JP7001954B2 - Carrier for electrostatic latent image development, two-component developer, developer for replenishment, image forming apparatus, process cartridge, and image forming method. - Google Patents

Description

The present invention relates to a carrier for developing an electrostatic latent image, a two-component developer using the carrier, a developer for replenishment, an image forming apparatus, a process cartridge, and an image forming method.

In image formation by the electrophotographic method, first, an electrostatic latent image is formed on an electrostatic latent image carrier such as a photoconductive substance, and a charged toner is attached to the electrostatic latent image to form a toner image. To form. Then, the toner image is transferred to a recording medium and then fixed to obtain an output image. In recent years, the technology of copiers and printers using the electrophotographic method is rapidly expanding from monochrome to full color, and the full color market tends to expand.

In full-color image formation, generally, three color toners of yellow, magenta, and cyan, or four color toners in which black is added are laminated to reproduce all colors. Therefore, in order to obtain a clear full-color image with excellent color reproducibility, it is necessary to smooth the surface of the fixed toner image to reduce light scattering. For this reason, many latent image images of conventional full-color copiers and the like achieve high gloss by increasing the amount of toner adhered to the electrostatic latent image in order to achieve smoothness of the toner image. Therefore, in the case of long-term printing, the resin component of the deteriorated toner and the toner pencil to which the wax adheres to the carrier surface have become a problem.
One of the problems in carrier deterioration caused by tonerspent is the increase in carrier resistance.

In the field of production printing, where the market has been expanding in recent years, higher image quality than ever is required. When the carrier resistance increases due to the toner penta, the carrier is transferred onto the electrostatic latent image carrier, so-called carrier adhesion occurs, and a problem occurs that the carrier appears as a white spot at the edge or center of the image. There's a problem. The demands on this issue have become more severe in recent years.

On the other hand, it is possible to maintain the resistance at a high level by designing the carrier resistance at a high level from the initial stage, but in that case, the charge on the carrier surface does not leak properly immediately after development, for example. When printing halftone, there is a problem that the edge becomes thin.

From the above, the initial resistance of the carrier is low, and maintaining that level is indispensable for stably obtaining high-quality images.
Various attempts have been made to achieve the above-mentioned technical concept. For example, in Patent Document 1, by using a plurality of incompatible resins for the carrier coating resin, the conductive fine particles are unevenly distributed in the coating layer, the spent resistance of the carrier coating resin is utilized, and the carrier made of the conductive fine particles is used. Means for achieving low resistance have been proposed.

However, in the conventional method, as the printing speed is increased, the effect of suppressing the toner spine by the coating resin is insufficient, the resistance increases with the number of printed sheets, and the problem of carrier adhesion is unavoidable.
Based on the above technical problems, the present invention can maintain sufficient resistance and control charge for image quality required in the field of production printing, and can suppress an increase in carrier resistance and carrier adhesion. In addition, even in high-speed machines that use low-temperature fixing toner, the electrostatic latency used in the two-component developer used in electrophotographic and electrostatic recording methods that enables continuous paper transfer at a printing density with a low image area ratio. It is an object of the present invention to provide a carrier for image development.

As a result of diligent studies, the present inventors have found that the above-mentioned problem can be solved by the following carrier for electrostatic latent image development (1).
(1) An electrostatic latent image developing carrier having a magnetic core material particle and a coating layer covering the surface thereof.
The coating layer is composed of a resin and a conductive inorganic powder, and the conductive inorganic powder contains a needle-like conductive inorganic powder.
0. When the average film thickness of the coating layer is D (μm), the average thickness of the needle-shaped conductive inorganic powder in the film thickness direction is H (μm), and the average length of the major axis is L (μm). 05 ≦ H / D ≦ 0.30,
0.30 ≤ D ≤ 2.00,
0.6 ≤ L ≤ 3.0
And
The resin is a carrier for electrostatic latent image development containing at least a silicone resin.

The carrier for electrostatic latent image development of the present invention can maintain sufficient resistance and control charge for the image quality required in the field of production printing, can suppress an increase in carrier resistance and carrier adhesion, and can also suppress carrier adhesion. Even in a high-speed machine using low-temperature fixing toner, it is possible to continuously pass paper with a print density of a low image area ratio.

It is a figure for demonstrating the cell used when measuring the volume resistivity of a carrier. It is a schematic diagram of an example of the process cartridge of this invention. It is a schematic diagram explaining the length l of the long axis of the needle-shaped conductive inorganic powder and the thickness h in the film thickness direction in the carrier of the present invention.

Hereinafter, the present invention (1) will be described in detail.
In addition, since the following (2) to (10) are also included in the embodiment of the present invention (1), these will also be described.
(2) The carrier for electrostatic latent image development according to (1) above, wherein the needle-shaped conductive inorganic powder is titanium oxide and the content in the coating layer is 5 to 40 area%.
(3) The carrier for electrostatic latent image development according to (2) above, wherein the titanium oxide has an antimony-doped tin oxide coating layer.
(4) The carrier for electrostatic latent image development according to any one of (1) to (3) above, wherein four or more layers of needle-shaped conductive inorganic powder in the coating layer are filled.
(5) A two-component developer having the carrier and toner for electrostatic latent image development according to any one of (1) to (4) above.
(6) The two-component developer according to (5) above, wherein the toner is a color toner.
(7) The replenishing developer containing a carrier and toner, which contains 2 to 50 parts by mass of toner with respect to 1 part by mass of the carrier, and the carrier is described in any one of (1) to (4) above. A replenishing developer that is a carrier for developing electrostatic latent images.
(8) An electrostatic latent image carrier, a charging means for charging the electrostatic latent image carrier, an exposure means for forming an electrostatic latent image on the electrostatic latent image carrier, and the electrostatic latent image. A developing means for developing a toner image by developing an electrostatic latent image formed on a carrier using the two-component developer according to (5) or (6) above, and the electrostatic latent image carrier. An image forming apparatus having a transfer means for transferring the toner image formed above to a recording medium and a fixing means for fixing the toner image transferred to the recording medium.
(9) The electrostatic latent image carrier, the charging member for charging the surface of the electrostatic latent image carrier, and the electrostatic latent image formed on the electrostatic latent image carrier are described in (5) or (1). A process cartridge having a developing unit for developing using the two-component developer according to 6) and a cleaning member for cleaning the electrostatic latent image carrier.
(10) The step of forming an electrostatic latent image on an electrostatic latent image carrier and the electrostatic latent image formed on the electrostatic latent image carrier are described in the above (5) or (6). A step of developing with a two-component developer to form a toner image, a step of transferring the toner image formed on the electrostatic latent image carrier to a recording medium, and a step of transferring the toner image to the recording medium. An image forming method comprising a step of fixing the image.

The carrier for electrostatic latent image development (hereinafter, also referred to as a carrier) of the present invention will be described in detail.
The carrier for developing an electrostatic latent image of the present invention is a carrier for developing an electrostatic latent image having a magnetic core material particle and a coating layer covering the surface thereof.
The coating layer is composed of a resin and a conductive inorganic powder, and the conductive inorganic powder contains a needle-like conductive inorganic powder.
0. When the average film thickness of the coating layer is D (μm), the average thickness of the needle-shaped conductive inorganic powder in the film thickness direction is H (μm), and the average length of the major axis is L (μm). 05 ≦ H / D ≦ 0.30,
0.30 ≤ D ≤ 2.00,
0.6 ≤ L ≤ 3.0
And
The resin is a carrier for electrostatic latent image development containing at least a silicone resin.
As a result, the highly conductive needle-shaped inorganic powder functions as a conduction circuit even when the toner is spun, and the initial resistance can be maintained, enabling long-term printing. Further, by containing the silicone resin as the coating layer resin, it is possible to prevent the toner spent itself from occurring.

In the carrier of the present invention, at least acicular conductive inorganic powder is contained in the coating layer, the average thickness of the coating layer is D (μm), and the average thickness of the acicular conductive inorganic powder in the film thickness direction is defined. When H (μm) and the average length of the major axis are L (μm), H / D satisfies 0.05 to 0.30, and in the coating layer, D is 0.30 to 2.00 μm, L. Is very important to be 0.6-3.0 μm.
The needle-shaped conductive inorganic powder in the coating layer does not align in a certain direction when the surface is observed, and forms a mesh-like conductive network that is crossed and entangled. The outermost surface is subject to collision in the developing device, and the coating layer is easily scraped. Toner spent is likely to occur in the recesses of the coating layer, especially in the recesses of the mesh. At that time, by using the carrier of the present invention, it is possible to maintain a low carrier resistance even if the toner is spun in a state where the network is functioning on the surface of the coating layer and inside the coating layer.

