CA1186574A - Ink jet recording sheet - Google Patents

Abstract

ABSTRACT

An ink jet recording sheet comprising a paper suppot applied on at least one surface thereof or internally with a composition which comprises an aqueous dispersion of polyvinylpyrrolidone, vinylpyrrolidone-vinyl acetate copolymer or a mixture thereof serving as a binder or sizing agent and a white filler. The white filler is contained in a weight ratio, to the binder, of 10 : 1 to 0.2 : 1 when the composition is applied on the surface of the paper support. When the composition is internally incorporated in the recording sheet, it comprises 10 to 60 parts by weight of the filler and 2 to 20 parts by weight of the binder per 100 parts by weight of pulp.

Description

DESCRIPTI~)~

2 INX JET RECORDING SHEET

3 This invention relates to ink jet recording and more

4 particularly, to recording papers for the ink jet recording.
6 Great interest has recently been attracted to the 7 recording by ink jet systems because of their reduced 8 noises, ease in color recording, possibility of high speed g recording, and utilization of ordinary papers. The ink jet 1~ systems are now bein~ used widely in the field of 11 facsimile, various types of printers and the like~ It is l~ ~enerally accepted that ordinary papers are satisfactorily 13 usable as recording paper for use in the ink jet recording 14 system. However, this does not mean that all the ordinary papers which are widely used at present are usable. In 16 order to obtain recorded matters of more excellent quality, 17 the recording paper itself should meet several requirements 18 which follo~: (l) The paper has an excellent ink 19 receptivity to allow ink dots deposited on the paper surface to be rapidly absorbed in the inside of paper; and 21 (2) The paper can suppress ink dots applied on the surface 22 from running or spreadin~.
23 Tne requirement (l) is the most fundamental one 24 which must be furnished ~7ith ink jet recording papers and '~ .

1 assumes great importance especially when color images are 2 produced by the ink je~ system. This is because in order 3 to produce color images, i~ is necessary to make a variety 4 of colors Erom combinations of yellow, cyan and magenta inks, so that inks of different colors are deposited on the 6 same portion of paper surface, resulting in large amounts 7 of inks per unit area.
8 The requirement t2~ is necessary for 9 obtaining clear recorded matters. By preventing ink dots from spreading, the optical density of recorded matter can 11 be increased. In general, the simplest method of 12 increasing the optical density of recorded matter is to 13 increase the concentration of dye in ink. However, this 14 method has its limit because of the tendency to clog a head nozzle~ Accordingly, it is important that recording papers 16 satisfy the above requirement.
17 Aside from the fundamental reguirements ll) and (2), 18 recording papers should satisfy the following further 19 requirements: (3) The degree of penetration of ink in the direction of depth or in the longitudinal direction is not 21 too great; and (4) The paper has an excellent brightness.
22 The optical density of recorded matter largely depends on 23 the state of the paper surface and if the degree of the 24 penetration in the direction of depth is too great, it is difficult tn make the optical density high.

5~7~

1 The recording paper to be applied in the ink jet 2 recording systen is generally made from bleached chemical 3 pulp to which fillers, dyes and, if re~uired, sizing agents 4 and strength improvers are added~
There have heretofore been proposed several types of

6 papers for ink jet recording. For ins~ance, Japanese

7 Laid~open Patent Application No. 52-74340 discloses an ink

8 jet recording paper which is characterized in that a ratio

9 of an air resistance to basis weight (g/m2)(air resist-ance/basis weight) is below 0.3 and that when an aqueous 11 ink ~or ink jet recording is dropped in an amount of 0.004 12 ml, an absorption time of ink is in the range of from two 13 seconds to 60 seconds. Further, Japanese Laid-open Patent 14 Application No. 52-53012 teaches a method of making recording papers which is characterized by applying a 16 coating to a base paper which has been incorporated with a 17 wet strength improver known per se and which has a Stockigt 18 sizing degree of below l second whereby the resulting 19 surface coated paper has a Stockigt sizing degree of below 3 seconds. In these laid-open patent applications, there 21 are described surface sizing agents including oxidized 22 starch, PVA, galactomannon gum, polyacrylamide, sodium 23 alginate, styrene-maleic acid copolymer, C~IC and other 24 cellulose derivatives, casein, soy bean protein and the like. In addition, there are -- 4 ~

1 mentioned,as sizing additives, hydrophobic materials or 2 latices,rosin and its derivatives, petroleum resins, 3 fumaric acid, maleic acid its derivatives, waxes, synthetic 4 resins, fatty acids, alkylketene dimers and the like, and, as pigment or filler,kaolin, calcium carbonate, aluminium 6 hydroxide, satin white, titanium oxide, and urea formalin 7 organic fillers.
8 Moreover~ there is proposed in Japanese Laid-open 9 Patent Application No. 55-5830 a sheet for ink jet recording which comprises a support and an ink-receptive 11 layer formed on the surface of the support, said sheet 12 having an opacity of 55.0 to 97.5%, an absorptivity of the 13 ink-receptive layer being in the range of 1.5 to 18.0 1~ mm/min. Also, Japanese Laid-open Patent Application No.
55-11~29 teaches a sheet for ink jet recording which has (1) two or more layers, ~2) an opacity of 55.0 to 97.5 17 (3) a top layer with a thickness of 1.0 to 16.0 microns, 18 and (~) an ink-receptivity of the top layer of 1.5 to 5.5 19 mm/min and that of a second layer of 5.5 to 60.0 mm/min.
The ink-receptive layer ~f these sheets is formed of 21 white pigments such as clay, talc, diatomaceous earth, 22 calcium carbonate, calcium sulfate, barium sulfate, 23 titanium oxide, zinc oxide, zinc sulfide, satin white, 24 aluminium silicate, lithopone and the likeO As binder resin, there are mentioned oxidized starch, etherified ~ 3~j~,f~

l starch~ gelatin, casein, carboxymethyl cellulose, 2 hydroethyethyl cellulose, polyvinyl alcohol and SBR latex.
3 we have made an extensive studies of ink jet 4 recording papers which satisfy the afore-mentioned requirements (l) to (4) and found that coating layers made 6 of combinations of sizing agents or binder resins and 7 pigments and fillers which have been known from the prior 8 laie-open patent applications do not show satisfactory g characteristics when applied for such recording purpose.
Especislly, the resins serving as the sizing agent or ll binder play an important role and it has been found that l~ the known resins are unsatisfactory in ink receptivity and ~ thus recorded matter using such resins as a surface coating 14 frequently shows insufficient optical densi~y.
lS It is accordingly an object o~ the present inven~ion 16 to provide an jet recording sheet which shows an improved 17 optical density, when recorded, over prior art 18 counterparts l~ It is another object of the invention to provide an ink jet recording sheet which shows an e~cellent ink 21- receptivity and is able to suppress ink dots from 22 spreading.
23 It is a further object of the invention to provide 24 an ink jet recording sheet which ensures a certain extent 7~

1 of wzter proof and eY.cellent f~stness of light of recorded 2 matter.
3 ~ccordins to the present invention, there is 4 proviaed a recording sheet for ink jet recording which comprises a paper support applied on at least one surface thereof or internally with a co~position characterized in that said compo-7 sition comprises an aqueous di~x~sion of polyvinylpyrroli~one, 8 vinylpyrrolidone-vinyl acetate copolymer or a mixture g thereof serving as a binder or sizing agent and a white filler, a said white filler being used in a weight ratio to 11 said binaer of 10 : 1 to 0.2 : 1 when said composition is 12 applied on the surface of said paper support and said 13 composition comprising 10 to 60 parts by weight of said 14 ~hite filler and 2 to 20 parts by weight of said binder per 100 parts by weight of stock pulp when said composition is 16 applied internally of the recording sheet.

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1 As having described hereinabove, one of features of 2 the present invention resides in use of polyvinyl-3 pyrrolidone (hereinafter abbreviated as PVP) and/or vinyl-4 pyrrolidone-vinyl acetate copolymer ~hereinafter abbreviated as PVP/VAc~. The PVP and PVP~VAc are 6 water-soluble polymers and have a film-forming property.
7 They are industrially applied as cosmetics, medical 8 supplies, adhesives, cleaning agents and soaps, 9 fiber-finishing agents, and inks~ and also in the field of lo lithographic printing and paper. PVP and PVP/VAc which are 11 applied in the field of the paper-making industry are used 12 as a decoloring agent for rags for regeneration, an 13 improver of cellulose paper to improve its tensile 14 strength, and a binder for the specific type of paper made of inorganic flakes or fibers.
16 When applied to inks making use of dyes, PVP renders 17 the dye more readily soluble, serves to prevent gelation, 18 and imparts deep color tone to even inks of low concentration 1~ of dye.
The PVP and PVP/VAc is soluble in water and 21 have generally an average molecular weight of several 22 thousands to several hundred thousands. These polymers may 23 be ones which are prepared by any of know techniq~es.

