JPH03130783A - Magnetic toner - Google Patents

Abstract

PURPOSE:To improve image quality by specifying the grain size distribution of the grain groups having <=5mum content ratio of each of the grain sizes of the magnetic toner to be used. CONSTITUTION:This toner contains the magnetic toner contg. 17 to 80number% <=5mum grain size, 5 to 50number% 6.35 to 12.7mum grain size and <=2.0vol.% >=16mum grain size. The volume average grain size thereof is specified to 4.5 to 9mum. Further, the toner particle sized <=5mum has the grain size distribution expressed by formula I. In the formula I, N, V denote the number % and volumetric % of the magnetic toner grains having <=5mum grain size; N denotes 17 to 80 positive number; k is 4.5 to 6.5 positive number. The mol. wt. corresponding to the main max. value of the chromatograph of the low mol. wt. is in a 2,000 to 80,000 range and the other max. value is provided on the low mol. wt. side. The reproducibility of fine lines is improved and the gradation characteristic of the image is obtd. if such magnetic toner is used. The definition is enhanced and the good image quality is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic toner used as a developer for developing electrostatic images in electrophotography, electrostatic recording, electrostatic printing, and the like.

More specifically, in direct or indirect electrophotographic development methods, negative chargeability provides a high-quality image by uniformly and strongly negatively charging a positive electrostatic charge image or by making a negative electrostatic charge image visible by reversal development. Regarding magnetic toner.

[Background technology]

2. Description of the Related Art In recent years, as image forming apparatuses such as electrophotographic copying machines have become widespread, their uses have expanded to a wide variety of uses, and demands on their image quality have become stricter.

When copying images such as general documents and books, it is required to reproduce extremely finely and faithfully, without being crushed or cut off, even down to the minute characters. especially,
When the latent image on the photoreceptor of an image forming apparatus is a line image with a diameter of 100 μm or less, fine line reproducibility is generally poor, and the sharpness of the line image is still not sufficient. In recent years, in image forming devices such as electrophotographic printers that use digital image signals, latent images are formed by dots with a constant potential, and solid areas, halftone areas, and light areas have a high dot density. It is expressed by changing. However, if the toner particles do not adhere to the dots faithfully and the toner particles protrude from the dots, the gradation of the toner image that corresponds to the ratio of dot densities in the black and white areas of the digital latent image cannot be obtained. There is a problem. Furthermore, when improving resolution by reducing dot size in order to improve image quality, it becomes more difficult to reproduce latent images formed from minute dots, resulting in poor resolution, poor gradation, and poor sharpness. This tends to result in images lacking in detail.

In addition, although the image quality is good initially, as copying or printing continues, the image quality may deteriorate. This development is thought to occur because, as copies or printouts continue, only toner particles that are easily developed are consumed first, and toner particles that are less developable accumulate and remain in the developing machine.

Up to now, several developers have been proposed for the purpose of improving image quality. Japanese Patent Publication No. 51-3244
The publication proposes a non-magnetic toner intended to improve image quality by regulating particle size distribution. In the toner,
The toner mainly has a particle size of 8 to 12 μm, which is relatively coarse, and according to the studies of the present inventors, it is difficult to uniformly “glue” the latent image with this particle size, and toner with a particle size of 5 μm or less is 30% by number or less, and 20 μm or more is 5% by number or less, which means that the particle size distribution is broad, which also tends to reduce uniformity. In order to form clear images using such coarse toner particles and a toner with a broad particle size distribution, it is necessary to layer the toner particles thickly to fill the gaps between the toner particles and reduce the apparent appearance. There is also the problem that it is necessary to increase the image density, and the amount of toner consumption necessary to achieve a predetermined image density increases.

Furthermore, in JP-A-54-72054, a non-magnetic toner having a sharper distribution than the former has been proposed, but the size of particles with intermediate weight is coarse (8.5 to 11.0 μm). As a high-resolution toner, there is still room for improvement.

In JP-A No. 58-129437, the average particle size is 6 to 6.
11 magnetic toner in which the particle diameter is 10 μm and the largest number of particles is 5 to 8 μm has been proposed, but the number of particles of 5 μm or less is as small as 15% by number or less, and images that lack sharpness tend to be formed.

According to studies conducted by the present inventors, it has been found that toner particles of 5 μm or less have the main function of clearly reproducing the outline of a latent image and densely applying the toner to the entire latent image.

In particular, in the electrostatic latent image on the photoreceptor, the electric field strength is higher at the edge part than the inside due to the concentration of electric lines of force.
The quality of the toner particles that collect in this area determines the sharpness of the image quality.

According to studies conducted by the present inventors, it has been found that the amount of particles of 5 μm or less is effective in solving the problem of sharpness of image quality.

Also, in U.S. Patent No. 4,299,900, 20
~35μm magnetism! - A jumping development method using a developer containing 10 to 50% by weight of toner has been proposed.

That is, efforts have been made to triboelectrically charge the magnetic toner, to uniformly and thinly apply a toner layer on the sleeve, and to improve the environmental resistance of the developer by adjusting the particle size of the toner. However, considering the stricter requirements such as fine line reproducibility and resolution, this is not sufficient and further improvements are required.

In addition, various old methods and devices have been developed for the final process of electrophotography, which is the process of fixing the toner image on a sheet such as paper, but the most common method currently is the compression heating method using a heated roller. be. The pressure heating method using a heating roller fixes the toner by passing the toner image surface of the fixing sheet onto the surface of the sheet while contacting the toner image surface under pressure with a material having a releasing property for the toner. In this method, the surface of the heat roller and the toner image on the sheet to be fixed come into contact with each other under pressure, so the thermal efficiency when fusing the toner image onto the sheet to be fixed is extremely good, and the fixing can be performed quickly. can. However, in the above method, since the surface of the heat roller and the toner image contact each other under pressure in a molten state, a part of the toner image adheres to and transfers to the surface of the fixing roller, and this is transferred again to the next sheet to be fixed. A so-called offset phenomenon may occur and stain the sheet to be fixed, and prevention of this is considered to be one of the essential conditions for the hot roller fixed fixing method.

