JP2008033305A - Image forming method and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming method not causing fixing unevenness, image dislocation or paper wrinkling, while satisfying low-temperature fixability by using a core/shell structure toner with ensured charging stability and heat storage stability in a fixing device constituted of an endless belt, and to provide an image forming apparatus. <P>SOLUTION: The image forming method is disclosed, comprising forming a toner image, transferring the toner image onto a recording medium and fixing the transferred toner image in a fixing device comprising a heating roller, an endless belt pressed into contact with the heating roller, a pressing member pressing the inner side of the endless belt and an end pressing member to locally elastically deform the heating roller and provided downstream from the pressing member, wherein the toner comprises toner particles comprising a core containing a resin, a colorant and a releasing agent and a shell on, and the toner particles exhibiting an average of eight-point mean thickness of the shell of 100 to 300 nm and meeting a requirement of an average of Hmax/Hmin being less than 1.50, wherein Hmax is a maximum thickness of the shell and Hmin is a minimum thickness of the shell. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming method and an image forming apparatus for forming a toner image by electrophotography.

  In an image forming method using an electrophotographic method, a toner image is fixed on a recording medium by passing a recording medium carrying a toner image between a pressure roller opposed to a heated roller as a method for fixing the image. Image forming methods are widely used.

  However, when the image forming method is applied to a high-speed copying machine, it is necessary to increase the load excessively, thicken the surface elastic layer, or increase the roller diameter in order to supply sufficient heat. However, when the load is increased or the surface elastic layer is enlarged, the shape at the pressing portion becomes non-uniform, causing problems such as uneven fixing, image misalignment, and paper wrinkles. In addition, the method of increasing the roll diameter has a problem that the apparatus is increased in size and the time until the heating roll is raised to a fixable temperature is increased. In order to solve such a problem and realize a fixing method corresponding to a high-speed image forming method, fixing is performed by a fixing device composed of a heating roller and an endless belt that contacts and presses the heating roller. Have been proposed (see, for example, JP-A-2-210480, JP-A-5-303300, JP-A-8-262903, and JP-A-2005-321462).

  On the other hand, in recent years, from the viewpoint of consideration for the global environment, a low melting point wax that could not be introduced by the conventional pulverization method as a technology capable of reducing the power consumption of the image forming apparatus and fixing at a low temperature was contained by a polymerization method. A toner (Patent Document 1) and a polymerized toner that forms a shell with a high glass transition point on a toner core with a low glass transition point have been proposed (Patent Document 2).

However, when the toner is used in the fixing device constituted by the endless belt, image shift due to a low melting point wax or a resin having a low glass transition point occurs. Also, in the core-shell toner, the influence of the shell greatly affects the fixing performance due to the balance between the heat melting temperature and the load pressure, and if the shell is thick, the low-temperature fixing effect is not sufficiently exhibited. Stability is lost and toner scattering occurs (Patent Documents 3 to 5).
JP 2000-321815 A Japanese Patent Laid-Open No. 11-174732 International Publication No. 98/25185 Pamphlet JP 2004-191618 A JP 2004-271638 A

  From the background described above, there is a need for a technique for designing a toner while controlling the thickness and uniformity of the thickness of the toner having a core / shell structure.

  The present invention has been made in view of the above problems, and in a fixing device composed of an endless belt, using a toner having a core / shell structure that ensures heat-resistant storage stability, while satisfying low-temperature fixability, an image It is an object of the present invention to provide an image forming method and an image forming apparatus that do not cause deviation and toner scattering.

  As a result of intensive studies by the inventors, it has been clarified that the object of the present invention is achieved by the following configuration.

1.
The toner image is formed by electrophotography, and the toner image transferred onto the recording medium is formed by pressing the endless belt against the heating roller, the endless belt pressed against the heating roller, and the endless belt inside the endless belt. In an image forming method in which fixing is performed by a fixing device including a pressing member and an end pressing member that elastically deforms the heating roller locally on the downstream side of the pressing member, at least resin and coloring are used as toner for forming the toner image Having a shell on the surface of the core containing the agent and the release agent, the 8-point average film thickness of the shell is 100 nm to 300 nm, the maximum film thickness of the shell is Hmax, and the minimum film thickness is Hmin. Sometimes, an image forming method using toner having Hmax / Hmin of less than 1.50.

2.
When the glass transition temperature of the resin constituting the core is Tg1, and the glass transition temperature of the resin constituting the shell is Tg2, Tg2−Tg1 ≧ 15 ° C., 20 ° C. ≦ Tg1 ≦ 40 ° C., 40 ° C ≦ Tg2. 2. The image forming method according to 1, wherein a toner is used.

3.
3. The image forming method according to 2, wherein a toner having a circularity of 0.945 or more is used as the toner.

4).
An image forming apparatus that forms an image by the image forming method according to any one of 1 to 3.

  According to the present invention, in a fixing device constituted by an endless belt, an image forming method that uses a core / shell structure toner with heat-resistant storage stability and that satisfies low-temperature fixability and that does not cause image displacement and toner scattering, and An image forming apparatus can be provided.

  The image shift at the time of fixing particularly regarded as a problem in the present invention refers to an image in which the image is disturbed due to the collapse of the toner image when there is a speed difference between the recording paper and the heating roller.

  This phenomenon is likely to occur in a toner image containing a low melting point wax (release agent) and / or a resin having a low glass transition point. The reason why it becomes difficult to occur by making a uniform core-shell structure as in the configuration of the present invention is not clear, but can be considered as follows.

  In the case of a toner containing a low melting point wax, if the formation of the core and shell is not complete, the low melting point wax penetrates locally into the recording paper, and the toner image easily moves at the interface with the recording paper surface. It is considered that the toner image moves partially uneven due to the difference in speed between the recording paper and the heating roller. Similarly, when a low glass transition point resin is contained, if the core and shell are not completely formed, the low glass transition point resin elutes on the recording paper surface and is strongly fixed to the recording paper by the anchor effect, but there is little elution. In the portion, the fixation is weak, and it is considered that the image shift occurs due to the non-uniform fixation force. In particular, in a fixing device having a structure in which the heating roller is locally pressed to be elastically deformed, it is predicted that the non-uniformity of the outflow will occur remarkably, and it is considered that the image shift occurs more remarkably.

  The toner production method, fixing method, image forming method, and image forming apparatus used in the present invention will be further described.

[Method of forming uniform toner shell layer and preferred range]
It has been found that specific methods for forming a uniform shell, that is, factors for controlling the formation of the shell include the following.
(1) Optimization of circularity of core particles during shell formation (2) Optimization of temperature conditions for shell formation (core Tg + 15 ° C. <temperature with shell <core Tsp)
The reason why a thin and uniform shell layer can be formed by the above-mentioned means is not clear, but for (1), the specific surface area of the core particle is small and the surface property is uniform at high circularity, and therefore, It is assumed that the resin fine particles forming the shell uniformly adhere to the core surface, and as a result, the core surface can be efficiently coated with a small amount of shell. The higher the degree of circularity after forming the core particles, the better, and 0.900 or more is preferable. However, if the circularity is extremely increased, industrial productivity and the like are lowered. Therefore, when other conditions are taken into consideration, the circularity after core particle formation is more preferably in the range of 0.900 to 0.930. Although it eliminates the difference in release property of the release agent caused by the thickness of the shell layer, fixing was performed at a lower temperature than before by setting the circularity in the range of 0.900 to 0.930. Even at times, the offset resistance is good and it is possible to avoid the occurrence of winding. Furthermore, since the release agent in the core can be eluted evenly, a stable fixing process is realized. Regarding (2), if the temperature at which the shell is attached to the surface of the core particles is higher than the Tsp of the core, the core component tends to flow out to the surface layer during the formation of the shell layer, so that it is difficult to form the shell layer. Conversely, it is presumed that the adhesion of the shell particles to the core surface does not occur at a temperature lower than the core Tg + 15 ° C.

[Preferable scope and reason of the present invention]
If the film thickness of the shell is 100 nm or less, storage stability cannot be ensured, and if it is 300 nm or more, the low-temperature fixability is not sufficiently exhibited. If the ratio (Hmax / Hmin) between the maximum film thickness Hmax and the minimum film thickness Hmin of the shell exceeds 1.50, storage stability and low-temperature fixability are not compatible, and charging stability is also poor. The finished toner circularity is preferably 0.945 or more. If it is less than 0.945, the shell shape is distorted, storage stability and low-temperature fixability are not compatible, and charging stability is also deteriorated. In particular, 0.960 or more is preferable.

[Reason for both heat-resistant storage and low-temperature fixability and reason for securing charging stability]
The reason is not clear, but I guess as follows. The shell thickness of 100 nm is the lower limit thickness that prevents the inner core from flowing out of the surface due to the compression of the toner by its own weight, and the inner core efficiently flows out to the surface when 300 nm penetrates the paper and the penetration depth and pressure are applied. This is the upper limit thickness. In addition, the reason why stable chargeability has been developed is that the thickness of the shell in the core-shell structure is aligned to the level specified in the present invention, so that there is no unevenness in the shell thickness and the chargeability to the core is improved. Since the contribution is made uniform, it is presumed that the charge distribution on the toner particle surface is made uniform and the charging property is secured.

