Non-magnetic toner for one component development and method for producing the same

Abstract

To provide a toner for nonmagnetic one component development having excellent fixability and heat-resistant storage property and capable of forming an image of desired density by charging the toner to a desired charge amount over a long period of time in various environments.SOLUTION: The toner for nonmagnetic one component development comprises toner particles including toner core particles containing at least a binder resin and a shell layer covering the toner core particles, wherein the toner particles do not contain magnetic powder. The shell layer is formed using spherical resin fine particles containing a charge control resin. The toner particle has an average particle diameter of at least 6 μm and no greater than 8 μm. When a surface of the toner particle is observed using a scanning electron microscope, a structure derived from the spherical fine resin particles is not observed in the shell layer, and an outer surface of the shell layer is smooth. When a cross-section of the toner particle is observed using a transmission electron microscope, cracks derived from interfaces between the fine resin particles are observed inside the shell layer in a direction substantially perpendicular to the surface of the toner core particle.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a toner for developing an electrostatic latent image, and more particularly to a toner for non-magnetic one-component development made of a non-magnetic toner, and a method for producing the toner for non-magnetic one-component development. [Background technology]

[0002] In general, in electrophotography, the surface of an electrostatic latent image carrier is charged by corona discharge or other methods, and then exposed to light such as a laser to form an electrostatic latent image. The formed electrostatic latent image is then developed with toner to form a toner image. The formed toner image is then transferred to a recording medium to obtain a high-quality image. Toners used in electrophotography are typically prepared by mixing a binder resin such as a thermoplastic resin with a colorant, a charge control agent, a release agent, a magnetic material, and other components, followed by kneading, pulverization, and classification to form toner particles (toner base particles) with an average particle size of 5 μm to 10 μm. Inorganic fine powders such as silica and titanium oxide are added to the toner base particles to provide fluidity, favorable charging properties, and improved cleaning performance of the toner from the photoreceptor drum.

[0003] For the purpose of obtaining good fixability in a low temperature range, improving storage stability at high temperatures, and improving blocking resistance, a toner having a core-shell structure has been used in which toner core particles using a binder resin with a low melting point are covered with a shell material made of a resin exhibiting a glass transition temperature (Tg) higher than that of the binder resin of the toner core particles.

[0004] Patent Document 1 discloses, as a specific example of a core-shell toner in which a shell layer made of charge-controlling resin particles is formed on the surface of a toner core particle, a toner obtained by externally adding toner base particles of a core-shell structure in which a shell made of an aggregated and fused layer of positively-charged charge-controlling resin particles is formed on the surface of a toner core particle made of aggregated and fused particles of binder resin particles and colorant particles, with positively-charged inorganic particles that have been hydrophobized with an amino group-containing compound.

[0005] Patent Document 2 describes a positively charged toner for developing electrostatic latent images, which is obtained by adding an external additive to toner base particles containing a binder resin and a colorant, and the binder resin contains a polyester resin, and the external additive has an average particle diameter of 200 to 1000 nm and an electrical resistivity of 1×10 15 Disclosed is a positively chargeable toner for developing electrostatic latent images, which contains negatively chargeable resin particles of Ωcm or less, silica having an average particle diameter of 50 to 300 nm, silica having an average particle diameter of 5 nm or more but less than 50 nm, and polytetrafluoroethylene particles having an average particle diameter of 100 to 1000 nm. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Patent Publication No. 2007 / 114502 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-180910 Summary of the Invention [Problem to be solved by the invention]

[0007] The shell layer of the toner described in Patent Document 1 is formed by fusing a positively charged charge control resin to the toner core particles by heating, resulting in a uniform film with no gaps. Therefore, the shell layer of the toner described in Patent Document 1 may be difficult to destroy by the pressure applied to the toner when fixing the toner on a recording medium. If the shell layer is not easily destroyed, it is difficult to fix the toner well on the recording medium.

[0008] In Patent Document 2, a positively charged toner for developing electrostatic latent images is mixed with a magnetic carrier to form a two-component developer, and physical properties such as fixability, heat-resistant storage stability, and image density are evaluated. It also describes that by incorporating a magnetic component into the toner particles, the toner can be used as a magnetic one-component developer. However, there is no description or suggestion of using a positively charged toner for developing electrostatic latent images as a toner for non-magnetic one-component development.

[0009] The toner described in Patent Document 2 uses a method in which toner is transported by at least one toner transport member and the transported toner visualizes an electrostatic latent image formed on a latent image carrier. However, in this case, the thickness of the toner layer transported on the surface of the toner transport member must be as thin as possible. Furthermore, since this toner needs to be charged by a developing device, the toner layer must be thin. If the toner layer is thick, only the area near the surface of the toner layer will be charged, making it difficult to charge the entire toner layer uniformly.

[0010] Therefore, various methods have been proposed as a means for regulating the toner layer thickness on the toner transport member. A typical example is to use a regulating blade, which is placed opposite the toner transport member, and the toner transported on the surface of the toner transport member is pressed down by a pressing member (regulating blade), thereby controlling the toner layer thickness. There is also a type that achieves the same effect by using a roller in place of a blade.

[0011] Furthermore, in recent years, in order to reduce the size and cost of fixing devices, oil-less fixing devices that do not include a fixing oil application mechanism or that reduce the amount of application have become mainstream, and as a measure to prevent offset, it has become necessary to include a release agent (wax) in the toner. However, if a large amount of wax is included in the toner, the amount of free wax or wax on the toner surface increases, and due to mechanical and thermal effects, the wax causes the toner to adhere to components such as the regulating blade and photosensitive member in the developing machine, resulting in the problem of white spots and white streaks in solid images caused by these adhered components.

[0012] In view of the above problems, an object of the present invention is to provide a toner for non-magnetic one-component development that has excellent fixing properties and heat-resistant storage properties, can charge the toner to a desired charge amount over a long period of time under various environments, and can form images of a desired density. [Means for solving the problem]

[0013] To achieve the above object, the first aspect of the present invention is a non-magnetic single-component toner for development, which comprises toner particles including toner core particles containing at least a binder resin and a shell layer covering the toner core particles, and the toner particles do not contain magnetic powder. The shell layer is formed using spherical resin fine particles containing a charge control resin. The toner particles have an average particle diameter of 6 μm to 8 μm, and when the surface of the toner particles is observed using a scanning electron microscope, no structure derived from the spherical resin fine particles is observed in the shell layer, and the outer surface of the shell layer is smooth. When the cross section of the toner particles is observed using a transmission electron microscope, cracks derived from the interfaces between the resin fine particles are observed inside the shell layer, in a direction approximately perpendicular to the surface of the toner core particles. [Effects of the Invention]

[0014] According to the first aspect of the present invention, it is possible to provide a non-magnetic one-component developing toner that has excellent fixing properties and heat-resistant storage stability, and that can be charged to a desired charge amount when forming images over a long period of time under various environments such as a high-temperature, high-humidity environment or a low-temperature, low-humidity environment, and that can form images of a desired density. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic diagram of an image forming apparatus 1 in which the non-magnetic one-component developing toner of the present invention is used. [Figure 2] FIG. 2 is a cross-sectional side view showing a schematic configuration of the image forming unit 30 including the developing unit 33 in FIG. [Figure 3] Schematic diagram showing a part of a cross section of non-magnetic one-component developing toner 101 of the present invention. [Figure 4]Transmission electron microscope photograph of the cross section of the toner of the present invention 1 [Figure 5] Transmission electron microscope photograph of the cross section of the toner of the present invention 2 [Figure 6] Transmission electron microscope photograph of the cross section of the toner of the present invention 3 [Figure 7] Transmission electron microscope photograph of the cross section of the toner of Comparative Example 1 [Figure 8] Transmission electron microscope photograph of the cross section of the toner of Comparative Example 2 [Figure 9] Transmission electron microscope photograph of the cross section of the toner of Comparative Example 3 [Figure 10] Transmission electron microscope photograph of the cross section of the toner of Comparative Example 5 DETAILED DESCRIPTION OF THE INVENTION

[0016] [1. Overall configuration of image forming device] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a schematic cross-sectional view of an image forming apparatus 1 in which the non-magnetic one-component toner of the present invention is used. In Fig. 1, the right side is the front side of the image forming apparatus 1, and the left side is the rear side.

[0017] The image forming apparatus 1 (here, a monochrome printer) includes a main housing 10 having a substantially rectangular parallelepiped casing structure, and a paper feed unit 20, an image forming unit 30, and a fixing unit 40 housed within the main housing 10. A front cover 11 is provided on the front side of the main housing 10, and a rear cover 12 is provided on the rear side. Each unit of the image forming unit 30 can be inserted or removed from the rear side of the main housing 10 by opening the rear cover 12. In addition, a paper discharge unit 13 is provided on the top surface of the main housing 10, to which sheets after image formation are discharged. In the following description, the term "sheet" refers to copy paper, coated paper, overhead projector sheets, cardboard, postcards, tracing paper, or other sheet material that undergoes image formation processing.

[0018] The paper feed unit 20 includes a paper feed cassette 21 that stores sheets on which image formation processing is performed. A portion of the paper feed cassette 21 protrudes further forward from the front surface of the main body housing 10. The upper surface of the portion of the paper feed cassette 21 that is stored within the main body housing 10 is covered by a paper feed cassette top plate 21U. The paper feed cassette 21 is equipped with a paper storage space that stores a stack of sheets, a lift plate that lifts up the stack of sheets for feeding, and the like. A paper feed unit 21A is provided above the rear end of the paper feed cassette 21. A paper feed roller 21B is arranged in this paper feed unit 21A to feed the topmost sheet of the stack of sheets in the paper feed cassette 21 one by one.

[0019] Image forming unit 30 performs an image forming operation to form a toner image (developer image) on a sheet sent out from paper feed unit 20. Image forming unit 30 includes a photosensitive drum 31, and a charging unit 32, an exposure unit 35, a developing unit 33, and a transfer roller 34 arranged around photosensitive drum 31.

[0020] The photosensitive drum 31 (image carrier) has a rotation shaft and an outer peripheral surface (drum body) that rotates around the rotation shaft. The outer peripheral surface of the photosensitive drum 31 is made of, for example, a known organic photoconductor (OPC), and a photosensitive layer composed of a charge generation layer, a charge transport layer, etc. is formed on the outer peripheral surface. The photosensitive layer is uniformly charged by a charging unit 32 (described later), and then irradiated with light by an exposure unit 35 to form an electrostatic latent image by attenuating the charge. The electrostatic latent image is then visualized by a developing unit 33 to form a toner image.

[0021] The charging unit 32 (charging device) is disposed at a predetermined distance from the outer peripheral surface of the photosensitive drum 31 and uniformly charges the outer peripheral surface of the photosensitive drum 31 without contacting the photosensitive drum 31. Specifically, the charging unit 32 has a charge wire 321 and a grid electrode 322 (see FIG. 2 for both). The charge wire 321 is a linear electrode extending in the direction of the rotational axis of the photosensitive drum 31 and generates a corona discharge between the charge wire 321 and the photosensitive drum 31. The grid electrode 322 is a lattice-shaped electrode extending in the direction of the rotational axis of the photosensitive drum 31 and is disposed between the charge wire 321 and the photosensitive drum 31. The charging unit 32 generates a corona discharge by passing a predetermined current through the charge wire 321 and uniformly charges the outer peripheral surface of the photosensitive drum 31 facing the grid electrode 322 to a predetermined surface potential by applying a predetermined voltage to the grid electrode 322.

