JP3209846B2 - Polyurethane resin composition, charging member and electrophotographic apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polyurethane resin composition having a so-called medium resistance, a charging member containing the resin composition , and an electrophotographic apparatus using the charging member.

[0002]

2. Description of the Related Art Recently, polyurethane resins are used in various products due to their good moldability and the like, and the market is expanding.

[0003] However, polyurethane resins are easily charged with static electricity. Therefore, it has been desired to develop a resin which has a low electric resistance and can easily conduct electricity. In other words, when the polyurethane resin is charged with static electricity, dirt and dust adhere to the resin surface and become dirty, and the resins adhere to each other due to the static electricity, thereby reducing work efficiency and reducing static electricity during processing of the resin. In many cases, sparks are generated due to charging.

[0004] For this reason, development for preventing static charge has been conventionally performed. As an example, there is a method of adding a cationic or nonionic surfactant to the resin as an antistatic agent. However, if the amount is not increased, the effect is not obtained, the economic efficiency is poor, and the bonding strength is weak. As a result, the resin may fall off from the resin, and the composition as the resin may be changed, which is not practical.

Further, there is a method of dispersing a conductive filler in a resin. However, this method is also not preferable because of problems such as the quantity and the moldability.

Further, there is a method of spraying the above-mentioned surfactant or the like on the resin after molding in a post-processing manner. Was.

On the other hand, recently, as a charging member for electrophotography, a contact charging member for directly contacting and charging a photoreceptor is disclosed in, for example,
It has been proposed as described in Japanese Patent Application Laid-Open No. 3-167380, which has advantages such as the ability to use a lower applied voltage and less ozone generation as compared with a conventionally used corona charging system. It has been recognized that.

This contact charging method is shown, for example, in FIG. Uniformly charging the photosensitive drum by an electrophotographic photosensitive drum (2) to the charging a member applying a charging roller a (1) contacting the driven eg an AC voltage V _AC and DC voltage V _DC (6).

As will be understood from the above description, the charging roller must maintain conductivity, and the periphery (1b) of the cored bar (1a) is made of an elastic material as shown in FIG. 2 in order to keep the contact portion uniform. Need to be 1b is a conductive elastic layer.
Conventionally, the conductivity has been adjusted by adding a conductive substance such as conductive carbon black to the elastic layer.

In order to improve these characteristics, the elastic layer is further coated with a member having a volume resistivity of 4.0 × 10 ⁹ Ωcm or more as described in, for example, JP-A-1-191161. Contact charging members have been proposed.

In any case, the resistance value of the binder resin used for the elastic layer is generally as high as 10 ¹⁰ Ωcm or more.
It is difficult to stably lower the resistance value, and there are problems such as resistance fluctuation due to energization and resistance fluctuation due to molding conditions.

According to the studies by the inventors, it has been found that these problems are caused by a difference in resistance between the binder resin and the conductive pigment. In other words, when the difference between the specific resistance values of the binder resin and the conductive pigment is large, electricity is transferred to the pigment (conductive control substance).
This is considered to be due to the fact that the flow concentrates on the part and the deterioration easily occurs.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and a polyurethane having a low electric resistance in which a conductivity adjusting substance is uniformly dispersed in a resin composition and has stable product performance. Resin composition , its polyurethane resin
An object of the present invention is to provide a charging member containing a composition , and an electrophotographic apparatus using the charging member.

[0014]

That is, according to the present invention, when a base polyol obtained by copolymerizing polypropylene glycol and polyethylene glycol is reacted with a polyisocyanate, these are reacted with a general formula (1) [Me (ClO ₄ ) _n ] _x. [R (OH) _y ] _z (1) (wherein, Me is an atom belonging to Group 1 or 2 of the periodic table, and R is a residue of the polyhydric alcohol or a derivative thereof excluding the hydroxyl group) Where n is 1 or 2, x is 1, 2, 3, 4
Or 5, y is 1, 2, or 3, z is 1, 2, 3, 4,
5 or 6) (addition of a chain extender or the like as necessary), and the electrical resistance is 10 ⁵ to 10 ⁹ Ωcm in volume resistivity. It is a polyurethane resin composition characterized by the above-mentioned.

