JPS62284365A - Image forming method - Google Patents

Abstract

PURPOSE:To enhance image quality and sharpness of a toner image by specifying the maximum particle diameter in the final particle distribution of the fine toner particles on a recording paper. CONSTITUTION:The maximum particle diameter of the fine toner particles on the recording paper is regulated to <=30mum, and the toner particles not ready to aggregate with each other are used. A latent image can be developed in a thin layer by using said toner of <=30mum maximum particle diameter, thus permitting the formed powder toner image to be sharpness and image quality and comparable with an offset print, and image density to be reproduced in a uniform state, especially, in a solid black image part.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an image forming method for electronic copying machines, etc. The present invention relates to an image forming method in which a latent image formed on the surface of a body is developed by applying toner.

(Prior art) Conventionally, in electrophotographic recording devices and electrostatic recording devices,
A static Tik image carrier such as a photoreceptor drum is irradiated with image information such as reflected light from a document or laser light to form an electrostatic latent image on its surface, and toner is attached to the latent image to form a toner image. The L/S image thus formed is transferred to paper in the next step and fixed, completing the copy.

In the dry developing device as mentioned above, the thickness is usually 10 μm.
Since the following fine particles are used as the toner, its ease of handling, safety, and maintainability are maintained well, and it is very conveniently used in many electronic copying applications.

(Problems to be Solved by the Invention) However, in conventional image forming methods using toner, the quality of the image inevitably deteriorates compared to offset printing or liquid developed images. . For example, in the liquid development method, the toner is 0.2
The toner particles are dispersed in the liquid as extremely small particles of about 0.3 μm, and the toner particles do not overlap.
Since (-1 is applied to the latent image in the state of one layer), the image reproduced thereby is very clear without blurring around the image unit.

On the other hand, toner images formed by the dry development method have the disadvantage that, as described above, unevenness in a-lightness, blurring, etc. of the image are likely to occur.

The reasons for this include various problems, as listed below.

For example, in the developing process, unnecessarily large particles may be produced due to uneven toner potential, as well as image stains due to variations in the size of toner particles or toner adhesion to unnecessary areas. There are causes such as the formation of large dots due to large lumps.

In addition, in the transfer process, the toner image formed on the surface of the photoreceptor drum is not completely transferred to the paper, and some of the toner remains untransferred on the surface of the photoreceptor drum, thereby causing the toner image to be transferred to the paper. In addition to unevenness in the resulting 1-screen image, a phenomenon may occur in which fine powder toner is scattered around the dots during transfer.

Furthermore, in the fixing process, the paper on which the toner image has been transferred is sandwiched and passed between a heating roller and a pressure roller, and when heating and pressure are applied, the toner becomes crushed. This may cause phenomena such as blurring of the periphery of the image.

Due to the various reasons mentioned above, copies made by electronic copying machines have a lower quality compared to offset printed images.
It is thought that defects such as not being clearly formed occur.

In contrast, conventionally, each component of an electronic copying machine,
Although many improvements have been made to the toner image transfer method, it is still not perfected.

Therefore, in addition to the many reasons mentioned above, the image forming method of the present invention focuses on the formation of a toner image on an image bearing member such as a photoreceptor drum. The present invention relates to a method of forming a latent image and preventing toner from adhering to the latent image, thereby making it possible to reproduce the shading of the image in good condition.

Conventional methods for forming an image on a photoreceptor drum, etc. are two methods: irradiating the document with a lamp, exposing the entire surface of the photoreceptor drum with the reflected light through a lens system, and inputting the read image into a storage device. The output from the storage device is converted into laser light and is applied to the surface of the photoreceptor drum.
A method in which the information is formed as a flying point (flying points), or a method in which the information is input in a line using liquid crystals, LEDs, etc., are used.

