JPH0338994B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to sheet materials, particularly base cysts covered by a microvoided, dispersed light-reflecting layer that is opaque but can be made transparent.

For centuries, paper has remained one of the most versatile materials created by mankind. It is constructed from commonly available cellulose-based materials and can be hard or flexible, rough or smooth, thick or thin, and can be provided in any desired color. After being used for a given purpose, it is often repulped and used again. However, in recent years the demand for paper has increased to such an extent that it has finally become necessary to recognize that cellulose-based raw materials are not inexhaustible. In addition, the energy required to produce paper has become a worldwide concern as there is increasing recognition that energy supplies are similarly finite. It has also been recognized that even when paper is used as a display medium, it is usually not possible or practical to remove displays that are used only once and are no longer needed or desired. Thus, there is a growing desire for paper substitutes, especially those that can be repeatedly and easily reused. That is, an alternative that is more expensive to manufacture will be cheaper in the long run if it can be reused a sufficient number of times.

Several US patents (e.g. no. 2299991, no.
Nos. 3,031,328 and 3,508,344) disclose composite sheet materials in which a light-colored, opaque, dull lacquer layer is coated onto a base sheet printed with a dark-colored or dark-colored indicia. The opacity and brightness of dull lacquer coatings are due to the inclusion of large numbers of microscopic voids, which can be either (1) heated or pressured (irreversible destruction of microscopic voids) or (2) substantially the same as the lacquer. By local application of a non-solvent liquid (filling of microscopic cavities) with a refractive index,
The coating is selectively transparent, allowing the underlying dark backing to be visible. The liquid used to impart transparency to the opaque microporous layer is evaporated after application and the composite sheet returns to its original appearance.

U.S. Pat. No. 2,854,350 discloses a structure functionally similar to that described above, except that a dull lacquer coating is replaced by a microporous layer of finely powdered calcium carbonate in an organic binder. Transparency is imparted by applying pressure locally or by treating specific areas with waxes, oils, or greases that have the same curvature as calcium carbonate (see U.S. Pat. No. 2,854,350). ). Other pigments may be added to the microporous highly plasticized resin binder (see US Pat. No. 3,247,006).

It is sometimes desirable to provide a microvoid-containing sheet material that can be made transparent by the application of a liquid, but cannot be easily made transparent by the application of heat or pressure. Sometimes. In such cases, U.S. Patent No. 4299880
The fine void content disclosed in the above publication is preferred.
According to the same application, a structure is disclosed with a microvoid-containing layer consisting essentially of particles held in a parallel state pseudo-sintered by a thermosetting binder and having a bonding value of at least 400 g-force. ing.

The above binding values were obtained by knife-coating a dispersion of the composition to be measured onto a clean gray cold rolled steel panel and, after drying, after proper curing of the composition.
A coating of ~60 micrometers thickness is obtained and used for measurements. Gardner Laboratories, Inc.
“Balance Beam Scrape−Adehesion and Mar
Using a tester, the sapphire tip needle is lowered into contact with the test panel and held in its fixed position while the ball bearing support platform moves the panel. The minimum g-force required to create a 50 micrometer deep scratch in the coating in one pass is measured at 40x magnification and is taken as the bond value.

To a greater or lesser degree, each of the above-mentioned products has the disadvantage that topical application of a clarifying liquid produces images that cannot maintain their initial sharp contours over time. Stated another way, the marking liquid not only penetrates the microscopic voids perpendicular to the surface, but also tends to sway laterally. As a result, the longer the clarifying liquid is held in contact with the microvoids-containing layer, the less clear the initial image becomes. For example, similar times (eg, 6, 8, and 9) or characters (eg, 1, i, and t) become difficult to distinguish from each other. Prior to this invention,
There was no known way to overcome this problem.

The present invention provides an improved sheet material of the type in which the base sheet is coated on at least one surface with an opaque white or pastel layer of a film-forming polymer containing interconnected microvoids. provided. This sheet material can be marked by applying a desired pattern of a colorless, transparent marking liquid with a refractive index approximately equal to the layer's constituents onto the exposed surface, thereby rendering the marked area transparent. It can be manufactured so as to show a certain display. Marking liquids for products are usually selected on the basis that they are non-reactive with the components of the layer and have a volatility suitable for the desired end use.