The important points of the present invention are summarized in the following five points.
First, the inorganic powder in the coating layer contains needle-like conductive inorganic powder. Since the inorganic powder needs to continue to function as a conduction path as described above, high conductivity, high hardness, and affinity with a resin are required. As a result of diligent studies by the inventors, it was found that the needle-shaped conductive inorganic powder is the most suitable.
In the present invention, the needle-shaped conductive inorganic powder may have an elongated shape, includes a rod-shaped shape, a columnar shape, and the like, and has an aspect ratio of 1.5 or more.
Further, the conductivity means that the powder specific resistance is ¹⁰⁶ Ω · cm or less.
Examples of the needle-shaped conductive inorganic powder include titanium oxide, potassium titanate, aluminum borate and the like.

The second is that the H / D is 0.05 to 0.30. It is preferably 0.10 to 0.25. This can be said to be a condition for the needle-like conductive inorganic powder to form an optimum network in the surface of the coating layer and the inside of the coating layer in order to achieve the technical concept. That is, if this value is less than 0.05, the needle-shaped conductive inorganic powder cannot be held by the resin, the needle-shaped conductive inorganic powder is detached with deterioration, the core material particles are exposed, and a significant decrease in resistance is caused. On the other hand, if it exceeds 0.30, the formation of the network is insufficient, the conductive path is lost due to the toner spent, and the carrier resistance increases.
The H / D value can be adjusted by adjusting the shape of the needle-shaped conductive inorganic powder using a classifier, adjusting the film thickness D of the coating layer by controlling the amount of resin, and the like. can.
Further, in order to form a more optimum network-like network and form a conductive path, the coating layer is formed by using a atomizing nozzle in which the droplet diameter of the sprayed coating layer forming liquid is 10 μm or less. Is preferable. When the droplet diameter is 10 μm or less, bias is less likely to occur in the droplet due to the difference in specific gravity between the coating resin component and the inorganic powder, the inorganic powder is less likely to aggregate, and the target mesh-like network is easily formed. Become. In addition, voids are less likely to be formed at the interface between the core material and the coating layer, and a tough coating layer can be obtained.

Thirdly, the D is 0.30 to 2.00 μm. It is preferably 1.0 to 1.6 μm. When this value is less than 0.30 μm, the coating layer is scraped with deterioration, and the core material particles are exposed, causing a significant decrease in resistance. On the other hand, if it exceeds 2.00 μm, the coating layer is scraped and the balance with the toner spent is inclined toward the spent side, which causes an increase in carrier resistance.

Fourth, the L is 0.6 to 3.0 μm. It is preferably 1.0 to 2.0 μm. If this value is less than 0.6 μm, the formation of the network in the coating layer is insufficient, the toner spent loses the conductive path, and the carrier resistance increases. If it exceeds 3.0 μm, the needle-shaped conductive inorganic powder will greatly protrude from the coating layer, and the surface of the photoconductor will be damaged.
The value of L can be set to 0.6 to 3.0 μm by classifying the needle-shaped conductive inorganic powder using a classifier.

Fifth, it contains a silicone resin as the coating layer resin. For example, when only the styrene acrylic resin is used, toner spint is likely to occur, which causes an increase in carrier resistance.

The filling state of the needle-shaped conductive inorganic powder, the film thickness of the coating layer, and the length of the long axis can be confirmed by a known method, but in the present invention, the measurement was performed by the following method. That is, it can be performed by cutting the carrier with FIB and observing the cross section thereof with SEM or the like.

The sample is adhered to the carbon tape and coated with osmium at about 20 nm for surface protection and conductive treatment. Using NVision40 manufactured by Carl Zeiss (SII), acceleration voltage 2.0 kV, aperture 30 μm, High Current ON, detector SE2, InLens, no conductive treatment, W. FIB treatment is performed at D 5.0 mm and sample inclination of 54 °. Using Thermo Fisher Scientific's electronically cooled SDD detector UltraDry (Φ30mm ² ) and analysis software Thermo Fisher Scientific's NORAN System6 (NSS), acceleration voltage 3.0kV, aperture 120μm, High Current ON, conduction treatment Os, With drift correction, W. Perform SEM observation with D 10.0 mm, measurement method Area Scan, integration time 10 sec, integration frequency 100 times, sample inclination 54 ° magnification 10000 times, import this into TIFF image, and use Image-Pro Plus manufactured by Media Cybernetics. After making an image of only particles, a binarization treatment was performed, and the resin-coated portion was decomposed into a white portion (needle-shaped conductive inorganic powder portion) and a black portion (resin portion). For the average thickness H in the film thickness direction and the average length L of the major axis of the white part, 10 needle-shaped conductive inorganic powders were randomly selected for each carrier particle, and 10 needle-shaped conductive inorganic powders were selected. The thickness h in the film thickness direction and the length l of the major axis are measured, and the average value of one of the carriers is obtained. Similarly, the average value of each particle is obtained for the carrier of 100 particles, and further, the average value of the 100 particles is obtained. It is a value obtained by averaging the values.
For the average film thickness D of the coating layer, the cross-sectional image of one particle is divided into eight from the center, the film thickness on the eight equal divisions is measured, and the average film thickness of one particle is obtained. Similarly, for carriers of 100 particles. Is also a value obtained by obtaining the average film thickness of each particle and further averaging the values of the average film thickness of the 100 particles.
Regarding the filled state, the area% of the needle-shaped conductive inorganic powder with respect to the coating layer was obtained from the white and black areas with respect to the carrier 100 particles, and the filled state was defined.

FIG. 3A shows the length l of the major axis of the needle-shaped conductive inorganic powder in the image of the cross section of the carrier, and FIG. 3B shows the thickness of the needle-shaped conductive inorganic powder in the film thickness direction. It is a schematic diagram which shows h.
The length l of the major axis of the needle-shaped conductive inorganic powder of the carrier is the maximum length indicated by the needle-shaped conductive inorganic powder in the cross-sectional observation of the carrier, and the thickness h in the film thickness direction is the film thickness. The maximum length in the direction.

The needle-shaped conductive inorganic powder is titanium oxide, and the content in the coating layer is preferably 5 to 40 area%. Titanium oxide has excellent whiteness, and even if the toner is in contact with titanium oxide located on the outermost surface, the color does not transfer to the toner side. In addition, the Mohs hardness is high, and even if the carriers collide with each other in the developing device or come into contact with the developing sleeve or screw, it is difficult to break or scrape.
By setting the content of titanium oxide in the coating layer to 5 area% or more, the film strength is increased, the core material is not exposed, and the resistance does not decrease with time. As a result, solid carrier adhesion is less likely to occur. Further, when the area is 40 area% or less, the damage given to the toner does not increase, so that the toner spend is less likely to occur, and the increase in resistance can be suppressed with time. As a result, edge carrier adhesion is less likely to occur.
As for the area%, the carrier is embedded with epoxy resin, and after curing, it is cut by ion milling, the cross-sectional SEM is observed, the image of one particle is divided into eight, the resin is black, and the needle-like conductive powder is white. , The area ratio was calculated by binarizing with analysis software. The core material is not included (it can be eliminated by adjusting the contrast because it appears gray in the image). It was calculated by taking the average of 100 particles.
Titanium oxide preferably has an antimony-doped tin oxide coating layer to enhance conductivity. Needle-shaped titanium oxide having an antimony ^- doped tin oxide coating layer has a low powder resistivity of ¹⁰⁰ to 102, and easily lowers the carrier resistance.
Further, in order to form a conductive network in the carrier coating layer, it is preferable that the needle-shaped conductive inorganic powders are in contact with each other in the coating layer and are in a laminated state. The laminated state indicates that they are filled to some extent when the cross section is observed.

The identification of Sb and Sn in the antimony-doped tin oxide coating layer is obtained from the following. AXIS / ULYRA (manufactured by Shimadzu / KRATOS) is used. The beam irradiation region is approximately 900 μm × 600 μm, and a range of 25 carriers × 17 is detected. Further, the penetration depth is 0 to 10 nm, and information near the carrier surface is detected.
The specific measurement method was carried out in a measurement mode: Al: 1486.6 eV, an excitation source: monochrome (Al), a detection method: a spectrum mode, and a magnet lens: OFF. First, the detected elements were identified by a wide area scan, and then peaks were detected by a narrow scan for each detected element. After that, the atomic% of Sb and Sn with respect to all the detected elements was calculated by the attached peak analysis software.

