JP5103360B2 - Developer for electrostatic latent image development - Google Patents

Description

  The present invention relates to a developer for developing an electrostatic latent image.

  In recent years, with the development of color printing technology based on electrophotography, it has become possible to obtain copies that faithfully reproduce original images. However, on the other hand, it may be used for counterfeiting of prohibited items such as banknotes and securities.

  Therefore, at the time of reading a document, regardless of whether the document is a specific document such as banknotes or securities, a tracking pattern that represents information related to image formation such as the identification number of the image forming apparatus and the image formation date, A technique has been proposed in which an image is embedded and printed as a specific pattern or color that is difficult to be recognized by the human eye, a so-called hidden pattern.

For example, Patent Document 1 proposes a method of printing by adding information such as a manufacturing number of an image forming apparatus to a yellow component of an output image signal as a specific pattern that is difficult for human eyes to identify.
In this way, by adding a specific pattern that is difficult to be recognized by the human eye to a copy, when a specific original that should not be copied is copied, it is a clue to specify the device that performed the copy. be able to.
JP-A-4-294682

  However, as described in Patent Document 1, in the method of adding a specific pattern to yellow toner, the specific pattern is printed as embedded information by yellow toner even in an area where an image is not formed (non-image area). The yellow toner was easily consumed excessively compared to the color toner.

  The present invention has been made in view of the above circumstances, and an object thereof is to realize a developer for developing an electrostatic latent image that can print embedded information without consuming excessive toner.

The developer for developing an electrostatic latent image of the present invention is a developer for developing an electrostatic latent image comprising a toner containing a binder resin and a pigment, and resin particles, and the resin particles are engraved on the surface. The maximum diameter of the surface on which the marking is applied is 5 to 25 μm.
Further, when the glass transition temperature of the resin particles is Tg1, and the glass transition temperature of the toner is Tg2, it is preferable that the following formula (1) is satisfied.
Further, when the melting point of the resin particles is Tm1 and the melting point of the toner is Tm2, it is preferable that the following formula (2) is satisfied.
Tg2 <Tg1 <Tg2 + 10 (1)
Tm2 <Tm1 <Tm2 + 10 (2)

The resin particle content is preferably 0.1 to 15 parts by mass with respect to 100 parts by mass of the toner.
The developer for developing an electrostatic latent image of the present invention is a dry developer.
The developer for developing an electrostatic latent image of the present invention is a wet developer in which the toner and the resin particles are dispersed in an insulating liquid carrier.

  According to the developer for developing an electrostatic latent image of the present invention, the embedded information can be printed without excessively consuming the toner.

The developer for developing an electrostatic latent image of the present invention (hereinafter sometimes simply referred to as “developer”) includes toner and resin particles.
[toner]
The toner used in the present invention contains a binder resin and a pigment.
Examples of the binder resin include styrene resins, acrylic resins, styrene-acrylic copolymer resins, olefin resins such as polyethylene and polypropylene, vinyl chloride resins, polyester resins, polyamide resins, polyurethane resins, Thermoplastic resins such as polyvinyl alcohol resins, vinyl ether resins, N-vinyl resins, styrene-butadiene resins, fluorine resins; bisphenol A type epoxy resins, hydrogenated bisphenol A type epoxy resins, novolac type epoxy resins, polyalkylenes Examples thereof include epoxy resins such as ether type epoxy resins and cycloaliphatic type epoxy resins, and thermosetting resins such as cyanate resins.

Examples of pigments include black pigments such as carbon black, acetylene black, lamp black, and aniline black; yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa Yellow pigments such as Yellow G, Hansa Yellow 10G, Benzidine Yellow G, Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake, Yellow CI Pigment Yellow; Orange pigments such as Vulcan Orange, Indanthrene Brilliant Orange GK; Bengala, Cadmium Red, Lead Tan, Mercury Cadmium, Permanent Red 4R, Lithium Red pigments such as Lured, Pyrazolone Red, Watching Red Calcium Salt, Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B, Magenta CI Pigment Red; Manganese Purple, Fast Violet B, Methyl Purple pigments such as violet lake; blue pigments such as bitumen, cobalt blue, alkali blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated, first sky blue, indanthrene blue BC; chrome green, Green pigments such as chromium oxide, pigment green B, malachite green lake, final yellow green G; zinc white, titanium oxide, antimony white, sulfur White pigments such as zinc; barite powder, barium carbonate, clay, silica, white carbon, talc, extender pigments such as alumina white and the like.
2-20 mass parts is preferable with respect to 100 mass parts of binder resin, and, as for content of a pigment, 5-15 mass parts is more preferable.

