JP2007003631A - Toner for electrostatic image development - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a toner for electrostatic image development in which fog is stably suppressed over a long period of time and generation of image stripes is suppressed. <P>SOLUTION: The toner for electrostatic image development comprises a binder resin, a colorant and an external additive, wherein the external additive comprises strontium titanate having 0.06 to 0.08 μm average particle size and alumina having 0.05 to 0.4 μm average particle size. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrostatic image developing toner used for developing a latent image formed in an electrophotographic method, an electrostatic recording method, an electrostatic printing method or the like.

  In recent years, with high image quality of printers, high performance is required for toner.

  Regarding high image quality using external additives, Patent Document 1 discloses black spots and fog in toners in which composite particles of strontium titanate and strontium carbonate having a number average particle size of 0.08 to 0.8 μm are mixed and added as external additives. And a technique for improving image streaking and stain resistance.

Further, Patent Document 2 discloses a toner having a specific composition, physical properties and particle size distribution, strontium titanate having a length average particle diameter of 0.2 to 2 μm as an external additive, and a length average particle diameter of 0.005 to 0.1 μm. A technique for improving fog and durability stability in a color toner having hydrophobized alumina is disclosed.
JP 2003-15349 A (Claim 1) JP 2000-206733 A (Claim 1)

  The mechanism for preventing fogging in the prior art is based on preventing the contamination of the regulating blade and the developing roller by the peeled fluidizing agent in Patent Document 1, and specifying the particle diameter and particle size distribution of the toner in Patent Document 2. It is estimated to be.

  An object of the present invention is to provide a toner for developing an electrostatic image in which fog is stably suppressed over a long period of time and generation of image streaks is suppressed.

  The present invention is an electrostatic charge image developing toner comprising a binder resin, a colorant and an external additive, wherein the external additive is strontium titanate having an average particle size of 0.06 to 0.08 μm and an average particle size. The present invention relates to an electrostatic charge image developing toner containing 0.05 to 0.4 μm of alumina.

  The toner for developing an electrostatic charge image of the present invention has an excellent effect that fog is stably suppressed over a long period of time and generation of image streaks is suppressed.

  The electrostatic image developing toner of the present invention contains at least a binder resin, a colorant, and an external additive, and contains strontium titanate having a specific average particle diameter and alumina as the external additive. It has one feature in that it has a remarkable effect particularly in suppressing fog over a long period of time. In the present invention, although the details of the mechanism for suppressing fogging are unknown, it is presumed that the charging uniformity of the toner is improved by the chargeability of the two kinds of particles. In particular, a remarkable effect is exhibited in a one-component development system in which toner is charged by passing through a gap between a regulating blade or the like and a developing roller.

  The average particle diameter of strontium titanate is 0.06 μm or more from the viewpoint of reducing fog, and 0.08 μm or less, preferably 0.065 to 0.08 μm, more preferably 0.07 to 0.08 μm from the viewpoint of image streaking prevention. Here, the average particle size of strontium titanate refers to a 50% particle size based on weight measured by an equivalent circular diameter from a transmission electron micrograph.

The average particle diameter of alumina is 0.05 to 0.4 μm, preferably 0.08 to 0.3 μm, and more preferably 0.1 to 0.3 μm from the viewpoint of reducing fog. Here, the average particle diameter of alumina refers to the particle diameter converted from the following formula (a) based on the BET specific surface area of alumina. In the present specification, the BET specific surface area is determined by a nitrogen adsorption method.
Average particle size [μm] = 6 / (Alumina density (3.99) [g / cm ³ ] × BET specific surface area [m ² / g]) (a)
Assuming that the equation (a) is a sphere having a particle diameter R,
BET specific surface area = S x (1 / m)
m (weight of particle) = 4/3 x π x (R / 2) ³ x density
S (surface area) = 4π (R / 2) ²
Is an expression obtained from

  The presence or absence of hydrophobization treatment in strontium titanate and alumina is not particularly limited. preferable. Examples of the hydrophobizing treatment include those obtained by treating the particle surface with a hydrophobizing agent such as silicone oil or hexamethyldisilazane.

  The weight ratio of strontium titanate to alumina (strontium titanate / alumina) is preferably 5/1 to 1/5, more preferably 4/1 to 1/4, from the viewpoint of sufficiently exerting the effect of the combination of both. 2/1 to 1/2 are more preferable.

  The total content of strontium titanate and alumina is preferably 0.1 to 2 parts by weight, and more preferably 0.2 to 1.5 parts by weight, based on 100 parts by weight of the toner before adding the external additive.

  In the toner of the present invention, other external additives may be used in combination as long as the effect of the present invention by strontium titanate and alumina is not impaired. For example, titanium oxide has an effect of stabilizing the charging. Therefore, it is effective and preferable for improving developability, which is a characteristic that is contrary to fogging.