It is preferable that the needle-shaped conductive inorganic powder is filled with four or more layers in the coating layer.
The specific method for measuring the state of the needle-shaped conductive inorganic powder in the coating layer is the same as the above-mentioned confirmation of the filling state, the film thickness of the coating layer, and the length of the major axis.
In the image decomposed into a white part (needle-shaped conductive inorganic powder part) and a black part (resin part) in the resin-coated part by performing the binarization treatment, an eight equal division line is drawn from the center on one carrier particle. At that time, the number of needle-shaped conductive inorganic powders detected in the film thickness direction on the eight lines was obtained, and the average thereof was taken as the number of layers of needle-shaped conductive inorganic powders in the coating layer of one particle. , It was performed on 100 carrier particles, and it was determined whether or not each particle was filled with 4 or more layers on average.

In the carrier of the present invention, the resin component in the coating layer hydrolyzes the following copolymer obtained by radically copolymerizing the following monomer as the A component and the monomer as the B component to generate a silanol group. It is preferable that the carrier contains a resin crosslinked by condensation using a catalyst, and is obtained by coating and then heat-treating.
The carrier can be produced by applying a resin solution to which the following copolymer is added to core material particles, drying the mixture, and then firing the carrier. The copolymer is hydrolyzed and condensed in the resin solution. And bridge.

Here, in the above formula, R ¹ , m, R ² , R ³ , X, and Y indicate the following.
R ¹ : Hydrogen atom or methyl group m: An integer of 1 to 8 [(CH ₂ ) _m is an alkylene group such as a methylene group, an ethylene group, a propylene group or a butylene group]
R ² : Alkyl group with 1 to 4 carbon atoms (methyl group, ethyl group, propyl group, isopropyl group, butyl group, etc.)
R ³ : Alkyl group having 1 to 8 carbon atoms (methyl group, ethyl group, propyl group, isopropyl group, butyl group, etc.) or alkoxy group having 1 to 4 carbon atoms (methoxy group, ethoxy group, propoxy group, butoxy) Basics)
In the component A, X = 10 to 90 mol%, more preferably 30 to 70 mol%.
In the B component, Y = 10 to 90 mol%, more preferably 30 to 70 mol%.
X + Y = 100 mol%.

The A component has an atomic group tris (trialkylsiloxy) silane in which a large number of alkyl groups having 1 to 4 carbon atoms are present in the side chain, and the surface energy increases when the ratio of the A component to the entire resin is high. Is reduced, and the adhesion of the resin component, wax component, etc. of the toner is reduced. When the A component is 10 mol% or more, a sufficient effect is obtained and the adhesion of the toner component is reduced. On the other hand, when it is 90 mol% or less, the B component increases, cross-linking proceeds, the toughness increases, the adhesiveness between the core material and the resin layer improves, and the durability of the carrier coating improves.
R ² is an alkyl group having 1 to 4 carbon atoms, and examples of the monomer serving as the A component include a tris (trialkylsiloxy) silane compound represented by the following formula.
In the following formula, Me is a methyl group, Et is an ethyl group, and Pr is a propyl group.
CH ₂ = CMe-COO-C ₃ H ₆ -Si (OSiMe ₃ ) ₃
CH ₂ = CH-COO-C ₃ H ₆ -Si (OSiMe ₃ ) ₃
CH ₂ = CMe-COO-C ₄ H ₈ -Si (OSiMe ₃ ) ₃
CH ₂ = CMe-COO-C ₃ H ₆ -Si (OSiEt ₃ ) ₃
CH ₂ = CH-COO-C ₃ H ₆ -Si (OSiEt ₃ ) ₃
CH ₂ = CMe-COO-C ₄ H ₈ -Si (OSiEt ₃ ) ₃
CH ₂ = CMe-COO-C ₃ H ₆ -Si (OSiPr ₃ ) ₃
CH ₂ = CH-COO-C ₃ H ₆ -Si (OSiPr ₃ ) ₃
CH ₂ = CMe-COO-C ₄ H ₈ -Si (OSiPr ₃ ) ₃
The method for producing the monomer as the component A is not particularly limited, but a method for reacting tris (trialkylsiloxy) silane with allyl acrylate or allyl methacrylate in the presence of a platinum catalyst, and JP-A-11-217389 are described. It can be obtained by a method of reacting a methacryloxyalkyltrialkoxysilane with a hexaalkyldisiloxane in the presence of a carboxylic acid and an acid catalyst.

The component B is a radically polymerizable bifunctional or trifunctional silane compound, and Y = 10 to 90 mol%, more preferably 30 to 70 mol%.
When the B component is 10 mol% or more, sufficient toughness can be obtained. On the other hand, when it is 90 mol% or less, the film is not hard and brittle, and film scraping is less likely to occur. In addition, the environmental characteristics are improved. If a large number of hydrolyzed cross-linking components remain as silanol groups, it is possible that the environmental characteristics (humidity dependence) are deteriorated.

Examples of the monomer as the B component include 3-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltriethoxysilane, and 3-methacry. Examples thereof include loxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacrythoxypropyltri (isopropoxy) silane, and 3-acryloxypropyltri (isopropoxy) silane.

In the present invention, the copolymer may have an acrylic compound (monomer) as the C component in the A component and the B component.
Examples of the product to which such a C component is added include the following copolymers.

In the formula, R ¹ , m, R ² , R ³ , X, Y, and Z indicate the following.
R ¹ : Hydrogen atom or methyl group m: Integer from 1 to 8 R ² : Alkyl group with 1 to 4 carbon atoms R ³ : Alkoxy group with 1 to 8 carbon atoms or alkoxy group with 1 to 4 carbon atoms X '= 10-40 mol%.
Y'= 10-40 mol%.
Z'= 30-80 mol% and
60 mol% <Y'+ Z'<90 mol%.
X'+ Y'+ Z'= 100 mol%.

The component C imparts flexibility to the coating film and improves the adhesiveness between the core material and the coating film. When the C component is 30 mol% or more, sufficient adhesiveness is obtained, and when it is 80 mol% or less, both the A component and the B component can be 10 mol% or more, so that the water repellency of the carrier film is obtained. , It becomes easy to achieve both hardness and flexibility (film scraping).

As the acrylic compound (monomer) to be the C component, acrylic acid ester and methacrylic acid ester are preferable, and specifically, methyl methacrylate, methyl acrylate, ethyl methacrylate, ethyl acrylate, butyl methacrylate, butyl acrylate and 2- (dimethyl). Examples thereof include amino) ethyl methacrylate, 2- (dimethylamino) ethyl acrylate, 3- (dimethylamino) propyl methacrylate, and 3- (dimethylamino) propyl acrylate. Of these, alkyl methacrylate is preferable, and methyl methacrylate is particularly preferable. Further, one kind of these compounds may be used alone, or a mixture of two or more kinds may be used.

Patent No. 3691155 is a technique for increasing durability by cross-linking a coating film. Patent No. 369115 describes a radical copolymerization of a magnetic particle surface having at least one functional group selected from the group consisting of an organopolysiloxane having a vinyl group at the terminal and a hydroxyl group, an amino group, an amide group and an imide group. It is a carrier for electrostatic charge image development characterized by coating a copolymer with a sex monomer with a thermosetting resin crosslinked with an isocyanate-based compound, but it has sufficient durability in peeling and scraping of the film. The current situation is that it has not been obtained.

The reason for this is not fully clear, but in the case of a thermosetting resin in which the above-mentioned copolymer is crosslinked with an isocyanate compound, as can be seen from the structural formula, isocyanate in the copolymer resin There are few functional groups per unit mass that reacts (crosslinks) with the compound, and it is not possible to form a two-dimensional or three-dimensional dense cross-linked structure at the cross-linking point. Therefore, if it is used for a long time, the film is easily peeled off or scraped (the abrasion resistance of the film is small), and it is presumed that sufficient durability is not obtained.

When the film is peeled off or scraped, the image quality changes due to a decrease in carrier resistance and carrier adhesion occurs. In addition, peeling / scraping of the film reduces the fluidity of the developer, causes a decrease in the pumping amount, and causes a decrease in image density, stains when TC is increased, and toner scattering.

The resin of the present invention is a copolymer resin having a large number of bifunctional or trifunctional crosslinkable functional groups (points) (2 to 3 times more per unit mass) even in terms of resin unit mass. Since this is further crosslinked by polycondensation, it is considered that the coating film is extremely tough and difficult to scrape, and high durability is achieved.
Further, since the crosslinking by the siloxane bond of the present invention has a larger binding energy and is more stable against thermal stress than the crosslinking by the isocyanate compound, it is presumed that the stability of the film over time is maintained.

