Indirect transfer medium and forgery prevention medium producing apparatus

According to one embodiment, an indirect transfer medium includes: a base material; and an image receiving layer on which an image is capable of being formed by ink-jet printing. The image receiving layer includes a vinyl acetate maleate copolymer as thermo-adhesive material. The image receiving layer is laminated on the base material.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2012-197859, filed on Sep. 7, 2012; the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to an indirect transfer medium and a forgery prevention medium producing apparatus.

BACKGROUND

Printing made on a fibrous medium such as paper with an ink-jet printer has the following drawbacks.

(1) Ink bleeds along fibers, and thus high image quality is not achieved.

(2) When water or a chemical adheres to the paper after printing, ink dye or ink pigment is removed from the paper and thus printed records are not preserved.

In order to address the drawback (1), paper coated with resin or the like for preventing the ink from bleeding to improve image quality, i.e., ink-jet printing paper, is widely used.

In order to address the drawback (2), in addition to the aforementioned technique, there has been proposed: a technique to add a cationic resin or the like to include a component for fixing dye and pigment onto the paper; and a technique to adhere a protective film onto the printed paper so that water or chemical does not make contact with ink components.

Furthermore, as a technique to address the drawbacks (1) and (2), there has been known an indirect transfer method for providing the bonding surface of a protective film, which is usually adhered onto paper after printing, with a high-quality image printing capability. Then, according to the indirect transfer method, the bonding surface is adhered onto a target medium after the printing is performed on the protective film.

However, there are a limited number of examples of indirect transfer methods for ink-jet printing, and also, known examples of indirect transfer media are often limited to use in iron-on transfer sheets and ID cards, for example. Therefore, there has not been proposed an indirect transfer method with high image quality, high durability, and high production efficiency, and that can be used for official documents and the like.

DETAILED DESCRIPTION

In general, according to one embodiment, an indirect transfer medium comprises: a base material; and an image receiving layer on which an image is capable of being formed by ink-jet printing. The image receiving layer includes a vinyl acetate maleate copolymer as thermo-adhesive material. The image receiving layer is laminated on the base material (11).

Exemplary embodiments will be described with reference to the accompanying drawings.

First Embodiment

FIG. 1is a schematic cross-sectional view illustrating a configuration of an ink-jet recording transfer medium according to a first embodiment.

An ink-jet recording transfer medium (hereinafter referred to as an indirect transfer medium)10roughly includes a base material11, and an ink-image receiving layer12laminated on the base material11.

The base material11serves as an overcoat layer (protective film) when the base material11is transferred onto a transfer target medium (transferred medium) such as paper.

The base material11is formed of hydrophobic materials such as an ultraviolet curable resin, a polyester resin, and polyethylene terephthalate. The base material11has optical transparency, and heat resistance strong enough to tolerate thermal transfer.

Consequently, the base material11serves as an overcoat layer, and ensures the fastness of printed records after thermal transfer.

The ink-image receiving layer12develops adherence property with respect to the transfer target medium by heating. The layer thickness thereof is designed to be 5 to 30 μm.

The ink-image receiving layer12contains a water-absorbent resin, a cationic resin, and a thermoplastic resin. As the water-absorbent resin, a modified polyester is used for example. As the cationic resin, a cationic vinyl compound is used for example. As the thermoplastic resin, a vinyl acetate maleate copolymer is used.

The following describes the compounding ratios of the respective resins in the ink-image receiving layer12when a modified polyester is used as the water-absorbent resin, a cationic vinyl compound is used as the cationic resin, and a vinyl acetate maleate copolymer is used as the thermoplastic resin.

In this case, an important factor for determining the properties of the ink-image receiving layer12is the compounding ratio of the vinyl acetate maleate copolymer as the thermoplastic resin.

In the first embodiment, the compounding ratio of the vinyl acetate maleate copolymer is set to be 10% to 40% by weight.

The reason for the compounding ratio of the vinyl acetate maleate copolymer to be set to equal to or greater than 10% by weight is that, when the compounding ratio is below 10% by weight, an amount of thermoplastic resin is so small that it can degrade adherence property with respect to the base material11.