[0022] The exposure unit 35 (exposure device) has a laser light source and optical devices such as mirrors and lenses, and irradiates the outer peripheral surface of the photosensitive drum 31 with light modulated based on image data provided from an external device such as a personal computer. In this way, the exposure unit 35 forms an electrostatic latent image on the outer peripheral surface of the photosensitive drum 31 that corresponds to the image based on the image data.

[0023] The developing unit 33 (developing device) is detachable from the main housing 10, and develops the electrostatic latent image formed on the outer peripheral surface of the photosensitive drum 31 by supplying non-magnetic single-component toner (developer) to the outer peripheral surface of the photosensitive drum 31. Developing the electrostatic latent image means forming a toner image (developer image) that manifests the electrostatic latent image. The detailed configuration of the developing unit 33 will be described later.

[0024] The transfer roller 34 is a roller for transferring the toner image formed on the outer peripheral surface of the photosensitive drum 31 onto a sheet. Specifically, the transfer roller 34 rotates around its axis, and has an outer peripheral surface that faces the outer peripheral surface of the photosensitive drum 31 at a position downstream of the developing roller 331 in the rotation direction of the photosensitive drum 31. The transfer roller 34 transfers the toner image carried on the outer peripheral surface of the photosensitive drum 31 to a sheet that passes through a nip portion between the transfer roller 34 and the outer peripheral surface of the photosensitive drum 31. During this transfer, a transfer voltage of opposite polarity to that of the toner is applied to the transfer roller 34.

[0025] The fixing unit 40 performs a fixing process to fix the toner image transferred to the sheet onto the sheet. The fixing unit 40 has a fixing roller 41 and a pressure roller 42. The fixing roller 41 has an internal heating source and heats the toner transferred to the sheet to a predetermined temperature. The pressure roller 42 is pressed against the fixing roller 41, forming a fixing nip between the fixing roller 41 and the pressure roller 42. When the sheet onto which the toner image has been transferred is passed through the fixing nip, the toner image is fixed onto the sheet by the heating by the fixing roller 41 and the pressure by the pressure roller 42.

[0026] A main transport path 22F and a reverse transport path 22B for transporting sheets are provided within the main body housing 10. The main transport path 22F extends from the paper feed unit 21A of the paper feed unit 20, via the image forming unit 30 and the fixing unit 40, to the paper discharge port 14 provided opposite the paper discharge unit 13 on the top surface of the main body housing 10. The reverse transport path 22B is a transport path for returning a sheet that has been printed on one side to the upstream side of the image forming unit 30 on the main transport path 22F when double-sided printing is performed on the sheet.

[0027] 2. Configuration of Image Forming Unit 30 2 is a cross-sectional view of the image forming unit 30 in the image forming apparatus 1 of this embodiment. As shown in FIG. 2, the developing unit 33 includes a developing housing 330 (developing container), a developing roller 331 (developer carrier), a supply roller 332, an agitating paddle 333, and a regulating blade 334.

[0028] The developing housing 330 contains a non-magnetic one-component developer consisting only of toner, and also contains a developing roller 331, a supply roller 332, a regulating blade 334, etc. The developing housing 330 is provided with an agitating chamber 335 that contains the developer (toner) in an agitated state. An agitating paddle 333 is disposed in the agitating chamber 335. The agitating paddle 333 agitates the toner in the agitating chamber 335.

[0029] The developing roller 331 includes a rotating shaft 331a and a roller portion 331b. The rotating shaft 331a is rotatably supported by a bearing portion (not shown) of the developing housing 330. The roller portion 331b is a cylindrical member laminated on the outer circumferential surface of the rotating shaft 331a (conductive substrate). The roller portion 331b is configured by laminating a coating layer (urethane layer) made of an uneven coating material such as urethane on the surface of a base rubber (silicone rubber layer). The roller portion 331b rotates integrally with the rotating shaft 331a as the rotating shaft 331a rotates. A toner layer (developer layer) of a predetermined thickness is formed on the surface of the roller portion 331b. The thickness of the toner layer is regulated (adjusted to a predetermined uniform thickness) by a regulating blade 334 (described later). The toner layer is charged by static electricity generated by contact (friction) between the regulating blade 334 and the roller portion 331b.

[0030] At a position facing the photosensitive drum 31, the developing roller 331 rotates in a direction (counterclockwise in FIG. 2) from the upstream side to the downstream side in the rotation direction (clockwise in FIG. 2) of the photosensitive drum 31. In other words, at a position facing the photosensitive drum 31, the developing roller 331 rotates in the same direction as the photosensitive drum 31.

[0031] Supply roller 332 is disposed opposite developing roller 331. Supply roller 332 holds the developer contained in stirring chamber 335 on its outer circumferential surface. Supply roller 332 also supplies the developer held on its outer circumferential surface to developing roller 331.

[0032] At a position facing the developing roller 331, the supply roller 332 rotates in a direction (counterclockwise in FIG. 2) from downstream to upstream in the rotation direction of the developing roller 331 (counterclockwise in FIG. 2). In other words, at a position facing the developing roller 331, the supply roller 332 rotates in the opposite direction to the developing roller 331. In order to move toner from the supply roller 332 to the developing roller 331, a predetermined supply voltage (DC voltage) is applied to the supply roller 332.

[0033] Developing roller 331 receives developer from supply roller 332 and holds a toner layer on its outer circumferential surface. Developing roller 331 then supplies developer to photosensitive drum 31. The axial lengths of developing roller 331 and supply roller 332 (direction perpendicular to the paper surface of FIG. 2) are approximately the same as the axial length of photosensitive drum 31. A predetermined developing voltage (DC voltage) is applied to developing roller 331 to move toner from developing roller 331 to photosensitive drum 31.

[0034] The regulating blade 334 is a thin plate-like member made of metal (for example, stainless steel). The regulating blade 334 is configured so that a base end 334a is fixed to the development housing 330 and a tip end 334b ​​is a free end. The regulating blade 334 comes into contact with the outer circumferential surface of the development roller 331 at a position upstream in the rotation direction of the development roller 331 from the position where the photosensitive drum 31 and the development roller 331 face each other.

[0035] The regulating blade 334 contacts the developing roller 331 with a constant regulating pressure (contact line pressure), so that the toner layer carried on the outer peripheral surface of the developing roller 331 is adjusted to a uniform thickness. In this way, the regulating blade 334 regulates the amount of toner on the outer peripheral surface of the developing roller 331. The regulating blade 334 also charges the toner carried on the outer peripheral surface of the developing roller 331 by rubbing the toner. The contact line pressure of the regulating blade 334 against the developing roller 331 is the contact pressure per unit length of the regulating blade 334 at the contact position between the regulating blade 334 and the outer peripheral surface of the developing roller 331. The regulating pressure of the regulating blade 334 is preferably 15 to 40 [N / m].

[0036] [3. Composition of non-magnetic one-component developing toner] The non-magnetic one-component toner (hereinafter simply referred to as toner) of the present invention comprises toner core particles containing at least a binder resin and a shell layer covering the toner core particles. The shell layer covering the toner core particles is made of a resin containing a charge control resin and is formed using spherical resin fine particles.

[0037] Furthermore, when the surface of the toner of the present invention is observed using a scanning electron microscope, no structure derived from spherical resin fine particles is observed in the shell layer of toner particles having a particle diameter of 6 μm or more and 8 μm or less. Furthermore, when the cross section of the toner of the present invention is observed using a transmission electron microscope, cracks derived from the interfaces between resin fine particles are observed inside the shell layer in a direction approximately perpendicular to the surface of the toner core particle. The toner structure and materials will be described below.

[0038] In the toner of the present invention, the entire surface of the toner core particles is covered with a shell layer. The state of the shell layer covering the surface of the toner for developing electrostatic latent images can be confirmed using a scanning electron microscope (SEM). The degree of smoothing of the shell layer and the interior of the shell layer of the toner for developing electrostatic latent images can be confirmed by observing the cross section of the toner using a transmission electron microscope (TEM).

[0039] Fig. 3 is a schematic diagram showing a portion of a cross section of a toner according to a preferred embodiment of the present invention, as observed using a TEM. As shown in Fig. 3, in toner 101, a shell layer 103 covers the entire surface of a toner core particle 102. The shell layer is formed by smoothing the outer surface of a resin fine particle layer formed by adhering a resin fine particle layer to a toner core particle using an external force.

[0040] The thickness of the shell layer 103 is not particularly limited as long as it does not impair the object of the present invention, and is preferably 0.03 μm to 1 μm, more preferably 0.04 μm to 0.7 μm, particularly preferably 0.05 μm to 0.5 μm, and most preferably 0.05 μm to 0.3 μm. Note that the shell layer of the toner of the present invention has convex portions, and therefore the thickness of the shell layer is non-uniform. Therefore, in the claims and specification of this application, the thickness of the thickest part of the shell layer is referred to as the "thickness of the shell layer."

[0041] If the shell layer is too thick, the shell layer is less likely to be destroyed by the pressure applied to the toner when fixing the toner to a recording medium. In this case, the binder resin and release agent contained in the toner core particles do not soften or melt quickly, making it difficult to fix the toner to a recording medium at low temperatures. On the other hand, if the shell layer is too thin, the strength of the shell layer is reduced. If the shell layer strength is low, the shell layer may be destroyed by impact during transportation, etc., and when the toner is stored at high temperatures, the toner is more likely to aggregate due to the release agent seeping out onto the toner surface from the destroyed shell layer.

[0042] The thickness of the shell layer 103 can be measured by analyzing a TEM image of a cross section of the toner 101 using commercially available image analysis software, such as WinROOF (manufactured by Mitani Shoji Co., Ltd.).

[0043] In the toner of the present invention, the shell layer 103 preferably has a convex portion 105 on the interface between the toner core particle 102 and the shell layer 103 and between two cracks 104, as shown in FIG. 3 . By having such convex portions 105 on the shell layer 103, the contact area between the toner core particle 102 and the shell layer 103 can be increased compared to when the shell layer does not have the convex portions 105. Thus, by providing the convex portions 105 on the shell layer, the adhesion between the toner core particle 102 and the shell layer 103 is improved, and the shell layer 103 is less likely to peel off from the toner core particle 102. For this reason, when the shell layer has the convex portions 105, a toner with good heat-resistant storage stability can be obtained.

[0044] More specifically, the shell layer formed using the resin fine particles of the toner for developing electrostatic latent images of the present invention is I) a step of attaching spherical resin fine particles to the surface of the toner core particle so as not to overlap in a direction perpendicular to the surface of the toner core particle, thereby forming a resin fine particle layer that covers the entire surface of the toner core particle; and II) applying an external force to the outer surface of the resin particle layer to deform the resin particles in the resin particle layer, thereby smoothing the outer surface of the resin particle layer and forming a shell layer.

