WO2012147402A1

WO2012147402A1 - Printing blanket and method for producing same

Info

Publication number: WO2012147402A1
Application number: PCT/JP2012/054409
Authority: WO
Inventors: 永見　晴資; 貴則岩崎
Original assignee: バンドー化学株式会社
Priority date: 2011-04-27
Filing date: 2012-02-23
Publication date: 2012-11-01
Also published as: JPWO2012147402A1

Abstract

This printing blanket of the invention has at least a three-layer structure composed of a first polyurethane elastic body layer, a canvas layer, and a second polyurethane elastic body layer. The tensile stress under 3% elongation in the direction that becomes the peripheral direction of the blanket cylinder is 100 MPa or greater. The first polyurethane elastic body layer and second polyurethane elastic body layer contain a conductivity-imparting agent, and the first polyurethane elastic body layer and second polyurethane elastic body layer are joined via openings between the threads of the canvas that forms the canvas layer.

Description

Blanket for printing and manufacturing method thereof

The present invention relates to a printing blanket and a manufacturing method thereof, and more particularly to a printing blanket including a polyurethane elastic body layer containing a conductivity imparting agent and a manufacturing method thereof.

2. Description of the Related Art Conventionally, in an offset printing machine or the like, a transfer mechanism for transferring ink to a printing material such as paper is constituted by a printing blanket and a blanket cylinder.
This printing blanket is required to exhibit desired characteristics not only in the thickness direction but also in the surface direction in order to exhibit excellent print quality. For example, printing blankets are required to have not only thickness characteristics such as surface hardness and compression strain but also surface characteristics such as tensile strength within a predetermined range.
For this reason, a canvas is adopted as a component of the printing blanket, and a polyurethane elastic body is laminated on one or both sides of the canvas to form a laminated structure of the canvas layer and the polyurethane elastic body layer on the printing blanket. In addition, a desired tensile strength is exhibited by the canvas layer and a desired characteristic is exhibited in the thickness direction by the polyurethane elastic layer.

Incidentally, in recent years, in electrophotographic apparatuses such as copying machines and laser printers, further improvement in printing quality has been demanded, and toner particles that have been refined to about 1 μm are contained in a liquid called a carrier. The use of dispersed liquid toner is being studied.
In such a liquid developing electrophotographic apparatus using a liquid toner, a method in which a printing blanket and a blanket cylinder are combined in addition to the photosensitive drum method used in the conventional dry developing method. The adoption of this transfer mechanism is being studied.

When a printing blanket is used for the transfer mechanism of the liquid developing electrophotographic apparatus, it has a predetermined conductivity in the thickness direction in order to use an electrical action for transferring the toner to the substrate. It will be required. On the other hand, it is not particularly required to impart conductivity in the thickness direction to a printing blanket used in conventional applications such as offset printing. For example, as shown in Patent Document 1 below, Adjustment of the surface resistivity for the purpose of countermeasures is being studied.
For this reason, there has been little research on a printing blanket having conductivity in the thickness direction.

Japanese Unexamined Patent Publication No. 2003-001964

In a liquid developing electrophotographic apparatus or the like, a printing blanket is required to have a volume resistivity in the range of 1 × 10 ⁴ Ω · cm to 1 × 10 ¹⁰ Ω · cm. If a canvas layer is formed in the same manner as in the printing blanket, no matter how many conductivity-imparting agents are contained and the electrical resistance value of the polyurethane elastic layer is lowered, the electrical resistance of the canvas layer causes the thickness direction. It becomes difficult to impart desired conductivity to the surface.

Conversely, if the blanket for printing is formed only with the polyurethane elastic layer without the canvas layer, the tensile strength may be insufficient.
That is, the conventional printing blanket has a problem that it is difficult to provide conductivity in the thickness direction which is required in a liquid developing electrophotographic apparatus or the like.
Such a problem is common to not only printing blankets used in liquid development electrophotographic apparatuses but also printing blankets that require conductivity in the thickness direction.

SUMMARY OF THE INVENTION An object of the present invention is to provide a printing blanket having predetermined mechanical characteristics and conductivity in the thickness direction, and thus used in a liquid developing electrophotographic apparatus. It is an object to provide a printing blanket suitable for the above.

The present invention related to a printing blanket for solving the above problems is a printing blanket used by being mounted on a blanket cylinder, the first polyurethane elastic layer, canvas layer from the blanket cylinder side to the outside, The first polyurethane elastic body has at least a three-layer structure in order of the second polyurethane elastic body layer, and the first polyurethane elastic body layer and the second polyurethane elastic body layer contain a conductivity-imparting agent. Layer and the second polyurethane elastic body layer are connected through an opening between the yarns of the canvas constituting the canvas layer, and the tensile stress at 3% elongation in the circumferential direction of the blanket cylinder is 100 MPa. As described above, the volume resistivity is 1 × 10 ⁴ Ω · cm or more and 1 × 10 ¹⁰ Ω · cm or less.

The “tensile stress at 3% elongation” in the present invention intends a value obtained by conducting a tensile test based on JIS K6251. That is, the tensile stress is obtained by taking a dumbbell-shaped test piece from the printing blanket so that the circumferential direction of the blanket cylinder is the longitudinal direction, performing a tensile test on the dumbbell-shaped test piece, and then extending. A value obtained by dividing the load at the time when 3% reaches the sample cross-sectional area is intended.

