 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, and iso-butyl methacrylate.
As the quaternary ammonium salt, a unit derived from a dialkylaminoalkyl (meth) acrylate through a quaternization step is used. Examples of the derived dialkylaminoalkyl (meth) acrylate include di (amino) ethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dipropylaminoethyl (meth) acrylate, dibutylaminoethyl (meth) acrylate and the like ( Lower alkyl) aminoethyl (meth) acrylate; dimethylmethacrylamide, dimethylaminopropylmethacrylamide are preferred. Further, hydroxy group-containing polymerizable monomers such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and N-methylol (meth) acrylamide can be used in combination during polymerization.

(1) -5-2 Negatively chargeable charge control agent As the charge control agent exhibiting negative chargeability, for example, an organometallic complex and a chelate compound are effective. Examples thereof include aluminum acetylacetonate and iron (II) acetylacetate. Examples thereof include naphthate, chromium 3,5-di-tert-butylsalicylate, and particularly preferably an acetylacetone metal complex, a salicylic acid metal complex or a salt, and particularly preferably a salicylic acid metal complex or a salicylic acid metal salt.

(1) -5-3 Amount of addition The above-described positively or negatively chargeable charge control agent is generally 1.5 to 15 parts by weight, preferably 2 in the toner (the total amount of the toner is 100 parts by weight). It is good to contain in the ratio of 0.0-8.0 weight part, More preferably, 3.0-7.0 weight part.
This is because when the amount of charge control agent added is less than the above range, it tends to be difficult to stably charge the toner to a predetermined polarity. Further, when an electrostatic latent image is developed using this toner to form an image, the image density tends to decrease or the durability of the image density tends to decrease. Furthermore, the dispersion of the charge control agent is likely to occur, so that there is a tendency to cause so-called fogging, and the contamination of the photoreceptor becomes severe.
On the other hand, when the addition amount of the charge control agent is larger than the above range, environmental resistance, in particular, charging failure and image failure under high temperature and high humidity tend to cause defects such as photoconductor contamination. Because there is.

(1) -6 External Additive In the toner of the present invention, fine particles (usually having an average particle diameter of 1.0 μm or less) such as colloidal silica, hydrophobic silica, alumina, and titanium oxide are used as the external additive. You may add externally.
This external additive is used to improve fluidity, storage stability, cleaning properties, and the like by surface treatment of the toner, and is generally 0.2 to 10.0 with respect to the total amount of toner. Used in parts by weight. The external addition of these fine particles is performed by stirring and mixing the magnetic toner in a dry manner. This stirring and mixing is performed using a Henschel mixer, a Nauter mixer, or the like so that the external additive is not embedded in the toner. Good to do.

(2) Coarse powder distribution (2) -1 Relational expression (1)
Further, the toner according to the present invention is characterized in that the degree of coarse powder distribution (S) satisfies the relational expression (1). Here, the degree of coarse powder distribution (S) can be defined as the ratio between the amount of change in particle size of toner particles and the amount of change in cumulative frequency corresponding thereto.
More specifically, as shown in FIG. 1, in a characteristic diagram comprising a particle size distribution (P) and a cumulative frequency curve (D) obtained by accumulating the particle size distribution (P) from the coarse powder side, The degree of coarse powder distribution (S) can be defined as the ratio (ΔY / ΔX) of the change amount ΔY (volume%) of the cumulative frequency to the change amount ΔX (μm) of the diameter. Here, the amounts of change ΔX and ΔY are obtained as positive values.
That is, this coarse powder distribution degree (S) is a line segment (L) connecting an arbitrary point G ₁ (X ₁ , Y ₁ ) and point G ₂ (X ₂ , Y ₂ ) on the cumulative frequency curve (D). ) Can be generally expressed as the following relational expression (2).
In addition, the cumulative frequency curve (D) used here is a curve obtained by accumulating from the coarse powder side as described above, and is a commonly used so-called cumulative frequency (cumulative when accumulating from the fine powder side). (D) = 100− (cumulative frequency) (%).
Further, the particle size of the toner particles shown in FIG. 1 can be measured using a particle size measuring device (“Cole Counter TA-II type” manufactured by Coulter Counter, Inc.) described later, using an aperture diameter of 100 μm.

