Film construction for use in a plain paper copier

[54] FILM CONSTRUCTION FOR USE IN A PLAIN PAPER COPIER

3,620,726 11/1971 Fu-Wua Chu et al 96/27 R

3,640,749 2/1972 Lorenz 117/28

3,773,417 11/1973 Pressman et al 355/3

4,071,362 1/1978 Takemaka et al 96/1.4

4,377,303 6/1982 Sahyun et al 430/11

4,656,087 4/1987 Lubianez 428/323

4,873,135 10/1989 Wittenbel et al 428/192

[75] Inventors: Joseph C. Carls; Alan J. Herbert;

Donald J. Williams, all of Austin,
Tex.

[73] Assignee: Minnesota Mining and

Manufacturing Company, St. Paul,
Minn.

[21] Appl. No.: 22,729

[22] Filed: Feb. 24,1993

Related U.S. Application Data

[62] Division of Ser. No. 788,138, Nov. 5, 1991, Pat. No. 5,208,093.

[51] Int. CI.* B32B 9/00

[52] U.S. CI 428/195; 428/206;

428/327; 428/500; 428/913

[58] Field of Search 428/195, 206, 327, 913,

428/323, 192, 413,40, 50; 156/235; 430/18, 97,

126

[56] References Cited

U.S. PATENT DOCUMENTS

2,143,214 3/1935 Selenyi 178/7.3

2,221,776 11/1938 Carlson 95/5

2,297,691 4/1939 Carlson 95/5

2,357,809 11/1940 Carlson 95/11

2,855,324 10/1958 VanDorn 117/25

3,017,560 1/1962 Polster 321/45

3,520,811 7/1970 Swoboda 252/62.54

FOREIGN PATENT DOCUMENTS

0052938 6/1982 European Pat. Off. G03G 7/00

0078475 5/1983 European Pat. Off. G03G 7/00

0104074 3/1984 European Pat. Off. G03G 7/00

0349227 6/1989 European Pat. Off. G03G 7/00

0332183 9/1989 European Pat. Off. G03G 7/00

OTHER PUBLICATIONS

Patent Abs. of Japan vol. 12, No. 443, Nov. 1980, Fukao.

Patent Abs. of Japan vol. 7, No. 270, Dec. 2, 1983.

Primary Examiner— Patrick J. Ryan

Assistant Examiner—William A. Krynski

Attorney, Agent, or Firm—Gary L. Griswold; Walter R.

Kirn; Darla P. Neaveill

[57] ABSTRACT

An electrographic article comprising a polymeric film having at least one polymeric receptor layer coated on at least one side thereof, said receptor layer having an equivalent or lower storage elasticity modulus than a toner resin used for forming images on said article.

9 Claims, 1 Drawing Sheet

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15

FILM CONSTRUCTION FOR USE IN A PLAIN
PAPER COPIER

This is a division of application Ser. No. 788,138, filed Nov. 5, 1991, now U.S. Pat. No. 5,208,093, issued May 4, 1993.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to electrography, and a method of development, transfer and fixing of dried toner electrographic images. Specifically, it relates to such images for use in overhead projectors, especially to color images for use therein.

2. Description of the Related Art

Electrography refers to the processes of electrophotography, electroradiography, and magnetography. The process of electrography has been described in numerous patents, such as U.S. Pat. Nos. 2,221,776, 20 2,297,691, and 2,357,809, (Carlson). The process, as taught in these and other patents, essentially comprises production of a latent electrostatic image using photoconductive media and the subsequent development and transfer of a visible image therefrom. A latent electrostatic image may also be formed by spraying the charge onto a suitable charger-retaining surface as taught, for example, in U.S. Pat. Nos. 2,143,214, 3,773,417, and 3,017,560. In magnetography, the latent image is magnetic and may be developed with appropriately magnetized or magnetizable developer particles, as described in U.S. Pat. No. 3,520,811.

Development of the latent image can be accomplished by deposition of developer particles on the electrostatic or magnetic latent image, the most common technique using powder, cascade, or less frequently, liquid developers.

It is well known in the art to use dry powder toner to develop a latent electrostatic image. U.S. Pat. No. 2,855,324 discloses thermoplastic coated receptors to which a dry toner image may be transferred by contact under pressure. U.S. Pat. No. 3,640,749 discloses coating a transferred dry powder image and receptor with a dispersion of a synthetic resin in water. U.S. Patent No. 4,071,362 discloses use of a receptive styrene-type resin 45 on a thermally resistant base film to fuse with thermoplastic coated dry toner particles (i.e., image-fixing is achieved by use of a special toner). U.S. Pat. No. 3,620,726 discloses the use of pigment developer of particle size within the range of 5.0 to 10.0 microns, 50 with not more than 50% of the particles being of less than 1 micron equivalent spherical diameter, thereby reducing background stain. As mentioned, this type of transfer may result in problems of durability.