  In the image forming method and the image forming apparatus of the present invention, when the glass transition temperature of the resin constituting the toner core is Tg1, and the glass transition temperature of the resin constituting the shell is Tg2, Tg2−Tg1 ≧ 15 ° C. It is more preferable to use a toner satisfying 20 ° C. ≦ Tg1 ≦ 40 ° C. and 40 ° C. ≦ Tg2.

[Technical idea of the present invention]
The present invention relates to a toner having a core / shell structure having a shell on the surface of a core containing at least a resin and a colorant, and has a low-temperature fixability by forming a shell layer having a core / shell structure thinly and uniformly. It is possible to provide a toner having both heat-resistant storage stability and stable chargeability.

  That is, the average shell thickness is 100 to 300 nm, and the ratio of the maximum thickness to the minimum thickness (Hmax / Hmin) of the shell is less than 1.50. It has been found that a toner having a structure can be obtained. Furthermore, in the present invention, the thickness of the shell can be actually measured and specified. Thus, it can be said that the present invention is the first to find a toner having a shell having a uniform film thickness by actually measuring the thickness of the shell layer.

  For example, the above-mentioned Patent Document 3 discloses a specific shell film thickness value, which is calculated from the mass of the shell component added during toner preparation. In this document, no description suggesting that the thickness of the shell is measured by a specific means or that a shell having a uniform thickness is formed is found.

  In order to achieve the object of the present invention, it is important to form a thin and uniform shell layer having no film thickness unevenness. In particular, in order to ensure charging stability, a layer having a completely uniform film thickness is required. It is considered preferable to form. However, this is extremely difficult to achieve, and the problem is particularly great when the invention is industrially implemented.

  According to the detailed examination by the inventor of this time, first, the film thickness of the shell needs to be set to 100 to 300 nm from the viewpoints of both the heat dependency of the core particles having the characteristic of low Tg and the low temperature fixability. In a toner having a thin shell with an average film thickness of 100 to 300 nm as in the invention, when the ratio of the maximum film thickness Hmax to the minimum film thickness Hmin (Hmax / Hmin) is 1.50 or more, the charging stability is significantly reduced. However, it has been found that if it is less than 1.50, the charging stability is greatly improved and the object of the present invention can be achieved.

[Reason for ensuring charging stability]
The toner according to the present invention achieves both low-temperature fixability and heat-resistant storage stability and also ensures stable chargeability. That is, when an image is formed using the toner according to the present invention, it has been found that the toner scattering in the machine and the occurrence of image blur on the printed image are eliminated, and a good charge rising performance is exhibited. . The reason why the stable chargeability has been developed in this way is probably because the thickness of the shell in the core-shell structure is aligned to the level specified by the present invention, so that there is no unevenness in the thickness of the shell. It is presumed that since the contribution of the charging property is made uniform, the charge distribution on the toner particle surface is made uniform to ensure the charging property.

  Hereinafter, definitions of physical property values and measurement methods in the present invention will be described, and a toner production method, a toner material to be used, an image formation method using the produced toner, an image formation apparatus, and the like will be further described.

[Measurement method of 8-point average film thickness of shell]
The film thickness of the shell in the toner of the present invention is measured from a photograph obtained by photographing a cross-sectional layer of the toner with a transmission electron microscope. As a transmission electron microscope, a model well known to those skilled in the art is usually sufficiently observed. For example, LEM-2000 type (Topcon Corporation), JEM-2000FX (JEOL Ltd.) and the like are used.

  Specifically, the toner particles are first sufficiently dispersed in a room temperature curable epoxy resin, then embedded, dispersed in styrene fine powder having a particle size of about 100 nm, and then subjected to pressure molding. After the necessary blocks were dyed with ruthenium tetroxide or osmium tetroxide, a flaky sample was cut out using a microtome with diamond teeth, and a transmission electron microscope (TEM) was used. Then, the photograph is taken at a magnification (about 10,000 times) in which the cross section of one toner enters the field of view.

  Next, in the above photograph, the boundary line that becomes the interface between the core particle and the shell is clarified while visually confirming the existence region of the colorant, wax, and the like.

  Next, as shown in FIG. 1, straight lines are drawn from the center of gravity C of the toner particles toward the surface at intervals of 45 °. The distance between them (that is, the thickness of the shell) is measured at 8 points, and the average value of the 8 points is taken as the film thickness of the shell of one toner particle.

  The 8-point average film thickness of the toner shell of the present invention is the average value obtained by measuring the 8-point average film thickness of the shell of one toner particle for 100 toner particles. Further, among the 100 toner particles, it is preferable that the number of particles having an 8-point average film thickness of 100 to 300 nm in one toner particle is 80% by number or more.

  Further, the (Hmax / Hmin) of the shell in the present invention is measured using a photograph of 100 toner particles used for the 8-point average film thickness measurement of the shell.

  Specifically, a straight line is drawn from the center of gravity of the toner particle toward the surface of the toner particle, and the maximum shell film thickness (Hmax) and the minimum shell film thickness (Hmin) in one toner particle are extracted, and (Hmax / Hmin). In the present invention, (Hmax / Hmin) is an average value of (Hmax / Hmin) for 100 toner particles.

  Further, (Hmax / Hmin) of 80 number% or more of toner particles in 100 toner particles is preferably less than 1.50. When the minimum thickness of the shell layer was as close as possible to 0 or 0, the thickness was measured as 10 nm.

  In the present invention, (Hmax / Hmin) is preferably 1.05 to 1.50, more preferably 1.05 to 1.40.

[Method of forming a shell having a uniform layer thickness]
As described above, in order to form a uniform shell layer for the low Tg core, the following three means can be mentioned. Hereinafter, the resin constituting the core is simply abbreviated as “resin constituting”.

(1) Widen Tg difference and SP value difference between core and shell When Tg1 is the glass transition temperature of the core and Tg2 is the glass transition temperature of the shell, it is preferable that Tg2−Tg1 ≧ 15 ° C. Alternatively, it is preferable that Tg2−Tg1 ≧ 20 ° C.

  Further, when the value of the solubility parameter of the core is SP1 and the value of the solubility parameter of the shell is SP2, the difference (ΔSP) between SP1 and SP2 is preferably 0.2 to 1.0, more preferably 0. 25-0.95 is good.

(2) Shelling after increasing the circularity of the core particles After increasing the circularity of the core particles to 0.900 or more, shelling is started.

(3) To optimize the shelling temperature It is preferable to perform shelling within the range of core Tg + 20 ° C. <shelling temperature <core Tsp.

  Hereinafter, the above (1) to (3) will be described in more detail.

  The solubility parameter value of each resin of the toner core part and the shell layer can be obtained from the composition of the constitution.

  The solubility parameter value of each resin can be obtained from the composition of the resin constituting the resin.

  Each solubility parameter value is calculated from the product of the solubility parameter value of each monomer (monomer) constituting the resin and the molar ratio. For example, assuming that the copolymer resin is composed of two types of monomers, X and Y, the mass composition ratio of each monomer is x, y (mass%), the molecular weight is Mx, My, When the solubility parameter values are SPx and SPy, the monomer ratios are x / Mx and y / My.

  Here, when the molar ratio of the copolymer resin is C, it is expressed as C = x / Mx + y / My, and the solubility parameter value SP of the copolymer waiting resin is represented by the following formula (1).

Formula (1) SP = {(x * SPx / Mx) + (y * SPy / My)} * 1 / C
The solubility parameter value (SP value) of the monomer is obtained as follows.

When calculating the solubility parameter value (SP value) of a certain monomer A, “Polym. Eng. Sci. Vol 14. Proposed by Fedors for atoms or atomic groups in the molecular structure of the monomer. p114 (1974) ", evaporation energy (Δ _ei ) and molar volume (Δ _vi ) are obtained and calculated from the following formula (2).

  However, for a double bond that is cleaved during polymerization, the cleaved state is the molecular structure.

Formula (2) σ = (ΣΔ _ei / Δ _vi ) ^1/2
The solubility parameter value of each monomer below is the value obtained by the above calculation method.

Styrene ... 10.55
Butyl acrylate ... 9.77
2-Ethylhexyl methacrylate 9.04
2-Ethylhexyl acrylate ... 9.22
Methyl methacrylate ... 9.93
Methacrylic acid ... 12.54
Acrylic acid ... 14.04
Using this value, the solubility parameter value of the copolymer is determined according to the above formula (1).

  In addition, when it is impossible to calculate the solubility parameter of the monomer by the calculation formula of the above formula (2), the specific value is a literature such as Polymer Handbook (published by Wiley) 4th edition or the like. A database provided by the administrative body “Materials and Materials Research Organization”, PolyInfo (http://polymer.nims.go.jp), solubility parameter items (http://polymer.nims.go.jp/guide/guide/) p5110.html).

  The solubility parameter value of each resin can be controlled by appropriately selecting the type of polymerizable monomer forming the copolymer and its ratio. In particular, the solubility parameter value is preferably controlled by the content of the acid monomer.