When the coarse particle distribution degree (S) is defined in this way, the relational expression (1) described above is obtained by changing the point G ₁ (X ₁ , Y ₁ ) to (D ₅₀ , 50) in the above expression (2), It can be understood that this corresponds to the case where G ₂ (X ₂ , Y ₂ ) is (D ₅₀ +2, A). Here, A represents the volume percentage of coarse powder that is 2 μm or more larger than the volume-based D ₅₀ .

In the present invention, the coarse powder distribution degree (S) in the relational expression (1) is set to a value of 17 or more. The reason for this is that, by configuring in this way, the content of coarse powder that deviates from an appropriate charged region can be controlled efficiently, and as a result, image characteristics can be maintained over a long period of time. Because.
On the other hand, when the coarse powder distribution degree (S) is less than 17, coarse particles on the coarse powder side that do not reach an appropriate charged region may not be developed in the development process and may stay in the developing device. For this reason, there is a problem in that the toner with poor charging increases, and the image density decreases as printing is repeated. In addition, poor dispersion of the charge control agent is likely to occur, which may cause so-called fogging and may cause photoconductor contamination.

Here, FIG. 2 shows a characteristic diagram in which the solid image density is evaluated after continuous printing of 150,000 sheets of A4 size paper with toner particles having different coarse powder distribution degrees (S). As can be understood from the characteristic diagram, when the coarse particle distribution degree (S) is 17 or more, the image density is maintained at a high value, but when it is less than 17, the decrease in the image density becomes remarkable. .
Moreover, it is preferable to make this coarse powder distribution degree (S) into the value within the range of 18-24, and it is more preferable to set it as the value within the range of 19-21. By defining in this way, even when toner particles containing a predetermined amount of coarse powder are used, it is possible to maintain the fluidity of the toner and prevent an initial density decrease due to variation in chargeability. .

Further, in FIG. 3, for toner particles having different coarse powder distribution degrees (S), the volume-based D ₅₀ before printing of the toner particles is set as D _1, and the volume-based D ₅₀ after printing 150,000 sheets of A4 size paper. the D ₅₀ when the D _2, shows a characteristic diagram showing an evaluation of the value represented by _{(D 2 -D 1) (D} 50 the amount of change in volume).
Here, as can be understood from this characteristic diagram, when the coarse powder distribution degree (S) is 17 or more, the volume-based D ₅₀ variation is small, and even after printing 150,000 sheets, the initial grain size is small. It can be seen that the diameter distribution is maintained. On the other hand, when the coarse powder distribution degree (S) is less than 17, it can be seen that the volume-based D ₅₀ change amount is large and the coarse powder amount is increased. That is, by setting the coarse powder distribution degree (S) to a value of 17 or more, the particle size distribution can be maintained over a long period of time and the image characteristics can be maintained even when repeated printing is performed. Become. Accordingly, the coarse powder distribution degree (S) is preferably a value within the range of 18 to 24, and more preferably a value within the range of 19 to 21.

FIG. 4 is a characteristic diagram showing cumulative frequency curves (D _a ) to (D _c ) having different coarse powder distribution levels (S) among the toner particles described above. These (D _a ) to (D _c ) show cumulative frequency curves in which the coarse powder distribution degree (S) is 20.7, 17.7, and 15.9, respectively. That is, it can be said that (D _a ) and (D _b ) among the cumulative frequency curves shown here are cumulative frequency curves satisfying the range of the coarse powder distribution degree in the present invention.
Further, the points (G _a1 ) to (G _c1 ) shown on the cumulative frequency curves (D _a ) to (D _c ) correspond to the cumulative frequency 50% in each curve, that is, D _50. G _a2 ) to (G _c2 ) correspond to particle sizes 2 μm larger than D ₅₀ .
That is, the gradient amounts of the straight lines (L _a ) to (L _c ) connecting the points (G _a1 ) to (G _c1 ) and the points (G _a2 ) to (G _c2 ) correspond to the respective cumulative frequency curves. It can be said that the coarse powder distribution degree (S) is shown.

