JPH0743947A - Nonmagnetic one-component developer - Google Patents

Abstract

PURPOSE:To eliminate various problems even when the particle diameter of toner particles is reduced and to attain high image qualilty at the time of forming an image with the toner particles by incorporating specified carbon black into the toner particles made of a fixing resin. CONSTITUTION:Carbon black having <=20nm average particle diameter and <=0.50 structure index is incorporated into toner particles made of a fixing resin by <=6 pts.wt. per 100 pts.wt. of the fixing resin. In the case of >20nm average particle diameter or >0.50 structure index, carbon black has low blackness and low coloring power and cannot satisfactorily blacken the toner particles when the carbon black is incorporated by <=6 pts.wt. per 100 pts.wt. of the fixing resin. In order to satisfactorily blacken the toner particles, >6 pts.wt. carbon black causing the rise of electric conductivity and the reduction of the extent of electrostatic charge is required.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is attracting attention as a simple developing method which replaces the conventional two-component magnetic brush developing method.
The present invention relates to a non-magnetic one-component developer used in a one-component insulating toner developing method.

[0002]

2. Description of the Related Art Conventionally, a so-called two-component magnetic brush development method using a two-component developer containing magnetic carrier particles and toner particles has been widely used in devices such as printers utilizing electrophotography. However, recently, as a simpler alternative developing method, a one-component insulating toner developing method has been proposed and is being developed.

In the one-component insulating toner developing method, a non-magnetic one-component developer containing toner particles is charged by frictional charging with a developing sleeve, and is adhered onto the developing sleeve by the action of a regulating blade and an image force. This is a method of forming a uniform thin layer of toner particles on a developing sleeve, transferring the toner particles from this thin layer to an electrostatic latent image on a photosensitive drum, and visualizing the electrostatic latent image. . The one-component insulating toner developing method is a contact developing method in which a thin layer and an electrostatic latent image are brought into direct contact with each other to visualize the electrostatic latent image by toner particles, and a thin layer and an electrostatic latent image. A void is provided between the toner particles and the toner particles, and the toner particles are roughly classified into two methods, that is, a non-contact developing method (jumping method) in which an electrostatic latent image is jumped to be visualized.

As the non-magnetic one-component developer used in the above-mentioned one-component insulating toner developing method, the one obtained by removing the magnetic carrier from the conventional two-component developer is generally used. That is, the non-magnetic one-component developer is composed of toner particles made of a fixing resin to which a colorant is internally added, and an external additive to be externally added to the toner particles. As the colorant,
In the case of black toner, carbon black is mainly used.

Since carbon black is involved in the image density, which is the most important factor in the recording performance of the developer, the magnitude of its coloring ability is a major requirement for material selection. In addition, since the carbon black itself has conductivity, it also plays a role as a means for controlling the electrical characteristics of the toner particles, which is related to the charging of the toner particles, and the amount of internal addition and the degree of dispersion, and other particles Characteristics are an important factor in determining developer performance.

For example, in ordinary toner particles, since a large amount of carbon black is used, the dispersibility of the carbon black in the fixing resin is improved as much as possible, the conductivity is increased due to aggregation, and the charge amount is accordingly decreased. In order to prevent the above, those having an average particle size of 20 nm or more and a structure index of more than 0.50 are generally used. The structure index as used herein refers to a value obtained by dividing the dibutyl phthalate oil absorption of carbon black by the specific surface area.

[0007]

Recently, in order to improve the quality of a formed image, toner particles tend to have a smaller particle size, and at present, particles having a particle size of 10 μm or less are predominant. However, if such a toner particle having such a small particle diameter has the same structure as the conventional one, various problems occur.

For example, a non-magnetic one-component developer containing toner particles of small particle size as a main component tends to cause problems such as reduction in image density and image fog due to insufficient initial charge amount. In addition, if the charge amount is insufficient, it is difficult to form a uniform thin layer of toner particles on the developing sleeve because the electrostatic adhesion of the toner particles cannot be maintained.