A base polyol obtained by copolymerizing polypropylene glycol and polyethylene glycol;
When reacting with polyisocyanate, these are reacted with a general formula (1) [Me (ClO ₄ ) _n ] _x. [R (OH) _y ] _z (1) (wherein Me is Group 1 of the periodic table or An atom belonging to Group 2 and R represent a residue excluding a hydroxyl group of a polyhydric alcohol or a derivative thereof, n is 1 or 2, x is 1, 2, 3, 4
Or 5, y is 1, 2, or 3, z is 1, 2, 3, 4,
5 or 6) (addition of a chain extender or the like as necessary), and the electrical resistance is 10 ⁵ to 10 ⁹ Ωcm in volume resistivity. a charging member which is characterized by containing a polyurethane resin sets Narubutsu.

Further, in the above charging member, the complex compound Me is lithium, sodium, potassium, calcium or barium. The complex compound is preferably liquid at normal temperature.

Further, in an electrophotographic apparatus having a photosensitive member, a latent image forming unit, a unit for developing the formed latent image, and a unit for transferring the developed image to a transfer material, the photosensitive member is charged as the latent image forming unit. An electrophotographic apparatus, wherein the charging member is used for processing.

Hereinafter, the present invention will be described.

The polypropylene glycol used in the present invention preferably has a number average molecular weight in the range of 300 to 1500, and if it is less than 300, the synthesized polyurethane resin composition
The resistance tends to be too low due to the high water absorption of the material , and the resistance does not tend to decrease if it exceeds 1500.

On the other hand, the polyethylene glycol preferably has a number average molecular weight in the range of 200 to 800. If the number average molecular weight is less than 200 , the water absorption of the synthesized polyurethane resin composition becomes high, so that the resistance tends to be too low. As the size increases, the crystallinity increases, and the operability tends to decrease.

The copolymer as the base polyol is obtained by copolymerizing polypropylene glycol having a predetermined average molecular weight and polyethylene glycol in blocks, alternately or by grafting.

The proportion of the copolymer serving as the base polyol is preferably polypropylene glycol: polyethylene glycol = 1: 9 to 8: 2 by weight, and if it is outside this range, the resistance will be low if the polypropylene glycol is too large. When the amount is too high and the amount of polyethylene glycol is too large, water absorption is large and moldability tends to deteriorate.

Examples of the polyisocyanate used in the present invention include hydrogenated diphenylmethane diisocyanate (hydrogenated MDI), tolylene diisocyanate (TDI) and diphenylmethane diisocyanate (MDI), which are generally used in the synthesis of polyurethane. MDI,
Xylylene diisocyanate (XDI), tetramethyl xylylene diisocyanate (TMXDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), etc. can all be used.

As the chain extender used for synthesizing the polyurethane in the present invention, any of those currently known can be used. For example, ethylenediamine, piperazine, isophoronediamine, 4,4-methylenebis (2 −
Diamines such as chloroaniline); amino alcohols such as N-methylethanolamine and monoethanolamine; and diols such as ethylene glycol, tetramethylene glycol and propylene glycol.

The complex compound used in the present invention is represented by the general formula described above, and Me (Cl
Examples of O ₄ ) _n include perchlorates such as sodium perchlorate, calcium perchlorate, barium perchlorate and the like. R in R (OH) _y is a residue of a polyhydric alcohol or a derivative thereof generally called a glycol, excluding a hydroxyl group. Examples of the glycol include ethylene glycol, ethylene glycol monomethyl ether, Ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monoisocyanyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, ethylene glycol monohexyl ether, diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol mono Ethyl ether, diethylene glycol monobutyl ether, diethylene glycol acetate Triethylene glycol, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol, polyethylene glycol, propylene glycol, propylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, diethylene glycol Propylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, tripropylene glycol, tripropylene glycol monomethyl ether, polypropylene glycol, trimethylene glycol, 1,4-butanediol, 1,5 pentanediol, hexylene glycol, Octylene glycol, guri Serine, glycerin mono or diacetate, glycerin monobutyrate and the like can be mentioned.

