JP2011227112A - Toner and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide toner with which no step-wise gloss variation occurs even if toner images are continuously fixed by using, for example, a fixing apparatus such as heated roller-belt type fixing apparatus in which the temperature difference easily occurs at the fixing nip.SOLUTION: There is provided toner having a domain-matrix structure that includes a domain containing resin formed by radical-polymerizable monomers having a plurality of carboxyl groups and has a domain forming resin with a greater weight average molecule weight than that of a matrix forming resin.

Description

  The present invention relates to a toner used for electrophotographic image formation and an image forming method for fixing a toner image using a fixing device for forming a wide fixing nip portion.

  In the field of electrophotographic image forming apparatuses, in recent years, it has become possible to form high-resolution images by using digital image processing technology, toner diameter reduction technology, etc. It has become possible to provide prints of toner images in the field. As a result, it is possible to provide high-quality prints quickly and on-demand without performing plate transcription, which was an essential process for printing. Print orders have been developed in the mainstream light printing field.

  In the field of light printing, high-speed continuous printing is often performed, and in particular, in a fixing process, melting and fixing a toner image in a short time has been a problem in realizing high-speed printing. Therefore, in order to efficiently melt the toner image, it has been studied to form a wide fixing nip portion, and a “heating roll / belt type fixing device” that forms a fixing nip portion with a heating roll and a belt-like pressure member, A so-called fixing device has been found (see, for example, Patent Documents 1 and 2).

  Patent Document 1 described above discloses a fixing device having a heating roller having a heat-resistant elastic layer and an endless belt having a pressure member disposed inside. In this fixing device, an endless belt is wound around a heating roller at a predetermined angle to form a wide nip portion therebetween. Then, the pressure member is pressed through the endless belt so that the heat-resistant elastic layer of the heating roller is distorted to increase the pressure in the vicinity of the exit of the nip portion, thereby realizing fixing capable of high-speed image formation. I am doing so.

  Patent Document 2 discloses a heating roller / pressure belt type fixing device and an amorphous polyester resin having a surface layer made of a vulcanized product of a fluororubber composition in which a predetermined amount of fluororesin particles are blended on a pressure belt outer peripheral surface. Is an invention of an image forming method in which a toner containing a binder resin is combined. Japanese Patent Laid-Open No. 2004-228688 aims to solve the problem of minute gloss unevenness and wax offset that occur when double-sided printing is performed at high speed. However, in order to increase the fixing speed, the nip width is reduced. There is also a statement that the request will be expanded.

  As described above, a heating roll / belt type fixing device capable of ensuring a wide fixing nip width has attracted attention as a fixing device that efficiently melts and fixes a toner image in a short time for high-speed print production.

JP 2001-356625 A JP 2007-171563 A

  By the way, when fixing a printed matter, an area where the heating roller and the printed matter are in contact with each other and an area where the heating roller and the pressure belt are in contact are formed in the fixing nip portion. By the time, a temperature difference occurs between the two regions. In the fixing device, it is desired that the nip portion is sufficiently heated until the next printed matter starts to be fixed so that such a temperature difference does not exist so that the next fixing can be performed. Therefore, in the prior art, attempts have been made to eliminate the temperature difference generated at the fixing nip portion in a short time by controlling the diameter of the heating roller, the temperature of the pressure belt, or the like.

  However, in continuous printing in which a printed material is conveyed and processed at a predetermined interval, it becomes more difficult to secure a heating time for eliminating the temperature difference in the fixing nip portion as the print production speed increases. In the conventional toner, if the next printed matter is fixed at the fixing nip portion where a temperature difference has occurred, uneven gloss in a step shape may be generated on the formed fixed image. This uneven uneven gloss was conspicuous as a band-like image defect.

  In particular, in the light printing field where there are many opportunities to perform continuous printing, there are cases where high-quality finishes are required, such as posters and photographic images, and uneven glossiness on the printed matter is clearly generated on printed matter. It becomes a problem. In addition, it is technically difficult to eliminate the temperature difference in the fixing nip in a short time, while prompt printing is required. Even if there is a slight temperature difference in the fixing nip, it affects the image quality. The toner has been required to have a performance of fixing a toner image without giving a toner.

  The present invention generates uneven uneven gloss even when a toner image is continuously fixed using a fixing device that easily generates a temperature difference in the fixing nip portion, such as a heating roller / belt type fixing device. An object of the present invention is to provide a toner and an image forming method. Specifically, even when performing image formation where it is difficult to eliminate the temperature difference at the fixing nip in a short period of time, such as continuous printing, good image quality without causing uneven gloss on the print The present invention provides a toner and an image forming method that can stably produce a printed material. Furthermore, in the light printing field where there are many opportunities to create posters and photographic images with high-speed continuous printing, it is possible to stabilize printed products with good gloss quality without defects such as uneven uneven gloss on the printed images. It is an object to provide a toner and an image forming method.

The present inventor has found that the above-described problems can be solved by the configuration described below. That is, the invention described in claim 1
"At least a toner containing a resin and having a domain matrix structure,
The domain contains a resin formed using a radical polymerizable monomer having at least a plurality of carboxyl groups,
The toner according to claim 1, wherein a weight average molecular weight of the resin contained in the domain is larger than a weight average molecular weight of the resin contained in the matrix. ].

The invention described in claim 2
2. The toner according to claim 1, wherein the radical polymerizable monomer having a plurality of carboxyl groups is itaconic acid. ].

The invention according to claim 3
3. The toner according to claim 1, wherein the resin contained in the domain has a weight average molecular weight of 80,000 or more and 500,000 or less. ].

The invention according to claim 4
The resin contained in the matrix is formed using at least a styrene monomer and a (meth) acrylic acid monomer. The toner according to item. ].

The invention described in claim 5
"at least,
Forming a toner image from the electrostatic latent image formed on the photoreceptor using toner; and
Transferring the toner image formed in the step of forming the toner image onto a transfer material;
An image forming method comprising a step of fixing the transfer material with a fixing unit comprising a heating roll and a belt-like pressure member,
In the step of fixing the transfer material, the transfer material is passed through a nip formed between the heating roll and the belt-shaped pressure member, and the toner image transferred to the transfer material is fixed. Is,
The toner is
At least containing a resin and having a domain matrix structure,
The domain contains a resin formed using a radical polymerizable monomer having at least a plurality of carboxyl groups,
The image forming method, wherein a weight average molecular weight of the resin contained in the domain is larger than a weight average molecular weight of a resin contained in the matrix. ].

The invention described in claim 6
The image forming method according to claim 5, wherein the radical polymerizable monomer having a plurality of carboxyl groups is itaconic acid. ].

The invention described in claim 7
The image forming method according to claim 5 or 6, wherein a weight average molecular weight of the resin contained in the domain is 80,000 or more and 500,000 or less. ].

The invention according to claim 8 provides:
The resin contained in the matrix is formed using at least a styrene monomer and a (meth) acrylic monomer. The image forming method according to item. ].

  According to the present invention, even when fixing is performed with a fixing device that easily generates a temperature difference in the fixing nip portion, such as a heating roller / belt type fixing device, the temperature difference existing in the fixing nip portion is not affected. The toner image can be fixed. Specifically, even when the next toner image is fixed in a state where the temperature difference generated in the fixing nip portion cannot be completely eliminated, such as during continuous printing, it is good without causing uneven glossiness in steps. This makes it possible to stably produce prints with high gloss quality. For example, in the light printing field where there are many opportunities for continuous printing, it is possible to stably produce printed materials such as posters and photographic images that require a high gloss quality finish without the hassle of printing. To.

FIG. 3 is a schematic diagram illustrating a cross-sectional structure of a toner according to the present invention. It is a schematic diagram showing a form of a heating roll / belt type fixing device. It is the figure which showed the fixing device of FIG.2 (b) in detail. 1 is a schematic diagram illustrating an example of an image forming apparatus capable of forming an image using a toner according to the present invention. FIG. 6 is a schematic diagram illustrating a mechanism in which a temperature difference is generated in a fixing nip portion of a heating roll / belt type fixing device. It is a conceptual diagram of a glossiness measuring device (gross meter).

  The present invention relates to a toner used in an electrophotographic image forming method, such as when performing continuous printing, even when image formation is being performed in a situation where a temperature difference is likely to occur in the fixing nip portion. The present invention relates to a toner that can perform stable fixing without causing uneven gloss. Specifically, it is possible to secure a wide fixing nip as in the case of a “heating roll / belt-type fixing device” composed of a heating roll and a belt-like pressure member, but on the other hand, a temperature difference is generated in the nip. Even in a fixing device having a structure that tends to occur, uneven glossiness in a step shape is not generated.

The present inventor has produced uneven uneven gloss on the fixed toner image even when the toner having the following configurations (1) to (3) has a temperature difference at the fixing nip. The present inventors have found that it is possible to create a printed material with a good finish without causing the image to be printed. That is,
(1) contains at least a resin and has a domain matrix structure;
(2) The domain constituting the toner particles contains a resin formed using a radical polymerizable monomer having at least a plurality of carboxyl groups. (3) The weight average molecular weight Mw of the resin contained in the domain is The weight average molecular weight Mw of the resin contained in the matrix constituting the toner particles is larger.

  Here, a mechanism in which a temperature difference is generated in the fixing nip when a fixing process is performed during continuous printing or the like, and uneven glossiness is generated will be described with reference to FIG. The fixing device shown in FIG. 5 is a heating roll / belt type fixing device shown in FIG. In FIG. 5, in order to clarify the state of the transfer sheet on the belt, the heating roller and the belt are shown apart from each other. However, in the heating roll / belt type fixing device, the heating roll and the belt are in contact with each other. Thus, a nip portion is formed, and the toner is fixed by passing the transfer sheet through the nip portion.

  First, when continuous printing or the like is performed, the transfer sheets P1 and P2 onto which the toner images are transferred are conveyed to the fixing nip N formed by the heating roller 242 and the pressure belt 243 at predetermined intervals. As shown in (a), the fixing nip N includes a region where the transfer sheets P1 and P2 are placed and a region where the pressure belt surface is exposed. Due to the presence of these regions, as shown in FIG. 5B, the surface of the heating roller 242 includes a region 242H having a high temperature formed by contact with the pressure belt 243 and the transfer sheets P1 and P2. A low temperature region 242L formed by the contact is formed. In FIG. 5B, the transfer sheet P3 disposed on the pressure belt 243 comes into contact with the low temperature region 242L of the heating roller, so that the toner is fixed under the condition that there is no temperature difference.

  The surface of the heating roller 242 has low heat conduction due to the presence of the heat resistant elastic layer and the like, and a certain amount of time is required to make the temperature of the entire surface of the heating roller uniform. In high-speed continuous printing or the like, the transfer material conveyance interval is short, so that the next transfer material P4 is fixed with the temperature difference remaining on the surface of the heating roller 242 as shown in FIG. . When the transfer sheet P4 is fixed in the state shown in FIG. 5C, that is, in the state where there is a temperature difference on the surface of the heating roller 242, the toner melting on the transfer sheet P4 varies. On the transfer sheet P4, there are a part in contact with the high temperature region 242H on the surface of the heating roller 242 and a part in contact with the low temperature region 242L, and a difference occurs in the fixing state between the two parts. This difference in the fixing state results in uneven uneven gloss as shown in FIG.

  In this way, a temperature difference occurs on the surface of the heating roller due to the presence of the area where the transfer material is present on the pressure belt and the area where the pressure belt is exposed. The toner image was fixed to cause uneven uneven gloss.

  In the fixing nip portion of the fixing device, the inventor tends to generate a temperature difference between a region where the heating roller and the printed material are in contact with each other and a region where the heating roller and the pressure belt are in contact with each other. The fluidity of the melted toner was considered to be affected. That is, since the fluidity of the molten toner depends on the temperature, it is considered that if there is a temperature difference in the fixing nip portion, the fluidity of the molten toner is changed, and uneven glossiness is generated. Based on this assumption, the inventor considered that it is necessary to develop a toner that does not cause a change in the fluidity of the molten toner even if a temperature difference exists in the fixing nip portion.

  In view of this, the present inventor has studied a toner having a matrix phase that melts in a low temperature region where the heating roller and the printed material are in contact with each other and a domain phase that softens and melts in a high temperature region where the heating roller and the belt are in contact. Such a structure was considered because the ratio of the area where the heating roller and the printed material are in contact (low temperature area) in the fixing nip area is the area where the heating roller and the printed material are not in contact (high temperature area). This is because the focus is on the fact that the ratio is larger than the ratio.