Among these methods, methods that use laser light and methods that use line input reproduce the toner image in a mesh pattern with respect to the latent image formed on the surface of the photoreceptor drum, but when full-surface exposure is performed However, when copying an off-reflection 1-print image, the 1-ner image will be reproduced in a mesh pattern.

However, in the conventional toner image forming method in which toner is attached to the eI image formed on the surface of a photoreceptor drum, etc., the toner image is rarely reproduced in good condition, and in many cases. , In addition to uneven shading in solid black areas, rough edges of lines and the image not being sharp, etc., the image may also be distorted and not reproduced clearly.
There are many drawbacks that require improvement, such as toner scattering in white areas resulting in smudged images.

The causes of these defects include the properties of the toner,
For example, in addition to problems such as particle size distribution, toner particle shape, and charging characteristics, the height of the magnetic brush when supplying toner from the developing device to the latent image, and ,
There are many problems such as ω of 1 henna being deposited on the latent image.

For the above-mentioned reasons, some copying systems using powder toner have had the disadvantage that it is not possible to obtain high-quality images comparable to offset printing.

(Object of the Invention) The present invention solves the drawbacks of conventional image forming methods as described above, and aims to offset the toner image reproduced on paper as a solid black image by powder formation. The purpose is to make it possible to obtain clear images with the image quality of a printing pot.

(Means and effects for solving the problems) The present invention has the following features:
A method for reproducing an image composed of fine toner particles, characterized in that the maximum particle diameter of the fine toner particles in the final particle size distribution on a recording paper is set to 30 μm or less, and further, the image is solid black. It is an image, and furthermore,
The image forming method 1iii is characterized in that the solid black image has an image density of 0.3 to 0.6.

Further, the toner used in the image forming method of the present invention is configured in a finer particle shape than conventional toner, and its m
A material with improved fJJ properties and charging properties is used.

Therefore, in the image forming method of the present invention, by adjusting the maximum particle diameter in the reproduced image as described above, an image of good quality can be obtained. be able to,
Clear copies of the offset printing kettle can be obtained.

In order to make the maximum particle size of the fine toner particles on the recording paper 30 μm or less, it is preferable to use a toner that does not easily aggregate, or to make the developed image a thin layer.

A fine powder with an average particle size of 3 to 10 μm is used to form a powder that does not easily cause agglomeration.

b. The particle size range of the toner is set to an average particle size of ±3 μm.

c. The shape of the toner is made almost spherical.

d. Adding fine powder of silica, fatty acid metal salts, fluorine compounds, etc. to the toner.

etc., and these can be used alone or in combination.

When used in combination, the above a and C, a and C and d, a
It is better to combine C and d such as and b and C1 or a and b.

The above can be obtained by melt-kneading and classifying finely pulverized powder, and C can be obtained by spheroidizing the finely pulverized powder with hot air, or by melting or dissolving the toner composition. By spray drying (9), the monomer constituting the binder resin of the toner can be polymerized in the presence of other constituent components of the toner, such as a colorant, an antistatic agent, or a magnetic powder. It is also possible to do so.

When producing toner using this polymerization process, first, ultrafine particles of 0.2 to 0.4 μm are formed by emulsion polymerization, etc., and then, using these ultrafine particles as cores, the ultrafine particles are grown by polymerization. A so-called seed polymerization method may be used to obtain a desired particle size.

When a 1-ner is formed by this seed polymerization method, the above-mentioned a.
A 1-ner satisfying b and c can be obtained.

When using such toner, the following phenomenon occurs on the recording paper: If the toner is formed thickly, it will be fixed. Aggregates of toner particles occur in the 3t12 toner image. This is because if the image is thick, the toner particles will stick together and form aggregates due to the effects of heat and pressure during fixing.

Therefore, to prevent aggregates from forming in the toner image after fixing,
Developing is performed so that the thickness of the developed toner image layer becomes thin.

