JP2005195670A - Image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming method with which unevenness in toner attaching amount (TMA) and image unevenness such as unevenness in gloss and unevenness in color difference are reduced, and a high image quality/high grade color image stably having a wide color reproduction range with no unevenness in gloss and coloring of an image can be formed. <P>SOLUTION: In the image forming method, a crystalline toner whose storage elastic modulus-to-temperature gradient in the range from Tm+20°C to Tm+50°C is ≤0.02 log(Pa)/°C is transferred as a toner image onto transfer paper having a formation index of ≥20 and this toner image is fixed within a fixing time of 50-500 ms. A maximum attaching amount of a monochrome toner is preferably ≤0.35 mg/cm<SP>2</SP>and a weight average particle diameter of the crystalline toner is preferably ≤5 μm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming method using an electrophotographic method or an electrostatic recording method using an electrostatic charge developing toner. More particularly, the present invention relates to an image forming method suitable for graphic arts and short run printing.

JP-A 63-2822752 JP-A-6-250439 JP-A-10-26842 JP 2001-117268 A JP 2003-98736 A Journal of the Imaging Society of Japan Vol.40 No.2 2001

  A method for visualizing image information through an electrostatic latent image such as electrophotography is currently used in various fields such as a copying machine and a printer with the development of the technology and the expansion of market demand.

  In electrophotography, an electrostatic charge image is formed on a photoreceptor by charging and exposure processes, the electrostatic latent image is developed with a developer containing toner, and visualized through a transfer / fixing process.

  The developer used here includes a two-component developer composed of a toner and a carrier, and a one-component developer using a magnetic toner or a nonmagnetic toner alone.

  The toner is usually produced by a kneading and pulverizing method in which a thermoplastic resin is melt-kneaded together with a pigment, a charge control agent, a release agent, etc., cooled, finely pulverized, and further classified. For example, inorganic and organic fine particles for improving fluidity and cleaning properties may be added to the toner particle surfaces. In the ordinary kneading and pulverizing method, the toner shape and the surface structure of the toner are indeterminate, and the toner shape and surface structure are intentionally difficult to control because they vary slightly depending on the pulverization properties of the materials used and the conditions of the pulverization process. is there. In particular, in the case of a material having a high pulverization property, the generation of fine powder or a change in toner shape is often caused by mechanical force in the developing machine. Due to these effects, in the two-component developer, the charging deterioration of the developer is accelerated by the adhesion of fine powder to the carrier surface, and in the one-component developer, the toner scattering occurs due to the expansion of the particle size distribution, and the toner shape Deterioration in developability due to change tends to cause image quality degradation.

  Further, when a toner such as wax is internally added to form a toner, the exposure of the release agent to the surface is often affected by the combination with a thermoplastic resin. In particular, in the case of a combination of a resin imparted with elasticity by a high molecular weight component and slightly pulverized resin and a brittle wax-type release agent such as polyethylene, a large amount of polyethylene is exposed on the toner surface. These are advantageous for releasability during fixing and cleaning of untransferred toner from the surface of the photoreceptor, but because the polyethylene on the surface layer is easily transferred by mechanical force, contamination of the developing roll, photoreceptor and carrier is prevented. It tends to occur, leading to a decrease in reliability. Further, since the toner shape is indefinite, the fluidity is not sufficient even when a fluidity aid is added, and the fine particles on the toner surface move to the concave portions due to the action of mechanical force during use. In particular, the fluidity is lowered or the fluidity aid is buried in the toner, so that the developability, transferability, and cleaning properties are deteriorated. Further, when the toner collected by cleaning is returned to the developing machine and used again, the image quality is likely to further deteriorate. If the flow aid is further increased in order to prevent these problems, black spots are generated on the photoconductor and the aid particles are scattered.

  In recent years, as a method for intentionally controlling the shape and surface structure of a toner, methods for producing a toner by an emulsion polymerization aggregation method such as Patent Document 1 and Patent Document 2 have been proposed.

  In the emulsion polymerization aggregation method, since a starting material is usually a finely divided raw material of 1 μm or less, a toner of about 1 to 25 μm can be prepared in principle. Specifically, a resin dispersion is generally prepared by emulsion polymerization or the like, while a colorant dispersion in which a colorant is dispersed in a solvent is prepared, and these resin dispersion and colorant dispersion are mixed to obtain a toner particle size. This is a manufacturing method in which the aggregated particles are formed by forming the corresponding aggregated particles and then heated to coalesce the aggregated particles to form a toner. In these methods, the toner surface and the interior usually have the same composition. It is difficult to control.

  With respect to this problem, a means for realizing more precise particle structure control by controlling freely from the inner layer to the surface layer even in the toner in the emulsion polymerization aggregation method as shown in Patent Document 3 has been proposed. ing. Furthermore, the present applicant has proposed a crystalline toner using a crystalline resin as a binder resin in Patent Documents 4 and 5 and the like. These toners can be easily reduced in particle size, and precise particle structure control has been realized, so that the image quality of conventional electrophotographic images is dramatically improved and high reliability is expected. It has become.

  On the other hand, in recent years, the image forming method by electrophotography using the toner / developer technology as described above has begun to be applied to a part of the printing area due to the progress of digitization and colorization, including on-demand printing. Practical application in the graphic arts and short run printing areas is beginning to become remarkable.

  In this specification, the graphic arts area refers to the general industry / sector related to the production of printed materials, such as prints with a small number of copies printed, and original artworks such as handwriting and paintings. This refers to the manufacturing-related business area of printed materials by mass production methods called replication, copying, and re-production.

  In the short run printing area, technology targeting not only monochrome printing but also short run color printing areas as represented by Fuji Xerox ColorDocuTech 60 has been developed by taking advantage of the characteristics of plateless printing in electrophotography. Significant progress is being made in terms of image quality, transfer paper compatibility, product price, and price per sheet (Non-Patent Document 1).

  However, compared to the original full-scale conventional printing, although there are on-demand characteristics as plateless printing, the image quality, texture, and image quality represented by its color reproduction range, resolution, and gloss characteristics. Due to uniformity, maintainability of image quality during long continuous printing, high price per sheet due to toner consumption at high image density, compatibility with thinner and thicker paper, oil during image fixing Image defects, poor writing performance, high power consumption due to high-temperature high-temperature fixing, transfer paper elongation, curl, waves, and misalignment of registration marks on both sides due to high-temperature and high-pressure image fixing. Cheap. In principle, the toner image made of a low-molecular resin having a relatively low softening point is heat-fixed. Therefore, the heat and mechanical durability of the image may be weaker than the printed image, and may be folded several times. When booked and stacked in multiple layers and exposed to high temperatures under high load conditions, there may be problems with durability against various stresses such as image loss, blocking, offset, light resistance due to outdoor exposure, weather resistance, etc. .

  In this way, it has been found that there are still a number of issues to replace printing in earnest and to appeal for the market value as a production material in the graphic arts field.

  With regard to the color reproduction region, the types of pigments that are practically used in the electrophotographic region are fewer than the types that are used in the original conventional printing ink, and further high-performance colorant technology is required. Since the usage conditions in the graphic arts range are broad compared to the office market, not only high color reproducibility but also various durability such as heat resistance, light resistance, water resistance, oil resistance, solvent resistance, scratch resistance, and bending strength Sexuality will be required.

  In systems such as image processing systems, photoreceptors, and exposures, the resolution is likely to be limited by the toner particle size and its particle size distribution, but the small particle size toner is charged in each process such as charging, development, transfer, fixing, and cleaning. There is a major technical problem in using it effectively and reliably.

  For example, a carrier or charging blade for uniformly charging a small particle size toner, a design of a charging roll, a developing system that obtains a high image density without generating background stains, and transfer with fine and high transfer efficiency. Transfer system, fixing system that supports the combination of small particle size toner and various paper types, and cleaning system that achieves stable image quality by removing small particle size toner completely from the photoreceptor or intermediate transfer body There is a need for improvement.

  In order to improve the in-plane uniformity and defects of the image, it is important to control the uniformity of the developing ability of the developer in the developing system. To meet the demands of the printing market for maintaining image quality, it is a highly durable developer that maintains stable and uniform development even during continuous printing of thousands of sheets, maintains stable and uniform development, and has little environmental dependency on temperature, humidity, etc. Must be optimized as a development system that can avoid the effects of paper dust and foreign matter, is highly durable, is less prone to defects and noise, and can maintain a uniform in-plane density.

  In a transfer system from a photoreceptor or an intermediate transfer member, an electrostatic transfer system is generally used in current electrophotography, but in the case of a color image in which the toner image thickness increases due to color superposition, toner scattering during transfer, etc. In order to suppress image deterioration due to toner, optimization to precisely control the behavior of the toner in the electric field is necessary from the toner material side and the transfer system side. In addition, a transfer system that can prevent toner scattering is also required.

  As a cleaning system, in combination with a highly durable photoconductor, blades, electrostatic brushes, magnetic brushes, webs, and simultaneous development cleaning methods are used to continuously and reliably apply toner whose shape is controlled such as small particles and spheres. In addition, it is important to optimize the cleaning system without depending on the environment from the toner material, structure, and hardware system.

  In order to reduce the price per sheet, it is necessary to reduce the toner consumption by reducing the toner particle size and optimizing the amount of colorant, which also affects the uniformity of image quality. It becomes easy. By realizing a highly reliable image forming system using the means described above, it is possible to reduce the “sag” (waste output for obtaining stable image quality), which has a large price impact in printing, and to reduce the maintenance load. It is also important to actually reduce the price per sheet.