  In other words, the matrix phase is formed by increasing the amount of resin that can be melted in the low temperature region where the heating roller and the printed product are in contact, and the resin that softens and melts in the high temperature region where the printed material is not in contact is reduced. A domain phase was formed. With such a structure, the resin in the matrix phase melts at a temperature in the low temperature region that occupies most of the fixing nip, and the resin in the domain phase softens and melts when the temperature in the high temperature region is received. It was considered that the fluidity of the matrix phase resin does not change.

  That is, the present inventor considered that even when a high temperature region exists in the fixing nip portion, the increase in the fluidity of the matrix phase resin due to the influence of the high temperature region is suppressed by softening and melting the resin of the domain phase. It is. Therefore, the molecular weight of the resin that forms the domain phase is made larger than the molecular weight of the resin in the matrix phase to promote softening and melting in the high temperature region, and the influence from the high temperature region does not affect the fluidity of the resin in the matrix phase. I did it.

  Based on such an idea, the present inventor has found that the problem of the present invention can be solved by a toner containing at least a resin having the constitutions (1) to (3).

  The toner is considered to exhibit the following behavior with respect to heat applied in the fixing process. First, in the low-temperature region in the fixing nip formed by the contact between the heating roller and the printed material, the resin contained in the domain phase is softened by the action of a high weight average molecular weight and a crosslinked structure formed through a plurality of carboxyl groups. Instead, the matrix phase resin melts.

  On the other hand, the resin in the domain phase is also softened and melted in the high temperature region in the fixing nip portion. The resin of the domain phase having a high weight average molecular weight and having a crosslinked structure in the molecule is softened and melted, so that the fluidity of the matrix phase resin does not increase under the influence of the high temperature region. . As a result, even if a high temperature region exists in the fixing nip portion, the fluidity of the toner melted in the high temperature region becomes the same level as that of the toner melted in the low temperature region. As described above, the toner image formed with the toner according to the present invention has the same fluidity in both the low-temperature region and the high-temperature region even if it is fixed by a fixing device having a structure that easily generates a temperature difference in the fixing nip portion. Since it melts and solidifies, printing can be made without causing uneven glossiness in steps.

  Hereinafter, the present invention will be described in detail.

  First, the toner according to the present invention will be described.

  The toner according to the present invention contains at least a resin and a colorant and has a domain / matrix structure. FIG. 1 is a schematic diagram showing a cross-sectional structure of a toner according to the present invention, and in this figure, the display of a colorant is omitted. As shown in FIG. 1, the toner T has a phase separation structure called “domain matrix structure” in which the domain phase D is dispersed in the matrix phase M which is a continuous phase, and is used for the toner T. The resin forms such a “domain matrix structure”.

  As a specific method for the resin constituting the toner to form the “domain matrix structure”, for example, the solubility parameter value (also referred to as SP value) of the resin contained in the matrix phase and the resin contained in the domain phase is used. ) There is a way to enlarge the difference. By increasing the difference in solubility parameter value between the domain phase and the matrix phase, it becomes difficult for the resin molecules contained in the matrix phase to be adsorbed in the domain phase, improving the incompatibility between the two, and a stable domain matrix It is thought to form a structure.

  As a specific method for expanding the difference in solubility parameter value between the resin of the matrix phase and the resin of the domain phase, for example, when forming the resin of the domain phase, the polymerizability having a plurality of polar groups such as carboxyl groups in the molecule There is a method using a monomer. This is because the compound containing many polar groups in the molecule has a tendency to have a large solubility parameter value. When forming a resin contained in the domain phase, radical polymerization having a plurality of polar groups. It is preferable to use a functional monomer. For example, those having a plurality of carboxyl groups such as itaconic acid are preferable.

  From such a viewpoint, the resin constituting the toner according to the present invention is formed by using a plurality of carboxyl groups such as itaconic acid as the resin contained in the domain. On the other hand, the resin contained in the matrix does not need to be formed using a polymerizable monomer having a plurality of carboxyl groups. For example, at least a styrene monomer and a (meth) acrylic monomer are used. And the like formed in a preferable manner.

  As seen in the toner produced in Examples described later, preferable examples of the resin contained in the toner domain according to the present invention were formed using, for example, methyl methacrylate, butyl acrylate, and itaconic acid. There is something. Moreover, as a preferable example of resin contained in a matrix, what was formed using styrene, butyl acrylate, and methacrylic acid is mentioned, for example. For the domain phase and the matrix phase formed by using the polymerizable monomer, for example, the domain phase resin and the matrix phase resin, the difference in solubility parameter value between the two resin phases becomes appropriate, and the Compatibility is obtained.

Here, the “solubility parameter value (SP value)” is a numerical value representing the magnitude of the cohesive energy of the substance. According to the method “Polym. Eng. Sci., Vol14, P147 (1974)” proposed by Ferors, when the evaporation energy and molar volume of an atom or atomic group are Δer and Δvi, respectively, the solubility parameter σ of the resin is And can be calculated by the following formula (1). That is,
Formula (1)
σ = (ΣΔer / ΣΔvi) ^1/2
The solubility parameter value of the vinyl copolymer can be calculated using the product of the solubility parameter value of each component and the molar ratio. For example, assuming that the copolymer resin is composed of two types of monomers, X and Y, the mass composition ratio of each monomer is x, y (mass%), the molecular weight is Mx, My, When the solubility parameter values are SPx and SPy, the monomer ratios are X / Mx (mol%) and y / My (mol%). Here, when the molar ratio of the copolymer resin is C, it is expressed as C = x / Mx + y / My, and the solubility parameter value SP of the copolymer resin is represented by the following formula (2).

Formula (2)
SP = [(x × SPx / Mx) + (y × SPy / My)] × 1 / C
The solubility parameter value can be controlled by changing the composition ratio of the monomers constituting the vinyl copolymer. For example, in a copolymer resin formed using styrene and methyl methacrylate, It has been confirmed that the solubility parameter value tends to decrease by decreasing the composition ratio of styrene and increasing the composition ratio of methyl methacrylate.

  In addition, the size of the domain phase of the toner according to the present invention, that is, the average domain diameter can be calculated by observing the cross-sectional structure of the toner particles with, for example, a transmission electron microscope (TEM). . Here, a method for calculating the size of the domain phase in the toner particles using a transmission electron microscope (TEM) will be described. The method for calculating the size of the domain phase in the toner particles using a transmission electron microscope is, for example, by preparing a sample by the following procedure, photographing the sample using a transmission electron microscope, and calculating from the obtained photographic image. Is possible.

  First, the toner is sufficiently dispersed in a room temperature curable epoxy resin, embedded, dispersed in styrene fine powder having a particle size of about 100 nm, and then pressure-molded to produce a block containing the toner. . If necessary, the prepared block is dyed with ruthenium tetroxide or osmium tetroxide, if necessary, and then cut into a 200-nm-thick flake using a microtome with diamond teeth. To prepare a measurement sample.

  The measurement sample thus thinned is set on a transmission electron microscope (TEM), and a photograph is taken of the cross-sectional structure of the clear toner. At this time, the magnification of the electron microscope is preferably set to a magnification that allows the cross section of one toner to enter the field of view. Specifically, the negative magnification is set to 280 times, and photographing is performed. Create a photo image. It is possible to calculate the size of the domain phase (average domain diameter) by analyzing the photographic image having a magnification of 12,000 thus created with a commercially available image processing apparatus “Luzex III (manufactured by Nireco)”. it can. Here, the “average domain diameter”, that is, “domain phase size” is equivalent to a circle for each domain existing in 20 toner particles, for example, when the created photographic image is analyzed by the image processing apparatus. The diameter is calculated, and the average value is defined as “average domain diameter”.

  As a specific model of a transmission electron microscope capable of observing the domain phase of the toner, for example, “LEM-2000 type (Topcon)”, “JEM-2000FX (Nippon Denshi)”, etc. Models that are usually well known among vendors are listed.

  In the toner according to the present invention, the domain phase size (average domain diameter) is preferably in the range of 100 nm to 150 nm.

In the toner according to the present invention, the resin has a domain / matrix structure, and the resin having such a structure can be produced by a known method. In particular,
(I) A method of encapsulating resin fine particles forming a domain phase in resin fine particles made of a resin forming a matrix phase, and aggregating the encapsulated resin fine particles to form a resin. (Ii) A resin fine particle forming a matrix phase It is possible to prepare a fine particle dispersion of a resin that forms a domain phase with the dispersion, respectively, by mixing both fine particle dispersions and aggregating both resin fine particles to form a resin. Among these, the method (i) is more advantageous than the method (ii) in producing a resin having a structure in which the domain phases are finely and uniformly distributed.

  In addition, the resin constituting the toner according to the present invention contains more resin that forms the matrix phase than resin that forms the domain phase. Specifically, it is preferable that the content of the resin that forms the domain phase is 2% by mass or more and 20% by mass or less with respect to the “sum of the resin that forms the matrix phase and the resin that forms the domain phase”. .

  As described above, in the present invention, the resin that forms the matrix phase is meltable by heat from a low temperature region formed by the contact between the heating roller and the transfer sheet in the fixing nip portion. . Further, the resin forming the domain phase is softened and melted in a high temperature region formed by contact between the heating roller and the belt member in the fixing nip portion. In this way, the domain phase resin softens and melts in a high temperature region, so even if there is a temperature difference in the fixing nip portion, there is no change in the fluidity of the toner due to the melting of the matrix phase resin. No step-like gloss unevenness due to the temperature difference in the nip portion is generated.

  In the toner according to the present invention, the resin contained in the domain phase is formed using at least a radical polymerizable monomer having a plurality of carboxyl groups. When forming the resin contained in the domain phase, the solubility parameter value of the domain phase can be increased by using a radical polymerizable monomer containing a plurality of carboxyl groups in the molecule such as itaconic acid. As a result, the adsorption of resin molecules contained in the matrix phase to the surface of the domain phase is suppressed, the incompatibility between the domain phase and the matrix phase is improved, and a stable phase separation structure is formed. The behavior of the contained resin with respect to temperature can be made clearer.

  That is, the resin contained in the matrix phase can be more reliably melted by heat from the low temperature region in the fixing nip, and the resin contained in the domain phase can be heated from the high temperature region in the nip. Make absorption more certain. As a result, the fluidity of the toner melted by the fixing device is maintained without being affected even if there is a temperature difference in the fixing nip portion, and a good toner image without stepped gloss unevenness is more reliably obtained. To form.

  Specific examples of the radical polymerizable monomer having a plurality of carboxyl groups (—COOH) include, for example, itaconic acid having two carboxyl groups, maleic acid, fumaric acid, aconitic acid having three carboxyl groups, and the like. Can be mentioned. Specific examples of the radical polymerizable monomer having a plurality of carboxyl groups are shown below.

  In the present invention, among the radical polymerizable monomers having a plurality of carboxyl groups, it is preferable to prepare a resin contained in the domain phase using itaconic acid. When a domain phase resin is formed using itaconic acid, the itaconic acid component is preferentially oriented on the resin surface (domain phase surface), and the solubility parameter value on the domain phase surface is more efficiently increased. As a result, it is considered that the incompatibility at the interface between the domain phase and the matrix phase is more effectively improved, and the effect of the present invention is more easily realized.

  In addition, itaconic acid tends to be more reactive than other radically polymerizable monomers having a plurality of carboxyl groups, so that it is reliably used in polymerization reactions when forming a resin contained in the domain phase. Thus, a plurality of carboxyl groups are incorporated into the resin molecule. Therefore, the radical polymerizable monomer having a plurality of carboxyl groups is not left unreacted, which is preferable from the viewpoint of reliably improving the incompatibility between the domain phase and the matrix phase.

  In the toner according to the present invention, the weight average molecular weight Mw of the resin contained in the domain phase is larger than the weight average molecular weight Mw of the resin contained in the matrix phase. By making the weight average molecular weight of the resin contained in the domain phase larger than the weight average molecular weight of the resin contained in the matrix phase, the resin in the matrix phase melts in a low temperature region. Also, by increasing the weight average molecular weight of the domain phase resin, the domain phase resin softens and melts in the high temperature region of the fixing nip, but by increasing the molecular weight, the matrix phase resin has a high temperature region. In order to prevent liquidity from rising due to the effects of As a result, even if there is a temperature difference in the fixing nip portion, the molten toner can be fixed without causing a change in fluidity, so that it is possible to form an image without uneven uneven gloss.

