JP3486512B2 - Electrophotographic developing carrier, two-component developer using the carrier - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-component developer used for developing an electric latent image in an image forming method such as an electrophotographic method or an electrostatic printing method, and a carrier used for the developer. .

[0002]

2. Description of the Related Art Conventionally, various electrophotographic methods have been described in US Pat. No. 2,297,691, JP-B-42-23910 and JP-B-43-24748.

The developing methods applied to these electrophotographic methods and the like are roughly classified into a dry developing method and a wet developing method. The former is further divided into a method using a two-component developer and a method using a one-component developer.

Of these, the two-component type developer is one in which the toner is charged to the required charging polarity and amount by friction with the carrier and the electrostatic latent image is developed by using electrostatic attraction.

Iron powder carriers have been widely used as carrier particles in the past, but ferrite carriers are nowadays used due to the fact that the charging characteristics greatly change depending on the humidity of the operating environment and that the particle surface easily changes chemically. It is becoming popular.

Generally, since a ferrite carrier has a higher resistance than an iron powder carrier, it does not disturb an electrostatic latent image when used as a developer for electrophotography, and therefore reproducibility of a fine line image and a highlight image. Is very good, and a high-definition image can be obtained.

However, due to the high resistance, an edge effect is likely to occur during development, and so-called white spots or image defects such as sweeping occur. Further, since the developing electric field strength decreases, there is a problem that the toner development amount and the image density as it is also decrease.

Various efforts have hitherto been made to solve these problems.

For example, JP-A-52-154639 and JP-A-2-160259 attempt to suppress the edge effect by using a carrier core material having a low resistance.

However, when a low resistance carrier core is used, it is difficult to obtain the above-mentioned high-definition image, and the latent image in the non-image area is generated by the charge injection into the latent image by the applied bias during development. Image potential lowers, and so-called fogging is likely to occur in development.

Further, as disclosed in, for example, Japanese Patent Application Laid-Open No. 62-280756, it is possible to use a carrier in which the carrier core surface is coated with a polymer containing conductive fine powder to reduce the electric resistance of the carrier surface. Being tried.

However, when such a carrier having a low surface electric resistance is used, the carrier adheres to the surface of the latent image carrier, that is, so-called carrier adhesion occurs, and the charge injection into the latent image becomes more remarkable. , A leak mark, a so-called white spot, occurs on the image.

Therefore, Japanese Patent Laid-Open No. 5-181319 discloses the use of a carrier core with a limited range of electric resistance.

However, even if such a carrier core is used, it is difficult to obtain a carrier sufficiently satisfying the contradictory functions of high-definition image reproduction and edge effect suppression.

On the other hand, another important function required of the carrier is the ability to quickly and highly charge the toner.

However, the ferrite carrier itself is often inadequate in terms of performance such as insufficient charge imparting ability to the toner and easy carrier contamination due to long-term use.

Therefore, in recent years, a so-called surface-coated ferrite carrier, in which carrier contamination is prevented by covering the surface of the carrier with an appropriate coating material, and the coating material itself has a charge imparting ability, has come to be frequently seen in recent years. It was

However, it is undeniable that the above-mentioned edge effect appears more conspicuously because the surface coating provides a higher resistance as a carrier.

Further, even in the case of the surface-coated ferrite carrier, it is unavoidable that physical change of the surface such as peeling of the coating material due to long-term use is unavoidable. For example, the coating material controls the charge amount of the toner. In this case, the toner charge amount often changes at the start of use and after long-term use. Therefore, it is necessary that the uncoated ferrite carrier core also has sufficiently high charge imparting ability.

Thus, when used as a developer,
At present, there is no carrier for electrophotographic development that satisfies all of the image characteristics, charging characteristics and durability.

[0021]

SUMMARY OF THE INVENTION An object of the present invention is to provide a two-component type developer which can solve the above problems.

That is, an object of the present invention is to provide a two-component developer capable of stably supplying a high-definition image without fog, leak marks, carrier adhesion, and edge effects for a long period of time.

Another object of the present invention is to provide a developing method which gives a very high-definition image using the above developer.

A further object of the present invention is to provide a two-component developer capable of stably providing a high-definition image for a long period of time, especially when the toner particle size is small.

[0025]

The above object is a carrier for electrophotographic development containing at least a magnetic substance, the carrier being 1 × 10 ⁸ Ω · cm under a sinusoidal AC voltage having an amplitude of 2 kV and a frequency of 2 kHz. Carrier core material showing the above impedance and conductivity on the surface of the carrier core material
A capacitor layer having a capacitor capacity component formed by coating with a coating material containing a material, and an electrostatic capacitance obtained from an applied voltage frequency dependency of impedance measured under a sinusoidal AC voltage having an amplitude of 2 kV of the carrier. Capacity is 1 x 1
It is achieved by using an electrophotographic developing carrier characterized by a value of 0 ^-15 F to 1 × 10 ^-11 F. Furthermore, the present invention provides a two-component developer having at least a toner and a carrier, wherein the carrier is the electrophotographic developing carrier of the present invention, and the two-component developer has an amplitude of 2 kV and a frequency of 2 kHz of a sine AC voltage. Below, an impedance of 1.2 × 10 ⁸ Ω · cm or more is shown, and the capacitance obtained from the applied voltage frequency dependency of the impedance measured under a sine AC voltage with an amplitude of 2 kV is 1 × 10 ⁻¹⁴ F to 1 A two-component developer having a value of × 10 ^-11 F is provided.