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l The commercially a~ailable vinylpyrrolidone and 2 vinyl acetate copolymer has a ratio of PV/VAc generally in 3 the range of 70/30 to 30/70.
4 The PVP and/or PVA/VAc is used in the practice of the invention together with a white pigment or filler.
6 Examples of the filler which i5 preferably used in combi-7 nation with the PVP resin or PVP/VAc copolymer as will 8 become apparent from examples appearing hereinafter include g clay, talc, calcium carbonate, calcium sulfate, calcium silicate diatomaceous earth, magnesium silicate, terra abla, ll activated clay, magnesium oxide, magnesium carbonate and 12 aluminium hydroxide. Aside from these, fillers which are 13 ordinarily employed in the paper-making industry such as 14 titanium oxide, silica, aluminium silicate, satin white, zinc oxide and the like may be usable though they are 16 inferior in optical density and the other characteristics 17 to those mentioned above.
18 In one aspect of the invention, an aqueous dispersion 19 of the PVP and/or PVP/VAc and the filler is applied onto at least one surface of paper support. The dispersion can 21 be readily prepared by adding a filler of a powder form 22 to an aqueous solution of the PVP and/or PVP/VAc~ In this 23 case, a ratio of the filler to the resin is generally in 24 the range of lO : l to 0.2 : l, preferably l : l to 0.5:1.
This will be particularly described in examples appearing 26 hereinafter. The aqueous dispersion is applied to a paper ~, J

_ 9 ~ 3~

1 support, which may be any of papers ordinarily employed 2 for ink jet rec~rding purpose, in an amount of 3 to 50 g/m2 3 on the dry basis. Preferably, -the coating amount is in 4 the range of from 10 to 30 g/m and most preferably a~out 20 g/m .
6 In order to improve water proof, the PVP and/or 7 PVP/VAc resin may be admixed with a sizing agent or binder 8 which is ordinarily e~ployed in the pape~-making industry, g including, for example, oxidized starch, PVA, styrene-maleic acid copolymer, C~IC, and 11 hydroxyethylcellulose. When the mixture is used, the PVP
12 and/or PVP/VAc resin should be contained in an amount of 13 not smaller than 33 wt% of the mixture when an added sizing 14 agent shows little or no water absorptivity and in an amount of not smaller than 20 wt% of the mixture when an 16 added sizing agent shows water absorptivity such as PVA.
17 When it is desired to control a hardness of the 18 PVP/VAc film, there may be added to the aqueous dispersion 19 or composition as usual plasticizers such as dimethyl ~o phthalate, glycerine, diethylene glycol, sorbitol ~1 allysulfonamide-formaldehyde, cellulose butyrate, cellulose ~ butyrate-propionate and the like.
23 In another aspcet of the present invention, the 24 aqueous dispersion or composition is mixed with stock pulp ~5 and then an ink jet recording paper is made from the ~6 mixture by any of known paper-making technigues. The paper l incorporating therein the PVP andJor PVP~VAc resin and 2 filler composition h~s several advantages: The making 3 process is simple; and The PVP or PVP/VAc is readily 4 soluble in water and is thus poor in water proof, so that 5 when a PVP or PVP/VAc-coated paper is dipped in water, the 6 coating layer is readily dissolved out but the internally 7 incorporated paper has a certain degree of water proof 8 though the filer is surely come off from the paper when g dipped in water. This is experimentally confirmed that when a surface coated recording paper is vertically dipped 11 in water, a coating layer composed of PVP or PVP/VAc and 12 white filler is come off from the paper support in 5 to 10 13 seconds. On the other hand, even when the internally 14 incorporated recording paper is dipped in water for 10 seconds, only several percent of filler is found to be come lfi off from the paper. In addition, it takes over one minute 17 before the pulp stnck of the paper itself is reduced into 18 pieces and dispersed in water. As a matter of course, such l9 a time varies depending on the amount of PVP or PVP/VAc. A
reason why the water proof is improved by internally 21 applying the composition is believed due to the fact that 22 the resin or binder component is uniformly mixed with a 23 pulp component and thus the speed of infiltration oE water 24 becomes slow and no coating layer is come off as will be experienced in the case of the surface coating.
26 The internally applied recording paper can be made 27 by one step without involving an additional coating process 28 and is thus much simpler in manufacturing step than the 1 surface-coated recording paper~
2 However, the resin and filler are usually in the 3 case in amounts greater than those required for the surface 4 coating technique. That is, as having defined hereinbefore, the PVP and/or PVP/VAc is used in an amount of 2 to 20 parts by weight and a white filler is used in an 7 amount of lO ~o 60 parts by weight both per lO0 parts by 8 weight of s~ock pulp~ The amount of the white filler, of 9 cource, varies ~ore or less depending on the type of the filler.
11 In order to further and much improve the water proof 12 of either type of the recording papers, it is favorable to 13 add to the PVP or PVP~VAc resin binder an aqueous emulsion-type 14 resin or a polymer soluble in alcohol which is capable of forming a water-proof film after drying. Water-soluble resin binders such as oxidized starch, PVA, CMC, 17 hydroxyethyl cellulose and the like serve to improve the 18 water proof as having described hereinbefore when u~ in combination 19 with PVP of PVP/VAC but are not potential for such purpose. For ins~ance, the coating layer obtained from the mixture of 21 the water-soluble resin binder and PVP or PVP~VAc is 22 dissolved in water in about lO to 15 seconds and an 23 increasing amount of the water-soluble resin binder gives 24 an adverse influence of ink receptivity.
Examples of the aqueous emulsion useful in the - 12 ~

1 practice of the invention are those of polyvinyl acetate, 2 ethylene-vinyl acetate copolymer (having an e~hylene 3 content of below 30%), acrylic esters,water-soluble shellac ~ the 4 like. Examples of polymers soluble in alcohol include polyvinyl butyral, polyacrylamide, polyamide-epichloro-6 hydrin, shellac, polyvinyl acetate and the like.
7 These resins are capable of forming films of relatively good water proof after drying. The amount of these resins 9 vary depending on the type of resin and other factors including the type and amount of filler and the thickness 11 of coating layer, but is generally in the range of 1 to 50 12 wt%, preferably 2 to 20 wt3, of a mixture of the resin and 13 PVP or PVP/VAc.
14 In addition to these resins, various additives may be added to the PVP or PVP/VAc and filler. In particular, the 16 resistance or the fastness to light of recorded matter is 17 one of important problems to solve.
18 Thenr we have made an intensive study vn the light 19 fastness or resistance. The most general way of improving the fastness to light of recorded matter is to use dyes which are 21 excellent in fastness to light. However, since inks to be 22 employed in the ink jet recording system are required not 23 to cause clogging of ink jet nozzles and to have a clear 24 color tone, dyes with excellent light fastness cannot always be employed. Basic dyes, acid dyes, or mordant dyes are - 13 - ~

1 clear in color tone and are now widely used for the ink jet 2 recording purpose but these dyes are not necessarily 3 excellent in light fastnessO
4 The improvement of light fastness of recorded matter c~n be reali~ed by adding to the aqueous dispersion or 6 composition of PVP and~or PVP/VAc and filler (1) 7 antioxidants, (2) UV absorber and (3) metal oxides, metal 8 chlorides or tannic acid capable of reacting with dyes to 9 convert the dyes into light-fast dyes.
Q During the course of our study, we have found that 11 though the light fastness more or less depend on the type 12 of dye, the light ~astness of recorded matter is poorer 13 than that of dye in liquid state and the fading is mainly 14 caused by photooxidation based on oxygen in air and light.
To prevent this, antioxidants have been found to be effective. Moreover, an investigation was conducted 17 to know the mechanism of the fading in relation to wavelength.
18 That is, glass filters were used to select desired ranges of 19 wavelength and a Xenone fade meter was used to measure the resistance to light of recorded matter. As a result, it 21 was found (1) that little fading took place in the wavelength 22 range of infrared rays, (2) that in the range of visible 23 light, fading occurred in a wavelength corresponding to a 24 main absorption peak of dye; (3) that fading by the ultraviolet light was as great as in (2).

1 For ins~ance, a magent~ ink composed of 79~ of 2 water, 20% of e~hylene glycol and 11% of ~asic Violet 3 showed light resistance as follows.

Wavelength (mn) Lowering Rate of Excitation Purity -6 Relative Value of Irradiation Energy 8 250 - 320 2.3~
9 320 - 380 1.~5 440 - 520 0.97 11 520 - 620 2.~2 12 Over ~20 0.024 14 From the results, it was considered that UV
absorbers were efective to prevent fading of recorded ?6 matter, which was experimentally found ture.
17 These antioxidants, UV absorbers, and compounds 18 capable of converting dyes into light-resistant dyes or 1~ pigments are used in amounts of 0.1 to 10 wt% of a mixture of the PVP or PVP~VAc and f.iller. These additives are 21 discussed in examples.
22 Then, the present invention is particularly 23 described by way of examples, which should not be oonstrued 24 as limiting the present invention.
It will be noted here that four types of PVP were 1 used having average molecular weights of 360,000 2 (hereinafter referred to as ~-90),160,000 (hereinafter 3 referred as K-60), 40,000 (hereinafter referred to as ~-30 4 and 10~000 (hereinafter referred to as ~-10) but little or no substantial difference in recording characteristics was 6 observed among them and K-~0 was used as the represer.tative 7 of PVP in examples. In addition, four types of PVP/~Ac B having VP/V~c ratios of 70/39, 60/40, 50/50 and 30/70, 9 respectively, were used to check recording characteristics.
As a result it was found that good results were obtained in any 11 cases withoug showing any significant differences among 12 them. Accordingly, a PVP~VAc resin having a VP/VAc ratio 13 f 50/50 was used in examples as the representative for the 11~ PVP/VAc.
The ink jet recording was carried out using an On-demand-type head with a diameter of no~zle of 40 microns 17 in which three ink jetting heads were used to discharge 18 therefrom different types of inks including _cyan, yellow and magenta.
19 ~y the combination of these inks, different colors of red, Z0 green, blue and sepia were made. The discharge of ink was 21 changed in seven stages by controlling an application 22 voltage and the recording of 6 lines/mm was conducted. In 23 the case of monochrome, amounts of discharge per unit area 24 in the respective stages are 2.6 x 10 4 cc/cm2 in first stage, 4.7 x 10 4 cc~cm2 in second stage, S.~ x 10 4 cc/cm2 p~

