JPH08156143A - Transfer roller for electrophotographic apparatus - Google Patents

Abstract

PURPOSE: To maintain stable printing performance for a long period of time with the surface layer of a photosensitive material drum which is used in contact with a transfer roller prevented from being eroded by specifying the residual amount of an organic solvent in polyurethane foam which constitutes the roller. CONSTITUTION: In a transfer roller for an electrophotographic apparatus which is made of a polyurethane foam prepared from a composition containing a polyisocyanate, a polyol, and a foaming conditioner, the conditioner contains a polysiloxane-polyoxyalkylene block copolymer of 3000-350,000wt. average molecular weight and an organic solvent, and the residual amount of an organic solvent in the polyurethane foam constituting the transfer roller is regulated at 50ppm or lower. Polyisocyanate which is generally used for the production of polyurethane foam such as MDI, TDI, a mixture of them, modified MDI, and modified TDI is used preferably.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer roller which does not damage a charge generation layer and a charge transfer layer on the surface of a photosensitive drum in an electrophotographic apparatus. The transfer roller of the present invention is used as a transfer roller of an electrophotographic apparatus such as an electrophotographic copying machine or a laser beam printer.

[0002]

2. Description of the Related Art Recently, as a method of transferring to paper or the like in an electrophotographic apparatus, a photosensitive material obtained by coating a binder made of polycarbonate containing a charge transfer substance in the upper layer and a charge generating substance in the lower layer on, for example, an aluminum drum. A method in which a body drum is used and a transfer roller made of polyurethane foam or the like is brought into contact with the transfer roller is often used.

The polyurethane foam forming the transfer roller has a very high density, and is a macromolecular polymer produced by a special production method in long-chain alkylbenzene as a foam stabilizer which is one of the main raw materials. Silicone compounds have been used. This foam stabilizer usually contains 50 to 60% by weight of long-chain alkylbenzene, but it is still a substance having extremely high viscosity, and is used as a foam stabilizer as it is without removing this solvent in handling. . Since this long-chain alkylbenzene is a substance having a considerably high boiling point, even if a small amount is vaporized and evaporated in the reaction curing step, most of it remains in the polyurethane foam produced as it is.

As described above, a considerable amount of long-chain alkylbenzene is mixed in the obtained transfer roller, and depending on the amount of the foam stabilizer used, for example, 3% by weight relative to the polyurethane foam constituting the transfer roller. % Will also be included. Further, in place of the long-chain alkylbenzene having a high boiling point, isopropyl alcohol, toluene and xylene, etc., a solvent having a relatively low boiling point is used as a reaction solvent,
Moreover, a low-viscosity diluent such as dioctyl phthalate or dibutyl phthalate is added to the solution containing the obtained copolymer, and then the solvent is vaporized and removed by drying under reduced pressure while heating, and the organic solvent is used as the diluent. There is also a method in which the foam stabilizer is replaced with.

However, in the case of the above-mentioned method, the conventional diluent used for imparting fluidity to the foam stabilizer is leached on the surface of the transfer roller after the roller is molded, which hinders normal paper feeding. The leached diluent adheres to the paper and causes problems such as stains. Also, when a polyurethane foam is molded by substituting the organic solvent with a diluent in this way, the residual solvent amount in the transfer roller is reduced to such an extent that the solvent does not substantially migrate to the photosensitive drum. However, further improvement is desired.

[0006]

As described above, it is inevitable that a certain amount of organic solvent such as long-chain alkylbenzene is mixed in the transfer roller, and that the boiling point of the long-chain alkylbenzene is 100. Even toluene or the like having a low temperature of ℃ or more cannot be completely removed by heating to a temperature of 140 ° C. or lower, which is the heat resistant temperature of the polyurethane foam, after roller molding. And
Depending on the remaining amount of the organic solvent in the transfer roller, the solvent may be transferred to the photosensitive drum that is in contact and stopped to disperse the charge generating substance and the charge transfer substance, especially when the apparatus is not operating. , Will erode polycarbonate that is often used as a binder to be contained.

