US3745012A - Photosensitive medium comprising a furfurylidene,a lower haloalkane,and a homopolymer of polyvinyl chloride as binder - Google Patents

Abstract

NEGATIVE-WORKING COPYING MATERIALS ARE PREPARED BY COATING A PAPER OR FILM SUBSTRATE WITH AN AMINE-FREE FORMULATION COMPRISING A HOMOPOLYMER OF POLYVINYL CHLORIDE, A CYCLIC ACETAL OF FURFURAL, AND A PHOTOGRSENSITIVE LOWER HALOALKANE. IMAGES ARE FORMED ON THE COPY MATERIALS BY EXPOSURE TO ULTRAVIOLET LIGHT AND FIXED BY HEATING.

Description

United States Patent i PHOTOSENSHTIVE MEDIUM COMPRlSlNG A FURFURYLIDENE, A LOWER HALOALKANE, AND A HOMOPOLYMER OF POLYVHNYL CHLORlDE AS BlNDER dward Zarebski, Holyoke, Mass, assignor to Scott Paper (Zompany, Philadelphia, Pa. No Drawing. Filed Feb. 4, 1972, Ser. No. 223,776 Int. Cl. Gillie 1/52 11.8. Ci. 9688 R 6 Claims ABSTRACT OF THE DiSCLOSURE Negative-working copying materials are prepared by coating a paper or film substrate with an amine-free formulation comprising a homopolymer of polyvinyl chloride, a cyclic acetal of furfural, and a photosensitive lower haloalkane. Images are formed on the copy materials by exposure to ultraviolet light and fixed by heat- BACKGROUND OF THE INVENTION Field of the invention The present invention relates generally to improved, negative-working, copy materials and to coating compositions useful in the preparation thereof. More particularly, the invention relates to copying materials comprising a paper or film substrate having coated thereon an aminefree layer comprising a homopolyrner of polyvinyl chloride, a cyclic acetal of furfural, and a photosensitive lower haloalkane. The copying materials are negative-Working and images are formed thereon by exposure to ultraviolet light and fixed by subsequent heating.

Description of the prior art Copying materials, as that term is commonly used, refers to any one of many products useful in the reproduction of graphic originals. On the basis of the type of copy obtained, these materials are referred to as either positive-working or negative-working. With the positiveworking materials, a print which is the exact duplicate of the original being reproduced is obtained. With the negative-working materials, however, the print obtained is the opposite of the original, i.e., the non-image, or clear, areas of the original will appear as the imaged portions of the copy and the imaged, or printed, areas of the original will not appear on the copy.

The most widely used negative-working copying materials are those employing silver halides. These materials, in addition to being expensive, generally require complex equipment and lengthy processing operations for development of the images. Many attempts have been made to produce negative-working, non-silver halide, copying materials, but none of those which have been developed and are reported in the literature have achieved significant commercial success due to a number of limitations which are inherent in these materials also.

Several negative-working imaging systems have been proposed in which a photosensitive haloalkane, such as iodoform, which is known to release hydrogen iodide (HI) when exposed to light, is combined with a compound containing a furan ring. See, for example, US. Pats. 1,587,269; 1,587,272; 1,587,273 and 1,587,274 issued to Beebe and US. Pats. 3,394,391 issued to Wiswell, 3,394,- 392 issued to Mattor and 3,394,394 and 3,394,395 both of which were issued to Mattor et al. Limitations of these systems which have restricted their use include, for example, (a) the presence of impurities in the coatings resulting in discoloration of the non-image areas of the copies produced, (b) the high temperatures required to fix the images resulting in a softening and distortion of 3,745,912 Patented July 10, 1973 the imaged material, (0) the use of amines which have a tendency to migrate away from the photosensitive layer during storage of the materials, (d) poor shelf life of the coated materials, (e) discoloration of the imaged materials and (f) the use of binder resins which require the use of toxic solvents or prevent the complete release of the photosensitive lower haloalkane from the non-image areas of the print during the fixing step. If the haloalkane is not removed from the non-image areas of the print, these areas will discolor upon repeated exposure to light.

