Mitsubishi Pencil Kabushiki Kaisha

Tsukasa Felt Shoji Co., Ltd.

Kazumi Goto

Shuji Ichikawa

Hiroshi Sasaki

Shigehiro Sasaki

Provided is an ink composition for osmotic seals, stamp pads or vermilion ink-pads comprising at least one organic solvent selected from the group consisting of glycol ethers, glycol ether acetates, esters and derivatives thereof, a colorant consisting of a pigment and/or a dye, a resin having a solubility of 7% or less in water or ethanol at 25.degree. C. and a fluorinated surfactant, wherein the foregoing ink composition is excellent in a seal sticking property against non-absorbing surfaces, a water resistance and an alcohol resistance so as to be able to stamp on various stamping surfaces such as resin surface, glass surface and metal surface and to be able to stamp certainly even on stamping surfaces having a releasing property or a water repellent property.

Ink composition

An ink composition for writing instruments comprising an organic solvent having an SP value of 5 to 15 and a vapor pressure of 0.01 to 45 mmHg at 20.degree. C., a colorant comprising a pigment and/or a dye, a resin having a solubility of 7% or less in water or ethanol at 25.degree. C. and a fluorinated surfactant, wherein the above ink composition can be used to write on various writing surfaces such as a resin surface, a glass surface and a metal surface, is excellent in a line sticking property against non-absorbing surfaces, a water resistance and an alcohol resistance and can also be used to write certainly even on writing surfaces having a releasing property in a water-repellent property.

Ink composition for writing instrument

A porous rubber stamp material having open cells is here disclosed which comprises a print layer 2 having a spring hardness of 30 to 40 and an ink-occluding layer 1 having a spring hardness of 10 to 20, and preferably, the ink-occluding layer 1 is provided with lugs 3. The porous rubber stamp material of the present invention can overcome faults of a conventional porous rubber stamp material having open cells and permits obtaining a very sharp imprint under any push pressure. Thus, the porous rubber stamp material of the present invention can be used for the continuous sealing of a private seal, an address seal, a date seal and the like.

Porous rubber stamp material having open cells

A process for producing a sponge rubber stamp having open cell of the present invention comprises the steps of superposing an unvulcanized rubber sheet (A) containing a water-easily soluble powder upon an unvulcanized rubber sheet (B) containing an acid-soluble powder, heating/pressing them to form an integral laminate, treating the integral laminate with water to make the layer (A) porous, sculpturing the surface of the layer (B) of the integral laminate by a laser beam to form a stamp surface thereon, and then treating the integral laminate with an aqueous acid solution. No microcracks occur in the stamp at the formation of the stamp surface, and the stamp surface precision and the durability of the obtained stamp are excellent. In addition, the formation of a prototype and a matrix of the stamp as well as the treatment of the stamp can be simplified.

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Yokohama, Japan

Kazumi Goto