JP4621639B2 - Electrophotographic developer carrier, developer, image forming method and process cartridge - Google Patents

Description

  The present invention relates to a carrier for electrophotographic developer comprising a magnetic core material particle and a resin layer covering the particle surface, a developer, an image forming method, and a process cartridge.

The electrophotographic development method uses a mixture of a one-component development method mainly composed of toner, a glass bead, a magnetic carrier, or a coated carrier whose surface is coated with a resin and a toner. There are two-component development systems.
The two-component development method uses a carrier and has a wide frictional charging area with respect to the toner. Therefore, the two-component development method has a stable charging characteristic as compared with the one-component method, and is advantageous in maintaining high image quality over a long period of time. Further, since the toner supply amount capability to the development area is high, it is often used particularly for a high-speed machine.
In a digital electrophotographic system that forms an electrostatic latent image on a photosensitive member with a laser beam or the like and visualizes the latent image, a two-component development system that takes advantage of the above-described features is widely adopted.

  In recent years, there has been an increasing demand for further stabilization and higher image quality of electrophotographic images. In particular, attempts have been made to minimize and increase the density of the minimum latent image unit (1 dot) for the purpose of improving the image quality. To that end, it is important to faithfully develop the minimized latent image. It has become. Further, for stable image quality, it is an important issue to reduce variation in the charge amount distribution of the developer.

In order to faithfully develop a latent image, it is considered effective to reduce the particle size of the carrier, and the use of various small particle size carriers has been proposed.
Patent Document 1 proposes a magnetic carrier having an average particle size of less than 30 μm, which is composed of ferrite particles having a spinel structure. However, this is a carrier that is not resin-coated, and is used under a low development electric field, has a poor developing ability, and is not resin-coated, and therefore has a short life.

Further, in Patent Document 2, in an electrophotographic carrier having carrier particles, the carrier has a 50% average particle diameter (D50) of 15 to 45 μm, and the carrier contains 1 to 20 carrier particles smaller than 22 μm. Containing 3% or less of carrier particles smaller than 16 μm, 2 to 15% of carrier particles of 62 μm or more, and 2% or less of carrier particles of 88 μm or more, The carrier has a specific surface area S _{1 of the} carrier measured by an air permeation method and a specific surface area S _{2 of the} carrier calculated by the following formula 1 satisfying the condition of the following formula 2: Carriers are listed.
S ₂ = (6 / ρ · D ₅₀ ) × 10 ⁴ (ρ is the specific gravity of the carrier)
1.2 ≦ S ₁ / S ₂ ≦ 2.0

The following advantages can be obtained when this small particle size carrier is used.
[1] Since the surface area per unit volume is large, sufficient triboelectric charging can be given to each toner. For this reason, the generation of low charge amount toner and reverse charge amount toner is small, and scumming is less likely to occur. Further, the toner around the dots is free from dust and bleeding, and the dot reproducibility is good.
[2] Since the surface area per unit volume is large and scumming is less likely to occur, the average charge amount of the toner can be reduced and a sufficient image density can be obtained.
[3] Since the carrier has a small particle size, a dense magnetic brush can be formed. Further, since the fluidity of the ears is good, the traces of the ears hardly occur in the image.

  Further, when the conventional carrier is made to have a small particle size, the irregularities on the surface of the core material are shrunk, and when viewed macroscopically, the surface property is improved and becomes close to a smooth state. Since the carrier with a smooth core surface is uniformly dispersed in the two-component developer, the stress on the carrier particles can be dispersed, so that local film scraping caused by stress concentration can be suppressed. Durability tends to improve.

However, even if the stress is evenly distributed, the carrier coating layer is scraped. When the surface properties of the carrier core material are increased, the stress can be evenly distributed to slow down the film scraping, but if used over a long period of time, the entire surface of the particle will be scraped, resulting in a residual film. It becomes almost no particles. Particles with no coating remaining are extremely weak in the ability to impart charge to the toner and do not function as a carrier. In addition, since the electrical resistance is low in the portion where the core surface is exposed due to the coating scraping, carrier adhesion due to injection charging is likely to occur, but the particle front where the coating does not remain has low resistance. Therefore, the probability that charges are injected is high, and as a result, carrier adhesion tends to occur.
JP 58-144839 A Japanese Patent No. 3029180

  The present invention has been made in view of the above-described prior art. That is, even when used for a long period of time, there is little deterioration in charge imparting ability, and carrier adhesion hardly occurs, and image density and graininess (roughness). The main object is to provide a carrier and a developer that are excellent in color and have little soiling.

The present inventors have intensively studied to solve the above problems. The present invention has been made based on this.
The said subject is solved by following (1)-( 15 ) of this invention.
(1) The ratio Dw of the number average particle diameter Dp to the weight average particle diameter Dw, having a weight average particle diameter Dw of 22 μm or more and 32 μm or less, comprising magnetic core material particles and a binder resin layer covering the particle surface. / Dp is 1.00 <Dw / Dp <1.20, particle size x [μm] is in the range of 0 <x <20, the content of particles is 7% by weight or less, and particle size y [μm] is 0 < In the carrier for an electrophotographic developer having a content of particles in the range of y <36 in the range of 90 wt% to 100 wt%, the BET specific surface area of the core particles is in the range of 900 cm ² / g to 2000 cm ² / g. A carrier for an electrophotographic developer, characterized in that

(2) The carrier for an electrophotographic developer according to (1) above, wherein the BET specific surface area of the core material particles is in the range of 1100 cm ² / g to 2000 cm ² / g.
(3) The above (1) or (2), wherein the magnetization when a 1000 oersted magnetic field is applied to the electrophotographic developer carrier is 50 emu / g or more and 100 emu / g or less. Carrier for electrophotographic developer.
(4) The carrier for an electrophotographic developer according to any one of (1) to (3), wherein the core particle is Mn—Mg—Sr ferrite, Mn ferrite or magnetite. .
(5) The volume resistivity when an electric field of 500 V / mm is applied to the electrophotographic developer carrier is 1 × 10 ¹¹ Ω · cm or more and 1 × 10 ¹⁶ Ω · cm or less, The carrier for an electrophotographic developer according to any one of (1) to (4).

(6) The carrier for electrophotographic development according to any one of (1) to (5), wherein the binder resin layer contains hard fine particles.
(7) The carrier for electrophotographic development according to (6), wherein the hard fine particles are any one of Si, Ti, and Al.
(8) The electrophotographic image described in (6) or (7) above, wherein the content of the hard fine particles is in the range of 5% by weight or more and 70% by weight or less of the weight of the binder resin layer. Development carrier.
(9) The carrier for an electrophotographic developer according to any one of (1) to (8), wherein the binder resin layer contains an aminosilane coupling agent.

( 10 ) A carrier for an electrophotographic developer, wherein the carrier for an electrophotographic developer according to any one of (1) to ( 9 ) is further subjected to an aging treatment.
( 11 ) An electrophotographic developer comprising the electrophotographic developer carrier according to any one of (1) to ( 10 ) and an electrostatic latent image developer toner.
( 12 ) The developer for electrophotography as described in ( 11 ) above, wherein the toner for electrostatic latent image developer has a weight average particle diameter of 2 to 7 μm.
( 13 ) An image forming method using the electrophotographic developer described in ( 11 ) or ( 12 ).
(14) a developer according to (11) or (12), a developing sleeve, a photosensitive body, according to above, wherein the applying an alternating current and / or direct current voltage as the developing bias (13) Image forming method.
( 15 ) A process cartridge comprising at least a photosensitive member and a developing means, comprising the developer according to ( 11 ) or ( 12 ).

The present invention is described in further detail below.
The present inventors have intensively studied to solve the above problems. As a result, the carrier particles have a weight average particle diameter Dw as small as 22 to 32 μm, and the ratio Dw / Dp of the number average particle diameter Dp to the weight average particle diameter Dw ranges from 1 <Dw / Dp <1. The content of particles having a particle diameter smaller than 20, 20 μm is 0 to 7% by weight, the content of particles smaller than 36 μm is 90 to 100% by weight, and the BET specific surface area is 900 cm ² / g or more. By adopting a surface shape with many irregularities of 2000 cm ² / g or less, it is possible to improve the image quality such as the reduction of background contamination due to the reduction in particle size and the improvement of dot reproducibility, and the effect of efficiently suppressing carrier adhesion. However, the present inventors have found that the generation of particles that can be scraped away without leaving the resin coating layer due to the improvement in surface properties, which is a side effect of reducing the particle size, can be suppressed.