  Specifically, the weight average molecular weight of the resin contained in the domain phase is preferably 80,000 or more and 500,000 or less. When the weight average molecular weight Mw is in the above range, the domain phase is in the high temperature region of the nip part. Softens and melts. Then, due to the softening and melting of the resin in the domain phase, the matrix phase resin is not affected by the high temperature region of the nip, and does not change the fluidity of the molten toner, causing uneven gloss in a step shape. There is no.

  On the other hand, the weight average molecular weight Mw of the resin contained in the matrix phase is preferably, for example, 10,000 or more and 30,000 or less. By setting the weight average molecular weight Mw in the above range, smooth melting by heat from a low temperature region formed by contact between the heating roller in the fixing nip portion and the transfer sheet is enabled. Further, when the weight average molecular weight Mw is in the above range, an appropriate viscosity and internal cohesive force are imparted to the molten toner, and the fracture of the molten toner at the time of fixing is avoided.

  In this way, by setting the weight average molecular weight Mw of the resin contained in the matrix phase within the above range, the toner is surely melted with heat from a low temperature region in the fixing nip portion, and the molten toner layer has an appropriate durability. It seems that has been granted.

  Furthermore, it is conceivable that an effect of promoting incompatibility between the matrix phase and the domain phase is also exhibited by making a certain difference between the weight average molecular weight of the resin contained in the domain phase.

  The weight average molecular weight Mw of the “resin contained in the domain phase” and the “resin contained in the matrix phase” constituting the toner according to the present invention is, for example, the GPC method (gel permeation chromatography). It can be measured and calculated by a known molecular weight measurement method. For example, the measurement of the weight average molecular weight by GPC method (gel permeation chromatography) is performed according to the following procedure.

In the method for measuring the weight average molecular weight by the GPC (gel permeation chromatography) method, first, a measurement sample is dissolved in tetrahydrofuran so that the concentration becomes 1 mg / ml. As dissolution conditions, treatment is performed at room temperature for 5 minutes using an ultrasonic disperser. Next, after processing the sample solution with a membrane filter having a pore size of 0.2 μm, 10 μl of the sample solution is injected into a measuring device (GPC device). Below, the specific example of the conditions at the time of measuring a weight average molecular weight by GPC method is shown below. That is,
Apparatus: HLC-8220 (manufactured by Tosoh Corporation)
Column: TSK guard column + TSK gel SuperHZM-M ₃ series (manufactured by Tosoh)
Column temperature: 40 ° C
Solvent: Tetrahydrofuran (THF)
Flow rate: 0.2 ml / min Detector: Refractive index detector (RI detector)
In the measurement of the molecular weight of a sample, the molecular weight distribution of the sample is calculated using a calibration curve measured using monodisperse polystyrene standard particles. It is preferable to prepare 10 points of polystyrene for calibration curve measurement.

  Next, the polymerizable monomer capable of producing the resin constituting the toner according to the present invention will be described other than the radical polymerizable monomer having a plurality of carboxyl groups described above. The polymerizable monomer used in the present invention is capable of undergoing a polymerization reaction with a radical polymerizable monomer having a plurality of carboxyl groups when forming a resin contained in the domain. Any radically polymerizable monomer that can be used is not particularly limited.

  Among such radically polymerizable monomers, those that are preferably used to form a domain phase resin and a matrix phase resin include, for example, styrene monomers and (meth) acrylic monomers. Is mentioned. Here, the “styrene monomer” is a vinyl polymerizable monomer containing a benzene ring as a functional group in the molecular structure. In addition to styrene, a methyl group or a phenyl group is added to the benzene ring. Also included are so-called styrene derivatives bonded with various functional groups such as hydrocarbon groups and halogen groups.

The “(meth) acrylic acid monomer” means a vinyl polymerizable monomer containing in its molecular structure at least one of a carboxyl group (—COOH) and a carboxylic acid ester structure (—COOR). Therefore, “methacrylic acid monomer” and “acrylic acid monomer” are collectively called “(meth) acrylic acid monomer”. That is, “(meth) acryl” means that the vinyl group site in the monomer structure is one of a methacryl group (CH ₂ ═C (CH ₃ ) COO—) and an acryl group (CH ₂ ═CHCOO—). It means that it is a structure. Specific examples of the “methacrylic acid monomer” include methacrylic acid (CH ₂ ═C (CH ₃ ) COOH) and a methacrylic acid ester derivative shown in the following (2). Specific examples of the “acrylic acid monomer” include acrylic acid (CH ₂ ═CHCOOH) and acrylic ester derivatives shown in the following (3).

  Hereinafter, specific examples of the styrene monomer are shown in the following (1), specific examples of the methacrylic ester derivatives are shown in the following (2), and specific examples of the acrylate derivatives are shown in the following (3).

(1) Styrene or styrene derivatives Styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert- Butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, etc. (2) Methacrylate derivative Methyl methacrylate (MMA) ), Ethyl methacrylate (EMA), n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, methacryl Acid phenyl Diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate, etc. (3) Acrylic acid ester derivatives Methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-acrylate Octyl, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, phenyl acrylate, and the like.

  Among the polymerizable monomers, styrene monomer is styrene, methacrylic acid monomer is methacrylic acid, methyl methacrylate, acrylic acid monomer is acrylic acid, and n-butyl acrylate. A copolymer formed using these is particularly preferable.

The domain contains a resin formed using a radically polymerizable monomer having at least a plurality of carboxyl groups. The styrene monomer or the (meth) acrylic acid monomer described above, In addition to the radical polymerizable monomer having a plurality of carboxyl groups (—COOH), the following radical polymerizable monomers can be used in combination. That is,
(1) Olefins Ethylene, propylene, isobutylene, etc. (2) Vinyl esters Vinyl propionate, vinyl acetate, vinyl benzoate, etc. (3) Vinyl ethers Vinyl methyl ether, vinyl ethyl ether, etc. (4) Vinyl ketones Vinyl methyl ketone, Vinyl ethyl ketone, vinyl hexyl ketone, etc. (5) N-vinyl compounds N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrolidone, etc. (6) Vinyl compounds Vinyl naphthalene, vinyl pyridine, etc. (7) Acrylic acid or methacrylic acid Derivatives Acrylonitrile, methacrylonitrile, acrylamide, etc.

  Moreover, it is also possible to use combining the polymerizable monomer which has polar groups other than the polymerizable monomer which has a some carboxyl group. Examples of polar groups other than the polymerizable monomer having a plurality of carboxyl groups include substituents such as sulfonic acid groups and phosphoric acid groups.

It is also possible to form a resin having a crosslinked structure using polyfunctional vinyls as the polymerizable monomer constituting the resin. Specific examples of the polyfunctional vinyls are listed below. That is,
Examples include divinylbenzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol diacrylate, neopentyl glycol dimethacrylate, neopentyl glycol diacrylate, and the like.

  Next, colorants and waxes that can be used to form a resin used for producing the toner according to the present invention will be described. First, known colorants can be used for the toner according to the present invention, and specific colorants are listed below.

  Examples of the black colorant include carbon black such as furnace black, channel black, acetylene black, thermal black, and lamp black, and magnetic powder such as magnetite and ferrite can also be used.

  Examples of the colorant for magenta or red include C.I. I. Pigment Red 2, 3, 5, 6, 7, 15, 15, 48: 1, 53: 1, 57: 1, 60, 63, 64, 68, the same 81, 83, 87, 88, 89, 90, 112, 114, 122, 123, 139, 144, 149, 150, 163, 166, 170, 177, 178, 184, 202, 206, 207, 209, 222, 238, 269, and the like.

  Examples of the colorant for orange or yellow include C.I. I. Pigment Orange 31 and 43, C.I. I. Pigment Yellow 12, 14, 15, 17, 74, 83, 93, 94, 138, 155, 162, 180, 185, and the like.

  Further, as a colorant for green or cyan, C.I. I. Pigment Blue 2, 3, 15, 15, 15: 2, 15: 3, 15: 4, 16, 17, 17, 60, 62, 66, C.I. I. Pigment Green 7 etc.

  Examples of the dye include C.I. I. Solvent Red 1, 49, 52, 58, 63, 111, 122, C.I. I. Solvent Yellow 2, 6, 14, 15, 16, 19, 21, 21, 33, 44, 56, 61, 77, 79, 80, 81, 82, the same 93, 98, 103, 104, 112, 162, C.I. I. Solvent Blue 25, 36, 60, 70, 93, 95, etc.

  These colorants can be used alone or in combination of two or more as required. Further, the amount of the colorant added is in the range of 1 to 30% by mass, preferably 2 to 20% by mass, based on the whole toner, and a mixture thereof can also be used. The number average primary particle size varies depending on the type, but is preferably about 10 to 200 nm.

  As a method for adding the colorant, the resin fine particles are added at the stage of agglomeration by the addition of the flocculant to color the polymer. The colorant can also be used by treating the surface with a coupling agent or the like.

Examples of the wax that can be used in the toner according to the present invention include conventionally known waxes. Specific examples include the following. That is,
(1) Long-chain hydrocarbon wax Polyolefin wax such as polyethylene wax and polypropylene wax, paraffin wax, sazol wax, etc. (2) Ester wax Trimethylolpropane tribehenate, pentaerythritol tetramyristate, pentaerythritol tetrasteare Rate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecanediol distearate, tristearyl trimellitic acid, distearyl maleate, etc. (3) Amide wax Ethylenediamine dibehenyl amide, trimellitic acid tristearyl amide, etc. (4) Dialkyl ketone waxes, distearyl ketone, etc. (5) Others Carnauba Vinegar, montan waxes, and the like.

  The melting point of the wax is usually 40 to 160 ° C, preferably 50 to 120 ° C, more preferably 60 to 90 ° C. By setting the melting point within the above range, the heat-resistant storage stability of the toner is ensured, and stable toner image formation can be performed even when fixing at a low temperature. Further, the wax content in the toner is preferably 1% by mass to 30% by mass, and more preferably 5% by mass to 20% by mass.

  Next, a toner manufacturing method according to the present invention will be described.

  The resin constituting the toner according to the present invention is composed of at least “resin contained in a matrix” and “resin contained in a domain”, and can be produced by a known production method. As a representative method for producing the toner according to the present invention, for example, emulsification in which a resin particle formed in an aqueous medium containing a surfactant is aggregated and fused in an aqueous medium to produce a toner. There is a method called the meeting method. In the emulsion association method, toners with uniform particle diameters and shapes can be more reliably produced, so toners used for digital image formation with high fine line reproducibility and fine dot image formation opportunities are produced. The above is also preferable.

  Examples of resin fine particles that are aggregated and fused by the above-described emulsion association method include “resin fine particles containing a resin that forms a matrix phase and a resin that forms a matrix phase” and “domain phase that are formed by the following procedure” Resin fine particles ”and“ resin fine particles forming a matrix phase ”. “Resin fine particles containing resin that forms the domain phase and resin that forms the matrix phase” is the first step of preparing the fine particles of the resin that forms the domain phase and then polymerizing in the presence of the fine resin particles that form the domain phase. A resin that forms a matrix phase by performing a reaction is formed. That is, it is an encapsulated structure type resin fine particle in which a resin that forms a matrix phase is bonded around a resin that forms a domain phase. The “resin fine particles forming the matrix phase” and the “resin fine particles forming the domain phase” are prepared by polymerizing polymerizable monomers forming the respective resins.

The toner production method by the emulsion association method is performed, for example, through the following steps. That is,
(1) Dissolution / dispersion step for dissolving or dispersing wax in radical polymerizable monomer (2) Polymerization step for preparing a dispersion of resin fine particles (3) Aggregating resin fine particles and colorant particles in an aqueous medium Aggregating and fusing step for forming aggregated particles to be toner base particles by fusing (4) aging step for aging associated particles by thermal energy to adjust the shape (5) from cooled aggregated particle dispersion Washing step of solid-liquid separating the associated particles and removing the surfactant and the like from the associated particles (6) Drying step of drying the washed associated particles Further, if necessary, after the drying step,
(7) There may be a step of adding an external additive to the dried association particles. The above steps will be described in detail later.