In addition to the binder resin and pigment described above, the toner may contain other components generally used in the toner, such as a release agent and a charge control agent, as necessary.
Examples of the release agent include waxes and low molecular weight olefin resins. Examples of waxes include polyhydric alcohol esters of fatty acids, higher alcohol esters of fatty acids, alkylene bis fatty acid amide compounds, natural waxes, and the like. Examples of the low molecular weight olefin resin include polypropylene, polyethylene, propylene-ethylene copolymer and the like having a number average molecular weight in the range of 1,000 to 10,000, preferably 2,000 to 6,000. Polypropylene is preferred.
When the toner contains a release agent, the content thereof is preferably 2 to 8 parts by mass, more preferably 3 to 8 parts by mass with respect to 100 parts by mass of the binder resin.

Examples of the charge control agent include a positive charge control agent and a negative charge control agent.
Examples of the positive charge control agent include azine compounds, nigrosine compounds, quaternary ammonium salt compounds, and higher fatty acid metal salts.
Examples of the negative charge control agent include an organometallic complex or a chelate compound.
When the toner contains a charge control agent, the content thereof is preferably 0.1 to 10.0 parts by mass, more preferably 0.5 to 5.0 parts by mass with respect to 100 parts by mass of the binder resin.

The toner can be produced by a known kneading and pulverizing method, polymerization method, spinning method or the like. For example, in the case of a kneading and pulverizing method, it is manufactured by the following procedure.
Necessary raw materials such as the binder resin, pigments for each color toner, release agent, charge control agent, etc. are mixed with a mixer such as a Henschel mixer, melted and mixed with a twin screw extruder, etc., then a cutter mill, etc. Coarsely pulverize with a hammer mill or the like. Thereafter, classification is performed by a classifier such as an airflow classifier to obtain toner mother particles corresponding to the toner of each color.

The toner base particles obtained in this way may be used as toner as they are, but if necessary, a toner base particle added with an external additive may be used as toner.
Examples of the external additive include inorganic oxides such as silica, titanium oxide, and alumina, and metal soaps such as calcium stearate.
The content of the external additive contained in the toner is preferably 0.1 to 5.0 parts by mass with respect to 100 parts by mass of the toner base particles.
The method of adding the external additive is not particularly limited, and examples thereof include a method of mixing the toner base particles and the external additive with a mixer such as a Henschel mixer.

The volume-based average particle size of the toner (toner base particles when an external additive is included) is preferably 3 to 10 μm.
The volume-based average particle size of the toner was calculated from the measured value of the particle size distribution measured using, for example, a particle size distribution measuring apparatus “Multimizer III” manufactured by Beckman Coulter, Inc. under the condition of an aperture diameter of 100 μm. It shall be expressed as a value.

In addition, the coefficient of variation (CV value) based on the number of toners (toner base particles when an external additive is included) is preferably 15 to 25%.
The volume-based CV value of the toner can be obtained from the following formula (3) by measuring the particle diameter using, for example, a particle size distribution measuring device “Multimizer III” manufactured by Beckman Coulter. As the CV value becomes smaller, the particle diameter tends to be uniform (the particle size distribution becomes sharper).
CV value = (standard deviation / number-based average particle diameter) × 100 (3)

[Resin particles]
The resin particles used in the present invention contain a resin.
As the resin contained in the resin particles, one or more of the binder resins exemplified above in the description of the toner can be selected and used. The resin contained in the resin particles may be the same type as the binder resin contained in the toner, or may be a different resin, but is preferably the same type.

In addition to the resin described above, the resin particles may contain a pigment, a charge control agent, and the like as necessary.
As the pigment and the charge control agent, one or more selected from the pigments and charge control agents exemplified above in the description of the toner can be used. The pigment and charge control agent contained in the resin particles may be the same type as the pigment and charge control agent contained in the toner, or may be different types, but are preferably the same type. In particular, the pigment contained in the resin particles is a pigment and a pigment that is suitable for color and can easily form a high-quality image comparable to a developer that does not contain resin particles, and can prevent image deterioration. It is preferable that they are the same.

