JPS59220746A - Magnetic toner for developing electrostatic charge image - Google Patents

Abstract

PURPOSE:To obtain a magnetic toner fixable with pressure in a wide temp. range by using 2 kinds of resins different in mol.wt. at the peak from each other for the binder of a magnetic toner. CONSTITUTION:A mixture of a high mol.wt. polymer (A) and a low mol.wt. polymer (B) is used for the binder of a pressure mixable toner, and a fine magnetic powder, such as iron or cobalt, is dispersed into this resin to form particles, and further, fine electrically conductive particles, such as electrically conductive carbon black or aluminum, are attached to the surfaces of these particles to obtain a magnetic toner for developing an electrostatic charge image. Thermoplastic resins, such as polystyrene, polyvinyltoluene, styrene-butadiene copolymer, having a peak mol.wt. of 80-500 thousand and 1-50 thousand are used for (A) and (B), respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic toner for developing electrostatic images.

Electrostatic images formed by electrophotography, electrostatic printing, electrostatic recording, etc. are usually developed using a developing toner, and then transferred to transfer paper and fixed to form a visible image. . At present, colored powder and granular materials such as C& are widely used as developing toners, but in particular, magnetic toners containing fine magnetic powder in resin particles are used alone as developers. In this respect, it is more advantageous than a so-called two-component developer which is used in combination with a carrier. In other words, in development using a two-component developer, only the toner is consumed, so the mixing ratio with the carrier changes and the image forming characteristics change, but in development using magnetic toner, this JJt has no such drawbacks.

Such magnetic toners can be broadly classified into conductive toners and insulating toners, each of which has advantages and disadvantages. As for conductive toner, it is preferable that an electrostatic image formed on an electrostatic image support made of a photoconductive photoreceptor etc. can be developed very clearly by the so-called electrostatic induction development method. The toner image formed in this way,
When the image is transferred onto a transfer paper using an electrostatic transfer method, which is a preferable transfer method, there is a problem that the transferred image has low sharpness due to disturbance of the electric lines of force.

The following methods have been proposed to solve the above problems. That is, this is a method in which a toner image obtained by developing an electrostatic image formed on an electrostatic image support is transferred onto an intermediate transfer member under pressure, and this toner image is transferred onto a transfer paper while simultaneously being fixed. According to such a pressure transfer method, it is possible to transfer a clear toner image formed by conductive toner to the transfer paper without disturbing the casing, that is, the image, resulting in good developability. Since transferability can be obtained, it is theoretically possible to form a clear visible image.

However, in the suppression transfer method, it is necessary to fix the toner image on the intermediate transfer member at the same time as it is pressed onto the transfer paper, and in order to achieve sufficient fixation, it is necessary to If the degree of heating is low, the fixation to the transfer paper will be insufficient and the transfer will also be insufficient, and as a result, a good visible image will not be formed on the transfer paper. The heating temperature of the imitation toner during transfer and fixing in the zero-pressure transfer method may be at least the temperature at which the toner particles are softened to the extent that the toner substance sticks to the transfer paper due to the applied pressing force. The heating temperature required in a heated roller fusing means that fuses the toner material to the transfer paper almost exclusively by heat may also be slightly lower.

However, conventionally known magnetic toners for developing electrostatic images have a high softening point, which makes it difficult to heat them to a considerably high temperature during transfer and fixing. However, when the toner is heated to a high temperature, the high temperature is also transferred to the intermediate transfer body that is in contact with the electrostatic image support, and as a result, the tangible support is heated through the intermediate transfer body. Therefore, when the electrostatic image support is a photoreceptor, its characteristics deteriorate and its service life is shortened. For example, in the case of a photoreceptor made of amorphous selenium, crystallization of selenium progresses at a temperature of about 50° C. or higher, and in the case of an organic photoreceptor, the characteristics change greatly depending on temperature. In order to prevent heat transfer to the electrostatic image support, it is necessary to increase the distance from the transfer and fixing area of the intermediate transfer member to the contact position with the electrostatic image support, or to install a cooling mechanism, etc. There is a disadvantage that it is necessary to cool the transfer body, and the apparatus becomes larger and more complicated.

