CA1124128A - Electrophotographic sheet material including a cellulosic base, a cellulose nitrate barrier film and a zinc oxide photoconductive layer - Google Patents
Electrophotographic sheet material including a cellulosic base, a cellulose nitrate barrier film and a zinc oxide photoconductive layerInfo
- Publication number
- CA1124128A CA1124128A CA320,452A CA320452A CA1124128A CA 1124128 A CA1124128 A CA 1124128A CA 320452 A CA320452 A CA 320452A CA 1124128 A CA1124128 A CA 1124128A
- Authority
- CA
- Canada
- Prior art keywords
- cellulose nitrate
- sheet material
- zinc oxide
- paper
- base
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G5/00—Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
- G03G5/14—Inert intermediate or cover layers for charge-receiving layers
- G03G5/142—Inert intermediate layers
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G5/00—Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
- G03G5/10—Bases for charge-receiving or other layers
- G03G5/101—Paper bases
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Photoreceptors In Electrophotography (AREA)
- Printing Plates And Materials Therefor (AREA)
Abstract
ELECTROPHOTOGRAPHIC SHEET MATERIAL
ABSTRACT
The present invention relates to an electrophotographic sheet material suitable for use as an offset printing master, comprising: a fibrous substrate, a continuous film of cellulose nitrate thereon and a layer of photo conductive material on said film.
ABSTRACT
The present invention relates to an electrophotographic sheet material suitable for use as an offset printing master, comprising: a fibrous substrate, a continuous film of cellulose nitrate thereon and a layer of photo conductive material on said film.
Description
rie,~ e .n~en~ion The present invention relates to electrophotographic sheet material. More particularly, this invention relates to improved electrophotographic sheet material suitable for use as an offset printing master.
~b~
Electrophotographic sheet material generally comprises a base sheet, for e~ample paper, having thereon a light-sensitive coating, e.g. one containing a photoconductive particulate material in an insulating binder. Typical of such coatings are those containing zinc oxide in a suitable resin binder, such as polyvinylacetate or modified polyvinylacetate. An electrostatic image may be formed on such sheet by exposure to light projected from an original, and a visj.ble image may then be developed and fixed. The sheet with the visible image so formed may then in turn serve as a master plate for offset printing. When used in such capacity, the sheet is treated with an aqueous solution designed to render the non-imaged areas of the sheet hydrophilic (or oleophobic) before running it on the offset press. Conventional sheets tend to be deleteriously affected by such treatment, as could only be expected, notably in that they quickly stretch and crease due to contact with the fountain solution on the press, become weak or delaminate and so on. This limits the number of copies that can be printed with a single conventional master and with a simple conventional master it would be rare to print more than about 1000 copies.
Improvemen~s have been proposed to make such offset printing masters more durable. Canadian patent 874,905 proposes to apply on a paper base a sizing layer containing a ma~or amount of dialdehyde starch in addition to the usual sizing agents, such as carboxymethyl cellulose, ~elatin and the like/ and to apply the photosensitive coating on said sizing layers.
Canadian patent 862,679 proposes an electrophotographic material having an electroconductive back layer, e.g. of a cationic late~ and an interlayer made of vinyl polymer and amino resinsO These expedients however are either not particularly effective or are very cumbersome and expensive. For example, applying the vinyl polymer and amino resins to paper and curing at a temperature of about 150C represents a complex and delicate task. Yet another proposal (Canadian patent 957,540) is to apply a resin coating, more particularly a ceLlulose ester coatin~, to the back of the pap~r but the results permit only upto 300 ; 20 copies to be printed.
, ~_ The present invention provides an electrophotographic printing sheet which can be produced in a simple manner and can serve as a master plate for consistently running off impressions on the order of upto five thousand or more using a conventional offset base paper. Accordingly the present invention relates to an electrophotographic sheet material for use as a master in offset printing and comprises a cellulosic base material, a continuous film of cellulose nitrate on said base material, and a photoconductive layer on said film.
t_ The cellulosic base material is preferably paper or a like cellulose fibrous sheet material of suitable characteristics. Among the characteristics expected of such paper, an important one is electrical resistivity which is controlled within specified limits.
The proper resistivity is generally imparted into the paper in a known manner, in the course of fabrication, e.g. by incorporating additives in the paper body, in the siæing, etc. The paper will generally be sized in a conventional manner and sometimes special ingredients will be incorporated in the sizing to make tbe paper less ab~orbent to water or solvents as examplified by the above mentioned incorporation of dialdehyde ~tarch.