The improvement provided by the present invention consists of a substance (typically an organic polymer) added to the microvoided layer that significantly increases the viscosity of the marking liquid. (For convenience, this thickening effect will be referred to hereinafter as "jellying"). When a marking liquid is applied to the surface of a microvoid layer, it penetrates into the layer, thickening or gelling, and when it comes into contact with a jelly material, its viscosity becomes very high and the microvoid layer of the marking liquid Passage inside will be delayed. That is, lateral shake is prevented. Subtle sky
It would be expected that vertical permeation of the water would be prevented as well and that no clearing would occur, which surprisingly does not occur in this case. As a result, not only can the display be easily produced, but it can also maintain substantially the same dimensions throughout the time that the layer is locally transparentized.

The jellifying material used in the practice of the present invention can be either natural or synthetic, but
However, it is characterized by the gelatinizing property of the marking liquid used. A simple test to determine the suitability of a given material for use with a particular marking fluid is to place 10 g of the candidate gelling material and 90 g of the marking fluid in a 500 c.c. glass jar and place the jar. It consists of tightly stoppering and tumbling it for 24 hours. If the above materials and the marking liquid form a uniform gel-like ball without leaving any liquid behind, the combination is judged to be suitable for practical use in the present invention.

To determine whether a given jellifying material-marking liquid combination is effective in the practice of the present invention,
The compatibility index of each of them
δ (measured in hildebrands) [A detailed discussion of compatibility indices, their measurement and calculation can be found in (1) Encyclopedia of Polymer Science and
Technology, New York (1965) vol. 3, p. 833 and (2) Encyclopedia of Chemical Technology,
Interscience, New York (1971), supplementary volume,
See page 889. It has also been found useful to consider the following: Generally, when the compatibility indices of the gelling material and the marking liquid differ by about 2 Hildebrands, the combination will tend to give a solution viscosity lower than that for smaller differences than is useful in the practice of this invention. Yes, and larger differences tend to result in insufficient gelation to prevent side runout.

A better understanding of the invention may be obtained by reference to the following representative, but non-limiting, example, in which all parts,
Ratios and percentages are by weight unless otherwise specified.

Example 1 Following the general procedure described in U.S. Pat. No. 2,854,350, 39.6 g of water, 0.4 g of sodium alginate, and 5 g of precipitated calcium carbonate were placed in a 4 oz. A control sample was prepared by ball milling for 1 day. The resulting composition was knife coated onto the surface of black 60-micrometer greaseproof paper to a thickness of about 200 micrometers and allowed to dry overnight at room temperature. The dried coating was approximately 25 micrometers thick.

In accordance with the present invention, 0.2 g of setrose acetate butyrate (Eastman Chemical Products,
A sample identical to the control example was prepared except that the composition included CB500-1, available from Co., Ltd. A 1.5-mm line was traced onto the surface of each of the two products using a felt-tipped pen filled with diethyl phthalate. The table below shows the width of the stroked lines measured over time.

Image width, mm Time, min Control sample Example 1 0 1.5 1.5 2 1.9 1.5 4 2.2 1.5 8 3.2 1.5 12 3.2 1.5 16 3.2 1.5 The control sample product was initially designed with horizontal lines that more than doubled the width of the line. In contrast, in the product of Example 1, diethyl phthalate gels upon contact with cellulose acetate butyrate, resulting in a substantially constant line width, that is, preventing lateral blurring. is observed.

Example 2 75.1 g acetone, 6.6 g
of polymethyl methacrylate (“Elvacite” 2041 manufactured by EIdu Pont), 1.6 g of diethyl phthalate, 1.1 g of polyacrylate (Rolrm & Haas
"Rhoplex" manufactured by Co. B-15) and 11.0 g of water.
A control sample was prepared by placing in an ounce (approximately 250 c.c.) jar and milling in a ball mill overnight. The resulting composition was knife coated onto the black greaseproof paper used in Example 1 and dried at room temperature to give a coating approximately 50 micrometers thick.

In accordance with the present invention, 1.0 g of methylcellulose ("Methocel" manufactured by Dow Chemical Company)
The sample was prepared similarly to the control sample, except that MC4000cp) was added to the composition prior to ball milling. Using a felt-tipped pen filled with 1,2-propanediol, apply on the surface of each product.
A 0.9-mm line was drawn and then measured over time.
The results are shown below.

Image Width, mm Time, Min Control Sample Example 2 0 0.9 0.9 1 1.2 1.0 5 1.2 1.0 10 1.2 0.9 Although not as shocking as the results shown in Example 1, the results of this example are 1 , 2-propanediol when gelatinized with methylcellulose to prevent lateral wobbling, the structures of the present invention have been shown to maintain significantly sharper images than the control samples.