[0026]

DETAILED DESCRIPTION OF THE INVENTION A detailed description of the structure of the present invention will be given below.

The first feature of the present invention is that the core material of the coated carrier used in the two-component developer has an amplitude of 2 k.
1 × 10 under a sine AC voltage of V and frequency of 2 kHz
^The purpose is to use a magnetic substance-containing core that exhibits an impedance of ⁸ Ω · cm or more.

As described above, when a material having a high electric resistance is selected as the carrier, it is possible to obtain a two-component type developer excellent in reproducibility of a fine line image and a highlight image. In the study by the present inventors, in particular, an amplitude of 2 kV and a frequency of 2
It was revealed that a very high-definition image can be obtained when a magnetic material-containing core showing an impedance of 1 × 10 ⁸ Ω · cm or more under a sine AC voltage of kHz is used. Further, it has been found that this characteristic is more remarkable especially when a small particle size toner for reproducing high image quality having an average particle size of 8 μm or more is used.

[0029] If the impedance at the measurement conditions described above using the magnetic substance-containing core of less than 1 × 10 ⁸ Ω · cm, it is not obtained satisfactory high quality image for disturbance of the electrostatic latent image is generated.

Here, the electric resistance value of the carrier greatly changes depending on the measurement conditions, and the measurement condition closely correlated with the developing characteristics is that the developer is used, that is, applied to the developer during development. The developing bias condition is preferably used. In general, a sinusoidal AC voltage having a frequency of about 2 kHz and an amplitude of about 2 kV is often used as a bias applied during development for obtaining a high image quality, and an amplitude of 2 k
It is clear that the impedance of the carrier, measured under a sinusoidal AC voltage of V, frequency 2 kHz, is closely correlated with its development characteristics.

For example, the above-mentioned Japanese Patent Laid-Open No. 5-181319.
In the publication, the applied electric field is 1 × 10 ^{3 to} 1 × 10 ⁴ V
1 × 10 ⁷ as the lower limit of the electric resistance in the range of / cm.
It is reported that Ω · cm or more is preferable, but in addition to the fact that the measurement conditions do not match the actual development conditions, the inventors of the present invention have found that the electric resistance of the carrier is still insufficient for obtaining a high-definition image. there were.

The second feature of the present invention is that an edge generated when a material having high electric resistance is used as a developer carrier by imparting a capacitor component to the surface of the above-mentioned carrier core having high electric resistance. It is to solve the problems such as the effect and the decrease in image density.

The mechanism of this operation will be described as follows.

When an AC electric field is applied, the capacitor layer on the surface of the carrier functions to reduce the resistance of the entire carrier due to the movement of charges inside the layer. Therefore, the edge effect is suppressed and a high image density can be obtained. On the other hand, since the leakage of charges to the outside of the capacitor layer does not occur, it is possible to faithfully develop without disturbing the electrostatic latent image, and a high-definition image without image defects such as fog, leak marks, or carrier adhesion It is judged that reproducibility can be obtained.

The capacitance of the capacitor component is 1 as a value obtained from the applied voltage frequency dependency of the carrier impedance measured under a sinusoidal AC voltage with an amplitude of 2 kV.
^{X10 -15} F to 1x10 ^-11 F are required and can be controlled within this range by the method described later.

When the above value is less than 1 × 10 ^-15 F, the edge effect or the reduction of the image density is not sufficiently suppressed, and 1
If it exceeds × 10 ^-11 F, the electric resistance of the carrier under an alternating electric field is too low, and it becomes difficult to obtain a high-definition image.

Regarding the capacitance of the carrier, the carrier having the capacitance of 1 × 10 ^{−10 to} 2.1 × 10 ⁻¹⁰ F is described in the examples and comparative examples of Japanese Patent Application Laid-Open No. 4-324457. There is. However, as described above, according to the study by the present inventors, the capacitance of the carrier is preferably in the range of 1 × 10 ^{−15 to} 1 × 10 ⁻¹¹ F, which is disclosed in JP-A-4-324457. When a carrier having a large capacity exceeding 1 × 10 ⁻¹⁰ F as described therein is used, the electric resistance under an alternating electric field is reduced, and it is difficult to obtain a high-definition image.

Further, in the present invention, in addition to the above characteristics, a ferrite core having a second ionization potential of a ferrite component metal other than Fe of 17 eV or less and a coercive force Hc of 100 oersted or less is used as the carrier core. As a result, it became clear that in addition to high density and high definition image characteristics, even charging characteristics can be stably obtained for a long period of time.

It is generally known that a metal having a lower ionization potential has a higher ability to give a negative charge to the toner. However, according to a study by the present inventors, the second ionization potential of a metal contained in a carrier component is particularly high. Was found to be closely correlated with the ability to impart charge to the toner.

This is because the valence of the metal in the carrier is 2 when the carrier in the developer replenishes the charge from the developer carrier.
It is considered that this is based on the phenomenon that the charge is applied to the toner after the valence decreases to the valence of 1 and the valence returns to the valence of 2 again. In particular, it has been found that when a metal having a second ionization potential of 17 eV or less is selected as the metal other than Fe in the ferrite component, the charge imparting ability to the toner becomes extremely high.

Further, it was confirmed that when the ferrite carrier having the above-mentioned constitution is used as the carrier core in the above-mentioned developer, the deterioration of the image characteristics during the durability is remarkably reduced. The reason for this is not clear, but the following explanation can be considered.