Therefore, research is underway to create a toner with a low softening point by using a binder resin with a low softening point, but toners that use a resin with a low softening point as a binder usually have an offset phenomenon. However, there are some drawbacks that can easily occur. To explain more specifically, in the contact heat fixing method, including the case of the pressure transfer method, a part of the toner to be fixed on the transfer paper is transferred to the intermediate transfer body and then transferred again to the subsequent transfer paper. The possibility that this phenomenon will occur actually occurs when heating is completed above the temperature that is specific to the material. The lowest temperature at which the phenomenon occurs (hereinafter referred to as the "offset occurrence temperature") is generally low. For this reason, the so-called fixable temperature range, which is above the softening point of the toner and below the onset temperature, is narrow, which poses a practical problem.

The present invention has been made based on the above-mentioned circumstances, and its objectives are to have a low softening point, suitable onset temperature, and therefore a wide fixing temperature range, as well as a material with good electrical conductivity. The object of the present invention is to provide a magnetic toner for developing an electrostatic image that can form a #8A visible image, especially in a process using a suppression transfer method.

The feature of the present invention is that the peak molecular weight is so, o
Particles of binder resin whose product components are a high molecular weight polymer portion having a peak molecular weight in the range of oo to 500,000, a low molecular weight polymer portion having a peak molecular weight in the range of 1,000 to 50,000, and a resin consisting of yop. The present invention will be described in detail below, in that a magnetic fine powder is contained therein, and conductive fine particles are adhered to the surface of the particle body.

In the present invention, the system is a mixture of polymer fraction 1 coalescence and low molecular weight 1 coalescence, and the peak molecular weight of the former is within the range of 500,000 to 500,000, and the peak molecular weight of the latter is within the range of 500,000 to 500,000. A resin having a molecular weight within the range of i, ooo to so, o o o is used as the main component of the binder, and fine magnetic powder is dispersed and contained in the binder resin particles, as well as other necessary additions. A magnetic toner for developing an electrostatic image is prepared by incorporating an agent into the toner and then depositing conductive fine particles on the surface of the particles.

In the above, the mixed resin as described above is, for example, i)
A mixing method in which such a Hatake Molecule Valuable Coalescence and a low molecular weight 1 polymer are produced separately and melt-kneaded, or both are dissolved and mixed in a common solvent; Although it can be produced by the 9-method of 1-merging for the 1-merging of the other, and other methods, the Machi method is preferred.

And, the size of the peak molecular weight is, for example, a case of MU!
It is a good idea to make adjustments so that they are within the acceptable range.

The mixed resin used as the main component of the binder of the non-inventive toner has a ratio of high molecular weight polymer to 100 parts by weight of low molecular weight polymer ranging from 10 to 60 parts by weight, especially 1
It is preferable to use 0 to 40 parts by weight. If this proportion is less than 101 parts by weight, the temperature at which offset occurs will not be low, and if it is more than 60 parts by weight, the softening point will be too low and the minimum temperature at which fixing can be achieved will become high. In addition, the peak molecular weight of the high molecular weight polymer portion is less than so, o o o or low molecular weight 1
When the peak molecular weight of the combined portion is i, ooo, the offset generation temperature is low, and conversely, the peak molecular weight of the molecular weight polymer portion exceeds 500,000 or the peak molecular weight of the low molecular weight polymer portion is 50,000. The softening point increases when the temperature exceeds .

The mixed resin is preferably a thermoplastic resin, and specific examples include polystyrene, polyvinyltoluene, styrene-butadiene copolymer resin, styrene-acrylic acid ester copolymer resin, and styrene-maleic anhydride copolymer resin. Combined fat and acrylic.

resin, xylene resin, ionomer resin, ketone resin, terpene resin, phenol-modified terpene resin, rosin, rosin-modified resin, maleic acid-modified phenolic resin,
Examples include petroleum resins, starch graft polymer resins, polyvinyl alcohol, polyvinylpyrrolidone, and others. These resins may be used alone or in combination of two or more, and are generally used in an amount of 30 to 65 M based on the total toner.

