JP2022035893A - Ink jet printing onto silicone rubber substrate - Google Patents

Abstract

To solve a problem that printing other than screen printing by using silicone ink was not employed for printed image having durability to a silicone rubber substrate, and there was not silicone ink usable in digital printing, and general ink was easily omitted from a surface.SOLUTION: By using silica hybrid ink for ink jet printing and applying surface modification treatment before printing and image heating treatment during printing, attached ink does not separate/condensate into a waterdrop-like shape, or blurred, and furthermore, an image which is strongly adhered onto a silicone rubber substrate is obtained.SELECTED DRAWING: None

Description

The present invention relates to a method for forming an image layer printed with an organic / inorganic silica hybrid ink on a silicone rubber base material and an image forming base material.

Since the vulcanized silicone rubber base material (hereinafter referred to as silicone rubber base material) has poor adhesiveness, a silicone ink in which a coloring pigment is dispersed in liquid silicone is used for surface decoration. This is because the curable silicone composition such as liquid silicone is excellent in leveling property and adhesiveness to the surface of the silicone rubber base material. Since printing is screen printing, a multicolor printed image is completed while the silicone ink image is vulcanized and cured for each color printing and fixed.

In Patent Document 1, a decorative layer for transfer, which is composed of a silicone ink layer, is formed on a flat substrate for transfer by screen printing, and the decorative layer is formed into a rubber-like elastic body such as silicone rubber as a decoration object. It is a method of transcription. Both the decorative layer and the object to be decorated are subjected to surface modification treatment for the purpose of improving adhesiveness, and the two are joined and transferred. Since there is no surface modification treatment on the flat substrate side on which the decorative layer is printed and formed, the decorative layer is easily peeled off and transferred to the object to be decorated. A silicone ink layer is formed on the flat substrate side to form a peeling layer, and an adhesive layer is formed on the layer. A method of forming and transferring a silicone ink layer of the above has also been proposed.

An image consisting of traditional analog printer ink such as polyvinyl or polyamide instead of silicone ink is formed on the transfer material, and liquid silicone rubber is injection molded to remove the transfer material, thereby making the image a silicone rubber base. Patent Document 2 describes a method for forming an insert sheet in which simultaneous coating is applied to a material. A typical example of the transfer material used in the present invention is one in which a release layer, a design layer, an adhesive layer, and the like are sequentially laminated on a removable substrate sheet.

As an adhesive for image transfer, an inkjet ink for transfer, which comprises an organic solvent containing an organic / inorganic hybrid composition capable of obtaining a silica hybrid cured film after drying and curing, is described in Patent Document 3 (the applicant is the same person as the applicant). ). A transfer printing method in which this adhesive ink is inkjet printed on a toner image or the like formed on a water transfer sheet to form an adhesive film layer, and an image is formed on an object to be printed via the adhesive film layer. It's a suggestion.

Special No. 6001222 Japanese Patent Application Laid-Open No. 8-294938 Special No. 6074563

As described above, it is possible to decorate the surface of a silicone rubber substrate with a curable silicone ink such as liquid silicone, but screen printing requires heat vulcanization and curing for each color printing, which is time-consuming. , The problem of analog printing such as the need for plate making cannot be avoided. In addition, there remains the problem that it is difficult to form a delicate or multicolored pattern.

The inkjet ink image described in Patent Document 1 needs to be printed not directly on the vulcanized and cured silicone rubber layer formed on the transfer material, but through an adhesive layer formed by screen printing of urethane-based ink or the like. In order to transfer and adhere the inkjet ink image layer sandwiched between the silicone rubber layers to the object to be decorated, both the object to be decorated and the flat substrate for transfer must be surface-modified. Irradiate with ultraviolet rays from an excimer lamp or the like, and apply weight in the direction in which they come into contact to hold them. The example of the holding time at room temperature described is about 24 hours, which is a very long process. Moreover, it is unknown what kind of inkjet ink it is.

Patent Document 2 describes the types of ink binder resins such as polyvinyl type and polyamide type used in offset printing and the like, but similarly to Patent Document 1, the formed image is adhered to the surface of a silicone rubber base material. Is via an adhesive layer. Since it is an insert sheet molding method, it cannot be applied to printing a molded silicone rubber base material.

