1. Field of the Invention
This invention relates to a recording material on which a record is made with ink and, in particular, to a recording material adapted for ink jet recording (hereinafter, referred to as "recording paper").
2. Description of the Prior Art
What is called ink jet recording is a means of recording by producing droplets of a recording liquid called "ink" based on various principles of action and causing the droplets to adhere to desired recording paper or the like.
Due to its low noise and capability of high speed and multicolored recording, the ink jet recording method is making rapid progress in recent years.
Meanwhile, the ink jet recording is desired to satisfy in particular the following requirements:
(1) The recording paper quickly absorbs a recording liquid (ink).
(2) When ink dots overlap one another particularly in multicolored or full-colored recording, a later applied ink droplet neither deforms the formerly applied ink dot nor causes it to flow.
(3) The diameter of ink dot on recording paper does not become larger than necessary.
(4) Ink dots have a shape close to a circle and smooth perimeter lines.
(5) Ink dots have a high optical density and distinct perimeter lines.
(6) The recording paper has a high brightness and shows a good contrast with ink dots.
(7) The color of ink does not vary depending upon the type of the recording paper.
(8) Ink droplets scatter around ink dots to the minimum possible extent.
(9) The recording paper does not undergo a substantial dimensional change (e.g. elongation and wrinkling) by recording.
To meet these requirements depends on the characteristics of the recording paper used. However, no recording paper has been found until now that has characteristics satisfies all of these requirements.
For example, Japanese Pat. Laid-open No. 74340/1977 proposed a multicolored ink jet recording paper having a permeability (sec)/basis weight (g/m.sup.2) of 0.3 or less and requiring a time of 2-60 seconds for absorbing 0.004 ml of water base ink. This recording paper is prepared by coating a base paper of about 40-80 g/m.sup.2 in basis weight with an aqueous solution containing oxidized starch and poly (vinyl alcohol), and finishing it with a machine calender after drying. However, the proposed recording paper, though it is capable of absorbing ink rapidly, has disadvantages in that it is liable to extend the diameters of ink dots, gradate perimeters of ink dots, and undergo a significant dimensional change by recording.