  For handling thin paper and thick paper, fixing after fixing from a fixing member such as a fixing roll is easy even for loose paper such as thin paper, plastic film, etc. In some cases, a toner material capable of low-temperature fixing capable of suppressing power consumption is essential. Fixing at a low temperature or low pressure reduces the stress on the transfer paper, and can suppress problems such as misregistration because the transfer paper can be prevented from stretching, curling and wavy. In order to avoid image defects such as spots and streaks due to oil and poor writing performance, an oilless toner containing an oilless fixing device and a release material inside the toner is required.

  In addition, in order to achieve image durability that is comparable to normal printed images and does not cause problems under various usage conditions, the resin properties used in conventional toners must be further improved. I must.

  In order to make the gloss characteristics of an image more flexible and uniform, it is important to optimize the fixing device as well as control the viscoelasticity of the toner. In order to obtain high-quality images based on offset printing, it is important to increase the market value to achieve the optimum gloss for the paper used. From three parties: toner, paper, and fixing system Optimization is required.

  Furthermore, a feature that has recently been promoted in fields such as on-demand printing is its environmental load performance. By making printing work on-demand through the network, it is possible to reduce the environmental burden associated with inventory, movement, and disposal of printed materials that are likely to occur during normal printing, etc. . In addition, since the organic solvent used in the ink used in a normal printing press is not used in the dry toner used in normal electrophotography, the environmental burden associated with VOC can be fundamentally reduced. However, for further improvement, not only the reduction of electrical energy due to image fixing and hardware condition maintenance, but also the odor and volatile content from the heated and melted resin generated during fixing, carcinogenicity, or the environment. Reduction or non-use of hormonal suspect substances, suppression of out-of-machine discharge of small particle size toner components are also important issues, and the recyclability of discarded toner and printing paper needs to be considered.

  As described above, in order to meet the demands of graphic arts and short run printing areas, a technique in which the conventional electrophotographic technique is further advanced as a total system is required.

  To obtain high-quality color images with excellent wear resistance and high durability, and high toner transfer efficiency, a toner with a flat viscosity after melting, that is, storage elasticity after melting the toner. It is effective to use a crystalline toner having a moderate temperature gradient, but at this time, gloss of the image and uneven color development occur.

  Therefore, the present invention has been made to solve the above problems in the image forming method, and the object of the present invention is to reduce image unevenness such as uneven toner amount, uneven gloss, and uneven color difference, and the like. It is an object of the present invention to provide an image forming method capable of forming a high-quality and high-quality color image having a wide color reproduction range without causing any uneven gloss or color development of the image.

  As a result of diligent studies to achieve the above object, the present inventors have used a crystalline toner having a flat viscosity after melting and a transfer paper having little unevenness of the surface to prevent this problem. Fixing time conditions of about 40 ms are common, but fixing is performed for a relatively long time, so that fixing stability is excellent, and image unevenness such as toner unevenness, color difference unevenness, and gloss unevenness is extremely small. The present invention has been completed by finding that it is excellent in development and transferability and can form high-quality and high-quality color images.

  In general electrophotographic transfer paper, even if it is coated paper (coated paper) with a smooth surface on the image transfer side, the quality of the base paper (base paper) is uneven, and the texture index is low. Since transfer paper is used (FIGS. 1-2), it is considered that this effect was unavoidable when crystalline toner was used to improve image quality and image quality. On the other hand, in the image forming method of the present invention, since the base paper is homogeneous and a transfer paper having a high texture index is used (FIG. 1-1), the influence of temperature unevenness during fixing is reduced, and the crystalline toner is used. It is considered that the characteristics were effectively extracted, and as a result, the image unevenness was extremely small, the development / transferability was excellent, and a color image with high image quality and high quality could be formed.

  That is, according to the present invention, a crystalline toner having a storage elastic modulus gradient of 0.02 log (Pa) / ° C. or less at Tm + 20 ° C. to Tm + 50 ° C. is used as a toner image on a transfer paper having a formation index of 20 or more. The image forming method is characterized by transferring and fixing the toner image with a fixing time of 50 ms to 500 ms. The gradient of the elastic modulus of the crystalline toner after melting with respect to the temperature is preferably small from the viewpoint of reducing the influence of temperature change during fixing and realizing the uniformity of the fixed image. Specifically, the gradient of the storage elastic modulus with respect to temperature at Tm + 20 ° C. to Tm + 50 ° C. is preferably 0.02 log (Pa) / ° C. or less, and more preferably 0.017 log (Pa) / ° C. or less.

  The fixing time is the time from when the portion to be fixed enters to the curl nip portion until it comes out. This fixing time can be controlled by adjusting the fixing speed. That is, the fixing time can be shortened by increasing the paper feed speed. Further, by using an elastic roll or the like, the fixing time can be extended by widening the nip width.

  Since the fixing time is set to be relatively long, the roll surface temperature at the time of fixing is sufficient to be lower than the conventional temperature. In electrophotographic image formation, heat fixing at a temperature far exceeding 100 ° C., which is usually the boiling point of water, is necessary, but in graphic arts and short run printing areas, fixing by evaporation of moisture from the transfer paper at the time of fixing. Image roughness due to unevenness and blistering (roughness of the image surface due to moisture evaporation), image unevenness due to these, and color differences between pages, and the like become problems. Also in the image forming method of the present invention, the roll surface temperature at the time of fixing is preferably low, specifically 140 ° C. or lower, and the lower the temperature is, the more preferable is 130 ° C. or lower because moisture evaporation is suppressed. The following is more preferable. By low-temperature fixing, a stable and high-quality fixed image can be provided even on a transfer medium containing water, and an image forming method excellent in energy saving can be provided.

In the image forming method of the present invention, the maximum amount of monochromatic toner is preferably 0.35 mg / cm ² or less, and more preferably 0.3 mg / cm ² or less from the viewpoint of realizing high image quality. . In particular, when the amount of toner paste per unit area is reduced for the purpose of improving the image quality, image unevenness such as toner unevenness, image unevenness, color difference unevenness, and gloss unevenness due to these effects may become more prominent. However, even when an image having a low toner amount (low TMA) is formed as compared with the conventional case, the image forming method of the present invention uses a transfer paper with less unevenness of texture and has a crystallinity. By reducing the temperature dependence of the storage elastic modulus after melting the toner below a certain level and fixing it for a long fixing time, the influence of temperature unevenness during fixing is reduced, and color unevenness and defects caused by image fixing unevenness are reduced. Occurrence can be suppressed, and it is possible to provide a fixed image with a small color difference due to nonuniformity of melting and the like, and it is possible to form an image with extremely excellent image quality without image defects.

  The weight average particle diameter of the crystalline toner is preferably 5 μm or less, more preferably 4.8 μm or less, and particularly preferably 4.5 μm or less. Compared to the conventional case, by using a toner with a smaller particle size, when forming an image with a low toner paste (low TMA), it suppresses the occurrence of uneven color and defects due to uneven fixing of the image. A high-quality image can be formed. Further, it is effective to make the toner having a smaller particle diameter more spherical, and to increase the amount of the colorant component contained in the toner than before, and by narrowing the particle size distribution of the toner, It is possible to reduce the occurrence of image defects such as scattering of the image line portion and voids in the character image in a uniform and wide reproduction range. By reducing the amount of toner adhered per unit area and using a toner having a small particle size, it is possible to form a high-quality and high-quality color image having excellent fixability and extremely few image defects.

  In another aspect of the present invention, the crystalline toner has a shape factor SF1 of 125 or less. The shape factor SF1 of the crystalline toner is preferably 125 or less in order to suppress the occurrence of color unevenness and defects in the development / transfer stage, to have good development / transferability, and to form a uniform image.

  In another embodiment of the present invention, the volume average particle size distribution index GSDv of the crystalline toner is 1.20 or less. In order to prevent toner scattering and image loss during development and transfer, the volume average particle size distribution index GSDv of the crystalline toner is preferably 1.20 or less.

  In another embodiment of the present invention, the colorant content of the crystalline toner is 8% by mass or more. In order to realize better coloring power, the colorant content of the crystalline toner is preferably 8% by mass or more, and more preferably 9% by mass or more.

  In another embodiment of the present invention, the surface property index value represented by the following formula of the crystalline toner is 2.0 or less.

(Surface property index value) = (actual value of specific surface area) / (calculated value of specific surface area)
(Calculated value of specific surface area) = 6Σ (n × R ² ) / {ρ × Σ (n × R ³ )}
(Where n = number of particles in the channel in the Coulter counter, R = channel particle diameter in the Coulter counter, ρ = toner density, and the number of channel divisions is 16.)

  By adjusting the surface property index value defined by the above formula to 2.0 or less, the crystalline toner used in the image forming method of the present invention exhibits a good transfer property, particularly a paper or transfer medium having a large surface roughness. Can achieve high image quality with high transfer efficiency.

  In order to reduce the unevenness of the transfer paper, which is the fixing medium, a base paper screen or vortex cleaner is installed just in front of the head box of the paper machine so that the flow direction of the raw material is not constant, guar gum, Locust bean gum, mannogalactan, deacetylated karaya gum, alginate, carboxymethylcellulose, methylcellulose, hydroxyethylcellulose, etc. It is not something.

