JP5203544B1 - Roller for liquid developing electrophotographic apparatus - Google Patents

Abstract

An object of the present invention is to provide a roller for a liquid developing electrophotographic apparatus useful for improving the image quality of the liquid developing electrophotographic apparatus. In order to solve this problem, the present invention is arranged in the liquid developing electrophotographic apparatus with the outer peripheral surface brought into contact with another member, and rotated around an axis to carry the liquid developer on the outer peripheral surface for conveyance. A roller for a liquid development electrophotographic apparatus used by having a surface layer forming the outer peripheral surface and an elastic body layer in contact with the surface layer from the inside, wherein the elastic body layer and the surface layer are predetermined. A roller for a liquid developing electrophotographic apparatus having the following characteristics is provided.
[Selection] Figure 2

Description

  The present invention relates to a roller for a liquid developing electrophotographic apparatus.

2. Description of the Related Art Conventionally, an electrophotographic apparatus has been widely used in which an electrostatic latent image drawn on a photosensitive member with a laser beam or the like is visualized with toner and transferred to a surface of paper or the like for printing.
In recent years, this toner has been finely divided to improve printing accuracy.
As a method for improving this printing accuracy, liquid development is performed by dispersing toner, for example, about 1 μm, in a liquid called a carrier mainly composed of liquid paraffin, silicone oil, mineral oil, or vegetable oil. An agent (liquid toner) is prepared, and the use of this liquid developer in an electrophotographic apparatus has been studied (see Patent Documents 1 and 2 below).

  In such a liquid developing electrophotographic apparatus, a developing roller for visualizing (developing) an electrostatic latent image with the liquid developer on the surface of the photoreceptor, and a liquid developer on the developing roller. Various rollers such as an anilox roller that pumps the liquid developer from the toner tank are used for supply (see Patent Document 3 below).

The developing roller is usually formed by surrounding an elastic body layer using an elastic body such as rubber or low-hardness resin on the outer periphery of a shaft body called a cored bar.
On the other hand, the anilox roller is usually made of metal or ceramics and is not made of a material that causes elastic deformation like the photoreceptor.
Some of the liquid developing electrophotographic apparatuses have such an anilox roller and a developing roller in direct contact with each other.
This type of liquid developing electrophotographic apparatus is formed so that the liquid developer pumped up by the anilox roller is conveyed to the photoconductor via the developing roller.

In such a liquid developing electrophotographic apparatus, the contact state between the anilox roller or the photoreceptor and the developing roller is mainly adjusted by the characteristic (elasticity) of the elastic layer of the developing roller.
However, the contact state required between the developing roller and the anilox roller is not always the same as the contact state required between the photoconductor and the developing roller.
Therefore, even if the characteristics of the elastic layer of the developing roller are adjusted, it may not be possible to make contact with both the photoreceptor and the anilox roller in an optimal state.
Therefore, as a liquid developing electrophotographic apparatus different from the liquid developing electrophotographic apparatus as described above, another roller having an elastic layer called a transport roller is disposed between the developing roller and the anilox roller. What has been developed.
That is, an attempt has been made to satisfactorily carry the liquid developer from the anilox roller to the photoreceptor by providing a roller suitable for contact with the anilox roller called a carry roller.

By the way, the anilox roller is usually provided with uniform irregularities on the entire surface so that the liquid developer can be adhered with a constant thickness.
More specifically, the outer surface of the anilox roller has irregularities such as a honeycomb pattern with fine depressions having hexagonal openings, a diamond pattern with fine depressions having rhombic openings, and a helical pattern with fine grooves. Is formed.
Therefore, in the case where the transport roller is used in contact with the anilox roller, the anilox roller is not brought into contact with the surface of the transport roller unless the transport roller is brought into contact with the anilox roller in such a way that the surface is intruded to some extent. The liquid developer transmitted from the toner tends to be non-uniform, and there is a risk that a defect in which the surface pattern of the anilox roller appears in the finally obtained image (hereinafter also referred to as “pattern unevenness”) may occur.
In addition, if the surface of the transport roller does not penetrate into the depressions or grooves of the anilox roller to some extent, the final image may be in a partially different hue (hereinafter also referred to as “color unevenness”) or partially There is a possibility that the color density is different (hereinafter also referred to as “density unevenness”).