(2) -2 Volume-based D ₅₀
Further, in FIG. 4, it is preferable that the range of D ₅₀ based on volume and 5 to 10 ([mu] m).
Here, the volume-based D _x means the particle size when the cumulative value reaches X (%) of the whole when the volume is accumulated in order from the particles having a smaller particle size. That is, the volume-based D ₅₀ is a volume average particle diameter, and by setting such a value within a predetermined range, the particle diameter distribution of the entire toner particles can be controlled, and the amount of fine powder and The amount of coarse powder can be contained in a well-balanced manner. Accordingly, the volume-based D ₅₀ is preferably set to a value within the range of 5 to 10 (μm), and more preferably set to a value within the range of 7 to 9 (μm).

(2) -3 Fine powder amount It is preferable to contain toner particles having a particle size of 4.0 (μm) or less in a range of 30 (number%) or less.
With this configuration, the amount of fine particles in the toner particles can be regulated within a predetermined range, and selective development can be effectively suppressed. That is, the range of the cumulative number% is preferably 30 (number%) or less, and more preferably 10 to 25 (number%) or less.

(2) -4 Average Circularity The toner in the present invention preferably has an average circularity of 0.92 to 0.96.
This is because if the average circularity is less than 0.92, the fluidity is deteriorated, the transfer efficiency is low, and the image density tends to decrease. On the other hand, when the average circularity is larger than 0.96, the fluidity and transfer efficiency are improved and the image density is easily maintained, but the charge adjustment becomes difficult. The average circularity can be determined using, for example, a flow type particle image analyzer (“FPIA-1000 type” manufactured by Sysmex Corporation).

(3) Latent Image Carrier (3) -1 Basic Configuration FIG. 5 is an enlarged cross-sectional view of a part of the photosensitive drum 11 as a latent image carrier used in the present invention. As shown in FIG. 5, as the photosensitive drum 11, it is preferable to use a laminated type photosensitive member configured by laminating a carrier blocking layer 20, a photosensitive layer 19, and a surface protective layer 18 on a conductive substrate 21. .

Further, the film thickness of the photosensitive drum 11 is 30 μm or less, preferably 10 to 30 μm. Here, in the present embodiment, the film thickness of the photosensitive drum 11 is the thickness from the surface of the conductive substrate 21 that is a base material to the surface of the photosensitive drum 11, that is, the carrier blocking layer 20, the photosensitive layer 19, and the surface protection. This refers to the total thickness of the layer 18.
This is because, when the film thickness of the photosensitive drum 11 exceeds 30 μm, the moving speed of the heat carrier increases, so that the dark decay characteristic (charge holding capacity per time of the photosensitive layer in the dark place) is lowered, resulting in a result. In addition, the latent image tends to flow in the direction of rotation of the photoconductor on the surface of the photoconductor, which causes a reduction in resolution.
In relation to the type of the photoreceptor, it is known that the resolution is improved as the thickness of the photoreceptor is reduced not only in the a-Si photoreceptor but also in the organic photoreceptor (OPC). In terms of cost, the longer the film thickness of the photoconductor, the longer the film formation time, and the higher the probability of adhesion of foreign substances and the like. The lower the production yield, the lower the total film thickness of the photoconductor, the lower the cost. Quality is stable.
On the other hand, when the film thickness of the photosensitive drum 11 is less than 10 μm, there is a possibility that the charging ability as the photosensitive member is lowered and it is difficult to obtain a predetermined surface potential. Further, the laser beam is irregularly reflected on the surface of the conductive substrate 21, which may cause a problem that interference fringes are generated in the half pattern. Therefore, the film thickness of the photosensitive drum 11 is preferably in the range of 10 to 30 μm from the viewpoints of charging capability, pressure resistance, dark decay characteristics, manufacturing cost, and quality.

  As a more preferable embodiment of the photosensitive drum 11, the thickness of the surface protective layer 18 is 20,000 mm or less, preferably 5,000 to 15,000 mm. When the thickness of the surface protective layer 18 is less than 5,000 mm, the pressure resistance characteristic against the negative current flowing in the opposite polarity to the charging polarity from the transfer roll 15 is deteriorated, and as a result, the surface is in a fast stage of 15,000 sheets or less. The protective layer 18 may be deteriorated. On the other hand, when the thickness of the surface protective layer 18 exceeds 20,000 mm, the film formation time becomes long, which is disadvantageous in terms of cost. Accordingly, the thickness of the surface protective layer 18 is preferably in the range of 5,000 to 15,000 mm in view of the balance between charging ability, wear resistance, environmental resistance and film formation time.