Further, the “volume resistivity” of the printing blanket is intended to be a value measured at a DC voltage of 250 V based on JIS K 6911.
In addition, when the volume resistivity based on JIS K 6911 is measured on a sheet sample or the like formed of different materials on the front and back sides, the measured value is more than can be determined as an error depending on which side is the positive side. May be different. In this specification, “volume resistivity is 1 × 10 ⁴ Ω · cm or more and 1 × 10 ¹⁰ Ω · cm or less” means that the inner surface in contact with the blanket cylinder is the positive electrode side and the outer surface in contact with the substrate is the negative electrode side. It is intended that both the measured value and the value measured by reversing these are within the above range.

In order to solve the above problems, the present invention provides a polyurethane raw material liquid containing a polyol, a polyisocyanate, and a conductivity-imparting agent, and immersing a canvas having openings between yarns on both sides of the canvas. A first polyurethane elastic body layer and a second polyurethane elastic layer which are made to impregnate the canvas with the polyurethane raw material liquid and harden the polyurethane raw material liquid and are connected to both sides of the canvas layer made of the canvas through the openings. A printing blanket manufacturing method is provided, wherein a printing blanket as described above is manufactured by forming a body layer.

In the present invention, since the first polyurethane elastic layer and the second polyurethane elastic layer are provided inside and outside the canvas layer, desired mechanical properties are imparted to the printing blanket in the thickness direction and the plane direction. Yes.
In addition, the conductivity imparting agent is contained in both of these polyurethane elastic layers, and the first polyurethane elastic layer and the second polyurethane elastic layer are connected through the opening between the yarns of the canvas. It is possible to suppress the current flowing in the thickness direction of these polyurethane elastic layers from being blocked by the canvas.
That is, according to the present invention, a printing blanket having predetermined mechanical characteristics and conductivity in the thickness direction is provided. For example, for printing suitable for use in a liquid developing electrophotographic apparatus. A blanket may be provided.

1 is a schematic sectional view showing a sectional structure of a printing blanket according to an embodiment.

Hereinafter, the case where the printing blanket according to the present invention is used in a liquid developing electrophotographic apparatus will be specifically described as a main example.

The printing blanket according to the present embodiment has a laminated structure as shown in FIG. 1, and the innermost layer in contact with the blanket cylinder (not shown) is constituted by the polyurethane elastic body layer 11.
The printing blanket according to the present embodiment is the outermost layer in addition to the three-layer structure in which the polyurethane elastic body layer 11, the canvas layer 12, and the polyurethane elastic body layer 13 are arranged in this order from the blanket cylinder side to the outside. It has a four-layer structure having the resin coating layer 14.
The polyurethane elastic layer 11 (hereinafter also referred to as “first polyurethane elastic layer 11”) serving as the innermost layer and the polyurethane elastic layer 13 (hereinafter referred to as “second polyurethane elastic layer 13”) outside the canvas layer 12 are used. Is connected through an opening between the yarns of the canvas forming the canvas layer 12.

The printing blanket 1 according to the present embodiment has the laminated structure as described above, and is mainly formed of the first polyurethane elastic body layer 11 and the second polyurethane elastic body layer 13 in the thickness direction such as compression elastic modulus and hardness. The mechanical characteristics are adjusted to a desired value.
In the printing blanket 1 according to the present embodiment, the mechanical properties in the plane direction such as tensile strength and elongation are mainly adjusted by the canvas layer 12, and 3 in the direction that is the circumferential direction of the blanket cylinder. It is formed so that the tensile stress at% elongation is 100 MPa or more.
Furthermore, the first polyurethane elastic layer 11 and the second polyurethane elastic layer 13 are connected to the printing blanket 1 of the present embodiment by forming the canvas layer 12 with a canvas having a predetermined opening. Moreover, by adding a conductivity-imparting agent to these polyurethane elastic body layers, predetermined conductivity in the thickness direction is imparted, and specifically, the volume resistivity is 1 × 10 ⁴ Ω · cm or more, It is formed to be 1 × 10 ¹⁰ Ω · cm or less.

In order to provide the printing blanket 1 with the characteristics as described above, in this embodiment, a canvas having a gap portion between yarns is used instead of a general canvas in which warps and wefts are closely plain-woven. The canvas used in the present embodiment is woven so that warps and wefts are provided at a predetermined interval, and the canvas is opened to a predetermined size between the yarns. A gap is provided.

In the conventional printing blanket, a canvas woven so that the yarns are in close contact with each other is used, but in this embodiment, conductivity in the thickness direction is imparted to the printing blanket. Therefore, it is an important requirement to use a canvas having an opening in this way.
That is, since canvas is usually formed using yarns made of synthetic fibers or natural fibers, it does not have conductivity, and the yarns are in a tight state like conventional printing blankets. If the canvas elastic layer is made to contain a large amount of conductivity imparting agent and its electrical resistance value is lowered, the canvas layer becomes a barrier and imparts desired conductivity in the thickness direction. Becomes difficult.

In the printing blanket 1 according to the present embodiment, the canvas layer 12 is formed using a canvas having an opening, and the first polyurethane elastic body layer 11 and the second polyurethane elastic body layer 13 are connected through the opening. Thus, an electric flow path through the opening is formed in the thickness direction so that the volume resistivity of the printing blanket 1 is 1 × 10 ⁴ Ω · cm or more and 1 × 10 ¹⁰ Ω · cm or less. Is formed.
The canvas layer 12 can be formed by overlapping one or more canvases having openings.

A wider opening is advantageous in securing the conductivity of the printing blanket 1, but if an excessively wide opening is formed in the canvas, it becomes difficult to exert a sufficient tensile strength on the printing blanket 1. .
For this reason, the canvas layer 12 is preferably formed of a canvas having an opening size of 0.1 mm square or more, and may be formed of a canvas having an opening size of 0.1 mm square or more and 4 mm square or less. preferable.
Further, the area ratio (opening ratio) of the opening in the entire canvas is preferably 5% or more and 70% or less, and more preferably 10% or more and 30% or less.