  The unevenness of formation can also be reduced by providing a coating layer on the base paper. The coating layer in the coated paper is formed to increase the smoothness, uniformity, opacity and whiteness of the transfer paper, reinforce the strength, and improve the image forming suitability of the transfer paper. The coating layer is mainly composed of a pigment, a pigment dispersant, a binder resin and the like. As the pigment, kaolin clay, delaminated clay, Georgia clay, China clay, calcium carbonate, satin white, titanium oxide, aluminum hydroxide and the like are used. As the pigment dispersant, sodium pyrophosphate, sodium polyacrylate, sodium hexametaphosphate, sodium tripolyphosphate, sodium styrene-maleic acid copolymer, and the like are used. As the binder resin, polyvinyl alcohol, carboxymethyl cellulose, styrene butadiene latex, various starches, casein, soy protein, vinyl acetate latex, vinyl acetate-dibutyl maleate copolymer, and the like are used.

  These coatings are applied to transfer paper using a roll coater, air knife coater, rod coater, cast coater, etc. after dispersion, dissolution and preparation of pigments and binders, infrared dryers, drum dryers, air cap dryers, It is dried by an air foil dryer or an air conditioner bare dryer.

  The average mass ratio is around 25% pigment and 5% binder resin with respect to 70% of the base paper.

  The transfer paper used in the image forming method of the present invention is usually formed using wood pulp as a main raw material, and a filler is blended in the transfer paper. The filler used here is a white filler such as heavy or light calcium carbonate, talc, kaolin, clay, titanium dioxide, zeolite, white carbon, among others, since the coloring property of the coloring material is good, calcium carbonate. Is preferred. This filler is blended in the range of 5 to 30% by mass, preferably 10 to 25% by mass in order to increase the gap of the transfer paper and improve the opacity. If it exceeds 30% by mass, the strength of the transfer paper is lowered and the generation of paper dust becomes remarkable, which is not preferable.

  The texture index of the transfer paper used in the image forming method of the present invention is 20 or more, preferably 25 or more. In the case of transfer paper (FIG. 1-1) having a high texture index, the quality of the base paper is particularly uniform. On the other hand, in the case of a transfer sheet having a low texture index (FIGS. 1-2), the paper quality of the base sheet is particularly uneven. When the texture index is less than 20, the color mixing blur is worsened and the density unevenness is worsened. This texture index is calculated by M.M. K. A 3D sheet analyzer (M / K950) manufactured by Systems was used, and the aperture of the analyzer was measured with a diameter of 1.5 mm. First, the sample is mounted on the rotating drum of the 3D sheet analyzer, and the local basis weight difference in the sample is detected by the light source mounted on the drum shaft and the photodetector outside the drum. Measure as The measurement target range at this time is defined by the diameter of the diaphragm attached to the light incident part of the photodetector. Next, the light intensity difference (deviation) is amplified, A / D converted, classified into 64 photometric basis weight classes, and 100,000 pieces of data are taken in one scan. Get the frequency. And the highest frequency (peak value) of the histogram is divided by the number of classes having a frequency of 100 or more out of those classified into classes corresponding to 64 micro basis weights. Calculated as an index. The transfer sheet texture index indicates that the larger the value, the less the paper quality is uneven and the texture is better.

  The crystalline toner used in the image forming method of the present invention is obtained by mixing at least one type of crystalline resin fine particle dispersion and at least one type of colorant dispersion, and adding an aggregating agent to form aggregated particles. The toner particles can be formed by heating to a temperature equal to or higher than the glass transition point of the resin fine particles and fusing the aggregated particles.

  As the colorant contained in the crystalline toner used in the image forming method of the present invention, for example, the following colorant can be used.

  Examples of the black pigment include carbon black, copper oxide, manganese dioxide, aniline black, activated carbon, nonmagnetic ferrite, and magnetite.

  Examples of yellow pigments include yellow lead, zinc yellow, yellow iron oxide, cadmium yellow, chrome yellow, hansa yellow, hansa yellow 10G, benzidine yellow G, benzidine yellow GR, selenium yellow, quinoline yellow, and permanent yellow NCG. be able to.

  Examples of the orange pigment include red chrome yellow, molybdenum orange, permanent orange GTR, pyrazolone orange, vulcan orange, benzidine orange G, indanthrene brilliant orange RK, and indanthrene brilliant orange GK.

  Red pigments include Bengala, Cadmium Red, Red Plum, Mercury Sulfide, Watch Young Red, Permanent Red 4R, Risor Red, Brilliantamine 3B, Brilliantamine 6B, Daypon Oil Red, Pyrazolone Red, Rhodamine B Lake, Lake Red C Naphthol red such as Rose Bengal, Eoxin Red, Alizarin Lake, Pigment Red 146, 147, 184, 185, 155, 238 and 269.

  Blue pigments include bitumen, cobalt blue, alkali blue rake, Victoria blue rake, fast sky blue, indanthrene blue BC, aniline blue, ultramarine blue, calco oil blue, methylene blue chloride, phthalocyanine blue, phthalocyanine green, malachite green oxare. Rate.

  Examples of purple pigments include manganese purple, fast violet B, and methyl violet lake.

  Examples of the green pigment include chromium oxide, chromium green, pigment green, malachite green lake, final yellow green G and the like.

  Examples of white pigments include zinc white, titanium oxide, antimony white, and zinc sulfide.

  Examples of extender pigments include barite powder, barium carbonate, clay, silica, white carbon, talc, and alumina white.

  Examples of the dye include various dyes such as basic, acidic, dispersed, and direct dyes, such as nigrosine, methylene blue, rose bengal, quinoline yellow, and ultramarine blue.

  These colorants are used alone or in combination. With respect to these colorants, for example, a dispersion of colorant particles can be prepared using a media type dispersing machine such as a rotary shearing homogenizer, a ball mill, a sand mill, or an attritor, or a high-pressure opposed collision type dispersing machine. Further, these colorants can be dispersed in an aqueous system by a homogenizer using a polar surfactant.

  The colorant for the crystalline toner used in the image forming method of the present invention is selected from the viewpoints of hue angle, saturation, brightness, weather resistance, OHP permeability, and dispersibility in the toner.

  The colorant can be added in the range of 4 to 20% by mass with respect to the total mass of the toner constituent solids.

  When using a magnetic substance as a black colorant, 12-240 mass% can be added unlike other colorants.

  The blending amount of the colorant is a necessary amount for securing the color developability at the time of fixing. Moreover, OHP transparency and color developability can be ensured by setting the center diameter (median diameter) of the colorant particles in the toner to 100 to 330 nm.

  The center diameter of the colorant particles was measured with, for example, a laser diffraction particle size distribution analyzer (LA-700, manufactured by Horiba, Ltd.).

  Further, when used as a magnetic toner, magnetic powder may be contained. Specifically, a material that is magnetized in a magnetic field is used, but a ferromagnetic powder such as iron, cobalt, or nickel, or a compound such as ferrite or magnetite is used.

  When the crystalline toner used in the image forming method of the present invention is obtained in an aqueous phase, it is necessary to pay attention to the aqueous phase migration of the magnetic material, and preferably the surface of the magnetic material is modified beforehand, for example, hydrophobized. It is preferable to perform a treatment or the like.

  The gradient of the storage elastic modulus after melting with respect to temperature is important in terms of reducing the influence of temperature change during fixing and realizing the uniformity of a fixed image. It is effective to use a crystalline toner using a crystalline resin as a resin. Examples of the crystalline resin include the following.

  As the crystalline resin, a crystalline polyester resin is preferable, and an aliphatic crystalline polyester resin having an appropriate melting point is more preferable. Hereinafter, a crystalline polyester resin will be described as an example.

Some crystalline aliphatic polyesters, such as polycaprolactone, progress through ring-opening polymerization, but many are synthesized from an acid (dicarboxylic acid) component and an alcohol (diol) component. , “Acid-derived constituent component” refers to a constituent site that was an acid component before the synthesis of the polyester resin, and “alcohol-derived constituent component” refers to a constituent site that was the alcohol component before the synthesis of the polyester resin. Point to.

  When the polyester resin is not crystalline, that is, amorphous, it is impossible to maintain toner blocking resistance and image storage stability while ensuring good low-temperature fixability. Therefore, in the present invention, the “crystalline polyester resin” refers to a resin having a clear endothermic peak rather than a stepwise endothermic amount change in differential scanning calorimetry (DSC). In the case of a polymer obtained by copolymerizing other components with respect to the crystalline polyester main chain, when the other components are 50% by mass or less, this copolymer is also called crystalline polyester.

<Acid-derived components>
The acid-derived constituent component is preferably an aliphatic dicarboxylic acid, and particularly preferably a linear carboxylic acid. For example, succinic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelic acid, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, 1,11-undecanedicarboxylic acid Acid, 1,12-dodecanedicarboxylic acid, 1,13-tridecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,16-hexadecanedicarboxylic acid, 1,18-octadecanedicarboxylic acid, etc., or lower alkyl esters thereof And acid anhydrides, but are not limited thereto.

  As the acid-derived constituent component, in addition to the above-mentioned aliphatic dicarboxylic acid-derived constituent component, constituent components such as a dicarboxylic acid-derived constituent component having a double bond and a dicarboxylic acid-derived constituent component having a sulfonic acid group are included. Is preferred.