Since a metal having a low ionization potential easily releases a negative charge, it is considered that the toner is quickly charged when the metal and the negative polarity toner come into contact with each other.
After that, the capacitor component of the carrier is rapidly polarized so as to cancel the polarity of the toner, and at the moment when the toner is separated from the surface of the carrier by the developing electric field, it returns to the non-polarized state, so that the toner flying to the latent image is not transferred to the carrier. It's hard to come back. That is, it is explained that the carrier spent and the deterioration of the developer are remarkably suppressed by reducing the long-term residual toner on the carrier.

It is also important that the coercive force Hc of the carrier used in the present invention is 100 oersted or less. When Hc exceeds 100 Oersted, since the attraction force between the developer carrier having a magnet inside and the developer is always strong, the toner is consumed by the development and the developer whose toner concentration is reduced and the fresh developer are Is not replaced smoothly, and as a result, only an image with low image density and image quality can be obtained.

Here, the content of the Fe component in the ferrite composition of the carrier is preferably 20 to 95 mol% in terms of Fe ₂ O ₃ . If it is less than 20 mol%, it is difficult to keep the impedance of the carrier within the above range, and if it exceeds 95 mol%, it is difficult to adjust the magnetic characteristics.

The average particle diameter of the carrier in the developer in the present invention is not limited, but the above-mentioned effect becomes remarkable especially when the average particle diameter is 50 μm or less. Generally, the smaller the carrier particle size, the larger the carrier surface area, and the faster the charging speed of the toner when mixed with the toner. On the other hand, since the surface area is large and the area in which carrier contamination is generated is large, the charging characteristics of the developer before and after long-time use are likely to largely change.

However, in the developer composition of the present invention, since the deterioration of the developer due to the durability is significantly suppressed, even if a carrier having a small particle size is used, the charging property of the developer is hardly changed before and after long-term use. Good results are obtained.

Further, although the average particle diameter of the toner in the developer in the present invention is not limited, a very high-definition image can be stably obtained over a long period of time, especially when the average particle diameter is 8 μm or less.

Generally, the smaller the average particle size of the toner, the higher the quality of the image obtained, but it is difficult to uniformly and quickly charge the individual toner particles, and the deterioration of the developer is remarkable. It is known that Therefore, when the toner is used for a long period of time, the smaller the particle diameter of the toner is, the more noticeable the fluctuation of the image characteristics and the deterioration of the fog.

However, when a toner having a small particle size is applied to the developer composition of the present invention, the charge imparting ability of the carrier is high and the deterioration of the developer is small, so that a high-definition image is long after the start of use. It is possible to obtain a stable value over time.

In the present invention, various methods can be used as a means for imparting a capacitor capacitance component to the carrier core material. For example, a material showing conductivity by a conduction band (so-called conduction band) can be used as a resin. There is a method in which it is dispersed in a resistance material and coated on the carrier surface. However, it is important that the conductive material is not exposed on the surface of the coating material during coating, and if there are many exposed portions, the carrier resistance will decrease, making it difficult to obtain a high-definition image.

Therefore, when a conductive material is used, it is also preferable to use a treatment for enhancing the affinity with the coating material or improving the dispersibility in the coating material. The following materials can be used as such a conductive material. That is, carbon black, graphite, tin oxide, titanium oxide, silicon oxide, bismuth oxide, indium oxide and other metal oxides are used. It is also preferable to use these after enhancing the affinity with the material to be the dispersion carrier by grafting the surface or treatment with various coupling agents.

It is possible to control the electrostatic capacity of the carrier by adjusting the addition amount of these conductive materials to the dispersion carrier, but the electrostatic capacity increases with increasing the addition amount, but the toner And the durability against fogging and the like deteriorates. Therefore, it is necessary to adjust the addition amount to an appropriate level. Generally, for dispersion carriers such as resins,
A preferable range is more than 0.1 parts by weight and 20 parts by weight or less. If the addition amount is 0.1 parts by weight or less, it is difficult to give a sufficient capacitance to the carrier, and if it is more than 20 parts by weight, the durability cannot be reduced.

The following materials can be used as a coating material when the above-mentioned conductive material is dispersed and coated on the carrier core. That is, styrene resins, acrylic resins, other vinyl polymers and their copolymers, melamine resins, polyamide resins, ionomer resins, polyester resins, epoxy resins, curable silicone resins and the like are used. A part of these may be substituted with a halogen atom or the like.

For coating the carrier core, for example, the core material is dipped in a solution obtained by mixing the polarizable material with a mixture of one or more kinds of the above-mentioned polymers in a suitable solvent. Then, a method of desolventizing, drying, baking at high temperature, or a method of suspending the core material in a fluidized bed, spray-coating the polymer solution, drying and baking at high temperature can be used.

When mixing the coating material and the polarizable material in a solvent, it is also preferable to use a dispersion device such as an attritor.

Further, in order to prevent the conductive material from being exposed from the surface of the coating material, the coating material containing no polarizable material may be coated again after the coating treatment as described above.

Several reports have been made so far on the carrier whose surface is coated with a coating material containing a conductive material, for example. For example, as a coated carrier with a coating material containing carbon black, there is disclosed in JP-A-4-20.
No. 4551, No. 5-181322, No. 5-2.
No. 41379 is disclosed.

However, in these publications, there is no description regarding the electrical characteristics of the carrier.

In the present invention, a high-definition image is achieved by using a carrier core having a specific impedance characteristic, and it has been proved that it is difficult to obtain a high-definition image by other cores.

