JP2013003225A - Toner, developing device, and image forming apparatus including the developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide toner that is used for a developing device including a developing roller and a thin layer forming member that comes into press-contact with the developing roller to regulate thickness of a toner layer, and prevents the occurrence of a phenomenon where toner adheres on the thin layer forming member, and the occurrence of image fogging on an output image, as well as a developing device, and an image forming apparatus including the developing device.SOLUTION: The melting point of wax included in toner and the exposure rate of wax on the surface of toner are regulated independent of a contact state of a thin layer forming member with the surface of a developing roller.

Description

  The present invention relates to a toner, a developing device, and an image forming apparatus including the developing device.

  A developing roller that carries toner on its surface and rotates about a rotation axis, and a thin layer forming member that controls the toner layer thickness by being pressed against the developing roller, are transported after being regulated by the thin layer forming member In a developing device that visualizes an electrostatic latent image on a photoconductor disposed opposite to a developing roller with toner, the toner is excessively loaded and the wax exposed on the toner surface may ooze out. .

  The exuded wax adheres to the thin layer forming member, and toner adheres to the wax. Thereafter, the toner adheres onto the thin layer forming member.

  In order to deal with such a problem, for example, in Japanese Patent Laid-Open No. 2008-225393 (Patent Document 1), as shown in FIG. 2, the thin layer forming member 101 is brought into contact with the surface of the developing roller 100, and the contact portion thereof In the developing device, the angle a between the tangent line at the center point B of the (nip part) and the tangent line at the point A moved 0.5 mm from the center point B along the thin layer forming member to the front end side is less than a predetermined value. By regulating the wax exposure rate on the surface and the toner charge amount, the phenomenon that the toner adheres to the thin layer forming member 101 side where the thin layer forming member 101 and the developing roller 100 come into contact does not occur, and the toner is not charged. A developing device that does not cause image fogging on an output image is disclosed.

JP 2008-225393 A

  However, in the developing device of Patent Document 1, since the toner charge amount when the thin layer forming member 101 is brought into contact with the surface of the developing roller 100 is defined, the contact state of the thin layer forming member 101 is greatly different. In some cases, the toner is fixed on the thin layer forming member, or the image fog is generated on the output image. Rather than changing the toner charge amount by contacting the thin layer forming member, changing the toner charge amount by changing the physical properties in the toner puts a load on the toner so that the toner adheres to the thin layer forming member. It was found that this phenomenon can be suppressed. It has also been found that the wax that oozes out from the toner causes the photoreceptor to be contaminated and the toner to adhere to the thin layer forming member.

  The present invention has been made in view of the above-described problems, and it is possible to form a thin layer only by defining the physical properties of the wax in the toner without depending on the contact state of the thin layer forming member with the surface of the developing roller. An object of the present invention is to provide a toner, a developing device, and an image forming apparatus including the developing device, in which a phenomenon that toner adheres to a member does not occur and an image fog does not occur on an output image.

  The present invention is a toner containing at least a binder resin and a wax, wherein the wax exposure rate on the toner surface is 15% or less, and the melting point of the wax is in the range of 80 to 100 ° C. Is.

  Further, the content of the wax contained in the toner is preferably 1 to 5 parts by mass with respect to 100 parts by mass of the binder resin.

  The amount of silica externally added to the toner is preferably 1.5 to 4 parts by mass with respect to 100 parts by mass of the binder resin.

  Further, the adhesion strength of the silica to the toner is preferably 20 to 35%.

  The volume average particle diameter of the toner is preferably 7 to 10 μm.

  The developing device of the present invention is provided with the toner.

  Further, the developing device includes a developing roller and a thin layer forming member that presses against the developing roller to regulate a layer thickness of the toner, and a line of a contact portion where the thin layer forming member and the developing roller contact each other The pressure is preferably 20 to 50 N / m.

  The image forming apparatus of the present invention includes the developing device.

  According to the present invention, the thin layer forming member can be defined by merely defining the melting point of the wax contained in the toner and the wax exposure rate on the toner surface without depending on the contact state of the thin layer forming member with the surface of the developing roller. It is possible to provide a toner, a developing device, and an image forming apparatus including the developing device, in which the phenomenon that the toner adheres to the image and the image fog does not occur on the output image can be provided.

1 is a schematic cross-sectional view illustrating a configuration of a developing device according to an embodiment of the present invention. It is a schematic sectional drawing which shows the structure of the image development apparatus used as the prior art example of this invention.