When the resin particles contain a pigment, the content is preferably 4 to 10 parts by mass with respect to 100 parts by mass of the resin contained in the resin particles.
If the pigment content is within the above range, the resin particles and the toner have the same color density (concentration), so that it is difficult to visually distinguish the resin particles from the toner in the resulting image. A uniform image can be easily formed. When the content of the pigment is out of the above range, the resin particles appear to be scattered on the image, which may appear as a dot pattern.
Therefore, it is particularly preferable that the content of the pigment contained in the resin particles is approximately the same as the content of the pigment contained in the toner.

When the resin particles contain a charge control agent, the content is preferably 1.5 to 15.0 parts by mass, and 1.5 to 8.0 parts by mass with respect to 100 parts by mass of the resin contained in the resin particles. Is more preferable.
If the content of the charge control agent is within the above range, the charging performance of the resin particles is not significantly different from the charging performance of the toner, so that a good image can be formed without deteriorating the developability of the toner.

The resin particles are engraved on the surface. More specifically, characters, symbols, and diagrams showing such information so that information such as toner identification numbers, toner manufacturer names, toner sales destinations, image forming apparatus identification numbers, and image formation dates can be read. Etc. are imprinted on the surface of the resin particles.
By using resin particles whose surface is engraved, toner and resin particles are included in the obtained image, and necessary information can be printed as embedded information. By observing such an image with a microscope or the like, it is possible to read the embedded information stamped on the surface of the resin particles. For example, if the information identifying the toner is stamped on the resin particles, the manufacturer of the toner, When the information for identifying the sales destination of the toner is engraved, the supplier of the sales destination can be specified. When the information for identifying the image forming apparatus is engraved, the image forming apparatus can be specified.

Therefore, for example, when a specific manuscript that should not be originally copied is copied using the developer of the present invention, information printed on the surface of the resin particles by observing the copy with a microscope or the like, for example, a toner manufacturer Or an image forming apparatus can be read, and a clue for identifying the person involved in copying can be obtained.
Note that the markings on the surface of the resin particles can be read by using a microscope or the like and are difficult to be recognized by human eyes, so that the appearance of the image is hardly affected.

  In addition, the developer of the present invention prints embedding information by imprinting the surface of the resin particles, and can obtain necessary information by reading the imprint on the surface of the resin particles. The toner and resin particles can be combined. Therefore, there is no need to add a specific pattern only to a specific toner (yellow toner) as in the prior art. Furthermore, since the present invention reads information on the formed image, the specific pattern is not printed in the non-image area. Therefore, the specific toner is not easily consumed excessively.

The resin particle has a maximum surface diameter of 5 to 25 μm, and preferably 7 to 15 μm.
If the maximum diameter is 5 μm or more, the surface of the resin particles can be prevented from being covered with the toner when mixed with the toner, so that the marking on the surface of the resin particles can be easily read. On the other hand, if the length of one side is 25 μm or less, a thin line image such as a barcode can be formed without degrading the image quality.
In the present invention, the “maximum diameter” means the diameter when the shape of the engraved surface is a circle, and circumscribes the shape when the shape of the engraved surface is a polygon. It is the diameter of a circle.

The shape of the resin particles is not particularly limited as long as the surface is engraved, and examples thereof include columnar bodies such as prisms and cylinders, pyramids such as pyramids and cones, and spheres. Among these, from the viewpoint of easy production, a column is preferable, and specifically, a substantially cubic or a substantially rectangular parallelepiped is preferable.
Moreover, when the shape of the resin particle is a column or a cone, the marking may be performed on at least one surface, but the marking may be performed on a plurality of surfaces or the entire surface.

When the resin particles are columns or cones, the surface on which the marking is applied is preferably the bottom surface (however, when the resin particles are columns, the bottom surface or the surface facing the bottom surface).
Moreover, 5-25 micrometers is preferable and, as for the height of a column or a cone, 8-20 micrometers is more preferable. If the height of the column or cone is 5 μm or more, it can be suppressed from being buried in the toner when mixed with the toner. On the other hand, if the height of the column or cone is 25 μm or less, a thin line image such as a barcode can be formed without degrading the image quality.