For this reason, in JP-A No. 49-65231, JP-A No. 50-27546, and JP-A No. 55-153944, a heat roller constant wear toner has been proposed that prevents offset by containing polyalkylene in the toner. has been done.

Further, as a toner that improves some of the problems associated with cleaning toners using polypropylene, Japanese Patent Application Laid-Open No. 63-241766 proposes a toner using polyalkylene having a specific molecular weight distribution.

However, when these toners were studied, it was found that in order to prevent offset, they must contain a corresponding amount of polyalkylene, and in this case, image fog tends to increase as the content increases during development. Since this is remarkable in negatively chargeable toners, the present invention was arrived at as a result of extensive research.

[Purpose of the invention]

An object of the present invention is to provide a magnetic toner that solves the above-mentioned problems.

A further object of the present invention is to provide a magnetic toner that has high image density, excellent fine line reproducibility, and excellent gradation.

A further object of the present invention is to provide a magnetic toner whose performance does not change even after long-term use.

A further object of the present invention is to provide a magnetic toner whose performance does not change due to environmental changes.

A further object of the present invention is to provide a magnetic toner with excellent transferability.

A further object of the present invention is to provide a magnetic toner that can provide high image density with low consumption.

Another object of the present invention is to provide a magnetic toner that can form toner images with excellent resolution, gradation, and fine line reproducibility even in image forming apparatuses using digital image signals.

A further object of the present invention is to provide a magnetic toner that prevents offset during fixed fixation with a hot roller by adding a small amount of polyalkylene, and prevents an increase in image fog due to the addition of polyalkylene.

A further object of the present invention is to provide a magnetic toner that is less likely to damage a photoreceptor.

[Summary of the invention]

More specifically, the present invention provides a magnetic toner comprising at least a binder resin, magnetic powder, and low molecular weight polyalkylene, in which magnetic toner particles having a particle size of 5 μm or less are 17 μm or less.
~80% by number is contained, and 10~50% by number of magnetic toner particles having a particle size of 6.35~2.7 μm are contained,
Magnetic toner particles having a particle size of 16 μm or more are contained in an amount of 2.0% by volume or less, and the volume average particle size of the magnetic toner is 4.0% by volume or less.
5 to 9 μm, and the group of magnetic toner particles of 5 μm or less is represented by the following formula % [In the formula, N indicates the number % of magnetic toner particles having a particle size of 5 μm or less, and ■ has a particle size of 5 μm or less. It shows the volume % of magnetic toner particles, k shows a positive number of 4.5 to 6.5, and N shows a positive number of 17 to 80. ] It has a particle size distribution that satisfies the following, and the content of the low molecular weight polyalkylene is 0.1-0.1 parts by weight per 100 parts by weight of the binder resin.
1 part by weight (preferably 0.3 to 1 part by weight).

[Detailed description of the invention]

The magnetic toner of the present invention having the above particle size distribution is capable of faithfully reproducing even the fine lines of a latent image formed on a photoconductor, and is capable of reproducing halftone dots and digital dot latent images. It also provides an image with excellent gradation and resolution. Furthermore, it maintains high image quality even when copying or printing is continued, and even in the case of high-density images, it is possible to perform good development with less toner consumption than conventional magnetic toner, making it economical. It also has the advantage of making the main body of a copying machine or printer more compact.

The reason why such an effect is obtained in the magnetic toner of the present invention is not necessarily clear, but it is presumed as follows.

That is, one of the characteristics of the magnetic toner of the present invention is that magnetic toner particles having a particle size of 5 μm or less account for 20 to 80% by number. Conventionally, in magnetic toner, 5μ
Magnetic toner particles with a size of less than m are difficult to control the amount of charge, impair the fluidity of the magnetic toner, and are actively used as components that cause toner scattering and stain machines, and as components that cause image fogging. It was considered necessary to reduce

However, according to studies conducted by the present inventors, it has been found that magnetic toner particles of 5 μm or less are an essential component for forming high-quality images.

For example, changing the surface potential on the photoreceptor using a magnetic toner having a particle size distribution ranging from 0.5 μm to 30 μm,
Developing a latent image by changing the surface potential on the photoreceptor, from a large development potential contrast in which a large number of toner particles are easily developed, to a halftone, to a small development potential contrast in which only a few toner particles are developed,
When the developed toner particles on the photoreceptor were collected and the toner particle size distribution was measured, it was found that there were many magnetic toner particles with a diameter of 8 μm or less, and particularly a large number of magnetic toner particles with a diameter of 5 μm or less. In other words, when magnetic toner particles with a particle size of 5 μm or less, which is suitable for development, are smoothly supplied to develop the latent image on the photoreceptor, the latent image is faithful to the latent image, does not protrude from the latent image, and is truly reproducible. This is an excellent image changer.

Further, in the magnetic toner of the present invention, 6.35 to 1
One of the characteristics is that the number of particles in the range of 2.7 μm is 5 to 50%. As mentioned above, this is related to the necessity of the presence of magnetic toner particles with a particle size of 5 μm or less.
Magnetic toner particles with a particle size of 5 μm or less have the ability to strictly cover a latent image and reproduce it faithfully, but the electric field strength at the edges around the latent image itself is higher than at the center.
As a result, toner particles tend to adhere more tightly inside the latent image than at the edges, and the image density may appear to be thinner. In particular, magnetic toner particles with a diameter of 5 μm or less have a strong tendency to do so.