  The associated particles serving as a toner base can be prepared through a process of aggregating and fusing resin fine particles and colorant fine particles. The shape of the associated particles can be controlled, for example, by controlling the heating temperature in the aggregation / fusion process and the heating temperature and time in the first aging process.

  Among these, time control in the aging process is the most effective. Since the ripening step is intended to adjust the circularity of the associated particles, the target circularity is reached by controlling this time.

  The associated particles serving as a toner base can be preferably prepared by, for example, salting out / fusion performed in the following procedure. That is, after the wax component is dissolved or dispersed in the polymerizable monomer that forms the resin, it is mechanically dispersed in an aqueous medium, and the polymerizable monomer is polymerized by a mini-emulsion polymerization method to obtain resin particles. Form. Then, the formed resin particles and colorant particles are salted out / fused as described later to form associated particles. In addition, the method of melt | dissolving a wax component in the above-mentioned polymerizable monomer can take any method, even if a wax component is melt | dissolved or fuse | melted.

  Hereinafter, each manufacturing process of the toner by the emulsion association method will be described.

(1) Dissolution / dispersion step In this step, a radical polymerizable monomer mixture solution is prepared by mixing and dissolving the above-mentioned plural types of radical polymerizable monomers that form the resin. The monomer mixed solution is added to an aqueous medium containing a surfactant having a critical micelle concentration (CMC) or less. Then, mechanical energy is applied to disperse the radical polymerizable monomer mixed solution in the aqueous medium to form droplets having a predetermined particle diameter. In addition, when mixing a radically polymerizable monomer, in addition to mixing and dissolving a plurality of types of polymerizable monomers, it is possible to add a wax or the like.

  Thus, in the emulsion association method, it is essential to disperse the radical polymerizable monomer solution into droplets in advance (emulsification treatment) by applying mechanical energy prior to the next polymerization step. Examples of such mechanical energy applying means include strong agitation such as homomixer, ultrasonic wave, and manton gorin or ultrasonic vibration energy applying means.

  In addition, the “aqueous medium” referred to here is one in which the main component (50% by mass or more) is made of water. Examples of components other than water forming the “aqueous medium” include organic solvents that dissolve in water, such as methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone, and tetrahydrofuran. Moreover, a well-known surfactant can be used for surfactant used for an aqueous medium.

(2) Polymerization step In this step, a water-soluble radical polymerization initiator is added to an aqueous medium in which droplets of the radical polymerizable monomer solution formed in the previous step are dispersed, and a polymerization reaction is performed in the droplets. To produce resin fine particles. An oil-soluble polymerization initiator can be used as the radical polymerization initiator added to the droplets. Moreover, when a radically polymerizable monomer mixed solution is prepared by adding wax in all steps, resin fine particles containing wax can be produced.

  In the present invention, the “resin fine particles containing a resin that forms a domain phase and a resin that forms a matrix phase” or “resin fine particles that form a domain phase” and “resin fine particles that form a matrix phase” described above in this polymerization step. Is produced.

  When producing “resin fine particles containing a resin that forms a domain phase and a resin that forms a matrix phase”, a resin fine particle dispersion having a structure in which the resin that forms the domain phase is encapsulated with the resin that forms the matrix phase is prepared. Will do. In this case, the resin that forms the domain phase is formed by the first polymerization reaction, and then the polymerization reaction is performed again in the presence of the resin that forms the domain phase to form the matrix phase around the resin that forms the domain phase. The resin to be formed is formed. In addition, when producing “resin fine particles forming a domain phase” and “resin fine particles forming a matrix phase”, a dispersion of resin fine particles forming a domain phase and a resin fine particle forming a matrix phase are obtained by polymerization. Each dispersion is prepared.

(3) Aggregation / fusion process This process agglomerates and fuses the resin fine particles produced in the above-described polymerization process, and a specific method is preferably a salting-out / fusion process. In the aggregation / fusion process, it is possible to coagulate and fuse together the resin fine particles and the colorant fine particles together with the internal additive particles such as the wax particles and the charge control agent.

  The colorant particles can be prepared by dispersing the colorant in an aqueous medium. The dispersion treatment of the colorant is performed in a state where the surfactant concentration is set to a critical micelle concentration (CMC) or more in water. The disperser used for the dispersion treatment of the colorant is not particularly limited, but preferably an ultrasonic disperser, a mechanical homogenizer, a pressure disperser such as a manton gorin or a pressure homogenizer, a sand grinder, a Getzmann mill, a diamond fine mill, or the like. There is a media-type disperser.

  A colorant (particle) that has been subjected to surface modification treatment can also be used. In the surface modification method of the colorant, the colorant is dispersed in a solvent, the surface modifier is added to the dispersion, and the temperature of the system is increased to perform the reaction. After completion of the reaction, the colorant is filtered, washed and filtered with the same solvent, and then dried to obtain a colorant (pigment) treated with the surface modifier.

  Here, “salting out / fusion” means that the aggregation and fusion of resin fine particles and the like proceed in parallel, and when the particles grow to a desired particle size, an aggregation terminator is added to stop the particle growth. It is a method in which heating is continuously performed to control the particle shape as necessary.

  That is, in the salting-out / fusion method, a salting-out agent comprising an alkali metal salt, an alkaline earth metal salt, a trivalent salt, or the like is added to a critical coagulation concentration in an aqueous medium in which resin fine particles and colorant fine particles are present. Add more and leave. Next, by heating to a temperature not lower than the glass transition point of the resin fine particles and not lower than the melting peak temperature of the mixture, the salting out (aggregation) of each fine particle described above proceeds, and at the same time, fusion is performed. Here, the alkali metal salts and alkaline earth metal salts used as the salting-out agent include the following. First, examples of the alkali metal include lithium, potassium, and sodium, and examples of the alkaline earth metal include magnesium, calcium, strontium, and barium. Of these, potassium, sodium, magnesium, calcium, and barium are preferable.

  When agglomeration and fusing are performed by salting out / fusing, it is preferable to shorten the time allowed to stand after adding the salting-out agent as much as possible. The reason for this is that depending on the standing time after salting out, the aggregation state of the particles may fluctuate and the particle size distribution may become unstable, or the surface properties of the fused particles may vary. This is because of concern. Moreover, it is preferable that the addition temperature of the salting-out agent is at least the glass transition temperature of the resin particles. The reason for this is that if the addition temperature of the salting-out agent is equal to or higher than the glass transition temperature of the resin particles, the salting-out / fusion of the resin particles proceeds rapidly, but it becomes difficult to control the particle size. This is because there are concerns about the occurrence of problems such as generation of particles having a particle size. A preferable range of the addition temperature of the salting-out agent is not higher than the glass transition temperature of the resin, but is generally 5 to 55 ° C, preferably 10 to 45 ° C.

  In addition, after adding the salting-out agent below the glass transition temperature of the resin particles, the temperature is raised as quickly as possible, and heated to a temperature that is equal to or higher than the glass transition temperature of the resin particles and equal to or higher than the melting peak temperature of the mixture. It is preferable to do. The time until this temperature rise is preferably less than 1 hour. Further, although it is necessary to quickly raise the temperature, the rate of temperature rise is preferably 0.25 ° C./min or more. The upper limit of the rate of temperature rise is not particularly specified, but if the temperature is raised rapidly, salting out proceeds rapidly, which may cause a problem that it is difficult to control the particle size. The following is preferred.

  In this agglomeration / fusion step, arbitrary fine particles such as resin fine particles and colorant fine particles are agglomerated and fused to obtain a dispersion of associated particles having a uniform particle size.

(4) Ripening step In this step, the associated particles formed in the aggregation / fusion step are continuously heated to make the shape of the associated particles uniform and smooth the surface. In this process, by controlling the heating temperature and time, the surface of the associated particles is smoothed and the shape is made uniform. Specifically, the heating temperature is set lower than the heating temperature in the aggregation / fusion process. By setting, the fusion of the resin fine particles is suppressed and the smoothing of the surface is promoted. In addition, by setting the time longer, the uniform shape of the associated particles is promoted.

(5) Washing step In this step, first, the associated particle dispersion is cooled. As cooling process conditions, it can cool at the cooling rate of 1-20 degreeC / min, for example. The cooling treatment method is not particularly limited, and there are known methods such as a method of cooling by introducing a refrigerant from the outside of the reaction vessel, and a method of cooling by directly introducing cold water into the reaction system.

  Next, the cooled associated particle dispersion is subjected to solid-liquid separation, and the associated particles subjected to the solid-liquid separation treatment are washed. When the aggregated particle dispersion is solid-liquid separated, the solid-liquid-separated wet aggregated particles are in the form of agglomerated aggregates in the form of a cake called a toner cake. Remove the surfactant and salting-out agent adhering to the surface. As a typical solid-liquid separation treatment, there is a filtration treatment. Specific methods of the filtration treatment include, for example, a centrifugal separation method, a vacuum filtration method using Nutsche, etc., a filtration method using a filter press, etc. is there.

(6) Drying Step This step is a step of obtaining toner base particles by pulverizing the washed toner cake and drying the associated particles. Examples of the drying apparatus that can be used in the drying process include known drying processors such as spray dryers, vacuum freeze dryers, and vacuum dryers, stationary shelf dryers, mobile shelf dryers, fluidized bed dryers, Use of a rotary dryer, a stirring dryer, or the like is also possible. The moisture content of the dried toner base particles is preferably 5% by mass or less, and more preferably 2% by mass or less.

  In the case where the aggregate is formed by the attractive force between the particles of the dried toner base particles, the aggregate can be crushed. Specific examples of the crushing treatment apparatus include mechanical crushing treatment apparatuses such as a jet mill, a Henschel mixer, a coffee mill, and a food processor.

(7) External Addition Processing Step This step is a step of preparing toner particles by adding and mixing external additives as necessary to the dried association particles.

  The associated particles produced through the steps up to the drying step can be used as toner particles as they are, but are known on the surface of the associated particles from the viewpoint of improving charging performance, fluidity, and cleaning properties as a toner. It is preferable to add particles such as inorganic fine particles and organic fine particles as external additives.

  The type of the external additive is not particularly limited, and examples thereof include the following inorganic fine particles, organic fine particles, and lubricants.

  As the inorganic fine particles, known ones can be used. For example, silica, titania, alumina, strontium titanate fine particles and the like are preferable, and if necessary, these inorganic fine particles are subjected to a hydrophobic treatment. Things can also be used.

  Specific examples of the silica fine particles include commercially available products R-805, R-976, R-974, R-972, R-812, R-809 manufactured by Nippon Aerosil Co., Ltd., HVK-2150 manufactured by Hoechst, H -200, commercially available products TS-720, TS-530, TS-610, H-5, MS-5 and the like manufactured by Cabot Corporation.

  As the titania fine particles, for example, commercially available products T-805 and T-604 manufactured by Nippon Aerosil Co., Ltd., commercially available products MT-100S, MT-100B, MT-500BS, MT-600, MT-600SS, JA- 1. Commercial products TA-300SI, TA-500, TAF-130, TAF-510, TAF-510T manufactured by Fuji Titanium Co., Ltd. Commercial products IT-S, IT-OA, IT-OB, IT- manufactured by Idemitsu Kosan Co., Ltd. OC etc. are mentioned.

  Examples of the alumina fine particles include commercial products RFY-C and C-604 manufactured by Nippon Aerosil Co., Ltd. and commercial products TTO-55 manufactured by Ishihara Sangyo Co., Ltd.

  As the organic fine particles, spherical organic fine particles having a number average primary particle diameter of about 10 to 2000 nm can be used. Specifically, homopolymers such as styrene and methyl methacrylate and copolymers thereof can be used.

  In addition, a lubricant can be used to further improve the cleaning property and transfer property. For example, there are metal salts of higher fatty acids as follows. That is, salts of zinc stearate, aluminum, copper, magnesium, calcium, etc., zinc oleate, salts of manganese, iron, copper, magnesium, etc., zinc palmitate, salts of copper, magnesium, calcium, etc., linoleic acid There are salts of zinc, calcium and the like, and zinc and calcium of ricinoleic acid.

  The addition amount of these external additives and lubricants is preferably 0.1 to 10.0% by mass with respect to the whole toner. As a method for adding external additives and lubricants, there is a method using a known mixing device such as a Turbuler mixer, a Henschel mixer, a Nauter mixer, a V-type mixer or the like.