As the carrier coating resin, a silicone resin, an acrylic resin, or a combination thereof can be used. This is because acrylic resin has strong adhesiveness and low brittleness, so it has excellent wear resistance, but on the other hand, it has high surface energy, so when combined with toner that is easy to spend, the toner component spendt Problems such as a decrease in the amount of charge due to accumulation may occur. In that case, this problem can be solved by using a silicone resin which has an effect that it is difficult to spent the toner component because the surface energy is low and it is difficult for the accumulation of the spent component to proceed due to film scraping. However, since silicone resin has weak adhesiveness and high brittleness, it also has a weakness of poor wear resistance. Therefore, it is important to obtain the properties of these two types of resin in a well-balanced manner, which makes it difficult to spend and resist. It is possible to obtain a coating film that also has wear resistance.

The term "silicone resin" as used herein refers to all generally known silicone resins, such as straight silicon consisting only of organoshirosan bonds, and silicone resins modified with alkyd, polyester, epoxy, acrylic, urethane, etc. However, it is not limited to this. For example, examples of the commercially available straight silicone resin include KR271, KR255, and KR152 manufactured by Shin-Etsu Chemical, and SR2400, SR2406, and SR2410 manufactured by Toray Dow Corning Silicone. In this case, it is possible to use the silicone resin alone, but it is also possible to simultaneously use other components that undergo a cross-linking reaction, a charge amount adjusting component, and the like. Further, as the modified silicone resin, KR206 (alkyd modified), KR5208 (acrylic modified), ES1001N (epoxy modified), KR305 (urethane modified) manufactured by Shin-Etsu Chemical Co., Ltd., SR2115 (epoxy modified) manufactured by Toray Dow Corning Silicone Co., Ltd. , SR2110 (alkyd modification) and the like.

In the coating layer of the present invention, non-needle-shaped conductive fine particles may be used in combination with the needle-shaped conductive inorganic powder in order to adjust the volume resistivity of the carrier. The conductive fine particles are not particularly limited, and examples thereof include conductive polymers such as carbon black, ITO, PTO, WTO, tin oxide, barium sulfate, zinc oxide, and polyaniline, and two or more of them may be used in combination.

Examples of the polycondensation catalyst used for polycondensing the copolymer include titanium-based catalysts, tin-based catalysts, zirconium-based catalysts, and aluminum-based catalysts. In the present invention, excellent results are obtained among these various catalysts. Among the titanium-based catalysts that bring about this, titanium diisopropoxybis (ethylacetoacetate) is the most preferable catalyst. It is considered that this is because the effect of promoting the condensation reaction of the silanol group is large and the catalyst is not easily inactivated.

In the present invention, the coating layer composition preferably contains a silane coupling agent. Thereby, the needle-shaped conductive inorganic powder and the non-needle-shaped conductive fine particles can be stably dispersed.
The silane coupling agent is not particularly limited, but is r- (2-aminoethyl) aminopropyltrimethoxysilane, r- (2-aminoethyl) aminopropylmethyldimethoxysilane, r-methacryloxypropyltrimethoxysilane, N. -Β- (N-vinylbenzylaminoethyl) -r-aminopropyltrimethoxysilane hydrochloride, r-glycidoxypropyltrimethoxysilane, r-mercaptopropyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, Vinyltriacetoxysilane, r-chloropropyltrimethoxysilane, hexamethyldisilazane, r-anilinopropyltrimethoxysilane, vinyltrimethoxysilane, octadecyldimethyl [3- (trimethoxysilyl) propyl] ammonium chloride, r-chlor Propylmethyldimethoxysilane, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, allyltriethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, dimethyldiethoxysilane, 1,3-divinyltetramethyl Examples thereof include disirazan, methacryloxyethyldimethyl (3-trimethoxysilylpropyl) ammonium chloride, and the like, and two or more thereof may be used in combination.

Commercially available silane coupling agents include AY43-059, SR6020, SZ6023, SH6026, SZ6032, SZ6050, AY43-310M, SZ6030, SH6040, AY43-026, AY43-031, SH6062, SH6020P, Z-6911, SZ6300, SZ6075, SZ6079, SZ6083, SZ6070, SZ6072, Z-6721, AY43-004, Z-6187, AY43-021, AY43-043, AY43-040, AY43-047, Z-6265, AY43-204M, AY43-048, Z-6403, AY43-206M, AY43-206E, Z6341, AY43-210MC, AY43-083, AY43-101, AY43-013, AY43-158E, Z-6920, Z-6940 (manufactured by Toray Silicone), etc. Can be mentioned.

The amount of the silane coupling agent added is preferably 0.1 to 10% by mass with respect to the silicone resin. When the amount of the silane coupling agent added is 0.1% by mass or more, the adhesiveness between the core material particles or the needle-like conductive inorganic powder and the silicone resin is improved, and the coating layer falls off during long-term use. If it is 10% by mass or less, toner filming does not occur during long-term use.

In the present invention, the coating layer has no film defects and has an average film thickness of 0.30 to 2.00 μm. If the average film thickness is less than 0.30 μm, it becomes difficult to sufficiently hold the needle-shaped conductive inorganic powder, and the needle-shaped conductive inorganic powder is likely to be separated from the film. On the other hand, if it exceeds 2.00 μm, needle-shaped conductive inorganic powder is taken into the resin layer, and it becomes difficult to exhibit sufficient conductivity.

In the present invention, the core material particles are not particularly limited as long as they are magnetic materials; ferromagnetic metals such as iron and cobalt; iron oxides such as magnetite, hematite and ferrite; various alloys and compounds; these magnetic materials are used. Examples thereof include resin particles dispersed in the resin. Among them, Mn-based ferrite, Mn-Mg-based ferrite, Mn-Mg-Sr ferrite and the like are preferable from the viewpoint of environmental consideration.

The carrier of the present invention preferably has a volume average particle size of 28 μm or more and 40 μm or less. When the volume average particle size of the carrier particles is 28 μm or more, carrier adhesion does not occur, and when it is 40 μm or less, the reproducibility of image details does not deteriorate, and a fine image can be formed. ..
The volume average particle size can be measured using, for example, the Microtrack particle size distribution meter model HRA9320-X100 (manufactured by Nikkiso Co., Ltd.).

The carrier of the present invention preferably has a volume resistivity of 8 to 16 (LogΩ · cm). When the volume resistivity is 8 (LogΩ · cm) or more, carrier adhesion does not occur in the non-image area, and when it is 16 (LogΩ · cm) or less, the edge effect does not reach an unacceptable level. ..
The volume resistivity can be measured using the cell shown in FIG. Specifically, first, a carrier (33) is placed in a cell (31) made of a fluororesin container in which an electrode (32a) having a surface area of 2.5 cm × 4 cm and an electrode (32b) are housed at a distance of 0.2 cm. ) Is filled, and tapping is performed 10 times with a drop height of 1 cm and a tapping speed of 30 times / minute. Next, a DC voltage of 1000 V was applied between the electrodes (32a) and (32b), and the resistance value r [Ω] after 30 seconds was measured using a high resistance meter 4329A (manufactured by Yokogawa Hewlett-Packard). Then, the volume resistivity [Ω · cm] can be calculated from the following equation 1.

The two-component developer of the present invention has the carrier and toner of the present invention.
The toner contains a binder resin and a colorant, and is preferably a color toner such as yellow, magenta, cyan, or black. Further, the toner particles may contain a mold release agent for application to an oilless system in which the toner sticking prevention oil is not applied to the fixing roller. Such toners are generally prone to filming, but the carriers of the present invention can suppress filming, so that the developer of the present invention maintains good quality for a long period of time. Can be done. Further, color toners, particularly yellow toners, generally have a problem that color stains are generated due to scraping of the coating layer of the carrier, but the developer of the present invention can suppress the generation of color stains.
The toner concentration in the two-component developer is preferably 3 to 10% by mass.

The toner can be produced by using a known method such as a pulverization method and a polymerization method. For example, when toner is produced by using a pulverization method, first, the melt-kneaded product obtained by kneading the toner material is cooled, then pulverized and classified to produce parent particles. Next, in order to further improve the transferability and durability, an external additive is added to the parent particles to prepare a toner.

At this time, the device for kneading the toner material is not particularly limited, but is a batch type two-roll; Banbury mixer; KTK type twin-screw extruder (manufactured by Kobe Steel Co., Ltd.), TEM type twin-screw extruder (Toshiba Machinery Co., Ltd.). Continuous twin-screw extruder such as twin-screw extruder (manufactured by KCK), PCM type twin-screw extruder (manufactured by Ikekai Iron Works), KEX type twin-screw extruder (manufactured by Kurimoto Iron Works); Examples thereof include a continuous type uniaxial kneader such as Ko Nida (manufactured by Buss).

