JP3017664B2 - Non-magnetic one-component developing toner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing roller for developing an electrostatic latent image and a toner used in a non-magnetic one-component developing system in which an electrostatic latent image carrier is in a contact type. In particular, the present invention relates to a non-magnetic one-component toner that can be used in a small low-speed printer employing an electrophotographic system.

[0002]

2. Description of the Related Art A conventional developing method using an electrostatic latent image and toner is roughly classified into a developing method using a two-component developer mainly composed of a toner and a carrier, or a developing method using only a toner. There is a developing method using a component developer. Generally, a developing method using a two-component developer using a non-magnetic toner and a carrier has the following disadvantages as compared with a developing method using a one-component developer. A toner concentration sensor for controlling the mixing ratio between the toner and the carrier is required. The durability of the carrier is limited, and when used for a long period of time, it is necessary to replace not only the toner but also the developer. Since a stirring mechanism for mixing the developer and the toner is required, the size of the developing machine tends to increase. On the other hand, the disadvantages of the developing method using a magnetic one-component developer include the following. The charging member is a developing roll or a blade, and the charging stability is poor and the charging ability is weak as compared with the case where the carrier is used as the charging member. The precision of the developing machine for uniformly forming the magnetic brush is required. The magnetic toner is inferior to the two-component non-magnetic toner in that the transferability, the fixability, the dependency on the environmental humidity are large, and the damage to the photoreceptor is large. Considering these problems comprehensively and also considering miniaturization of the apparatus, a developing method using a non-magnetic one-component toner is extremely effective. In recent years, several developing methods have been put into practical use. I have.

[0003]

In the non-magnetic one-component developing system, most of the devices have a developing roll carrying toner and an electrostatic latent image carrier in contact with each other. Blades and toner supply rolls are disposed in contact with each other. According to this developing method, the toner can be charged relatively easily, but the toner is easily fused to a member such as a blade or a developing roll due to the large number of contact portions with the developing roll. Therefore, as a solution, a high pressure may be applied to the toner by using a styrene / (meth) acrylate copolymer resin having a high glass transition temperature (Tg) or a polyester resin having a large gel component as a main material of the toner. A toner is designed so that fusion does not easily occur even when the temperature rises due to friction. However, when this solution is implemented, it is necessary to set the fixing temperature to a relatively high temperature. Therefore, in view of energy consumption, the developing method is not suitable for a recent power saving type apparatus.

[0004] Many of the small optical printers released in recent years are equipped with an electrostatic latent image carrier (photoreceptor) carrying negative charges. In this case, a roller is used to prevent ozone generation. In many cases, a charging device of a brush type or a brush type is mounted. Therefore, damage to the electrostatic latent image carrier is greater than when a corona charging device is mounted,
There was a problem with the durability of the printer.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and the means are as follows. In other words, the invention according to claim 1 is a developing device having at least a developing roll for carrying and transporting toner, a toner layer thickness regulating member provided in pressure contact with the developing roll, and a developing device provided in contact with the developing roll. For use in a reversal developing system equipped with a positively-charged electrostatic latent image carrier (photoreceptor) obtained by the method described above. The toner has a volume average particle diameter (D ₅₀ ), a BET multipoint method (nitrogen adsorption method). The specific surface area (S) measured in the above and D ₅₀ × S are within the following range,
And blended positively chargeable charge control agent, the toner particle surface
0.1-2.0% by weight of hydrophobized silica and spherical
A non-magnetic one-component developing toner having 0.3 to 1.5% by weight of magnetic powder adhered thereto . 8.0 ≦ D ₅₀ ≦ 13.0 (μm) 1.0 ≦ S ≦ 2.2 (m ² / g) 12.0 ≦ K × D ₅₀ × S ≦ 20.0 (where K is the true specific gravity of the toner) The invention according to claim 2, wherein the binder resin, which is a main component of the toner, is a styrene-acrylate copolymer, a styrene-methacrylate copolymer, or a styrene-acrylate-methacrylate copolymer. The non-magnetic one-component developing toner according to claim 1, wherein the resin has an acrylic component amount of 20 to 40% by weight. Claim 3 is characterized in that in the above, the carbon content in the toner is 2 to 8% by weight .

