JP2003076233A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus which transfers a toner image to newly be transferred to a transfer material at a high transfer ratio and does not re-transfer already transferred toner to a photoreceptor even when a plurality of toner images are superposed and transferred by using the toner having small particle size toner or toner with uniform particle size distribution and particle shape. SOLUTION: The image forming apparatus has at least an electrifying means, an image exposure means, a toner developing means and a transfer means in this order around a photoreceptor. The image forming apparatus transfers the toner image formed on the photoreceptor to the transfer material and forms the image. The image forming apparatus is further provided with a means to irradiate a non-image region on a photoreceptor surface with light between the toner developing means and the transfer means while leaving a predetermined unexposed region around the toner image.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus used in a copying machine, a printer or the like.

[0002]

2. Description of the Related Art At present, in most image forming apparatuses which are required to have high image quality at high speed, an electrostatic latent image type image forming method centering on an electrophotographic method is adopted.

The reason therefor is that high-quality images can be stably obtained at high speed, and that they can be applied to color images and digital image formation. Therefore, it is considered that the electrostatic latent image type image forming method will continue to occupy a large amount in the future.

However, the performance demand level of the image forming technology in the market is high and is increasing year by year. Therefore, further improvement in performance is required even in the electrostatic latent image system.

Of these demands, needless to say, the biggest one is further improvement in image quality. As a countermeasure against this, it is effective to reduce the particle size of the toner and to make the particle size distribution and particle shape uniform. Is.

However, reducing the particle size of the toner, aligning the particle distribution, and the particle shape often cause other problems, and practical application is difficult without these measures.
In particular, at the time of forming a color image, the problem itself has not been clarified.

[0007]

In order to increase the transfer rate of the toner image from the photoconductor to the intermediate transfer body or the image support, the voltage applied to the transfer roller or the transfer wire electrode is increased. Expose the entire surface,
A method of controlling the surface of the photoconductor or the toner to have an appropriate charge by pre-transfer charging has been used. However, each of these methods has a problem. For example, in the case where a leak occurs in a minute space and an image is missing, the toner in the image area is scattered to the peripheral area, and the charge of the photoconductor or the toner is appropriately controlled. Difficult to do. Thus, conventionally, there was a limit to increase the transfer rate without causing image defects,
The tendency becomes even stronger when a toner having a small particle size or a toner having a uniform particle size distribution and particle shape is used.

Particularly, in a color copying machine or a color printer, usually, a plurality of photoconductors are used, and monochromatic color images formed by the respective photoconductors are sequentially transferred to produce a superposed color image. If the transfer rate decreases in such a case, not only the image density decreases but also the color balance is disturbed, which is a serious problem.

When the current value flowing at the time of transfer is increased in order to increase the transfer rate, for example, the toner once transferred to the intermediate transfer member is also more likely to be retransferred to the photosensitive member in the subsequent transfer.

In many cases, an intermediate transfer member is used for color image formation, and primary transfer to the intermediate transfer member and secondary transfer from the intermediate transfer member to the image support are performed twice. In this case, the influence of the transfer rate becomes greater.

In order to avoid the above problems, a toner image formed by using a toner having a small particle size or a toner having a uniform particle size distribution and particle shape is transferred a plurality of times to form a superimposed color image. However, it is necessary to find a method that can obtain a sufficient transfer rate even if they are collectively transferred.

As described above, in a tandem type color image forming apparatus or the like, it is necessary to transfer a plurality of toner images by superimposing them on an intermediate transfer body or an image support. The toner image has already been transferred onto the intermediate transfer member or the image support (both of which may be referred to as a transfer material),
When a toner image is further transferred onto it, a toner image to be newly transferred to the transfer material is formed at a high transfer rate, and it is necessary to select conditions under which the already transferred toner is not retransferred to the photoconductor.

However, when a toner having a small particle size or a toner having a uniform particle size distribution and particle shape is used, this condition range is narrow, and the appropriate condition may not be found in practice. In order to put these toners into practical use, it is necessary to devise a method capable of widening this range.

The present invention has been made to solve the above problems. That is, an object of the present invention is to provide an image forming apparatus capable of obtaining a sufficient transfer rate even when transferring a toner image formed using a toner having a small particle size or a toner having a uniform particle size distribution and particle shape. Especially.

Further, even if a plurality of toner images using toners having a small particle size or a toner having a uniform particle size distribution and particle shapes are superposed and transferred, the toner image to be newly transferred to the transfer material has a high transfer rate. It is an object of the present invention to provide an image forming apparatus in which the toner that has been transferred by the above method and that has already been transferred is not retransferred to the photoconductor.

[0016]

Means for Solving the Problems As a result of intensive studies by the present inventors, it was found that the object of the present invention can be achieved by adopting any of the following constitutions.

[1] At least a charging unit, an image exposing unit, a toner developing unit, and a transferring unit are provided around the photosensitive member in this order, and the toner image formed on the photosensitive member is transferred to a transfer material to form an image. In the image forming apparatus, an image forming apparatus is provided between the toner developing means and the transfer means, and has means for irradiating the non-image area on the surface of the photoconductor with light, leaving a predetermined unexposed area around the toner image. apparatus.