A coated carrier containing a coating material containing a general conductive material is also disclosed in JP-A-4-3601.
No. 58, No. 4-372960, No. 5-107.
No. 819, No. 5-289412, No. 5-30
It is disclosed in Japanese Patent No. 3238.

However, even in these publications,
There is no description about the carrier core and electrical properties of the carrier after coating, and as described above, addition of a simple conductive agent to the carrier coating material directly leads to deterioration of image quality. That is, only when the conductive material is not exposed from the surface of the coating material after coating and further the capacitor component of a specific range is applied to the carrier, it is possible to suppress the high-definition image reproduction and the edge effect like the carrier in the present invention. Thus, a coated carrier satisfying both requirements can be obtained.

One of the further characteristics of the present invention is that when the carrier and the toner are mixed to prepare a two-component developer, it is set so as to have impedance and capacitance characteristics within a specific range. .

Generally, a developer obtained by mixing a toner and a carrier has a higher electric resistance than that of the carrier alone. Therefore, in order to obtain a high-definition image while suppressing problems such as an edge effect and a low image density, a carrier characteristic It is difficult to improve only by itself, and it is necessary to control the electric characteristics of the developer.

As a result of the inventors' earnest studies on the balance of impedance and capacity as a developer, when the carrier and toner are mixed, the amplitude is 2 kV and the frequency is 2 kH.
1.2 × 10 ⁸ Ω · cm under z sinusoidal voltage
Capacitance obtained from the dependency of applied voltage frequency on the impedance measured under the sinusoidal AC voltage having the amplitude of 2 kV as described above is 1 × 10 ⁻¹⁴ F to 1 ×.
It has been found that a developer that gives a high-definition image with no edge effect at high image density can be obtained by adjusting the value to be 10 ⁻¹¹ F.

Here, the impedance of the developer is 1.2.
If it is less than × 10 ⁸ Ω · cm or the capacity exceeds 1 × 10 ⁻¹¹ F, the electrical resistance characteristics of the developer under an AC electric field are deteriorated, and it becomes difficult to obtain a high-definition image. Also,
If the capacity is less than 1 × 10 ⁻¹⁴ F, it becomes difficult to prevent the edge effect and the decrease in image density.

As a method of obtaining such a developer, adjustment by the mixing ratio of the carrier and the toner in the developer in consideration of the electrostatic capacity of the carrier can be mentioned. That is, the electrostatic capacity of the carrier is C _C (pF), and the toner concentration in the developer is N _{C.
In the} present invention, the toner and the above-mentioned carrier are mixed while the balance between the two is adjusted so that 1 × 10 ⁻¹² ≦ C _C × N _T ≦ 40 × 10 ⁻¹² when _T (% by weight) is ^satisfied. The developer can be obtained. Here, C _C × N _T <1 × 10
^In the case of ^−12, the capacity of the capacitor of the developer is small, so it is insufficient to suppress the edge effect during development under an alternating electric field, and in the case of 40 × 10 ⁻¹² <C _C × _NT , the reverse Since the capacity is too high, it is difficult to obtain a high definition image.

Further, in the present invention, of the developer carrier and the magnet roller incorporated therein, both the magnet roller and the developer carrier are rotated, or the magnet roller is fixed and the developer carrier is rotated. Then, a two-component developer containing at least a carrier and a toner is circulated and conveyed on the developer carrier, and the latent image is developed with the toner in the development area of the latent image carrier and the developer carrier opposite thereto. In an image forming method for transferring a toner image formed on a latent image carrier onto a transfer material, the two-component developer is the above-described two-component developer of the present invention, and an AC component and a DC component are used in the developing area. A major feature is that an alternating electric field having a component is formed and the latent image is developed under the condition that the frequency νkHz of the alternating electric field is 1.0 or more.

That is, the developer has a function of canceling the adverse effect of high resistance such as edge effect in the electrostatic field under an alternating electric field of high frequency, so that the frequency νkHz of the alternating electric field is 1.0 or more. By combining with a developing method for developing a latent image under a certain condition, the effect of suppressing the image density and suppressing the edge effect becomes more remarkable. ν <1.
In the case of 0, the image density becomes slightly low, and the edge effect becomes an image that is slightly conspicuous.

Further, in the above-mentioned developing method, the voltage for attracting the toner from the latent image carrier to the developer carrying member between the latent image carrier and the developer carrying member and the flying from the developer carrying member to the latent image carrying member. This is a developing method of developing a latent image with toner by applying a voltage to the image area at least once and then applying a voltage to the non-image area in a direction to pull back the toner. More preferably, the first voltage for directing the toner from the latent image carrier to the developer carrier and the second voltage for directing the toner from the developer carrier to the latent image carrier are more preferred. The time for applying the third voltage between the first voltage and the second voltage to the developer carrier is longer than the total time for applying the toner to the carrier, so that the toner on the latent image carrier is regenerated. Especially for the purpose of arranging and reproducing faithfully to the latent image Masui.

Specifically, in the developing area, an electric field between the latent image holding member and the developer carrying member, the toner is directed from the latent image holding member to the developer holding member, and the toner is transferred from the developer holding member to the latent image holding member. After the electric field directed to the latent image carrier is formed at least once, the toner moves from the developer carrier to the latent image carrier in the image area of the latent image carrier, and the toner in the non-image area of the latent image carrier moves to the latent image carrier. The latent image held on the latent image carrier is developed by the toner of the developer carried on the developer carrier by forming an electric field from the developer carrier to the developer carrier for a predetermined time. In the image portion of the latent image carrier, the toner is latent from the developer carrying body from the total time of forming the electric field of the toner from the image carrying body to the developer carrying body and the electric field of the toner going from the developer carrying body to the latent image carrying body. Toward the image carrier, in the non-image part of the latent image carrier It is preferred that the toner is increased towards the time of forming the electric field directed to the developer carrying member from the latent image holding member.