  In addition, when the resin particle is a sphere, the maximum diameter of the surface on which the marking is applied means the diameter of the sphere, and the diameter is 5 to 25 μm, and preferably 8 to 20 μm. If the diameter of the sphere is within the above range, the marking on the surface of the resin particles can be easily read without degrading the image quality.

The resin particles whose surface is engraved can be produced, for example, by the following method.
That is, necessary raw materials such as the above-described resin, pigment, charge control agent and the like are mixed with a mixer such as a Henschel mixer, melt-mixed with a twin screw extruder or the like, and then molded into a plate shape to obtain a resin plate. Next, with a mold engraved with characters, symbols, figures, etc. inverted, the resin plate is punched out to the desired shape and size, and the letters, symbols, figures, etc. engraved on the mold are on the surface. Obtain engraved resin particles.

[Others]
The developer of the present invention may contain a carrier as necessary.
When the developer is used as a dry developer, examples of the carrier include magnetic particles or resin particles in which a magnetic material is dispersed in a binder resin.
Examples of magnetic materials include magnetic metals such as iron, nickel, cobalt, alloys thereof, alloys containing rare earths, hematite, magnetite, manganese-zinc ferrite, nickel-zinc ferrite, manganese-magnesium Examples thereof include soft ferrites such as ferrite and lithium ferrite, iron-based oxides such as copper-zinc ferrite, and mixtures thereof.
Examples of the binder resin include vinyl resins, polyester resins, epoxy resins, phenol resins, urea resins, polyurethane resins, polyimide resins, cellulose resins, polyether resins, and mixtures thereof.
Magnetic particles are produced by a known method such as a sintering method or an atomizing method.
The carrier may have a coating layer made of a coating resin on its surface.

  When a developer is used as a wet developer (liquid developer), an insulating liquid carrier is used as a carrier. Specifically, aliphatic hydrocarbon, alicyclic hydrocarbon, aromatic hydrocarbon, halogenated A hydrocarbon, polysiloxane, etc. are mentioned, These can be used individually or in mixture. In particular, a normal paraffin solvent and an isoparaffin solvent are preferable in terms of odor, harmlessness, and cost.

[Developer for electrostatic latent image development]
The developer of the present invention includes the toner described above, resin particles, and, if necessary, a carrier.
The toner and resin particles in the developer are preferably a combination satisfying the following formula (1) when the glass transition temperature of the resin particles is Tg1 and the glass transition temperature of the toner is Tg2.
Tg2 <Tg1 <Tg2 + 10 (1)

  If the toner and resin particles satisfy the above formula (1), the temperature and pressure conditions for fixing the image transferred on the recording material such as paper are set to the conditions that only the toner melts. it can. Therefore, in the image fixed on the recording material, the resin particles can exist without being melted, so that the information stamped on the surface of the resin particles can be read with a microscope or the like. The resin particles are fixed on the recording material by the melted toner.

Since the glass transition temperatures of the toner and the resin particles correspond to the glass transition temperatures of the resins contained in the toner and the resin particles, a resin in which the glass transition temperature of the resin in the toner and the resin particles satisfies the above formula (1) is selected. Thus, it is preferable to produce toner and resin particles.
The glass transition temperature of the resin contained in the toner and the resin particles is not particularly limited as long as it satisfies the above formula (1). For example, the glass transition temperature of the binder resin contained in the toner is preferably 30 to 70 ° C.

A glass transition temperature can be calculated | required from the change point of the to-be-heated measured using a differential scanning calorimeter (DSC).
Specifically, an endothermic curve is measured using a differential scanning calorimeter “DSC-6200” manufactured by Seiko Instruments Inc. as a measuring device. This endothermic curve was measured by placing 10 mg of a measurement sample in an aluminum pan, using an empty aluminum pan as a reference, and measuring at a temperature range of 25 to 200 ° C. and a temperature increase rate of 10 ° C./min under normal temperature and humidity. It is obtained by doing. In the obtained endothermic curve, the temperature indicating the intersection of the tangent of the curve at the start of temperature rise and the tangent of the curve where the energy first decreases is defined as the glass transition temperature.

