JPH0786696B2 - Toner for electrostatic image development - Google Patents

Description

The present invention relates to an electrostatic image developing toner used in an electrophotographic system utilizing static electricity.

[Background of the Invention]

Generally, in electrophotography, a uniform electrostatic charge is applied to a latent image carrier having a photosensitive layer made of a photoconductive material, and then image exposure is performed to electrostatically charge the surface of the latent image carrier. An electrostatic latent image is formed, and this electrostatic latent image is developed with a developer to form a toner image. The obtained toner image is transferred to a transfer material such as paper and then fixed by means such as heating or pressing to form a copied image.

Therefore, in order to form an image with good image quality, it is necessary that the toner has a high fluidity, and the surface of the latent image carrier is contaminated by the toner substance during use, or heat, Since it deteriorates due to light or the like, it is necessary to polish the surface appropriately to make it new.

In order to meet such a demand, the following electrostatic image developing toner has been conventionally known.

(1) Toner for electrostatic image development, which is obtained by adding and mixing 1 to 30 mμ of silica fine particles and 150 to 5000 mμ of inorganic fine particles to resin particle powder of 5 to 30 μm (see JP-A-57-179866). .

(2) to the resin particles, the two electrostatic image developing toner obtained by adding and mixing the inorganic fine particles is a specific surface area by BET method of 0.5 to 30 m ² / g and 40 to 400 ² / g, respectively (JP Sho-60-3
See 2060 publication).

[Problems to be solved by the invention]

However, these techniques have the following problems.

(1) When the toner is agitated in the developing device, the inorganic fine particles having a small particle size are likely to be embedded in the toner particles, and therefore, the fluidity is low at the initial stage of image formation and the toner is not supported on the developer carrier. It becomes difficult to carry the toner in a stable layered form, and the amount of toner adhered to the image portion of the latent image carrier is insufficient in the end, resulting in a decrease in image density and an unclear image.

(2) In the case of forming an image many times,
The effect of improving the fluidity due to the inorganic fine particles having a small particle diameter is not exhibited, and as a result, fog is generated at an early stage, or the image density is greatly reduced, and thus a stable image cannot be formed many times.

[Object of the Invention]

The present invention has been made under the above circumstances, and an object thereof is to provide an electrostatic image developing toner having excellent fluidity and polishing properties.

[Means for solving problems]

The electrostatic image developing toner of the present invention has an average particle size of 1 mμ or more 50
First inorganic fine particles of mμ or less and average particle size of 6 mμ or more and 100
The second inorganic fine particles are less than mμ and are larger than the average particle size of the first inorganic fine particles by at least 5 mμ or more, and the third inorganic fine particles having an average particle size of 100 mμ or more and 5000 mμ or less. It is characterized in that three kinds of inorganic fine particles are added to and mixed with the resin particle powder.

[Advantageous effects of the invention]

According to the electrostatic image developing toner of the present invention, since the resin particle powder is formed by adding and mixing three kinds of inorganic fine particles each having a specific average particle diameter and different in average particle diameter, The presence of the inorganic fine particles gives the toner high fluidity, the presence of the large-sized inorganic fine particles gives the toner high abrasiveness, and the presence of the medium-sized inorganic fine particles makes Inorganic fine particles having a small particle size are less likely to be embedded in the toner, and even when the inorganic fine particles having a small particle size are embedded in the toner particles, the fluidity is prevented from being lowered, and as a result, the fluidity and the polishing property are reduced. It becomes an excellent toner.

As described above, since the toner has excellent fluidity and abrasiveness, the toner particles are easily attracted and adhered to the image portion of the latent image carrier in the developing step, and such development is not performed smoothly. The entire latent image is made uniform, and as a result, a toner image having a high image density and good image quality without fog can be stably formed many times.

[Specific configuration of the invention]

Basically, the toner for electrostatic image development of the present invention basically comprises three kinds of inorganic fine particles having different average particle diameters in a resin particle powder in which a binder resin contains a colorant and other additives. It is added and mixed.

