JP2007271766A - Nonmagnetic monocomponent electrophotographic toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide nonmagnetic monocomponent electrophotographic toner which prevents the occurrence of white streaks due to aggregation of external additives, deterioration of a photoreceptor and contamination of a charging roll. <P>SOLUTION: Three kinds of inorganic substance particles different in particle size have been added to the toner, wherein the three kinds of inorganic substance particles are first inorganic substance particles having an average particle size of 1-20 nm, second inorganic substance particles having an average particle size of 20-50 nm which is larger than the average particle size of the first inorganic substance particles, and third inorganic substance particles having an average particle size of ≥50 nm which is larger than the average particle size of the second inorganic substance particles, and these inorganic substance particles are characterized in that primary aggregates have a particle size of ≤1.2 μm measured with a laser diffraction/scattering system particle size distribution measuring device. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a non-magnetic one-component electrophotographic toner, and more particularly to a non-magnetic one-component electrophotographic toner to which a plurality of types of inorganic substance particles are externally added.

  In electrophotographic image formation, an electrostatic latent image is generally formed by applying a uniform electrostatic charge to a drum having a photosensitive layer made of a photoconductive material, and then exposing the image to a charged toner. The toner image is developed and visualized, and the obtained toner image is transferred to a sheet.

  As the developer, there are a two-component developer mainly composed of a carrier and a toner, and a one-component developer which does not require a carrier. In the case of a two-component developer, the toner is charged by friction due to mixing of the carrier and the toner. In the case of a one-component developer, the toner is frictioned between the toners or by friction with a doctor blade pressed against the developing roll.

  Regardless of the type of developer, a method of adding an external additive to the surface of toner particles is widely known mainly for the purpose of adjusting the fluidity and chargeability of the toner.

  In response to the recent high demands on toner, toner external addition technology has also made remarkable progress. A plurality of types of external additives (inorganic fine particles, resin fine particles, etc.) having different particle diameters, and different surface treatments are applied to carry the respective functions.

  For example, a toner is proposed in which a small particle size silica that imparts fluidity and a large particle size silica that prevents adhesion between the toners are added as external additives (see, for example, Patent Document 1). In addition, a toner having three types of external additives each having a hydrophobized treatment added has been proposed (see, for example, Patent Document 2).

  However, when the amount of the external additive is increased, various problems caused by the aggregation of the external additive occur. Aggregation of the external additive means that the uniform adhesion to the toner and the dispersion of the external additive deteriorate in the external addition process, and the external additive aggregates and mixes in the toner. Is generated. For example, white streaks occur in the image due to aggregation of external additives. Further, the aggregates damage the photoconductor or cause filming. Further, when cleaning the transfer residual toner by bringing a cleaning blade into contact with the photoconductor after transfer, the aggregate of the external additive is smaller than the toner particles, so that it passes through the blade without being cleaned, and the charging roll , The uniform charging of the photoreceptor is inhibited, and image defects are caused. There is also a problem that optimum charging cannot be applied.

The problem caused by such an agglomerate of the external additive has been conventionally present, but becomes more prominent as the amount of the external additive added increases. This is particularly noticeable when a plurality of different external additives are added simultaneously.
JP-A-6-47157 JP 2004-258265 A

  An object of the present invention is to provide a non-magnetic one-component electrophotographic toner which is made under such circumstances and prevents white streaks caused by aggregation of external additives, deterioration of a photoreceptor and contamination of a charging roll. To do.

  As a result of studies conducted by the present inventors to improve the above problems, when a plurality of types of external additives having different particle sizes are added simultaneously, the particle size of the primary aggregate of the external additive is nonmagnetic. It has been found that the problem caused by aggregation of the external additives of the toner used in the one-component development system is greatly affected. In general, the primary particle size of the external additive has been regarded as a problem, but the actual behavior of the external additive is not the primary particle size, but the primary aggregate. Is demonstrating. For example, catalog value: 1 μm when titania having a particle size of 100 nm is measured with a dry particle size distribution meter. Even if it is applied to a mixer to break up the titania agglomeration, the particle size measured by a dry particle size distribution meter is hardly changed. From this, it can be easily inferred that titania functions as a primary aggregate even after being externally supported on the toner.

