JPH10221929A - Electrifying member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrifying member with excellent productivity which does not produce a tuck on the surface of a body to be electrified, which does not produce cracks in the film even in a low temp. environment or which does not produce wrinkles in the surface layer even when the film is formed in a short time at rather high temp. SOLUTION: This electrifying member is used to apply voltage and electrify the surface of a body to be electrified while the electrifying member is pressed to the surface of the objective body. The electrifying member 1 has a structure of at least two layers comprising a conductive elastic layer 1b formed on a conductive base body 1a and a surface layer 1c to cover the elastic layer 1b. The surface layer 1c consists of a siloxane-modified polyurethane resin having -30 to 50 deg.C glass transition temp. This modified polyurethane resin is produced by the reaction of org. polyisocyanates with long-chain polyols and a siloxane component, or by the reaction of these with a chain-extending agent. The siloxane component is preferably included by 0.5 to 30wt.% of the sum of the long-chain polyols and the siloxane component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic copying machine,
The present invention relates to a charging member in an image forming apparatus such as an electrophotographic apparatus such as a laser printer, a facsimile, or a composite OA apparatus thereof, or an electrostatic recording apparatus. More specifically, the present invention relates to a charging member that uniformly presses a member to be charged by being pressed against the surface of the member to be charged such as a photoconductor or a dielectric.

[0002]

2. Description of the Related Art A contact charging method for charging a surface of an object to be charged by pressing the surface of the object to be charged such as a photoreceptor and applying an external voltage has a lower applied voltage than a corona charging method. There is an advantage that it can be completed. As such a charging member, rolls, belts, blades, and the like in which a conductive elastic layer and a conductive coating film are coated thereon are widely used. It is well known that a surface layer made of a conductive coating film is formed of N-methoxymethylated nylon or polyurethane resin in which a conductive agent such as carbon black is dispersed. But N
-Methoxymethylated nylon has a problem that the viscosity of a solution in which the methoxymethylated nylon is dissolved changes with time, and the resistance of the cured film increases due to crosslinking. On the other hand, polyurethane resins generally have high tackiness, and there is a problem that a tack is generated between the polyurethane resin and an object to be charged during long-term storage for one month or more, and in the worst case, the film is peeled off. In addition, since the roll does not rotate smoothly due to a lack of rotational torque due to the tack, image defects such as "image distortion", so-called moiré, occur in an image such as a halftone.

In order to solve these problems, a urethane-modified acrylic resin containing 5 to 80% by weight of an acrylic resin component, or a resin layer containing the modified acrylic resin as a main component and further containing monoisocyanate is brought into contact with a member to be charged. A charging member as a layer has been proposed in JP-A-7-31493 and JP-A-8-21696.
Incidentally, the glass transition temperature of the urethane-modified acrylic resin is preferably in the range of room temperature to about 80 ° C. However, even in the charging member described in the above publication, due to the hardness of the acrylic resin film, when the thickness of the elastic layer is large or when the elastic layer has a large linear expansion coefficient, for example, silicone rubber is used. In this case, there is a problem that wrinkles are generated on the surface in the process of cooling after the resin of the surface layer is thermally cured. For example, if the composition is cured at a low temperature of 60 ° C. or less for about 24 hours, wrinkles can be prevented, but there is a problem that productivity is significantly reduced. Further, when the charging member is stored in a warehouse or the like maintained at about −20 ° C., there is a large problem that a film crack occurs due to a difference in linear expansion coefficient from the elastic layer and hardness of the surface layer. I have. When wrinkles or film cracks occur on the surface of the charging roll, not only problems in appearance quality but also insufficient charging at the wrinkles or film cracks cause black streaks and image defects.

[0004]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems, and there is no occurrence of tack between the surface of the member to be charged and the film even in a low temperature environment. An object of the present invention is to provide a charging member which does not crack and has excellent productivity without wrinkles occurring in a surface layer even when formed at a relatively high temperature in a short time.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on a charging member used in an image forming apparatus in order to prevent the occurrence of image quality defects mainly due to tack, and found that the member to be charged is A siloxane-modified polyurethane resin is used as a base polymer as the surface layer of the charging member that comes into contact with the base member, and the glass transition temperature of the charging member is adjusted to a predetermined range, so that the charging member can be, for example, 50%.
In the environment of 90 ° C. and 90% RH, the surface
No tackiness after standing for months, no film cracking even when quenched to -40 ° C, and no wrinkles on the coating film appearance even when a cured film is formed in a short time at 100 ° C or more. It has been found that they are not found, and the present invention has been accomplished. That is, the charging member of the present invention is an elastic member that charges a member to be charged by applying a voltage while being pressed against the surface of the member to be charged, and the elastic member is a conductive member formed on a conductive substrate. It has at least a two-layer structure of an elastic layer and a surface layer, and the surface layer is made of a siloxane-modified polyurethane resin having a glass transition temperature of -30 to 50 ° C.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
When the charging member of the present invention is used as a charging roll,
As shown in FIG. 1, a conductive elastic layer 1b is formed on the outer peripheral surface of a rod-shaped or tubular conductive substrate 1a, and the outer peripheral surface is further covered with a surface layer 1c. Also, if necessary, a resistance control layer may be interposed between the elastic layer 1b and the surface layer 1c, and an intermediate layer may be further interposed between the elastic layer 1b and the resistance control layer or the surface layer 1c. You may. The conductive substrate 1a functions as an electrode and a support member of the charging member. For example, a metal or alloy such as aluminum, copper alloy, and stainless steel (SUS); It is made of a conductive material such as resin. The outer diameter of the conductive substrate is usually 4
〜12 mm.