The inventors of the present invention have used a two-component developer of the present invention having specific electric resistance characteristics to form an alternating electric field and develop the developing electric field so that the alternating electric field is periodically turned off. It has been found that when image development is carried out by using, excellent image quality can be achieved due to high image density and high-definition image reproducibility without carrier adhesion.

The two-component developer of the present invention has a specific electric resistance characteristic as described above, and the carrier serving as a constituent component also has a specific composition, so that the triboelectric chargeability with the toner rises. In particular, when it is composed of a carrier having an average particle size of 50 μm or less and a toner having an average particle size of 8 μm or less, very high-definition image reproduction is possible.

On the other hand, in the case of a carrier having a small particle diameter, there is a concern that the carrier may adhere to the latent image holding member during development, but by combining with the developing electric field described in the present invention, carrier adhesion does not occur. . The reason for this is not clear yet, but it can be considered as follows.

That is, in the conventional continuous sine wave or rectangular wave, when the electric field strength is increased in order to achieve high image density, the toner and the carrier are integrally formed between the latent image holding member and the developer holding member. Although a high-definition image can be obtained by reciprocating, the carrier strongly rubs against the latent image carrier, resulting in carrier adhesion. This tendency becomes more remarkable as the amount of fine powder carrier increases.

However, in the present invention, when the above-mentioned specific developing electric field is applied, the toner or the carrier makes a reciprocating motion which does not reciprocate between the developer carrying member and the latent image holding member in one pulse, and thereafter, When the potential difference V _cont between the surface potential of the latent image holding member and the DC component of the developing bias is V _cont <0 when the third voltage is applied, the DC component acts to fly the carrier from the developer carrying member. By controlling the magnetic characteristics of the carrier and the magnetic flux density in the developing area of the magnet roller, carrier adhesion can be prevented. When V _cont > 0, the force of the magnetic field and the direct current component cause the carrier to move to the developer carrier side. Work to attract,
No carrier adhesion occurs.

As the toner binder resin in the developer of the present invention, various material resins conventionally known as electrophotographic toner binder resins are used. For example, polystyrene, styrene-styrene copolymers such as styrene-butadiene copolymers, styrene-acrylic copolymers, polyethylene, ethylene-vinyl acetate copolymers, ethylene-copolymers such as ethylene-vinyl alcohol copolymers. , Phenolic resins, epoxy resins, acrylic phthalate resins, polyamide resins, polyester resins, maleic acid resins and the like. In addition, the manufacturing method and the like of each resin are not particularly limited.

Among these resins, particularly when a polyester resin having a high negative chargeability is used, the effect of the present invention is great. That is, the polyester resin is excellent in fixability,
While suitable for color toners, they have a strong negative charging ability and tend to become excessively charged, but when a polyester resin is used in the constitution of the present invention, the adverse effects are improved and excellent toners can be obtained.

In particular,

[0079]

[Chemical 1]

(Wherein R is an ethylene or propylene group, x and y are each an integer of 1 or more, and x +
The average value of y is 2 to 10. ), A bisphenol derivative or a substitution product represented by the formula (1) is used as a diol component, and a carboxylic acid component composed of a divalent or higher carboxylic acid or an acid anhydride thereof or a lower alkyl ester thereof (eg, fumaric acid, maleic acid, maleic anhydride, phthalate An acid, terephthalic acid, trimellitic acid, pyromellitic acid, etc.) is more preferable because it has a sharp melting property.

Examples of the colorant used in the toner of the developer of the present invention include carbon black, lamp black, iron black, ultramarine blue, nigrosine dye, aniline blue, phthalocyanine blue, phthalocyanine green, Hansa yellow G, rhodamine 6G and chalcone. Conventionally known dyes and pigments such as oil blue, chrome yellow, quinacridone, benzidine yellow, rose bengal, triarylmethane dyes, monoazo dyes and disazo dyes may be used alone or in combination.

A fluidity improver may be added to the toner of the developer of the present invention for the purpose of improving fluidity. As the fluidity improver used in the present invention, any agent can be used as long as the fluidity can be increased by adding it to the toner as compared with before and after the addition.

For example, fluorine-based resin powder, that is, fine powder of vinylidene fluoride, fine powder of polytetrafluoroethylene, or the like; or fatty acid metal salt, that is, zinc stearate, calcium stearate, lead stearate, or the like; or metal oxide, that is, zinc oxide. Powders, titanium oxide fine powder, silica fine powder, alumina fine powder, and surface-treated metal oxides obtained by subjecting these metal oxides to surface treatment with a silane coupling agent, titanium coupling agent, silicone oil, or the like.

The measuring method in the present invention will be described below.

(1) Method of measuring triboelectric charge amount The measuring method will be described in detail with reference to the drawings.