It is also known that a photosensitive resin, such as a vinyl chloride polymer, a vinyl chloride-vinyl acetate copolymer or a vinylidene chloride polymer, will produce visible images upon exposure to actinic light. See, for example, U.S. Pats. 2,712,996; 2,754,210; 2,772,158 and 2,772,159 issued to Elliott. However, because these resins do degrade when exposed to heat and/or light, the stability of both the unimaged and imaged materials is poor.

SUMMARY OF THE INVENTION DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, improved, negativeworlring, copying materials are prepared by coating a paper or film substrate with an amine-free formulation comprising a homopolymer of polyvinyl chloride, a cyclic acetal of furfural and a photosensitive lower haloalkane.

The substrate in the present invention may be either paper or film. Preferred bases include paper, cellulose acetate films, and polyester films which have been treated with a suitable subbing layer including, for example, cellulose acetate butyrate.

The formulation is prepared by dissolving the components in an organic solvent such as, for example, acetone, toluene, methyl ethyl ketone, and tetrahydrofuran.

Polyvinyl chloride homopolymers have been found to be especially useful as binder resins in the copying materials of the present invention. These polymers are soluble in conventional, non-toxic solvents and result in copy materials which do not soften when heated, remain clear and colorless in the non-image areas during storage and during the light exposure and heat curing steps, and allow iodoform, or other haloalkane, to pass from the copy material during the heat fixing step.

A cyclic acetal of furfural is also required. While some of the prior art systems have employed other types of compounds containing a furan ring, it has been found that only the cyclic acetals of furfural can be employed in the copy materials of this invention. Other compounds such as those containing basic nitrogen groups result in problems such as poor image density; discolored background or non-image areas, and poor aging characteristics of the coated, unimaged material. Cyclic acetals useful in carrying out the present invention include, but are not limited to, the following:

2-(2-fury1) -1.3 dioxane CH3 E 0... o

2-(2-furyl)-4,6 dimethyl 1,3 dioxane Cyclic acetals of the type useful in the present invention can be prepared by the following general procedure:

0.50 mole of the diol and 1.0 gram of para-toluenesulfonic acid are dissolved in 150 cc. of tetrahydrofuran and the resulting solution is placed in a 4 necked 1 liter flask equipped with stirring apparatus, an addition funnel, a Dean-Stark trap and a thermometer. 150 cc. of pentane are added and the reaction mixture is heated to reflux and 0.50 mole of furfural (1.0 mole when the diol is pentaerythritol) are added dropwise through the addition funnel. After the addition of the furfural is complete, the reaction mixture is refluxed until no more water is evolved. The reaction mixture is then neutralized with an aqueous solution of sodium carbonate and the resulting phases are separated. The upper, organic phase containing the product is first extracted with warm water to remove any unreacted diol or furfural and the solvent is then removed on a flash evaporator. Solid products are purified by recrystallization from methyl alcohol and liquid products by fractional distillation at reduced pressure.

Several of the compounds specifically enumerated above had the following physical properties:

Melting point 0.)

Compound Physical state (or boiling point) White crystals- 161-162.

Colorless liquid 61-63 at 0.5 mm

hits crystals 7. Colorless crystals... 24-26 (boiling point 81 at V White crystals 2446.

ing Copying Material filed concurrently herewith by William F. Lonczak.

The coating solution is applied to the substrate by conventional methods. These are well known in the art and include, for example, bead-coating, reverse roll, betweenthe-roll coating, and spray coating.

Negative-working copying materials prepared in accordance with the present invention can be imaged by exposing, beneath a partially opaque master, to ultraviolet light in the range of from about 3000 angstroms to about 5000 angstroms. It is especially preferred to employ a light source having an output in the range of from about 3300 angstroms to about 4500 angstroms. The light exposure results in the formation of an image in the light-struck areas of the copy material-i.e., those areas corresponding to the non-image areas of the master. After exposure the print is fixed by heating. It is especially preferred to heat the copy material to a temperature of from about 140 C. to about 160 C. for approximately two minutes. The effect of the heating is to remove the photosensitive lower haloalkane from the background, or non-image areas of the print and to develop, or fix, the image formed upon exposure to light.

