JPS63108354A - Insulating magnetic encapsulated toner - Google Patents

Abstract

PURPOSE:To prevent a magnetic powder from scratching the surface of a latent image bearing body by specifying the longest size to shortest size ratio of the magnetic powder to be added into core particles. CONSTITUTION:The toner of the titled is obtained by coating each core particle containing a magnetic powder with a resin, and the melt viscosity of the core particles is controlled to 0.5-50 poises and the longest size (l) to shortest size (s) ratio is regulated to 1.0-1.5, thus permitting the magnetic particles not to scratch the latent image bearing body, accordingly, the toner material to be prevented from attaching to the scratched parts and causing image stains and poor cleaning.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a magnetic material used to develop an electric latent image or a magnetic latent image in electrophotography, electrostatic printing, magnetic recording, etc. Regarding capsule toner.

[Prior Art] Conventionally, methods for developing electrical latent images or magnetic latent images obtained by various methods including electrophotography include:
A powder cloud method, a magnetic brush development method, a fur brush development method, a cascade development method, and the like are known, and among them, the magnetic brush development method is generally widely used. The developer used in this magnetic brush method is a two-component developer made by mixing a carrier made of a magnetic material such as iron powder and a toner made of fine resin powder in which a colorant is dispersed; Two-component developers are known, consisting of magnetic toner that contains magnetic powder such as magnetite dispersed therein, but two-component developers suffer from carrier contamination when used continuously and fluctuations in the mixing ratio of toner and carrier. Because of the difficulty of having to deal with fluctuations in toner density caused by toner density, one-component developers, that is, magnetic toners, are currently in widespread use.

In addition, in order to retain the toner image formed by developing the latent image with such toner, so-called "fixing" is required.
The fixing method generally involves passing a toner image transferred onto paper or the like as a recording medium between a pair of heated rollers and melting and adhering it. This heating fixing method is
It requires a large capacity heat source and requires a considerable amount of time to preheat to a temperature at which sufficient fixing can be achieved. In contrast to the hot roller fixed fixing method that has been widely used in the past, from the viewpoint of energy saving and zero waiting time, pressure fixing methods using only pressure using a rigid roller or pressure and supplementary heating have been proposed. There is.

Toners suitable for such pressure fixing methods are those with a large amount of deformation due to pressure and generally low melt viscosity, but such toner materials also tend to cause toner particles to form a bond with each other in the developing device and during storage. Blocking (or caking) is likely to occur due to adhesion and aggregation.

This tendency to easily block is also a phenomenon that is similarly observed when toner materials that are fixed at relatively low temperatures or with a low amount of heat are selected.

As a means to solve this problem, capsule toners in which a soft core material with a low melt viscosity is coated with a resin with a higher melt viscosity are disclosed in JP-A-50-139745 and JP-A-58-15.
It has been proposed in No. 3947, No. 58-174957, etc.

[Problems to be solved by the invention] However, in the core material of such a capsule toner,
Ordinary magnetic powders, such as cube-shaped ones and needle-shaped ones as shown in Figures 1(b) and (c).

If the outer shape and surface shape are angular, the surface of the latent image carrier such as a photoreceptor will be damaged, and the toner resin will adhere to the scratched portion, resulting in image stains and poor cleaning.

This is because such core particles with low melt viscosity are deformed by the pressure during cleaning to wipe toner particles from the latent image carrier, and the protrusions on the surface of the magnetic powder exposed at that time become H1
This is thought to be due to damage to the Rm holder. For this reason, if blade cleaning is used that applies strong pressure to the latent image carrier during cleaning, the main body will be seriously damaged. In addition, when an organic photoconductor having a resin on its surface is used as a latent image carrier, the toner resin has a close compatibility with the toner resin, so that the adhesion of the toner resin to the Wi image carrier increases.

Furthermore, images fixed with insulating magnetic capsule toner often have fog.

This is because compared to two-component toner, which is charged due to friction during development between toners coated with the same resin, it is charged by sufficient mixing of the toner and a carrier having the opposite polarity. Although it may be difficult to maintain, the impact of its establishment is significant.