[2] The image forming apparatus as described in [1], wherein the toner used in the toner developing means has a volume average particle diameter of 3 to 8 μm.

[3] The particle size of toner particles used in the toner developing means is D (μm), the natural logarithm lnD is plotted on the horizontal axis, and the horizontal axis is divided into a plurality of classes at intervals of 0.23. When the histogram showing the distribution is created, the sum of the relative frequency (m1) of the toner particles included in the most frequent class and the relative frequency (m2) of the toner particles included in the second most frequent class after the most frequent class ( The image forming apparatus according to [1], wherein M) is 70% or more.

[4] The image forming apparatus according to [1], wherein the toner used in the toner developing means has an average circularity of 0.95 to 0.99.

[5] The image forming apparatus according to [1], wherein the toner used in the toner developing means is produced by a polymerization method.

[6] The image forming apparatus according to [1], wherein the developer used in the toner developing means is a two-component developer.

[7] The image forming apparatus as described in [1], wherein the light amount of the image exposing means and the light amount of the light irradiating means can be set independently of each other.

[8] The image according to [1], wherein the sum of the exposure area by the image exposure means and the light irradiation area by the light irradiation means is 50% or more of the entire image area on the photoconductor. Forming equipment.

[0025]

[9] In the image forming apparatus described in [1], the transfer material transferred by the transfer unit described in [1] is an intermediate transfer member, and a superimposed color image transferred and formed on the intermediate transfer member The image forming apparatus according to [1], wherein the image is transferred onto the image support by the second transfer means.

[10] The light source of the light irradiating means is
The image forming apparatus according to [1], which is commonly used by a plurality of photoconductors.

[11] The light source of the light irradiating means is
The image forming apparatus as described in [1], which is used in common with a light source of the image exposing means.

[12] At least one photoconductor, a plurality of toner developing means, and a transfer means for transferring the formed plurality of toner images to an intermediate transfer body, and a color image is formed by superposition on the intermediate transfer body. In the image forming apparatus that
An image forming apparatus, wherein the intermediate transfer member transmits at least 1% or more of light having a wavelength of 400 to 900 nm, and irradiates light having a wavelength of 400 to 900 nm from the back surface of the intermediate transfer member in a transfer region.

[13] Image formation for forming a color image by superimposing color images having a transfer means for transferring a plurality of toner images formed by at least one photoconductor and a plurality of toner developing means to an image support. In the apparatus, an image forming apparatus characterized in that a holder for holding an image support transmits at least 1% of light having a wavelength of 400 to 900 nm, and irradiates light having a wavelength of 400 to 900 nm from the back surface of the holder in a transfer region. .

[14] The image forming apparatus as described in [12] or [13], wherein the toner used in the toner developing means has a volume average particle diameter of 3 to 8 μm.

[15] The particle size of the toner particles used in the toner developing means is D (μm), the natural logarithm lnD is plotted on the horizontal axis, and the horizontal axis is divided into a plurality of classes at intervals of 0.23. When you create a histogram showing the distribution,
The relative frequency (m1) of the toner particles included in the most frequent class,
The image forming apparatus according to [12] or [13], wherein the sum (M) with the relative frequency (m2) of the toner particles included in the second most frequent class is 70% or more. .

[16] The image forming apparatus as described in [12] or [13], wherein the toner used in the toner developing means has an average circularity of 0.95 to 0.99.

[17] The image forming apparatus as described in [12] or [13], wherein the toner used in the toner developing means is produced by a polymerization method.

[18] The image forming apparatus as described in [12] or [13], wherein the developer used in the toner developing means is a two-component developer.

[19] The image forming apparatus as described in [12] or [13], wherein the light emitted from the back surface of the intermediate transfer member or the holding member is emitted from an LED.

[20] The image forming apparatus as described in [12] or [13], characterized in that the light source of the light emitted from the back surface of the intermediate transfer member or the holding member is commonly used by a plurality of photoconductors.

[21] The light emitted from the back surface of the intermediate transfer body or the holding body is a transfer area, and is irradiated on the upstream side of the transfer means in the traveling direction of the intermediate transfer body or the holding body. The image forming apparatus according to [12] or [13].

[22] The image forming apparatus as described in [12] or [13], wherein the transfer means is in the form of a roller to which a voltage is applied.

[23] The image forming apparatus as described in [12] or [13], wherein the transfer means is a corotron charger using a wire to which a voltage is applied.

The above inventions [1] to [11] and [1]
In the inventions 2] to [23], the former is sometimes referred to as the first invention and the latter is sometimes referred to as the second invention because the configurations are slightly different.

The non-image area in the first aspect of the invention means the toner in the entire image area on the surface of the photoconductor (for example, if the B4 plate image is formed, the B4 plate image is formed). It refers to the area of the part where the image is not formed.

The transfer area in the second aspect of the invention is an area where the toner image on the surface of the photoconductor is in contact with the surface of the intermediate transfer body or the surface of the image support, and the transfer is performed. The intermediate transfer member is for temporarily carrying the toner image formed by toner development, and the image support is for carrying the final image. Note that these may be collectively referred to as a transfer material.