[Glass transition temperature Tg]
In the toner of the present invention, when the glass transition temperature of the resin A is Tg1 and the glass transition temperature of the resin B is Tg2, it is preferable that Tg2−Tg1 ≧ 15 ° C. and 20 ° C. ≦ Tg1 ≦ 40 ° C. .

  The glass transition temperature of the resin A forming the core and the resin B forming the shell layer can be controlled by appropriately selecting the type, amount and molecular weight of the polymerizable monomer forming the copolymer. It is. The method for adjusting the glass transition temperature is, for example, selecting the type of polymerization monomer of the resin B constituting the shell layer and the resin A constituting the core part from the compounds described later, and setting the glass transition temperature of both to the above range. This can be achieved by adjusting the ratio and molecular weight. However, the exemplified compounds clearly show the means for accomplishment and are not limited to these.

  The glass transition temperature can be measured using a DSC-7 differential scanning calorimeter (Perkin Elmer) and a TAC7 / DX thermal analyzer controller (Perkin Elmer).

  As a measurement procedure, 4.5 to 5.0 mg of toner is precisely weighed to 2 digits after the decimal point, sealed in an aluminum pan (KITNO.0219-0041), and set in a DSC-7 sample holder.

  The reference used an empty aluminum pan. As measurement conditions, the measurement temperature is 0 to 200 ° C., the temperature increase rate is 10 ° C./min, the temperature decrease rate is 10 ° C./min, and the heat-cool-heat control is performed. went.

  The glass transition temperature draws an extension of the baseline before the rise of the first endothermic peak and a tangent line indicating the maximum slope between the rise of the first peak and the peak apex, and the intersection is taken as the glass transition point. Show.

[Measurement method of circularity of core particles for toner]
The circularity of the present invention is a value measured using “FPIA-2100” (manufactured by Sysmex Corporation). Specifically, the core particles are blended with an aqueous solution containing a surfactant, and after ultrasonic dispersion for 1 minute, the dispersion is performed. Then, using “FPIA-2100”, in the measurement condition HPF (high magnification imaging) mode, HPF Measurement is performed at an appropriate concentration of 3000 to 10,000 detections. Within this range, reproducible measurement values can be obtained. The circularity is a value defined by the following formula.

Circularity = (perimeter of a circle having the same area as the particle projection image) / (perimeter of the particle projection image)
The average circularity is a value calculated by adding the circularity of each particle and dividing by the total number of particles.

  In the present invention, the degree of circularity after core particle formation is preferably as high as possible and is preferably 0.900 or more. When the circularity is 0.900 or more, it becomes easier to produce a shell having a higher uniformity of shell thickness than that of less than that. However, if the circularity is extremely increased, industrial productivity and the like are lowered. Therefore, when other conditions are taken into consideration, the circularity after core particle formation is more preferably in the range of 0.900 to 0.930.

  The present invention eliminates the difference in the release property of the release agent caused by the thickness of the shell layer. However, by setting the circularity in the range of 0.900 to 0.930, the temperature is lower than the conventional one. Even when fixing is performed, the anti-offset property is good, and it is possible to avoid the occurrence of winding. Furthermore, since the release agent in the core can be eluted evenly, a stable fixing process is realized.

[Softening point Tsp]
A method for measuring the softening point of the toner of the present invention will be described.

In an environment of 20 ± 1 ° C. and 50 ± 5% RH, 1.1 g of toner is placed in a petri dish and flattened and left to stand for 12 hours or more, and then 37436 N / cm using a molding machine SSP-A (manufactured by Shimadzu Corporation). ² Pressurize with a force of (3820 kg / cm ² ) for 30 seconds to produce an in-mold sample having a diameter of 1 cm.

  In an environment of 24 ± 5 ° C. and 50 ± 20% RH, the above molded sample was loaded with a load of 196 N (20 kgf), a starting temperature of 60 ° C., a preheating time of 300 seconds, and a heating rate of 6 with a flow tester CFT-500D (manufactured by Shimadzu Corporation). Extruded from the end of preheating using a 1 cm diameter piston through a cylindrical die hole (1 mm x 1 mm) under the condition of ° C / min, and measured at a setting of an offset value of 5 mm by the melting temperature measurement method of the temperature rising method. The offset method temperature T (offset) was defined as the softening point of the toner. T (offset) is a temperature (T) measured by the offset method.

  In the toner particles of the present invention, the core portion preferably occupies 80% by mass or more and the shell layer occupies 2 to 15% by mass.

[Toner material used in the present invention]
(1) Binder resin The resin A forming the core part and the resin B forming the shell layer are preferably styrene-acrylic copolymer resins. In addition, as a monomer for producing a resin that forms the core portion, a polymerizable monomer that lowers the glass transition temperature (Tg) of a copolymer such as propyl acrylate, propyl methacrylate, butyl acrylate, and 2-ethylhexyl acrylate is used. Copolymerization is preferred. Moreover, the monomer for producing the resin forming the shell layer is copolymerized with a polymerizable monomer that raises the glass transition temperature (Tg) of a copolymer such as styrene, methyl methacrylate, and methacrylic acid. Is preferred.

  The resin constituting the toner according to the present invention will be described in more detail.

  As the resin used for each of the core and shell structures of the toner according to the present invention, a polymer obtained by polymerizing a polymerizable monomer as described below can be used.

  The resin according to the present invention contains a polymer obtained by polymerizing at least one polymerizable monomer as a constituent component. Examples of the polymerizable monomer include styrene, o-methylstyrene, m- Methylstyrene, p-methylstyrene, α-methylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert-butylstyrene, p Styrene or styrene derivatives such as -n-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, methyl methacrylate, ethyl methacrylate, methacryl N-butyl acid, isopropyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, Methacrylate derivatives such as n-octyl acrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, phenyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate, methyl acrylate, ethyl acrylate, acrylic Acrylate derivatives such as isopropyl acid, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, phenyl acrylate, Olefins such as ethylene, propylene, isobutylene, halogenated vinyls such as vinyl chloride, vinylidene chloride, vinyl bromide, vinyl fluoride, vinylidene fluoride, vinyl propionate, vinyl acetate , Vinyl esters such as vinyl benzoate, vinyl ethers such as vinyl methyl ether and vinyl ethyl ether, vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone and vinyl hexyl ketone, N-vinyl carbazole, N-vinyl indole, N There are N-vinyl compounds such as vinylpyrrolidone, vinyl compounds such as vinylnaphthalene and vinylpyridine, and acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile and acrylamide. These vinyl monomers can be used alone or in combination.

  Further, it is more preferable to use a combination of monomers having an ionic dissociation group as the polymerizable monomer constituting the resin. For example, it has a substituent such as a carboxyl group, a sulfonic acid group, a phosphoric acid group as a constituent group of the monomer, specifically, acrylic acid, methacrylic acid, maleic acid, itaconic acid, cinnamic acid, fumar Acid, maleic acid monoalkyl ester, itaconic acid monoalkyl ester, styrene sulfonic acid, allyl sulfosuccinic acid, 2-acrylamido-2-methylpropane sulfonic acid, acid phosphooxyethyl methacrylate, 3-chloro-2-acid phosphooxy And propyl methacrylate.

  Furthermore, polyfunctionality such as divinylbenzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol diacrylate, neopentyl glycol dimethacrylate, neopentyl glycol diacrylate, etc. It is also possible to use a crosslinkable resin by using a functional vinyl.

(2) Colorant As the colorant used in the toner of the present invention, carbon black, a magnetic material, a dye, a pigment, and the like can be arbitrarily used. As the carbon black, channel black, furnace black, acetylene black, thermal black Lamp black or the like is used. Magnetic materials include ferromagnetic metals such as iron, nickel and cobalt, alloys containing these metals, compounds of ferromagnetic metals such as ferrite and magnetite, alloys that do not contain ferromagnetic metals but exhibit ferromagnetism by heat treatment, For example, a kind of alloy called Heusler alloy such as manganese-copper-aluminum, manganese-copper-tin, chromium dioxide, or the like can be used.

  As the dye, C.I. I. Solvent Red 1, 49, 52, 58, 63, 111, 122, C.I. I. Solvent Yellow 19, 44, 77, 79, 81, 82, 93, 98, 103, 104, 112, 162, C.I. I. Solvent Blue 25, 36, 60, 70, 93, 95 etc. can be used, and a mixture thereof can also be used. Examples of the pigment include C.I. I. Pigment Red 5, 48: 1, 53: 1, 57: 1, 122, 139, 144, 149, 166, 177, 178, 222, C.I. I. Pigment Orange 31 and 43, C.I. I. Pigment Yellow 14, 17, 93, 94, 138, 156, 158, 180, 185, C.I. I. Pigment green 7, C.I. I. Pigment Blue 15: 3, 60, etc. can be used, and a mixture thereof can also be used. The number average primary particle diameter varies depending on the type, but is preferably about 10 to 200 nm.