FIG. 2is a graph for explaining a relationship between a peeling ratio (%) of a base material serving as an overcoat layer and a compounding ratio of a vinyl acetate maleate copolymer, which is a thermoplastic resin. This relationship is used for determining the compounding ratio of the vinyl acetate maleate copolymer.

When a peeling ratio acceptable for practical use, which was determined based on experiments, is taken to be P %, the compounding ratio of the vinyl acetate maleate copolymer having the peeling ratio of less than or equal to P % is greater than or equal to 10% by weight.

Meanwhile, the reason for the compounding ratio of the vinyl acetate maleate copolymer to be set to less than or equal to 40% by weight is that adhesive strength with respect to paper, which is assumed as a transfer target medium, lowers when the compounding ratio exceeds 40% by weight. Furthermore, because the vinyl acetate maleate copolymer, which is a thermoplastic resin, has fluidity during thermal transfer, printing may be smeared when the compounding ratio of the vinyl acetate maleate copolymer is too high.

As a consequence, the compounding ratio of the vinyl acetate maleate copolymer being set to 10% to 40% by weight ensures adhesive strength with respect to the base material11and paper, which is assumed as a transfer target medium. This further allows the printing quality to remain at a high quality level.

The second important factor for determining the properties of the ink-image receiving layer12is the compounding ratio of the cationic vinyl compound as a cationic resin.

In the first embodiment, the compounding ratio of the cationic vinyl compound is set to be 5% to 10% by weight.

The reason for the compounding ratio of the cationic vinyl compound to be set to greater than or equal to 5% by weight is that, when the compounding ratio is below 5% by weight, the retentive strength of anionic aqueous ink used in ink-jet printing lowers and thus the quality of an image formed lowers.

Meanwhile, the reason for the compounding ratio of the cationic vinyl compound to be set to less than or equal to 10% by weight is that, when the compounding ratio exceeds 10% by weight, cohesion occurs during the mixing of materials constituting the ink-image receiving layer12and thus homogeneously mixed materials cannot be obtained.

The compounding ratio of the modified polyester as a water-absorbent resin is adjusted, after the compounding ratio of the vinyl acetate maleate copolymer and the compounding ratio of the cationic vinyl compound are determined, to be 100% by weight as a whole including some additives (for example, dispersant, antifoaming agent, and surfactant). As a result, in the first embodiment, the compounding ratio of the modified polyester is set to be 55% to 80% by weight.

With the ink-image receiving layer12in the first embodiment, an aqueous ink used in ink-jet printing turns into a dry condition in 0.42 seconds per 1 pl (picoliter) thereof. The dry condition here means that, unless otherwise noted, ink is not transferred onto another medium such as copying paper or a SUS plate when the other medium is pressed against an image formed portion (printed portion) with a loading of 70 g/cm2.

With the ink-image receiving layer12in the first embodiment, the diameter (micrometers) of an image dot formed with an aqueous ink used for ink-jet printing can be controlled to a value obtained by the following Equation (1) using the volume of ink (picoliters):

The value D represented by Equation (1) is about 25 μm for an image dot of an image formed (printed) with 3 pl of ink, and about 42 μm for an image dot of an image formed (printed) with 6 pl of ink.

The ink-image receiving layer12in the first embodiment is designed such that the roundness of dots formed is less than or equal to 10% of the average radius of the dots.

FIG. 3is a schematic diagram illustrating a configuration of an ink-jet forgery prevention medium producing apparatus.

A view on a left hand side ofFIG. 3is a side view of a conveyance system of the forgery prevention medium producing apparatus.

A view on a right hand side ofFIG. 3is a front view of the conveyance system of the forgery prevention medium producing apparatus.

A forgery prevention medium producing apparatus50includes: an indirect transfer medium roll51in which the indirect transfer medium10laminated on a conveying-base material59in a long sheet form is wound around an indirect transfer medium roller52in a roll form; and an ink-jet printing unit53that serves as an ink-jet image forming unit and forms an ink-jet printed image on the indirect transfer medium10.