The toner of the present invention is manufactured, for example, as follows. That is, fine magnetic powder and other additives are mixed into a binder resin whose main component is the above-mentioned mixed resin, heated and kneaded to disperse the fine magnetic powder, etc., and the resulting resin body is pulverized. The conductive fine particles are mixed and heat-treated to form a powder, and the conductive fine particles are coated on the surface of the binder resin particles in which the magnetic fine powder and the like are dispersed. fuse.

As the magnetic fine powder, commonly used ones can be used, and specific examples thereof include metals such as cobalt, iron, and nickel, aluminum, cobalt, copper, iron, lead, nickel, and aluminum. Gnesium, tin, zinc, gold, silver, selenium, titanium, tungsten, zirconium, alloys of other metals, metal oxides such as aluminum oxide, iron oxide, nickel oxide, ferromagnetic ferrite, other fine powders, or mixtures thereof. can be mentioned.

The magnetic fine powder having an average particle diameter of 0.05 to 3 microns is suitably used, and its proportion to the total toner is usually 10 to 80% by weight, preferably 35 to 65% by weight.

As the conductive fine particles, conductive 11La carbon black is suitable, but fine particles of silver, copper, aluminum, iron, and other metals can also be used. The conductive fine particles have an average particle size of 5 to 100 millimicrons.

It is preferable to use 0.5~
5 parts by weight.

Such conductive fine particles are deposited on the surface of toner particles by mixing conductive fine particle powder with a pulverized binder resin in which the magnetic fine powder described above is dispersed, and then placing the conductive fine particles in a high-temperature atmosphere. It is advantageous to use a method in which the heat treatment is carried out by means of a spray drying method. According to this method, the ultrafine particles of the top toner particles that are sprayed melt and coalesce with other toner particles and disappear, and the surfaces of particles of an appropriate size melt and the conductive particles fuse together. , the spheroidization of the particle shape is promoted.

As mentioned above, because conductive fine particles are attached,
The toner of the present invention has electrical conductivity, and this electrical conductivity is 1000
Conductivity in DC electric field of V/cn1 is 10-4 to 10
-12 shi is preferred.

The particle size of the toner of the present invention is 1 to 50 microns, particularly 7 to 30 microns.
Microns are preferred for use.

The magnetic toner of the present invention is used to form an image in an apparatus using a pressure transfer method as shown in FIG. 1 or 2, for example.

In FIG. 1, an electrostatic latent image forming section 1 transfers an image-like electrostatic latent image formed on an electrostatic charge carrier 2a on a rotating drum 2 to a developing section 3. As shown in FIG. In this developing section 3, the magnetic toner according to the present invention is rotated toward the electrostatic charge carrier 2a in a state of standing up on the sleeve 3a by a magnet provided in the developing sleeve 3a, and is rotated by a halfway operation cutter 3C. The toner particle accumulation column is aligned with the electrostatic latent image, facing the electrostatic latent image at a certain distance, and being in direct contact with the electrostatic latent image, or by making contact with the electrostatic latent image after a very small gap. A reverse charge is induced at the tip of the panicle, and the toner particles sequentially move toward the latent image in proportion to the amount of charge on the electrostatic latent image, forming a toner image.

The toner image formed in this way is formed on the electrostatic charge carrier 2a within the allowable range of the three-dimensional toner particle accumulation structure strength.
The material is brought into contact with, for example, about 0.1 to 9/cm2 and heated to exhibit mold releasability, and is transferred to the transfer paper 7 that passes between the transfer roller 4 and the suppression roller 24 pressed against the roller 24, It will be established.

The rotating drum 2, which has transferred the toner image onto the transfer roller 24, is neutralized by a static eliminating section 8, residual toner is removed by a cleaning device [9, and the drum 2 is used for the next process. In the image forming process in the apparatus shown in FIG.
Since there is no toner image, it is possible to form a toner image of the same image in the next process VC2, thereby making it possible to achieve so-called retention.