  However, the particle size of the primary aggregate has never been discussed. The present inventors have found that the problem caused by the aggregation of the external additive of the toner can be solved by setting the particle size of the primary aggregate of the external additive to a predetermined value or less.

  That is, the present invention is a toner obtained by externally adding three kinds of inorganic substance particles having different particle diameters, and the three kinds of inorganic substance particles are first inorganic substance particles having an average particle diameter of 1 to 20 nm and average particles. A second inorganic material particle having a diameter of 20 to 50 nm and an average particle size larger than the first inorganic material particle; and an average particle size of 50 nm or more and an average particle size larger than the second inorganic material particle Non-magnetic particles characterized in that they are third inorganic material particles, and these inorganic material particles have a primary aggregate particle size of 1.2 μm or less measured by a laser diffraction / scattering particle size distribution measuring device. A one-component electrophotographic toner is provided.

  In the electrophotographic toner of the present invention, the first inorganic substance particles and the second inorganic substance particles can be silica, and the third inorganic substance particles can be titania.

  The electrophotographic toner of the present invention preferably has an average particle diameter of 5 to 7 μm.

  The present invention is also the above-described toner, and an elastic developing roll for carrying and transporting the toner, and the thickness of the toner so as to form the toner in a thin layer on the elastic developing roll. An electrophotographic toner for use in a developing device comprising a toner layer regulating member and having a conveying speed of the elastic developing roll of 100 mm / second or more.

  According to the present invention, the primary aggregates measured by a laser diffraction / scattering particle size distribution measuring device each have a particle size of 1.2 μm or less, a small particle size external additive, a medium particle size external additive, and By externally adding three types of external additives, large particle size external additives, aggregation of the external additives is prevented, and fogging, white stripes, deterioration of the photoreceptor, and charging roll contamination caused by the aggregation of the external additives are prevented. An electrophotographic toner that can be prevented is provided.

  The best mode for carrying out the invention will be described below.

  An electrophotographic toner according to an embodiment of the present invention is a toner obtained by externally adding three types of inorganic substance particles having different particle diameters. These inorganic substance particles are obtained by a laser diffraction / scattering particle size distribution measuring apparatus. The measured primary aggregate particle size is 1.2 μm or less.

  The three types of inorganic substance particles are a first inorganic substance particle having an average particle diameter of 1 to 20 nm, a second inorganic substance having an average particle diameter of 20 to 50 nm and an average particle diameter larger than that of the first inorganic substance particle. And third inorganic substance particles having an average particle diameter of 50 nm or more and an average particle diameter larger than that of the second inorganic substance particles.

  Among these inorganic substance particles, the first inorganic substance particles impart fluidity to the toner to improve the toner replenishment property, the second inorganic substance particles improve the solid followability of the toner, and the third The inorganic substance particles have a function of improving transferability.

  Examples of the material of the first to third inorganic substance particles include silica, titania, alumina, zirconia, and the like, and silica and titania are preferable.

  The first to third inorganic substance particles may all be the same material or different materials. However, since it is difficult to obtain a silica having a large particle diameter, it is desirable that the first inorganic substance particles and the second inorganic substance particles are silica, and the third inorganic substance particles are titania.

  In the present invention, the average particle size of the primary aggregate of the external additive is limited to 1.2 μm or less because the external additive exists as an aggregate rather than as primary particles and behaves. This is because not only the particle size of the particles but also the particle size of the primary aggregate has a great influence on the properties of the toner. The primary aggregate refers to an aggregate that cannot be further divided even when the aggregate is pulverized and pulverized by a dry process.

  If the average particle size of the primary aggregate of the external additive exceeds 1.2 μm, fogging due to the aggregation of the external additive, white stripes, deterioration of the photoreceptor, and charging roll contamination may occur.