[0007] The conductive elastic layer has a predetermined resistance value and a predetermined hardness so that the charging member can be uniformly charged by pressing the charging member against the surface of the charging member with an appropriate nip width or nip pressure. It is provided to fit in. This elastic layer is formed by dispersing a conductive agent in a rubber material. Examples of the rubber material include isoprene rubber, chloroprene rubber, norbornene rubber, silicone rubber, urethane rubber, fluorine rubber, acrylic rubber, SB
R, NBR, EPDM, styrene-butadiene-styrene rubber, and the like, and two or more of these rubber materials may be blended. Among them, silicone rubber, SBR, E
PDM is preferably used. These rubber materials may be foamed or non-foamed. Examples of the conductive agent include various metals or alloys such as carbon black, graphite, aluminum, copper, nickel and SUS, tin oxide, indium oxide, titanium oxide, zinc oxide, potassium titanate, tin oxide-antimony oxide composite oxide, and oxide. One or two or more kinds of fine particle powders such as various conductive metal oxides such as a tin-indium oxide composite oxide, and those obtained by subjecting the surface of an insulating material to a conductive treatment can be used. The thickness of the conductive elastic layer may be usually in the range of 1 to 5 mm, and preferably in the range of 2 to 4 mm. Also,
The volume resistivity of the elastic layer when 100 V is applied is 10 ³ to 1
0 ⁹ is preferably in the range of range in particular 10 ⁵ to 10 ⁷ [Omega] cm of [Omega] cm.

When the conductive elastic layer is made of, for example, a rubber material other than silicone rubber or foamed rubber, a rubber material can be blended with a softening agent to lower the rubber hardness. In this case, it is preferable to provide an intermediate layer on the elastic layer since the surface of the member to be charged may be contaminated by oozing out of the softener or bleeding of the rubber itself. The intermediate layer is preferably made of a polyamide resin, a polyurethane resin, a fluororubber or the like in which an appropriate conductive agent such as carbon black is blended. Among these resins, N-methoxymethylated polyamide resin and fluorine rubber containing vinylidene fluoride as a main component are preferable. The thickness of the intermediate layer is not particularly limited, but may be usually in the range of 2 to 50 μm. Further, in order to adjust the charging member to a predetermined resistance value in cooperation with the surface layer, a resistance control layer can be provided on the elastic layer or the intermediate layer. The resistance control layer is made of polyurethane or epichlorohydrin-ethylene oxide copolymer rubber containing an appropriate conductive agent such as lithium perchlorate, or a polyurethane ionomer having an ionic segment such as a sulfonic acid group, a carboxyl group, or an amino group in a molecule. It is formed singly or by appropriately blending a conductive agent or blending a rubber material. The volume resistivity of the resistance control layer is preferably in the range of 10 ⁶ to 10 ¹⁰ Ωcm when a voltage of 100 V is applied. Its film thickness is 10-500μ
It is preferable that the thickness be in the range of m, more preferably in the range of 50 to 200 μm.

The surface layer is formed from a thin film in which a conductive agent as described above is dispersed in a siloxane-modified polyurethane resin as a base polymer. An appropriate polymer material such as a urethane polymer can be blended with the base polymer as long as the object of the present invention is not impaired. The blending ratio is preferably 30% by weight or less, more preferably 20% by weight or less based on all the polymers constituting the surface layer. As the siloxane-modified polyurethane resin, a reaction product obtained by reacting an organic polyisocyanate with a long-chain polyol and, if necessary, a chain extender in the presence of a catalyst is generally used. The siloxane component introduced into the urethane polymer can be previously introduced into the long-chain polyol by a known method. Also,
Like the polyol component or the chain extender, it can be used as a reaction raw material having two or more active hydrogens in the polyurethane conversion reaction. In any case, as a siloxane component as a reaction raw material, a polysiloxane having a hydroxyl group or an amino group at a terminal or a side chain is suitably used. The siloxane-modified polyurethane resin in the present invention may be further modified with an amine. In this case, it is preferable to introduce an amine component as a substituent into one or both of the long-chain polyol and the chain extender.