  The component derived from a dicarboxylic acid having a double bond is derived from a lower alkyl ester or acid anhydride of a dicarboxylic acid having a double bond, in addition to a component derived from a dicarboxylic acid having a double bond. Components are also included. The dicarboxylic acid-derived constituent component having a sulfonic acid group is derived from a lower alkyl ester or acid anhydride of a dicarboxylic acid having a sulfonic acid group, in addition to a constituent component derived from a dicarboxylic acid having a sulfonic acid group. Components are also included.

  The dicarboxylic acid having a double bond can be suitably used to prevent hot offset at the time of fixing since the entire resin can be crosslinked using the double bond. Examples of such dicarboxylic acids include, but are not limited to, fumaric acid, maleic acid, 3-hexenedioic acid, and 3-octenedioic acid. Moreover, these lower alkyl esters, acid anhydrides, etc. are also mentioned. Among these, fumaric acid, maleic acid and the like are preferable in terms of cost.

  The dicarboxylic acid having a sulfonic acid group is effective in that it can favorably disperse a coloring material such as a pigment.

  Further, when emulsifying or suspending the entire resin in water to produce toner mother particles into fine particles, if there are sulfonic acid groups, emulsification or suspension is possible without using a surfactant, as will be described later. . Examples of such a dicarboxylic acid having a sulfone group include, but are not limited to, 2-sulfoterephthalic acid sodium salt, 5-sulfoisophthalic acid sodium salt, and sulfosuccinic acid sodium salt. Moreover, these lower alkyl esters, acid anhydrides, etc. are also mentioned. Among these, 5-sulfoisophthalic acid sodium salt is preferable in terms of cost.

  Content of acid-derived components other than aliphatic dicarboxylic acid-derived components (dicarboxylic acid-derived components having double bonds and / or dicarboxylic acid-derived components having sulfonic acid groups) in the acid-derived components 1 to 20 mol% is preferable, and 2 to 10 mol% is more preferable.

When the content is less than 1 constituent mol%, pigment dispersion may not be good, the emulsified particle diameter may be large, and adjustment of the toner diameter by aggregation may be difficult. On the other hand, if it exceeds 20 component mol%, the crystallinity of the polyester resin is lowered, the melting point is lowered, the image storage stability is deteriorated, or the emulsion particle size is too small to dissolve in water, and no latex is produced. Sometimes.
In the present invention, “constituent mol%” refers to the percentage when each constituent component (acid-derived constituent component, alcohol-derived constituent component) in the polyester resin is 1 unit (mol).

<Constituents derived from alcohol>
The alcohol component is preferably an aliphatic dicarboxylic acid, for example, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol. 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-dodecanediol, 1,12-undecanediol, 1,13-tridecanediol, 1,14-tetradecanediol 1,18-octadecanediol, 1,20-eicosanediol, and the like, but are not limited thereto.

  When the alcohol-derived constituent component is an aliphatic diol-derived constituent component, the content of the aliphatic diol-derived constituent component is 80 constituent mol% or more, and other components are included as necessary. Furthermore, when the alcohol-derived constituent component is an aliphatic diol-derived constituent component, the content of the aliphatic diol-derived constituent component is preferably 90 constituent mol% or more.

  When the content of the aliphatic diol-derived constituent component is less than 80 constituent mol%, the crystallinity of the polyester resin is lowered and the melting point is lowered, so that toner blocking resistance, image storage stability, and low-temperature fixability are deteriorated. End up.

  Other components included as necessary include diol-derived components having double bonds and diol-derived components having sulfonic acid groups.

  Examples of the diol having a double bond include 2-butene-1,4-diol, 3-butene-1,6-diol, 4-butene-1,8-diol, and the like.

  Examples of the diol having a sulfonic acid group include 1,4-dihydroxy-2-sulfonic acid benzene sodium salt, 1,3-dihydroxymethyl-5-sulfonic acid benzene sodium salt, and 2-sulfo-1,4-butanediol sodium. Examples include salts.

  When adding an alcohol-derived component other than these linear aliphatic diol-derived components, that is, when adding a diol-derived component having a double bond and / or a diol-derived component having a sulfonic acid group, The content of the diol-derived constituent component having a double bond and / or the diol-derived constituent component having a sulfonic acid group in the alcohol-derived constituent component is preferably 1-20 constituent mol%, and more preferably 2-10 constituent mol%.

  When the content of the alcohol-derived constituent component other than the aliphatic diol-derived constituent component is less than 1 constituent mol% with respect to the total alcohol-derived constituent component, the pigment dispersion is not good or the emulsion particle size is increased. In some cases, it is difficult to adjust the toner diameter by aggregation. On the other hand, if it exceeds 20 component mol%, the crystallinity of the polyester resin is lowered, the melting point is lowered, the image storage stability is deteriorated, or the emulsion particle size is too small to dissolve in water, and no latex is produced. Sometimes.

  The melting point of the binder resin of the crystalline toner used in the image forming method of the present invention is preferably 50 to 120 ° C, more preferably 60 to 110 ° C. When the melting point is lower than 50 ° C., the storage stability of the toner and the storage stability of the toner image after fixing become a problem. On the other hand, when the temperature is higher than 120 ° C., sufficient low-temperature fixing cannot be obtained as compared with the conventional toner.

  For the measurement of the melting point of the crystalline resin, a differential scanning calorimeter (DSC) was used, and the input shown in JIS K-7121 when measuring from room temperature to 150 ° C. at a heating rate of 10 ° C. per minute. It can be determined as the melting peak temperature of the compensated differential scanning calorimetry. The crystalline resin may show a plurality of melting peaks, but in the present invention, the maximum peak is regarded as the melting point.

  The method for producing the polyester resin is not particularly limited, and can be produced by a general polyester polymerization method in which an acid component and an alcohol component are reacted. For example, direct polycondensation, transesterification method, etc. Produced separately for different types. The molar ratio (acid component / alcohol component) when the acid component reacts with the alcohol component varies depending on the reaction conditions and the like, and cannot be generally stated, but is usually about 1/1.

  The production of the polyester resin can be carried out at a polymerization temperature of 180 to 230 ° C., and the reaction system is reacted under reduced pressure as necessary to remove water and alcohol generated during condensation.

  When the monomer is not dissolved or compatible at the reaction temperature, a solvent having a high boiling point may be added as a solubilizer and dissolved. In the polycondensation reaction, the dissolution auxiliary solvent is distilled off. If there is a monomer with poor compatibility in the copolymerization reaction, the monomer with poor compatibility and the monomer and the acid or alcohol to be polycondensed may be condensed in advance before polycondensation with the main component. .

  Catalysts that can be used in the production of the polyester resin include alkali metal compounds such as sodium and lithium, alkaline earth metal compounds such as magnesium and calcium, and metal compounds such as zinc, manganese, antimony, titanium, tin, zirconium, and germanium. , Phosphorous acid compounds, phosphoric acid compounds, amine compounds, etc., specifically, sodium acetate, sodium carbonate, lithium acetate, lithium carbonate, calcium acetate, calcium stearate, magnesium acetate, zinc acetate, stearic acid Zinc, zinc naphthenate, zinc chloride, manganese acetate, manganese naphthenate, titanium tetraethoxide, titanium tetrapropoxide, titanium tetraisopropoxide, titanium tetrabutoxide, antimony trioxide, triphenylantimony, trib Ruantimony, tin formate, tin oxalate, tetraphenyltin, dibutyltin dichloride, dibutyltin oxide, diphenyltin oxide, zirconium tetrabutoxide, zirconium naphthenate, zirconyl carbonate, zirconyl acetate, zirconyl stearate, zirconyl octylate, germanium oxide, triphenyl Examples of the compound include phosphite, tris (2,4-di-t-butylphenyl) phosphite, ethyltriphenylphosphonium bromide, triethylamine, and triphenylamine.

  When the emulsion aggregation method is used, the method for producing a crystalline toner for developing an electrostatic charge image used in the image forming method of the present invention is to form aggregated particles containing the crystalline polyester in a dispersion containing at least crystalline polyester fine particles. It is preferable to include at least a coagulation step, an adhesion step of attaching amorphous polymer fine particles to the surface of the aggregated particles, and a fusion step of fusing the aggregated particles by heating. preferable. Hereinafter, each step will be described in detail.

-Emulsification process-
In the emulsification step, the raw material dispersion is a solution in which a binder resin emulsified particle (hereinafter abbreviated as “resin particle”) is mixed with an aqueous medium and, if necessary, a dispersion containing a colorant and a release agent. Is formed by applying a shearing force. Therefore, the binder resin needs to be dispersed in advance as resin particles in the raw material dispersion.

  As an average particle diameter of the said resin particle, it is 1 micrometer or less normally, and it is preferable that it is 0.01-1 micrometer. When the average particle diameter exceeds 1 μm, the particle diameter distribution of the finally obtained crystalline toner for developing electrostatic images is broadened or free particles are generated, which tends to deteriorate performance and reliability. On the other hand, when the average particle size is within the above range, there are no disadvantages, and the uneven distribution among the toners is reduced, the dispersion in the toners is improved, and the variation in performance and reliability is advantageous. The average particle diameter can be measured using, for example, a Coulter counter.

  Examples of the dispersion medium in the dispersion include an aqueous medium and an organic solvent.