  The laser diffraction / scattering particle size distribution measuring method used for measuring the average particle size of the primary aggregate of the external additive is to detect the relationship between the scattered light intensity and angle of the laser light irradiated to the particles, A calculation method based on the Mie scattering theory.

  FIG. 1 shows an image forming apparatus for forming an image using the electrophotographic toner of the present invention described above.

  The image forming apparatus shown in FIG. 1 includes a developing device 1 and a photosensitive drum 2. The developing device 1 includes a toner hopper 3 that contains toner therein, a supply roll 4 that supplies toner to the developing roll, and a toner supplied from the supply roll 4 to the photosensitive drum 2, so that the surface of the photosensitive drum 2 A developing roll 5 made of an elastic body that develops the electrostatic latent image, and a doctor blade 6 that is in sliding contact with the developing roll 5 and regulates the thickness of the toner layer on the surface of the developing roll 5 are provided. Around the photosensitive drum 2, there are a charging roll 7 for uniformly charging the surface of the photosensitive drum 2, and an LED 8 for exposing a document image to the surface of the charged photosensitive drum 2 to form an electrostatic latent image. Has been placed.

  Under the photosensitive drum 2, a transfer belt 9 runs along with the rotation of the photosensitive drum 2, and contacts the photosensitive drum 2 by the transfer sheet 10, and the developed toner image is transferred to the paper 11. The

  The toner that has not been transferred and remains on the surface of the photosensitive drum 2 even after the transfer is removed by the cleaning blade 12.

  Even when the above-described toner of the present invention is mounted on the image forming apparatus configured as described above and the elastic developing roll is transported at a high speed of 100 mm / second or more, white streaks caused by aggregation of the external additive are generated. Further, deterioration of the photoreceptor and charging roll contamination do not occur.

Example A polyester resin and a magenta pigment (CI Pigment Red 57: 1) were charged and kneaded in a pressure kneader so that the weight ratio of resin: pigment was 7: 3, and the resulting kneaded product was blended with a feather mill ( (2 mm pass) to obtain a pigment master batch. Next, 83 parts by weight of a polyester resin (softening point 147 ° C., glass transition point 75 ° C.) as a binder resin, 10 parts by weight of a magenta pigment master batch as a colorant, and “Carnauba wax No. 1 powder” (Kato) as a release agent. Western imports) 6 parts by weight, 1 part by weight of “LR-147” (manufactured by Nippon Carlit Co., Ltd .: organoboron compound) as a charge control agent is weighed to a total of 50 kg, and put into a 150 L Henschel mixer, Mix for 3 minutes at 1000 rpm. The mixture was supplied to a continuous two-roll kneader with a table feeder to obtain a kneaded product. The raw material supply amount was 25 kg / h.

  The obtained kneaded product is cooled with a cooling belt, and then coarsely pulverized with a Rotoplex (manufactured by Hosokawa Micron Co., Ltd., 2 mm diameter screen). Grinding and classification were performed so as to obtain 6.0 μm, and colored fine particles were obtained.

  External additives were added and mixed with the colored fine particles obtained as described above in the types and ratios shown in the following table to obtain 12 types of toner samples.

  The polyester masterbatch and the polyester resin used as the binder resin use polyoxyethylenated bisphenol A and polyoxypropylenated bisphenol A as alcohol monomers, and terephthalic acid and dodecenyl succinic acid as carboxylic acid monomers. What was used as an ingredient was used.

  The conditions of the kneader, the measuring method of each characteristic value, and the mixing conditions are shown below.

1. Kneading machine conditions A continuous two-roll type kneading machine having a roll diameter of 0.16 m and an effective roll length of 0.7 m was used under the conditions shown in Table 1 below.

2. Measurement of softening point For 1 g of sample, a flow tester (manufactured by Shimadzu Corporation, CFT-500D) was used as the apparatus, and the temperature at which half of the sample flowed out by the 1/2 method was defined as the softening point. The measurement conditions are as follows.