Example 3 16 parts xylene, 16 parts diisobutyl ketone, 8 parts heptane, 11.39 parts thermosetting acrylic resin (Henkel Corp. G-
CURE868RX-60), 0.2 parts di(dioctylpyrophosphate) ethylene titanate (Kenrich
Petrochemical Inc. KR-2385), 0.5 to 100 copies
Calcium carbonate, with a particle size of 15 micrometers
and Part 2.17 “Desmodur” N-75 (Mobay
Polymeric Biuret 75 of 195 equivalents of 1.6-hexamethylene diisocyanate, manufactured by Chemical Corp.
A control coating composition was prepared by mixing a 1:1 xylene:2-ethoxyethyl acetate solution containing % solids. This composition was coated onto the black greaseproof paper of Example 1 and cured for 30 minutes at about 90°C to give a dry coating about 25 micrometers thick.

In accordance with the present invention, 4 parts of carboxypolymethylene ("Carbopol" manufactured by BFGoodrich Chemical Co.)
941) in the coating composition.
The same product as the control sample was prepared. A 1.0 mm line was then marked on the surface of each sheet using a felt-tipped pen filled with tetraethylene glycol.
After 30 minutes, the line width on the control product was 1.9 mm;
On the other hand, the line width on the product of Example 3 was only 1.1 mm.

Example 4 20 g xylene, 7.6 g methyl isobutyl ketone, 7.6 g ethylene glycol monoethyl ether acetate, 0.2 g di(dioctyl pyrophosphate) ethylene titanate, 13.0 g thermosetting acrylic resin, 100.0 g 0.5 ~15 micrometer calcium carbonate, and 2.5 g "Desmodur"
N-75 was mixed together to prepare a microporous control coating composition. This composition was coated onto the black greaseproof paper of Example 1 and cured by heating at about 90°C for 45 minutes.

According to the invention, 2 g of "Kraton" 1107
(Isoprene:styrene:isoprene block copolymer having a 25% toluene solution viscosity at 23°C of 1.6 Pa·S) was prepared in the coating composition, but the same as that of the control sample was prepared. did. A line was then marked on both the control sample and the product of Example 4 using a felt-tipped pen containing a mixture of saturated branched hydrocarbons with a distillation range of 244° to 286°C, the width of which varied over time. was measured. The results are shown below.

Image Width, mm Hours, Minutes Control Sample Example 4 0 1.0 1.0 3 1.2 1.0 5 1.2 1.0 11 1.2 1.0 30 1.3 1.0 50 1.2 0.9 Example 5 8.0 parts of an oil-free thermosetting alkyd resin having an equivalent weight of 400 (“Aroplaz” 6022.Ashland
Chemical Co), 56.0 parts ethylene glycol monoethyl ether acetate, 100.0 parts isopropyl triisostearoyl titanate pigment,
and 3.8 parts of "Desmodur" N-75 were mixed together to prepare a microporous control composition. This composition was coated onto 64-micrometer dark brown greaseproof paper and cured for 6 minutes at 230 DEG C. to give a dry coating approximately 25 micrometers thick.

A product identical to the control sample was prepared in accordance with the present invention, except that the coating composition also contained 2.0 parts cellulose acetate butyrate and 2.0 parts carboxypolymethylene. A 1.5 mm line was then marked on each coated product using a felt-tipped pen containing dibutyl phthalate and its width was measured over time. The results are shown below.

Image Width, mm Hours, Minutes Control Sample Example 5 0 1.5 1.5 0.5 1.8 1.5 1.0 2.0 1.5 2.0 2.4 1.6 1440 4.1 1.6 1440 Markings except that the marks on both products disappeared due to evaporation of the liquid before the end of the minute. Similar results were obtained using propylene glycol as the liquid.

The above examples are illustrative of the case where the jellifying material is added directly to the microvoiding coating composition. As shown in the following examples, the same effect can be achieved by adding a jelly-forming substance to the micropores in a post-treatment to coat the micropores.

Example 6 A sample was prepared in substantially the same manner as the control sheet of Example 1. In accordance with the present invention, a portion of this control sample was coated with a 5% solution of cellulose acetate butyrate in methyl isobutyl ketone, all excess was then wiped off the surface, and the solvent was then allowed to evaporate at room temperature. A felt-tipped pen containing diethyl phthalate was stroked across the treated and untreated areas to create a line, which was initially
It was mm wide. After 30 minutes, the line on the untreated portion was 5 mm wide, while the line on the treated portion was still 2 mm wide. In a similar manner, a felt-tipped pen containing dioctyl phthalate was stroked across the treated and untreated areas to create a line that was initially 1 mm wide. After 13 days, the lines on the untreated areas had become too wide to be discernible anymore, while the lines on the treated areas were still 1 mm wide and easily recognizable.