The average particle diameter of titanium oxide is preferably 10 to 50 nm, more preferably 10 to 30 nm, from the viewpoint of chargeability and fluidity. Here, the average particle diameter of titanium oxide is 4.2 g / cm ³ as the density of titanium oxide instead of the density of alumina, and is converted based on the BET specific surface area according to the formula (a).

  The content of titanium oxide is preferably 0.1 to 5 parts by weight and more preferably 0.2 to 2 parts by weight with respect to 100 parts by weight of the toner before being processed with the external additive.

  From the viewpoint of reducing fog and improving developability, it is preferable that silica is used in combination as an external additive. The average particle diameter of silica is preferably 5 to 50 nm. In particular, it is preferable that at least two types of silica having different average particle diameters are used in combination. In this case, the difference in average particle diameter of silica is preferably 10 nm or more, and more preferably 15 to 40 nm.

Silica with a large particle size is mainly effective for improving the developer, and silica with a small particle size is mainly effective for reducing fogging. Silica having an average particle size of 30 to 50 nm (large particle size silica) and average particle It is preferable that silica having a diameter of 5 to 16 nm (small particle diameter silica) is used in combination. The weight ratio of these silicas (large particle size silica / small particle size silica) is preferably 9/1 to 2/8. Here, the average particle diameter of silica is converted based on the BET specific surface area according to the formula (a) using 2.2 g / cm ³ as the density of silica instead of the density of alumina.

  Silica is preferably hydrophobized with a treating agent such as silicone oil or hexamethyldisilazane.

  The total content of silica is preferably 0.01 to 10 parts by weight and more preferably 0.1 to 5 parts by weight with respect to 100 parts by weight of the toner before being processed with the external additive.

  Examples of the binder resin in the present invention include polyester resins, vinyl resins such as styrene-acrylic resins, epoxy resins, polycarbonates, polyurethanes, hybrid resins having two or more resin components, and the like. Among them, polyester is preferable from the viewpoint of durability and fixability. The polyester content is preferably 50 to 100% by weight in the binder resin, more preferably 70 to 100% by weight, and still more preferably 100% by weight.

  The raw material monomer of the polyester is not particularly limited, and a known alcohol component and a known carboxylic acid component such as carboxylic acid, carboxylic acid anhydride, or carboxylic acid ester are used.

  Alcohol components include alkylenes of bisphenol A such as polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene (2.2) -2,2-bis (4-hydroxyphenyl) propane (Carbon number 2 to 3) Oxide (average added mole number 1 to 16) adduct, ethylene glycol, propylene glycol, glycerin, pentaerythritol, trimethylolpropane, hydrogenated bisphenol A, sorbitol, or alkylene thereof (carbon number 2 -4) Oxide (average added mole number 1-16) adduct and the like.

  The carboxylic acid component includes dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, fumaric acid, maleic acid, adipic acid and succinic acid, alkyl groups having 1 to 20 carbon atoms such as dodecenyl succinic acid and octenyl succinic acid, or carbon. Trivalent or higher polyvalent carboxylic acids such as succinic acid, trimellitic acid and pyromellitic acid substituted with alkenyl groups having 2 to 20 carbon atoms, anhydrides of these acids and alkyls of these acids (1 to 3 carbon atoms) ) Esters and the like.

  The polyester can be produced, for example, by subjecting an alcohol component and a carboxylic acid component to condensation polymerization at a temperature of 180 to 250 ° C. in an inert gas atmosphere, if necessary, using an esterification catalyst.

  From the viewpoint of durability and fixability, the softening point of the polyester is preferably 80 to 165 ° C, the glass transition point is preferably 50 to 85 ° C, and the acid value is preferably 0.5 to 60 mgKOH / g. The desired softening point and acid value can be obtained by adjusting the condensation polymerization temperature, reaction time, and the like.

  As the colorant, dyes and pigments used as toner colorants can be used. Carbon black, phthalocyanine blue, permanent brown FG, brilliant first scarlet, pigment green B, rhodamine-B base, solvent red 49, Solvent Red 146, Solvent Blue 35, Quinacridone, Carmine 6B, Disazo Yellow, etc., and these can be used alone or in admixture of two or more. Either toner or full color toner may be used. The content of the colorant is preferably 1 to 40 parts by weight and more preferably 3 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

  In the present invention, in addition to the binder resin and the colorant, a release agent, a charge control agent, a fluidity improver, a conductivity modifier, an extender pigment, a reinforcing filler such as a fibrous substance, an antioxidant, You may use suitably additives, such as anti-aging agent and a cleaning property improving agent, as a raw material.