The weight ratio of the perchlorate and the glycol constituting the complex compound in the present invention is preferably 1: 9 to 8: 2, more preferably 2: 8 to 6:
4. The amount of the complex compound added to the polyurethane resin is preferably 0.05 to 30% by weight based on the weight of the resin.
And more preferably 0.1 to 5% by weight. If the addition amount is less than 0.05% by weight, the effect of lowering the resistance tends to decrease, and if it exceeds 30% by weight, the processability during kneading tends to deteriorate, and foaming is also performed. In such a case, the stability tends to decrease.

The complex salt with the polyhydric alcohol used in the present invention has good compatibility with the polyurethane raw material, so that it can be easily added, and its dispersibility is uniform and very good. In addition, there is no concern about deterioration of the composition and physical properties of the polyurethane resin composition, and in addition to good stability of electrical properties over a long period of time, there is no operational risk such as ignition or explosion, and handling is easy. is there. Polyurethane resin
The composition can be processed into a hard resin or rubber, or can be used as a polyurethane foam which is a soft or hard foam.

The resin composition containing the polyurethane copolymer thus obtained and having a volume resistivity of 10 ⁵ to 10 ⁹ Ωcm can be used for an electrophotographic charging member. The resin composition can be molded into any shape such as a blade type, a roller type, and a block type, and the power source is a DC power source, DC + AC
It can be used with either power supply.

Unlike the case of dispersing the pigment, it is possible to obtain a stable electric property without fear of remarkable decrease and increase in resistance due to segregation of the pigment.

The machine to be used can be applied to a facsimile, a micro printer, and the like in addition to a copying machine and a page printer.

[0031]

The present invention will be described below with reference to examples. Example 1 Laser beam printer (trade name: Laser Shot A)
408, manufactured by Canon Inc.), the developing DC bias of the printer body is -400 V, and the surface potential of the drum is -70 V.
An image was displayed by applying a DC voltage of −550 V and an AC voltage of −1.2 KV _PP for setting the voltage to 0 V.

As a charging member, HDI and ethylenediamine are added in required amounts to a prepolymer obtained by block copolymerizing polypropylene glycol (PPG) having an average molecular weight of 500 and polyethylene glycol (PEG) having an average molecular weight of 800 in a weight ratio of 3: 7. Further, a resin composition synthesized by adding 5% by weight of a complex compound of Ca (ClO ₄ ) ₂ and CH ₃ CH ₂ OCH ₂ CH ₂ OH at a weight ratio of 4: 6 was molded into a roller mold. Using. The volume resistivity of the resin composition was 3 × 10 ⁸ .

The image evaluation by the charging member of the present invention was carried out visually at the initial stage and after outputting 3000 images. (Image evaluation conditions) Process speed 48mm / s Photoconductor Laminated OPC drum Photosensitive drum diameter φ30mm Charger Polyurethane roller Core diameter φ6mm Charging roller diameter φ12mm Charging roller resistance 3 × 10 ⁸ Ωcm Drum surface potential -700V Development DC bias -400V Table 1 shows the evaluation results. Example 2 Using a monocolor copying machine (trade name: NP6030, manufactured by Canon Inc.), the developing DC bias of the copying machine body was -250.
V, and a DC voltage of -1400 V for setting the surface potential of the drum to -680 V, and an image was displayed.

As a charging member, PP having an average molecular weight of 700
G, a required amount of TDI and piperazine were added to a prepolymer obtained by block copolymerizing PEG having an average molecular weight of 500 at a weight ratio of 6: 4, and NaClO ₄ and CH ₃ CH ₂ O were further added.
Image evaluation was performed using a resin composition formed by adding 10% by weight of a complex compound with CH ₂ CH ₂ OH in a weight ratio of 3: 7 and formed into a roller mold. The volume resistivity of the resin composition was 7 × 10 ⁶ .

The other evaluation methods were the same as in Example 1 . (Image evaluation conditions) Process speed 200mm / s Photoconductor Laminated OPC drum Photosensitive drum diameter φ30mm Charger Polyurethane roller Core diameter φ6mm Charging roller diameter φ16mm Charging roller resistance 7 × 10 ⁶ Ωcm Drum surface potential -680V Development DC bias -250V The evaluation results are shown in Table 1 . Example 3 As a charging member, necessary amounts of TDI and monoethanolamine were added to a prepolymer obtained by alternately copolymerizing PPG having an average molecular weight of 600 and PEG having an average molecular weight of 350 at a ratio of 5: 5, and further adding Ba (ClO ₄ ). ₂ and CH ₃ OCH ₂ CH ₂ O
Image evaluation was performed using a roller-shaped resin composition synthesized by adding 20% by weight of a complex compound of CH ₂ CH ₂ OH in a weight ratio of 2: 8. The volume resistivity of the resin composition was 4 × 10 ⁶ .