When crushing the cooled molten kneaded product, it is roughly pulverized using a hammer mill, a rotoplex, or the like, and then finely pulverized using a pulverizer using a jet stream, a mechanical pulverizer, or the like. be able to. It is preferable to grind so that the average particle size is 3 to 15 μm.
Further, when classifying the crushed molten kneaded product, a wind power type classifier or the like can be used. It is preferable to classify the matrix particles so that the average particle size is 5 to 20 μm.

When toner is produced by using a polymerization method, a resin solution in which a resin synthesized by a polymerization reaction is dissolved in advance is used as a dispersant (assistant) agent such as a surfactant or a water-soluble resin, inorganic fine particles, resin fine particles, or the like. In the presence of the dispersion stabilizer, a dissolved resin suspension method is used in which the solvent is dispersed in an aqueous medium and the solvent is removed by heating, depressurization or the like to obtain a toner. According to this dissolved resin suspension method, uniform toner can be obtained without classification.

Further, when the external additive is added to the matrix particles, the external additive is crushed and adheres to the surface of the matrix particles by mixing and stirring using mixers.

The binder resin is not particularly limited, but is a homopolymer of styrene such as polystyrene, polyp-styrene, polyvinyltoluene and its substitutions; styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene. -Vinyltoluene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-methacrylic acid copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer , Styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinylmethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene Sterite-based copolymers such as copolymers, styrene-isoprene copolymers, styrene-maleic acid ester copolymers; polymethylmethacrylate, butylpolymethacrylate, vinylchloride, vinylacetate, polyethylene, polyester, polyurethane. , Epoxy resin, polyvinyl butyral, polyacrylic acid, rosin, modified rosin, terpene resin, phenol resin, aliphatic or aromatic hydrocarbon resin, aromatic petroleum resin and the like, and two or more thereof may be used in combination.

The binder resin for pressure fixing is not particularly limited, but is a polyolefin such as low molecular weight polyethylene and low molecular weight polypropylene; ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, and styrene-methacrylic acid copolymer. , Ethylene-methacrylic acid ester copolymer, ethylene-vinyl chloride copolymer, ethylene-vinyl acetate copolymer, olefin copolymer such as ionomer resin; epoxy resin, polyester, styrene-butadiene copolymer, polyvinylpyrrolidone, Examples thereof include a methyl vinyl ether-maleic anhydride copolymer, a maleic acid-modified phenol resin, and a phenol-modified terpene resin, and two or more thereof may be used in combination.

The demand for low temperature fixability is increasing for energy saving, and it is strongly desired to lower the melting point of the toner. The melting point of the toner can be lowered by using a resin component having a low molecular weight for low temperature fixability. Further, by combining the low molecular weight polyester resin component and the high molecular weight polyester resin component obtained by the elongation reaction (ester elongation polymerization) of the prepolymer, a toner having improved trade-off hot offset and deterioration of storage stability can be obtained. ..

The colorant (pigment or dye) is not particularly limited, but is limited to cadmium yellow, mineral fast yellow, nickel titanium yellow, nables yellow, naphthol yellow S, Hansa yellow G, Hansa yellow 10G, benzidine yellow GR, quinoline yellow lake, etc. Yellow pigments such as permanent yellow NCG and tartrazine lake; orange pigments such as molybdenum orange, permanent orange GTR, pyrazolone orange, vulcan orange, indance lembrilliant orange RK, benzidine orange G, indance lembrilliant orange GK; red iron oxide, cadmium Red pigments such as Red, Permanent Red 4R, Resole Red, Pyrazolon Red, Watching Red Calcium Salt, Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamin Lake B, Alizarin Lake, Brilliant Carmine 3B; Fast Violet B, Methyl Violet Lake Purple pigments such as cobalt blue, alkaline blue, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated, first sky blue, indanslen blue BC and other blue pigments; chrome green, chromium oxide, pigment Green pigments such as Green B and Malakite Green Lake; azine pigments such as carbon black, oil furnace black, channel black, lamp black, acetylene black and aniline black, metal salt azo dyes, metal oxides, composite metal oxides and the like. Examples include black pigments, and two or more of them may be used in combination.

The release agent is not particularly limited, and examples thereof include polyolefins such as polyethylene and polypropylene, fatty acid metal salts, fatty acid esters, paraffin wax, amide wax, polyhydric alcohol wax, silicone varnish, carnauba wax, and ester wax. , Two or more types may be used together.

Further, the toner may further contain a charge control agent. The charge control agent is not particularly limited, but is niglocin; an azine dye having an alkyl group having 2 to 16 carbon atoms (see Japanese Patent Publication No. 42-1627); I. Basic Yellow 2 (CI 41000), C.I. I. Basic Yellow 3, C.I. I. Basic Red 1 (CI 45160), C.I. I. Basic Red 9 (CI 42500), C.I. I. Basic Violet 1 (CI 42535), C.I. I. Basic Violet 3 (CI 42555), C.I. I. Basic Violet 10 (CI 45170), C.I. I. Basic Violet 14 (CI 42510), C.I. I. Basic Blue 1 (CI 42025), C.I. I. Basic Blue 3 (CI 51005), C.I. I. Basic Blue 5 (CI 42140), C.I. I. Basic Blue 7 (CI 42595), C.I. I. Basic Blue 9 (CI 52015), C.I. I. Basic Blue 24 (CI 52030), C.I. I. Basic Blue25 (CI52025), C.I. I. Basic Blue 26 (CI 44045), C.I. I. Basic Green 1 (CI 42040), C.I. I. Basic dyes such as Basic Green 4 (CI 42000); lake pigments of these basic dyes; C.I. I. Quadruple ammonium salts such as Solvent Black 8 (CI 26150), benzoylmethylhexadecylammonium chloride, decyltrimethylchloride; dialkyltin compounds such as dibutyl, dioctyl; dialkylstinborate compounds; guanidine derivatives; vinyl with amino groups Polyamine resins such as system polymers and condensate polymers having an amino group; Metal complex salts of monoazo dyes; Sartylic acid described in Japanese Patent Publication No. 55-42752, Japanese Patent Publication No. 59-7385; Zn, Al, Co, Cr, Fe, etc. of dialkylsartyl acid, naphthoic acid, dicarboxylic acid, etc. Metal complexes; sulfonated copper phthalocyanine pigments; organic boron salts; fluorine-containing quaternary ammonium salts; calix-allene compounds and the like, but two or more of them may be used in combination. For color toners other than black, a metal salt of a white salicylic acid derivative or the like is preferable.

The external additive is not particularly limited, but is an inorganic particle such as silica, titanium oxide, alumina, silicon carbide, silicon nitride, or boron nitride; a poly having an average particle size of 0.05 to 1 μm obtained by a soap-free emulsifying polymerization method. Examples thereof include resin particles such as methyl methacrylate particles and polystyrene particles, and two or more of them may be used in combination. Of these, metal oxide particles such as silica and titanium oxide whose surface is hydrophobized are preferable. Furthermore, by using silica that has been hydrophobized and titanium oxide that has been hydrophobized in combination, and by increasing the amount of titanium oxide that has been hydrophobized compared to silica that has been hydrophobized, the amount of titanium oxide that has been hydrophobized is increased with respect to humidity. A toner having excellent charge stability can be obtained.

By using the carrier of the present invention as a replenishing developer composed of a carrier and toner and applying it to an image forming apparatus that forms an image while discharging excess developing agent in the developing apparatus, a stable image can be obtained over an extremely long period of time. Quality is obtained. That is, the deteriorated carriers in the developing apparatus and the non-deteriorated carriers in the replenishing developer are replaced to keep the charge amount stable for a long period of time, and a stable image can be obtained. This method is particularly effective when printing a high image area. When printing a high image area, the carrier charge deterioration due to the toner spent on the carrier is the main carrier deterioration, but by using this method, the carrier replenishment amount increases when the image area is high, so the deteriorated carriers are replaced. The frequency goes up. As a result, a stable image can be obtained over an extremely long period of time.

The mixing ratio of the replenishing developer is preferably 2 to 50 parts by mass of the toner with respect to 1 part by mass of the carrier. When the amount of toner is 2 parts by mass or more, the carrier concentration in the developing apparatus does not become too high, so that the charged amount of the developing agent is unlikely to increase. Further, since the amount of charge of the developer is unlikely to increase, it is possible to prevent the developing ability from being lowered and the image density from being lowered. Further, when the amount is 50 parts by mass or less, the carrier ratio in the replenishing developer does not decrease, the frequency of carrier replacement in the image forming apparatus increases, and an effect on carrier deterioration can be expected.