In the carrier of the present invention, the weight average particle diameter Dw is 22 to 32 μm, preferably 23 μm to 30 μm. When the weight average particle diameter Dw is smaller than the above range, the magnetic binding force applied to the particles becomes weak, so that it is difficult to prevent carrier adhesion even if the particle size distribution is sharpened. When the weight average particle diameter Dw is larger than the above range, carrier adhesion is less likely to occur, but the toner is not developed faithfully with respect to the latent image, so that the variation in dot diameter increases and the graininess decreases.
The carrier adhesion indicates a phenomenon in which a carrier adheres to an image portion or a background portion of an electrostatic latent image. Carrier adhesion is not preferable because it causes inconveniences such as damage to the photosensitive drum and the fixing roller. On the other hand, when the ratio Dw / Dp of the number average particle diameter Dp and the weight average particle diameter Dw is larger than 1.20, the ratio of the fine particles increases and the carrier adhesion resistance deteriorates.

The content of particles having a particle size of less than 20 μm in the carrier is preferably 7% by weight or less, more preferably 5% by weight or less, more preferably 3% by weight or less.
When the particles smaller than 20 μm are larger than 7% by weight, the particle size distribution is widened, and particles with small magnetization are present everywhere in the magnetic brush, and the carrier adhesion is rapidly deteriorated.
The content ratio of carrier particles having a particle size smaller than 20 μm is preferably 0.5% by weight or more. If it is 0.5% by weight or more, a desired value can be obtained without cost.
Further, in the carrier particles having a weight average particle diameter Dw of 22 to 32 μm, a carrier having a sharp particle size distribution in which particles smaller than 36 μm are 90% by weight or more, more preferably 92% by weight or more is magnetic for each carrier particle. The variation in binding force is reduced, and carrier adhesion resistance can be greatly improved.

In the present invention, the weight average particle diameter Dw referred to for the carrier, the carrier core material, and the toner is calculated based on the particle diameter distribution (relationship between the number frequency and the particle diameter) of the particles measured on the basis of the number.
The weight average particle diameter Dw in this case is represented by the following formula.
D _w = {1 / Σ (nD ³ )} × {Σ (nD ⁴ )} (1)
In the formula (1), D represents a representative particle size (μm) of particles present in each channel, and n represents the total number of particles present in each channel. The channel indicates a length for equally dividing the particle size range in the particle size distribution diagram. In the present invention, a length of 2 μm is adopted.

Further, as the representative particle size of the particles present in each channel, the lower limit value of the particle size stored in each channel was adopted.
In the present invention, the number average particle diameter Dp of the carrier and the carrier core material particles is calculated based on the particle diameter distribution of the particles measured on the basis of the number. The number average particle diameter Dp in this case is represented by the following formula.
D _p = (1 / ΣN) × (ΣnD) (2)
In formula (2), N represents the total number of particles measured, n represents the total number of particles present in each channel, and D represents the lower limit value of the particle size present in each channel (2 μm).

As a particle size analyzer for measuring the particle size distribution in the present invention, a Microtrac particle size analyzer (model HRA9320-X100: manufactured by Honeywell) was used.
The measurement conditions are as follows.
[1] Particle size range: 100-8 μm
[2] Channel length (channel width): 2 μm
[3] Number of channels: 46
[4] Refractive index: 2.42

The BET specific surface area of the carrier core material for an electrophotographic carrier of the present invention is 900 to 2000 cm ² / g, more preferably 1100 to 2000 cm ² / g. In the carrier core material satisfying the weight average particle size and particle size distribution, the carrier having a BET specific surface area in the above range has effective irregularities on the particle surface while having a small particle size and a sharp particle size distribution.
As described above, when the particle size is reduced, the surface properties of the core material particles are improved. The carrier (coating carrier) in which a resin coating layer is formed on core particles with high surface properties (coating carrier) is stable as a coating carrier because the entire outermost surface is a coating layer up to a certain degree of hazard. When the excess hazard is applied, the core material is exposed on the entire surface, and the function as a coat carrier cannot be achieved. Therefore, the present inventors have found that this problem can be solved by intentionally forming moderate irregularities on the surface of the core particle by setting the BET specific surface area within the above range. That is, by forming appropriate irregularities on the surface of the particle core material, there is a demerit that the coating layer of the convex portion is scraped off early, but the coating resin is not easily collided with other carrier particles in the concave portion. When the toner remains for a long time and is viewed at a microscopic level such as the toner particle size, the toner can perform sufficient friction / collision to generate charging with the coating resin of the recess. Therefore, when electrophotographic development is performed for a very long period of time, stable development can be maintained for a longer time than when core particles having a high surface property are used.

In the core particle having the particle size and particle size distribution of the present invention, when the BET specific surface area is smaller than 900 cm ² / g, the unevenness of the particle surface is small, so that the coating resin of the concave portion is easily scraped, and the above effect is sufficiently obtained. I can't do that. Particles having a BET specific surface area of more than 2000 cm ² / g are too uneven on the particle surface, and therefore friction / impact charging between the coating resin and the toner in the recesses is less likely to occur. Moreover, it is difficult to industrially produce particles having a BET specific surface area of more than 2000 cm ² / g.
The measurement of the BET surface area of the core particle for electrophotographic carrier is to determine the surface area according to the BET equation from the adsorption of nitrogen by the sample and the pressure change generated at that time.
This measurement was performed using a Micromeritics specific surface area automatic measuring device (TriStar 3000 / Surface Area and Porosity Analyzer).

The conventional small particle size carrier has a very big problem that the carrier easily adheres to it, and it has been a cause of generation of scratches on the photoreceptor and flaws on the fixing roller.
In particular, when the carrier has an average particle size of less than 32 μm, the roughness is greatly improved and the image quality is improved, but the carrier adhesion is very likely to occur and the problem is great. As a result of extensive studies by the present inventors on this issue, the following has been found.

で表わされる。ここで、Ｋはキャリアの質量であり、

（：キャリアの半径、：キャリアの真比重）
Ｍは単位質量当りの磁化である。また、

は、キャリアの存在する位置における磁界の強さ（Ｈ）の勾配である。
キャリアに対する磁気束縛力（Ｆｍ）は、キャリア半径（ｒ）の３乗に比例するから、キャリアの小粒径化に伴って、粒径の３乗の割合で急激に小さくなり、キャリア付着が非常に起き易くなる。 Carrier adhesion to the background portion of the image or the image portion is caused by adhesion in the form of carrier particles or a cut magnetic brush when Fm <Fc. (Fm: magnetic binding force, Fc: force causing carrier adhesion)
The force Fc that causes carrier adhesion is related to the development potential, background potential, centrifugal force applied to the carrier, carrier resistance, and developer charge amount. Therefore, in order to prevent carrier adhesion, it is effective to set each parameter so as to reduce Fc. However, since it is closely related to developing ability, background stain, toner scattering, etc., it should be changed greatly. Is currently difficult.
On the other hand, regarding the magnetic binding force Fm,

It is represented by Where K is the mass of the carrier,

(: Carrier radius, true carrier specific gravity)
M is the magnetization per unit mass. Also,

Is the gradient of the magnetic field strength (H) at the position where the carrier exists.
Since the magnetic binding force (Fm) on the carrier is proportional to the third power of the carrier radius (r), it rapidly decreases with the third power of the particle size as the carrier becomes smaller, and the carrier adhesion is extremely It is easy to get up.

  Therefore, the inventors have made a prototype of a sample in which the magnetization of the carrier is shaken and studied, and the magnetization when applying a magnetic field of 1000 oersted (Oe) is 50 emu / g or more, more preferably 70 emu / g or more. It has been found that carrier adhesion is improved. From the viewpoint of carrier adhesion, the upper limit value is not particularly limited, and usually about 150 emu / g is the upper limit. However, too strong magnetization may impair the smoothness of the magnetic brush. It is preferable that it is 100 emu / g or less.

  When carrier adhesion occurs, it may cause damage to the photosensitive drum and the fixing roller, resulting in a decrease in image quality. If the magnetization of the carrier core particles is smaller than the above range, a sufficiently strong magnetic binding force Fm cannot be obtained, and carrier adhesion tends to occur, which is not preferable in practice.