  Examples of the aqueous medium include water such as distilled water and ion exchange water, and alcohols. These may be used individually by 1 type and may use 2 or more types together. In the present invention, it is preferable to add and mix a surfactant in the aqueous medium. Although it does not specifically limit as surfactant, For example, anionic surfactants, such as a sulfate ester type | system | group, a sulfonate salt type | system | group, a phosphate ester type | system | group, soap type; Nonionic surfactants such as polyethylene glycol-based, alkylphenol ethylene oxide adduct-based, polyhydric alcohol-based, and the like. Among these, anionic surfactants and cationic surfactants are preferable. The nonionic surfactant is preferably used in combination with the anionic surfactant or the cationic surfactant. The said surfactant may be used individually by 1 type, and may use 2 or more types together.

  Specific examples of the anionic surfactant include sodium dodecylbenzenesulfonate, sodium dodecylsulfate, sodium alkylnaphthalenesulfonate, sodium dialkylsulfosuccinate and the like. Specific examples of the cationic surfactant include alkylbenzene dimethyl ammonium chloride, alkyl trimethyl ammonium chloride, distearyl ammonium chloride and the like. Among these, ionic surfactants such as anionic surfactants and cationic surfactants are preferable.

  Examples of the organic solvent include ethyl acetate and toluene, which are appropriately selected according to the binder resin.

  When the resin particle is a homopolymer or copolymer (vinyl resin) of a vinyl monomer such as the ester having a vinyl group, the vinyl nitrile, the vinyl ether, or the vinyl ketone. By conducting emulsion polymerization or seed polymerization of the vinyl monomer in an ionic surfactant, resin particles made of a vinyl monomer homopolymer or copolymer (vinyl resin) are made ionic. A dispersion obtained by dispersing in a surfactant is prepared.

  When the resin particle is a resin other than a homopolymer or a copolymer of the vinyl monomer, the resin can be dissolved in an oily solvent having a relatively low solubility in water. The resin is dissolved in the oily solvent, and this solution is dispersed in water together with an ionic surfactant and polymer electrolyte using a disperser such as a homogenizer, and then the oily solvent is evaporated by heating or decompression. Thus, a dispersion liquid in which resin particles made of resin other than vinyl resin are dispersed in an ionic surfactant is prepared.

  On the other hand, when the resin particles are a crystalline polyester and an amorphous polyester resin, some or all of the functional groups that contain a functional group that can be anionic by neutralization, have self-water dispersibility, and can be hydrophilic. Is neutralized with a base and can form a stable aqueous dispersion under the action of an aqueous medium. In the crystalline polyester and the amorphous polyester resin, the functional group that can become a hydrophilic group by neutralization is an acidic group such as a carboxyl group or a sulfone group. As the neutralizing agent, for example, sodium hydroxide, potassium hydroxide, water Examples thereof include inorganic bases such as lithium oxide, calcium hydroxide, sodium carbonate and ammonia, and organic bases such as diethylamine, triethylamine and isopropylamine.

  Further, when a polyester resin that does not disperse in water, that is, does not have self-water dispersibility, is used as a binder resin, the resin solution and / or an aqueous medium mixed with the resin solution, as described later, 1 μm easily when dispersed with a polymer electrolyte such as a surfactant, polymer acid, polymer base, etc., heated above the melting point, and treated with a homogenizer or pressure discharge type disperser capable of applying a strong shear force The following microparticles can be made. When this ionic surfactant or polymer electrolyte is used, it is appropriate that the concentration in the aqueous medium is about 0.5 to 5 wt%.

  In addition, conventional resins can be used at the same time for the purpose of further modifying the above-mentioned resins. Examples of these binder resins include vinyl naphthalene, vinyl chloride, vinyl bromide, vinyl fluoride, vinyl acetate. Vinyl esters such as vinyl propionate, vinyl benzoate, vinyl butyrate, such as methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, n-octyl acrylate, 2-acrylic acid 2- Methylene aliphatic carboxylic esters such as chloroethyl, phenyl acrylate, methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide such as vinyl methyl ether, vinyl ethyl ether ,vinyl Monomers having a nitrogen-containing polar group such as vinyl ethers such as sobutyl ether, N-vinyl compounds such as N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrolidone, methacrylic acid and acrylic acid In addition, homopolymers and copolymers of vinyl monomers such as vinyl carboxylic acids such as cinnamic acid and carboxyethyl acrylate, and / or various polyesters, and various waxes can also be used.

  In the case of vinyl monomers, emulsion polymerization can be carried out using an ionic surfactant or the like to create a resin fine particle dispersion, and in the case of other resins, it is oily and has a relatively high solubility in water. If it is soluble in a low solvent, dissolve the resin in those solvents, disperse in fine particles in water with a disperser such as a homogenizer together with an ionic surfactant or polymer electrolyte, and then heat or reduce the solvent. The resin fine particle dispersion can be obtained by evaporating.

  The center diameter (median diameter) of the fine particles in the resin fine particle dispersion of the present invention thus obtained is 1 μm or less, preferably 50 to 400 nm, more preferably 70 to 350 nm.

  The center diameter of the resin fine particles was measured, for example, with a laser diffraction particle size distribution measuring device (LA-700, manufactured by Horiba, Ltd.).

  Also, magnetic materials such as ferrite, magnetite, reduced iron, cobalt, nickel, manganese and other metals, alloys, and compounds containing these metals are used as internal additives, and quaternary ammonium salt compounds, nigrosine-based as charge control agents. Various commonly used charge control agents such as compounds, dyes composed of complexes of aluminum, iron, chromium, and triphenylmethane pigments can be used, but the ionic strength that affects aggregation and temporary stability Materials that are difficult to dissolve in water are preferred in terms of control and reduction of wastewater contamination.

  Specific examples of the release agent used in the present invention include, for example, low molecular weight polyolefins such as polyethylene, polypropylene and polybutene, silicones which show a softening point by heating, oleic acid amide, erucic acid amide, ricinoleic acid amide, stearin Fatty acid amides such as acid amides, plant waxes such as carnauba wax, rice wax, candelilla wax, tree wax, jojoba oil, animal waxes such as beeswax, montan wax, ozokerite, ceresin, Examples thereof include mineral-based and petroleum-based waxes such as paraffin wax, microcrystalline wax, microcrystalline wax, Fischer-Tropsch wax, and modified products thereof.

  These waxes are hardly dissolved in a solvent such as toluene at room temperature or very little even if dissolved.

  These waxes are dispersed in water together with ionic surfactants, polymer electrolytes such as polymer acids and polymer bases, heated above the melting point, and have a strong shearing ability and pressure discharge type dispersers. (Gorin homogenizer, manufactured by Gorin Co., Ltd.) can be dispersed in the form of fine particles to prepare a dispersion of particles of 1 μm or less.

  Further, if necessary, a polymerizable ultraviolet stable monomer may be contained in order to improve the weather resistance of the image.

  Examples of polymerizable UV-stable monomers are 4- (meth) acryloyloxy-2,2,6,6-tetramethylpiperidine, 4- (meth) acryloylamino-2,2,6,6-tetrapiperidine, 4- (meth) acryloyloxy-1,2,2,6,6-pentamethylpiperidine, 4- (meth) acryloylamino-1,2,2,6,6 pentamethylpiperidine, 4-cyano-4- (meth) Piperidine compounds such as acryloylamino-2,2,6,6-tetramethylpiperidine, 1- (meth) acryloyl 4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine are effective. .

  These can be used alone or in combination of two or more.

  It is desirable to add these release agents in the range of 5 to 25% by mass with respect to the total mass of the toner constituting solids, in order to ensure the releasability of the fixed image in the oilless fixing system.

  The particle size of the obtained release agent particle dispersion was measured, for example, with a laser diffraction particle size distribution analyzer (LA-700, manufactured by Horiba, Ltd.). In addition, when using a release agent, after the resin fine particles, colorant particles and release agent particles are aggregated, it is possible to add a resin fine particle dispersion to adhere the resin fine particles to the surface of the aggregated particles. It is desirable from the viewpoint of securing the property.

  Examples of surfactants used for emulsion polymerization, seed polymerization, pigment dispersion, resin particles, release agent dispersion, aggregation, or stabilization thereof include sulfate ester, sulfonate, phosphate ester, soap Anionic surfactants such as amines, cationic surfactants such as amine salt types and quaternary ammonium salt types, and nonionic surfactants such as polyethylene glycols, alkylphenol ethylene oxide adducts, and polyhydric alcohols It is also effective to use them in combination, and general means such as a rotary shear type homogenizer, a ball mill having a media, a sand mill, and a dyno mill can be used for dispersion.

  In addition, the crystalline toner used in the image forming method of the present invention is dried in the same manner as a normal toner for the purpose of imparting fluidity and improving cleaning properties, and then inorganic fine particles such as silica, alumina, titania and calcium carbonate, and vinyl-based toner. Resin fine particles such as resin, polyester, and silicone can be used by adding to the toner particle surface while applying shear in a dry state.

  When adhering to the toner surface in water, examples of inorganic fine particles include silica, alumina, titania, calcium carbonate, magnesium carbonate, and tricalcium phosphate. It can be used by dispersing with a surfactant, polymer acid or polymer base.

