JP2003270969A - Image forming device - Google Patents

Abstract

(57) [Problem] To provide an image forming apparatus which shows stable image fixability and can print an image without roughness even when the type of toner or transfer material is changed. An image forming apparatus according to the present invention includes: a recording medium;
A developing unit configured to develop the electrostatic latent image formed on the recording medium with a developer to form a toner image; and a transfer unit configured to transfer the toner image onto a transfer material. The surface roughness Ra of the unfixed toner image is 2.0 μm or less at L = 0.8 mm. Ra = (1 / L) ∫ 0 L f (x) dx In the image forming apparatus of the present invention comprises a fixing means further comprising a fixing rotator and the pressure rotating body, elastic in at least one of them rotating body A layer is provided, and Ra of the unfixed toner image is 2.5 μm or less.

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 for electrophotography and a toner used therefor.

[0002]

2. Description of the Related Art Conventionally, various electrophotographic methods have been described in US Pat. No. 2,297,691, Japanese Patent Publication No. 49-23910, and Japanese Patent Publication No. 43-24748. Uses a photoconductive material,
An electrical latent image is formed on the photoconductor by various means, then the latent image is developed with dry toner, the toner image is transferred to paper, etc., and then fixed by heating, pressing, etc., and a copy is made. I will get it.

The methods for developing an electric latent image are roughly classified into
Liquid developing method that uses a developer in which various pigments and dyes are finely dispersed in an insulating organic liquid, and a coloring agent such as carbon black on natural or synthetic resin such as cascade method, magnetic brush method, powder cloud method There is a dry developing method using a toner having dispersed therein, and the dry developing method further includes a one-component developing method and a two-component developing method using a carrier.

As a transfer method, a charge transfer method using a charger, a roller method using a roller, and a belt transfer method provided with a medium resistance layer which is often mounted in recent years have been proposed.

Next, methods of heating and fixing a toner image on a transfer material are roughly classified into a contact fixing method and a non-contact fixing method. The former is heating roller fixing, belt fixing, the latter is flash fixing, and oven (atmosphere). ) Fixation is raised. Rush fixing and oven fixing do not deteriorate the image quality and can be said to be a method that can reproduce the quality of unfixed toner well. However, the fixing performance is so inefficient that it cannot be compared with the former heating roller fixing or the like, and in recent years it has hardly been installed. On the other hand, in the heating roller fixing method, since the toner image and the heating roller are in direct contact,
It is a fixing method with extremely high thermal efficiency and can be downsized, so that it is widely used.

However, the heating roller fixing method has a drawback that the toner image formed on the transfer material largely affects the image quality because the toner image and the transfer material are in direct contact with each other. That is, when a uniform and dense toner image is formed on the transfer material, it does not significantly deteriorate the image quality even when contacted with the heating roller and heated, but when a non-uniform and sparse toner image is formed, After fixing, the toner image may be widened or the gloss may be uneven, which may impair the image quality.

As a technique for solving this problem, some proposals have hitherto been made. For example, JP-A-6-230
No. 602, a magnetic toner for controlling the ratio of the height of a toner image before fixing to that of a toner image after fixing within a specific range is disclosed in JP-A-8-2.
No. 20793 discloses a toner having a specific porosity measured under a constant load, and Japanese Patent Application Laid-Open No. 8-278659 discloses a toner having a specific particle size distribution and having a porosity determined from a tap density. Toner having a specific range, JP-A-10-4
Japanese Patent No. 8874 discloses a toner containing an inorganic fine powder containing a silicone compound, having a specific particle size distribution, and having a porosity determined from a tap density in a specific range.

Further, in recent years, the image quality has become higher and higher, and the toner particle size tends to become smaller. When the toner particle size is small, even if pressure is applied between the fixing rollers, it is difficult to apply pressure to the toner particles, making it difficult to uniformly fix the toner image. This tendency becomes remarkable especially in the case of a fixing device having a low surface pressure. Further, when thin paper is used as the transfer material, the surface pressure becomes lower, the toner image surface property deteriorates, and the image quality deteriorates. Further, when thick paper is used, the surface pressure becomes high, so that the toner is crushed and unevenness is emphasized, and the image quality deteriorates. This phenomenon is particularly remarkable in the case of digital development, and the reproducibility of independent dots is greatly affected. The density of the halftone should be uniform, but if microscopic density unevenness occurs, it gives a rough impression when viewed with the naked eye, and greatly deteriorates the apparent image quality.

Here, the granularity (GS) is usually used as the physical evaluation value of roughness. First, noise is the Wiener spectrum (Wi
enerSpectrum: WS). Average value is 0
G (u) = ∫g (x) exp (−2πiux) dx Equation 1 WS (u) = F (u) 2 Equation 2 u is a spatial frequency. The granularity GS is a value obtained by integrating the product of WS and a visual frequency characteristic (Visual Transfer Function: VTF), and is expressed by the following equation. GS = exp (-1.8 <D>) ∫WS (u) (1/2) VTF (u) du Formula 3 Exp (-1.8 <D>) is the difference between the density and the brightness perceived by humans. Is a coefficient for correcting. <D> represents the average value of the density.

The granularity has a high correlation with the subjective evaluation of the smoothness / roughness of an image. The smaller the granularity value, the smoother the image quality becomes, and conversely, the larger the granularity value, the rougher and poorer the image quality becomes. It is generally known that the granularity is preferably 0.7 or less, and when the granularity exceeds 1.0, an image with a bad impression is not obtained, which is not preferable.

[0011]

However, in the above-mentioned conventional transfer means, the transfer efficiency is improved by applying pressure to the toner image at the time of transfer, and the peripheral technology thereof is improved, but the toner image after transfer is improved. Is not taken into consideration. Therefore, if microscopic density unevenness occurs after the development, the image is faithfully transferred even in the transfer step, so that a rough impression is given even after fixing, and the apparent image quality is greatly deteriorated.