Usually, the intermediate transfer member is made of silicone rubber or a resin film which does not expand or contract, and the like, and the image support is plain paper, processed paper or the like. further,
The holding member carries and conveys the image supporting member.

[0044]

BEST MODE FOR CARRYING OUT THE INVENTION The structure of the first invention and the components used therein will be described.

FIG. 1 is a sectional view for explaining the structure of a color copying machine which is an example of the image forming apparatus according to the embodiment of the present invention.

FIG. 2 is an enlarged sectional view of the image forming portion 10Y for forming a yellow image for explaining the first invention. A means (also referred to as a light irradiation means) 9Y for irradiating the non-image area with light while leaving a predetermined unexposed area around the toner image on the surface of the photoreceptor is a toner developing means 4Y and a transfer means 7.
It exists between Y. FIG. 3 is also a view for explaining the first invention, and FIG. 3A is a partially enlarged view of the toner image X formed by development on the photoconductor 1Y and a non-image area portion around the toner image X. Is shown. Further, FIG. 3B shows a partially enlarged view of the photosensitive body surface after light irradiation with leaving a predetermined unexposed area. In the transfer area, W is an unexposed non-image area.

The image forming apparatus main body GH shown in FIG. 1 is called a tandem type color image forming apparatus, and comprises a plurality of sets of image forming units 10Y, 10M, 10C and 10K, a belt-shaped intermediate transfer member 6, and a sheet-shaped intermediate transfer member 6. It has a paper conveying means and a fixing device 24.

Image forming section 1 for forming a yellow image
0Y is a charging unit 2Y, an image exposing unit 3Y, and a toner developing unit 4 which are arranged around a photoconductor 1Y as an image forming body.
It has Y, a light irradiation means 9Y, and a cleaning means 8Y. The image forming unit 10M that forms a magenta image is
It has a photoreceptor 1M as an image forming body, a charging means 2M, an image exposing means 3M, a toner developing means 4M, a light irradiating means 9M, and a cleaning means 8M. The image forming unit 10C that forms a cyan image includes a photoreceptor 1C as an image forming body,
Charging means 2C, image exposing means 3C, toner developing means 4C,
It has a light irradiation means 9C and a cleaning means 8C.
The image forming unit 10K that forms a black image has a photoreceptor 1K as an image forming body, a charging unit 2K, an image exposing unit 3K, a toner developing unit 4K, a light irradiation unit 9K, and a cleaning unit 8K. The charging unit 2Y and the image exposure unit 3Y, the charging unit 2M and the image exposure unit 3M, the charging unit 2C and the image exposure unit 3C, and the charging unit 2K and the image exposure unit 3K constitute a latent image forming unit.

The intermediate transfer member 6 is an endless belt,
It is stretched by a plurality of rollers and is rotatably supported.

Image forming units 10Y, 10M, 10C and 1
The color image of each color formed from 0K is sequentially transferred (primary transfer) onto the rotating intermediate transfer body 6 by the transfer means 7Y, 7M, 7C and 7K to form a superimposed color image. . As shown in a partially enlarged cross-sectional view of the image forming portion in FIG. 2, before the transfer by the transfer means, the light irradiating means 9Y, 9M, 9C and 9K are provided on the respective photoreceptor surfaces as shown in FIG. The non-image area is irradiated with light, leaving a predetermined unexposed area around the toner image.

The image support P housed in the paper feed cassette 20 is fed by the paper feed means 21 and fed by the paper feed roller 22.
After passing through A, 22B, 22C, the registration roller 23, etc., it is conveyed to the transfer means 7A, and the superimposed color image is transferred onto the image support P (secondary transfer). The image support P on which the color image has been transferred is fixed by the fixing device 24, is sandwiched by the paper ejection rollers 25, and is ejected outside the apparatus by the paper ejection tray 26.
Placed on top.

On the other hand, after the color image is transferred to the image support P by the transfer means 7A, the residual toner on the intermediate transfer body 6 from which the image support P is separated is removed by the cleaning means 8A.

5Y, 5M, 5C and 5K are toner replenishing means for replenishing the toner developing means 4Y, 4M, 4C and 4K with new toner.

An image reading device YS including an automatic document feeding device 201 and a document image scanning exposure device 202 is installed above the image forming apparatus main body GH. The original d placed on the original table of the automatic original feeding device 201 is conveyed by the conveying means, and the image of one side or both sides of the original is scanned and exposed by the optical system of the original image scanning exposure device 202, and the line image sensor CCD is exposed. Is read.

The analog signal photoelectrically converted by the line image sensor CCD is subjected to analog processing, A / D conversion, shading correction, image compression processing, etc. in an image processing section, and then an image writing section (image exposing means) 3Y. ,
3M, 3C, 3K and light irradiation means 9Y, 9M, 9C, 9K
Send a signal to.

The automatic document feeder 201 is provided with an automatic double-sided document conveying means. Since the automatic document feeder 201 can continuously read the contents of a large number of documents d fed from the document table and store them in the storage means (electronic RDH function), copying is possible. It is conveniently used when copying the contents of a large number of originals by the function or when transmitting a large number of originals d by the facsimile function.