  In the present invention, a surfactant can be used for resin emulsion polymerization, pigment dispersion, resin fine particle dispersion, mold release agent dispersion, aggregation, and aggregation particle stabilization. Specifically, sulfate surfactants, sulfonates, phosphates, soaps and other anionic surfactants, amine salts, quaternary ammonium salts and other cationic surfactants, polyethylene glycols, It is also effective to use a nonionic surfactant such as an alkylphenol ethylene oxide adduct system or a polyhydric alcohol system. As a dispersing means, a general method such as a ball mill, sand mill, or dyno mill having a rotary shear homogenizer or a media is used. Can be used

  After completing the coalescence and coalescence process of the aggregated particles, the desired toner particles are obtained through an optional washing process, solid-liquid separation process, and drying process. Replacement cleaning is desirable. Moreover, although there is no restriction | limiting in particular in a solid-liquid separation process, From the point of productivity, suction filtration, pressure filtration, etc. are suitable. Further, the drying process is not particularly limited, but freeze drying, flash jet drying, fluidized drying, vibration fluidized drying and the like are preferably used from the viewpoint of productivity.

  The cumulative volume average particle diameter D50 of the crystalline toner used in the image forming method of the present invention is suitably in the range of 3.0 to 4.8 μm, more preferably in the range of 3.0 to 4.5 μm. When D50 is less than 3.0 μm, the chargeability becomes insufficient and the developability may be lowered. On the other hand, if it exceeds 4.8 μm, the uniformity of the image is lowered.

  The volume average particle size distribution index GSDv of the crystalline toner used in the image forming method of the present invention is preferably 1.20 or less. When GSDv exceeds 1.20, the resolution is lowered, causing image defects such as toner scattering and fogging.

  For the toner, the following resin fine particle dispersion, colorant particle dispersion, and release agent particle dispersion were prepared, respectively, and a metal salt polymer was added while mixing and stirring the mixture at a predetermined ratio. To form aggregated particles. Next, an inorganic hydroxide is added to adjust the pH in the system from weakly acidic to neutral, and then the mixture is heated to a temperature equal to or higher than the glass transition point of the resin fine particles to fuse and unite. After completion of the reaction, a desired toner is obtained through sufficient washing, solid-liquid separation, and drying processes.

  The image forming method of the present invention reduces image unevenness such as toner unevenness, color difference unevenness, and gloss unevenness, and is suitable for graphic arts and short run printing areas and has a stable and wide color reproduction range. A quality color image can be formed.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited at all.

The cumulative volume average particle size D50 and the average particle size distribution index of the present invention are based on the particle size distribution measured by a measuring instrument such as Coulter Counter TAII (manufactured by Nikka Kisha Co., Ltd.) or Multisizer II (manufactured by Nikka Kisha Co., Ltd.). The cumulative distribution is drawn from the small particle size side for the divided particle size range (channel), and the particle size that becomes 16% cumulative is the volume D16v, the number D16P, the particle size that becomes 50% cumulative. Is defined as a volume D50v, a number D50P, and a particle size of 84% cumulative is defined as a volume D84v, a number D84P. Using these, the volume average particle size distribution index (GSDv) is calculated as (D84v / D16V) ^1/2 and the number average particle size distribution index (GSDp) is calculated as (D84P / D16P) ^1/2 .

The shape factor SF1 of the crystalline toner used in the image forming method of the present invention is suitably in the range of 100 to 140, preferably 110 to 135 from the viewpoint of image formability. The shape factor SF1 of the present invention is obtained as follows. First, an optical microscope image of the toner dispersed on the slide glass is taken into a Luzex image analyzer through a video camera, and the peripheral length (ML) and the projection area (A) of 50 or more toners are measured. (Multiplier / projected area = ML ² / A × π / 4 × 100) was defined as the toner shape factor SF1.

<Measurement of melting point>
The melting point (Tm) of the crystalline polyester resin was measured as follows.

  Measurement was performed using a thermal analyzer of a differential scanning calorimeter (manufactured by Mac Science: DSC3110, thermal analysis system 001) (hereinafter abbreviated as “DSC”). The measurement was performed from room temperature to 150 ° C. at a heating rate of 10 ° C. per minute, and the melting point was obtained by analyzing according to JIS standards (see JIS K-7121).

  In addition, all the half value widths in the endothermic peak of the crystalline polyester resin are 6 ° C. or less, and it was confirmed that the crystalline polyester resin has crystallinity. In addition, the amorphous polymer showed a glass transition point (Tg) because no clear melting point was observed.

<Measurement of viscoelasticity>
The viscoelasticity of the crystalline toner was measured as follows.

  It measured using the rotating plate type | mold rheometer (RDA2RHIOS system Ver.4.3.2, the product made from a rheometrics scientific FE Co., Ltd.).

  The measurement was carried out by setting each electrophotographic toner to be measured on a sample holder, with a heating rate of 1 ° C./min, a frequency of 1 rad / sec, a strain of 20% or less, and a detection torque within the range of the measurement compensation value. In addition, the sample holder was properly used for 8 mm and 20 mm as needed.

  The specific measurement content is a change in the storage elastic modulus GL with respect to a temperature change. The value of | logGL (Tm + 20) −logGL (Tm + 50) | / 30 was calculated using the obtained change in the storage elastic modulus GL with respect to the temperature change.

(Measurement of texture index)
The texture index was measured by the following method.

  Using a Micro Formation Tester from MKS, light is irradiated from the back of the transfer paper affixed to a transparent Pyrex (registered trademark) drum, and the amount of light transmitted through the paper is received by the detector. After conversion, it is converted into data by AD conversion. At that time, data is collected over the entire area of 180 × 250 mm by moving the high source and detector in the axial direction of the drum. The light intensity distribution of the data is divided into 64 equal parts (classification), and a histogram of the frequency number per light intensity can be written. At that time, the formation index (FI ground index) is obtained by taking the ratio of the number of classes in which frequencies of 100 or more have appeared and the frequency of the peak class.

  FI = ((peak value (frequency)) / (number of classes of 100 degrees or more)) × (1/100)

-Preparation of crystalline polyester resin dispersion (1)-
In a heat-dried three-necked flask, 92.5 mol% of dimethyl sebacate and 7.5 mol% of 5-t-butylisophthalic acid, ethylene glycol (2 mol times the amount of the acid component), and Ti ( OBu) ₄ (0.012% by mass with respect to the acid component), and then the pressure in the container is reduced by a depressurization operation, and an inert atmosphere is established with nitrogen gas. Reflux was performed for 5 hours. Then, excess ethylene glycol was removed by distillation under reduced pressure, the temperature was gradually raised to 220 ° C., and the mixture was stirred for 2 hours. When the mixture became viscous, the molecular weight was confirmed by GPC, and the weight average molecular weight became 12,000. The vacuum distillation was stopped and air-cooled to obtain crystalline polyester (1).

  Next, 80 parts by mass of the crystalline polyester (1) and 720 parts by mass of deionized water are placed in a stainless beaker, placed in a warm bath, and heated to 95 ° C. When the crystalline polyester resin melted, the mixture was stirred at 8000 rpm using a homogenizer (manufactured by IKA: Ultra Tarrax T50). Next, while 20 parts by mass of an aqueous solution obtained by diluting 1.6 parts by mass of an anionic surfactant (Daiichi Kogyo Seiyaku Co., Ltd .: Neogen RK) is added dropwise, the emulsion is dispersed and the crystallinity having an average particle size of 0.15 μm. A polyester resin dispersion (1) [resin particle concentration: 10% by mass] was prepared.

-Preparation of crystalline polyester resin dispersion (2)-
In a heat-dried three-necked flask, 85 mol% dimethyl sebacate, 15 mol% n-octadecenyl succinic anhydride, and ethylene glycol (1.5 mol times the acid component) and Ti (OBu) ₄ as a catalyst (0.012% by mass with respect to the acid component), and then depressurize the air in the container by a depressurization operation, and then in an inert atmosphere with nitrogen gas and reflux at 180 ° C. for 6 hours with mechanical stirring. Went. Then, excess ethylene glycol was removed by distillation under reduced pressure, the temperature was gradually raised to 220 ° C., and the mixture was stirred for 3 hours. When the mixture became viscous, the molecular weight was confirmed by GPC, and the weight average molecular weight was 22,000. The distillation under reduced pressure was stopped and air-cooled to obtain crystalline polyester (3).

  Next, 80 parts by mass of the crystalline polyester (3) and 720 parts by mass of deionized water are placed in a stainless beaker, placed in a warm bath, and heated to 95 ° C. When the crystalline polyester resin is melted, the mixture is stirred at 8000 rpm using a homogenizer (manufactured by IKA: Ultra Turrax T50). Next, while 20 parts by weight of an aqueous solution obtained by diluting 1.6 parts by weight of an anionic surfactant (Daiichi Kogyo Seiyaku Co., Ltd .: Neogen RK) is added dropwise, the dispersion is emulsified and dispersed, and the average particle size is 0.16 μm. A polyester resin dispersion (3) [resin particle concentration: 10% by mass] was prepared.

-Preparation of crystalline polyester resin dispersion (3)-
In a heat-dried three-necked flask, an acid component of 90.5 mol% of 1,10 dodecanedioic acid, 2 mol% of sodium dimethyl-5-sulfonate, 7.5 mol% of 5-t-butylisophthalic acid, 9 Nonanediol 100 mol% and Ti (OBu) ₄ (0.014% by mass with respect to the acid component) as a catalyst were added, and then the air in the container was depressurized by depressurization and further inert with nitrogen gas. Under an atmosphere, reflux was performed at 180 ° C. for 6 hours with mechanical stirring. Then, excess ethylene glycol was removed by distillation under reduced pressure, the temperature was gradually raised to 220 ° C., and the mixture was stirred for 2 hours. When the mixture became viscous, the molecular weight was confirmed by GPC, and the weight average molecular weight became 11,000. The distillation under reduced pressure was stopped and air-cooled to obtain crystalline polyester (3).