The toner and resin particles in the developer are preferably a combination satisfying the following formula (2) when the melting point of the resin particles is Tm1 and the melting point of the toner is Tm2.
Tm2 <Tm1 <Tm2 + 10 (2)

  If the toner and resin particles satisfy the above formula (2), the temperature and pressure conditions for fixing the image transferred on the recording material such as paper are set to the conditions that only the toner melts. it can. Therefore, in the image fixed on the recording material, the resin particles can exist without being melted, so that the information stamped on the surface of the resin particles can be read with a microscope or the like. The resin particles are fixed on the recording material by the melted toner.

Since the melting points of the toner and the resin particles correspond to the melting points of the resins contained therein, the toner and the resin particles are selected by selecting a resin that satisfies the above formula (2), respectively, in the toner and the resin particles. Is preferably produced.
The melting point of the resin contained in the toner and the resin particles is not particularly limited as long as it satisfies the above formula (2). For example, the melting point of the binder resin contained in the toner is preferably 100 to 140 ° C.

The melting point can be measured using a differential scanning calorimeter (DSC).
Specifically, the endothermic curve is measured using DSC in the same manner as the measurement of the glass transition temperature. The temperature showing the endothermic peak in the obtained endothermic curve is defined as the melting point.

  The content of the resin particles in the developer is preferably 0.1 to 15 parts by mass and more preferably 5 to 10 parts by mass with respect to 100 parts by mass of the toner. If the content of the resin particles is 0.1 parts by mass or more, the resin particles can be prevented from being buried in the toner when the developer is prepared. Therefore, if the image obtained from the developer of the present invention is observed with a microscope or the like, the information stamped on the surface of the resin particles can be easily read. On the other hand, if the content of the resin particles is 15 parts by mass or less, the ratio of the toner in the developer can be secured, so that the image can be sufficiently fixed on the recording material.

The developer of the present invention may be used as a wet developer as well as a dry developer.
When the developer is used as a dry developer, the developer is obtained by mixing toner, resin particles, and, if necessary, a carrier with a mixer such as a Henschel mixer.

On the other hand, when the developer is used as a wet developer, the toner, the resin particles, and the insulating liquid carrier are mixed with a dispersing machine such as a sand grinder to obtain a developer in which the toner and the resin particles are dispersed in the liquid carrier.
The wet developer can also be produced as follows. First, a liquid carrier is used as a polymerization medium, and various additives necessary for polymerization such as a monomer constituting a binder resin, a polymerization initiator, a pigment contained in the toner, and a release agent and a charge control agent are liquidized as necessary. The polymer is dissolved in a carrier and the monomer is radically polymerized by heating to precipitate polymer particles (toner). By adding separately produced resin particles to this, a developer in which toner and resin particles are dispersed in a liquid carrier can be obtained without solvent substitution.

The developer of the present invention described above is engraved with information such as the toner identification number, toner manufacturer name, toner sales destination, image forming apparatus identification number, and image formation date on the surface having a maximum diameter of 5 to 25 μm. Therefore, necessary information can be printed as embedded information without degrading image quality. And the information stamped on the surface of the resin particle can be read by observing an image formed from the developer of the present invention with a microscope or the like.
Therefore, for example, when the information for identifying the toner is stamped, the manufacturer of the toner is displayed. When the information for identifying the seller of the toner is stamped, the dealer of the seller is displayed. If it is engraved, the image forming apparatus can be specified.

  Therefore, for example, when a specific manuscript that should not be originally copied is copied using the developer of the present invention, information printed on the surface of the resin particle by observing the copy with a microscope or the like, for example, a toner manufacturer And embedded information such as an image forming apparatus can be read, and a clue for identifying what is involved in copying can be obtained.

  Further, the developer of the present invention prints embedded information by imprinting information on the surface of the resin particles, and the necessary information can be obtained by reading the imprint, so the toner of each color can be obtained regardless of the color of the toner. Resin particles can be combined. Therefore, there is no need to add a specific pattern only to a specific toner (yellow toner) as in the prior art. Furthermore, since the present invention reads information on the formed image, the specific pattern is not developed in the non-image area. Therefore, the specific toner is not easily consumed excessively.

The developer of the present invention is suitable for a developer used in a general image forming apparatus employing an electrophotographic system, such as a printer, a copying machine, a facsimile machine, and a complex machine thereof.
The developer of the present invention is suitable as a developer for preventing counterfeiting of copy-prohibited items such as banknotes and securities.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to a following example.
The “parts” shown below represent “parts by mass”.