However, we found that 6.35-12.7 μm
It has been found that this problem can be solved and further clarity can be achieved by containing toner particles in the range of 5% to 50% by number. In other words, this is thought to be because toner particles in the particle size range of 6.35 to 12.7 μm have a suitably controlled amount of charge compared to magnetic toner particles with a particle size of 5 μm or less, but the edge of the latent image The toner is supplied to the inner side, where the electric field strength is lower than the edge area, to compensate for the lack of adhesion of the inner toner particles to the edge area, and a uniform developed image is formed, resulting in high density, resolution and gradation. It provides excellent sharp images.

Furthermore, for particles with a particle size of 5 μm or less, the number %
(N) and volume % (V), N/V = -0,04
N+k (However, 4.5≦≦6.5; 17≦N≦
Another feature of the magnetic toner of the present invention is that it satisfies the following relationship: 80). This range is shown in FIG. 4, and the magnetic toner of the present invention having a particle size distribution that satisfies this range along with other features can achieve excellent developability.

While studying the state of particle size distribution of 5 μm or less, the present inventors found that there is a state of existence of fine powder most suitable for achieving the purpose as shown in the above formula. In other words, for a certain value of N, a large N/V means that 5 μm
It shows that it contains a wide range of particles, including N/
It is understood that a small V indicates that the abundance of particles around 5 μm is high and there are few particles with a particle size smaller than that, and the value of N/V is in the range of 1.3 to 5.82. When N is within the range of 17 to 80 and the above relational expression is further satisfied, good fine line reproducibility and high resolution can be achieved.

Further, it is preferable that the amount of magnetic toner particles having a particle size of 16 μm or more is 2.0% by volume or less, and is as small as possible.

The magnetic toner of the present invention solves the conventional problems and can withstand the recent strict demands for high image quality by adopting a concept completely different from the conventional viewpoint.

The configuration of the present invention will be explained in more detail.

It is preferable that magnetic toner particles having a particle size of 5 zz m or less account for 17 to 80% of the total number of particles, preferably 25 to 80% of the total number of particles.
60% by number is good, more preferably 30-55% by number
is good. If the number of magnetic toner particles with a particle size of 5 μm or less is less than 17%, there will be less effective magnetic toner particles for high image quality, and especially as the toner is used for continuous copying or printing, the effective magnetic toner particles will decrease. As the components decrease, the balance of the particle size distribution of the magnetic toner as shown in the present invention deteriorates, and the image quality gradually deteriorates. In addition, if the silica content exceeds 60% by number, magnetic toner particles tend to aggregate with each other.If the silica content is the same as when it is 60% by number or less, toner agglomerates with a particle size larger than the original particle size will result, resulting in roughness. The image quality becomes poor, the resolution decreases, or the difference in density between the edges and the inside of the latent image increases, resulting in a hollow image.It is therefore necessary to increase the amount of silica. It is difficult to solve the above problems even by increasing the amount of .

In addition, 5 to 50 particles in the range of 6.35 to 12.7 μm
% by number, preferably 15 to 45% by number
is good. If the number is more than 50%, the image quality deteriorates, and more development than necessary occurs, that is, too much toner is applied, leading to an increase in toner consumption.

On the other hand, if it is less than 10% by number, it becomes difficult to obtain high image density. In addition, N/V=-
There is a relationship of 0.04N+, which indicates a positive number in the range of 4.5≦ and ≦6.5. Preferably 4.5≦≦6.0, more preferably 4.5≦≦5.5. As shown above, 17≦N≦80, preferably 25≦N≦50,
More preferably, 30≦N≦50.

When k < 4.5, the number of magnetic toner particles having a particle size smaller than 5.0 μm is small, resulting in poor image density, resolution, and sharpness. The presence of an appropriate amount of fine magnetic toner particles, which were conventionally thought to be unnecessary, contributes to achieving close packing of toner during development and forming a uniform image without roughness. In particular, by uniformly filling in thin lines and image contours, visual sharpness is further enhanced. That is, K<4. ．． No. 5 is inferior in these properties due to the lack of this particle size distribution component.

From another point of view, in terms of production, it is necessary to cut a large amount of fine powder by classification or the like in order to satisfy the condition of k<4.5, which is disadvantageous in terms of yield and toner cost.

Furthermore, when k > 6.5, the image density tends to decrease as copying is continued due to the presence of more fine powder than necessary. This phenomenon occurs when excessive fine powder magnetic toner particles with more charge than necessary adhere to the developing sleeve and prevent the normal magnetic toner from being carried and charged on the developing sleeve. Conceivable.

Further, the amount of magnetic toner particles having a particle size of 16 μm or more is preferably 2.0% by volume or less, more preferably 1.0% by volume or less, and still more preferably 0.5% by volume or less. If the amount is more than 2.0% by volume, it not only hinders fine line reproduction, but also causes coarse toner particles of 16 μm or more to protrude on the thin layer surface of toner particles developed on the photoreceptor during transfer. , the delicate contact state between the photoreceptor and the transfer paper via the toner layer is irregular,
This causes fluctuations in transfer conditions and is a cause of defective transfer images. In addition, the volume average diameter of the magnetic toner is 4.5~
9 .mu.m1, preferably 5 to 8.5 .mu.m, and this value cannot be considered in isolation from each of the above-mentioned constituent elements. If the volume average particle diameter is 4 μm or less, in applications with a high image area ratio such as graphic images, the amount of toner applied on the transfer paper is small, which tends to cause problems such as low image density. This is considered to be due to the same reason as the reason why the density inside the edge portion of the latent image decreases as described above. When the volume average particle diameter is 9 μm or more, the resolution is not good, and even if copying is good at the beginning, image quality tends to deteriorate with continued use.

The particle size distribution of toner can be measured by various methods.
In the present invention, a Coulter counter was used.