Japanese Patent No. 3377843 Japanese Patent No. 3378778 Japanese Unexamined Patent Publication No. 2011-180189

As a countermeasure against the above problems, it is conceivable to make the elastic layer such as a transport roller sufficiently flexible so as to provide followability to the fine surface shape of the anilox roller.
However, simply reducing the rebound resilience of the elastic layer such as the transport roller to exert its flexibility, it takes time to restore the original shape after the elastic layer is elastically deformed by contact with other members. It will take.
For example, while the liquid developing electrophotographic apparatus is stopped, the conveyance roller and the developing roller that are in contact with the anilox roller are in a state in which the elastic layer is recessed at the contact point with the anilox roller.
Then, even after the liquid developing electrophotographic apparatus is started, the elastic layer remains strained for a while, and the liquid developer carrying state at the strain remaining portion is different from the surroundings, and streaky irregularities appear on the image. (Hereinafter also referred to as “straight spot”).

In addition, it is not a problem peculiar to the conveyance roller and the developing roller that is in contact with the anilox roller, and the problem that it becomes easy to generate the unevenness immediately after the start by improving the followability to the partner material to be contacted. Common to a roller for a liquid developing electrophotographic apparatus that is disposed in a liquid developing electrophotographic apparatus with an outer peripheral surface thereof in contact with the member and used for transporting the liquid developer by carrying the liquid developer on the outer peripheral surface. It is a problem.
An object of the present invention is to solve such problems, and to provide a roller for a liquid developing electrophotographic apparatus useful for improving the image quality of the liquid developing electrophotographic apparatus.

  In order to complete the present invention, the present inventors have found that the problem described above can be solved by providing a surface having a predetermined physical property on the outer side of the elastic layer having the predetermined physical property. It has arrived.

That is, the present invention relating to a roller for a liquid developing electrophotographic apparatus for solving the above-mentioned problems is arranged in the liquid developing electrophotographic apparatus by bringing the outer peripheral surface into contact with another member, and the liquid developer is placed on the outer peripheral surface. A roller for a liquid development electrophotographic apparatus that is used by being rotated about an axis to be carried and having a surface layer that forms the outer peripheral surface, and an elastic layer that contacts the surface layer from the inside, The elastic body layer is formed of a polyurethane elastic body obtained by reacting a polyester polyol and a bifunctional isocyanate. The polyurethane elastic body has a JISA hardness of 30 degrees or more and 60 degrees or less and a compression set of 2% or less. The surface layer is formed of a cured product of the thermosetting resin composition to a thickness of 1 μm or more and 20 μm or less, and the storage layer of the cured product in a temperature range of 10 ° C. to 50 ° C. The characteristic factor is 1 × 10 ⁸ Pa or more and 1 × 10 ¹⁰ Pa or less, and Tan δ in the temperature range of the cured product is 0.2 or less.

The roller for a liquid developing electrophotographic apparatus of the present invention has a surface layer having a predetermined viscoelastic property with a predetermined thickness on the surface of an elastic layer having a predetermined physical property. Even a member having such a fine dent or groove shows a good contact state and is excellent in resilience after deformation.
Accordingly, it is possible to suppress the possibility of occurrence of uneven stripes and color unevenness in an image printed by the liquid developing electrophotographic apparatus, and a liquid developing electrophotographic apparatus having improved image quality as compared with the conventional liquid developing electrophotographic apparatus. May be provided.

The figure which showed typically the structure of the liquid development electrophotographic apparatus. The schematic perspective view which showed the roller which concerns on one Embodiment of this invention. The graph which shows the viscoelastic characteristic (storage elastic modulus, temperature dependence of Tan (delta)) of the formation material of a surface layer. The schematic diagram which shows the residual deformation amount investigation method in an Example. The schematic diagram which shows the image evaluation method in an Example.

  Hereinafter, preferred embodiments of the present invention will be described (based on the accompanying drawings).

  First, a liquid developing electrophotographic apparatus in which a roller for a liquid developing electrophotographic apparatus according to this embodiment is used will be described with reference to FIG.