  Hereinafter, a developing device according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view showing the configuration of the developing device 1 of the present invention. In the following, the developing device of the present invention will be described, but it goes without saying that a general technique of an electrophotographic copying apparatus can be applied to other configurations.

  The developing device 1 of the present invention is a developing device that develops an electrostatic latent image by supplying toner 2 to the electrostatic latent image on the surface of the photoreceptor 3. The developing device 1 includes a developing tank 4 that contains toner 2, a developing roller 5 that carries the toner 2 and conveys it to the surface of the photoreceptor 3, a supply roller 6 that supplies the toner 2 onto the developing roller 5, and a developing tank. 4, a stirring member 7 that stirs and conveys the toner 2, a doctor blade 8 as a thin layer forming member that regulates the layer thickness of the toner 2 on the developing roller 5, and a support that supports the doctor blade 8 in the developing tank 4. A member 9 and a power source 10 for applying a bias to the developing roller 5 are included.

  The developing roller 5, the supply roller 6, and the stirring member 7 are rotatably provided in the developing tank 4, and are rotated counterclockwise as indicated by arrows.

  The photosensitive member 3 has a diameter of 30 mm, and the gap with the developing roller 5 disposed so as to face the photosensitive member 3 is set to 200 ± 20 μm by a gap holding member (not shown). The rotation direction of the photosensitive member 3 was a clockwise direction indicated by an arrow, and the peripheral speed was 150 mm / sec.

  The developing tank 4 is a container member made of, for example, a hard synthetic resin and having an approximately rectangular parallelepiped appearance.

  In the present invention, the developing roller 5 is made of aluminum, has a diameter of 16 mm, a thickness of 1 mm, and is sandblasted so that the arithmetic average roughness Ra of the surface is 0.3 to 0.8 μm. The developing roller 5 is driven to rotate around the axis at a peripheral speed of 145 mm / sec.

  The supply roller 6 has a metal core (not shown) provided with a porous elastic member such as urethane foam. The supply roller 6 rubs the developing roller 5 while adsorbing the toner 2 to the holes on the surface. As a result, the toner 2 is supplied to the developing roller 5 and the excess toner 2 remaining on the developing roller 5 after the development is cleaned.

  The biting amount of the contact portion between the supply roller 6 and the developing roller 5 is set to 0.5 mm, and the longitudinal direction of the contact portion, that is, the width in the axial direction of the supply roller 6 is set to 300 mm. The supply roller 6 was a urethane sponge having an Asker C hardness of 5 degrees. The diameter was 14 mm. The peripheral speed was 145 mm / sec.

  The stirring member 7 includes a plurality of blade pieces that protrude radially outward from the rotating shaft portion, and the blade pieces are formed in a thin plate shape using a resin such as PET (Polyethylene Terephthalate). .

  The doctor blade 8 is a plate-like member that extends parallel to the axial direction of the developing roller 5, and, for example, a resin 8 a made of urethane is attached to the contact position with the developing roller 5 in order to prevent toner adhesion. ing. The doctor blade 8 and the developing roller 5 are in contact with each other with a linear pressure of 20 to 50 N / m. This linear pressure can be changed by the thickness of the doctor blade 8, the material of the resin 8 a, and the contact position with the developing roller 5.

The doctor blade 8 is made of, for example, a conductive resin, stainless steel, phosphor bronze, or the like. In the present invention, phosphor bronze having a thickness of 0.1 mm is used, and the resin 8a is a urethane resin having a thickness of 1 mm. The linear pressure at this time was 30 N / m. Further, the layer thickness of the toner 2 on the developing roller 5 at this time was in the range of 0.6 to 0.8 mg / cm ² .

  The power source 10 applies a direct current bias of about −400 V to −2000 V to the developing roller 5 and is set as needed according to the gap between the developing roller 5 and the photoreceptor 3 and a desired image density. In the present invention, it was set to -900V.

  Examples of the component of the toner 2 used in the present invention include a binder resin, a colorant, a wax, and a charge control agent. Examples of the binder resin include styrene resins, acrylic resins, styrene-acrylic resins, olefin resins, vinyl chloride resins, polyester resins, polyamide resins, polyurethane resins, polyvinyl alcohol resins, vinyl ether resins. One kind or two or more kinds of conventionally known various thermoplastic resins such as resin, N-vinyl resin, styrene-butadiene resin, etc. can be used. Particularly, styrene resin, styrene-acrylic resin, polyester resin. Is preferred. These resins have a softening point of 120 to 150 ° C. and a glass transition point of 55 to 75 in order to be satisfactorily fixed on the surface of a printing medium such as recording paper by a heat fixing unit used in a normal image forming apparatus. It is preferable that it is in the range of ° C., and a part thereof may have a crosslinked structure.