Capsule toner made of core particles with low melt viscosity is generally fixed by passing it between a pair of copper rollers with a linear pressure of about 10 to 30 kg/cm, but the toner spreads due to pressure collapse at this time. , is larger than other toners, and therefore has a similar fog, and an unfixed image of a capsule toner made of core particles with a low melting viscosity is transferred to a heat fixing device and When the image is fixed using a pressure fixing device, blurring becomes more noticeable in the latter case.

The conspicuousness of this fog is the same when a capsule toner made of core particles with a low melt viscosity is fixed by heat. That is, a capsule toner made of core particles with a low melt viscosity spreads more widely due to its melting during heat fixing than other toners.

[Means and effects for solving the problems] The present invention provides an insulating magnetic capsule toner that solves the above-mentioned drawbacks.

That is, the present invention provides an insulating magnetic capsule toner in which core particles containing magnetic powder and having a melt viscosity at 100° C. of 0.5 to 50 poise, more preferably 1 to 20 poise are coated with a resin, in which the magnetic powder has a This insulating magnetic capsule toner is characterized by being spherical with a dimension/shortest dimension ratio of 1.0 to 1.5.

The magnetic powder according to the present invention has a rounded spherical shape as shown in FIG. 1(a).

When magnetic particles having a mirror-like cubic or acicular surface shape as shown in FIGS. 1(b) and 1(C) are contained in core particles having a low melt viscosity as in the present invention, During cleaning, the capsule toner is deformed or crushed at the contact area between the cleaning member and the latent image carrier, and the exposed magnetic particles at this time damage the latent image carrier. The material will stick, causing image stains and poor cleaning.

This tendency occurs when an organic photoconductor with a resin on the surface, which has relatively low surface hardness and is highly compatible with toner resin, is used as a latent image carrier, and when a pressure load is applied to the latent image carrier as a cleaning method. It was great when using a large blade cleaning.

On the other hand, when spherical magnetic particles as shown in FIG. 1(a) are used, even if the magnetic particles are exposed due to deformation or crushing of the toner during cleaning, the latent image carrier will not be damaged. Furthermore, according to the studies of the present inventors, especially in the case of spherical capsule toner, the spherical magnetic particles are cubic,
It was also found that there was less exposure to the capsule toner surface compared to acicular magnetic particles. This is thought to be due to the shape factor of the magnetic particles.
When a magnetic capsule toner using acicular magnetic powder was observed under an electron microscope, the exposure of one spherical magnetic powder particle was clearly less than that of other magnetic powder particles. Therefore, when spherical magnetic powder is used as the magnetic powder particles of the magnetic capsule toner, it becomes easy to encapsulate it inside the core particle of the capsule toner, thereby improving the insulation and environmental stability of the capsule toner itself. Damage to the latent image carrier due to exposure of magnetic powder can also be prevented.

The spherical magnetic powder particles used in the present invention are spherical as shown in FIG. 1, and the ratio 1/s of the longest dimension to the shortest dimension S is 1.0 to 1.5, more preferably 1. 0
~1.3 is used.

To obtain such spherical magnetic powder particles, for example, as magnetite, a wet method is usually used in which iron oxide is precipitated from an iron ion solution, and can be obtained by adjusting the manufacturing process conditions.

For example, it is manufactured as follows.

A ferrous salt reaction aqueous solution containing a ferrous hydroxide colloid obtained by reacting a ferrous salt aqueous solution with an alkali equivalent to 0.80 to 0.9 g with respect to Fe2 in the ferrous salt aqueous solution. a first stage in which spherical magnetite particles are produced from the ferrous hydroxide colloid by passing an oxygen-containing gas while heating in a temperature range of 70°C to 100°C; After the completion of the reaction, 1.00 equivalents or more of alkali is added to the remaining Fe2'', and spherical magnetite particles are generated by the second stage reaction, which is heated and oxidized under the same conditions as the first stage reaction, and then washed with water and separated from the furnace. , dry and grind.

Furthermore, the magnetic particles used in the present invention have a magnetic permeability of 1.0M.
In the case of Hz, it is preferably 3.80 to 6.00 (7), more preferably 3.95 to 5.80.

The maximum magnetic permeability can be expressed as shown below.