The magnetization can be measured as follows.
Using a BH tracer (BHU-60 / manufactured by Riken Denshi Co., Ltd.), 1.0 g of carrier core particles are packed in a cylindrical cell and set in an apparatus. The magnetic field is gradually increased and changed to 3000 oersted, then gradually reduced to zero, and then the opposite magnetic field is gradually increased to 3000 oersted. Further, after gradually reducing the magnetic field to zero, a magnetic field is applied in the same direction as the first. In this way, the BH curve is shown, and the 1000 oersted magnetization is calculated from the figure.

Examples of the core particles used in the carrier of the present invention, which are 50 emu / g or more when a 1000 oersted magnetic field is applied, include, for example, iron, cobalt and other ferromagnetic materials, magnetite, hematite, Li-based ferrite, Mn- Examples thereof include Zn-based ferrite, Cu—Zn-based ferrite, Ni—Zn-based ferrite, Ba-based ferrite, and Mn-based ferrite.
Ferrite is a sintered body generally represented by the following formula.
(MO) _x (NO) _y (Fe ₂ O ₃ ) _z
However, x + y + z = 100 mol%, and M and N are Ni, Cu, Zn, Li, Mg, Mn, Sr, Ca, etc., respectively, and the divalent metal oxide and the trivalent iron oxide Consists of a complete mixture.

  As the material of the core material particles constituting the carrier of the present invention, various conventionally known magnetic materials are used, but more preferable core material particles having a magnetization of 70 emu / g or more when a 1000 oersted magnetic field is applied. Examples thereof include magnetite, Mn—Mg—Sr ferrite, and Mn ferrite.

In the carrier of the present invention, the volume resistivity is preferably 1 × 10 ¹¹ to 1 × 10 ¹⁶ [Ω · cm], more preferably 1 × 10 ¹² to 1 × 10 when an electric field of 500 V / mm is applied. ¹⁴ [Ω · cm].
When the resistivity of the carrier is lower than 1 × 10 ¹¹ [Ω · cm], when the developing gap (the closest distance between the photosensitive member and the developing sleeve) becomes narrow, charge is induced in the carrier and the carrier adheres. It becomes easy to do. In particular, when the linear velocity of the photosensitive member and the linear velocity of the developing sleeve are large, a tendency of deterioration is observed. In addition, it is remarkable when an AC bias is applied. Usually, a color toner developing carrier is generally used having a low resistance in order to obtain a sufficient toner adhesion amount.
On the other hand, if it is larger than 1 × 10 ¹⁶ [Ω · cm], charges having a polarity opposite to that of the toner are likely to be accumulated, and the carrier is easily charged to cause carrier adhesion.

The carrier resistivity can be measured by the following method.
As shown in FIG. 1, a cell (11) made of a fluororesin container containing electrodes (12a) and (12b) having a distance between electrodes of 2 mm and a surface area of 2 × 4 cm is filled with a carrier (13), A DC voltage of 100 V is applied, and the DC resistance is measured with a high resistance meter 4329A (4329A + LJK 5HVLVWDQFH OHWHU; manufactured by Yokogawa Hewlett-Packard Co., Ltd.).

When filling the carrier resistance, fill the cell until it overflows into the cell, tapping the entire cell 20 times, and then using a non-magnetic horizontal spatula along the top edge of the cell. Scrape it flat in one operation. No pressure is required during filling.
The carrier resistivity can be adjusted by adjusting the resistance of the coating resin on the core particles and controlling the film thickness. Moreover, it is also possible to add conductive fine powder to the coating resin layer for carrier resistance adjustment. As the conductive fine particles, conductive ZnO, metal or metal oxide powder such as Al, SnO ₂ doped with SnO ₂ or the various elements that have been prepared in a variety of _{ways, TiB 2, ZnB 2, MoB} 2 , etc. Borides, silicon carbide, polyacetylene, polyparaphenylene, poly (para-phenylene sulfide), conductive polymers such as polypyrrole and polyaniline, carbon black such as furnace black, acetylene black and channel black.

For these conductive fine powders, use a dispersing machine that uses media such as a ball mill or bead mill, or a stirrer equipped with blades that rotate at high speed after the conductive fine powder has been added to the solvent or coating resin solution used for coating. By doing so, it can be uniformly dispersed in the coating resin solution.
For the purpose of reinforcing the resin coating layer (coating film) and making the coating film stronger, other hard fine particle components can be contained in the coating film. Among these, metal oxide and inorganic oxide particles are preferably used because they have a uniform particle size and high affinity with the resin component and show a remarkable reinforcing effect of the coating film. As such fine particles, conventionally known materials such as alumina, titanium oxide, zinc oxide and iron oxide can be used alone or in combination, and silica, titanium oxide and alumina are particularly effective.

The metal oxide particles are introduced into the coating by, for example, dissolving solubilized polyamide (N-alkoxyalkylated polyamide resin) in methanol while heating as necessary, and adding the metal oxide particles to the dissolved solution. Mix and disperse uniformly using a disperser such as a homogenizer. The obtained dispersion solution is mixed with a non-aqueous solvent solution of a condensable silicone resin having a silanol group (and / or a hydrolyzable group) separately prepared, and stirred with a homogenizer, and then a charge adjusting agent, a resistance adjusting agent, etc. Are mixed to prepare a coating solution, which is applied to the carrier core material.
The content of the hard fine particles contained in the resin coating layer (coating) is preferably 5% to 70%, more preferably 2 to 40%. The content of the hard fine particles is appropriately selected depending on the particle diameter and specific surface area of the fine particles to be used. However, if it is less than 5%, the wear resistance effect of the coating is hardly exhibited, and if it exceeds 70%, the particles are likely to be detached. .

The resin coating layer can obtain a carrier having higher resin film strength by containing an aminosilane coupling agent.
Examples of the aminosilane coupling agent used in the present invention include the following. The content is preferably 0.001 to 30% by weight.
H ₂ N (CH ₂ ) ₃ Si (OCH ₃ ) ₃ MW 179.3
H ₂ N (CH ₂ ) ₃ Si (OC ₂ H ₅ ) ₃ MW 221.4
H ₂ NCH ₂ CH ₂ CH ₂ Si (CH ₃ ) ₂ (OC ₂ H ₅ ) MW 161.3
H ₂ NCH ₂ CH ₂ CH ₂ Si (CH ₃ ) (OC ₂ H ₅ ) ₂ MW 191.3
H ₂ NCH ₂ CH ₂ NHCH ₂ Si (OCH ₃ ) ₃ MW 194.3
H ₂ NCH ₂ CH ₂ NHCH ₂ CH ₂ CH ₂ Si (CH ₃ ) (OCH ₃ ) ₂ MW 206.4
H ₂ NCH ₂ CH ₂ NHCH ₂ CH ₂ CH ₂ Si (OCH ₃ ) ₃ MW 224.4
(CH ₃ ) ₂ NCH ₂ CH ₂ CH ₂ Si (CH ₃ ) (OC ₂ H ₅ ) ₂ MW 219.4
(C ₄ H ₉ ) ₂ NC ₃ H ₆ Si (OCH ₃ ) ₃ MW 291.6

Since the resin layer has high charge imparting performance, a silicone resin has been preferably used conventionally. Also in the present invention, it is not always necessary to contain it, but it is possible and desirable to contain a silicone resin in the resin layer.
By including a resin component obtained by crosslinking a thermoplastic resin and a guanamine resin and / or a resin component obtained by crosslinking a thermoplastic resin and a melamine resin, an appropriate elasticity can be given to the resin layer. This makes it possible to absorb a strong impact on the coating resin due to friction with the toner or friction between the carriers generated during agitation for tribocharging the developer, suppressing toner spent on the carrier and preventing film abrasion. The effect of can be obtained.

  When the resin component in which a thermoplastic resin and a guanamine resin are cross-linked is contained in the resin layer, the elasticity of the coating film resin is optimal by setting the content range of the guanamine resin to 20 to 50% by weight. Become. By setting the content of the guanamine resin to 20% by weight or more, the crosslinking reaction between the thermoplastic resin and the guanamine resin becomes effective, and the effect of improving the wear resistance becomes higher. On the other hand, by setting it to 50% by weight or less, it becomes easy to prevent excessive curing of the resin layer due to excessive crosslinking reaction between the thermoplastic resin and the guanamine resin, and sufficient shock absorbing performance is obtained due to insufficient elasticity due to excessive curing of the resin layer. It becomes easy to avoid the situation that cannot be demonstrated.