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

(3) Wax (release agent)
Examples of the wax that can be used in the toner according to the present invention include conventionally known waxes. Specifically, polyolefin waxes such as polyethylene wax and polypropylene wax, long-chain hydrocarbon waxes such as paraffin wax and sazol wax, dialkyl ketone waxes such as distearyl ketone, carnauba wax, montan wax, and trimethylolpropane. Tribehenate, pentaerythritol tetramyristate, pentaerythritol tetrastearate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecanediol distearate, trimellit Ester waxes such as acid tristearyl and distearyl maleate, ethylenediamine dibehenyl amide, trimellitic acid tristearyl amide, etc. Such as amide waxes.

  The melting point of the wax is usually 40 to 160 ° C, preferably 50 to 120 ° C, more preferably 60 to 90 ° C. By setting the melting point within the above range, the heat-resistant storage stability of the toner is ensured, and stable toner image formation can be performed without causing cold offset or the like even when fixing at a low temperature. Further, the wax content in the toner is preferably 1% by mass to 30% by mass, and more preferably 5% by mass to 20% by mass.

  The polymerization initiator, chain transfer agent, and surfactant that can be used in the toner production method will be described.

(4) Radical polymerization initiator usable in the present invention The resin constituting the core and shell constituting the toner according to the present invention is produced by polymerizing the aforementioned polymerizable monomer, but is used in the present invention. Possible radical polymerization initiators include the following. Specifically, as the oil-soluble polymerization initiator, 2,2′-azobis- (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexane) -1-carbonitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, azobisisobutyronitrile and other azo or diazo polymerization initiators, benzoyl peroxide, methyl ethyl ketone peroxide , Diisopropylperoxycarbonate, cumene hydroperoxide, t-butyl hydroperoxide, di-t-butyl peroxide, dicumyl peroxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide, 2,2-bis- ( 4,4-t-butylperoxycyclohexyl) propane Tris - like the like (t-butylperoxy) polymeric initiator having a side chain a peroxide-based polymerization initiator or a peroxide, such as triazines.

  Moreover, when forming resin particles by an emulsion polymerization method, a water-soluble radical polymerization initiator can be used. Examples of the water-soluble polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate, azobisaminodipropane acetate, azobiscyanovaleric acid and its salts, hydrogen peroxide and the like.

  Generally used chain transfer agents can be used for the purpose of adjusting the molecular weight of the resin constituting the composite resin particles.

  The chain transfer agent is not particularly limited, and examples thereof include mercaptans such as octyl mercaptan, dodecyl mercaptan, tert-dodecyl mercaptan, n-octyl-3-mercaptopropionate, terpinolene, carbon tetrabromide and α-methyl. Styrene dimer or the like is used.

(5) Dispersion stabilizer It is also possible to use a dispersion stabilizer in order to appropriately disperse the polymerizable monomer and the like in the reaction system. Dispersion stabilizers include tricalcium phosphate, magnesium phosphate, zinc phosphate, aluminum phosphate, calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate, barium sulfate , Bentonite, silica, alumina and the like. Furthermore, those generally used as surfactants such as polyvinyl alcohol, gelatin, methylcellulose, sodium dodecylbenzenesulfonate, ethylene oxide adduct, and higher alcohol sodium sulfate can be used as the dispersion stabilizer.

  The surfactant used in the present invention will be described.

  In order to perform polymerization using the above-mentioned radical polymerizable monomer, it is necessary to perform oil droplet dispersion in an aqueous medium using a surfactant. Although it does not specifically limit as surfactant which can be used in this case, The following ionic surfactant can be mentioned as an example of a suitable thing.

  Examples of ionic surfactants include sulfonates (sodium dodecylbenzenesulfonate, sodium arylalkylpolyethersulfonate, 3,3-disulfonediphenylurea-4,4-diazo-bis-amino-8-naphthol-6 Sodium sulfonate, ortho-carboxybenzene-azo-dimethylaniline, 2,2,5,5-tetramethyl-triphenylmethane-4,4-diazo-bis-β-naphthol-6-sodium sulfonate, etc.), sulfuric acid Ester salts (sodium dodecyl sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, etc.), fatty acid salts (sodium oleate, sodium laurate, sodium caprate, sodium caprylate, sodium caproate, potassium stearate) Beam, calcium oleate and the like).

  Nonionic surfactants can also be used. Specifically, polyethylene oxide, polypropylene oxide, combination of polypropylene oxide and polyethylene oxide, ester of polyethylene glycol and higher fatty acid, alkylphenol polyethylene oxide, ester of higher fatty acid and polyethylene glycol, ester of higher fatty acid and polypropylene oxide, sorbitan ester Etc.

[Method for producing toner for developing electrostatic image]
Next, a method for producing an electrostatic charge image developing toner according to the present invention will be described.

The toner according to the present invention is produced, for example, through the following steps.
(1) Dissolution / dispersion step for dissolving or dispersing the release agent in the radical polymerizable monomer (2) Polymerization step for preparing a dispersion of resin fine particles (3) Resin fine particles and colorant particles in an aqueous medium Agglomeration and fusion step for agglomerating and fusing the particles to obtain core particles (associate particles) (4) first aging step for adjusting the shape by aging the associated particles with thermal energy (5) in the core particle dispersion Shell forming step of adding shell resin particles to aggregate and fuse the shell particles on the surface of the core particles to form core-shell structured colored particles (6) Thermal energy of the core-shell structured colored particles The second aging step for adjusting the shape of the core-shell structured colored particles (7) The colored particles are solid-liquid separated from the cooled colored particle dispersion, and the surfactant is removed from the colored particles. Cleaning process to remove (8) Cleaning process Drying step The drying the colored particles, after drying if necessary,
(9) There may be a step of adding an external additive to the dried colored particles. The above process will be described in detail later.

  When the toner according to the present invention is manufactured, first, resin particles and colorant particles are associated and fused to produce core particles (hereinafter referred to as core particles). Next, resin particles are added to the core particle dispersion, and the resin particles are aggregated and fused on the surface of the core particles to coat the surface of the core particles to produce colored particles having a core / shell structure. As described above, the toner according to the present invention is a toner having a core-shell structure in which resin particles are added to a dispersion of core particles prepared by various manufacturing methods and fused to the core particles. .

  As described above, the toner according to the present invention is characterized in that the thickness of the shell is extremely thin and the film thickness is constant. After the shell is formed, a toner having a small particle size with a constant particle size and a uniform shape is obtained. preferable. In order to produce a toner having such a structure and shape, the core particles are made to have a uniform shape with a uniform particle size, and shell resin particles are added to the core particles to form a shell. Become. In addition, when the shell is formed, the shape of the toner is finally controlled to give an appropriate shape. For that purpose, it is most important to prepare core particles having a uniform shape with uniform particle sizes. is there. With such core particles, resin fine particles forming a shell uniformly adhere to the surface thereof, and as a result, toner particles having a very uniform film thickness can be produced.

  The core particles constituting the toner according to the present invention are produced by a production method in which resin fine particles and colorant particles are aggregated and fused. The shape of the core particles is controlled, for example, by controlling the heating temperature in the aggregation / fusion process and the heating temperature and time in the first aging process.

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

  The core part constituting the toner according to the present invention is, for example, after dissolving or dispersing the release agent component in the polymerizable monomer forming the resin (A), and then mechanically dispersing fine particles in the aqueous medium. A method of salting out and fusing the composite resin fine particles formed through the step of polymerizing the polymerizable monomer by the miniemulsion polymerization method and the colorant particles, which will be described later, is preferably used. When the release agent component is dissolved in the polymerizable monomer, the release agent component may be dissolved or melted or dissolved.

  Hereinafter, each manufacturing process of the toner according to the present invention will be described.

(1) Dissolution / dispersion step This step is a step of preparing a radical polymerizable monomer solution in which the release agent compound is dissolved in the radical polymerizable monomer and the release agent compound is mixed.

(2) Polymerization step In a preferred example of this polymerization step, a radical polymerizable monomer solution in which a wax is dissolved or dispersed in an aqueous medium containing a surfactant having a critical micelle concentration (CMC) or less is added. Then, mechanical energy is applied to form droplets, and then a water-soluble radical polymerization initiator is added to advance the polymerization reaction in the droplets. An oil-soluble polymerization initiator may be contained in the droplet. In such a polymerization process, mechanical energy is imparted and forcedly emulsified (formation of droplets) is essential. Examples of the mechanical energy applying means include strong stirring such as homomixer, ultrasonic wave, and manton gorin or ultrasonic vibration energy applying means.

  By this polymerization step, resin fine particles containing a wax and a binder resin are obtained. Such resin fine particles may be colored fine particles or non-colored fine particles. The colored resin fine particles can be obtained by polymerizing a monomer composition containing a colorant. In the case of using uncolored resin fine particles, a dispersion of colorant fine particles is added to the dispersion of resin fine particles in the agglomeration / fusion process described later to melt the resin fine particles and the colorant fine particles. Color particles can be obtained by attaching.

(3) Aggregation / fusion process As a method of aggregation and fusion in the fusion process, a salting-out / fusion method using resin fine particles (colored or non-colored resin fine particles) obtained in the polymerization process is preferable. . In the agglomeration / fusion step, the internal additive fine particles such as the release agent fine particles and the charge control agent can be agglomerated and fused together with the resin fine particles and the colorant fine particles.