Further, the invention described in Japanese Patent Laid-Open No. 6-230602, which was devised to solve the problem of the heating roller fixing system, regulates the amount of change in the height of the toner image. Image uniformity has not been discussed. Further, the above-mentioned other related arts regarding the toner also define the porosity of the toner alone, and do not represent the state of the toner image immediately before entering the most important heating roller fixing device. That is, conventionally, a toner prescription that matches the fixing property has not been made for the purpose of improving the fixing property and the image quality.

Therefore, the object of the present invention is to make the surface property of the toner image after fixing uniform even if the toner particle size and the type of transfer material are changed, and to provide stable fixing property and uniform image quality without graininess. An image forming apparatus that can be provided is provided.

[0014]

As a result of earnest studies, the inventors of the present invention have taken into consideration the matching between the fixing unit and the transfer unit and the toner to be transferred, and in view of the improvement of image quality, especially the uniformity of halftone density. It has been found that the above object can be achieved by selectively transferring the toner.

That is, according to the first aspect of the present invention,
A recording medium, a developing unit that develops the electrostatic latent image formed on the recording medium with a developer including a toner containing a resin and a wax component to form a toner image, and the toner image on the transfer material. An image forming apparatus comprising: a transfer unit configured to transfer to an image forming apparatus, wherein the following surface roughness Ra of an unfixed toner image transferred onto the transfer material after passing through the transfer unit is 2.0 μm or less. To be done. Ra = (1 / L) ∫ ₀ ^L f (x) dx In the above formula, L is a reference value of length and L = 0.8 mm, f
(X) represents a roughness curve.

The present invention is an image forming apparatus for thermally fixing an unfixed toner image transferred onto a transfer material such as paper after development using a toner composed of at least a resin and a wax as a toner component, and immediately before starting the fixing with a heating roller. The surface roughness Ra of the toner image is 2.0 or less.

Here, Ra will be described. Ra, that is, the definition of surface roughness and the measuring method are defined in JIS Standard B060.
1. Surface roughness according to 1-Definition and indication. Surface roughness Ra
Is a parameter that represents the surface roughness of each part randomly extracted from the surface of the object (hereinafter referred to as the object surface), that is, arithmetic average roughness (Ra), maximum height (R).
y), ten-point average roughness (Rz), average interval of irregularities (S
m), average spacing of local peaks (S) and load length ratio (t
p) is defined as the respective arithmetic mean value. How to ask
Extract only the reference value from the roughness curve in the direction of its average value,
Taking the X-axis in the direction of the average value of this extracted portion and the Y-axis in the direction of the vertical magnification, when the roughness curve is represented by Y = f (x), the value obtained by the following formula is expressed in micrometers. I mean something. Here, L = 0.8 mm. Ra = (1 / L) ∫ ₀ ^L f (x) dx As an example of measurement, for example, a super-depth shape measuring microscope VK-
It can be measured using Model 8500 (manufactured by Keyence Corporation).

The surface roughness Ra of the toner image immediately before entering the heating roller fixing device represents the uniformity of the toner image. The smaller Ra is, the higher the uniformity is. When the surface roughness Ra of the toner image exceeds 2.0, the surface of the toner image after fixing becomes non-uniform, resulting in fixability and microscopic density unevenness, and image quality deteriorates.

According to the second aspect of the present invention, the recording medium and the electrostatic latent image formed on the recording medium are developed with a developer composed of a toner containing a resin and a wax component. A developing unit that forms a toner image, a transfer unit that transfers the toner image onto a transfer material, and a rotatable rotatable fixing member and a pressure rotating member are provided between the fixing rotating member and the pressure rotating member. Fixing in which the unfixed toner image transferred by the transfer unit to the formed nip is heat-fixed to the transfer material by heating by the heating unit provided inside at least one of the fixing rotating body and the pressure rotating body. And an elastic layer is provided on at least one surface of the fixing rotator and the pressure rotator, and the unfixed toner image transferred onto the transfer material after passing through the transfer means is The surface roughness Ra is 2.
An image forming apparatus having a thickness of 5 μm or less. Will be provided. Ra = (1 / L) ∫ ₀ ^L f (x) dx In the above formula, L is a reference value of length and L = 0.8 mm, f
(X) represents a roughness curve.

In the second aspect of the present invention, the image forming apparatus passes a support carrying a toner image composed of at least resin and wax as a toner component between two rollers to form a toner image. Heat fixing,
It is equipped with a heating roller fixing device. In this apparatus, at least one of the fixing rotator and the pressure rotator has an elastic layer, and the surface roughness Ra of the toner image immediately before entering the heating roller fixing device is 2.5 or less.

When the surface roughness Ra of the toner image exceeds 2.5, the surface of the toner image after fixing becomes non-uniform, resulting in fixability and microscopic density unevenness, and image quality deteriorates. Compared to the first aspect of the present invention, the surface roughness of the toner image may be larger when a heating roller fixing device in which at least one of the fixing rotator and / or the pressure rotator has elasticity is used. This is because the surface of the toner image and the contact point with the transfer material are brought into closer contact with each other due to the elasticity of the rotating body, and the fixability, microscopic uneven density, and uneven gloss are reduced.

Next, the fixing means portion of the image forming apparatus according to the second aspect of the present invention will be described with reference to the drawings. 4, 7 and 8 are partial views of the device, which are provided for explaining the features of the present invention in comparison with the conventional device. The entire image forming apparatus will be described later.

FIG. 4 is an enlarged view of the conventional fixing means. The transfer material sent from the conveyor belt (not shown here) is conveyed between the fixing roller and the pressure roller, and is brought into pressure contact with the fixing roller heated to a constant temperature by the heater by the action of the pressure cam to transfer the transfer material. The upper toner is melted and fixed on the transfer material. The fixing roller uses a coating felt and a blade to uniformly apply oil and clean the fixing roller.