(3) -2 Material and Hardness The material (photosensitive layer material) constituting the photosensitive layer 19 is not particularly limited, but in the present invention, it is preferably an amorphous silicon (a-Si) photosensitive member. The Vickers hardness of the outermost surface of the amorphous silicon photoreceptor is preferably 300 or less.
With this configuration, it is possible to effectively obtain a polishing effect on the surface of the photoreceptor by the external additive described above, and to maintain stable image characteristics over a long period of time. become.
Other suitable materials include inorganic materials such as a-SiC, a-SiO, and a-SiON. Among these materials, it is also preferable to use a-SiC because it has a particularly high resistance and higher charging ability, wear resistance, and environmental resistance can be obtained.

In addition, when a-SiC is used as the photosensitive material, it is preferable to use a material in which the ratio of Si and C (carbon) is within a predetermined range. As such a-SiC, a-Si _1-X C _X (value of X is less than 0.3 to ₁ ), preferably a-Si _1-X C _X (value of X is 0.5 to 0). .95 or less). A-SiC in which the ratio of Si to C is in the above range has a particularly high resistance of 10 ¹² to 10 ¹³ Ωcm, and the flow of latent image charges in the direction of the photoconductor on the surface of the photoconductor is small. Excellent maintenance ability and moisture resistance.
The photosensitive drum in the present invention is not particularly limited to the a-Si photosensitive drum, and various organic photosensitive (OPC) drums are used in place of the a-Si photosensitive drum 11 described above. Also good.

(3) -3 Surface potential The surface potential (charging potential) of the photosensitive drum 11 is in the range of +200 to +500 V, preferably in the range of +200 to +300 V. This is because when the surface potential is less than +200, the development electric field is insufficient and it is difficult to ensure the image density.
On the other hand, if the surface potential exceeds +500, depending on the film thickness of the photosensitive drum 11, the charging ability is insufficient, black spots on the image as a result of dielectric breakdown of the photosensitive layer are likely to occur, or the amount of ozone generated There is a problem that increases. In particular, when the film thickness of the photoconductor 11 is reduced, the charging ability of the photoconductor drum 11 tends to decrease correspondingly.
Accordingly, the surface potential of the surface of the photosensitive drum 11 is preferably within the above range from the viewpoint of the balance between developability and the charging ability of the photosensitive member.

(4) Manufacturing Method Next, a toner manufacturing method according to the present invention will be described.
First, in addition to the binder resin and magnetic powder described above, if necessary, waxes, colorants, charge control agents, and additives are premixed using a known method and then melted. A toner resin composition is prepared by kneading.
Here, the preliminary mixing treatment is preferably performed using, for example, a Henschel mixer, a ball mill, a super mixer, a dry blender, or the like, and the melt-kneading treatment is performed using a twin screw extruder, a single screw extruder, or the like. Is preferred.
Next, the obtained resin composition for toner is finely pulverized using a known method, and then subjected to powder classification to obtain toner particles.
Here, the fine pulverization process is preferably performed using, for example, an airflow pulverizer, and the classification process is preferably performed using, for example, an air classifier.
The toner thus obtained can be mixed with an external additive or the like using a known method, whereby a toner containing the external additive can be obtained. As the external treatment method, for example, a Henschel mixer can be used.

[Second Embodiment]
In the second embodiment, an image forming method using a magnetic one-component toner for developing an electrostatic latent image used in a jumping development method in which an electrostatic latent image formed on a latent image carrier is developed by a developer carrier. The electrostatic latent image is composed of toner particles containing at least a binder resin and magnetic powder, and the coarse particle distribution degree (S) of the toner particles satisfies the relational expression (1). An image forming method using a magnetic one-component toner for image development.
Hereinafter, the contents already described in the first embodiment are omitted, and the second embodiment focuses on the configuration of the image forming apparatus and the image forming method using the magnetic latent component developing toner described above as the second embodiment. explain.