  The term “salting out / fusion” as used herein means that aggregation and fusion are performed in parallel, and when the particles have grown to a desired particle size, an aggregation terminator is added to stop the particle growth. The heating for controlling the particle shape according to the above is performed continuously.

  The “aqueous medium” in the agglomeration / fusion step is one in which the main component (50% by mass or more) is made of water. Examples of components other than water include organic solvents that dissolve in water, such as methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone, and tetrahydrofuran.

  The colorant fine particles can be prepared by dispersing the colorant in an aqueous medium. The dispersion treatment of the colorant is performed in a state where the surfactant concentration is set to a critical micelle concentration (CMC) or more in water. The disperser used for the dispersion treatment of the colorant is not particularly limited, but preferably an ultrasonic disperser, a mechanical homogenizer, a pressure disperser such as a manton gorin or a pressure homogenizer, a sand grinder, a Getzmann mill, a diamond fine mill, or the like. Examples thereof include a medium type disperser. Examples of the surfactant used include the same surfactants as those described above. The colorant (fine particles) may be surface-modified. In the surface modification method of the colorant, the colorant is dispersed in a solvent, the surface modifier is added to the dispersion, and the system is reacted by raising the temperature. After completion of the reaction, the colorant is separated by filtration, washed and filtered with the same solvent, and dried to obtain a colorant (pigment) treated with the surface modifier.

  The salting out / fusing method, which is a preferred agglomeration and fusing method, is a salting out method comprising alkali metal salt, alkaline earth metal salt, trivalent salt, etc. in water in which resin fine particles and colorant fine particles are present An agent is added as a coagulant having a critical coagulation concentration or higher, and then salting-out proceeds by heating to a temperature above the glass transition point of the resin fine particles and above the melting peak temperature (° C.) of the mixture. At the same time, it is a process of fusing. Here, the alkali metal salt and the alkaline earth metal salt which are salting-out agents include lithium, potassium, sodium and the like as the alkali metal, and examples of the alkaline earth metal include magnesium, calcium, strontium and barium. Preferably, potassium, sodium, magnesium, calcium, and barium are used.

  When agglomeration and fusion are performed by salting out / fusion, it is preferable to make the time allowed to stand after adding the salting-out agent as short as possible. The reason for this is not clear, but there are problems that the aggregation state of the particles fluctuates depending on the standing time after salting out, the particle size distribution becomes unstable, and the surface property of the fused toner fluctuates. appear. The temperature for adding the salting-out agent needs to be at least the glass transition temperature of the resin fine particles. The reason for this is that if the temperature at which the salting-out agent is added is equal to or higher than the glass transition temperature of the resin fine particles, the salting out / fusion of the resin fine particles proceeds rapidly, but the particle size cannot be controlled. There arises a problem that particles having a particle size are generated. Although the range of this addition temperature should just be below the glass transition temperature of resin, generally it is 5-55 degreeC, Preferably it is 10-45 degreeC.

  Further, the salting-out agent is added at a temperature not higher than the glass transition temperature of the resin fine particles, and then the temperature is raised as quickly as possible to a temperature not lower than the glass transition temperature of the resin fine particles and not lower than the melting peak temperature (° C.) of the mixture. Heat to. The time until this temperature rise is preferably less than 1 hour. Further, although it is necessary to quickly raise the temperature, the rate of temperature rise is preferably 0.25 ° C./min or more. The upper limit is not particularly clear, but if the temperature is increased instantaneously, salting out proceeds rapidly, so there is a problem that particle size control is difficult, and 5 ° C./min or less is preferable. By this fusing step, a dispersion of associated particles (core particles) formed by salting out / fusing resin fine particles and arbitrary fine particles is obtained.

(4) First aging step And, in the present invention, by controlling the heating temperature of the coagulation / fusion step and particularly the heating temperature and time of the first aging step, the particle size is constant and the distribution is narrow. The core particle surface is controlled so as to have a smooth but uniform shape. Specifically, the heating temperature is lowered in the aggregation / fusion process to suppress the progress of fusion between the resin particles to promote homogenization, the heating temperature is lowered in the first aging process, and the time The surface of the core particles is controlled to have a uniform shape by increasing the length.

(5) Shelling step In the shelling step, the resin particle dispersion for the shell is added to the core particle dispersion to agglomerate and fuse the resin particles for the shell onto the surface of the core particles. The resin particles are coated to form colored particles.

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

(6) Second ripening step Resin for shell which is added to a core particle after adding a terminator such as sodium chloride to stop the particle growth at the stage when colored particles become a predetermined particle size by shelling. Heating and stirring are continued for several hours in order to fuse the particles. In the shelling step, a shell having a thickness of 100 to 300 nm is formed on the surface of the core particle. In this way, resin particles are fixed to the surface of the core particles to form a shell, and rounded and colored particles having a uniform shape are formed.

  In the present invention, it is possible to control the shape of the colored particles in the true sphere direction by setting the time of the second aging step longer or by setting the aging temperature higher.

(7) Cooling Step / Solid-Liquid Separation / Washing Step This step is a step of cooling (rapid cooling) the dispersion of the colored particles. As a cooling treatment condition, cooling is performed at a cooling rate of 1 to 20 ° C./min. The cooling treatment method is not particularly limited, and examples thereof include a method of cooling by introducing a refrigerant from the outside of the reaction vessel, and a method of cooling by directly introducing cold water into the reaction system.

  In this solid-liquid separation / washing step, a solid-liquid separation process for solid-liquid separation of the colored particles from the dispersion of colored particles cooled to a predetermined temperature in the above-described step, and a solid-liquid separated toner cake (in a wet state) A cleaning treatment for removing deposits such as a surfactant and a salting-out agent from an aggregate obtained by agglomerating certain colored particles into a cake is performed. Here, the filtration method is not particularly limited, such as a centrifugal separation method, a vacuum filtration method using Nutsche or the like, a filtration method using a filter press or the like.

(8) Drying step This step is a step of drying the washed cake to obtain dried colored particles. Examples of dryers used in this process include spray dryers, vacuum freeze dryers, vacuum dryers, etc., stationary shelf dryers, mobile shelf dryers, fluidized bed dryers, rotary dryers It is preferable to use a stirring dryer or the like. The water content of the dried colored particles is preferably 5% by mass or less, more preferably 2% by mass or less. In addition, when the dried colored particles are aggregated by weak interparticle attractive force, the aggregate may be crushed. Here, as the crushing treatment device, a mechanical crushing device such as a jet mill, a Henschel mixer, a coffee mill, a food processor, or the like can be used.

(9) External Addition Processing Step This step is a step of preparing a toner by mixing the dried colored particles with an external additive as necessary.

  As an external additive mixing device, a mechanical mixing device such as a Henschel mixer or a coffee mill can be used.

  The mass average particle diameter (dispersed particle diameter) of the composite resin particles is preferably in the range of 10 to 1000 nm, more preferably in the range of 30 to 300 nm.

  The mass average particle diameter is a value measured using an electrophoretic light scattering photometer “ELS-800” (manufactured by Otsuka Electronics Co., Ltd.).

[Image Forming Method and Image Forming Apparatus According to the Present Invention]
The toner according to the present invention may be used as a one-component developer or a two-component developer, but is particularly preferably used as a two-component developer.

  Next, an image forming method in which the toner according to the present invention can be used will be described. The toner according to the present invention is used in, for example, a high-speed image forming apparatus having a printing speed of 300 to 400 mm / sec (65 to 85 sheets / min output performance in terms of A4 transfer paper). Specifically, a printer that can create a large amount of documents on demand in a short time can be mentioned. Further, the present invention can be applied to an image forming method in which the temperature of the fixing roller is 150 ° C. or lower, preferably 130 ° C. or lower and 100 ° C. or higher.

  This is because the toner according to the present invention has sufficient durability even though the shell covering the surface is thin, and the shell can fix the toner in a short time. It is called.

  FIG. 2 is an example of an image forming apparatus capable of using the toner according to the present invention, and shows a cross-sectional view thereof.

  FIG. 2 is a schematic view showing an example of the image forming apparatus of the present invention.

  As shown in FIG. 2, the image forming apparatus 1 is called a tandem type color image forming apparatus, and includes a plurality of sets of image forming units 9Y, 9M, 9C, and 9K, a belt-like intermediate transfer member 6 and a feeding unit. The paper unit, the conveyance unit, the toner cartridges 5Y, 5M, 5C, and 5K, the fixing device 60 according to the present invention, the operation unit 91, and the like are included.

  An image forming unit 9Y that forms a yellow image includes a charging unit 2Y, an exposure unit 3Y, a developing unit 4Y, a transfer unit 7Y, and a cleaning unit 8Y arranged around an image carrier (hereinafter referred to as a photoreceptor) 1Y. Have

  The image forming unit 9M that forms a magenta image includes a photoreceptor 1M, a charging unit 2M, an exposure unit 3M, a developing device 4M, a transfer unit 7M, and a cleaning unit 8M.

  The image forming unit 9C that forms a cyan image includes a photoreceptor 1C, a charging unit 2C, an exposure unit 3C, a developing device 4C, a transfer unit 7C, and a cleaning unit 8C.

