JPH06317927A - Photoconductive toner - Google Patents

Abstract

PURPOSE:To provide a photoconductive toner excellent in resolution. CONSTITUTION:This toner is a photoconductive toner for digital light input having >=3 contrast gamma as the inclination of a pseudo-straight line part in light attenuation characteristics to a specified wavelength. Light energy required to reduce potential by electrification from 90% to 10% as the variation of the surface potential of this toner by irradiation with light is <=50muJ/cm<2>. This toner leaves >=90% of its electric charge retentivity when irradiated with light whose energy is half or less of exposure (E1/2) reduced to half.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoconductive toner, and more particularly to a photoconductive toner used in a printer, a copying machine or the like which does not use a photoconductor.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing a copying machine using a conventional electrophotographic method by the Carlson process. In the figure, 1 is a photoconductor drum having a photoconductive material coated on its surface, 2 is a corona charger for charging the surface of the photoconductor drum 1, 3 is a charge charged on the surface of the photoconductor drum, 4
Is light for illuminating the surface of the photosensitive drum 1, 5 is a developing unit, 6
Is toner stored in the developing device 5, 7 is a magnetic material for attaching the toner 6 to the photosensitive drum 1, 6a is toner attached to the photosensitive drum 1, 8 is recording paper for recording an image,
6b is a toner deposited on the recording paper 8, 9 is a transfer device for applying a DC bias to the recording paper 8, 10 is a fixing device for fixing the toner 6b deposited on the recording paper 8, and 11 is a residual charge of the photosensitive drum 1. Is a cleaner for cleaning the photosensitive drum 1, and 13 is a pre-exposure lamp for exposing the photosensitive drum 1 before charging.

Next, the operation will be described. An image forming method using an electrophotographic method is widely known, and the most popular one is the Carlson process at present. The surface of the photoconductor drum 1 having the surface coated with the photoconductive material is exposed by the pre-exposure lamp 13 and then charged by the corona charger 2. Then, by irradiating the light 4, the electrostatic charge 3 of the charged portion is selectively lost to form an electrostatic latent image. Then, the developing device 5 is used to selectively deposit the toner 6 on the portion where the charge is lost. Then, the toner 6a on the photosensitive drum 1 is transferred onto the recording paper 8 by the transfer device 9, and the toner 6b adhered to the recording paper 8 by pressure or heat is fixed by the fixing device 1.
Fix at 0.

In recent years, there has been a demand for colorization of such printers and copiers, and as shown in FIG. 4, those equipped with three developing devices 5 in the same manner as described above have come to be used. It was Yellow as toner 6,
The three colors of magenta and cyan are used, and the photosensitive drum 1
Is also a multi-exposure recording system in which light 3 of four colors is used by rotating three times.

Further, high-speed recording, cost reduction of equipment,
With the demand for smaller size and lighter weight, a new photosensitive drumless system and one-shot full color system have been proposed as the recording system itself. One of these methods is a recording method using a photoconductive toner. For example, as shown in FIG. 5, the photoconductive toner 17 charged by the charger 16 is applied on the drum 15 on which the photoconductor is not applied, and the photoconductive toner 17 is irradiated by the light 4 to obtain the photoconductive property. The electrostatic charge of the toner 17 is neutralized through the drum 15. After that, the transfer device 9 transfers the photoconductive toner 17 that has lost the charge in the case of a printer and the photoconductive toner 17 that holds the charge in the case of a copying machine onto the recording paper 8 respectively, and the pressure or It is fixed by heat. When color recording is performed using the photoconductive toner 17, the photoconductive toner 17 has photoconductive sensitivities to blue, green, and red light, for example, as shown in FIG. There has been proposed a method in which photoconductive toners 17 of three colors of yellow, magenta and cyan are mixed and used, and exposed with light 4 of three colors of blue, green and red. This is a magazine (JAP
AN DISPLAY, 1986, Abstracts 56
8 to 571) and JP-A-53-103739. The photoconductive toner is also described in JP-A-60-258558.