Usually, the fixing roller has an offset such as tetrafluoroethylene-perfluoroalkyl vinyl ether (PFA) or polytetrafluoroethylene (PTFE) on the surface of a metal cylinder composed of a high heat conductor such as aluminum or iron. The prevention layer is covered. A heating lamp (heater) is arranged inside the fixing roller. The metal cylinder of the pressure roller is often made of the same material as the fixing roller, but an RTV or silicone rubber layer may be provided on the surface of the metal cylinder. In each case, the surface thereof is coated with an offset prevention layer such as PFA or PTFA. The fixing roller and the pressure roller rotate by being pressed against each other by springs (not shown) at both ends. Considering the fixing performance, the pressing force normally gives a surface pressure of about 15 N / cm to maintain a good fixing property. In such a conventional fixing unit, since the heat conductivity is good, the roller surface hardness is high, and the surface pressure is high, the fixing performance is improved, but the image quality is deteriorated.

In contrast to the above-mentioned conventional fixing means, the fixing means used in the apparatus of the second aspect of the present invention is shown in FIGS. 7 and 8.
Will be explained. However, these drawings are mere examples, and any device is included in the present invention as long as the requirements described in the claims are satisfied.

FIG. 7 shows a fixing device using a belt-shaped pressure rotating member. In the present invention, as shown in FIG. 7, the fixing roller is made elastic, and the surface pressure is reduced by using the belt as the pressing means.
At the same time, by increasing the nip width, compatibility with fixing performance is achieved. It is preferable that the core metal of the fixing roller 31 is made of aluminum, an elastic layer having a thickness of 400 μm, for example, is provided on the outer side thereof, and a fluororesin layer is provided as a release layer on the surface layer thereof. Fluororesin layer is PFA or FEP
In some cases, a base material is used as a base material, and a material for improving wear resistance and a material for adjusting a resistance value are mixed if necessary. Silicone rubber, fluororubber, etc. are used for the elastic layer, but in the case of internal heating in which the halogen heater 32 is provided inside as in the present embodiment, a material having high thermal conductivity is used for the rubber layer.

The pressure belt 36 has a base material made of a seamless polyimide film or the like. A fluororesin layer may be provided on the outside as a release layer. If necessary, a silicone rubber layer may be provided on the film layer, and a fluororesin layer may be provided on the silicone rubber layer. A plurality of belt supporting rollers are provided inside the pressure belt. The apparatus shown in FIG. 7 is composed of two inlet side pressure belt rollers 35 and an outlet side pressure belt roller 37 as shown in the figure. Although not shown, the tension of the pressure belt 36 is applied to the outlet side pressure belt roller 37, and an appropriate pressure is applied at the nip portion.

Next, the behavior of the transfer material will be shown. The toner image 33 formed on the transfer material 34 by an image forming apparatus (not shown) enters the fixing device. The transfer material 34 is a pressure belt 36.
It is delivered to the fixing nip. Fixing roller 31
Is driven by a driving device (not shown), and the pressure belt 36 rotates around the fixing roller 31 to insert the transfer material 34 into the nip portion. The surface pressure of the nip portion formed by the fixing roller 31 and the pressure belt 36 is 4.9 N / cm ² or less so as not to collapse the image in the nip portion,
Normal pressure roller system surface pressure (9.8 N / cm ² or more)
The heat is transmitted to the toner 33 with a much smaller pressure.
On the other hand, the nip passage time is set to be long in order to ensure the fixing property due to the low pressure. Therefore, the toner 33 on the transfer material 34 is sufficiently heated in the nip at a low pressure for a long time even if the temperature of the heating roller is 140 ° C. It has melted and settled.
As a result, the surface roughness Ra of the unfixed toner image is improved (decreased) as compared with the case of using the conventional fixing means, and as a result, if the surface roughness Ra of the unfixed toner image is 2.5 μm or less, the fixing is performed. It has become possible to suppress the unevenness of characteristics and microscopic density and uneven gloss.

FIG. 8 shows roller fixing. As a basic configuration, a fixing roller 51 having a heating means 55 (hereinafter referred to as “heater”) such as a halogen lamp, and an elastic layer 56 such as foamed silicone rubber on a core metal 58 are provided.
And a pressure roller 52 that is in pressure contact with. A release layer 57 made of a PFA tube or the like is provided on the elastic layer 56 of the pressure roller 52. The fixing roller 51 is provided with an elastic layer 53 of silicone rubber or the like on a core metal (not shown), and for the purpose of preventing adhesion due to toner viscosity,
A resin surface layer 54 such as a fluororesin having good releasability is formed. The thickness of the elastic layer 53 is usually preferably about 100 to 500 μm in consideration of image quality and heat transfer efficiency during fixing. The resin surface layer 54 is composed of a PFA tube or the like like the pressure roller 52, and its thickness is preferably about 10 to 50 μm in consideration of mechanical deterioration. Temperature detecting means (not shown) is provided on the outer peripheral surface of the fixing roller 51, and by detecting the surface temperature of the fixing roller 51,
The heater 55 is controlled so that the temperature is kept substantially constant. In the fixing device having such a configuration, the fixing roller 5
1 and the pressure roller 52 are pressed against each other with a predetermined pressure to form a fixing nip portion, and are rotated by being driven by a driving unit (not shown), so that the transfer material S is transferred to the fixing nip portion. Nip and convey in the direction of the arrow. At this time, the fixing roller 5
1 is controlled to a predetermined temperature by the heater 55,
When the toner image T on the transfer material S passes between the rollers, the toner image T is melted by heat while receiving pressure and is discharged from the roller pair to be cooled and fixed on the transfer material S as a permanent image.