B=μ■HILm: Maximum magnetic permeability At this time, B and H represent the magnetic flux density and magnetic field, respectively.It can be seen that a material with a larger maximum permeability than this shows high magnetization in a constant magnetic field, and the magnetic field is caused by the magnet. If created, the material would be strongly attracted to the magnet.

The one-component magnetic toner containing a ferromagnetic material with a maximum magnetic permeability of 6.00 or more generates a strong magnetic force on the developing sleeve by the magnetic field of a magnetic force generating means such as a permanent magnet disposed inside the sleeve. It becomes firmly stuck to the surface, making it almost impossible to transport it, and this magnetic force can cause damage during development.
This becomes stronger than the Coulomb force, which is the main driving force for development, and the toner cannot be developed.

In addition, in the case of insulating magnetic capsule toner whose surface is coated with resin, the toner charge used for development, that is, the triboelectric charge, is
Most of the charge is applied by the friction of the developing sleeve, and the part due to the friction between the toners is extremely small. This is because the toner surfaces are covered with the same resin, so friction between the toner surfaces cannot generate frictional charges from each other. This is because there is no Therefore, the maximum permeability of magnetic particles is 3.80
In the following cases, there is only a weak interaction between the toner and the permanent magnet inside the toner carrier such as a developing sleeve, and sufficient frictional electrification cannot be obtained between the toner and the surface of the toner carrier. In addition, charge distribution between toner particles and on the surface of toner particles becomes non-uniform, which tends to cause fogging in which toner adheres to non-image areas on the surface of the latent image carrier.

This phenomenon is particularly noticeable under severe conditions regarding development characteristics, such as high temperature, high humidity, and low temperature, low humidity.

However, the maximum permeability of magnetic powder is 3.80 to 6.00.
Within this range, sufficient transportability and interaction can be obtained between the toner carrier such as the developing sleeve and the insulating magnetic capsule toner, and a good image without fogging can be obtained.

The value of maximum magnetic permeability in the present invention is determined by a very commonly used method of uniformly winding a toroidal magnetic core, applying an appropriate alternating magnetic field, and determining the inductance change at that time. obtained from. The specific measuring method is to add and mix the binder resin powder 5P to the magnetic powder 20 to be measured. 15 g of this mixture was placed in a ring-shaped mold and molded at a pressure of 1.0 ton/c<2> to obtain a toroidal magnetic core, which was used as a measurement sample. Further, this toroidal sample is wound with a uniform number of turns of 120 to 180, and this is placed in a bridge circuit, and a frequency of 0.5 MHz to 5.0 MHz is applied.
The alternating current magnetic field is changed appropriately up to 0 MHz, the inductance at that time is determined, and the magnetic permeability gs can be obtained based on the following formula.

The particle size of the magnetic powder of the present invention is 0. O1-2ILm, more preferably 0.1-1IL■, is used in a proportion of 40-200 parts by weight, more preferably 50-120 parts by weight per 100 parts by weight of the core resin.

Furthermore, the magnetic powder used in the present invention is preferably one that has been subjected to a hydrophobization treatment.By performing the hydrophobization treatment, the humidity characteristics of the toner itself are improved, and the development characteristics are less likely to change due to environmental changes. The compatibility between the core material resin with such a low melt viscosity and the magnetic powder increases, and the magnetic powder can be sufficiently encapsulated in the core particles, making it possible to easily obtain an insulating magnetic capsule toner, which can be used as a latent image carrier. There is also less damage to the surface.

Examples of methods for hydrophobizing magnetic powder include method 1.
Hydrophobic treatment is performed using a titanium coupling agent, a silane coupling agent, etc. in a proportion of 0.01 to 5 parts by weight per 0.00 parts by weight. Hydrophobization treatment is generally performed by adding a coupling agent to toluene, while stirring dried magnetic powder in various mills.
After solubilization in a solvent in which a coupling agent such as benzene is soluble,
This is done by dropwise mixing at a rate that provides sufficient dispersion, allowing the reaction to occur, and then evaporating and removing the solvent and reaction by-products.

1 of the core particles of the insulating magnetic capsule toner according to the present invention
Melt viscosity at 00°C is 0.5 to 50 poise
, more preferably l w 25poise.

If it is less than 0.5 poise, the core particles will be too soft even at room temperature, and the magnetic capsule toner will be destroyed by impact during development, which is undesirable.