Since the silica hybrid cured film has affinity for both organic polymers and inorganic substances, it is said that it adheres to a wide range of materials, and the range of the base material to be transferred described in Patent Document 3 is from various plastics, glass, and metals. It is described as a flexible material such as rubber. There is no mention of adhesive suitability for silicone rubber, which has poor adhesiveness. We actually tried to transfer the toner image to the silicone rubber with the adhesive ink, but even if it adhered, strong adhesion could not be achieved. The image is easily dropped by peeling the cellophane tape. Even if the adhesive layer itself adheres, it seems impossible to retain the toner image layer thicker than the adhesive layer. Therefore, it can be concluded that the image transfer to a flexible material such as rubber described in the patent is unexpected for silicone rubber. Further, Patent Document 3 is a proposal of a transfer printing method, and there is no reference to direct printing on silicon rubber. A pigment was mixed with the adhesive ink and printing was actually attempted, but due to the low wettability of the silicon rubber surface, the adhered ink was separated and condensed into innumerable small polka dots, and normal image density could not be obtained. .. Since the surface of the base material can be seen between the polka-dotted inks, if the base material is white, the image color will appear light. For transfer purposes, since the substrate to be printed is water transfer paper, the adhesive ink does not separate and condense in the form of polka dots, and no surface treatment is required. No consideration is given to heat treatment during printing to prevent bleeding.

An object of the present invention is to provide a method for forming an inkjet printing layer that strongly adheres to a silicone rubber using a silica hybrid ink.

The first problem-solving means of the present invention is to perform surface modification treatment using an organic solvent containing an organic / inorganic hybrid composition in which a silica hybrid cured film can be obtained after drying and curing as an ink in order to achieve the above object. This is a method for forming a silica hybrid ink image layer on a silicone rubber base material, which comprises printing and forming an image layer with an inkjet printer while keeping the surface of the silicon rubber base material above a certain temperature.

The second problem-solving means is to use an organic solvent containing an organic / inorganic hybrid composition to obtain a silica hybrid cured film after drying and curing as an ink, and use an inkjet printer on a transfer sheet whose surface is kept at a certain temperature or higher. After the image layer is printed and formed in the above image layer, the image layer is covered with liquid silicone to form a silicone rubber film layer that acts as an adhesive layer between the image layer and the silicone rubber base material to be transferred. Is a method for forming a silica hybrid ink image layer on a silicone rubber base material, which comprises transferring.

Further, the third problem-solving means is to cover the image layer after printing and forming the image layer with liquid silicone to form a silicone rubber film layer in either the first or second problem-solving means. This is a method for forming a silica hybrid ink image layer characterized by the above on a silicone rubber base material.

Further, the fourth problem-solving means is that in the first to third problem-solving means, the organic polymer of the organic / inorganic hybrid composition is a thermosetting unsaturated polyester resin, a polyvinyl butyral resin, or an epoxy resin. It is a method for forming a silica hybrid ink image layer on a silicone rubber base material, which is characterized by containing a single resin or two or more kinds of resins.

Further, the fifth problem-solving means is an image layer made of a silica hybrid cured film containing a heat-curable unsaturated polyester resin, a polyvinyl butyral resin, an epoxy resin alone, or two or more kinds of resins as an organic polymer. It is an image printed matter characterized in that silicone rubber is adhered to at least one side of the front side or the back side.

Further, in the sixth problem-solving means, in the fifth problem-solving means, silica having a single particle diameter in the range of 1 to 100 nm is dispersed in the silica hybrid cured film at a concentration of 10% by weight to 50% by weight. It is an image printed matter characterized by being.