To avoid such durability problems, various liquid 55 developers have been employed as disclosed in U.S. Pat. 4,337,303, (Sahyun et al.). The liquid toner is encapsulated into a homogeneous continuum of particles within the soft or softened receptor coating. At least 75% of the transferred particles must be embedded within the surface such that they do not protrude.

Particles have also been used in transparencies. U.S. Pat. No. 4,869,955, (Ashcraft et al.) discloses a transparency comprising a polyester support, and at least one toner receptor layer comprising a mixture of an acrylate binder, a polymeric antistatic agent having carboxylic acid groups, a crosslinking agent, and two types of beads, i.e., a butylmethacrylate modified polymeth

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acrylate bead and submicron polyethylene or tetrafluoroethylene beads. The smaller beads are disclosed to improve scratch resistance, and have a particle size of less than one micron, while the polymethacrylate beads are disclosed to assist in transport of the film through the copier and have a particle size of from about 1 to about 5 microns in size.

Where full color images are desired, additional considerations are required. Frequently the prior art processes using dry developing methods showed bright, full color images when the film was inspected, but showed an overall gray tone when the image was projected. As a result the color-tone reproduction range was very narrow.

European patent application no.0349,227, discloses a transparent laminate film for full color image forming comprising two transparent resin layers. The first resin layer is heat-resistant, and the second resin layer must be compatible with a binder resin constituting the toner to be used for color image formation. The second resin layer must have a larger elasticity than that of the binder resin of the toner at a fixing temperature of the toner, preferably in the range of 5 to 1000 times larger than such binder elasticity. While it is stated at page 5, lines 8-26, that resins of the same "kind", i.e., type, e.g., styrene-type or polyester-type, may be used as the toner binder and the second transparent resin layer, the resins must still differ in storage elasticity modulus as previously stated.

It is further specifically stated at page 7, lines 9-14, that where the melt viscosity of the second layer becomes lower than the viscosity of the toner binder resin, it is difficult to develop good color mixing.

It has now been discovered that a good image, even a good full-color image is provided by an electrographic article having a polymeric receptor layer wherein the storage elasticity modulus is equivalent to, or less than that of the toner resin.

It has also been discovered that using polymeric, silica or starch particles in transparent electrographic articles creates a sufficient gap between the film and smooth surfaces with which it contacts that transfer of fuser oil to the projector glass and pooling of fuser oil between the article and a protective sleeve is reduced or eliminated.

SUMMARY OF THE INVENTION

The present invention provides an electrographic article comprising a polymeric film having at least one polymeric receptor layer coated on at least one side thereof, said receptor layer having an equivalent or lower storage elasticity modulus than a toner resin used for forming images on said article.

Preferable articles of the invention comprise a polymeric receptor layer having a storage elasticity modulus about equivalent to the toner resin.

One specific embodiment of the invention provides an electrographic article capable of providing a good full color image when the image is projected.

One preferred embodiment of the invention further comprises polymeric or starch particles, at least 50% of such particles protruding from the polymeric receptor layer, preferably at least 75%, prior to imaging with a toner. Preferably, when starch particles are used, particles are present in an amount such that distribution in the polymeric receptor layer is greater than about 2 particles/MM22. The particles have an average particle size of at least about 5 fim. When polymeric particles, 3

e.g., polymethylmethacrylate (PMMA), polystyrene, and the like are used, particles are present in an amount such that distribution in the polymeric receptor layer is greater than about 5 particles/mm2. These particles also have an average particle size of at least about S ftm. 5

Yet another preferred embodiment of the invention provides an electrographic article having Attached releasably thereto an overlay, at least a portion of such overlay being opaque. The overlay is preferably a porous sheet which reduces fuser problems due to elastic- 10 ity of the porous sheet. It also minimizes slippage of the film in the fuser, in xerographic machinery, and by reducing the maximum temperature of the film, fuser exit creasing is decreased.

The following terms have these meanings when used 15 herein.

1. The term "transparency" means a transparent electrographic article carrying a toner image suitable for projection on an overhead projector.

2. The terms "copier", "copying machine" are used 20 interchangeably to refer to any electrographic or xerographic apparatus which is capable of forming an image on an article of the invention.

3. The terms "envelope", "sleeve" and "cover" are used interchangeably to refer to a protective article for 25 a transparency, typically consisting of a pocket of transparent plastic sheet material open along at least one side edge for insertion of the transparency.