The forgery prevention medium producing apparatus50further includes: a plurality of indirect transfer medium conveying shafts54serving as a first conveying unit that conveys the indirect transfer medium10together with the conveying-base material59as a whole in the arrow A direction in the view on the left hand side ofFIG. 3; a tension control shaft62that maintains the tension (tensile force) of the indirect transfer medium10at constant during conveyance through rotation of a rotating arm62B around a rotational shaft62A as the center of rotation by a drive mechanism not illustrated; and a heat roller (thermal transfer roller)55that performs thermal transfer of the indirect transfer medium10onto a transfer target medium56.

The forgery prevention medium producing apparatus50further includes: a base-material collecting roll57that winds up and collects the conveying-base material59after the transfer; a transfer-target medium conveying unit60that includes a thermocompression-bonding smoothing plate61formed with roller holes61A through which respective parts of a plurality of conveying rollers60A are projected on the upper surface side and that serves as a second conveying unit conveying the transfer target medium56as a transfer target medium in the arrow B direction, and a controller70that controls the whole forgery prevention medium producing apparatus50.

In the above-described configuration, the ink-jet printing unit53has an ink-jet head53A, and the ink-jet printing unit53is driven by a scanning motor not illustrated, which is driven under the control of the controller70. The ink-jet printing unit53is integrally scanned with the ink-jet head53A in the sub-scanning direction (left-right direction inFIG. 3B) orthogonal to the main-scanning direction, which is the conveying direction of the indirect transfer medium10, along an operation guide shaft not illustrated.

The heat roller55includes a rotating arm55B to rotate around a rotational shaft55A as the center of rotation. When transfer operation is not performed, the heat roller55separates the conveying-base material59from the transfer target medium56through the rotating arm55B.

The tension control shaft62includes the rotating arm62B to rotate around the rotational shaft62A as the center of rotation.

Next, the operation of the forgery prevention medium producing apparatus50will be described.

FIG. 4is a flowchart of an operation of the forgery prevention medium producing apparatus.

Upon receiving print information via a connector or a network not illustrated (S11), the controller70rotates the base-material collecting roll57to draw out the indirect transfer medium10from the indirect transfer medium roll51. In synchronization with of the drawing out of the indirect transfer medium10, the ink-jet printing unit53performs scanning to form an image corresponding to the print information received, on the indirect transfer medium10(S12).

FIG. 5is a diagram for explaining an image forming state.

The controller70forms (prints) an image with the ink-jet printing unit53while maintaining the tension of the indirect transfer medium10constant using the indirect transfer medium conveying shafts54and the tension control shaft62.

Consequently, as illustrated inFIG. 5, the image is formed with ink supplied by the ink-jet printing unit53on the ink-image receiving layer12of the indirect transfer medium10and is retained thereon.

The controller70subsequently rotates the conveying rollers60A of the transfer-target medium conveying unit60, and causes the transfer target medium56in a sheet form or a booklet form (for example, a passbook and a passport) to move up to and stop at a transfer start position (S13).

The controller70then conveys the indirect transfer medium10, on which printing has been finished, via the indirect transfer medium conveying shafts54until a printed portion reaches the transfer start position, and stops the indirect transfer medium10. In this case, the time duration until when the image formed on the indirect transfer medium10(image forming surface) is made in contact with other members including the tension control shaft62is set to be greater than or equal to 10 seconds and less than or equal to 30 seconds, and is controlled such that the dry condition is met before the indirect transfer medium10makes contact with other members including the tension control shaft62.

FIG. 6is a diagram for explaining the transfer of the indirect transfer medium, and the operation during the transfer in the first embodiment.

The controller70next heats up the heat roller55. The controller70then rotates the rotating arm55B around the rotational shaft55A as the center of rotation with the drive mechanism not depicted, to move the heat roller55such that the indirect transfer medium10is pressed against the transfer target medium56by the heat roller55.