When the initial charge amount is insufficient, a method of increasing the electric characteristics of the toner particles is used to improve the charge amount. Specifically, it is attempted to reduce the internal addition amount of carbon black, which is a conductivity control material, to improve the charge rising characteristics and the saturation value of the charge amount. However, since carbon black is a coloring component of toner particles as described above, it is not desirable to reduce the internal addition amount too much. In particular, in consideration of dispersibility as described above, carbon black having a large average particle size and a large structure index has a low blackness and a weak coloring power. The image density of a part is reduced, and black graying due to fading of the color is likely to occur, resulting in unevenness in the formed image, which impairs the subjective quality of the image.

The present invention has been made in view of the above circumstances, and provides a non-magnetic one-component developer which does not have the above-mentioned various problems and can sufficiently cope with high quality of a formed image. It is intended to be provided.

[0011]

In order to solve the above-mentioned problems, the inventors of the present invention have proposed, regarding carbon black as a colorant, which is an important factor affecting the charging characteristics of a non-magnetic one-component developer, Various studies were conducted. Then, carbon black having an average particle diameter of 20 nm or less and a structure index of 0.50 or less is used, and the carbon black is internally added to the toner particles at a ratio of 6 parts by weight or less with respect to 100 parts by weight of the fixing resin. However, it has been found that it is effective in improving the initial charge amount of the developer, maintaining the image density of the solid portion of the formed image, and preventing unevenness of the formed image.

Therefore, the non-magnetic one-component developer of the present invention has an average particle diameter of 2 in the toner particles made of the fixing resin.
A carbon black having a structure index of 0 nm or less and a structure index of 0.50 or less is internally added at a ratio of 6 parts by weight or less to 100 parts by weight of the fixing resin. The present invention will be described below.

In the present invention, the carbon black internally added as a colorant in the toner particles is limited to those having an average particle diameter of 20 nm or less and a structure index of 0.50 or less as described above. The blending ratio of the above carbon black to 100 parts by weight of the fixing resin is limited to 6 parts by weight or less. The average particle size of carbon black is 20
nm or structure index is 0.50
If the amount exceeds 6, the blackness is low and the coloring power is weakened. If 6 parts by weight or less is added to 100 parts by weight of the fixing resin, the toner particles cannot be colored in a sufficiently dark black color. Then, to obtain a satisfactory black color, the fixing resin 1
A large amount of carbon black, which exceeds 6 parts by weight, must be blended with respect to 00 parts by weight, resulting in an increase in conductivity and a corresponding decrease in the amount of charge.

On the other hand, if the average particle size is 20 nm or less and the structure index is 0.50 or less, the packing density for the fixing resin constituting the toner particles is large, and a satisfactory black color can be obtained with a smaller amount of the compound. , The amount of carbon black compounded is 6 with respect to 100 parts by weight of the fixing resin.
When the amount is less than or equal to parts by weight, the conductivity of the toner particles can be reduced and the amount of charge can be improved.

The average particle diameter of carbon black is preferably 10 nm or more, especially in the above range. If the average particle size is less than 10 nm, the cohesiveness becomes too strong, and even if added in a small amount of 6 parts by weight or less based on 100 parts by weight of the fixing resin, the particles cannot be uniformly dispersed in the toner particles, and the conductivity is rather increased. May increase and the charge amount may decrease.

Further, the structure index is preferably in the range of 0.25 or more in the above range.
If the structure index is less than 0.25, the cohesiveness becomes too strong, and even if added in a small amount of 6 parts by weight or less based on 100 parts by weight of the fixing resin, the particles cannot be uniformly dispersed in the toner particles. The conductivity may increase and the charge amount may decrease.