In the apparatus shown in FIG. 2, a transfer belt roller is used for the transfer member. At the time of transfer, consideration is given to minimizing the Stize vector for the three-dimensional particle accumulator. The toner image formed in the same manner as in the example explained in FIG.
For example, the contact with W4 to about 0.15 ice/cm2
The image is transferred onto the transfer belt 13 which has been prepared. The transfer belt 13 is suspended between the transfer roller 10, the pressure roller 211, and the tension roller 12. (sein thread transfer). The transfer belt 13 to which this Tofu image has been transferred moves in the direction of the arrow, and near the transfer point to the transfer paper 7, it is heated by the infrared heater 5 and exhibits releasability, and between the pressure roller 11 and the roller While passing through, the transfer belt 13 is transferred onto the transfer paper 7.

The device having the configuration shown in FIG. 2 is also capable of retention in the same way as the device having the configuration shown in FIG.

In addition, the transfer belt 13 after transferring the toner image to the transfer paper 7
In the belt cleaning group [14, residual toner and paper dust on the transfer paper are cleaned, and further, the transfer surface of the transfer belt 13 can be neutralized by a static eliminator 15. For this cleaning method, a roller with felt or the like provided on the outer circumferential surface, a rubber blade, a polymeric material, or a metal scraper is used.

Further, as a static eliminator, a corona discharger, a ribbon made of conductive fiber, or the like is often used.

The intermediate transfer member such as the transfer row 24 or the transfer belt 13 may be any material as long as it transfers magnetic toner, and usually, at least the surface of the transfer member (transfer layer) is made of natural rubber, turretan rubber, Styrene-butadiene rubber, silicone rubber, ethylene-propylene rubber, and seven-layer rubber are used for the ranal transfer body, but silicone rubbers obtained by low-temperature vulcanization or room-temperature vulcanization are particularly suitable. This natural comb must be an ordinary natural rubber mainly composed of polycis-1,4-isoprene, and urethane rubber is a rubber whose constituent units are urethane bonds produced by the reaction of diisocyanate and glycols or diamines. The following are Parcolan (Vulko mouth, manufactured by Sumitomo Bayer Urethane ■), Hyblen [Mitsui Toatsu Chemical ■], Desmoban [manufactured by Sumitomo Bayer Urethane @], Paraglen [manufactured by Nippon Polyurethane ■], Nissan (ESta).
ne, manufactured by Gutdrich], Adiprene CAdip
Styrene-butadiene rubber is a comonomer of styrene monomer and butadiene monomer, and usually contains a large proportion of butadiene monomer. There are various types of silicone rubber, but methyl silicone rubber, methyl vinyl silicone rubber, methylphenyl silicone rubber, etc. are commonly used.

Fluororubber is a polymer containing a fluorine atom in its molecule, such as ethylene trifluoride and vinylidene fluoride.
polymer, propylene pentafluoride-vinylidene heptafluoride copolymer, glopylene hexafluoride-vinylidene difluoride copolymer (for example, Piton, manufactured by DuPont), ethylene chloride trifluoride-vinylidene fluoride copolymer, fluorine-containing nitrone rubber,
i,i-dihydroperfluorobutyl acrylate rubber, etc. are commonly used.

In addition, materials for the transfer layer include synthetic natural rubber (Califlex IR, manufactured by Shell Kagaku ■), ethylene-propylene rubber (Nodel, manufactured by DuPont), acrylonitrile-butadiene rubber (Hiker, manufactured by Nippon Zeon ■), and organic polysulfide. Rubber [Made by Thiokol, Thiokol ■],
Acrylic ester copolymer rubber [Hiker 4021,
Gutdrich Co., Ltd.], and organic polysiloxane rubber [Shin-Etsu Silicone, Shin-Etsu Chemical Co., Ltd.] caps.

The transfer layer made of these materials preferably has a smooth surface, is a cylindrical elastic body, and has a rubber hardness of 5 to 7.
Preferably it is 0 degrees.