The image forming method of the present invention is a step of forming an electrostatic latent image on an electrostatic latent image carrier, and a two-component development of the electrostatic latent image formed on the electrostatic latent image carrier of the present invention. A step of developing with an agent to form a toner image, a step of transferring the toner image formed on the electrostatic latent image carrier to a recording medium, and a step of fixing the toner image transferred to the recording medium. Has a process.

The process cartridge of the present invention comprises an electrostatic latent image carrier, a charging member that charges the surface of the electrostatic latent image carrier, and an electrostatic latent image formed on the electrostatic latent image carrier. It has a developing unit for developing with the two-component developer of No. 1 and a cleaning member for cleaning the electrostatic latent image carrier.
FIG. 2 shows an example of the process cartridge of the present invention. The process cartridge (10) contains an electrostatic latent image formed on a photoconductor (11) which is an electrostatic latent image carrier, a charging device (12) for charging the photoconductor (11), and a photoconductor (11). After transferring the toner image formed on the developing apparatus (13) and the photoconductor (11) that develops using the two-component developer of the present invention to form a toner image onto a recording medium, the toner image is transferred onto the photoconductor (11). A cleaning device (14) for removing toner remaining in the image processing device (14) is integrally supported, and the process cartridge (10) is removable from the main body of an image forming device such as a copying machine or a printer.

Hereinafter, a method of forming an image using an image forming apparatus equipped with a process cartridge (10) will be described. First, the photoconductor (11) is rotationally driven at a predetermined peripheral speed, and the peripheral surface of the photoconductor (11) is uniformly charged to a positive or negative predetermined potential by the charging device (12). Next, the peripheral surface of the photoconductor (11) is irradiated with exposure light from an exposure apparatus such as a slit exposure type exposure apparatus and an exposure apparatus that scans and exposes with a laser beam, and an electrostatic latent image is sequentially formed. Further, the electrostatic latent image formed on the peripheral surface of the photoconductor (11) is developed by the developing apparatus (13) using the two-component developer of the present invention to form a toner image. Next, the toner image formed on the peripheral surface of the photoconductor (11) was fed from the paper feed unit between the photoconductor (11) and the transfer device in synchronization with the rotation of the photoconductor (11). It is sequentially transferred to the transfer paper. Further, the transfer paper on which the toner image is transferred is separated from the peripheral surface of the photoconductor (11), introduced into the fixing device, fixed, and then printed out as a copy to the outside of the image forming device. Will be done. On the other hand, the surface of the photoconductor (11) after the toner image is transferred is cleaned by removing the residual toner by the cleaning device (14), and then statically eliminated by the static elimination device, and is repeatedly used for image formation. Will be done.

(Image forming device)
The image forming apparatus of the present invention includes an electrostatic latent image carrier, a charging means for charging the electrostatic latent image carrier, and an exposure means for forming an electrostatic latent image on the electrostatic latent image carrier. A developing means for developing an electrostatic latent image formed on the electrostatic latent image carrier with a developer to form a toner image, and a toner image formed on the electrostatic latent image carrier. It has a transfer means for transferring to a recording medium and a fixing means for fixing the toner image transferred to the recording medium, and other means appropriately selected as necessary, for example, static elimination means, cleaning means, and the like. It has recycling means, control means, etc., and uses the two-component developer of the present invention as the developer.
The image forming apparatus may be an image forming apparatus used in the field of production printing.

Continuous paper passing at a print density with a low image area ratio is an environment in which the toner is more stressed on the carrier because the toner in the developing unit is less likely to be replaced and the carrier is in contact with the carrier for a long time, and the influence on the carrier is large. Since the carrier of the present invention can suppress an increase in carrier resistance and carrier adhesion, it is possible to enable continuous paper transfer with a print density of a low image area ratio even in a high-speed machine using a low-temperature fixing toner. can.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. In addition, "part" represents a mass part.

(Resin synthesis example 1)
300 g of toluene was put into a flask equipped with a stirrer, and the temperature was raised to 90 ° C. under a nitrogen gas stream. Next, 3-methacryloxypropyltris (trimethylsiloxy) silane represented by CH ₂ = CMe-COO-C ₃ H ₆ -Si (OSiMe ₃ ) ₃ (Me is a methyl group in the formula) 84. 4 g (200 mmol: Cyraplane TM-0701T / manufactured by Chisso Co., Ltd.), 3-methacryloxypropylmethyldiethoxysilane 39 g (150 mmol), methyl methacrylate 65.0 g (650 mmol), and 2,2'-. A mixture of 0.58 g (3 mmol) of azobis-2-methylbutyronitrile was added dropwise over 1 hour. After completion of the dropping, a solution prepared by dissolving 0.06 g (0.3 mmol) of 2,2'-azobis-2-methylbutyronitrile in 15 g of toluene was further added (2,2'-azobis-2-methylbuty). A total amount of lonitrile (0.64 g = 3.3 mmol) was mixed at 90 to 100 ° C. for 3 hours and subjected to radical copolymerization to obtain a methacrylic copolymer R1.

[Example of manufacturing needle-shaped conductive inorganic powder]
Using several grades of needle-shaped conductive titanium oxide (manufactured by Ishihara Sangyo), the size was adjusted to a desired size by air flow classification and crushing by a vibrating sieve to obtain inorganic powders 1 to 14. As the inorganic powder 15, a mixture of spherical inorganic powder alumina (manufactured by Sumitomo Chemical Co., Ltd.) AA-1.5, an average particle size of 1.5 μm and the inorganic powder 1 at a mass ratio of 1: 1 was used.
The types of the obtained inorganic powders and the average length L (μm) of the major axis of the needle-shaped conductive inorganic powders are described below.
The inorganic powders 1 and 3 to 14 are needle-shaped conductive titanium oxide having an antimony-doped tin oxide film, and the inorganic powder 2 is needle-shaped conductive titanium oxide having no antimony-doped tin oxide film.
The inorganic powder 4 and the inorganic powder 10, the inorganic powder 5 and the inorganic powder 9 and the inorganic powder 11, and the inorganic powder 6 and the inorganic powder 12 have the same average length L of the major axis of the needle-shaped conductive titanium oxide, but the aspect ratio. The ratio is different.
The needle-shaped conductive titanium oxide of the inorganic powders ¹ to 14 had an aspect ratio of 4 to 30 and a resistivity of the powder ratio of 100 to ¹⁰⁶ Ω · cm.

[Example of core material manufacturing]
MnCO ₃ , Mg (OH) ₂ , Fe ₂ O ₃ and SrCO ₃ powders were weighed and mixed to obtain a mixed powder. This mixed powder was calcined in an air oven at 800 ° C. for 2 hours in a heating furnace, and the obtained calcined product was cooled and then pulverized to obtain a powder having a particle size of 3 μm or less. 1% by mass of a dispersant was added to this powder together with water to form a slurry, and this slurry was supplied to a spray dryer for granulation to obtain granulated products having an average particle size of about 40 μm. This granulated product was loaded into a baking furnace and baked in a nitrogen atmosphere at 1150 ° C. for 4 hours.
After crushing the obtained calcined product with a crusher, the particle size was adjusted by sieving to obtain spherical ferrite particles having a volume average particle size of about 35 μm and a BET specific surface area of 0.18 m ² / g. The component analysis of this granulated product revealed that MnO: 44.5 mol%, MgO: 0.5 mol%, and Fe ₂ O ₃ : 55 mol%.

<Toner manufacturing example>
-Synthesis of polyester resin A-
65 parts of ethylene oxide 2 mol adduct of bisphenol A, 86 parts of propion oxide 3 mol adduct of bisphenol A, 274 parts of terephthalic acid and 2 parts of dibutyltin oxide are put into a reaction vessel equipped with a cooling tube, a stirrer and a nitrogen introduction tube. Then, the reaction was carried out at 230 ° C. for 15 hours under normal pressure. Next, the polyester resin A was synthesized by reacting under reduced pressure of 5 to 10 mmHg for 6 hours. The obtained polyester resin A has a number average molecular weight (Mn) of 2,300, a weight average molecular weight (Mw) of 8,000, a glass transition temperature (Tg) of 58 ° C., an acid value of 25 mgKOH / g, and a hydroxyl value. It was 35 mgKOH / g.

-Synthesis of prepolymers (polymers that can react with active hydrogen group-containing compounds)-
682 parts by mass of bisphenol A ethylene oxide 2 mol adduct, 81 parts by mass of bisphenol A propylene oxide 2 mol adduct, 283 parts by mass of terephthalic acid, trimellitic anhydride in a reaction vessel equipped with a cooling tube, a stirrer and a nitrogen introduction tube. 22 parts by mass and 2 parts by mass of dibutyltin oxide were charged and reacted at 230 ° C. for 8 hours under normal pressure. Then, the reaction was carried out under reduced pressure of 10 to 15 mHg for 5 hours to synthesize an intermediate polyester.
The obtained intermediate polyester has a number average molecular weight (Mn) of 2,100, a weight average molecular weight (Mw) of 9,600, a glass transition temperature (Tg) of 55 ° C., an acid value of 0.5, and a hydroxyl value. It was 49.