The photoconductive toner 17 used in this image forming method is generally an inorganic photoconductive substance such as zinc oxide together with a coloring agent in a binder resin, or an organic photoconductive substance such as a quinacridone pigment or a phthalocyanine pigment. Resin fine particles in which a substance is dispersed are used.

[0007]

The conventional photoconductive toner as described above has an analog property as a light attenuation characteristic. Therefore, after the initial charging, the charge disappears according to the amount of light irradiated. When this photoconductive toner is used in monochrome printers and digital copying machines, the binarized light is applied to the charged photoconductive toner, but the light intensity of the irradiation spot is not uniform and it is the center of the spot. Has a peak. Therefore, there is a problem in that the attenuation of the charged electric charge has a distribution, and when transferred to the recording paper, the edge portion of the image is particularly blurred. When a color image is obtained using a mixture of three photoconductive toners of yellow, magenta, and cyan, which have photoconductive sensitivity to blue, green, and red light, respectively,
The spectral sensitivities of the respective photoconductive toners are not independent but overlap a little. FIG. 7 shows the sensitivity of the photoconductive toner to the wavelength of light. As can be seen in the figure, since yellow (Y), magenta (M), and cyan (C) have overlapping portions, when the digitized image signal is exposed with light of three colors of blue, green, and red, There is also a problem that the charge of the photoconductive toner other than the purpose is also attenuated, resulting in an image having poor color reproducibility.

The present invention has been made to solve the above problems, and an object thereof is to obtain a photoconductive toner capable of obtaining an image with excellent resolution. Still another object is to obtain a photoconductive toner capable of obtaining an image with good color reproducibility.

[0009]

According to a first aspect of the present invention, there is provided a photoconductive toner which is a digital light having a hardness value γ of 3 or more, which is an inclination of a pseudo straight line portion in a light attenuation characteristic with respect to a specific wavelength. It is for input.

In addition to the invention of claim 1, the photoconductive toner according to the invention of claim 2 has a change rate of the surface potential of the photoconductive toner of 90% of the charging potential due to light irradiation.
From 50 to 10% of the light energy required
It is characterized by being μJ / cm ² or less.

Further, in addition to the invention of claim 1 or claim 2, the photoconductive toner according to the invention of claim 3 is the same as that of the photoconductive toner in the irradiation of light with an energy of half or less of the half-exposure amount (E _1/2 ). The charge retention rate remains 90% or more.

Further, the photoconductive toner according to the invention of claim 4 is a mixture of the photoconductive toners according to any one of claims 1 to 3, each of which has three primary colors based on the subtractive color mixture method. It is characterized by being.

[0013]

In the photoconductive toner according to the present invention, the light attenuation characteristics, the light sensitivity, and the charge retention rate and the light energy amount due to the induction effect are set to optimum values. Therefore, this photoconductive toner has a digital light attenuation characteristic, and an image with excellent resolution can be obtained by neutralizing only the charge of the target photoconductive toner with the signal-processed light. If a color photoconductive toner having a digital light attenuation characteristic is used, an image having excellent resolution and good color reproducibility can be obtained.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In a printer, a digital copying machine, or the like in which an image is expressed by dots, if the photoconductive toner has a digital light attenuation characteristic, the desired photoconductive property is obtained by the signal-processed light. By neutralizing only the electrostatic charge of the toner, blurring of the edge portion is eliminated, and an image with high resolution, easy control, and good color reproducibility can be obtained. Usually, in the evaluation of photographic materials, as shown in Corona Publishing Co., Ltd., "Basics of Photographic Engineering, Non-Silver Photographs," edited by the Photographic Society of Japan, page 51, to show the relationship between input and output to recording materials , A logarithmic graph in which the horizontal axis represents the input energy and the vertical axis represents the output. In the present invention, for example, the photoconductive toner is evaluated by the light input energy and the light attenuation characteristics of the charging potential.