[0045] The degree of smoothing of the shell layer may be such that, when the surface of the toner of the present invention is observed using a scanning electron microscope, no structure derived from the spherical resin fine particles used to form the shell layer is observed on the outer surface of the shell layer of toner particles having a particle diameter of 6 μm to 8 μm. If the state of the shell layer of toner having a particle diameter of 6 μm to 8 μm is in this state, the shell layer is formed in most of the toner particles contained in the toner so that the surface of the core particle is not exposed. When the state of the outer surface of the shell layer is confirmed using scanning electron microscope observation, the particle diameter of the toner particles is the circle equivalent diameter calculated from the projected area of ​​the toner on the electron microscope image.

[0046] 3, in the toner 101, the entire surface of the toner core particle 102 is covered with the shell layer 103. Furthermore, since the shell layer 103 covers the entire surface of the toner core particle 102 so that the outer surface is smooth, the release agent and the like are less likely to bleed onto the surface of the toner 101 when the toner 101 is stored at high temperatures. Depending on the shape of the toner core particle 102, the resin fine particles may overlap in a direction perpendicular to the surface of the toner core particle.

[0047] Furthermore, because the toner 101 has cracks (voids) 104 inside the shell layer 103, the shell layer is likely to break from the cracks due to the pressure applied to the toner when the toner is fixed onto a recording medium. As a result, the binder resin and release agent contained in the toner core particles 102 of the toner 101 are quickly softened or melted, making it easy to fix the toner onto a recording medium at low temperatures.

[0048] [4. Toner Materials] The toner of the present invention comprises a toner core particle containing at least a binder resin and a shell layer covering the entire surface of the toner core particle. The toner core particle may contain a release agent, a charge control agent, a colorant, a magnetic powder, etc. in the binder resin as needed. Furthermore, the surface of the toner of the present invention may be treated with an external additive, if desired.

[0049] Hereinafter, the essential or optional components constituting the toner for developing electrostatic latent images of the present invention, namely, the binder resin, the release agent, the charge control agent, the colorant, the magnetic powder, the resin particles forming the shell layer, and the external additives, and the method for producing the toner for developing electrostatic latent images of the present invention will be described in order.

[0050] (binder resin) The toner core particles in the toner of the present invention contain a binder resin. The binder resin contained in the toner core particles is not particularly limited as long as it is a resin that has been conventionally used as a binder resin for toner. Specific examples of binder resins include thermoplastic resins such as styrene-based resins, acrylic-based resins, styrene-acrylic-based resins, polyethylene-based resins, polypropylene-based resins, vinyl chloride-based resins, polyester resins, polyamide resins, polyurethane resins, polyvinyl alcohol-based resins, vinyl ether-based resins, N-vinyl-based resins, and styrene-butadiene resins. Among these resins, polystyrene-based resins and polyester resins are preferred in terms of the dispersibility of colorants in the binder resin, the chargeability of the toner, and the fixability to paper. Polystyrene-based resins and polyester resins will be described below.

[0051] The polystyrene resin may be a homopolymer of styrene or a copolymer with other copolymerizable monomers copolymerizable with styrene. Specific examples of other copolymerizable monomers copolymerizable with styrene include p-chlorostyrene; vinylnaphthalene; ethylenically unsaturated monoolefins such as ethylene, propylene, butylene, and isobutylene; vinyl halides such as vinyl chloride, vinyl bromide, and vinyl fluoride; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate, and vinyl butyrate; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, n-octyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, Examples include (meth)acrylic acid esters such as α-methyl chloroacrylate, methyl methacrylate, ethyl methacrylate, and butyl methacrylate; other acrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide; vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone, and methyl isopropenyl ketone; and N-vinyl compounds such as N-vinylpyrrole, N-vinylcarbazole, N-vinylindole, and N-vinylpyrrolidene. Two or more of these copolymerizable monomers can be combined and copolymerized with a styrene monomer.

[0052] The polyester resin can be obtained by condensation polymerization or co-condensation polymerization of a divalent or trivalent or higher alcohol component and a divalent or trivalent or higher carboxylic acid component. The components used in synthesizing the polyester resin include the following alcohol components and carboxylic acid components.

[0053] Specific examples of the dihydric or trihydric or higher alcohol component include diols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; bisphenol A, hydrogenated bisphenol A, and polyoxyethylene bisphenols such as hydroxypropylated bisphenol A and polyoxypropylated bisphenol A; and trihydric or higher alcohols such as sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-trihydroxymethylbenzene.

[0054] Specific examples of the divalent or trivalent or higher carboxylic acid component include divalent carboxylic acids such as maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, or alkyl or alkenyl succinic acids such as n-butylsuccinic acid, n-butenylsuccinic acid, isobutylsuccinic acid, isobutenylsuccinic acid, n-octylsuccinic acid, n-octenylsuccinic acid, n-dodecylsuccinic acid, n-dodecenylsuccinic acid, isododecylsuccinic acid, and isododecenylsuccinic acid. Carboxylic acids include trivalent or higher carboxylic acids such as 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,5-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra(methylenecarboxyl)methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, and empol trimer acid. These divalent or higher carboxylic acid components may be used as ester-forming derivatives such as acid halides, acid anhydrides, and lower alkyl esters. Here, "lower alkyl" refers to an alkyl group having 1 to 6 carbon atoms.

[0055] When the binder resin is a polyester resin, the softening point of the polyester resin is preferably 70°C or higher and 130°C or lower, and more preferably 80°C or higher and 120°C or lower.

[0056] As the binder resin, it is preferable to use a thermoplastic resin because it has good fixability to paper. However, in addition to using a thermoplastic resin alone, a crosslinking agent or a thermosetting resin can be added to the thermoplastic resin. By adding a crosslinking agent or a thermosetting resin to introduce a partial crosslinked structure into the binder resin, it is possible to improve the heat-resistant storage stability and durability of the toner without reducing the fixability of the toner. When a thermosetting resin is used, the amount of crosslinked portions (gel amount) of the binder resin extracted using a Soxhlet extractor is preferably 10% by mass or less, more preferably 0.1% by mass or more and 10% by mass or less, based on the mass of the binder resin.

[0057] Thermosetting resins that can be used together with thermoplastic resins are preferably epoxy resins or cyanate resins. Specific examples of suitable thermosetting resins include bisphenol A epoxy resins, hydrogenated bisphenol A epoxy resins, novolac epoxy resins, polyalkylene ether epoxy resins, cycloaliphatic epoxy resins, and cyanate resins. These thermosetting resins can be used in combination of two or more.

[0058] The glass transition point (Tg) of the binder resin is preferably 40° C. or higher and 70° C. or lower. If the glass transition point is too high, the low-temperature fixability of the toner tends to decrease. If the glass transition point is too low, the heat-resistant storage stability of the toner tends to decrease.

[0059] The glass transition point of the binder resin can be determined from the change point in the specific heat of the binder resin using a differential scanning calorimeter (DSC). More specifically, the glass transition point of the binder resin can be determined by measuring the endothermic curve of the binder resin using a differential scanning calorimeter DSC-6200 manufactured by Seiko Instruments Inc. as the measuring device. 10 mg of a measurement sample is placed in an aluminum pan, and an empty aluminum pan is used as a reference. The glass transition point of the binder resin can be determined from the endothermic curve of the binder resin obtained by measuring at room temperature and normal humidity in a measurement temperature range of 25°C to 200°C at a heating rate of 10°C / min.

[0060] The weight average molecular weight (Mw) of the binder resin is not particularly limited as long as it does not impair the object of the present invention. Typically, the weight average molecular weight (Mw) of the binder resin is preferably 20,000 or more and 300,000 or less, and more preferably 30,000 or more and 2,000,000 or less. The weight average molecular weight of the binder resin can be determined by gel permeation chromatography (GPC) using a calibration curve prepared in advance using standard polystyrene resins.

[0061] Furthermore, when the binder resin is a polystyrene-based resin, the binder resin preferably has peaks in both a low molecular weight region and a high molecular weight region in its molecular weight distribution measured by gel permeation chromatography or the like. Specifically, the peak in the low molecular weight region preferably exists in a molecular weight range of 3,000 to 20,000, and the peak in the high molecular weight region preferably exists in a molecular weight range of 300,000 to 1,500,000. Furthermore, for polystyrene-based resins with such molecular weight distribution, the ratio (Mw / Mn) of the number average molecular weight (Mn) to the mass average molecular weight (Mw) is preferably 10 or more. When the binder resin has peaks in the low molecular weight region and the high molecular weight region within such ranges in its molecular weight distribution, a toner with excellent low-temperature fixability and capable of suppressing high-temperature offset can be obtained.

[0062] (mold release agent) The toner core particles preferably contain a release agent for the purpose of improving fixability and offset resistance. The type of release agent that can be contained in the toner core particles is not particularly limited as long as it does not impair the object of the present invention. Wax is preferred as the release agent, and examples of wax include carnauba wax, synthetic ester wax, polyethylene wax, polypropylene wax, fluororesin wax, Fischer-Tropsch wax, paraffin wax, montan wax, and rice wax. Two or more of these release agents can be used in combination. Adding such a release agent to the toner can more efficiently suppress the occurrence of offset and image smearing (staining around the image when the image is rubbed).

[0063] When a polyester resin is used as the binder resin, from the viewpoint of compatibility, one or more release agents selected from the group consisting of carnauba wax, synthetic ester wax, and polyethylene wax are preferably used as the release agent. When a polystyrene resin is used as the binder resin, from the viewpoint of compatibility, Fischer-Tropsch wax and / or paraffin wax are preferably used as the release agent.

[0064] Fischer-Tropsch wax is a linear hydrocarbon compound with few isostructural molecules and few side chains, produced by utilizing the Fischer-Tropsch reaction, which is a catalytic hydrogenation reaction of carbon monoxide.

[0065] Among Fischer-Tropsch waxes, those having a mass average molecular weight of 1,000 or more and having an endothermic peak bottom temperature observed by DSC measurement in the range of 100° C. to 120° C. are more preferred. Examples of such Fischer-Tropsch waxes include Sasolwax C1 (endothermic peak bottom temperature: 106.5° C.), Sasolwax C105 (endothermic peak bottom temperature: 102.1° C.), and Sasolwax SPRAY (endothermic peak bottom temperature: 102.1° C.), all of which are available from Sasol.

[0066] The amount of the release agent used is not particularly limited as long as it does not impair the object of the present invention. Specifically, the amount of the release agent used is preferably 1% by mass or more and 10% by mass or less, based on the total mass of the toner core particles. If the amount of the release agent used is too small, the desired effect of suppressing offset and image smearing in the formed image may not be achieved. If the amount of the release agent used is too large, the toner particles may fuse together, resulting in a decrease in the heat-resistant storage stability of the toner.

[0067] (charge control agent) The toner core particles may contain a charge control agent for the purpose of improving the charge level of the toner and the charge rise characteristics, which are indicators of whether the toner can be charged to a predetermined charge level in a short time, and obtaining a toner with excellent durability and stability. When developing by positively charging the toner, a positively charging charge control agent is used, and when developing by negatively charging the toner, a negatively charging charge control agent is used.