In selecting a canvas, what kind of opening is formed and what area ratio may be confirmed by a dimension measuring instrument such as a video microscope or a magnifying projector.

As the canvas, natural fibers such as cotton and hemp, synthetic fibers such as polyester, polyamide, polyetheretherketone, and those made of semi-synthetic fibers such as acetate can be adopted, twisted yarns made of such fibers, Spun yarn and flat yarn can be used for warp and weft.
However, in the present embodiment, as described above, a predetermined opening in the canvas is required to cause the printing blanket 1 to exert a tensile stress of 100 MPa or more while forming a gap between the yarns in order to prevent this. In addition, it is preferable that the canvas is formed of a thread having excellent strength, and a canvas formed of a thread made of aromatic polyamide (aramid) fiber is preferably used for forming the canvas layer 12.

Note that both the warp and the weft of the canvas may be formed of aramid fibers, or only one of them may be formed of aramid fibers.
However, when only one of the warp and the weft is an aramid yarn such as an aramid twisted yarn, an aramid spun yarn, an aramid yarn, the aramid yarn is used so that at least this aramid yarn is effectively used for the tensile strength of the printing blanket. Preferably, the canvas layer is formed by adjusting the direction of the canvas so as to extend in the circumferential direction of the blanket cylinder.

As such a preferred canvas, for example, a spun yarn made of para-aramid fiber, which is a polymer of p-phenylenediamine and terephthalic acid chloride, or a twisted yarn having a thickness of 180 dTex to 350 dTex and warp and weft The canvas adopted in any of the above can be mentioned.
The canvas forming the canvas layer 12 is subjected to surface treatment on warps and wefts for the purpose of improving the adhesion between the first polyurethane elastic layer 11 and the second polyurethane elastic layer 13. Also good.

The first polyurethane elastic body layer 11 in contact with the canvas layer 12 from the inside and the second polyurethane elastic body layer 13 in contact with the canvas layer 12 from the outside are mechanical characteristics in the thickness direction of the printing blanket 1 as described above. It has a big influence on. Therefore, it is preferable that both polyurethane elastic body layers are adjusted to a predetermined hardness in that the printing blanket 1 of the present embodiment can exhibit excellent printability, the first polyurethane elastic body layer 11, The second polyurethane elastic body layer 13 preferably has a JIS-A hardness of not less than 30 degrees and not more than 60 degrees.

In the printing blanket 1 of the present embodiment, since the innermost layer for contacting the blanket cylinder is constituted by the first polyurethane elastic body layer 11, the first polyurethane elastic body layer 11, the blanket cylinder, From the viewpoint of adhesion, the surface roughness of the first polyurethane elastic layer 11 is preferably 20 μm or less in terms of the 10-point average roughness (Rz) defined in JIS B0601.

The first polyurethane elastic layer 11 is usually formed with a uniform thickness, and the printing blanket 1 of the present embodiment is thinner than the second polyurethane elastic layer 13. .
The second polyurethane elastic body layer 13 and the resin coating layer 14 are also usually formed so that their thicknesses are uniform.

The printing blanket 1 according to the present embodiment usually has a total thickness of 0.3 mm to 5.0 mm when used in a liquid developing electrophotographic apparatus, depending on the application.
Of these, the first polyurethane elastic body layer 11 is usually 20 μm to 1.0 mm in thickness, and the second polyurethane elastic body layer 13 is usually 200 μm to 4.9 mm in thickness.
The canvas layer 12 is usually set to a thickness of 100 μm to 1.0 mm, and the resin coating layer 14 is usually set to a thickness of 5 μm to 60 μm.

In the printing blanket 1 according to the present embodiment, the raw materials used for forming the first polyurethane elastic layer 11 and the second polyurethane elastic layer 13 may be made common or different.
The polyurethane for forming these polyurethane elastic body layers may be a thermosetting polyurethane or a thermoplastic polyurethane, but the physical properties can be easily adjusted, and a conductivity-imparting agent. Thermosetting polyurethane is preferable in that it can be easily dispersed.

The polyol constituting the thermosetting polyurethane is not particularly limited, and examples thereof include polyester polyols, polyolefin polyols, polyether polyols, polycarbonate polyols, polyacrylic polyols, and polyether ester polyols.
These polyols can be used singly or in combination of two or more.

The hydroxyl value (OHV) of the polyol is not particularly limited, but is preferably 50 to 160 in that a cured product having an appropriate hardness can be formed.
In addition, the said hydroxyl value is a value calculated | required by the method according to JISK0070.

The average number of functional groups of the polyol is not particularly limited, but is preferably 2 to 3 in that a polyurethane having an appropriate hardness can be formed.
In addition, the said average functional group number means the theoretical functional group number determined by the number of active hydrogen groups of the initiator molecule | numerator used for manufacture of a polyol.
However, the actual number of functional groups may be different due to the influence of side reactions during polymerization.

Examples of the polyester polyol include compounds having 2 or more ester bonds and 2 or more hydroxyl groups in the molecule.
Specifically, for example, ethylene glycol, diethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, cyclohexanedimethanol, glycerin, 1,1,1-trimethylolpropane, and one or two other low molecular polyols A condensation polymer of at least one species with one or more of glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, terephthalic acid, isophthalic acid, dimer acid, other low molecular carboxylic acid and oligomeric acid, Alternatively, ring-opening polymers such as propionlactone, valerolactone, and caprolactone can be used.