But unsized papers can also be used, particularly very dense and highly bonded papers. Generally, special grades of paper a~e used for the making of offse~
plates, such as Allied Grade X904 or Glatfelter DTMB or LTMP Grades of offset base paper (made respectively by the Allied Paper Company and the ~latfelter Company3 or other suitable or similar base materials.
The photoconductive layer, which will form the top coating of the sheet material, is normally a dispersion of photoconductive zinc oxide in a resin system, but other similar materials may be used to form the photoconductive layer. The zinc oxide layer is generally applied as a dispersion of zinc oxide in a resin solution, the solvent being generally an organic non-polar compound, preferably a hydrocarbon such as toluene or the like. The art of ~orming and applying the photoconductive zinc oxide layer is highly specialized and often relies on an accumulated know-how and skills, however it is not part of the present invention.
The cellulose nitrate fllm is applied on the fibrous base material to form an intermediate layer between the base and the photoconductive layer. The film is applied in the form of a solution of cellulose nitrate in a suitable solvent, e.g. an alcohol, an ether-alcohol mixture, glycol ether or the like.
Various types oE cellulose nitrate are available in commerce, differing from one another in viscosity (at given concentration~, nitrogen content, etc. Examples are the nitrocellulose products sold by the ~ercules Company under the trademarks RS, AS and SS Nitro-cellulose. Solutions of a wide range of viscosity and/or solids content may be usedO The viscosity will be chosen on the basis of ease of application with given equipment and, using Meyer rods of suitable dimension, we have found the range of viscosit:ies from about 50 to about 1,000 cps to be suitable. The solids contenk must be such that, upon evaporation o l:he solvent, a continuous cellulose nitrate film is formed on the base material. We have found the range of between about 1/2 lb to 6 lbs of cellulose ni~rate per ream (3,300 sq fk) of paper to be suitable~ depending on the surface, the absorptivity etc. of the paper; for example, in the case of a paper base of high absorptivity a greater amount of cellulose nitrate will have to be used to ensure the formation of a conti~uous film. The cellulose nitrate coat weight must not be too high, since it may adversely affect curl, electrical properties, stiffness and for flexibility of ~he base plate; whereas, if it is too low it may no~ be durable enough.
One of the requirements with regard to an electrophotographic paper base is that its electro-conductive properties be such as to permit a sufficient-ly rapid dissipation of electrostatic charges after exposure to light of the photosensitive layer. Such resistivity should not, in any case, exceed about 1013 ohms/sq cm., and since the addition of a celiulose nitrate precoat does not substantially modify the resistivity of tbe base paper over a relative humidity range of about 10 to 80%, it is a material uniquely suited for the purpose herein described.
The resistance of cellulose nitrate to organic aromatic solvents, such as are generally used in zinc oxide-resin dispersion make it further suitable as a barrier layer between the base paper and the photocon-ductive layer during the zinc oxide coating operation.
Additionally, the cellulose nitrate improves the water holdout and dimensional stability of the base sheet which contributes significantly to obtaining improved press run capacity.
Care should be taken not to cause the thu~
pre~coated base paper to acquire a curl and in certain cases, it may be necessary to employ compatible conven-tional techniques to avoid curl.
The inYention will be further illustrated by means of the following examples:
Cellulose nitrate~ sold under the name RS
Nitrocellulose (Hercules Trademark) 1/4 sec., was dissolved in glycol ether sold in the trade as CELLOSOLVE (Union Carbide trademark) in the proportion of 14 gm cellulose nitrate and 86 gm CELLOSOLVE (TM).
The thus prepared solution was applied by Meyer bar coating methods onto Allied Grade X904, 78 lb. offset base paper. The solvent was allowed to evaporate and the resulting continuous film o~ cellulose nitrate amounted to about two pounds per ream (3,300 sq ft) of paper. The thus pre-coated paper was then used as a substrate for a conventlonal zinc oxide coating applied at a weight of about 22 lbs per ream (3,300 sq. ft~)o The electrophotographic paper thus produced, when imaged and toner developed, was used as a plate in an offset press. The number of impressions obtained with each plate was always in excess of 5000. When the same paper was used, without pre-coating with cellulose nitrate, as a substrate for a zinc oxide photosensitive coating, the resulting electrophotographic plates run in a similar manner in an ofset press, produced only 500-1000 impressions.