FIG. 1 is a graph for explaining the light attenuation characteristics of the photoconductive toner according to the present invention, in which the horizontal axis shows the light input energy (μJ / cm ² ) on the log scale.
The vertical axis represents the charging potential (V) on a log scale. In the figure, a solid line 20 is a characteristic curve representing the light attenuation characteristic of the photoconductive toner according to the first embodiment of the present invention. The gradient of the pseudo straight line portion at the center of the characteristic curve is an amount defined by the degree of hard gradation γ, and is related to the grayscale expression capability of the obtained image, that is, the gradation. The broken line 21 represents the light attenuation characteristic of the conventional photoconductive toner. As shown by the solid line 20, the photoconductive toner according to the present invention has a characteristic that the potential is not attenuated until a certain amount of light energy having a light attenuation characteristic is irradiated, and is rapidly attenuated when a certain amount or more is irradiated. . It can be said that the steeper the gradient of the attenuation (hardness γ), the more the photoconductive toner has digital characteristics. On the other hand, the conventional photoconductive toner having the characteristic indicated by the broken line 21 has a gentle attenuation and can be regarded as having the analog characteristic.

When this optical attenuation characteristic is represented by the γ value, the γ value is 3
It has been experimentally found that the above photoconductive toners are preferable. When a photoconductive toner having a γ value of 3 or more is used in an image forming apparatus, blurring of the edge portion due to the distribution of light energy during exposure is eliminated, and an image with excellent resolution can be obtained. When the γ value is 3 or less, it cannot be regarded as having a digital characteristic.

Further, if this light attenuation characteristic is expressed by light sensitivity,
The change rate of the surface potential is 90% to 10% of the charging potential
The optical energy required to lower the temperature to 50 μJ / cm
^It has been experimentally found that photoconductive toners of ² or less are preferable. When the photoconductive toner having such characteristics is used in the image forming apparatus, blurring of the edge portion due to the distribution of light energy at the time of exposure is eliminated, an image with excellent resolution can be obtained, and an image can be obtained particularly at high speed. 50 μJ / cm
Anything that requires more than ^two light energies cannot be considered to have digital properties. The conventional device shown by the broken line 21 requires light energy of about 500 μJ / cm ² .

It has been experimentally found that a photoconductive toner having a charge retention rate of 90% or more is preferable for light irradiation with an energy of half or less of the half-exposure amount (E _1/2 ). This is equivalent to defining the slope in the portion of the graph of the solid line 20 in FIG. 1 where the light input energy is small, and it is clear that only about 50% remains in the broken line 21. Therefore, the remaining charge retention rate is 90
If it is less than%, the slope of this portion is large and cannot be regarded as having digital characteristics. If a photoconductive toner having such characteristics is used in an image forming apparatus,
Blurring of the edge portion due to the distribution of light energy during exposure is eliminated, and the final recorded image with the highest resolution can be obtained.

Furthermore, by using a photoconductive toner which is a mixture of the above-mentioned characteristics and each of which has three primary colors based on the subtractive color mixture method, color reproduction is excellent and resolution is excellent. A color image is obtained.

Example 1. The photoconductive toner according to Example 1 of the present invention will be described below. Using 10 parts of titanyl phthalocyanine, 45 parts of polycarbonate, 550 parts of 1,2-dichloroethane as a material, thoroughly mixing with a ball mill, spray-drying this with a two-fluid nozzle type spray dryer, and light with an average particle size of 12 μm. A conductive toner was prepared. The photoconductive toner thus obtained was dispersed on a conductive substrate made of aluminum to form a thin layer of the photoconductive toner. This was positively charged by a corona charger and then irradiated with monochromatic light of 780 nm to examine the light attenuation characteristics. As a result, an induction effect was observed, and the γ value was 5.3. The rate of change in the surface potential of the photoconductive toner is 90% of the charging potential.
The light energy required to reduce from 10% to 10% is
It was 40 μJ / cm ² , and 90% or more of the charge retention rate remained after light irradiation with an energy of half the half-exposure amount (E _1/2 ) or less. When this photoconductive toner was used for image formation, a high-resolution image was obtained.