The light source of the light irradiation means used in the present invention is
The tungsten lamp, neon lamp, LED, semiconductor laser light element, etc. are not particularly limited. However, because it is necessary to irradiate the non-image area with light leaving a predetermined unexposed area, it is necessary to control the irradiation area in an imagewise manner.
D, a semiconductor laser optical device is preferable.

The non-image area is a portion other than the area which is actually image-exposed in the entire image area (for example, the size of B4 when an image of B4 is formed) used for image formation on the surface of the photoconductor. is there. In the digital exposure type image forming apparatus, the setting can be easily made from the image data. Further, although it is necessary to leave a predetermined unexposed area, it is preferable that an appropriate range is an unexposed area having a width of 0.3 to 1.5 mm around the image exposure area. If it is less than 0.3 mm, the toner may scatter from the image area, and if it exceeds 1.5 mm, the unexposed area may be adversely affected by charging.

Since the light quantity of the light irradiation means and the light quantity of the image exposure means have respective appropriate values, it is desirable that the light quantity can be changed independently. Further, the sum of the exposure area by the image exposure means and the light irradiation area by the light irradiation means is preferably 50% or more of the entire image area on the photosensitive member in order to improve the transfer rate. However, it is preferable to use the light source of each light irradiation unit in common in terms of downsizing and cost reduction of the entire image forming apparatus. The same applies to the case where the light source of the image exposure unit and the light source of the light irradiation unit are shared in each image forming unit.

Although it is not always necessary to use an intermediate transfer member as in the above-mentioned apparatus, a method of using an intermediate transfer member is generally used to stably maintain a high transfer rate of toner and prevent image shift. Is preferred.

Next, the second invention will be described. Since it has many common points with the first invention, the description will be focused on the different points.

FIG. 4 is a schematic view showing a main part of an image forming section having means for irradiating light from the back surface of the intermediate transfer member.

As shown in the main part of the image forming section in FIG. 4, there is no light irradiation means as in the first invention structurally, and there is a means 11Y for irradiating light from the back surface of the intermediate transfer member in the transfer area, which has a wavelength of 400. Light of ˜900 nm is irradiated (the yellow image forming portion is shown, but of course, other image forming portions have 11M, 11C, and 11K, respectively). Intermediate transfer member 6
Alternatively, in the case of the structure in which the image is directly transferred to the image support, the support uses a support that transmits at least 1% or more of light having a wavelength of 400 to 900 nm. In FIG. 4, Z is a transfer area, and T is toner on the photoconductor. Further, in order to effectively increase the transfer rate, as shown in FIG.
Alternatively, it is preferable to irradiate the transfer area on the upstream side of the transfer means 7Y in the traveling direction of the holder of the image support. Also,
For cost reduction and size reduction, it is preferable that the light source is commonly used in the transfer area of each color image forming section.

The light source of the means for irradiating light from the back is
The tungsten lamp, neon lamp, LED, semiconductor laser light element, etc. are not particularly limited. However, the LED is preferable because it is easy to control the irradiation area and the light amount.

The toner used in the present invention, its shape, and the image forming apparatus or other requirements will be described below.

The technology and requirements relating to the constituent features of the present invention, the toner used and the shape thereof, the image forming apparatus, and the like will be described below.

1. Photoreceptor The photoreceptor in the present invention may be either an organic or inorganic photoreceptor as long as it is a so-called electrophotographic photoreceptor, and is not particularly limited. However, the most widely used in recent years is an organic photoconductor (OPC).

In the organic photoreceptor, a phthalocyanine pigment, a perylene pigment or the like is usually used as a charge generating substance, fine particles of these pigments are dispersed in a resin and then applied to form a charge generating layer, and a trimethylamine compound or the like is used for charge transport. A laminate type is used which is used as a substance and is coated with a resin to form a charge transport layer.

2. Charging means, image exposing means, toner developing means, transfer means which are commonly used in electrophotographic image forming apparatuses can be used in the present invention.

That is, the charging means is a corotron, a scorotron type corona charger, a roller charger, a brush charger or the like.

A semiconductor laser light source, an LED light source, or the like is used as the image exposure means, and these are exposed in a beam or spot shape to imagewise expose the uniformly charged surface of the photoreceptor to form a latent image.

The toner developing means may be of a one-component or two-component developing system, and these may be any developing device capable of using the developer described later.

3. Toner used in the present invention
To solve the problem that occurs in an image forming apparatus for forming a high-quality image with high resolution, high sharpness, and no fog, using a toner with a small particle size, a narrow particle size distribution, and a uniform shape Is.

Therefore, a toner having a small particle diameter is used, but specifically, the volume average particle diameter is 3 to 8.
It is preferably μm. If the thickness is less than 3 μm, the charging may not be sufficiently performed, and the toner may be scattered to deteriorate the image quality and adversely affect the human body. If it exceeds 8 μm, the image quality may not be good. The volume average particle size can be measured by Coulter Counter TA-II or Coulter Multisizer (both manufactured by Coulter Co.).