The specific structure of the pressure roller is, for example, as used in the examples described later, in which the outer diameter is 30 mm, the wall thickness is 6 mm, and the surface is covered with a conductive PFA tube. 42HS (measured by Asuka C hardness meter). Further, the fixing roller can be made of an aluminum cored bar and have a wall thickness of t = 0.4 mm. In this structure, a pressure of 88 N on one side is applied to both ends of the roller to obtain the nip N, and the surface pressure at that time is 9.3 N / cm.
^{It is 2} .

Similarly, in roller fixing, by providing elastic layers on the fixing roller and the pressure roller to suppress the surface pressure, the surface roughness Ra of the unfixed toner image is increased as compared with the conventional fixing means.
When the surface roughness Ra of the unfixed toner image is 2.5 μm or less, it becomes possible to suppress fixability, microscopic density unevenness, and uneven gloss.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION In the following, more preferable modes will be specifically described as embodiments of the present invention. FIG. 1 is a schematic diagram of an image forming apparatus. Here, a digital copying machine using a well-known electrophotographic method will be described as an example. A drum-shaped photoreceptor 1 as a recording medium is provided inside. Photoconductor 1
An exposure means and a developing means for irradiating an LD (not shown) onto the photoconductor through a charging charger 23 for carrying out an electrophotographic copying process and a polygon motor 19 along the rotation direction around the periphery of 6, transfer means 8 including transfer charger / separation charger, cleaning means 11
Are arranged.

The exposure means forms an electrostatic latent image on the photosensitive member based on the image signal read by the reading plate 20 from the document placed on the contact glass 18 on the upper surface of the image forming apparatus. The electrostatic latent image formed on the photoconductor is developed by the developing device 6 to form a toner image, and the toner image is transferred to the transfer material fed from the paper feeding roller 5 in the paper feeding device. Is electrostatically transferred by the transfer charger in. The transfer material carrying the toner image by the transfer is separated from the photoconductor by the separation charger and the separation claw, and is conveyed to the fixing roller provided in the fixing unit 15 and the pressure roller. After being fixed there, it is ejected out of the machine.

FIG. 2 shows an outline of the image forming process. The process proceeds in the following order. (1) Charging In the dark, the photoreceptor is negatively charged by corona discharge. The grid on the casing keeps the potential on the photoconductor constant. (2) Exposure The laser light passes through various lenses as shown in FIG. 1 and is reflected by a polygon mirror that rotates at high speed.
It is projected onto the photoreceptor. Laser light is emitted corresponding to the image portion (black portion), and the negative charge disappears. (3) Development A visible image is formed by applying a negative bias to the toner negatively charged by frictional charging and pushing the toner into a portion (image portion) having no negative charge on the photoconductor. (4) P sensor The developed image density on the photoconductor is read by the photo sensor, and the toner replenishment is determined based on the value.
Toner density control is performed by turning off N. (5) Transfer By applying a positive charge from the back surface of the transfer material that is in close contact with the photoreceptor, the negatively charged toner in the image area is transferred to the transfer material. (6) Separation The positive charge applied to the transfer material in the transfer step is removed by the separation charger to eliminate the attraction between the photoconductor and the transfer material, and the transfer material is separated. Separation pawls are provided to ensure separation. (7) PCC By applying a negative charge to the photoconductor, the positive charge remaining on the photoconductor at the time of transfer is erased. (8) Cleaning After the electric charge is removed from the toner remaining on the photoconductor with a conductive fur brush, the toner is scraped off with a cleaning blade. (9) Charge elimination In order to erase the residual charge on the photoreceptor,
The entire surface is exposed to prepare for the next image forming cycle.

Further, in the image forming apparatus of the present invention, the fixing property of the toner can be further improved and the granularity of the image can be improved by devising the width of the discharge area of the transfer means. FIG. 3 is an enlarged view of the conventional transfer means. The transfer material sent from the registration roller comes into contact with the photoconductor and is attracted to the photoconductor by the discharge action of the transfer charger. At this time, the toner on the photoconductor is transferred to the transfer material. Then, the reverse charge discharged from the separation charger abruptly weakens the adsorption force, resulting in separation from the photoconductor.

Here, conventionally, as shown in the figure, the area where the transfer charger is discharged is designed to be wider than the area where the transfer material is in contact. However, in the present invention, as shown in FIG. 5, the opening of the transfer charger is narrowed to design the discharge region to be narrow. As a result, the transfer material is not yet affected by the charger at the position where it abuts on the photoconductor, and even at the peeling position, it is possible to perform peeling by the discharge from the separation charger without being affected by the transfer.

The transfer means used in the present invention is shown in FIG.
And the means shown in FIG. 6 is preferable, but all other structures are included as long as they have the structure described in the claims. FIG. 5 shows a transfer device of a charger system. Since the charger itself is not in contact with the photoconductor and the transfer material, unlike the roller method described later, the effect of pressing force cannot be expected at the time of transfer, so the conventional transfer charger part has an opening width as described below. 12 mm → 6 mm ”, and the charge wire position is further separated from the photoconductor by 3 mm. In the present invention, the width of the discharge region is 10 mm or less,
The transit time of the transfer material in the discharge region is preferably 50 ms or less. Specifically, for example, a scorotron charger is used which can complete the transfer in a short time of 40 ms or less in a discharge area having a width of about 9 mm with respect to the photoconductor. Furthermore, the energy applied to the charge wire is made a constant voltage and combined with a scorotron charger, so that high energy can be emitted by concentrating in a narrow area. Also,
It is configured so that the discharge is performed only in the area in contact with the photoconductor. As a result, the toner is selectively transferred, specifically, the toner having the same toner particle size, mass and charge amount is easily transferred, and the surface roughness Ra of the unfixed toner image is improved.

