JP2007033719A - Toner for electrostatic image development, developer for electrostatic image development and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a toner for electrostatic image development less liable to cause image defects and having high density and high masking property. <P>SOLUTION: The toner is a white toner for electrostatic image development including a colorant and a binder resin comprising a crystalline resin and a noncrystalline resin, wherein the content of the crystalline resin in the toner is 5-25 mass% and the content of the colorant in the toner is 15-40 mass%. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a toner for developing an electrostatic image for printing use using an electrophotographic method, an electrostatic recording method, and the like, a developer for developing an electrostatic image, and an image forming method.

  Electrophotographic methods for visualizing image information through an electrostatic latent image are currently used in various fields, and details thereof are described in various documents (for example, see Patent Documents 1 and 2). In the electrophotographic method, generally, an electrostatic latent image is formed on a photoreceptor in a charging / exposure process, and the electrostatic latent image is developed with a developer containing toner in a developing process to form a toner image. In the transfer step, the toner image is transferred onto a transfer material such as paper or sheet. In the fixing step, the toner image is fixed on the transfer material using heat, solvent, pressure, etc. How to get.

  In recent years, electrophotography is generally a so-called full-color machine in which black toner is added to magenta, cyan, and yellow toners. Recently, a wide range of electrophotographic methods have begun to be used in addition to printers and copiers, and applications close to printers are eagerly desired. However, since so-called full-color machines are for general offices, they cannot be used for printing purposes, for example, from paper recording media such as flyer advertisements, books and magazines to display plates for recording media other than paper such as home appliances and automobiles. In particular, there are many special colors for printing, and high density and white are particularly demanding colors that cannot be produced by full-color machines. In general, printing requires high density and high concealment, but the current full-color machine cannot handle it.

  In order to achieve the above requirements, a high color density and high hiding property can be obtained by using a colorant corresponding to a special color and increasing the colorant density. For example, in white toner, a white colorant typified by titanium oxide is generally used. However, in order to obtain a high density and high hiding property, a much larger amount than a conventional toner colorant density must be added. On the other hand, a method of adding 1 to 50% of a white pigment and further adding a blue pigment to improve the whiteness and using it is disclosed (for example, see Patent Document 3). When a large amount of white toner pigment is added, for example, when a conductive material such as titanium oxide is used, the pigment is exposed on the toner surface and the charge tends to decrease in proportion to the amount of pigment. In order to avoid this, a white pigment is kneaded in advance, a method of preventing the pigment from being exposed to the toner surface by using, for example, a polymerization method (for example, see Patent Document 4), and the toner surface is surfaced by a shearing force. A method of modifying and dealing with the pigment surface exposure by means of a process is also disclosed (for example, see Patent Document 5).

When a general full-color toner (for example, yellow, magenta, cyan, black, etc.) is fixed in an overlapping manner with respect to acquisition of concealment, as described above, while maintaining a certain level of chargeability without impairing the chargeability of individual toners Image formation is possible.
However, the present situation is that the concealability is insufficient when the image is fixed on a transparent fixed image carrier for printing or outdoor posters. Therefore, the colorant is increased and the amount of applied toner is increased to obtain the concealing property. Conversely, white toner or colorless toner is positively imaged to make the multiple toner layer uniform and prevent the toner layer from collapsing during fixing (eliminating unevenness caused by multiple image formation), and obtaining a good fixed image. (For example, refer to Patent Document 6). However, the toner amount at the time of fixing actually increases, and there is a problem that the amount of heat at the time of fixing increases. In addition, when a large amount of colorant is added, the fixing temperature at the time of fixing similarly increases. This is presumably because the colorant put in order to obtain the concealability works like a filler material in the molten toner and raises the melt viscosity at the time of fixing.

After fixing, the image strength such as scratches is slightly improved, but the image strength due to bending is reduced. This is due to the filler effect of the colorant, which increases toner hardness but also increases brittleness. On the contrary, it becomes weak.
In order to avoid the problem of the fixed image strength, a method of lowering the apparent melt viscosity by lowering the molecular weight or glass transition temperature (Tg) of the binder resin or increasing the Wax amount has been tried. In addition, a method of creating a domain / matrix structure with resins having different miscibility and ensuring image strength stability has been tried (for example, see Patent Document 7). However, there is a problem in terms of toner storage properties, and it is currently difficult to satisfy all of the concealability, chargeability, fixability, image strength, and toner storage properties.

  In view of the above problems, it has been proposed to use a crystalline resin as a toner from the viewpoint of achieving both fixability and toner storage (see, for example, Patent Document 8). However, when a crystalline resin is simply used, there is a problem in the fixing property to paper, and there is a possibility that fixing failure occurs before the image strength. In order to improve the fixability, a method of mixing with an amorphous resin has been proposed. However, if simple mixing is performed, plasticization proceeds and the image strength becomes weak over time.

As described above, in order to improve the concealability of the transparent fixed image carrier or the like, the concentration of the colorant in the fixed image must be increased. To that end, it is essential to increase the amount of the colorant of the toner alone and the amount of applied toner. As this defect, charge reduction is promoted (toner flight during development, hereinafter referred to as fog). Further, when the amount of toner per unit area at the time of fixing (4-color superposition or the like) is increased, the amount of fixing heat is increased and the molten state is varied. This is because the melting method changes between the toner layer close to the surface of the fixing roll and the toner layer close to the paper side, and the paper side becomes insufficiently melted. As a result, voids are formed in the fixed toner layer, which becomes an image quality defect. That is, for example, when a transparent image carrier such as OHP is used, the concealability is greatly impaired, and when light (sunlight, illumination) is applied from the back, light is transmitted from the gap (hereinafter referred to as a pinhole). ) As a result, the product value is significantly reduced. Conversely, if the fixing temperature is raised and the toner layer in the vicinity of the paper side is sufficiently melted, the toner layer in the vicinity of the surface of the fixing roll is excessively melted and the melt viscosity is extremely lowered. As a result, the air and water vapor accumulated in the gaps on the paper side cause image destruction called blisters. This is because the fixing roll side melts too much when the cross section of the fixed image is seen, and the image is covered with a lid, and the air and water vapor in the toner layer on the paper side that has not been sufficiently melted cannot be released. It is done. Further, when the fixing temperature is further increased to eliminate the melting difference, a high temperature offset is generated. This restricts the amount of applied toner and makes it difficult to achieve both concealment and high temperature offset. On the other hand, when fixed on an OHP sheet, the transmission density is regulated to be 0.05 or more (for example, see Patent Document 9). By simply increasing the colorant density, a transparent image carrier such as OHP is assumed. In some cases, a high concealment image such as a printed matter cannot be obtained.
US Pat. No. 2,297,691 U.S. Pat. No. 2,357,809 JP 63-108355 A Japanese Patent Laid-Open No. 10-260554 JP-A-5-158283 Japanese Unexamined Patent Publication No. 7-5738 JP-A-4-150484 Japanese Patent Publication No. 56-13943 JP-A-11-194524

  An object of the present invention is to solve the conventional problems and achieve the following objects. That is, an object of the present invention is to develop an electrostatic charge image developing toner that is less prone to image defects and has a high density and high concealing property, an electrostatic charge image developing developer using the toner, and an image using the developer. It is to provide a forming method.

The above problem is solved by the following means. That is, the present invention
<1> A white electrostatic charge image developing toner comprising a colorant and a binder resin comprising a crystalline resin and an amorphous resin, wherein the content of the crystalline resin in the toner is 5 The toner for developing an electrostatic charge image is characterized in that it is ˜25% by mass, and the content of the colorant in the toner is 15 to 40% by mass.

<2> The electrostatic charge image developing toner according to <1>, wherein hydrophobic oxide fine particles having a BET specific surface area of 40 to 250 m ² / g are added as an external additive.

  <3> An electrostatic charge image developing developer comprising the electrostatic charge image developing toner according to <1> or <2> and a carrier.

  <4> The developer for developing an electrostatic charge image according to <3>, wherein a surface of the carrier is coated with a resin.

  <5> A developing step of developing the electrostatic latent image formed on the surface of the image carrier using a plurality of colors of toner including at least white toner to obtain a toner image, and fixing the toner image to obtain a fixed image And a fixing step, wherein the toner for developing an electrostatic charge image according to <1> or <2> is used as the white toner, and the transmission density of the fixed image is 3. The image forming method is characterized in that it is 00 or more.

  <6> The toner according to <5>, wherein four-color toners of three colors selected from yellow, magenta, cyan, and black toners and the white toner are used as the plurality of color toners. The image forming method described.

  According to the present invention, an electrostatic charge image developing toner that is less likely to cause image defects and has high density and high concealability, an electrostatic charge image developing developer using the toner, and an image forming method using the developer Can be provided.