Under the condition of the indirect transfer medium10being pressed against the transfer target medium56by the heat roller55, the controller70rotates the conveying rollers60A of the transfer-target medium conveying unit60to add heat (100 to 180° C.) by the heat roller55to the whole transfer target area. As a result, as illustrated inFIG. 6, the indirect transfer medium10is transferred onto the transfer target medium56(S14).

The controller70then further rotates the conveying rollers60A of the transfer-target medium conveying unit60. Upon rotation of the conveying rollers60A, the controller70stops the rotation of the indirect transfer medium roll51and the base-material collecting roll57. Consequently, the controller70discharges a forgery prevention medium56A while peeling off the conveying-base material59that conveys the indirect transfer medium10(S15).

The controller70then rotates the base-material collecting roll57to collect the conveying-base material59after the transfer and peel-off (S16).

The above-described process produces the forgery prevention proof medium56A with the indirect transfer medium10transferred onto the transfer target surface thereof.

As in the foregoing, the indirect transfer medium10in the first embodiment enables forming of an image of high image quality without ink bleeding along fibers even when printing is performed by ink-jet printing.

Furthermore, because the indirect transfer medium10is fast-dry, the forgery prevention medium56A is produced at low cost and in a short period of time even when an ink-jet printer and a transfer device that performs transfer are integrally configured as a forgery prevention medium producing apparatus.

Moreover, the forgery prevention medium56A obtained by transferring (thermocompression bonding) the indirect transfer medium10onto the transfer target medium56has superior image quality, and because the surface thereof is covered with the base material11as an overcoat, the forgery-proof medium56A has durability.

Second Embodiment

An indirect transfer medium according to a second embodiment will be described.

The indirect transfer medium in the second embodiment is an embodiment in which a functional layer with a predetermined function is provided between the base material and the ink-image receiving layer of the first embodiment.

FIG. 7is a schematic cross-sectional view illustrating a configuration of the indirect transfer medium in the second embodiment.

An indirect transfer medium20in the second embodiment includes a functional layer13provided between the base material11and the ink-image receiving layer12of the indirect transfer medium10of the first embodiment.

In the second embodiment, a peel-off layer131, a protective layer132, and an optical layer133are used as the functional layer13. However, the configuration of the functional layer is not restricted to the configuration in the second embodiment, and can be changed as necessary.

In the following, the indirect transfer medium20of the second embodiment is explained with reference toFIGS. 1 and 7.

In the second embodiment, the functional layer13with a desired function provided between the ink-image receiving layer12and the base material11improves convenience in transfer and enables addition of function, which cannot be achieved by simply performing the thermal transfer of printed records onto other media.

In an example ofFIG. 7, the peel-off layer131, the protective layer132, the optical layer133, and the ink-image receiving layer12are laminated on the base material11in the foregoing order. Thus, selectively applying heat to a specific position of the indirect transfer medium20allows only a part thereof to be adhered to a transfer target medium (transferred medium), and allows the peel-off layer131and the protective layer132to be peeled off.

As a consequence, when the indirect transfer medium20is formed in a roll form, printing and transferring can be performed continuously.

Furthermore, the protective layer132bonded to a forgery prevention medium via the ink-image receiving layer12allows the fastness of printed records after bonding to be retained.

Moreover, because the optical layer133is laminated between the protective layer132and the ink-image receiving layer12, information by printing, hologram, or the like can be recorded together. The indirect transfer medium20in the second embodiment thus enables production of printed records that cannot be duplicated easily.

The base material11, however, is not necessary to have the function of an overcoat layer. Thus, the base material11may not need to have optical transparency. More specifically, the base material11only needs to have the function that allows the ink-image receiving layer12and the functional layer13to be retained until the thermal transfer to the transfer target medium (for example, paper) is performed.

As for the configuration of the functional layer13, it is not limited to have only the peel-off layer131, the protective layer132, and the optical layer133, but it is possible to omit a part of the layers or to laminate a additional layer having another function as necessary.

Next, with reference toFIG. 3again, the production of a forgery prevention medium using the indirect transfer medium20in the second embodiment will be described.