Example 2. Hereinafter, the photoconductive toner according to the second embodiment of the present invention will be described. As the material, 10 parts of titanyl phthalocyanine, 48 parts of polycarbonate, 550 parts of 1,2-dichloroethane were thoroughly mixed with a ball mill and spray-dried with a two-fluid nozzle type spray dryer to obtain a photoconductive material having an average particle diameter of 12 μm. Toner was prepared. The photoconductive toner thus obtained was sprinkled on a conductive substrate made of aluminum to form a thin layer of toner. This was positively charged by a corona charger and then irradiated with monochromatic light of 780 nm to examine the light attenuation characteristics. As a result, an induction effect was observed, and the γ value was 3.1. The rate of change of the surface potential of the photoconductive toner is 90% to 10% of the charging potential.
The optical energy required to reduce the amount to 50% is 50 μJ /
cm ^2, and in the light irradiation of the half decay exposure amount less than half of the energy of the (E _1/2), the charge retention remained 90% or more. When this photoconductive toner was used for image formation, an image with high resolution was obtained.

Comparative Example. Hereinafter, a conventional photoconductive toner will be described as a comparative example. As a material, 10 parts of titanyl phthalocyanine, 60 parts of polycarbonate, 550 parts of 1,2-dichloroethane were thoroughly mixed with a ball mill and spray-dried with a two-fluid nozzle type spray dryer to obtain a photoconductive material having an average particle diameter of 12 μm. Toner was prepared. The photoconductive toner thus obtained was sprinkled on a conductive substrate made of aluminum to form a thin layer of toner. This was positively charged by a corona charger and then irradiated with monochromatic light of 780 nm to examine the light attenuation characteristics. As a result, an induction effect was observed, and the γ value was 1.5. When this photoconductive toner was used for image formation, only an image with low resolution was obtained.

Although the above-described Examples 1 and 2 are examples regarding a photoconductive toner for a single color, for example, cyan, the same applies to other yellow and magenta, and the light attenuation characteristics set in the present invention, If the photosensitivity and the charge retention rate due to the induction effect and the optimum value of the amount of light energy are used, the photoconductive toner has a digital light attenuation characteristic, and the target photoconductive property is obtained by the signal-processed light. A high-resolution image can be obtained by neutralizing only the electrostatic charge of the toner.

Example 3. Further, a mixture of three primary colors based on the subtractive color mixture method is used as a photoconductive toner, and the light attenuation characteristics, the light sensitivity, and the charge retention rate and the light energy amount due to the induction effect set in the present invention are set. If the optimum value of is set, the photoconductive toner has a digital light-attenuating property, and if only the charge of the target photoconductive toner is neutralized by the signal-processed light, a high resolution is obtained. In addition, an image with good color reproducibility can be obtained.

For example, a case where a color image is obtained by mixing photoconductive toners of three colors of yellow, magenta, and cyan, which have photoconductive sensitivity to blue, green, and red light, respectively, will be described. . As photoconductors exhibiting yellow and magenta colors, sulfur, selenium, or zinc, cadmium, mercury, antimony, titanium,
Examples include oxides of bismuth and lead, sulfides, selenium compounds, anthracene, anthraquinone, polyvinylcarbazole, polyvinylanthracene, polyacetylene, and the like. A predetermined sensitizer is added to these photoconductors so as to have a sensitivity wavelength region in a predetermined visible light region by sensitizing a dye or the like. In addition, quinacridone, perylene,
It can be prepared using an azo pigment, squarylium, a rhodanine derivative or the like. FIG. 2 shows the sensitivity of the photoconductive toner to the wavelength of light. Since the photoconductive toner according to the present invention has a digital light attenuation characteristic, the spectral sensitivity of each photoconductive toner as shown in FIG. 2 is yellow (Y) as compared with that shown in FIG. ，
Since the magenta (M) and cyan (C) overlap portions are eliminated, the sensitivity becomes independent. Therefore, when the digitized image signal is exposed with light of three colors of blue, green, and red, an image with good color reproducibility is obtained without attenuating the charge of the photoconductive toner which is not intended. That is, since digital characteristics are imparted to the photoconductive toner, there is an effect that a threshold value for light attenuation can be obtained, and a recorded matter with high resolution and good color reproduction can be easily obtained.