FIG. 6 shows a roller type transfer means. It can be said that this method is better than the charger method, because the effect of pressing force during transfer can be expected. However, since the conventional method does not consider the surface roughness Ra of the unfixed toner image specified in the present invention, the pressing force is generally small,
Also, the contact width is wider. In the present invention, it is preferable to use such a roller or belt as a member that comes into contact with the recording medium, that is, the photoconductor via the transfer material, and the contact width between the photoconductor and the roller is 10 mm or less. The time for transfer material to pass is 50
It is preferably ms or less. Furthermore, it is preferable to have a supporting means rotatable about an axis substantially parallel to the contact width. Specifically, in the transfer means of the present invention, for example, the transfer roller is made of an elastic body having a hardness of 60 Hs (using an Asuka C hardness meter), the contact width is about 1.5 mm, and the pressing force is a surface pressure of 1 N.
/ Cm. Roller resistance is 10 × E8 to E10Ω ・ c
It is appropriate to use a medium resistance product of m and apply an applied voltage of 800V. Higher resistance is possible, but
The applied voltage also increases, which is not preferable.

It was found that when the contact width of the transfer area is 10 mm or less, pressure is applied to the toner image during transfer, and as a result, the surface roughness Ra of the unfixed toner image is improved (decreased). Furthermore, the amount of toner developed during development is about 80
Since the target image density can be achieved in%, it was found that it is also effective in reducing the toner consumption amount. Of course, it is easy to apply the same thing as the roller method to the belt method.

The toner used in the apparatus of the present invention preferably has an average circularity of 0.92 or more, more preferably 0.95 or more. By setting the average circularity of the toner to 0.92 or more, the surface roughness Ra of the toner image immediately before entering the heating roller fixing device is further improved, thereby further improving the uniformity of the surface of the toner image after fixing. . As a result, the fixability, microscopic density unevenness, and gloss uniformity are further enhanced. A toner having an average circularity of 0.92 or more can be produced by a method such as crushing by mechanical impact or heat treatment.

The average circularity can be measured using, for example, a flow type particle image analyzer FPIA-2100 manufactured by SYSMEX. For the measurement, a 1% NaCl aqueous solution was prepared using primary sodium chloride, and then filtered through a 0.45 μm filter, and 50-100 ml of this solution was mixed with a surfactant, preferably an alkylbenzene sulfonate, as a dispersant. Add 1-5 ml and add 1-10 mg of sample. This was subjected to a dispersion treatment for 1 minute with an ultrasonic disperser, and a dispersion having a particle concentration adjusted to 5000 to 15000 particles / μl was measured using this dispersion. At this time, the diameter of a circle having the same area as the two-dimensional image area captured by the CCD camera is taken as the circle equivalent diameter, and particles having a circle equivalent diameter of 0.6 μm or more are effective from the accuracy of the CCD pixel and the average circularity is determined. It was used to calculate The average circularity can be obtained by calculating the circularity of each particle, adding up the circularity of each particle, and dividing by the total number of particles. The average circularity of each particle can be calculated by dividing the perimeter of a circle having the same projected area as the particle image by the perimeter of the particle projected image.

The toner used in the apparatus of the present invention preferably has a bulk density of 0.30 g / cm ³ or more. When the bulk density of the toner is 0.30 g / cm ³ or more,
Surface roughness R of the toner image just before entering the heating roller fixing device
a becomes even better, which further improves the uniformity of the surface of the toner image after fixing. As a result, the fixability and the uniformity of microscopic density unevenness are further enhanced. The bulk density of the toner is measured using a powder tester (PTN type: manufactured by Hosokawa Micron Corporation).

Further, the toner used in the apparatus of the present invention preferably contains 1.0 to 3.0% by weight of inorganic fine powder as an external additive. 1.0% by weight of inorganic fine powder added
In the following cases, the toner does not have sufficient fluidity, is likely to aggregate, and tends to have a broad charge distribution. When 3.0 wt% or more is added, the surface roughness Ra of the toner image just before entering the heating roller fixing device is satisfactory, but the adhesiveness to the transfer material is deteriorated, and thus the fixing property is deteriorated. Therefore, by containing inorganic fine powder in an amount of 1.0 to 3.0% by weight as an external additive, the surface roughness Ra of the toner image immediately before entering the heating roller fixing device is further improved, whereby the toner image after fixing is fixed. Surface uniformity is further enhanced. As a result, the fixability, microscopic density unevenness, and gloss uniformity are further enhanced.

The ratio of the weight average particle diameter to the number average particle diameter of the toner used in the apparatus of the present invention, Xw / Xn, is preferably 1.3 or less. By setting Xw / Xn of the toner to be 1.3 or less, the surface roughness Ra of the toner image immediately before entering the heating roller fixing device is further improved, thereby further improving the uniformity of the surface of the toner image after fixing. . As a result, the fixability, microscopic density unevenness, and gloss uniformity are further enhanced.

The weight average particle diameter of the toner used in the apparatus of the present invention is preferably 4 to 10 μm. It is more preferably 4 to 8 μm, and most preferably 4 to 6 μm. When the weight average particle diameter of the toner is 4 μm or less, the surface roughness Ra of the toner image just before entering the heating roller fixing device is not a problem, but even if pressure is applied between the fixing rollers, it is difficult to apply pressure to the toner particles. It becomes difficult to fix the toner image uniformly. Particularly in the case of a fixing device having a low surface pressure, this tendency becomes remarkable, which is not preferable. On the other hand, when it is 10 μm or more, there is no particular problem with the fixability, but the resolution is poor, which is not preferable. The toner particle size can be measured, for example, by Coulter
MULTISIZER IIe can be used. In this case, the aperture diameter is 100 μm.