In the case where the toner according to the present invention is a toner compatible with so-called low-temperature fixing that can be melted at a lower fixing temperature than before, particles containing a resin that can be melted at a lower heating temperature are thermally stable resin. It is preferable to use a so-called core-shell structure coated with. When preparing a toner having a core-shell structure, between the aggregation / fusion process (4) and the aging process (5),
(4-1) Resin particles for shells are added to the associated particle dispersion liquid constituting the core particles to aggregate and fuse the shell particles on the surface of the core particles to form toner base particles having a core-shell structure. (4-2) Associating particles having a core-shell structure are aged by thermal energy, and two steps of a second aging step of adjusting the shape of the associated particles of the core-shell structure are added. Otherwise, it is possible to prepare a toner having a core-shell structure by following the same procedure.

  In the shelling step, the final toner shape and particle size can be controlled. In the shelling step, since the resin particles for the shell are added to each core particle under the same conditions, it is preferable that the core particles have a uniform particle size and shape. If the core particles have the same particle size and shape as described above, the resin particles for forming a shell are easily uniformly adhered to the surface of the core particles, and a toner having a uniform thickness and a uniform thickness is formed. Particles can be produced reliably. Hereinafter, the shelling step and the second aging step will be described in detail.

(4-1) Shelling Step When a core-shell toner is formed, a shelling step and a second ripening step for advancing the fusion of shell resin particles are added after the ripening step (5) described above. . In the shelling step, the resin particle dispersion for the shell is added to the associated particle dispersion that becomes the core particles, and the resin particles for the shell are aggregated and fused on the surface of the core particles. These resin particles are coated to form associated particles that serve as a base of toner particles.

  Specifically, the core particle dispersion is added with the dispersion of the resin particles for shells while maintaining the temperature in the aggregation / fusion process and the aging process, and slowly over several hours while continuing the heating and stirring. The resin particles for shell are coated on the surface of the core particles to form associated particles. The heating and stirring time is preferably 1 hour to 7 hours, particularly preferably 3 hours to 5 hours.

(4-2) Second ripening step After the shelling, the particle growth is stopped by adding a terminator such as sodium chloride at the stage where the associated particles have reached a predetermined particle size, and then adheres to the core particles. Heating and stirring are continued for several hours in order to fuse the shell resin particles. In the shelling step, a shell having a thickness of 100 to 300 nm is formed on the surface of the core particle. In this way, the resin particles are fixed to the surface of the core particles to form a shell, and rounded and uniform shaped particles can be formed.

  When producing a toner with a core-shell structure, the shape of the associated particles formed by setting the time of the second aging step longer or setting the aging temperature higher can be controlled in the true sphere direction. It is.

  Next, a polymerization initiator, a dispersion stabilizer, a surfactant and the like used when the toner according to the present invention is produced in an aqueous medium will be described.

When the binder resin constituting the toner according to the present invention is formed using a vinyl polymerizable monomer, a known oil-soluble or water-soluble polymerization initiator can be used. Specific examples of the oil-soluble polymerization initiator include the following azo or diazo polymerization initiators and peroxide polymerization initiators. That is,
(1) Azo or diazo polymerization initiator 2,2'-azobis- (2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 1,1'-azobis (cyclohexane-1 -Carbonitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, azobisisobutyronitrile, etc. (2) peroxide-based polymerization initiators benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl Peroxycarbonate, cumene hydroperoxide, t-butyl hydroperoxide, di-t-butyl peroxide, dicumyl peroxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide, 2,2-bis- (4 4-t-butylperoxycyclohexyl) propane, tris (T-butylperoxy) triazine Further, when forming the resin particles by emulsion polymerization is a water-soluble radical polymerization initiators can be used. Examples of the water-soluble polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate, azobisaminodipropane acetate, azobiscyanovaleric acid and its salts, hydrogen peroxide and the like.

  In addition, a known chain transfer agent can be used for adjusting the molecular weight of the resin particles. Specific examples include octyl mercaptan, dodecyl mercaptan, tert-dodecyl mercaptan, n-octyl-3-mercaptopropionic acid ester, terpinolene, carbon tetrabromide, and α-methylstyrene dimer.

  In addition, a dispersion stabilizer is used from the viewpoint of stably polymerizing polymerizable monomers in a dispersed state in an aqueous medium, and stably agglomerating and fusing resin particles dispersed in the aqueous medium. It is preferable to use it.

  Examples of the dispersion stabilizer include tricalcium phosphate, magnesium phosphate, zinc phosphate, aluminum phosphate, calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate, Examples include barium sulfate, bentonite, silica, and alumina. In addition, polyvinyl alcohol, gelatin, methylcellulose, sodium dodecylbenzenesulfonate, ethylene oxide adduct, higher alcohol sodium sulfate and the like that can be generally used as a surfactant can be used as a dispersion stabilizer.

  Further, when polymerization is performed using a polymerizable monomer in an aqueous medium, it is necessary to uniformly disperse oil droplets of the polymerizable monomer in the aqueous medium using a surfactant. In this case, usable surfactants are not particularly limited, but for example, the following ionic surfactants can be used as preferable ones. Examples of the ionic surfactant include a sulfonate, a sulfate ester salt, and a fatty acid salt. Examples of the sulfonate include sodium dodecylbenzenesulfonate, sodium arylalkylpolyethersulfonate, and 3,3-disulfonediphenyl. Urea-4,4-diazo-bis-amino-8-naphthol-6-sulfonate sodium, ortho-carboxybenzene-azo-dimethylaniline, 2,2,5,5-tetramethyl-triphenylmethane-4,4 -Sodium diazo-bis-β-naphthol-6-sulfonate.

  Examples of sulfate salts include sodium dodecyl sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, and sodium octyl sulfate. Fatty acid salts include sodium oleate, sodium laurate, sodium caprate, sodium caprylate, Examples include sodium caproate, potassium stearate, and calcium oleate.

  Nonionic surfactants can also be used. Specifically, polyethylene oxide, polypropylene oxide, a combination of polypropylene oxide and polyethylene oxide, esters of polyethylene glycol and higher fatty acids, alkylphenol polyethylene oxide, higher fatty acids and Examples include polyethylene glycol esters, higher fatty acid and polypropylene oxide esters, sorbitan esters, and the like.

  Next, the developer using the toner according to the present invention will be described.

  The toner according to the present invention can be used for both a one-component developer (including magnetic and non-magnetic) that forms an image without using a carrier and a two-component developer that forms an image using a carrier. is there.

  When used as a two-component developer, it can be prepared by mixing toner and carrier. The mixing amount of the toner with respect to the carrier is preferably 2 to 10% by mass. The mixing apparatus for mixing the toner and the carrier is not particularly limited, and examples thereof include a Nauter mixer, a W cone, and a V-type mixer.

  The carrier is preferably a ferrite carrier having a volume average particle size of 10 to 60 μm and a saturation magnetization value of 20 to 80 emu / g. Thus, by using a carrier having a small carrier particle size and a low saturation magnetization value, the magnetic brush on the developing sleeve becomes soft, and an electrophotographic image with good sharpness can be formed.

  The volume average particle diameter of the carrier can be measured by, for example, a laser diffraction particle size analyzer “HELOS (manufactured by Shinpatec Corporation)” equipped with a wet disperser. The saturation magnetization can be measured by, for example, “DC magnetization characteristic automatic recording device 3257-35 (manufactured by Yokogawa Electric Corporation)”.

  It is preferable that the carrier has magnetic particles as a core (core) and the surface thereof is coated with a resin. The resin used for coating the carrier core material is not particularly limited, and various resins can be used. For the positively chargeable toner, for example, a fluorine-based resin, a fluorine-acrylic acid-based resin, a silicone-based resin, a modified silicone-based resin, or the like can be used, and a condensation type silicone-based resin is preferable. For negatively chargeable toners, for example, acrylic-styrene resins, mixed resins of acrylic-styrene resins and melamine resins and cured resins thereof, silicone resins, modified silicone resins, epoxy resins, polyesters Resin, urethane resin, polyethylene resin, etc. can be used. Among these, a mixed resin of an acrylic-styrene resin and a melamine resin, a cured resin thereof, and a condensation type silicone resin are preferable. If necessary, a two-component developer can be formed by adding a charge control agent, an adhesion improver, a primer treatment agent, a resistance control agent, and the like.

  When the toner is used as a non-magnetic one-component developer that forms an image without using a carrier, the toner is rubbed against and pressed against the charging member and the developing roller surface during image formation. Image formation by the non-magnetic one-component development method can simplify the structure of the developing device, and thus has an advantage that the entire image forming device can be made compact. Therefore, when the toner according to the present invention is used as a non-magnetic one-component developer, a full color print can be created with a compact color printer, and a full color print excellent in color reproducibility can be created even in a space-limited work environment. Is possible.

  A magnetic toner which is one of the one-component developers can be produced by using magnetic fine particles as a colorant. As the magnetic fine particles, particles such as ferrite and magnetite having an average primary particle diameter of 0.1 to 2.0 μm are used. The addition amount of the magnetic fine particles is preferably 20 to 70% by mass in the toner.

  Further, from the viewpoint of imparting fluidity, it is possible to mix known inorganic fine particles. As the inorganic fine particles, inorganic oxide particles such as silica, titania and alumina are preferable, and these inorganic fine particles are more preferably hydrophobized with a silane coupling agent or a titanium coupling agent.

  Next, the “heating roller / belt type fixing device” used in the image forming method according to the present invention will be described with reference to FIGS. FIG. 2 is a schematic diagram showing an example of a fixing device having a heating roller and a pressure belt, and FIG. 3 is a schematic diagram showing the fixing device shown in FIG. 2B in detail.

  The fixing device 24 shown in FIG. 2 includes a heating roller 242, a pressure belt 243, and a heat source 244, and the pressure belt 243 contacts the heating roller 242 to form a nip portion N having a certain width. The fixing device 24 in FIG. 2A has a tension roller 245 provided in a pressure belt 243, and the tension belt 243 is pressed against the heating roller 242 by the tension roller 245 so that the nip portion N is formed. To form. The fixing device 24 shown in FIG. 2B includes a pressure contact member 246 provided in a pressure belt 243, and forms a nip portion N by pressing the pressure contact member 246. The nip width of the nip portion N formed by the fixing device 24 of FIG. 2A is determined by the structure of the tension roller 245 and the pressure contact pressure, and the nip formed by the fixing device 24 of FIG. The nip width of the portion N is determined by the structure of the pressure contact member 246 and the pressure contact pressure.

  The fixing of the toner image performed by the fixing device 24 shown in FIGS. 2 and 3 will be described. The heating roller 242 constituting the fixing device 24 is rotated in the direction of arrow B by a motor (not shown), and the pressure belt 243 is also rotated by the rotation of the heating roller 242. A transfer material P onto which the toner image T has been transferred by a transfer device (not shown) is conveyed to the fixing device 24 from the right side of the drawing toward the nip portion N (in the direction of arrow A). When the transfer material P is inserted into the nip portion N, the toner image T on the transfer material P is melted by the pressure applied to the nip portion N and the heat applied from the halogen lamp 244 via the heating roller 242. The melted toner image T is fixed on the transfer material P.

  The transfer material P after fixing is peeled off without being wound around the heating roller 242 due to the effects of both the release layer 241 c on the heating roller 242 and the distortion at the nip portion N. Here, as means for assisting the separation of the transfer material P, for example, a separation assisting means 248 as shown in FIG. 3 can be provided on the downstream side of the nip portion N in the rotation direction of the heating roller 242. The peeling assisting means 248 includes, for example, a peeling assisting sheet 248a and a guide 248b that holds the peeling assisting sheet 248a, and the peeling assisting sheet 248a is opposed to the rotation direction of the heating roller 242 via the guide 248b (reverse direction). Is arranged.

  The heating roller / belt type fixing device shown in FIGS. 2 and 3 can secure a wide nip portion N. By securing the wide nip portion N, stable fixing performance and high fixing efficiency can be obtained. The nip width of the nip portion N formed by the heating roller 242 and the pressure belt 243 is preferably, for example, 5 mm to 40 mm, and more preferably 10 mm to 30 mm. By setting the nip width of the nip portion N within the above range, a wide nip width can be secured and the toner image can be efficiently melted. It is also preferable for increasing the rising speed from turning on the power to starting printing.

