JP2782266B2 - Magnetic toner - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic toner used for developing an electrostatic latent image formed in an electrophotographic method, an electrostatic printing method, or the like.

[Prior Art] As a conventional developing method using a one-component magnetic toner, there are representative ones such as US Pat. No. 3,866,574, US Pat. No. 3,890,929 and US Pat. No. 3,893,418.

In the developing method, a proposal has been made to provide a certain gap between the latent image holding member and the toner carrying member, apply an asymmetrical AC pulse bias thereto, and control the flying of the high-resistance one-component toner. FIG. 1 shows a schematic diagram of the waveform at that time. In terms of content, the gap between the latent image holding member and the toner
m (preferably 50 to 180 μm), frequency 1.5 to 10 KH
z (preferably 4 to 8 KHz), development time (T _A ) is 10 μsec ≦
T _A ≦ 200 .mu.sec (preferably 30μsec ≦ T _A ≦ 70μsec), stripping time (T _D) is 100μsec ≦ T _D ≦ 500sec (preferably
100 μsec ≦ T _D ≦ 180 μsec), and the developing voltage (T _A ) is V _A ≦ −15
0 V, stripping voltage (V _D ) is V _D ≧ 400 V and V _D −V _A ≦ 800 V
(Preferably -200V≤V _A ≤-150V and 400V≤V _D ≤450V)
And so on. With this method, flying adhesion of toner particles to a non-image portion is prevented, and gradation and line reproducibility are improved. FIG. 2 shows the above schematic diagram.

In addition, high-resistance one-component developer (volume resistance of 10 ¹⁰ Ωcm or more)
As a latent image developing method using, there are known an impression developing method (US Pat. No. 3,405,682 and the like), a jumping developing method (JP-A-55-18656-18659 and the like), and particularly a jumping developing method. Is a developing area, which is the closest part between the toner carrier and the latent image carrier, and the toner is applied to the toner carrier and the latent image carrier by an AC bias voltage applied between the toner carrier and the latent image carrier. Reciprocating between
Eventually, the toner is selectively transferred to and adhered to the surface of the latent image holding member according to the latent image pattern, and is visualized. These have a duty ratio of 50%, and the development time and the reverse development time are the same (see FIG. 3).

However, there is a patent related to the above-mentioned jumping development method in which the duty ratio of an alternating bias voltage applied between the toner carrier and the latent image carrier is controlled in accordance with the remaining amount of the developer in order to adjust the image density. (JP-A-60-73647).

Here, the “duty ratio of the AC bias electric field” is defined as in the following equation.

a: Application time of an electric field component (developing-side bias component) having a polarity in the direction of transferring toner to the latent image holding member side in one cycle of an AC bias in which the electric field polarity alternates between positive and negative. (At this time, the DC bias electric field has been removed.) B: Application time of the electric field component (reverse developing side bias component) of the polarity in the direction of separating the toner from the latent image holding member.

The development-side bias component refers to the portion a in FIG. 4 when the latent image potential of the latent image holding member is V _S (polarity is positive) and the polarity of the toner used is negative. The side bias component refers to a portion b in FIG.

As in the previous example, in order to prevent toner from adhering to the non-image area, the absolute value of the alternating bias voltage is kept low,
Further, in a developing method in which the developing-side voltage is reduced, a sufficient image density may not be obtained.

In the conventional example of the latter stage described above, the current side bias voltage is large, so that the developability of the solid latent image (high potential area) is high, while the reverse developing side bias in the low potential area is large, so that the developed toner is excessive. The image tends to be peeled off and has no gradation.

Also, the allowable range for setting the voltage (DC and AC components (V _pp & frequency)) is narrow. That is, if the voltage is adjusted (for example, the DC component is reduced or the AC component is increased) to increase the density, background fouling (hereinafter, referred to as fog) occurs. AC
Increasing the frequency is effective for fogging, but the reproducibility of characters and lines is poor (thin).

As a means for improving the above two developing methods, the developing electric field is increased when the developing-side bias is applied, and the developing-side time is set to a short time so that the image density is high, the gradation is excellent, and the fog is improved. Images can be obtained.

Here, the developing method used in the present invention described above will be described.

The force that causes the toner to fly from the toner carrier to the latent image holding member must give an acceleration a so that the toner can sufficiently reach the latent image surface by the AC bias electric field. The force f is given by m ·, where m is the weight of the toner. If the charge of the toner is q, the distance from the toner carrier is d, and the alternating bias electric field is And the force at which the toner reaches the latent image surface is determined by the balance between the electrostatic attraction force with the toner carrier and the electric field force.

The present inventors have studied using a magnetic toner having a particle size distribution ranging from 0.5 μm to 30 μm in order to see the relationship between the toner particle size and the developability of the developing bias. This is because when a constant developing-side voltage (approximately 1000 V) is applied between the toner carrier and the latent image carrier (approximately 250 μm) in a pulsed manner, the toner starts to adhere to the latent image carrier (image after transfer and fixing). The image density
Make it 1.0 or more. 3.) The pulse width and the particle size distribution of the toner are observed. That is, the surface potential of the latent image holder is kept constant, the pulse width is changed to develop the latent image, the developed toner particles on the latent image holder are collected, and the toner particle size distribution is measured. It was found that there were many magnetic toner particles of 8 μm or less. It was also found that as the pulse width was further reduced, finer magnetic toner particles increased. That is, it can be seen that the smaller the particle size of the toner, the earlier the time to reach the latent image holding member.