The toner according to the present invention has a narrow particle size distribution. Specifically, the toner particle size is D (μm).
In the histogram showing the number-based particle size distribution in which the natural logarithm lnD is plotted on the horizontal axis and the horizontal axis is divided into a plurality of classes at 0.23 intervals, the relative frequency (m1) of toner particles included in the most frequent class is represented. And the relative frequency (m2) of the toner particles included in the second most frequent class after the most frequent class, the sum (M) is preferably 70% or more. When the sum (M) of the relative frequency (m1) and the relative frequency (m2) is 70% or more, the dispersion of the particle size distribution of the toner particles becomes narrow, so that a high quality image can be obtained.

In the present invention, the histogram showing the number-based particle size distribution has a natural logarithm lnD (D: particle size of individual toner particles) in a plurality of classes (0 to 0) at intervals of 0.23.
0.23: 0.23 to 0.46: 0.46 to 0.69:
0.69 to 0.92: 0.92 to 1.15: 1.15
1.38: 1.38 to 1.61: 1.61 to 1.84:
1.84-2.07: 2.07-2.30: 2.30-
2.53: 2.53 to 2.76 ...), which is a histogram showing a number-based particle size distribution, which is a histogram of a sample measured by a Coulter Multisizer manufactured by Coulter Inc. according to the following conditions. Transfer the particle size data to the computer via the I / O unit,
It is created by a particle size distribution analysis program in the computer.

Measurement conditions (1) Aperture: 100 μm (2) Sample preparation method: Electrolyte solution [ISOTON R-1
1 (manufactured by Coulter Scientific Japan)
An appropriate amount of a surfactant (neutral detergent) is added to 50 to 100 ml and stirred, and 10 to 20 mg of a measurement sample is added thereto. This system is prepared by subjecting it to an ultrasonic disperser for 1 minute.

The shape of the toner according to the present invention has an average value (average circularity) of the shape factors represented by the following formula of 0.95.
˜0.99, more preferably 0.9
40 to 0.975.

Shape factor = (circle perimeter obtained from equivalent circle diameter) / (perimeter of particle projection image) It is also preferable that the distribution of the shape factor is sharp, and the standard deviation of the circularity is 0.
It is preferably 10 or less, and the CV value calculated by the following formula is preferably less than 20%, more preferably less than 10%.

CV value = {(standard deviation of circularity) / (average circularity)} × 100 By setting this average circularity to 0.95 to 0.99, the shape of the toner is made irregular to some extent. be able to. That is, the image quality can be improved by setting the average circularity to 0.99 or less. Also, by setting the average circularity of 0.95 or more, to suppress the degree of irregular shape of the particles,
Fragmentability of particles due to stress during long-term use can be suppressed.

4. Method of Producing Toner The method of producing the toner according to the present invention is not particularly limited, but it is preferable to use a so-called polymerization method in which toner particles are produced during a polymerization reaction without performing kneading and pulverization classification as in a so-called pulverization method. This is because a product having a small particle size, a narrow particle size distribution, and a uniform particle shape can be easily produced.

For example, a suspension polymerization method or emulsion polymerization of a monomer in a liquid added with an emulsion of necessary additives to produce fine polymer particles, followed by organic solvent, flocculant, etc. It can be manufactured by a method of adding and associating. At the time of association, a method of preparing by mixing with a dispersion liquid such as a release agent or a colorant necessary for the constitution of the toner to allow association, or dispersing a toner constituent component such as a release agent or a colorant in a monomer Then, a method of emulsion polymerization may be used. Here, the association means that a plurality of resin particles and colorant particles are fused.

In the suspension polymerization method, a polymerizable monomer in which these various constituent materials are dissolved or dispersed is used in an aqueous medium containing a dispersion stabilizer by using a homomixer or a homogenizer to obtain a toner having a desired size. Disperse in oil drops. Then, the reaction mixture is transferred to a reaction device having a stirring mechanism and heated to advance the polymerization reaction. After the reaction is completed, the dispersion stabilizer is removed, filtered, washed, and dried to prepare the toner according to the present invention.

As a method for producing the toner according to the present invention, there is also a method in which resin particles produced by emulsion polymerization or the like are associated or fused in an aqueous medium. The method is not particularly limited, for example,
JP-A-5-265252 and JP-A-6-32994
The methods described in JP-A No. 7 and JP-A No. 9-15904 can be mentioned.

A method of associating a plurality of resin particles and dispersed particles of a constituent material such as a colorant, or a plurality of fine particles composed of a resin and a colorant, particularly after dispersing them in water with an emulsifier, the critical aggregation At the same time as adding a coagulant at a concentration higher than that for salting out, heat-bonding is performed at a temperature not lower than the glass transition temperature of the formed polymer itself to gradually grow the particle size while forming fused particles, and to obtain the target particle size. When a large amount of water is added to stop the particle size growth, the particle surface is smoothed while heating and stirring to control the shape, and the particles are heated and dried in a fluid state in a water-containing state. The toner according to the present invention can be formed. Here, an organic solvent that is infinitely soluble in water may be added simultaneously with the coagulant.

As the polymerizable monomer constituting the resin, styrene, methacrylic acid ester, acrylic acid ester and olefins can be used alone or in combination.