Other conditions were the same as those in Example 2 . Table 1 shows the results. Comparative Example 1 A required amount of HDI and ethylenediamine were added to a prepolymer obtained by block copolymerizing PPG having an average molecular weight of 200 and PEG having an average molecular weight of 100 at a ratio of 2: 8 as a charging member, and synthesized without adding a complex compound. Image evaluation was performed using a resin molded into a roller mold. The volume resistivity of the resin was 3 × 10 ⁴ .

Other various conditions were the same as in Example 1 . Table 1 shows the results. Comparative Example 2 A required amount of HDI and isophoronediamine was added to a prepolymer obtained by block copolymerizing PPG having an average molecular weight of 1200 and PEG having an average molecular weight of 1500 at a ratio of 10: 1 as a charging member, and synthesized without adding a complex compound. Image evaluation was performed using a molded resin in a roller mold. The volume resistivity of the resin was 6 × 10 ¹² .

Other conditions were the same as those in Example 1 . Table 1 shows the results.

[0039]

[Table 1]

[0040]

The polyurethane resin composition of the present invention can reduce the resistance of the resin by dispersing a small amount of the complex compound, and has an antistatic function. Further, the present invention provides an electrophotographic charging member having a medium resistance and a stable resistance, and a good image can be obtained even when only a DC electric field is applied or when an AC electric field is superimposed on a DC electric field.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an electrophotographic apparatus of the present invention.

FIG. 2 is a cross-sectional view of a roller-type charging member in the case of a single layer of the resin composition of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Contact charging member 1a Core metal 1b Conductive elastic layer (polyurethane resin composition ) 2 Photoconductor drum 3 Developing unit 4 Transfer unit 5 Cleaning unit 6 Power supply 7 Power supply 8 Transfer material

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-714 (JP, A) JP-A-48-58093 (JP, A) JP-A-4-298518 (JP, A) JP-A-5-58093 88508 (JP, A) JP-A-3-38663 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 75/00-75/16 C08K 3/00-13/08 G03G 15/02

Claims (4)

(57) [Claims] When a base polyol obtained by copolymerizing polypropylene glycol and polyethylene glycol is reacted with a polyisocyanate, these are reacted with a general formula (1) [Me (ClO ₄ ) _n ] _x · [R (OH) _{y Z} (1) (wherein, Me represents an atom belonging to Group 1 or 2 of the periodic table, R represents a residue of a polyhydric alcohol or a derivative thereof excluding a hydroxyl group, n represents 1 or 2, x Is 1,2,3,4
Or 5, y is 1, 2, or 3, z is 1, 2, 3, 4,
The polyurethane resin composition obtained by adding a complex compound represented by formula (5) or (6), having an electric resistance of 10 ⁵ to 10 ⁹ Ωcm in volume resistivity. 2. When reacting a base polyol obtained by copolymerizing polypropylene glycol and polyethylene glycol with a polyisocyanate, these are reacted with a general formula (1) [Me (ClO ₄ ) _n ] _x · [R (OH) _{y Z} (1) (wherein, Me represents an atom belonging to Group 1 or 2 of the periodic table, R represents a residue of a polyhydric alcohol or a derivative thereof excluding a hydroxyl group, n represents 1 or 2, x Is 1,2,3,4
Or 5, y is 1, 2, or 3, z is 1, 2, 3, 4,
Wherein the polyurethane resin composition has a volume resistivity of 10 ⁵ to 10 ⁹ Ωcm and is obtained by adding a complex compound represented by formula (5) or (6). Element. 3. The charging member according to claim 2, wherein Me of the complex compound is lithium, sodium, potassium, calcium, or barium. 4. An electrophotographic apparatus having a photosensitive member, a latent image forming unit, a unit for developing the formed latent image, and a unit for transferring the developed image to a transfer material, wherein the photosensitive member is charged as the latent image forming unit. electrophotographic apparatus which comprises using a charging member according to claim 2 or 3, wherein for processing.