Conventionally, it has been difficult to control the charge amount of magnetic toner particles having a size of 8 μm or less in a magnetic toner, and it has been easy to overcharge. For this reason, the toner particles having a size of 8 μm or less have a strong reflection force on the toner carrier, adhere to the surface of the toner carrier, inhibit the triboelectric charging of other particles, generate poorly-charged toner particles, and generate roughness and density. It could cause a decline, and it was thought that aggressive reduction was necessary.

However, according to the study of the present inventors, it has been found that magnetic toner particles having a size of 8 μm or less are good components for forming high-quality image quality.

The electric field may be increased in order to fly the toner of 8 μm or less which tends to collect near the toner carrier. However, simply increasing the developing-side bias voltage is because toner particles fly to the latent image side regardless of the latent image pattern.
The tendency is strong for toner particles of 8 μm or less, and fog is a problem. Further, fogging can be prevented by increasing the reverse developing bias voltage, but when a large alternating bias electric field is applied between the latent image holding member and the toner carrying member, a discharge is directly generated between the latent image holding member and the toner carrying member. Disturbs the image quality.

Also, when the reverse developing bias voltage is increased, not only the non-latent image portion but also the toner developed into the latent image pattern is peeled off, and the reflection power on the latent image holding member is relatively weak.
The toner particles of about 11 .mu.m are removed, and the visualized pattern of the latent image portion is also disturbed, so that the toner adhesion is deteriorated, the gradation and line reproducibility are deteriorated, and it is easy to cause dropping in the image.

From the above results, it is necessary to make the toner near the toner carrier fly and reciprocate without increasing the alternating bias electric field so much and keeping the reverse developing side bias voltage low.

Therefore, not only the magnitude of the alternating bias electric field but also the application time t were controlled. In other words, the developing bias electric field is increased without changing the frequency of the alternating bias, the application time of the developing bias electric field is shortened, and accordingly, the reverse developing bias electric field is suppressed low, and the application time is increased. A method of controlling the duty ratio of the alternating bias was used.

By using this method, the developing-side bias electric field is sufficiently strengthened, so that the toner particles of 8 μm or less, which is an essential component for improving the image quality on the toner carrier, are effectively fly and reciprocated. This has prevented the adhesion to the surface of the toner carrier.

Furthermore, even if the reverse development side bias electric field is kept low,
Conversely, when applied for a sufficiently long time, a force for separating excess toner adhering to portions other than the latent image pattern from the latent image holding member can be obtained, fogging can be prevented, and 8-11 μm, which is an essential component for toner adhesion, is used. The toner particles are not stripped. As an example, FIGS. 6 to 8 show the waveforms of the alternating bias voltage used in the present invention.

In the developing method used in the present invention, since the developing-side bias electric field of the alternating bias electric field is so strong that the toner near the toner carrier can fly, the toner having a large charge amount near the toner carrier is more strongly developed into a latent image pattern. Therefore, it can strongly adhere to the weak latent image pattern due to the electrostatic force of the toner with a high charge amount. Magnetic toner particles having a size of 8 μm or less can be effectively used, and good image quality can be obtained.

[Problems to be Solved by the Invention] However, if the image forming method using such a developing method is repeatedly used, the image density decreases, fog increases, or the resolving power and line reproducibility deteriorate. Image quality may be degraded.

At this time, when the particle size distribution of the toner in the developing device was measured, it was found to be different from the initial value, and it was found that the deterioration of the image quality was due to the selective development of the toner.

For example, if a large amount of toner particles having a large particle diameter are contained in the magnetic toner, these particles tend to be small-charged toner particles, remain without being developed, and change the particle size distribution of the magnetic toner. And so on. Alternatively, even if the charge amount is too low or too high, the particle size distribution tends to change, resulting in image quality deterioration.

In general, in the one-component developing method, when image formation is repeated, toner having a small particle size adheres to the surface of the toner carrier due to the reflection force due to the high charge amount, and inhibits the triboelectric charging of other toner particles. In some cases, toner particles that do not have a sufficient charge amount increase, causing a decrease in density.
Such development is particularly likely to appear in a low-temperature and low-humidity environment.

Such development is accelerated when the toner on the toner carrier is not consumed (for example, an image white background portion), resulting in a decrease in image density. On the other hand, when the toner is consumed from such a state (for example, a black portion of the image), the development is eased and the density gradually recovers.

Therefore, if an image is formed in a state in which a consuming part (image part) and an unconsumed part (non-image part) are present on the toner carrier, a difference in density on the image (that is, a high density in the consuming part, At low concentration).

Such development is hereinafter referred to as carrier memory. Considering the formation mechanism, this carrier memory
Canceled by toner consumption. That is, the power is reduced for each rotation of the toner carrier. Therefore,
If this phenomenon is light, the memory on the image is lost once, but if it is heavy, it may appear many times.

Therefore, in the magnetic toner used in the present invention,
It has been found that the particle size distribution of the magnetic toner and the triboelectric charge amount on the toner carrier are important factors for obtaining good durability, environmental characteristics, and excellent image quality.

That is, an object of the present invention is to provide an image forming apparatus which has excellent durability used in a developing method using an asymmetric developing bias which has solved the above-mentioned problems, and has a high image density even when used for a long period of time. Stabilizes the image with no image, and has high gradation and stable high image density even in low-temperature and low-humidity environment, and prevents or reduces toner carrier memory even in long-term continuous use. It is to provide a magnetic toner.

Means and Action for Solving the Problems The present inventors provide a magnetic toner having a triboelectric charge amount suitable for the developing method used in the present invention on a toner carrier and having a particle size distribution. This has achieved this objective.