  In addition, since the heating roller / belt type fixing device can secure a wide width of the nip portion N, sufficient fixing performance can be obtained, and sufficient releasability can be obtained even if the strain amount of the nip portion N is small. can get. Therefore, the total load of the pressure contact member 246 can be reduced, and the heat resistant elastic body layer 242b can be thinned.

  Next, the heating roller 242, the pressure belt 243, the pressure contact member 246, and the lubricant supply member 247 constituting the fixing device 24 shown in FIGS. 2 and 3 will be described in detail.

  The heating roller will be described in detail with reference to FIG. As shown in FIG. 3, the heating roller 242 has a heat-resistant elastic body layer 242b and a release layer (heat-resistant resin layer) 242c around a cylindrical metal core (core metal) 242a. A halogen lamp 244, which is a heat source, is disposed inside the core 242a. The surface temperature of the heating roller 242 is measured by the temperature sensor 248, and the obtained measurement signal is fed back to a temperature controller (not shown) to adjust the heat generation of the halogen lamp 244.

  Thus, the heating roller 242 is heated by the built-in heating member 244, and the surface thereof is preferably heat-resistant and does not adhere to the toner melted by heating.

  In addition, the core 242a of the heating roller 242 described above can use a metal cylinder having high thermal conductivity such as iron, aluminum, and stainless steel. The outer diameter and thickness of the core 242a are not particularly limited. For example, in an iron core, the outer diameter can be about 20 mm to 35 mm, and the thickness can be about 0.3 mm to 0.5 mm. . Note that the outer diameter and thickness of the core 242a vary depending on the material of the core 242a, so that the optimal dimensions can be determined as appropriate.

  Further, when the outer diameter of the core 242a constituting the heating roller 242 is reduced or the thickness is reduced, the thickness of the heat-resistant elastic body layer 242b and the release layer 242c formed on the surface of the core 242a is the same as the conventional thickness. Even so, the diameter of the heating roller 242 is reduced. As a result, it is possible to produce a heating roller having a lower heat capacity than the heating roller used in the conventional fixing device, so that the waiting time until the start of the fixing process is shortened and the halogen lamp 244 as a heating source has a low output. Can be a thing. Further, it is possible to reduce the thermal resistance difference between the inner surface and the outer surface of the heating roller 242 and speed up the thermal response. As a result, the power consumption can be reduced and the fixing process can be performed at a higher speed.

  The heat-resistant elastic layer 242b formed on the surface of the core 242a is not particularly limited as long as it is an elastic body having heat resistance, and a known elastic material can be used. Specific examples include elastic materials such as rubber materials and elastomer materials having a rubber hardness according to JIS-A of about 25 ° to 40 °. For example, silicone rubber and fluorine rubber are preferable. The thickness of the heat resistant elastic layer 242b is preferably about 0.3 mm to 1.0 mm, although it depends on the rubber hardness of the elastic material used.

  The release layer (heat resistant resin layer) 242c formed on the heat resistant elastic layer 242b may be any resin as long as it is a heat resistant resin. For example, a fluororesin or a silicone resin may be used. Can be mentioned. Among these resins, the release layer 242c is required to have release properties and wear resistance, and therefore, a fluororesin is particularly preferably used. Specific examples of the fluororesin include, for example, PFA (perfluoroalkyl vinyl ether copolymer resin), PTFE (polytetrafluoroethylene polymer resin), FEP (tetrafluoroethylene hexafluoropropylene copolymer resin), Examples include tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymers. Among these, PFA is optimal from the viewpoints of heat resistance and workability.

  The thickness of the release layer 242c is preferably in the range of 5 μm to 30 μm, and more preferably in the range of 10 μm to 20 μm. By setting the thickness of the release layer 242c in the range of 5 μm to 30 μm, wrinkles may occur even if the surface of the heating roller 242 is distorted when the nip portion N is formed by pressing firmly with the pressure belt 243. There is no. Further, by setting the thickness of the release layer 242c in the range of 5 μm to 30 μm, an appropriate hardness is imparted to the release layer 242c, which is preferable for preventing the occurrence of image defects such as uneven gloss.

  The release layer 242c can be formed by a known method, for example, a dip coating method, a spray coating method, a roll coating method, a bar coating method, a spin coating method, or the like. It is.

  Next, the pressure belt 243 that presses against the heating roller 242 to form the nip portion N preferably has releasability in addition to heat resistance and flexibility, and has a base layer and its surface (heating roller). A structure in which a release layer is coated on a surface in contact with 242 or both surfaces) is preferable. Moreover, the thing processed seamlessly without the seam of an edge part is preferable.

  The base layer constituting the pressure belt 243 is formed of, for example, a resin such as polyimide, polyamide, or polyamideimide, and the thickness is preferably about 50 μm to 125 μm, more preferably about 75 μm to 100 μm. For the release layer formed on the surface of the base layer, for example, a fluororesin such as PFA (perfluoroalkoxy) is preferably used, and the thickness is preferably about 5 μm to 20 μm. As a specific form of the pressure belt 243 using such a resin, for example, a silicone rubber elastic layer is provided on a polyimide base material, and a PFA (perfluoroalkoxy) tube is provided on the surface layer. There is a layer structure. There is also a two-layer structure in which a fluororesin release material layer in which a conductive material is added is provided on a base material of polyperfluoroalkyl vinyl ether, polyimide or polyetherimide on a polyester base material.

  The fixing device 24 shown in FIG. 3 for explaining the fixing device 24 in FIG. 2B in detail has a pressure contact member 246 and a lubricant supply member 247 in addition to the heating roller 242 and the pressure belt 243 described above. is there. The pressure contact member 246 presses the heating roller 242 via the pressure belt 243, and includes two pressure pads 246a and 246b and a holder 246c. Here, the holder 246c holds the two pressure pads 246a and 246b.

  As shown in FIG. 3, the pressure contact member 246 shown in the fixing device 24 is arranged so that the pressure pads 246 a and 246 b press the heating roller 242 via the pressure belt 243. In the fixing device 24 of FIG. 3, the pressure contact member 246 has two pressure pads, but the pressure pad 246a applies a strong nip pressure, and the pressure pad 246b applies a weak nip pressure. The two pressure pads 246a and 246b are held by a holder 246c made of metal or the like.

  As shown in FIG. 3, a wide nip portion N can be secured by disposing a pressure pad 246 b that applies a weak nip pressure on the inlet side of the nip portion N. In addition, a strong nip pressure can be formed between the nip portion N and the heating roller 242 by disposing a pressure pad 246 a that applies a strong nip pressure on the outlet side. Further, in order to reduce the sliding resistance between the inner peripheral surface of the pressure belt 243 and the pressure pads 246a, b, a low friction layer is provided on the contact surface of the pressure pad 246a and the pressure pad 246b with the pressure belt 243. Is also possible.

  Further, a belt traveling guide can be attached to the holder 246c so that the pressure belt 243 smoothly slides and rotates. Since the belt running guide rubs against the inner surface of the pressure belt 243, it is preferably formed of a member having a low coefficient of friction, and a material having low heat conduction is preferably used in order to make it difficult to remove heat from the pressure belt 243. .

  The heating roller / belt fixing device can also apply a lubricant such as silicone oil, fluorine oil, or grease between the surfaces of the pressure pads 246a, b and the inner surface of the pressure belt 243. When these lubricants are used for a long time, they may adhere to the heating roller 242 via the pressure belt 243, and the lubricant gradually decreases due to the adhesion, and eventually becomes exhausted. When the lubricant is depleted, torque is increased. Therefore, as shown in FIG. 3, in the heating roller / belt fixing device, it is possible to provide a lubricant supply member 247 that holds and supplies the lubricant corresponding to the life of the fixing device in order to prevent depletion of the lubricant. .

  The lubricant holding member 247a constituting the lubricant supply member 247 preferably has a large number of continuous pores, has heat resistance at a fixing temperature and has an appropriate elastic modulus, and is formed of, for example, felt or sponge. The The lubricant permeation restriction film 247b constituting the lubricant supply member 247 preferably has a large number of continuous pores, has heat resistance at a fixing temperature, and has a small friction coefficient. For example, a fluororesin is stretched. A molded one is used.

  The lubricant holding member 247 a is impregnated with a lubricant, and the lubricant permeation amount regulating film 247 b of the lubricant supply member 247 is in contact with almost the entire area of the pressure belt 243 in the axial direction. The lubricant is supplied to the entire inner peripheral surface of the pressure belt 243 by the rotation of the pressure belt 243. Since the supply amount of the lubricant does not need to be increased, the contact pressure of the lubricant supply member 247 with respect to the pressure belt 243 may be as small as possible.

  It is preferable to continue supplying a minute amount of the lubricant to the inner peripheral surface of the pressure belt 243 over a long period of time. Further, the amount of lubricant supplied to the inner peripheral surface of the pressure belt 243 is determined by changing the porosity of the porous lubricant permeation amount regulating film 247b, thereby allowing the lubricant permeation amount in the lubricant permeation amount regulating membrane 247b. Is regulated and changed.

  The lubricant supply member 247 preferably makes the amount of lubricant supplied to the vicinity of the central portion of the pressure belt 243 in the axial direction larger than the amount of lubricant supplied to the vicinity of the end of the pressure belt 243 in the axial direction. Such a lubricant supply method is realized, for example, by making the contact width of the lubricant supply member 247 near the center of the pressure belt 243 wider than the contact width at the end. Alternatively, the contact pressure of the lubricant supply member 247 in the vicinity of the central portion is also realized by making it larger than the contact pressure at the end portion.

  The lubricant supplied from the lubricant supply member 247 is applied to the inner surface of the pressure belt 243, but has a releasing property because it may adhere to the heating roller 242 via the pressure belt 243. Of these, silicone oil is preferred.

  Specific examples of the silicone oil include dimethyl silicone oil, amino-modified silicone oil, carboxy-modified silicone oil, silanol-modified silicone oil, and sulfonic acid-modified silicone oil. Among these, amino-modified silicone oil is preferable from the viewpoint of handling because it is possible to effectively maintain the starting torque and driving torque of the fixing device in a desired low range.

  Next, an image forming apparatus capable of performing the image forming method according to the present invention will be described with reference to FIG. FIG. 4 is a schematic view showing an example of an image forming apparatus capable of forming an image using the toner according to the present invention.

  In FIG. 4, 1Y, 1M, 1C and 1K are photoreceptors, 4Y, 4M, 4C and 4K are developing devices, 5Y, 5M, 5C and 5K are primary transfer rolls as primary transfer means, and 5A is a secondary transfer. Secondary transfer roll as means, 6Y, 6M, 6C and 6K are cleaning devices, 7 is an intermediate transfer member unit, 24 is a heating roll / belt type fixing device shown in FIGS. 2 and 3, and 70 is an intermediate transfer member. .

  This image forming apparatus is called a tandem color image forming apparatus, and includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, an endless belt-shaped intermediate transfer body unit 7 as a transfer unit, and a transfer material P. An endless belt-shaped paper feeding / conveying means 21 for conveyance and a heating roll / belt type fixing device 24 as fixing means are provided. A document image reading device SC is disposed on the upper part of the main body A of the image forming apparatus.

  As one of the different color toner images formed on each photoconductor, an image forming unit 10Y that forms a yellow image includes a drum-shaped photoconductor 1Y as a first photoconductor, and a periphery of the photoconductor 1Y. A charging unit 2Y, an exposure unit 3Y, a developing unit 4Y, a primary transfer roll 5Y as a primary transfer unit, and a cleaning unit 6Y. An image forming unit 10M that forms a magenta image as another different color toner image is disposed around a drum-shaped photoconductor 1M as a first photoconductor, and the photoconductor 1M. A charging unit 2M, an exposure unit 3M, a developing unit 4M, a primary transfer roll 5M as a primary transfer unit, and a cleaning unit 6M.

  In addition, an image forming unit 10C that forms a cyan image as one of other different color toner images is disposed around the photoconductor 1C as a drum-type photoconductor 1C as a first photoconductor. The charging unit 2C, the exposure unit 3C, the developing unit 4C, the primary transfer roll 5C as the primary transfer unit, and the cleaning unit 6C are provided. Further, as one of the other different color toner images, the image forming unit 10K that forms a black image includes a drum-shaped photoconductor 1K as a first photoconductor, and a charge disposed around the photoconductor 1K. Means 2K, exposure means 3K, developing means 4K, primary transfer roll 5K as primary transfer means, and cleaning means 6K.