In addition, the charge transfer substance that constitutes an organic photoconductor, which is a photoconductor that is widely used in recent years, is a highly sensitive material, and is an aromatic or aliphatic substance having a low polarity such as long-chain alkylbenzene. When the particles intrude into the charge transfer layer, there arises a problem that first, the polycarbonate as the binder in which the charge transfer material is dispersed is eroded, and then the charge transfer material itself is extracted. The present invention overcomes the above-mentioned drawbacks and provides a transfer roller that does not contain an organic solvent in an amount sufficient to transfer to a photosensitive drum and erode the charge generation layer and the charge transfer layer on the surface thereof, and to form polyurethane foam. An object of the present invention is to obtain a transfer roller that does not cause problems such as paper stains depending on the used foam stabilizer diluent.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to achieve the above object, and as a result, have determined that the amount of the organic solvent remaining in the transfer roller is a specific trace amount, and that the reaction solvent such as toluene is used as a reaction solvent. The organic solvent used is replaced by a reactive diluent that participates in the reaction during foam formation, and in some cases reheating of the resulting transfer roller ensures thorough solvent removal, and The use of polyalkylene glycol, which does not leach to the foam surface and acts as a polyol component in the foam formation process as described above, as a diluent that replaces the solvent eliminates the above-mentioned drawbacks. The present invention has been completed and the present invention has been completed.

The transfer roller for an electrophotographic apparatus of the first invention is
In a transfer roller for an electrophotographic apparatus, which is made of a polyurethane foam produced by using a composition containing a polyisocyanate, a polyol and a foam stabilizer, the foam stabilizer is a polysiloxane having a weight average molecular weight of 3000 to 350,000.
A polyoxyalkylene block copolymer and an organic solvent are contained, and the residual amount of the organic solvent in the polyurethane foam constituting the transfer roller is 50 ppm or less.

A third invention is the transfer roller for an electrophotographic apparatus of the first invention, wherein the foam stabilizer further contains polyalkylene glycol, and the weight ratio of the copolymer to the polyalkylene glycol is It is in the range of 3: 7 to 7: 3, and the copolymer has a weight average molecular weight of 750 to 250.
0 polysiloxane and weight average molecular weight of 1500 to 45
00 is a block copolymer with a polyether.

As the above-mentioned "polyisocyanate", those generally used in the production of polyurethane foam can be used without particular limitation, but among them, MDI, T
DI or a mixture thereof and modified products of MDI and TDI are preferable. The polyol contained in the above-mentioned “polyol” component is not particularly limited as to its type,
Polypropylene glycol, polypropylene adipate, polycaprolactone and the like are preferable. In particular, a polymer polyol, that is, a polyol obtained by graft-polymerizing an ethylenically unsaturated compound such as acrylonitrile, styrene, or methyl methacrylate to a polyether polyol is preferable, and they are used in the state of an insoluble and highly stable suspension. To be done.

The "polysiloxane / polyoxyalkylene block copolymer" (hereinafter referred to as a copolymer), which is a component of the "foam stabilizer", is used in an organic solvent such as toluene described in the second invention. Manufactured. The nature of the solution is usually a solution containing about 40 to 50% by weight of the copolymer, but the solution has a high viscosity because the molecular weight of the copolymer is very large.
However, if it is used as it is, a large amount of solvent remains in the transfer roller, so the handling property will decrease, but the organic solvent should be used in a reduced amount, or "polyalkylene glycol" should be added to the reaction solution. After that, remove the organic solvent as much as possible by means of heating, decompression, etc.,
It is preferable to replace the organic solvent with polyalkylene glycol before use.

In any case, the organic solvent remaining in the polyurethane foam constituting the obtained transfer roller is
Must be "50 ppm or less", especially 30 ppm
The following is preferred. If the amount of organic solvent is less than this level, there is almost no transfer to the photosensitive drum,
The charge generation layer and the like are not eroded.

The "copolymer" is a "polysiloxane".
A part having a "weight average molecular weight of 3000 to 350,000" can be used. If the weight average molecular weight is less than 3,000, the ability to stabilize the foam is poor, and if it exceeds 350,000, the viscosity becomes extremely high and handling becomes difficult. The weight average molecular weight of the copolymer is particularly preferably in the range of 10,000 to 100,000, and in this range, a high-density polyurethane foam can be stably molded. In addition, the polysiloxane portion and the polyoxyalkylene portion are the fourth and fifth
As in the invention, it is preferable that they are composed of dihydropolydimethylsiloxane and dimethallyl polyether, respectively. With such a copolymer, a high-density polyurethane foam can be stably molded.