That is, in the present invention, a latent image holding member for holding an electrostatic image and a toner holding member for holding a magnetic toner on the surface are arranged at a fixed gap in a developing section, and the magnetic toner is placed on the toner holding member. In an image forming method of controlling the thickness to be smaller than the gap, conveying the toner to the developing unit, and applying a DC voltage and an asymmetric alternating voltage between the toner carrier and the latent image holding member, an alternating bias voltage including a DC bias voltage is provided. And a binder resin used in a developing method for making the developing-side voltage component equal to or larger than the reverse developing-side voltage component (stripping voltage component), and making the application time of the developing-side voltage shorter than that of the reverse developing-side voltage. In a magnetic toner having at least magnetic powder, the magnetic toner contains 33% by number or less of magnetic toner particles having a particle diameter of 8 μm or less, and has a number average particle diameter of 8 μm.
Magnetic toner particles having a particle diameter of 16 μm or more and 16% by volume or less, and the volume average particle diameter of the magnetic toner is 10 μm to 14 μm, and the magnetic toner particles are triboelectrically charged on the toner carrier. And the volume average particle diameter of the magnetic toner satisfies the following general formula (1), The magnetic toner has the following general formula (2)
Satisfies the following.

The magnetic toner of the present invention contains 16% by volume or less of magnetic toner particles having a particle size of 16 μm or more, and has a volume average particle size of 10 to
It is 14 μm, preferably 11 to 13 μm. When the volume average particle diameter of the magnetic toner exceeds 14 μm, the content ratio is reduced in the present invention.
Particles having a particle size of 16 μm or more, which are regulated to be 16% by volume or less, relatively increase.

When the magnetic toner having a particle diameter of 16 μm or more is more than 16% by volume, not only does it hinder the reproduction of fine lines, but in the transfer, the coarse toner of 16 μm or more is applied to the thin layer surface of the toner particles developed on the photoreceptor. The presence of the protruding particles makes the delicate state of close contact between the photoconductor and the transfer paper via the toner layer irregular, causing fluctuations in the transfer conditions and causing poor transfer images.

Furthermore, in the developing method of the present invention, toner particles of 16 μm or more cannot fly on the latent image holding member unless they have a sufficient charge amount,
In many cases, the toner remains on the toner carrier, causing a change in the particle size distribution, or inhibiting the triboelectric charging of the toner particles, lowering the developing ability, and causing image quality deterioration.

Further, regarding the particle diameter, in the magnetic toner of the present invention, 8
Another feature is that 33% by number or more of magnetic toner particles having a particle diameter of not more than μm are contained, and the number average particle diameter is 8 to 11 μm.

Here, in the present invention, the number average particle diameter of the magnetic toner particles is set to 8 to 11 μm. This is because the ratio of the toner particles of 8 to 11 μm which is an essential component for mounting the toner described above is large. It indicates that.

In the developing method used in the present invention, toner particles having a size of 8 μm or less are prevented from sticking to the surface of the toner carrier in order to fly the toner particles well. The state tends to occur, and the toner mass becomes larger than the original particle size, resulting in rough image quality, lowering the resolution, or increasing the density difference between the edge portion and the inside of the latent image. It may be.

Further, the present inventors have determined that the proportion of particles having a particle size of 8 μm or less (33
In order to see the relationship between the number of particles having a volume average of 10 to 14 μm and the volume percentage of 16 μm or more, 0 ≦ x ≦ 16
Within the range of (volume%), the number% of 8 μm or less is defined as 0 ≦ y ≦
Magnetic toners having various particle size distributions were prepared within the range of 33 (number%), and these were used in the development method of the present invention and studied. (However, x and y indicate real numbers.) When the magnetic toner is 8 μm or less, 33% by number, and when the magnetic toner is 16 μm or more,
In the case of having a particle size distribution of 16% by volume, if the ratio of both fine powder and coarse powder is large at the same time, though within the limits of each regulation, the particle size distribution will eventually become broad and the copy test will be good at the beginning, but the durability will be good As a result, image deterioration occurs. In order to obtain a usable particle size distribution, when 8 μm or less is set to 33% by number, almost 16 μm or more is almost cut, or when 16 μm or more is set to 16% by volume, 8 μm is used.
m or less must be cut to sharpen the particle size distribution. However, in the case where the proportion of particles having a particle size of 8 μm or less and 16 μm or more was cut from both, a material usable within a range having a certain degree of latitude was obtained. Then, what kind of range is the usable range was further examined, and the ratio (volume%) of the particles having 16 μ or more was determined.
It was found that the following general formula (2) holds true for the ratio (number%) of particles having a particle size of 8 μm or less.

On the other hand, with respect to the triboelectric charge amount of the magnetic toner on the toner carrier, good development can be achieved if the magnetic toner is charged on the toner carrier so as to fall within the range of the general formula (1), preferably the general formula (3). And an image with excellent image quality can be obtained depending on the developing method used in the present invention.

In the case of Q <0.5 (μc / g) R, the magnetic toner particles of 8 to 11 μm are peeled off from the latent image holding member by the reverse-developing side bias, so that the toner adhesion is deteriorated, and it is easy to cause dropping or line disturbance. .

On the other hand, when Q> 13 + 0.5 (μc / g) R, the magnetic toner particles of 8 μm or less become hard to fly even by the developing-side bias in the present invention, realizing high image quality which is the effect of the magnetic toner of 8 μm or less. become unable. Further, the toner particles tend to accumulate on the toner carrier, hindering the triboelectric charging of other toner particles, thereby deteriorating the developing ability, causing a decrease in image density, memory of the carrier, roughness, fog, etc. become.

Although the particle size distribution of the toner can be measured by various methods, in the present invention, the measurement was performed using a Coulter counter.