Temperature increase rate: 6 ° C / min Load: 20kg
Nozzle: 1mm diameter, 1mm length
3. Measurement of glass transition point (Tg) A differential scanning calorimeter (manufactured by Shimadzu Corporation: DSC-60) was used as a device, and 8 mg of a sample was heated to 160 ° C. at 10 ° C./min, and 35 at a temperature decreasing rate of 10 ° C./min. After cooling to 10 ° C., the temperature was raised again to 160 ° C. at 10 ° C./min, and the intersection of two tangents of the curve portion obtained by the transition was used as the glass transition point at the second temperature rise.

4). Measurement of toner particle size A small amount of toner, purified water, and a surfactant were placed in a beaker and dispersed with an ultrasonic cleaner. The sample was measured with Multisizer II (Coulter). The aperture was 100 μm, the count was 50,000, and the volume average particle size was obtained.

5). Measurement of primary agglomerated particle size of external additive Use LA-950 (trade name: manufactured by HORIBA, Ltd.) dry unit as a laser diffraction / scattering particle size distribution measuring device, and disperse with compressed air of 0.3 MPa. The volume average particle size was measured with the refractive index of the external additive being 2.5. A sample for measurement was prepared by adding about 1 to 2 cups of each external additive to 30 to 50 ml of water with a spatula, and dispersing for about 1 minute with an ultrasonic cleaner, and collecting about 1 g of the sample as a sample.

6). External additive mixing conditions 3.0 kg of colored fine particles were charged into a 20 L Henschel mixer. An external additive was added and mixed with 100 parts by weight of the colorant fine particles under the conditions shown in the following table. As the stirring blade, a strong stirring blade was attached and rotated at a wind speed of 40 m / sec.

  The characteristic test method and evaluation criteria will be described below.

Test 1-Flowability A powder tester manufactured by Hosokawa Micron Corporation was used as the device, and a sieve having a mesh size of 250, 150, 75 µm from the top was used. 2 g of toner was weighed, placed gently on the top sieve stacked in three stages, vibrated for 15 seconds with an amplitude of 1 mm, and the degree of aggregation was determined as follows.

Weight% of toner remaining on sieve having aperture of 250 μm = W1
Weight% of toner remaining on sieve with 150 μm openings × 0.6 = W2
Weight% of toner remaining on a sieve having an opening of 75 μm × 0.2 = W3
Aggregation degree (%) = W + W2 + W3
Fluidity = 100−degree of aggregation (%)
Evaluation criteria of fluidity Fluidity 80 or more: ◎
Fluidity 70 or more and less than 80: ○
Less than 70 fluidity: x
Test 2-White streaks due to external additive aggregation Non-magnetic one-component developing device "Casio Page Presto N-5" (Casio Computer Co., Ltd .: 29 color printers per minute (A4 horizontal), process speed 129 mm / sec) And 16,000 sheets of 5% print images were continuously printed in a normal environment (25 ° C., 50% RH). In the middle, solid images and halftone images were printed every 2,000 sheets, and evaluated according to the following criteria based on the number of white lines generated by blade fusion.

◎: Not generated up to 16,000 sheets ○: Generated after 14,000 sheets (a level that does not cause any practical problems)
X: Generation test with less than 14,000 sheets 3-Photoconductor degradation 5 using normal paper (XEROX-P paper A4 size) in the normal environment (25 ° C, 50% RH) using the apparatus used in Test 1. After 30,000 sheets of% printed images are printed continuously, halftone images and solid images are printed, and it is checked whether there is any image deterioration due to photoconductor filming and photoconductor scratches. The surface of the photoreceptor was observed and evaluated according to the following criteria.

◎: Photoconductor deterioration is not observed ○: Image does not appear, but photoconductor is deteriorated ×: Photoconductor deterioration enough to appear in image 4-Charging roll contamination In evaluation of test 3 In addition to confirming image deterioration due to contamination of the charging roll, contamination on the charging roll was also confirmed. Evaluation was made according to the following criteria.