  The image forming unit 9K that forms a black image includes a photoreceptor 1K, a charging unit 2K, an exposure unit 3K, a developing device 4K, a transfer unit 7K, and a cleaning unit 8K.

  The intermediate transfer body 6 is wound around a plurality of rollers 6A, 6B, and 6C and is rotatably supported.

  Each color image formed by the image forming units 9Y, 9M, 9C, and 9K is sequentially primary-transferred onto the rotating intermediate transfer body 6 by the transfer means 7Y, 7M, 7C, and 7K, and the combined color image. Is formed.

  The paper P stored in the paper feed cassette 20 as the paper feed means is fed one by one by the paper feed roller 21, is conveyed to the transfer means 7 A through the registration roller 22, and the color image is transferred onto the paper P. Is secondarily transferred.

  The paper P on which the color image has been transferred is fixed by a fixing device 60, which is a fixing device of the present invention, and is sandwiched by a paper discharge roller 25 through transport rollers 23, 24, which are transport means, and is discharged outside the machine. It is placed on the paper tray 26.

[Configuration of Fixing Device (Fixing Device) Used in the Present Invention]
Next, the fixing device 60 used in the image forming apparatus of the present embodiment will be described. FIGS. 3A and 3B are side sectional views showing the configuration of the fixing device 60 of the present embodiment. The fixing device 60 includes a heating roller 61 as an example of a rotating member, an endless belt 62 as an example of a belt member, and a pressure contact member 64 as an example of a pressure member pressed from the heating roller 61 via the endless belt 62. The main part is composed.

  The heating roller 61 is a cylindrical roll configured by laminating a heat-resistant elastic body layer and a release layer around a metal core (cylindrical cored bar) 611 and is rotatably supported to be 194 mm / Rotates at a surface speed of s.

  Inside the heating roller 61, a halogen heater 66 having a rating of 600 W is disposed as a heat source. On the other hand, a temperature sensor 69 is disposed in contact with the surface of the heating roller 61. The control unit of the image forming apparatus controls lighting of the halogen heater 66 based on the temperature measurement value by the temperature sensor 69 so that the surface temperature of the heating roller 61 maintains a predetermined set temperature (for example, 175 ° C.). It is adjusted.

  The endless belt 62 is a seamless endless belt, and is rotated by a pressure contact member 64 and a belt guide member disposed inside the endless belt 62, and edge guide members disposed at both ends of the endless belt 62. It is supported freely. And it arrange | positions so that it may press-contact with the heating roller 61 in the nip part N, and it rotates with the movement speed of 194 mm / s following the heating roller 61.

  Next, the pressure contact member 64 is disposed inside the endless belt 62 while being pressed against the heating roller 61 via the endless belt 62, and forms a nip portion N with the heating roller 61. A pre-nip member 64a for securing a wide nip portion N is disposed on the inlet side (upstream side) of the nip portion N. Further, by locally pressing the surface of the fixing roll 61, the toner image surface is smoothed to give image gloss, and the surface of the fixing roll 61 is distorted (dented) to form a down curl on the paper P. The peeling nip member 64b is disposed on the outlet side (downstream side) of the nip portion N. Further, the pressure pad 64 is provided with a low friction sheet 69 as an example of a rubbing member on the surface in contact with the endless belt 62 in order to reduce the sliding resistance between the inner peripheral surface of the endless belt 62 and the pressure pad 64. It has been.

  The pressure pad 64 and the low friction sheet 69 are supported by a metal holder 65.

  The heating roller 61 is connected to a drive motor (not shown) and rotates in the direction of arrow C. Following this rotation, the endless belt 62 also rotates in the same direction as the heating roller 61. The transfer paper P on which the toner image is electrostatically transferred in the secondary transfer portion of the image forming apparatus shown in FIG. 1 is guided by the fixing entrance guide and conveyed to the nip portion N. When the transfer paper P passes through the nip portion N, the toner image on the transfer paper P is fixed by the pressure acting on the nip portion N and the heat supplied from the heating roller 61. In the fixing device 60 of the present embodiment, since the nip portion N can be widely configured by the concave pre-nip member that substantially follows the outer peripheral surface of the heating roller 61, stable fixing performance can be ensured.

  In the vicinity of the downstream side of the nip portion N, the transfer transfer paper P peeled off from the heating roller 61 by the end pressure contact member 68 is completely separated from the heating roller 61 and is discharged to the discharge portion of the image forming apparatus. A peeling assisting member for guiding to is provided. The peeling auxiliary member is held by the baffle holder in a state where the peeling baffle is close to the heating roller 61 in a direction (counter direction) opposite to the rotation direction of the heating roller 61.

  Next, each member constituting the fixing device 60 will be described in detail. First, in the heating roller 61, the core (base material) 611 is formed of a cylindrical body having an outer diameter of 30 mm, a thickness of 1.8 mm, and a length of 360 mm formed of a metal having high thermal conductivity such as iron, aluminum, and SUS. ing. The heat-resistant elastic layer is composed of an elastic body having high heat resistance, and it is particularly preferable to use an elastic body such as rubber or elastomer having a rubber hardness of about 15 to 45 ° (JIS-A). Specifically, silicone rubber, fluorine rubber, or the like can be used. In the fixing device 60 of the present embodiment, the core 611 is coated with a silicone HTV rubber having a rubber hardness of 35 ° (JIS-A) with a thickness of 600 μm.

  For the release layer, for example, a heat-resistant resin such as a silicone resin or a fluororesin is used, and a fluororesin is suitable from the viewpoint of the releasability to the toner and the wear resistance. As the fluororesin, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP) and the like can be used. The thickness of the release layer is preferably 5 to 30 μm. In the fixing device 60 of the present embodiment, PFA with a thickness of 30 μm is coated and the surface is finished close to a mirror surface state.

  The endless belt 62 is a seamless endless belt whose original shape is formed in a cylindrical shape so that a defect due to the seam does not occur in the output image. The base layer and the surface of the base layer on the heating roller 61 side or It is comprised from the mold release layer coat | covered on both surfaces. The base layer is formed of a polymer such as thermosetting polyimide, thermoplastic polyimide, polyamide, or polyamideimide, and has a thickness of 30 to 200 μm, preferably 50 to 125 μm, and more preferably about 75 to 100 μm. The release layer coated on the surface of the base layer is made of a fluororesin such as PFA, PTFE, or FEP, and has a thickness of about 5 to 100 μm, preferably about 10 to 30 μm.

  In the fixing device 60 of the present embodiment, an endless belt 62 having a configuration in which a release layer made of PFA having a thickness of 30 μm is laminated on a base layer made of thermosetting polyimide having a circumferential length of 94 mm, a thickness of 75 μm, and a width of 320 mm. Used.

  As described above, the pressure contact member 64 disposed inside the endless belt 62 is composed of a pre-nip member and an end pressure contact member, and is supported by the holder so as to press the heating roller 61 with a load of 350 N by a spring or an elastic body. Has been. As the prenip member, an elastic body such as silicone rubber or fluorine rubber, a leaf spring, or the like can be used, and the surface on the heating roller 61 side is formed with a concave curved surface that substantially follows the outer peripheral surface of the heating roller 61. In the fixing device 60 of the present embodiment, silicone rubber having a width of 10 mm, a thickness of 5 mm, and a length of 320 mm is used.

  The end pressure contact member is made of a heat-resistant resin such as PPS (polyphenylene sulfide), polyimide, polyester, polyamide, or a metal such as iron, aluminum, or SUS. As the shape of the end pressure contact member, the outer surface shape in the nip portion N is formed as a convex curved surface having a constant radius of curvature. In the fixing device 60 according to the present embodiment, the endless belt 62 is wrapped around the heating roller 61 by the pressure contact member 64 at a winding angle of about 40 ° to form a nip portion N having a width of about 10 mm.

  Further, a lubricant application member is disposed along the longitudinal direction of the fixing device 60. The lubricant application member is disposed so as to be in contact with the inner peripheral surface of the endless belt 62 and supplies an appropriate amount of lubricant. As a result, the lubricant is supplied to the sliding portion between the endless belt 62 and the low friction sheet, and the sliding resistance between the endless belt 62 and the pressure contact member 64 via the low friction sheet is further reduced. Smooth rotation is achieved. Further, it has an effect of suppressing wear on the inner peripheral surface of the endless belt 62 and the surface of the low friction sheet.

  As the lubricant, a lubricant that has durability against long-term use under a fixing temperature environment and can maintain wettability with the inner peripheral surface of the endless belt 62 is suitable. For example, liquid oil such as silicone oil or fluorine oil, grease in which a solid substance and a liquid are mixed, or a combination thereof can be used. Examples of the silicone oil include dimethyl silicone oil, methylphenyl silicone oil, amino-modified silicone oil, carboxy-modified silicone oil, silanol-modified silicone oil, and sulfonic acid-modified silicone oil. In the fixing device 60 of the present embodiment, Methylphenyl silicone oil (KF53: manufactured by Shin-Etsu Chemical Co., Ltd.) is used.