It is most preferable that the developed toner image is formed of toner particles in a substantially middle layer, but if the developed toner image is developed to form a layer of 40 um or less, the maximum particle diameter of the toner on the recording paper can be 30 μI or less. Further, in the developing process, it is preferable to seal the developing device so that the toner does not aggregate due to moisture absorption or compression of the toner.

Development is carried out by forming a single layer of toner on a toner carrier by magnetic force or electrostatic force, and developing this toner layer without contacting the electrostatic latent carrier, or even if the toner layer misses contact with the electrostatic latent carrier. Develop so that only the surface area of the image is in contact with the image. Further, the toner of the present invention may be a -component developer or a two-component developer.

When the toner is charged 19 more intensively than in normal development, a thinner developed toner image 19 is produced. In the case of normal one-component development, the charge matrix of the toner is 2 to 7 μc/g, and in the case of two-component development, it is 12 to 20 μc/g, but in the case of the present invention, it is 9 to 1-5 μC/g, respectively. , 22-37
It is preferable to set the value to μc/g.

In other words, during development, toner particles in 2 to 3 layers near the surface of a single layer of toner are attracted by the electrostatic attraction force with the electrostatic latent image and migrate to the electrostatic latent image carrier, but inside the single layer of toner. The charge speed of the toner is determined so that electrostatic repulsion between toner particles prevents migration.

After developing the electrostatic latent image to a thickness of approximately 40 μm or less, the electrostatic latent image is transferred and fixed to form an image.

(Example) The image forming method of the present invention will be described according to the illustrated example.

As shown in FIG. 1, the solid black image output as a copy is of course formed by toner being dispersed in accordance with the image density. Because toner particles 1, small particles 2, or minute particles 3 are dispersed in a non-uniform mixture, even in images with the same density, the toner particles tend to be uneven, resulting in completely uniform toner particles. A toner image of image@density is not formed.

The solid black image shown in Figure 1 above shows the case where the output density is 0.3 to 0.6. Graded (=j) on the limit sample.

Therefore, in the examples and conventional examples described later, the results of evaluations are shown in the same manner as in the case described above.

Also, humans look at a copy and judge whether it is good or bad.
Of course, this refers to the final image, and we cannot see the image quality or image formation during the copying process, nor do we know how the conditions for the development process are set. , which is not a problem.

Accordingly, as shown in FIG. It is necessary to analyze the distribution state of toner in an image.

Therefore, the inventors of the present invention investigated how a human would look when the particle size distribution of the toner is in a copied image. It has been found that the maximum particle size of the 1-ner fine powder plays an important role. (This maximum particle size is
After) As shown in E, d9 of the particle size distribution on the print
The method of the present invention can be applied to both line images and halftone dot images, but is especially suitable for solid black images and roughness when the output density is 0.3 to 0.6. It has been found to be particularly effective for images of

The fact that the above-mentioned solid black image is reproduced well means that
It can also be said that this is a necessary condition for other images, such as high-density solid black images, lines, halftone dots, etc., to become clearly visible.

Conventional example 1 (a) A ZnO-based photoreceptor was used, and the charging voltage was set to 800
Form a latent image with V, and create two components for that latent image! - Magnetic brush development was performed using This developer is
The carrier is styrene resin (30wt%) and magnetic powder (7%).
The toner used was a polyester resin with a particle size of 12 μm and no external additives added.

Then, the toner image formed as described above is
When transferring from the photoreceptor to paper, sticky 6 transfer was performed using a silicone rubber roller as an intermediate medium, and the paper was placed on the rubber roller to perform thermal transfer and fixing simultaneously.

The toner image thus formed had an output density of 0.5, and the maximum particle size of the toner particles in that case was 62 μm. ...■(b>) In the method shown in (a) above, the same polyester toner was used as the toner, and 1 wt % of silica was added as an external additive.

As a result, the output density of the formed toner image was 0.45, and the maximum particle size was 45 μm.・・・
...■ Conventional Example 2 (a) A Se-based photoreceptor is used, a latent image is formed in the same manner as in Example 1, and the latent image is developed with a two-component developer. A 1-stage image was formed.