Next, a developing method to which the toner of the present invention is applied will be described in detail. FIG. 1 is a schematic configuration diagram of a developing device using the non-magnetic one-component toner of the present invention.
In the figure, 1 is a positively charged photosensitive drum which is a cylindrical electrostatic latent image carrier, 2 is a hopper, 3 is toner, 4a is a toner layer thickness regulating member, and 4b is a fixing member of the toner layer thickness regulating member. ,
Reference numeral 5 denotes a developing roller using an elastic rubber sleeve, 6 denotes a toner leakage prevention and scraping member, and 7 denotes a stirrer. In this developing device, on the photosensitive drum 1,
An electrostatic latent image is formed by a known electrophotographic method. The toner 3 is contained in the hopper 2, and the toner is carried by the layer thickness regulating member 4a on the sleeve of the developing roller 5 so as to have a constant layer thickness, and is conveyed. The sleeve of the developing roller and the photosensitive drum 1 are 1 to 5 mm
It is installed in contact with the nip width. The toner carried by the developing roller 5 is conveyed by the rotation of the developing roller, comes into contact with the photosensitive drum 1 having an electrostatic latent image, and the electrostatic latent image is visualized.

The present invention relates to a toner used in the above-mentioned developing method. The feature of the present invention is that the volume average particle diameter (D ₅₀ ) and the specific surface area (S) of the toner fall within the following numerical limits. The use of the object solves the problems of the prior art. 8.0 ≦ D ₅₀ ≦ 13.0 (μm) 1.0 ≦ S ≦ 2.2 (m ² / g) 12.0 ≦ K × D ₅₀ × S ≦ 20.0 (where K is the true specific gravity of the toner) in a) in the above equation, the volume average particle diameter (D ₅₀₎ showed a volume-based integrated 50% value by Coulter counter type TA-II, in addition, the specific surface area (S) is measured by a BET multiple method by nitrogen adsorption method Is calculated. Further, the true specific gravity (K) of the toner is calculated as 1.15 g / cm ³ . In this case, the volume average particle diameter of the toner is 8.0 μm.
When the diameter is smaller than m, fusing of the toner to the developing roll or the like and fogging on the non-image area occur, while when it is larger than 13.0 μm, poor image quality of characters and lines occurs. When the specific surface area of the toner is smaller than 1.0 m ² / g, or when K ×
If D ₅₀ × S is less than 12.0, the surface of the toner particles is too smooth, the charging performance is reduced, and image defects such as generation of fog and toner scattering around characters are increased. The specific surface area of the toner is 2.2 m ² / g.
If D ₅₀ × S is larger than 20.0, the unevenness of the toner surface increases, the friction with the toner layer thickness regulating member or the like increases, and the toner temperature rises locally and the toner temperature increases. The fusion of the toner to the layer thickness regulating member and the developing sleeve occurs. In addition, a more preferable range of the specific surface area is 1.0 to 2.0 m ² / g. In order to make the specific surface area and K × D ₅₀ × S within the above ranges, spheroidization or surface treatment is required after pulverization and classification. Specifically, it is conceivable to allow the toner particles to pass through a surface reforming machine represented by Nara Machinery Co., Ltd.'s trade name “Nara Hybridizer” or a hot air flow.

[0008] Further, the toner of the present invention has a toner particle surface.
Hydrophobic silica and spherical magnetic particles
It is required that fine powder of conductive powder be attached. In that case
Hydrophobic treatment of the surface with the content to the toner particles by weight%
0.1 to 2.0% by weight of silica and 0.3 to 0.3% of magnetic powder
By adjusting to 1.5% by weight, the rise of charging
And an image with less fog can be obtained. this
If the silica content is less than 0.1% by weight, the fluidity of the toner is
Poor, on the other hand, more than 2.0 wt% fog
It is not preferable because it is produced. Also, the amount of magnetic powder added is 0.3
If the amount is less than 10% by weight, the effect of charging rise cannot be exhibited.
On the other hand, if the content is more than 1.5% by weight, the toner is excessively charged, resulting in poor transfer.
It is not preferable because it shifts. In addition, spherical magnetic powder has eight sides.
Of electrostatic latent image carrier compared to magnetic powder of body or needle type
The effect of preventing damage to the surface and extending the service life
Play.