~ 16 -1 in third stager 7 0 x 10 cc/cm2 in fourth stage, 7.9 x 10 4 2 cc/cm2 in fifth stage, 8.7 x 10-4 cc/cm2 in sixth stage, 3 and 9.4 x 10 cc/cm2 in seventh stage, respectively. In 4 the case of blue in color, the amounts of discharge in the respective stages become double and in the case of sepia 6 color, they become ~hree times. Accordingly, the severest 7 recording conditions are those for the sepia color in the 8 seventh stage. Aside from these recordings, a recording of 9 2 lines/~ was also conducted for comparison.
Recorded matters were evaluated according to the 11 following measurements or observations~ easurement of 12 optical drensity of the respective colors in the seventh 13 staye; ~) Judgement of a stage of sepia color where 14 inks start to run or spread so as to check a degree of the running or spreading of the inks (which show a degree 16 of ink receptivity of paper); (3) ~l~ uremen-t of a time before the 17 sepia color of the seven-th stage is apparently dried after 18 application thereof; and (4) ~easurement of a rate of area 19 of recorded matter of the first stage in which two lines~mm were recorded (to know a degree of spreading of ink dots or 21 a degree of so-called sharpness.
22 Example 1 23 In this example, calcium carbonate was used as a 24 white pigment and different types of binder resins were 2~ used including PVP and PVP/VAc to be used in the present 1 invention.
2 To a 5% aqueous solution or dispersion of each 3 binder resin was added 15 wt% of calcium carbonate of a 4 powder form having a size of 0.1 to 0.2 microns, followed by fan agitating to give a slurry. This s:Lurry was applied 6 onto a commercially available groundwood paper by means of 7 a wire bar, followed by roll pressing to obtain a surface-8 coated paper. The coated layer had a thickness of 5 to 9 20 microns, i.e. 0.3 - 2.0 g of the coating was applied onto an A-4 size paper.
11 The respective recording papers thus made were 12 subjected to the recording procedure and evaluated 13 according to the measuring methods described hereinabove.
14 The test results are shown in Table 1.

Table 1 _ . ~
Stage Optical where Drying Rate of Binder resin density spreading time area (%) starts to (seconds~
appear PVP 1.03 ~7 ~10 14,4 PYPJVAc 0.99 >7 <10 14.8 Oxydized 1.14 4 180 11.2 starch Polyacryl- 0.52 2 200 20.5 amide PVA 0.96 6 60 15.0 Sodium 0.83 9 180 20.1 alu~inate Styrene- 0.78 q 250 22.2 maleic acid copolymer C~IC 0.87 5 220 17.6 Casein 0.82 3 320 13.2 Soybean 0.72 3 300 14.6 protein Gelatin 0.83 5 290 21.5 SBR latex 0.69 4 450 18.9 Hydroxyethyl 0.85 6 80 18 r 2 cellulose Etherified 0.69 5 170 17.6 starch _, .

In this table, the optical density was determined - 13 ~ 5'~

1 with respect to the magenta color of the seventh stage and 2 other six colors showed a similar tendency.
3 As will be clearly seen from the results of Table 1, 4 the binder resin gives a great influence on the characteristics of ink spreading, drying t~ and-~e like ~
the PVP/VAc resins involve no spreading or running at the 7 seventh stage and are thus much more excellent than the 8 other binder resins. PVA and hydroxyethyl cellulose rank 9 second to PVP and PVP/VAc with respect to optical density but these resins were infe~ior in spreading 11 characteristic, i.e. spreading occurred at the 12 sixth stage, and required a drying time of as long as 60 to 13 80 seconds. As to the optical density and rate o areat 14 oxidized starch was excellent and PVP and PVP~VAc showed such characteristics next to oxidized starch.
Example 2 17 In this example, PVP and PVP/VAc were used as a 18 binder resin and different types of white pigments were 19 used in combination for comparative purpose.
To a 10~ aqueous solution of PVP or PVP~VAc was 21 added each of white pigments to be tested to give a slurry 22 in the same manner as in Example 1 and the slurry was 23 applied in the same manner as in Example 1 to obtain a 24 surface coated paper. The type and amount of white pigment and the results of recorded matter are shown in Table 2 below with regard to the PVP binder resin.

- ~o -s~
Table 2 -White Stase pigment Optical where Drying Rate of Whitely (amount density spreadin~ time area fading by wt.) ,tarts to (seconds) (%) phenomenon appear clay 1.11 6 15 13.7 no (20%) talc 1.00 >7 <10 11.5 no (~0%) calcium 1.11 >7 <10 14.9 no carbonate (20~) calcium 0.97 >7 <10 12.0 no sulfate (20~) calcium 0.97 >7 <10 10.4 no silicate ~lno diato- 0.98 7 <10 16.5 no maceous earth (15~) aluminium 0.92 7 14 13.9 no hydroxide ~20~) titanium 0.85 6 15 14.8 yes oxide t20%) silica 0.82 7 20 14.5 yes (20~) aluminium 0.87 7 20 10.9 yes silicate ~20%) satin 0.80 7 15 11.7 yes white (20-) ~inc 0.87 7 15 13.9 yes oxide (20%) 1 As will be appreciated from the results of Table 2, 2 with -~itanium oxide, silica, aluminium silicate, satin 3 white and zinc oxide, there appears a whitely fading 4 phenomenon where an entirety of image is observed as white and the optical density does not become higher than 0.9.
6 This is because an ink does not remain on the surface of 7 th~ coated paper and the white pigment deposits out on the 8 paper surface. In contrast thereto, clay, talc, calcium 9 carbonate, calcium sulfate, calcium silicate, diatomaceous earth and aluminium hydroxide show no fading phenomenon 11 and optical densities of above 0.9. The white pigments 12 causing the fading phenomenon cannot be used in large 13 amounts and do not show an effect of increasing the whiteness 14 of paper though usable in the practice of the invention.
In this sense, the white pigments showing no fading 16 phenomenon are conveniently and preferably used. Preferable 17 pigments further include magnesium silicate, terra abla, 18 activated clay, magnesium oxide and magnesium carbonate.
19 As regards the spreading characteristic and drying time, there is not a significant difference depending on the type 21 of pigment, revealing that such characteristics are mainly 22 dependent of the type of binder.
23 In Table 2, the binder used was PVP and similar 24 results were obtained when PVP/VAc was used except that the optical density was reduced by about 0.5 in all the cases.

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Example 3 In this example~ PVP was used as binder resin and calcium carbonate, calcium silicate and talc ~Jere used as pigment to determine an effect of a ratio by weight of the binder and the white pigment on the recordi.ng characteristics. The coated paper ~as made in the same manner as in Example 1. In Table 3, there are shown results of 2 test using calcium carbonate.

Table 3 _ .
Stage Whitely where Drying Rate of fading PVP Calcium Optical spreading time area pheno-~%) carbonate density starts to ~seconds) ~%) menon appear . .
2 20 0.857 15 14.8 yes 0.98>7 ~10 16.3 no 1.11>7 <10 13.0 no 1.19>7 <10 12.2 no 1.24>7 <10 6.5 no 1.12>7 <10 9.7 no 0.97>7 <10 11.6 no 0.84>7 <10 1~.8 no 2 0.75>7 ~10 20.0 no 1 0.58>7 <10 32.0 no ~ 23 ~

1 As will be clear from the results of Table 3, high 2 optical density cannot be obtained when amo1mts of PVP
3 and calcium car~onate are too great or too small. That is, 4 in order to obtain good recording characteristics, a PVP/calcium carbonate (with an average size of O.l to 0.2 6 microns) ratio by weight is preferably in the range of lO :
7 l to 0.25 : l. When a similar test was conducted using a 8 calcium silicate powder having an average particle size of 9 O.l micron and a talc powder having an average size of 0.2 to 0.3 microns, it was found that a preferable weight ratio 11 was in the range of lO : l to 0.5 : l for calcium sllicate 12 and 5: l to 0.~ : l for talc. The weight ratio is, of 13 course, dependent on the size of white pigment and the 14 weight ratio of PVP or PVPJVAc and a white pigment is conveniently in the range of lO : l to 0.2 : l.
Furthermore, when the composition comprising calcium 17 carbonate and PVP was applied in different thicknesses 18 ranging from 4 microns to 28 microns, no significant 19 difference in recording characteristics was found in this range of thicknesses.
21 In addition, four types of paper support showing 22 different water absorptivities were used to check their 23 influence on the recording characteristics. As a result, 24 it was found that when the coated layer had a thickness of above 8 microns, inclusive, good results were obtained in _ ~4 - ~ ~3~ ~ 7 1 any cases.
2 From the above, the coated layer should preferably 3 have a thickness of 8 microns or more, and the coating com-4 position of the invention can be widely applied to a wide variety of paper supports.
6 Example 4 7 In this example, PVP and other binder resins were 8 used in combination. As a white pigment, talc (Chinese 9 talc) were used. Amounts of the binder resin and talc were, respectively~ 20%. Coated papers were made 11 substantially in the same manner as in Example l, with the 12 results summari~ed in Table 4 below.