(1) Image Forming Apparatus (1) -1 Basic Configuration When carrying out the image forming method of the second embodiment, the image forming apparatus can be suitably used for an image forming apparatus as shown in FIG.
This image forming apparatus includes a developing system based on a magnetic one-component jumping developing system, and uses a photosensitive drum 11 as a latent image carrier. Around the photosensitive drum 11, a scorotron charger 12, an exposure device 13, a developing device 14, a transfer roll 15, a cleaning blade (cleaning means) 16 and a static elimination lamp (erase means) 17 are arranged.

  In this image forming apparatus, the photosensitive drum 11 is charged by a scorotron charger 12 and exposed to an optical signal converted based on print data to form an electrostatic latent image on the photosensitive drum 11. On the other hand, the developing device 14 conveys toner by the rotation of a developing sleeve 14a (developer carrying member) that includes a magnet roller (not shown) that is disposed opposite to the photosensitive drum 11 and fixed inside. As the toner passes between the magnetic blade (not shown) and the developing sleeve 14a, a thin toner layer is formed on the surface of the developing sleeve 14a. Then, toner is supplied from the thin toner layer onto the photosensitive drum 11, and the electrostatic latent image formed on the photosensitive drum 11 is developed.

  The developed toner image is transferred to a transfer material (printing paper or the like) by the transfer roll 15. On the other hand, the toner (waste toner) remaining on the surface of the photosensitive drum 11 without being transferred to the transfer material is removed by the cleaning blade 16. The waste toner temporarily stays near the tip of the cleaning blade 16 and is gradually pushed out by the subsequent waste toner so as to move toward a conveying member such as a screw roller (not shown) to a waste toner container (not shown). Be transported. Afterimage charges are removed from the surface of the photosensitive drum 11 from which the waste toner has been removed by the charge eliminating lamp 17.

(1) -2 Development Sleeve The development sleeve 14a preferably has a ten-point average roughness Rz of 2.0 to 8.0 μm on the surface thereof. If the ten-point average roughness Rz is less than 2.0 μm, the image density may be lowered due to a decrease in toner conveyance force, and the toner layer on the developing sleeve 14a is disturbed, resulting in poor image quality. On the other hand, if Rz exceeds 8.0 μm, the amount of toner transport increases, layer disturbance occurs, image quality deteriorates, and leakage from the protrusion on the surface of the sleeve 14a to the photosensitive drum 11 occurs. There is a possibility that the image quality is deteriorated as a black spot. The ten-point average roughness Rz can be measured using, for example, a surface roughness measuring instrument “Surfcoder SE-30D” manufactured by Kosaka Laboratory.

  As a material used for the developing sleeve 14a, for example, aluminum, stainless steel (SUS), or the like can be used. When considering high durability, it is preferable to use SUS as a sleeve material, and for example, SUS303, SUS304, SUS305, SUS316, or the like can be used. In particular, it is more preferable to use SUS305 having weak magnetism and easy to process.

(1) -3 Charger The scorotron charger 12 includes a shield case, a corona wire, a grid, and the like, and the distance between the corona wire and the grid is preferably set to 5.3 to 6.3 mm. The distance between the grid and the photosensitive drum 11 is preferably 0.4 to 0.8 mm. When this distance is less than 0.4 mm, spark discharge may occur, and when it exceeds 0.8 mm, there is a problem that charging ability is lowered.

(1) -4 Transfer Roll The transfer roll 15 is in contact with the photosensitive drum 11, and is preferably rotated at a linear speed difference of 3 to 5% with respect to the photosensitive drum 11 when driven. If this linear velocity difference is less than 3%, the transferability may be reduced, and there is a possibility that hollowing out may occur. On the other hand, if the linear velocity difference exceeds 5%, the slip between the transfer roll 15 and the photosensitive drum 11 becomes large and jitter. May increase.

  The material used for the transfer roll 15 is preferably foamed EPDM (foamed body of ethylene-propylene-diene terpolymer). By using the foam in this manner, the toner contaminated in the case of a paper jam or the like enters the foamed bubbles, so that after the operation is resumed, the first paper can be prevented from being soiled. Further, by using a foam material, it is not necessary to clean the transfer roll 15, and the cost can be reduced. The rubber hardness of the transfer roll 15 is preferably 35 ° ± 5 ° (Asuka C: Japan Rubber Association standard “SRIS-0101C type”). If the rubber hardness is less than 30 °, transfer failure occurs. If the rubber hardness is greater than 40 °, the nip with the photosensitive drum 11 becomes small, and the conveying force decreases.