  Next, 80 parts by mass of the crystalline polyester (3) and 720 parts by mass of deionized water are placed in a stainless beaker, placed in a warm bath, and heated to 95 ° C. When the crystalline polyester resin is melted, the mixture is stirred at 8000 rpm using a homogenizer (manufactured by IKA: Ultra Turrax T50). Next, while 20 parts by mass of an aqueous solution obtained by diluting 1.6 parts by mass of an anionic surfactant (Daiichi Kogyo Seiyaku Co., Ltd .: Neogen RK) is added dropwise, the emulsion is dispersed and the crystallinity of 0.15 μm in average particle size A polyester resin dispersion (3) [resin particle concentration: 10% by mass] was prepared.

-Preparation of crystalline polyester resin dispersion (4)-
80 parts by mass of polycaprolactone PLACCEL H1P (weight average molecular weight 10,000, melting point 60 ° C.) and 720 parts by mass of deionized water are put into a stainless beaker, placed in a warm bath, and heated to 95 ° C. When the crystalline polyester resin is melted, the mixture is stirred at 8000 rpm using a homogenizer (manufactured by IKA: Ultra Turrax T50). Next, while 20 parts by mass of an aqueous solution obtained by diluting 1.6 parts by mass of an anionic surfactant (Daiichi Kogyo Seiyaku Co., Ltd .: Neogen RK) is added dropwise, the emulsion is dispersed and the crystallinity having an average particle size of 0.15 μm. A polyester resin dispersion (4) [resin particle concentration: 10% by mass] was prepared.

−Preparation of amorphous resin fine particle dispersion (1) −
Styrene 480 parts by mass n-butyl acrylate 120 parts by mass Acrylic acid 12 parts by mass Dodecanethiol 12 parts by mass

  The components are mixed and dissolved to prepare a solution.

  On the other hand, 12 parts by weight of an anionic surfactant (manufactured by Rhodia, Dowfax) is dissolved in 250 parts by weight of ion-exchanged water, and the solution is added and dispersed and emulsified in a flask. (Monomer emulsion A)

  Furthermore, 1 part by mass of an anionic surfactant (manufactured by Rhodia, Dowfax) is dissolved in 555 parts by mass of ion-exchanged water and charged into a polymerization flask.

  The polymerization flask is sealed, a reflux tube is installed, and the polymerization flask is heated to 75 ° C. with a water bath while being slowly stirred while injecting nitrogen.

  9 parts by mass of ammonium persulfate was dissolved in 43 parts by mass of ion-exchanged water and dropped into the polymerization flask via a metering pump over 20 minutes, and then the monomer emulsion A was added for 200 minutes via the metering pump. Add dropwise.

  Thereafter, the polymerization flask is kept at 75 ° C. for 3 hours while continuing the slow stirring to complete the polymerization.

  As a result, an anionic resin fine particle dispersion (1) having a fine particle central diameter of 240 nm, a glass transition point of 54 ° C., a weight average molecular weight of 25,000, and a solid content of 42% was obtained.

−Preparation of amorphous resin fine particle dispersion (2) −
The resin fine particle dispersion (1) was prepared in the same manner as the resin fine particle dispersion (1) except that the amount of acrylic acid was changed to 9 parts by mass and the amount of dodecanethiol was changed to 15 parts by mass. An anionic resin fine particle dispersion (2) having 210 nm, a glass transition point of 51 ° C., a weight average molecular weight of 20,000 and a solid content of 42% was obtained.

-Preparation of colorant particle dispersion (1)-
Yellow pigment (Clariant Japan, PY74) 50 parts by weight Anionic surfactant (Daiichi Kogyo Seiyaku, Neogen R) 5 parts by weight Ion-exchanged water 200 parts by weight

  The above components were mixed and dissolved, and dispersed for 10 minutes with a homogenizer (manufactured by IKA, Ultra Tarrax) to obtain a Yellow colorant particle dispersion (1) having a center diameter of 200 nm and a solid content of 21.5%.

-Preparation of colorant particle dispersion (2)-
The colorant particle dispersion (1) was prepared in the same manner as the colorant particle dispersion (1) except that a cyan pigment (manufactured by Dainichi Seika Co., Ltd., copper phthalocyanine B15: 3) was used instead of the yellow pigment. Thus, a Cyan colorant particle dispersion (2) having a center diameter of 190 nm and a solid content of 21.5% was obtained.

-Preparation of colorant particle dispersion (3)-
In the preparation of the colorant particle dispersion (1), except that a magenta pigment (manufactured by Dainichi Ink Chemical Co., PR122) was used instead of the yellow pigment, it was prepared in the same manner as the colorant particle dispersion (1). A colorant particle dispersion (3) having a center diameter of 160 nm and a solid content of 21.5% was obtained.

-Preparation of colorant particle dispersion (4)-
The colorant particle dispersion (1) was prepared in the same manner as the colorant particle dispersion (1) except that a black pigment (Cabot, carbon black) was used instead of the yellow pigment. A colorant particle dispersion (3) having a nm and a solid content of 21.5% was obtained.

-Preparation of release agent particle dispersion-
HNP09 (manufactured by Nippon Seiwa Co., Ltd., melting point 75 ° C.) 50 parts by mass Anionic surfactant (Rohia Dowfax) 5 parts by mass Ion-exchanged water 200 parts by mass

  The components were heated to 110 ° C. and sufficiently dispersed with a homogenizer (IKA, Ultra Tarrax T50), and then dispersed with a pressure discharge homogenizer (Gorin homogenizer, Gorin), with a center diameter of 120 nm, A release agent particle dispersion having a solid content of 21.0% was obtained.

[Preparation of crystalline toner particles (1)]
(Preparation of crystalline toner particles)
Crystalline resin fine particle dispersion (1) 331 parts by mass (resin 33.1 parts by mass)
Amorphous resin fine particle dispersion (1) 52 parts by mass (21.84 parts by mass of resin)
Colorant particle dispersion liquid (1) 39.5 parts by mass (pigment 8.5 parts by mass)
Release agent particle dispersion 38.1 parts by mass (release agent 8 parts by mass)
Polyaluminum chloride 0.15 parts by mass

  After thoroughly mixing and dispersing the above components in a round stainless steel flask with a homogenizer (IKA, Ultra Turrax T50), the flask was heated to 42 ° C. with stirring in an oil bath for heating, and then heated at 47 ° C. to 60 ° C. After holding for a minute, 68 parts by mass (28.56 parts by mass of resin) of the amorphous resin fine particle dispersion (1) was added and gently stirred. Thereafter, the temperature was raised to 45 ° C. and maintained at the same temperature for 120 minutes, and it was confirmed with a Coulter counter that the particle size distribution became narrower.

  Thereafter, the pH in the system was adjusted to 6.5 with a 0.5 mol / liter aqueous sodium hydroxide solution, and then heated to 95 ° C. while stirring was continued.

  During the temperature increase to 95 ° C., the pH in the system was lowered to 5.2, but was maintained as it was.

  After completion of the reaction, the mixture was cooled, filtered, thoroughly washed with ion exchange water, and then solid-liquid separated by Nutsche suction filtration. Then, it was re-dispersed in 3 liters of ion-exchanged water at 40 ° C. and stirred and washed at 300 rpm for 15 minutes. This washing operation was repeated 5 times, followed by solid-liquid separation by Nutsche suction filtration, and then vacuum-dried for 12 hours to obtain crystalline toner particles.

  When the particle size of the crystalline toner particles was measured with a Coulter counter, the cumulative volume average particle size D50 was 4.3 μm, the volume average particle size distribution index GSDv was 1.20, and the surface property index was 1.55. Further, the shape factor SF1 of the crystalline toner particles obtained from the shape observation by Luzex was a spherical shape of 125.

  To 50 parts by mass of the above crystalline toner particles, 1.5 parts by mass of hydrophobic silica (manufactured by Cabot, TS720) was added and mixed by a sample mill to obtain an externally added toner.

  Then, using a ferrite carrier having an average particle diameter of 50 μm coated with 1% of polymethyl methacrylate (manufactured by Soken Chemical Co., Ltd.), the externally added toner was weighed so that the toner concentration was 5%, A developer was prepared by stirring and mixing for a minute.

[Preparation of crystalline toner particles (2)]
In Example 1, the crystal resin fine particle dispersion (1) is changed to the crystal resin fine particle dispersion (2), the colorant particle dispersion (1) is changed to the colorant particle dispersion (2), and heated at 95 ° C. Crystalline toner particles were obtained in the same manner as in the case of the crystalline toner particles (1) except that the pH at that time was maintained at 4.0.

  The cumulative volume average particle diameter D50 of the crystalline toner particles is 4.00 μm, the volume average particle size distribution index GSDv is 1.19, and the surface property index is 1.40. The shape factor SF1 was 118 and spherical.

  Using these crystalline toner particles, an externally added toner was obtained in the same manner as in Example 1 to further prepare a developer.