  When the softening point is less than 120 ° C., offset occurs. On the other hand, when the softening point is higher than 150 ° C., the fixing property is not sufficient. When the glass transition point is less than 55 ° C., the single particles of the toner 2 tend to aggregate and image defects due to fusion of the toner 2 occur. On the other hand, when the glass transition point is higher than 75 ° C., the fixing property is not sufficient. The softening point of the binder resin can be measured by a flow tester (manufactured by Shimadzu Corporation, CFT-500), and the glass transition point can be measured by a differential scanning calorimeter (manufactured by Perkin Elma, DSC-7).

  As the colorant, dyes and pigments commonly used as the colorant of toner 2 can be used. For example, nigrosine dye, carmine dye, various basic dyes, acid dyes, oil dyes, anthraquinone dyes, benzidine yellow organic pigments, Examples thereof include carbon blacks such as quinanthrine organic pigments, rhodamine organic pigments, phthalocyanine organic pigments, zinc oxide, titanium oxide, furnace black, acetylene black, and thermal black. One type of colorant may be used alone, or two or more types may be used in combination.

  Wax is added for the purpose of preventing offset, and one or more of olefin waxes, ester waxes, plant waxes, mineral waxes, animal waxes, petroleum waxes, Fischer-Tropsch waxes, etc. Two or more types can be used.

  As the charge control agent, it is preferable to use a negatively chargeable charge control agent for the toner 2 used in the present invention. Examples of negatively chargeable charge control agents include metal-containing azo dyes, oxynaphthoic acid metal complexes, salicylic acid metal complexes, phenol condensates, quaternary ammonium salts, and boron complexes. In addition, a positively chargeable charge control agent can be used in combination to such an extent that good negative chargeability is not impaired. Examples of the positively chargeable charge control agent include nigrosine dyes of azine compounds, quaternary ammonium salts, quaternary ammonium salt molybdenum complexes, quaternary ammonium salts, and triphenylmethane derivatives. These charge control agents may be used alone as a mixture. The addition amount of the negative charge control agent is preferably 5 parts by mass or less with respect to 100 parts by mass of the binder resin. When the amount exceeds 5 parts by mass, problems such as a high charge amount of the toner 2 and a decrease in image density and poor transferability from the photoreceptor 3 to a toner support (not shown) occur.

  The components of the toner 2 having the above-described configuration are pulverized or polymerized by an existing manufacturing method to obtain a toner 2 having a volume average particle diameter of 7 to 10 μm. The volume average particle diameter was measured with a Coulter counter (manufactured by Beckman Coulter, Multisizer 3).

Further, silica or titanium oxide is externally added to the obtained toner 2 for the purpose of improving the fluidity of the toner 2. Titanium oxide has the effect of making the charge between the single particles of the toner 2 uniform, and the addition amount is preferably 0.5 to 1.5 parts by mass with respect to 100 parts by mass of the binder resin. If the titanium oxide is less than 0.5 parts by mass, the effect of uniformizing the charge between the single particles of the toner 2 cannot be sufficiently exerted, and if added more than 1.5 parts by mass, the charge amount of the toner 2 is drastically reduced. As a result, image defects such as fogging occur in the output image. The external addition process uses a mixing device such as a Henschel mixer.
<Example 1>
In this embodiment, a polyester resin is used as the binder resin of the toner, the softening point is 130 ° C., and the glass transition point is 63 ° C. As the colorant, 6 parts by mass of carbon black was added to 100 parts by mass of the binder resin. As the wax, 2 parts by mass of plant-based wax, carnauba wax, was added. Next, as the melting point of the wax, the temperature showing the maximum endothermic peak in an endothermic curve obtained by differential thermal analysis measurement using a differential scanning calorimeter was measured. As a result, the melting point of the carnauba wax of this example was 84 ° C. As a charge control agent, 1.5 parts by mass of a negatively charged boron complex was added. The volume average particle diameter of the toner was 8.7 μm. In the external addition treatment, 2.8 parts by mass of silica having a particle size of 12 nm was added and mixed and stirred for 1 minute with a Henschel mixer.