(1) -5 Cleaning Blade In this embodiment, the cleaning blade 16 is used as a cleaning means for the surface of the photosensitive drum 11. The cleaning blade 16 is disposed downstream of the transfer roll 15 in the rotation direction of the photosensitive drum 11, and the tip thereof is in contact with the photosensitive drum 11. Thereby, waste toner remaining on the surface of the photosensitive drum 11 without being transferred to the transfer material can be removed.

  The cleaning blade 16 is preferably an elastic blade having elasticity. Thereby, it is possible to prevent the surface of the photosensitive drum 11 from being damaged. Examples of the elastic material include urethane rubber, silicone rubber, and elastic resin. The cleaning blade 16 is obtained by forming an elastic material into a blade shape or attaching an elastic material to the tip of a blade of metal or the like.

(1) -6 Latent image carrier The latent image carrier used in the second embodiment can have the same contents as described in the first embodiment.

(2) Magnetic one-component toner for electrostatic latent image development The toner for electrostatic latent image development used in the second embodiment is for developing an electrostatic latent image formed on a latent image carrier with a developer carrier. A magnetic one-component toner for developing an electrostatic latent image used in a jumping development method, comprising toner particles containing at least a binder resin and magnetic powder, and a coarse powder distribution degree of the toner particles Any magnetic monocomponent toner for developing an electrostatic latent image characterized in that (S) satisfies the following relational expression (1) can be preferably used.
The details can be the same as those described in the first embodiment.

  Hereinafter, the present invention will be described in more detail based on examples. Needless to say, the following description exemplifies the present invention, and the scope of the present invention is not limited to the following description.

[Example 1]
(1) Production of toner particles First, 50 parts by weight of a binder resin, 43 parts by weight of magnetic powder, 3 parts by weight of a release agent and 4 parts by weight of a positive charge control agent are mixed with a Henschel mixer and melted with a twin screw extruder. After kneading, the mixture was cooled and coarsely pulverized with a hammer mill. This coarsely pulverized product is further finely pulverized by a mechanical pulverizer, and then the classification point of coarse and fine powders is determined by an airflow classifier [“Elbow Jet Classifier EJ-LABO type” manufactured by Nittetsu Mining Co., Ltd.]. Classification was performed by changing the angle of the classification zone to obtain magnetic toner particles.
Next, 1 part by weight of silica (manufactured by Nippon Aerosil Co., Ltd. [RA-200H]) and titanium oxide (manufactured by Titanium Industry Co., Ltd. [ST-100]) are added to 100 parts by weight of the obtained magnetic toner particles. 4 parts by weight were added, stirred and mixed with a Henschel mixer, and these external additives were adhered to the surface of the magnetic toner particles to prepare magnetic one-component toners shown in Table 1.

Moreover, as a binder resin, molecular weight (Mw) 47,000, molecular weight peaks 5,000 and 931,000, THF insoluble content 5%, molecular weight distribution (Mw / Mn) 29.0, glass transition point (Tg) 58 ° C. Styrene-acrylic copolymer and magnetic powder of 796 kA / m with a coercive force of 5.0 kA / m, saturation magnetization of 82 Am ² / kg, residual magnetization of 11 Am ² / kg, and number average particle diameter of 0.22 μm. A face-piece magnetic particle, a wax (“Sazol Wax H1” manufactured by Sazol) as a release agent, and a quaternary ammonium salt (“Bontron P-51” manufactured by Orient Chemical Co.) as a positive charge control agent, respectively. Using.

(2) Measuring method of particle size distribution Moreover, the particle size distribution was measured using "Cole Counter TA-II type" manufactured by Coulter Counter Co., Ltd., using an aperture diameter of 100 µm. Specifically, an interface for outputting volume average distribution and number average distribution and a personal computer were connected to the call counter TA-II type.
Next, a 1% sodium chloride aqueous solution was prepared using reagent grade sodium chloride as the electrolyte. 0.1 to 5 ml of a surfactant (“Maipet” main component: alkylbenzene sulfonate manufactured by Kao Co., Ltd.) as a dispersant is added to 100 to 150 ml of this electrolytic solution, and 0.5 to 50 mg of a measurement sample toner is further added. Suspended.
Next, the suspended electrolyte solution is subjected to a dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and then the particle size distribution of the toner is measured with the above-mentioned Cole Counter TA-II type using a 100 μm aperture. Then, the volume distribution and the number distribution were obtained.
Finally, from this volume distribution and number distribution, the volume average particle diameter (D ₅₀ ) of the toner, the volume% of coarse powder 2 μm or more larger than D ₅₀ and the number% of 4.0 μm or less were obtained. The obtained results are shown in Table 1.