[Production of resin particles]
<Resin particle A>
100 parts of a polyester resin (glass transition temperature: 55 ° C., melting point: 125 ° C.) as a resin, 5 parts of carbon black (manufactured by Tegusa, “PRINTEX 90”) as a pigment, and a charge control agent (manufactured by Fujikura Kasei Co., Ltd., “FCA201PS” 4) was added, and the mixture was mixed for 2 minutes with a Henschel mixer (Mitsui Mining Co., Ltd., “FM-10C type”), then melt kneaded with a twin screw extruder to prepare a toner kneaded product. The obtained toner kneaded product was molded into a plate shape having a thickness of 10 μm to obtain a resin plate. Next, the resin plate was punched out so that it became a substantially square with a side length of 8 μm with a mold in which 8 characters of 1 × 1 μm in size (inverted “A”) were engraved. A substantially rectangular parallelepiped resin particle A in which the letter A was engraved on 8 × 8 μm was obtained.
The maximum diameter of the resin particles was measured using a laser diffraction / scattering particle size measuring device (“LA-700” manufactured by Horiba, Ltd.).

Moreover, the glass transition temperature and melting | fusing point of resin were measured as follows.
10 mg of a measurement sample is put in an aluminum pan, an empty aluminum pan is used as a reference, these are set on a differential scanning calorimeter (“DSC-6200” manufactured by Seiko Instruments Inc.), and measured at normal temperature and humidity. Measurement was performed under conditions of a range of 25 to 200 ° C. and a heating rate of 10 ° C./min to obtain an endothermic curve.
In the obtained endothermic curve, the temperature indicating the intersection of the tangent of the curve at the start of temperature rise and the tangent of the curve where the energy first decreases was defined as the glass transition temperature. This is defined as the glass transition temperature (Tg1 [° C.]) of the resin particles.
The temperature showing the endothermic peak in the endothermic curve was taken as the melting point. This is the melting point (Tm1 [° C.]) of the resin particles.

<Resin particle B>
Resin particles B were produced in the same manner as the resin particles A, except that the resin plate was punched out with a mold so that the length of one side of the surface to be engraved was approximately 5 μm.

<Resin particles C>
Resin particles C were produced in the same manner as the resin particles A, except that the resin plate was punched with a mold so that the length of one side of the surface to be engraved was approximately 15 μm.

<Resin particle D>
Resin particles D were produced in the same manner as the resin particles A except that the resin plate was punched out with a mold so that the length of one side of the surface to be engraved was approximately 3 μm.

<Resin particle E>
Resin particles E were produced in the same manner as the resin particles A, except that the resin plate was punched out with a mold so that the length of one side of the surface to be engraved was approximately 20 μm.

[Example 1]
<Manufacture of toner>
As a binder resin, 100 parts of a polyester resin (glass transition temperature: 52 ° C., melting point: 122 ° C.), 5 parts of carbon black (manufactured by Tegusa, “PRINTEX 90”) as a pigment, and a charge control agent (manufactured by Fujikura Kasei Co., Ltd.) , "FCA201PS") and 4 parts of wax (Sanyo Kasei Co., Ltd., "Sun Wax LEL-250") are added as a release agent, and Henschel mixer (Mitsui Mining Co., Ltd., "FM-10C type") is used. After mixing for 2 minutes, a toner kneaded material was prepared by melt-kneading with a twin screw extruder. The obtained toner kneaded product is coarsely pulverized with a cutter mill or the like, further finely pulverized with a hammer mill, and classified with an airflow classifier. The volume-based average particle diameter is 7.0 μm, the number-based variation coefficient (CV value). ) 25% toner was obtained.

In addition, the glass transition temperature and melting | fusing point of binder resin were measured like the measuring method of the glass transition temperature and melting | fusing point of resin contained in a resin particle.
The glass transition temperature of the binder resin is the glass transition temperature of the toner (Tg2 [° C.]), and the melting point of the binder resin is the melting point of the toner (Tm2 [° C.]).