[0068] The type of charge control agent that can be contained in the toner core particles is not particularly limited as long as it does not impair the object of the present invention, and can be appropriately selected from charge control agents that have been used in toners. Specific examples of positively chargeable charge control agents include azine compounds such as pyridazine, pyrimidine, pyrazine, orthooxazine, metaoxazine, paraoxazine, orthothiazine, metathiazine, parathiazine, 1,2,3-triazine, 1,2,4-triazine, 1,3,5-triazine, 1,2,4-oxadiazine, 1,3,4-oxadiazine, 1,2,6-oxadiazine, 1,3,4-thiadiazine, 1,3,5-thiadiazine, 1,2,3,4-tetrazine, 1,2,4,5-tetrazine, 1,2,3,5-tetrazine, 1,2,4,6-oxatriazine, 1,3,4,5-oxatriazine, phthalazine, quinazoline, and quinoxaline; azine phthalazine; Examples of suitable positively charged charge control agents include direct dyes made from azine compounds such as Fast Red FC, Azin Fast Red 12BK, Azin Violet BO, Azin Brown 3G, Azin Light Brown GR, Azin Dark Green BH / C, Azin Deep Black EW, and Azin Deep Black 3RL; nigrosine compounds such as nigrosine, nigrosine salts, and nigrosine derivatives; acid dyes made from nigrosine compounds such as Nigrosine BK, Nigrosine NB, and Nigrosine Z; metal salts of naphthenic acid or higher fatty acids; alkoxylated amines; alkylamides; and quaternary ammonium salts such as benzylmethylhexyldecylammonium and decyltrimethylammonium chloride. Among these positively charged charge control agents, nigrosine compounds are particularly preferred because they provide a more rapid charge buildup. These positively charged charge control agents can be used in combination of two or more.

[0069] Resins having a quaternary ammonium salt, a carboxylate, or a carboxyl group as a functional group can also be used as positively charged charge control agents. More specifically, examples include styrene-based resins having a quaternary ammonium salt, acrylic-based resins having a quaternary ammonium salt, styrene-acrylic resins having a quaternary ammonium salt, polyester resins having a quaternary ammonium salt, styrene-based resins having a carboxylate, acrylic resins having a carboxylate, styrene-acrylic resins having a carboxylate, polyester resins having a carboxylate, styrene-based resins having a carboxyl group, acrylic resins having a carboxyl group, styrene-acrylic resins having a carboxyl group, and polyester resins having a carboxyl group. The molecular weight of these resins is not particularly limited as long as it does not impair the object of the present invention, and they may be oligomers or polymers.

[0070] Among resins that can be used as positively charged charge control agents, styrene-acrylic resins having a quaternary ammonium salt as a functional group are more preferred because the charge amount can be easily adjusted to a value within a desired range. Specific examples of preferred acrylic comonomers to be copolymerized with styrene units in styrene-acrylic resins having a quaternary ammonium salt as a functional group include (meth)acrylic acid alkyl esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, and isobutyl methacrylate.

[0071] The quaternary ammonium salt may be a unit derived from a dialkylaminoalkyl (meth)acrylate, a dialkyl (meth)acrylamide, or a dialkylaminoalkyl (meth)acrylamide via a quaternization process. Specific examples of dialkylaminoalkyl (meth)acrylates include dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dipropylaminoethyl (meth)acrylate, and dibutylaminoethyl (meth)acrylate. Specific examples of dialkyl (meth)acrylamides include dimethylmethacrylamide, and specific examples of dialkylaminoalkyl (meth)acrylamides include dimethylaminopropyl methacrylamide. Hydroxy-containing polymerizable monomers such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and N-methylol (meth)acrylamide may also be used in combination during polymerization.

[0072] Specific examples of negatively chargeable charge control agents include organic metal complexes, chelate compounds, monoazo metal complexes, acetylacetone metal complexes, aromatic hydroxycarboxylic acids, aromatic dicarboxylic acid-based metal complexes, aromatic monocarboxylic acids, aromatic polycarboxylic acids, and their metal salts, anhydrides, esters, and phenol derivatives such as bisphenols. Among these, organic metal complexes and chelate compounds are preferred. As organic metal complexes and chelate compounds, acetylacetone metal complexes such as aluminum acetylacetonate and iron(II) acetylacetonate, and salicylic acid metal complexes or salicylic acid metal salts such as 3,5-di-tert-butylsalicylate chromium are more preferred, with salicylic acid metal complexes or salicylic acid metal salts being particularly preferred. These negatively chargeable charge control agents can be used in combination of two or more.

[0073] The amount of the positively or negatively chargeable charge control agent used is not particularly limited as long as it does not impair the objectives of the present invention. The amount of the positively or negatively chargeable charge control agent used is typically preferably 0.1% by mass or more and 10% by mass or less, based on the total mass of the toner core particles. If the amount of charge control agent used is too small, it is difficult to stably charge the toner to a predetermined polarity, which can result in the image density of the formed image falling below the desired value or making it difficult to maintain the image density over a long period of time. Furthermore, it is difficult for the charge control agent to be uniformly dispersed, which can easily cause fogging in the formed image or contamination of the latent image bearing portion by toner components. If the amount of charge control agent used is too large, poor environmental resistance can result in poor charging under high temperature and high humidity conditions, which can easily cause image defects in the formed image, or contamination of the latent image bearing portion by toner components.

[0074] (coloring agent) The toner core particles may contain a colorant as needed. The colorant that can be contained in the toner core particles can be a known pigment or dye, depending on the color of the toner. Specific examples of suitable colorants that can be added to the toner include black pigments such as carbon black, acetylene black, lamp black, and aniline black; yellow pigments such as yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa yellow G, Hansa yellow 10G, benzidine yellow G, benzidine yellow GR, quinoline yellow lake, permanent yellow NCG, tartrazine lake, monoazo yellow, and diazo yellow; orange pigments such as red yellow lead, molybdenum orange, permanent orange GTR, pyrazolone orange, and induthrene brilliant orange GK; red iron oxide, cadmium red, red lead, mercury cadmium sulfide, permanent red 4R, lithol red, and pyrazolone. Examples of suitable colorants include red pigments such as Ron Red, Watching Red calcium salt, Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B, and Monoazo Red; purple pigments such as Manganese Purple, Fast Violet B, and Methyl Violet Lake; blue pigments such as Prussian Blue, Cobalt Blue, Alkali Blue Lake, Victoria Blue (partially chlorinated), Fast Sky Blue, Indanthrene Blue BC, and Phthalocyanine Blue; green pigments such as Chrome Green, chromium oxide, Pigment Green B, Malachite Green Lake, and Final Yellow Green G; white pigments such as zinc oxide, titanium oxide, antimony white, and zinc sulfide; and extender pigments such as baryte powder, barium carbonate, clay, silica, white carbon, talc, and alumina white. These colorants can also be used in combination of two or more types to adjust the toner to a desired hue.

[0075] The amount of the colorant used is not particularly limited as long as it does not impair the object of the present invention. Specifically, the amount of the colorant used is preferably 1% by mass or more and 10% by mass or less, and more preferably 2% by mass or more and 7% by mass or less, based on the total mass of the toner core particles.

[0076] The colorant may also be used as a masterbatch in which the colorant is dispersed in advance in a resin material such as a thermoplastic resin. When the colorant is used as a masterbatch, the resin contained in the masterbatch is preferably the same type of resin as the binder resin.

[0077] (Resin fine particles) The shell layer in the toner for developing electrostatic latent images of the present invention is made of a resin containing a charge control resin. The shell layer is formed from resin fine particles. Therefore, resin fine particles made of a resin containing a charge control resin are used as the resin fine particles used to form the shell layer. By making the shell layer from a resin containing a charge control resin, when forming images over a long period of time under various environments, such as a high-temperature, high-humidity environment or a low-temperature, low-humidity environment, the toner can be charged to a desired charge amount, thereby enabling the formation of images of a desired density.

[0078] The material for the resin microparticles is preferably a polymer of a monomer having an unsaturated bond, since it is easy to form a shell layer with a predetermined structure. The charge-control resin is preferably a copolymer of a monomer having an unsaturated bond and a chargeable functional group that imparts chargeability to the resin, and a monomer having an unsaturated bond but no chargeable functional group. The monomer having an unsaturated bond and a chargeable functional group, which is used to impart positive chargeability to the resin, is preferably a monomer having a nitrogen-containing polar functional group such as a quaternary ammonium group and an unsaturated bond. On the other hand, the monomer having an unsaturated bond and a chargeable functional group, which is used to impart negative chargeability to the resin, is preferably a monomer having a fluorine-substituted hydrocarbon group or a sulfo group and an unsaturated bond.

[0079] The type of monomer having an unsaturated bond is not particularly limited as long as it is possible to synthesize a resin having sufficient physical properties as a shell layer. A vinyl-based monomer is preferred as the monomer having an unsaturated bond. The vinyl group contained in the vinyl-based monomer may be substituted with an alkyl group at the α-position. The vinyl group contained in the vinyl-based monomer may be substituted with a halogen atom. The alkyl group that the vinyl group may have is preferably an alkyl group having 1 to 6 carbon atoms, more preferably a methyl group or an ethyl group, and particularly preferably a methyl group. The halogen atom that the vinyl group may have is preferably a chlorine atom or a bromine atom, more preferably a chlorine atom.

[0080] Specific examples of vinyl monomers that do not have a nitrogen-containing polar functional group, a fluorine-substituted hydrocarbon group, or a chargeable functional group such as a sulfo group include styrenes such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, p-methoxystyrene, p-ethoxystyrene, p-phenylstyrene, p-chlorostyrene, and 3,4-dichlorostyrene; ethylenically unsaturated monoolefins such as ethylene, propylene, butylene, and isobutylene; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide, and vinyl fluoride; vinyl acetate, propylene, and the like. Examples of suitable (meth)acrylic acid esters include vinyl esters such as vinyl propionate, vinyl benzoate, and vinyl butyrate; (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, propyl (meth)acrylate, n-octyl (meth)acrylate, dodecyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, stearyl (meth)acrylate, 2-chloroethyl (meth)acrylate, phenyl (meth)acrylate, and methyl α-chloroacrylate; (meth)acrylic acid derivatives such as acrylonitrile; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, and vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, and methyl isopropenyl ketone; and vinyl naphthalenes. Among these, styrenes are preferred, and styrene is more preferred. These monomers can be used in combination of two or more.

[0081] Examples of vinyl monomers having a nitrogen-containing polar functional group, which is a positively chargeable functional group, that are used as monomers for positively chargeable charge control resins include N-vinyl compounds, amino(meth)acrylic monomers, and methacrylonitrile(meth)acrylamide. Specific examples of N-vinyl compounds include N-vinyl compounds such as N-vinylpyrrole, N-vinylcarbazole, N-vinylindole, and N-vinylpyrrolidone. Furthermore, preferred examples of amino(meth)acrylic monomers include compounds represented by the following formula: CH2=C(R1)-(CO)-XN(R2)(R3) ···(1) (In formula (1), R1 represents hydrogen or a methyl group. R2 and R3 each represent a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. X represents -O-, -OQ-, or -NH. Q represents an alkylene group having 1 to 10 carbon atoms, a phenylene group, or a combination of these groups.)