(3) Measuring method of average circularity Further, as an average circularity, a flow type particle image analyzer (“FPIA-1000” manufactured by Sysmex Corporation) is used, and an average circularity of a particle group having an equivalent-circle diameter larger than 2 μm. Asked.

(4) Image characteristics and durability Further, as the image characteristics and durability, the obtained magnetic one-component toner is a page printer “FS-9500DN” (printing speed) manufactured by Kyocera Mita Co., Ltd. equipped with an amorphous silicon photoreceptor. : 50 sheets / min [A3 size], linear velocity: 230 mm / sec), and the following evaluation items were evaluated. As the material of the developing sleeve, SUS305 (10-point average roughness Rz 5.2 μm) was used.

(5) Evaluation (5) -1 Solid Image Density An image having an image evaluation pattern printed at the initial stage in a normal temperature and humidity environment (20 ° C., 65% RH) was used as an initial image. Thereafter, continuous printing was performed, and after 150,000 sheets and 300,000 sheets, an image evaluation pattern was printed again to obtain a post-endurance image.
Next, the obtained solid image was measured using a Macbeth reflection densitometer (RD914), and the density was measured at nine portions of the solid portion. The average value (ID) was determined as the solid image density according to the following criteria. And evaluated. The obtained results are shown in Table 2.
○: Solid image density is a value of 1.30 or more.
Δ: Solid image density is a value of 1.20 or more and less than 1.30.
X: Solid image density is a value less than 1.20.

(5) -2 Image Density Uniformity Further, regarding the image density uniformity, the density uniformity of the image evaluation pattern obtained by the solid image density evaluation was visually observed and evaluated according to the following criteria. The obtained results are shown in Table 2.
○: Density unevenness is not seen throughout.
Δ: Density unevenness is partially observed, but there is no practical problem.
X: Density unevenness is observed throughout.

(5) -3 Evaluation of background fog In addition, the fog of the image of the image evaluation pattern obtained by the solid image density evaluation was visually observed and evaluated according to the following criteria. The obtained results are shown in Table 2. ○: No fog is observed in the whole.
Δ: Fog is partially observed, but there is no practical problem.
X: Fog is seen throughout.

(5) -4 Evaluation of Particle Size Distribution Further, in the evaluation of the solid image density, the toner particle size distribution [volume average particle size ( D ₅₀ ), and the volume percentage of coarse powder larger than D ₅₀ by 2 μm or more] was measured. The obtained results are shown in Table 3.

(5) -5 Evaluation of the developing sleeve Further, regarding the relationship between the ten-point average roughness (Rz) of the developing sleeve surface and the uniformity of the image density, the density of the image evaluation pattern obtained by the solid image density evaluation is uniform. The properties were visually observed and evaluated according to the following criteria. Table 4 shows the obtained results.
○: Density unevenness is not seen throughout.
Δ: Density unevenness is partially observed, but there is no practical problem.
X: Density unevenness is observed throughout.

[Examples 2-6, Comparative Examples 1-3]
In the same manner as in Example 1, magnetic monocomponent toners having the particle size distribution and the average circularity shown in Table 1 were obtained. The obtained results are shown in Table 1. Next, the characteristics of this toner were evaluated in the same manner as in Example 1. The obtained results are shown in Tables 2 and 3.

[Examples 7 to 11]
For Examples 7 to 11, as shown in Table 4, toner particles were prepared and evaluated in the same manner as in Example 1 except that the ten-point average roughness (Rz) of the developing sleeve surface was changed. Table 4 shows the obtained results.