Examples of the polyolefin-based polyol include compounds having 4 or more olefins and 2 or more hydroxyl groups in the molecule.
Specifically, for example, after polymerizing a diene compound such as butadiene and isoprene and optionally styrene and acrylonitrile in the presence of an anionic polymerization catalyst such as metal lithium, metal potassium and metal sodium, ethylene oxide, A polyol obtained by addition polymerization of alkylene oxide such as propylene oxide, or a polyol obtained by radical polymerization of the diene compound with a radical initiator having a hydroxyl group such as hydrogen peroxide, or hydrogenating these And the like.

Examples of the polyether polyol include compounds having two or more ether bonds and two or more hydroxyl groups in the molecule.
Specifically, for example, ethylene oxide, propylene oxide, propylene oxide, butylene oxide, or an alkylene oxide such as a mixture thereof in ethylene glycol, diethylene glycol, propylene glycol, glycerin, trimethylolpropane, or the like in the presence of an alkali catalyst or the like. Examples include polyalkylene polyols obtained by addition polymerization, polytetramethylene glycol obtained by polymerizing tetrahydrofuran under a cationic catalyst, or a mixture thereof.

Examples of the polycarbonate polyol include 1,6-hexanediol polycarbonate polyol, 1,6-hexanediol and 1,4-butanediol polycarbonate polyol, 1,6-hexanediol and 1,5-pentanediol. Examples thereof include polycarbonate polyol, polycarbonate polyol of 1,6-hexanediol and 3-methyl-1,5-pentanediol.

Examples of the polyacrylic polyol include a polymer compound obtained by polymerizing an acrylic acid derivative monomer, or a polymer compound obtained by copolymerizing an acrylic acid derivative monomer and other monomers, with a hydroxyl group at the terminal. What you have.
Among them, those obtained by polymerizing acrylic acid derivative monomers such as ethyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and hydroxybutyl methacrylate alone, and acrylic polyols copolymerized by adding other monomers such as styrene are preferably used. .

Examples of the polyether ester-based polyol include compounds having two or more ether bonds, two or more ester bonds, and two or more hydroxyl groups in the molecule.
Specifically, for example, one or more of glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, terephthalic acid, isophthalic acid, dimer acid, other low molecular carboxylic acid and oligomeric acid, and ethylene Glycol, diethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, cyclohexanedimethanol, glycerin, 1,1,1-trimethylolpropane, and other low molecular polyols, one or more conventionally known methods And those obtained by polycondensation with.
Specifically, for example, a polycondensate of adipic acid, diethylene glycol, and trimethylolpropane can be used.

The polyether ester polyol preferably has a hydroxyl value (OHV) of 50 to 160 and an average number of functional groups of 2 to 3 in that a polyurethane elastic layer having an appropriate hardness can be formed. .
Specifically, the polyether ester-based polyol has a hydroxyl value (OHV) of 57 to 64 and the average number of functional groups of 2 to 3, and a hydroxyl value (OHV) of 150. It is more preferable to mix with a polyetherester polyol having an average functional group number of 2 to 3 and use it for forming the polyurethane elastic layer.
The polyether ester polyol having a hydroxyl value (OHV) of 150 to 160 and an average functional group number of 2 to 3 is a polyether having a hydroxyl value (OHV) of 57 to 64 and an average functional group number of 2 to 3. It has a function of reducing the viscosity of the mixture with the ester-based polyol, and can be expected to improve workability when forming the polyurethane elastic body layer.
More specifically, the polyetherester polyol is preferably a polycondensate of adipic acid, diethylene glycol, and trimethylolpropane.

In the polyether ester polyol mixture, the polyether ester polyol having a hydroxyl value (OHV) of 150 to 160 and an average number of functional groups of 2 to 3 is 10 to 30% by mass in the polyol. It is preferably included.
The liquid developing electrophotographic apparatus includes 10 to 30% by mass of the polyether ester-based polyol having a hydroxyl value (OHV) of 150 to 160 and an average functional group number of 2 to 3 in the total polyol. The polyurethane elastic body layer can be provided with an appropriate hardness required for a printing blanket for printing.

The polyisocyanate for forming a polyurethane together with such a polyol is not particularly limited. Specifically, for example, 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diene is used. Isocyanate (2,6-TDI), 4,4'-diphenylmethane diisocyanate (4,4'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), 1,4-phenylene diisocyanate, polymethylene Aromatic polyisocyanates such as polyphenylene polyisocyanate, tolidine diisocyanate (TODI), 1,5-naphthalene diisocyanate (NDI), hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMHDI), lysine diisocyanate , Norbornene diisocyanate methyl (NBDI), xylylene diisocyanate (XDI), tetramethyl xylylene diisocyanate (TMXDI) and other aliphatic polyisocyanates, transcyclohexane-1,4-diisocyanate, isophorone diisocyanate (IPDI), H6XDI ( Examples thereof include alicyclic polyisocyanates such as hydrogenated XDI) and H12MDI (hydrogenated MDI), carbodiimide-modified polyisocyanates of the above polyisocyanates, or isocyanurate-modified polyisocyanates.
These polyisocyanates are used singly or in combination of two or more, preferably a mixture of 2,4-TDI and 2,6-TDI (2,4-TDI / 2 , 6-TDI = 80/20 mass ratio) can be used.

In addition, regarding the combination of the above polyol and polyisocyanate, when the printing blanket 1 according to this embodiment is used in a liquid development electrophotographic apparatus, the liquid toner directly contacts the surface of the resin coating layer 14. Therefore, at least the second polyurethane elastic body layer 13 inside the resin coating layer 14 preferably exhibits excellent resistance to liquid paraffin, silicon oil, mineral oil, vegetable oil and the like used as a carrier for toner particles. .
That is, when the thickness of the second polyurethane elastic layer 13 is changed by swelling by the carrier, or the compression elastic modulus or the like is changed, the print quality may be deteriorated, so that excellent print quality can be maintained. It is preferable that carrier resistance is imparted to at least the second polyurethane elastic layer 13.
In order to exhibit such carrier resistance, it is preferable to form the second polyurethane elastic body layer 13 with polyurethane by a combination of polyester polyol and difunctional isocyanate.