In other words, the measuring device is Coulter counter TA.
- Interface (manufactured by Nikkaki) that outputs number distribution and volume distribution using IF type (manufactured by Coulter) and cx-
i Connect a personal computer (manufactured by Canon), and prepare a 1% Na (l aqueous solution) using primary sodium chloride as the electrolytic solution.
Into 50 ml, add 0.1 to 5 ml of a surfactant as a dispersant, preferably an alkylbenzene sulfonate, and further add 2 to 20 mg of the measurement sample. The electrolytic solution in which the sample was suspended was dispersed for about 1 to 3 minutes using an ultrasonic disperser, and then dispersed using the Coulter Counter TAU type using a 100μ aperture, based on the number of pieces.
The particle size distribution of the 40μ particles was measured and the values according to the invention were determined therefrom.

The true density of the magnetic toner of the present invention is I, 45 to 1.70.
g/crr? It is preferable that it is, more preferably 1.50 to 1.65 g/crt? It is. Within this range, the magnetic toner of the present invention having a specific particle size distribution can be most effective in terms of high image quality and durability stability. When the true density of the magnetic toner is less than 1.45, the weight of the magnetic toner particles themselves is too light, which tends to cause reversal fog, crushing of thin lines due to excessive coverage of toner particles, scattering, and deterioration of resolution. In addition, if the true density of the magnetic toner is higher than 1.70, the image density will be distorted and the image will lack sharpness, such as broken thin lines, and the magnetic force will also be relatively large, so the toner spikes will become long or branched. In this case, when the latent image is developed, the image quality tends to be disturbed and the image becomes rough.

The true density of magnetic toner can be measured by several methods, but in this application, when measuring fine powder, the following method is adopted as an accurate and simple method.

A stainless steel cylinder with an inner diameter of 10 mm and a length of approximately 5 cm, and an outer diameter of approximately 10 mm that can be inserted tightly into the cylinder.

A disc (A) with a height of 5 mm, an outer diameter of about 10 mm, and a length of about 8 mm.
Prepare a cm piston (B). Place the disk (A) at the bottom of the cylinder, then about 1 g of the sample to be measured, and gently push the piston (B). A force of 400 kg/c% was applied to this using a hydraulic press, and the product was compressed for 5 minutes and taken out. Weigh the weight of this compressed sample (wg) L
/diameter of compressed sample in micrometer (Dcm),
The height (Lcm) is measured and the true density is calculated using the following formula.

In order to obtain even better development characteristics, the magnetic toner of the present invention has a residual magnetization σ of 1 to 5 emu/g.

It is preferably 2 to 4.5 emu/g, and the saturation magnetization σS
is 20-40 emu/g, and the coercive force Hc
It is preferable that the magnetic field satisfies a magnetic property of 40 to 100 days (Oe) (in both cases, the measured magnetic field is IK Oe).

However, in negatively charged magnetic toners, there is a tendency for fog to increase as the volume particle size decreases, and the present inventors have investigated how to reduce fog by reducing the amount of low molecular weight polyalkylene in the toner having the particle size distribution of the present invention. We found that it is possible to reduce

In addition, if the particle size distribution of the present invention is used, the amount of polyalkylene exposed on the toner surface per unit weight of the toner increases, which effectively works against offset, and even if the amount of low molecular weight polyalkylene is reduced compared to conventional methods. It has the same effect as before.

In addition, the low molecular weight polyalkylene used in the present invention has a molecular weight distribution with multiple peaks, and specifically, the chromatogram in gel permeation chromatography has at least two maximum values. Ori,
The molecular weight corresponding to the main maximum value is 2,000 to so
, ooo, and preferably has at least one other maximum value on the lower molecular weight side than the main maximum value. Preferably l/30-115 of the molecular weight of the main maximum value
, more preferably, there is another maximum value at a position of 1/20 to 1/10.

The low molecular weight polyalkylene used in the present invention is preferably a propylene-ethylene copolymer, and more preferably contains 1 to 10% by weight of ethylene units based on the low molecular weight polyalkylene.

If there is only one maximum value in the GPC chromatogram, or if there are other maximum values only on the high molecular weight side of the main maximum value, the OPC photoreceptor is likely to be damaged.

Further, these trends are remarkable in toners having a particle size within the range of the present invention, which tends to be strongly influenced by the addition of polyalkylene.

As the binder resin used in the toner of the present invention, the following binder resins for toners can be used when a heated pressure roller fixing device having an oil coating device is used.

For example, monopolymers of styrene and its substituted products such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene; styrene-p-chlorostyrene copolymers, styrene-vinyltoluene copolymers, styrene-vinylnaphthalene copolymers , styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-methyl chloromethacrylate copolymer, styrene-
Acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile- Styrenic copolymers such as indene copolymers: polyvinyl chloride, phenolic resin, naturally modified phenolic resin, natural resin-modified maleic acid resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin, polyester resin, polyurethane, polyamide Resin, furan resin, epoxy resin, xylene resin, polyvinyl butyral, terpene resin, coumaron indene resin, petroleum resin, etc. can be used.

In the heating and pressure roller fixing method, which does not apply much oil, when a part of the toner image on the toner image support member is transferred to the roller, a so-called offset phenomenon occurs, and the adhesion of the toner to the toner image support member becomes an important problem. be. Toners that are fixed with less thermal energy usually tend to block or cake during storage or in a developing device, so these problems must also be taken into consideration. The physical properties of the binder resin in the toner are most responsible for these phenomena, but according to the research of the present inventors, reducing the content of magnetic material in the toner causes the toner image to become weaker on the toner image supporting member during fixing. Although the adhesion of the toner to the toner is improved, offset is more likely to occur, and blocking or caking is also more likely to occur. Therefore, when using the heated pressure roller fixing method in which little oil is applied in the present invention, the selection of the binder resin is more important. Preferred binding materials include crosslinked styrenic copolymers or crosslinked polyesters.