FIG. 1 is an illustration of an apparatus for measuring the triboelectric charge of toner. First, about 0.5 to 0.9 g of the developer collected from the sleeve of the developing device is put into a metal measuring container 12 having a screen 13 of 500 mesh on the bottom, and a lid 14 made of metal is placed. At this time, the total weight of the measuring container 12 is weighed and set as W ₁ (g). Next, in the suction device 11 (at least the portion in contact with the measurement container 12 is an insulator), suction is performed from the suction port 17 to adjust the air volume control valve 16 to adjust the vacuum gauge 1
The pressure of 5 is 250 mmAq. In this state, the toner is suctioned sufficiently, preferably for about 2 minutes to remove the toner by suction. The potential of the electrometer 19 at this time is V (volt). Here, 18 is a capacitor, and the capacitance is C (μF). Further, the total weight of the measurement container after suction is weighed and is W ₂ (g). The triboelectric charge amount (mC / kg) of this toner is calculated by the following formula.

Toner triboelectric charge amount (mC / kg) = (C × V) / (W ₁ −W ₂ ).

(2) Fog measuring method Fog was measured by REFLECTMET manufactured by Tokyo Denshoku Co., Ltd.
ER MODEL TC-6DS was used for measurement, and for cyan toner images, an aver filter was used, and the value was calculated from the following formula. The smaller the number, the less fog.

Fog (reflectance) (%) = reflectance on standard (%)-reflectance (%) of non-image area of sample

(3) Measurement of physical properties of carrier (3-1) The magnetic characteristics of the carrier were measured by using a BHU-60 type magnetization measuring device (manufactured by Riken measurement).

The measurement sample is weighed about 1.0 and the inner diameter is 7 mm.
It is packed in a cell with φ and a height of 10 mm, and set in the above device. In the measurement, the applied magnetic field is gradually added and changed up to 3000 Oersted. Next, the applied magnetic field is reduced to finally obtain the hysteresis curve of the sample on the recording paper. From this, the saturation magnetization, remanent magnetization, and coercive force are obtained.

(3-2) As an apparatus for measuring the carrier particle size distribution, SRA type of Microtrack particle size analyzer (Nikkiso Co., Ltd.) was used, and the range setting was 0.7 to 125 μm.

(3-3) The impedance of the carrier, coated carrier and developer was measured using the cell shown in FIG. That is, the cell A is filled with a sample, the electrodes 21 and 22 are arranged so as to be in contact with the filled sample 27, a sine AC voltage is applied between the electrodes, and the current flowing at that time is measured by an AC ammeter 24. Sought by. The measurement condition is that the contact area of the filled sample with the cell is S = 2.
cm ² , thickness d = 3 mm, load of the upper electrode was 15 kg, and the impedance value at that time was AC voltage (amplitude / amplitude /
Current value) × (S / d)

(3-4) The electrostatic capacities of the coated carrier and the developer were determined as follows.

In the impedance measurement described in (3-3), when a sine AC voltage having an amplitude of 2 kV is applied between the electrodes 21 and 22, the frequency is appropriately changed between 0 and 4 kHz, and the AC voltage is changed each time. The current value is read by the ammeter 24 for use. Next, based on the obtained data, a graph of (frequency) ^-2 against (impedance) ² is created, and the slope a is obtained. For the capacitance C (F), the value of the slope a is used, and C
= (2πa ^1/2 ) ⁻¹ .

[0096]

EXAMPLES The present invention will now be specifically described with reference to examples, but the present invention is not limited thereto.

[Manufacture Example 1 of Carrier] CaO, MgO and Fe ₂ O ₃ were weighed and mixed so that the concentrations were 20, 20, and 60 in mol% concentration, respectively. The obtained mixed powder was calcined at 1000 ° C. or lower, pulverized, and then added with an aqueous polyvinyl alcohol solution as a binder resin so as to be 1 to 3% by weight with respect to the pulverized sample, and granulated by a spray dryer. The obtained granulated powder is fired at 1100 to 1300 ° C., pulverized,
The carrier core material A was obtained by classification.

Carbon black 0.1 part by weight Curing type silicone resin xylene solution 100 parts by weight (concentration of 10% by weight in terms of solid content) The carrier coating material was dispersed and mixed for 1 hour with an attritor manufactured by Mitsui Kinzoku Co., Ltd. Apply 1 part by weight of resin to carrier core material A with Okada Seiko Spiracoater,
The coated carrier 1 was obtained by drying and heating. The obtained carrier physical property values are shown in Table 1 together with the coating materials using them.

[Carrier Production Example 2] The carrier coating material used in Carrier Production Example 1 was mixed with a homomixer for 15 minutes, and then coated on carrier core material A, dried and heated in the same manner as in Carrier Production Example 1. A coated carrier 2 was obtained. The obtained carrier physical property values are shown in Table 1 together with the coating materials using them.

[Carrier Production Example 3] Carbon black 0.13 parts by weight Curing type silicone resin xylene solution 100 parts by weight (10% by weight concentration in terms of solid content) After mixing the above carrier coating materials with a homomixer for 15 minutes, The carrier core material A was coated with 0.8 parts by weight in terms of resin in the same manner as in Carrier Production Example 1 to once obtain a coated carrier. Next, the coated carrier was coated with 0.2 parts by weight of a curable silicone resin containing no carbon black in the same manner as the resin to obtain a coated carrier 3 in which two layers were coated. The properties of the obtained carrier are shown in Table 1 together with the coating material using the same.

[Carrier Production Examples 4 to 5 ] After coating the coating materials shown in Table 1 with a homomixer for 15 minutes, the coated carriers 4 to 5 having the contents shown in Table 1 were prepared by the same method as in Carrier Production Example 2. Obtained.

[Carrier Production Examples 7 to 13] The coating materials shown in Table 1 were dispersed and mixed in an attritor for 1 hour, and then the same procedure as in Carrier Production Example 1 was followed to obtain the coated carriers 7 to 10 having the contents shown in Table 1. I got 13.