The toner according to the present invention contains at least a resin and a colorant, but if necessary, it may contain a releasing agent which is a fixing property improving agent, a charge control agent and the like. Further, an external additive composed of inorganic fine particles, organic fine particles or the like may be added to the toner particles containing the resin and the colorant as main components.

As the colorant used in the toner according to the present invention, carbon black, a magnetic substance, a dye, a pigment or the like can be optionally used. Examples of the carbon black include channel black, furnace black, acetylene black, thermal black, Lamp black or the like is used. Ferromagnetic metals such as iron, nickel and cobalt as magnetic materials, alloys containing these metals, ferrite, compounds of ferromagnetic metals such as magnetite, alloys that do not contain ferromagnetic metals but exhibit ferromagnetism by heat treatment, For example, manganese-copper-aluminum, manganese-copper-tin, and other types of alloys called Heusler alloys, chromium dioxide, and the like can be used.

As the dye, C.I. I. Solvent Red 1, 49, 52, 58, 63, 111, 1
22, C.I. I. Solvent Yellow 19, 44, 7
7, ibid 79, ibid 81, ibid 82, ibid 93, ibid 98, ibid 10
3, 104, 112, 162, C.I. I. Solvent Blue 25, 36, 60, 70, 93, 9
5 and the like can be used, and a mixture thereof can also be used. As the pigment, C.I. I. Pigment Red 5,
48: 1, 53: 1, 57: 1, 122, 1
39, 144, 149, 166, 177, 1
78, ibid. 222, C.I. I. Pigment Orange 31, the same 43, C.I. I. Pigment Yellow 14, Same 17 and Same 9
3, 94, 138, C.I. I. Pigment Green 7, C.I. I. Pigment Blue 15: 3, 60 and the like, and a mixture thereof can also be used. The number average primary particle size varies depending on the type, but is generally about 10
About 200 nm is preferable.

5. Developer and Developing Conditions Next, the developer and developing conditions used in the present invention will be described.

The toner used in the present invention may be used as a one-component developer or a two-component developer, but is preferably a two-component developer.

When used as a one-component developer, there is a method of using the toner as it is as a non-magnetic one-component developer, but usually, the magnetic particles are prepared by containing magnetic particles of about 0.1 to 5 μm in the toner particles. Used as a developer. As a method of containing it, it is common to incorporate it in the non-spherical particles in the same manner as the colorant.

Further, it can be used as a two-component developer by mixing with a carrier. In this case, conventionally known materials such as metals such as iron, ferrite and magnetite, alloys of these metals with metals such as aluminum and lead are used as the magnetic particles of the carrier. Ferrite particles are particularly preferable. The volume average particle diameter of the magnetic particles is 15
˜100 μm, more preferably 25 to 60 μm.

The volume average particle diameter of the carrier is typically measured by a laser diffraction type particle size distribution measuring apparatus "HELOS" equipped with a wet disperser (SYMPATIC (SYMP).
(Made by ATEC)).

The carrier is preferably a carrier in which magnetic particles are further coated with a resin, or a so-called resin dispersion type carrier in which magnetic particles are dispersed in a resin. The resin composition for coating is not particularly limited, but, for example, an olefin resin, a styrene resin, a styrene-acrylic resin, a silicone resin, an ester resin, a fluorine-containing polymer resin, or the like is used. The resin for forming the resin-dispersed carrier is not particularly limited, and known ones can be used. For example, styrene acrylic resin, polyester resin, fluorine resin, phenol resin, etc. can be used. it can.

The developing method can be used either in contact or in non-contact. When a non-contact development method is adopted, non-contact regular development or non-contact reversal development can be carried out. The DC developing electric field at that time is 1 × 10 in absolute value.
³ to 1 × 10 ⁵ V / cm, preferably 5 × 10 ³ to 1 × 1
When it is 0 ⁴ V / cm and less than 10 ³ V / cm, the development is insufficient and sufficient image density cannot be obtained, and when it exceeds 10 ⁵ V / cm, the image quality is deteriorated and fogging occurs.

AC bias is 0.5 to 4 kV (p-
p), preferably 1 to 3 kV (pp), and the frequency is 0.1 to 10 kHz, preferably 2 to 8 kHz. When the AC bias is less than 0.5 kV (pp), the toner adhering to the carrier does not separate, the non-contact development becomes insufficient, and the image density becomes insufficient. When the AC bias exceeds 4 kV (pp), the carrier in the developer flies and carrier adheres to the photoconductor. Further, if the frequency of the AC bias is less than 0.1 kHz, the toner is not sufficiently detached from the carrier, resulting in insufficient development and lowering of image density. Further, when the frequency of the AC bias exceeds 10 kHz, the toner cannot follow the fluctuation of the electric field, resulting in defective development and a decrease in image density.

6. Other Configurations A so-called contact heating method can be cited as a suitable fixing method used in the present invention. In particular, as the contact heating method, a heat pressure fixing method, a heat roller fixing method, and a pressure contact heating fixing method in which fixing is performed by a rotating pressure member containing a fixedly arranged heating body can be mentioned.

The image forming apparatus of the present invention can be applied to general electrophotographic apparatuses such as copying machines, laser printers, LED printers and liquid crystal shutter type printers. It can be widely applied to devices such as light printing, plate making, and facsimile.