These crosslinked copolymers are tetrahydrofuran (TH
F) Preferably, the insoluble content is 25% to 60%.

If it is less than 25%, a slight offset occurs when fixing with a heated pressure roller that hardly applies oil.

Further, if it is 60% or more, the fixing performance is slightly inferior.

Further, it is more preferable that the gel permeation chromatogram of the tetrahydrofuran soluble portion has two maximum values.

Examples of comonomers for the styrene monomer in the styrenic copolymer include acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, and methacrylate. Acid, monocarboxylic acid having a double bond such as methyl methacrylate, ethyl methacrylate, methacrynitrile, octyl methacrylate, acrylonitrile, methacrinitrile, acrylamide, etc. or substituted products thereof; for example, maleic acid, butyl maleate, maleic acid Dicarboxylic acids and their substituted products having double bonds, such as methyl acid, dimethyl maleate, etc.; Vinyl esters, such as vinyl chloride, vinyl acetate, vinyl benzoate, etc.; For example, ethylene, propylene, butylene, etc. Ethylene olefins; vinyl ketones such as vinyl methyl ketone and vinyl hexyl ketone; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether; and other vinyl monomers singly or in combination. Used above.

As the crosslinking agent, compounds having two or more polymerizable double bonds are mainly used, such as aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; for example, ethylene glycol diacrylate,
Carboxylic acid esters having two double bonds such as ethylene glycol diacrylate; divinyl compounds such as divinyl aniline, divinyl ether, divinyl sulfide, and divinyl sulfone; and compounds having three or more vinyl groups; singly or Used as a mixture.

Note that gel permeation chromatography (GPC) chromatographs showing molecular weight and molecular weight distribution differ slightly depending on the measurement method. Therefore, the measurement method used in the present invention will be described.

GPC measurement of the low molecular weight polyalkylene of the present invention was performed by the following method.

at a temperature of 135°C and 0-dichlorobenzene (
0.1% ionol addition), measured flow rate 1.0 m
Inject 400 μl of a sample solution with a concentration of 0.1% by weight at a flow rate of f/min. A calibration curve created using a monodisperse polystyrene standard sample is used to measure the molecular weight of the sample.

The column to be used is not limited in any way, but for example, A-80M manufactured by Shodex, TSK g manufactured by Tosoh.
There are e l G M H-HT, etc.

In addition, the THF-insoluble portion of the binder resin in the present invention refers to a polymer component that has become insoluble in THF in the resin composition (
It can be used as a parameter to indicate the degree of crosslinking of a resin composition containing a crosslinking component. The THF-insoluble content is defined by the value measured as follows.

That is, weigh out 0.5 to 1.0 g of a resin sample (24 mesh bath, 60 mesh powder) to W+g.
), put it in a thimble filter paper (for example, Toyo Roshi Model No. 86R), apply it to a Soxhlet extractor, and add THFlOO as a solvent.
~200mj! After evaporating the soluble components extracted with a solvent for 6 hours, vacuum drying at 100°C for several hours, and weighing the amount of THF-soluble resin components (W
2g). The THF-insoluble content of the resin is determined from the following formula.

In the present invention, the molecular weight of the peak and/or shoulder of a chromatogram by GPC (gel permeation chromatography) is measured under the following conditions.

That is, the column was stabilized in a heat chamber at 40°C, and THF was added to the column at this temperature as a solvent.
(tetrahydrofuran) at a flow rate of 1 ml per minute,
Measurement is performed by injecting 50 to 200 μl of a THF sample solution of the resin adjusted to a sample concentration of 0.05 to 0.6% by weight. In measuring the molecular weight of the sample, the molecular weight distribution of the sample was calculated from the relationship between the logarithm value and the count number of a calibration curve prepared using several types of monodisperse polystyrene standard samples. As a standard polystyrene sample for creating a calibration curve, for example, a polystyrene sample manufactured by Pressure Chemical Co., Ltd. or a polystyrene sample manufactured by Toyo Tsudani Gyosha Co., Ltd. with a molecular weight of 6 x 10", 2
．． lX10", 4X10", 1.75XIO',
5. lX10', 1. lXl0', 3.9XIO', 8
．． 6X10'.

It is appropriate to use at least 10 standard polystyrene samples of 2 x 10' or 4,48 x 10'. Further, an RI (refractive index) detector is used as a detector.

In addition, in order to accurately measure the molecular weight range of 103 to 4XIO', it is preferable to combine a plurality of commercially available polystyrene gel columns.
μmstyrage+ 500. 10"
, 10', 10'.

Combination of lO6 and 5hodex manufactured by Showa Denko
KF80M, KF-801, 803, 804, 805
combination, combination of KA-802, 803, 804, 805, or Toyo Soda type TSKgel G100
OH, G2000H.

G2500H, G3000H, G4000H, G500
0H.

A combination of G6000) (, G700OH, and GMH is preferred.

Further, in the magnetic toner of the present invention, it is preferable to use a charge control agent by blending it into the toner particles (internally adding it) or mixing it with the toner particles (externally adding it). The charge control agent makes it possible to control the amount of charge optimally depending on the development system.
In particular, in the present invention, it is possible to further stabilize the balance between particle size distribution and charge, and by using a charge control agent, it is possible to separate functions for high image quality in each particle size range as described above. and mutual complementarity can be made clearer.

Negative charge control agents that can be used in the present invention include:
For example, a metal complex of a monoazo dye or a salt thereof, a metal complex of salicylic acid, an alkyl salicylic acid, a dialkyl salicylic acid or a naphthoic acid or a salt thereof are used.