A solution similar to the one in Example 1 was prepared consisting of cellulose nitrate sold under the name SS Nitrocellulose (TM) 1/2 sec. in ethyl alcohol in the proportion of 10 gm nitrate to 90 gm solvent. The formulation was applied onto a paper in the same manner as the preceding example to form a film of a weight of about 3 lbs. per ream (3,300 sq. ft.). A zinc oxide photoconductive coating of a weight of 20 lbs. per ream (3,300 sq. ft.) ~as applied onto the thus pre-coated paper. Plates prepared from this electrophotograph;c paper were used on a conventional offset press and about 5000 impressions were produced with only minimal stretch (about 0.2%) of the offset plate in both the machine and cross-machine directions. A zinc oxide coated identical paper base, but without the intermediate film of cellulose nitrate stretched about 0.4% in the machine direction and about 2% in the cross machine direction after about 1000 impressions.
A paper base having a high solvent holdout and sold as E,~. Eddy Silicone Coating base (TM) by the E.B.
Eddy Company was coated cn both sides with a solution of ~S Nitrocellulose (TM) and having l/2 second vi~cosity, was dissolved in OELLOSOLVE (TM) in the proportion lO g.
nitrate ~o 90 9 solvent. This solution, when applied to the paper and dried, provided a pre-coating of 2 lb~/ream (3,300 sq. ft.) of substrate. An overcoat of 22 lb./ream (3,300 sq. ft.) of zinc oxide was applied to the precoated substrate. The substrate, so-coated, when imagedy developed, converted and run in an offset press as the offset plate provided about 1,090 impressions per plate. A similar base material with the ,zinc oxide overcoat, but without the cellulose nitrate coating provided about 50 impressions per plate.
The description and examples provided above are for the purpose o~ providing a complete disclosure of the invention, and alterations and modifications within the scope of the appended claims, may occur to those skilled in the art.
~b~
Electrophotographic sheet material generally comprises a base sheet, for e~ample paper, having thereon a light-sensitive coating, e.g. one containing a photoconductive particulate material in an insulating binder. Typical of such coatings are those containing zinc oxide in a suitable resin binder, such as polyvinylacetate or modified polyvinylacetate. An electrostatic image may be formed on such sheet by exposure to light projected from an original, and a visj.ble image may then be developed and fixed. The sheet with the visible image so formed may then in turn serve as a master plate for offset printing. When used in such capacity, the sheet is treated with an aqueous solution designed to render the non-imaged areas of the sheet hydrophilic (or oleophobic) before running it on the offset press. Conventional sheets tend to be deleteriously affected by such treatment, as could only be expected, notably in that they quickly stretch and crease due to contact with the fountain solution on the press, become weak or delaminate and so on. This limits the number of copies that can be printed with a single conventional master and with a simple conventional master it would be rare to print more than about 1000 copies.
Improvemen~s have been proposed to make such offset printing masters more durable. Canadian patent 874,905 proposes to apply on a paper base a sizing layer containing a ma~or amount of dialdehyde starch in addition to the usual sizing agents, such as carboxymethyl cellulose, ~elatin and the like/ and to apply the photosensitive coating on said sizing layers.
Canadian patent 862,679 proposes an electrophotographic material having an electroconductive back layer, e.g. of a cationic late~ and an interlayer made of vinyl polymer and amino resinsO These expedients however are either not particularly effective or are very cumbersome and expensive. For example, applying the vinyl polymer and amino resins to paper and curing at a temperature of about 150C represents a complex and delicate task. Yet another proposal (Canadian patent 957,540) is to apply a resin coating, more particularly a ceLlulose ester coatin~, to the back of the pap~r but the results permit only upto 300 ; 20 copies to be printed.
, ~_ The present invention provides an electrophotographic printing sheet which can be produced in a simple manner and can serve as a master plate for consistently running off impressions on the order of upto five thousand or more using a conventional offset base paper. Accordingly the present invention relates to an electrophotographic sheet material for use as a master in offset printing and comprises a cellulosic base material, a continuous film of cellulose nitrate on said base material, and a photoconductive layer on said film.
t_ The cellulosic base material is preferably paper or a like cellulose fibrous sheet material of suitable characteristics. Among the characteristics expected of such paper, an important one is electrical resistivity which is controlled within specified limits.
The proper resistivity is generally imparted into the paper in a known manner, in the course of fabrication, e.g. by incorporating additives in the paper body, in the siæing, etc. The paper will generally be sized in a conventional manner and sometimes special ingredients will be incorporated in the sizing to make tbe paper less ab~orbent to water or solvents as examplified by the above mentioned incorporation of dialdehyde ~tarch.
