1. Field of the Invention
The present invention relates to a material for recording which is suitable to ink jet recording using liquid ink such as aqueous ink or oily ink or solid ink which is a solid at ambient temperature and is subjected to printing after it is melted and liquefied, and, particularly, to a recording sheet which has excellent ink receiving ability and is reduced in bleeding with time.
2. Description of the Related Art
Along with recent rapid development of information industries, a variety of information process systems have been developed. This is accompanied with the development of recording methods and equipment suitable to each information system and these methods and equipment have been put to practical use. Among these recording methods, an ink jet recording method is being widely used in home use as well as in offices because it enables recording in various recording materials and the hardware used in this method is relatively inexpensive, compact and has high soundless characteristics.
Also, along with the recent progress in high-resolution ink jet printers, so-called photograph-like high quality recorded materials have come to be available. In addition, along with the development of hardware (equipment), various recording sheets for ink jet recording are being developed.
The general characteristics required for such recording sheets are, for example, as follows: (1) it must have quick drying properties (the rate of absorption of ink must be high), (2) the diameter of an ink dot must be proper and uniform (any bleeding does not occur), (3) it must have good granularity, (4) the circularity of a dot must be high, (5) the color density must be high, (6) the chroma must be high (the color must not be subdued), (7) the light resistance and water resistance of an image portion must be high, (8) even if it is stored for a long time, it is resistant to the bleeding of an image, (9) it must have high whiteness, (10) it must have high preservation ability, (11) it must have high resistance to deformation and good dimensional stability (curling is sufficiently small) and (12) it has good running characteristics in a hardware.
Moreover, besides the above characteristics, glossiness and surface smoothness are required and it is also required for a printed paper to have a texture similar to a silver salt photograph in applications for photo glossy paper to be used to obtain a photo-like high quality recorded material.
As recording sheets to be used for ink jet recording, those obtained by applying a pigment such as silica and a water-soluble binder to a support made of paper or a plastic film as described in, for example, the respective publications of Japanese Patent Application Laid-Open (JP-A) No. 55-51583, JP-A No. 55-144172, JP-A No. 55-150395, JP-A No. 56-148582, JP-A No. 56-148583, JP-A No. 56-148584, JP-A No. 56-148585, JP-A No. 57-14091, JP-A No. 57-38185, JP-A No. 57-129778, JP-A No. 57-129979, JP-A No. 60-219084 and JP-A No. 60-245588 are known. However, all of these proposed recording sheets have very low glossiness and are unsatisfactory for applications such as photo glossy paper.
Also, recording sheets using a pseudoboehmite sol and a water-soluble binder are proposed in the respective publications of JP-A No. 2-276670, JP-A No. 3-215082, JP-A No. 3-281383 and JP-A No. 6-199035. Although these recording sheets fulfill the requirements as to the gloss characteristics to some extent, there are, for example, the problems that the production cost of the pseudoboehmite is high and it is difficult to prepare a coating solution.
Further, proposed in JP-A No. 4-223190 is ink jet recording paper provided with a recording layer comprising 5 to 20 g/m2 of synthetic silica and polyvinyl alcohol (PVA) on substrate paper coated with 0.1 g/m2 of borax or boric acid. The aforementioned technologies are intended only to improve the film strength of a recording layer reduced in the content of a binder. The recording paper has inferior glossiness and is hence unsatisfactory for applications such as photo glossy paper.
Recording materials using various water-soluble polymers to impart glossiness are proposed. For example, those obtained by applying polyvinyl alcohol, polyvinylpyrrolidone or gelatin to a support made of paper or a plastic film as described in the respective publications of JP-A No. 58-89391, JP-A No. 58-134784, JP-A No. 58-134786, JP-A No. 60-44386, JP-A No. 60-132785, JP-A No. 60-145879, JP-A No. 60-168651 and JP-A No. 60-171143 are known. These recording sheets have superior glossiness, but are inferior in the rate of drying ink and are hence unsatisfactory for applications such as photo glossy paper.
On the other hand, ink jet recording sheets which fulfill the aforementioned requirements as to the characteristics of ink jet recording sheets and as to the production cost are proposed in the respective publications of JP-A No. 7-276789, JP-A No. 8-174992, JP-A No. 11-115308 and JP-A No. 11-192777.