As the resin used for the toner used in the apparatus of the present invention, all conventionally known resins can be used. For example, styrene, poly-α-stillstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene. -Maleic acid copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-chloromethyl acrylate copolymer,
Styrene resin such as styrene-acrylonitrile-acrylic acid ester copolymer (styrene or homopolymer containing styrene substitution), polyester resin, epoxy resin, vinyl chloride resin, rosin-modified maleic acid resin, phenol resin , Polyethylene resin, polypropylene resin, petroleum resin, polyurethane resin, ketone resin, ethylene-ethyl acrylate copolymer, xylene resin, polyvinyl butyrate resin, etc., but polyester resin is particularly preferable.

The polyester resin is obtained by polycondensation of alcohol and carboxylic acid. Examples of the alcohol used include glycols such as ethylene glycol, diene glycol, triethylene glycol, and propylene glycol, 1,4-bis (hydroxymeth) cyclohexane, and etherified bisphenols such as bisphenol A, and other divalent glycols. Examples thereof include alcohol monomers and trihydric or higher polyhydric alcohol monomers. Examples of the carboxylic acid include divalent organic acid monomers such as maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, succinic acid and malonic acid, 1,2,4-benzenetricarboxylic acid, 1 2,5-benzenetricarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid,
1,2,4-naphthalenetricarboxylic acid 1,2,5-
Hexanetricarboxylic acid, 1,3-dicarboxyl-2
Examples include trivalent or higher polyvalent carboxylic acid monomers such as methylenecarboxypropane, 1,2,7,8-octanetetracarboxylic acid. The Tg of the polyester resin is preferably 58 to 75 ° C. The above resins can be used alone, but may be used in combination of two or more kinds. Further, the production method of these resins is not particularly limited, and bulk polymerization,
Any of solution polymerization, emulsion polymerization, suspension polymerization and the like can be used.

In the toner used in the present invention, a wax component can be used in order to improve releasability at the time of fixing. For example, polyolefin wax such as polypropylene wax and polyethylene wax, and natural wax such as candelilla wax, rice wax and carnauba wax can be used. The amount of the wax component added is preferably 0.5 to 10 parts by weight.

In the toner used in the present invention, it is possible to incorporate polarity control in order to control the polarity. Examples of the polarity control agent in this case include nigrosine dyes, quaternary ammonium salts, amino group-containing polymers, metal-containing azo dyes, salicylic acid complex compounds, and phenol compounds.

As the colorant used in the toner used in the apparatus of the present invention, all of the pigments and dyes conventionally used as toner colorants can be applied. Specifically, carbon black, lamp black, iron black, ultramarine,
Nigrosine dye, aniline blue, chalco oil blue, oil black, azo oil black and the like are not particularly limited. The amount of colorant used is 1 to 10 parts by weight, preferably 3 to 7 parts by weight.

The method for producing the toner used in the present invention may be a conventionally known method, such as a binder resin, a colorant, a wax component,
In other cases, a charge control agent or the like is mixed using a mixer or the like, kneaded using a kneader such as a heat roll or an extruder, solidified by cooling, and crushed by crushing with a jet mill or the like, then Can be obtained by classification.

If necessary, other additives may be added to the toner. Examples of the additive include silica, aluminum oxides, and titanium oxides. When the main purpose is to impart high fluidity, hydrophobically treated silica or rutile-type fine particle titanium oxide having an average primary particle size of 0.001 to 1 μm, preferably 0.005 to 0.1 μm is appropriately selected. You can choose
In particular, organic silane surface-treated silica or titania is preferable, and it is usually used in a proportion of 0.1 to 5% by weight, preferably 0.2 to 2% by weight.

Further, for example, when the toner of the present invention is used as a two-component dry toner, as a carrier to be mixed and used, glass, iron, ferrite, nickel, zircon, silica or the like as a main component, a particle size is used. 30-1000μ
m powder, or styrene with the powder as a core material
Acrylic resin, silicone resin, polyamide resin,
It can be appropriately selected and used from those coated with polyvinylidene fluoride resin or the like.

[0054]

EXAMPLES The present invention will be specifically described below with reference to examples. However, the present invention is not limited to the following examples.

(Examples 1 to 11) The toner formulations prepared below and the evaluation results of the images obtained by using the toner and the image forming apparatus of the present invention will be described. Toner formulation Styrene-n-butyl acrylate copolymer 85 parts by weight Carbon black (Mitsubishi Kasei # 44) 10 parts by weight Charge control agent (Spiron Black TR-H: Hodogaya Chemical Co., Ltd.) 2 parts by weight Carnauba wax 4 parts by weight The above formulation was kneaded using a twin-screw extruder, pulverized, and classified to obtain the weight average particle size shown in Table 1 below. Then, using a Henschel mixer, silica fine powder (R-972: manufactured by Client Japan) was mixed according to the formulation shown in Table 1 to obtain toners used in Examples 1 to 11. Each toner and a carrier obtained by coating spherical ferrite particles having an average particle size shown in Table 1 with a silicone resin are shown in Table 1.
A developer having the toner concentration described was prepared. For Ra, an unfixed test chart prepared using each of the obtained toners was used as an ultra-depth shape measuring microscope VK-850.
It was measured using a 0 type (manufactured by Keyence Corporation). The measurement results are also shown in Table 1.

An image was printed by the image forming apparatus shown in FIG. 1 using each of the developers manufactured as described above. The fixing device shown in Table 1 was used as the fixing device, and the temperature of the surface of the fixing roller was varied to fix the unfixed toner image. The fixing speed at this time was 300 mm / s. The fixing means shown in Table 1 specifically used the following 1-3. 1 Conventionally, the conventional fixing device shown in FIG. 4 was used. 2 Belt fixing The belt fixing device shown in FIG. 7 was used. The outer diameter of the fixing roller is 50 mm, the core material is aluminum, and the wall thickness is 1 mm.
An elastic layer of μm was provided. The pressure belt had a base material composed of a seamless polyimide film. 3 Roller fixing The roller fixing device shown in FIG. 8 was used. The pressure roller had an outer diameter of 30 mm, a wall thickness of 6 mm, and was coated with a conductive PFA tube on the surface. The rubber hardness on the shaft was 42 Hs (measured by Asuka C hardness meter). The fixing roller is made of aluminum and has a wall thickness of 0.
It was 4 mm. A pressure of 88 N on one side was applied to both ends of the roller, and the surface pressure at that time was 9.3 N / cm ² .