The organic polyisocyanate includes aliphatic diisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, 3-methyl-1,5-pentane diisocyanate, lysine diisocyanate, isophorone diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated xylylene diisocyanate. Alicyclic diisocyanate such as hydrogenated tetramethylxylylene diisocyanate, hydrogenated diphenylmethane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-xylylene diisocyanate Isocyanate, p-xylylene diisocyanate, diphenyl-4,4'-diisocyanate, 2-nitrodiphenyl-4,4 - diisocyanate, 3,
3'-dimethoxydiphenyl-4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate, diphenylmethane-4,4'-diisocyanate,
3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, β, β-diphenylpropane-4,4 '
-Diisocyanate, diphenyl ether-4,4'-
Aromatic diisocyanates such as diisocyanate, 1,4-naphthylene diisocyanate, and 1,5-naphthylene diisocyanate; polymers thereof; polyol adducts such as trimethylolpropane; and polyisocyanates having terminal isocyanate groups and polyols. Polymers.

The long-chain polyols include a) polyester polyols, b) polycarbonate polyols, c) polybutadiene-based polyols, d) polyether polyols, and copolymerized polyols thereof. a) Polyester polyols include polyester polyols and polyester amide polyols obtained by a condensation reaction of a dibasic acid or a reactive acid derivative thereof such as an ester, an acid halide or an acid anhydride with a glycol or an amino alcohol alone or in a mixture. is there. Examples of the dibasic acid include dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, azelaic acid, phthalic acid, isophthalic acid, terephthalic acid, hexahydrophthalic acid, hexahydroisophthalic acid, hexahydroterephthalic acid, and naphthalenedicarboxylic acid. And their reactive acid derivatives. Examples of the glycol include ethylene glycol, propylene glycol, 1,3-propanediol, 1,2-butanediol, 1,4-butanediol, 1,5-pentanediol, neopentylene glycol, and 1,6-hexanediol. , 3-methyl-1,5-pentanediol, 1,8-octanediol, 1,9-nonanediol, diethylene glycol, triethylene glycol,
Dipropylene glycol, 1,4-cyclohexanedimethanol, bisphenol A ethylene oxide or propylene oxide adduct alone or a mixture thereof are used. As the amino alcohol,
Examples thereof include ethanolamine, propanolamine, and ε-aminohexanol. Further, a part of the above glycol can be substituted with a diamine such as hexamethylenediamine, isophoronediamine, xylylenediamine and the like. Furthermore, a lactone-based polyester polyol obtained by ring-opening polymerization of a lactone monomer such as ε-caprolactone is also included.

B) The polycarbonate polyol is generally obtained by a dealcoholation reaction between the above-mentioned polyhydric alcohol such as glycol and ethylene carbonate, dimethyl carbonate, diethyl carbonate, diphenyl carbonate or the like. c) Examples of the polybutadiene-based polyol include polybutadiene in which two or more hydroxyl groups are substituted on the polymer main chain or at the terminal. d) Polyether polyols such as polyethylene glycol, polypropylene glycol, and polyoxytetramethylene polyol obtained by ring-opening polymerization of ethylene oxide, propylene oxide, tetrahydrofuran, and the like; copolymers of these polyether polyols and polybutadiene-based polyols; A polyester ether polyol having the above-mentioned polyester polyol or polycarbonate polyol as a copolymer component is exemplified. These long-chain polyols are synthesized by a known method, and preferably have a molecular weight in the range of 300 to 10,000 in consideration of the fact that the surface layer is generally formed by a coating method. Chain extenders generally have a molecular weight of 3
A compound having two or more active hydrogens in the molecule of less than 00, and a polyol component, a polyamine component, an amino alcohol component and the like of the long-chain polyol are used. In addition, water and urea can also be used as chain extenders.

The siloxane component is not particularly limited, but a polysiloxane in which two or more hydroxyl groups or amino groups are substituted at terminals or side chains, particularly at both terminals, is preferably used. Specific examples of the siloxane component include polydimethylsiloxane, polymethylethylsiloxane, polydiethylsiloxane, polymethylbutylpolysiloxane, polymethylvinylsiloxane, polymethyltrifluoropropylsiloxane, and polymethylphenylsiloxane substituted with the above functional groups. Is mentioned. As described above, these siloxane components can be introduced into the main chain or side chain of the long-chain polyol by a known method, or can be used as a raw material for a polyurethane reaction. The siloxane component in the siloxane-modified polyurethane resin is 0.5 to 30 with respect to the long-chain polyol and the siloxane component.
It is preferable that the content is contained by weight (wt)%, particularly 1 to 20 wt%. If the siloxane modification ratio is less than 0.5 wt%, the effect of preventing tackiness cannot be sufficiently exhibited.
On the other hand, when the modification ratio is higher than 30 wt%, it is difficult to dissolve the surface layer in a solvent when forming the surface layer by the coating method, and the coating liquid becomes cloudy or the viscosity increases, so that a uniform coating film cannot be obtained.