[0082] In the above formula (1), specific examples of R2 and R3 include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a tert-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, a 2-ethylhexyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group (lauryl group), an n-tridecyl group, an n-tetradecyl group, an n-pentadecyl group, an n-hexadecyl group, an n-heptadecyl group, an n-octadecyl group (stearyl group), an n-nonadecyl group, and an n-icosyl group.

[0083] In the above formula (1), specific examples of Q include a methylene group, a 1,2-ethane-diyl group, a 1,1-ethylene group, a propane-1,3-diyl group, a propane-2,2-diyl group, a propane-1,1-diyl group, a propane-1,2-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a heptane-1,7-diyl group, an octane-1,8-diyl group, a nonane-1,9-diyl group, a decane-1,10-diyl group, a p-phenylene group, an m-phenylene group, an o-phenylene group, and a divalent group obtained by removing a hydrogen atom from the 4-position of a phenyl group contained in a benzyl group.

[0084] Specific examples of the amino(meth)acrylic monomer represented by the above formula include, for example, N,N-dimethylamino(meth)acrylate, N,N-dimethylaminomethyl(meth)acrylate, N,N-diethylaminomethyl(meth)acrylate, 2-(N,N-methylamino)ethyl(meth)acrylate, 2-(N,N-diethylamino)ethyl(meth)acrylate, 3-(N,N-dimethylamino)propyl(meth)acrylate, 4-(N,N-dimethylamino)butyl(meth)acrylate, pN,N-dimethylaminophenyl(meth)acrylate, Acrylate, pN,N-diethylaminophenyl (meth)acrylate, pN,N-dipropylaminophenyl (meth)acrylate, pN,N-di-n-butylaminophenyl (meth)acrylate, pN-laurylaminophenyl (meth)acrylate, pN-stearylaminophenyl (meth)acrylate, (pN,N-dimethylaminophenyl)methyl (meth)acrylate, (pN,N-diethylaminophenyl)methyl (meth)acrylate, (pN,N-di-n-propylaminophenyl)methyl (meth)acrylate, (p N,N-di-n-butylaminophenyl)methylbenzyl (meth)acrylate, (pN-laurylaminophenyl)methyl (meth)acrylate, (pN-stearylaminophenyl)methyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylamide, N,N-diethylaminoethyl (meth)acrylamide, 3-(N,N-dimethylamino)propyl (meth)acrylamide, 3-(N,N-diethylamino)propyl (meth)acrylamide, pN,N-dimethylaminophenyl (meth)acrylamide, pN,N- Diethylaminophenyl (meth)acrylamide, pN,N-di-n-propylaminophenyl (meth)acrylamide, pN,N-di-n-butylaminophenyl (meth)acrylamide, pN-laurylaminophenyl (meth)acrylamide, pN-stearylaminophenyl (meth)acrylamide, (pN,N-dimethylaminophenyl)methyl (meth)allylamide, (pN,N-diethylaminophenyl)methyl (meth)acrylamide, (pN,N-di-n-propylaminophenyl)methyl (meth)acrylamide, (pN,Examples include (N-di-n-butylaminophenyl)methyl(meth)acrylamide, (pN-laurylaminophenyl)methyl(meth)acrylamide, and (pN-stearylaminophenyl)methyl(meth)acrylamide.

[0085] Examples of vinyl monomers having a fluorine-substituted hydrocarbon group, which is a negatively chargeable functional group, that are used as monomers for negatively chargeable charge control resins include fluoroalkyl(meth)acrylates such as 2,2,2-trifluoroethyl acrylate, 2,2,3,3-tetrafluoropropyl acrylate, 2,2,3,3,4,4,5,5-octafluoroamyl acrylate, and 1H,1H,2H,2H-heptadecafluorodecyl acrylate, as well as trifluorochloroethylene, vinylidene fluoride, ethylene trifluoride, ethylene tetrafluoride, trifluoropropylene, hexafluoropropene, and hexafluoropropylene. Among these, fluoroalkyl(meth)acrylates are preferred.

[0086] Examples of vinyl monomers having a sulfo group, which is a negatively chargeable functional group, that can be used as a monomer for a negatively chargeable charge control resin include 2-acrylamido-2-methylpropanesulfonic acid, sodium styrenesulfonate, and sulfoalkyl(meth)acrylic acid monomers such as sulfoethylacrylic acid, sulfoethylmethacrylic acid, and sodium sulfoethylmethacrylate. Among these, 2-acrylamido-2-methylpropanesulfonic acid is preferred.

[0087] The method for addition polymerization of the monomer having an unsaturated bond is not limited as long as it does not impair the object of the present invention, and any method such as solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization, etc. can be selected.

[0088] Examples of polymerization initiators that can be used in the polymerization of the vinyl monomers described above include known polymerization initiators such as potassium persulfate, sodium peroxodisulfate, potassium peroxodisulfate, ammonium peroxodisulfate, acetyl peroxide, decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, azobisisobutyronitrile, azobismethylbutyronitrile, 2,2'-azobis-2,4-dimethylvaleronitrile, 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, t-butylperoxy-2-ethylhexanoate, t-butylperbenzoate, dicyclohexyl peroxide, and dicumyl peroxide. The amount of these polymerization initiators used is preferably 0.1% by mass or more and 15% by mass or less based on the total mass of the monomers.

[0089] The method for polymerizing the vinyl monomers is not limited as long as it does not impair the object of the present invention, and any method such as solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization, etc. can be selected.

[0090] When an aqueous medium is used to perform addition polymerization of a monomer having an unsaturated bond, such as emulsion polymerization or suspension polymerization, a surfactant can be used. The surfactant is not limited as long as it does not impair the objectives of the present invention and can be appropriately selected from the group consisting of anionic surfactants, cationic surfactants, and nonionic surfactants. Examples of anionic surfactants include sulfate ester salt surfactants, sulfonate salt surfactants, phosphate ester salt surfactants, and soap. Examples of cationic surfactants include amine salt surfactants and quaternary ammonium salt surfactants. Examples of nonionic surfactants include polyethylene glycol surfactants, alkylphenol ethylene oxide adduct surfactants, and polyhydric alcohol surfactants, which are derivatives of polyhydric alcohols such as glycerin, sorbitol, and sorbitan. Among these surfactants, it is preferable to use at least one of anionic surfactants and nonionic surfactants. These surfactants may be used alone or in combination of two or more.

[0091] When the charge control resin is a copolymer of a monomer having an unsaturated bond and a chargeable functional group that imparts chargeability to the resin, and a monomer having an unsaturated bond but not a chargeable functional group, the molar ratio of the constituent unit derived from the monomer having the chargeable functional group and the unsaturated bond to the preceding constituent unit in the charge control resin is preferably 0.1 mol % or more and 10 mol % or less, more preferably 0.3 mol % or more and 7 mol % or less.

[0092] The content of the charge control resin in the resin constituting the resin microparticles is not particularly limited as long as it does not impair the object of the present invention. The content of the charge control resin in the resin that is the material for the resin microparticles is preferably 80% by mass or more, more preferably 90% by mass or more, and particularly preferably 100% by mass, based on the total mass of the resin microparticles. When the resin constituting the resin microparticles is a mixture of a charge control resin and a resin that does not have a chargeable functional group, the resin that does not have a chargeable functional group can be a polymer of one or more monomers selected from the above-mentioned vinyl monomers that do not have a chargeable functional group. Furthermore, the resin microparticles may be prepared using a resin containing the above-mentioned colorant, if necessary.

[0093] A mixture of a charge-controlling resin and a resin that does not have a chargeable functional group can be prepared by melt-kneading two or more resins using a melt-kneading device such as a twin-screw extruder, or by dissolving two or more resins in an organic solvent to obtain a resin solution, and then removing the organic solvent from the resulting solution.

[0094] Alternatively, the shell layer may be formed by combining resin particles made of a resin containing a charge control resin with resin particles made of a resin not having a chargeable functional group. In this case, the ratio of the mass of the resin particles made of a resin containing a charge control resin to the total mass of the resin particles used to form the shell layer is preferably 80 mass% or more, more preferably 90 mass% or more. In this case, the resin particles not having a chargeable functional group may be resin particles made of a polymer of one or more monomers selected from the above-mentioned vinyl monomers not having a chargeable functional group.

[0095] The glass transition point of the resin constituting the resin microparticles is not particularly limited as long as it does not impair the objectives of the present invention. Typically, the glass transition point is preferably 45°C or higher and 90°C or lower, and more preferably 50°C or higher and 80°C or lower. The softening point of the resin constituting the resin microparticles is also not particularly limited as long as it does not impair the objectives of the present invention. Typically, the softening point is preferably 100°C or higher and 250°C or lower, and more preferably 110°C or higher and 240°C or lower. The softening point of the resin is preferably higher than the softening point of the binder resin contained in the toner core particles, and more preferably 10°C or higher and 140°C or lower. By setting the temperature characteristics of the resin constituting the resin microparticles within this range, the portions of the resin microparticles in contact with the toner core particles are less likely to deform when the resin microparticles are embedded in the toner core particles, and therefore, convex portions derived from the shape of the resin microparticles before they change into shell layers are more likely to be formed on the inner surface of the shell layer.

[0096] The mass average molecular weight (Mw) of the resin constituting the resin microparticles is not particularly limited as long as it does not impair the object of the present invention. Typically, the mass average molecular weight is preferably 20,000 or more and 1,500,000 or less, and more preferably 200,000 or more and 400,000 or less. The mass average molecular weight (Mw) of the resin that is the material for the resin microparticles can be measured by gel permeation chromatography according to a conventionally known method.

[0097] The average particle diameter of the resin fine particles is not particularly limited as long as it does not impair the object of the present invention, but is preferably 0.03 μm to 1 μm, more preferably 0.04 μm to 0.7 μm, particularly preferably 0.05 μm to 0.5 μm, and most preferably 0.05 μm to 0.3 μm. When resin fine particles with such particle diameters are used, the surfaces of the toner core particles are easily uniformly coated with the resin fine particles in a single layer, and a shell layer with the desired structure is easily formed. If the average particle diameter of the resin fine particles is too small, it is difficult to form a shell layer with a desired thickness on the surfaces of the toner core particles, making it difficult to obtain a toner with excellent heat-resistant storage stability. On the other hand, if the average particle diameter of the resin fine particles is too large, it is difficult to uniformly attach the resin fine particles to the surfaces of the toner core particles. As a result, it is difficult to form a shell layer with the desired structure, making it difficult to obtain a toner with excellent heat-resistant storage stability.

[0098] The average particle size of the resin microparticles can be adjusted by adjusting the polymerization conditions, or by known pulverization methods, classification methods, etc. The average particle size of the resin microparticles can be determined as a number-average particle size by measuring the particle sizes of 50 or more resin microparticles in an electron micrograph taken using a field emission scanning electron microscope (JSM-6700F, manufactured by JEOL Ltd.).