~4 18 ,-19 "' 2~

~ 25 Table 4 Stage Weight Optical where Drying Rate of Binder resin ratio density spreadin~ time area starts (seconds) ~%) appear PVP~PVA 1/1 0.94 '7 <10 12.9 PVP/PVA 1/2 0.94 >7 13 12.5 PVP/PVA 1/5 0.92 7 40 12.7 PVP/oxidized 1/1 1.10 >7 :24 10.
starch PVP~oxidized 1/2 1.05 7 53 11.8 starch PVP/oxidized 1/5 0792 5 190 13.0 starch PVP/styrene- 1/1 0.86 7 50 15.5 maleic copolymer PVP/styrene- 1/2 0.86 7 62 16.9 copolymer PVP/styrene- 1/5 0,89 5 280 22.0 copolymer PVP/- 1/1 0.93 >7 1~ 13.7 hydroxyethyl cellulose As will be appreciated from the above results, binder resins such as PVA, oxidized starch and the like show more excellent ink receptivity when applied in combination with PVP.
greater amount of PVP is desirable in view of ~he 1 ink receptivity, Though the conten~ of PVP depends on the 2 type of the second binder, it is in the range of over 20 wt~
3 when the binder resin used in combination with PVP shows 4 water absorptivity such as PVA and in the r,ange of 33 wt%
when the second binder resin shows no water absorptivity.
6 Example 5 7 In this example, characteristics of ink jet 8 recording papers made by a size press technique are 9 aescribed.
Different types of binder and calcium carbonate were 11 mixed in a ratio of 1:1 in an aqueous medium to obtain 10%
12 slurries. Each slurry was coated on a commercially 13 available ~roundwood paper by a size press system to obtain 1l~ a surface coated paper with a coating spread of 4.0 g/m2.
The results are shown in Table 5 below.

Table 5 Stage ~eight Optical where Drying Rate of Binder resin ratio density spreading time area starts (seconds) (%) appear PVP 1.18 >7 <10 11.0 PVP/VAc 0.98 >7 <10 13.0 PVP/PVA 1/1 0.~6 >7 18 14.7 PVP/- 1/1 1.14 7 20 12.5 oxidized starch - 27 ~

1 From the above results~ i~ will be seen that ~he 2 characteristics of the recording papers made by the size 3 press technique are substantially the same as those of the 4 recordins papers obtained by the wire bar~ For instance, the recording paper of the coated type using PVP/VAc as 6 binder had an optical density of 0.99, a spreading stage 7 of >7, a drying time of <lO, and a rate of area of <lO as 8 shown in Table l, which are almost the same as those of 9 Table 5. In the PVP/PVA and PVP/oxidized starch systems, the recording characteristics are almost the same as those 11 of Table 4. ~ccordingly, the size press technique can be 12 used similarly with the surface coating method.
13 Example 6 14 In this example, binder resins and calcium carbonate used as white pigment were applied internally or mixed with pulp.
t7 LBKP and NBKP were mixed in a ratio of l : 2 and 18 beaten in a refiner. Then, light calcium carbonate was 19 added to the pulp in an amount of 30 parts by weight per lO0 parts by weight of the pulp and PVP or ~VP/VAc was 21 added in an amount of ranging from 0.5 to 30 wt% based on 22 the pulp. The pulp composition was subjected to a 23 paper-making process using a Fourdriner test machine -to 24 make a paper with a basis weight of 70 g/m2~ The thus made papers were each subjected to the calender rolls to give - ~7 -recording papers.
The recording papers ~ere applied with in};s and evaluated in the same ma~er a~ described hereinbefore, with the result shown in Table 6 below.

Tabl e 6 Stage Amount Optical where Drying Rate of Binder resin (~) density spreading time area starts to(seconds) (%) appear PVP 0.5 0.80 6 lS 19.3 PVP 1 0.85 7 10 17.5 PVP 2 0.96 ~7 <10 15.6 PVP 5 0.98 >7 <10 15.4 PVP 10 1.00 ~7 <10 15~0 PVP 20 1.00 >7 <10 15.}
PVP 30 1.01 ~7 <10 15.3 PVP/VAc 0.5 0.72 5 20 20.1 PVP/VAc 1 0O82 6 15 17.9 PVP/VAc 2 0.92 7 10 16.1 PVR/VAc 5 0.95 >7 10 16.0 PVP/VAc 10 0.98 >7 <10 15.9 PVP/VAc 20 0.98 >7 ~10 15.9 PVP/VAc 30 0.98 >7 <10 15.5 1 In the table, the optical density is obtained 2 from the magenta color of the seventh stage and as regards 3 the other six colors, a similar tendency is observed.
4 As will be appreciated from the above results, where the binder content is 0~5% or 1%, the optical density, 6 stage where spreading appeared, drying time and r~te of 7 area are not satisfactory. Accordingly, the binder resin 8 should be contained in an amount of at least 2~ of the 9 pulp. This is much larger as compared with an amount of an strength improver ordinarily employed in the paper-making 11 industry (generally in the range of 0.2 to 1 wt%). On the 12 other hand, the recording papers in which 30% of PVP or 13 PVP~VAc based on the pulp is contained show excellent 14 recording characteristics but become sticky to the touch.
In addition, such papers show a blocking tendency.
16 Gathering the above, the content of PVP or PVP/VAc 17 is in the range of 2 wt% to 20 wt~ of the pulp.
18 Example 7 19 In this example, an amount of PVP was set at 10~ by weight of pulp but an amount of calcium was changed.
21 Recording papers were each made and evaluated in the same 22 manner as in Example 6. The test results are shown in Tabe 23 7 below.

_ 30 ~ 7 Table 7 Stage Amount Optical where Drying Rate of White filler (%) density spreading time area starts to (seconds) (%) appear _ _ _ _ _ _, _ calcium 3 0.83 7 20 21.0 carbonate 0.91 7 15 16.5 " 10 0.96 >7 '10 15.2 1.01 >7 <10 14.9 1.00 >7 <10 15.0 0.97 >7 <10 14.1 ~ 60 0~83 >7 <10 12~
n 70 O. 45 >7 <10 10.3 As will be apparent from the above results, good recording characteristics are obtained when the content o the white filler is in the range of 10 to 60 wt% of the pulp. 1ess contents are disadvantageous in that the optical density is poor while larger contents lead to the whitely fading phenomenon. Accordingly, an effective amount of calcium carbonate is in the range of 10 to 60 wt% of the pulp. In this connection, the content of calcium carbonate more or less depends on the content of PVP,e.g. when the content of PVP is 2%, the upper limit in content of calcium carbonate was found to be 40%. Similar 1 results were obtained ~7hen PVP/VAc was used instead of PVP.
2 The above procedure was repeated using other several 3 white pigments in different amounts. As a result~ it was 4 found that a suitable content of clay was in the range of l0 to 60 wt% of the pulpi that of talc ranc~ed from lU to 60 6 wt~, that of calcium sulfate ranged from 5 to 40 wt%~ that 7 of calcium silicate ranged from l0 to 40 wt%, that of 8 diatomaceous ear~h ranged from l0 to 60 wt%, that of satin 9 white ranged from 5 to 50 wt~, and that of zinc oxide ranged from 15 to 40 wt~. Generally speaking, white 11 pigments are effectively usable in tha range of l0 to 60 12 wt~ of pulp. Other usable white pigments in this internal 13 application te~hnique are aluminium hydroxide, silica, 14 aluminium silicate, magnesium silicate, terra abla, activated clay, magnesium oxide, magnesium carbonate, 16 aluminium oxide and the like. Among the white pigments, 17 preferable ones are those mentioned with respect to the 18 surface coating method.
l9 The following three examples illustrate water proof, film-forming resins added to the basic composition used in 21 the present invention.
2~ Example 8 ~3 In this example, binder resin made of 90 parts by ~4 weight of PVP and l0 parts by weight of different types of film-forming polymers were used.

- 32 ~ 5'~

1 To 10~ aqueous or alcoholic solutions of various 2 binder resin mixtures was added calcium carbonate powder 3 with a slze of 0.1 to 0.2 microns in an amount of as great 4 as three times the binder resin mixture, followed by agitating with a fan to give slurries. Each slurry was 6 applied onto a commercially available groundwood paper by a 7 wire bar and the thus applied paper was roll pressed to 8 obtain surface coated papers. The thickness of the coated 9 layer was in the range of 5 to 20 microns. The thus obtained papers were recorded and evaluated in the same 11 manner as in Example 1 except for water proofO That is, ~2 the water proof was evaluated as follows: a time before 13 the coated layer was completely separated from a coated 14 paper specimen with a siæe of 1 cm x 2 cm after having immersed the coated paper vertically in water was measured.
16 The test results are shown in Table 8 below.

