JPH096038A - Toner for nonmagnetic one-component development - Google Patents

Abstract

PURPOSE: To obtain a toner used in a nonmagnetic one-component developing system in which a developing roll for developing an electrostatic charge image and an electrostatic latent image carrier (photoreceptor) are kept in contact with each other and not causing the fusion of the toner to the developing roll, etc. CONSTITUTION: This toner is a toner used in a reversal developing system mounted with a developing device with at least a developing roll for carrying and transferring a toner and a member regulating the thickness of a toner layer disposed in press contact with the developing roll and further mounted with an electrostatic latent image carrier having positive electrification ability disposed in contact with the developing roll. The toner has 8.0-13.0μm vol. average particle diameter (D50 ) and 1.0-2.2m<2> /g specific surface area (S) measured by a BET multipoint method (nitrogen adsorption method) and satisfies 12.0<=K×D50 ×S<=20.0 (K is the true specific gravity of the toner).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner used in a non-magnetic one-component developing system in which a developing roll for developing an electrostatic latent image and an electrostatic latent image carrier are in contact with each other. In particular, the present invention relates to a non-magnetic one-component toner that can be used in a small-sized low-speed printer adopting an electrophotographic method.

[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 is required to control the mixing ratio of toner and carrier. There is a limit to the durability of the carrier, and it is necessary to replace not only the toner but also the developer for long-term use. 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 the magnetic one-component developer are as follows. 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 accuracy of the developing machine is required to uniformly form the magnetic brush. The magnetic toner is inferior to the above-mentioned two-component non-magnetic toner in that the transferability, the fixing property, the dependency on the environmental humidity are large, and the damage to the photoconductor is large. Considering these problems comprehensively and considering the miniaturization of the device together, the developing method using the non-magnetic one-component toner is extremely effective, and several developing methods have been put to practical use in recent years. There is.

[0003]

In the non-magnetic one-component developing system, most of the devices have a developing roll carrying toner and an electrostatic latent image bearing member in contact with each other, and the developing machine is pressed against the developing roll. A blade and a toner supply roll are arranged in contact with each other. According to this developing method, the toner can be charged relatively easily, but the toner is likely to be fused to a member such as a blade or a developing roll because there are many contact portions with the developing roll. Therefore, when a styrene / (meth) acrylic acid ester copolymer resin having a high glass transition temperature (Tg) or a polyester resin containing a large amount of gel component is used as a main material of the toner as a solution, a high pressure is applied to the toner. The toner is designed so that fusion does not easily occur even if the temperature rises due to friction. However, when this solution is implemented, it is necessary to set the fixing temperature to a relatively high level. Therefore, from the viewpoint of the amount of energy used, this is a developing method that is not suitable for a recent power saving type apparatus.

Most of the small-sized optical printers released in recent years are equipped with an electrostatic latent image carrier (photoreceptor) that carries a negative charge. In this case, a roller is used to prevent ozone generation. In many cases, the type or brush type charging device is installed. Therefore, damage to the electrostatic latent image carrier is greater than when a corona charging device is installed,
There was a problem with the durability of the printer.

[0005]

The present invention aims to solve the above-mentioned problems, and the means are as follows. That is, the invention of claim 1 is a developing device having at least a developing roll for carrying and conveying toner, a toner layer thickness regulating member provided in pressure contact with the developing roll, and provided in contact with the developing roll. For use in a reversal development system equipped with the positively charged electrostatic latent image bearing member (photoreceptor) having a volume average particle diameter (D ₅₀ ), BET multipoint method (nitrogen adsorption method) A non-magnetic one-component developing toner having a specific surface area (S) and D ₅₀ × S measured in the following range and containing a positively chargeable charge control agent. 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) According to the invention of claim 2, the binder resin as a main component of the toner is a styrene / acrylic acid ester copolymer, a styrene / methacrylic acid ester copolymer or a styrene / acrylic acid ester / methacrylic acid ester copolymer. The non-magnetic one-component developing toner according to claim 1, wherein the amount of acrylic component of the resin is 20 to 40% by weight. A third aspect of the present invention is characterized in that the carbon content in the toner is 2 to 8% by weight.
According to a fourth aspect of the present invention, the surface of the toner particles is made to have 0.1 to 2.0% by weight of silica which has been subjected to a hydrophobic treatment, and 0.3 to 0.5% of spherical magnetic powder.
It is characterized by depositing 1.5% by weight.