The glass transition temperature (Tg) of the siloxane-modified polyurethane resin is adjusted in the range of -30 to 50 ° C. The Tg generally increases by increasing the molar ratio of the chain extender of the hard segment component to the long-chain polyol, and decreases by not using or reducing the molar ratio of the chain extender. By changing the proportion of extender used,
It can be adjusted to a desired value. In addition, for example, in the case of a long-chain polyol having a multi-block copolymer structure having a hard segment and a soft segment, the ratio of the hard segment of the polyol component is also changed, or the long-chain polyol is constituted by any one of the segments. By changing the molecular weight, Tg can be appropriately adjusted. Where T
When g is lower than -30 ° C, the resin becomes tacky even when the siloxane modification rate of the polyurethane resin is increased, and tack occurs. On the other hand, Tg is 50 ° C.
If the temperature is higher, the surface layer may be cracked in a low-temperature environment, for example, by leaving the charging member of the present invention in an environment of −40 ° C. or lower. In addition, when the surface layer is formed by a coating method, the surface layer has insufficient flexibility and causes wrinkles when the coating film is cured at a relatively high temperature.

When the siloxane-modified polyurethane resin is further modified with an amine, the amine component is not particularly limited as long as it is a basic nitrogen-containing compound capable of forming a polymer main chain. Among them, an amino-substituted compound obtained by introducing at least one of the following tertiary amine components into the long-chain polyol and / or the chain extender as described above is preferably used. It is also desirable that the long-chain polyol into which the amine component is introduced has a molecular weight in the range of 300 to 10,000. As the tertiary amine component, N-
Methyldimethanolamine, N-methyldiethanolamine, N-methyldipropanolamine, N-methyldibutanolamine, N-methyldihexanolamine,
N-methyldioctanolamine, these N-ethyl-substituted compounds, N-propyl-substituted compounds, N-butyl-substituted compounds, N-phenyl-substituted compounds, 3-dimethylamino-1,2-propanediol, 4-dimethylamino-
1,2-butanediol, 5-dimethylamino-1,2
-Pentanediol, these diethylamino compounds,
p- (2-hydroxymethyl-3-hydroxypropyl) -N, N-dimethylaniline, p- (3-hydroxymethyl-4-hydroxybutyl) -N, N-dimethylaniline, these diethylaniline compounds, triphenyl Amine compounds, N- (3-dimethylaminopropyl) diisopropanolamine, and the like.

In the surface layer, the same conductive agent as that of the fine powder for imparting conductivity to the elastic layer is dispersed. However, when the siloxane-modified polyurethane resin is further modified with an amine, it is preferable to use a conductive agent having a pH of 6 or less that interacts with the amine-modified polyurethane resin, and carbon black is particularly preferably used.
That is, since carbon black can be easily adjusted to pH 6 or less by oxidation treatment, it is advantageous in terms of cost. Suitable carbon blacks include
Mogul-L oxidized to pH 2.5, Regal-4 oxidized to pH 4.0, commercially available from Cabot Corporation
00R, Monarch1000 oxidized to pH 2.5, and the like.

When carbon black having a pH of 6 or less is dispersed in an amine-modified polyurethane resin, the dispersibility of the carbon black is reduced by acid-base interaction between amino groups of the polyurethane resin and functional groups such as hydroxyl groups and carboxy groups of the carbon black. Improve dramatically. At the same time, secondary aggregation of carbon black is suppressed by this chemical interaction, so that there is no variation in the resistance value of the surface layer, and the uniformity of resistance of the charging member is dramatically improved. Therefore, image quality defects such as black streaks and white spots caused by non-uniform resistance do not occur, and no dispersion aid or the like is used.
There is no occurrence of image quality defects due to tacking or contamination of the surface of the member to be charged by the bleed. When the siloxane-modified polyurethane resin is further modified with an amine, 0.02 to 1.0 mmol, preferably 0.1 to 0.3 mmol, of an amine component per 1 g of the resin is introduced into the molecule. Is appropriate. 0.02 mmol of the above amine component
If it is less than 3, the acid-base interaction with the conductive agent is not sufficiently performed, so that it is difficult to uniformly disperse the conductive agent in the surface layer. On the other hand, when the amount is more than 1.0 mmol, the reaction with the organic polyisocyanate proceeds rapidly, so that the pot life of the coating solution prepared when forming the surface layer becomes short, which is not practical.