Also, the toner of the present invention prevents ozone generation.
Non-contact type charging device (corona charging device etc.)
Longer life of electrostatic latent image carrier by using
To be positively charged organic optical semiconductor (OPC) or Se
The development of the reversal development method using a representative electrostatic latent image carrier
Used for imaging systems. Therefore, the toner of the present invention
-For positive charging of nigrosine and quaternary ammonium salts
And a charge control agent used as a binder. Sa
In addition, styrene / acrylic acid
Stel copolymer, styrene / methacrylic acid ester copolymer
Coalescence or styrene / acrylate / methacrylic
Preferred are those selected from luate ester copolymers,
The acrylic component content of the resin is preferably 20 to 40% by weight.
Or 25% by weight to 35% by weight
In addition to improving the fixability of
This constitutes a toner with less blur. Acrylic
When the amount is less than 20% by weight, the positive chargeability is easily inhibited.
And a system with a weak charging capability such as the non-magnetic one-component developing system
In the system, toner particles charged to the opposite polarity are easily generated.
If the acrylic component is more than 40% by weight, the volume of the toner
The specific resistance decreases, the absolute value of the charge decreases, and the image deteriorates.
Tends to occur. Further, by setting the carbon content in the toner to 2 to 8% by weight, preferably 3 to 7% by weight, a sufficient charge amount can be obtained even with a weak charge providing ability of non-magnetic one-component development.
It is intended to obtain an image with sufficient image density and less fog. 8 carbons in toner
If the content is more than 10% by weight, the volume resistivity of the toner is reduced, and the charging performance is deteriorated. If the amount of carbon is less than 2% by weight, the image density becomes insufficient.
Hereinafter, the present invention will be described in detail.

[0010]

According to the present invention, there is provided a developing method in which a developing roller using a non-magnetic one-component toner and an electrostatic latent image carrier are in contact with each other. As a result of intensive studies to minimize the fusion of the toner to the electrostatic latent image carrier, the toner was fused to each member by setting the volume average particle diameter and specific surface area of the toner within a certain range. In this way, the life of the developing device and the electrostatic latent image carrier in the non-magnetic one-component system was successfully minimized. Hereinafter, the action mechanism of the specific surface area of the toner, which is a main component of the present invention, will be described.

That is, as the specific surface area of a toner having a certain particle diameter increases, the surface shape of the particles becomes coarser.
The surface area in contact with the charging member increases due to increased irregularities, etc., and the charging property improves, but the probability of local temperature rise due to friction with the member increases, and toner fusion to each member also increases. As a result, the life of the developing device and the electrostatic latent image carrier is shortened. On the other hand, the smaller the specific surface area, the smoother the surface, and eventually approaches a true sphere, but if it is too smooth, the surface that can contribute to charging decreases, causing a decrease in chargeability and deteriorating image quality. cause. In order to solve this problem, any modification on the device side, such as enlarging the area of the charging member or increasing the pressure, causes a problem that the fusion of toner increases. The present invention achieves the object by paying attention to the specific surface area and the volume average particle diameter, combining them within a specific numerical limitation range, and applying to the developing method specified in claim 1.

Examples and Comparative Examples (the following parts are parts by weight) The mixture consisting of the above blend is melt-kneaded in a melt-kneader,
Rolled into a sheet through two rolls, cooled, coarsely pulverized into chips of 3 mm square or less by a hammer mill, then pulverized by a jet air type pulverizer, and further charged positively by a process of an air flow classifier, And a volume average particle diameter (D ₅₀ ) determined by a Coulter counter is 7.2 μm,
8.4 μm, 9.6 μm, 10.5 μm, 11.4 μm
m, 13.0 μm of toner particles were obtained.

Further, as a post-treatment, for each of the toner samples, HVK-2150 (manufactured by Hoechst) was added to HVK-2150 (positive chargeable silica fine powder) per 100 parts by weight of toner.
5 parts by weight and magnetic powder MAT305 (manufactured by Toda Kogyo KK)
0 parts by weight, and stirred and mixed with a Henschel mixer to obtain toner particles No. 1 for non-magnetic one-component development. 1-6 were obtained. The sample No. For each of Nos. 1 to 6, before the post-treatment, the toner particles are subjected to a surface treatment based on the application of a mechanical compressive force and a frictional force by "Nara Hybridizer" (manufactured by Nara Machinery Co., Ltd.). And sample No. Samples 7 to 12 were obtained. Sample No. 1
Sample No. 6 to No. 6 were subjected to a heat treatment at a jacket temperature of 55 ° C. for 15 minutes using a Henschel mixer. 13-18 were obtained. For the 18 types of toner samples, a photoconductor of a 4029 printer manufactured by IBM as a printer equipped with a developing device adopting a non-magnetic one-component developing system and a positively charged electrostatic latent image carrier is used as an OPC, A printing test was performed using a photoconductor whose charging polarity was modified so as to be positive. Table 1 shows the results.