  When a resin component obtained by crosslinking a thermoplastic resin and a melamine resin is contained in the resin layer, the elasticity of the resin of the coat film is optimal by setting the content range of the melamine resin to 20 to 50% by weight. Become. By setting the content of the melamine resin to 20% by weight or more, the crosslinking reaction between the thermoplastic resin and the melamine resin becomes effective, and the effect of improving the wear resistance becomes higher. On the other hand, by setting it to 50% by weight or less, it becomes easy to prevent excessive resin layer curing due to excessive crosslinking reaction between the thermoplastic resin and the melamine resin, and sufficient shock absorption performance is obtained due to insufficient elasticity due to excessive resin layer curing. It becomes easy to avoid the situation that cannot be demonstrated.

  A silicone resin or the like can be used as the thermoplastic resin used here, but a particularly preferable resin is an acrylic resin. Here, all acrylic resins can be used, but those having a Tg of 20 to 100 ° C., preferably 25 to 80 ° C. are particularly preferable. When Tg is less than 20 ° C., blocking occurs even at room temperature, which is not preferable because of poor storage stability. On the other hand, when Tg exceeds 100 ° C., the coating film resin is too hard and elasticity cannot be obtained, so that the impact cannot be absorbed and a sufficient improvement effect cannot be obtained.

  The resin layer preferably contains a charge control agent in order to set the charge amount of the developer to an optimum value. In particular, when either aromatic sulfonic acid or phosphoric acid is used as the charge control agent, the reaction with the guanamine resin becomes preferable, and the effect of controlling the charge is remarkable. The charge control agent is not limited to those listed here, and for example, carbon black, an acidic catalyst, or the like can be used alone or in combination. Carbon black that is generally used for carriers or toners can also be used. As the acidic catalyst, for example, Catalyst 4040 (manufactured by Mitsui Cytec) or the like can be used. As the acidic catalyst, those having a reactive group such as a fully alkylated type, a methylol group type, an imino group type, and a methylol / imino group type can be used, but are not limited thereto. These can also be used for the purpose of a resistance regulator.

The carrier of the present invention pulverizes or pulverizes a magnetic material, classifies the pulverized particles so as to obtain a predetermined particle size, and forms a resin film on the surface of the core material particles obtained by the classification. Can be obtained.
The classification includes wind classification, sieve classification (sieving), and the like. Particularly in sieve classification, clogging can be prevented by applying ultrasonic vibration to the wire mesh, and classification can be performed with high yield / efficiency.
The ultrasonic vibration that vibrates the wire mesh can be obtained by supplying a high-frequency current to the converter and converting it into ultrasonic vibration. The converter in this case uses a PZT vibrator. In order to vibrate the wire mesh by ultrasonic vibration, the ultrasonic vibration generated by the converter is transmitted to a resonance member fixed to the wire mesh. The resonance member to which the ultrasonic vibration is transmitted resonates by the ultrasonic vibration, and vibrates the wire mesh fixed to the resonance member. The frequency for vibrating the wire mesh is 20 to 50 kHz, preferably 30 to 40 kHz.

The shape of the resonance member may be any shape suitable for vibrating the wire mesh, and is usually a ring shape. The vibration direction for vibrating the wire mesh is preferably a vertical direction.
FIG. 2 is an explanatory structural diagram of a vibration sieve with an ultrasonic oscillator. In FIG. 2, (1) is a vibration sieve, (2) is a cylindrical container, (3) is a spring, (4) is a base (support), (5) is a wire mesh, (6) is a resonance ring, (7 ) Is a high-frequency current cable, (8) is a converter, and (9) is a ring frame.
In order to operate the vibration sieve with ultrasonic oscillator (circular sieve) shown in FIG. 2, high-frequency current is supplied to the converter (8) via the cable (7). The high-frequency current supplied to the converter (8) is converted into ultrasonic vibration. The ultrasonic vibration generated in the converter (8) vibrates the resonant ring (6) to which the converter (8) is fixed and the ring-shaped frame (9) connected thereto in the vertical direction. Due to the vibration of the resonance ring (6), the metal ring (5) fixed to the resonance ring (6) and the frame (9) vibrates in the vertical direction.

The carrier of the present invention is classified by classifying the pulverized particles of the magnetic material, or in the case of a core material such as ferrite or magnetite, at the stage of producing the primary granulated product before firing, and further firing and classification. Thus, a core material can be obtained. It can also be produced by forming a resin film on the surface of the core material and then classifying the resin-coated particles. The classification of the particles at each stage is preferably performed using the above-described vibration sieving machine equipped with an ultrasonic oscillator.
The carrier of the present invention can be used as it is, but by applying an appropriate stress as aging before use, it is possible to prevent a change due to initial shaving of the convex portion. Examples of the aging method include, but are not limited to, agitation with a carrier alone, agitation with toner, agitation with other abrasives, and application of stress by an instrument. Further, when aging is performed together with the toner, it can be used as a developer as it is.

The developer of the present invention can be produced by using the carrier of the present invention and a toner.
The toner used in the present invention preferably has a weight average particle size of 2.0 to 7.0 μm, more preferably 2.0 to 5.0 μm.
A toner particle size of 7 μm or less is preferable because it easily comes into contact with the coating resin in the carrier recess. Furthermore, when the weight average particle diameter is 5 μm or less, the graininess is improved and high image quality can be achieved. If the weight average particle size is less than 2 μm, background stains are likely to occur, and image quality stability over time also decreases.
The particle size of the toner can be measured using a Coulter counter (manufactured by Coulter Counter).

The ratio of the toner to the carrier is preferably 2 to 25 parts by weight, more preferably 3 to 20 parts by weight with respect to 100 parts by weight of the carrier, but is not limited thereto.
In the present invention, when the carrier of the present invention is used and the carrier coverage with the toner is 50%, the charge amount of the toner is 10 to 50 μC / g, and the weight average particle diameter of the toner is 3.5 to 7.5 μm. When the distance between the developing sleeve and the photoconductor is 0.4 mm or less and an AC voltage is applied as the developing bias, carrier adhesion is small and high image quality can be obtained.

  The toner used in the present invention contains a colorant, fine particles, a charge control agent, a release agent and the like in a binder resin mainly composed of a thermoplastic resin. Can be used. This toner can be produced by various toner production methods such as a polymerization method and a granulation method, and may be either indefinite or spherical. Either magnetic toner or non-magnetic toner can be used.

As the binder resin for the toner, the following can be used alone or in combination.
Styrene binder resins such as polystyrene, polyvinyltoluene and other styrene and substituted homopolymers, styrene-p-chlorostyrene copolymers, styrene-propylene copolymers, styrene-vinyltoluene copolymers, styrene-acrylic Acid methyl copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer , Styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer Coalescence, styrene-malein Copolymers, Styrene copolymers such as styrene-maleic acid ester copolymers; As acrylic binders, polymethyl methacrylate and polybutyl methacrylate may be mentioned; in addition, polyvinyl chloride, polyvinyl acetate, polyethylene, Polypropylene, polyester, polyurethane, epoxy resin, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenol resin, aliphatic or aliphatic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, paraffin wax, etc. Is mentioned.

In addition, the polyester resin can lower the melt viscosity while ensuring the stability during storage of the toner, as compared with the styrene or acrylic resin. Such a polyester resin can be obtained, for example, by a polycondensation reaction between an alcohol and a carboxylic acid.
Examples of the alcohol include diols such as polyethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-propylene glycol, neopentyl glycol, 1,4-butenediol, , 4-bis (hydroxymethyl) cyclohexane, bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylenated bisphenol A and other etherified bisphenols, which are saturated or unsaturated having 3 to 22 carbon atoms Divalent alcohol units substituted with hydrocarbon groups, other divalent alcohol units, sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaesitol, dipenta Esitol Tripentaerythritol, sucrose, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylol Mention may be made of trihydric or higher alcohol monomers such as ethane, trimethylolpropane and 1,3,5-trihydroxymethylbenzene.

  Examples of the carboxylic acid used to obtain the polyester resin include monocarboxylic acids such as palmitic acid, stearic acid, and oleic acid, maleic acid, fumaric acid, mesaconic acid, citraconic acid, terephthalic acid, cyclohexanedicarboxylic acid, Succinic acid, adipic acid, sebacic acid, malonic acid, divalent organic acid monomers in which these are substituted with a saturated or unsaturated hydrocarbon group having 3 to 22 carbon atoms, anhydrides of these acids, lower alkyl esters And dimer from linolenic acid, 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic 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- A trivalent or higher polyvalent carboxylic acid monomer such as methylenecarboxypropane, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid embol trimer acid, and anhydrides of these acids; Can be mentioned.