In the above publication of JP-A No. 7-276789, a recording sheet is proposed in which a colorant receptor layer formed of an inorganic pigment fine particle and a water-soluble resin and having a three-dimensional structure having a high void ratio is disposed on a support. This structure is said to ensure that the aforementioned ink-absorbing ability is improved and color mixing bleeding in printing is sufficiently suppressed whereby a high-resolution image can be obtained. This colorant receptor layer may be formed by compounding a large amount of particles having a small size. It is necessary to decrease the amount of a binder used for the formation of a layer so that voids are formed. Therefore, this sheet has the drawback that cracks occur if the coating layer is dried quickly, thereby damaging the transparency and appearance of the colorant receptor layer.
As a method used to prevent cracks of the ink receptor layer, a method in which the viscosity of a binder in a coating solution is increased is proposed in JP-A No. 9-109545. In this method, however, there is the fear of reduced workability and occurrence of uneven coating, showing that this method does not reach a practically effective level.
A method of preventing cracks by using a coating solution comprising an inorganic particle, polyvinyl alcohol (PVA) and boric acid or borate is disclosed in the respective publications of JP-A No. 7-76161 and JP-A No. 10-119423. In this method, also, a large reduction in workability is caused by a rise in the viscosity of the coating solution. This method also poses the problem of the inferior stability of the solution with time and does not reach a practically effective level.
An ink jet recording sheet provided with a colorant receptor layer, which comprises a fine inorganic pigment particle and a water-soluble resin and has a high void ratio, on a support is proposed in the respective publications of JP-A No. 10-119423 and JP-A No. 10-217601.
These ink jet recording sheets have good ink-absorbing ability and high ink-receiving ability enough to form a high-resolution image and exhibits high glossiness due to its structure. However, a support coated with a resin such as polyethylene on both sides thereof is used as the support in view of glossiness and texture, and therefore a high-boiling point solvent contained in the colorant receptor layer is not vaporized and the solvent is not absorbed in the support. Consequently, the high-boiling point solvent remains unremoved in the colorant receptor layer, giving rise to the problem that when the sheet is stored under high temperature and humidity after an image is printed, the solvent is diffused together with a dye in the colorant receptor layer, causing the bleeding of the image with time (hereinafter referred to as xe2x80x9cbleeding with timexe2x80x9d where necessary).
Also, it is widely adopted to add a compound having an amino group or an ammonium salt, especially, a polymer compound containing these group and salt with the intention of fixing a dye component in ink in the ink jet recording sheet.
For instance, many compounds are used, these compounds including (co)polymers of a diallylammonium salt derivative as disclosed in the respective publications of JP-A No. 60-83882, JP-A No. 64-75281 and JP-A No. 59-20696, allylamine salt copolymers as disclosed in the respective publications of JP-A No. 61-61887 and JP-A No. 61-72581, (meth)acrylates having an ammonium salt, (meth)acrylamide type polymers and vinyl (co)polymers such as a vinylbenzylammonium salt (co)polymer as disclosed in the respective publications of JP-A No. 6-340163, JP-A No. 4-288283, JP-A No. 9-300810, JP-A No. 8-318672, JP-A No. 10-272830 and JP-A No. 63-115780, modified polyvinyl alcohol (PVA) as described in, for example, JP-A No. 10-44588, amine/epichlorohydrin co-adduct as described in JP-A No. 6-23468, JP-A No. 11-277888, dihalide/diamine co-adduct as described in JP-A No. 10-119418 and polyamidines as described in the respective publications of JP-A No. 11-58934 and JP-A No. 11-28860. The use of these compounds is to fix a dye and to prevent bleeding.
However, because all of these compounds are water-soluble polymers basically, the water-soluble dye can be incompletely fixed and, particularly, an improvement in bleeding under high temperature and humidity has been insufficiently made yet.
Also, if the sheet is stored in a clear file or the like immediately after an image is printed, bleeding with time likewise occurs because the sheet is in the condition that water in ink and a high-boiling point solvent (glycerin and a diethylene glycol derivative) contained in a small amount in ink remain unremoved.
In the meantime, the ratio of inorganicity/organicity (I/O value) is known as one of indexes showing the magnitude of the polarity of a compound. Also, an index which is the equivalency of an ammonium salt per unit mass of a polymer solid and expressed by meq/g is called cation density. In the aforementioned publications, the ratio of inorganicity/organicity (I/O value) or the cation density (meq/g) is not prescribed in each compound added for the purpose of fixing the aforementioned dye component in ink. However, when such a value is calculated, the ratio of inorganicity/organicity (I/O value) is in the vicinity of 1.5 to 7.0 and the cation density (meq/g) is in the vicinity of 3.2 to 7.0. There is the case where the ratio of inorganicity/organicity (I/O value) is hereinafter simply called xe2x80x9cI/O valuexe2x80x9d.