  Next, using the image forming apparatus in which the toner of the present embodiment is applied to the developing device 1 of the present invention, an A4 original having an image area ratio of 4% is used, and 40,000 plain papers are passed through to perform a copying test. went.

  Various evaluation and measurement methods are described below.

  A method for measuring the wax exposure rate on the toner surface will be described. First, a solution is prepared by adding 20 ml of n-hexane to 1 g of toner before external addition treatment and stirring for 10 minutes. Then, this solution was suction-filtered and vacuum-dried.

  The wax exposure rate on the toner surface is calculated from an endothermic peak area obtained by differential thermal analysis measurement using a differential scanning calorimeter before and after adding n-hexane, and can be expressed by the following formula (1).

In this embodiment, the wax exposure rate on the toner surface was 6.3%.

  A method for measuring the adhesion strength of silica to the toner will be described. First, 40 ml of a 0.2% by weight polyoxyethylene octylphenyl ether aqueous solution is added to 2 g of the toner after the external addition treatment and stirred for 1 minute. Next, this aqueous solution was subjected to ultrasonic vibration of 40 μA for 4 minutes using an ultrasonic homogenizer (manufactured by Nippon Seiki Co., Ltd., US-300T). After standing for 3 hours, the supernatant was removed, and 50 ml of pure water was added to the remaining toner and stirred for 5 minutes. After suction filtration, 50 ml of pure water was added again and stirred for 5 minutes. After suction filtration again, it was vacuum dried for 24 hours.

  The adhesion strength of silica to the toner is calculated from the strength of silicon obtained by fluorescent X-ray measurement using a fluorescent X-ray analyzer (manufactured by Rigaku Co., Ltd., XRF) before and after the above measurement treatment, and the following equation (2) Can be expressed as

In this example, the adhesion strength of silica to the toner was 29%.

  The toner charge amount was measured by sucking a certain amount of toner on the developing roller 5 using a suction type small charge amount measuring device (210HS-2A, manufactured by Trek Japan Co., Ltd.).

  The toner conveyance amount can be obtained by calculating the amount of suction toner per unit area from the area on the developing roller 5 sucked at the time of measuring the toner charge amount and the amount of suction toner.

  The image density was measured by using a spectrophotometric densitometer (X-Rite 938, manufactured by X-Rite) to measure the optical density of the image portion of the output image output in the copying test.

  The fog is calculated by the following procedure for the density of the non-image area. Using a whiteness meter (manufactured by Nippon Denshoku Industries Co., Ltd., Z-Σ90 COLOR MEASURING SYSTEM), the whiteness of plain paper before printing was measured in advance. Next, the whiteness of the non-image portion of the plain paper after printing is measured using a whiteness meter, and then the difference from the whiteness before printing is obtained. This difference was defined as fog. If it was less than 0.4, it was determined to be good, and if it was 0.4 or more and less than 1.0, it was determined to be slightly poor, and if it was 1.0 or more, it was determined to be defective because fog was clearly visible to the naked eye.

  For the layer thickness unevenness, the layer thickness of the toner on the developing roller 5 was visually observed. At the same time, using a halftone image A4 manuscript, a plain paper was passed horizontally, a copy test was performed, and an output image was obtained. When white streaks due to layer thickness unevenness appear in the output image, it is determined as defective, and when white streaks due to layer thickness unevenness do not appear in the output image, but streaks appear in the toner layer thickness on the developing roller 5, It was judged as good when it was judged as slightly defective and no white streaks due to uneven layer thickness appeared in the output image and no streaks appeared in the toner layer thickness on the developing roller 5.

  The results are shown in Table 1.