[0099] The amount of resin particles used is not particularly limited as long as it does not impair the object of the present invention. The amount of resin particles used is typically preferably 1 part by mass or more and 20 parts by mass or less, and more preferably 3 parts by mass or more and 15 parts by mass or less, per 100 parts by mass of toner core particles. If the amount of resin particles used is too small, the entire surface of the toner core particles may not be covered with the resin particles. If the entire surface of the toner core particles cannot be covered with the resin particles, the toner is likely to aggregate during storage at high temperatures, and the heat-resistant storage stability is likely to deteriorate. If the amount of resin particles used is excessive, the shell layer is likely to become thick. In this case, it is difficult to obtain a toner with excellent fixability.

[0100] (external additives) The toner of the present invention can be treated with an external additive, if desired, after forming a shell layer on the surface of the toner core particle. Hereinafter, the particles treated with an external additive are also referred to as "toner base particles."

[0101] The type of external additive is not particularly limited as long as it does not impair the object of the present invention, and can be appropriately selected from external additives that have been conventionally used for toners. Specific examples of suitable external additives include silica and metal oxides such as alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, and barium titanate. These external additives can be used in combination of two or more types.

[0102] The particle size of the external additive is not particularly limited as long as it does not impair the object of the present invention, and is typically preferably 0.01 μm or more and 1.0 μm or less.

[0103] The amount of external additive used is not particularly limited as long as it does not impair the object of the present invention. The amount of external additive used is typically preferably 0.1% by mass to 10% by mass, more preferably 0.2% by mass to 5% by mass, based on the total mass of toner base particles produced by forming a shell layer on the surface of toner core particles. If the amount of external additive used is too small, the hydrophobicity of the toner is likely to decrease. As a result, the toner becomes more susceptible to the effects of water molecules in the air in high-temperature, high-humidity environments, which can lead to problems such as a decrease in image density of formed images due to an extreme decrease in the toner charge amount and a decrease in toner fluidity. Furthermore, if the amount of external additive used is too large, excessive charge-up of the toner may result in a decrease in image density.

[0104] [5. Method for manufacturing non-magnetic one-component developing toner] The method for producing the electrostatic latent image developing toner described above is not particularly limited as long as the toner core particles and the shell layer are formed so as to have the predetermined structures. If necessary, the toner core particles coated with the shell layer may be used as the toner base particles, and an external additive treatment may be performed to attach an external additive to the surface of the toner base particles. As a suitable method for producing the electrostatic latent image developing toner described above, the method for producing the toner core particles, the method for forming the shell layer, and the external additive treatment will be described below in this order.

[0105] (Method of manufacturing toner core particles) The method for producing toner core particles is not particularly limited as long as it can satisfactorily disperse optional components such as a colorant, a release agent, a charge control agent, and a magnetic powder in a binder resin. A specific example of a suitable method for producing toner core particles includes a method in which a binder resin and components such as a colorant, a release agent, a charge control agent, and a magnetic powder are mixed in a mixer or the like, and then the binder resin and components to be blended in the binder resin are melt-kneaded in a kneader such as a single-screw or twin-screw extruder, and the cooled kneaded product is pulverized and classified. The average particle size of the toner core particles is not particularly limited as long as it does not impair the object of the present invention, but is generally preferably 5 μm or more and 10 μm or less.

[0106] (Method of forming shell layer) The shell layer is formed using spherical resin particles. More specifically, I) a step of attaching spherical resin fine particles to the surface of the toner core particle so as not to overlap in a direction perpendicular to the surface of the toner core particle, thereby forming a resin fine particle layer that covers the entire surface of the toner core particle; and II) applying an external force to the outer surface of the resin fine particle layer to deform the resin fine particle in the resin fine particle layer, thereby smoothing the outer surface of the resin fine particle layer and forming a shell layer; The method includes:

[0107] As described above, a preferred method for forming a shell layer using resin fine particles is to use a mixer capable of mixing toner core particles and resin fine particles under dry conditions. A specific example is a method for forming a shell layer on the surface of toner core particles using a mixer capable of adhering resin fine particles to the surface of toner core particles while applying a mechanical external force to the toner core particles having the resin fine particles adhered to their surfaces. Examples of mechanical external forces include shear forces applied to toner core particles due to shear between toner core particles or shear between toner core particles and the inner wall, rotor, stator, or the like when the toner core particles move at high speed through the narrow space in the mixer, and impact forces applied to toner core particles due to collision between toner core particles or collision between toner core particles and the inner wall, or the like, of the mixer.

[0108] A more specific method will be described. First, toner core particles and resin microparticles are mixed in a mixer to uniformly adhere the resin microparticles to the surfaces of the toner core particles so that the resin microparticles do not overlap in a direction perpendicular to the surface of the toner core particles. When large-sized toner core particles come into contact with small-sized resin microparticles, the surfaces of the toner core particles, which can be considered flat at a microscopic level, contact each other face-to-face, making it easy for the resin microparticles to adhere to the toner core particles. On the other hand, when resin microparticles come into contact with each other, the curved surfaces of the two resin microparticles come into contact, resulting in point-to-point contact. Therefore, even if additional resin microparticles adhere to the resin microparticles already adhering to the surfaces of the toner core particles during the process of adhering the resin microparticles to the toner core particles, the mechanical external force applied by the mixer to the toner core particles to which the resin microparticles have adhered easily detaches the resin microparticles from the resin microparticles. For this reason, in the method described below, the toner core particles are coated with resin microparticles so that the resin microparticles do not overlap in a direction perpendicular to the surface of the toner core particles.

[0109] When the resin microparticles are attached to the toner core particles, the aforementioned mechanical external force is applied to the resin microparticle layer on the surface of the toner core particles. The application of the mechanical external force to the resin microparticle layer on the surface of the toner core particles causes the resin microparticles to become embedded in the toner core particles and deform, smoothing the outer surface of the resin microparticle layer covering the entire surface of the toner core particles, and transforming the resin microparticle layer into a shell layer. While the outer surface of the shell layer is smoothed, the boundaries between the resin microparticles remain inside the shell layer. As a result, cracks are formed inside the shell layer formed using the resin microparticles in a direction approximately perpendicular to the surface of the toner core particles.

[0110] In this case, if the material of the toner core particle is as hard as or slightly harder than the resin fine particles that form the shell layer, the inner surface of the shell layer (the surface on the toner core particle side) may become smooth. On the other hand, if the material of the toner core particle is softer than the resin fine particles that form the shell layer, the part of the resin fine particles that contact the toner core particle is less likely to deform when the resin fine particles are embedded in the toner core particle, and therefore protrusions derived from the shape of the fine particles before they change into the shell layer are likely to form on the inner surface of the shell layer. In this case, the protrusions are formed between two cracks in the shell layer.

[0111] In the above-mentioned method, if the external mechanical force is weak, the resin particles may not deform to the desired extent, and a shell layer of the desired shape may not be formed. The conditions for forming a shell layer of the desired shape vary depending on the device used to form the shell layer. By gradually changing the operating conditions so that the external mechanical force applied to the toner core particles coated with the resin particles is increased and checking the shell layer structure of the toner obtained under each condition, it is possible to determine suitable conditions for forming a desired shell layer for various devices. However, if the external mechanical force is too strong, for example, the resin particles may be deformed too severely, preventing cracks from forming inside the shell layer in a direction approximately perpendicular to the toner core particles, or the external mechanical force may be converted into heat, resulting in problems such as melting of the toner core particles or the resin particles.

[0112] Examples of devices that can coat toner core particles with resin fine particles while applying a mechanical external force to the toner core particles coated with the resin fine particles include the Hybridizer NHS-1 (manufactured by Nara Machinery Works, Ltd.), Cosmos System (manufactured by Kawasaki Heavy Industries, Ltd.), Henschel Mixer (manufactured by Nippon Coke and Engineering Co., Ltd.), Multipurpose Mixer (manufactured by Nippon Coke and Engineering Co., Ltd.), Compozi (manufactured by Nippon Coke and Engineering Co., Ltd.), Mechanofusion device (manufactured by Hosokawa Micron Corporation), Mechanomill (manufactured by Okada Precision Industries, Ltd.), and Nobilta (manufactured by Hosokawa Micron Corporation).

[0113] (External addition treatment method) The method for treating the toner base particles with the external additive is not particularly limited, and the toner base particles can be treated according to a conventionally known method. Specifically, the treatment conditions are adjusted so that the particles of the external additive are not embedded in the toner base particles, and the toner base particles are treated with the external additive using a mixer such as a Henschel mixer or a Nauta mixer.

[0114] The electrostatic latent image developing toner of the present invention described above has excellent fixing properties and heat-resistant storage properties, and when forming images over a long period of time under various environments such as high-temperature, high-humidity environments and low-temperature, low-humidity environments, the toner can be charged to a desired charge amount, thereby forming images of a desired density. Therefore, the electrostatic latent image developing toner of the present invention can be suitably used in various image forming devices. The effects of the present invention will be more specifically described below using examples. However, the present invention is not limited to these examples in any way. [Example]

[0115] [Manufacturing Example 1] (Production of polyester resins a and b) A reaction vessel was charged with 1960 g of a propylene oxide adduct of bisphenol A, 780 g of an ethylene oxide adduct of bisphenol A, 257 g of dodecenyl succinic anhydride, 770 g of terephthalic acid, and 4 g of dibutyltin oxide. Next, a nitrogen atmosphere was placed inside the reaction vessel, and the temperature inside the reaction vessel was raised to 235°C while stirring. After the reaction was continued at this temperature for 8 hours, the pressure inside the reaction vessel was reduced to 8.3 kPa and the reaction was continued for 1 hour. The reaction mixture was then cooled to 180°C, and trimellitic anhydride was added to the reaction vessel to achieve the desired oxidation rate. The temperature of the reaction mixture was then raised to 210°C at a rate of 10°C / hour, and the reaction was continued at the same temperature. After the reaction was completed, the contents of the reaction vessel were removed and cooled to obtain polyester resin a. Additionally, amorphous polyester resin b with different mass average molecular weights was obtained by appropriately modifying the preparation conditions for the amorphous polyester resin a.

[0116] [Manufacturing Example 2] (Production of toner core particles) A mixture was obtained by mixing 89 parts by weight of a binder resin (the polyester resin obtained in Production Example 1), 5 parts by weight of a release agent (Polypropylene Wax 660P (manufactured by Sanyo Chemical Industry Co., Ltd.)), 1 part by weight of a charge control agent (P-51 (manufactured by Orient Chemical Industries Co., Ltd.)), and 5 parts by weight of a colorant (Carbon Black MA100 (manufactured by Mitsubishi Chemical Corporation)) in a mixer. The mixture was then melt-kneaded in a twin-screw extruder to obtain a kneaded product. The kneaded product was coarsely pulverized in a grinder (Rotoplex (manufactured by Toa Machinery Works, Ltd.)), and the coarsely pulverized product was then finely pulverized in a mechanical grinder (Turbo Mill (manufactured by Turbo Kogyo Co., Ltd.)) to obtain a finely pulverized product. The finely pulverized product was classified using a classifier (Elbow Jet (manufactured by Nittetsu Mining Co., Ltd.)) to obtain toner core particles having a volume average particle diameter (D50) of 7.0 μm. The volume average particle diameter of the toner core particles was measured using a Coulter Counter Multisizer 3 (manufactured by Beckman Coulter, Inc.).