Next, the 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 in which the non-magnetic one-component toner of the present invention is used.
In the figure, 1 is a positively charging photosensitive drum that 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 is a developing roller using an elastic rubber sleeve, 6 is a member for preventing toner leakage and a scraping member, and 7 is 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 accommodated in the hopper 2, and the toner is carried and conveyed on the sleeve of the developing roller 5 by the layer thickness regulating member 4 a so as to have a constant layer thickness. 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 of. The toner carried by the developing roller 5 is conveyed by the rotation of the developing roller and comes into contact with the photosensitive drum 1 having an electrostatic latent image, so that the electrostatic latent image is visualized.

The present invention relates to a toner used in the above-mentioned developing method, which is characterized in that the volume average particle diameter (D ₅₀ ) and the specific surface area (S) of the toner are within the following numerically limited ranges. The problem of the prior art is solved by using the thing. 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 the above formula, the volume average particle size (D ₅₀ ) shows a 50% value by volume based on Coulter Counter TA-II type, and the specific surface area (S) was measured by the BET multiplex method by the nitrogen adsorption method. It is calculated by 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 μ.
If it is smaller than m, the toner is fused to the developing roll and fog occurs in the non-image area, while if it is larger than 13.0 μm, the image quality of characters and line portions is deteriorated. When the specific surface area of the toner is smaller than 1.0 m ² / g, or K ×
When D ₅₀ × S is less than 12.0, the surface of the toner particles becomes too smooth and the charging performance deteriorates, resulting in image defects such as fog generation and toner scattering around characters. The specific surface area of the toner is 2.2 m ² / g
If it is larger, or 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, etc. increases, and the temperature of the toner locally rises. Toner is fused to the layer thickness regulating member, the developing sleeve and the like. 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, it is necessary to spheroidize or surface-treat after pulverizing and classifying. Specifically, it is conceivable to pass the toner particles through a surface reformer represented by the product name “Nara Hybridizer” manufactured by Nara Machinery Co., Ltd. or a hot air flow.

Further, since the toner of the present invention uses a non-contact type charging device (corona charging device, etc.) while preventing the generation of ozone, the life of the electrostatic latent image bearing member is prolonged. Positively chargeable organic photo-semiconductor (OPC) and S
It is used in a reversal development type developing system using an electrostatic latent image carrier represented by e. Therefore, the toner of the present invention contains a charge control agent such as nigrosine or a quaternary ammonium salt used for positive charging. Further, the resin for toner is preferably selected from styrene / acrylic acid ester copolymer, styrene / methacrylic acid ester copolymer, or styrene / acrylic acid ester / methacrylic acid ester copolymer. The amount of the acrylic component of 20 to 40% by weight, preferably 25 to 35% by weight improves the fixability at low temperature, assists the positive charging performance, and constitutes a toner with less fog. is there. When the amount of the acrylic component is less than 20% by weight, the positive charging property is liable to be impaired, and in a system having a weak charging ability such as the non-magnetic one-component developing system, toner particles which are charged in the opposite polarity are easily generated. If the acrylic component is more than 40% by weight, the volume resistivity of the toner is lowered, the absolute value of the charge amount is lowered, and the image deterioration is apt 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 the weak charge imparting ability of the non-magnetic one-component development.
It is possible to obtain an image with sufficient image density and less fog. The amount of carbon in the toner is 8
If it is more than 5% by weight, the volume resistivity of the toner is lowered and the charging performance is lowered, so that fog occurs in the image. If the amount of carbon is less than 2% by weight, the image density will be insufficient.
Further, in the toner of the present invention, it is preferable to adhere hydrophobized silica and fine powder of magnetic powder having a spherical particle shape to the surface of the toner particles. In that case, the content of the toner particles in the toner is wt%, the surface of the silica is 0.1 to 2.0 wt% and the magnetic powder is 0.3 to 1.5 wt%.
By adjusting the above, it is possible to obtain an image in which the rise of charging is good and the fog is small. In this case, if the silica content is less than 0.1% by weight, the fluidity of the toner becomes poor,
On the other hand, if it exceeds 2.0% by weight, fog is generated, which is not preferable. On the other hand, if the addition amount of the magnetic powder is less than 0.3% by weight, the effect of rising the charging cannot be exhibited, while if it is more than 1.5% by weight, the charging is excessively caused and a transfer failure occurs, which is not preferable. Further, the magnetic powder having a spherical shape has the effect of preventing damage to the surface of the electrostatic latent image carrier and prolonging its life, as compared with the octahedral or needle-shaped magnetic powder. Less than,
The present invention will be described in detail.