[Transfer material (transfer paper)]
The transfer material P used in the present invention is a support for holding a toner image, and is usually called an image support, a recording material, or transfer paper. Specifically, various transfer materials such as plain paper and fine paper from thin paper to thick paper, coated printing paper such as art paper and coated paper, commercially available Japanese paper and postcard paper, plastic film for OHP, cloth, etc. However, it is not limited to these.

  EXAMPLES The present invention will be described below with reference to examples, but of course the present invention is not limited to these embodiments. In addition, the following "part" represents a "mass part".

<< Preparation of Resin Particle 1 for Core Part >>
As described below, the first-stage polymerization, the second-stage polymerization, and then the third-stage polymerization were performed to prepare “core part resin particles 1” having a multilayer structure.

(1) First-stage polymerization 4 parts of anionic surfactant (Structural Formula 1) shown below in 3040 parts of ion-exchanged water in a 5 L reaction vessel equipped with a stirrer, temperature sensor, cooling pipe, and nitrogen introducing device The dissolved surfactant solution was charged, and the internal temperature was raised to 80 ° C. while stirring at a stirring speed of 230 rpm under a nitrogen stream.

(Structural Formula 1) C ₁₀ H ₂₁ (OCH ₂ CH ₂ ) ₂ SO ₃ Na
To this surfactant solution, an initiator solution in which 10 parts of a polymerization initiator (potassium persulfate: KPS) was dissolved in 400 parts of ion-exchanged water was added, the temperature was adjusted to 75 ° C., 532 parts of styrene, n- A monomer mixture composed of 200 parts of butyl acrylate, 68 parts of methacrylic acid and 16.4 parts of n-octyl mercaptan was added dropwise over 1 hour, and the system was polymerized by heating and stirring at 75 ° C. for 2 hours. (First stage polymerization) was performed to prepare resin particles. This is designated as “resin particle A1”.

  The “resin particle A1” prepared by the first stage polymerization had a mass average molecular weight (Mw) of 16,500.

(2) Second stage polymerization (formation of intermediate layer)
In a flask equipped with a stirrer, a monomer mixture consisting of 101.1 parts of styrene, 62.2 parts of n-butyl acrylate, 12.3 parts of methacrylic acid, and 1.75 parts of n-octyl mercaptan was released into a mold release solution. As the agent, 93.8 parts of paraffin wax “HNP-57” (manufactured by Nippon Seiki Co., Ltd.) was added, and the mixture was heated to 90 ° C. and dissolved to prepare a monomer solution.

  On the other hand, a surfactant solution in which 3 parts of an anionic surfactant (Structural Formula 1) is dissolved in 1560 parts of ion-exchanged water is heated to 98 ° C., and this surfactant solution is a dispersion of resin particles A1. After adding 32.8 parts of "resin particles A1" in terms of solid content, the monomer solution of the wax was mixed for 8 hours using a mechanical disperser "CLEAMIX" (M Technique Co., Ltd.) having a circulation path. Dispersion liquid was prepared, which contained emulsified particles having a dispersed particle diameter of 340 nm.

  Next, an initiator solution prepared by dissolving 6 parts of potassium persulfate in 200 parts of ion-exchanged water was added to this dispersion, and this system was heated and stirred at 98 ° C. for 12 hours for polymerization (second stage polymerization). ) To obtain resin particles. This resin particle is referred to as “resin particle A2”. Mw of “resin particle A2” prepared by the second stage polymerization was 23,000.

(3) Third stage polymerization (formation of outer layer)
An initiator solution in which 5.45 parts of potassium persulfate is dissolved in 220 parts of ion-exchanged water is added to the “resin particles A2” obtained as described above, and styrene 293. A monomer mixed solution consisting of 8 parts, 154.1 parts of n-butyl acrylate, and 7.08 parts of n-octyl mercaptan was added dropwise over 1 hour. After completion of dropping, the mixture was heated and stirred for 2 hours to perform polymerization (third stage polymerization), and then cooled to 28 ° C. to obtain “resin particle 1 for core part”. Mw of “resin particle A3” prepared by the third stage polymerization was 26,800.

  The volume average particle diameter of the composite resin particles (resin particles) constituting the “core part resin particles 1” was 125 nm. The resin particles had a glass transition temperature (Tg) of 28.1 ° C. and a solubility parameter value (SP value) of 10.09.

<< Preparation of Resin Particle 6 for Core Part >>
202.5 parts of styrene, 211.5 parts of n-butyl acrylate, 36 parts of methacrylic acid, n-octyl mercaptan used in the second stage polymerization (formation of outer layer) in the preparation of “resin particle 3 for core part” “Core part resin particles 6” were prepared in the same manner except that the initiator solution was changed to 5.2 parts and 5.1 parts of potassium persulfate dissolved in 197 parts of ion-exchanged water.

<< Preparation of Resin Particle 7 for Core Part >>
In the preparation of “core part resin particles 3”, 115.9 parts of styrene, 47.4 parts of n-butyl acrylate, 12.3 parts of methacrylic acid, n-type used in the first stage polymerization (formation of inner layer) “Core part resin particles 7” were prepared in the same manner except that the initiator solution was changed to 1.8 parts of octyl mercaptan and 6.1 parts of potassium persulfate in 237 parts of ion-exchanged water.

<< Preparation of Resin Particle 8 for Core Part >>
In the preparation of “core part resin particles 3”, 193.5 parts of styrene, 220.5 parts of n-butyl acrylate, 36.0 parts of methacrylic acid, n- “Core part resin particles 9” were prepared in the same manner except that 5.8 parts of octyl mercaptan and 5.1 parts of potassium persulfate were changed to an initiator solution dissolved in 197 parts of ion-exchanged water.

<< Resin particles for shell layer >>
(Preparation of resin particle 1 for shell layer)
In the first-stage polymerization of the above “core part resin particles 1”, styrene is changed to 624 parts, 2-ethylhexyl acrylate is 120 parts, methacrylic acid is 56 parts, and n-octyl mercaptan is changed to 16.4 parts. Polymerization reaction and post-reaction treatment were performed in the same manner except that the monomer mixture was used, and “shell layer resin particles 1” were prepared.

(Preparation of resin particle 3 for shell layer)
In the preparation of “resin particle 1 for shell layer”, a monomer mixed solution in which styrene is changed to 548 parts, 2-ethylhexyl acrylate is changed to 156 parts, methacrylic acid is changed to 96 parts, and n-octyl mercaptan is changed to 16.5 parts. In the same manner except that it was used, the polymerization reaction and the treatment after the reaction were carried out to prepare “resin particle 3 for shell layer”.

(Preparation of resin particle 7 for shell layer)
In preparation of “resin particle 1 for shell layer”, a monomer mixed solution in which 528 parts of styrene, 208 parts of 2-ethylhexyl acrylate, 64 parts of methacrylic acid, and 16.5 parts of n-octyl mercaptan was used. In the same manner as described above, polymerization reaction and post-reaction treatment were performed to prepare “resin particle 7 for shell layer”.

(Preparation of resin particle 8 for shell layer)
Monomer in which “Styrene layer resin particles 1” was prepared by changing 666.4 parts of styrene, 109.6 parts of 2-ethylhexyl acrylate, 24 parts of methacrylic acid, and 16.5 parts of n-octyl mercaptan. In the same manner except that the mixed solution was used, a polymerization reaction and a post-reaction treatment were performed to prepare “resin particle 8 for shell layer”.

<Production of toner>
Toners 1 to 15 were produced as follows.

<Preparation of Toner 1>
(Preparation of dispersion 1 of colorant particles)
90 parts of the anionic surfactant (1) was dissolved in 1600 parts of ion-exchanged water with stirring. While stirring this solution, 400 parts of carbon black “Regal 330” (Cabot Corporation) is gradually added, and then dispersed using a stirring device “Claremix” (Mtechnics Corporation). Agent particle dispersion 1 "was prepared.

  The particle diameter of the colorant particles in this “colorant particle dispersion liquid 1” was 110 nm as measured using an electrophoretic light scatterometer (ELS-800: manufactured by Otsuka Electronics Co., Ltd.).

(Salting out / fusion (association / fusion) process) (core formation)
444 parts (converted to solid content) of “core part resin particles 1”, 900 parts of ion-exchanged water, and 200 parts of “colorant particle dispersion 1”, a temperature sensor, a cooling pipe, a nitrogen introducing device, and a stirring device Was stirred in a reaction vessel equipped with. After adjusting the temperature in the container to 30 ° C., 5 mol / liter sodium hydroxide aqueous solution was added to this solution to adjust the pH to 8-11.

Next, an aqueous solution in which 2 parts of magnesium chloride hexahydrate was dissolved in 1000 parts of ion-exchanged water was added over 10 minutes at 30 ° C. with stirring. After standing for 3 minutes, the temperature was raised and the system was heated to 65 ° C. over 60 minutes. In this state, the particle size of the associated particles was measured with “Coulter Counter TA-II” (manufactured by Coulter Co.). When the particle median system (D ₅₀ ) reached 5.5 μm, 40.2 parts of sodium chloride was used. An aqueous solution in which 1000 parts of ion-exchanged water is dissolved is added to stop the growth of the particle size, and further, the fusion is continued by heating and stirring at a liquid temperature of 70 ° C. for 1 hour as an aging treatment. Formed.