In this example, since the melting point of the wax was 84 ° C. and the wax exposure rate on the toner surface was 6.3%, the fog and the layer thickness unevenness were good at the 40th sheet.
<Example 2>
In this example, compared to Example 1, it was the same as Example 1 except that the melting point was changed by using an ester wax. Since the melting point of the wax was 95 ° C. and the wax exposure rate on the toner surface was 6.3%, even with the 40,000th sheet, both fog and layer thickness unevenness were good.
<Example 3>
In this example, compared with Example 1, it was the same as Example 1 except that the wax exposure rate on the toner surface was changed by changing the kneading state with the binder resin. Since the melting point was 84 ° C. and the wax exposure rate on the toner surface was 13%, both fog and layer thickness unevenness were good on the 40,000th sheet.
<Example 4>
This example was the same as Example 1 except that the wax content was changed as compared to Example 1. Since the wax content was 4 parts by mass, fog and layer thickness unevenness were good at the 40,000th sheet.
<Example 5>
In this example, compared with Example 1, it was the same as Example 1 except that the amount of silica was changed. Since the amount of silica was 3.5 parts by mass, fog and layer thickness unevenness were good at the 40,000th sheet.
<Example 6>
In this example, compared with Example 1, it was the same as Example 1 except that the amount of silica was changed. Since the amount of silica was 2 parts by mass, fog and layer thickness unevenness were good at the 40,000th sheet.
<Example 7>
This example was the same as Example 1 except that the adhesion strength of silica to the toner was changed by changing the mixing and stirring time in the Henschel mixer as compared with Example 1. Since the adhesion strength of silica to the toner was 22%, both fog and layer thickness unevenness were good at the 40,000th sheet.
<Example 8>
This example was the same as Example 1 except that the adhesion strength of silica to the toner was changed by changing the mixing and stirring time in the Henschel mixer as compared with Example 1. Since the adhesion strength of silica to the toner was 34%, fog and layer thickness unevenness were good at the 40,000th sheet.
<Example 9>
In this example, the same as Example 1, except that the volume average particle diameter of the toner was changed by changing the pulverization time as compared with Example 1. Since the volume average particle diameter of the toner is 7.2 μm, the fog and the layer thickness unevenness were good at the 40,000th sheet.
<Example 10>
In this example, the same as Example 1, except that the volume average particle diameter of the toner was changed by changing the pulverization time as compared with Example 1. Since the volume average particle diameter of the toner is 9.4 μm, the fog and the layer thickness unevenness were good at the 40,000th sheet.
<Example 11>
In this embodiment, compared with the first embodiment, it is the same as the first embodiment except that the linear pressure at the contact portion where the doctor blade 8 and the developing roller 5 are in contact is changed. Since the linear pressure at the contact portion where the doctor blade 8 and the developing roller 5 are in contact is 45 N / m, the fog and the layer thickness unevenness were good at the 40,000th sheet.
<Example 12>
In this embodiment, compared with the first embodiment, it is the same as the first embodiment except that the linear pressure at the contact portion where the doctor blade 8 and the developing roller 5 are in contact is changed. Since the linear pressure of the contact portion where the doctor blade 8 and the developing roller 5 are in contact is 25 N / m, both fog and layer thickness unevenness were good at the 40,000th sheet.
<Comparative Example 1>
This comparative example was the same as Example 1 except that the melting point was changed as compared to Example 1. By changing from carnauba wax to paraffin wax, the melting point of the wax was 76 ° C. As described above, since the melting point of the wax was less than 80 ° C., the toner was not uniformly charged, and the toner charge amount was lower than that of Example 1 at the 40th sheet. As a result, fog was somewhat poor and layer thickness unevenness was poor.
<Comparative example 2>
This comparative example was the same as Example 1 except that the melting point of the wax was changed as compared to Example 1. By changing from carnauba wax to polyethylene wax, the melting point of the wax was 110 ° C. Thus, since the melting point of the wax exceeded 100 ° C., the toner did not melt, and the fixability was poor at the 40,000th sheet. As a result, an output image was not obtained.
<Comparative Example 3>
This comparative example was the same as Example 1 except that the wax exposure rate on the toner surface was changed by changing the kneading state with the binder resin as compared with Example 1. Since the wax exposure rate on the toner surface exceeded 15% and was 16.2%, charging of the toner was hindered, and the toner charge amount was lower than that of Example 1 at the 40th sheet. As a result, fog was somewhat poor and layer thickness unevenness was poor.
<Comparative example 4>
This comparative example was the same as Example 1 except that the wax content was changed as compared to Example 1. Since the content of the wax exceeds 5 parts by mass and is 6 parts by mass, the charging of the toner is inhibited, and the toner charge amount at the 40th sheet is significantly lower than that in Example 1. As a result, both fog and layer thickness unevenness were defective.
<Comparative Example 5>
This comparative example was the same as Example 1 except that the wax content was changed as compared to Example 1. Since the wax content was 0.7 parts by mass, less than 1 part by mass, the toner did not melt, and the fixability was poor at the 40,000th sheet. As a result, an output image was not obtained.
<Comparative Example 6>
This comparative example was the same as Example 1 except that the amount of silica was changed as compared to Example 1. Since the amount of silica is 1.0 part by mass, which is less than 1.5 parts by mass, the toner cannot be sufficiently charged, and the toner charge amount is significantly lower at the 40,000th sheet than in Example 1. It was. As a result, both fog and layer thickness unevenness were slightly poor.
<Comparative Example 7>
This comparative example was the same as Example 1 except that the amount of silica was changed as compared to Example 1. Since the amount of silica exceeds 4 parts by mass and 4.5 parts by mass, the toner cannot be melted, and the fixability is poor at the 40,000th sheet. As a result, an output image was not obtained.
<Comparative Example 8>
This comparative example was the same as Example 1 except that the adhesion strength of silica to the toner was changed by changing the mixing and stirring time in the Henschel mixer as compared to Example 1. Since the adhesion strength of silica with respect to the toner exceeds 35% and is 40%, the toner surface is overloaded, and the toner charge amount at the 40th sheet is significantly lower than that in Example 1. As a result, both fog and layer thickness unevenness were defective.
<Comparative Example 9>
This comparative example was the same as Example 1 except that the adhesion strength of silica to the toner was changed by changing the mixing and stirring time in the Henschel mixer as compared to Example 1. Since the adhesion strength of silica with respect to the toner is 16%, which is less than 20%, the silica easily falls off from the toner surface, and the toner charge amount at the 40th sheet is significantly lower than that in Example 1. As a result, both fog and layer thickness unevenness were slightly poor.
<Comparative Example 10>
This comparative example was the same as Example 1 except that the volume average particle diameter of the toner was changed by changing the pulverization time as compared with Example 1. Since the volume average particle diameter of the toner exceeds 10 μm and is 11.3 μm, the surface area of the toner is reduced, and the toner charge amount at the 40,000th sheet is significantly lower than that in Example 1. As a result, the fog became defective.
<Comparative Example 11>
This comparative example was the same as Example 1 except that the volume average particle diameter of the toner was changed by changing the pulverization time as compared with Example 1. Since the volume average particle diameter of the toner is 6.2 μm, which is less than 7 μm, the electrostatic adhesive force with the developing roller 5 is increased and the developability of the toner is deteriorated. Compared to 1, the image density was significantly lower. As a result, the layer thickness unevenness became defective.
<Comparative Example 12>
This comparative example was the same as Example 1 except that the linear pressure at the contact portion where the doctor blade 8 and the developing roller 5 contacted was changed as compared to Example 1. Since the linear pressure of the contact portion where the doctor blade 8 and the developing roller 5 are in contact is 15 N / m, which is less than 20 N / m, the toner cannot be charged sufficiently, and the 40th sheet is compared with the first embodiment. The toner charge amount was significantly reduced. As a result, both fog and layer thickness unevenness were defective.
<Comparative Example 13>
This comparative example was the same as Example 1 except that the linear pressure at the contact portion where the doctor blade 8 and the developing roller 5 contacted was changed as compared to Example 1. Since the linear pressure of the contact portion where the doctor blade 8 and the developing roller 5 are in contact exceeds 50 N / m and is 60 / m, the toner surface is overloaded and the 40th sheet is compared with the first embodiment. The image density was greatly reduced. As a result, the layer thickness unevenness became defective.