[0010]

The present invention is a developing method of a type in which a developing roll using a non-magnetic one-component toner and an electrostatic latent image bearing member are in contact with each other, while obtaining good low-temperature fixing performance for the toner, the developing roll and the toner layer thickness regulating member. Further, as a result of diligent studies for extremely reducing the fusion of the toner to the electrostatic latent image carrier, as a result of setting the volume average particle diameter and the specific surface area of the toner within a certain range, the fusion of the toner to each member The amount of adhesion was minimized, and the life of the developing device and the electrostatic latent image carrier in the non-magnetic one-component system was successfully extended. The action mechanism of the specific surface area of the toner, which is the main constituent feature of the present invention, will be described below.

That is, when the specific surface area of a toner having a constant particle diameter becomes large, the surface shape of the particle becomes rough.
Since there are many irregularities, the surface area in contact with the charging member will be large and the charging property will be good, but the probability of a local temperature rise due to friction with the member will also increase, and the toner fusion to each member will also increase. 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 becomes, the smoother the surface becomes, and finally, the surface approaches a true sphere, but if it becomes too smooth, the surface that can contribute to charging is reduced and the charging property is deteriorated, resulting in deterioration of image quality. cause. In order to solve this, if the area of the charging member is widened, the pressure is increased, or the like is modified on the side of the apparatus, both of them cause a problem of increasing toner fusion. 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 limit range, and applying them to the developing method specified in claim 1.

Examples and comparative examples (parts below are parts by weight) Melt and knead the mixture consisting of the above mixture with a melt kneader,
It is rolled into a sheet through two rolls, cooled, roughly crushed into chips of 3 mm square or less by a hammer mill, then crushed by a jet air type crusher, and further charged positively by a treatment process of an air stream classifier, Moreover, the volume average particle diameter (D ₅₀ ) measured by a Coulter counter is 7.2 μm,
8.4 μm, 9.6 μm, 10.5 μm, 11.4 μ
m, 13.0 μm toner particles were obtained.

Further, as a post-treatment, for each of the toner samples, positively chargeable silica fine powder HVK-2150 (manufactured by Hoechst) was added to 100 parts by weight of the toner.
5 parts by weight and magnetic powder MAT305 (manufactured by Toda Kogyo Co., Ltd.)
0 parts by weight was added, and the mixture was stirred and mixed with a Henschel mixer to obtain toner particles No. 1 for non-magnetic one-component development. 1 to 6 were obtained. In addition, the sample No. Prior to post-treatment, 1 to 6 were subjected to surface treatment based on imparting mechanical compressive force and frictional force to toner particles by a trade name; “Nara Hybridizer” (manufactured by Nara Machinery Co., Ltd.), and then similar post-treatment. Sample No. 7-12 samples were obtained. In addition, the sample No. 1
After the post-treatment of 6 to 6, the toner was heat-treated in a Henschel mixer at a jacket temperature of 55 ° C. for 15 minutes, and then subjected to the same post-treatment. 13-18 were obtained. For the 18 kinds of toner samples, a photoreceptor of a IBM 4029 printer as a printer equipped with a developing device adopting a non-magnetic one-component developing system and a positively charging electrostatic latent image carrier is used for OPC, and A printing test was carried out by using the one modified so that the polarity of charging the photoreceptor was positive. Table 1 shows the results.