The liquid developing electrophotographic apparatus in the present embodiment is configured using a photoreceptor and various rollers.
More specifically, the liquid developing electrophotographic apparatus is formed in a cylindrical shape, rotates around the central axis of the cylindrical shape, and forms a visible image on the outer peripheral surface with a liquid developer, and the photosensitive member 1. And an intermediate transfer roller 2 disposed with its outer peripheral surface being in contact with each other.
The intermediate transfer roller 2 is provided in a liquid developing electrophotographic apparatus so that a visible image formed on the photoreceptor 1 is primarily transferred onto the surface thereof and then secondarily transferred to a printing material A such as paper.
Further, the liquid developing electrophotographic apparatus is provided with a pressure roller 3 and the like arranged with the outer peripheral surface thereof in contact with the intermediate transfer roller 2.
The pressure roller 3 is rotated with the printing material A such as paper sandwiched between the pressure transfer roller 2 and the intermediate transfer roller 2 while pressing the printing material A against the intermediate transfer roller 2. The liquid developing electrophotographic apparatus is provided so that the printed image A is moved in the rotation direction and the developed image primarily transferred to the intermediate transfer roller 2 is secondarily transferred to the printed material A.

Further, in the liquid developing electrophotographic apparatus, the photosensitive member 1 is disposed with its outer peripheral surface in contact with the photosensitive member 1, and rotates around the axis together with the photosensitive member 1 so that the liquid developer carried on the outer peripheral surface is transferred to the photosensitive member 1. A developing roller 6 for supplying the toner to the photoconductor 1 and a toner tank X for storing the liquid developer Y supplied to the photoreceptor 1 through the developing roller 6.
Further, in the liquid developing electrophotographic apparatus, the outer peripheral surface is in contact with the liquid developer Y accommodated in the toner tank X, and is rotated around the axis so as to adhere to the outer peripheral surface and pump up the liquid developer. An anilox roller 4 and a transport roller 5 for supplying the liquid developer attached to the outer peripheral surface of the anilox roller 4 to the developing roller 6 with the outer peripheral surface being in contact with the anilox roller 4. ing.
That is, in the liquid developing electrophotographic apparatus according to this embodiment, the liquid developer Y pumped up from the toner tank X by the anilox roller 4 is transmitted from the anilox roller 4 to the transport roller 5 and is carried on the outer peripheral surface of the transport roller 5. It is configured to be.
In the liquid developing electrophotographic apparatus, the liquid developer Y is transported to the developing roller 6 when the transport roller 5 rotates about the axis, and the liquid developer rotates about the axis. By doing so, it is formed so as to be conveyed to the photoreceptor 1.

In the liquid developing electrophotographic apparatus of this embodiment, a bias voltage is applied to the developing roller 6 and a charge is applied to separate the liquid developer supplied from the transport roller 5 into a carrier layer and a toner aggregation layer in the developing roller 6. An aggregating roller 7 is further provided, and a squeeze roller 8 for squeezing out the carrier of the liquid developer supplied from the developing roller 6 to the photoreceptor 1 is further provided.
Further, in the liquid developing electrophotographic apparatus of this embodiment, the surfaces of the polishing roller 9 and the developing roller 6 that finely polish the surface of the photoconductor 1 to keep the surface of the photoconductor 1 in contact with the photoconductor 1 to be clean. And a cleaning blade 10 'for cleaning the surface of the photoreceptor, and a cleaning blade 10' for cleaning the surface of the photoreceptor.

Next, the liquid developing electrophotographic apparatus roller of the present invention will be specifically described with reference to FIG.
The transport roller 5 of this embodiment is used with its outer peripheral surface being in contact with both the developing roller 6 and the anilox roller 4 in order to transport the liquid developer from the anilox roller 4 to the developing roller 6. An elastic body layer 52 formed of an elastic body is provided around the outer periphery of the cored bar 51 so that a good contact state can be formed therebetween.
Furthermore, the transport roller 5 of this embodiment includes a surface layer 53 that forms the outer peripheral surface of the transport roller 5 outside the elastic body layer 52.

The elastic body layer 52 is formed of a polyurethane elastic body having a JIS-A hardness of 30 degrees or more and 60 degrees or less and a compression set of 2% or less, and is usually formed to have a thickness of 1 mm or more and 10 mm or less. Yes.
Further, as the polyurethane elastic body forming the elastic body layer 52 in the transport roller 5 of this embodiment, a polyurethane elastic body obtained by reacting a polyester polyol and a bifunctional isocyanate is used.
In addition, although it does not specifically limit as said polyester polyol, It is preferable to employ | adopt the polyester polyol by which dicarboxylic acid, bifunctional glycol, and polyfunctional glycol more than trifunctional are reacted.