Examples of the above polyalkylene glycol include polyethylene glycol, polypropylene glycol, polybutylene glycol, and the like.
As in the invention, the molecular weight is 100-3000, especially 200-
2000 polypropylene glycol is preferred. If you use polypropylene glycol in the above molecular weight range,
The foam stabilizer obtained has an appropriate viscosity and is easy to handle, and it is sufficiently consumed in the foam-forming reaction as a part of the polyol component and does not remain in the transfer roller.

The amount ratio of the copolymer and the polyalkylene glycol is 10 as in the case of the third invention.
When the content is 0% by weight, the content of the copolymer is 30 to 70% by weight,
The range of 70 to 30% by weight of polyalkylene glycol, particularly 30 to 50% by weight of copolymer, and the range of 70 to 50% by weight of polyalkylene glycol are preferable. When the amount ratio of the copolymer is less than 30% by weight, when the amount of the copolymer is sufficient to function as a foam stabilizer, the amount of polyalkylene glycol inevitably becomes large, and the polyurethane foam for a transfer roller is obtained. Is unfavorable since it will impair the physical properties of.
On the other hand, when it exceeds 70% by weight, the viscosity of the foam stabilizer is too high and it becomes difficult to handle.

The above copolymer can be represented by the following general formula. X [(Me ₂ SiO) _l (Me) ₂ SiRO (C ₂ H ₄ O) _m (C ₃ H ₆ O) _n -R] _y X [In the above formula, X is H (Me ₂ SiO) _l (Me ) ₂ Si- or R'O (C ₂ H ₄
O) _m (C ₃ H ₆ O) _n -R-represents a terminal blocking group selected from
l, m, n (any one of m and n may be 0)
And y are average numbers, which are values within which the molecular weight of this copolymer falls within the above range. Further, R represents a divalent hydrocarbon group having 2 to 10 carbon atoms, and R ′ represents a monovalent hydrocarbon group having 2 to 10 carbon atoms and containing an unsaturated group. Incidentally, Me represents a methyl group, and may be another short chain alkyl group such as an ethyl group or an isopropyl group. ]

Further, specific examples of the foam stabilizer containing the above-mentioned copolymer as a main component include the following. 1) Polydimethylsiloxane / polyoxyalkylene block copolymer X [(Me ₂ SiO) ₁₈ (Me) ₂ SiCH ₂ CH (CH ₃ ) CH ₂ -O (C ₂ H ₄ O) ₄₅ (C ₃ H ₆ O)
Polypropylene glycol (molecular weight: 400) solution containing 40% by weight of ₁₅ CH ₂ CH (CH ₃ ) CH ₂ ] ₁₇ X [where X is H (Me ₂ SiO) ₁₈ (Me) ₂ Si- or CH = C (CH ₃ ) CH ₂ -O (C
It is a terminal blocking group selected from any of ₂ H ₄ O) ₄₅ (C ₃ H ₆ O) ₁₅ CH ₂ CH (CH ₃ ) CH ₂ —. ]

2) Polydimethylsiloxane having the following composition
Polyoxyalkylene block copolymer X [(Me ₂ SiO) ₂₅ (Me) ₂ SiCH ₂ CH (CH ₃ ) CH ₂ -O (C ₂ H ₄ O) ₄₀ (C ₃ H ₆ O)
₁₈ CH ₂ CH (CH ₃ ) CH ₂ ] ₂₅ X solution containing 30% by weight of polypropylene glycol (molecular weight: 200) [wherein X is H (Me ₂ SiO) ₂₅ (Me) ₂ Si- or CH = C (CH ₃ ) CH ₂ -O (C
It is a terminal blocking group selected from any of ₂ H ₄ O) ₄₀ (C ₃ H ₆ O) ₁₈ CH ₂ CH (CH ₃ ) CH ₂ —. 3) Polydimethylsiloxane / polyoxyalkylene block copolymer X [(Me ₂ SiO) ₁₀ (Me) ₂ SiCH ₂ CH (CH ₃ ) CH ₂ -O (C ₂ H ₄ O) ₂₂ (C ₃ H ₆ O)
Polypropylene glycol (molecular weight: 800) solution containing 50% by weight of ₁₀ CH ₂ CH (CH ₃ ) CH ₂ ] ₂₀ X [wherein X is H (Me ₂ SiO) ₁₀ (Me) ₂ Si- or CH = C (CH ₃ ) CH ₂ -O (C
It is a terminal blocking group selected from any of ₂ H ₄ O) ₂₂ (C ₃ H ₆ O) ₁₀ CH ₂ CH (CH ₃ ) CH ₂ —. ]

[0020]

In the application of the transfer roller for the electrophotographic apparatus, the polyurethane foam formed by chemical foaming using water, methylene chloride, flon, etc. as the foaming agent has too low hardness, and it is difficult to obtain the dimensional accuracy as the roller, and the tensile strength and Since mechanical strength such as abrasion resistance is also insufficient, mechanical foam is usually used. Further, in order to make the foam have a high density composed of minute open cells, a foam stabilizer having a specific high molecular weight is used. In this way, a foam having high mechanical strength and having appropriate hardness and flexibility is formed.