[0026]

As described above, according to the first aspect of the invention, for a specific wavelength, a digital optical input for which the degree of hardness γ, which is the inclination of the pseudo linear portion in the optical attenuation characteristic, is 3 or more. By doing so, there is an effect that the blur of the edge portion due to the distribution of the light energy at the time of exposure is eliminated, and the photoconductive toner having an image with excellent resolution can be obtained.

According to the invention of claim 2, claim 1
In addition to the invention described above, the light energy required to reduce the surface potential change rate of the photoconductive toner from 90% to 10% of the charging potential by light irradiation is set to 50 μJ / cm ² or less, and Is excellent, and there is an effect that a photoconductive toner capable of obtaining a high-speed image is obtained.

According to the invention of claim 3, claim 1
Alternatively, in addition to the invention of claim 2, the half-exposure amount (E _1/2 )
In the case of light irradiation with an energy of half or less of the above, by making the charge retention rate 90% or more, there is an effect that the photoconductive toner which finally becomes a recorded image with the highest resolution can be obtained.

According to the invention of claim 4, claim 1
In addition to the invention according to any one of claims 3 to 3, a photoconductive toner, which is a mixture of three primary colors based on the subtractive color mixture method, can produce a color image with good color reproduction and excellent resolution. There is an effect to be obtained.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing a relationship between a light energy (μJ / cm ² ) and a potential (V) of a photoconductive toner according to the present invention.

FIG. 2 is a characteristic diagram showing the sensitivity of the photoconductive toner according to the present invention to the wavelength of light to be exposed.

FIG. 3 is a configuration diagram showing a single-color copying machine using an electrophotographic method by the Carlson process.

FIG. 4 is a configuration diagram showing a color copying machine using an electrophotographic method by the Carlson process.

FIG. 5 is a configuration diagram showing a monochromatic copying machine using a photoconductive toner.

FIG. 6 is a configuration diagram showing a color copying machine using a photoconductive toner.

FIG. 7 is a characteristic diagram showing sensitivity of a conventional photoconductive toner to a wavelength of light to be exposed.

[Explanation of symbols]

 17 Photoconductive toner 20 Optical attenuation characteristics of photoconductive toner

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiroyuki Ishikawa 1-23-37 Edobori, Nishi-ku, Osaka City, Sakata Inx Co., Ltd. (72) Wei Nagae 8-1-1 Tsukaguchihonmachi, Amagasaki Mitsubishi Electric Corporation Materials Devices Laboratory (72) Inventor Kasuko Wakita 8-1-1 Tsukaguchi Honcho, Amagasaki City Mitsubishi Electric Corporation Materials Devices Laboratory (72) Inventor Makoto Kakuda 8-1-1 Tsukaguchi Honmachi, Amagasaki Mitsubishi Electric Corporation Materials Device Laboratory

Claims (4)

[Claims] 1. A photoconductive toner for digital light input, which has a hardness value γ of 3 or more, which is an inclination of a pseudo straight line portion in a light attenuation characteristic with respect to a specific wavelength. 2. The light energy required to reduce the surface potential change rate of the photoconductive toner from 90% to 10% of the charging potential by light irradiation is 50 μJ / cm ² or less. The photoconductive toner according to claim 1. 3. The charge retention rate of 90% or more remains in light irradiation with an energy of half or less of the half exposure amount (E _1/2 ), according to claim 1 or 2. Photoconductive toner. 4. The photoconductive toner according to claim 1, wherein the photoconductive toner is a mixture of three primary colors based on the subtractive color mixture method.