The above-mentioned charge control agent (one that does not function as a binder resin) is preferably used in the form of fine particles. In this case, the number average particle size of this charge control agent is specifically 4
The thickness is preferably .mu.m or less (more preferably 3 .mu.m or less).

When internally added to the toner, such a charge control agent is added in an amount of 0.1 to 20 parts by weight (or even 0.1 to 20 parts by weight) per 100 parts by weight of the binder resin.
．． 2 to 10 parts by weight) is preferably used.

Further, it is preferable to add fine silica powder to the magnetic toner of the present invention. A magnetic toner having a particle size distribution characteristic of the present invention has a larger specific surface area than conventional toners. When magnetic toner particles are brought into contact with the surface of a cylindrical conductive sleeve that has a magnetic field generating means inside for triboelectrification, the number of times the toner particle surface contacts the sleeve increases compared to conventional magnetic toner, and the toner particles Particle wear and sleeve surface contamination are more likely to occur. When the magnetic toner according to the present invention is combined with fine silica powder, wear is significantly reduced due to the presence of the fine silica powder between the toner particles and the sleeve surface. As a result, the life of the magnetic toner and the sleeve can be extended, and stable charging properties can also be maintained, making it possible to obtain a developer having a magnetic toner that is better for long-term use. Furthermore, the magnetic toner particles having a particle size of 5 μm or less, which play a major role in the present invention, are more effective due to the presence of fine silica powder, and can stably provide high-quality images.

As the silica fine powder, both silica fine powder produced by a dry method and a wet method can be used, but from the viewpoint of filming resistance and durability, it is preferable to use a silica fine powder produced by a dry method.

The dry method mentioned here is a method for producing fine silica powder produced by vapor phase oxidation of a silicon halide compound. For example, this method utilizes the thermal decomposition oxidation reaction of silicon tetrachloride gas in oxygen and hydrogen, and the basic reaction formula is as follows.

5iCj? 4 +2H2+02→5in2+4HC1 Also, in this manufacturing process, it is also possible to obtain a composite fine powder of silica and other metal oxides by using other metal halide compounds such as aluminum chloride or titanium chloride together with a silicon halide compound. , also include them.

Commercially available fine silica powder produced by vapor phase oxidation of a silicon halogen compound used in the present invention includes, for example, those commercially available under the following trade names.

AERO3IL 130 (Japan Aerosil Co., Ltd.) 20000 Ca-0-5iL (CABOTO Co., Ltd.) Wacker HDK N 20 (WACKER
-CHEMIE GMBH) 80 Various conventionally known methods can be applied to produce the silica fine powder used by a wet method.

For example, the general reaction formula for the decomposition of sodium silicate with an acid is shown below.

Na20 ・XSiO2+HC1+H20-+5io2
anH20+NaC1 Other methods include decomposition of sodium silicate with ammonia salts or alkali salts, generation of alkaline earth metal silicate from sodium silicate and then decomposition with acid to form silicic acid, and method of converting sodium silicate solution into ion exchange resin. There are methods such as using silicic acid, and using natural silicic acid or silicate.

The silica fine powder referred to herein can be any of anhydrous silicon dioxide (silica) and other silicates such as aluminum silicate, sodium silicate, potassium silicate, magnesium silicate, and zinc silicate.

Commercially available fine silicic acid powders synthesized by a wet method include those sold under the following trade names, for example.

Curflex Neep Sealton Seal, Fine Seal Vita Seal Silton, Silnetx Starsil Himezil Thyroid Hi-5il Durosil Ultrasjl Manosi
l (7 Nosil) Hoesch Sil-3tone Shionogi Pharmaceutical Japan Silica Tokuyama Soda Taki Himizusawa Chemical Kamishima Chemical Ehime Pharmaceutical Fuji Davison Chemical Pittsburgh Plate Glass
Co.

(Pittsburgh Plate Glass) Fi…stoff-GesellschaftMarq
uart (Fürstzuf Gesellschaft Markorth) Hardman and Ho1den (Hardman and Holden) Chemische Fabrik Hoesch
K-G (Hiemitsussie Fabrik Herrash) Stoner Rubber Co, (Stoner Na
1co Quso Santocell Imsil Rubber Nalco Chem, Co, Philadelphia Quartz Co Monsanto Chemical Co , (Monsanto Chemical) 111inois Minerals Co, (Illinois Minerals Co., Ltd.) Mineral) Calcium 5r13kat (Calcium silicate) Calsil Fortafil Microca
l (Microcal) Chemische Fabrik Hoes
chK-G
rquart
Marquardt) Imperial Chemical Industry
riesLtd, (Imperial Chemical Industries) Joseph Crosfield & 5ons L
td.

(Jiecef Crossfield and Sons) Manosil Hardm
an and Ho1den (Hardman and
Holden) Vulkasil Farb
enfabriken Bryer, A, G, (- ya) Tufknit Durha
m Chemicals Ltd, (Doulham Chemicals) Silmos Shiraishi Kogyo Starex Jinba Kagaku Fricosil
Multi-wood fertilizer - Of the silica fine powders mentioned above, those with a specific surface area of 30 d1g or more due to nitrogen adsorption measured by the BET method (
Particularly, those within the range of 50 to 4.0 Ord/g) give good results. The silica fine powder is preferably used in an amount of 0.01 to 8 parts by weight, preferably 0.1 to 5 parts by weight, per 100 parts by weight of the magnetic toner.

Further, the fine silica powder used in the present invention is desirably treated to be hydrophobic, and has a water wettability of 60% or more, preferably 80% or more.

In order to make it hydrophobic, it is treated with a treatment agent that reacts with or physically adsorbs the silica fine powder, such as a silane coupling agent or an organosilicon compound.

Examples of such treatment agents include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane,
Allyl phenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilylacrylate , vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyljethoxysilane,
Hexamethyldisiloxane, 1,3-divinyltetramethyldisiloxane, 1,3-diphenyltetramethyldisiloxane, and having 2 to 12 siloxane units per molecule, one each for the terminally located unit. There are dimethylpolysiloxanes containing hydroxyl groups bonded to Si. These can be used alone or in a mixture of two or more.

The water wettability of silica in the present invention is measured as follows. 200m! ! Collect 0.1 g of sample into a separating funnel and add 100 mj of ion-exchanged water! Add using a graduated cylinder. This was heated for 10 minutes at 9 rpm in a tarbuta shaker mixer T2C type.

After leaving the separating funnel for 10 minutes, 20 to 30
After extracting ml, it is fractionated into a 10 mm cell, the ion exchange water is used as a blank, and the turbidity of the water layer is measured using a colorimeter (wavelength: 500 nm).The transmittance % with respect to the blank is defined as the water wetness.

If the water wettability of the silica fine powder is 60% or less, image density fluctuations are likely to occur under high temperature and high humidity conditions.

The magnetic toner of the present invention may contain additives, if necessary. As the colorant, conventionally known dyes and pigments can be used, and usually 0.5 to 20 parts by weight may be used per 100 parts by weight of the binder resin. Other additives include, for example, lubricants such as zinc stearate, or abrasives such as cerium oxide, silicon carbide, or flow agents such as colloidal silica, aluminum oxide, anti-caking agents, or e.g. carbon black, tin oxide. There are conductivity imparting agents such as

Furthermore, the magnetic toner of the present invention may also serve as a colorant, but it contains a magnetic material. The magnetic materials contained in the magnetic toner of the present invention include iron oxides such as magnetite, γ-iron oxide, ferrite, and iron-rich ferrite;
Metals such as cobalt, nickel or these metals with aluminum, cobalt, copper, lead, magnesium, tin,
Examples include alloys with metals such as zinc, antimony, beryllium, bismuth, cadmium, calcium, kanganese, selenium, titanium, tungsten, and vanadium, and mixtures thereof.

These ferromagnetic materials preferably have an average particle size of 0.1-1 μm, preferably 0.1-0.5 μm, and are contained in the magnetic toner in an amount of 60-130 parts by weight per 100 parts by weight of the resin component. parts, preferably 65 to 120 parts by weight per 100 parts by weight of the resin component.

To prepare the magnetic toner for developing electrostatic images according to the present invention, magnetic powder, vinyl or non-vinyl thermoplastic resin, pigment or dye as a coloring agent, charge control agent, and other additives are used as necessary. etc. are sufficiently mixed using a mixer such as a ball mill, and then melted, kneaded, and kneaded using a heat kneader such as a heated roll, niegu, or extruder to make the resins compatible with each other. The magnetic toner according to the present invention can be obtained by dispersing or dissolving it, cooling and solidifying it, and then pulverizing and strictly classifying it.

The magnetic toner of the present invention is preferably applied to an image forming method in which a latent image is developed while flying the toner from a toner carrier such as a cylindrical sleeve to a latent image carrier such as a photoreceptor. That is, the magnetic toner is given a triboelectric charge mainly through contact with the sleeve surface, and is applied in a thin layer onto the sleeve surface.

The thickness of the thin layer of magnetic toner is formed to be thinner than the gap between the photoreceptor and the sleeve in the development area. When developing a latent image on the photoreceptor, it is preferable to apply an alternating electric field between the photoreceptor and the sleeve, and then cause the magnetic toner having triboelectric charges to fly from the sleeve to the photoreceptor.

Examples of the alternating electric field include a pulsed electric field, an alternating current bias, or a combination of alternating current and direct current bias.

EXAMPLES Hereinafter, the present invention will be specifically explained using Examples, but these are not intended to limit the present invention in any way.

Note that all parts in the following formulations are parts by weight.

Example 11"2 The above materials were thoroughly mixed in a blender, and then kneaded in a twin-screw kneading extruder set at 150°C. The obtained kneaded material was cooled and coarsely pulverized using a cutter mill, then finely pulverized using a pulverizer using a jet stream, and the obtained pulverized powder was classified using a fixed wall type wind classifier. A classified powder was produced. Furthermore, the obtained classified powder is strictly classified and removed at the same time to remove ultra-fine powder and coarse powder using a multi-division classifier that uses the Coanda effect (elbow jet classifier manufactured by 8 Iron Mining Co., Ltd.), and the volume average particle size is 8.
．． 05 μm black fine powder A (magnetic toner) was obtained.

The obtained black fine powder had a triboelectric charge of -20 μc/g after being mixed with an iron powder carrier.

For reference, the classification process using a multi-division classifier is shown in the first section.
It is schematically shown in the figure, and a cross-sectional perspective view (stereoscopic view) of the multi-division classifier is shown in FIG.

Negatively charged hydrophobic dry silica (BET specific surface area 200rd/g,
0.8 parts by weight (water wettability: 95%) was added and mixed in a Henschel mixer to obtain a negatively charged one-component magnetic developer (magnetic toner to which silica was externally added).

The particle size distribution and magnetic properties of this magnetic toner were as shown in Table 1.

An image was formed using the magnetic toner externally added with silica using a laser beam printer LBP-8II (manufactured by Canon) using a commercially available OPC and having a developing device shown in FIG.

At this time, the fixing pad for cleaning the roller of the fixing device was removed, and the image quality and the presence or absence of an offset phenomenon were observed.

The results are shown in Table 2.

The multi-division classifier used in this example and the classification process using the classifier will be explained with reference to FIGS. 1 and 2. In FIGS. 1 and 2, the multi-segment classifier 1 has a side wall having a shape indicated by 22.24, and a lower wall having a shape indicated by 22.24.
The side wall 23 and the lower wall 25 each have a knife-type classification edge 17. 18,
This classification edge 17. 18, the classification zone is divided into three parts. A raw material supply nozzle 16 opening into the classification chamber is provided below the side wall 22, and a Coanda block 26 is provided which is bent downward in the direction of extension of the bottom tangent of the nozzle to draw an elongated arc. The upper wall 27 of the classification chamber is provided with a knife-shaped edge 19 toward the bottom of the classification chamber, and a tube 14-15 opening into the classification chamber is provided at the upper portion of the classification chamber. Also, popular tube 14. 15 has the first damper-like structure. Second gas introduction adjustment means 20.21 and static pressure gauge 28
．． 29 is provided. At the bottom of the classification chamber, there is a discharge pipe 1 that has a discharge port that opens into the chamber, corresponding to each fractionation area.
1. 12. 13 is provided. The classified powder is introduced into the classification area from the supply nozzle 16 under reduced pressure, and moves in a curved line 30 due to the Coanda effect of the Coanda block 26 and the action of the high-speed air flowing in at that time, and the coarse powder 11, It was classified into black fine powder 12 and ultrafine powder 13 having a predetermined volume average particle diameter and particle size distribution.

Example 1 was carried out in the same manner as in Example 1, except that the amount of the low molecular weight ethylene-propylene copolymer was changed to 0.4 parts by weight.

The results are shown in Table 2.

Example 1 was repeated except that the THF-insoluble content of the styrene/butyl acrylate/divinylbenzene copolymer was 50%.

The results are shown in Table 2.

Examples except that the amount of magnetite is 110 parts by weight, the particle size of the black fine powder is the particle size distribution of black fine powder B in Table 1, and the amount of silica fine powder added is 1.2 parts by weight. It was carried out in the same manner as I.

The results are shown in Table 2.

Example 1 was carried out in the same manner as in Example 1 except that the following materials were used as the materials.

The results are shown in Table 2.

X amount I” The amount of magnetite is 120 parts, and the particle size of the black fine powder is as shown in Table 1.
Example 5 was carried out in the same manner as in Example 5, except that the particle size distribution of black fine powder C was set as follows, and the amount of silica fine powder added was 1.5 parts by weight.

The results are shown in Table 2.

Comparison Example 1 The same procedure as in Example 1 was conducted except that the low molecular weight propylene-ethylene copolymer was not included.

The results are shown in Table 2.

Comparison 1 The same procedure as in Example 1 was carried out except that the amount of the low molecular weight propylene-ethylene copolymer was changed to 2 parts by weight.

The results are shown in Table 2.

The process was carried out in the same manner as in the example except that the THF-insoluble content of the styrene/butyl acrylate/divinylbenzene copolymer was changed to 10%.

The results are shown in Table 2.

9 Comparison 1'' Same as Example 1 except that the amount of magnetite was 60 parts by weight, the particle size of black fine powder was particle size distribution D in Table 1, and the amount of silica fine powder added was 0.6 parts by weight. went.

The results are shown in Table 2.

Compare with Example 1 except that the amount of magnetite was 140 parts by weight, the particle size of the black fine powder was set to the particle size distribution E in Table 1, and the amount of silica fine powder added was increased to 1.8 parts by weight. I did the same.

The results are shown in Table 2.

Example 1 was carried out in the same manner as in Example 1, except that the low molecular weight ethylene-propylene copolymer was used as a low molecular weight polypropylene having only one maximum value in the GPC chromatogram (corresponding molecular weight: 45,000).

The results are shown in Table 2.

table table

[Brief explanation of the drawing]

In the accompanying drawings, FIG. 1 shows an explanatory view of a classification process using a multi-part classification means, FIG. 2 shows a schematic cross-sectional perspective view of the multi-part classification means, and FIG. 3 shows an example and a comparative example. A schematic cross-sectional view of the developing device used for image development is shown in FIG.
FIG. 4 is a graph plotting the number percent (N)/volume percent (V) of particles having a particle size of 5 μm or less in the magnetic toner. ■...Multi-division classification device 11...Coarse powder 12...Powder having a predetermined particle size 13...Fine powder 26...Coanda block 31...-component magnetic developer 32...Blade 33...Sleeve 34...Photosensitive drum 35...Fixed magnet 36...Bias applying means Z key ratio %, urine r^arako G weight %

Claims (2)

[Claims] (1) In a magnetic toner containing at least a binder resin, magnetic powder, and 0.1 to 1 part by weight of low molecular weight polyalkylene per 100 parts by weight of the binder resin, the magnetic toner particles having a particle size of 5 μm or less are 17 Contains ~80% by number, 6
．． Magnetic toner particles having a particle size of 35 to 12.7 μm are contained in an amount of 5 to 50% by number, magnetic toner particles having a particle size of 16 μm or more are contained in an amount of 2.0% by volume or less, and the volume average diameter of the magnetic toner particles is is 4.5 to 9 μm, and 5 μm
The following magnetic toner particle group is expressed by the following formula N/V=-0.04N+k [where N represents the number % of magnetic toner particles having a particle size of 5 μm or less, and V represents the magnetic toner particle having a particle size of 5 μm or less. It shows the volume % of particles, and k shows a positive number from 4.5 to 6.5. However, N represents a positive number from 17 to 80. ] has a particle size distribution that satisfies the above, and the chromatograph in gel permeation chromatography of the above-mentioned low molecular weight polyalkylene has at least two maximum values, and the molecular weight corresponding to the main maximum value is 2,0
00 to 80,000 and having at least one other maximum value on the lower molecular weight side than the main maximum value. (2) The magnetic toner according to claim 1, wherein the binder resin has a content insoluble in tetrahydrofuran (THF) of 25% to 60% by weight.