Recording medium for water-based ink and method for determining ink absorbing characteristic thereof

A recording medium for water-based ink, comprising a paper base, the paper base having a Stöckigt sizing degree of not shorter than 5 seconds and not longer than 50 seconds, and an ink receptive layer formed on a surface of the paper base, the ink receptive layer containing amorphous silica, an adhesive and a substance reactive with an ink colorant, wherein:

• a droplet of 4 μl distilled water dropped onto a surface of the ink receptive layer is absorbed in a first absorbing state of absorbing the droplet at a first absorbing speed (V1) (μl/sec) within one second after the dropping, a second absorbing stage of absorbing the droplet at a second absorbing speed (V2) (μl/sec) for at least 2 seconds after the first absorbing stage, and a third absorbing stage of absorbing the droplet at a third absorbing speed (V3) (μl/sec) after the second absorbing stage and within 8 seconds after the dropping, the droplet absorption in the first to third absorbing stages satisfying the following relationship:
• 0<V2<V3<V1,
• the second absorbing speed (V2) (μl/sec) being higher than 0.01 (μl/sec) and lower than 0.32 (μl/sec), and given that an inflection point from the first to the second absorbing stage is (a), an inflection point from the second to the third absorbing stage is (b), a final point of the third absorbing stage is (c), absorption quantities at the points (a), (b) and (c) are (qa), (qb) and (qc), respectively, and the times up to the points (a), (b) and (c) are (ta), (tb) and (tc), respectively, the absorption quantity (qa) at the inflection point, (a), is not smaller than 1.5 μl and not larger than 2.0 μl and the absorption quantity (qb−qa) in the second absorbing stage is not smaller than 0.3 μl and not larger than 1.0 μl,
• wherein the ink receptive layer has a pHB satisfying the following relationship:
• 5<pHB≦7,
• the paper base has a pHA and the ink receptive layer has the pHB both satisfying the following relationship:
• 1<(pHB−pHA)<4,
• the ink receptive layer has a thickness of not smaller than 25 μm and not larger than 35 μm, and the weight of the paper base and the ink receptive layer is in the range of not smaller than 180 g/m2 and not larger than 300 g/m2.

A recording medium for water-based ink to be recorded using water-based ink containing an anion colorant, the recording medium having on a surface of a paper base an ink receptive layer, the ink receptive layer comprising a porous layer containing an inorganic pigment and a substance reactive with the ink colorant, wherein:

• a droplet of 4 μl distilled water dropped onto a surface of the ink receptive layer is absorbed in a first absorbing stage of absorbing the droplet at a first absorbing speed (V1) (μl/sec) within one second after the dropping, a second absorbing stage of absorbing the droplet at a second absorbing speed (V2) (μl/sec) for not shorter than 2 seconds after the first absorbing stage, and a third absorbing stage of absorbing the droplet at a third absorbing speed (V3) (μl/sec) after the second absorbing stage, the droplet absorption in the first to third absorbing stages satisfying the following relationships:
• 0<V2<V1
• 0<V2<V3,
• the second absorbing speed (V2) (μl/sec) being higher than 0.01 (μl/sec) and lower than 0.32 (μl/sec), and given that an inflection point from the first to the second absorbing stage is (a), an inflection point from the second to the third absorbing stage is (b), a final point of the third absorbing stage is (c), absorption quantities at the points (a), (b) and (c) are (qa), (qb) and (qc), respectively, and the times up to the points (a), (b) and (c) are (ta), (tb) and (tc), respectively, the absorption quantity qa at the inflection point, (a), is not smaller than 1.3 μl and not larger than 2.0 μl, and the absorption quantity (qb−qa) in the second absorbing stage is not smaller than 0.3 μl and not larger than 1.0 μl,
• wherein the ink receptive layer has a pHB satisfying the following relationship:
• 5<pHB≦7,
• the paper base has a pHA and the ink receptive layer has the pHB both satisfying the following relationship:
• 1<(pHB−pHA)<4,
• the ink receptive layer has a thickness of not smaller than 25 μm and not larger than 35 μm, and the weight of the paper base and the ink receptive layer is in the range of not smaller than 180 g/m2 and not larger than 300 g/m2.

A recording medium for water-based ink, comprising a paper base and an ink receptive layer formed on a surface of the paper base, the ink receptive layer containing amorphous silica, an adhesive and a substance reactive with an ink colorant, wherein:

• a droplet of 4 μl distilled water dropped onto a surface of the ink receptive layer is absorbed in a first absorbing stage of absorbing the droplet at a first absorbing speed (V1) (μl/sec) within one second after the dropping, a second absorbing stage of absorbing the droplet at a second absorbing speed (V2) (μl/sec) for at least 2 seconds after the first absorbing stage, and a third absorbing stage of absorbing the droplet at a third absorbing speed (V3) (μl/sec) after the second absorbing stage, the droplet absorption in the first to third absorbing stages satisfying the following relationships:
• 0<V2<V1
• 0<V2<V3,
• the second absorbing speed (V2) (μl/sec) being higher than 0.01 (μl/sec) and lower than 0.32 (μl/sec), and given that an inflection point from the first to the second absorbing stage is (a), an inflection point from the second to the third absorbing stage is (b), a final point of the third absorbing stage is (c), absorption quantities at the points (a), (b) and (c) are (qa), (qb) and (qc), respectively, and the times up to the points (a), (b) and (c) are (ta), (tb) and (tc), respectively, the absorption quantity (qa) at the inflection point, (a), is not smaller than 1.3 μl and smaller than 2.0 μl, the absorption quantity (qb) at the inflection point, (b), is larger than the absorption quantity (qa) in the first absorbing stage and smaller than 2.5 μl, and the absorption quantity (qb−qa) in the second absorbing stage is not smaller than 0.3 μl and not larger than 1.4 μl,
• wherein the ink receptive layer has a pHB satisfying the following relationship:
• 5<pHB≦7,
• the paper base has a pHA and the ink receptive layer has the pHB both satisfying the following relationship:
• 1<(pHB−pHA)<4,
• the ink receptive layer has a thickness of not smaller than 25 μm and not larger than 35 μm, and the weight of the paper base and the ink receptive layer is in the range of not smaller than 180 g/m2 and not larger than 300 g/m2.