The above carbon black has a lower dispersibility and is more likely to aggregate than ordinary carbon black, but as described above, the packing density in the fixing resin constituting the toner particles is large,
Since it has a higher degree of blackness and stronger coloring power than ordinary carbon black, addition of a small amount of 6 parts by weight or less based on 100 parts by weight of the fixing resin, which does not cause aggregation, makes the toner particles sufficiently dark black. Can be colored. Therefore, it is possible to simultaneously satisfy the contradictory requirements of improving the initial charge amount, maintaining the image density of the solid portion of the formed image, and preventing unevenness of the formed image.

The specific surface area of carbon black and the oil absorption of dibutyl phthalate, which are the criteria for determining the structure index, are not particularly limited in the present invention, but in order to define the structure index within the above range, the specific surface area is 200 m ² / g. As described above, the oil absorption of dibutyl phthalate is preferably 100 ml / 100 g or less. The packing density of the carbon black for the fixing resin is substantially determined by the average particle size and the structure index as described above, but other factors such as the type of the fixing resin are also involved, so the range is particularly limited in the present invention. Not done. However, considering the coloring power of carbon black and the like, the filling density is preferably in the range of 4.5 to 25.0 g / l.

The coloring power of the above carbon black is not particularly limited in the present invention, but for example, DI
100 to 1 represented by the coloring power specified in N 53234.
It is preferably in the range of 30. Other physical properties of carbon black are not particularly limited in the present invention, but a pH value of about 8 to 10 is preferable.

The carbon black used in the present invention is selected from various conventionally known carbon blacks such as channel black, roller black, disc black, gas furnace black, oil furnace black, thermal black, acetylene black and the like. It suffices to select carbon black that satisfies the above respective characteristics.

As described above, the blending amount of carbon black is limited to the range of 6 parts by weight or less relative to 100 parts by weight of the fixing resin. If the blending amount of carbon black exceeds the above range, the initial charge amount decreases, which causes problems such as a decrease in image density and image fog. In addition, when the developer is repeatedly used in the developing device for a long period of time, the amount of charge is significantly reduced. In addition, the compounding amount of carbon black is preferably in the range of 4.0 to 5.5 parts by weight with respect to 100 parts by weight of the fixing resin in the above range.

The fixing resin constituting the toner particles includes, for example, polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene. -Vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylic acid ester copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, Styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-phenyl acrylate copolymer, etc.), styrene-methacrylic acid ester copolymer (styrene-methyl methacrylate copolymer, styrene-methacrylic acid) Ethyl acid copolymer,
Styrene resins such as styrene-butyl methacrylate copolymer, styrene-phenyl methacrylate copolymer), styrene-α-chloromethyl acrylate copolymer, styrene-acrylonitrile-acrylic ester copolymer (styrene or Styrene-substituted homopolymer or copolymer), polyvinyl chloride, low molecular weight polyethylene, low molecular weight polypropylene, ethylene-ethyl acrylate copolymer, polyvinyl butyral, ethylene-vinyl acetate copolymer, rosin-modified maleic acid Resins, phenol resins, epoxy resins, polyester resins, ionomer resins, polyurethane resins, silicone resins, ketone resins, xylene resins, polyamide resins and the like can be mentioned, and these can be used alone or in admixture of two or more.

The fixing resin is preferably neutral. Neutral fixing resins do not adversely affect the charging characteristics of toner particles, and are often more transparent than acidic or basic fixing resins, which adversely affects the coloring of toner particles by carbon black. There is no fear.
In addition to the above two components, various additives such as a charge control agent and a release agent (offset preventing agent) may be internally added to the toner particles.

As the charge control agent, one or both of two types of charge control agents for controlling positive charge and controlling negative charge are used depending on the polarity of the toner particles. As the charge control agent for controlling the positive charge, for example, an organic compound having a basic nitrogen atom, such as a basic dye, an aminopyrine, a pyrimidine compound, a polynuclear polyamino compound, an aminosilane, or the like, and a filler surface-treated with each of the above compounds Etc.

