MARKING MATERIALS

Abstract: A marking material comprising an adhesive layer on at least one surface of a base, the base comprising a continuous porous plastic film having an average pore size of 0.2 to 50 gamma m, an air permeability of 2 to 120 sec/100 cc and a thickness of at least 20 mu m.

Description: MARKING MATERIALS Technical Field This invention relates to an improvement in marking materials for decoration and marking used by application to outdoor signs, gasoline tanks for two-wheeled vehicles, vehicular body surfaces and the like. More particularly, this invention relates to an improvement in air-permeable marking materials without causing peeling or blistering, etc. even on evolution of gases (outgassing) from the adherend to be applied. Background Art Prior art air-permeable marking materials are explained by referring to Figures 3 to 7 wherein Figures 3 to 7 are sectional views illustrating conventional air-permeable marking materials wherein 1 is the base; 2 is the adhesive layer; 3 is a hole; 4 is a porous layer; 5 is the adherend; and 6 is the marking. A marking material shown in Figure 3 has a construction wherein an adhesive layer 2 is laminated to a base 1, and venting holes 3 are mechanically or chemically formed therein. A marking material as shown in Figure 4 has a construction, wherein a base 1 is formed from an air-permeable fibrous material. A marking material as shown in Figure 5 has a construction wherein an air-permeable porous layer 4 such as a foam, paper or fibrous material is formed between a base 1 and an adhesive layer 2. (See for example the laid-open publication of Japanese UM application Kokai (laid-Open) No. 90980/84). A marking material as shown in Figure 6 has a construction wherein an adhesive layer 2 is formed from an expanded porous material. Furthermore, as shown in Figure 7, there is an air-impermeable marking material having a construction wherein a base 1 is extremely thick (about 250 μm or above) and the strength thereof is increased to enclose an escaping gas . If a desired marking is provided on the marking material of Figure 3 and has too large a pore size (usually formed by printing methods such as offset, gravure or screen printing, or coating methods such as roll coating or knife coating) , the surface conditions are bad with poor gloss, and the marking material cannot be put to vertical use. If the pore size is too small, pores are filled in forming the marking, and the air permeability is unfavorably inferior. The working of pore size is very difficult with bad workability. In the marking material shown in Figure 4, the base 1 has low mechanical strength and is easily broken. The smoothness of the base 1 is poor, and it is difficult to obtain a glossy marking material. The marking material shown in Figure 5 has porous layer 4 of low mechanical strength which not only tends to cause layer cleavage but also is incapable of outgassing outside, thereby causing blistering, etc. on application to an adherend evolving a great volume of gases (for example application to molded RIM bumpers or FRP plates or application to polyethylene containers filled with gasoline). The marking material shown in Figure 6 not only has a low bonding strength and tends to peel from the adherend but also is incapable of letting a large volume of gases escape to the outside, thereby causing blistering, - etc. in the same manner as the marking material shown in Figure 5. The marking material shown in Figure 7 arouses no problem in a short time after application to an adherend, but there is a problem of rather severe blistering, peeling, etc. with the lapse of time. Summary of the Invention In accordance with the invention, there is provided a marking material comprising an adhesive layer on at least one surface of a base, said base being formed from a continuous porous plastic film having an average pore size of 0.2 to 50 μm, an air permeability of 2 to 120 sec/100 cc and a thickness of at least 20 μm. Thus, the object of this invention is to provide marking materials to which a marking of good appearance conditions can be given without causing problems of peeling, blistering, etc. even on application to adherends evolving a great volume of gases. Brief Description of the Drawings Figure 1 is a sectional view showing the marking material of this invention; Figure 2 is a sectional view of a marking material of this invention, which is given marking and applied to an adherend; Figures 3 to 7 are sectional views illustrating conventional air-permeable marking materials wherein: 1 is the base; 2 is the adhesive layer; 3 is a hole; 4 is a porous layer; 5 is the adherend; and 6 is the marking. Detailed Description Marking materials of this invention are explained by referring to Figure 1. Such materials have a construction wherein a base 1 is formed from a continuous porous plastic film having an average pore size of 0.2 to 50 μm, an air permeability of 2 to 120 sec/100 cc (measured by the Gurley method provided for in the JIS P8117) and a thickness of at least 20 μm, and an adhesive layer 2 contained on one side of the base 1. A release material may be further laminated to the surface of the adhesive layer 2 to facilitate the handling of the marking materials. If the average pore size is smaller than 0.2 μm, the holes are filled by the marking formed on the marking materials, and the air permeability is unfavor¬ ably inferior. If the average pore ' size exceeds 50 μm, poor appearance of the marking is produced, and the material cannot be placed into practical use. The average pore size within the range of 20 to 20 μm is particularly preferred for providing glossy marking while obtaining effective air permeability. If the air permeability (measured in sec/100 cc by the Gurley method provided for in the JIS P8117) exceeds 2 sec/100 cc (the lower value meaning a greater air permeability, and the value exceeding 2 sec/100 cc meaning a smaller value, the surface smoothness of the base 1 is inferior, and poor appearance of the marking is produced. If the air permeability is below 120 sec/100 cc (the numerical value is increased in this case), the air permeability is unfavorably inferior. The air perme¬ ability of 10 to 50 sec/100 cm is more preferred, considering the strength and air permeability performance of the base 1. In the case of marking 6 provided on the whole surface of the marking materials as shown in Figure 2, a number of holes on the surface of the marking materials are filled by the marking 6 (ink or clear coating) to thus reduce the air permeability. However, an escaping gas A evolved