- 33 ~

Table 8 .~
Stage ~inder resin Optical where ink Drying :Rate of Water mixture density spreading time area proof starts to (seconds~ (%) appear -PVP 1.03 >7 <10 14.~ 5 PVP~VAc 0.99 >7 <10 14.8 5 PVP+oxidiz- 1.11 >7 14 10.0 7 ed starch PVP+PV~ 1.00 >7 10 12.2 5 PVP+hydro- 0.98 ~7 12 13.1 5 xyethyl cellulose PVP+poly- 0.95 7 15 1~.5 25 vinyl acetate PVP~ethyl- 0.94 7 19 13.9 30 ene~vinyl-acetate copolymer PVP+acrylic 0.97 7 17 13.9 25 ester resin PVP+water- 1.01 7 13 12.8 40 soluble shellac PVP+ poly- 0.98 7 15 14.5 35 vinyl butyral*
PVP+poly- 0.95 7 14 14.3 20 acryl-amide*
PVP~poly- 0.93 7 14 13.9 25 amide-epi-chloro-hydrin*
PVP-~ 1.00 7 13 14.5 60 shellac* _ __ Note: These resins were dissolved in methanol.

1 From the above results, it will be appreciated ~at when 2 PVP or PVP/VAc is used singly, the water proof is 5 seconds 3 or lessO In addition, s~stems of PVP or PVP/VAc to -~7hich 4 other water~soluble polymers such as oxidized starch, PVA
and hydroxyethyl cellulose have been added show a sligh~
6 improvement in water proof. On the other hand, binder 7 resin mixtures in which l0 wt% of aqueous emulsion~type 8 polymers such as polyvinyl acetate, ethylene-vinyl acetate 9 copolymer, acrylic ester resin and water-soluble shellac show a water proof of over 25 seconds, thus improving the water 11 proof remarkably. These binder resin mixtures are 12 slightly inEerior in recording characteristics, i.e. the 13 spreading stage of seven and a drying time of 13 - l9, to 14 the PVP or PVP/VAc resin alone. However~ these slight degrees of deterioration of the characteristics are almost 16 negligible and the improvement in water proof is much more 17 effective. Similar results are obtained when polyvinyl 18 butyral, polyacrylamide, polyamide-epichlorohydrin, shellac 19 and the like are used as dissolved in methanol solvent.
Aside from the resins mentioned above, other resins 21 are also usable in combination with PVP andfor PVP/VAc 22 including vinyl acetate-acrylonitrile complymer, styrene 23 resin, styrene-acrylonitrile copolymer, methacrylic ester 24 resin, polyamide resin, melamine resin, melamine-urea resin and the like.

- 3~ -Example 9 In this example, an influence of polyvinyl acetate in a binder resin composed ~f PVP and polyvinyl acetate was checked. To an aqueous 10~ solu~ion of the binder resin was added talc (Chinese talc) in an amount of two times the binder resin to gi~e a slurry~ Then, Examle 8 was repeated with the results shown in Table 9.

Table 9 Stage Weight Optical where ind Drying Rate of Water Binder resin ratio density spreading time area proof starts to (sec) (~
appear .
PVP/poly- 9~2 1.0~ 7 10 14.75 vinyl acetate " 95/5 1.02 7 12 14.318 n 30/10 0.97 7 15 14.825 n 80/20 0.98 7 19 14.233 n S0/40 0~95 7 20 14.245 n 50/50 0.95 6 23 14.760 40/60 0.93 5 49 15.2100 n 20/80 0.93 5 125 16~.6 120 ~ ~5 ~

1 As will clear from the above results, the proof t~
2 water is more i~proved as the amount of polyvinyl acetate 3 is increased. However, the oPtical density, spreading 4 characteristic and drying time become more deteriorated ~7ith an increasing a~ount of polyYinyl acetate~ For 6 instance, the drying time is 49 seconds for the binder 7 system of PVP/polyvinyl acetate = 40/60. This time is 8 longer than a time of from completion of image formation 9 till withdrawal of the recorded matter from a machine and is not thus practical. Taking the above into 11 consideration, a maximum amount of polyvinyl acetate should 12 be 50%, i.e. it is necessary that polyvinyl acetate does 13 not exceed that of PVP. On the other hand, the binder 14 system containing 2% of polyvinyl acetate does show little effects and thus polyvinyl acetate should be over 2%.
16 The above procedure was repeated using different 17 types of film-forming and water-proof polymers to determine 1B the range of addition of each polymer which may more or 19 less depend on the type and amount of white pigment, and thickness of the coated layer. The results are shown in 21 Table l0.

,7 ~
Tabl e 10 .. .. , _ Binder resin Possible range of addition PVP/ethylene vinyl acetate copolymer 98/2 - 60/40 on a wei gh t bas i s PVP/acrylic ester resin 98/2 - 60/40 PVP/water shellac 99/1 - 70/30 PVP/polyvinyl ~utyral 49/l - 70/30 PVPpolyacryla~ide 93/1 - 70/30 P~P/polyamide-epichlorohydrin 99/1 - 60/~0 PVP/shellac 99/1 70/30 PVP-VAc/polyvinyl acetate 98/2 - 50/50 PVP-VAc/ethylene-vinyl acetate 98/2 - 60~40 copolymer PVP-V~c/acrylic ester resin 9a~2 - 60~40 PVP-V`Ac/water shellac 99/1 - 70/30 PVP-VAc/polyvinyl butyral 99/1 70/30 PVP-VAc/polyacrylamide 99/1 - 70/30 PVP-VAc~polyamide-epichlorohydrin g9/1 - 60/40 PVP/shellac 99/1 - 70/30 From the above results, it is generally possible to use these water proof-impar~ing resins in the range of 1 to 50 wt~ of the mixture with PVP or PVP/VAc provided that the type and amount of white pigment and the thickness of the coated layer are properly controlle~.
Example 10 In this example, characteristics of ink jet ,7 - 38 ~

recordin~ papers made by the size press technique are shown .
Various binders (PVP : additive polymer = 90 : 10) an~ calci~m carbonate were mixed in a ~eight ratio of l : 2 to ~ive 10% slurries. Each slurry was applied onto a commercially vailable groundwood paper by the si~e press method in an amount of 4.0 g/m2 on a dry basis to give a surface coated paper. The thus obtained coated papers had recording characteristics shown in Table ll.

Table ll Stage Optical where ink Drying Rate of Water ~inder resin density spreading time area proof starts to (seconds) (%) ~seconds) appear PVP 1.04 7 1~ 1~.2 5 PVP/VAc 1.00 7 10 14.6 5 PVP/poly- 0.g5 7 14 1~.3 31 vinyl acetate PVP/- 0.98 7 20 14.0 23 acrylic ester resin P~P/poly- 0.97 7 15 lg.3 40 vinyl butyral PVP/water 1.01 7 15 13.0 45 shellac PVP/ethyl- 0.94 7 l8 14.5 35 ene-vinyl acetate copolymer PVP VAc/- 0.93 7 17 14.8 40 polyvinyl acetate 1 As will be clearly seen from the above results, the 2 characteristics of the recording papers made by the size 3 press method are excellent similarly to those of the 4 recording papers made by the wire bar coating method~ As for the water proof, the recording papers made by the size 6 press method are slightly superior to those obtained by ~he 7 wire bar coating method. Thus, the size press technique 8 can be used similarly with ~ surface coating method.
9 The ~ollowing examples deal with the manner of imparting light resistance to recorded matter in which 11 antioxidants, Ultraviolet absorbers and compounds capable 12 of reacting with dyes for convertion into light-resistant 13 dyes.
14 The measurement of light resistance was conducted according to a method as prescribed in JIS L0843-71 using a 16 2.5 KW xenon fade meter of an air-cooling type (made by 17 Suga Tester K.K.). The irradiation energy was 464 18 J/cm2-Hr, which is 9.6 times that of an average sunlight 19 and 380 times that of a fluorescent lamp.
The ink jet recording was carried out using an 21 On-demand-type head having a nozzle diameter of40 microns 22 and a voltage of 200 V was applied to the recording system.
23 ~hen a recorcing of 6 lines/mm~ was effected, a aischarge 24 per unit area was 7.9 x lO cc/cm2.
Recording papers used ~ere made by applying onto a r ~ '30 --1 commercially available high quality paper three types of 2 coating composition comprising three types of binders of 3 polyvinyl alcohol, oxidized starch/polyvinyl alconol 4 (30/70) and polyvinyl alcohol/polyvinylpyrrolidone (40/60) and calcium carbonate as white filler in a binder-to-filler 6 ratio of l : l J respectively. The coating amount was 40 7 g/m2. The three types of recording papers were designated 8 as recording papers A, B and C respectively. Antioxidants, 9 UV absorbers and the specific type of compounds capable of reacting with dyes were dissolved in binder to make 11 recording papers. It will be noted that these additives 12 are effective for any recording papers which are to be 13 applied with dyes for recording purpose and application of 14 these additives to recording papers outside the scope of the invention is also described in the following examples 16 to evidence the excellency of these additives.
17 Example ll 18 Various metal oxides and organic acids were added to 19 the binders in such an amount that they were contained in the surface coating in an amount of 0.5 g/m2. ~hen, 21 recording papers were made substantially in the same manner 22 as in the foregoing examples.
23 Then, a magenta ink made of 79% by weight of water, 24 20% by weight of ethylene glycol and l% by weight of C.I.
Basic Violet lO was prepared and used for recording on the 26 respective recording papers~ The recorded papers we~e -- ~0 ~

- 41 ~ 7~

1 irradiated for 12 hours in the xenone fade meter and their 2 optieal density was measured. The test results are 3 shown in Table 12 belo~7.