Examples of the dicarboxylic acid preferable as a starting material for the polyester polyol include adipic acid and sebacic acid.
Moreover, as said bifunctional glycol, a C2-C6 thing is preferable, for example, and it is preferable that they are either diethylene glycol, 1, 4- butanediol, or 3-methylpentanediol.
Furthermore, the trifunctional or higher polyfunctional glycol is preferably trimethylolpropane.

In the present embodiment, it is preferable to employ the polyester polyol as described above as a material for forming the elastic body layer 52, because the polyurethane elastic body to be obtained is liquid paraffin, silicon as compared with the case where other polyols are used. This is because it is difficult to swell against substances generally used as carriers such as oil, mineral oil, or vegetable oil.
That is, the polyester polyol as described above is added to the elastic layer in that the volume change in the elastic layer during the use period of the transport roller 5 and the deterioration of the image quality of the liquid developing electrophotographic apparatus can be more reliably prevented. It is preferable to use it as a forming material.

  Among them, adipic acid; a difunctional glycol of any one of diethylene glycol, 1,4-butanediol, and 3-methylpentanediol; a polyester polyol obtained by reacting three components of trimethylolpropane is unlikely to cause a volume change due to a carrier. This is particularly effective for forming the elastic layer.

The bifunctional isocyanate for forming a polyurethane elastic body together with such a polyester polyol is not particularly limited, and examples thereof include tolylene diisocyanate (TDI), xylene diisocyanate (XDI), and diphenylmethane diisocyanate (MDI). Either can be used preferably.
In particular, it is preferable to use either tolylene diisocyanate or xylene diisocyanate.
By using tolylene diisocyanate or xylene diisocyanate as the bifunctional isocyanate, the volume change of the elastic body layer due to the carrier can be reduced, and the decrease in printing accuracy of the liquid developing electrophotographic apparatus can be further suppressed.
Moreover, by using tolylene diisocyanate or xylene diisocyanate, the curing reaction with the polyester polyol can be carried out at a higher reaction rate than when diphenylmethane diisocyanate is used.
Therefore, by using tolylene diisocyanate or xylene diisocyanate, it is possible to shorten the manufacturing time when the transport roller 5 is manufactured, and the production efficiency of the transport roller 5 can be improved.

In this embodiment, since it is preferable to give the elastic layer 52 a certain degree of electrical conductivity, the polyurethane elastic body contains graphite and carbon black.
Carbon black usually has a size of 1 μm or less (several tens of nm), whereas graphite usually has a size exceeding 1 μm, and its particle size is larger than that of carbon black. It is one or more orders of magnitude larger, and has a more developed crystal structure than carbon black.
Therefore, graphite has a semi-metallic electronic state, and the conductivity of the particles themselves is usually superior to that of carbon black.

In addition, the expression of conductivity by carbon black is greatly affected by the formation of the structure.
Therefore, for example, when conductivity is imparted to the elastic layer only with carbon black, it is difficult to recognize the interrelationship between the carbon black content and the electrical characteristics, and abruptly with a certain content as a boundary. May change electrical properties.
On the other hand, since graphite is excellent in the conductivity of the particles themselves, it is easier to adjust the electrical properties depending on the content compared to carbon black.

Furthermore, when a voltage is continuously applied to a transport roller that exhibits conductivity in the elastic layer only with carbon black, the tunnel effect in the structure of the carbon black may be changed.
Moreover, since such a change may occur in a short period of time, the electrical characteristics of such a transport roller may change immediately.
On the other hand, when graphite is used in combination, it is difficult to be affected by such effects. Therefore, even if continuous voltage application is performed on the transport roller, it is difficult to cause a change in the electrical characteristics of the elastic layer.