[0100]

EXAMPLES Next, the concrete aspects of the present invention will be shown to further explain the constitution and effects of the present invention, but the constitution of the present invention is not limited thereto.

Example 1 The following evaluations were performed using the color copying machine shown in FIG.

Each photosensitive member had a diameter of 60 mm, a photosensitive layer in which a phthalocyanine pigment was dispersed in polycarbonate was used, and a photosensitive layer coated to a total film thickness of 25 μm including a charge transporting layer was used. Each of the photoconductors was adjusted to a non-exposed portion potential of −600 V and an exposed portion potential of −50 V or less, imagewise exposed using a semiconductor laser light source (300 μW), and developed by a two-component developing method.

The volume average particle diameter of the toner is 6.0 μm, M
(M1 + m2) was 85% and the average circularity was 0.98.

The transfer speed of the intermediate transfer member was 180 mm / s, and the seamless semi-conductive resin belt (10 ⁸ Ω · c
m) was used. Further, the transfer (primary transfer) means from each photoconductor to the intermediate transfer member has a diameter of 20 mm on the back surface of the intermediate transfer member.
Install the foam resin roller (10 ⁶ Ω · cm) of
The constant current was controlled to μA.

As a transfer (secondary transfer) means from the intermediate transfer member to the image support (plain paper), a semiconductor roller was pressed against the intermediate transfer member from the back surface of the plain paper, and a constant current was controlled to 80 μA.

As the fixing means (apparatus), a heat roller and a pressure roller in which a heater is arranged are used.

An LED was used as a light irradiating means between the developing means and the transferring means, and a non-image area was left while leaving a 1 mm width around the photosensitive member exposure area by the image exposing means.

When an actual shooting test was conducted up to 200,000 copies, an image free from image bleeding and image dropout was obtained. Further, as shown in FIG. 5, a good result that the transfer rate was 95% or more from the beginning was obtained. The reason why the transfer rate fluctuates is that the image forming apparatus is temporarily stopped at the number of copies.

On the other hand, when the light irradiation by the light irradiation means is not performed, the transfer rate of 80% or more cannot be obtained from the beginning,
The transfer rate tended to decrease with the repeated copying.

Example 2 The same image forming apparatus as in Example 1 was used, but pre-transfer exposure was not performed, and at the stage where the foaming roller of the primary transfer means was in contact with the back surface of the intermediate transfer member as shown in FIG. The back surface of the intermediate transfer member was exposed with an LED light source.

The volume average particle diameter of the toner is 6.0 μm, M
(M1 + m2) was 85% and the average circularity was 0.98.

When the real shot test was carried out up to 200,000 copies, an image free from image bleeding and image dropout was obtained. Further, as shown in FIG. 6, a good result that the transfer rate was 95% or more from the beginning was obtained.

On the other hand, when light irradiation from the back surface was not performed by the light irradiation means, a transfer rate of 80% or more was not obtained from the beginning, and the transfer rate tended to decrease as the copying was repeated.

[0114]

According to the present invention, there is provided an image forming apparatus capable of obtaining a sufficient transfer rate even when a toner image formed by using a toner having a small particle size or a toner having a uniform particle size distribution and particle shape is transferred. You can do it.

Further, even if a plurality of toner images using toners of small particle size or toners of uniform particle size distribution and particle shape are superposed and transferred, the toner image to be newly transferred to the transfer material has a high transfer rate. It is possible to provide an image forming apparatus in which the toner that has been transferred by the above method and that has already been transferred is not retransferred to the photoconductor.

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a color copying machine that is an example of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of an image forming unit that forms a yellow image.

FIG. 3 is a partially enlarged view of a toner image formed on a photoconductor by development and a non-image area portion around the toner image.

FIG. 4 is a schematic diagram showing a main part of an image forming unit having a means for irradiating light from the back surface of the intermediate transfer member.

FIG. 5 is a diagram showing a transfer rate of 200,000 copies in Example 1.

FIG. 6 is a diagram showing a transfer rate of 200,000 copies in Example 2.

[Explanation of symbols]

1Y, 1M, 1C, 1K Photoconductors 2Y, 2M, 2C, 2K Charging means 3Y, 3M, 3C, 3K Image exposure means 4Y, 4M, 4C, 4K Toner developing means 6 Intermediate transfer bodies 7Y, 7M, 7C, 7K Transfer Means 9Y, 9M, 9C, 9K Means for irradiating light (light irradiating means) 10Y, 10M, 10C, 10K Image forming sections 11Y, 11M, 11C, 11K Means for irradiating light from the back surface

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 15/16 103 G03G 21/00 342 (72) Inventor Masashi Saito 2970 Ishikawacho, Hachioji, Tokyo Konica Stocks In-house (72) Inventor Hiroshi Morimoto 2970 Ishikawa-cho, Hachioji, Tokyo Konica Stock Company F-term (reference) 2H027 DE07 EA08 EC06 EC10 ED15 ED24 FA28 2H030 AB02 AD02 AD17 BB13 BB18 BB23 BB42 BB46 BB63 2H035 AA09 AC02 AB10 AB02 AB02 AZ09 AZ11 2H200 FA16 GA12 GA16 GA23 GA33 GA34 GA45 GA47 GA57 GA58 GA59 GA66 GA69 GB02 GB04 GB22 HA03 HA12 HB03 HB04 HB12 JA02 JB13 JC04 JC16 JC17 JC19 MB02 MC20 PA03 PA22 PA26 PA30