In the present invention, the average particle size of the inorganic fine particles refers to the average particle size of primary particles (particles separated into individual unit particles). This average particle diameter can be obtained by converting from the specific surface area obtained by the BET method, for example. Specifically, it can be determined by an electron micrograph.

Three types of inorganic fine particles with different average particle sizes have an average particle size of 1 mμ
The first inorganic fine particles having a size of 50 mμ or more and the average particle size of 6
second inorganic fine particles having an average particle diameter of 100 μm or more and less than 100 mμ and having an average particle diameter larger than that of the first inorganic fine particles by at least 5 mμ or more; and third inorganic fine particles having an average particle diameter of 100 mμ or more and 5000 mμ or less It is composed of By using the three kinds of inorganic fine particles having the average particle diameter in such a specific range, the toner can surely exhibit the characteristics according to the average particle diameter of each inorganic fine particle, and as a result, the toner has high fluidity. And high abrasiveness is surely imparted.

In the first inorganic fine particles, when the average particle diameter is excessively large, it becomes difficult to impart high fluidity to the toner,
Further, it becomes difficult to draw out the toner onto the developer carrying member (drawing property), and it is impossible to form a stable layered developer layer. On the other hand, when the average particle diameter is too small, the inorganic fine particles are likely to be scattered and each device in the apparatus is contaminated, resulting in a defective image.

The content ratio of the first inorganic fine particles is 0.01 to 5 of the toner.
It is preferably in the weight%. When the content ratio is too large, scattering easily occurs, while when it is too small, it becomes difficult to impart high fluidity to the toner.

When the average particle diameter of the second inorganic fine particles is excessively large, it is difficult to prevent the fluidity of the toner from decreasing. On the other hand, when the average particle diameter is too small, the inorganic fine particles are likely to be embedded in the toner, resulting in a decrease in fluidity. The content ratio of the second inorganic fine particles is 0.01% of the toner.
It is preferably about 5% by weight. When the content ratio is too large, scattering easily occurs, while when it is too small,
It becomes difficult to prevent deterioration of the fluidity of the toner.

When the average particle diameter of the third inorganic fine particles is excessively large, the abrasiveness becomes excessively large, and the surface of the latent image carrier is easily damaged. On the other hand, when the average particle size is too small, the polishing property is low and the characteristics of the latent image carrier are likely to deteriorate. The content ratio of the third inorganic fine particles is preferably 0.1 to 15% by weight of the toner. When the content ratio is excessively large, the polishing property becomes excessively large and the surface of the latent image carrier is easily damaged. On the other hand, when the content ratio is too small, the polishing property is deteriorated and the surface of the latent image bearing member is likely to deteriorate early.

The total content of the first inorganic fine particles, the second inorganic fine particles, and the third inorganic fine particles is preferably 20% by weight or less of the toner. When the content ratio is excessively large, scattering is likely to occur.

Examples of the inorganic fine particles include silica, alumina, titania, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, silica sand, clay, mica, wollastonite, diatomaceous earth, various inorganic oxides. Fine particles of pigment, chromium oxide, cerium oxide, red iron oxide, antimony trioxide, magnesium oxide, zirconium oxide, barium sulfate, barium carbonate, calcium carbonate and the like can be used.

The first inorganic fine particles, the second inorganic fine particles, and the third inorganic fine particles may be selected from the same substance or may be selected from different substances.

The toner constituting the electrostatic image developer of the present invention preferably has a small particle size, specifically, a weight average particle size of 6 to 20.
It is preferably in the range of μm. By using a toner having such a small particle diameter, it is possible to form an image having excellent fine line reproducibility and gradation. The weight average particle diameter of the toner is measured by a “Coulter counter” (manufactured by Coulter Co.), and the particle diameter when the weight accumulation reaches 50% by weight is defined as the weight average particle diameter.