By the way, the surface of the transport roller 5 is preferably smooth. For example, the surface layer 53 preferably has a surface roughness (10-point average surface roughness: RzJIS) of 2 μm or less.
In order to easily form such a smooth surface layer 53, the surface roughness (ten-point average surface roughness: RzJIS) of the elastic layer 52 is preferably 7 μm or less.
On the other hand, when the size of the graphite contained in the elastic layer 52 is excessively large, the surface roughness of the elastic layer 52 becomes rough, and the surface roughness of the surface layer 53 is adversely affected. There is a risk of giving.
Therefore, the graphite to be contained preferably has an average particle size of 8 μm or less, and more preferably 3 μm or more and 5 μm or less.
The term “average particle size” used for the size of graphite and the like is intended to be a D50 value measured by a particle size distribution analyzer using a laser diffraction scattering method.

The graphite may be either natural graphite or artificial graphite, but artificial graphite is preferable because it is easily available and the quality is more stable.
The carbon black contained in the elastic layer 52 together with the graphite is produced by pyrolyzing hydrocarbons such as furnace black and acetylene produced by a furnace method in which oil or gas is incompletely combusted in a high-temperature gas. In addition to acetylene black, channel black or the like can be employed.

  The content of graphite and carbon black in the elastic body layer 52 is not particularly limited, and can usually be contained so that the proportion of the polyurethane elastic body is 1 to 10% by mass, Preferably, it can be respectively contained so that it may become 1-5 mass%.

In this embodiment, the elastic layer 52 has a JIS-A hardness of 30 degrees or more and 60 degrees or less because the hardness of the elastic layer 52 is 30 degrees or more, such as the anilox roller 4. This is because it is possible to suppress the possibility that the time until the deformation received by contact with other members is restored will be prolonged, and it is easy to perform the work of adjusting the smoothness of the surface of the elastic layer such as cutting. is there.
Also, the elastic layer 52 has a JIS-A hardness of 30 degrees or more and 60 degrees or less because the elastic layer 52 has a hardness of 60 degrees or less so as to have good contact with the anilox roller 4. This is because it is easy to form the state, and the risk that the surface pattern of the anilox roller 4 appears in the image formed by the photoreceptor 1 can be more reliably suppressed.
That is, in this embodiment, the elastic layer 52 having a JIS-A hardness of 30 degrees or more and 60 degrees or less is formed on the transport roller 5 in order to improve the printing accuracy of the liquid developing electrophotographic apparatus.
In addition, this JIS-A hardness intends the type A durometer hardness (instantaneous value) prescribed | regulated to JISK6253 measured in the standard state.

In addition, the compression set of the elastic layer 52 is set to 2% or less because the elastic layer 52 exhibits a compression set of 2% or less, and the anilox roller 4 and the like. This is because the time until the deformation received by the contact with the member is restored can be made sufficiently short.
The compression set of the elastic body layer 52 can be confirmed by performing a test specified in JIS K 6262 on a test piece made of the same material as the elastic body layer 52.
Specifically, the compression set of the elastic layer 52 should be confirmed by performing a compression set test under the conditions of a compression strain (ratio of compressing the test piece) of 25%, a test temperature of 23 ° C., and a test time of 22 hours. Can do.

It is important that the surface layer 53 formed on the outer periphery of the elastic body layer 52 is formed to have a thickness of 1 μm or more and 20 μm or less by a cured product of the thermosetting resin composition, and 10 ° C. It is an important requirement that the storage elastic modulus in a temperature range of ˜50 ° C. is 1 × 10 ⁸ Pa or more and 1 × 10 ¹⁰ Pa or less.
Further, it is important that the surface layer 53 is formed of a cured product exhibiting a property that Tan δ in the temperature range is 0.2 or less.

  The material of the surface layer 53 is not particularly limited as long as it has the above characteristics, but in the present embodiment, the thermosetting polyurethane resin composition or the thermosetting is used. It is preferable to form with the hardened | cured material of a fluororesin composition.

As the thermosetting polyurethane resin composition for forming the surface layer 53, a composition containing an acrylic urethane resin or the like as a base resin can be employed.
In addition, as the thermosetting fluororesin composition, one containing a fluorocarbon having an unsaturated bond in the molecule as a base resin can be employed.

Incidentally, the storage modulus of the cured product of the thermosetting resin composition is 1 × ¹⁰ 8 Pa or more, 1 × ¹⁰ 10 that it is important that Pa or less is the storage modulus 1 × ¹⁰ 10 Pa This is because the conveyance roller 5 can be made excellent in followability with respect to the surface shape of the anilox roller 4 by making the following.
In addition, it is important that the storage elastic modulus of the cured product of the thermosetting resin composition is 1 × 10 ⁸ Pa or more, because the surface layer 53 can be excellent in resilience to deformation, and “Skimura” is used. This is because defects can be suppressed.