Example 7 A control sheet substantially the same as the control sheet of Example 2 was prepared. In accordance with the present invention, a portion of this control sample was then treated with a 2% aqueous solution of methylcellulose ("Methocel" MC Standard 4000 cps), excess solution was wiped from the surface, and the sample was then dried at room temperature. Next, using a felt-tipped pen containing 1,2-propanediol, mark a 0.7 mm line on the surface of both the control sample and the treated material of this Example 7, increasing the line width on each over time. It was measured. The results are shown below.

Image Width, mm Hours, Minutes Control Sample Example 7 0 0.7 0.7 1 1.4 0.7 2 1.6 0.7 10 1.9 0.7 20 2.0 0.8 Example 8 17.5 parts of xylene, 17.5 parts of methyl ethyl ketone, 100 parts of dry ground calcium carbonate with a particle size of 0.5 to 15 micrometers and
A control sample sheet was prepared by mixing 13 parts of thermosetting acrylic resin and then milling the mixture for two days. Next, 2.5 parts of 1,6-hexamethylene diisocyanate was added to a high molecular weight binder, and milling was continued using a ball mill for an additional 4 hours. This dispersion was knife-coated on the black grease-resistant paper used in Example 1, dried at 90°C for 1 minute,
It was then cured at the same temperature for 45 minutes to obtain a dry coating approximately 50 micrometers thick. 5 of cellulose acetate butyrate was applied to the control sheet coated surface area.
% methyl ethyl ketone solution (Eastman
CAB500-1) was applied and after the solution had permeated, the excess amount was wiped off and the sample was dried at room temperature. Next, using a felt-tipped pen containing diethyl phthalate, mark a 1.2 mm line on the surface of both the control sample and the treated material of this Example 8,
The width of each line was measured over time. The results are shown below.

Image Width, mm Hours, Minutes Control Sample Example 7 0 1.2 1.2 3 1.3 1.2 36 1.5 1.2 As mentioned above, it is highly desirable to maintain a sharp and clear image when the applied display is read visually. desired. However, it may be more desirable to retain their initial dimensions when this indicia is inspected by optical property recognition (OCR) or optical mark reading (OMR) equipment.

Even if the microvoid-forming coating composition is directly added,
Even when applied to microvoid-containing coatings, it is preferred that the gelling material occupy a minimum amount of the void volume. Adding too much gelling material reduces the size of the void to the point where it can effectively diffuse the white light. Jelly material is up to 50% empty
There is no problem in occupying the volume, but preferably 1 to 10
%.

As a general guide to selecting gelling agents and marking liquids that work effectively together, they are illustrated in the table below. Marking liquid gelling agent diethyl phthalate
Cellulose acetate butyrate dibutyl phthalate Same as above Dioctylphthalate Same as above Triacetin Same as above General esters Same as above Isopropanol Carboxypolymethylene water Same as above Ethylene glycol Carboxypolymethylenetetraethylene glycol Same as above General glycols and alcohols
Same as above Dodecene styrene: isoprene: styrene block copolymer undecane Same as above Octane Same as above General branched and linear saturated hydrocarbons Same as above Typically, a marking liquid with the desired development properties is selected and then a suitable gelling agent is selected. is selected.

Having thus described and illustrated the invention, it will be apparent that numerous variations in coating compositions, marking fluids, etc. are within the skill of those skilled in the art.

Product name “Aroplaz”, “Carbopol”,
"Desmodur", "Elvacite", "Methocel" and "Rhoplex" are registered trademarks.

Claims (1)

[Scope of Claims] 1. (a) a base sheet; (b) a solid component provided on at least one surface of the base sheet and a first organic polymer; and said opaque layer does not act as a solvent for the first organic polymer but is intended to represent a colorless liquid having a refractive index similar to that of said solid component. in a sheet material used to apply to the exposed surface of said opaque layer to render said layer partially transparent in accordance with a particular pattern to display a particular pattern; A sheet material characterized in that a second organic polymer having a different compatibility index and becoming jelly-like when in contact with the liquid is incorporated in the opaque layer. 2 (a) a base sheet; and (b) a solid component provided on at least one surface of the base sheet and a first organic polymer, and having interconnected microscopic cavities formed by both. an opaque layer, said opaque layer not acting as a solvent for the first organic polymer but displaying a colorless liquid having a refractive index similar to said solid component according to a particular pattern; , a method for producing a sheet material for use in applying to the exposed surface of said opaque layer to render said layer partially transparent and displaying a particular pattern, said sheet material having a compatibility with said liquid of about 2 Hildebrand different. A method for producing a sheet material, characterized in that a second organic polymer having an index and becoming jelly-like when in contact with the liquid is blended into the opaque layer.