  Examples of the epoxy resins include polycondensates of bisphenol A and epichlorohydrin, such as Epomic R362, R364, R365, R366, R367, R369 (above, Mitsui Petrochemical Co., Ltd.), Epototo YD- Commercially available products such as 011, YD-012, YD-014, YD-904, YD-017 (above, manufactured by Tohto Kasei Co., Ltd.), Epcot 1002, 1004, 1007 (above, manufactured by Shell Chemical Co., Ltd.), etc. .

Examples of the colorant used in the present invention include carbon black, lamp black, iron black, ultramarine, nigrosine dye, aniline blue, phthalocyanine blue, Hansa Yellow G, rhodamine 6G lake, calco oil blue, chrome yellow, quinacridone, and benzidine yellow. Well-known dyes such as rose bengal, triallylmethane dyes, monoazo dyes, disazo dyes, dyes and pigments can be used alone or in combination.
It is also possible to make a magnetic toner by adding a magnetic material to the toner. As the magnetic material, a fine powder such as a ferromagnetic material such as iron or cobalt, magnetite, hematite, Li-based ferrite, Mn-Zn-based ferrite, Cu-Zn-based ferrite, Ni-Zn ferrite, or Ba ferrite can be used.

For the purpose of sufficiently controlling the triboelectric chargeability of the toner, so-called charge control agents such as metal complex salts of monoazo dyes, nitrohumic acid and salts thereof, salicylic acid, naphthoic salts, dicarboxylic acid Co, Cr, Fe, etc. Compounds, quaternary ammonium compounds, organic dyes and the like can be contained.
Furthermore, a release agent may be added to the toner used in the present invention as necessary.

As the release agent, low molecular weight polypropylene, low molecular weight polyethylene, carnauba wax, microcrystalline wax, jojoba wax, rice wax, montanic acid wax and the like can be used alone or in combination, but are not limited thereto. is not.
An external additive can be added to the toner. In order to obtain a good image, it is important to impart sufficient fluidity to the toner. As the external additive, in addition to inorganic fine particles, general hydrophobic treated inorganic fine particles can be used in combination, but the average particle diameter of the hydrophobized primary particles is 1 to 100 nm, more preferably 5 nm to 70 nm. It is preferable to contain inorganic fine particles. Moreover, it is preferable that the specific surface area by BET method of inorganic fine particles is 20-500 m < ² > / g.

Any known one can be used as long as the conditions are satisfied. Examples include silica fine particles, hydrophobic silica, fatty acid metal salts (such as zinc stearate and aluminum stearate), and metal oxides (such as titania, alumina, tin oxide, and antimony oxide). Good.
Particularly suitable additives include hydrophobized silica, titania, titanium oxide, and alumina fine particles. As silica fine particles, HDK H 2000, HDK H 2000/4, HDK H 2050EP, HVK21, HDK H 1303 (above, manufactured by Clariant Japan), R972, R974, RX200, RY200, R202, R805, R812 (above, Japan) Aerosil). Further, as titania fine particles, P-25 (manufactured by Nippon Aerosil Co., Ltd.), STT-30, STT-65C-S (above, manufactured by Titanium Industry Co., Ltd.), TAF-140 (manufactured by Fuji Titanium Industry Co., Ltd.), MT-150W, Examples include MT-500B, MT-600B, MT-150A (manufactured by Teica). In particular, as hydrophobized titanium oxide fine particles, T-805 (manufactured by Nippon Aerosil Co., Ltd.), STT-30A, STT-65S-S (manufactured by Titanium Industry Co., Ltd.), TAF-500T, TAF-1500T (and above) , Manufactured by Fuji Titanium Industry Co., Ltd.), MT-100S, MT-100T (manufactured by Teika), IT-S (produced by Ishihara Sangyo Co., Ltd.), and the like.

  Hydrophobized silica fine particles, titania fine particles, alumina fine particles and other inorganic fine particles are obtained by treating hydrophilic fine particles with a silane coupling agent such as methyltrimethoxysilane, methyltriethoxysilane, or octyltrimethoxysilane. be able to.

The image forming method of the present invention is a method of developing a latent image using the developer of the present invention. In this method, when a voltage obtained by superimposing an AC voltage on a DC voltage is applied as a developing bias applied from the outside, a sufficient image density can be obtained. In particular, the granularity of highlights is improved.
Furthermore, when only a DC voltage is applied as a developing bias, carrier adhesion and edge effects are greatly improved, and the margin against dirt is increased, so that the toner coverage on the carrier can be increased, and toner charging The amount and the developing bias can be lowered, and the image density can be increased.

  The process cartridge of the present invention at least integrally supports a photosensitive member and a developing device that develops the electrostatic latent image formed on the surface of the photosensitive member using the developer of the present invention, and is detachable from the image forming apparatus main body. It is. The process cartridge can further integrally support means such as a charging brush for charging the surface of the photoreceptor and a blade for wiping off the developer remaining on the surface of the photoreceptor.

Next, examples of the image forming method and the image forming apparatus of the present invention will be described in detail with reference to the drawings. However, these examples are for explaining the present invention and are not intended to limit the present invention. Absent.
FIG. 3 is a diagram showing an example of the developing device used in the present invention, and modifications as will be described later also belong to the category of the present invention.
In FIG. 3, the developing device disposed opposite to the photosensitive member (20) which is a latent image carrier has a developing sleeve (41) as a developer carrier, a developer containing member (42), and a regulating member. The doctor blade (43), the support case (44), and the like.

A toner hopper (45) serving as a toner accommodating portion for accommodating the toner (21) is joined to the support case (44) having an opening on the photosensitive member (20) side. In the developer accommodating portion (46) for accommodating the developer composed of the toner (21) and the carrier (23) adjacent to the toner hopper (45), the toner (21) and the carrier (23) are agitated. A developer stirring mechanism (47) is provided for imparting friction / release charges to (21).
Inside the toner hopper (45), a toner agitator (48) and a toner replenishing mechanism (49) are disposed as toner supplying means rotated by a driving means (not shown). The toner agitator (48) and the toner replenishing mechanism (49) send out the toner (21) in the toner hopper (45) toward the developer container (46) while stirring.

A developing sleeve (41) is disposed in the space between the photoconductor (20) and the toner hopper (45). The developing sleeve (41) that is driven to rotate in the direction of the arrow by a driving means (not shown) is disposed inside the developing sleeve (41) so as to be in a relative position with respect to the developing device in order to form a magnetic brush by the carrier (23). And a magnet (not shown) as magnetic field generating means.
A doctor blade (43) is integrally attached to the developer accommodating member (42) on the side facing the side attached to the support case (44). In this example, the doctor blade (43) is disposed in a state where a certain gap is maintained between the tip thereof and the outer peripheral surface of the developing sleeve (41).

  Using such a device without limitation, the image forming method of the present invention is performed as follows. That is, with the above configuration, the toner (21) sent out from the toner hopper (45) by the toner agitator (48) and the toner replenishing mechanism (49) is transported to the developer accommodating portion (46), where the developer agitation is performed. By stirring by the mechanism (47), a desired friction / peeling charge is imparted, and is carried on the developing sleeve (41) as a developer together with the carrier (23) and faces the outer peripheral surface of the photoreceptor (20). The toner image is formed on the photoconductor (20) by being electrostatically coupled to the electrostatic latent image formed on the photoconductor (20) only by being conveyed to the position.

  FIG. 4 is a diagram illustrating an example of an image forming apparatus having the developing device of FIG. Around the drum-shaped photoreceptor (20), a charging member (32), an image exposure system (33), a developing device (40), a transfer device (50), a cleaning device (60), and a static elimination lamp (70) are arranged. In this example, the surface of the charging member (32) is in a non-contact state with a surface of about 0.2 mm from the surface of the photoreceptor (20), and the photoreceptor is driven by the charging member (32). When charging (20), charging unevenness is reduced by charging the photosensitive member (20) with an electric field in which an alternating current component is superimposed on a direct current component by a voltage applying means (not shown) on the charging member (32). It is possible and effective. The image forming method including the developing method is performed by the following operation.