Table 12 (1) . ~
Optieal Density (O.D, ) 6 Rec-ording Additive IrradiatiGn Irradiation O.D~(12 hours)/ paper time time O.D.(0 hors) (0 hour) (12 hours) 8 ----- ----. -- _ __ A nil 0~93 0~41 0.44 A pnosphorus 0.84 0.6B 0.81 tungstie acid 11 A phosphorus 0.8g 0.82 0.92 molybdic aeid A phosphorus 0.91 0.88 0.97 13 ~ungs~
molybdic acid A chromic 0.88 0.83 0.94 chloride 16 A tannic 0.99 0.99 1.00 acid B nil 0.97 0.42 0.43 B phosphoru~ 0.91 0.78 0.92 19 tungstic aeid B phosphorus 0.93 0.86 O.g2 molybdie aeid B phosphorus 0.96 0.90 0.94 22 tuncsten molylidie aeid B chromic 0.89 0.84 0.94 24 chloride ~ 42 ~ 7~
_ _ Table 12 (2)_ _ Op~ical Density (O.D.) Rec-orcing Additive Irradiation Irradiation O.D.(12 ho~rs)/
paper time timeO.D.(0 hors) (0 hour) (12 hours) B tannic 0.99 0.98 0.99 acid C nil 0.88 0.35 0.40 C phosphorus 0.85 0.62 0.73 tungstic acid C phosphorus 0.88 0.81 0.92 molybdic acid C phosphorus 0.87 0.82 0.94 tungsten molibdic acid C chromic 0.81 0.76 0.94 chloride C tannic 0.92 0.82 0.89 acid As will be seen from the above results, the additives are fo~nd to remarkably improve the light resistance of recorded matter. In practice, the phosphorus-containing acids are preferably used because of their excellency in color retentivity.
Example 12 Various inks composed of 76 to 79 % by weight of water 20 % by weight of ethylene glycol and 1 to 4 % by weight of different types of dyes were made and applied on a recording paper D which was made by applying 0.5 g/m2 of phosphorus molybdic acid to the recording paper A and a 1 recording paper E applied with 0.5 g/m2 of tannic acid 2 similarly to the case of the recording paper D.
3 The light resistance was measured in the same manner 4 as in Example 11 with the results shown in Table 13 below.

6 Table 13 (1) 7 Optical Density ~O.D.) Rec-8 ording Dye Irradiation Irradiation O.D.(12 hours)/
paper time time O.D,(0 hour) 9 ~0 hour) (12 hours) lo A C.I.Basic 0.57 . 0.39 0.69 Yellow 11 D " 0.59 0.49 0.83 E " 0.61 0.52 0.85 A C.I.Basic 0.79 0.35 0.44 t4 P~ed 1 D " 0.77 0.53 0.69 16 E ~ 0.71 0.51 0.72 17 A C.I.Basic 0.78 0.56 0.72 Red 3 t8 D n 0,75 0.54 0.85 E n 0.74 0.62 0.84 A C.I.Basic 0.97 0.37 0.38 21 Violet 14 22 D n G.91 0.63 0.69 23 E n 0.93 0.69 0.75 - 4~ -Table 13 (2) _ Optical Density tO.D.) Rec-ording Dye Irradiation I~radiation O.D.(12 hours)/
paper time timeO.D.~0 hour) t0 hour) (12 hours) _ __ _ _ _ .
A C.I~Basi~ 0.79 0.46 0.58 ~]ue 3 D " 0.77 0.57 0.74 E " 0.73 0.55 0.77 A C.I.~brdant 0.41 0.30 0.73 Orange 4 D n 0.39 0.30 0.77 E " 0~42 0.32 0.77 A C.I.Mb~dant 0.77 0.5g 0.77 Red 15 D " 0.72 0.61 0.85 E " 0O75 0.67 0.89 A C.I.M~r~ant 0.71 0.62 0.87 Violet 5 D n 0.73 0.67 0.92 E ~ 0.68 0.62 0.91 A C.I.Mordant 0.82 0.75 0.91 Black 7 D n 0.79 0.75 0.95 E n 0.83 0.78 0.94 A C.I.Acid 0.51 0.21 0.41 Yellow 17 D n 0.53 0.44 0.83 E n 0.52 0.47 0.90 - ~4 -- 45 ~
Table 13 (3) .
Optical Density (O.D.
Rec-ordingDye Irradiation Irradiation O.D.(12 hours)/
paper time timeO.D,(C hour) (0 hour) (12 hours) A C.I.Acid 0.63 0.42 0.69 Orange 7 D n 0.63 0~49 0.78 E " 0 . 63 0 . 580 . 92 A C.I.Acid 0.80 0.38 0.47 Red 88 D n 0.82 0.63 0.77 E n 0078 0.70 0~89 A C.I.Acid 0.92 0.32 0.35 Violet 49 D " 0.95 0.71 0~75 E " 0.90 0~75 0.83 A C.I.Acid 0.81 0.72 0.88 Blue 7 D " 0.80 0.77 0.96 E " 0.83 0.81 0.98 A C.I.Acid 1.00 0.83 0.83 Black 2 D n 1~03 0~98 0~95 E n 1.03 1.02 0.99 A C.I.Acid 0.94 0.86 0.91 Black 31 D " 0~93 0~91 0.98 E " 0.95 0.94 0.99 _ -- ~5 --1 From the above results, it will be seen that the 2 phosphorus molybdic acid and ~N~C acid showed a very 3 remarkable effect of light resistance on the basic dyes and 4 acid dyes and a fair effect on the mordant dyes. ~owever, little effects on the direct dyes and disperse dyes were 6 recognized.
7 In these examples ll and 12, five compounds are 8 illustrated and other effective additives includes halides 9 and o~:ides of at least one metal such as of barium, manganese, iron, copper, calcium, magnesium, cobalt and 11 nickel.
12 The amount of these additives varies depending on 13 the type thereoE but is generally in the range of O.l to 14 10% by weight of the coating composition in case of the surface-coated recording paper. Larger amounts give an adverse effect on the recording characteristics.
17 As will be appreciated from the results of Example 18 ll, the additives show their ligh~-resistant effect 19 independently of the type of coating. Further, their effect is also developed when the additives are 21 incorporated in paper or applied by dipping paper in 22 solutions of the additives. This is particularly described 23 in Example l3 and l4.
24 Example l A commercially available high quality paper showing ,q '~

1 a relatively high degree of ~ater absorptivity was used on 2 which recording was conducted by an ink jet recording 3 technique using an ink as used in Example :11. After 4 completion of the recording, the recorded lDatter was dipped in acetone or methanol solutions of 2 wt% of phosphorus 6 tungstic acid, phosphorus molybdic acid, ph~sphorus tungsten mol~x~c acid, 7 chromic chloride and tannic acid, then driled, and subjected 8 to the measuremenL of light resistance. The results are 9 shown in Table 1~.

11 Table 14 12 Optical Density ~O.D~) 13 Additive Irradiation Irradiation D.C. (12 hours)/
time time D.C. (0 hours) 1l~ (0 hour) (12 hours) .
nil 0.88 0.40 0.45 16 phosphorus 0.91 0.66 0.73 tungstic acid phosphorus 0.83 0.76 0.92 18 molybdic acid 19 phosphorus 0.88 0.85 0.97 tungsten molybdic acid 21 chromic 0.83 0.79 0.97 22 chloride tannic 0.95 0.93 0.98 23 acid - 48 - ~ 5 ~

1 These additives can improve the light resistance of 2 recorded matter when applied by the dipping method as will 3 be seen from the above results.
4 Example l4 LBKP having a freeness (C.S.F) of 400 ml was used as 6 stock pulp to which were added lO wt~ of talc, 0.2 wt~ of a 7 wet strength improver and 0.5 wt% of additives each based ~ on the solid component of pulp. The thus added pulps were 9 each used to make papers with a basis weight of 50 9/m2 in a usual manner.
11 The~,an ink with the same composition as used in 12 Example 13 was used to record on the thus made papers and 13 the recorded matters were subjected to the measurement of 14 light resistance. The results are shown in Table 15 below.

- ~8 -- ~9 -Table 15 1 Optical Density (O.D.) 2 Additive Irradiation Irradiation D.C. (12 hours)/
time time D.C. (0 hours) 3 (0 hour) (12 hours) 4 nil 0~82 0.~0 0~q9 phosphorus 0~86 Or68 01~79 ungstic acid phosphorus 0~79 0~77 0~97 7 molybdic acid 8 phosphorus 0.84 0.80 0.95 tun~sten g mol~bdic acid chromic 0~79 0~71 0~90 chloride tannic 0.91 0.89 0.98 12 acid The additive-incorporated papers show improved light resistance over the additive-free paper.
Example 15 Example 11 was repeated using various antioxidants, with the results shown in Table 16 below, in which the three recording papers are indicated as A', B' and C' corresponding to recording papers A, B and C or Example 11.
~0 _ ~9 _ ~ '7 Table 16 (l) Optical density Rec-ording Antioxidant Irra- Irra- O.D.(12 hrs)/
paper diation diation O.D.(0 hr) time time (0 hr) (12 hrs) A' nil 0.93 0.41 0.44 n hydroquinone 0.95 0.95 l.00 - " hydroquinon dimethyl 0.97 0.70 0.72 ether butylhydroxyanisole 0.93 0.82 0~88 n p-tert-butylphenol 0.97 0.65 0.67 " p-tert-butylcatechol 0.97 0.97 l.00 n 2,6-di-tert-butyl- l.00 0.98 0.98 phenol 2,6-tert-butyl-p- 0.99 0.57 0.57 cresol " methylhydroquinone 0.92 0.85 0.92 n 2,2'-azobis- 0.87 0~53 0.61 isobutyronitrile n benzotriazole 0.94 0.43 0.46 n diphenylamine 0.94 0.73 0.78 n 11 l-diphenyl~2- l.01 0.84 0.83 picrylhydrazine " pyrogallol 0.94 0.84 0.89 B' nil 0.97 0.42 0.43 " hydroquinone 0.93 0.97 0.98 n hydroquinone l.00 0.69 0.69 dimethyl ether " butylhydroxyanisole 0.99 0.84 0.~5 Table 16 (2) . _ _ Optical density Rec~
ording Antioxidant Irra- Irra- O.D.~12 hrs)/
paper diation diation O.D.(0 hr) time time (0 hr) (12 hrs) .
B' p-tert-butylphenol 1.04 0.75 0.72 n p-tert- 1.07 1.03 0.96 butylcatechol 2,6-di-tert- 1.05 1.03 0.98 butylphenol n 2,6-di-tert-butyl- 1.06 0.66 0.62 p-cresol methylhydroquinone 0.98 0.95 0.97 2,2'-azobis- 0.89 0.64 0.72 isobutyronitrile benz~triazole 1.03 0.~9 0.48 diphenylamine 1.01 0.81 0.80 n l,l-diphenyl-2- 1.09 0.93 0.85 picryl-hydrazine n pyrogallol 1.00 0.91 0.91 C' nil 0.88 0O35 0.40 n hydroquinone 0.92 0.90 0.98 hydroquinone 0.96 0.69 0.72 dimethyl ether butylhydroxyanizole 0.91 0.80 0.88 " p-tert-butylphenol 0.95 0.60 0.63 n p-tert-butylcatechol 0.90 0.89 0.99 n ~6-di-tert- 0 97 0.98 butylphenol Table 16 (3) Optical density Rec-ording ~ntioxidant Irra~ Irra- O~Do (12 hrs)/
paper diation diation O~D~ (O hr) time time (0 hr) ~12 hrs) .
C' 2,6-di-tert-butyl- 0.97 0.47 0.48 p-cresol methylhydroquinone 0.90 0.75 0.83 2,2'-azobis- 0.81 0.43 0.53 isotutyronitrile n benzotriazole 0.91 0.38 0.42 n aiphenylamine 0.88 0.50 0.57 " 1,1-diphenyl-2- 0.97 0.76 0.78 picrylhydra~ine " pyrogallol 0.91 0.81 0.89 These results reveal that the addition of antioxidants can remarkably improve the light resistance.
The degree of the inprovement more or less depends on the type of antioxidant and hydroquinone, p-tert-butylcatechol, 2,6-di-tert-butylphenol and methylhydroquinone are particularly excellent in improving the light resistance.
Aside from those mentioned above, there are usable styrenated phenol t 2,2'-methylenebis(4-ethyl-6-t-butyl-phenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), 2,2'-thiobis(4-methyl-6-t-butylphenol), alkylthiodi propionates, J~

1 2-mercaptoben70imidazole, N n-butyl-p-aminophenol, phenyl-2 enediamines, ~-naphtylamine, N-phenyl ~-naphthylamine, 3 N,N'-disalicylidene-1,2-propylenediamine, phenothiazine, 4 tris(nonylphenyl)phosphite, triphenylphosphite, tris(3,5-di-t-butyl-4,g-hydroxyphenylphophate, dithiocarbamate, 6 anthogenate, dihydrquinoline derivatives, mercaptobenzi-7 midazoles, monoisopropyl citrate, ethyl protocathecuate, 8 alkyl gallates, nordihydroguaiaretic acid, L-sorbic acid, 9 and the like.
E~ample 16 11 Various inks composed of 77 to 79 wt~ of water, ~0%
12 by weight of ethylene glycol and 1 to 3~ by weight o:E
13 different types of dyes were made and applied on a 1~l recordiny paper D' which was made by incorporating 0.5 9/m2 of methylhydroquinone in the recording paper A'. The light 16 resistance was measured in the same manner as in Example 17 15. The results are shown in Table 17 below.

~3~'7~

Table 17 Optical Density (O.D.) Rec-ording Dye Irradiation Irradiation ODD.(12 hrs)/
paper time timeO.D.(0 hr) (0 hr) (12 hrs) -D' C.I,Basic 0.95 0 90 0.95 Violet 14 A' " 0.97 0.37 0.38 D' C.I.Basic 0.79 0.73 0.92 Blue 3 A' ~ 0.79 0.46 0.58 D' C.I Basic 0.53 0.51 0.97 Yello~
A' n 0.57 0.39 0.69 D' C.I.Basic 0.78 0.69 0.89 Red 1 A' " 0.79 0.35 0.4~
Dl C.I.Basic 0.77 0.75 0.97 Red 13 A' n 0.78 0.56 0.72 D' C.I.Acid 0.57 0.52 0.92 Yellow 17 A' n 0.51 0.21 0.81 D' C.I.Acid 0.61 0.97 0.77 Orange 7 A~ n 0.63 0.43 0.69 D' C.I.Acid 0.82 0.57 0~70 Red 88 A' n 0.80 0.38 0.47 - 5~ -- 55 - ~ f`~

1 From the above results, it will be seen that tho~gh 2 an influence of the antioxidants on the light resistance 3 varies depending on the type of dye, good results are 4 obtained in all the cases. Accordingly, the addition of antioxidant is believed effective in improving the light 6 resistance by application to various types of dye.
7 The amount of the antioxidants also varies depending 8 on the type but is generally in the ranse of O.l to 10% by 9 weight of the coating composition when such composition is applied by the surface coating technique. Larger amounts 11 give an adverse effect on the recording characteristics.
12 The antioxidants can also be applied by dipping 13 paper in solutions o~ antioxidants or internally 14 incorporated paper. This is particularly described in examples which follow.
16 Example l7 17 A commercially available high quality paper showing 18 a relatively high degree of water absorptivity was used and 19 an ink jet recording using an ink of C.I. Basic Violet lO
was conducted on such paper~ The recorded paper was then 21 dipped an acetone solution of each of antioxidants (2 wt~) 22 for 2 seconds. After drying, the light resistance of the 23 dipped paper was measured using the xeon fade meter. The 24 results are shown in Table l8 below.

~ '7'~

Table 18 -Optical Density (O.D.) Antioxidant Irradiation Irradiation O.D.
time time (12 hrs)/
(0 hour) (12 hours) OO~.
(0 hr) nil 0.91 0.38 0.42 hydroquinone 0.91 0.89 0.98 p-tert-butylcatechol 0.93 0.92 0.99 2,2-di-tert-butylphenol 0.93 0.90 0.97 methylhydroqinone 0.88 0.86 0~98 butylhydroxyanisole 0.88 0.83 0~94 diphenylamine 0.90 0.79 0.88 pyrogallol - 0.89 0.80 0.90 As will be seen from the above results, the dipping method is also effective in improving the light resistance similarly to the surface coating method.
Example 18 LBKP having a freeness (C.S.F) of 400 ml was used as starting pulp to which were added lO wt% of talc, 2 wt% oE
a wet strength improver and 0.5 wt% of antioxidants each based on the solid component of pulp. The thus added pulps were each used to make papers with a basis weight of 50 g~m2 in a usul manner.

- 57 ~

1 ~hen, an ink with the same composition as used in 2 Example 17 was used and applied on the thus made papers, 3 follo~ed by measuring the light resistance. The results 4 are shown in Table 19 below.

6 Table 19 _ 7 Optical Density (O.D.
8 Antioxidant Irradiation Irradiation O~D~
time time (12 hrs)/
9 (0 hour) (12 hours) OoD~
~0 hr) nil 0.85 0.38 0.45 hydroquinone 0.86 0.81 0.94 p-tert-butylcatechol 0.89 0~83 0.93 2,6-di-tert-butylphenol 0.90 0.83 0.92 methylhydroquinone 0.85 0.80 0.94 butylhydroxyanisole 0.84 0.79 0.94 di~henylamine 0.88 0.75 0.85 pyrogallol 0.83 0.79 0.95 Thus, the incorporation of the antioxidants in paper is also effective in improving the light resistance.

Example 19 Example 11 was repeated using various UV absorbers, with the results shown in Table 20 below, in which the 1 three recording papers are indicated as A'', B " and C'' Z correspondin~ to recordiny papers A, B and C of Example 11.

4 Table 20 (1) Optical Density ~O.D.) Rec-6ording UV absorber Irra- Irra- O.D.(12 hrs)/
paper diation diation O.D.(0 hr) 7 time time t0 hr~ (12 hrs) Al' nil 0.93 0~41 0.44 " 2-hydroxy-4- 1.00 0.79 0.79 octoxybenzophenone 11 " 2-hydroxy-4- 0.96 0.83 0.86 methoxybenzo-12 phenone 13 " phenylsalicylate 0.91 0~70 0.77 14 . p-t-butylphenyl 0.92 0.77 0.83 salicylate B'' nil 0.97 0.42 0.43 " 2-hydroxy-4- 1.02 0.83 0.81 17 octoxybenzo-phenone n 2-hydroxy-4- 0.98 0.82 0.84 19 methoxy-benzophenone " phenyl salicylate 0.94 0.71 0.76 " p-t-butylphenyl 0.93 0.74 0~80 22 salicylate 23 C'' nil 0.88 0.35 0.40 24 a 2-hydroxy-4- 0.98 0.85 0.87 octoxy-benzophenone - 5~ --~ s9 -Table 20 (2) Optical Density ~O.D~) Rec-ording UV absorber Irra- Irra- O.D.(12 hrs)/
paper diation diation O.D.(0 hr) time time ~0 hr) tl2 hrs) C'' 2-hydroxy-4- 0.91 0.76 0.84 methoxy-benzophenone " phenyl salicylate 0.~9 0.67 0.75 " p-t-butylphenyl 0.90 0.69 0.77 salicylate These results show that the addition oE the UV

absorbers is effective in improving the light resistance.
Example 20 Various inks composed of 77 to 79 wt% of water, 20 wt% of ethylene glycol and 1 to 3 wt% of various dyes were made and applied on a recording paper D' which was made by incorporating 0.5 g/m2 of 2-hydroxy-~-octoxybenzophenone as UV a bsorber in the coating layer of the recording paper A''. The light resistance was measured in the same manner as in Example 19. The results are shown in Table 21 below.

Table 21 (1) -Optical Density (O.D.) Rec ordinc Dye Irradiation Irradiation O.D.(12 hrs)/
paper time timeO.D.(0 hr) (0 hr) (12 hrs) A'' COI.Basic 0.97 0.37 0.38 Violet 14 D'' n 0.99 0.810.82 A'' C.I.Basid 0.79 0.46 0.58 Blue 3 D " " 0.83 0.750.90 A' ' C.I.Basic 0.57 0.39 0.69 Yell ow 11 D'' " 0.59 0.510.86 A' ' C.I.Basic 0.79 0.35 0.44 Red 1 Dl I n 0.81 0~700~86 A' ' C.I.Basic 0.78 0.56 0.72 Red 13 Dl I n 0.77 0.680.8B
A' ' C.I.Basic 0.51 0.21 0.41 Yellow 17 D " " 0.54 0.410.76 A'l C.I.Acid 0.63 0.43 0.69 Orange 7 D'' " 0.63 0.580.92 A'' C.I.Acid 0.80 0~38 0.47 Red 88 D" n 0.77 0.690.90 A'' C.I.Acid 0~92 0.32 0.35 Violet 49 D ~ I n O . 91 35 - 61 ~

Table 21 (2) _ Optical Density (O.D.) Rec ording Dye Irradiation Irradiation O.D.(12 hrs)~
paper time timeO.D.(0 hr~
(9 hr) (12 hrs) . . _ A''C.I.Acid 0.81 0.720.88 Blue 7 D~ I n 0.85 0.780.92 A''C.I.Acid l.00 0.830~83 Black ~
D'' n 1.05 1.040.99 A''C.I.Acid 0.94 0.860.91 Black 31 D'' " 0.95 0.910.96 A"C.I.Direct 0.48 0.340.71 Yellow 50 D'' " 0.49 0.430.88 A "C.I.Direct 0.71 0.470.66 Red 80 ,D'' n 0,70 0.600.86 The influence of the benzophenone on the light resistance more or less depends on the type of UV absorber but good results are obtained in all cases.
When the UV absorbers are applied by the surface coating technique, the,y are generally used in an amount of 0.1 to lO~t% of the coating composition of binder and - 62 ~ r~

1 filler. Similarly to the antioxidants and compounds 2 capable of reactin~ with dye, larger amounts give an 3 adverse effect on the recording characterist:ics.
4 Example 21 A commercially available high quality paper showing a 6 relatively high degree of water absorptivity was used and 7 an inkk jet recording using an ink of C.I. Basic Violet 10 8 was conducted on such paper. The recvrded paper was then 9 dipped in an acetone solution of each of UV absorbers (2 wt%) and dried, after which it W2S subjected to the 11 measurement of light resistance. The results are shown in 12 l'able 22 below.

14 Table 22 .. _ . _ . . . .
Optical ~ensity (O.D.) 16 UV absorber Irradiation Irradiation O.D.
time time tl2 hrs~/
17 ~0 hr) (12 hrs) O.D. (O hr) nil 0.90 0.38 0.42 2-hydroxy-4-octoxy- 0.93 0.71 0.76 benzophenone 21 2-hydroxy-4-methoxy- 0.91 0.77 0.85 22 ben~ophenone 23 phenyl salicylate 0.89 0.68 0.76 p-t-butylphenyl 0.90 0.59 0.66 24 salicylate 7'~
- 63 ~

1 ~s will be clear from the above results, the dipping 2 method is effective in improving the light resistanceO
3 Exmple 22 4 LBKP having a freeness (C.S.F) of 400 ml was used as starting pulp to which were added 10~7t~ of talc, 2 wt% of a 6 wet strength improver and 0.5 wt~ of UV absorbers each 7 based on the solid component of p~lp. The thus added pulp 8 were used to make papers with a basis weight of 50 9/m2 in 9 a usual manner.
Then an ink with the same composition as used in 11 Example 21 was used and applied on the thusmade papers, 12 followed by measuring the light resistance. The results 13 are shown in Table below.

Table 22 .
Optical Density (O.D.) 17 ~V absorber Irradiation Irradiation O.D.
time time (12 hrs)/
18 (0 hr) tl2 hrs) O.D.
(0 hr) nil 0.82 0.39 0.47 2-hydroxy-4-octoxy- 0.88 0.63 0.72 21 benzophenone 22 2-hydroxy-4-methoxy- 0.85 0.67 0.79 benzophenone phenyl salicylate 0.85 0.58 0.68 p-t-butylphenyl 0O81 0.51 0.63 salicylate ~ 64 ~

1 The UV absorbers can be e~fectively utilized even by 2 the internal application method as will be apparently seen 3 from the above results.

Claims (11)

Claims

1. An ink jet recording sheet which comprises a paper support applied on at least one surface thereof or internally with a composition characterized in that said composition comprises an aqueous dispersion of polyvinyl-pyrrolidone, vinylpyrrolidone-vinyl acetate copolymer or a mixture thereof serving as a binder or sizing agent and a white filler, said white filler being contained in a weight ratio to said binder of 10 : 1 to 0.2 : 1 when said composition is applied on the surface of said paper support and said composition comprises 10 to 60 parts by weight of said white filler and 2 to 20 parts by weight of said binder per 100 parts by weight of pulp when said composition is applied internally of the recording paper.

2. An ink jet recording sheet according to Claim 1, wherein said composition is applied on the surface of the paper support in an amount of 3 to 50 g/m2 on a dry basis.

3. An ink jet recording sheet according to Claim 1, wherein said filler is clay, talc, calcium carbonate, calcium sulfate, calcium silicate, diatomaceous earth, magnesium silicate, terra abla, activated clay, magnesium oxide, magnesium carbonate or aluminium hydroxide in the form of a powder.

4. An ink jet recording sheet according to Claim 1, further comprising a binder resin used in combination with the first-mentioned binder resin, said first-mentioned binder resin being used in an amount of at least 20 wt% of the combination when the second-mentioned binder resin shows water absorptivity or in an amount of at least 33 wt%
of the combination when said second-mentioned binder resin shows little water absorptivity.

5. An ink jet recording sheet according to Claim 1, further comprising a plasticizer to control a hardness of the film formed from the binder resin.

6. An ink jet recording sheet according to Claim 1, further comprising an aqueous emulsion-type resin or an alcohol-soluble resin, which shows a water proof property when dried in the form of a film, in an amount of 1 to 50 wt% of a combination with the binder resin, whereby the resulting coating is imparted with water proof.

7. An ink jet recording sheet according to Claim 1, further comprising 0.1 to 10 wt% of an antioxidant, UV
absorber or compound capable of reacting with dye, so that the light resistance of an ink to be applied on the recording sheet is improved.

8. An ink jet recording sheet according to Claim 7, wherein the antioxidant, UV absorber or compound capable of reacting with dye is contained at least in the surface layer of the recording sheet.

3. An ink jet recording sheet according to Claim 7, wherein the antioxidant, UV absorber or compound capable of reacting with dye is contained in the recording sheet.

10. An ink jet recording sheet according to any of Claim 7 through 9, wherein the compound capable of reacting with dye is phosphorus tungstic acid, phosphorus molybdic acid or phosphorus tungsten molybdic acid.

11. An ink jet recording sheet which comprises a paper support applied on at least one surface thereof or internally with a composition characterized in that said composition com-prises an aqueous dispersion of polyvinylpyrrolidone , vinyl-pyrrolidone-vinyl acetate copolymer or a mixture thereof serving as a binder or sizing agent and a white filler , said white filler being contained in a weight ratio to said binder of 1:1 to 0.5:1 when said composition is applied on the surface of said paper support and said composition comprises 10 to 60 parts by weight of said white filler and 2 to 20 parts by weight of said binder per 100 parts by weight of pulp when said composition is applied internally of the recording paper .