Examples of the conductivity-imparting agent to be contained in the polyurethane elastic layer include inorganic particles such as carbon black, graphite, and metal particles, organic particles such as metal-coated resin particles and conductive polymer particles, carbon fibers, metal fibers, Examples thereof include inorganic fibers such as metal-coated glass fibers, and organic fibers such as metal-coated resin fibers and conductive polymer fibers.
Among these, as the conductivity imparting agent, carbon black and graphite are preferable, and in particular, both of the first polyurethane elastic body layer 11 and the second polyurethane elastic body layer 13 contain them. It is preferable.

Carbon black usually has a size of 1 μm or less (several tens of nm), whereas the graphite usually has a size exceeding 1 μm, and the particle size is larger than that of carbon black. Is larger than 1 order and has a crystal structure developed compared to 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, since the expression of conductivity due to carbon black is greatly affected by the formation of the structure, for example, when conductivity is imparted to the polyurethane elastic layer with only carbon black, the content of carbon black It is difficult to recognize the interrelation between the electric characteristics and the electric characteristics, and the electric characteristics may be suddenly changed at a certain content.
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 the polyurethane elastic body layer in which only carbon black is employed as a conductivity imparting agent, a change occurs in the tunnel effect in the structure of carbon black formed therein, and Such a change may occur in a short period.
That is, if the conductivity imparting agent for the polyurethane elastic layer is only carbon black, the electrical characteristics of the printing blanket may be changed immediately. On the other hand, the combined use of graphite makes it difficult to be affected by such effects, and it is possible to make it difficult to change the electrical characteristics even when continuous power application is performed.

Examples of the carbon black include furnace black produced by a furnace method in which oil and gas are incompletely burned in a high-temperature gas, acetylene black produced by thermally decomposing hydrocarbons such as acetylene, and channel black. Can be adopted.
When the furnace black is employed as a conductivity imparting agent, for example, carbon blacks such as FEF, ISAF, and HAF that are classified by general names can be employed.

The carbon black, although not particularly limited DBP oil absorption is preferably 65 ^~ 168cm 3 / 100g.
By DBP oil absorption of the carbon black is 65cm ^3/100 g or more, it is ongoing voltage application to the printing blanket 1 according to the present embodiment first, second

polyurethane elastomer layer

11 and 13 There is an advantage that less likely to alter the electrical resistance value, by DBP oil absorption amount is less 168cm ^3/100 g, has the advantage of capable of facilitating the formation of the polyurethane elastomer layer.

The DBP oil absorption amount is obtained by substituting the void volume in carbon black having a constant mass with a liquid and using the capacity as an index.
Specifically, it refers to the amount of oil (cm ³ ) contained per 100 g of carbon black, and is a value measured by a method based on ASTM D3493-85a.
The DBP oil absorption can be an index representing the three-dimensional state of the aggregate of primary particles of the carbon black.
That is, it is considered that carbon black tends to form a chain-like aggregate (structure) when the DBP oil absorption amount is large. Therefore, the one where the DBP oil absorption amount is larger can exhibit conductivity with a smaller content, and can further suppress the change in the electric resistance value due to continuous voltage application.

On the other hand, the graphite preferably has an average particle size of 8 μm or less, and preferably has an average particle size of 3 to 5 μm.

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 particle size of carbon black is usually determined by direct observation with an electron microscope and is represented by an arithmetic average value of measured values obtained by measuring the size of a plurality of particles.

The polyurethane elastic body layer preferably contains carbon black in any proportion within the range of 1% by mass to 4% by mass, and graphite is preferably within the range of 3% by mass to 6% by mass. It is preferable to make it contain in either ratio.
It is preferable that the carbon black is included in the amount of 1 to 4% by mass. By adding 1% by mass or more of the carbon black to the polyurethane elastic layer, the polyurethane elastic layer is imparted with appropriate conductivity. It is because it can do.
Moreover, since the carbon black also functions as a reinforcing material, an appropriate hardness can be imparted to the polyurethane elastic layer by containing 1% by mass or more in the polyurethane elastic layer.
That is, it is preferable that the first polyurethane elastic layer 11 and the second polyurethane elastic layer 13 both have a JIS-A hardness of 30 degrees to 60 degrees, By containing 1% by mass or more of carbon black, these can exhibit excellent conductivity, and these can be made preferable hardness as described above.

In addition, it is preferable that the carbon black content is 4% by mass or less. Even if carbon black is excessively contained, not only the polyurethane elastic layer can exhibit more conductivity than necessary, but also the polyurethane elastic layer. This is because there is a possibility that dispersion in the inside becomes non-uniform, and there is a possibility that an aggregate due to carbon black is contained.

It is preferable that the content of the graphite is 3% by mass or more and 6% by mass or less because when the graphite is contained in the polyurethane elastic body layer by 3% by mass or more, the graphite blanket 1 is continuous. Even if electricity is applied, the electric resistance value can be made more difficult to change, and by setting the content to 6% by mass or less, there is an advantage that the hardness of the polyurethane elastic body layer can be adjusted more appropriately. It is.

In the printing blanket 1 of the present embodiment, the resin coating layer 14 provided so as to cover the surface of the second polyurethane elastic body layer 13 may be formed of a resin composition containing a conductivity-imparting agent. it can. In addition, since it is preferable to give the resin coating layer 14 carrier resistance similarly to the second polyurethane elastic body layer 13, for example, the resin coating layer 14 is formed of a polyester-based thermoplastic polyurethane or the like. It is preferable to make it.