  A series of image forming processes can be described as a negative-positive process. A photoconductor (20) represented by a photoconductor (OPC) having an organic photoconductive layer is neutralized by a static elimination lamp (70) and is uniformly negatively charged by a charging member (32) such as a charging charger or a charging roller. A latent image is formed by laser light emitted from an image exposure system (33) such as a laser optical system (in this example, the absolute value of the exposed portion potential is lower than the absolute value of the non-exposed portion potential). Is called.

  Laser light is emitted from a semiconductor laser and scans the surface of the photoconductor (20) in the direction of the rotation axis of the photoconductor (20) by a polygonal polygonal mirror (polygon) that rotates at high speed. The latent image formed in this way is developed with a developer composed of a mixture of toner and carrier supplied on a developing sleeve (41) which is a developer carrying member in the developing device (40), and the toner image is developed. It is formed. At the time of developing the latent image, a DC voltage of an appropriate magnitude or an AC voltage is applied to the developing sleeve (41) from a voltage application mechanism (not shown) between the exposed portion and the non-exposed portion of the photosensitive member (20). A developing bias with a superimposed voltage is applied.

On the other hand, a transfer medium (for example, paper) (80) is fed from a paper feed mechanism (not shown), and is synchronized with the leading edge of the image by a pair of upper and lower registration rollers (not shown), so that the photoconductor (20). And the transfer device (50) to transfer the toner image. At this time, it is preferable that a potential having a polarity opposite to the polarity of toner charging is applied to the transfer device (50) as a transfer bias. Thereafter, the transfer medium (80) is separated from the photoreceptor (20) to obtain a transfer image.
The toner remaining on the photoconductor (20) is collected in a toner collection chamber (62) in the cleaning device (60) by a cleaning blade (61) as a cleaning member.
The collected toner may be transported to the developer container (46) and / or the toner hopper (45) by a toner recycling means (not shown) and reused.

The image forming apparatus may be a device in which a plurality of the developing devices described above are arranged, and the toner images are sequentially transferred onto the transfer medium, then sent to the fixing mechanism, and the toner is fixed by heat or the like. An apparatus may be used in which a plurality of toner images are transferred to a transfer medium and transferred together onto a transfer medium and fixed in the same manner.
FIG. 5 shows another example of the image forming apparatus used in the present invention. The photosensitive member (20) has at least a photosensitive layer provided on a conductive support, is driven by driving rollers (24a) and (24b), is charged by a charging member (32), and is charged by an image exposure system (33). Transfer using a transfer device (50) having image exposure, development by a developing device (40), exposure before cleaning by an exposure light source (26) before cleaning, cleaning by a brush-like cleaning means (64) and a cleaning blade (61), The charge removal by the charge removal lamp (70) is repeated. In FIG. 5, the pre-cleaning exposure is performed on the photoconductor (20) (in this case, the support is translucent in this case) from the support side.

  FIG. 6 shows an example of the process cartridge of the present invention. In this process cartridge, a photosensitive member (20), a proximity brush-shaped charging member (32), a developing device (40) containing the developer of the present invention, and a cleaning device having at least a cleaning blade (61) are integrated. And is detachable from the main body of the image forming apparatus. In the present invention, the above-described components can be integrally combined as a process cartridge, and the process cartridge can be configured to be detachable from a main body of an image forming apparatus such as a copying machine or a printer.

  To provide a carrier and a developer that have little deterioration in charge imparting ability even after long-term use, are less likely to cause carrier adhesion, have good image density and granularity (roughness), and have little background contamination. In addition, an excellent image forming method can be provided.

Hereinafter, the present invention will be described with reference to examples and comparative examples. In addition, this invention is not limited to the Example illustrated here. In the following, “parts” represents parts by weight.
<Production example>
(Example of toner production)
(Production Example 1)
Polyester resin 100 parts Quinacridone-based magenta pigment 3.5 parts Fluorine-containing quaternary ammonium salt 3.5 parts The above components are thoroughly mixed in a blender, melt-kneaded in a twin-screw extruder, and allowed to cool. Coarsely pulverize with a cutter mill, then finely pulverize with a jet airflow fine pulverizer, and further classified with an air classifier to obtain toner base particles having a weight average particle diameter of 6.8 μm and a true specific gravity of 1.22 g / cm ^3. It was.
Further, 0.8 parts of hydrophobic silica fine particles (R972: manufactured by Nippon Aerosil Co., Ltd.) were added to 100 parts of the toner base particles, and mixed with a Henschel mixer to obtain toner A.

(Production Example 2)
Toner B was obtained in the same manner as in Production Example 1 except that the pulverization and classification steps were adjusted so that the weight average particle diameter was 7.2 μm.
(Production Example 3)
Toner C was obtained in the same manner as in Production Example 1 except that the pulverization and classification steps were adjusted so that the weight average particle size was 2.2 μm.
(Production Example 4)
Toner D was obtained in the same manner as in Production Example 1 except that the pulverization and classification steps were adjusted so that the weight average particle diameter was 1.9 μm.

(Example of carrier production)
(Production Example 1)
Silicone resin solution [solid content 20wt%] 75 parts
(SR2411: Made by Toray Dow Corning)
Acrylic resin solvent [solid content 50wt%] 10 parts
(Hitaroid 3001: made by Hitachi Chemical Co., Ltd.)
Toluene 100 parts Butyl cellosolve 100 parts The above materials were dispersed with a homomixer for 10 minutes to prepare a resin layer forming solution. Using the core material a shown in Table 1 as the carrier core material, 30 g / min of the above resin solution on the surface of the core material at a temperature of 55 ° C. in an atmosphere of 55 ° C. using a Spira coater (Okada Seiko Co., Ltd.). It was applied in a ratio and dried. The layer thickness was adjusted depending on the liquid amount. The obtained carrier was baked by standing in an electric furnace at 150 ° C. for 1 hour, and after cooling, it was crushed using a sieve having an opening of 100 μm to obtain Carrier I shown in Table 2.

(Production Example 2)
A carrier II shown in Table 2 was obtained in the same manner as in Production Example 1 except that the core material b shown in Table 1 was used as the carrier core material.
(Production Example 3)
A carrier III shown in Table 2 was obtained in the same manner as in Production Example 1 except that the core material c shown in Table 1 was used as the carrier core material.
(Production Example 4)
A carrier IV shown in Table 2 was obtained in the same manner as in Production Example 1 except that the core material d shown in Table 1 was used as the carrier core material.
(Production Example 5)
A carrier V shown in Table 2 was obtained in the same manner as in Production Example 1 except that the core material e shown in Table 1 was used as the carrier core material.

(Production Example 6)
A carrier VI shown in Table 2 was obtained in the same manner as in Production Example 1 except that the core material f shown in Table 1 was used as the carrier core material.
(Production Example 7)
A carrier VII in Table 2 was obtained in exactly the same manner as in Production Example 1 except that the core material g in Table 1 was used as the carrier core material.
(Production Example 8)
A carrier VIII in Table 2 was obtained in the same manner as in Production Example 1 except that the core material h in Table 1 was used as the carrier core material.
(Production Example 9)
A carrier IX shown in Table 2 was obtained in the same manner as in Production Example 1 except that the core material i shown in Table 1 was used as the carrier core material.
(Production Example 10)
A carrier X shown in Table 2 was obtained in the same manner as in Production Example 1 except that the core material j shown in Table 1 was used as the carrier core material.

(Production Example 11)
A carrier XI shown in Table 2 was obtained in the same manner as in Production Example 1 except that the core material k shown in Table 1 was used as the carrier core material.
(Production Example 12)
A carrier XII shown in Table 2 was obtained in the same manner as in Production Example 1 except that the core material 1 shown in Table 1 was used as the carrier core material.
(Production Example 13)
A carrier XIII shown in Table 2 was obtained in the same manner as in Production Example 1 except that the core material m shown in Table 1 was used as the carrier core material.
(Production Example 14)
A carrier XIV shown in Table 2 was obtained in the same manner as in Production Example 1 except that the core material n shown in Table 1 was used as the carrier core material.
(Production Example 15)
A carrier XV shown in Table 2 was obtained in the same manner as in Production Example 1 except that the core material o shown in Table 1 was used as the carrier core material.
(Production Example 16)
A carrier XVI shown in Table 2 was obtained in the same manner as in Production Example 1 except that the core material p shown in Table 1 was used as the carrier core material.