The action of the first problem-solving means is that high adhesive strength can be obtained without an adhesive layer on a silicone rubber base material, which is difficult to adhere, and because it is a digital printing method of inkjet printing, it is more than screen printing using silicone ink. Printing work is much easier, high-quality images can be obtained by surface modification treatment of silicone rubber base material and printing while keeping the base material surface above a certain temperature, and inkjet addition to conventional silicone rubber. The number of surface modification treatments can be reduced compared to the decoration method, and if a flatbed type printer is used, it is possible to print directly on a three-dimensional object, so it is possible to add an image to the silicone rubber base material without molding an insert sheet. Even when the image layer is covered with a silicon layer and cured, it is not necessary to apply a load to hold the image layer, and the image layer can be cured in a short time.
High adhesive strength to the silicone rubber substrate can be obtained by using the silica hybrid ink. This is because the silica hybrid cured film contains silica having a hydrophilic silanol group. In the industrial world, an adhesive-imparting agent is used to sufficiently adhere the silicone rubber composition to the surface of the resin molded body. In the adhesive-imparting agent, the functional groups that work for bonding are alkoxysilyl groups and hydrosilyl groups. Groups, silanol groups, etc. This is the reason why the ink of the present invention can obtain a strong adhesive force superior to that of other types of ink. Direct printing using silica hybrid ink can eliminate the need for an adhesive layer for adhering the silicone rubber composition and the image layer, which are required in the conventional method. However, the surface modification treatment of silicone rubber is also indispensable for obtaining high adhesiveness.
The high wettability obtained by the surface modification treatment is also effective in improving the image quality. Silicone rubber is used if printing is performed while keeping the surface of the base material at a certain temperature or higher to rapidly evaporate the solvent in the ink. However, normal image density can be obtained. The constant temperature or higher is preferably 55 ° C. or higher, more preferably 70 ° C. or higher at a standard inkjet printing speed in consideration of productivity. This temperature can be further reduced if the printing speed is extremely slowed down and the substrate surface adherent ink is given time to dry. As a method of keeping the surface of the base material above a certain temperature, a method of warming the base material to a sufficiently high temperature before mounting the printer, a printer table heating device for heating after mounting the printer, a heat ray irradiating device for heating the base material, and the like. One of the methods of heating while printing using a hot air blower or the like, or a method of combining them can be adopted.
As the surface modification treatment, frame treatment, corona discharge treatment, plasma treatment, itro treatment for adhering silicon oxide fine powder, and the like are effective. The silicone rubber base material referred to in the present invention means not only the silicone rubber base material itself but also a member having a surface coated with a silicone rubber layer.

Since the action of the second problem-solving means is transfer printing, it becomes easy to form an image even with a silicone rubber base material having a shape that is difficult to print directly. If the image layer is covered with liquid silicone that acts as an adhesive layer and transferred, The image can be strongly adhered to the silicone rubber substrate without surface modification treatment.
As for the transfer sheet, the water transfer paper on which the water-soluble layer is formed, the hydraulic transfer film composed of the water-soluble layer, the release film on which the non-silicone-based release layer such as fluororesin is formed, and the base material itself such as polyethylene resin have peelability. A film can be used. Silica hybrid ink can print clear images on these transfer sheets if it is printed while keeping the temperature above a certain level and rapidly evaporating the solvent in the ink. Since this constant temperature is described in the first problem-solving means, it is omitted here.
The reason why the silica hybrid ink printed image adheres strongly to the silicone rubber base material is also described in the first problem-solving means, but the silicone rubber film layer formation of the second problem-solving means is performed before the drying and curing of the image layer is completed. It is preferable to do it. The reason is that the silica hybrid cured film after drying and curing tends to be hydrophobic and has a low surface wettability, which reduces the adhesive force of the silicone rubber film layer to the image layer.
The surface modification treatment described in the first problem-solving means is for the purpose of modifying the surface of a vulcanized silicone rubber substrate having poor adhesiveness. In the second problem-solving means, since the image layer is in contact with the adhesive layer made of liquid silicone having sufficient adhesive strength to the silicone rubber base material, the surface modification treatment of the silicone rubber base material becomes unnecessary. The film layer, which is vulcanized and cured during or after transfer, adheres strongly to both the image and the substrate.

The action of the third problem-solving means is to improve the wear resistance, chemical resistance, stretchability of the base material, aesthetics, and the like of the image.
The silicone rubber film layer should be transparent for the visibility of the image. However, if the underlying silicone rubber base material is made transparent and the image is viewed from the base side, the image background can be made by making the silicone rubber film layer white. Although the reason is described in the second problem-solving means, it is preferable that the silicone rubber film layer is formed before the completion of drying and curing of the image layer. The film layer can be formed by screen printing, painting, transfer, or the like using liquid silicone, and the film layer is vulcanized and cured by heat treatment after formation.