The above organic polyisocyanate, long-chain polyol, chain extender, siloxane component and amine component can be used alone or as a mixture of two or more. The siloxane-modified urethane polymer can be produced by a known polyurethane reaction. As the catalyst at that time, tertiary amines such as triethylamine, carboxylic acid metal salts such as potassium acetate and zinc stearate, and organic metal compounds such as dibutyltin dilaurate, dioctyltin dilaurate, and dibutyltin oxide are used. The polyurethane conversion reaction can be carried out by mixing a reaction raw material and a catalyst in the absence of a solvent, but performing the reaction in an organic solvent is advantageous in forming a surface layer by a coating method. It is. That is, a conductive agent is added to the solution of the raw material or product of the polyurethane conversion reaction, and the polymer material is further blended as necessary, and then, depending on the viscosity and the solid content concentration of the obtained dispersion, an organic compound is added. A solvent is added to dilute the solution so that it can be easily applied, and a curing agent is added as necessary. Then, the surface layer can be formed more easily by applying the obtained coating liquid onto the conductive elastic layer, the intermediate layer, or the resistance control layer, and then drying and curing. Organic solvents include benzene, toluene,
A single or mixed solvent such as methyl ethyl ketone (MEK), methyl isobutyl ketone, dioxane, and ethyl acetate is used. As the curing agent, a polyisocyanate compound is used, and a low molecular weight compound having an isocyanate group at a molecular terminal is preferable. For example, Coronate L,
2030, HX, HL (manufactured by Nippon Polyurethane Industry Co., Ltd.),
Death module L, N-3300, HT (manufactured by Bayer), Takenate D-102, D-160N, D-17
0N (manufactured by Takeda Pharmaceutical Co., Ltd.).

The volume resistivity of the surface layer is in the range of 10 ⁵ to 10 ¹¹ Ωcm when a voltage of 100 V is applied, and more preferably 10 ⁷ to 10 ⁹ Ω.
It is preferably in the range of cm. Volume resistivity is 10 ⁵ Ωc
If it is less than m, an excessive current flows on the surface of the member to be charged, and if a pinhole is present on the surface of the member to be charged, leakage tends to occur. On the other hand, when the volume resistivity is larger than 10 ¹¹ Ωcm, it becomes difficult to charge the member to be charged at a low voltage, and an image quality defect occurs due to an insufficient charge amount.
The thickness of the surface layer is preferably in the range of 1 to 50 μm. If the thickness is less than 1 μm, a leak is likely to occur on the surface of the member to be charged. On the other hand, if the film thickness is greater than 50 μm,
With the existing coating method, it is difficult to form a coating film having a predetermined thickness unless overcoating is performed, and even if a coating film is formed, film thickness unevenness occurs.

The charging member of the present invention has an outer diameter of 8 to 18 mm.
And preferably in the range of 10 to 14 mm. The volume resistivity is 10 ⁵ to 10 ¹⁰
It is preferably in the range of Ωcm. This is adjusted within the above range by appropriately combining the resistivity of the conductive elastic layer and the surface layer, the resistivity and the thickness of the intermediate layer and the resistance control layer formed as necessary. Is possible. It is preferable that a voltage is applied between the conductive base (1a) of the charging member and the member to be charged (for example, the photoconductor 11 shown in FIG. 4) to perform constant current control.

As described above, a roll-shaped charging member (charging roll)
Has been described, the form of the charging member of the present invention,
The present invention is applicable to a blade, a brush, a belt, or the like. As shown in FIG. 2A, the blade-shaped charging member has a two-layer structure,
A conductive elastic layer 2b on the side opposite to the member to be charged on which the charging member 2 is pressed is adhered and fixed to a plate-shaped conductive substrate 2a, and a surface layer 2c is coated on the elastic layer 2b. I have. In the case of a belt-shaped charging member, as shown in FIG. 2B, the charging member 3 having a two-layer structure that moves in the direction of the arrow includes an electrode roll (conductive base) 3a and a belt transport roll 4,
4 'and is pressed against the member to be charged by the electrode roll 3a. The belt-shaped charging member 3 does not necessarily need to be moved, and may be a fixed film-shaped charging member. The layer structure of each charging member may be three or four layers as described above. The charging member of the present invention can be applied to a transfer device and the like other than the charger. When used as a charging member in a transfer device, the charging member is pressed against a member to be charged such as a photoreceptor via a transfer material such as paper, and its volume resistivity is adjusted to a range of 10 ⁷ to 10 ¹⁰ Ωcm. .

The charging member of the present invention has the following operation. The present invention uses a siloxane-modified polyurethane resin having a polymer main chain or a side chain substituted by polysiloxane as a base polymer of a surface layer, and the Tg of the resin is −30 to 30.
The temperature was adjusted to the range of 50 ° C. Therefore, there is no occurrence of tack, wrinkles, and film cracks in the surface layer, and there is no possibility of image quality defects resulting from these. That is, even if the charging member is left in contact with the surface of the member to be charged in a high-temperature and high-humidity environment of, for example, 50 ° C. and 90% RH for 2 months, no tack is generated. Further, even if the charging member is placed in an environment of, for example, about −40 ° C., no film crack occurs. Furthermore, since the siloxane-modified polyurethane resin is rich in flexibility, even when the coating film is cured at a relatively high temperature of, for example, 100 ° C. or higher for a short time when the surface layer is formed by a coating method, wrinkles may appear on the coating film appearance. Is not seen. In the siloxane-modified polyurethane resin, the siloxane component is added to the long-chain polyol component and the siloxane component of the polyurethane polymer in an amount of from 0.5 to 3%.
When 0 wt% is contained, the above-described tack prevention effect can be sufficiently exhibited.