[0014]

[Table 1]

The method of evaluating the printing characteristics is as follows. (1) Image density (ID); Macbeth reflection densitometer RD9
Image density of solid image of 1 cm ² by 14 (2) Fog (BG); Colorimetric color difference meter Z- by Nippon Denshoku Co., Ltd.
1001DP (3) Solid black; Visual evaluation of solid black image on the entire A4 size copy paper (4) Image quality; Visual evaluation of image quality of characters and lines (5) Fusing; Developing roll and toner after printing 20000 sheets Visual evaluation of toner fusion to the layer thickness control member

The evaluations of black solid, image quality and fusion are as follows. (Evaluation of solid black) ×: Image density reduction or blurring occurs in the A4 full black solid image after the first rotation of the sleeve. Δ: Image in the A4 full black solid image after the second rotation of the sleeve. Density reduction or blurring occurs ◯: No image density reduction or blurring in A4 solid black solid image (evaluation of image quality) ×: Reproducibility such as toner scattering around characters and thickening of one dot fine line of 600 DPI Poor property Δ: Scattering of toner around characters is slightly noticeable, but 60
Reproducibility of 1-dot thin line of 0DPI is good. ○: Scattering of toner around characters is inconspicuous and 600D
Reproducibility of 1-dot fine line of PI is also good (evaluation of fusion) X: fusion of toner is seen on the toner layer thickness regulating member or the sleeve of the developing roll, and image defects such as streaks caused by this are observed in the image. Occurrence Δ: Some toner fusion is observed on the toner layer thickness regulating member or sleeve, but there is no image defect such as streaks in the image, and there is no practical problem. ○: Toner layer thickness regulating member or developing roller sleeve As shown in Table 1, there is no fusion of the toner on the sample No. 1 which is the non-magnetic one-component developing toner of the present invention. 8-12 and No. 15-18
Does not cause the toner fusion to the toner layer thickness regulating member or the developing roll, which is apt to occur in the prior art. In addition, the image density was 1.37 to 1.49 and fog was 0.88 in the process of continuous copying from the initial number of printed sheets to 20,000 sheets.
It was confirmed that the following good conditions were 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; 13 to 14 have a toner specific surface area of 2.2 m ² / g or more or K × D ₅₀ × S.
Since it is 20 or more, as described above, the unevenness of the toner surface increases and the toner fusion occurs.

[0017]

According to the present invention, the volume average particle diameter of toner, the specific surface area, and the product of both are numerically limited to a specific range so that the toner is not fused to the toner layer thickness regulating member or the developing roll. Moreover, it is possible to provide a toner that can maintain good image density and image quality.

[Brief description of drawings]

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 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

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Ryozo Okuno 3-1, Soba-cho, Shizuoka-shi, Shizuoka Prefecture Tomoegawa Paper Mill Chemicals Division

Claims (4)

[Claims] 1. A developing device having at least a developing roll carrying and carrying toner, a toner layer thickness regulating member provided in pressure contact with the developing roll, and a positive charging provided in contact with the developing roll. A toner used in a reversal development system equipped with an electrostatic latent image carrier, the volume average particle diameter (D ₅₀ ) of the toner, and a specific surface area (S) measured by the BET multipoint method (nitrogen adsorption method). , And D ₅₀ × S within the following range, and a positively chargeable charge control agent is blended therein. 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. The binder resin as a main component of the toner is selected from styrene / acrylic acid ester copolymer, styrene / methacrylic acid ester copolymer or styrene / acrylic acid ester / methacrylic acid ester copolymer,
The non-magnetic one-component developing toner according to claim 1, wherein the amount of 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. 4. A toner particle surface comprising 0.1 to 2.0% by weight of hydrophobized silica and 0.3 to 0.5 parts of spherical magnetic powder.
The non-magnetic one-component developing toner according to claim 1, wherein the toner is attached in an amount of 1.5% by weight.