Examples of the charge control agent for controlling the negative charge include a compound containing a carboxyl group (eg, metal chelate of alkylsalicylic acid), metal complex dye, fatty acid soap, metal salt of naphthenic acid and the like. The charge control agent is
0.1 to 10 parts by weight with respect to 100 parts by weight of the fixing resin,
Preferably, 0.5 to 5 parts by weight is internally added.

Examples of the release agent (anti-offset agent) include aliphatic hydrocarbons, aliphatic metal salts, higher fatty acids, fatty acid esters or partially saponified products thereof, silicone oil, and various waxes. Above all,
Aliphatic hydrocarbons having a weight average molecular weight of about 1,000 to 10,000 are preferable. Specifically, one or a combination of two or more of low molecular weight polypropylene, low molecular weight polyethylene, paraffin wax, a low molecular weight olefin polymer composed of olefin units having 4 or more carbon atoms is suitable.

The release agent is internally added in an amount of 0.1 to 10 parts by weight, preferably 0.5 to 8 parts by weight, based on 100 parts by weight of the fixing resin. The toner particles, a mixture obtained by homogeneously premixing the above components by a dry blender, a Henschel mixer, a ball mill, etc., using a kneading device such as a Banbury mixer, roll, uniaxial or biaxial extrusion kneader After uniformly melt-kneading, the obtained kneaded product is cooled and pulverized, and if necessary, classified, or may be produced by a suspension polymerization method or the like.

The particle size of the toner particles is preferably 10 μm or less for the purpose of improving the image quality of the formed image as described above, but the constitution of the present invention can be applied to ordinary toner particles having a particle size of more than 10 μm. Can be adopted. The surface of the toner particles may be sprinkled with a surface treatment agent (fluidizing agent) to improve fluidity and chargeability. As the surface treatment agent, various conventionally known materials such as inorganic fine particles and fluorine resin particles can be used, and in particular, a silica-based surface treatment agent containing hydrophobic or hydrophilic silica fine particles, for example, ultrafine particulate anhydrous silica or Colloidal silica and the like are preferably used.

As described above, the non-magnetic one-component developer of the present invention uniformly charges the toner particles and deposits them on the developing sleeve to form a uniform thin layer of the toner particles. It is used in a one-component insulating toner developing method in which toner particles are transferred to an electrostatic latent image to visualize the electrostatic latent image. In addition, the non-magnetic one-component developer of the present invention is a contact method in which the thin layer and the electrostatic latent image are brought into direct contact with each other in the one-component insulating toner developing method described above to visualize the thin layer and the electrostatic latent image. It can be used in any of the non-contact methods in which a toner particle is jumped to an electrostatic latent image by providing a gap between the electrostatic latent image and the latent image.

Besides, various design changes can be made without departing from the scope of the present invention.

[0031]

EXAMPLES The present invention will be described below based on Examples and Comparative Examples. Example 1, Comparative Examples 1 and 2 100 parts by weight of styrene-acrylate-butyl methacrylate copolymer as a fixing resin, 3 parts by weight of a nigrosine dye as a charge control agent for controlling the positive charge, and polypropylene as a releasing agent. 2.5 parts by weight of wax was mixed with 5 parts by weight of carbon black having the properties shown in Table 1, melt-kneaded, pulverized and classified to produce toner particles A to C having an average particle size of 9 μm.

[0032]

[Table 1]

Then, the above toner particles A to C are sprinkled with hydrophobic silica particles (product number RA200 manufactured by Nippon Aerosil Co., Ltd.) as external additives, respectively, to obtain Example 1, Comparative Example 1,
No. 2 positively chargeable non-magnetic one-component developer was manufactured. The external additive amount of the external additive is 0.3 with respect to 100 parts by weight of the toner particles.
It was made into a weight part.