◎: No charging roll contamination ○: Image does not appear but charging roll contamination ×: Charging roll contamination enough to appear in image 12 types of toner samples were tested and evaluated. The results are shown in Tables 2 and 3 below.

  Abbreviations for surface treatment are as follows.

PDMS: Polydimethylsiloxane RS: Alkylsilane In addition, inorganic materials with various particle sizes and various surface treatments used as the first external additive and the second external additive are obtained from Nippon Aerosil Co., Ltd. did.

  The titania used for the third external additive is obtained by subjecting each surface treatment to anatase-type titanium oxide (Fuji Titanium Industry Co., Ltd.).

  From the above table, the following can be understood. That is, in the toners according to Examples 1 to 4 in which three kinds of inorganic fine particles having different primary particle diameters each having a primary aggregate particle diameter of 1.2 μm or less are externally added, white streaks caused by aggregation of the external additive Was not generated, the photoreceptor was not deteriorated, and the charging roll was not contaminated.

  In contrast, the toner of Comparative Example 1 to which the first inorganic fine particles were not added was poor in fluidity and could not be evaluated. Further, in the toner of Comparative Example 2 in which the second inorganic fine particles were not added, white streaks due to aggregation of the external additive were generated, and the photoreceptor was deteriorated. Further, in the toner of Comparative Example 3 to which the third inorganic fine particles were not added, the photoreceptor was deteriorated and the charging roll was contaminated.

  Further, Comparative Example 5 in which alumina was added instead of silica as the first inorganic fine particles had slightly poor fluidity, and was evaluated as x in the above table.

  In the toners of Comparative Examples 4 and 6 in which the primary aggregate particle size of the third inorganic fine particles exceeds 1.2 μm, white streaks due to the aggregation of the external additive are generated, and the photoreceptor is deteriorated. It was. Furthermore, in the toner of Comparative Example 7 in which the primary aggregate particle size of the second inorganic fine particles exceeded 1.2 μm, white streaks due to the aggregation of the external additive occurred.

  In addition, since the alumina used in Comparative Example 7 did not aggregate, the primary aggregate particle size could not be measured, and even in this case, white streaks due to the aggregation of the external additive occurred.

1 is a diagram schematically illustrating an image forming apparatus that performs image formation using toner according to an embodiment of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Developing device, 2 ... Photosensitive drum, 3 ... Toner hopper, 4 ... Supply roll, 5 ... Developing roll, 6 ... Doctor blade, 7 ... Charging roll, 8 ... LED, 9 ... Transfer belt, 10 ... Transfer sheet, 11 ... paper, 12 ... cleaning blade.

Claims (4)

  A toner externally added with three kinds of inorganic substance particles having different particle diameters, wherein the three kinds of inorganic substance particles are first inorganic substance particles having an average particle diameter of 1 to 20 nm and an average particle diameter of 20 to 50 nm. Second inorganic material particles having an average particle size larger than the first inorganic material particles, and third inorganic material particles having an average particle size of 50 nm or more and an average particle size larger than the second inorganic material particles These inorganic substance particles have a primary aggregate particle size of 1.2 μm or less as measured by a laser diffraction / scattering particle size distribution measuring apparatus, and the toner is a non-magnetic one-component electrophotographic toner .   2. The nonmagnetic one-component electrophotographic toner according to claim 1, wherein the first inorganic substance particles and the second inorganic substance particles are silica, and the third inorganic substance particles are titania.   The nonmagnetic one-component electrophotographic toner according to claim 1, which has an average particle diameter of 5 to 7 μm.   An elastic developing roll for carrying and transporting toner; and a toner layer regulating member for regulating the thickness of the toner so as to form the toner in a thin layer on the elastic developing roll. The non-magnetic one-component electrophotographic toner according to claim 1, wherein the toner is used in a developing device having a conveying speed of 100 mm / second or more.

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