As the conductivity-imparting agent contained in the resin coating layer 14, the same conductivity-imparting agent as exemplified with respect to the material for forming the polyurethane elastic layer can be employed.
However, since the resin coating layer 14 has unevenness on the surface or has a possibility of affecting the printing quality if the electric characteristics are locally different, the surface is smooth and has a fine conductivity. It is preferable that the imparting agent is uniformly dispersed.
More specifically, the resin coating layer 14 is preferably formed such that the surface roughness is 7 μm or less in terms of the 10-point average roughness (Rz) defined in JIS B0601. For this purpose, the resin coating layer 14 does not contain a material having a large particle size such as graphite as the conductivity-imparting agent, and the conductivity-imparting agent contained in the resin coating layer 14 is substantially only carbon black. It is preferable.
In addition, from the above, carbon black contained in the resin coating layer 14 has a smaller particle diameter than that used for forming the polyurethane elastic body layer, and has a high DBP oil absorption, which is advantageous for structure formation. Black is preferred.
Specifically, we are preferable that the particle size is 60nm or less, DBP oil ^absorption, 160cm 3/100 g or ^more, is preferably not more than 190 cm 3/100 g.
In addition, it is preferable that content of carbon black in the resin coating layer 14 is set to any ratio within the range of more than 0 mass% and 50 mass% or less.

Since the printing blanket 1 according to this embodiment has the canvas layer 12 formed of the canvas having an opening as described above, the first polyurethane elastic layer 11 and the second polyurethane elastic layer 13 are formed as described above. And the resin coating layer 14 can be made excellent in electroconductivity. And by this, desired electroconductivity can be provided with respect to the printing blanket 1, and the printing blanket can have the volume resistivity calculated | required in this kind of application. Specifically, the printing blanket can have a volume resistivity of 1 × 10 ⁴ Ω · cm to 1 × 10 ¹⁰ Ω · cm.

In addition, such a volume resistivity is required for the printing blanket because it exhibits a high volume resistivity exceeding the above range. If the thickness is not reduced, a desired conductivity is provided in the thickness direction. This is because it cannot be demonstrated.
That is, the thickness is limited and it is difficult to adjust the mechanical properties in the thickness direction such as the compression modulus within a suitable range.
Further, if it is intended to obtain a material having a low volume resistivity less than the above range, there is a possibility that a large amount of a conductivity imparting agent must be contained, and as a result, the first polyurethane elastic layer 11 and the second This is because it becomes difficult to impart desired elasticity to the polyurethane elastic layer 13.

The printing blanket according to the present embodiment is preferably formed of thermosetting polyurethane in adjusting the physical properties of the first polyurethane elastic layer 11 and the second polyurethane elastic layer 13 as described above. However, if an attempt is made to contain a large amount of carbon black or graphite in these, a large amount of a conductivity imparting agent such as carbon black or graphite is contained in the polyurethane in a liquid state before thermosetting.
If it does so, the viscosity of the polyurethane raw material liquid used for formation of the 1st polyurethane elastic body layer 11 or the 2nd polyurethane elastic body layer 13 will become high, and it will become difficult to employ | adopt general shaping | molding methods, such as cast molding.
That is, by defining the volume resistivity of the printing blanket as described above, the printing blanket can be manufactured by a simple manufacturing method such as cast molding.

Next, a method for manufacturing the printing blanket 1 will be described.
The printing blanket 1 of the present embodiment can be manufactured by cast molding as described above. For example, a raw material liquid adjusting step for adjusting a polyurethane raw material liquid containing a polyisocyanate, a polyol, and a conductivity-imparting agent, An impregnation step of immersing a canvas for forming the canvas layer 12 in the polyurethane raw material liquid so that the polyurethane raw material liquid is present in a predetermined thickness on both sides of the canvas and impregnating the canvas with the polyurethane raw material liquid; And a canvas layer formed by using a canvas having an opening between yarns as the canvas, which can be prepared by performing a curing process for curing the polyurethane raw material liquid in which the canvas is immersed. Forming a first polyurethane elastic layer and a second polyurethane elastic layer connected to each other through the opening. Rukoto can.

The raw material liquid adjusting step is carried out, for example, by dispersing a conductivity-imparting agent such as carbon black or graphite in a polyester polyol, vacuum degassing, and further mixing a bifunctional polyisocyanate with the polyester polyol. be able to.
Dispersion of the conductivity-imparting agent in the polyester polyol can be carried out using a general stirring device such as a homogenizer.

The impregnation step can be carried out using a mold having an outer mold and an inner mold that can be combined to form a cylindrical cavity.
For example, a cylindrical or columnar inner mold and an inner peripheral surface having a diameter larger than the outer periphery of the inner mold, the inner mold is accommodated in the inner space, and the cavity is interposed between the inner mold and the inner mold. A mold having an outer mold capable of forming a tee can be mentioned.
Since the impregnation step is preferably performed under reduced pressure, a mold that can make the cavity into a sealed space and make the cavity into a reduced pressure state by evacuation or the like is used. Is preferred.

The impregnation step will be described in more detail. In the impregnation step, for example, the canvas is wound around the outer periphery of the inner mold to be accommodated in the outer mold, and the canvas is held in a cylindrical shape in the cavity. It can be carried out by injecting the polyurethane raw material liquid into a state in which the inside of the cavity is evacuated and decompressed.