[0034]

[Table 2]

Comparative Examples 3 and 4 6.5 parts by weight of the same carbon black as that used in the toner particles A was added to 100 parts by weight of a styrene-acrylate-butyl methacrylate copolymer as a fixing resin. Part (toner particle D) or 8.5 parts by weight (toner particle E)
Toner particles D and E were prepared in the same manner as in 1. and the same hydrophobic silica particles as described above were sprinkled to produce positively chargeable non-magnetic one-component developers of Comparative Examples 3 and 4.

[0036]

[Table 3]

Positively charging type non-magnetic material 1 of each of the above examples and comparative examples
The following tests were conducted on the component developers to evaluate their characteristics. Charge rising characteristic test 0.03 g of the positively charging type non-magnetic one-component developer of each of the above-mentioned Examples and Comparative Examples and 0.97 g of a non-coated carrier used for a normal two-component developer are placed in a polypropylene container (polyester). The container was placed in a container, the content volume of which was 3 ml), and allowed to stand in the working environment for 1 day to adjust the humidity. Next, one of the plastic containers was placed in a mini bottle (internal volume: 300 ml), and the mini bottle was rotated by a ball mill rotating device. And after rotating a predetermined number of times,
The charge amount was obtained by measuring the Faraday gauge voltage using a blow-off charge amount measuring device manufactured by Toshiba Chemical Co., using the total amount of the sample in the plastic container.

Measurement of Initial Image Density, Evaluation of Image Defect The positive charging type non-magnetic one-component developer of each of the examples and comparative examples was used in a printer adopting a contact type one-component insulating toner developing method to develop a developing sleeve and a photoconductor. Copying was performed with a bias voltage different from that of the drum, and the image density of the formed image was measured with a reflection densitometer (Model No. TC-6D manufactured by Tokyo Denshoku Co., Ltd.). The presence or absence of various image defects in the formed image was visually observed.

Measurement of Electrical Properties The conductivity (Ωcm), dielectric constant and dielectric loss tangent tan δ of the positive charging type non-magnetic one-component developer of each of the above Examples and Comparative Examples are shown in FIG.
It measured using the measuring device shown in. The measuring device of FIG.
A cylindrical shield case 11 holds cylindrical electrodes 12 and 13 with flanges and a ring body 14 in an electrically independent state via an insulating ring 15, respectively. The reference numerals 12 and 13 are connected to the electrical characteristic measuring device 16, and the ring body 14 is grounded.

Then, in the above-mentioned measuring device, the powdery sample S is filled in the space formed by the cylindrical electrodes 12 and 13 and the ring body 14, and the upper cylindrical electrode 1
2 is pressed downward as indicated by an arrow in the figure to compress the sample S, and an AC voltage of a predetermined frequency is applied from the electrical characteristic measuring device 16 between the cylindrical electrodes 12 and 13 to compress the sample S. The electrical characteristics (conductivity, permittivity and dielectric loss tangent tan δ) of the sample S in the state are measured.

As the electric characteristic measuring device 16,
An impedance analyzer manufactured by Yokogawa Hewlett-Packard Company is preferably used. According to the above measuring apparatus, since it is not necessary to perform compression molding of the sample S in advance, the coating of the conductive coating can be performed more easily than the case where the electrical characteristics of the molded product is measured after compression molding the sample. The condition can be evaluated.

The above results are shown in Tables 4-6.

[0043]

[Table 4]

[0044]

[Table 5]

[0045]

[Table 6]

As can be seen from the results of Tables 4 to 6 above, carbon black having an average particle size of more than 20 nm and a structure index of more than 0.50 was applied to the fixing resin 10
5 parts by weight of toner particles B and C internally added to 0 parts by weight of the developers of Comparative Examples 1 and 2 and carbon black having an average particle size of 20 nm or less and a structure index of 0.50 or less are internally added. Also, the amount of internal addition is 1 for fixing resin
Toner particles D, E exceeding 6 parts by weight with respect to 00 parts by weight
Comparative Examples 2 to 4 among the developers of Comparative Examples 3 and 4 using
Of Comparative Examples 1 and 2 had insufficient initial image density.