In this case, the two-component developer is a styrene resin (30wt%, magnetic powder 7Qwt%) for gear↑7, and a polyester resin with a size of 5μm for l-f-. Using.

The toner image thus formed has an output CIff of 0.55 and a maximum particle size of 53 μm.
Met. (b) A toner having the same components was used in the method shown in (a), but 3 wt % of silica was added to the toner as an external additive.

In this case, the alarm concentration was 0.55 and the maximum particle size was 40LtIll.・・・・・・■Example
1 Development was carried out in the same manner as in Conventional Example 1 using a two-component developer. In this case, in particular, the toner was sharply classified, d 90/ (11o = 2 (conventional Shinoha 4), the particle size was 9 μm, and 4 wt% of silica was added as an external additive. .

As a result, the output concentration was 0.40 and the maximum particle size was 25 μm. . . . Example 2 In the same manner as in Example 1 described above, a 3e type photoreceptor was used to form a latent image.

A toner image was formed on the i8I& using a two-component developer.
90/d10=2. In addition, silica to which 2 wt % of silica was added as an external additive was used.

The toner image thus formed had a particle size of 0.5 and a maximum particle size of 15 μI. . . . Example 3 A Se-based photoreceptor was used and charged at a voltage of 5 oov to form a latent stock.

Then, -component magnetic brush development was performed on the latent image.

The 1-ner used for this purpose was a styrene/acrylic resin containing 50% resin and 50% magnetic powder, and a mixture thereof with an antistatic agent. Then, the particle size of this toner is 10 μ-, and d 90 / d 10 =
It was classified into 2.

A thin layer of this toner is formed on the surface of the developing roller (Ti1 roller), and MF! is applied to the photoreceptor. The film was developed to form a toner image.

As a result, the output density of the 1-screen image was 0.05, and the maximum particle size was 28 μm. . . . Example 4 The same developer and developing method as in Example 3 were used, but an organic type photoreceptor was used and charged at 800 μm.

As a result, the output density of the 1q-sized horse chestnut image was 0.45, and the maximum particle size was 21 μm.・・・
...■ The graph in FIG. 2 compares the above embodiment with the conventional example and summarizes it in a table.

In FIG. 2, the relationship between the maximum particle diameter (μm) and granularity is plotted.

In this graph, when the maximum particle diameter is 20 μm or less,
The image quality is comparable to offset printing on coated paper, and the image quality is 30
It has been found that at micrometers or less, the image quality is comparable to offset printing on plain paper by 1!7.

In addition, in the above-described embodiments of the present invention, an example is shown in which a photoreceptor drum is used as the electrostatic latent image forming member, but this is not limited to the photoreceptor drum.
Of course, this is possible by using the photoreceptor bell 1 or other members.

(Effects of the Invention) As described above, the image forming method of the present invention grasps the fine particle 1-toner reproduced as a toner image from the concept of the maximum particle diameter on paper, and sets the maximum particle diameter to 30 μm or less. so that it can be set to 1 and by, thereby 1!
The resulting 1-toner image will be printed with a clear high quality equivalent to that of offset printing.

The toner image obtained by the image forming method of the present invention is reproduced with uniform image density, especially in the solid black image part, and the output density is 0.3.
~0.6 results in the best reproduction.

Furthermore, in the image forming method of the present invention, a conventionally used electronic copying machine can be used, and thereby high-quality copies can be made in 14 minutes.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing the distribution state of toner particles in a solid black image, and Figure 2 is a graph showing the relationship between the maximum particle diameter of l-toner and the granularity of the reproduced gutter image. be. Symbols in the diagram

Claims (1)

[Claims] (1) A method for reproducing an image composed of fine toner particles, characterized in that the maximum particle diameter of the fine toner particles in the final particle size distribution on a recording paper is 30 μm or less.