[0023]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to the following Examples. (Image Forming Apparatus) FIG. 3 is an explanatory view of an image forming apparatus in which the charging member of the present invention shown in FIG. 1 is mounted on a charging section. FIG.
In the image forming apparatus U, a cylindrical photoconductor (drum) 11 that rotates in the direction of the arrow is disposed inside the main body of the image forming apparatus U, and functions as an electrostatic latent image carrier. A laser writing device 12 that writes an electrostatic latent image on the surface of the photoconductor 11 is arranged on one side inside the image forming apparatus U main body. Photoconductor 11
A charger 13 for uniformly charging the surface of the photoreceptor 11 in order along its rotation direction, a developing device 14 for visualizing the electrostatic latent image, and a paper (transfer material) for the visualized toner image And a cleaning device 16 for removing residual toner on the photoreceptor 11 are provided respectively. The developing device 14 has a container 14a for storing toner. In the container 14a, there are provided stirring members 14b, 14b for stirring toner, a rotatable developer carrier 14c, and a toner supply roller 14d for supplying toner to the carrier 14c. The developer carrier 14c faces the opening of the container 14a and is supported by the container 14a with a slight gap from the surface of the photoconductor 11. Further, the cleaning device 16 includes the casing 1.
6a. A metal blade holder 16b is fixed to the casing 16a, and a cleaning blade 16c is fixed to a distal end of the blade holder 16b. The cleaning blade 16c has an edge portion at the tip thereof,
It is in contact with the surface.

At the lower part of the main body of the image forming apparatus U, a paper feed tray 17 for storing paper is arranged. Paper tray 1
A paper take-out roller 18 for taking out paper one by one from a paper feed tray 17 is disposed above an end of the paper tray 7. A pair of paper transport rollers 19 is provided above the side of the paper take-out roller 18.
A pair of paper guides 20 for guiding the paper conveyed by the printer are arranged. A heating roll 21a and a pressure roll 21b are provided on the upper side of the other side inside the image forming apparatus U main body.
Is provided, and the fixing device 21
A transfer path 22 for transferring the sheet on which the toner image has been transferred is provided between the transfer device 15 and the transfer device 15. Above the fixing device 21, a pair of discharge rollers 23 and a transport path 24 for guiding the sheet on which the toner image is fixed from the fixing device 21 to the discharge rollers 23 are provided. A discharge tray 25 on which sheets discharged from the discharge roller 23 are placed is formed on the upper surface of the image forming apparatus U main body.

(Charger) FIG. 4 is an enlarged view of a main part of FIG. 3 and shows the structure of the charger. Referring to FIG.
Is provided with the charging roll 1. The charging roll 1 is supported at both ends of the conductive base 1 a by support members 31 fixed to the casing 16 a of the cleaning device 16. The charging roll 1 is pressed against and contacts the surface of the photoconductor 11 by the urging forces of two pressure springs 32 each having one end fixed to the support member 31 and the other end fixed to the end of the base 1a. A metal pad holder 33 is fixed to the support member 31, and a sheet-like cleaning pad 34 fixed to the tip end of the pad member 33 removes even a small amount of toner adhered to the surface of the charging roll 1. It has become. Furthermore, the substrate 1 of the charging roll 1
a includes a DC power supply 35 and an AC power supply 3 connected in series.
A superimposed oscillation voltage is applied from 6. Therefore, the charging roll 1 can uniformly charge the surface of the photoconductor 11 rotating in a predetermined direction while being in contact with the surface layer 1c.

The operation of the image forming apparatus U in the present invention is as follows.
This is the same as the conventional one, and is briefly described as follows. As described above, the surface of the photoconductor 11 rotating in the direction of the arrow is uniformly charged by the charging roll 1 to which the superimposed oscillation voltage is applied. Photoreceptor 1 uniformly charged
In 1, an electrostatic latent image is written by the laser writing device 12. The electrostatic latent image on the photoconductor 11 is developed into a toner image by the developing device 14. The toner image is transferred to a sheet conveyed from the sheet feed tray 17 by the transfer unit 15. After the transferred toner image is fixed by the fixing device 21, the sheet is discharged onto a discharge tray 25 by a discharge roller 23.
After the toner image is transferred to the paper, the photosensitive member 11
The toner remaining on the surface is removed by the blade 1 of the cleaning device.
6c to prepare for the next image forming process.