[0014]

[Table 1]

The evaluation method of the printing characteristics is as follows. (1) Image density (ID); Macbeth reflection densitometer RD9
Image density of the solid image of 1 cm ² by 14 (2) Fog (BG); Nippon Denshoku colorimeter colorimeter Z-
1001DP (3) Black solid; Visual evaluation of black solid image on the entire surface of A4 size copy paper (4) Image quality; Visual evaluation of character and line image quality (5) Fusing; Development roll and toner after printing 20,000 sheets Visual evaluation of the presence or absence of toner fusion to the layer thickness regulating member

The evaluation of solid black, image quality and fusion was performed as follows. (Evaluation of solid black) ×: Image density reduction or blurring occurs after the first rotation of sleeve in A4 full solid black image △: After second rotation of sleeve in A4 full black solid image Image density reduction or blurring occurs. ○: Image density reduction and no blurring in A4 full black solid image (Evaluation of image quality) ×: Lots of toner scatter around characters, 1-dot thin line of 600 DPI : The scattering of the toner around the characters is slightly conspicuous, but the fineness of one dot fine line of 600 DPI is good. ○: The scattering of the toner around the characters is not conspicuous, and the fineness of one dot of 600 DPI is small. Good reproducibility (evaluation of fusion) ×: fusion of toner was observed on the toner layer thickness regulating member or the sleeve of the developing roll, and image defects such as streaks caused by this in the image △: -Some toner fusion is observed on the layer thickness regulating member or sleeve, but there are no image defects such as streaks in the image and there is no practical problem. As is clear from Table 1, Sample No. 1 which is the non-magnetic one-component developing toner of the present invention is not fused. Nos. 8 to 12 and Nos. 15-18
Does not cause the fusion of the toner to the toner layer thickness regulating member or the developing roll, which tends to occur in the prior art. The image density was 1.37 to 1.49 and fog was 0.8 in the course of continuous copying of 20,000 sheets from the initial number of prints.
It was confirmed that a good condition of 8 or less was maintained, and that the image quality of solid black, characters and line portions was also good. On the other hand, the sample No. of the comparative example. Nos. 1 to 7 and No. 1; Nos. 13 and 14 have a specific surface area of 2.2 m ² / g or more or KXD ₅₀ of the toner.
Since xS was 20 or more, the unevenness of the toner surface was increased as described above, and the toner was fused.

[0017]

According to the present invention, the toner is not fused to the toner layer thickness regulating member or the developing roll by limiting the volume average particle diameter, the specific surface area and the product of the two to a specific range. Moreover, it is possible to provide a toner capable of maintaining good image density and good image quality.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of an apparatus used in the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor drum 2 hopper 3 toner 4a toner layer thickness regulating member 4b fixing member 5 developing roller 6 toner leakage prevention and scraping member 7 stirrer

──────────────────────────────────────────────────続 き Continuing on the front page (51) Int.Cl. ⁷ Identification code FIG03G 9/08 361 301 (72) Inventor Ryozo Okuno 3-1, Yohombacho, Shizuoka-shi, Shizuoka Pref. (56) References JP-A-3-259161 (JP, A) JP-A-4-338977 (JP, A) JP-A-6-202460 (JP, A) (58) Fields surveyed (Int. (Cl. ⁷ , DB name) G03G 9/08

Claims (3)

(57) [Claims] 1. A developing device having at least a developing roll for carrying and transporting a toner, a toner layer thickness regulating member provided in pressure contact with the developing roll, and a positive charge provided in contact with the developing roll. For use in a reversal developing system equipped with a neutral electrostatic latent image carrier, having a volume average particle diameter (D ₅₀ ) of the toner and a specific surface area (S) measured by a BET multipoint method (nitrogen adsorption method). , And D ₅₀ × S are within the following range, and a positively chargeable charge control agent is blended ,
0.1 to 2. Hydrophobized silica is applied to the surface of the toner particles.
0% by weight and 0.3 to 1.5% by weight of spherical magnetic powder
Non-magnetic one-component developing toner which is characterized in that is. 8.0 ≦ D ₅₀ ≦ 13.0 (μm) 1.0 ≦ S ≦ 2.2 (m ² / g) 12.0 ≦ K × D ₅₀ × S ≦ 20.0 (where K is the true specific gravity of the toner) Is) 2. A binder resin, which is a main component of the toner, is selected from a styrene / acrylate copolymer, a styrene / methacrylate copolymer or a styrene / acrylate / methacrylate copolymer.
2. The non-magnetic one-component developing toner according to claim 1, wherein the amount of the acrylic component of the polymer is 20 to 40% by weight. 3. The non-magnetic one-component developing toner according to claim 1, wherein the carbon content of the toner is 2 to 8% by weight.