In the case of producing a foam by mechanical foaming, it is preferable to use substantially only a metal catalyst, and the excess resinification reaction and the foaming reaction for producing carbon dioxide by the reaction between water and isocyanate are It is desirable not to have a sufficient amount of amine catalyst coexisting at a practical rate prior to the reaction cure step. As the metal catalyst, stanas octoate, dibutyltin diacetate, dibutyltin dilaurate, nickel acetylacetate and the like suitable for polyurethane foam can be used, and the amount thereof is 0.1 to 0 relative to 100 parts by weight of the polyol. About 3 parts by weight is preferable.

[0022]

EXAMPLES The transfer roller for an electrophotographic apparatus of the present invention will be described in more detail below with reference to examples. Example 1 The following formula: CH ₂ = C (CH ₃ ) CH ₂ -O (C ₂ H ₄ O) ₄₅ (C ₃ H ₆ O) ₁₅ CH ₂ C (CH ₃ ) = C
A dimethallyl polyether represented by H ₂ and the following formula: H (Me ₂ S
iO) ₁₈ (Me) ₂ SiH represented by dihydropolydimethylsiloxane is reacted using toluene as a reaction solvent,
An alternating block copolymer having a weight average molecular weight of 80,000 was obtained. Polypropylene glycol having a molecular weight of 700 was added to the reaction product in a weight ratio of 1: 1 with the copolymer. Then, toluene was removed by a rotary evaporator. Using this as a foam stabilizer (of solution A below),
The following solutions A and B were prepared.

Solution A: Prepared by mixing the following three components. Polymer polyol; (manufactured by Mitsui Toatsu Chemicals, Inc., trade name "POP24 / 20") 100 parts by weight Foam stabilizer; foam stabilizer prepared as described above, 10 parts by weight Metal catalyst (nickel acetyl acetate 10 times diluted) Product, manufactured by OSi Specialties, product name "L
c5615 ") 2 parts by weight Solution B: polyisocyanate modified MDI (manufactured by Nippon Polyurethane Co., Ltd., trade name" M
TL ")

The solution A having the above composition and the solution B having an isocyanate index of 107 were stirred and mixed by a dynamic mixer for 1 minute while feeding nitrogen gas,
It is poured into the mold as it is, and then primary cured at 160 ° C for 30 minutes, then secondary cured at 110 ° C for 4 hours, and then a metal shaft is press-fitted and adhered to it, the end is cut, the surface is polished, etc. Then, a transfer roller was obtained.

Example 2 The transfer roller of Example 1 was heated at 120 ° C. for another 4 hours. Comparative Example 1 Foam stabilizer (OSi using long-chain alkylbenzene as a reaction solvent)
Product name "L-561" manufactured by Specialties.
4 ”) was used to obtain a transfer roller in the same manner as in Example 1. This transfer roller is set to 120 as in the second embodiment.
Reheat at 4 ° C. for 4 hours.

The transfer rollers of Examples 1 and 2 and Comparative Example 1 were arranged side by side with the photosensitive drum in the circumferential direction and pressure-bonded with a load of about 1 kg. In this state, it was allowed to stand for one month in a thermo-hygrostat adjusted to a temperature of 40 ° C. and a relative humidity of 85%. After one month,
The photoconductor drum was taken out of the tank, and an electron micrograph (magnification: 1000 times) of the surface was taken to observe the surface condition. Further, print evaluation was actually performed using this photosensitive drum.