The "parts" used in the following compositions indicate "parts by weight". Example 1 100 parts of a millable silicone rubber compound containing carbon black as a conductive agent (SE4637: manufactured by Toray Dow Corning) and a vulcanizing agent paste containing peroxide (RC-450 PFD: manufactured by Toray Dow Corning). Five parts were kneaded with an open roll for 10 minutes to prepare a kneaded silicone rubber in which carbon black was uniformly dispersed. Next, the outer diameter 6 previously treated with a primer
mm SUS shaft (1a) was inserted and supported concentrically at the center of a cylindrical mold having an inner diameter of 12 mm. The cavity of the mold is filled with the rubber kneaded material by an injection molding method,
A roll for heating and curing at a mold temperature of 170 ° C. for 3 minutes to form a carbon black-containing silicone rubber molded article having an outer diameter of 11.8 mm (thickness of 2.9 mm) as a conductive elastic layer (1b). Was formed. The hardness of the elastic layer (1b) is JIS
A is 35 ° and its volume resistivity is 5 × 10 ⁶ Ωcm
Met. Further, when the extraction treatment was performed with a toluene solvent for 24 hours by the Soxhlet method, the total extraction amount was 2.5
%Met.

Further, the organic polyisocyanate, the amine-modified polyester polyol having a siloxane modification ratio of 5 wt%, and a chain extender were added to MEK / toluene (1: 1).
Paint (XN2)
68: manufactured by Nippon Polyurethane Industry Co., Ltd.), a particle diameter of 24 nm, an oil absorption of 60 ml / 100 g, and a specific surface area of 1
75 parts of carbon black (the above Mogul-L) oxidized to pH 2.5 at 38 m ² / g was added. Next, after a dispersion treatment for 6 hours by a sand grinder mill, 10 parts of an isocyanate-based curing agent (Coronate 3041: manufactured by Nippon Polyurethane Industry Co., Ltd.) was added, and the mixture was stirred and mixed to prepare a coating solution. Diphenylmethane-4,4'-diisocyanate (MDI) is used as the organic polyisocyanate, ethylene glycol / neopenthylene glycol / terephthalic acid / isophthalic acid (PEs 2000) in the hard segment and 1,4 in the soft segment as the long-chain polyol.
-Polybutanediol / adipic acid (BA1000) copolymerized polyester polyol, 1,4-butanediol (1,4-BD) as a chain extender, and N-methyldiethanolamine as an amine component introduced into the long-chain polyol. Each was used. Further, 1.65 mol of MDI and 0.1 mol of 1,4-BD are added to 1 mol of the long-chain polyol.
Used in 2 mole proportions.

The obtained coating solution was applied to the outer peripheral surface of the elastic layer (1b) by a dip coating method at a lifting speed of 300 mm / min. After touch drying by air drying, heating in an oven at 120 ° C. for 30 minutes to cure the polyurethane resin modified with siloxane and amine, and to form an elastic layer (1b)
A 6 μm-thick surface layer (1c) formed of a uniform cured film was formed thereon. Thus, the charging roll (1) was manufactured. The resin has a Tg of 43 ° C. and a number average molecular weight (M
n) was 2.2 × 10 ⁴ . Further, 0.15 mmol of the above amine component was contained in 1 g of the resin, and the urethane group concentration was 1.47 mmol / g.

Example 2 Using a polyester polyol having a siloxane modification rate of 2 wt% (paint number: XN256: manufactured by Nippon Polyurethane Industry Co., Ltd.), 1.58 mol of MDI was used as an organic polyisocyanate per mol of long-chain polyol. Except that the amount of the amine component used was changed,
A charging roll was manufactured in the same manner as in Example 1. The above polyester polyol has a hard S (segment) of 1,
It comprises a copolymerized long-chain polyol of 6-hexanediol / isophthalic acid (HI1000) and the above-mentioned BA1000 of soft S. The Tg of the polyurethane resin modified with siloxane and amine was 1 ° C., and Mn was 3.3 × 10 ⁴ . Further, 0.2 mmol of the amine component was contained in 1 g of the resin.
Contained, and the urethane group concentration was 2.07 mmol / g.

Example 3 The polyether polyol having a siloxane modification ratio of 10 wt% (model number of paint: XN279: manufactured by Nippon Polyurethane Industry Co., Ltd.) was used, and MDI was 1.10 with respect to 1 mol of a long-chain polyol as an organic polyisocyanate. A charging roll was produced in the same manner as in Example 1, except that the charging roll was used in a molar ratio and the chain extender and the amine component were not used. The above-mentioned polyether polyol consists only of soft S polyethylene glycol (PEG1000). The Tg of the siloxane-modified polyurethane resin is -28 ° C,
Mn was 1.9 × 10 ⁴ . The urethane group concentration in 1 g of the resin was 1.66 mmol.