As silicone rubber, KE-40, 41, 42, 42
S1KE-441, 44, 45, 45S, Kh-471
,47,48,KE-67,103,1205,120
6,1300,1600,KE-12,16,17,6
2,1091,1093,1400 (all room temperature vulcanization type), Kl;-104,106,1201,1202,
1204, KE-1212, and 1800 (all low-temperature vulcanization type) [all manufactured by Shin-Etsu Chemical] are commercially available, and these can be used as a substrate. stainless steel,
Metals such as nickel belts, polyester, polyimide,
A polymer film such as polyimide amide or polysulfone on which the transfer layer removing material is provided is usually used.

In the magnetic toner of the present invention, the main component of the binder resin is s.
o, o o o A high molecular weight polymer portion having a peak molecular weight within the range of 500,000 and 1,000 to 50,
Since it is a mixed resin consisting of a low molecular weight polymer portion having a peak molecular weight within the range of 0.000, it has a low softening point and utilizes the suppression transfer method, as is clear from the explanation of the examples below. In the image forming process where offset occurs, the temperature is low. Therefore, a wide fixable temperature range is obtained, and the toner image supported on the intermediate transfer member can actually be transferred and fixed onto the transfer paper at a low heating temperature. , it is possible to avoid heating the intermediate transfer member to high temperatures, e.g. when the electrostatic image support is a heat-sensitive photoconductive photoreceptor, other special measures e.g. Countermeasures against high temperatures, such as increasing the length of the intermediate transfer member that reaches the photoreceptor, become more difficult.

In addition, since the magnetic toner of the present invention is conductive, it is possible to form a clear toner image corresponding to an electrostatic charge image by using the electrostatic induction development method, and furthermore, by using the suppression transfer method as described above. By transferring the toner image to the transfer paper using the original method, it is possible to achieve a clear fixation without disturbing the clear toner image and without causing any offset phenomenon. A visible image can be formed.

The reason why such a pervasive effect is achieved is that the binder resin product is a mixed resin and has at least two peak molecular weights, each of which has a specific molecular weight range. It is presumed that conductive fine particles are adhered to the surface of the toner particles. That is, if the binder resin produced does not satisfy the conditions of the present invention, insufficient fixing or offset phenomenon will occur, and conductive fine particles are not deposited on the surface of toner particles. When dispersed in toner particles, the toner has a high softening point and the above-mentioned effects are not achieved.Examples of the present invention will be described, but the present invention is limited thereto. It is not something that will be done. In the following, "part" represents "dobe".Example 1 The peak molecular weight obtained by combining styrene, methyl methacrylate, and n-butyl acrylate in a heavy chain ratio of 75:5:20 was 315. The peak molecular weight obtained by copolymerizing 20s1 of high molecular weight polymer portions of ,000 and styrene, methyl methacrylic acid, and n-butyl acrylate in a ratio of 70:15:15 in M amount is 8,170.
A mixed resin consisting of 100 parts of low molecular weight 1 combined portion of is used as a binder resin, and 40 parts of the binder resin and 60 parts of triiron tetroxide fine powder [BL-100j (manufactured by Titanium Kogyo Co., Ltd.)] were mixed and heated. After kneading, crush and add 1
．． 6% by weight of conductive carbon black "Palcan A magnetic toner of the present invention having a diameter of 15.0 microns was produced. This is referred to as "toner 1".

Examples 2 and 3 The amount of molecular weight polymer moiety in the binder resin was 30
A total of two types of magnetic toners of the present invention were produced in the same manner as in Example 1, except that the amounts were changed to 40 parts and 40 parts. These are referred to as "toner 2" and "toner 3", respectively.

Example 4 The polymer ttX combined portion was composed of styrene, methyl methacrylate, and acrylic flln-butyl in a ratio of 40:30 by weight.
: 25 parts of a copolymer with a peak molecular weight of 210,000 obtained by copolymerizing at a ratio of 30%, the low molecular weight polymer part being styrene and n-butyl acrylate.
The magnetic material of the present invention was prepared in the same manner as in Example 1 except that a mixed resin consisting of 100 parts of a copolymer having a peak molecular weight of 4.870 obtained by copolymerizing at a ratio of 85:15 was used as the binder resin. Manufactured toner. This is referred to as "Toner 4".0 Comparative Example 1 Styrene and n-butyl acrylate were mixed with Mfjk at 85:
The peak molecular weight obtained by copolymerizing at a ratio of 15% is 1.
A comparative magnetic toner was prepared in the same manner as in Example 1, except that a resin having a value of 10,700 was used as the binder resin. This is referred to as "comparison toner l".