DESCRIPTION OF SYMBOLS 1 Developing device 2 Toner 3 Photoconductor 4 Developing tank 5 Developing roller 6 Supply roller 7 Stirring member 8 Doctor blade 8a Resin 9 Support member 10 Power supply

Claims (8)

A toner containing at least a binder resin and a wax,
The wax exposure rate on the toner surface is 15% or less,
A toner having a melting point of the wax in a range of 80 to 100 ° C.   The toner according to claim 1, wherein a content of the wax contained in the toner is 1 to 5 parts by mass with respect to 100 parts by mass of the binder resin.   The toner according to claim 1, wherein the amount of silica externally added to the toner is 1.5 to 4 parts by mass with respect to 100 parts by mass of the binder resin.   The toner according to claim 1, wherein the adhesion strength of the silica to the toner is 20 to 35%.   The toner according to claim 1, wherein a volume average particle diameter of the toner is 7 to 10 μm.   A developing device comprising the toner according to claim 1.   The developing device includes a developing roller and a thin layer forming member that presses against the developing roller to regulate a layer thickness of the toner, and a linear pressure at a contact portion where the thin layer forming member and the developing roller are in contact with each other. The developing device according to claim 6, wherein the developing device is 20 to 50 N / m.   An image forming apparatus comprising the developing device according to claim 6.