Further, the volume-based average particle size of the toner was calculated from the measured value of the particle size distribution measured under the condition of an aperture diameter of 100 μm using a particle size distribution measuring device (manufactured by Beckman Coulter, “Multimizer III”). .
Further, the CV value of the toner was obtained from the following formula (3) by measuring the particle diameter using a particle size distribution measuring device.
CV value = (standard deviation / number-based average particle diameter) × 100 (3)

<Manufacture of developer>
In a Henschel mixer (Mitsui Mining Co., Ltd., “FM-10C type”), 100 parts of the toner obtained above and 5 parts of resin particles A are added, and the mixture is stirred and mixed at 20 ° C. and 2000 rpm for 2 minutes. Obtained.
A carrier obtained by coating Fe-based ferrite with a polyester resin (average particle size: 45 μm) was used as a carrier, and 6 parts of the resulting mixture was added to 100 parts of this carrier to obtain a developer.

<Evaluation>
(1) Confirmation of engraving A developer is set in a color multifunction machine (manufactured by Kyocera Mita, “KM-C3232”), and the printing rate is 100 in a normal temperature and humidity environment (temperature: 25 ° C., relative humidity 60% RH). % Was printed and a solid image was output. The obtained solid image was observed with an optical microscope (magnification 1500 times), and it was judged whether the information stamped on the surface of the resin particles could be read. “○” indicates that the marking on the surface of the resin particle can be read, “△” indicates that the marking can be read if the visual field range is changed, and “×” indicates that the marking cannot be read even if the visual field range is changed. " The results are shown in Table 1.

(2) Appearance Evaluation The appearance of the solid image output in the same manner as in the evaluation in (1) was visually observed with 10 monitors. An average of 10 determination results, with 3 points when it is determined that there is no discomfort, 2 points when it is determined that slight unevenness can be confirmed, and 1 point when it is determined that unevenness or poor hue can be clearly confirmed Values of 2.5 points or more were rated as “◯”, 2.0 points or more, less than 2.5 points as “Δ”, and less than 2.0 points as “x”. The results are shown in Table 1.

[Examples 2-3, Comparative Examples 1-2]
A developer was produced in the same manner as in Example 1 except that the types of resin particles shown in Table 1 were used, and each evaluation was performed. The results are shown in Table 1.

  From the results shown in Table 1, when the images obtained from the developers of the respective examples were observed with an optical microscope, the characters imprinted on the surface of the resin particles could be read. In addition, an image having almost no image unevenness or poor hue could be formed. In particular, the developers obtained in Examples 1 and 2 were able to form high-quality images without any sense of incongruity.

On the other hand, when the image obtained from the developer of Comparative Example 1 was observed with an optical microscope, it was not possible to read the characters imprinted on the surface of the resin particles. This is because the resin particles having a side length of 3 μm (maximum diameter is 4.2 μm) are used because the surface of the resin particles is covered with toner, and the characters stamped on the surface are used. Could not read.
When an image obtained from the developer of Comparative Example 2 was observed with an optical microscope, characters imprinted on the surface of the resin particles could be read. However, since resin particles having a side length of 20 μm (maximum diameter is 28.3 μm) are used, the obtained image has image unevenness and poor hue, resulting in image deterioration. It was.

Claims (6)

A developer for developing an electrostatic latent image, comprising a toner containing a binder resin and a pigment, and resin particles,
The developer for developing an electrostatic latent image, wherein the resin particles are engraved on a surface, and a maximum diameter of the engraved surface is 5 to 25 μm. 2. The developer for developing an electrostatic latent image according to claim 1, wherein when the glass transition temperature of the resin particles is Tg1 and the glass transition temperature of the toner is Tg2, the following formula (1) is satisfied.
Tg2 <Tg1 <Tg2 + 10 (1) 3. The developer for developing an electrostatic latent image according to claim 1, wherein when the melting point of the resin particles is Tm1 and the melting point of the toner is Tm2, the following formula (2) is satisfied.
Tm2 <Tm1 <Tm2 + 10 (2)   The developer for electrostatic latent image development according to any one of claims 1 to 3, wherein the content of the resin particles is 0.1 to 15 parts by mass with respect to 100 parts by mass of the toner.   The electrostatic latent image developing developer according to claim 1, wherein the developer is a dry developer.   The electrostatic latent image developing developer according to claim 1, wherein the toner and the resin particles are a wet developer dispersed in an insulating liquid carrier.