But unsized papers can also be used, particularly very dense and highly bonded papers. Generally, special grades of paper a~e used for the making of offse~
plates, such as Allied Grade X904 or Glatfelter DTMB or LTMP Grades of offset base paper (made respectively by the Allied Paper Company and the ~latfelter Company3 or other suitable or similar base materials.
The photoconductive layer, which will form the top coating of the sheet material, is normally a dispersion of photoconductive zinc oxide in a resin system, but other similar materials may be used to form the photoconductive layer. The zinc oxide layer is generally applied as a dispersion of zinc oxide in a resin solution, the solvent being generally an organic non-polar compound, preferably a hydrocarbon such as toluene or the like. The art of ~orming and applying the photoconductive zinc oxide layer is highly specialized and often relies on an accumulated know-how and skills, however it is not part of the present invention.
The cellulose nitrate fllm is applied on the fibrous base material to form an intermediate layer between the base and the photoconductive layer. The film is applied in the form of a solution of cellulose nitrate in a suitable solvent, e.g. an alcohol, an ether-alcohol mixture, glycol ether or the like.
Various types oE cellulose nitrate are available in commerce, differing from one another in viscosity (at given concentration~, nitrogen content, etc. Examples are the nitrocellulose products sold by the ~ercules Company under the trademarks RS, AS and SS Nitro-cellulose. Solutions of a wide range of viscosity and/or solids content may be usedO The viscosity will be chosen on the basis of ease of application with given equipment and, using Meyer rods of suitable dimension, we have found the range of viscosit:ies from about 50 to about 1,000 cps to be suitable. The solids contenk must be such that, upon evaporation o l:he solvent, a continuous cellulose nitrate film is formed on the base material. We have found the range of between about 1/2 lb to 6 lbs of cellulose ni~rate per ream (3,300 sq fk) of paper to be suitable~ depending on the surface, the absorptivity etc. of the paper; for example, in the case of a paper base of high absorptivity a greater amount of cellulose nitrate will have to be used to ensure the formation of a conti~uous film. The cellulose nitrate coat weight must not be too high, since it may adversely affect curl, electrical properties, stiffness and for flexibility of ~he base plate; whereas, if it is too low it may no~ be durable enough.
One of the requirements with regard to an electrophotographic paper base is that its electro-conductive properties be such as to permit a sufficient-ly rapid dissipation of electrostatic charges after exposure to light of the photosensitive layer. Such resistivity should not, in any case, exceed about 1013 ohms/sq cm., and since the addition of a celiulose nitrate precoat does not substantially modify the resistivity of tbe base paper over a relative humidity range of about 10 to 80%, it is a material uniquely suited for the purpose herein described.
The resistance of cellulose nitrate to organic aromatic solvents, such as are generally used in zinc oxide-resin dispersion make it further suitable as a barrier layer between the base paper and the photocon-ductive layer during the zinc oxide coating operation.
Additionally, the cellulose nitrate improves the water holdout and dimensional stability of the base sheet which contributes significantly to obtaining improved press run capacity.
Care should be taken not to cause the thu~
pre~coated base paper to acquire a curl and in certain cases, it may be necessary to employ compatible conven-tional techniques to avoid curl.
The inYention will be further illustrated by means of the following examples:
Cellulose nitrate~ sold under the name RS
Nitrocellulose (Hercules Trademark) 1/4 sec., was dissolved in glycol ether sold in the trade as CELLOSOLVE (Union Carbide trademark) in the proportion of 14 gm cellulose nitrate and 86 gm CELLOSOLVE (TM).
The thus prepared solution was applied by Meyer bar coating methods onto Allied Grade X904, 78 lb. offset base paper. The solvent was allowed to evaporate and the resulting continuous film o~ cellulose nitrate amounted to about two pounds per ream (3,300 sq ft) of paper. The thus pre-coated paper was then used as a substrate for a conventlonal zinc oxide coating applied at a weight of about 22 lbs per ream (3,300 sq. ft~)o The electrophotographic paper thus produced, when imaged and toner developed, was used as a plate in an offset press. The number of impressions obtained with each plate was always in excess of 5000. When the same paper was used, without pre-coating with cellulose nitrate, as a substrate for a zinc oxide photosensitive coating, the resulting electrophotographic plates run in a similar manner in an ofset press, produced only 500-1000 impressions.