[0103]

[Table 1]

[Toner Production Example 1] Polyester resin obtained by condensing propoxylated bisphenol and fumaric acid 100 parts by weight Phthalocyanine pigment 4 parts by weight Di-tert-butylsalicylic acid aluminum compound 4 parts by weight was sufficiently prepared with a Henschel mixer. After mixing, the mixture was melt-kneaded by a twin-screw extrusion type kneader, cooled, coarsely pulverized to about 1 to 2 mm using a hammer mill, and then finely pulverized by an air jet type fine pulverizer. Further, the obtained finely pulverized material was classified to obtain a negative triboelectrative cyan-colored powder having a weight average particle diameter of 8.5 μm.

100 parts by weight of the colored powder and 1.0 part by weight of titanium oxide fine powder (T805 manufactured by Nippon Aerosil Co., Ltd.) were mixed with a Henschel mixer to obtain a cyan toner 1.

[Toner Production Example 2] The weight average particle diameter was 6.0.
Cyan Toner 2 was obtained in the same manner as in Toner Production Example 1 except that alumina fine powder having a surface made hydrophobic by a silane coupling agent was used instead of the titanium oxide fine powder.

[Example 1] The above-mentioned cyan toner 2 and carrier 4 were mixed so that the toner concentration in the developer would be 6% by weight to obtain a developer. The obtained developer had an impedance of 2 × 10 ⁸ Ω · cm and a capacitance of 5 × 10 ⁻¹⁴ F. A color copying machine CLC700 (manufactured by Canon Inc.) was used, and a non-continuous alternating electric field shown in FIG. 4 was applied as a developing bias by connecting to an external power source. The evaluation was carried out by developing 30,000 sheets at a development contrast of 300 V under the temperature and humidity. The obtained results are shown in Table 2.

As is clear from Table 2, the above-mentioned developers gave high-definition images with no edge effect from the initial stage to after 30,000 sheets. In addition, the amount of charge remained stable, fogging was small, and no stain was found inside the machine.

The following examples and comparative examples are also shown in Table 2.
It was shown to.

[0110]

[Table 2]

[Embodiment 2] The same evaluation as in Embodiment 1 was carried out except that the alternating electric field shown in FIG. 3 was applied as the developing bias. No image was obtained. The charge amount also remained stable, and there was no particular problem with fogging and stains inside the machine.

[Embodiment 3] Cyan toner 1 and carrier 4
And were mixed so that the toner concentration in the developer would be 8% by weight to obtain a developer. When this developer was used and evaluated in the same manner as in Example 1, an image having a relatively good image quality without an edge effect was obtained from the initial stage to after 30,000 sheets. The amount of charge remained stable, there was little fog, and there was no stain inside the machine.

[Embodiment 4] Cyan toner 1 and carrier 1
Was mixed in such a manner that the toner concentration in the developer was 4% by weight, and the same evaluation as in Example 1 was carried out except that the developer was used. An image of various quality was obtained. The amount of charge also remains stable,
There was little fog and no dirt was seen inside the aircraft.

[Examples 5 to 7] The same evaluation as in Example 1 was carried out except that the carrier 5, 10 or 11 was used as the carrier. As shown in Table 2, the edge effect was observed from the initial stage to after 30,000 sheets. A high-definition image with no image was obtained. In addition, the amount of charge remained stable, fogging was small, and no stain was found inside the machine.

[Embodiment 8] The same evaluation as in Embodiment 1 was carried out except that the alternating electric field shown in FIG. 5 was applied as the developing bias, and a slight edge effect was observed from the initial stage to after 30,000 sheets. However, an image with no particular problem was obtained.
The charge amount also remained stable, and there were no particular problems in terms of image quality, fog, and stains inside the machine.

[Embodiment 9] Cyan toner 2 and carrier 2
Was mixed in such a manner that the toner concentration in the developer was 14% by weight, and the same evaluation as in Example 1 was conducted except that the developer was used. A stable image was obtained. Since the electrostatic capacity of the developer was large, the electrostatic latent image was disturbed and the image quality was slightly degraded, but there was no problem in practical use. The edge effect was not particularly observed.

[Example 10] The same evaluation as in Example 1 was conducted except that the cyan toner 1 and the carrier 1 were mixed so that the toner concentration in the developer was 1.5% by weight, and the mixture was used as the developer. As a result, a slight edge effect was observed from the beginning, and after 30,000 sheets, the image quality was slightly deteriorated, but there was no problem in practical use. It is considered that this is because the electrostatic capacity of the developer was rather small and the edge effect was not sufficiently suppressed.

[Example 11] The same evaluation as in Example 1 was carried out by using the cyan toner 2 and the carrier 3,
Although the edge effect was slightly observed from the initial stage to after 30,000 sheets, a practically problem-free image was obtained.

[Comparative Example 1] Cyan toner 2 and carrier 2
When the same evaluation as in Example 1 was performed using and, only an image with a remarkable edge effect was obtained. This is probably because the carbon was exposed to the surface due to insufficient dispersion of carbon in the carrier coating material, and the coated carrier did not have sufficient capacitance.

[Comparative Example 2] Cyan toner 2 and carrier 7
Was mixed in such a manner that the toner concentration in the developer was 10% by weight, and the same evaluation as in Example 1 was carried out except that the developer was used. Only an image with poor image quality was obtained from the initial stage to 30,000 sheets. I couldn't do it. It is considered that this is because the electrostatic latent image is disturbed because the electrostatic capacity of the developer and the electrostatic capacity C _C of the carrier used are large.