  The electrostatic image developing toner of the present invention is a white electrostatic image developing toner comprising a colorant and a binder resin composed of a crystalline resin and an amorphous resin, wherein the crystalline resin is used as the crystalline resin. It contains crystalline polyester, the content of the crystalline polyester in the toner is 5 to 25% by mass, and the content of the colorant in the toner is 15 to 40% by mass.

  When the content of the colorant is less than 15% by mass, the whiteness becomes too low and a good concealment name cannot be obtained. On the other hand, if it exceeds 40% by mass, fogging due to lowering of charge, image strength at the time of fixing will be lost, image loss at the time of transfer due to adhesion of free colorant, and colorant adhesion to the carrier will occur in the developer, and charge maintenance will be significantly impaired. It will be. In addition, as content of the said coloring agent, 20-35 mass% is more preferable from a viewpoint from which more favorable white is obtained, and 25-30 mass% is especially preferable.

Moreover, generation | occurrence | production of a blister or a pinhole can be avoided by containing 5-25 mass% of crystalline resin. This is particularly effective when multiple toner layers are formed.
Although details are unknown, it is considered that the crystalline resin acts as follows during fixing. When blisters or pinholes are considered as defects at the time of fixing, voids in a multiple toner layer (for example, a layer in which four color toners are laminated) become a problem. Crystalline resins are known to have extremely low melt viscosity above the melting point due to their physical properties, and are also known to become cloudy depending on the degree of crystallinity, but this characteristic is effective in suppressing blisters and pinholes. It is considered effective. In other words, with respect to blisters, the porosity increases when the fixing temperature is low at the time of fixing, but here the crystalline resin acts to fill the voids due to the low viscosity, that is, it acts like a filler in the molten state. Show. On the other hand, when the fixing temperature is high, the voids are reduced and blisters are generated, but the difference in melt viscosity of the crystalline resin also works effectively for blisters. In other words, since the crystalline resin is contained in the toner in a fixed ratio at the time of fixing, an interface is formed between the crystalline resin and the amorphous resin when melted. As a result, air and water vapor preferentially diverge through the low-viscosity crystalline resin interface and suppress blistering. Moreover, the hole opened locally by the blister is filled with a crystalline resin having a low viscosity. The pinhole is suppressed by the white turbidity of the crystalline resin, and is particularly effective in suppressing the pinhole because it is preferentially filled in the gap.

  Here, it is essential that the content of the crystalline resin is 5 to 25% by mass. When the amount is less than 5% by mass, a sufficient filling effect cannot be obtained, and an effective interface with respect to the blister cannot be formed with the amorphous resin at the time of fixing and melting. On the other hand, if it exceeds 25% by mass, the filling of the voids and the formation of the interface work sufficiently, but the toner resistance starts to decrease. This is because the resistance of the crystalline resin itself is low, and the toner resistance cannot be maintained without a certain proportion of the amorphous resin. As a result, the toner is injected and charged, causing development failure and transfer failure. In addition, content of crystalline resin becomes like this. More preferably, it is 8-20 mass%, Most preferably, it is 10-15 mass%.

  By using the white toner of the present invention satisfying the contents of the crystalline resin and the colorant, high whiteness can be obtained while preventing generation of voids at the time of fixing. An image having a good concealing property can be formed.

<Description of toner constituent materials>
Next, constituent materials of the toner for developing an electrostatic charge image of the present invention (hereinafter sometimes simply referred to as “toner”) will be described.

(Binder resin)
The toner particles of the present invention include, as binder resins, monoolefins such as ethylene, propylene, butylene, and isoprene, vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate, and vinyl butyrate, methyl acrylate, phenyl acrylate, Α-methylene aliphatic monocarboxylic acid esters such as octyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate and dodecyl methacrylate, vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl butyl ether, vinyl methyl ketone Homopolymers or copolymers of vinyl ketones such as vinyl hexyl ketone and vinyl isopropenyl ketone. Among these, particularly typical binder resins include polystyrene, styrene-alkyl acrylate copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polystyrene, polypropylene, and the like. Further examples include polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin and the like.

  In the present invention, a crystalline resin and an amorphous resin are used as the binder resin. However, the crystalline resin is not a stepwise change in endothermic amount in differential scanning calorimetry (DSC). It has a good endothermic peak. Specifically, it means that the half-value width of the endothermic peak when measured at a heating rate of 10 ° C./min is within 6 ° C. On the other hand, a resin having a half-value width exceeding 6 ° C. or a resin in which no clear endothermic peak is observed means an amorphous resin, but a clear endothermic peak is recognized as an amorphous resin used in the present invention. It is preferable to use a resin that cannot be used.

-Crystalline resin-
In the present invention, it is preferable to use crystalline polyester as the crystalline resin. Furthermore, an aliphatic crystalline polyester resin having an appropriate melting point is more preferable.
The crystalline polyester resin and all other polyester resins used in the toner of the present invention are synthesized from a polyvalent carboxylic acid component and a polyhydric alcohol component. In the present invention, a commercially available product may be used as the polyester resin, or an appropriately synthesized product may be used.

  Examples of the polyvalent carboxylic acid component include oxalic acid, succinic acid, glutaric acid, adipic acid, peric acid, azelaic acid, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, 1,12 -Aliphatic dicarboxylic acids such as dodecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,18-octadecanedicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, naphthalene-2,6-dicarboxylic acid, malonic acid, mesaconic acid Aromatic dicarboxylic acids such as dibasic acids and the like, and the anhydrides and lower alkyl esters thereof are also included, but not limited thereto.

  Examples of the trivalent or higher carboxylic acid include 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, and the like, and anhydrides thereof. And lower alkyl esters. These may be used individually by 1 type and may use 2 or more types together.

  Moreover, as a polyvalent carboxylic acid component, it is preferable that the dicarboxylic acid component which has a sulfonic acid group other than the above-mentioned aliphatic polyvalent carboxylic acid and aromatic polyvalent carboxylic acid is contained. The dicarboxylic acid having a sulfonic acid group is effective in that it can favorably disperse a colorant such as a pigment.

  Examples of the 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. The divalent or higher carboxylic acid component having a sulfonic acid group is preferably contained in an amount of 0 to 20 mol%, more preferably 0.5 to 10 mol%, based on all carboxylic acid components constituting the crystalline polyester. If it exceeds 20 mol%, not only the crystallinity of the polyester resin may be lowered, but also, for example, when the aggregation coalescence method is used, the process of coalescence after aggregation is adversely affected, and the toner diameter is adjusted. May be difficult, and is not preferable.

  Furthermore, it is more preferable to contain a dicarboxylic acid component having a double bond in addition to the above-mentioned aliphatic polyvalent carboxylic acid and aromatic polyvalent carboxylic acid. A dicarboxylic acid having a double bond can be suitably used in order to prevent hot offset at the time of fixing because it can be cross-linked radically through the double bond. Examples of such dicarboxylic acids include, but are not limited to, maleic acid, fumaric acid, 3-hexenedioic acid, and 3-octenedioic acid. In addition, these lower esters, acid anhydrides and the like are also included. Among these, fumaric acid, maleic acid and the like are mentioned in terms of cost.

  As the polyhydric alcohol component, an aliphatic diol is preferable, and a linear aliphatic diol having 7 to 20 carbon atoms in the main chain portion is more preferable. The branched aliphatic diol may lower the crystallinity of the polyester resin and lower the melting point, which may lead to deterioration in toner blocking resistance, image storage stability, and low-temperature fixability. Further, when the number of carbon atoms is less than 7, when the polycondensation with aromatic dicarboxylic acid is performed, the melting point becomes high and fixing at low temperature may be difficult. On the other hand, when the number exceeds 20, it is difficult to obtain practical materials. easy. The carbon number is more preferably 14 or less.

  Specific examples of the aliphatic diol suitably used for the synthesis of the crystalline polyester used in the toner of the present invention include ethylene glycol, 1,3-propanediol, 1,4-butanediol, and 1,5. -Pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12- Examples include, but are not limited to, dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,18-octadecanediol, 1,14-eicosandecanediol, and the like. Among these, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol are preferable in view of availability.

  Examples of the trivalent or higher alcohol include glycerin, trimethylolethane, trimethylolpropane, pentaerythritol and the like. These may be used individually by 1 type and may use 2 or more types together.

  Among the polyhydric alcohol components, the content of the aliphatic diol component is preferably 80 mol% or more, and more preferably 90% or more. If the content of the aliphatic diol component is less than 80 mol%, there is a concern that the crystallinity of the polyester resin may be lowered. In this case, the melting point is lowered, and toner blocking resistance, image storage stability, and low-temperature fixability are deteriorated. May end up.