On the other hand, the embodiment 1 which is the constitution of the present invention
It was found that the developer No. 1 has excellent characteristics such as charge buildup and initial image density. Example 2, Comparative Examples 5 and 6 100 parts by weight of a styrene-acrylate-butyl methacrylate copolymer as a fixing resin, 3 parts by weight of a metal complex as a charge control agent for controlling a negative charge, and polypropylene as a release agent. 2.5 parts by weight of wax was mixed with 5 parts by weight of carbon black having the characteristics shown in Table 7, melt-kneaded, pulverized and classified to have an average particle size of 9 μm.
Toner particles F to H were manufactured.

[0048]

[Table 7]

Then, the above-mentioned toner particles F to H were sprinkled with hydrophobic silica particles (product number R974 manufactured by Nippon Aerosil Co., Ltd.) as external additives, respectively, to obtain Example 2, Comparative Examples 5 and 6.
The negative charging type non-magnetic one-component developer of was manufactured. The amount of the external additive added was 0.3 parts by weight with respect to 100 parts by weight of the toner particles.

[0050]

[Table 8]

Comparative Examples 7 and 8 6.5 parts by weight of the same amount of carbon black as that used in the toner particles F was added to 100 parts by weight of a styrene-acrylate-butyl methacrylate copolymer as a fixing resin. Parts (toner particles I) or 8.5 parts by weight (toner particles J) except that the toner particles I and J are prepared in the same manner as the toner particles F and are sprinkled with the same hydrophobic silica particles as described above. The negative charging type non-magnetic one-component developers of Comparative Examples 7 and 8 were manufactured.

[0052]

[Table 9]

Negative charging type non-magnetic material 1 of each of the above Examples and Comparative Examples
With respect to the component developer, each of the tests described above was performed and the characteristics thereof were evaluated in the same manner as described above except that the bias polarity of the printer used was reversed. The results are shown in Tables 10-12.

[0054]

[Table 10]

[0055]

[Table 11]

[0056]

[Table 12]

As can be seen from the results of Tables 10 to 12, carbon black having an average particle size of more than 20 nm and a structure index of more than 0.50 was internally added to 5 parts by weight with respect to 100 parts by weight of the fixing resin. In the developers of Comparative Examples 5 and 6 using the toner particles G and H, the initial image density was insufficient. Furthermore, the average particle size is 2
Even if carbon black having a structure index of 0 nm or less and a structure index of 0.50 or less is internally added, the amount of the internal addition is 10
The developers of Comparative Examples 7 and 8 using the toner particles I and J in an amount of more than 6 parts by weight with respect to 0 parts by weight were insufficient in the charge rising characteristics and the initial image density.

On the other hand, the second embodiment which is the configuration of the present invention
It was found that all of the above developers are excellent in the above respective characteristics.

[0059]

As described in detail above, according to the present invention, carbon black having an average particle size of 20 nm or less and a structure index of 0.50 or less is mixed in an amount of 6 parts by weight or less with respect to 100 parts by weight of the fixing resin. Since the non-magnetic one-component developer is formed by internally adding it to the toner particles, the non-magnetic one-component developer of the present invention does not have various problems even if the particle size is reduced, and a formed image is obtained. It is possible to sufficiently deal with the high image quality of.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a measuring device for evaluating the electrical characteristics of a developer.

Claims (1)

[Claims] 1. A toner particle is uniformly charged and deposited on a developing sleeve to form a uniform thin layer of the toner particle, and the toner particle is transferred from this thin layer to an electrostatic latent image and the electrostatic latent image is transferred. A non-magnetic one-component developer used in a one-component insulating toner developing method for visualizing an electric latent image, in which toner particles made of a fixing resin have an average particle diameter of 20 nm or less and a structure index of 0.50 or less. Carbon black, fixing resin 1
A non-magnetic one-component developer which is internally added at a ratio of 6 parts by weight or less with respect to 00 parts by weight.