The binder resin of the toner is not particularly limited, and a conventionally known resin can be used.

Specifically, for example, polyester resin, styrene-acrylic resin, epoxy resin, polyamide resin, polyurethane resin or the like can be used.

The polyester resin used as the binder resin of the toner is obtained by polycondensation of an alcohol monomer and a carboxylic acid monomer, and examples of the alcohol monomer used include ethylene glycol, diethylene glycol, triethylene glycol, 1 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-butenediol and other diols, 1,4-bis (hydroxymethyl) cyclohexane, and bisphenol A, Hydrogenated bisphenol A, polyoxyethylenated bisphenol A,
Examples include etherified bisphenols such as polyoxypropylene bisphenol A and other dihydric alcohol monomers. Examples of the carboxylic acid monomer include maleic acid, fumaric acid, mesaconic acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, Examples thereof include malonic acid, anhydrides of these acids, dimers of lower alkyl esters and linoleic acid, and other divalent organic acid monomers.

In addition to the above divalent monomers, if necessary, trivalent or higher polyvalent monomers may be used. Examples of the trihydric or higher polyhydric alcohol monomer include sorbitol,
1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, sucrose, 1,2,4-butanetriol, 1,2,5-pentanetriol, Glycerol, 2-
Mention may be made of methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxymethylbenzene and the like. Further, as the trivalent or higher polycarboxylic acid monomer, for example, 1,2,4-benzenetricarboxylic acid, 1,3,5-benzenetricarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, 2,5 , 7-Naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4
-Butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, tetra (methylenecarboxy)
Mention may be made of methane, 1,2,7,8-octanetetracarboxylic acid, empol trimer acid, and anhydrides of these acids, and others.

As the styrene-acrylic resin used as the binder resin of the toner, a resin containing an α, β-unsaturated ethylenic monomer as a constituent unit can be preferably used. Specific examples of such α, β-unsaturated ethylenic monomers include styrene, o-methylstyrene,
m-methylstyrene, p-methylstyrene, α-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert-butylstyrene, pn-hexylstyrene, p- n-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, 3,4
Aromatic vinyl monomers such as dichlorostyrene; eg methyl acrylate, ethyl acrylate, acrylic acid n
-Butyl, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, α-chloroacrylic acid Acrylic esters such as methyl; methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-methacrylate
Butyl, isobutyl methacrylate, n-methacrylic acid
-Methacrylic acid esters such as octyl, dodecyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate; Examples thereof include vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide and vinyl fluoride; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate and vinyl butyrate; and others.

Examples of colorants used in toners include carbon black, nigrosine dye (CINo.50415B), aniline blue (CINo.50405), and calco oil blue (CIN).
o.azoic Blue 3), chrome yellow (CINo.14090),
Ultramarine Blue (CINo.77103), DuPont Oil Red (CINo.26105), Quinoline Yellow (CIN)
o.47005), methylene blue chloride (CI No.5201
5), Phthalocyanine Blue (CINo.74160), Malachite Green Oxalate (CINo.42000), Lamp Black (CINo.77266), Rose Bengal (CINo.454)
35), mixtures thereof, and the like.
The content of the colorant is preferably 0.1 to 20 parts by weight with respect to 100 parts by weight of the binder resin. When the content ratio of the colorant is too small, a good visible image may not be obtained due to a decrease in image density, while when the content ratio of the colorant is too large, various properties of the toner may be adversely affected. .

Examples of other additives used in the toner include a release agent and a charge control agent.

Examples of the releasing agent include polyolefin, fatty acid metal salt, fatty acid ester, partially saponified fatty acid ester, higher fatty acid, higher alcohol, liquid or solid paraffin wax, amide wax, polyhydric alcohol ester, silicone varnish, and aliphatic Fluorocarbon or the like can be used. These release agents may be used in combination. The content of the release agent is preferably 0.5 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

Various pigments or dyes can be used as the charge control agent. These charge control agents may be used in combination. The charge control agent content is 100% binder resin.
It is preferably 0.1 to 10 parts by weight with respect to parts by weight.