Table 1 shows the amount of the residual organic solvent in the polyurethane foams constituting the transfer rollers of Examples 1 and 2 and Comparative Example 1, and the number of holes having a diameter of 1 μm or more on the surface of the photosensitive drum (inside of 50 μm square). Also, the results of print evaluation are shown. Each property was measured as follows. Residual organic solvent amount: quantified by gas chromatography Number of holes: scanning electron micrograph (magnification: 1000 times)

[0028]

[Table 1]

According to the results shown in Table 1, in Example 1, the toluene remaining in the foam stabilizer remained in the roller even though the amount was the upper limit of the present invention. In halftone (halftone dot) printing, which has a negative effect on the image quality and is possible with delicate charge adjustment, a thin streak appears, but it can be sufficiently put to practical use. Further, in Example 2, by reheating the roller, the residual amount of toluene was reduced to about half the amount in Example 1, the photosensitive drum was not affected at all, and stable use was possible for a long period of time. It turns out to be Laura. On the other hand, in Comparative Example 1, the long-chain alkylbenzene remained in the transfer roller, and most of it remained even after heating. Therefore, a large number of holes were formed in the charge transfer layer on the surface of the photosensitive drum, resulting in printing. In the evaluation, it can be seen that the black horizontal line runs and cannot be used at all.

It should be noted that the present invention is not limited to the specific embodiments described above, but can be variously modified within the scope of the present invention in accordance with the purpose and application. That is,
Any reaction solvent can be used as long as it can dissolve the catalyst for producing the copolymer and is a liquid at a temperature of about 70 to 80 ° C., and xylene, isopropyl alcohol and the like can also be preferably used. Further, as the diluent for the foam stabilizer, not only polyalkylene glycol but also the one which can impart fluidity to the foam stabilizer, for example, the same polyols other than the polyalkylene glycol used for foam formation are used. You may.

Further, the foam stabilizer is usually used in an amount of about 1 to 4 parts by weight per 100 parts by weight of the polyol used for producing polyurethane foam, but more than 4 parts by weight, for example, 8 parts by weight. About 12 parts by weight may be used. By using such a large amount of foam stabilizer, the bubbles can be stabilized. The specific gravity of the polyurethane foam is preferably in the range of 0.3 to 0.9, particularly 0.4 to 0.7, and in this range, the obtained transfer roller has appropriate hardness and flexibility. Is preferable.

[0032]

According to the transfer roller of the first aspect of the present invention, the surface layer of the photosensitive drum used for contact is not corroded, and stable printing performance is maintained for a long period of time. Further, when the foam stabilizer of the third invention, particularly the foam stabilizer using the polypropylene glycol having a specific molecular weight of the sixth invention as a diluent is used, the raw material for polyurethane foam can be easily handled and is a diluent. The polyalkylene glycol acts as a polyol component for forming a foam, and does not stain the paper or the like with a diluent, and the organic solvent remaining in the transfer roller can be suppressed to a very small amount. Furthermore, the fourth
By using the specific copolymer of the fifth invention, it is possible to obtain a transfer roller having more uniform and appropriate hardness and flexibility.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area B29K 105: 04

Claims (6)

[Claims] 1. A transfer roller for an electrophotographic apparatus comprising a polyurethane foam produced by using a composition containing a polyisocyanate, a polyol and a foam stabilizer, wherein the foam stabilizer has a weight average molecular weight of 3000 to 350,000.
Of the polysiloxane / polyoxyalkylene block copolymer and organic solvent, the residual amount of the organic solvent in the polyurethane foam constituting the transfer roller is 50 p.
A transfer roller for an electrophotographic apparatus, which is pm or less. 2. The transfer roller for an electrophotographic apparatus according to claim 1, wherein the organic solvent is at least one selected from isopropyl alcohol, toluene and xylene. 3. The foam stabilizer further comprises a polyalkylene glycol, and the weight ratio of the copolymer to the polyalkylene glycol is in the range of 3: 7 to 7: 3, and the copolymer is 2. The transfer roller for an electrophotographic apparatus according to claim 1, which is a block copolymer of a polysiloxane having a weight average molecular weight of 750 to 2500 and a polyether having a weight average molecular weight of 1500 to 4500. 4. The transfer roller for an electrophotographic apparatus according to claim 1, wherein the polysiloxane part of the copolymer is composed of dihydropolydimethylsiloxane and the polyoxyalkylene part is composed of dimethallyl polyether. 5. The transfer roller for an electrophotographic apparatus according to claim 3, wherein the polysiloxane part of the copolymer is composed of dihydropolydimethylsiloxane and the polyoxyalkylene part is composed of dimethallyl polyether. 6. The transfer roller for an electrophotographic apparatus according to claim 3, wherein the polyalkylene glycol is polypropylene glycol having a weight average molecular weight of 100 to 3000.