from the adherend escapes even from the cut end surfaces of the marking materials. If the thickness of the base 1 is below 20 μm, the area of th cut end surface of the marking materials is small, and the air permeability will be unfavorably inferior. The thickness of the base 1 is preferably in the range of 60 to 200 μm taking into account the stabilized air permeability, economic efficiency and workability, etc. of the marking materials. The base 1 of this invention can be produced by the respective methods of sintering, mixed extracting, phase separation and drawing as disclosed in the post-exam publication of Japanese Patent Kokoku (Post-Exam Publn.) No. 5327/84 and the like, and general-purpose thermoplastic materials such as vinyl chloride, polyethylene, acrylic, urethane and polypropy- lene may be used. An adhesive capable of providing sufficient adhesive force to the base to be laminated to the adherend may be sufficiently used, and a coating thickness within the ordinarily used range provides sufficient air permeability without performing working. Therefore, a general-purpose adhesive such as acrylic, rubber, silicone and the like may be used. Examples The marking materials of this invention are described in more detail by way of the following non-limiting examples. Example 1 To a vinyl chloride organosol (manufactured by Sumitomo 3M Ltd.), was added 20% by weight of ethyl alcohol, and the resulting mixture was stirred with a propeller mixer at 800 rpm for 15 min. The stirred mixture was cast to form a continuous porous base by the phase separation method. An acrylic adhesive having a dry thickness of 30 μm (manufactured by Sumitomo 3M Ltd. ) and a release material were laminated to base 1 to form a marking material. The whole base surface of the resulting marking material was printed with a #3900 series ink manufactured by Sumitomo 3M Ltd. by screen printing. After drying, the printing was similarly coated with "Clear Coating GA-1 1 ® manufactured by Sumitomo 3M Ltd. to a dry thickness of about 10 μm. The resultant marking material was used to carry out the following tests: (a) Blistering test l) A 500-cc wide-mouthed polyethylene bottle manufactured by Sanko Plastic K.K. was filled with gasoline, and sealed, followed by application of the above-mentioned material to the surface of the bottle. The marking material was allowed to stand at 25 C and 65% RH for one month, and inspected visually for blistering. (2) The above-mentioned marking material was applied to an RIM molded article of an automobile bumper (manufactured by Mitsubishi Belting Ltd.) within 24 hours after molding. The resulting molded article was placed in an oven at 80 C for 48 hours and then inspected visually for blistering. Evaluation was made on the following criteria in both tests(T) and( ). (g) No occurrence of blistering Q Occurrence of minute blistering / Occurrence of partial blistering x Occurrence of blistering on the whole surface (b) Appearance conditions The marking surface of the marking material similar to the above-mentioned (a) was inspected by visual examination, and evaluation was made on the following criteria: (g) Very glossy Q Glossy (Good appearance conditions)« Matte x Rough surface (Bad appearance, i.e., without gloss and bad conditions relative to the spread of ink) (c) Surface gloss Gloss of the marking surface of the marking material similar to the above-mentioned (a) was measured at 60 (a digital gloss meter "VG-2P-D3" manufactured by Nippon Denshoku Kogyo Co., Ltd. was used). Results of evaluation of the Example and the Comparative Example are shown in Tables 1 to 3. Table 1 shows evaluation results of tests with varying average pore size at a base thickness of 70 μm and an air permeability of 30 sec/100 cc. Table 2 shows evaluation results of tests with varying air permeability at a base thickness of 70 μm and an average pore size of 10 um. Table 3 shows evaluation results of tests with varying base thickness at an average base pore size of 10 μm and an air permeability of 30 sec/100 cc. Table 1 Results x were obtained in both the blistering tests 1 and 2 of the conventional marking materials shown in Figures 3, 5, 6 and 7 cited above, and results x were obtained in the appearance conditions of the conventional marking material shown in Figure 4 cited above. Table 2 Table 3 Example 2 A continuous porous polypropylene film (manufactured by Sumitomo 3M Ltd.) was used as a base, and the surface of the base was primed with a chlorinated polypropylene (manufactured by Toyo Kasei Kogyo Co., Ltd.). An acrylic adhesive and a release material were laminated to the primed base similarly to Example 1 to form a marking material. Marking was provided on the base in the manner similar to Example 1, and evaluation of the aforesaid blistering tests (respectively collected in one mark since similar results were obtained in (T) and( ~ 2)) , appearance conditions and surface gloss was made. Evaluation results of this Example and a Comparative Example are shown in Tables 4 to 6. Table 4 shows evaluation results of tests with varying average pore size at a base thickness of 80 μm and an air permeability of 38 sec/100 cc. Table 5 shows evaluation results of tests with varying air permeability at a base thickness of 80 μm and an average pore size of 3.2 μm. Table 6 shows evaluation results of tests with varying base thickness at an average base pore size of 3.2 μm and an air permeability o 38 sec/100 cc. Table 4 Table 5 Table 6 As explained above, the base of the marking materials of this invention is formed from a continuous porous plastic film having an average pore size of 0.2 to 50 μm, an air permeability of 2-120 sec/100 cc and a thickness of 20 μm or above, and marking having good matte to glossy appearance conditions can be provided on the base. Furthermore, a marking material having sufficient air permeability can be obtained even if marking is provided all over the surface. Since there is no porous layer between the base and the adhesive layer, the marking materials having a high strength can be provided without causing layer cleavage.

Claims: . . MARKING MATERIALS Claims 1. Marking material comprising an adhesive layer on at least one surface of a base, said base being formed from a continuous porous plastic film having an average pore size of 0.2 to 50 μm, an air permeability of 2 to 120 sec/100 cc and a thickness of at least 20 μm.

Inventors: SASAKI MAKOTO, SASAKI, MAKOTO
Applicants: MINNESOTA MINING & MFG, MINNESOTA MINING AND MANUFACTURING COMPANY
Application year: 1985
Main classification: C09J7
IPC codes: C09J7, G09F3