As a result, the canvas is immersed in the polyurethane raw material liquid in the cavity, and the polyurethane raw material liquid can be present at a predetermined thickness on both sides of the canvas.
In addition, after the inside of the cavity is sufficiently decompressed by evacuation, in order to inject the polyurethane raw material liquid into the cavity, the polyurethane raw material liquid is impregnated from the outside to the inside of the canvas so that the inside of the canvas The polyurethane raw material liquid can be made to wrap around, and bubbles can be prevented from being mixed into the canvas layer formed by the canvas and the polyurethane elastic body layer formed by the polyurethane raw material liquid present on both surfaces of the canvas.

If necessary, short cylindrical spacers whose inner diameter is slightly larger than the inner mold and whose outer diameter is equal to or less than the inner circumference of the outer mold are attached to both ends of the inner mold in the longitudinal direction. By wrapping the canvas around the outer periphery of the spacer, inside the spacer, the canvas can be separated from the surface of the inner mold by the thickness of the spacer so that the canvas is wound around the inner mold. The thickness of the polyurethane raw material liquid existing inside the canvas can be adjusted by the spacer.
That is, an inner portion of the canvas is a portion that becomes the first polyurethane elastic body layer 11, and the thickness of the first polyurethane elastic body layer 11 formed by using the spacer can be adjusted.

In addition, after this impregnation process, the said polyurethane raw material liquid can be heated with this metal mold | die, this polyurethane raw material liquid can be hardened in the said cavity, and the said hardening process can be implemented.
The temperature and time in the curing step may be appropriately adjusted depending on the content of the polyurethane raw material liquid to be used. For example, when the polyurethane raw material liquid is semi-cured to such an extent that it can be demolded, the semi-cured product is removed from the mold. Then, it may be post-cured (aftercured) in a heating furnace.

Thus, since the three-layer structure of the polyurethane elastic body layer / the canvas layer / the polyurethane elastic body layer is formed from the inside to the outside in the obtained cylindrical molded product, the resin prepared separately The printing blanket 1 of this embodiment can be provided by providing the resin coating layer 14 by applying a solution to the outer peripheral surface of the molded product and drying the solution.
If necessary, the surface smoothness of the resin coating layer may be improved by polishing the outer surface of the molded product before applying the resin solution.

In such a printing blanket manufacturing method, since the surface state of the inner mold is reflected in the surface state of the first polyurethane elastic body layer 11, the inner mold having a predetermined surface roughness is used. Is preferred.
That is, the printing blanket according to the present embodiment is formed so that the surface of the first polyurethane elastic layer 11 has a 10-point average roughness (Rz) specified in JIS B0601 of 20 μm or less as described above. Therefore, it is preferable to use an inner mold having a surface roughness (10-point average roughness) of 20 μm or less as the inner mold.

In particular, in the present embodiment, since the first polyurethane elastic body layer 11 is formed by the polyurethane raw material liquid impregnated from the outside through the canvas, the above-described inner mold is used, and thus the above-described after the curing step. In order to obtain a suitable printing blanket, it is possible to greatly reduce the necessity of adjusting the surface roughness of the first polyurethane elastic body layer 11 by performing a polishing process.

In the printing blanket obtained by such a manufacturing method, since the first polyurethane elastic layer and the second polyurethane elastic layer are connected through the opening between the yarns of the canvas, these polyurethane elastic layers are arranged in the thickness direction. It can suppress that the electric current which flows is interrupted | blocked by the canvas layer, and shows favorable electroconductivity in the thickness direction.
Moreover, the printing blanket obtained by such a production method is based on a carrier even when used in a liquid development electrophotographic apparatus because a polyester polyol and a bifunctional polyisocyanate are used for forming a polyurethane elastic layer. The characteristic change can be suppressed.

Note that the matters not specifically described above can be employed within the range that does not significantly impair the effects of the present invention with respect to known matters in the conventional printing blanket and its manufacturing method. The printing blanket of the invention and the manufacturing method thereof are not limited to the above examples.

Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples.

(Polyurethane elastic layer)
For the formation of the polyurethane elastic layer, a polyurethane raw material liquid consisting of “Formulation 1” in Table 1 below was used.

(Canvas)
For the formation of the canvas layer, three types of canvas shown in Table 2 below were used.

(Resin coating layer)
For the formation of the resin coating layer, a resin solution having a carbon black content of about 16.7% by mass as shown in Table 3 below was used.

(Production of blanket for printing)
A blanket for printing has an inner mold having an outer diameter of 565 mm and a length of 400 mm, and an outer mold having an inner diameter of 584 mm and a length of 560 mm, and is sealed when the inner mold and the outer mold are combined. A mold capable of forming a cylindrical cavity was used.
Specifically, first, a canvas is wound around the inner mold so that the warp is in the circumferential direction, and the inner mold is accommodated in the outer mold, and the inside of the cavity is decompressed to 1300 Pa. The polyurethane raw material liquid produced based on this was poured into the cavity, and the canvas was immersed in the polyurethane raw material liquid.
In this state, thermosetting at 150 ° C. × 60 min is performed, after-molding is performed at 120 ° C. × 120 min after demolding, and the three-layer structure of the first polyurethane elastic layer / the canvas layer / the second polyurethane elastic layer from the inside A cylindrical molded article having
The outer surface is polished until the total thickness of the molded product is 2 mm, the resin solution having the composition shown in Table 3 is applied and dried on the outer surface, and the resin coating layer that is the outermost layer has a thickness of 30 μm. A blanket for printing was produced.

(Evaluation)
A 10 mm-thick test piece was prepared using a polyurethane raw material liquid having the same composition as that used in the production of the printing blanket, and the JIS-A hardness of the test piece was measured using a type A durometer hardness meter. .
In addition, a dumbbell-shaped test piece (JIS No. 3 dumbbell) was sampled so that the circumferential direction (warp direction) of the printing blanket was the length direction, and a tensile test was conducted according to JIS K6251. Tensile stress at 1% elongation And tensile stress at 3% elongation.
Furthermore, volume resistivity and surface resistivity were measured at 250 VDC using a resistivity meter “HIRESTA UP” manufactured by Mitsubishi Chemical Analytech.
The measurement is performed in two ways: when the measurement ring probe (model name “URSS”) is brought into contact with the surface of the resin coating layer, and when the ring probe is brought into contact with the first polyurethane elastic layer. It carried out in.
Further, the surface roughness (10-point average roughness (Rz) defined in JIS B0601) was measured on both sides of the printing blanket. In addition, regarding the surface of the first polyurethane elastic layer, the surface roughness was measured in two ways, the warp direction and the weft direction of the canvas.

Printing blankets were prepared using the three canvases A to C, and the above evaluation was performed on these three printing blankets.
The evaluation results are summarized in Table 4 below.
When the canvas B is used, the canvas does not have an opening, so that the polyurethane raw material liquid is not impregnated inside the canvas and the first polyurethane elastic body layer is not formed. The volume resistivity and surface resistivity from the elastic layer side were measured by bringing the probe into contact with the canvas exposed.

When these printing blankets were used in the liquid developing electrophotographic apparatus, the printing blanket of Example 1 and the printing blanket of Comparative Example 2 were able to exert a sufficient transfer electric field on the surface of the resin coating layer. However, with the printing blanket of Comparative Example 1, a sufficient transfer electric field could not be obtained.
In addition, the printing blanket of Example 1 showed no problem with respect to the tensile strength, but the printing blanket of Comparative Example 2 had a low tensile strength, so that when the blanket cylinder was rotated, the surface of the printing blanket surface was reduced. As a result, the peripheral speed fluctuated.
Furthermore, since the printing blanket of Comparative Example 2 has a rough inner surface roughness in contact with the blanket cylinder, the image corresponding to the canvas texture appears in the transferred image.

From the above, it can be seen that according to the present invention, it is possible to provide a printing blanket suitable for an application required to have conductivity in the thickness direction, such as a liquid developing electrophotographic apparatus.

Claims

A blanket for printing that is used by being attached to a blanket cylinder,
It has at least a three-layer structure in the order of a first polyurethane elastic body layer, a canvas layer, and a second polyurethane elastic body layer from the blanket body side to the outside, and the first polyurethane elastic body layer and the second polyurethane elastic layer A conductivity-imparting agent is contained in the polyurethane elastic body layer, and the first polyurethane elastic body layer and the second polyurethane elastic body layer are connected through an opening between yarns of the canvas constituting the canvas layer, The tensile stress at 3% elongation in the circumferential direction of the blanket cylinder is 100 MPa or more, and the volume resistivity is 1 × 10 4 Ω · cm or more and 1 × 10 10 Ω · cm or less. Blanket for printing.
The printing blanket according to claim 1, wherein the canvas layer is formed of a canvas having a size of the opening of 0.1 mm square or more.
3. The polyurethane used for transferring toner in a liquid developing electrophotographic apparatus and constituting at least the second polyurethane elastic layer is a polyurethane obtained by reacting a polyester polyol and a bifunctional polyisocyanate. Printing blanket.
The first polyurethane elastic body layer constitutes the innermost layer in contact with the blanket cylinder, and the surface roughness of the first polyurethane elastic body layer is 20 μm in terms of the 10-point average roughness (Rz) defined in JIS B0601. The printing blanket according to any one of claims 1 to 3, wherein the printing blanket is formed as follows.
The first polyurethane elastic body layer and the second polyurethane elastic body layer both have a JIS-A hardness of not less than 30 degrees and not more than 60 degrees. Blanket for printing described in 1.
The printing blanket according to any one of claims 1 to 5, wherein the conductivity-imparting agent is carbon black and graphite.
The canvas constituting the canvas layer is woven with warps and wefts, and the warps or the wefts extend in the circumferential direction of the blanket cylinder, and the threads extending in the circumferential direction are aromatic. The printing blanket according to any one of claims 1 to 6, wherein the printing blanket is formed of a polyamide fiber.
The resin coating layer further has an outermost layer laminated on the outside of the second polyurethane elastic layer, and the surface roughness of the resin coating layer is 10 points as defined in JIS B0601. The printing blanket according to any one of claims 1 to 7, wherein the printing blanket is formed to have an average roughness (Rz) of 7 µm or less.
A polyurethane raw material liquid containing a polyol, a polyisocyanate, and a conductivity-imparting agent is immersed in a canvas having openings between yarns so that the polyurethane raw material liquid is present on both sides of the canvas and the polyurethane raw material liquid is added to the canvas. The first polyurethane elastic body layer and the second polyurethane elastic body layer connected through the opening are formed on both sides of the canvas layer made of the canvas by impregnating and curing the polyurethane raw material liquid. A method for producing a printing blanket according to any one of the preceding claims.
The method for producing a printing blanket according to claim 9, wherein the canvas is immersed in the polyurethane raw material solution under reduced pressure.
A cylindrical or columnar inner mold and an outer mold having an inner peripheral surface larger in diameter than the outer periphery of the inner mold, and the inner mold is accommodated in the outer mold and sealed cylindrical Using a mold capable of forming a cavity, wrapping the canvas around the outer periphery of the inner mold and storing it in the outer mold, and by injecting the polyurethane raw material liquid after depressurizing the cavity The method for producing a printing blanket according to claim 10, wherein the canvas is immersed in the polyurethane raw material liquid under reduced pressure, and the polyurethane raw material liquid is cured in the cavity.