Next, 411 parts by mass of the intermediate polyester, 89 parts by mass of isophorone diisocyanate, and 500 parts by mass of ethyl acetate were charged in a reaction vessel equipped with a cooling tube, a stirrer and a nitrogen introduction tube, and reacted at 100 ° C. for 5 hours. A prepolymer (a polymer capable of reacting with the active hydrogen group-containing compound) was synthesized.
The free isocyanate content of the obtained prepolymer was 1.60% by mass, and the solid content concentration of the prepolymer (150 ° C., after standing for 45 minutes) was 50% by mass.

-Synthesis of ketimin (the active hydrogen group-containing compound)-
30 parts by mass of isophorone diamine and 70 parts by mass of methyl ethyl ketone were charged in a reaction vessel in which a stirring rod and a thermometer were set, and the reaction was carried out at 50 ° C. for 5 hours to synthesize a ketimine compound (the active hydrogen group-containing compound). The amine value of the obtained ketimine compound (the active hydrogen machine-containing compound) was 423.

-Making a masterbatch-
Henschel mixer (manufactured by Mitsui Mining Co., Ltd.) with 1,000 parts of water, 540 parts of carbon black Printex35 (manufactured by Degussa) with DBP oil absorption of 42 mL / 100 g and pH of 9.5, and 1,200 parts of polyester resin A. Was mixed using. Next, using two rolls, the obtained mixture was kneaded at 150 ° C. for 30 minutes, then rolled and cooled, and pulverized with a palperizer (manufactured by Hosokawa Micron Co., Ltd.) to prepare a master batch.

-Preparation of water-based medium-
306 parts of ion-exchanged water, 265 parts of a 10 mass% suspension of tricalcium phosphate and 1.0 part of sodium dodecylbenzene sulfonate were mixed and stirred to uniformly dissolve them to prepare an aqueous medium.

-Measurement of critical micelle concentration-
The critical micelle concentration of the surfactant was measured by the following method. Analysis was performed using an analysis program in the Sigma system using a surface tension meter Sigma (manufactured by KSV Instruments). The surfactant was added dropwise to the aqueous medium in an amount of 0.01% by mass, and the interfacial tension after stirring and standing was measured. From the obtained surface tension curve, the concentration of the surfactant whose surface tension does not decrease even when the surfactant is dropped was calculated as the critical micelle concentration. When the critical micelle concentration of sodium dodecylbenzenesulfonate with respect to the aqueous medium was measured with a tensiometer Sigma, it was 0.05% by mass with respect to the mass of the aqueous medium.

-Preparation of toner material liquid-
70 parts of polyester resin A, 10 parts by mass of prepolymer and 100 parts of ethyl acetate were placed in a beaker and dissolved by stirring. Add 5 parts of paraffin wax (HNP-9, manufactured by Nippon Seiko Co., Ltd., melting point 75 ° C.), 2 parts of MEK-ST (manufactured by Nissan Chemical Industries, Ltd.), and 10 parts of masterbatch as a mold release agent, and add an ultra viscomill (bead mill). After 3 passes under the condition that 80% by volume of zirconia beads having a particle size of 0.5 mm was filled at a liquid feeding speed of 1 kg / hour and a peripheral speed of a disc of 6 m / sec using (manufactured by IMEX), the above-mentioned ketimin 2.7 was used. A part by volume was added and dissolved to prepare a toner material liquid.

-Emulsification or preparation of dispersion-
Put 150 parts by mass of the aqueous medium in a container, stir at a rotation speed of 12,000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.), add 100 parts by mass of the toner material liquid to this, and add it for 10 minutes. The mixture was mixed to prepare an emulsified or dispersion (emulsified slurry).

-Removal of organic solvent-
100 parts by mass of the emulsified slurry was charged in a flask in which a stirrer and a thermometer were set, and the solvent was removed at 30 ° C. for 12 hours while stirring at a stirring peripheral speed of 20 m / min.
After removing the organic solvent, it was aged at 35 ° C. for 10 hours to obtain a dispersed slurry.

-Washing-
After 100 parts by mass of the dispersed slurry was filtered under reduced pressure, 100 parts by mass of ion-exchanged water was added to the filtered cake, mixed with a TK homomixer (at a rotation speed of 12,000 rpm for 10 minutes), and then filtered. 300 parts by mass of ion-exchanged water was added to the obtained filtered cake, mixed with a TK homomixer (rotation speed 12,000 rpm for 10 minutes), and then filtered twice. To the obtained filtered cake, 20 parts by mass of a 10 mass% sodium hydroxide aqueous solution was added, mixed with a TK homomixer (rotation speed 12,000 rpm for 30 minutes), and then filtered under reduced pressure. 300 parts by mass of ion-exchanged water was added to the obtained filtered cake, mixed with a TK homomixer (rotation speed 12,000 rpm for 10 minutes), and then filtered. 300 parts by mass of ion-exchanged water was added to the obtained filtered cake, mixed with a TK homomixer (rotation speed 12,000 rpm for 10 minutes), and then filtered twice. Further, 20 parts by mass of 10% by mass hydrochloric acid was added to the obtained filtered cake, mixed with a TK homomixer (rotation speed 12,000 rpm for 10 minutes), and then filtered.

-Adjusting the amount of surfactant-
300 parts by mass of ion-exchanged water was added to the filtered cake obtained by the above washing, and the electric conductivity of the toner dispersion liquid was measured when mixed with a TK homomixer (at a rotation speed of 12,000 rpm for 10 minutes). , The surfactant concentration of the toner dispersion was calculated from the calibration curve of the surfactant concentration prepared in advance. From that value, ion-exchanged water was added so that the surfactant concentration became the target surfactant concentration of 0.05% by mass, and a toner dispersion was obtained.

-Surface treatment process-
The toner dispersion liquid adjusted to the predetermined surfactant concentration was heated in a water bath at a heating temperature of T1 = 55 ° C. for 10 hours while mixing at 5000 rpm with a TK homomixer. After that, the toner dispersion was cooled to 25 ° C. and filtered. Further, 300 parts by mass of ion-exchanged water was added to the obtained filtered cake, mixed with a TK homomixer (rotation speed 12,000 rpm for 10 minutes), and then filtered.

-Drying-
The obtained final filtered cake was dried at 45 ° C. for 48 hours in a circulation dryer and sieved with a mesh having a mesh size of 75 μm to obtain toner matrix particles 1.

-External processing-
Further, with respect to 100 parts by mass of the toner matrix particles 1, 3.0 parts by mass of hydrophobic silica having an average particle size of 100 nm, 1.0 part of titanium oxide having an average particle size of 20 nm, and hydrophobicity having an average particle size of 15 nm. 1.5 parts by mass of silica fine powder was mixed with a Henshell mixer to obtain [Toner 1].

(Example 1)
Silicone resin solution [solid content 20% by mass]: 237 parts, aminosilane [Toray Dow Corning Silicone Co., Ltd., SH6020P, solid content 100% by mass]: 12 parts, resin solution of the methacrylic copolymer R1 (solid content) 24 parts by mass): 24 parts, No. as needle-like inorganic powder. A resin solution was obtained by diluting 1: 140 parts, titanium diisopropoxybis (ethylacetacetate) TC-750 (manufactured by Matsumoto Fine Chemical Co., Ltd.): 25 parts as a catalyst with toluene: 1360 parts.
Using the ferrite particles as the core particles, the atomizing nozzle AM25S-ISTL (manufactured by Atmax) was used in the fluidized bed coating device, and the temperature in the fluidized tank was controlled to 65 ° C. for each of the resin solutions. Was applied (droplet diameter 6.0 μm) and dried. The obtained carrier was calcined in an electric furnace at 250 ° C. for 1 hour to obtain a carrier. The obtained carrier (930 parts by mass) and the toner 1 (70 parts by mass) were mixed and stirred at 81 rpm for 4 minutes using a turbuler mixer to prepare a developer for evaluation.
Further, the replenishing developer was prepared by using the carrier and the toner so that the toner concentration was 95% by mass.

(Examples 2 to 10, Comparative Examples 1 to 6)
The production method was the same as in Example 1, and only the material and the number of copies were changed to the materials and the number of copies shown in Table 2, and carriers were prepared in the same manner to prepare a developer.