When the toner constituting the electrostatic image developer of the present invention is a magnetic toner, magnetic particles are dispersed and contained in the binder resin. Such a magnetic material is a substance that is strongly magnetized in that direction by a magnetic field, such as iron, ferrite, magnetite or other iron, nickel, a ferromagnetic metal such as cobalt, or an alloy or compound containing these metals, An alloy that does not contain a ferromagnetic element, but becomes ferromagnetic by proper heat treatment, such as manganese-copper-aluminum or manganese-copper-
Examples thereof include alloys of a type called Heusler alloy such as tin or chromium dioxide. The content ratio of such magnetic particles is 20 to 7 with respect to 100 parts by weight of the binder resin.
It is preferably 5 parts by weight. Since some of these magnetic particles exhibit a function as a coloring agent, when such magnetic particles are used, the toner does not need to contain the coloring agent.

In the present invention, a developer may be formed by using a carrier together with the toner. The carrier is not particularly limited. Specifically, an uncoated carrier made of magnetic particles, a resin-coated carrier obtained by coating the surface of magnetic particles with a resin, a magnetic substance-dispersed carrier in which magnetic fine particles are dispersed and contained in a binder resin, etc. Can be used. Of these, a resin-coated carrier is particularly preferable.

The weight average particle diameter of the carrier is 5 of the weight average particle diameter of the toner.
It is preferably in the range of 20 times. When such a carrier having a small particle size is used in combination with the toner, the magnetic repulsive force between the carrier particles becomes small due to the small particle size of the carrier, so that in the developer layer carried on the developer carrier. The density of the carrier particles can be increased, and therefore the amount of the toner attached to the carrier particles and supplied to the developing space can be increased, and as a result, a high-density toner image can be formed.

The magnetic material used for the carrier is a substance that is strongly magnetized in that direction by a magnetic field, for example, iron, ferrite, magnetite or other iron, nickel, cobalt, or other ferromagnetic metal, or an alloy containing these metals or Compounds, alloys containing no ferromagnetic elements but exhibiting ferromagnetism by appropriate heat treatment, for example, alloys of the type called Heusler alloys such as manganese-copper-aluminum or manganese-copper-tin, or chromium dioxide. Can be mentioned.

The resin that can be used to obtain the resin-coated carrier is not particularly limited, and examples thereof include styrene resin, acrylic resin, styrene-acrylic resin, vinyl resin, ethyl resin, rosin modified resin. Examples of the resin include polyamide resin, polyester resin, fluororesin, and silicone resin. Of these, styrene-acrylic resin is particularly preferable. These resins may be used in combination.

As the styrene-acrylic resin used for the resin-coated carrier, a copolymer resin of a styrene monomer and an acrylic acid ester monomer and / or a methacrylic acid ester monomer is particularly preferable. The styrene-based monomer component hardens the resin and enables efficient triboelectric charging with the toner, while the acrylate and methacrylic acid ester monomer components have the effect of strengthening the resin. Due to the effect, the coating layer becomes hard and tough, and a resin-coated carrier having good durability can be obtained. In the case of obtaining the styrene-acrylic resin, the use ratio of the styrene monomer and the acrylic acid ester monomer and / or the methacrylic acid ester monomer is 9 by weight.
It is preferably 0:10 to 10:90. Further, by appropriately changing the use ratio of these, the charge amount of the toner in the frictional charging between the resin-coated carrier and the toner can be controlled to a considerable extent.

[Specific Examples of the Invention]

Specific examples of the present invention will be described below, but the present invention is not limited to these examples.

(Manufacture of Toner) Binder resins of the types and proportions shown in Table 1 below,
After mixing the internal additives with a Henschel mixer, 3
After sufficiently kneading with a main roll, cooling, coarse pulverization, fine pulverization with a jet mill, and further classification, each resin particle powder was obtained.

