JPH06157956A - Recording ink - Google Patents

Abstract

PURPOSE:To obtain a recording ink specified in the penetration amount per sheet of paper, ensuring clear-cut letters free from color boundary blur and feathering to be written on sheets of plain paper with penetration dryability and letter feathering preventiveness compatibilized with each other. CONSTITUTION:This recording ink has >=10mL/m<2> penetration amount per sheet of paper at t<1/2>=0.28sec<1/2> determined by Bristow's method. It is preferable that the upper limit of the penetration amount is 30mL/m<2> and the penetration rate 8-160mL/m<2>.-sec<1/2> at a linear part in the Bristow's method. Ink penetration amount is regulated by incorporating the ink with, e.g. a dodecyl ethylene glycol alkyl ether as penetrating agent or sodium dioctyl sulfocuccinate which allows a greater penetration amount within a shorter time than the alkyl ether. To lower the penetration rate for the purpose of feathering prevention, e.g. sodium polyacrylate is incorporated into the ink.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-based ink for ink jet recording, which can be used as a water-based ink for water-based writing instruments.

[0002]

2. Description of the Related Art Conventionally, the permeation rate into paper is 0.25 m.
^{L / m 2 · ms 1/} 2 or more (in the display unit of the present invention 7.90
^{6mL / m 2 · sec 1/} 2 or more ink has been proposed. However, when this ink is used for printing, a clear image can be obtained with less bleeding and feathering of the character portion, but in the case of color printing, the drying due to permeation is slow, and therefore the second and When the dots of the third color are overlapped, mixed color blur occurs at the color overlap portion and the boundary portion of each color (hereinafter, these are collectively referred to as color boundary blur).

[0003]

DISCLOSURE OF THE INVENTION The present invention has found a permeation characteristic condition of an ink capable of satisfying seemingly contradictory permeation dryness and prevention of feathering of a character portion, and it is clear that there is no color boundary bleeding and no feathering. The present invention is intended to provide an ink capable of forming various characters on plain paper.

[0004]

The constitution of the present invention for solving the above-mentioned problems is a recording ink having a permeation amount and a permeation speed as described in the scope of claims for paper.

FIG. 1 shows the principle of measuring the permeation rate of an ink liquid into paper by the Bristow method. Ink is taken with a 40 μl microsyringe and l (nozzle gap) =
Permeation transfer is performed from a nozzle opening of 1 mm, w (nozzle width) = 1.75 cm onto paper that rotates at a speed of υ (paper moving speed) = 0.5 to 50 mm / sec. At this time, when the transition length is L (cm), the ink penetration amount V is

[0006]

[Equation 1]

[0007] is required.

The transition time t at that time is t = 1 / υ = 1.0 / υ (sec) (2). Lucas-Washburn's relational expression (3) is known as a theoretical expression when ink permeation progresses in a capillary of paper due to ink permeation wetness.

[0009]

[Equation 2]

Γ: radius of capillary tube of paper γ _L : surface tension of ink θ: contact angle of ink with liquid η: viscosity of ink Therefore, it is expected that V is proportional to √t. Actually, due to the roughness of the paper surface, ink transfer occurs instantaneously. If this transfer amount is V ₀ ,

[0011]

[Equation 3]

[0012] next penetration rate is determined to be _{d (V-V 0) /} d√t (mL / m 2 · sec 1/2) (5).

FIG. 2 shows a range in which the print quality is well known [ref. 1] and the proper quality range of the present invention.
√T = In ^{0.3 (sec 1/2),} V = V 0 + (2~
20) (mL / m ² ), d (V-V ₀ ) /d√t=8.0
^{~160.0 (mL / m 2 · sec} 1/2) is preferred. The embodiment (inks B, C, D, G, H, and
I) and comparative examples (inks A, E, F, J) are shown.

[0014]

【Example】

 Examples and comparative examples

[0015]

[Table 1]

[0016]

[Table 2]

Details of the ink formulation are shown below.

[0018]

[Table 3]

The role of each component in this formulation is as follows.

Sodium dioctylsulfosuccinate as a penetrant has a larger permeation amount in a shorter time than dodecylethylene glycol alkyl ether. Therefore, since the drying due to the permeation is fast, color boundary bleeding hardly occurs. However, if it is too much like (Ink-E), feathering will occur.

Also, the penetration rate can be reduced by adding sodium polyacrylate. Therefore, it is possible to prevent feathering from occurring.

[0022]

The effects of the present invention described above are summarized as follows.

[0023] ^{(1) √t = 0.28sec 1/} 2 (t =
A predetermined amount (10.0 mL / m) in a short time of 0.08 sec.
² ) If the above ink is permeated, permeation drying is sufficiently performed, and bleeding at color boundaries can be prevented.

(2) The ink permeation rate is 8.0 (mL /
m ² · sec ^1/2) Slow and the same osmotic drying is slower than, also called feathering occurs caused uneven penetration of larger than 160.0, the lateral ink.
By adequate penetration drying if ^{8.0~160.0 (mL / m 2 · sec} 1/2), no bleeding color boundaries, and can print that does not occur feathering.

[0025] ^{(3) √t = 0.28sec 1/} 2 (t =
If there is a penetration of more than 30.0 mL / m ^{2 in} a short time (0.08 sec), an unclear image will be formed due to feathering of the image and dot thickening. It is good if it is 30.0 mL / m ² or less.

(4) When viewed more strictly, the quality varies depending on the type of paper. Among them, the amount (V ₀ ) transferred to the surface at t≈0 due to the difference in the surface viscosity of the paper is corrected. If the value of (V-V ₀ ) is smaller than 2.0 mL / m ^2, a problem occurs due to insufficient drying. (Vt _{= 0.08-}
It is good if V ₀ ) is 2.0 mL / m ² or more.

[Brief description of drawings]

FIG. 1A is an explanatory diagram of a principle of measuring an ink liquid on paper by a Bristow method. b is a transfer ink pattern obtained by the Bristow method.

FIG. 2 is a graph showing the relationship between √t and the ink penetration amount.

[FIG. 3] Same as above.

FIG. 4 Same as above.

FIG. 5 Same as above.

Claims (4)

[Claims] Penetration amount of the ink to 1. A paper, in √t = 0.28sec ^1/2 in the Bristow's method, 1
A recording ink having a concentration of 0.0 mL / m ² or more. Penetration amount of the ink to 2. A paper, in √t = 0.28sec ^1/2 in the Bristow's method, 3
2. The amount is 0.0 mL / m ² or less.
The recording ink described. Penetration amount of 3. The ink for paper, penetration of the net, excluding the amount of transferring the surface at t ≒ 0 in the Bristow's method is the √t = 0.28sec ^1/2, 2.0~
A recording ink having a content of 20.0 mL / m ² . 4. The permeation rate of ink into paper is 8.0 to 160.0 mL / m ² · in the straight line portion in the Bristow method.
recording ink, which is a sec ^1/2.