FIG. 8is a diagram for explaining an image forming state.

The controller70of the forgery prevention medium producing apparatus50illustrated in the view on the left hand side ofFIG. 3forms (prints) an image with the ink-jet printing unit53while maintaining the tension of the indirect transfer medium20constant using the indirect transfer medium conveying shafts54and the tension control shaft62.

Consequently, as illustrated inFIG. 8, the image is formed with ink supplied by the ink-jet printing unit53on the ink-image receiving layer12of the indirect transfer medium20and is retained thereon.

The controller70subsequently rotates the conveying rollers60A of the transfer-target medium conveying unit60and causes the transfer target medium56in a sheet form or a booklet form (for example, a passbook and a passport) to move up to and stop at a transfer start position.

The controller70then conveys the indirect transfer medium20, on which printing has been finished, via the indirect transfer medium conveying shafts54until a printed portion reaches the transfer start position, and stops the indirect transfer medium20. In this case, the time duration until when the image formed on the indirect transfer medium20(image forming surface) is made in contact with other members including the tension control shaft62is set to be greater than or equal to 10 and less than or equal to 30 seconds, and is controlled such that the dry condition is met before the indirect transfer medium20makes contact with other members including the tension control shaft62.

FIG. 9is a diagram for explaining the transfer of the indirect transfer medium and the operation during the transfer in the second embodiment.

The controller70heats up the heat roller55. The controller70then rotates the rotating arm55B around the rotational shaft55A as the center of rotation with the drive mechanism not illustrated, to move the heat roller55such that the indirect transfer medium20is pressed against the transfer target medium56by the heat roller55.

Under the condition in which the indirect transfer medium20is pressed against the transfer target medium56by the heat roller55, the controller70rotates the conveying rollers60A of the transfer-target medium conveying unit60to apply heat (100 to 180° C.) by the heat roller55to the whole transfer target area. As a result, as illustrated inFIG. 9, the indirect transfer medium20is transferred onto the transfer target medium56.

The controller70then further rotates the conveying rollers60A of the transfer-target medium conveying unit60. Upon the rotation of the conveying rollers60A, the controller70stops the rotation of the indirect transfer medium roll51and the base-material collecting roll57. Consequently, the controller70discharges the forgery prevention medium56A while peeling off the peel-off layer131and the base material11of the indirect transfer medium20.

The controller70then rotates the base-material collecting roll57to collect the base material11and the peel-off layer131after the transfer and peel-off.

The above-described process produces the forgery prevention medium56A with the indirect transfer medium20(except for the base material11and the peel-off layer131) transferred onto the transfer target surface thereof.

As in the foregoing, the indirect transfer medium20in the second embodiment enables forming of an image of high image quality without ink bleeding along fibers even when printing is performed by ink-jet printing.

Furthermore, because the indirect transfer medium20is fast-dry, the forgery prevention medium56A is produced at low cost and in a short period of time even when an ink-jet printer and a transfer device that performs transfer are integrally configured as a forgery prevention medium producing apparatus.

Moreover, the forgery prevention medium obtained by transferring (thermocompression bonding) the indirect transfer medium20onto the transfer target medium56has superior image quality.

When the indirect transfer medium20is formed in a roll form, printing and transferring can be performed continuously, whereby the effective production speed of the forgery prevention medium56A is improved, and thus work efficiency is improved.

While the second embodiment describes the case in which the base material11and the peel-off layer131are peeled off at the boundary surface between the peel-off layer131and the protective layer132, the place of peeling may be the boundary surface between the base material11and the peel-off layer131, or the peel-off layer131can be partially peeled off to remain on both the base material11and the peel-off layer131. More specifically, as long as there are no defects on all of the protective layer132, the optical layer133, the ink-image receiving layer12, ink31, and the transfer target medium56, the place of peeling can be anywhere.

First Modification

FIG. 10is a schematic diagram illustrating a configuration of a forgery prevention medium producing apparatus according to a first modification of embodiment(s).