Toners were manufactured by mixing each of these resin particle powders with external additives in the types and proportions shown in Table 2 below.

In Table 2, "strontium titanate fine particles" and "barium titanate fine particles" in the column of external additive are produced as follows.

Strontium titanate fine particles 117.6 g of strontium carbonate and 127.8 g of titanium oxide were wet mixed by a ball mill for 24 hours, filtered and dried. This mixture was molded at a pressure of 15 kg / cm ² and at 1400 ° C.
Sintering was carried out for 3 hours and pulverized by a mechanical pulverizing means to obtain strontium titanate fine particles having an average grain size of 1010 mμ.

Barium titanate fine particles 203.3 g of barium carbonate and 127.8 g of titanium oxide were wet-mixed by a ball mill for 24 hours, filtered, and dried. This mixture was molded at a pressure of 15 kg / cm ² and heated at 1200 ° C for 5
Sintering was performed for a period of time, and the particles were pulverized by a mechanical pulverizing means to obtain strontium titanate fine particles having an average grain size of 3000 mμ.

(Production of Carrier) Styrene-methyl methacrylate resin (monomer composition ratio =
30:70) was dissolved in a solvent to prepare a coating solution, which was applied to iron powder particles using "Spiracoater" (made by Okada Seiko Co., Ltd.), and then heated and dried to obtain an average particle size of 100 μm. A resin coated carrier was manufactured. This is carrier C1.

(Preparation of developer) (1) One-component developer Toners T11 to T14, T21 to T24, T31 to T which are magnetic toners
34 are one-component developers 11 to 14, 21 to 24, and 31 to 34, respectively.

The static dry density of Toner 21 for use in the present invention was 0.55 as measured by Tap Denser (manufactured by Seishin Enterprise Co., Ltd.).

(2) Two-component developer Each of toners T41 to T44, which are non-magnetic toners, and carrier C1 were mixed to prepare a two-component developer having a toner concentration of 2.5% by weight. These are two-component developers
41 to 44.

(Live shooting test 1) Under the environmental conditions of temperature 20 ° C and relative humidity 60%, the above 1
Electrophotographic copying machine "U-Bix1200" using component developer
Using a modified machine, the development process was performed based on the contact-type development conditions, and a live-copy test was performed to form copied images 30,000 times in succession, and the following items were evaluated. The results are shown in Table 3 below.

Fog "Sakura densitometer" (Konishi Roku Photo Industry Co., Ltd.)
Manufactured) was used to measure the density of the white background portion of the original image and the density of the copy image portion corresponding to the white background portion, and the relative density of both was determined. However, the reflection density of the white background part of the original image
It was set to 0.0. In the evaluation, when the relative concentration was less than 0.01, it was rated as “◯”, when it was 0.01 or more and less than 0.03, it was rated as “Δ”, and when it was 0.03 or more, it was rated as “x”.

Image Density "Sakura Densitometer" (Konishi Roku Photo Industry Co., Ltd.)
Manufactured image) to measure the density of the copy image part corresponding to the white background area where the original image density is 0.0 and the maximum density of the copy image part corresponding to the image part of the original image such as characters and diagrams, and It was judged by the concentration. In the evaluation, when the relative density was 1.0 or more, “◯” was given, when 0.7 or more and less than 1.0, “Δ” was given, and when less than 0.7, “x” was given.

Stickiness Visually observe the surface of the developer carrying member immediately after passing through the developing space, and when the sticking is hardly observed and is good, it is `` ○ '', and when the sticking is slightly recognized but is at a practical level, it is `` △ ''. When there was a lot of clinging and there was a problem in practical use, it was marked as "x".

Note that “stickiness” refers to a phenomenon in which the toner adheres strongly to the surface of the developer carrying member and a large amount of toner is conveyed.