(Production Example 17)
Silicone resin solution [solid content 20wt%] 75 parts
(SR2411: Made by Toray Dow Corning)
Acrylic resin solvent [solid content 50wt%] 10 parts
(Hitaroid 3001: made by Hitachi Chemical Co., Ltd.)
Charge control agent (carbon black) 2 parts Toluene 100 parts Butyl cellosolve 100 parts The carrier XVII shown in Table 2 was obtained in exactly the same manner as in Production Example 15 except that the above-mentioned materials were used as the resin layer forming liquid.

(Production Example 18)
Silicone resin solution [solid content 20wt%] 75 parts
(SR2411: Made by Toray Dow Corning)
Acrylic resin solvent [solid content 50wt%] 10 parts
(Hitaroid 3001: made by Hitachi Chemical Co., Ltd.)
Charge control agent (carbon black) 10 parts Toluene 100 parts Butyl cellosolve 100 parts Carrier XVIII in Table 2 was obtained in exactly the same manner as in Production Example 15 except that the above-mentioned materials were used as the resin layer forming liquid.
(Production Example 19)
Silicone resin solution [solid content 20wt%] 75 parts
(SR2411: Made by Toray Dow Corning)
Acrylic resin solvent [solid content 50wt%] 10 parts
(Hitaroid 3001: made by Hitachi Chemical Co., Ltd.)
Charge control agent (carbon black) 12 parts Toluene 100 parts Butyl cellosolve 100 parts The carrier XIX shown in Table 2 was obtained in exactly the same manner as in Production Example 15 except that the above-mentioned materials were used for the resin layer forming liquid.

(Production Example 20)
Silicone resin solution [solid content 20wt%] 75 parts
(SR2411: Made by Toray Dow Corning)
Acrylic resin solvent [solid content 50wt%] 10 parts
(Hitaroid 3001: made by Hitachi Chemical Co., Ltd.)
Charge control agent (carbon black) 2 parts Zinc oxide fine particles 15 parts Toluene 100 parts Butyl cellosolve 100 parts The carrier XX in Table 2 is exactly the same as in Production Example 15 except that the above materials were used for the resin layer forming liquid. Got.
(Production Example 21)
Silicone resin solution [solid content 20wt%] 75 parts
(SR2411: Made by Toray Dow Corning)
Acrylic resin solvent [solid content 50wt%] 10 parts
(Hitaroid 3001: made by Hitachi Chemical Co., Ltd.)
Charge control agent (carbon black) 2 parts Silica particles 15 parts Toluene 100 parts Butyl cellosolve 100 parts The carrier XXI in Table 2 was prepared in the same manner as in Production Example 15 except that the above materials were used for the resin layer forming liquid. Obtained.

(Production Example 22)
Silicone resin solution [solid content 20wt%] 75 parts
(SR2411: Made by Toray Dow Corning)
Acrylic resin solvent [solid content 50wt%] 10 parts
(Hitaroid 3001: made by Hitachi Chemical Co., Ltd.)
Charge control agent (carbon black) 2 parts Titania particles 15 parts Toluene 100 parts Butyl cellosolve 100 parts The carrier XXII in Table 2 was prepared in exactly the same manner as in Production Example 15 except that the above-mentioned materials were used for the resin layer forming liquid. Obtained.
(Production Example 23)
Silicone resin solution [solid content 20wt%] 75 parts
(SR2411: Made by Toray Dow Corning)
Acrylic resin solvent [solid content 50wt%] 10 parts
(Hitaroid 3001: made by Hitachi Chemical Co., Ltd.)
Charge control agent (carbon black) 2 parts Alumina particles 15 parts Toluene 100 parts Butyl cellosolve 100 parts The carrier XXIII in Table 2 was prepared in exactly the same manner as in Production Example 15 except that the above materials were used for the resin layer forming liquid. Obtained.

(Production Example 24)
Silicone resin solution [solid content 20wt%] 75 parts
(SR2411: Made by Toray Dow Corning)
Acrylic resin solvent [solid content 50wt%] 10 parts
(Hitaroid 3001: made by Hitachi Chemical Co., Ltd.)
Charge control agent (carbon black) 2 parts Alumina particles 4 parts Toluene 100 parts Butyl cellosolve 100 parts Except for using the above-mentioned materials as the resin layer forming liquid, the carrier XXIV in Table 2 was prepared in the same manner as in Production Example 15. Obtained.

(Production Example 25)
Silicone resin solution [solid content 20wt%] 75 parts
(SR2411: Made by Toray Dow Corning)
Acrylic resin solvent [solid content 50wt%] 10 parts
(Hitaroid 3001: made by Hitachi Chemical Co., Ltd.)
Charge control agent (carbon black) 2 parts Alumina particles 5 parts Toluene 100 parts Butyl cellosolve 100 parts The carrier XXV shown in Table 2 is used in exactly the same manner as in Production Example 15 except that the above materials are used for the resin layer forming liquid. Obtained.

(Production Example 26)
Silicone resin solution [solid content 20wt%] 75 parts
(SR2411: Made by Toray Dow Corning)
Acrylic resin solvent [solid content 50wt%] 10 parts
(Hitaroid 3001: made by Hitachi Chemical Co., Ltd.)
Charge control agent (carbon black) 2 parts Alumina particles 70 parts Toluene 100 parts Butyl cellosolve 100 parts Except for using the above-mentioned materials as the resin layer forming liquid, the carrier XXVI in Table 2 was prepared in the same manner as in Production Example 15. Obtained.
(Production Example 27)
Silicone resin solution [solid content 20wt%] 75 parts
(SR2411: Made by Toray Dow Corning)
Acrylic resin solvent [solid content 50wt%] 10 parts
(Hitaroid 3001: made by Hitachi Chemical Co., Ltd.)
Charge control agent (carbon black) 2 parts Alumina particles 75 parts Toluene 100 parts Butyl cellosolve 100 parts Except for using the above-mentioned materials as the resin layer forming liquid, the carrier XXVII in Table 2 was prepared in the same manner as in Production Example 15. Obtained.

(Production Example 28)
Silicone resin solution [solid content 20wt%] 75 parts
(SR2411: Made by Toray Dow Corning)
Acrylic resin solvent [solid content 50wt%] 10 parts
(Hitaroid 3001: made by Hitachi Chemical Co., Ltd.)
Charge control agent (carbon black) 2 parts Aminosilane coupling agent (H ₂ N (CH ₂ ) ₃ Si (OCH ₃ ) ₃ ) 1.5 parts Alumina particles 15 parts Toluene 100 parts Butyl cellosolve 100 parts Resin layer forming material Carrier XXVIII in Table 2 was obtained in the same manner as in Production Example 15 except that the above was used.
(Production Example 29)
Silicone resin solution [solid content 20wt%] 75 parts
(SR2411: Made by Toray Dow Corning)
Guanamin resin solvent [solid content 77wt%] 6.5 parts
(My coat 106: made by Mitsui Cytec)
Charge control agent (carbon black) 2 parts Aminosilane coupling agent (H ₂ N (CH ₂ ) ₃ Si (OCH ₃ ) ₃ ) 1.5 parts Alumina particles 15 parts Toluene 100 parts Butyl cellosolve 100 parts Resin layer forming material Carrier XXIX in Table 2 was obtained in the same manner as in Production Example 15 except that the above was used.

(Production Example 30)
Silicone resin solution [solid content 20wt%] 75 parts
(SR2411: Made by Toray Dow Corning)
Melamine resin solvent [volatile content 0wt%] 5 parts
(Cymel 303: made by Mitsui Sydec)
Charge control agent (carbon black) 2 parts Aminosilane coupling agent (H ₂ N (CH ₂ ) ₃ Si (OCH ₃ ) ₃ ) 1.5 parts Alumina particles 15 parts Toluene 100 parts Butyl cellosolve 100 parts Resin layer forming material A carrier XXX shown in Table 2 was obtained in the same manner as in Production Example 15 except that the above was used.