In other words, the Coulter Counter TA is used as a measuring device.
-An interface (manufactured by Nikkaki) that outputs the number distribution and volume distribution and a CX-1 personal computer (manufactured by Canon) are connected using Type II (manufactured by Coulter), and the electrolyte is approximately 1% sodium chloride. Prepare 1% NaCl aqueous solution. For example, ISOTON-II (manufactured by Coulter Scientific Japan) can be used. As a measuring method, a surfactant as a dispersing agent, preferably an alkylbenzene sulfonate in 0.1 to 5 ml of the electrolytic aqueous solution 100 to 150 ml is used.
ml and then 2 to 20 mg of the measurement sample. The electrolytic solution in which the sample was suspended was subjected to a dispersion treatment for about 1 to 3 minutes with an ultrasonic disperser, and the Coulter Counter TA-II was used, and a 100 μ aperture was used as an aperture. The particle size distribution was measured and the values according to the invention were determined therefrom.

Hereinafter, a specific example of an apparatus in which the developing step is performed in the present invention is shown in FIG. 5, and the configuration of the present invention will be described in more detail. However, this does not limit the present invention in any way.

In FIG. 5, reference numeral 1 denotes a latent image holder (so-called photosensitive member) such as a rotating drum type in a transfer type electrophotographic method, an insulator such as a rotating drum type in a transfer type electrostatic recording method, photosensitive paper in an electrofax method, In the direct electrostatic recording method, an electrostatic latent image is formed on a surface of a latent image holding member such as an electrostatic recording sheet by a latent image forming process device or the same process mechanism which is omitted in the drawing, and the surface moves in the direction of the arrow. I have.

Reference numeral 2 denotes an overall reference number of a developing device, reference numeral 21 denotes a hopper containing a high-resistance one-component developer (hereinafter, referred to as a toner), and reference numeral 22 denotes a rotating cylinder (hereinafter, referred to as a sleeve) as a toner carrier (a developer layer supporting member). Inside the magnetic generating means 23 such as a magnetic roller
Is built in.

The sleeve 22 has a substantially right half circumferential surface exposed in the hopper 21 and a left half circumferential surface exposed outside the hopper, and is supported by a bearing. Reference numeral 24 denotes a doctor blade serving as a toner application member disposed with the lower side edge portion approaching the upper surface of the sleeve 22, and reference numeral 27 denotes a stirring member for the toner in the hopper.

The axis of the sleeve 22 is substantially parallel to the generatrix of the latent image carrier 1 and is closely opposed to the surface of the latent image carrier 1 with a small gap α.

The surface moving speeds (peripheral speeds) of the latent image holder 1 and the sleeve 22 are substantially the same, or the peripheral speed of the sleeve 22 is slightly higher. Further, between the latent image bearing member 1 and the sleeve 22 and the alternating bias voltage applying means S ₀ by the DC bias voltage applying means S _1, a DC voltage and an AC voltage is superimposed is applied.

Thus, the substantially right half peripheral surface of the sleeve 22 is always in contact with the toner reservoir in the hopper 21, and the toner near the surface of the sleeve 22 forms a magnetic adhesion layer on the surface of the sleeve 22 by the magnetic force of the in-sleeve magnetism generating means 23. In addition, it is adhered and held by electrostatic force. When the sleeve 22 is rotated deposited toner layer on the sleeve 22 surface is advice service as a thin layer toner layer T ₁ of the substantially uniform thickness each part in the process of passing through the doctor blade 24 position. The toner is charged mainly by frictional contact between the surface of the sleeve 22 with the rotation of the sleeve 22 and the toner in the toner reservoir near the sleeve 22, and the toner thin layer surface of the sleeve 22 is held by the latent image holding member with the rotation of the sleeve 22. Rotate to one side,
The latent image carrier 1 and the sleeve 22 pass through the developing area A which is the closest part. During this passage, the toner of the thin toner layer on the side of the sleeve 22 flies by the DC and AC electric fields generated by the DC and AC voltages applied between the latent image holder 1 and the sleeve 22, and the surface of the latent image holder 1 in the developing area A And the sleeve 22 reciprocate. And finally the toner image T ₂ are sequentially formed by selectively transition adhere according to the potential pattern of the latent image to the toner latent image bearing member 1 surface of the sleeve 22 side.

The surface of the sleeve 22 where the toner has been selectively consumed after passing through the developing area A receives the re-supply of toner by re-rotating to the toner reservoir of the hopper 21, and the toner of the sleeve 22 is always supplied to the developing area A. thin layer T ₁ side is rotated, repeatedly copying step is performed.

By the way, such a developing method (one-component non-contact developing method)
As one of the problems in the case of adopting the method, there is a case where the phenomenon of development deterioration due to an increase in the adhesive force of the toner near the surface of the sleeve 22 occurs. That is, the rotation of the sleeve 22 causes the toner and the sleeve 22 to always come into contact friction, and the charge amount of the toner gradually increases, so that the electrostatic force (Coulomb force) with the sleeve 22 increases, and the toner flies to the latent image holding member 1 This is a phenomenon in which the force is weakened, stays in the vicinity of the sleeve 22, hinders the triboelectric charging of other toners, and lowers the developing property. This occurs due to a low-temperature and low-humidity environment or a repetition of a copying process.

In the developing method used in the present invention, the gap between the sleeve 22 and the latent image holding member 1 was set to 0.3 mm in the embodiment, but from 0.1 mm to 0.5 mm, sufficient development was achieved by the developing method according to the present invention. It is possible.

Since the developing-side bias is larger than in the conventional developing method, it is possible to develop even if the gap between the sleeve 22 and the latent image holding member 1 is large.

If the absolute value of the alternating bias voltage is 1.0 kV or more, a sufficiently satisfactory image can be obtained. Further, considering the leakage to the latent image holding member 1, the absolute value of the alternating bias voltage is 1.0 k
It is desirable to be higher than V and lower than 2.0 kV. However, this leak naturally varies depending on the gap between the sleeve 22 and the latent image holding member 1.