  The endless belt-like intermediate transfer body unit 7 has an endless belt-like intermediate transfer body 70 as an intermediate transfer endless belt-like second image carrier that is wound around a plurality of rolls and is rotatably supported.

  Each color image formed by the image forming units 10Y, 10M, 10C, and 10K is sequentially transferred onto the rotating endless belt-shaped intermediate transfer body 70 by the primary transfer rolls 5Y, 5M, 5C, and 5K, and is combined. A colored image is formed. A recording member P such as a sheet as a transfer material accommodated in the sheet feeding cassette 20 is fed by the sheet feeding / conveying means 21, passes through a plurality of intermediate rolls 22 A, 22 B, 22 C, 22 D, and a registration roll 23, and is secondary. A color image is transferred onto the recording member P at a time by being conveyed to a secondary transfer roll 5A as a transfer means. The recording member P to which the color image has been transferred is fixed by the heat roll type fixing device 24, is sandwiched by the paper discharge roll 25, and is placed on the paper discharge tray 26 outside the apparatus.

  On the other hand, after the color image is transferred to the recording member P by the secondary transfer roll 5A, the residual toner is removed by the cleaning unit 6A from the endless belt-shaped intermediate transfer body 70 from which the transfer material P is separated by curvature.

  During the image forming process, the primary transfer roll 5K is always in pressure contact with the photoreceptor 1K. The other primary transfer rolls 5Y, 5M, and 5C are in pressure contact with the corresponding photoreceptors 1Y, 1M, and 1C, respectively, only during color image formation.

  The secondary transfer roll 5A comes into pressure contact with the endless belt-shaped intermediate transfer body 70 only when the transfer material P passes through the secondary transfer roll 5A.

  In this manner, a toner image is formed on the photoreceptors 1Y, 1M, 1C, and 1K by charging, exposure, and development, and the toner images of each color are superimposed on the endless belt-shaped intermediate transfer body 70, and the transfer material P And fixed by heating and pressurizing with a heating roller / belt type fixing device 24. The photoreceptors 1Y, 1M, 1C, and 1K after transferring the toner image to the transfer material P are cleaned by the cleaning device 6A after the toner remaining on the photoreceptor is transferred, and then the above charging, exposure, and development cycle. The next image formation is performed.

  Note that the image forming apparatus shown in FIG. 4 can also perform non-magnetic one-component image formation. By replacing the two-component development type development apparatus with a non-magnetic one-component development type development apparatus, Magnetic one-component image formation can be performed.

  Examples of the present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.

1. Production of “resin fine particle dispersions A1 to A9” “Resin fine particle dispersions A1 to A9” were produced by the following procedure.

(1) Production of “resin fine particle dispersion A1” In a reaction vessel equipped with a stirrer, a temperature sensor, a cooling tube, and a nitrogen introducing device, 3 parts by mass of an anionic surfactant of the following structural formula (1) A surfactant aqueous solution was prepared by dissolving in parts by mass.

(Structural Formula 1): C ₁₀ H ₂₁ (OCH ₂ CH ₂ ) ₂ SO ₃ Na
In this surfactant aqueous solution, 40 parts by mass of itaconic acid was added, and the temperature was raised to 80 ° C. while stirring at a stirring speed of 230 rpm under a nitrogen stream.

After adding an initiator aqueous solution in which 10 parts by mass of potassium persulfate (KPS) is dissolved in 400 parts by mass of ion-exchanged water in the surfactant aqueous solution to which itaconic acid has been added, a monomer mixed solution comprising the following compounds is added: It was dripped over 2 hours. That is,
Methyl acrylate 630 parts by mass n-butyl acrylate 130 parts by mass After completion of the dropwise addition of the monomer mixed solution, the polymerization temperature was increased to 80 ° C. for 2 hours by heating and stirring to carry out the polymerization reaction. A “resin fine particle dispersion A1” containing resin fine particles of a copolymer formed from a monomer was prepared. The “resin fine particles A1” had a weight average molecular weight Mw of 300,000.

(2) Production of “resin fine particle dispersions A2 and A3” In the production of “resin fine particle dispersion A1,” 5 parts by mass of potassium persulfate (KPS) was dissolved in 400 parts by mass of ion-exchanged water. I changed it to something. Otherwise, “resin fine particle dispersion A2” was prepared in the same procedure. Further, “resin fine particle dispersion A3” was prepared in the same procedure except that an initiator aqueous solution in which 2.5 parts by mass of potassium persulfate (KPS) was dissolved in 400 parts by mass of ion-exchanged water was used. The produced “resin fine particles A2” had a weight average molecular weight Mw of 500,000, and the “resin fine particles A3” had a weight average molecular weight Mw of 650,000.

(3) Preparation of “resin fine particle dispersions A4 and A5” In preparing “resin fine particle dispersion A1”, when preparing a monomer mixed solution, in addition to the above compound, n-octyl mercaptan was added in an amount of 0.47. Part by mass was added. “Resin fine particle dispersion A4” was prepared by taking the same procedure except that the n-octyl mercaptan was added to the monomer mixed solution. Moreover, when preparing a monomer mixed solution, except having added 10.0 mass parts of n-octyl mercaptan, "resin fine particle dispersion A5" was produced by taking the same procedure. The produced “resin fine particles A4” had a weight average molecular weight Mw of 80,000, and the “resin fine particles A5” had a weight average molecular weight Mw of 63,000.

(4) Production of “resin fine particle dispersion A6” In the production of “resin fine particle dispersion A1”, 40 parts by mass of maleic acid was added to the surfactant aqueous solution instead of 40 parts by mass of itaconic acid. Otherwise, “resin fine particle dispersion A6” was prepared in the same procedure. The produced “resin fine particles A6” had a weight average molecular weight Mw of 295,000.

(5) Production of “resin fine particle dispersions A7 and A8” In the production of the “resin fine particle dispersion A1”, the amount of itaconic acid added to the aqueous surfactant solution and methyl methacrylate in the monomer mixed solution And the addition amount of n-butyl acrylate were changed as follows, and “resin fine particle dispersions A7 and A8” were prepared in the same procedure except for the above.

(Resin fine particle dispersion A7)
Itaconic acid 20 parts by weight Methyl methacrylate 652 parts by weight n-butyl acrylate 128 parts by weight (resin fine particle dispersion A8)
Itaconic acid 80 parts by weight Methyl methacrylate 584 parts by weight n-butyl acrylate 136 parts by weight The produced “resin fine particles A7” had a weight average molecular weight Mw of 280,000 and “resin fine particles A8” had a weight average molecular weight Mw of 330,000. It was.

(6) Preparation of “resin fine particle dispersion A9” In the preparation of “resin fine particle dispersion A1”, a monomer used for forming resin fine particles without adding itaconic acid to the surfactant aqueous solution was prepared. A monomer mixed solution was prepared as follows. That is,
Styrene 520 parts by mass n-butyl acrylate 200 parts by mass Methacrylic acid 68 parts by mass "Resin fine particle dispersion A9" was prepared in the same procedure. The produced “resin fine particles A9” had a weight average molecular weight Mw of 298,000.

2. 2. Production of “Toners 1 to 19” 2-1. Preparation of “Toner 1” (1) Preparation of “resin fine particle dispersion B1” (first stage polymerization)
A surfactant solution is prepared by dissolving 7 parts by mass of sodium polyoxyethylene-2-dodecyl ether sulfate in 800 parts by mass of ion-exchanged water in a reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introducing device. And heated to 82 ° C. Thereafter, 125 parts by mass of the “resin fine particle dispersion A1” (in terms of solid content) and a monomer mixed solution containing the following compounds were added, and a mechanical disperser “Clearmix” (M Technique Co., Ltd.) having a circulation path was added. Manufactured) for 1 hour to mix and disperse to prepare a dispersion containing emulsified particles.

Styrene 218 parts by weight n-butyl acrylate 97 parts by weight Methacrylic acid 23 parts by weight n-octyl mercaptan 5.5 parts by weight Paraffin wax “WBM-1” 180 parts by weight Next, potassium persulfate (KPS) 11 in the above dispersion An initiator aqueous solution in which parts by mass are dissolved in 200 parts by mass of ion-exchanged water is added, and this system is heated at 82 ° C. for 1 hour to perform a polymerization reaction to produce a “resin fine particle dispersion a1A1”. did.

(Second stage polymerization)
An initiator aqueous solution in which 11 parts by mass of potassium persulfate (KPS) is dissolved in 400 parts by mass of ion-exchanged water is added to the above-mentioned “resin fine particle dispersion a1A1”, and the following compound is prepared under a temperature condition of 82 ° C. The monomer mixed solution contained was added dropwise over 1.5 hours. That is,
Styrene 393 parts by mass n-butyl acrylate 145 parts by mass n-octyl mercaptan 7 parts by mass After completion of dropping, the mixture was stirred at the above temperature for 2 hours to conduct a polymerization reaction, and then the temperature of the liquid was cooled to 28 ° C. Thus, “resin fine particle dispersion B1” containing “resin fine particles B1” containing “resin A1” was produced.

  In addition, when the above-mentioned first stage polymerization and second stage polymerization were carried out under the conditions in which “resin fine particles A1” were not present, a “resin fine particle dispersion” (“resin fine particle dispersion B13” described later) was produced. The weight average molecular weight Mw of the resin fine particles was 20,000.

(2) Preparation of “Colorant Fine Particle Dispersion” While stirring a solution of 90 parts by mass of sodium dodecyl sulfate in 1600 parts by mass of ion-exchanged water, 420 parts by mass of “CI Pigment Blue 15: 3” Was gradually added. Next, a “colorant fine particle dispersion C” was prepared by carrying out a dispersion treatment using a mechanical disperser “CLEAMIX” (manufactured by M Technique Co., Ltd.). When the particle diameter of “colorant fine particles C” in the prepared “colorant fine particle dispersion” was measured with an electrophoretic light scattering photometer “ELS-800 (manufactured by Otsuka Electronics Co., Ltd.)”, the volume-based median diameter was 210 nm. there were.

(3) Production of “toner base particle 1” (aggregation and fusion process)
In a reaction vessel equipped with a stirrer, temperature sensor, cooling pipe, nitrogen introduction device,
"Resin fine particle dispersion B1" 300 parts by mass (solid content conversion)
Ion-exchanged water 1400 parts by weight “Colorant fine particle dispersion C” 12 parts by weight (solid content conversion)
After adjusting the liquid temperature to 25 ° C., a 5 mol / liter sodium hydroxide aqueous solution was added to adjust the pH to 10.

  Next, an aqueous solution in which 50 parts by mass of magnesium chloride hexahydrate was dissolved in 50 parts by mass of ion-exchanged water was added over 10 minutes at 30 ° C. with stirring. After the addition was held for 3 minutes, the temperature was raised and the system was heated to 90 ° C. over 60 minutes, and agglomeration and fusion were performed while maintaining the temperature at 90 ° C. In this state, the particle size of the agglomerated particles is measured using “Multisizer 3 (manufactured by Beckman Coulter)”. When the volume-based median diameter is 6.5 μm, 50 parts by mass of sodium chloride is added to ion-exchanged water 200 The aqueous solution dissolved in the mass part was added to stop the growth of the particles.

(Aging process)
Furthermore, as a ripening step, the mixture was heated and stirred at a liquid temperature of 98 ° C., and aggregated particles were formed while progressing fusion between particles until the average circularity was 0.965 as measured by “FPIA-2100”. Thereafter, the liquid temperature was cooled to 30 ° C., hydrochloric acid was added to adjust the pH to 2.0, and stirring was stopped.

(Washing and drying process)
The agglomerated particle dispersion prepared through the above steps was subjected to solid-liquid separation using a basket-type centrifuge “MARK III model number 60 × 40 (manufactured by Matsumoto Kikai Co., Ltd.)” to form a wet cake of the agglomerated particles. This wet cake was washed with ion exchange water at 45 ° C. until the electric conductivity of the filtrate reached 5 μS / cm with the basket-type centrifuge, and then transferred to “Flash Jet Dryer (manufactured by Seishin Enterprise Co., Ltd.)” A “toner base particle 1” was produced by performing a drying process until the water content became 1.0 mass%.