Claims (23)

[Claims] 1. At least a charging means is provided around the photoconductor,
In an image forming apparatus that has an image exposure unit, a toner developing unit, and a transfer unit in this order, and transfers a toner image formed on a photoconductor to a transfer material to form an image, between the toner developing unit and the transfer unit, An image forming apparatus comprising means for irradiating a non-image area on a surface of a photoconductor with light while leaving a predetermined unexposed area around a toner image. 2. The image forming apparatus according to claim 1, wherein the toner used in the toner developing means has a volume average particle diameter of 3 to 8 μm. 3. A particle size distribution on a number basis in which the particle diameter of toner particles used in the toner developing means is D (μm), the natural logarithm lnD is plotted on the horizontal axis, and the horizontal axis is divided into a plurality of classes at 0.23 intervals. When a histogram indicating is created, the sum (M) of the relative frequency (m1) of the toner particles included in the most frequent class and the relative frequency (m2) of the toner particles included in the next most frequent class. ) Is 70% or more, The image forming apparatus according to claim 1. 4. The image forming apparatus according to claim 1, wherein the toner used in the toner developing means has an average circularity of 0.95 to 0.99. 5. The image forming apparatus according to claim 1, wherein the toner used in the toner developing means is produced by a polymerization method. 6. The image forming apparatus according to claim 1, wherein the developer used in the toner developing means is a two-component developer. 7. The image forming apparatus according to claim 1, wherein the light quantity of the image exposing means and the light quantity of the light irradiating means can be set independently of each other. 8. The image forming method according to claim 1, wherein the sum of the exposure area by the image exposure means and the light irradiation area by the light irradiation means is 50% or more of the entire image area on the photosensitive member. apparatus. 9. The transfer material transferred by the transfer means is an intermediate transfer body, and the superimposed color image transferred and formed on the intermediate transfer body is transferred to an image support by the second transfer means. The image forming apparatus according to claim 1, wherein: 10. The image forming apparatus according to claim 1, wherein the light source of the light irradiating means is commonly used by a plurality of photoconductors. 11. The image forming apparatus according to claim 1, wherein the light source of the light irradiating means is used in common with the light source of the image exposing means. 12. An intermediate transfer member having at least one photosensitive member, a plurality of toner developing units, and a plurality of toner images formed thereon, the transfer unit transferring the toner images to the intermediate transfer member. In the image forming apparatus, the intermediate transfer member transmits at least 1% or more of light having a wavelength of 400 to 900 nm, and the intermediate transfer member has a wavelength of 4 nm from the back surface of the intermediate transfer member.
An image forming apparatus characterized by irradiating light having a wavelength of from 0 to 900 nm. 13. An image forming apparatus for forming a color superimposed color image, comprising a transfer means for transferring a plurality of toner images formed by at least one photoconductor and a plurality of toner developing means onto an image support. In the above image forming apparatus, the holding member holding the image supporting member transmits at least 1% or more of light having a wavelength of 400 to 900 nm, and irradiates light having a wavelength of 400 to 900 nm from the back surface of the holding member in the transfer region. 14. The volume average particle diameter of the toner used in the toner developing means is 3 to 8 μm.
The image forming apparatus according to 2 or 13. 15. The particle size of toner particles used in the toner developing means is D (μm), and the natural logarithm lnD is plotted on the horizontal axis,
When a histogram showing a number-based particle size distribution in which the horizontal axis is divided into a plurality of classes at intervals of 0.23 is created, the relative frequency (m1) of toner particles included in the most frequent class and the next to the most frequent class 14. The image forming apparatus according to claim 12, wherein the sum (M) of the toner particles included in the high frequency class and the relative frequency (m2) is 70% or more. 16. The image forming apparatus according to claim 12, wherein the toner used in the toner developing means has an average circularity of 0.95 to 0.99. 17. The image forming apparatus according to claim 12, wherein the toner used in the toner developing means is produced by a polymerization method. 18. The image forming apparatus according to claim 12, wherein the developer used in the toner developing means is a two-component developer. 19. The image forming apparatus according to claim 12, wherein the light emitted from the back surface of the intermediate transfer member or the holding member is emitted from an LED. 20. The image forming apparatus according to claim 12, wherein the light source for the light emitted from the back surface of the intermediate transfer member or the holding member is commonly used by a plurality of photoconductors. 21. The light emitted from the back surface of the intermediate transfer member or the holding member is a transfer area, and is irradiated on the upstream side of the transfer means in the traveling direction of the intermediate transfer member or the holding member. Item 12. The image forming apparatus according to Item 12 or 13. 22. The transfer means is of a roller shape to which a voltage is applied, and is used.
The image forming apparatus described. 23. The image forming apparatus according to claim 12, wherein the transfer means is a corotron charger using a wire to which a voltage is applied.