[Comparative Example 3] The carrier 8 was used in place of the carrier 4, and the same evaluation as in Example 1 was carried out. As a result, only an image with a remarkable edge effect was obtained from the initial stage to after 30,000 sheets. It is considered that this is because the electrostatic capacities of the coated carrier and the developer are small.

[Comparative Example 4] The same evaluation as in Example 1 was carried out using the carrier 9 instead of the carrier 4, and only images of poor image quality were obtained from the initial stage to after 30,000 sheets. It is considered that this is because the image quality deteriorated because the impedance of the carrier core used was small. No particular problem was observed in the edge effect.

[Example 12] The same evaluation as in Example 1 was carried out using the carrier 12 instead of the carrier 4,
Although there was no particular problem in the initial stage, the image quality and fog were slightly deteriorated after 30,000 sheets, and stains inside the machine were also observed. It is considered that this is because the charge imparting ability of the carrier was low and the developer was deteriorated for the reason described above, but there was no problem in practical use.

[Example 13] The same evaluation as in Example 1 was conducted except that the cyan toner 2 and the carrier 13 were mixed so as to have a toner concentration of 10% by weight in the developer to obtain a developer. From 30,000 sheets to 30,000 sheets, an image having no problem in practical use was obtained although the edge effect and fog were slightly conspicuous. There was also a slight stain inside the aircraft. It is considered that this is because the electrostatic capacity of the developer and the charge imparting ability of the carrier are small, and the developer is slightly deteriorated for the reasons described above, but both are at a level where there is no particular problem in practical use. there were.

[0125]

[0126]

As described above, according to the present invention,
In electrophotography, it is possible to stably obtain a high-definition, high-density image for a long period while suppressing the edge effect.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an apparatus for measuring a triboelectric charge amount of toner.

FIG. 2 is a circuit diagram of an apparatus for measuring the impedance of powder.

FIG. 3 is a waveform diagram of an alternating electric field used for a developing bias.

FIG. 4 is a waveform diagram of an alternating electric field used for a developing bias.

FIG. 5 is a waveform diagram of an alternating electric field used for a developing bias.

[Explanation of symbols]

11 suction machine 12 Measuring container 13 screens 14 lid 15 Vacuum gauge 16 Air flow control valve 17 Suction port 18 capacitors 19 electrometer 21,22 electrodes 23 Insulator (resin etc.) 24 AC ammeter 25 AC voltmeter 26 power supply 27 samples 28 Guide ring

Continuation of the front page (56) Reference JP-A-8-202084 (JP, A) JP-A-8-137140 (JP, A) JP-A-8-44170 (JP, A) JP-A-8-6302 (JP , A) JP-A-7-271194 (JP, A) JP-A-7-160059 (JP, A) JP-A-4-77751 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB) Name) G03G 9/10

Claims (6)

(57) [Claims] 1. An electrophotographic developing carrier containing at least a magnetic material, the carrier being 1 × 10 ⁸ Ω · under a sinusoidal AC voltage having an amplitude of 2 kV and a frequency of 2 kHz.
A carrier core material having an impedance of cm or more and a coating material containing a conductive material on the surface of the carrier core material
And a capacitance of 1 × 10 ⁻¹⁵ F obtained from the dependency of the impedance of the carrier measured under a sinusoidal AC voltage with an amplitude of 2 kV on the applied voltage frequency. To 1 × 10 ⁻¹¹ F, a carrier for electrophotographic development. 2. The carrier core material is made of ferrite containing at least one metal having a second ionization potential of 17 eV or less as a metal other than Fe, and the carrier has a coercive force Hc of 100 oersted or less. The described electrophotographic developing carrier. 3. The carrier core material comprises a Fe component containing Fe ₂
The carrier for electrophotographic development according to claim 1 or 2, which is ferrite containing 20 to 95 mol% in terms of O ₃ . 4. A two-component developer having at least a toner and a carrier, the carrier being an electrophotographic developing carrier containing at least a magnetic substance, the carrier being under a sinusoidal AC voltage having an amplitude of 2 kV and a frequency of 2 kHz. Carrier core material showing an impedance of 1 × 10 ⁸ Ω · cm or more and a conductive material on the surface of the carrier core material
A capacitor layer having a capacitor capacitance component formed by coating with a coating material containing
The capacitance obtained from the applied voltage frequency dependency of the impedance measured under a sinusoidal alternating voltage of kV is 1 × 10.
^A carrier having a value of ⁻¹⁵ F to 1 × 10 ⁻¹¹ F, and the two-component developer has an impedance of 1.2 × 10 ⁸ Ω · cm or more under a sinusoidal AC voltage having an amplitude of 2 kV and a frequency of 2 kHz. And the capacitance obtained from the applied voltage frequency dependence of the impedance measured under a sinusoidal AC voltage with an amplitude of 2 kV has a value of 1 × 10 ⁻¹⁴ F to 1 × 10 ⁻¹¹ F. Component developer. 5. The carrier core material is made of ferrite containing at least one metal having a second ionization potential of 17 eV or less as a metal other than Fe, and the carrier has a coercive force Hc of 100 oersted or less. The two-component developer described. 6. The carrier core material comprises a Fe component containing Fe ₂
The two-component developer according to claim 4, which is a ferrite containing 20 to 95 mol% in terms of O ₃ .