Draw-out property The draw-out property of the toner to the developing sleeve constituting the developer carrying member was visually observed and judged. The evaluation was "Good" when it was good, "Fair" when it was slightly bad but at a practical level, and "Poor" when it was bad and practically problematic.

Kamakura Phenomenon When the occurrence of the kamakura phenomenon is hardly observed, it is "○", when the occurrence of the kamakura phenomenon is slightly recognized, but when it is at the practical level, it is "△", and the occurrence of the kamakura phenomenon is remarkable and there is a problem in practical use. The case was designated as "x".

The "kamakura phenomenon" refers to a phenomenon in which the toner powder in the toner hopper has a bridge-like shape and the toner is not conveyed.

(Real shot test 2) The development conditions were changed as follows, and the number of image formations was 50,000
Except for the number of times, a live-copy test was conducted in the same manner as the above-mentioned real-copy test 1, and evaluated in the same manner. The results are shown in Table 4 below.

[Development conditions (non-contact type development method)] Latent image carrier Drum-shaped photoreceptor with organic photoconductive photosensitive layer (polarity of electrostatic latent image: +) AC bias voltage: 2.0kV (peak-peak) (Value, frequency: 1.5 kHz) (Real shooting test 3) A real copying test was performed in the same manner as the above-mentioned real copying test 1 except that the developing conditions were changed as follows, and evaluated in the same manner. The results are shown in Table 5 below.

[Development conditions (non-contact type development method)] Latent image bearing member Drum-shaped photosensitive member comprising organic photoconductive photosensitive layer (polarity of electrostatic latent image: +) AC bias voltage: 1.3kV (peak / peak) (Value, frequency: 1.2kHz) (Live-action test 4) Under the environmental conditions of temperature 20 ° C and relative humidity 60%, the above 2
Electrophotographic copying machine "U-Bix1600" using component type developer
Then, the developing process was performed under the following developing conditions, and a continuous shooting test for forming a copied image was continuously performed 10,000 times.
The results are shown in Table 6 below.

[Development conditions (contact type development method)] Latent image bearing member Drum-shaped photosensitive member comprising selenium photosensitive layer (polarity of electrostatic latent image: +) AC bias voltage: None As can be understood from the results of the above-described actual shooting tests 1 to 4, according to the present invention, it is possible to form a good image with clear image quality without fog and high image density.
Further, almost no contamination due to toner scattering is observed, and a good image can be stably formed many times. Then, when the non-contact type developing method is applied, the above effects are remarkably excellent.

On the other hand, when the developer for comparison is used, since the toner contains two kinds of inorganic fine particles having different average particle diameters, sticking and fogging occur in the early stage of image formation. The image density becomes low, and a good image cannot be formed. Further, in the case of forming an image a number of times, fog is gradually increased and the image density is lowered, so that a good image cannot be stably formed.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-60-186851 (JP, A) JP-A-60-136755 (JP, A) JP-A-62-2272 (JP, A) JP-A-59- 220744 (JP, A) JP 58-105163 (JP, A) JP 56-154742 (JP, A)

Claims (2)

[Claims] 1. A first inorganic fine particle having an average particle size of 1 mμ to 50 mμ and a second inorganic fine particle having an average particle size of 6 mμ to less than 100 mμ and at least 5 mμ larger than the average particle size of the first inorganic fine particle. Inorganic particles and average particle size of 100mμ or more 5000
A toner for developing an electrostatic image, characterized in that three kinds of inorganic fine particles having different average particle diameters, which are composed of third inorganic fine particles having a particle size of mμ or less, are added to and mixed with a resin particle powder. 2. The content ratio of the first inorganic fine particles is 0.01 to 5% by weight, the content ratio of the second inorganic fine particles is 0.01 to 5% by weight, and the content ratio of the third inorganic fine particles is 0.1 to 5. The toner for developing an electrostatic image according to claim 1, wherein the toner content is 15% by weight and the total content of these inorganic fine particles is 20% by weight or less.