⊚ Fixability Evaluation Method A Ricoh standard printer test chart was printed using the above image forming apparatus and each toner. This was used as a sample for evaluation of fixing property, and then a mending tape (manufactured by 3M Co.) was attached to a dot image having an image density of 1.3 to 1.7 parts in a gray scale portion on the test chart, and a constant pressure was applied. After that, I slowly peeled it off. The image density before and after that was measured by a Macbeth densitometer, and the fixing ratio was calculated by the following formula. Further, the temperature of the fixing roller was lowered stepwise, and the temperature when the fixing ratio shown by the following formula was 80% or less was defined as the fixing temperature. That is, the lower the fixing temperature, the better the fixability. Fixing ratio (%) = tape-attached image density / image density × 100 The evaluation results are shown in Table 1 below.

Granularity Measurement Method The same sample as the above-mentioned fixability evaluation sample was used as a granularity measurement sample. The grayscale portion in the test chart was read at 1000 dpi with a GenaScan 5000 scanner (manufactured by Dainippon Screen Co., Ltd.) to obtain image data. From this image data, the density distribution was converted, and the granularity was calculated by the above equation 3. The smaller the granularity, the better the image. The measurement results are shown in Table 1 below.

(Comparative Examples 1 to 3) In the same manner as in Examples,
The developers of Comparative Examples 1 to 3 shown in Table 1 below were manufactured. Images were evaluated in the same manner as in the examples, using the same image forming apparatus as those of the examples except that each of these developers was used and the transfer means and the fixing means shown in Table 1 were provided. The evaluation results are also shown in Table 1 below.

[0060]

[Table 1]

[0061]

According to the present invention, a toner containing at least a resin and a wax is used as a toner component.
By making the toner image on the transfer material just before heat fixing uniform, the surface roughness of the toner image can be suppressed to be small, and even if the toner particle size or the type of transfer material changes, the toner image of the toner image after fixing can be reduced. The surface property becomes uniform, stable fixing property, and uniform image quality without graininess can be obtained.

(Claim 2) By elasticizing the surface layer of the rotating member of the fixing means, image deterioration in the fixing device can be suppressed. In addition to the above item 1, the surface of the toner image after fixing is further improved. Uniformity, stable fixing properties, and uniform image quality without graininess can be obtained.

(Claim 3) Since the average circularity of the unfixed toner just before entering the fixing device is 0.92 or more, the surface roughness Ra of the toner image just before entering the fixing device is further improved. The uniformity of the surface of the toner image after fixing is further enhanced.

(Claim 4) The surface roughness Ra of the toner image immediately before entering the fixing device is further improved, whereby the uniformity of the surface of the toner image after fixing is further improved. As a result, the fixing property, the image density variation, the gloss, and the granularity are further improved.

(Claim 5) By containing 1.0 to 3.0% by weight of the inorganic fine powder as an external additive, the surface roughness Ra of the toner image immediately before entering the fixing device is further improved,
This further improves the uniformity of the surface of the toner image after fixing. As a result, the fixability, microscopic density unevenness, and gloss uniformity are further enhanced.

(Claim 6) The ratio Xw / Xn of the weight average particle diameter to the number average particle diameter of the toner is 1.3 or less,
The surface roughness Ra of the toner image immediately before entering the fixing device is further improved, which further improves the uniformity of the surface of the toner image after fixing. As a result, the fixability, microscopic density unevenness, and gloss uniformity are further enhanced.

(Claim 7) The weight average particle diameter of the toner is 4 to
By setting the thickness to 10 μm, the surface roughness Ra of the toner image immediately before entering the fixing device can be suppressed to be small, and even if pressure is applied between the fixing rollers, the toner particles are likely to be pressed and the toner image is uniformly fixed. be able to. This is particularly effective in the case of a fixing device having a low surface pressure such as belt fixing.

(Claim 8) High energy is concentrated in a narrow area to be discharged, and the discharge is performed only in the area in contact with the photosensitive member. Since the same toner was easily transferred selectively, the surface roughness Ra of the unfixed toner image was improved.

(Claim 9) The transfer roller is made of an elastic body, and the pressing force is increased so that the toner image is pressed uniformly. Since the narrower area is transferred in a short time, the surface roughness Ra of the unfixed toner image is improved (small). Furthermore, the amount of toner developed during development is about 80
Since the target image density can be achieved in%, it was also effective in reducing the toner consumption amount.

(Claim 10) The surface pressure at the nip portion can be suppressed to a low level, and the elastic body allows the toner image to be pressed uniformly. The surface roughness Ra of the deposited toner image is improved (small), and as a result, the surface roughness Ra of the unfixed toner image is 2.
Even if the thickness is 5 μm or less, it becomes possible to suppress fixability, microscopic density unevenness, and uneven gloss.

(Claim 11) The power supply applied to the charge wire is a constant voltage, and the discharge opening is narrowed, so that the electric field effect is enhanced and high energy can be discharged in a short time.

(Claim 12) Since the roller is in contact with the photoconductor through the roller, the pressing force can be increased and the toner image is uniformly pressed.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an entire image forming apparatus of the present invention.

FIG. 2 is a schematic diagram for explaining an image forming process of the image forming apparatus of the present invention.

FIG. 3 is a schematic sectional view of a transfer unit used in a conventional image forming apparatus.

FIG. 4 is a schematic sectional view of a fixing unit used in a conventional image forming apparatus.