(Production Example 31)
50 parts of silicone resin solution [solid content 20wt%]
(SR2411: Made by Toray Dow Corning)
Acrylic resin solvent [solid content 50wt%] 10 parts
(Hitaroid 3001: made by Hitachi Chemical Co., Ltd.)
Melamine resin solvent [volatile content 0wt%] 5 parts
(Cymel 303: made by Mitsui Sydec)
Charge control agent (carbon black) 2 parts Aminosilane coupling agent (H ₂ N (CH ₂ ) ₃ Si (OCH ₃ ) ₃ ) 1.5 parts Alumina fine particles 15 parts Toluene 100 parts Butyl cellosolve 100 parts Resin layer forming material Carrier XXXI shown in Table 2 was obtained in the same manner as in Production Example 15 except that the above was used.
(Production Example 32)
Using 7 parts of toner a obtained in Toner Production Example 1 and 93 parts of Carrier XXXI obtained in Carrier Production Example 31, the mixture was stirred and mixed for 10 minutes with a mixer. Thereafter, the toner was recovered and the toner was removed by airflow classification to obtain a carrier XXXII shown in Table 2.

Example 1
Using 7 parts of the toner obtained in Toner Production Example 1 and 93 parts of Carrier I obtained in Carrier Production Example 1, a developer was prepared by stirring and mixing with a mixer for 10 minutes.
An image was formed using the obtained developer, and tests were conducted on image quality (background stain, graininess), carrier adhesion margin, background stain after 50k run, and background stain after 100k run.
The image was created using Imagio Color 4000 (Ricoh Digital Color Copier / Printer Combined Machine) under the following development conditions.
Development gap (photosensitive member-developing sleeve): 0.35 mm
Doctor gap (Development sleeve-Doctor): 0.65mm
Photoconductor linear velocity 200mm / sec
(Developing sleeve linear velocity / photosensitive member linear velocity) = 1.80
Writing density: 600 dpi
Charging potential (Vd): -600V
Potential after exposure of the portion corresponding to the image portion (solid document) (V1): -150V
Development bias: DC component -500 V / AC bias component: 2 KHZ, -100 V to -900 V, 50% duty

The test methods employed in the following image forming examples are as follows.
(1) Background stain: The stain on the background portion of the image was visually evaluated. The symbols in the table are
◎: Very good ○: Good □: No problem △: Usable ×: Defect (× is an unacceptable level)
It was.
(2) Uniformity of highlight portion: The granularity (brightness range: 50 to 80) defined by the following formula was measured on transfer paper, and the numerical value was replaced with a rank as shown below.
Granularity = exp (aL + b) ∫ (WS (f)) 1/2 VTF (f) df
L: Average brightness
f: Spatial frequency (cycle / mm)
WS (f): Power spectrum of brightness fluctuation
VTF (f): Visual spatial frequency characteristics
a, b: The coefficient rank is as follows.
◎ (very good): 0 or more and less than 0.1 ○ (good): 0.1 or more and less than 0.2 △ (available): 0.2 or more and less than 0.3 × (defect (unacceptable level)): 0.3 or more

(3) Carrier adhesion: If carrier adhesion occurs, it may cause damage to the photosensitive drum and the fixing roller, leading to a reduction in image quality. Even if carrier adhesion occurs, only a part of the carrier is transferred to the paper, and therefore, evaluation was performed by transferring it from the photosensitive drum with an adhesive tape.
Create an image pattern of 2 dot lines (100 lpi / inch) in the sub-scanning direction, apply -400 V as a DC bias component, develop, and the number of carriers attached between the 2 dot line lines (area 100 cm ² ) The evaluation was performed by transferring with an adhesive tape and visually observing the number.
The symbols in Table 3 are as follows.
◎: Very good ○: Good □: No problem △: Usable ×: Defect (unacceptable level)

(4) Soil after 50k run and 100k run:
A running evaluation of 50,000 sheets and 100,000 sheets was performed using a character image chart with an image area ratio of 6% while supplying magenta toner a used for initial image printing. The background of the background under the above development conditions was evaluated for rank according to the same criteria as (1).
These evaluation results are shown in Table 3.
(Examples 2-28, Comparative Examples 1-7)
The tests were carried out using the carriers II to XXXII instead of the carrier I used in Example 1 and using the same as the developer in Example 1. Further, a test was carried out on the carrier XXXI using toners B to D as developers in the same manner as in Example 1.
The evaluation results are shown in Table 3 in the same manner as in Example 1.

It is a perspective view of the resistance measurement cell used for the measurement of the electrical resistivity of a carrier. It is structural drawing which shows description of the vibration sieve machine with an ultrasonic oscillator. It is a figure explaining an example of the image development apparatus suitable for performing the electrophotographic developing method of this invention. 1 is a diagram illustrating an example of an image forming apparatus suitable for executing an image forming method using an electrophotographic developing method of the present invention. It is a figure explaining another example of the image forming apparatus suitable for performing the image forming method using the electrophotographic developing method of this invention. It is a figure explaining an example of the process cartridge of this invention.

Explanation of symbols

1 Vibrating Sieve 2 Cylindrical Container 3 Spring 4 Base 5 Wire Mesh 6 Resonant Ring 7 High Frequency Current Cable 8 Converter (Transducer)
9 Ring-shaped frame 11 Cell 12a Electrode 12b Electrode 13 Carrier 14 Nozzle part (compressed gas)
15 Blow-off cage 16 Carrier 17 Toner 18 Electrometer

20 Photosensitive drum 21 Toner 23 Carrier 24a Driving roller 24b Driving roller 26 Exposure light source 32 before cleaning Image carrier charging member 33 Image exposure system 40 Developing device 41 Developing sleeve 42 Developer containing member 43 Developer supply regulating member 44 Support case 45 Toner hopper 46 Developer container 47 Developer agitation mechanism 48 Toner agitator 49 Toner replenishment mechanism 50 Transfer mechanism 60 Cleaning mechanism 61 Cleaning blade 64 Brush-like cleaning means 70 Static elimination lamp 80 Intermediate transfer medium

Claims (15)

The weight average particle diameter Dw is 22 μm or more and 32 μm or less, and the ratio Dw / Dp between the number average particle diameter Dp and the weight average particle diameter Dw is composed of magnetic core material particles and a binder resin layer covering the particle surface. The content of particles having a range of 1.00 <Dw / Dp <1.20, particle size x [μm] of 0 <x <20 is 7% by weight or less, and particle size y [μm] is 0 <y <36. In the carrier for an electrophotographic developer having a particle content of 90 wt% or more and 100 wt% or less, the BET specific surface area of the core particles is in the range of 900 cm ² / g or more and 2000 cm ² / g or less. A carrier for an electrophotographic developer characterized by ^{2. The} carrier for an electrophotographic developer according to claim 1, wherein the core material particles have a BET specific surface area of 1100 cm ² / g or more and 2000 cm ² / g or less.   3. The electrophotographic developer according to claim 1, wherein magnetization when a magnetic field of 1000 oersted is applied to the carrier for electrophotographic developer is 50 emu / g or more and 100 emu / g or less. Career.   The carrier for an electrophotographic developer according to claim 1, wherein the core particle is Mn—Mg—Sr ferrite, Mn ferrite or magnetite. The volume resistivity when an electric field of 500 V / mm is applied to the carrier for an electrophotographic developer is 1 × 10 ¹¹ Ω · cm or more and 1 × 10 ¹⁶ Ω · cm or less. The carrier for an electrophotographic developer according to any one of -4.   The carrier for electrophotographic development according to any one of claims 1 to 5, wherein the binder resin layer contains hard fine particles.   The carrier for electrophotographic development according to claim 6, wherein the hard fine particles are oxides of Si, Ti, or Al.   The carrier for electrophotographic development according to claim 6 or 7, wherein the content of the hard fine particles is in the range of 5 wt% to 70 wt% of the weight of the binder resin layer.   The carrier for an electrophotographic developer according to claim 1, wherein the binder resin layer contains an aminosilane coupling agent. The electrophotographic developer carrier according to claim 1-9, further characterized in that subjected to an aging treatment, a carrier for an electrophotographic developer. Electrophotographic developer composed of the electrophotographic toner for developer carrier and the electrostatic latent image developer according to claim 1-10. 12. The electrophotographic developer according to claim 11 , wherein the toner for electrostatic latent image developer has a weight average particle diameter of 2 to 7 [mu] m. Image forming method which comprises using an electrophotographic developer according to claim 11 or claim 12. A developer according to claim 11 or 12, the developing sleeve, a photosensitive member, an image forming method according to claim 13, wherein the applying an alternating current and / or DC voltage as a developing bias. 13. A process cartridge comprising at least a photosensitive member and a developing means, wherein the developer according to claim 11 or 12 is contained.

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