  The circularity of the “core part 1” was measured by “FPIA2100” (manufactured by Systex) and found to be 0.920.

(Formation of shell layer (shelling operation))
Next, at 65 ° C., 23.4 parts (in terms of solid content) of “resin particle 1 for shell layer” was added, and an aqueous solution obtained by dissolving 2 parts of magnesium chloride hexahydrate in 1000 parts of ion-exchanged water was added for 10 minutes. After the addition, the temperature was raised to 70 ° C. (shelling temperature), and stirring was continued for 1 hour to fuse the particles of “resin particle 1 for shell layer” to the surface of “core part 1”. Thereafter, an aging treatment was performed at 75 ° C. to a predetermined circularity to form a shell layer.

  Here, 40.2 parts of sodium chloride was added, cooled to 30 ° C. under the condition of 8 ° C./min, and the generated fused particles were filtered and repeatedly washed with 45 ° C. ion-exchanged water. By drying with warm air, “Toner 1” having a shell layer on the surface of the core portion was obtained.

  The glass transition temperature (Tg) was measured by the method described above.

  The mass average molecular weight was measured by the method described above.

<Preparation of Toner 2-15>
The “core portion resin particles 1” and “shell layer resin particles 1” used in the production of “toner 1” are used as the core portion resin particles shown in Table 3 and the shell layer resin particles shown in Table 3. “Toners 2 to 15” were prepared in the same manner except that the core particle circularity and shelling temperature shown in Table 4 were changed.

  The cross-sectional views of the “toners 1 to 15” obtained above were observed with a TEM, and the 8-point average film thickness (Have) of each shell layer and the calculated Hmax / Hmin were calculated according to the method described above.

  The physical properties of the toner are shown in Table 4 below.

《External treatment process》
1% by weight of hydrophobic silica (number average primary particle size = 12 nm, degree of hydrophobicity = 68) and hydrophobic titanium oxide (number average primary particle size = 20 nm, degree of hydrophobicity) were prepared in the above “Toners 1-15”. = 63) was added in an amount of 1.2% by mass and mixed with a Henschel mixer to prepare "Toners 1-18".
<< Preparation of developer >>
Next, a ferrite carrier coated with an acrylic resin and having a volume average particle size of 40 μm was mixed with each of the prepared toners to prepare “Developers 1 to 18” having a toner concentration of 6%.
<Evaluation>
For the print image, a commercially available multi-function machine “Sitios 9331” (manufactured by Konica Minolta Business Technologies, Inc.) adopting a print image electrophotographic method is used, the linear velocity is 300 mm, the developing roller is 9 mm in outer diameter, and FIG. A fixing device having the configuration and a fixing device having the configuration (B) were sequentially changed to perform printing, and a printed image was created. The following items were evaluated for the state of the multifunction device and the print image.

  The following evaluation was performed using “Examples 1 to 12” and “Comparative Examples 1 to 3” produced above. In addition, ◎ and ○ of the evaluation criteria are passed and × is rejected.

<Heat resistant storage>
Take 0.5 g of toner in a 10 ml glass bottle with an inner diameter of 21 mm, close the lid, shake 600 times at room temperature with Tap Denser KYT-2000 (manufactured by Seishin Enterprise), and then remove the lid at 55 ° C. and 35% RH. For 2 hours. Next, the toner is placed on a 48 mesh sieve (aperture 350 μm) while being careful not to break up the toner aggregates, set on a powder tester (manufactured by Hosokawa Micron), and fixed with a press bar and knob nut. After adjusting the vibration intensity to a feed width of 1 mm and applying vibration for 10 seconds, the ratio (mass%) of the amount of toner remaining on the sieve was measured.

  The toner aggregation rate is a value calculated by the following formula.

Toner aggregation rate (%) = {(residual toner mass on sieve (g)) / 0.5 (g)} × 100
The heat resistant storage stability of the toner was evaluated according to the criteria described below.

A: The toner aggregation rate is less than 15% (toner has excellent heat-resistant storage property)
○: Toner aggregation rate of 15% or more and less than 20% by mass (good heat storage stability of toner)
X: The toner aggregation rate exceeds 20% (the toner has poor heat storage stability and is unsuitable for use)
<Low temperature fixability>
The heating roller surface temperature of the fixing device of the evaluation machine is changed so that the paper surface temperature changes in increments of 10 ° C. within the range of 80 to 150 ° C., and the toner image is fixed at each changed temperature to produce a fixed image. did. In creating the printed image, high-quality paper (80 g / m ² ) of A4 size was used.

  The fixing strength of the printed image obtained by fixing is fixed using a method in accordance with the mending tape peeling method described in Chapter 9 Section 1.4 of “Basics and Applications of Electrophotographic Technology: Electrophotographic Society”. The rate was evaluated.

Specifically, after a 2.54 cm square solid black print image with a toner adhesion amount of 0.6 mg / cm ² was prepared, images before and after peeling with “Scotch Mending Tape” (manufactured by Sumitomo 3M) The density was measured, and the residual ratio of the image density was determined as the fixing ratio.

  The “transfer material (paper) surface temperature” at which the fixing rate is 95% or more is defined as the minimum fixing temperature. The surface temperature of the transfer material (paper) was measured with a non-contact thermometer. The image density was measured with a reflection densitometer “RD-918” (manufactured by Macbeth).

Evaluation criteria A: Fixing is possible at a minimum fixing temperature of less than 100 ° C. ○: Fixing is possible at a minimum fixing temperature of 100 ° C. or more and less than 130 ° C. ×: Fixing is possible at a minimum fixing temperature of 130 ° C. or more <Fixed image misalignment>
The evaluation of fixed image misalignment was made by printing a full-color single color solid image on an A4 recording sheet (transfer material) and another line (0.5 mm width) in the direction perpendicular to the recording sheet moving direction to 5 mm. 100 images printed with an interval of 10 were output to check for the occurrence of image misalignment.

  ◎ and ○ are acceptable levels.

Evaluation Criteria A: No image misalignment O: Image misalignment occurs at 1 to 4 locations x: Image misalignment occurs at 5 locations or more <Toner Scattering>
Evaluation was based on the charge rising performance when the toner was supplied to the developing device. Specifically, using a manuscript with a pixel ratio of 75% and a large image area, printing 1000 sheets in a print mode in which toner consumption (supply amount) is remarkably large, and then toner scattering in the machine due to a charge rise failure The state of was visually evaluated.

Evaluation Criteria ◎: Contamination due to toner scattering is not visually confirmed ○: Contamination due to toner scattering feels almost free and practically no problem ×: Contamination due to toner scattering is visually confirmed and practically problematic

  Regarding the heat-resistant storage property, the low-temperature fixability, and the toner scattering, the fixing devices (A) and (B) both showed the same evaluation results, but the fixing misalignment was described respectively.

  As is apparent from Table 5 above, Examples 1 to 12 within the present invention all exhibit good characteristics, but Comparative Examples 1 to 3 outside the present invention have problems with at least any of the characteristics.

  Furthermore, when the print speed at the time of print image creation was changed to 400 mm / sec, 490 mm / sec, and 600 mm / sec and the same evaluation was performed, in Examples 1 to 16, all evaluation items were good. Results were obtained.

FIG. 3 is a schematic diagram of a toner having a core / shell structure. FIG. 3 is a cross-sectional view of an image forming apparatus in which the toner according to the present invention can be used. FIG. 3 is a cross-sectional view illustrating an example of a fixing device according to the present invention.

Explanation of symbols

4Y, 4M, 4C, 5K Developing device 5Y, 5M, 5C, 5K Toner cartridge 6 Intermediate transfer member 9Y, 9M, 9C, 9K Image forming unit 60 Fixing device 61 Heating roller 62 Endless belt 64 Pressure contact member 66 Halogen heater 68 End Pressure contact member 69 Temperature sensor 611 Core (base material)
T Toner A Core B Shell C Colorant D Wax N Nip part P Transfer material (transfer paper, etc.)

Claims (4)

The toner image is formed by electrophotography, and the toner image transferred onto the recording medium is formed by pressing the endless belt against the heating roller, the endless belt pressed against the heating roller, and the endless belt inside the endless belt. In an image forming method in which fixing is performed by a fixing device including a pressing member and an end pressing member that elastically deforms the heating roller locally on the downstream side of the pressing member, at least resin and coloring are used as toner for forming the toner image Having a shell on the surface of the core containing the agent and the release agent, the 8-point average film thickness of the shell is 100 nm to 300 nm, the maximum film thickness of the shell is Hmax, and the minimum film thickness is Hmin. Sometimes, an image forming method using toner having Hmax / Hmin of less than 1.50. When the glass transition temperature of the resin constituting the core is Tg1 and the glass transition temperature of the resin constituting the shell is Tg2, Tg2−Tg1 ≧ 15 ° C., 20 ° C. ≦ Tg1 ≦ 40 ° C., 40 ° C ≦ Tg2. The image forming method according to claim 1, wherein toner is used. The image forming method according to claim 2, wherein a toner having a circularity of 0.945 or more is used as the toner. An image forming apparatus that forms an image by the image forming method according to claim 1.

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