FIG. 5 is a schematic sectional view showing charge transfer means used in the image forming apparatus of the present invention.

FIG. 6 is a schematic sectional view showing a roller transfer means used in the image forming apparatus of the present invention.

FIG. 7 is a schematic sectional view showing a belt fixing unit used in the image forming apparatus of the present invention.

FIG. 8 is a schematic sectional view showing a roller fixing unit used in the image forming apparatus of the present invention.

[Explanation of symbols]

1 photoconductor 2P sensor fan 3 manual feed table 4 cassettes 5 paper feed rollers 6 developing means 7 P sensor 8 Transfer means 9 Separation means 10 PCC 11 Cleaning means 12 Conveyor belt 13 Conveyor fan 14 Main motor 15 Fixing means 16 Exhaust fan 17 Scanner power supply fan 18 Contact glass 19 polygon motor 20 Image reading board 21 lens 22 Static elimination lamp 23 Charger 24 fluorescent light 31 fixing roller 32 halogen heater 33 toner 34 Transfer material 35 Pressure Belt Roller: Entrance 36 pressure belt 37 Pressure Belt Roller: Exit 38 Exit guide plate 39 Peeling claw 40 discharge roller 51 fixing roller 52 Pressure roller 53, 56 Elastic layer 54 resin surface 55 Heating means 57 Release layer 58 core metal T toner image S transfer material

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 15/20 102 G03G 15/20 102 (72) Inventor Kumi Hasegawa 1-3-3 Nakamagome, Ota-ku, Tokyo No. 6 In Ricoh Co., Ltd. (72) Inventor Toshiaki Higaya 1-3-6 Nakamagome, Ota-ku, Tokyo In-house Ricoh Co. (72) Yutaka Takahashi 1-3-6 Nakamagome, Ota-ku, Tokyo In stock company Ricoh (72) Inventor Tadashi Kasai 1-3-6 Nakamagome, Ota-ku, Tokyo F term in stock company Ricoh (reference) 2H005 AA15 CB13 EA05 EA10 2H033 AA10 BA11 BA58 BB03 BB05 BB06 BB18 BB29 BB34 BB39 2H200 FA16 GA23 GA34 GA44 GA59 GB03 GB12 GB13 GB22 GB25 HA02 HA12 HA28 HB03 HB12 HB22 HB29 HB46 HB47 HB48 JA02 JA26 JA27 JA28 KA02 KA07 KA14 MB06 MC02 NA02 NA09 NA15

Claims (12)

[Claims] 1. A recording medium, a developing unit for developing an electrostatic latent image formed on the recording medium with a developer composed of a toner containing a resin and a wax component to form a toner image, and the toner. A transfer means for transferring an image onto a transfer material, wherein the following surface roughness Ra of the unfixed toner image transferred onto the transfer material after passing through the transfer means is 2.0 μm or less. Image forming apparatus. Ra = (1 / L) ∫ ₀ ^L f (x) dx (where L is a reference value of length and L = 0.8 mm,
f (x) represents a roughness curve. ) 2. A recording medium, a developing unit for developing an electrostatic latent image formed on the recording medium with a developer composed of a toner containing a resin and a wax component to form a toner image, and the toner. Transfer means for transferring an image onto a transfer material,
An unfixed toner image transferred by the transfer means to a nip formed between the fixing rotator and the pressure rotator, the unfixed toner image being transferred to the fixing rotator. And a fixing unit that heat-fixes the transfer material by heating by a heat generating unit provided inside at least one of the pressure rotator, and at least one surface of the fixing rotator and the pressure rotator has an elastic property. An image forming apparatus, wherein a layer is provided and the following surface roughness Ra of the unfixed toner image transferred onto the transfer material after passing through the transfer means is 2.5 μm or less. Ra = (1 / L) ∫ ₀ ^L f (x) dx (where L is a reference value of length and L = 0.8 mm,
f (x) represents a roughness curve. ) 3. The image forming apparatus according to claim 2, wherein the pressure rotating body has a belt shape. 4. The image forming apparatus according to claim 1, wherein the toner average circularity of the unfixed toner image is 0.92 or more. 5. The image forming apparatus according to claim 1, wherein the toner of the unfixed toner image has a bulk density of 0.30 g / cm ³ or more. 6. The toner according to claim 1, wherein the toner of the unfixed toner image contains 1.0 to 3.0% by weight of inorganic fine powder as an external additive. Image forming apparatus. 7. The ratio of the weight average particle diameter Xw of the toner of the unfixed toner image to the number average particle diameter Xn, Xw / Xn is 1.3.
The image forming apparatus according to any one of claims 1 to 6, wherein: 8. The toner of the unfixed toner image has a weight average particle diameter of 4 to 10 μm.
7. The image forming apparatus according to any one of 7. 9. The transfer means has a width of a discharge area of 10 mm or less when directly transferring from the recording medium to a transfer material, and a transfer time of the transfer material of 50 ms or less. The image forming apparatus according to any one of claims 1 to 8, wherein the image forming apparatus is a charge transfer unit that completes discharge in a region within a contact width with which a material contacts. 10. The image forming apparatus according to claim 9, wherein the power source applied to the charge wire of the charger used for the transfer means is a constant voltage and the discharge opening is a narrow scorotron charger. . 11. The recording medium when the transfer means has a member which is in the form of an elastic body and is in contact with the recording medium, which is a belt-like member or a roller, and which directly transfers from the recording medium to a transfer material. Width of contact with the member that comes into contact with
Below, and the transit time of the contact width of the transfer material is 50 ms
It has the following, and it has the support means which can rotate with respect to the axis | shaft substantially parallel to the said contact width, It is characterized by the above-mentioned.
The image forming apparatus according to any one of 0. 12. The image forming apparatus according to claim 11, wherein in the transfer means, the transfer material is pressed against the recording medium via a roller.