(4) External Addition Treatment Toner 1 was produced by adding the following external additive to the produced “toner base particle 1” and performing an external addition treatment with a Henschel mixer (manufactured by Mitsui Miike Mining Co., Ltd.).

Hexamethylsilazane-treated silica (average primary particle size 12 nm, hydrophobicity 68)
1.0 part by mass n-octylsilane-treated titanium dioxide (average primary particle size 20 nm, hydrophobicity 63)
0.3 parts by mass The external addition treatment by the Henschel mixer was performed under the conditions of a peripheral speed of the stirring blade of 35 m / second, a treatment temperature of 35 ° C., and a treatment time of 15 minutes.

  By the above procedure, “Toner 1” having a volume-based median diameter of 6.5 μm was produced.

2-2. Preparation of “Toners 2-19” (1) Preparation of “Toners 2-9” In the preparation of “resin fine particle dispersion B1,” “resin fine particle dispersion A1” was changed to “resin fine particle dispersion A2 to A9”. “Resin fine particle dispersions B2 to B9” were produced by changing to parts (solid content conversion) and taking the other procedures. Then, by adopting the same procedure except that the “resin fine particle dispersion B1” used in the aggregation / fusion process for producing the “toner base particle 1” is changed to “resin fine particle dispersions B2 to B9”, “ Toners 2 to 9 "were prepared. “Toners 2 to 9” all had a volume-based median diameter of 6.5 μm.

(2) Preparation of “Toners 10 and 11” In the preparation of “resin fine particle dispersion B1”, the amount of n-mercaptan used in the first stage polymerization was changed to 11.2 parts by mass, and the second stage polymerization was performed. The amount of n-mercaptan used in 1 was changed to 18.0 parts by mass. Otherwise, the same procedure was followed to prepare “resin fine particle dispersion B10”. In addition, when the above-mentioned first-stage polymerization and second-stage polymerization were carried out under the condition in which “resin fine particles A1” were not present to form “resin fine particle dispersion”, the weight average molecular weight Mw of the resin fine particles contained was 10 000.

  In addition, in the preparation of the “resin fine particle dispersion B1”, the amount of n-mercaptan used in the first stage polymerization was changed to 4.5 parts by mass, and the amount of n-mercaptan used in the second stage polymerization was changed. Was changed to 6.5 parts by mass. Otherwise, the same procedure was followed to prepare “resin fine particle dispersion B11”. When the resin fine particle dispersion was formed by performing the first-stage polymerization and the second-stage polymerization under the condition where “resin fine particles A1” were not present, the weight average molecular weight Mw of the resin fine particles contained was 30,000. Met.

  Then, by adopting the same procedure except that the “resin fine particle dispersion B1” used in the aggregation / fusion process of the production of “toner base particle 1” is changed to “resin fine particle dispersions B10 and B11”, “ Toners 10 and 11 "were prepared. “Toners 10 and 11” both had a volume-based median diameter of 6.5 μm.

(3) Production of “Toner 12” In the production of “resin fine particle dispersion A5” described above, the amount of n-mercaptan used in preparing the monomer mixed solution was changed to 2.5 parts by mass. The polymerization reaction at a liquid temperature of 80 ° C. performed after completion of the dropwise addition of the monomer mixed solution was shortened to 1 hour to prepare “resin fine particle dispersion A10”. The “resin fine particles A10” had a weight average molecular weight Mw of 28,000.

  Next, the “resin fine particle dispersion A1” used in the preparation of the “resin fine particle dispersion B11” was changed to 355 parts by mass (in terms of solid content) of the above “resin fine particle dispersion A10”, and the other procedures were the same. Was used to prepare “resin fine particle dispersion B12”. The first-stage polymerization and the second-stage polymerization described above were performed under the condition where the “resin fine particles A10” were not present to form a “resin fine particle dispersion”, and the weight average molecular weight of the resin fine particles contained was measured. 30,000.

(4) Production of “Toner 13” In the production of “resin fine particle dispersion B1”, the first stage polymerization was performed without adding “resin fine particle dispersion A1” to the surfactant solution. Otherwise, the same procedure was used to prepare “resin fine particle dispersion B13” containing no resin formed using itaconic acid.

Next, each material used in the aggregation / fusion process performed when the toner base particles are produced,
"Resin fine particle dispersion B13" 263 parts by mass (solid content conversion)
"Resin fine particle dispersion A1" 37 parts by mass (solid content conversion)
Ion-exchanged water 1400 parts by weight “Colorant fine particle dispersion C” 12 parts by weight (solid content conversion)
Changed to Other than that, “Toner 13” was prepared by following the same procedure. “Toner 13” had a volume-based median diameter of 6.3 μm.

(5) Preparation of “Toners 14 to 16” The amount of “resin fine particle dispersion A1” added to the surfactant solution when the first stage polymerization is performed in the preparation of the “resin fine particle dispersion B1” is as follows. Other than that, the same procedure was followed except that “resin fine particle dispersions B14 to B16” were produced. Then, “toner 14 to 16” having a volume-based median diameter of 6.5 μm was prepared using the “resin fine particle dispersions B14 to B16” when the toner base particles were prepared. That is,
(Toner 14)
"Resin fine particle dispersion A1" 18 parts by mass (solid content conversion)
(Toner 15)
"Resin fine particle dispersion A1" 219 parts by mass (solid content conversion)
(Toner 16)
"Resin fine particle dispersion A1" 355 parts by mass (solid content conversion)
The volume-based median diameters of “Toners 14 to 16” were all 6.5 μm.

(6) Production of “Toners 17 to 19” “Resin fine particle dispersion B13” and “Resin fine particle dispersion” used in the aggregation / fusion process performed when producing toner base particles in the production of “Toner 13”. “Toners 17 to 19” were produced by following the same procedure except that the amount of addition of “A1” was changed as follows. That is,
(Toner 17)
"Resin fine particle dispersion B13" 294 parts by mass (solid content conversion)
"Resin fine particle dispersion A1" 6 parts by mass (solid content conversion)
(Toner 18)
"Resin fine particle dispersion B13" 240 parts by mass (solid content conversion)
"Resin fine particle dispersion A1" 60 parts by mass (solid content conversion)
(Toner 19)
"Resin fine particle dispersion B13" 213 parts by mass (solid content conversion)
"Resin fine particle dispersion A1" 87 parts by mass (solid content conversion)
The volume-based median diameters of “Toners 17 to 19” were all 6.3 μm.

  The production conditions and the like of “Toners 1 to 19” produced by the above procedure are shown in Table 1 below.

2. Preparation of “Developers 1 to 19” Each of the “Toners 1 to 19” was mixed with a ferrite carrier having a volume average particle diameter of 50 μm formed by coating a silicone resin. 19 "was prepared.

3. Evaluation Experiment Evaluation was performed on a commercially available composite printer “bizhub PRO C550 (manufactured by Konica Minolta Business Technologies, Inc.)” corresponding to the two-component development type image forming apparatus shown in FIG. The one equipped with a mold fixing device was used. In the heating roller / belt fixing device, the heating roller heat source was adjusted so that the temperature on the pressure belt surface was 120 ° C.

  The evaluation procedure is as follows. For “Developers 1 to 19”, 500 sheets of A4 size are continuously printed, and at the start of continuous printing, the 10th sheet, the 100th sheet, and the 500th sheet are printed. A sample of a step-like gloss unevenness evaluation sample was output. Two types of uneven gloss evaluation samples were prepared, one in which a solid image was output on the entire surface of an A4-size image support and the other in which a halftone image was output. The continuous printing by the image forming apparatus was performed in a so-called normal temperature and normal humidity environment at a temperature of 20 ° C. and a relative humidity of 55% RH.

  Here, “Examples 1 to 17” are those using “Toners 1 to 8, 10, 11, 13 to 19”, and “Comparative Examples 1 and 2” are those using “Toners 9 and 12”. .

<Quantitative evaluation of uneven luster in steps>
Using the above-mentioned evaluation sample that output an A4 size solid image, the glossiness at 10 points is measured at equal intervals from one end to the other end in the longitudinal direction, and the difference in gloss within the same print is measured. Asked. In addition, the measuring method of glossiness was performed using the following measuring apparatus, evaluation was as follows, and (double-circle) and (circle) were set as the pass. That is,
Evaluation criteria:
A: The difference between the maximum and minimum gloss values (gloss difference) is 1% or less (no problem)
○: Gloss difference exceeds 1% and is less than 5% (no problem at a level that is hardly visible)
X: Gloss difference is 5% or more (there is a problem at the level where the difference can be seen visually)
The glossiness was measured using a gloss meter “GMX-203 (Murakami Color Research Laboratory Co., Ltd.)” having the configuration shown in FIG. The measurement angle, that is, the angle indicated by θ in FIG. 6 was set to 75 °, and the measurement was performed based on the above-mentioned “JIS Z8741 1983 method 2”. 6 and 70 are light sources, 71 is an optical system, 72 is a sample, 73 is an optical system for light reflected from the sample, and 74 is a light receiver. S ₁ and S ₂ are slits, α ₁ is the opening angle of the optical image, β ₁ is the opening angle in the vertical plane, α ₂ is the opening angle of the light receiver, and β ₂ is the opening angle in the vertical plane.

<Visual evaluation of uneven luster in steps>
The sample for evaluation which output the A4 size halftone image described above was visually observed using a magnifying glass having a magnification of 5 times, and evaluated as follows. Note that the halftone image was output as the sample for evaluation for visual observation on the assumption that a toner image according to the present invention output a photographic image.

Evaluation criteria:
◎: No unevenness of stepped gloss is observed and no problem ○: Some unevenness of stepped gloss is observed, but it is judged that there is no problem in practical use ×: Clear stepped gloss Unevenness is observed and it is determined that there is a problem. The above results are shown in Table 2 below.

  As shown in Table 2, each of “Examples 1 to 17” using the toner satisfying the configuration of the present invention has a stepped shape on both the solid image and the halftone image in a state where continuous printing is performed. It was confirmed that gloss unevenness was not generated. On the other hand, “Comparative Examples 1 and 2” using toner that does not have the configuration of the present invention has a stepped gloss on both the solid image and the halftone image from the vicinity of the 10th sheet at the early stage after the start of continuous printing. It was confirmed that unevenness was generated.

1 Image forming device 24 Fixing device (heating roller / belt type fixing device)
242 Heating roller 243 Pressure belt 244 Heat source 245 Tension roller 246 Thickness contact member 247 Lubricant supply member D Domain phase M Matrix phase N Fixing nip P Transfer material T Toner image

Claims (8)

A toner containing at least a resin and having a domain matrix structure,
The domain contains a resin formed using a radical polymerizable monomer having at least a plurality of carboxyl groups,
The toner according to claim 1, wherein a weight average molecular weight of the resin contained in the domain is larger than a weight average molecular weight of the resin contained in the matrix.   The toner according to claim 1, wherein the radical polymerizable monomer having a plurality of carboxyl groups is itaconic acid.   The toner according to claim 1, wherein the resin contained in the domain has a weight average molecular weight of 80,000 or more and 500,000 or less.   The resin contained in the matrix is formed using at least a styrene monomer and a (meth) acrylic acid monomer. The toner described in 1. at least,
Forming a toner image from the electrostatic latent image formed on the photoreceptor using toner; and
Transferring the toner image formed in the step of forming the toner image onto a transfer material;
An image forming method comprising a step of fixing the transfer material with a fixing unit comprising a heating roll and a belt-like pressure member,
In the step of fixing the transfer material, the transfer material is passed through a nip formed between the heating roll and the belt-shaped pressure member, and the toner image transferred to the transfer material is fixed. Is,
The toner is
At least containing a resin and having a domain matrix structure,
The domain contains a resin formed using a radical polymerizable monomer having at least a plurality of carboxyl groups,
The image forming method, wherein a weight average molecular weight of the resin contained in the domain is larger than a weight average molecular weight of a resin contained in the matrix.   6. The image forming method according to claim 5, wherein the radical polymerizable monomer having a plurality of carboxyl groups is itaconic acid.   The image forming method according to claim 5 or 6, wherein the resin contained in the domain has a weight average molecular weight of 80,000 or more and 500,000 or less.   8. The resin according to claim 5, wherein the resin contained in the matrix is formed using at least a styrene monomer and a (meth) acrylic acid monomer. The image forming method described in 1.

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