If it exceeds 50 poige, the core particles are too hard, deformation due to pressure decreases, pressure fixing performance is poor, and deformation due to heat also decreases when fixing with heat, increasing the amount of heat required to obtain the same fixing performance. I don't like it.

In the method for measuring melt viscosity in the present invention, various viscosity meters are used, but in the present invention, a rotating double cylinder (rotor)
The shear rate was measured using a type viscometer at a shear rate of 10 seconds.

In the case of a rotor type viscometer, the sliding speed is determined by the following formula.

'-(Rh/Re)2 Rc: Cup radius (C intestine) Rb: Rotor radius (+, s) ω: Rotor rotational angular velocity N: Number of rotations (RP intestine) Also, the friction stress is S = N/2tRb2h M: Viscous torque h: Rotor height C■) and the melt viscosity is η=S/D It is.

The melt viscosity of the core particles in the present invention is the melt viscosity of a mixture of core resin, magnetic particles, and other internal additives, and includes the melt viscosity of the core resin, the particle size of the magnetic particles, and their content. By adjusting the following, it is possible to adjust the melt viscosity of the core particles according to the present invention.

The resin used as the core material resin of the magnetic capsule toner of the present invention is 1, for example, preferably has 12 to 5 carbon atoms.
0 polyethylene wax, polyethylene oxide, paraffin, fatty acids, fatty acid esters, fatty acid amides, fatty acid metal salts, higher alcohols, ethylene-vinyl acetate,
In addition to cyclized rubber, polymers and copolymers containing a hydrocarbon chain in their structure, such as polyethylene and polypropylene, paraffin wax, microcrystalline wax,
Montan wax, Ceresin wax, Osikelite,
carnauba wax, rice wax.

Examples include waxes such as shellac wax and amide wax.

These can be used alone or as a compound in a mixed state, but their preferred melt viscosity is 1 to 1 at 100°C.
It is 100 cps.

As the shell material resin, known resins can be used, and for example, there are resins consisting of heptamers such as primary. Styrene and its substituted products such as styrene, p-chlorostyrene, and p-dimethylamino-styrene; methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, N, N methacrylate - Esters of acrylic or methacrylic acid such as dimethylaminoethyl ester; halfesters, half-amides or diesterimides of maleic anhydride or maleic anhydride; vinylpyridine;
Nitrogen-containing vinyls such as vinyl imidazole; vinyl acetals such as vinyl formal and vinyl butyral; vinyl monomers such as vinyl chloride, acrylonitrile, and vinyl acetate; vinylidene monomers such as vinylidene chloride and vinylidene fluoride; olefin monomers such as ethylene and propylene. . Also polyester, polycarbonate, polysulfonate, polyamide, polyurethane, polyurea, epoxy resin.

Rosin, modified rosin, terpene resin, phenolic resin,
Homopolymers, copolymers, or mixtures of aliphatic or alicyclic hydrocarbon resins, aromatic petroleum resins, melamine resins, polyether resins such as polyphenylene oxide, or 1,000-onythyl resins can be used.

Capsule toner can be obtained by coating these shell materials by a known method, but the present invention also includes so-called double-wall capsule toner, which is coated with a first shell material and then further coated with a second shell material. It will be done.

The shell material thickness for the capsule toner core particle is 1 usually 0.01
However, by using the magnetic particles of the present invention, even if the shell material thickness is relatively thin from 0.01 to IJL, which brings out the characteristics of the core material with low melt viscosity,
It does not damage the latent image carrier.

Other internal and external additives such as dyes and pigments, charge control agents, and fluidizing agents 1 such as silicon oxide particles may be added to the insulating magnetic gel toner of the present invention as required.

This is because (1) the melt viscosity of the core particles of the present invention matches the appropriate viscosity during suspension granulation, and (1) the spherical magnetic powder is more likely to form particles by stirring in the suspension medium than other magnetic powders. This is because the amount of magnetic powder present in each core particle is uniform even when developing the core particles, and the particle size distribution of the core particles themselves is also relatively sharp, resulting in a magnetic capsule toner with excellent development characteristics.