  Examples of mold release agents include polypropylene wax, polyethylene wax, synthetic wax such as Fischer Tropu, coal wax such as montan wax, petroleum wax such as paraffin wax, and wax such as alcohol wax. Or a mixture of two or more thereof. The content of the release agent is preferably 1 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

  As the charge control agent, any one of negative chargeability and positive chargeability can be used. Examples of the negatively chargeable charge control agent include metal-containing azo dyes, copper phthalocyanine dyes, metal complexes of salicylic acid alkyl derivatives, and nitroimidazole derivatives. Examples of the positively chargeable charge control agent include nigrosine dyes, triphenylmethane dyes, quaternary ammonium salt compounds, polyamine resins, and imidazole derivatives. Also, a polymer type such as a resin can be used. The content of the charge control agent is preferably 0.1 to 8 parts by weight and more preferably 0.2 to 5 parts by weight with respect to 100 parts by weight of the binder resin.

  The toner of the present invention can be obtained by subjecting an untreated toner containing a binder resin and a colorant and, if necessary, various additives to a surface treatment with an external additive. The untreated toner is preferably a pulverized toner. For example, a binder resin, a colorant, and the like are mixed with a mixer such as a Henschel mixer or a ball mill, and then melted and kneaded with a hermetic kneader or a single or twin screw extruder. After cooling, coarsely pulverized using a hammer mill or the like, further pulverized by a fine pulverizer or mechanical pulverizer using a jet stream, and predetermined by a classifier using a swirling airflow or a classifier using the Coanda effect It is obtained by classifying to a particle size of

  The surface treatment process of the untreated toner with the external additive is preferably a dry mixing method in which the external additive and the untreated toner are mixed using a high-speed stirrer such as a Henschel mixer or a super mixer, a V-type blender or the like. The external additives may be mixed in advance and added to a high-speed stirrer or a V-type blender, or may be added separately.

The volume median particle size (D ₅₀ ) of the toner of the present invention is preferably from 3 to 15 μm, more preferably from _{5 to} 10 μm. In the present specification, the volume-median particle size (D ₅₀ ) means a particle size at which the cumulative volume frequency calculated by the volume fraction is 50% when calculated from the smaller particle size.

  The toner of the present invention can be used as a one-component developing toner as it is or as a two-component developer by mixing with a carrier. However, since the toner of the present invention is excellent in chargeability, it can be developed with a regulating blade or the like. The effect of the present invention is more remarkably exhibited by using the toner as one-component developing toner that charges the toner by passing through the gap with the roller.

[Softening point]
Using a flow tester (Shimadzu Corp., CFT-500D), a 1 g sample was heated at a heating rate of 6 ° C / min, and a 1.96 MPa load was applied by a plunger, and extruded from a nozzle with a diameter of 1 mm and a length of 1 mm. . The amount of plunger drop of the flow tester is plotted against the temperature, and the temperature at which half of the sample flows out is taken as the softening point.

[Glass transition point]
Using a differential scanning calorimeter (DSC210, manufactured by Seiko Denshi Kogyo Co., Ltd.), the sample was heated to 100 ° C at a temperature increase rate of 10 ° C / min and allowed to cool to -10 ° C at a temperature decrease rate of 100 ° C / min for 3 minutes. Thereafter, the temperature is raised to 25 ° C. at a temperature rising rate of 60 ° C./min, held for 2 minutes, and measurement is started at a temperature rising rate of 10 ° C./min. The glass transition point is defined as the temperature at the intersection of the base line extension below the glass transition point and the tangent that indicates the maximum slope from the peak rising portion to the peak apex.

[Acid value]
Measured by the method of JIS K0070.

[Volume-median particle diameter of toner (D ₅₀ )]
Measuring machine: Coulter Multisizer II (Beckman Coulter, Inc.)
Aperture diameter: 100 μm
Measurement particle size range: 2-60μm
Analysis software: Coulter Multisizer AccuComp version 1.19 (Beckman Coulter)
Electrolyte: Isoton II (Beckman Coulter, Inc.)
Dispersion: Emulgen 109P (manufactured by Kao Corporation, polyoxyethylene lauryl ether, HLB: 13.6) 5% electrolyte dispersion condition: 10 mg of measurement sample is added to 5 ml of dispersion, and dispersed for 1 minute with an ultrasonic disperser. Then, 25 ml of the electrolytic solution is added, and further dispersed with an ultrasonic disperser for 1 minute.
Measurement conditions: Add 100 ml of electrolyte and dispersion in a beaker, measure 30,000 particles at a concentration that can measure the particle size of 30,000 particles in 20 seconds, and determine the volume-median particle size ( determine the D _50).