[0117] [Manufacturing Example 3] (Production of Resin Fine Particles A) A 2000 mL flask equipped with a stirrer, thermometer, condenser, and nitrogen inlet tube was used as the reaction vessel. 16 g of diethylaminoethyl methacrylate and 16 g of methyl paratoluenesulfonate were added to the reaction vessel containing 180 g of isobutanol as a solvent. The reaction vessel was placed on a mantle heater, and nitrogen gas was introduced into the reaction vessel through the nitrogen inlet tube to create an inert atmosphere inside the reaction vessel. Next, the internal temperature of the reaction vessel was raised to 80 °C while stirring the mixture in the flask at a stirring speed of 100 rpm. The quaternization reaction was carried out at this temperature for 1 hour with continued stirring at a stirring speed of 100 rpm.

[0118] After the quaternization reaction, 214 g of styrene, 72 g of butyl acrylate, and 12 g of the peroxide initiator t-butylperoxy-2-ethylhexanoate (manufactured by Arkema Yoshitomi Co., Ltd.) were added to the reaction vessel. The internal temperature of the reaction vessel was raised to 95°C (polymerization temperature), and the contents of the reaction vessel were stirred at a stirring speed of 100 rpm for 3 hours. Next, 6 g of t-butylperoxy-2-ethylhexanoate was added to the reaction vessel. The contents of the reaction vessel were then stirred at a stirring speed of 100 rpm for 3 hours at 95°C to complete the polymerization reaction and obtain a resin particle dispersion. The obtained resin particle dispersion was freeze-dried to obtain powdered resin particle A. The number-average particle diameter of resin particle A was 0.10 μm and the molecular weight was 225,000.

[0119] The number-average particle diameter of the resin microparticles was measured by the following method. First, a photograph of the resin microparticles was taken at a magnification of 100,000 times using a field emission scanning electron microscope (JSM-6700F, manufactured by JEOL Ltd.). The electron micrograph was further enlarged as necessary, and the number-average particle diameter of 50 or more resin microparticles was measured using a ruler, calipers, etc.

[0120] (Production of Resin Particles B) A 1000 mL reaction vessel equipped with a stirrer, thermometer, condenser, and nitrogen inlet was charged with 450 mL of distilled water and 0.52 g of dodecylammonium chloride. The contents of the reaction vessel were stirred under a nitrogen atmosphere while the temperature inside the reaction vessel was raised to 80°C. After the temperature was raised, 120 g of a 1% by weight aqueous solution of potassium persulfate (polymerization initiator) and 200 g of ion-exchanged water were added to the reaction vessel. Next, a mixture consisting of 15 g of butyl acrylate, 165 g of methyl methacrylate, and 3.6 g of n-octyl mercaptan (chain transfer agent) was added dropwise to the reaction vessel over 1.5 hours, and polymerization was continued for an additional 2 hours to obtain an aqueous dispersion of resin microparticles. The resulting aqueous dispersion of resin microparticles was freeze-dried to obtain resin microparticles B. Resin microparticles B had a number-average particle diameter of 0.102 μm and a mass-average molecular weight of 197,000.

[0121] (Production of Resin Particles C) The preparation conditions for the above-mentioned resin fine particles A were appropriately changed to obtain resin fine particles C having a different molecular weight. The mass average molecular weight of the resin fine particles C was 384,000.

[0122] [Preparation of Toners of Invention 1, Comparative Examples 1, 2, and 5] (Preparation of Toner Base Particles) 100 g of the toner core particles obtained in Production Example 2 were coated with 10 g of the resin microparticles of the type shown in Table 1 obtained in Production Example 3, and a shell layer was formed on the surface of the toner core particles. A powder processing device (Multipurpose Mixer MP type (manufactured by Nippon Coke & Engineering Co., Ltd.)) was used for the shell formation process. The toner core particles and the resin microparticles were placed in the processing tank of the powder processing device and processed at the rotation speed and for the processing time shown in Table 1 to obtain toner base particles. In Invention 1, the temperature inside the tank of the powder processing device was controlled to be in the range of 50°C to 60°C.

[0123] (External addition treatment) To the obtained toner base particles, 2.0 mass % of titanium oxide (EC-100 (manufactured by Titan Kogyo Co., Ltd.)) and 1.0 mass % of hydrophobic silica (RA-200H (manufactured by Nippon Aerosil Co., Ltd.)) were added relative to the mass of the toner base particles, and the mixture was stirred and mixed in a Henschel mixer (manufactured by Mitsui Mining Co., Ltd.) at a rotational peripheral speed of 30 m / s for 5 minutes to obtain a toner.

[0124] [Preparation of Toner of Invention 2] 100 g of the toner core particles obtained in Production Example 2 using the amorphous polyester resin b obtained in Production Example 1 were used to coat the toner core particles with the resin fine particles A obtained in Production Example 3, thereby forming a shell layer on the surface of the toner core particles.

[0125] A surface modification device (fine particle coating device SFP-01 type (manufactured by Powrex Corporation)) was used to form the shell layer. The toner core particles were circulated in the fluidized bed of the surface modification device at an inlet air temperature of 80°C. 300 g of an aqueous dispersion containing 10 g of resin fine particles A obtained in Production Example 3 was sprayed into the fluidized bed of the surface modification device at a spray rate of 5 g / min for 60 minutes to obtain toner base particles. The obtained toner base particles were subjected to external addition treatment in the same manner as in Invention 1 to obtain the toner of Invention 2.

[0126] [Preparation of Toner of Invention 3] 100 g of the toner core particles obtained in Production Example 2 using the amorphous polyester resin a obtained in Production Example 1 were used to coat the toner core particles with the resin fine particles C obtained in Production Example 3, thereby forming a shell layer on the surface of the toner core particles.

[0127] A surface modification device (fine particle coating device SFP-01 type (manufactured by Powrex Corporation)) was used to form the shell layer. The toner core particles were circulated in the fluidized bed of the surface modification device at an inlet air temperature of 80°C. 300 g of an aqueous dispersion containing 10 g of resin fine particles C obtained in Production Example 3 was sprayed into the fluidized bed of the surface modification device at a spray rate of 5 g / min for 60 minutes to obtain toner base particles. The obtained toner base particles were subjected to external addition treatment in the same manner as in Invention 1 to obtain the toner of Invention 3.

[0128] [Toner Preparation of Comparative Example 3] 100 g of the toner core particles obtained in Production Example 2 were coated with 10 g of the resin particles A obtained in Production Example 3 to form a shell layer on the surface of the toner core particles.

[0129] A surface modification device (fine particle coating device SFP-01 (manufactured by Powrex Corporation)) was used to form the shell layer. The toner core particles were circulated in the fluidized bed of the surface modification device at an inlet air temperature of 80°C. 300 g of an aqueous dispersion containing 10 g of resin fine particles A obtained in Production Example 3 was sprayed into the fluidized bed of the surface modification device at a spray rate of 5 g / min for 60 minutes to obtain toner base particles. The obtained toner base particles were subjected to external addition treatment in the same manner as in Invention 1 to obtain the toner of Comparative Example 3.

[0130] [Toner Preparation of Comparative Example 4] The toner core particles obtained in Production Example 2 were used as toner base particles, and external addition treatment was carried out in the same manner as in Invention 1 to obtain a toner of Comparative Example 4.

[0131] [Check the shell layer structure] The surfaces of the toners of Inventions 1 to 3 and Comparative Examples 1 to 5 were observed using a scanning electron microscope (SEM) according to the method below, and the state of coating of the toner core particles with the shell layer and the state of the surface of the shell layer were confirmed. Furthermore, according to the method below, photographs of the cross sections of the toners of Inventions 1 to 3 and Comparative Examples 1 to 5 were taken using a transmission electron microscope (TEM). Using the obtained TEM photographs, the surface state of the shell layer, the internal state of the shell layer, and the shape of the inner surface of the shell layer were confirmed. TEM photographs of the cross sections of the toners of Inventions 1 to 3 are shown in Figures 4 to 6, respectively, and TEM photographs of the cross sections of the toners of Comparative Examples 1 to 3 and 5 are shown in Figures 7 to 10, respectively. Note that the toner of Comparative Example 4 was not subjected to a shell-forming treatment, so SEM observation of the toner surface and TEM observation of the toner cross section were not performed for the toner of Comparative Example 4.

[0132] (Observation of the toner surface) The surfaces of the toner particles were observed at a magnification of 10,000 times using a scanning electron microscope (JSM-6700F (manufactured by JEOL Ltd.)).

[0133] (Method of photographing the cross section of toner) Toner samples were embedded in resin to create samples. Using a microtome (EM UC6, manufactured by Leica), 200-nm-thick slice samples for cross-sectional observation of the toner were created from the resulting samples. The resulting slice samples were observed at 50,000x magnification using a transmission electron microscope (TEM, JSM-6700F, manufactured by JEOL Ltd.), and images of the cross sections of selected toner samples were taken.

[0134] When the surfaces of the toners of Invention 1 and Comparative Example 5 were observed under a scanning electron microscope (SEM), for toner particles with a particle diameter of 6 μm to 8 μm, no approximately spherical particles derived from the resin fine particles used to form the shell layer were observed in the shell layer. The TEM photographs of the cross sections of the toners of Inventions 1 to 3 shown in FIGS. 4 to 6 also confirmed that the shell layers of the toners of Inventions 1 to 3 do not contain approximately spherical particles on their surfaces and that their outer surfaces are smooth. The TEM photographs of the cross sections of the toners of Inventions 1 to 3 confirmed that cracks existed within the shell layers of the toners of Inventions 1 to 3 in a direction approximately perpendicular to the surface of the toner core particles. Furthermore, the TEM photographs of the cross sections of the toners of Inventions 1 to 3 confirmed that the shell layer of the toner of Invention 1 had a convex portion between two cracks on its inner surface.

[0135] In addition, the cross section of the toner of Comparative Example 5 was observed using a TEM. From the TEM photograph of the cross section of the toner of Comparative Example 5 shown in Figure 10, it was found that the structure of the shell layer of the toner of Comparative Example 5 was similar to the structure of the shell layer of the toner of Invention 1.

[0136] When the surfaces of toner particles having a particle diameter of 6 μm to 8 μm in the toners of Comparative Examples 1 and 2 were observed using an SEM, it was confirmed that the surfaces of the toner core particles were coated with resin fine particles that remained in a spherical particle state. Furthermore, the TEM photographs of the cross sections of the toners of Comparative Examples 1 and 2 shown in Figures 7 and 8 also confirmed that the surfaces of the toner core particles of Comparative Examples 1 and 2 were coated with resin fine particles that remained in a particle state.

[0137] When the surfaces of toner particles of Comparative Example 3 having a particle diameter of 6 μm to 8 μm were observed using an SEM, it was confirmed that no approximately spherical particles derived from spherical resin microparticles were observed in the shell layer, and that the outer surface of the shell layer was smooth. The TEM photograph of the cross section of the toner of Comparative Example 3 shown in FIG. 9 also confirmed that the outer surface of the shell layer of the toner of Comparative Example 3 was smooth. However, the TEM photograph of the cross section of the toner of Comparative Example 3 confirmed that no cracks were present inside the shell layer of the toner of Comparative Example 3 in a direction approximately perpendicular to the surface of the toner core particle. This is presumably because the raw material of the shell layer (resin microparticles A) was completely fused due to the high temperature used during shell layer formation.