Next, the alternating bias frequency is preferably 1.0 kHz to 5.0 kHz. When the frequency is 1.0 kHz or less, the gradation is improved, but it is difficult to eliminate fog. This is because, in the low frequency region where the number of reciprocating movements of the toner is small, the pressing force of the toner against the latent image holding member due to the developing bias electric field becomes too strong even in the non-image area, and the toner is stripped off by the reverse developing bias electric field. This is considered to be because the toner adhered to the non-image area cannot be completely removed. When the frequency is 5.0 kHz or more, a bias electric field on the reverse development side is applied before the toner sufficiently contacts the latent image holding member 1, so that the developability is significantly reduced. That is, the toner itself cannot respond to the high-frequency electric field.

In particular, according to the present invention, the frequency of the alternating bias electric field is 1.5 k.
The optimum image quality was shown from Hz to 3kHz.

The duty ratio that satisfies the alternating bias electric field waveform of the present invention may be less than approximately 50%, but in consideration of image quality, the duty ratio is preferably 10% and 40%. When the duty ratio is 40% or more, the above-mentioned disadvantage is conspicuous and not very preferable, and the effect of the present invention is not so much seen. If the duty ratio is 10% or less, the above-described alternating bias electric field response of the toner itself is deteriorated, and the developability is reduced. Particularly, the optimum value of the duty ratio is 15% ≦ duty ratio ≦ 35%.

Further, as the alternating bias waveform, for example, a waveform such as a rectangular wave, a sine wave, a sawtooth wave, and a triangular wave can be applied.

Examples of the binder resin used in the magnetic toner of the present invention include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, and p-methylstyrene.
-Phenylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, p-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert-butylstyrene, pn-hexylstyrene, Styrene such as pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, and derivatives thereof; ethylene-unsaturated monoolefins such as ethylene, propylene, butylene, and isobutylene Unsaturated vinylenes such as butadiene; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide and vinyl bromide; vinyl esters such as vinyl acetate, vinyl propionate and vinyl benzoate; methyl methacrylate, methacrylic Ethyl acrylate, propyl methacrylate, n-butyl methacrylate, methacryl Isobutyl acid, methacrylic acid n
-Octyl, dodecyl methacrylate, methacrylic acid-2
Α-methylene aliphatic monocarboxylic esters such as ethylhexyl, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate and diethylaminoethyl methacrylate; methyl acrylate, ethyl acrylate, n-butyl acrylate, acrylic acid Acrylic esters such as isobutyl, propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate and phenyl acrylate;
Vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and methyl isopropenyl ketone; N-vinyl pyrrole;
N-vinyl carbazole, N-vinyl indole, N-
N-vinyl compounds such as vinyl pyrrolidone; vinyl naphthalenes; acrylic or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide; vinyl compound derivatives having a carboxyl group such as acrylic acid, methacrylic acid, maleic acid, and fumaric acid A half ester such as maleic acid half ester or fumaric acid half ester; a homopolymer or a copolymer containing a monomer component composed of a vinyl compound such as maleic anhydride, maleic ester, or fumaric acid ester derivative;
Polyester, polyurethane, epoxy resin, polyvinyl butyral, rosin, modified rosin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, haloparaffin, paraffin wax, etc. alone or Can be mixed and used. Above all, a polyester resin is particularly preferably used as a binder resin in consideration of development characteristics.

The composition of the polyester resin used in the present invention is as follows.

As the dihydric alcohol component, ethylene glycol, propylene glycol, 1,3-butanediol, 1,4
-Butanediol, 2,3-butanediol, diethylene glycol, triethylene glycol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 2-ethyl-1,3-hexanediol, hydrogenated bisphenol A Or a bisphenol represented by the formula (A) and a derivative thereof; (Wherein R is an ethylene or propylene group, x and y are each an integer of 0 or more, and the average value of x + y is 0 to 10.) Diols represented by the formula (B); Is mentioned.

Examples of the divalent acid component include benzenedicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid, and phthalic anhydride or anhydrides thereof, and lower alkyl esters; alkyl dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and azelaic acid. Acids or anhydrides thereof, lower alkyl esters; alkenyl succinic acids or alkyl succinic acids such as n-dodecenyl succinic acid, n-dodecyl succinic acid or anhydrides thereof, lower alkyl esters; fumaric acid, maleic acid, citraconic acid, itaconic acid And dicarboxylic acids and their derivatives, such as unsaturated dicarboxylic acids or their anhydrides and lower alkyl esters.

Further, a trivalent or higher valent alcohol component and a trivalent or higher valent acid component which also serve as a crosslinking component can be used in combination.

Examples of the trihydric or higher polyhydric alcohol component in the present invention include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2, Four
-Butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxy Benzene and the like.

Further, as the trivalent or higher polycarboxylic acid component in the present invention, for example, trimellitic acid, pyromellitic acid, 1,1,
2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-
Naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, tetra (methylenecarboxyl) methane, 2,7,8
Octanetetracarboxylic acid, empol trimer acid, and their anhydrides and lower alkyl esters; (Wherein X is an alkylene group or alkenylene group having 5 to 30 carbon atoms having at least one side chain having 3 or more carbon atoms), and polyhydric compounds such as anhydrides and lower alkyl esters thereof. Examples include carboxylic acids and derivatives thereof.

The alcohol component used in the present invention is 40-60mo
l%, preferably 45-55 mol%, as acid component 60-40mo
l, preferably 55 to 45 mol%.