From the results shown in Table 2 and Table 3, Examples 1 to 6 have no problem with respect to image density, uniformity of image density, and background fogging, and have high resolution, good reproducibility of fine lines, and high-quality printing. Achieved.
This is presumably because the toner thin layer on the sleeve could be stably formed over a long period of time, in addition to having no adverse effect on the photosensitive drum. In addition, the durability evaluation result was good regardless of the amount of fine powder of 4.0 μm or less.
From this result, it can be seen that the coarse powder distribution and the image density maintainability are closely related. Further, although the coarse powder slightly increases due to the durability evaluation, it can be seen that this increase has little influence on the obtained image. On the other hand, in Comparative Examples 1 to 3, the toner charging characteristics on the sleeve tend to be poor, the toner thin layer gradually becomes thin, and as a result of a long-term test, image non-uniformity appears. In particular, the fogging was severe, the coarse powder distribution deviated from the appropriate development range, and the image density could not be maintained over a long period of time, so the durability evaluation was interrupted. One of the reasons for the suspension was that the fog level deteriorated along with the durability evaluation.
It can also be seen that the durability evaluation results are poor regardless of the amount of fine powder of 4.0 μm or less. Further, the accumulation of coarse powder in the developing device is obvious, and it can be seen that this adversely affects the physical properties. In addition, the result of the comparative example 1 and the comparative example 3 from which average circularity differs has shown the substantially equivalent result, and the influence of circularity was not seen.

It is a characteristic view which shows a particle size distribution and a cumulative frequency curve. It is a characteristic view which shows the relationship between coarse powder distribution degree and image density. It is a characteristic diagram showing the relationship between the D ₅₀ of the coarse powder distribution maps and volume. It is a characteristic view which shows the relationship between a coarse powder distribution degree and a cumulative frequency curve. It is sectional drawing which shows the laminated structure of a latent image carrier. 1 is a schematic diagram illustrating an example of an image forming apparatus according to the present invention.

Explanation of symbols

  11: Photosensitive drum, 12: Scorotron charger, 13: Exposed body, 14: Developer, 15: Transfer roll, 16: Cleaning blade, 17: Static elimination lamp, 18: Surface protective layer, 19: Photosensitive layer, 20: Carrier blocking layer, 21: conductive substrate

Claims (9)

A magnetic one-component toner for developing an electrostatic latent image used in a jumping development method in which an electrostatic latent image formed on a latent image carrier is developed by a developer carrier,
The electrostatic particles are composed of toner particles containing at least a binder resin and magnetic powder, and the coarse particle distribution (S) of the toner particles satisfies the following relational expression (1). Magnetic one-component toner for developing latent images.

  2. The magnetic one-component toner for developing an electrostatic latent image according to claim 1, wherein the coarse powder distribution degree (S) is set to a value within a range of 18 to 24 (volume% / [mu] m). An electrostatic latent image developing magnetic one-component toner according to claim 1 or 2 that is characterized in that a value within the range of the volume-based D ₅₀ of 5 to 10 ([mu] m). When the volume-based D ₅₀ before printing of the toner particles is D ₁ and the volume-based D ₅₀ after printing 150,000 sheets of A4 size paper is D ₂ , it is expressed by (D ₂ -D ₁ ). 4. The magnetic one-component toner for developing an electrostatic latent image according to claim 1, wherein the value is 1.0 (μm) or less.   5. The electrostatic capacity according to claim 1, wherein a ten-point average roughness (Rz) of the sleeve surface of the developer carrying member is set to a value within a range of 2 to 8 (μm). Magnetic one-component toner for developing latent images.   The electrostatic toner according to claim 1, wherein the toner particles contain toner particles having a particle diameter of 4.0 (μm) or less in a range of 30 (number%) or less. Magnetic one-component toner for developing latent images.   7. The magnetic one-component toner for developing an electrostatic latent image according to claim 1, wherein an average circularity of the toner particles is set to a value in a range of 0.92 to 0.96. .   The static image bearing member according to any one of claims 1 to 7, wherein the latent image bearing member is an amorphous silicon photosensitive member, and the Vickers hardness of the outermost surface of the amorphous silicon photosensitive member is set to 300 or less. Magnetic one-component toner for developing electrostatic latent images.   An image forming method using the magnetic one-component toner for developing an electrostatic latent image according to any one of claims 1 to 8.

Images