(Comparative Example 7)
The production method is the same as in Example 1, and the resin solution is styrene methyl methacrylate instead of the silicone resin solution, the resin solution of the methacrylic copolymer R1, and the titanium diisopropoxybis (ethylacetacetate) TC-750. A carrier was prepared using 515 parts of a resin solution [solid content 20% by mass] of a copolymer (copolymer ratio 20:80, average molecular weight 50,000) to prepare a developer.

The obtained carrier characteristics are shown in the table below.
The evaluation of the columns of the needle-shaped conductive titanium oxide, the antimond-tin oxide film, and the filler layer of 4 layers or more was performed according to the following evaluation criteria.
○: Included, ×: Not included

<Evaluation of developer characteristics>
Ricoh's RICOH Pro C7110S (Ricoh's digital color copier / printer multifunction device) was evaluated using the developing agents of Examples and Comparative Examples.

First, carrier adhesion evaluation was carried out. After running 100,000 and 600,000 images with an image area ratio of 0.5% using the developer of Examples and Comparative Examples on Ricoh's RICOH Pro C7110S (Ricoh's digital color copier / printer multifunction device). The results were evaluated for solid carrier adhesion, edge carrier adhesion, and photoconductor scratches shown below. The evaluation criteria are shown below.

(Adhesion of solid carrier)
After running the above-mentioned predetermined number of sheets, a solid image is imaged under predetermined development conditions (charging potential (Vd): -600V, potential after photosensitization of the portion corresponding to the image portion (solid original): -100V, development bias: DC-500V). The image formation was interrupted by a method such as turning off the power inside, and the number of carriers attached to the photoconductor after transfer was counted and evaluated. The region to be evaluated was a region of 10 mm × 100 mm on the photoconductor.
Rank A is a state where the number of carriers attached is 0,
Rank B is a state where the number of carriers attached is 1 to 3,
Rank C is a state where the number of carriers attached is 4 to 7.
Rank D is a state where the number of carriers attached is 8 to 10.
Rank E is a state where the number of carriers attached is 11 to 15.
Rank F is a state in which the number of carriers attached is 16 or more.
Ranks A to D were accepted, and Ranks E and F were rejected.

(Adhesion of edge carrier)
The solid image of the solid carrier adhesion evaluation was carried out under the same conditions except that the solid image was changed to a 2-dot line (100 lpi / inch) image in the sub-scanning direction on the photoconductor. Next, the 2-dot lines developed on the photoconductor were transferred with an adhesive tape (area 100 cm ² ), and the number of the lines was counted to evaluate the carrier adhesion.
Rank A is a state where the number of carriers attached is 0,
Rank B is a state where the number of carriers attached is 1 to 3,
Rank C is a state where the number of carriers attached is 4 to 6.
Rank D is a state where the number of carriers attached is 7 to 8.
Rank E is a state where the number of carriers attached is 9 to 11.
Rank F is a state in which the number of carriers attached is 12 or more.
Ranks A to D were accepted, and Ranks E and F were rejected.

(Photoreceptor scratch)
The photoconductor scratch was evaluated by the surface roughness Ra of the photoconductor surface.
The surface roughness of the photoconductor was measured using a non-contact contour shape measuring instrument (manufactured by Mitaka Kohki Co., Ltd.). The arithmetic mean roughness Ra was obtained by scanning 50 mm to the left and right from the center of the photoconductor at a measurement pitch of 1 μm. The height when not in use is set to 0.
Rank A has a roughness change of less than 0.2 μm.
Rank B has a roughness change of 0.2 μm or more and less than 0.4 μm.
Rank C has a roughness change of 0.4 μm or more and less than 0.6 μm.
Rank D has a roughness change of 0.6 μm or more and less than 0.8 μm.
Rank E has a roughness change of 0.8 μm or more and less than 1.0 μm.
Rank F is in a state where the amount of change in roughness is 1.0 μm or more.
Ranks A to D were accepted, and Ranks E and F were rejected.

(Resistance stability)
The amount of change in carrier resistance was measured by the following method. Measuring the resistance of the carrier The carrier 33 is put into a cell 31 composed of a fluororesin container containing the electrodes (32a) and (32b) of the parallel electrodes, the distance between the electrodes (32a) and (32b), the electrodes 32a having a surface area of 2.5 cm × 4 cm, and the electrodes 32b (FIG. 1). (See), DC1000V was applied, and the resistance value after 30 seconds was measured with a high-resist meter. The value obtained by converting the obtained value into the volume resistivity is used as the initial resistance value (R1). Next, the toner in the developer after running is removed by a blow-off device, resistance is measured for the obtained carrier by the same method as the resistance measurement method, and the obtained value is converted into volume resistivity. , Deterioration resistance value (R2).
The amount of change was determined by the following equation 2.
| (R1-R2) | / R1 × 100 ・ ・ ・ ・ Equation 2
The evaluation criteria are shown below.
Rank A has the above change amount of 0 or more and less than 3,
Rank B has the above change amount of 3 or more and less than 6.
Rank C has the above change amount of 6 or more and less than 8.
Rank D has the above change amount of 8 or more and less than 10.
Rank E has the above change amount of 10 or more and less than 12.
Rank F is in a state where the amount of change is 12 or more.
Ranks A to D were accepted, and Ranks E and F were rejected.

The results of the image evaluation are shown in Table 4.

10 Process cartridge 11 Photoreceptor 12 Charging means 13 Developing means 14 Cleaning means 31 Cell 32a, 32b Electrode 33 Carrier

Japanese Patent No. 2714590

Claims (9)

A carrier for electrostatic latent image development having magnetic core material particles and a coating layer covering the surface thereof.
The coating layer is composed of a resin and a conductive inorganic powder, and the conductive inorganic powder contains a needle-like conductive inorganic powder.
The needle-shaped conductive inorganic powder is titanium oxide having an antimony-doped tin oxide coating layer.
The resin is at least a silicone resin and the following formula (1).

(In the formula, R ¹ , m, R ² , R ³ , X, Y, and Z indicate the following.
R ¹ : Hydrogen atom or methyl group
m: Integer from 1 to 8
R ² : Alkyl group with 1 to 4 carbon atoms
R ³ : Alkyl group having 1 to 8 carbon atoms or alkoxy group having 1 to 4 carbon atoms
X'= 10-40 mol%.
Y'= 10-40 mol%.
Z'= 30-80 mol% and
60 mol% <Y'+ Z'<90 mol%.
X'+ Y'+ Z'= 100 mol%. )
Contains hydrolysis, condensation, and crosslinks of the copolymer represented by.
0. When the average film thickness of the coating layer is D (μm), the average thickness of the needle-shaped conductive inorganic powder in the film thickness direction is H (μm), and the average length of the major axis is L (μm). 05 ≦ H / D ≦ 0.30,
0.30 ≤ D ≤ 2.00,
0.6 ≤ L ≤ 3.0
A carrier for developing electrostatic latent images. The carrier for electrostatic latent image development according to claim 1, wherein the content of the needle-shaped conductive inorganic powder in the coating layer is 5 to 40 area%. The carrier for electrostatic latent image development according to claim 1 or 2, wherein four or more layers of needle-shaped conductive inorganic powder in the coating layer are filled. A two-component developer having the carrier and toner for developing an electrostatic latent image according to any one of claims 1 to 3. The two-component developer according to claim 4, wherein the toner is a color toner. A replenishing developer containing a carrier and toner, which contains 2 to 50 parts by mass of toner with respect to 1 part by mass of the carrier, and the carrier is for electrostatic latent image development according to any one of claims 1 to 3. A replenishing developer that is a carrier. An electrostatic latent image carrier, a charging means for charging the electrostatic latent image carrier, an exposure means for forming an electrostatic latent image on the electrostatic latent image carrier, and an electrostatic latent image carrier. The developing means for forming a toner image by developing the electrostatic latent image formed in the above using the two-component developer according to claim 4 or 5, and the toner formed on the electrostatic latent image carrier. An image forming apparatus having a transfer means for transferring an image to a recording medium and a fixing means for fixing the toner image transferred to the recording medium. 2. The second aspect of claim 4 or 5, wherein the electrostatic latent image carrier, the charging member for charging the surface of the electrostatic latent image carrier, and the electrostatic latent image formed on the electrostatic latent image carrier are described. A process cartridge having a developing unit for developing with a component developer and a cleaning member for cleaning the electrostatic latent image carrier. The step of forming an electrostatic latent image on the electrostatic latent image carrier and the electrostatic latent image formed on the electrostatic latent image carrier are subjected to the two-component developer according to claim 4 or 5. A step of forming a toner image by developing the toner image, a step of transferring the toner image formed on the electrostatic latent image carrier to a recording medium, and a step of fixing the toner image transferred to the recording medium. Image forming method to have.

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