Comparative Example 2 A resin with a peak molecular weight of 84,400 obtained by copolymerizing styrene, methyl methacrylate, and n-butyl acrylate in a ratio of 50:20; 30 in terms of M amount was used as a binder. A comparative magnetic toner was prepared in the same manner as in Example 1 except that the resin was used as the resin. This is referred to as "comparison toner 2."

Comparative Example 3 40 ttlS and 60 parts of each of the same binder resin and triiron tetroxide fine powder as in Example 1 were mixed with 10% by weight of carbon black, heated and kneaded, and then ground. Heat treatment and classification were performed by a spray drying method under the same conditions as in Example 1, thereby producing a comparative magnetic toner in which conductive fine particles were dispersed in toner particles.

This is referred to as a "comparison toner." The reason for increasing the amount of carpump sick added here is to increase the conductivity by 10-7'L/
This is to keep it close to /cm.

The softening point and conductivity of each of Toner 1 to Toner 4 and Comparative Toner 1 to Comparative Toner 3 obtained as described above were measured. It is sufficient to repeat the operation of forming a copy image with each toner using an electrophotographic copying machine equipped with an electrostatic charge carrier 2a, by changing the set temperature of the heater 5. The minimum set temperature at which fixing is achieved, that is, the minimum fixable temperature (T1) and the offset generation temperature [(T2
) was sought. The results are shown in Table 1.

Furthermore, what is the softening point? Using a 4-type flow tester (manufactured by Shimadzu Sakusakusho), the load was 20Kr/1MK2, and the nozzle diameter was 1.
A curve showing the relationship between plunger drop amount and temperature (softening
If the crystallinity of the S-shaped curve in the m curve) is set to 11, this is the temperature equivalent to h/2. Also, the conductivity is 1000 V/σ direct current! This is the value at r.

M4 1 6 As may be seen from the results in Table 1, Toner 1 to Toner 4, which are the magnetic toners of the present invention, have the lowest fixable temperature (
T1) is low, and the offset generation temperature Ji (T2) is A<40.degree. C. to 60.degree. C., which provides a wide fixable temperature range. On the other hand, for Comparative Toner 1 and Comparative Toner 2, in which the binder resin has only one peak molecular weight, the temperature range in which both falling and fixing is possible is considerably narrower than the normally required minimum of 30°C, making it difficult to put into practical use. unacceptable. Furthermore, in comparison toner 3 in which conductive fine particles are dispersed in toner particles, the minimum fixable temperature (T1) is higher than that in toner 1. Furthermore, all the copied images formed with Toners 1 to 4 were clear and good.

[Brief explanation of drawings]

FIGS. 1 and 2 are explanatory diagrams each showing an example of a 1ffll image forming apparatus using a press transfer method in which the magnetic toner of the present invention is suitably used. 1... Static latent image forming section 2... Rotating drum 3.
...Development s4...Transfer roller 5...
Heater 6...Press low shift...Transfer paper 8...Electrostatic section 9...Cleaning bowl 10...Transfer roller 11...Pressure roller 12
...Funnyonroshi 13...Transfer belt 14.
・Belt cleaning device 15 ・Removal of ridges

Claims (1)

[Claims] ■) A high molecular weight polymer portion with a peak molecular weight in the range of 80,000 to 500,000 and a peak molecular weight in the range of 1,000 to 1,000.
A fine magnetic powder is contained in particles of a binder resin whose production component is a resin consisting of a low molecular weight polymer portion in the range of 0 to 50,000, and conductive fine particles are formed on the surface of the particles. 1. A magnetic toner for developing an electrostatic image, characterized in that the toner is coated with a magnetic toner. 2) Claim 1, wherein the conductivity in a DC electric field of 1000 V'/cIn is 10-4 to 1012
A magnetic toner for developing an electrostatic image as described in . The magnetic toner for electrostatic charge development according to claim 1, which is used for phantom pressure transfer.