Resin production example 1
Polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane 2450 g, Polyoxyethylene (2.2) -2,2-bis (4-hydroxyphenyl) propane 975 g, terephthalic acid 963 g, trimellitic acid 298 g , Dodecenyl succinic acid 343 and 10 g of dibutyltin oxide were placed in a 5-liter four-necked flask equipped with a nitrogen inlet tube, a dehydrating tube, a stirrer, and a thermocouple. / Theoretical product water amount × 100) was reacted until it reached 90%, and then the reaction was performed at 8.3 kPa until the desired softening point was reached, to obtain Resin A. Resin A had a softening point of 149.8 ° C., a glass transition point of 63.2 ° C., and an acid value of 3.4 mgKOH / g.

Examples 1-5 and Comparative Examples 1-6
92.0 parts by weight of resin A, 1.0 part by weight of charge control agent “T-77” (Hodogaya Chemical Co., Ltd.), 2.0 parts by weight of paraffin wax “HNP-9” (manufactured by Nihon Seiki Co., Ltd.) and carbon black “Mougul-L” (Made by Cabot) 5.0 parts by weight were mixed in advance using a Henschel mixer, melt-kneaded using a twin screw extruder, pulverized and classified using a collision plate pulverizer and dispersion separator, and volume-medium particles An untreated toner having a diameter (D ₅₀ ) of 8.0 μm was obtained. The content of particles of 5 μm or less in the untreated toner was 3.5% by volume.

  External additives shown in Table 1 were added to 100 parts by weight of the untreated toner and mixed with a Henschel mixer to obtain a toner.

Test Example 1 [Fog]
The toner was mounted on a commercially available non-magnetic one-component non-contact development type printer, and 20,000 sheets of character images with a printing rate of 5% were continuously printed on A4 size (210 mm × 297 mm) paper. On the way, at the time of printing up to 20 sheets (initial stage), print blank paper (printing rate: 0%), stop the machine, and transparent mending tape (Scotch (registered trademark) mending tape 810 on the surface of the photoreceptor) 3M, width: 18 mm) was attached. The peeled tape was affixed to unused white paper, and white cardboard was overlaid on the tape-pasted paper. The density of the tape is measured with a colorimeter (Gretag-Macbeth's Spectroeye) using the standard white light source D50, the observation field of view 2 °, and the absolute white standard at the density standard DIN NB. The difference from the ding tape was calculated. After printing 20,000 sheets (after printing), white paper was printed in the same manner, the density difference from the mending tape was determined, and evaluated according to the following evaluation criteria. The results are shown in Table 1.

[Evaluation criteria for fogging]
◎: Concentration difference is less than 0.11 ○: Concentration difference is 0.11 or more and less than 0.12 △: Concentration difference is 0.12 or more and less than 0.13 ×: Concentration difference is 0.13 or more

Test Example 2 [Developability]
In Test Example 1, the density of the half-tone image of the 20,000th sheet was measured using a colorimeter (Gretag-Macbeth, Spectroeye), the light emission conditions were standard light source D50, observation field of view 2 °, and density reference DIN NB. The measurement was performed based on the criteria and evaluated according to the following criteria. The results are shown in Table 1.

[Development evaluation criteria]
◎: 0.41 or more ○: 0.26 or more, less than 0.41 △: 0.20 or more, less than 0.26 ×: Less than 0.20

Test Example 3 [Stripes]
After printing in Test Example 1, the presence or absence of streaks on the developing roller, which is one of the causes for causing streaks on the image, was visually observed.

  From the above results, it can be seen that, in contrast to the comparative example, in the example, fogging is suppressed even after printing, and no developing roller streaking that causes image streaking is generated. In particular, in Example 1 in which titanium oxide and hydrophobic silica were used in combination, good results were also obtained in developability having characteristics contrary to fog.

  The electrostatic image developing toner of the present invention is suitably used for developing a latent image formed in electrophotography, electrostatic recording method, electrostatic printing method and the like.

Claims (6)

  An electrostatic charge image developing toner comprising a binder resin, a colorant and an external additive, wherein the external additive comprises strontium titanate having an average particle size of 0.06 to 0.08 μm and an average particle size of 0.05 to 0.4 μm. A toner for developing an electrostatic image, comprising the alumina.   2. The toner for developing an electrostatic image according to claim 1, wherein the strontium titanate is a particle that has not been subjected to a hydrophobic treatment.   The electrostatic image developing toner according to claim 1, wherein the alumina is particles that have not been hydrophobized.   4. The electrostatic image developing toner according to claim 1, wherein the weight ratio of strontium titanate to alumina is 5/1 to 1/5.   The toner for developing an electrostatic charge image according to claim 1, wherein the external additive further contains titanium oxide.   6. The electrostatic charge image developing toner according to claim 1, wherein the external additive further contains silica.