As used herein, all parts, percents, and ratios are by weight unless specifically otherwise defined. 30

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an electrographic article having an overlay consisting of a sensing stripe.

FIG. 2 shows an electrographic article having an 35 opaque overlay consisting of a sensing stripe and a tab.

FIG. 3 shows an electrographic article having an opaque overlay consisting of a single opaque sheet having one or more transparent windows.

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DETAILED DESCRIPTION OF THE
INVENTION

Polymeric film layers useful as a substrate in electrographic articles of the invention include heat-resistant films such as polyester, e.g., polyethylene terephthalate, 45 polymethyl-methacrylate, cellulose triacetate, polyethylene, polystyrene film, polyvinylidene fluoride, polyvinyl chloride, such as polyamides, and polyimides. Preferred film layers include polyethylene terephthalate. Such films are widely commercially available from such 50 companies as Minnesota Mining and Manufacturing (3M), ICI and E.I. DuPont de Nemours (DuPont).

The substrate should preferably have a thickness of from about 50 /x to about 150 u..

Useful polymeric receptor layers include thermoplas- 55 tic resins such as polyester resins, styrene resins, polymethylmethacrylate resins, epoxy resins, polyurethane resins, vinyl chloride resins, and vinyl chloride-vinyl acetate resins.

Preferred receptor layers include polyester resins, 60 e.g., polyesters based on bisphenol A, such as ATLACTM382E, (also sold as Atlactmr 32-629), available from Reichold Chemical as well as bisphenol A monomers and their derivatives, (e.g., the dipropylene glycol ether of bisphenol A). A suitable carrier 65 binder such as Vitel PE 222 polyester resin, available from The Goodyear Tire and Rubber Company, is also present when bisphenol A monomers or their deriva

4

tives are used to facilitate coating. The thickness of the receptor is preferably between about 0.5 to about 10 u.m, more preferably from about 1 to about 6.5 /im.

When full color images are made in the electrographic apparatus, the color image is developed, then finished or "fixed". The fixing device involves the use of heated rollers which are coated with a silicone oil to prevent smearing of the images, and to provide easy release of the image from the roller's surface. Images on transparencies require much more effective coalescence of toner particles than images on paper because the transparency image is projected. Therefore, a longer residence time is usually needed in the fixing device in order to fix the image. During this residence time, the fuser deposits much more oil onto the surfaces of the film than would be deposited during the shorter residence time of paper being imaged. This oil gives the transparency an objectionable sensation to the touch. Further, while the oil does not seem to have a detrimental effect on the image when projected, it is transferred onto the projector stage, where it transfers onto subsequently used transparencies, as well as the hands and possibly clothing of the presenter.

Transparencies are frequently inserted for use into an envelope or cover,.e.g., those disclosed in U.S. Pat. No. 4,402,585, (Gardlund), incorporated herein by reference. These envelopes are commercially available from 3M under the trademark Flip-Frame TM. The envelope provides convenient usage, and notebook storage. Further, it protects the transparency image from damage caused by distortion of the film, creasing, scratching, smearing, tearing, and the like. This is especially important with full color transparencies, which are expensive. However, the use of the envelope provides a further problem when a large amount of fuser oil is present.

The oil migrates to the regions where the transparency touches the sleeve, forming visible pools as large as several centimeters. When projected, the edges of the pools are visible and quite objectionable.

It has been found that adding certain polymeric, silica or starch particles reduces the pooling of the oil at the edges of the sleeves and inhibits transfer of the oil to projection stages.

Useful polymeric particles include, but are not limited to, polymethacrylate, and modified polymethacrylate particles such as polybutylmethacrylate, polymethylmethacrylates, hydroxyethymethacrylate, and mixtures or copolymers thereof, polystyrene, polyethylene, and the like. It is preferred to make such particles as a dispersion to obtain uniformity of size, and shape, and to crosslink the particles to promote nonaggregation. Preferred polymeric particles range in size from about 5 ixm to about 25 fim, and are present in amounts of greater than 5 particles/mm2. At the larger end, the particles may be somewhat visible; however they do not affect the fusing or the quality of the image.

Useful starch particles are from about 5 to about 25 fim in diameter, more preferably from about 10 to about 20 u,m in diameter. Larger particles are effective to reduce the oil pooling, but have the problem of being visible when projected. Smaller particles, i.e., less that 5 fim, in diameter may be used, but a higher loading is requited to effectively reduce the oil pooling. This often results in higher haze of the final image. Also, the smaller particles are not effective in regions of the transparency where the thickness of the toner layer exceeds the extent to which the particles normally protrude from the receptor layer. This is especially important