A solution similar to the one in Example 1 was prepared consisting of cellulose nitrate sold under the name SS Nitrocellulose (TM) 1/2 sec. in ethyl alcohol in the proportion of 10 gm nitrate to 90 gm solvent. The formulation was applied onto a paper in the same manner as the preceding example to form a film of a weight of about 3 lbs. per ream (3,300 sq. ft.). A zinc oxide photoconductive coating of a weight of 20 lbs. per ream (3,300 sq. ft.) ~as applied onto the thus pre-coated paper. Plates prepared from this electrophotograph;c paper were used on a conventional offset press and about 5000 impressions were produced with only minimal stretch (about 0.2%) of the offset plate in both the machine and cross-machine directions. A zinc oxide coated identical paper base, but without the intermediate film of cellulose nitrate stretched about 0.4% in the machine direction and about 2% in the cross machine direction after about 1000 impressions.
A paper base having a high solvent holdout and sold as E,~. Eddy Silicone Coating base (TM) by the E.B.
Eddy Company was coated cn both sides with a solution of ~S Nitrocellulose (TM) and having l/2 second vi~cosity, was dissolved in OELLOSOLVE (TM) in the proportion lO g.
nitrate ~o 90 9 solvent. This solution, when applied to the paper and dried, provided a pre-coating of 2 lb~/ream (3,300 sq. ft.) of substrate. An overcoat of 22 lb./ream (3,300 sq. ft.) of zinc oxide was applied to the precoated substrate. The substrate, so-coated, when imagedy developed, converted and run in an offset press as the offset plate provided about 1,090 impressions per plate. A similar base material with the ,zinc oxide overcoat, but without the cellulose nitrate coating provided about 50 impressions per plate.
The description and examples provided above are for the purpose o~ providing a complete disclosure of the invention, and alterations and modifications within the scope of the appended claims, may occur to those skilled in the art.
Claims (4)
1. An electrophotographic sheet material comprising;
a cellulosic base material, a continuous barrier film consisting of cellulose nitrate on said base material, a photoconductive layer comprising zinc oxide on the surface of said film remote from interface between said base material and said film.
a cellulosic base material, a continuous barrier film consisting of cellulose nitrate on said base material, a photoconductive layer comprising zinc oxide on the surface of said film remote from interface between said base material and said film.
2. Electrophotographic sheet material as defined in Claim 1, wherein said substrate is an offset base paper.
3. Electrophotographic sheet material as defined in Claim 2 wherein said continuous film or cellulose nitrate constitutes between 1/2 to 6 lb. per ream (3,300 sq. ft.) of said sheet material.
4. Process for the preparation of electrophotographic sheet material comprising; coating a fibrous base material with a solution of cellulose nitrate, removing solvent from said solution on said base material thereby to form a continuous barrier film consisting of said cellulose nitrate, coating a layer of photoconductive material comprising zinc oxide on said continuous film of cellulose nitrate.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA320,452A CA1124128A (en) | 1979-01-29 | 1979-01-29 | Electrophotographic sheet material including a cellulosic base, a cellulose nitrate barrier film and a zinc oxide photoconductive layer |
| EP80300248A EP0015071A3 (en) | 1979-01-29 | 1980-01-28 | Electrophotographic sheet material and process for its preparation |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA320,452A CA1124128A (en) | 1979-01-29 | 1979-01-29 | Electrophotographic sheet material including a cellulosic base, a cellulose nitrate barrier film and a zinc oxide photoconductive layer |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1124128A true CA1124128A (en) | 1982-05-25 |
Family
ID=4113411
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA320,452A Expired CA1124128A (en) | 1979-01-29 | 1979-01-29 | Electrophotographic sheet material including a cellulosic base, a cellulose nitrate barrier film and a zinc oxide photoconductive layer |
Country Status (2)
| Country | Link |
|---|---|
| EP (1) | EP0015071A3 (en) |
| CA (1) | CA1124128A (en) |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA874905A (en) * | 1971-07-06 | Seimiya Ryubun | Electrophotographic printing masters | |
| NL275381A (en) * | 1961-03-03 | |||
| GB1153506A (en) * | 1966-10-14 | 1969-05-29 | Eastman Kodak Co | Photoconductive Materials |
| US3640708A (en) * | 1970-09-09 | 1972-02-08 | Eastman Kodak Co | Barrier layers for electrophotographic elements containing a blend of cellulose nitrate with a tetrapolymer having vinylidene chloride as the major constituent |
| DE2210140A1 (en) * | 1971-03-03 | 1972-09-21 | Canon Kk | Barrier layer - for photo-conducting recording material |
-
1979
- 1979-01-29 CA CA320,452A patent/CA1124128A/en not_active Expired
-
1980
- 1980-01-28 EP EP80300248A patent/EP0015071A3/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| EP0015071A2 (en) | 1980-09-03 |
| EP0015071A3 (en) | 1980-11-12 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |