JPH10181193A - Back print recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a satisfactory image by printing from a light diffusion ink transmission layer side, and reducing a printed dot size observed from a transparent base material side of a recording medium observed from the base material side smaller than that observed from the transmission layer side. SOLUTION: The recording medium 1 is obtained by sequentially providing an ink receiving layer 3 and a light diffusion ink transmission layer 4 on a transparent base material 2, and recorded from the layer 4 side with ink droplet 5. Dots 7 as elements of an image formed of the droplets 5 are such that dot diameter observed from the material A side is smaller than that observed from the transmission layer side. As a result of such a shape of the dot, an image of higher quality can be realized. More particularly, highly precise and high resolution recording is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called back print recording medium for observing printing from a surface opposite to a recording surface on which recording has been performed.

2. Description of the Related Art There is known a recording medium called a so-called back print in which printing is observed from a surface opposite to a recording surface on which recording is performed. Such a recording medium is basically formed on a transparent substrate,
An ink receiving layer for absorbing and fixing the ink composition and a light diffusion ink transmitting layer containing silica as a main component are provided. Then, printing is performed from the ink transmission layer side by, for example, an inkjet recording method. Then, the ink passes through the ink permeable layer and reaches the ink receiving layer. This ink image is observed from the transparent substrate side by reflected light or transmitted light. Since the printed image to be observed has a texture due to the gloss and smoothness of the transparent base material, it is used for printing an image for which a high-class feeling is desired.

On the other hand, a recording medium using a polyvinyl acetal resin as an ink receiving layer is disclosed, for example, in JP-A-6-21.
No. 9042, JP-A-8-72390, JP-B-5-23597 and the like. However, as far as the present inventors know, there is no known example of using a polyvinyl acetal resin for an ink receiving layer of a back print recording medium.

[0004]

SUMMARY OF THE INVENTION The present inventors have found that, in a so-called back print recording medium, the printed dot diameter observed from the transparent substrate side is changed to the printed dot diameter observed from the light diffusion ink transmitting layer side. It has been found that by making the size smaller than that, a good image can be formed. The present invention is based on this finding.

Accordingly, an object of the present invention is to provide a back print recording medium capable of realizing a good image.

The recording medium according to the present invention comprises at least an ink receiving layer and a light-diffusing ink permeable layer provided on a transparent substrate in this order, and performs printing from the light-diffusing ink permeable layer side. A recording medium that allows printing to be observed from the side such that the printed dot diameter observed from the transparent base material side is smaller than the printed dot diameter observed from the light diffusion ink transmitting layer side. It is constituted in.

[0007]

DETAILED DESCRIPTION OF THE INVENTION The recording medium according to the present invention is provided with at least an ink receiving layer and a light diffusion ink transmitting layer on a transparent substrate in order. Printing is performed from the light diffusion ink transmitting layer side, and the recorded print image is observed from the transparent substrate side.

The structure of a preferred embodiment of the recording medium according to the present invention is as shown in FIG. In the figure, recording medium 1
The ink receiving layer 3 and the light diffusion ink transmitting layer 4 are sequentially provided on a transparent substrate 2. Recording is performed on such a recording medium from the light diffusion ink transmitting layer 4 side by the ink droplets 5. Recording is preferably performed by an ink jet recording method. In the recording medium according to the present invention, the dots 7 which are elements of the image formed by the ink droplets 5 are:
The ink receiving layer 3 has a shape as shown in FIG. That is, the dot diameter observed from the transparent base material side (the side of the arrow A in the figure) becomes smaller than the dot diameter observed from the light diffusion ink transmitting layer side. In the present invention, the fact that the dot diameter observed from the transparent substrate side (the side of the arrow A in the figure) becomes smaller than the dot diameter observed from the light diffusion ink transmitting layer side is compared by the equivalent circular diameter. May be.

As a result of the dot having such a shape, a higher quality image can be realized. Specifically, high-definition, high-resolution recording becomes possible. In particular, according to the present invention,
It has been possible to effectively prevent the generation of particulate points that may be observed in a printed image obtained by ink jet recording, and to realize a printed image comparable to a photograph. Further, the printed image has an advantage that a good image can be observed even when the image is observed by either reflected light or transmitted light. Further, the water resistance and preservability of the image are good, and the stickiness after printing is reduced. In addition, an effect peculiar to the back print that the image is glossy and excellent in abrasion resistance can of course be obtained.

The manner in which an image is recorded on a recording medium according to the present invention will be further described with reference to FIG. FIG. 2A shows a light diffusing ink transmitting layer 4 of a recording medium 1 in which an ink receiving layer 3 and a light diffusing ink transmitting layer 4 are sequentially provided on a transparent substrate 2.
FIG. 7 is a diagram illustrating a state in which ink droplets 5 are printed from the side by an inkjet recording method. When the ink droplets 5 adhere to the light diffusion ink transmission layer 4, as shown in FIG. 2B, the ink droplets 5 penetrate through the light diffusion ink transmission layer 4 toward the ink receiving layer 3. The ink composition 6 that is transmitting through the light diffusion ink transmitting layer 4 may penetrate while increasing its diameter, or may penetrate while reducing its diameter, but it is preferable that the ink composition 6 penetrates without changing its diameter. preferable. The ink composition 6 then reaches the ink receiving layer 3. During the transmission through the ink receiving layer 3, the ink composition 6 permeates while reducing its diameter, as shown in FIG. Eventually, most of the ink composition 6 reaches the ink receiving layer 3 and forms one dot which is an element of an image. The shape is as shown in FIG.
The dot diameter observed from the transparent substrate side is smaller than the dot diameter observed from the light diffusion ink transmitting layer side. Depending on the amount of the ink composition to be printed, as shown in the figure, the ink composition does not penetrate to the boundary between the ink receiving layer 3 and the transparent substrate 2, and the ink composition in the ink receiving layer 3 Permeation of things may stop. Such an embodiment is also included in the present invention as long as the dot diameter observed from the transparent substrate side is smaller than the dot diameter observed from the light diffusion ink transmitting layer side.

According to a preferred embodiment of the present invention, the above-mentioned dot shape can be realized in an ink receiving layer containing a polyvinyl acetal resin. Therefore, according to the present invention, there is provided a recording medium having an ink receiving layer comprising a polyvinyl acetal resin.

According to a preferred embodiment of the present invention, the degree of acetalization of polyvinyl acetal is preferably about 2 to 20 mol%, more preferably 5 to 15 mol%.
It is about. When the degree of acetalization of the polyvinyl acetal is within the above range, it is possible to obtain an ink receiving layer capable of forming a dot having high transparency and high roundness, and the adhesion of the ink receiving layer to the base material. The advantage that it is excellent is also obtained. Furthermore, while the ink absorption speed is high and the absorption amount is large, there is also obtained an advantage that the ink has excellent water resistance, ink fixability, and image storability (particularly, no bleeding at high humidity). . In addition, there is an advantage that bleeding between colors in color printing called bleed can be effectively prevented. Interestingly, when polyvinyl acetal is used as the ink receiving layer, there is an advantage that cracks that are likely to occur during the production of the light diffusion ink transmitting layer formed thereon, particularly during drying, can be effectively prevented. Can be

The polyvinyl acetal resin used in the present invention can be obtained by reacting polyvinyl alcohol with an aldehyde to form acetal. It can also be obtained by using polyvinyl acetate as a starting material and performing saponification and acetalization. Here, the acetalization may be performed by a conventionally known method such as a dissolution method, a precipitation method, and a homogeneous method.

The polyvinyl alcohol is not particularly limited, but generally has a degree of polymerization of about 300 to 4500, more preferably 500 to 4500. When a polyvinyl acetal resin obtained from polyvinyl alcohol having a high degree of polymerization is used, there is a tendency that an ink receiving layer having favorable ink fixing properties and water resistance is obtained. The degree of saponification of polyvinyl alcohol is not particularly limited, but is preferably about 80.0 to 99.5 mol%.

Examples of aldehydes condensed with polyvinyl alcohol include resin aldehydes such as formaldehyde, acetaldehyde, butyraldehyde, hexyl aldehyde, octyl aldehyde and decyl aldehyde;
Benzaldehyde, 2-methylbenzaldehyde, 3-
Methylbenzaldehyde, 4-methylbenzaldehyde, other alkyl-substituted benzaldehydes, chlorbenzaldehyde, other halogen-substituted benzaldehydes; aromatic aldehydes such as phenylacetaldehyde, β-phenylpropionaldehyde, and other phenyl-substituted alkylaldehydes; An aromatic aldehyde having a substituent such as a hydroxy group, an alkoxy group, an amino group, a cyano group, and the like can be given. It is also possible to use an aldehyde having a condensed aromatic ring such as naphthaldehyde and anthralaldehyde.

It is preferable to use a polyvinyl acetal resin obtained from an aromatic aldehyde, since an ink receiving layer having excellent fixability, water resistance and transparency of the ink can be obtained.

The degree of acetalization of the polyvinyl acetal resin used in the present invention is preferably in the range of about 2 to 20 mol%, more preferably about 5 to 15%, and most preferably about 7 to 10%. It is. By using a resin having the above degree of acetalization, an ink receiving layer having excellent fixing properties and water resistance of the ink can be obtained.

In the present invention, commercially available polyvinyl acetal resins may be used. Specific examples thereof include Eslek KX-1 (acetalization degree 8 mol%) and KW-1 (acetalization degree 9 mol%). %) (Both manufactured by Sekisui Chemical Co., Ltd.).

The ink receiving layer of the recording medium according to the present invention comprises:
It may be formed as a film of the above-mentioned polyvinyl acetal resin on a transparent substrate. Specifically, it can be obtained by preparing a solution in which the above-mentioned polyvinyl alcohol resin is dissolved in an appropriate solvent (for example, a mixed solvent of water and isopropyl alcohol), applying the solution on a substrate, and drying. it can. The coating may be performed using a known means, for example, using a roll coater, an air knife coater, a blade coater, a rod coater, a bar coater, a comma coater, or the like.

The ink receiving layer of the recording medium according to the present invention comprises:
In addition to the polyvinyl acetal resin, for example, other water-soluble resins, water-proofing agents, surfactants, preservatives, ultraviolet absorbers and the like may be added.

In the recording medium according to the present invention, the thickness of the ink receiving layer may be appropriately determined in consideration of the characteristics required for the recording medium, but is preferably about 3 to 15 μm, more preferably about 5 to 10 μm. is there.

Examples of the transparent substrate of the recording medium according to the present invention include polyester resins, polyolefin resins, polystyrene resins, and polyvinyl chloride resins. The thickness is generally preferably about 50 to 300 μm in consideration of the transportability of the printer. According to a preferred embodiment of the present invention, it is preferable that the surface of the transparent substrate in contact with the ink receiving layer is subjected to an easy adhesion treatment.
This treatment can improve the adhesion to the ink receiving layer. This easy adhesion treatment may be performed by a known method, specifically, by subjecting the surface of the base material to a corona discharge treatment, or a solution or emulsion of an acrylic resin, a polyester resin, a urethane resin, or the like to a thickness of about several μm or less. It may be carried out by coating with a layer. According to another preferred embodiment of the present invention, it is preferable that the surface of the transparent substrate on the side not in contact with the ink receiving layer is subjected to an antistatic treatment. This processing can effectively prevent the recording media from sticking to each other due to static electricity or the like.
This antistatic treatment may be performed by a known method, and specifically, may be performed by adding a surfactant having an antistatic performance to a resin solution or a resin emulsion and applying the same. More specifically, the surface resistance is 1x
The resistance may be set to 10 ¹⁵ Ω or less, preferably 1 × 10 ¹³ Ω or less. Moreover, a desired pattern, for example, a mesh pattern may be applied to the surface of the base material, or the base material may be subjected to a surface treatment to further impart gloss.

The light diffusion ink transmitting layer of the recording medium according to the present invention may be configured to be generally used as a light diffusion ink transmitting layer of a back print recording medium. Therefore, for example, it may be composed of a binder resin, a whitening agent, a porous body, and the like. According to a preferred embodiment of the present invention, the light diffusion ink transmitting layer may be configured to contain at least a carboxyl group-modified polyvinyl alcohol, colloidal silica, a whitening agent, and synthetic silica. Use of a carboxyl group-modified polyvinyl alcohol is preferable because it greatly improves the storage stability of a printed image. As the carboxyl group-modified polyvinyl alcohol, a commercially available product can be used. For example, Gohsenal T-215, 230, 330, 35 available from Nippon Synthetic Chemical Industry Co., Ltd. as the Gohsenal T series
0, 330H and the like. Especially the degree of saponification is 99m
It is preferable to use 330H which is ol% or more. Colloidal silica is usually an anionic colloidal dispersion in which ultrafine particles of silicic anhydride (silica) are stably dispersed in water, and is produced, for example, as follows. First, an aqueous solution of sodium silicate is passed through a cation exchange resin to form a sol having a SiO ₂ / Na ₂ O ratio of 60 to 130. Next, this is heated and baked at 60 ° C. or more to grow into independent dispersed particles, and further polymerized and deposited by adding a sol that has passed through an ion exchange resin layer. As a result, colloidal silica can be obtained as a stable sol that grows to an average particle diameter of 3 nm to 200 nm. In the present invention, commercially available colloidal silica can be used. For example, Ludox manufactured by Du Pont, Syton manufactured by Monsanto, and Nal
Co., Ltd., Nalcoag, Nissan Chemical Co., Ltd., Snowtex, etc. can be used. Examples of the whitening agent used in the present invention include titanium oxide, white fluorescent pigment, fluorescent dye and the like. The whiteness of the recording medium according to the present invention may be appropriately determined in consideration of ink permeability, ink absorption amount, and the like. As the whitening agent, a commercially available one can be used, and examples thereof include white dye (manufactured by Sumitomo Chemical Co., Ltd.) which is a fluorescent dye.

According to a preferred embodiment of the present invention, the light-diffusing ink-receiving layer preferably comprises synthetic silica. This is because the ink permeability can be improved by adding the synthetic silica. The particle diameter, pore volume, and average pore diameter of the synthetic silica may be appropriately determined from the viewpoint of ink absorption and ink permeability. As the synthetic silica, commercially available ones can be used. For example, as synthetic silica, Mizukasil, Mizukasorb (manufactured by Mizusawa Chemical Co., Ltd.), Fine Seal, Tokuseal, Leoloseal, Excelica (manufactured by Tokuyama), Thylsia (manufactured by Fuji Silysia Chemical) And Aerosil (manufactured by Nippon Aerosil Co., Ltd.) can be used.

In the recording medium according to the present invention, the thickness of the light diffusion ink transmitting layer is preferably about 15 to 40 μm, more preferably about 20 to 35 μm.

The light-diffusing ink-permeable layer is prepared by dissolving or dispersing the above-mentioned components in a suitable solvent on a transparent substrate, and preparing the coating solution on the ink-receiving layer formed on the substrate. It can be obtained by coating and drying.
Coating may be performed using a known means, for example, a roll coater, an air knife coater, a blade coater,
It may be performed using a rod coater, a bar coater, a comma coater, or the like.

By combining the light-diffusing ink-transmitting layer having the above composition and the ink-receiving layer containing the polyvinyl acetal resin, high-definition and high-resolution recording in which ink absorption and ink transmission are well-balanced. A recording medium capable of performing the above can be provided.

According to a preferred embodiment of the present invention, the total light transmittance of the recording medium according to the present invention is preferably about 20 to 80%, more preferably about 30 to 70%. Here, the total light transmittance means a value obtained by a measurement method B defined in JIS-K-7105. Specifically, the percentage of the ratio between the irradiation light amount (T1) and the transmitted light amount (T2), that is, (T2 / T1) × 100 is the total light transmittance.

According to a preferred embodiment of the present invention, the whiteness of the recording medium observed from the transparent substrate side of the recording medium according to the present invention is preferably about 50 to 90, and more preferably 70 or more. . Here, whiteness refers to JIS-
Hunter brightness or JIS defined in P-8123
-Means ISO whiteness defined in P-8148.

The recording medium according to the present invention is used in a recording system using an ink composition. Examples of the recording method using the ink composition include an ink jet recording method, a recording method using a writing instrument such as a pen, and various other printing methods. Further, the ink composition is not limited to the liquid ink, and includes a solid colorant and a colorant which is used by heating and melting. In particular, the recording medium according to the present invention is preferably used for an ink jet recording method.
That is, it is preferably used for a recording method including a step of discharging droplets of an ink composition onto a recording medium according to the present invention and attaching ink droplets to the recording medium.

Further, according to a preferred embodiment of the present invention, it is preferable to use an ink composition containing at least a colorant, an organic solvent, water and a surfactant. In particular, by printing with an ink composition whose permeability to a recording medium has been enhanced by a surfactant, it is possible to realize excellent image quality with higher density. Preferred examples of the surfactant include an acetylene glycol, an anionic surfactant having a polyoxyethylene group, and the like.

Here, preferred specific examples of acetylene glycol include compounds represented by the following formula (I).

[0033]

Embedded image (In the formula, 0 ≦ m + n ≦ 50, R ¹ , R ² , R ³ , and R ⁴ are each independently an alkyl group.) Specific examples of the compound represented by the above formula (I) include olphin Y, Surfynol 82, Surfynol 44
0, Surfinol 465, Surfinol 485 (Ai
r Products and Chemicals. Inc.). These may be used alone or in combination of two or more.

Examples of the anionic surfactant having a polyoxyethylene group include polyoxyethylene alkyl ether sulfate, polyoxyethylene alkyl phenyl ether sulfate, polyoxyethylene styrenated phenyl ether sulfate, and polyoxyethylene alkyl. Surfactants such as ether phosphates and polyoxyethylene alkyl phenyl ether phosphates are exemplified, and polyoxyethylene alkyl ether sulfates or polyoxyethylene alkyl phenyl ether sulfates are preferred.
In the anionic surfactant having a polyoxyethylene group, inorganic ions such as potassium, sodium, and ammonium, and amines such as monoethanolamine and diethanolamine are preferable, and ammonium ions are particularly preferable as a counter ion for forming a salt.

Here, the ink composition means a black ink composition when performing monochrome printing, and a color ink composition when performing color printing, specifically, a yellow ink composition and a magenta ink. Composition, and cyan ink composition, and in some cases, black ink composition. Further, the recording medium according to the present invention is a total of six color inks of a yellow ink composition, two magenta ink compositions having different color densities, two cyan ink compositions having different color densities, and a black ink composition. It may be used in a recording method using the composition. According to such a six-color ink composition and the recording medium according to the present invention, excellent gradation properties, no particle points,
A print image comparable to a photograph can be realized.

The coloring agent contained in the ink composition includes
Any of a dye and a pigment may be used.

The dyes include direct dyes, acid dyes, food dyes, basic dyes, reactive dyes, disperse dyes, vat dyes,
Various dyes usually used for ink jet recording, such as a soluble vat dye and a reactive disperse dye, can be used.

As the pigment, inorganic pigments and organic pigments can be used without any particular limitation. As the inorganic pigment, in addition to titanium oxide and iron oxide, carbon black produced by a known method such as a contact method, a furnace method, and a thermal method can be used. Examples of organic pigments include azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, chelated azo pigments, etc.) and polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazines) Pigments, thioindigo pigments, isoindolinone pigments, quinofuralone pigments, etc., dye chelates (eg, basic dye chelates, acid dye chelates, etc.), nitro pigments, nitroso pigments, aniline black and the like can be used.

According to a preferred embodiment of the present invention, these pigments are preferably added to the ink as a pigment dispersion obtained by dispersing in an aqueous medium with a dispersant or a surfactant. As preferred dispersants, use can be made of dispersants conventionally used or to be used conventionally for preparing pigment dispersions, for example polymeric dispersants. It will be apparent to those skilled in the art that the dispersant and surfactant contained in this pigment dispersion will also function as the dispersant and surfactant of the ink composition.

The amount of the pigment added to the ink is 0.5 to 25.
% By weight, more preferably 2 to 15% by weight.
It is about.

According to a preferred embodiment of the present invention, the ink composition used in the present invention preferably further contains a wetting agent comprising a high-boiling organic solvent. Preferred examples of the high boiling organic solvent include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, propylene glycol, butylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, glycerin, Polyhydric alcohols such as trimethylolethane and trimethylolpropane, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl Ether, triethylene glycol monobutyl ether Alkyl ethers of polyhydric alcohols such as urea, 2-pyrrolidone, N- methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, triethanolamine and the like.

The amount of the wetting agent added is 0.5% of the ink.
Preferably, it is in the range of 2 to 20% by weight.

Further, the ink composition used for recording on the recording medium according to the present invention can be prepared by adding a dispersant, a surfactant, an ultraviolet absorber, a pH adjuster, a preservative, a fungicide and the like. Good.

The recording medium according to the present invention may be recorded with the ink composition in the same manner as a conventionally known back print recording medium. Further according to a preferred embodiment of the present invention,
After the image is recorded, it is preferable to provide a protective layer on the light diffusion ink transmitting layer from the viewpoint of improving the storage stability. This protective layer can prevent the influence of humidity, moisture, light, ozone, etc. on the recording medium. Specifically, the recording medium may be coated with an ultraviolet absorbent, an antioxidant, or a quencher containing a low moisture-permeable film or synthetic paper, or may be adhered with an adhesive, or the film may be laminated. . Also,
By providing an adhesive on these protective layers, the recording medium itself may be attached.

[0045]

EXAMPLES The present invention will be described in detail with reference to the following Examples, but the present invention is not limited to these Examples.

Example 1 An ink receiving layer was formed on a substrate as follows. As a substrate, a polyethylene terephthalate film having a thickness of 100 μm, one surface of which was subjected to easy adhesion treatment by coating with water-dispersed polyester was prepared. Polyvinyl acetal resin (KX-1 solid content 8%, acetalization degree 8mol%, solvent composition: isopropyl alcohol /
(Water = 40/60, manufactured by Sekisui Chemical Co., Ltd.) was dissolved in a mixed solvent of isopropyl alcohol / water to a concentration of 7% to obtain a coating liquid. This coating solution is applied to the surface of the base material on which the adhesive treatment has been performed, using an applicator.
The ink was dried in a constant-temperature dryer at 2 ° C. for 2 minutes to form an ink receiving layer having a thickness of 7 μm.

Next, a light diffusion ink transmitting layer was formed on the ink receiving layer as follows. First, the following components were mixed to obtain a uniformly dispersed coating liquid. Carboxyl group-modified polyvinyl alcohol resin (anionic, saponification degree 99 mol% or more, polymerization degree 2200, T-330H manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 4.5% by weight silica (Sylysia 446, average particle diameter 4.5 microns, Fuji) Silysia chemical Ltd.) 12 wt% of titanium oxide (average particle size 0.26 micron) 2 wt% fluorescent pigment (manufactured by Shinroihi Co.) 2% by weight of colloidal silica (Snowtex C, anionic, SiO ₂ concentration: 20%) 10 Weight% isopropyl alcohol / water = 40/60 mixed solution Remaining amount The obtained coating liquid is applied on the ink receiving layer using an applicator, and then dried in a constant temperature dryer at 110 ° C. for 3 minutes. A back print recording medium having a 25 μm thick light diffusion ink transmitting layer was obtained.

Example 2 A back print recording medium was obtained in the same manner as in Example 1 except that the thickness of the light diffusion ink transmitting layer was changed to 15 μm by adjusting the amount of the coating liquid to be applied.

Example 3 A back print recording medium was obtained in the same manner as in Example 1 except that the thickness of the light diffusion ink transmitting layer was changed to 35 μm by adjusting the amount of the coating liquid to be applied.

Comparative Example 1 A back print recording medium was obtained in the same manner as in Example 1 except that the polyvinyl acetal resin was replaced with polyvinyl alcohol (PVA-117, manufactured by Kuraray Co., Ltd.) to form an ink receiving layer.

Preparation of Ink Composition An ink composition was obtained by mixing the following components, and ink sets 1 and 2 were obtained. Ink set 1 Yellow ink C.I. I. Direct Yellow 86 1.5% by weight C.I. I. Direct Yellow 23 1.5 wt% Diethylene glycol monobutyl ether 10 wt% Surfynol TG 0.8 wt% Diethylene glycol 20 wt% Triethanolamine 0.2 wt% Ion exchange water 66 wt% Cyan ink C.I. I. Direct Blue 199 3% by weight Diethylene glycol monobutyl ether 10% by weight Surfinol TG 0.8% by weight Diethylene glycol 20% by weight Triethanolamine 0.2% by weight Ion exchange water 66% by weight Magenta ink C.I. I. Reactive Red 147 3% by weight Diethylene glycol monobutyl ether 10% by weight Surfinol TG 0.8% by weight Diethylene glycol 20% by weight Triethanolamine 0.2% by weight Ion exchange water 66% by weight Black ink I. Direct Black 168 3% by weight Diethylene glycol monobutyl ether 10% by weight Surfinol TG 0.8% by weight Diethylene glycol 20% by weight Triethanolamine 0.2% by weight Deionized water 66% by weight The surface tension and viscosity of all the above inks are as follows. About 30
mN / m and 4 mPa · s, and pH was about 9.

Ink set 2 Yellow ink C.I. I. Pigment Yellow 17 3% by weight Styrene acrylic resin emulsion (solid content 30%) 3% by weight Maltitol 10% by weight Glycerin 10% by weight Triethanolamine 1% by weight 2-pyrrolidone 2% by weight Polyoxyethylene alkyl ether ammonium sulfate 0. 8% by weight ion exchange water 70.2% by weight magenta ink C.I. I. Pigment Red 122 3% by weight Styrene acrylic resin emulsion (solid content 30%) 3% by weight Maltitol 10% by weight Glycerin 10% by weight Triethanolamine 1% by weight 2-pyrrolidone 2% by weight Polyoxyethylene alkyl ether ammonium sulfate 0. 8% by weight ion exchange water 70.2% by weight cyan ink C.I. I. Pigment Blue 15: 3 3% by weight Styrene acrylic resin emulsion (solid content 30%) 3% by weight Maltitol 10% by weight Glycerin 10% by weight Triethanolamine 1% by weight 2-pyrrolidone 2% by weight Polyoxyethylene phenyl ether sulfate ammonium salt 0.8% by weight ion exchanged water 70.2% by weight black ink I. Pigment Black 7 3% by weight Styrene acrylic resin emulsion (solid content 30%) 3% by weight Maltitol 10% by weight Glycerin 10% by weight Triethanolamine 1% by weight 2-pyrrolidone 2% by weight Polyoxyethylene alkyl ether sulfate ammonium salt 0. 8% by weight Deionized water 70.2% by weight The surface tension and viscosity of all the above inks are about 35.
mN / m and 3 mPa · s, and the pH is about 9.
It was 5.

Ink set 3 A color ink concentration of the cyan ink and magenta ink of the above ink set 1 which was reduced to 1/4 was further prepared as light cyan ink and light magenta ink.
A color ink set was used.

Printing Evaluation Test Using the ink set obtained as described above, images were printed on the back print recording media of Examples 1 to 3 and Comparative Example 1, and the quality of the obtained printed image was evaluated as follows. Was evaluated as follows. The ink sets 1 and 2 were printed using a color inkjet printer MJ910C (manufactured by Seiko Epson Corporation), and the ink set 3 was printed using a recording device equipped with a prototype ink jet recording head for six colors. Was. (1) Dot Diameter The equivalent circle diameter per dot was measured with 100 samples on the transparent substrate side and the printing side (light diffusion ink absorbing layer side). (2) Print Density The reflection density and the transmission density of the transparent substrate were measured using TR-927 (manufactured by Macbeth). (3) Bleed Bleed at adjacent boundaries was visually observed using inks of different colors, and evaluated according to the following criteria. -There is no bleed and the border is clear--. -Bleeding occurs and the border is blurred and unclear-
×. (4) Ink absorptivity The ink amount of 15 mg / inch ² per color, and the color of blue created with magenta and cyan (total ejection amount 30 mg
/ Inch ² ) was printed at 100% duty. Further, the print density is set to 90%, 70%, 60%, 50%, 40%
%, 30%, 20%, and 10% duty. The ink absorbency was evaluated based on the% duty at which bleeding or ink bleeding was first observed on the printed matter. (5) Ink permeability The image data of the Japan Standards Association was printed, and the sharpness of the image was visually observed. Further, using a light board, light was applied from the back side, and the sharpness of the image was visually observed. The results were evaluated according to the following criteria. -The image is reproduced vividly with good ink permeability--The image is unclear due to poor ink permeability-x. (6) Ink absorption speed Printing was performed with an ink amount of 15 mg / inch ² per color, and the time until the ink was completely absorbed was measured. (7) Storage Property (Room Storage Property) The printed matter on which the human image was printed was left in a place where direct sunlight does not enter for 3 months, and the presence or absence of discoloration was visually observed. The results were evaluated according to the following criteria. -No change from the initial state---Discoloration compared to the initial state-× (8) Ink fixability The printed matter on which a human image is printed is obtained under the environment of 40 ° C and 85% at 1%.
It was left for a week and visually observed for discoloration. The results were evaluated according to the following criteria. -No change from the initial state---Discoloration compared to the initial state-x (9) Light transmittance The light transmittance of the unprinted recording medium is JIS K7.
The measurement was carried out in accordance with the rules of No. 105. (10) Whiteness The ISO whiteness of a non-printed recording medium is determined according to JIS P
It was measured according to 8148.

The above results were as shown in the following table.

[0056]

[Table 1]

[0057]

[Table 2]

[Brief description of the drawings]

FIG. 1 is a partial sectional view of a recording medium according to the present invention. The recording medium 1 has an ink receiving layer 3 and a light diffusion ink transmitting layer 4 provided on a transparent base material 2 in this order. Recording is performed on the recording medium 1 by the ink droplets 5 from the light diffusion ink transmitting layer 4 side. The dots 7 serving as elements of the image formed by the ink droplets 5 are formed on the transparent substrate 2 in the ink receiving layer 3.
The dot diameter observed from the side, that is, the side indicated by arrow A in the figure, is smaller than the dot diameter observed from the light diffusion ink transmitting layer 4 side.

FIG. 2 is a diagram showing how an image is recorded on a recording medium according to the present invention. FIG. 2A shows an ink jet recording method in which an ink droplet 5 is formed from a light diffusion ink transmitting layer 4 side of a recording medium 1 in which an ink receiving layer 3 and a light diffusing ink transmitting layer 4 are sequentially provided on a transparent substrate 2. It is a figure showing signs that it is printed by a method. FIG. 2B shows a state in which the ink droplets 5 adhere to the light diffusion ink transmitting layer 4 and penetrate the light diffusion ink transmitting layer 4 toward the ink receiving layer 3. FIG. 2 (c)
FIG. 4 is a view showing a state in which the ink composition 6 subsequently reaches the ink receiving layer 3 and penetrates while reducing its diameter. Also,
FIG. 2D is a view showing a state in which most of the ink composition 6 finally reaches the ink receiving layer 3 to form one dot as an element of an image.

Claims (16)

[Claims] An ink-receiving layer and a light-diffusing ink-transmitting layer are provided at least on a transparent substrate in order, and printing is performed from the light-diffusing ink-transmitting layer side, and printing can be observed from the transparent substrate side. A recording medium, wherein a printed dot diameter observed from a transparent base material side is smaller than a printed dot diameter observed from a light diffusion ink transmitting layer side. 2. The recording medium according to claim 1, wherein said ink receiving layer contains a polyvinyl acetal resin. 3. The recording medium according to claim 2, wherein the polyvinyl acetal resin has an acetalization degree of 2 to 20 mol%. 4. The light-diffusing ink transmission layer according to claim 1, wherein the light-diffusing ink-transmitting layer contains at least a carboxyl group-modified polyvinyl alcohol, colloidal silica, a whitening agent, and synthetic silica. Recording medium. 5. A light diffusion ink transmitting layer having a thickness of 15 to 40 μm.
m, and the thickness of the ink receiving layer is 3 to 15 μm.
The recording medium according to claim 1. 6. The recording medium according to claim 1, wherein the total light transmittance of the recording medium is 20 to 80%. 7. The recording medium according to claim 1, wherein the whiteness of the recording medium observed from the transparent substrate side is 50 to 90. 8. The recording medium according to claim 1, wherein the surface of the transparent substrate on the side in contact with the ink receiving layer is subjected to an easy adhesion treatment. 9. The antistatic treatment of the surface of the transparent substrate on the side not in contact with the ink receiving layer.
9. The recording medium according to any one of 8. 10. An ink-jet method comprising the steps of: discharging a droplet of an ink composition onto a recording medium according to claim 1, and attaching the ink droplet to the recording medium. Recording method. 11. An ink composition comprising: a colorant; an organic solvent;
The inkjet recording method according to claim 10, comprising at least water and a surfactant. 12. The ink jet recording method according to claim 11, wherein the colorant is a pigment and the surfactant is an anionic surfactant having a polyoxyethylene group. 13. The ink jet according to claim 10, wherein a yellow ink composition, a magenta ink composition, a cyan ink composition, and optionally a black ink composition are used as the ink composition. Recording method. 14. An ink composition comprising a total of six colors including a yellow ink composition, two magenta ink compositions having different color densities, two cyan ink compositions having different color densities, and a black ink composition. The inkjet recording method according to any one of claims 10 to 12, wherein an ink composition is used. 15. An image recorded by the ink jet recording method according to any one of claims 10 to 14,
Records. 16. The recorded matter according to claim 15, wherein after the image is recorded, a protective layer is provided on the light diffusion ink transmitting layer.