[0138] [Evaluation of toner fixability, heat-resistant storage stability, image density, and toner charge amount] The toners of Inventions 1 to 3 and Comparative Examples 1 to 5 were evaluated for fixability, heat-resistant storage stability, image density, and toner charge amount under specified conditions according to the following methods. The evaluation results for each toner are shown in Table 1. A page printer (PA2000 (manufactured by Kyocera Document Solutions)) modified to allow adjustment of the fixation temperature was used as the evaluation machine. The evaluation machine was left to stand for 10 minutes with the power turned off, and then turned on and used.

[0139] (adhesion) The fixing temperature was set to 180°C, and fixing was performed using a fixing heat roller with a diameter of 30 mm and a linear speed of 100 mm / sec. An evaluation image was obtained using an evaluation machine under an environment of normal temperature and humidity (20°C, 65% RH). The image density of the obtained evaluation image before rubbing was measured using a Gretag Macbeth SpectroEye (manufactured by Gretag Macbeth).

[0140] Next, a 1 kg weight covered with fabric was rubbed back and forth 10 times so that only the weight of the weight was applied to the image, and the image density after rubbing was measured. The fixation rate was calculated from the image density before and after rubbing using the following formula. The fixation property was evaluated from the calculated fixation rate according to the following criteria. ○ was judged as pass, and △ and × were judged as fail. Fixation rate (%) = (image density after rubbing / image density before rubbing) x 100 ○: Retention rate is 95% or higher. △: Retention rate is over 90% but less than 95%. ×: Retention rate is less than 90%.

[0141] (Heat-resistant storage stability) The toner was stored for 100 hours at 50° C. Then, according to the manual of a powder tester (manufactured by Hosokawa Micron Corporation), the toner was sieved through a 140 mesh (opening 105 μm) sieve under conditions of rheostat scale 5 and time 30 seconds, and the cohesion degree (%) was calculated using the following cohesion degree calculation formula, and evaluated according to the following criteria, with ○ representing pass and △ and × representing fail. (cohesion degree calculation formula) Cohesion (%) = mass of toner remaining on the sieve / mass of toner before sieving × 100 ○: Cohesion degree is 20% or less. △: Cohesion degree is more than 20% and less than 50%. ×: Cohesion degree exceeds 50%.

[0142] (Image density and toner charge amount under specified conditions) According to the following method, the initial toner charge amount and image density, and the toner charge amount and image density after continuous image formation were evaluated under each of the environments of normal temperature and normal humidity (20°C, 65% RH), high temperature and high humidity (32.5°C, 80% RH), and low temperature and low humidity (10°C, 20% RH).

[0143] (Image density) An evaluation machine was used to form an image evaluation pattern on a recording medium at a fixing temperature of 180°C to obtain an initial image. Subsequently, 2,500 continuous images were formed at a printing rate of 4%, and then an image evaluation pattern was formed on the recording medium to obtain an image after continuous image formation. The image density of the solid image in the image evaluation pattern at the initial stage and after continuous image formation was measured using a reflection densitometer (RD914, manufactured by Gretag Macbeth). The image density was evaluated according to the following criteria, with ○ representing a pass and △ and × representing a fail. ○: 1.25 or above. △: Less than 1.24, 1.20 or more. ×: Less than 1.20.

[0144] (charge amount) After the initial image was formed, the initial toner charge amount was measured. Next, 2,500 consecutive images were formed at a printing rate of 4%, and then the toner charge amount after the consecutive image formation was measured. The charge amount was measured using a charge amount measuring device (Q / M Meter 210HS (manufactured by TRek Corporation)). The charge amount was evaluated according to the following criteria, with ○ representing a pass and △ and × representing a fail. ○: 20.0 or more, 25.0 or less △: 19.0 or more and less than 20.0, or more than 25.0 and less than 26.0. ×: Less than 19.0, more than 26.0.

[0145] (Regulatory blade attached) After forming 2500 images in each environment, adhesion of the regulating blade was visually confirmed. The adhesion was evaluated according to the following criteria: ◯ was judged as pass, and △ and × were judged as fail. ○: No adhesion △: Slight adhesion ×: Adhesion

[0146] (white streak) After forming 2500 images in each environment, the images were visually inspected to check for the occurrence of white streaks. The white streaks were evaluated according to the following criteria, with ◯ representing pass, and Δ and × representing fail. 〇: No occurrence ×: Occurred

[0147] Table 1 shows the evaluation results of the toners of Inventions 1 to 3 and Comparative Examples 1 to 5 with respect to fixability, heat-resistant storage stability, image density, charge amount, regulating blade adhesion, and white streaks, along with the toner manufacturing conditions.

[0148] [Table 1]

[0149] The toners of inventions 1 to 3 comprise toner core particles containing at least a binder resin and a shell layer of a predetermined structure that covers the entire surface of the toner core particles. The shell layer is made of a resin that includes a charge control resin. When observed using a scanning electron microscope, toner particles having a particle size within a specific range do not exhibit substantially spherical particles derived from resin fine particles in the shell layer. Furthermore, when a cross section of the toner is observed using a transmission electron microscope, numerous cracks are observed within the shell layer in a direction substantially perpendicular to the surface of the toner core particles. This demonstrates that when images are formed over a long period of time under various environments, such as high-temperature, high-humidity environments and low-temperature, low-humidity environments, the toner can be charged to a desired charge amount, and images of a desired density can be formed regardless of the usage environment.

[0150] In particular, it has been found that a non-magnetic one-component development unit 33 equipped with a developing roller having a silicone rubber layer laminated on a conductive substrate and a urethane layer laminated on top of the silicone rubber layer, and a stainless steel regulating blade that contacts the developing roller, and in which the regulating pressure of the regulating blade is 15 to 40 N / m, can form images of the desired density regardless of the usage environment.

[0151] It is clear from the toners of Comparative Examples 1 and 2 that it is difficult to obtain a toner with good heat-resistant storage stability when nearly spherical particles derived from spherical resin microparticles are observed on the surface of the shell layer of the toner core particle. When a structure derived from spherical resin microparticles is observed on the surface of the shell layer, it is presumed that this is because gaps remain between the resin microparticles that have deformed to some extent and that cover the shell layer, which makes it easy for components such as the release agent contained in the toner core particle to seep out onto the toner surface.

[0152] Furthermore, SEM observation of the toners of Inventions 1 to 3 and Comparative Example 1 revealed that by increasing the rotation speed of the device used to form the shell layer, the roughly spherical particles derived from the resin fine particles could no longer be observed on the surface of the shell layer. In other words, according to Inventions 1 to 3 and Comparative Example 1, by increasing the rotation speed of the device used to form the shell layer, the deformation of the resin fine particles progresses, It can be seen that the outer surface of the shell layer is smoothed.

[0153] With the toner of Comparative Example 1, when images are formed over a long period of time in various environments such as a high-temperature, high-humidity environment or a low-temperature, low-humidity environment, it is difficult to charge the toner to the desired charge amount, and therefore it is difficult to form images with the desired density. This is presumably because, since spherical resin particles remain on the surface of the shell layer of the toner core particle, excessive stress is applied to the toner during image formation over a long period of time, and the resin particles are easily liberated from the toner, and the liberated resin particles prevent stable charging of the toner.

[0154] It is clear from the toner of Comparative Example 3 that it is difficult to obtain a toner with good fixing properties when cracks approximately perpendicular to the surface of the toner core particle are not observed inside the shell layer. This is presumably because the shell layer is less likely to be destroyed by the pressure applied to the toner when fixing the toner.

[0155] According to the toner of Comparative Example 4, when the toner core particles are not covered with a shell layer, it is difficult to obtain a toner with good heat-resistant storage stability, and it is not possible to obtain the desired charge amount and image density from the initial image. Note that, due to abnormalities such as toner scattering, evaluation of 2,500 sheets of image formation was not performed.

[0156] According to Comparative Example 5, when the material of the shell layer does not contain a charge control resin, it is difficult to form an image in the initial image because it is difficult to charge the toner to the desired charge amount in a high-temperature, high-humidity environment. [Industrial Applicability]

[0157] The present invention can be applied to a non-magnetic one-component developing toner for use in electrophotography. By utilizing the present invention, it is possible to provide a non-magnetic one-component developing toner that is excellent in fixability and heat-resistant storage stability, can be charged to a desired charge amount over a long period of time under various environments, and can form images of a desired density. [Explanation of symbols]

[0158] 100 Image forming device 33 Development unit (developing device) 331 Developing roller 334 Regulatory Blade 101 Toner 102 Toner core particles 103 Shell Layer 104 Crack 105 Convex part

Claims

1. toner core particles containing at least a binder resin; a shell layer covering the toner core particles; A non-magnetic one-component toner for development, which comprises toner particles containing the shell layer is formed using spherical resin particles containing a charge control resin, when the surfaces of the toner particles are observed using a scanning electron microscope, for the toner particles having an average particle diameter of 6 μm or more and 8 μm or less, no structure derived from the spherical resin fine particles is observed in the shell layer, and the outer surface of the shell layer is smoothed; A non-magnetic one-component developing toner, characterized in that, when a cross section of the toner particle is observed using a transmission electron microscope, cracks originating from the interfaces between the resin fine particles are observed inside the shell layer in a direction approximately perpendicular to the surface of the toner core particle.

2. 2. The toner for non-magnetic one-component development according to claim 1, wherein the mass average molecular weight of the resin particles is 200,000 or more and 400,000 or less.

3. 2. The toner for non-magnetic one-component development according to claim 1, wherein the thickness of the shell layer is 0.05 [mu]m or more and 0.3 [mu]m or less.

4. 2. The non-magnetic one-component developing toner according to claim 1, wherein, when a cross section of the electrostatic latent image developing toner is observed using a transmission electron microscope, a convex portion of the shell layer is observed on the interface between the toner core particle and the shell layer and between the two cracks.

5. A method for producing the non-magnetic one-component toner according to any one of claims 1 to 4, comprising the steps of: The shell layer is prepared by the following steps I) and II): I) a step of adhering spherical resin fine particles to the surfaces of the toner core particles to form a resin fine particle layer that covers at least a part of the surfaces of the toner core particles; II) applying an external force to the outer surface of the resin fine particle layer to deform the resin fine particles in the resin fine particle layer, thereby smoothing the outer surface of the resin fine particle layer and forming a shell layer; 1. A method for producing a toner for non-magnetic one-component development, comprising the steps of:

6. A developing device using the non-magnetic one-component toner according to any one of claims 1 to 4, the developing roller has a silicone rubber layer laminated on a conductive base material and a urethane layer laminated on the silicone rubber layer, The developing device is characterized in that the regulating blade is a stainless steel blade, and the regulating pressure by the regulating blade is 15 to 40 N / m.

7. An image forming apparatus comprising the developing device according to claim 6.

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