The trivalent or higher polyvalent component accounts for 5 to 60 mol of all components.
% Is desirable.

The alcohol component of the polyester resin preferred in the present invention is, for example, a bisphenol derivative represented by the formula (A), and the acid component is phthalic acid, terephthalic acid, isophthalic acid or anhydride thereof; succinic acid,
n-dodecenyl succinic acid or its anhydride; dicarboxylic acids such as fumaric acid, maleic acid, and maleic anhydride; and trimellitic acid or its tricarboxylic acid anhydride, and the like.

This is because the polyester resin obtained with these acids and alcohols has good fixability and excellent offset resistance as a heat roller fixing toner having sharp melting characteristics.

Further, the glass transition temperature of the polyester resin obtained here is 50 to 70 ° C., preferably 55 to 65 ° C., and the number average molecular weight n is 1,500 to 10,000, preferably 2,000 to 7,000, and the weight average molecular weight w is 6,000 to 200,000. Is 10,000-15
Desirably, it is 0,000.

It is desirable that the acid value is 100 or less, preferably 50 or less, and the hydroxyl value is 60 or less, preferably 30 or less.
This is because when the number of terminal groups of the molecular chain increases, the toner becomes more environmentally dependent on the charging characteristics of the toner when it is made into a toner.

Here, the acid value and hydroxyl value of the resin were measured by the following method.

A 2 to 10 g sample is weighed in a 200 to 300 ml Erlenmeyer flask, and about 50 ml of a mixed solvent of methanol: toluene = 30: 70 is added to dissolve the resin. If the solubility is poor, a small amount of acetone may be added. Using a mixed indicator of 0.1% bromthymol blue and phenol red, titrate with a pre-specified N / 10 potassium hydroxide-alcohol solution, and calculate the acid value from the consumption of the alcoholic potassium solution by the following formula (4). I asked.

Acid value = KOH (ml number) × N × 56.1 / sample weight (g number) (4) (where N is a factor of N / 10 KOH) Also, the hydroxyl value is determined by adding an excess of an acetylating agent such as acetic anhydride to the sample. Acetylation is performed by heating, and the ketone value of the produced acetylated product is measured, and then calculated according to the following formula (5).

(However, A represents the ketone value after acetylation, and B represents the saponification value before acetylation.) Examples of the magnetic material contained in the magnetic toner of the present invention include iron oxides such as magnetite, maghematite, and ferrite. And iron oxides containing other metal oxides; metals such as Fe, Co, Ni, or these metals and Al, Co, Cu, Pb, Mg, Ni,
Examples include alloys with metals such as Sn, Zn, Sb, Be, Bi, Cd, Ca, Mn, Se, Ti, W, and V, and mixtures thereof.

These ferromagnetic materials have an average particle size of about 0.1 to 2 μm, and have a magnetic characteristic at 10 Ke applied of a coercive force of 20 to 150 e, a saturation magnetization of 50 to 200 emu / g (preferably 50 to 100 emu / g), and a residual magnetization of 2 to 200 emu / g. A value of ~ 20 emu / g is desirable.

In the magnetic toner of the present invention, it is preferable to use a charge control agent internally or externally added to the toner so as to obtain a triboelectric charge amount suitable for a developing method.

As the positive charge control agent used in the present invention, known agents can be used. For example, nigrosine and its modified products such as aliphatic metal salts, quaternary ammonium salts, diorganotin oxides, diorganotin borates, etc. can be used alone or in combination.
More than one kind can be used in combination. Of these, nigrosine and quaternary ammonium salts are particularly preferably used.

Also, the general formula Can be used as a positive charge control agent, or a copolymer with a polymerizable monomer such as styrene, an acrylate or a methacrylate as described above. (Part or all of).

On the other hand, known negative charge control agents used in the present invention can be used, for example, carboxylic acid derivatives and metal salts thereof,
An alkoxylate, an organometallic complex, a chelate compound or the like can be used alone or in combination of two or more. Among these, acetylacetone metal complexes, salicylic acid metal complexes, naphthoic acid metal complexes, and monoazo metal complexes are particularly preferably used.

In the toner of the present invention, any appropriate fragrance or dye can be used as a colorant, if necessary.

Further, an additive may be added to the toner of the present invention as needed. Such additives include lubricants such as, for example, Teflon, polyvinylidene fluoride, metal salts of fatty acids;
Abrasives such as cerium oxide, strontium titanate, silicon carbide; colloidal silica, alumina, or silica, alumina treated with a silicone oil, various modified silicone oils, silane coupling agents, silane coupling agents having a functional group, etc. Fluidity imparting agents, casing inhibitors; conductivity imparting agents such as carbon black tin oxide; and fixing aids such as low molecular weight polyethylene. Further, for the purpose of improving the releasability at the time of hot roll fixing, low molecular weight polyethylene, low molecular weight polypropylene,
A wax-like substance such as microcrystalline wax, carnauba wax and sasol wax can be added to the toner of the present invention in an amount of about 0.5 to 5% by weight.

In producing the toner according to the present invention, the above-mentioned toner constituent materials are sufficiently mixed by a ball mill or other mixer, then kneaded well using a heat kneader of a hot roll kneader or an extruder, and cooled and solidified. , Mechanical pulverization, a method of obtaining a toner by classification, other, for example, after dispersing the constituent materials in a binder resin solution,
A method of obtaining a toner by spray drying; or a method of mixing a monomer to form a binder resin with a predetermined material to form an emulsified suspension and then polymerizing to obtain a toner; or a core material and a shell In a so-called microcapsule toner made of a material, a method of including a predetermined material in a core material, a shell material, or both of them can be applied.

In the present invention, the charge amount of the toner layer on the toner carrier was determined using a so-called suction Faraday cage method. In this suction-type Faraday cage method, the outer cylinder is pressed against the toner carrier to suck all the toner on a certain area on the toner carrier, collected by a filter of the inner cylinder, and the toner carrying amount is calculated based on the weight increase of the filter. The weight of the toner layer on the body can be calculated. At the same time, the charge amount on the toner carrier can be obtained by measuring the charge amount accumulated in the inner cylinder electrostatically shielded from the outside.

[Examples] Hereinafter, the present invention will be described more specifically with reference to Examples.
This does not limit the invention in any way. FIG. 9 shows the relationship between the volume average particle diameter of the magnetic toner of the present invention and the amount of charge on the toner carrier, and FIG.
The relationship between the volume% of 16 μm or more and the number% of 8 μm or less is shown.

Example 1 Crosslinked polyester resin 100 parts by weight Magnetic iron oxide 60 parts by weight Low molecular weight ethylene-3 parts by weight Propylene copolymer 3,5-di-tert-butyl 2 parts by weight Chromium salicylate complex After the above materials were mixed well in a blender, they were kneaded with a biaxial kneading extruder set at 150 ° C. The obtained kneaded material was cooled, coarsely pulverized by a cutter mill, and then finely pulverized using a fine pulverizer using a jet stream, and the obtained finely pulverized powder was classified by a fixed wall type air classifier. A classified powder was produced. Furthermore, the ultrafine powder and the coarse powder are simultaneously strictly classified and removed by a multi-segment classification device (Nippon Mining Co., Ltd. Elbow Jet Classifier) using the Coanda effect to obtain black fine powder (magnetic toner). Obtained. Table 1 shows the particle size distribution of the magnetic toner.

0.4 parts by weight of hydrophobic dry silica (BET specific surface area: 300 m ² / g) was added to 100 parts by weight of the obtained black fine powder magnetic toner,
Mix with a Henschel mixer.

The alternating bias waveform of the magnetic toner was changed to 6th in an image forming apparatus having the above-described amorphous silicon photoreceptor.
Table 2 shows the result of copying 10,000 sheets using the alternating bias power supply shown in the figure (duty ratio 20%) and the charge amount of the toner on the toner carrier measured during the test. Obviously, the image was excellent in gradation, free of fog and high in image density. Further, no toner carrier memory was observed even in durability. Good results were also obtained in a copy test in an environment of 15 ° C. and 10% RH.

Example 2 In place of the magnetic toner used in Example 1, the particle size distribution as shown in Table 1 obtained by changing the addition amount of the magnetic substance, the charge control agent, and the silica and controlling the pulverization and classification conditions was obtained. A copy test was performed in the same manner as in Example 1 except that the toner having the toner was used. The results are shown in Table 2, and a stable and clear image was always obtained.

Example 3 An alternating bias waveform is shown in FIG.
%) By using a developing bias power supply and changing the addition amount of the magnetic substance in place of the magnetic toner used in Example 1 and controlling the conditions for finely pulverizing and classifying, the particles have a particle size distribution as shown in Table 1. A copy test was performed in the same manner as in Example 1 except that toner was used. The results are shown in Table 2, and a stable and clear image was always obtained.

Good results were also obtained in a copy test under a 15 ° C., 10% RH environment.

Example 4 Styrene-butyl acrylate 100 parts by weight-divinylbenzene copolymer (polymerization monomer weight ratio 75-24-1 w: 300,000) Magnetic iron oxide 60 parts by weight Low molecular weight ethylene-4 parts by weight Propylene copolymer Monoazo metal Complex 2 parts by weight The particle size distribution of the magnetic toner obtained in the same manner as in Example 1 using the above materials is shown in Table 1.

Using this toner, an alternating bias waveform is shown in FIG. 8 (duty ratio 35%). A copy test was performed in the same manner as in Example 1 except that a developing bias power supply was used.

The results are shown in Table 2, and an image of clearly excellent image quality was obtained.

Example 5 The particle size distribution as shown in Table 1 obtained by controlling the amount of addition of the magnetic substance, the charge control agent, and silica instead of the magnetic toner used in Example 4 and controlling the pulverization classification conditions was obtained. A copy test was carried out in the same manner as in Example 1 except that the developing bias power source shown in FIG. 7 (duty ratio: 30%) was used and the developing bias power supply was used. The results are shown in Table 2. As a result, a high-quality image was always stably obtained except that a light toner carrier memory was observed.

Good results were obtained in the copy test under the environment of 15 ° C and 10% RH.

Embodiment 6 An alternating bias waveform is shown in FIG.
%) A copy test was performed in the same manner as in Example 1 except that a developing bias power supply was used. Table 2 shows the results.
In this case, good results were obtained as in Example 1.

Comparative Example 1 Crosslinked polyester resin 100 parts by weight Magnetic iron oxide 50 parts by weight Low molecular weight ethylene-4 parts by weight Propylene copolymer 3,5-di-tert-butyl 2 parts by weight Chromium salicylate complex Table 1 shows the particle size distribution of the magnetic toner obtained in the same manner as in Example 1 using the above materials.

Using this toner, a copy test was performed in the same manner as in Example 1. Table 2 shows the results.

The image density was low due to hollow, and fogging also occurred. Further, toner carrier memory occurred. In addition, 15 ℃, 10
In a copy test in a% RH environment, an image was severely deteriorated in density due to durability and poor in gradation.

Comparative Example 2 A copy test was performed in the same manner as in Example 1 except that a toner having a particle size distribution as shown in Table 1 obtained by controlling the pulverization and classification conditions from the crushed product obtained in Example 1 was used. Was done. The results are shown in Table 2. As a result, an image having a slightly low density was obtained at the initial stage, but the image was gradually roughened when copying was repeated, fogging occurred, and the gradation was deteriorated.

Comparative Example 3 Styrene butyl acrylate 100 parts by weight-divinylbenzene copolymer (polymerization monomer weight ratio 75-24-1 w: 300,000) Magnetic iron oxide 60 parts by weight Low molecular weight ethylene-4 parts by weight Propylene copolymer 3,5 -Di-tert-butyl 3 parts by weight Zinc salicylate complex The particle size distribution of the magnetic toner obtained in the same manner as in Example 1 using the above materials is shown in Table 1.

Using this toner, a copy test was performed in the same manner as in Example 1. The results are shown in Table 2. As a result, a good image was obtained in the initial stage, but when copying was repeated, the density was reduced, and the toner carrier memory was also observed. 15 ℃, 10% R
This tendency was remarkable in the copying test under the H environment.

Comparative Example 4 Instead of the magnetic toner used in Comparative Example 3, the particle size distribution as shown in Table 1 was obtained by changing the amount of the magnetic substance, charge control agent, silica added, and controlling the conditions for finely pulverized classification. A copy test was performed in the same manner as in Example 1 except that toner was used. The results are shown in Table 2. The image density was low, fogging occurred, and the gradation was poor.

Comparative Example 5 The alternating bias waveform is shown in FIG.
%) A copy test was performed in the same manner as in Example 1 except that a developing bias power supply was used. Table 2 shows the results.
The gradation was poor, and fog was slightly observed. In addition, the toner carrier memory has come to be seen due to durability.

Evaluation criteria for Examples 1 to 6 and Comparative Examples 1 to 5 are shown below.

Fog ○: No background fog even when viewed with a loupe.

○ △: Fog is slightly visible when viewed with a loupe, but is not visually observed.

Δ: Although fog is slightly visible, it is practically acceptable.

Δ ×: Fine spots are clearly visible on a white background.

×: Larger spots are visually observed, and the white background is slightly gray.

Gradation ○: Vivid and faithful reproduction from black to halftone to white background even in photocopying.

△: The character image was clearly and faithfully reproduced, although the copying of the photograph was somewhat inferior.

Δ: The original chart was faithfully reproduced.

C: Poor reproducibility of thin characters.

×: Not only characters but also reproducibility of thick lines are poor.

Toner carrier memory ：: Does not occur.

○ △: It may be very weak depending on the original chart.

Δ: Despite the occurrence of memory, it is hardly noticeable for a text document.

Δ ×: clearly seen on the image.

×: The image is disturbed by the memory.

[Effects of the Invention] Since the present invention is a magnetic toner having a specific particle size distribution and a triboelectric charge amount, it exhibits the following excellent effects when applied to a developing method using an asymmetric developing bias.

(1) An image having excellent durability, high image density and no fog is provided.

(2) An extremely high-quality image rich in gradation is provided.

(3) The image density does not decrease even in a low-temperature and low-humidity environment.

(4) No toner carrier memory is generated even by long-term continuous copying.

[Brief description of the drawings]

6 to 8 are schematic diagrams of alternating bias waveforms in the developing method used in the present invention, FIGS. 1 and 3 are schematic diagrams of alternating bias waveforms used in other developing methods, and FIG. 2 is a schematic diagram of flying adhesion of toner. FIG. 4 is a schematic diagram of an alternating bias waveform showing the developing side bias (a) and the reverse developing side bias (b). FIG. 5 is a schematic explanatory view of the developing device. FIG. 9 is a volume average particle of the magnetic toner. FIG. 10 is a graph plotting the diameter and the value of the triboelectric charge amount (μc / g) on the toner carrier, and FIG. 10 shows the number% of the number distribution of the magnetic toner particle size of 8 μm or less and the volume% of the volume distribution of 16 μm or more in the volume distribution. It is the graph which plotted the value of and. In FIG. 5, T is a toner, T ₁ is a thin toner layer, T ₂ is a toner image, A is a development area, α is a gap between a latent image holding member and a toner holding member, S ₀ is an alternating bias applying means, S ₁ Is a DC bias applying means, 1 is a latent image holding member, 21 is a hopper, 22 is a toner carrier, 23 is a magnetic generating means, 24 is a doctor blade, and 27 is a stirring member.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masaaki Taya 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Masaki Uchiyama 3-30-2 Shimomaruko, Ota-ku, Tokyo Within Canon Inc. (58) Field surveyed (Int.Cl. ⁶ , DB name) G03G 9/083

Claims (1)

(57) [Claims] 1. A developing device in which a latent image holding member for holding an electrostatic image and a toner holding member for holding a magnetic toner on a surface are arranged at a predetermined gap in a developing section. It is transported to the development section with the thickness being regulated to be thinner than
A DC voltage and an asymmetrical alternating voltage are applied between the toner carrier and the latent image holding member, and the developing-side voltage component of the alternating bias voltage including the DC bias voltage is the same as the reverse developing-side voltage component (stripping voltage component). Or, in a magnetic toner having at least a binder resin and a magnetic powder used in a developing method in which the application time of the developing-side voltage is made smaller than that of the reverse developing-side voltage, the magnetic toner has a particle diameter of 8 μm or less. 33% by number or less of magnetic toner particles having
The magnetic toner particles having a number average particle diameter of 8 μm to 11 μm, containing 16% by volume or less of magnetic toner particles having a particle diameter of 16 μm or more, and having a volume average particle diameter of 10 μm to 14 μm. The triboelectric charge amount on the body and the volume average particle diameter of the magnetic toner satisfy the following general formula (1), The magnetic toner has the following general formula (2)
A magnetic toner characterized by satisfying the following.