Comparative Examples 1 to 12 A charging roll was manufactured in the same manner as in Example 1 except for the items shown in Table 1 below. In Table 1, the numerical values given to the hard S and soft S of the polyol mean the average molecular weight of the segment. “NPG” of the chain extender is neopentylene glycol, and “IPDA” is isophorone diamine. When this IPDA is used, the concentration of the urea group generated by the reaction with the MDI of the organic polyisocyanate is shown. The Tg and Mn of the siloxane-modified polyurethane resin are shown in Table 2 below.

[0033]

[Table 1]

The volume resistivity of the siloxane-modified polyurethane resin constituting the surface layer was measured as follows. That is, a cylindrical electrode having a diameter of 10 mm and a width of 3.5 mm is pressed against the outer periphery of the charging roll with a load of 30 g, and a voltage of 100 V is applied between the charging roll shaft (1a) and the electrode to rotate the roll once. The resistance value at 180 points was measured every 2 ° while performing the measurement. The average resistance value (log Ωcm) was determined for each roll at three portions, a portion slightly apart from both ends and a central portion. Table 2 shows the measured volume resistivity and the tensile properties of the resin.

[0035]

[Table 2]

(Characteristics of Surface Layer and Image Evaluation Test) Next, each charging roll was mounted on a charger (13) of an electrostatic recording type printer (XP-10: manufactured by Fuji Xerox Co., Ltd.). This printer has a DC voltage of -350 V from the power supply (35), a frequency of 450 Hz from the power supply (36), and a peak-to-peak (V
_PP ) A superposed oscillating voltage with an AC voltage of 1.7 kV is applied to the shaft (1a) of the charging member. After leaving such a printer in a high-temperature and high-humidity (45 ° C./95% RH) environment for one month, the process after the charging process forms an image on a sheet according to a conventional method, and forms the image on the photoconductor (OPC) surface. The presence or absence of image quality defects due to tack was investigated. Moreover, after leaving each charging roll at room temperature for 2 hours or more using a thermal test machine,
It was left in an environment rapidly maintained at -40 ° C for 4 hours, returned to room temperature again, and examined for the occurrence of film cracking due to thermal shock. Then, in each of the examples, when the siloxane-modified polyurethane resin was cured, it was visually inspected whether or not wrinkles “appearance wrinkles” occurred on the formed surface layer. The results are shown in Table 3 below. further,
An image evaluation test was carried out by the above-mentioned printer equipped with each charging roll, and a normal environment, low temperature and low humidity (10 ° C./15
% RH) and high-temperature and high-humidity (35 ° C./85% RH) environments were evaluated for environmental dependence of charging performance. Table 3 summarizes the evaluation results. In Table 3, ○ indicates that good results were obtained, and X indicates that tack, film cracking, and wrinkles occurred.

[0037]

[Table 3]

[0038]

According to the charging member of the present invention, the Tg of the siloxane-modified polyurethane resin serving as the base polymer of the surface layer is adjusted in the range of -30 to 50 ° C. In addition, image quality defects such as moire due to tack and peeling of the film do not occur. In addition, since siloxane-modified polyurethane resin is rich in flexibility,
Even when the resin is cured at a relatively high temperature, no wrinkles are generated. Therefore, a film can be formed in a short time, and the productivity is excellent. For the same reason, even if the charging member is placed in a low temperature environment of, for example, about −40 ° C., the film does not crack. Therefore, image quality defects due to wrinkles and cracks in the surface layer do not occur.

[Brief description of the drawings]

FIG. 1A is a perspective view of a charging member having a two-layer structure shown as one embodiment of the present invention, and FIG. 1B is a cross-sectional view thereof.

FIG. 2A and FIG. 2B are explanatory views of different types of the charging member of the present invention.

FIG. 3 is an explanatory diagram of an image forming apparatus equipped with the charging member of the present invention.

FIG. 4 is an enlarged view of a main part of the charger shown in FIG.

[Explanation of symbols]

1-3: charging member, 1a-3a: conductive substrate, 1b, 2
b: conductive elastic layer, 1c, 2c: surface layer, 11: charged body (photoconductor).

Claims (3)

[Claims] 1. An elastic member that charges a member to be charged by applying a voltage while being pressed against the surface of the member to be charged, the elastic member comprising a conductive elastic layer formed on a conductive substrate and A charging member comprising at least a two-layer structure with a surface layer, wherein the surface layer is made of a siloxane-modified polyurethane resin having a glass transition temperature of -30 to 50C. 2. The siloxane-modified polyurethane resin is a reaction product of an organic polyisocyanate, a long-chain polyol, and a siloxane component, or a reaction product thereof with a chain extender. The charging member according to claim 1, wherein the component is contained in an amount of 0.5 to 30% by weight. 3. The charging member according to claim 1, wherein the thickness of the surface layer is in a range of 1 to 50 μm.