In order to describe the present invention so that it may be more clearly understood, the following examples are set forth. These examples are set forth primarily for the purpose of illustration, and any specific enumeration of detail contained therein should not be interpreted as a limitation on the concept of this invention.

EXAMPLE I A coating formulation was prepared comprising Methyl ethyl ketone cc 100 Opalon 600a polyvinyl chloride homopolymer available from Monsanto Company, St. Louis,

MO. gms 10.0 Iodoform m 1.0 Difurfurylidene pentaerythritol gm 1.0

EXAMPLE II A coating formulation was prepared comprising Percent Methyl ethyl ketone 76.49

GAP 2a polyvinyl chloride homopolymer available from Great American Plastics, Inc., Fitchburg, Mass. 14.32 OK412a silica available from DeGussa 4.87 Difurfurylidene pentaerythritol 2.16

and

Iodoform 2.16

The formulation was reverse roll coated on a Crane rag 14 pound paper base and dried. The material was exposed, beneath a partially opaque master, to ultraviolet light in a Super Ozamatic operating at 10 feet per minute. The result was an image in the light-struck areas i.e., those areas corresponding to the clear or non-image areas of the original. The image was fixed by heating the exposed material to a temperature of about C. for about two minutes.

The print had a density of about 3.0 when measured in a photoelectric densitometer calibrated for visual density according to the ASA specification for reflectance density, PH2..17-l958.

By comparison a material prepared from a formulation utilizing polyphenylene oxide as the resin resulted in a brownish print on a yellow background.

EXAMPLE III A coating formulation was prepared, as in Example I], and coated onto a polyester base which had been treated with a suitable bonding layer. The coated material was then dried, exposed and fixed as in Example 11. The resulting black image had a density of about 2.2 when measured as in Example 1.

EXAMPLE IV The formulation was reverse roll coated on Crane 100% rag, 14 pound, paper base and dried. The material was exposed and fixed, as in Example II, resulting in a black image on a clear background. The image areas had a maximum density of 3.10 when measured as in Example 11.

EXAMPLE V A coating formulation was prepared comprising Percent Methyl ethyl ketone 76.49 GAPS52 14.32

OK412 4.87 2-(2-furyl)-4-methyl-l,3-dioxane 2.34 Iodoform 2.16

The formulation was reverse roll coated on Crane rag, 14 pound, paper base and dried. The material was exposed and fixed, as in Example II, resulting in a black image on a clear background. The print had a maximum density of 3.10 when measured as in Example II.

What is claimed is:

1. In an amine-free photosensitive coating composition comprising a cyclic acetal of furfural, a photosensitive lower haloalkane and a binder resin, the improvement which comprises utilizing a homopolyrner of polyvinyl chloride as the binder resin.

2. A coating composition as claimed in claim 1, in which the cyclic acetal of furfural is difurfurylidene pentaerythritol.

3. A coating composition, as claimed in claim 1, in which the photosensitive lower haloalkane is iodoform.

4. In a negative-working copy material comprising a paper or film substrate having coated on one surface thereof an amine-free layer comprising a cyclic acetal of furfural, a photosensitive lower haloalkane and a binder resin, the improvement which comprises utilizing a homopolymer of polyvinyl chloride as the binder resin.

5. A copy material, as claimed in claim 4, in which the cyclic acetal of furfural is difurfurylidene pentaerythritol.

6. A copy material, as claimed in claim 4, in which the photosensitive lower haloalkane is iodoform.

References (lifted UNITED STATES PATENTS 7/1968 Mattor et a1 96-90 R 7/1968 MattOr 9690R U.S. Cl. X.R.