  If necessary, monovalent acids such as acetic acid and benzoic acid and monovalent alcohols such as cyclohexanol benzyl alcohol can also be used for the purpose of adjusting the acid value and hydroxyl value.

  The method for producing the crystalline 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. Examples thereof include direct polycondensation and transesterification. Depending on the type of monomer, it can be used separately.

  The production of the crystalline polyester resin is preferably carried out at a polymerization temperature of 180 to 230 ° C., and the reaction can be carried out while reducing the pressure in the reaction system as necessary and removing water and alcohol generated during condensation. When the monomer is not dissolved or compatible with the reaction temperature, a solvent having a high boiling point may be added as a solubilizer and dissolved. The polycondensation reaction is preferably carried out while distilling off the solubilizing auxiliary solvent. When a monomer having poor compatibility exists in the copolymerization reaction, the monomer having poor compatibility and the acid to be polycondensed with the monomer are previously prepared. Alternatively, it is preferable to polycondense together with the main component after condensing with alcohol.

  Catalysts that can be used in the production of the crystalline polyester resin include alkali metal compounds such as sodium and lithium; alkaline earth metal compounds such as magnesium and calcium; metals such as zinc, manganese, antimony, titanium, tin, zirconium, and germanium Compounds: Phosphorous acid compounds, phosphoric acid compounds, amine compounds, and the like, and specific examples include the following compounds.

  For example, sodium acetate, sodium carbonate, lithium acetate, lithium carbonate, calcium acetate, calcium stearate, magnesium acetate, zinc acetate, zinc stearate, zinc naphthenate, zinc chloride, manganese acetate, manganese naphthenate, titanium tetraethoxide, titanium Tetrapropoxide, titanium tetraisoproxide, titanium tetrabutoxide, antimony trioxide, triphenylantimony, tributylantimony, tin formate, tin oxalate, tetraphenyltin, dibutyltin dichloride, dibutyltin oxide, diphenyltin oxide, zirconium tetrabutoxide, naphthenic acid Zirconium, zirconyl carbonate, zirconyl acetate, zirconyl stearate, zirconyl octylate, germanium oxide, triphenyl Sufaito, tris (2, 4-t-butylphenyl) phosphite, ethyltriphenylphosphonium bromide, triethylamine, compounds such as triphenyl amine.

As melting | fusing point of crystalline resin in this invention, Preferably it is 50-100 degreeC, More preferably, it is 60-80 degreeC. If the melting point is lower than 50 ° C., the storage stability of the toner and the storage stability of the toner image after fixing may become a problem. There is a case.
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 crystalline resin used in the toner of the present invention preferably has a weight average molecular weight (Mw) of 5,000 to 20,000 as determined by gel permeation chromatography (GPC) method of tetrahydrofuran (THF) soluble content. The molecular weight (Mn) is preferably 1500 to 7000, the molecular weight distribution Mw / Mn is preferably 1.4 to 4.5, and more preferably 1 .5 to 3.0.

  If the weight average molecular weight and the number average molecular weight are smaller than the above ranges, problems such as high temperature offset during fixing (caused by sudden drop in toner melt viscosity) and solidification during toner storage may occur. . On the other hand, when the molecular weight is larger than the above range, there is a problem that, for example, in the kneading and pulverizing method, the pulverizability is extremely deteriorated (becomes difficult to break) during the production.

  The molecular weight was measured with a THF solvent using a TSO gel GPC / HLC-8120, a Tosoh column / TSKgel SuperHM-M (15 cm), and a molecular weight prepared from a monodisperse polystyrene standard sample. It is calculated using a calibration curve.

-Amorphous resin-
As the non-crystalline resin in the present invention, a known resin material can be used, but non-crystalline polyester resin is particularly preferable. The amorphous polyester resin used in the present invention is obtained mainly by condensation polymerization of polyvalent carboxylic acids and polyhydric alcohols.

  When an amorphous polyester resin is used, it is advantageous in that a resin particle dispersion can be easily prepared by adjusting the acid value of the resin or by emulsifying and dispersing using an ionic surfactant. .

  Examples of polyvalent carboxylic acids include aromatic carboxylic acids such as terephthalic acid, isophthalic acid, phthalic anhydride, trimellitic anhydride, pyromellitic acid, naphthalenedicarboxylic acid, maleic anhydride, fumaric acid, succinic acid, alkenyl. Examples thereof include aliphatic carboxylic acids such as succinic anhydride and adipic acid, and alicyclic carboxylic acids such as cyclohexanedicarboxylic acid. These polyvalent carboxylic acids can be used alone or in combination. Among these polycarboxylic acids, aromatic carboxylic acids are preferably used, and in order to ensure good fixability, it is preferable to take a crosslinked structure or a branched structure. It is preferable to use a carboxylic acid (trimellitic acid or acid anhydride thereof) in combination.

  Examples of polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol, glycerin and other aliphatic diols, cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A, etc. And aromatic diols such as bisphenol A ethylene oxide adduct and bisphenol A propylene oxide adduct. One or more of these polyhydric alcohols can be used. Among these polyhydric alcohols, aromatic diols and alicyclic diols are preferable, and among these, aromatic diols are more preferable. In order to ensure good fixability, it is preferable to take a crosslinked structure or a branched structure. More specifically, a trihydric or higher polyhydric alcohol (glycerin, trimethylolpropane, pentaerythritol) may be used in combination with the diol. A polyester resin obtained by polycondensation of a polyvalent carboxylic acid and a polyhydric alcohol is further added with a monocarboxylic acid and / or monoalcohol to esterify the hydroxyl group and / or carboxyl group at the polymerization terminal, thereby producing a polyester. The acid value of the resin may be adjusted. Examples of the monocarboxylic acid include acetic acid, acetic anhydride, benzoic acid, trichloroacetic acid, trifluoroacetic acid, propionic anhydride, etc., and examples of the monoalcohol include methanol, ethanol, propanol, octanol, 2-ethylhexanol, trifluoroethanol, Examples include trichloroethanol, hexafluoroisopropanol, and phenol.

  The amorphous polyester resin can be produced by subjecting the polyhydric alcohol and polyhydric carboxylic acid to a condensation reaction according to a conventional method. For example, the above polyhydric alcohol and polyvalent carboxylic acid, if necessary, a catalyst is added, blended in a reaction vessel equipped with a thermometer, a stirrer, a flow-down condenser, and in the presence of an inert gas (such as nitrogen gas), Heat at an appropriate temperature (for example, about 150 to 250 ° C.), continuously remove by-product low molecular compounds out of the reaction system, stop the reaction when a predetermined acid value is reached, cool, It can manufacture by acquiring the reaction material to do.

  Examples of the catalyst used for the synthesis of the amorphous polyester resin include esterification catalysts such as organic metals such as dibutyltin dilaurate and dibutyltin oxide and metal alkoxides such as tetrabutyl titanate. The amount of such a catalyst added is preferably 0.01 to 1.00% by mass relative to the total amount of raw materials.

  The amorphous resin used in the toner of the present invention has a weight average molecular weight (Mw) of 5,000 to 1,000,000 as measured by gel permeation chromatography (GPC) method of tetrahydrofuran (THF) soluble content. The molecular weight (Mn) is preferably 2000 to 10000, the molecular weight distribution Mw / Mn is preferably 1.5 to 100, and more preferably 2 to 60. It is.

When the weight average molecular weight and the number average molecular weight are smaller than the above ranges, while effective for low-temperature fixability, not only the hot offset resistance is remarkably deteriorated, but also the glass transition point of the toner is lowered. The storage stability such as toner blocking is also adversely affected. On the other hand, if the molecular weight is larger than the above range, the hot offset resistance can be sufficiently provided, but the low-temperature fixability is deteriorated and the oozing of the crystalline polyester phase present in the toner is inhibited, so that the document storage stability is reduced. May be adversely affected. Therefore, it becomes easy to satisfy both the low-temperature fixability, the hot offset resistance, and the document storage stability by satisfying the above conditions.
The molecular weight of the amorphous resin can be measured by the same method as the molecular weight of the crystalline resin described above.

  Further, the acid value of the non-crystalline polyester resin (mg number of KOH necessary to neutralize 1 g of resin) is easy to obtain the molecular weight distribution as described above, and the granulation property of the toner particles by the emulsion dispersion method. It is preferable to be 1 to 30 mg KOH / g because it is easy to ensure and the environmental stability of the obtained toner (charge stability when temperature and humidity change) are easily maintained. The acid value of the polyester resin can be adjusted by controlling the carboxyl group at the terminal of the polyester according to the blending ratio of the raw polyhydric carboxylic acid and polyhydric alcohol and the reaction rate. Or what has a carboxyl group in the principal chain of polyester is obtained by using trimellitic anhydride as a polyvalent carboxylic acid component.

  In the present invention, a styrene acrylic resin can also be used as a known non-crystalline resin. Examples of monomers that can be used in this case include styrenes such as styrene, parachlorostyrene, and α-methylstyrene: methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, and lauryl acrylate. And esters having vinyl groups such as 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, and the like: Vinyl nitriles such as acrylonitrile and methacrylonitrile: Vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether: Vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone and vinyl isopropenyl ketone: Polyolefins such as ethylene, propylene and butadiene: Single amount And a copolymer obtained by combining two or more of these, or a mixture thereof. Furthermore, epoxy resins, polyester resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, etc., non-vinyl It is also possible to use a condensation resin, a mixture of these with the vinyl resin, or a graft polymer obtained when a vinyl monomer is polymerized in the presence of these resins.

  The glass transition temperature of the amorphous resin used in the present invention is preferably 35 to 100 ° C., and more preferably 50 to 80 ° C. from the viewpoint of the balance between storage stability and toner fixing property. . When the glass transition temperature is less than 35 ° C., the toner tends to be blocked during the storage or in the developing machine (a phenomenon in which toner particles are aggregated into a lump). On the other hand, if the glass transition temperature exceeds 100 ° C., the toner fixing temperature tends to increase, which is not preferable.

  Moreover, it is preferable that the softening point of an amorphous resin exists in the range of 80-130 degreeC. More preferably, it is the range of 90-120 degreeC. When the softening point is less than 80 ° C., there is a concern that the image stability of the toner and the toner after fixing and during storage may deteriorate, and when the softening point exceeds 130 ° C., the low-temperature fixability may deteriorate. There is.

  Here, the softening point of the amorphous resin was measured by a flow tester (manufactured by Shimadzu Corp .: CFT-500C), preheating: 80 ° C./300 sec, plunger pressure: 0.980665 MPa, die size: 1 mmφ × 1 mm, heating rate : Refers to an intermediate temperature between the melting start temperature and the melting end temperature under the condition of 3.0 ° C./min.

  The content of the amorphous resin in the toner of the present invention is preferably 5 to 79% by mass, and more preferably 30 to 60% by mass.

(Release agent)
The release agent used in the toner of the present invention is not particularly limited as long as it is a known release agent. For example, natural waxes such as carnauba wax, rice wax, and candelilla wax, low molecular weight polypropylene, and low molecular weight polyethylene. , Sazol wax, microcrystalline wax, Fischer-Tropsch wax, paraffin wax, montan wax and the like, or mineral / petroleum wax, fatty acid ester, montanic acid ester, etc. It is not a thing. Moreover, these mold release agents may be used individually by 1 type, and may be used together 2 or more types.

  The melting point of the release agent is preferably 50 ° C. or higher, more preferably 60 ° C. or higher, from the viewpoint of storage stability. Moreover, it is preferable that it is 110 degrees C or less from a viewpoint of offset resistance, and it is more preferable that it is 100 degrees C or less.

The content of the release agent is preferably in the range of 1 to 30 parts by mass and more preferably in the range of 2 to 20 parts by mass with respect to 100 parts by mass of the binder resin.
When the content of the release agent is less than 1 part by mass, the effect of adding the release agent is small, and hot offset at a high temperature may be caused. On the other hand, if the amount exceeds 30 parts by mass, the chargeability may be adversely affected, and the mechanical strength of the toner may be reduced, which may be easily destroyed by stress in the developing machine and cause carrier contamination. is there. Further, when used as a color toner, the domain tends to remain in a fixed image, and in the case of a transparent medium such as an OHP film, there is a problem that transparency is deteriorated.

(Charge control agent)
The toner in the present invention can contain a charge control agent as required. At that time, a colorless or light-color charge control agent that does not affect the color tone is preferable, particularly when used for a color toner or the like. As the charge control agent, known ones can be used, but azo metal complexes, metal complexes or metal salts of salicylic acid or alkylsalicylic acid are preferably used. The toner can also contain other known components such as low molecular weight propylene, low molecular weight polyethylene, and an anti-offset agent such as wax.

(Coloring agent)
The colorant used in the white electrostatic image developing toner of the present invention is not particularly limited as long as it is a known colorant, and examples thereof include titanium oxide, zinc white, antimony white, zinc sulfide, and silicon oxide. In particular, titanium oxide is preferable from the viewpoint that both chargeability and concealability can be achieved. This titanium oxide can be obtained by any production method such as sulfuric acid method or chlorine method, and any crystal structure such as anatase type, rutile type or brookite type can be used.

  Further, in the full-color image forming method, each color toner such as yellow, magenta, cyan, and black is used together with the white toner of the present invention. The colorant used for the toner is particularly a known colorant. Although not limited, for example, carbon black such as furnace black, channel black, acetylene black, thermal black, inorganic pigments such as Bengala, bitumen, titanium oxide, fast yellow, disazo yellow, pyrazolone red, chelate red, brilliant carmine, para brown Azo pigments such as copper phthalocyanine, phthalocyanine pigments such as metal-free phthalocyanine, condensed polycyclic pigments such as flavantron yellow, dibromoanthrone orange, perylene red, quinacridone red, dioxazine violet, Rom Yellow, Hansa Yellow, Benzidine Yellow, Slen Yellow, Quinoline Yellow, Permanent Orange GTR, Pyrarozone Orange, Vulcan Orange, Watch Young Red, Permanent Red, Dupont Oil Red, Resol Red, Rhodamine B Lake, Lake Red C, Rose Bengal, aniline blue, ultramarine blue, calco oil blue, methylene blue chloride, phthalocyanine blue, phthalocyanine green, malachite green oxalate, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 122, C.I. I. Pigment 57: 1, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 180, C.I. I. Pigment yellow 74, C.I. I. Pigment blue 15: 1, C.I. I. Examples thereof include various pigments such as CI Pigment Blue 15: 3, and these can be used alone or in combination of two or more.

  Further, the toner of the present invention can contain other known components such as an anti-offset agent as necessary. At that time, a colorless or light-colored component that does not affect the color tone is preferable. Examples of the offset preventing agent include low molecular weight propylene, low molecular weight polyethylene, and wax.

<Physical properties of toner>
The toner of the present invention preferably has a volume average particle size of 14 μm or less, more preferably 5 to 12 μm, and further preferably 6 to 10 μm. When the volume average particle size exceeds 14 μm, it becomes difficult to maintain good chargeability (charge amount and charge distribution) and appropriate chargeability over a long period of time, and reproducibility and gradation of fine dots. The graininess improving effect tends to be poor. On the other hand, if the volume average particle diameter is less than 5 μm, the fluidity of the toner may be deteriorated, and it becomes difficult to give sufficient chargeability from the carrier, fogging to the background portion occurs, and density reproducibility is lowered. May be easier.

  In the measurement of the particle size of the toner of the present invention (measurement when the particle diameter is 2 μm or more), a Coulter counter TA-II type (manufactured by Beckman-Coulter) is used as the measuring device, and the electrolyte is ISOTON-II ( Beckman-Coulter) was used. As a measurement method, 0.5 to 50 mg of a measurement sample is added to 2 ml of a 5% aqueous solution of a surfactant (sodium alkylbenzenesulfonate) as a dispersant. This was added to 100 ml of the electrolytic solution. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 minute, and the particle size distribution of particles of 2 to 60 μm is measured using the Coulter counter TA-II with an aperture diameter of 100 μm. Volume average distribution and number average distribution were obtained. For the particle size range (channel) obtained by dividing the measured particle size distribution, a volume cumulative distribution and a number cumulative distribution are drawn from the smaller particle size, and the cumulative particle size that becomes 50% cumulative is the volume average particle size and number average particle size. It was. The number of particles to be measured was 50,000.

  The particle size distribution of the toner particles is preferably 6 to 25% by number, more preferably 6 to 16% by number of toner particles having a particle size of 4 μm or less. When the toner particles having a particle size of 4 μm or less are less than 6% by number, there are few particles that contribute to minute dot reproducibility and graininess, and they are selectively consumed because they are effective particle sizes, so repetitive copying In this case, toner having a particle size that hardly contributes to development stays in the developing machine, and there is a concern that the image quality gradually deteriorates. On the other hand, if it exceeds 25% by number, the fluidity of the toner is deteriorated, so that the developer transportability is lowered, and there is a concern that the developability is adversely affected. On the other hand, toner particles having a particle diameter of 16 μm or more are preferably 1.0% by volume or less. If it exceeds 1.0% by volume, the fine line reproducibility and gradation may be adversely affected. During transfer, coarse toner particles of 16 μm or more are present in the toner layer, so that the electrostatic force between the photosensitive member and the transfer member can be reduced. Since it works to hinder the adhesion state, there is a risk of lowering transfer efficiency and eventually image quality. Because toner particles have such a particle size distribution, faithful reproducibility to fine latent image dots even in repetitive copying of documents with large image areas such as photographs, paintings, pamphlets, etc. Can be expected.

<External additive>
In order to have process compatibility in the copying machine, it is necessary that the toner is excellent in fluidity, caking resistance, fixing property, charging property, cleaning property and the like. Conventionally, for example, inorganic oxides such as silica and titanium oxide are externally added to the toner, and the silica is excellent in caking resistance and fluidity-imparting ability, but is inherent in the core. Due to the strong negative chargeability, there is a drawback that the environment dependence of charging is large. For this reason, JP-A-46-5782, JP-A-48-47345, JP-A-48-47346, JP-A-64-73354, JP-A-1-237561, etc. Various proposals have been made to hydrophobize the surface of the silica. However, conventionally, it has not been sufficiently achieved to improve the environmental dependency of charging without adversely affecting the caking resistance and fluidity of the silica. When titanium oxide is externally added to the toner, the charge level becomes low. Even with the same core, the surface hydrophobizing agent makes it easy to control the charge level and environmental dependency, but there are problems with cohesiveness after hydrophobizing treatment. Since the amount of hydrophobic treatment is limited, it is difficult to lower the charge level beyond a certain level. The titanium oxide is generally produced by purifying TiO (OH) ₂ obtained by a sulfuric acid method (wet method) using ilmenite ore, followed by heating and firing. In the titanium oxide obtained by such a production method, naturally, aggregated particles generated as a result of dehydration condensation also exist. However, it is not easy to redisperse such agglomerated particles with existing technology.

  When crystalline titanium oxide (rutile: specific gravity 4.2, anatase: specific gravity 3.9) is taken out as fine powder, secondary aggregation and tertiary aggregation are formed, and the effect of improving the fluidity of the toner is remarkably higher than that of silica. Inferior. In particular, along with the demand for high image quality in the market in recent years, there is a tendency for the diameter of the toner to progress. However, since the adhesion between particles increases by reducing the diameter of the toner, the fluidity of the toner further deteriorates, and the titanium oxide The fluidity-imparting ability of is further reduced.

  Therefore, for the purpose of achieving both improvement in fluidity and environmental dependency of charging, external addition to a toner using hydrophobic titanium oxide and hydrophobic silica that have been subjected to surface hydrophobization treatment is carried out. This is proposed in Japanese Patent No. 136755. However, there is a problem that either one of the characteristics of silica and titanium oxide tends to appear due to stress such as stirring, and it is difficult to compensate for each other's defects over a long period of time. For example, although the hydrophobic titanium oxide can initially improve the charging characteristics and fluidity of the toner, it is a coupling agent due to the collision between the toner and the carrier by stirring, or the friction between the toner, the blade and the sleeve. Is peeled off from the surface, and the charging characteristics of the toner are greatly changed. In the case of the hydrophobic titanium oxide, the reactivity of the surface of the titanium oxide core with respect to the coupling agent is weak, and it is assumed that the bond with the coupling agent is very weak compared to the case of silica. The In addition, the powder fluidity is deteriorated by embedding these external additives in the toner surface, and the contamination (spent) of these external additives on the carrier surface occurs.

  On the other hand, external addition of hydrophobic amorphous titanium oxide is proposed in Japanese Patent Laid-Open Nos. 5-204183 and 5-72797. However, in this case, since the adhesive force between the amorphous titanium oxide and the photoconductor is strong, there are problems such as scratching the photoconductor during cleaning and causing white spots on the image.

  Accordingly, an external additive can be added to the toner for developing an electrostatic charge image of the present invention, and among these, hydrophobic oxide fine particles are preferably used from the viewpoint of fluidity improvement, charge controllability, and heat storage property.

As the hydrophobic oxide fine particles, hydrophobic titanium oxide fine particles are preferable, and hydrophobic titanium oxide fine particles having a BET specific surface area of 40 to 250 m ² / g are particularly preferably used. The BET specific surface area is more preferably 80 to ²⁰⁰ m ² / g. If the BET specific surface area is larger than 250 m ² / g, it is effective for improving fluidity, but it becomes difficult to control the adhesion state on the toner particles and is easily embedded in the toner particle surface. There is a concern that the chargeability may decrease. Further, when the specific surface area is less than 40 m ² / g, there is a concern that the fluidity imparting ability is reduced, and filming or scratches on the surface of the photoreceptor (latent image carrier) may be induced.

Here, the measurement of the BET specific surface area was performed by the following method.
That is, it is obtained by adsorbing nitrogen gas using a SA3100 type specific surface area pore distribution measuring device (manufactured by Beckman Coulter, Inc.) as a measuring device.

Examples of the hydrophobic titanium oxide fine particles include those obtained by subjecting titanic oxide particles such as TiO ₂ and K ₂ O. (TiO ₂ ) n to a hydrophobic treatment. As the external additive, in addition to the hydrophobic titanium oxide fine _{particles, SiO 2, Al 2 O 3} , CuO, ZnO, SnO 2, CeO 2, Fe 2 O 3, MgO, BaO, CaO, K 2 O, Inorganic oxide particles such as Na ₂ O, ZrO ₂ , CaO.SiO ₂ , Al ₂ O ₃ .2SiO ₂ , CaCO ₃ , MgCO ₃ , BaSO ₄ , MgSO ₄ can also be used in combination.

  The hydrophobizing treatment can be performed by immersing an inorganic oxide in the hydrophobizing agent. Although there is no restriction | limiting in particular as a hydrophobization processing agent, For example, a silane coupling agent, a silicone oil, a titanate coupling agent, an aluminum coupling agent etc. are mentioned. These may be used individually by 1 type and may use 2 or more types together. Of these, silane coupling agents are preferred. As the silane coupling agent, for example, any of chlorosilane, alkoxysilane, silazane, and a special silylating agent can be used. Specifically, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, tetraethoxysilane, methyl Triethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, isobutyltriethoxysilane, decyltrimethoxysilane, hexamethyldisilazane, N, O- (bistrimethylsilyl) acetamide, N, N- (trimethylsilyl) ) Urea, tert-butyldimethylchlorosilane, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysila , Γ-methacryloxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-mercaptopropyl Examples include trimethoxysilane and γ-chloropropyltrimethoxysilane. The amount of the hydrophobizing agent varies depending on the kind of the inorganic oxide fine particles and cannot be generally defined, but is usually about 5 to 50 parts by mass with respect to 100 parts by mass of the inorganic oxide fine particles. Is preferred.

  The specific gravity of the hydrophobic titanium oxide fine particles is preferably 2.8 to 3.8, more preferably 3.0 to 3.6. When the specific gravity of hydrophobic titanium oxide fine particles is within the above numerical range, the specific gravity is smaller than that of conventional titanium oxide in improving the environmental dependency and fluidity of charging. This is advantageous in that the amount can be reduced and other characteristics can be compatible without impairing the transparency of the color toner. On the other hand, if the specific gravity of the hydrophobic titanium oxide fine particles is less than 2.8, it is necessary to add an excess of a hydrophobizing agent (for example, a silane compound), and this causes a partial reaction between the hydrophobizing agents. In addition, aggregates are easily formed and desired fluidity cannot be obtained. When the specific gravity of the hydrophobic titanium oxide fine particles exceeds 3.8, it is difficult to disperse on the toner surface during blending, and even if dispersed uniformly, the hydrophobic titanium oxide fine particles on the toner convex portions move to the concave portions due to stress in the development process. In the two-component developer, the hydrophobic titanium oxide fine particles that have been released are transferred to the carrier surface in a two-component developer because the desired fluidity and chargeability are reduced, or the convex hydrophobic titanium oxide fine particles are easily released. There is a case where the volume specific resistance value is greatly changed, and an excellent image quality cannot be obtained stably for a long period of time.

As the hydrophobic titanium oxide fine particles, those obtained by reacting TiO (OH) ₂ with a silane compound, in particular, can use a larger amount of silane compound than those obtained by baking and hydrophobizing. As a result, the specific gravity is preferably reduced. Moreover, when TiO (OH) ₂ and a silane compound are reacted, the silane compound can be reacted during the hydrolysis of TiO (OH) ₂ , and as a result, titanium oxide generated from TiO (OH) ₂ is primary particles. In this state, it can be surface-treated with a silane compound to obtain hydrophobic titanium oxide fine particles in a primary particle state without agglomeration, and has excellent fluidity and caking resistance, and excellent transparency required for color toners. This is advantageous in that a color image can be provided.

Here, the hydrophobic titanium oxide fine particles obtained by reacting TiO (OH) ₂ and a silane compound can be produced, for example, as follows. First, TiO (OH) ₂ is prepared by a sulfuric acid method (wet process) using an ilmenite ore represented by the following formula.
FeTiO ₂ + 2H ₂ SO ₄ → FeSO ₄ + TiOSO ₄ + 2H ₂ O
TiOSO ₄ + 2H ₂ O → TiO (OH) ₂ + H ₂ SO ₄

Next TiO (OH) ₂ produced, after preferably added silane compound TiO (OH) ₂ in aqueous dispersion, hydrophobized some or all of the OH groups in the TiO (OH) _2, the The reaction product can be obtained by filtration, washing, drying and grinding. The silane compound is not particularly limited, and examples thereof include the above-described silane compounds, that is, the above-described silane coupling agents, silicone oils, titanate-based coupling agents, aluminum-based coupling agents, and the like. Agents are preferred. As a usage-amount of a silane compound, about 2-50 mass parts is preferable normally with respect to 100 mass parts of TiO (OH) ₂ , About 5-20 mass parts is more preferable. In this reaction, the specific gravity, negative chargeability, etc. of the hydrophobic titanium oxide fine particles can be finely adjusted by appropriately selecting the kind of silane compound, the treatment amount, and the like. That is, when the treatment amount of the silane compound is increased, hydrophobic titanium oxide fine particles having a small specific gravity and high charge imparting ability can be obtained. On the other hand, when the treatment amount of the silane compound is reduced, the hydrophobic oxide having a large specific gravity and low charge imparting ability is obtained. Titanium fine particles are obtained.

  The electrostatic image developing toner of the present invention described above is not particularly limited as long as it has the above-described configuration, and can be appropriately manufactured according to a conventionally known method.

<Developer for developing electrostatic image>
As a developing method of the developer by the electrophotographic method, for example, a carcass developing method described in US Pat. No. 2,618,552, a magnetic brush method described in US Pat. No. 2,874,063, and US Pat. No. 2,895,847 are disclosed. And a jumping brush developing method in which development is performed by applying a bias electric field between the developer carrying member and the photosensitive member. Among them, a typical method of so-called two-component developer obtained by mixing a carrier and a toner is a magnetic brush method. In this method, magnetic particles such as steel and ferrite are used as a carrier, a developer composed of toner and a magnetic carrier is supported by a magnet, and the developer is formed in a brush shape by the magnetic field of the magnet. Next, when the magnetic brush comes into contact with the electrostatic latent image on the photoreceptor, the toner in the brush is attracted according to the amount of charge of the latent image and developed. The carrier is roughly classified into a coated carrier having a coating film on the surface and an uncoated carrier having no coating film on the surface. Therefore, various coated carriers have been developed and put into practical use. The properties of the coated carrier are required to at least be able to impart appropriate chargeability (charge amount and charge distribution) to the toner and to maintain the appropriate chargeability over a long period of time. Therefore, as various coated carriers that do not change the chargeability of the toner, are excellent in impact resistance and friction resistance, and are stable with respect to environmental changes such as humidity and temperature, for example, Japanese Patent Application Laid-Open No. 61-80161. As described in JP-A-61-80162 and JP-A-61-80163, a copolymer of a nitrogen-containing fluorinated alkyl (meth) acrylate and a vinyl monomer, or a fluorinated alkyl (meta There is a method of obtaining a coated carrier having a relatively long life by coating the surface of the carrier core material with a copolymer of acrylate and a nitrogen-containing vinyl monomer. Moreover, the surface of the carrier core material is coated with the polyamide resin described in JP-A-1-18150 or the melamine resin described in JP-A-2-79862, respectively, and is cured to be a relatively hard coating film. It is described to obtain a coated carrier having

  However, in the case of these carriers, there is a problem that contamination (impact) on the carrier surface by the toner component cannot be prevented. In order to prevent the impaction, for example, a surface energy such as a silicone resin as described in JP-A-60-186844 or a fluorine resin as described in JP-A-64-13560 can be used. It is also considered to form a carrier coating film using a resin having a small size. However, in such a carrier, although the silicone resin and the fluorine-based resin are relatively abundant in the vicinity of the carrier surface, there are only a few in the thickness direction of the coating layer. When used for a period, the effect of the resin is gradually lost due to wear of the coating film, and conversely, the impact is gradually generated. In addition, when performing continuous copying using such a developer, an image with excellent density reproducibility and image quality can be obtained initially, but after tens of thousands of copies, the image density decreases and The tonality and graininess become poor. In particular, when a large amount of titanium oxide is used such as a toner whose colorant concentration is increased in order to obtain the above-described high concentration, especially white toner, image quality deterioration due to contamination (impact) on the carrier surface is inevitable.

  On the other hand, in the developer of the present invention comprising the above-described toner and carrier, it is preferable to use a core material whose surface is coated with a coating resin containing a resin such as a fluorine-based resin.

The core material preferably has an electric resistance of 1 × 10 ^7.5 to 1 × 10 ^9.5 Ω · cm. If this electrical resistance is less than 1 × 10 ^7.5 Ω · cm, when the toner concentration in the developer is reduced by repeated copying, charges may be injected into the carrier and the carrier itself may be developed. On the other hand, if the electric resistance is greater than 1 × 10 ^9.5 Ω · cm, the image quality such as the outstanding edge effect and pseudo contour may be adversely affected.

  As shown in FIG. 1, the electrical resistance is measured by holding the measurement sample 3 with a thickness H and sandwiching it between the lower electrode 4 and the upper electrode 2 and measuring the thickness with a dial gauge while applying pressure from above. The electrical resistance was measured with a high voltage ohmmeter 5. Specifically, the carrier sample was filled in the lower electrode 4 of 100φ, the upper electrode 2 was set, a load of 3.43 kg was applied from above, and the thickness was measured with a dial gauge. Next, a voltage was applied and the current value was read to determine the volume resistivity.

(Core material)
The core material is not particularly limited as long as the above conditions are satisfied. For example, magnetic metals such as iron, steel, nickel, and cobalt, alloys of these with manganese, chromium, rare earth, and magnetic materials such as ferrite and magnetite. An oxide etc. are mentioned. Among these, ferrite, particularly an alloy with manganese, lithium, strontium, magnesium or the like is preferable from the viewpoint of core surface properties and core material resistance.

(Coating resin)
The resin used for the coating resin is particularly preferably a fluorine-based resin, and the fluorine-based resin can be appropriately selected according to the purpose, but polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polychloro Known resins such as fluorine-based resins such as trifluoroethylene can be used. These may be used individually by 1 type and may use 2 or more types together.

  In the carrier, it is preferable that at least resin particles and / or conductive particles are dispersed in the coating film coated with the coating resin. When the resin particles are dispersed in the coating film, they are uniformly dispersed in the thickness direction and the tangential direction of the carrier surface. Surface formation similar to that at the time of use can be maintained, and good charge imparting ability for the toner can be maintained for a long period of time. Further, when conductive particles are dispersed in the coating film, the conductive film is uniformly dispersed in the thickness direction and the tangential direction of the carrier surface. Even if it wears out, it can always maintain the same surface formation as when it is not used, and carrier deterioration can be prevented for a long time. In addition, when the resin particle and electroconductive particle are disperse | distributed to a coating film, the above-mentioned effect can be show | played simultaneously.

  Examples of the resin particles include thermoplastic resin particles and thermosetting resin particles. Among these, thermosetting resins are preferable from the viewpoint of relatively easily increasing the hardness, and resin particles made of nitrogen-containing resin containing N atoms are preferable from the viewpoint of imparting negative chargeability to the toner. In addition, these resin particles may be used individually by 1 type, and may use 2 or more types together. The average particle diameter of the resin particles is preferably about 0.1 to 2 μm, and more preferably 0.2 to 1 μm, for example. If the average particle size of the resin particles is less than 0.1 μm, the dispersibility of the resin particles in the coating film is very poor. On the other hand, if the average particle size exceeds 2 μm, the resin particles easily fall off from the coating film. It may not be effective. As conductive particles, metal particles such as gold, silver and copper, carbon black particles, semiconductive oxide particles such as titanium oxide and zinc oxide, titanium oxide, zinc oxide, barium sulfate, aluminum borate, potassium titanate Examples thereof include particles whose surface such as powder is covered with tin oxide, carbon black, metal or the like. These may be used individually by 1 type and may use 2 or more types together. Among these, carbon black particles are preferable from the viewpoints of production stability, cost, conductivity, and the like. The type of carbon black is not particularly limited, but carbon black having a DBP oil absorption of about 50 to 250 ml / 100 g is preferable because of excellent production stability.

  In the carrier, specifically, the surface of the core material (carrier core material) is coated with the coating resin. As a method of immersing in the coating film forming liquid containing the coating resin, the coating film forming liquid is used as the carrier core material. And a kneader coater method in which the carrier core material is mixed with a coating film forming solution in a state where the carrier core material is suspended by flowing air, and the solvent is removed. Among these, the kneader coater method is preferable in the present invention. The solvent used in the coating film forming solution is not particularly limited as long as it can dissolve only the coating resin, and can be selected from known solvents such as toluene, Aromatic hydrocarbons such as xylene, ketones such as acetone and methyl ethyl ketone, and ethers such as tetrahydrofuran and dioxane.

  The developer for developing an electrostatic charge image of the present invention has an absolute value of 20 to 50 μC / g when the toner concentration (toner / carrier ratio) is 8% and the charge generation environment is 25 ° C. and 50 RH%. Preferably, it is 25 to 45 μC / g, more preferably 27 to 40 μC / g. When the absolute value of the charge amount is less than 20 μC / g, background fogging, image blanking, carrier scattering, and the like may occur. On the other hand, if it exceeds 50 μC / g, the image density may be lowered due to poor development. This amount of charge can be appropriately adjusted depending on, for example, the amount of carrier coating resin, the amount of crosslinked melamine resin fine particles, the amount of fluorine in the coating resin, and the like.

  The electrostatic charge image developer of the present invention can be prepared by mixing the above-mentioned specific carrier and specific toner, but this preparation method is not particularly limited and is appropriately performed according to a conventionally known method.

(Image forming method)
In the image forming method of the present invention, the electrostatic latent image formed on the surface of the image carrier is developed using a plurality of color toners including at least the white electrostatic charge image developing toner of the present invention to obtain a toner image. And a fixing step of fixing the toner image to obtain a fixed image. As the plurality of color toners, it is preferable to use four color toners of three color toners selected from yellow, magenta, cyan and black toners, and the white toner.

  In particular, when a fixed image is obtained using a plurality of colors of toner on a transparent medium such as an OHP sheet, the transmission density of the image is preferably 2.60 or more as a concealing property, and is 3.00 or more. Although it is particularly preferable, the transmission density can be achieved by obtaining a fixed image by the image forming method of the present invention.

In the present invention, the transmission density was measured with X-rite 341 (manufactured by X-rite). More specifically, an electrophotographic copying machine (ColorDocuTech 60 manufactured by Fuji Xerox Co., Ltd.) is used, and a full color OHP film (manufactured by Fuji Xerox Co., Ltd.) has a monochromatic toner amount of 5 g / m ² per unit area (20 g / m by superimposing four colors). ² ) A printout was made so that A 5 × 5 cm patch was prepared for the sample image, and five points at the center and four corners were measured, and the average value was taken as the transmission density.

  In the image forming method, each step is not particularly limited and can be performed by a conventionally known method, and other steps can be provided.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, these examples do not limit the present invention. In the following, “part” and “%” mean “part by mass” and “% by mass” unless otherwise specified.

-Preparation of yellow toner particles A-
・ Polyester resin: 82 parts (terephthalic acid / bisphenol A ethylene oxide adduct /
Linear polyester by condensation polymerization of cyclohexanedimethanol,
Tg = 65 ° C., Mn = 4500, Mw = 18000)
・ C. I. Pigment Yellow 180 (manufactured by Clariant Japan): 10 parts, paraffin wax HNP9 (melting point 75 ° C .: manufactured by Nippon Seiki): 8 parts The above components are sufficiently premixed with a Henschel mixer and melt kneaded with a twin-screw roll mill. After cooling, the mixture was finely pulverized with a jet mill, and further classified twice with an air classifier to produce yellow toner particles A having an average volume particle size of 7.2 μm and a colorant concentration of 10%.

-Preparation of magenta toner particles B-
C. I. Pigment Yellow 180 instead of C.I. I. Magenta toner having the same volume particle size of 7.8 μm and a colorant concentration of 8%, except that Pigment Red 122 (manufactured by Dainichi Seika Co., Ltd.) was used and the content was changed to 8 parts. Particle B was produced.

-Preparation of Sian toner particles C-
C. I. Pigment Yellow 180 instead of C.I. I. Pigment Blue 15: 3 (manufactured by Dainichi Seika Co., Ltd.) was used and the content was changed to 4 parts. The formulation was the same as that of yellow toner particles A, and the average volume particle size was 7.5 μm and the colorant concentration was 4%. Sian toner particles C were produced.

−Preparation of black toner particles D−
C. I. Except for using carbon black (R330: manufactured by Cabot Corporation) instead of CI Pigment Yellow 180 and changing the content to 6 parts, the same volume formulation as the yellow toner particles A, the average volume particle size of 8.0 μm, and the colorant concentration 6% black toner particles D were produced.

-Preparation of white toner particles E-
<Method for producing crystalline polyester resin>
A heat-dried three-necked flask was charged with 98 mol% dimethyl sebacate, 2 mol% dimethyl-5-sulfonic acid sodium salt, 100 mol% ethylene glycol, and 0.3 parts of dibutyltin oxide as a catalyst. The air inside was made an inert atmosphere with nitrogen gas, and the mixture was stirred and refluxed at 180 ° C. for 5 hours by mechanical stirring. Thereafter, the temperature was gradually raised to 230 ° C. under reduced pressure, and the mixture was stirred for 2 hours. When it became viscous, it was air-cooled to stop the reaction, and then dried to synthesize a crystalline polyester resin. It was Tg = 64 degreeC, Mn = 4600, Mw = 9700 of the crystalline polyester resin obtained by molecular weight measurement (polystyrene conversion) by gel permeation chromatography.

・ Crystalline polyester resin ・ ・ ・ ・ ・ ・ 20 parts ・ Amorphous polyester resin ・ ・ ・ ・ ・ ・ 42 parts (Terephthalic acid / bisphenol A ethylene oxide adduct /
Linear polyesters by condensation polymerization of cyclohexanedimethanol.
(Tg = 62 ° C., Mn = 4,000, Mw = 12,000)
・ Titanium oxide (CR60: Ishihara Sangyo) ・ ・ ・ ・ ・ ・ 30 parts ・ Paraffin wax HNP9 (melting point 75 ° C .: made by Nippon Seiki) ・ ・ ・ ・ ・ ・ 8 parts The mixture is melt-kneaded with a biaxial roll mill, finely pulverized with a jet mill after cooling, and further classified twice with a wind classifier. White toner particles having an average volume particle size of 7.0 μm and a colorant concentration of 30% E was produced.

-Preparation of white toner particles F-
Except that the content of titanium oxide was changed to 20 parts and the content of the amorphous resin polyester resin was changed to 52 parts, the same formulation as the white toner particles E, an average volume particle size of 7.4 μm, and a colorant concentration of 20% White toner particles F were prepared.

-Preparation of white toner particles G-
Except that the content of titanium oxide was changed to 40 parts and the content of the amorphous resin polyester resin was changed to 32 parts, the formulation was the same as that of the white toner particles E, the average volume particle diameter was 6.9 μm, and the colorant concentration was 40%. White toner particles G were prepared.

-Preparation of white toner particles H-
Except for changing the titanium oxide content to 15 parts and the amorphous resin polyester resin content to 57 parts, the same formulation as the white toner particles E, with an average volume particle size of 7.2 μm and a colorant concentration of 15% White toner particles H were prepared.

-Preparation of white toner particles I-
Except that the content of titanium oxide was changed to 12 parts and the content of the amorphous resin polyester resin was changed to 60 parts, the formulation was the same as that of the white toner particles E, the average volume particle size was 7.5 μm, and the colorant concentration was 12%. White toner particles I were prepared.

-Preparation of white toner particles J-
Except that the content of titanium oxide was changed to 45 parts and the content of the amorphous resin polyester resin was changed to 27 parts, the formulation was the same as that of the white toner particles E, the average volume particle size was 6.8 μm, and the colorant concentration was 45%. White toner particles J were prepared.

-Preparation of white toner particles K-
White toner particles K having an average volume particle diameter of 7.5 μm and a colorant concentration of 30% were prepared in the same manner as the white toner particles E, except that the crystalline polyester resin used was replaced with an amorphous polyester resin. .

-Preparation of white toner particles L-
Except for changing the content of the crystalline polyester resin to 45 parts and the non-crystalline polyester resin content to 17 parts, the formulation is the same as that of the white toner particles E, the average volume particle size is 7.0 μm, and the colorant concentration is 30%. White toner particles L were prepared.

-Preparation of hydrophobic titanium oxide fine particles A-
First, ilmenite was used as an ore, dissolved in sulfuric acid to separate iron powder, and TiO (OH) ₂ was produced using a wet precipitation method in which TiOSO ₄ was hydrolyzed. In the process of producing TiO (OH) ₂ , dispersion adjustment and water washing for hydrolysis and nucleation were performed. Next, 100 parts of TiO (OH) ₂ obtained in 1000 parts of water was dispersed, and 20 parts of isobutyltrimethoxysilane was added dropwise thereto while stirring at room temperature. Subsequently, this was filtered and water washing was repeated. Then, the titanium oxide surface hydrophobized with isobutyltrimethoxysilane was dried at 150 ° C. to prepare hydrophobic titanium oxide fine particles A having a BET specific surface area of 120 m ² / g and a specific gravity of 3.4.

-Preparation of hydrophobic titanium oxide fine particles B-
In the preparation of the hydrophobic titanium oxide fine particles A, except that the amount of isobutyltrimethoxysilane was changed to 10 parts, it was carried out in the same manner as the preparation of the hydrophobic titanium oxide fine particles A, and the BET specific surface area was 100 m ² / g. Hydrophobic titanium oxide fine particles B having a specific gravity of 3.5 were prepared.

-Production of hydrophobic titanium oxide fine particles C-
The preparation of the hydrophobic titanium oxide fine particles A was carried out in the same manner as the preparation of the hydrophobic titanium oxide fine particles A except that the amount of isobutyltrimethoxysilane was changed to 30 parts and the drying temperature was changed to 180 ° C. There was 32m ² / g, specific gravity was prepared hydrophobic fine titanium oxide particles C is 3.2.

-Preparation of hydrophobic titanium oxide fine particles D-
In 1000 parts of water, 100 parts of TiO (OH) ₂ obtained in the preparation of the hydrophobic titanium oxide fine particles A was dispersed, and 25 parts of methyltrimethoxysilane was added dropwise thereto while stirring at room temperature. Subsequently, this was filtered and water washing was repeated. Then, the titanium oxide surface-hydrophobized with methyltrimethoxysilane was dried at 180 ° C. to prepare hydrophobic titanium oxide fine particles D having a BET specific surface area of 280 m ² / g and a specific gravity of 3.3.

-Hydrophobic silicon dioxide fine particles E-
As hydrophobic silicon dioxide fine particles F, “RX200” (BET specific surface area of 140 m ² / g and specific gravity of 2.2) manufactured by Nippon Aerosil Co., Ltd. was used.

-Production of carrier A-
・ Ferrite particles (electric resistance 1 × 10 ⁸ Ω · cm, volume average particle size 35 μm)
··· 100 parts · Toluene ··· 14 parts · Perfluorooctylethyl acrylate / methyl methacrylate copolymer
(Copolymerization ratio 40:60, Mw = 50,000) ··· 1.6 parts · Carbon black (VXC-72: manufactured by Cabot Corporation) ··· 0.12 parts · Cross-linked melamine resin (average particle size) 0.3 μm)... 0.3 parts The above components excluding ferrite particles are dispersed with a stirrer for 10 minutes to prepare a coating film forming solution. Was put in a vacuum degassing kneader and stirred at 60 ° C. for 30 minutes, and then the pressure was reduced and toluene was distilled off to form a coating film on the surface of the ferrite particles, whereby carrier A was produced. In the perfluorooctylethyl acrylate / methyl methacrylate copolymer used as the resin in the coating film, carbon black particles and cross-linked melamine resin particles were diluted with toluene and dispersed. The carbon black and the cross-linked melamine resin particles were uniformly dispersed.

-Production of carrier B-
Carrier B was prepared with the same formulation as Carrier A, except that the perfluorooctylethyl acrylate / methyl methacrylate copolymer used as the resin in the coating film was replaced with a silicone resin (SR2411: manufactured by Toray Dow Corning Silicone). .

  The compositions of the toner, external additive, and carrier obtained by the above method are shown in Tables 1, 2, and 3, respectively.

Example 1
Using the toner particles having the combinations shown in Table 4 below, 0.6 parts of the external additive shown in Table 4 is externally added to each 100 parts of the toner particles, and mixed with a Henschel mixer to add the external additive toner of each color. Produced. Further, 8 parts of each externally added toner and 92 parts of the carrier listed in Table 4 were mixed to prepare each color developer.

(Examples 2-11 and Comparative Examples 1-5)
Except that the toner particles, external additives, and carriers used were changed to those shown in Table 4, in the same manner as in Example 1, the external color toners and developers in Examples 2 to 11 and Comparative Examples 1 to 5 were used. Was made.

[Evaluation]
The following evaluations were performed using the obtained color developers. In the following evaluation test, a copy test was carried out using an electrophotographic copying machine (Color DocuTech 60 manufactured by Fuji Xerox Co., Ltd.) with each obtained color developer contained in a developer machine. The results are shown in Table 5.

-Measurement of image thickness-
Ten OHP sheets printed with four colors superimposed were stacked and the thickness was measured using a micrometer.

-Evaluation of concealment-
A copy test was performed on a full-color OHP film (Fuji Xerox Co., Ltd.) so that the amount of single-color toner per unit area was 5 g / m ² (20 g / m ² for four color overlay). The transmission density of the 100,000th sample image was measured with X-rite 341 (manufactured by X-rite) and evaluated according to the following criteria. The sample image was prepared as a 5 × 5 cm patch, and five points at the center and four corners were measured, and the average value was taken as the transmission density. Table 5 shows the film thickness (calculated value from the toner amount) of the obtained sample image together with the transmission density.
○: Transmission density of 3.00 or more Δ: Transmission density of 2.60 or more and less than 3.00 ×: Transmission density of less than 2.60

-Evaluation of image intensity-
The first and 100,000th sample images were obtained in the same manner as described above, and a surface tester (HEIDON Type 14DR: manufactured by Shinto Kagaku Co., Ltd.) was used with a needle having a needle tip diameter of 0.2 mm with a load of 50 g. Five locations were scratched and the degree of loss was visually observed and evaluated according to the following criteria.
○: Only the surface is scratched and there is no image defect △: Part of the image is missing ×: More than half of the image is missing

-Evaluation of charge amount-
In each of the examples and comparative examples, the white developer used was left in an electrophotographic copying machine (Color DocuTech 60 manufactured by Fuji Xerox Co., Ltd.) at 25 ° C. and 50% RH for 24 hours, and then developed in the electrophotographic copying machine. The machine was idled for 3 minutes, 2 g of white developer was sampled from the sleeve, and the initial charge amount was measured using a blow-off measuring device TB200 (manufactured by Toshiba Corporation). The cage uses a 16 μm mesh. The measurement environment was measured under conditions of 25 ° C./50% RH.
Further, the white developer after the copy test of 100,000 sheets was sampled from the sleeve, and the charge amount was similarly measured using a blow-off measuring device.

-Image quality evaluation-
A copy test of a chart with density gradation was performed, and the image quality of the first and 100,000th images was evaluated as follows.
The initial image quality was visually evaluated for its gradation, density uniformity, and the presence or absence of edge effects. On the other hand, the image quality after copying 100,000 sheets was evaluated visually from the viewpoints of graininess, gradation / pseudo contour, density reproducibility, and other image quality defects. Note that C2 paper (Fuji Xerox Co., Ltd.) was used as the photographic paper.
○: No problem △: Level with some defects but no problem ×: Image quality defect

  In Table 5, * 1 indicates the occurrence of blister / pinhole, * 2 indicates the density defect, * 3 indicates the edge effect and false contour defect, * 4 indicates the occurrence of fog, and * 5 indicates the occurrence of color streaking.

It is explanatory drawing which shows the method of measuring the electrical resistance of a carrier.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Guard electrode 2 Upper electrode 3 Measurement sample 4 Lower electrode 5 High voltage resistance meter 6 Sample holding ring 7 DC stabilized power supply

Claims (3)

A white electrostatic charge image developing toner comprising a colorant and a binder resin composed of a crystalline resin and an amorphous resin,
The content of the crystalline resin in the toner is 5 to 25% by mass,
The toner for developing an electrostatic charge image, wherein the content of the colorant in the toner is 15 to 40% by mass.   An electrostatic charge image developing developer comprising the electrostatic charge image developing toner according to claim 1 and a carrier. A developing step of developing a latent image formed on the surface of the image carrier using a plurality of color toners including at least white toner to obtain a toner image; and a fixing step of fixing the toner image to obtain a fixed image; A multicolor image forming method comprising:
The toner for developing an electrostatic charge image according to claim 1 is used as the white toner.
And a transmission density of the fixed image is 3.00 or more.

Images