  In addition, it is important that the tan δ of the cured product is 0.2 or less. By forming the surface layer 53 with a cured product having a Tan δ of 0.2 or less, the surface layer 53 has excellent resilience to deformation. This is because it is possible to suppress defects due to “straight spot”.

Furthermore, it is important that the thickness of the surface layer 53 is 1 μm or more and 20 μm or less with such a cured product, and it is expected as a surface layer by forming a surface layer with a thickness of 1 μm or more. This is because it is easy to exercise the function.
Further, by setting the thickness of the surface layer 53 to 20 μm or less, it is easy to reflect the characteristics of the elastic layer 52 on the surface physical properties of the transport roller 5 and to easily suppress “pattern unevenness” in which the pattern of the anilox roller 4 appears on the printed matter. Because.

Note that the storage modulus and Tan δ value of the cured product can be confirmed by the following test method.
That is, using a dynamic viscoelasticity measuring device “Rheogel-E4000” manufactured by UBM Co., Ltd., measuring a tensile elastic modulus at a frequency of 10 Hz on a test piece having a thickness of 200 μm, a resulting complex elastic modulus The storage elastic modulus (E ′) and Tan δ (E ″ / E ′) can be obtained from the storage elastic modulus “E ′” which is the real part of the imaginary part and the loss elastic modulus “E ″” which is the imaginary part.

Further, in the present embodiment, it is preferable to impart electrical conductivity to the surface layer 53, and it is preferable to contain graphite and carbon black as in the elastic layer 52.
The surface layer 53 and the elastic layer 52 may be made of materials other than those for imparting electrical conductivity, such as additives used in general rubber molded products and resin molded products. An agent can be included.
As said additive, a pigment, an antistatic agent, etc. can be suitably contained in the formation material of the said surface layer in the range by which the effect of this invention is not impaired remarkably, for example.

  Moreover, as the said metal core 51, the thing which consists of metals, such as copper, iron, aluminum, nickel, and its alloy, and these, for example, generally plated by means, such as hot dipping, electrolytic plating, and electroless plating, were given to these What is used for a typical roller can be adopted.

As a method for producing such a transport roller 5, a generally used method for producing a polyurethane roller can be used.
More specifically, for example, after a polyurethane elastic body is provided around a core metal using a mold or the like, the surface of the polyurethane elastic body is polished and adjusted to a predetermined surface smoothness to thereby adjust the elastic body. A layer can be formed.
Further, the surface layer can be formed by adopting a method in which a surface layer forming thermosetting resin solution is directly applied to the surface of the elastic body layer by dip coating or the like and thermally cured. .
Further, if necessary, after the thermosetting, the outer peripheral surface of the surface layer may be polished to adjust the surface roughness.

In this embodiment, the transport roller as described above has been described as an example of the roller for the liquid developing electrophotographic apparatus. However, the use of the roller for the liquid developing electrophotographic apparatus of the present invention is limited to the transport roller. It is not something.
For example, in a liquid developing electrophotographic apparatus in which a developing roller is provided in such a manner that a transport roller or the like is not provided and is brought into contact with an anilox roller, the liquid developing electrophotography of the present invention is provided on the developing roller. An apparatus roller may be employed.
In addition, in order to quickly restore the deformation caused by contact with other members and prevent the occurrence of uneven stripes, rollers other than those used in contact with the anilix roller such as the developing roller and transport roller The same applies to the case where the roller for a liquid developing electrophotographic apparatus of the present invention is employed, and such a roller is also within the scope intended by the present invention.

  EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these.

<Manufacture of conductive roller>
The following roller was manufactured as a conductive elastomer member for an electrophotographic apparatus.

(Elastic layer)
The formation shown in Table 1 below was used for forming the elastic layer.

(Surface layer)
For the formation of the surface layer, the formulations shown in Table 2 below were used.
In addition, the composition which consists of other mixing | blendings (blending 1-4, 7) except the mixing | blending 5 and 6 among the following Table 2 is a thermosetting resin composition which shows thermosetting.

(Production of rollers)
A polyurethane elastic body was formed by the blend A in Table 1 so that the thickness of the core metal with a diameter of 24 mm was about 3.5 mm and the length in the axial direction was about 20 cm.
The surface of this polyurethane elastic body was polished to form an elastic layer having a thickness of 3 mm and a surface roughness (10-point average surface roughness: RzJIS) of 4 μm.
A surface layer was formed on the outer peripheral surface of the elastic layer by applying and drying (thermosetting) the coating liquid shown in Formulation 1-7, thereby producing an evaluation roller.

Separately from this, a sample for hardness measurement and a compression set sample were prepared by blending A, and the JISA hardness and compression set (compression strain 25%, temperature 23 ° C., time 22 hours) were measured. As a result, the following results were obtained.
JISA hardness: 50 degrees Compression set: 1.0%

Moreover, the sample for a viscoelasticity measurement was produced by the mixing | blending 1-7, and the storage elastic modulus (E ') and Tan (delta) were measured.
The evaluation results are shown in FIG.
In addition, specific numerical data at 25 ° C. and 50 ° C. among the evaluation results shown in FIG.
As shown in FIG. 3 and Table 3, the thermosetting resin composition of Formulation 1-4 has a storage elastic modulus of 1 × 10 ⁸ in a temperature range of 10 ° C. to 50 ° C. of the cured product. From Pa to 1 × 10 ¹⁰ Pa, it was confirmed that Tan δ in the temperature range of the cured product was 0.2 or less.
On the other hand, in blends 5 and 6, the storage elastic modulus near 50 ° C. was less than 1 × 10 ⁸ Pa, and in blend 7, Tan δ near 50 ° C. exceeded 0.2.

(Roller evaluation)
The following evaluation was performed about the obtained roller for evaluation.
(Electric resistance value)
A roller was set so that the elastic layer was in contact with the outer peripheral surface of the SUS (stainless steel) drum (φ30 mm) over the entire length, and a load of 500 gf was applied to both ends of the core metal toward the central axis of the SUS drum.
In this state, the SUS drum is rotated at a rotation speed of 30 rpm to rotate the roller together, and a resistance value of the elastic layer is calculated from a current value that flows by applying a DC voltage of 100 V between the metal core and the SUS drum. did. The results are shown in Table 3 below.

(Surface roughness)
In addition, Table 3 shows the results of measuring the surface roughness (ten-point average surface roughness: RzJIS) of the surface layer.

(Evaluation of restoring force: Investigation of residual contact deformation (see Fig. 4))
A metal roller having a diameter of 50 mm ("P" in FIG. 4) is supported so that the rotation axis is horizontal, and the rotation axis of the metal roller and the rotation axis of the evaluation roller are parallel to the horizontal direction. A production roller and an evaluation roller were arranged.
Then, the evaluation roller is moved closer to the metal roller, and the evaluation roller (“Q” in FIG. 4) is positioned at a position closer to the metal roller by 600 μm than the position where the evaluation roller and the metal roller are in contact with each other. did.
That is, the metal roller and the evaluation roller were positioned in a state where the evaluation roller was subjected to deformation of 600 μm in the rotation axis direction by the metal roller.
And after making it pass in this state for 15 hours, the roller for evaluation was rotated and the metal roller was made to rotate with rotation of this roller for evaluation.
Immediately after rotation with a laser displacement meter ("R" in FIG. 4) with a measurement spot applied to a position opposite to the contact position with this metal roller (position rotated 180 degrees) and after 60 seconds have elapsed. The amount of residual deformation was measured.
The results are shown in Table 3.

(Image evaluation)
An image obtained using an evaluation roller was evaluated at 23 ° C. and 50 ° C. using a simple type evaluation machine as schematically shown in FIG.
That is, the anilox roller is rotated by bringing the lower end portion of the anilox roller 4 ′ supported so that the rotation axis is horizontal into contact with the liquid surface of the liquid developer Y ′ accommodated in the toner tank X ′. Liquid developer can be pumped up.
Then, the evaluation roller 5 ′ was disposed above the anilox roller 4 ′, and the evaluation roller 5 ′ was disposed so that the lower end portion thereof was in contact with the upper end portion of the anilox roller 4 ′.

  This evaluation roller was installed so that the nip width was 3 mm with respect to the anilox roller.

Further, the developing roller 6 ′ was disposed above the evaluation roller 5 ′ and arranged so that the nip width with the evaluation roller 5 ′ was 2 mm.
In addition, a regulating blade 41 for regulating the liquid developer pumped up by the anilox roller 4 ′ was brought into contact with the anilox roller 4 ′ so that the excess liquid developer was not carried on the evaluation roller 5 ′.
Further, cleaning blades 51 ′ and 61 ′ were brought into contact with the evaluation roller 5 ′ and the developing roller 6 ′, respectively.

Then, after maintaining this state for 5 minutes and after maintaining for 15 hours, each roller is rotated, and after 60 seconds from the start of rotation, the rotation is stopped and the surface of the developing roller 6 ′ is mended. After the tape was affixed, it was peeled off, and the liquid developer carried on the surface of the developing roller 6 ′ was copied onto the mending tape side.
At this time, it was visually confirmed whether or not the unevenness of stripes and the helical pattern (pattern unevenness) of the anilox roller appearing in the liquid developer taken out due to the nip mark appeared.
A case where no unevenness or pattern unevenness was observed was judged as “◯”, a case where it was slightly observed was judged as “Δ”, and a case where it was observed as a whole was regarded as “x”.
In addition, this image evaluation was implemented on two kinds of temperature conditions, 23 degreeC conditions and 50 degreeC conditions.
The results are shown in Table 3.

  From the above, it can be seen that according to the present invention, a roller for a liquid developing electrophotographic apparatus useful for improving the image quality of the liquid developing electrophotographic apparatus is provided.

1: photoconductor, 2: intermediate transfer roller, 3: pressure roller, 4: anilox roller, 5: transport roller, 6: developing roller, 7: aggregation roller, 8: squeeze roller, 9: polishing roller, 10, 10 ': cleaning blade, A: substrate, X: toner tank, Y: liquid developer

Claims (6)

A roller for a liquid developing electrophotographic apparatus which is arranged in a liquid developing electrophotographic apparatus with an outer peripheral surface brought into contact with another member, and is used by rotating around an axis to carry and transport a liquid developer on the outer peripheral surface. There,
A surface layer that forms the outer peripheral surface, and an elastic layer in contact with the surface layer from the inside, and the elastic layer is formed of a polyurethane elastic body obtained by reacting a polyester polyol and a bifunctional isocyanate; The polyurethane elastic body has a JISA hardness of 30 degrees or more and 60 degrees or less and a compression set of 2% or less, and the surface layer is formed with a thickness of 1 μm or more and 20 μm or less by a cured product of the thermosetting resin composition. The storage elastic modulus of the cured product in a temperature range of 10 ° C. to 50 ° C. is 1 × 10 ⁸ Pa or more and 1 × 10 ¹⁰ Pa or less, and Tan δ in the temperature range of the cured product is 0.2 or less. A roller for a liquid developing electrophotographic apparatus, comprising:   The roller for a liquid developing electrophotographic apparatus according to claim 1, wherein the surface layer is formed of a thermosetting polyurethane resin composition or a cured product of a thermosetting fluororesin composition.   2. The liquid development electrophotographic apparatus according to claim 1, wherein the polyester polyol used for forming the elastic layer is a polyester polyol obtained by reacting a dicarboxylic acid, a bifunctional glycol, and a trifunctional or higher polyfunctional glycol. Roller for equipment.   The roller for a liquid developing electrophotographic apparatus according to claim 1, wherein the elastic layer contains graphite and carbon black.   The surface roughness (ten-point average surface roughness: RzJIS) of the elastic layer is 7 μm or less, and the surface roughness (ten-point average surface roughness: RzJIS) of the surface layer is 2 μm or less. Roller for liquid developing electrophotographic apparatus.   A developing roller for visualizing the electrostatic latent image with the liquid developer; and an anilox roller for pumping the liquid developer to be supplied to the developing roller from a toner tank in which the liquid developer is stored. 2. The liquid developing electrophotographic apparatus according to claim 1, wherein an outer peripheral surface is used in contact with both the developing roller and the anilox roller so as to convey the liquid developer from the anilox roller to the developing roller. Roller for liquid developing electrophotographic apparatus.

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