In the forgery prevention medium producing apparatus50in the above description, the ink-jet head53A of the ink-jet printing unit53is configured to be driven by the scanning motor not illustrated, which is driven under the control of the controller70, and to be scanned in the sub-scanning direction orthogonal to the main-scanning direction, which is the conveying direction of the indirect transfer medium10, along an operation guide shaft not depicted.

However, as illustrated inFIG. 10, a line ink-jet head53B as an ink-jet head can perform printing for one line in one go.

This configuration can simplify the configuration of the apparatus because a mechanism for scanning the ink-jet head is not needed and improve the image forming speed, whereby a forgery prevention medium can be produced at a higher speed.

Second Modification

FIG. 11is a schematic diagram illustrating a configuration of a forgery prevention medium producing apparatus according to a second modification of embodiment(s).

In the above description, the controller70is configured to maintain the tension (tensile force) of the indirect transfer medium constant during conveyance with the tension control shaft62by rotating the rotating arm62B around the rotational shaft62A as the center of rotation with the drive mechanism not depicted. In contrast, the second modification is configured to maintain the tension (tensile force) of the indirect transfer medium constant during conveyance not by rotating the tension control shaft62but by driving it linearly with a biasing member such as a spring.

Consequently, the mounting space for the tension control shaft62can be made small, and eventually, downsizing of the forgery prevention medium producing apparatus can be achieved.

Third Modification

FIG. 12is a schematic diagram illustrating a configuration of a forgery prevention medium producing apparatus according to a third modification of embodiment(s).

In the above description, it is configured that the transfer target medium56, which is a transfer target medium, is conveyed on a fixed conveying path configured as the thermocompression-bonding smoothing plate61by the conveying rollers60A.

As for the conveying method of the transfer target medium56, however, the mechanism only needs to move the indirect transfer medium10or20and the transfer target medium56in a coordinated manner. For example, as illustrated inFIG. 12, it is possible to adopt a configuration in which the thermocompression-bonding smoothing plate61itself is moved by the conveying rollers60A.

Example

A more specific example will be described.

The present example is an example corresponding to the first embodiment.

In the present example, a resin mixture constituting the ink-image receiving layer12is obtained at the following compounding ratios:

The polyoxyalkylene lauryl ether as an additive is added to improve wettability of when coating is performed.

The foregoing materials are sufficiently kneaded to obtain a material to form the ink-image receiving layer12, and then uniformly applied (coating) onto a 25 μm thick polyethylene terephthalate film base material as the base material11using, for example, a bar coater.

By drying it in an oven at 100° C. for 10 minutes, the indirect transfer medium10with a film thickness of 33 μm is obtained (the layer thickness of the ink-image receiving layer12was 8 μm).

On the indirect transfer medium10of this example, solid printing was made with an ink amount of 1.3 ml (milliliters) on an area of 1 cm2. In 10 seconds, it turned into the dry condition under which the ink is not transferred onto copying paper (made by Fuji Xerox) even when a load of 70 g/cm2was applied.

An image dot formed with 6 pl of ink had a diameter of 42±2 μm.

The roundness of the image dot formed was 2 μm, and thus mixing the above-described materials of the water-absorbent resin, the cationic resin, and the thermoplastic resin (vinyl acetate maleate copolymer) at the foregoing compounding ratios can form an image dot close to a true circle stably.

Moreover, through thermocompression bonding of the image forming surface (printing surface) of the ink-image receiving layer12as an adhering surface at greater than or equal to 100° C., more preferably at greater than or equal to 150° C. and less than or equal to 180° C., the ink-image receiving layer12adheres to a paper medium.

The base material11is not limited to a polyethylene terephthalate film, and as long as it is a film that transmits at least the light of a wavelength from 300 to 900 nm (nanometers) (near-ultraviolet rays, visible light, and near-infrared rays), the material thereof is not specifically limited.

The present example provides a fast-dry ink-jet indirect transfer medium, which can contribute to improvement in work efficiency (such as reduction of processing time) and provide superior image quality in the indirect transfer medium and eventually in the forgery-proof medium.