Like the ink jet recording sheets as described in the respective publications of JP-A No. 57-36692, JP-A No. 10-180034, JP-A No. 11-20302 and JP-A No. 8-244336, ink jet recording sheets which contain an amino group and an ammonium salt like the aforementioned compound and contain a water-insoluble base latex are known. These ink jet recording sheets are improved in water resistance by using the hydrophobic latex.
However, in the ink jet recording sheets using such a hydrophobic latex, the hydrophobic latex must be compounded in a large amount to impart sufficient water resistance, giving rise to the problem that the light resistance of an image and miscibility with a pigment are resultantly impaired.
Also, many of these sheets use a crosslinkable monomer (specifically, a monomer having two or more polymerizable functional groups in its molecule) in order to form a latex of a hydrophilic monomer unit such as an amino group or an ammonium salt. Therefore, aqueous ink has difficulty in penetrating into the monomer particle and the ink-receiving ability is not sufficient. Moreover, in the case of using a receptor layer made of a porous film, the voids of the porous film are clogged, because a granular compound is added, thus inhibiting the ink absorbing ability.
Also, the latex using a crosslinkable monomer in this manner is insoluble in an organic solvent or the like and it is therefore difficult to handle it. In addition, examples of a part of latex using no crosslinkable monomer are known. Even in the case of such a latex compound, there are no descriptions concerning compounds having a low I/O value and a low cation density.
Further, a recording material comprising 1 mass % or more of a monomer unit containing a quaternary ammonium salt and a copolymer which is substantially insoluble in water is disclosed in JP-A No. 1-188387.
Such a compound surely exhibits an I/O value and cation density which are low to some extent. However, the I/O value of the compound used in the recording material is the order of 1.4 to 1.8 and there is no description of compounds having an I/O value lower than the above range and a low cation density. There is also no description concerning such a concept as to decrease the I/O value and the cation density. Further, there is also no description that the frequency of the occurrence of bleeding with time on an ink jet recording sheet is improved by adding such a compound.
Also, an example in which the ratio of inorganicity/organicity (I/O value) is prescribed in a compound is described in JP-A No. 10-217601. In this case, however, only nonionic copolymers other than ammonium salts are prescribed. Also, this method uses a unit having a high I/O value (high hydrophilic properties) as a copolymer unit, which is quite different from the concept intended to decrease the I/O value of the compound.
The inventors of the present invention have noted the inorganicity/organicity ratio and cation density of compounds added to fix the aforementioned dye component in ink to solve various problems in the prior art to thereby attain the following object.
It is an object of the present invention to provide an ink jet recording sheet which is free from bleeding with time and can keep an image stably even if it is stored for a long period of time under high temperature and humidity after an image is printed.
Another object of the present invention is to provide an ink jet recording sheet which can avoid the occurrence of cracks, is strong, has high surface glossiness, possesses high ink-absorbing ability, can form an image with high-resolution and high density, has good color-developing ability and is superior in light resistance and water resistance of an image portion.
The inventors of the present invention have made earnest studies to solve these problems and, as a result, found that these problems can be solved using an ink jet recording sheet having the following structures, resulting in the patent application of this case.
A first aspect of the present invention is an ink jet recording sheet comprising a polymer which contains a quaternary ammonium base in its molecule, of which the ratio of inorganicity/organicity (I/O value) calculated based on an organic conceptual diagram is 1.0 or less and the cation density (meq/g) is 3.0 or less and which is soluble in at least one of water and an organic solvent.
A second aspect of the present invention is an ink jet recording sheet provided with a colorant receptor layer on a support, the colorant receptor layer containing a polymer which contains an inorganic pigment fine particle, a water-soluble resin and a quaternary ammonium base in its molecule, of which the ratio of inorganicity/organicity (I/O value) calculated based on an organic conceptual diagram is 1.0 or less and the cation density (meq/g) is 3.0 or less and which is soluble in at least one of water and an organic solvent.
A third aspect of the present invention is an ink jet recording sheet according to the above aspect, wherein the colorant receptor layer is obtained by applying a first coating solution containing the inorganic pigment fine particle and the water-soluble resin to the support and by applying a second coating solution containing the polymer, at least at one time of (1) a time when the first coating solution is applied, (2) a time during drying the coating layer before the coating layer shows a falling drying rate and (3) a time after the coating layer has dried and formed a coating film.