Methods for producing the insulating magnetic capsule toner according to the present invention include, for example, spray drying, interfacial polymerization, coacervation, phase separation, 1n-situ polymerization, US Pat. No. 3,338,991, 3.3211i
, No. 848, No. 3,502,582, etc. can be used, but the method for producing the core particles is after melting and kneading the core material.

A suspension granulation method is preferred in which particles are formed by stirring the kneaded material in a suspension medium that does not dissolve the kneaded material.

[Example] Next, the present invention will be explained in more detail with reference to Examples.

The mixture of Example 1 (melt viscosity at 100°C 20 cps).

was added, and core particles were produced by the suspension granulation method described above. The core particles had a melt viscosity of 18 poise at 100°C.

This core particle was encapsulated by a spray method to obtain an insulating magnetic capsule toner.

1 part by weight of hydrophobic silica fine powder was externally added to 100 ffi parts of the toner, and an organic semiconductor photosensitive drum was formed using an image forming apparatus (PC-20 modified a manufactured by Canon Co., Ltd.) as shown in FIG. After developing and transferring 15,000 sheets of A4 size using blade cleaning,
There were only slight scratches on the photosensitive drum surface, and no toner fusion occurred on the photosensitive drum.The 0 image density also had a Dsax (reflection density) of 1-3 to 1.4 on the Macbeth densitometer (trade name).
and high enough.

A clear image without fogging was obtained. Low temperature and low humidity (5℃
, 10%) and under high temperature and high humidity conditions (32°C, 90%).

Comparative Example 1 Magnetic powder was placed in a cubic shape as shown in Figure 1(b).
Example 1 except that the maximum magnetic permeability of z was 2.9.
A capsule toner was obtained in the same manner as in Example 1, and development and transfer were performed in the same manner as in Example 1.

After developing 4,000 sheets, there were scratches on the surface of the photosensitive drum, and from the 6,000th sheet onward, toner stains were observed in the scratched areas, and stains were also found on the transferred image copy surface. After that, after the 10,000th print, cleaning defects started to appear.

The image also shows fog when D saw is 1.1 to 1.2.
This fog became especially severe under high temperature and high humidity conditions, and under low temperature and low humidity conditions.

Example 2.3 A capsule toner was obtained in the same manner as in Example 1, except that the core material and magnetic powder were changed to those listed in Table 1, and development and transfer were performed in the same manner as in Example 1. The results are also listed in Table 1.

Comparative Example 2 A capsule toner was obtained in the same manner as in Example 1, except that the core material and magnetic powder were changed to those listed in Table 2, and development and transfer were performed in the same manner as in Example 1. The results are also listed in Table 2.

[Effects of the Invention] As explained above, the insulating magnetic capsule toner according to the present invention provides a developer having good development characteristics with little damage to a latent image carrier, especially an organic photoconductor.

[Brief explanation of the drawing]

FIG. 1(a) is a schematic diagram of an electron micrograph of spherical magnetic particles according to the present invention, where letters indicate the longest dimension and S indicates the shortest dimension. Figure 1(b) is a cubic magnetic body, Figure 1(,C)
is a schematic diagram of an acicular crystal magnetic material. . FIG. 2 shows an embodiment of an image forming apparatus using the insulating magnetic capsule toner according to the present invention. Reference numeral 1 denotes a photosensitive drum having an organic photoconductor on its surface, which rotates in the direction of the arrow to form a latent image using a known method. Reference numeral 2 denotes a developing sleeve for developing the insulating magnetic capsule toner according to the present invention, which is equipped with a permanent magnet inside, and the toner is thinly coated on the developing sleeve. Then, the insulating magnetic capsule toner is developed. 3 is a transfer paper to which the developed image is transferred, and 4 is a transfer charger. Reference numeral 5 denotes a blade cleaning device for cleaning the insulating magnetic capsule toner remaining without being transferred, and a blade is installed in a direction opposite to the direction in which the drum rotates.

Claims (1)

[Claims] (1) In an insulating magnetic capsule toner in which core particles containing magnetic powder and having a melt viscosity of 0.5 to 50 poise at 100°C are coated with a resin, the magnetic powder has a longest dimension/shortest dimension ratio of 1.0 to An insulating magnetic capsule toner characterized in that it is a spherical substance with a diameter of 1.5.