[Preparation of crystalline toner particles (3)]
In the preparation of the crystalline toner particles (2), the crystalline resin fine particle dispersion (1) is changed to the crystalline resin fine particle dispersion (2), and the colorant particle dispersion (2) is changed to the colorant particle dispersion (3). In the same manner as in the crystalline toner particles (2) except that the maximum value of the aggregation temperature is 45 ° C. and the PH at 95 ° C. is a constant value of 3.8. Thus, crystalline toner particles were obtained.

  The cumulative volume average particle diameter D50 of the crystalline toner particles was 4.8 μm, the volume average particle size distribution index GSDv was 1.18, the surface property index was 1.30, and the shape factor SF1 was 118 spherical.

  Using these crystalline toner particles, an externally added toner was obtained in the same manner as in Example 1 to further prepare a developer.

[Preparation of crystalline toner particles (4)]
In the preparation of the crystalline toner particles (2), the crystalline resin fine particle dispersion (3) was changed to the crystalline resin fine particle dispersion (4), and the pigment dispersion (2) was increased by 1.5 parts by mass as a toner. Crystalline toner particles were obtained in the same manner as the crystalline toner particles (2) except that the maximum value of the aggregation temperature was 40 ° C. and the pH at 95 ° C. was kept constant at 3.8.

  The cumulative volume average particle diameter D50 of the crystalline toner particles is 3.7 μm, the volume average particle size distribution index GSDv is 1.16, the surface property index is 1.30, and the shape factor SF1 is 115.

  Using these crystalline toner particles, an externally added toner was obtained in the same manner as in Example 1 to further prepare a developer.

[Preparation of crystalline toner particles (5)]
In preparation of the crystalline toner particles (1), the amorphous resin fine particle dispersion (1) is changed to the amorphous resin fine particle dispersion (2), and the pigment dispersion (2) is increased by 1.5 parts by mass as a toner. Thus, crystalline toner particles were obtained in the same manner as the crystalline toner particles (2) except that the maximum value of the aggregation temperature was 43 ° C. and the PH at 95 ° C. was kept constant at 4.0.

  The cumulative volume average particle diameter D50 of the crystalline toner particles is 4.6 μm, the volume average particle size distribution index GSDv is 1.19, the surface property index is 1.40, and the shape factor SF1 is 120 potatoes. .

  Using these crystalline toner particles, an externally added toner was obtained in the same manner as in Example 1 to further prepare a developer.

[Preparation of crystalline toner particles (6)]
In the preparation of the crystalline toner particles (4), the non-crystalline resin fine particle dispersion (1) is changed to the non-crystalline resin fine particle dispersion (2). A crystalline toner particle was obtained in the same manner as the crystalline toner particle (2) except that the value was a constant value of 4.0.

  The cumulative volume average particle diameter D50 of the crystalline toner particles is 4.5 μm, the volume average particle size distribution index GSDv is 1.19, the surface property index is 1.38, and the shape factor SF1 is 120 potatoes. .

  Using these crystalline toner particles, an externally added toner was obtained in the same manner as in Example 1 to further prepare a developer.

(Comparative Example 1)
[Preparation of comparative toner particles (1)]
In Example 1, this crystalline toner was prepared in the same manner as in Example 1 except that the pigment dispersion (2) was reduced by 1.5 parts by mass and the PH at 95 ° C. was maintained at 5.5. The cumulative volume average particle diameter D50 of the particles was 4.8 μm, the volume average particle size distribution index GSDv was 1.22, the surface property index was 2.10, the shape factor SF1 was 135, and the shape was somewhat indefinite.

(Comparative Example 2)
[Preparation of comparative toner particles (2)]
In Example 1, the crystalline resin dispersion was not used. Only the amorphous resin dispersion 1 was used. The same procedure as in Example 1 was carried out except that the pigment dispersion (2) was reduced by 1.5 parts by mass as the toner, the highest man at the time of aggregation was set at 52 ° C., and the pH at 95 ° C. was maintained at 4.0. The toner particles had a cumulative volume average particle diameter D50 of 5.7 μm, a volume average particle size distribution index GSDv of 1.22, a surface property index of 1.80, a shape factor SF1 of 125 and a potato shape.

  Evaluation was conducted while changing the fixing time from 55 ms to 200 ms, changing the fixing temperature (fixing roll surface temperature) from 100 ° C. to 140 ° C., changing the toner amount, and monitoring the image quality.

<Evaluation of actual machine>
(Fixing machine 1)
FIG. 2 is a schematic configuration diagram illustrating a main part of the fixing device 1 used in the actual device evaluation. A modified fixing machine (free belt nip fixing machine) from the DPC 2220 manufactured by Fuji Xerox Co., Ltd., changing the fixing nip width to the heat roll load and the shape of the pressure pad 4 on the free belt 3 side to make the fixing time variable. Used.

(Fixing machine 2)
FIG. 3 is a schematic configuration diagram illustrating a main part of the fixing device 2 used in the actual device evaluation. Between the fixing belt 20 and the pressure nip portion of the transfer paper after the transfer paper is peeled off, there are first, second, third and three heating portions. The first heating unit 50 is used for heating the belt by moving the heat taken from the belt by the cooling unit to a heating body (plate: aluminum) with a heat pipe. The second heating unit 30 is a heating (aluminum) roll in contact with the back surface of the belt. The third heating unit 31 is a heating (aluminum) roll in contact with the belt surface.

  The fixing belt temperature at the peeling portion is cooled to a temperature at which the viscosity is such that the toner is easily separated from the belt. In this embodiment, cooling to 100 ° C. or lower (90 ° C. or lower is desirable). The fixing belt temperature in front of the pressure nip is heated to a temperature equal to or higher than the melting temperature of the toner. In this example, it is heated to 175 ° C. The first heating unit is heated to about 115 to 120 ° C., the second heating unit is heated to about 160 to 170 ° C., and the third heating unit is heated to 175 ° C.

  In the fixing device 2, the fixing time is the time from the entry of the transfer paper to the discharge.

(Transfer paper)
The transfer sheets used in the examples and comparative examples are all manufactured by Fuji Xerox Co., Ltd., and the texture index of each transfer sheet is 38 for JD paper, 23 for C2 paper, and 13 for S paper.

<Evaluation of character line image defect>
The developer obtained above is attached to a color image forming apparatus (Fuji Xerox DC1250 modified machine), image formation is performed, and the amount of monochromatic toner per unit area is changed, and characters and line images are determined according to the following criteria: evaluated.

○: Very good with no defects ○: Good with no defects △: Slight occurrence of defects, but acceptable X: Image defects may occur and there may be image quality problems

<Evaluation of line image scattering>
The developer obtained above was attached to a color image forming apparatus (Fuji Xerox DC1250 modified machine), image formation was performed, and the amount of toner paste was changed to evaluate line image scattering according to the following criteria.

◎: Very good with no scattering ○: Good with no scattering Δ: Slight occurrence of scattering, but acceptable X: There is scattering and there is a problem in image quality

<Evaluation of uneven color difference>
The developer obtained above was attached to a color image forming apparatus (Fuji Xerox DC1250 modified machine), image formation was performed, and the amount of toner paste was changed to evaluate unevenness in color difference according to the following criteria.

◎: Very good with no color difference uniformity ○: Good with no color difference △: Slight color difference is acceptable, but acceptable X: There is a color difference, and there is a problem in image quality

<Evaluation of uneven luster>
The developer obtained above was attached to a color image forming apparatus (Fuji Xerox DC1250 modified machine), image formation was performed, and the amount of toner paste was changed to evaluate unevenness in color difference according to the following criteria.

A: Extremely good without uneven glossiness ○: Good without uneven glossiness Δ: Slightly uneven glossiness is acceptable, but acceptable X: There is uneven glossiness, and there is a problem in image quality

  The evaluation results are shown in Table 1.

FIG. 1-1 is a conceptual diagram of coated paper having a high formation index. FIG. 1-2 is a conceptual diagram of a coated paper having a low texture index. FIG. 2 is a schematic configuration diagram illustrating a main part of the fixing device 1 used in the actual device evaluation. FIG. 3 is a schematic configuration diagram illustrating a main part of the fixing device 2 used in the actual device evaluation.

Explanation of symbols

2 ... Heat fixing roll (roll member), 3 ... Endless belt (free belt, belt member), 4 ... Pad member (pressure pad, pressure applying member), 8 ... Halogen lamp (heating source),
DESCRIPTION OF SYMBOLS 20 ... Fixing belt, 30 ... 1st heating roll (2nd heating part, inside heating means, strong heating means), 31 ... 2nd heating roll (3rd heating part, outside heating means, adjustment heating means), 40 ... Addition Pressure conveying belt (pressurizing means), 50 ... heat circulator (first heating unit, heating means and cooling means), T ... toner image, P ... transfer paper

Claims (3)

  A crystalline toner having a gradient with respect to the temperature of storage elastic modulus at Tm + 20 ° C. to Tm + 50 ° C. of 0.02 log (Pa) / ° C. or less is transferred as a toner image onto a transfer paper having a formation index of 20 or more. Is fixed for a fixing time of 50 ms to 500 ms. The image forming method according to claim 1, wherein the maximum amount of monochromatic toner is 0.35 mg / cm ² or less. The image forming method according to claim 1, wherein the crystalline toner has a weight average particle diameter of 5 μm or less.

Images