The action of the fourth problem-solving means is that it is not necessary to pay attention to the crosslinking timing of the liquid silicone. That is, the work can be carried out according to the procedure described in the second problem-solving means.
Describe the reason for this. As the organic polymer of the hybrid solvent, many thermosetting and thermoplastic resins such as acrylic resin, ester resin, ketone resin, polyurethane resin, polyvinyl acetal resin and epoxy resin can be used. However, in the work procedure of the second problem-solving means, the liquid silicone to be the film layer covering the image is applied before the hybrid ink is completely cured. The liquid silicone to be applied is in a mixed state with a curing agent that serves as a cross-linking catalyst. That is, this working procedure means that the curing of the image layer made of the hybrid ink proceeds in the presence of the liquid silicone cross-linking catalyst. The organic polymer of the hybrid ink must be a resin that can be reliably cured in the presence of a cross-linking catalyst. Thermosetting resins that are thermosetting in the presence of a cross-linking catalyst include unsaturated polyester resin, polyvinyl butyral resin, epoxy resin, phenol resin, resole resin, alkyd resin, urea resin, melamine resin, polyurethane resin, and diallyl phthalate resin. And so on.
Among these, a resin that does not inhibit the curing of silicone rubber is preferable in consideration of the influence on the liquid silicone side. Three types of unsaturated polyester resin, polyvinyl butyral resin, and epoxy resin can be selected as the organic polymer satisfying both of these conditions. These may be used alone as a resin, or may be used in combination of two or more.

The action of the fifth problem-solving means is described in detail in the fourth problem-solving means, and will be omitted here.

The action of the sixth problem-solving means is not only to obtain a high adhesive force between the image layer and the silicone rubber, but also to obtain flexibility to the extent that the silicone rubber does not fall off even if it expands and contracts. .. In the adhesive ink of Patent Document 3, it is described that the concentration of silica dispersed in the silica hybrid cured film in the range of 1 to 100 nm is 5% by weight to 80% by weight, but for the purpose of the present invention. Flexibility is also important. Silica plays an important role in obtaining high adhesive strength, but the larger the amount, the harder the film. In the present invention, the preferred range is 10% by weight to 50% by weight. The weight% referred to here is a weight% calculated by excluding the weight of the pigment component that colors the ink.

As described above, according to the present invention, it is possible to form an inkjet printing layer that strongly adheres to a silicone rubber substrate by using a silica hybrid ink.

A mode for carrying out the present invention will be described.

A silica hybrid inkjet ink for direct printing using a thermosetting resin as an organic polymer and an ink for silicone rubber II (trademark, Sanryu Co., Ltd.) were mounted on a flatbed type inkjet printer NF-4850 (trademark, Sanryu Co., Ltd.). A heat-drying device was installed to prevent the directly printed ink from being repelled by the surface of the silicone rubber substrate and separated and condensed into innumerable small polka dots. The heat-drying device does not completely cure the ink, but is intended to obtain high-quality image quality without bleeding. It comes with a far-infrared irradiation unit that heats the printed image unit and a table that heats the substrate to be printed. It consists of a heater.
A 2 mm-thick silicone rubber sheet substrate subjected to the corona discharge surface modification treatment was placed on a table heated to 55 ° C., and a four-color image was printed while irradiating far infrared rays to a print surface temperature of 70 ° C. The image was printed without blurring and normal density was obtained. After printing, it was placed in a drying oven set at 130 ° C. for 1 hour for curing. After applying 10 times of stretching deformation to double the length of the base material of the silicone rubber sheet taken out from the drying furnace, a grid-grained cellophane tape peeling was tried. There was no image part that was peeled off and dropped off. The wear resistance of the nail is not as good as that of the silicone ink image, but it was at a practical level without an overcoat depending on the commercial application. Further, a silicone rubber film layer was formed on the image layer by screen printing and vulcanized and cured. In this case, the wear resistance level reached the same level as that of the silicone ink image.

Applying the same printing and heating conditions used in Example 1, the image receiving sheet of water transfer paper B (trademark, Sanryu Co., Ltd.) having a water-soluble layer formed on a water-permeable substrate was warmed to 55 ° C. The four-color image was printed while irradiating far-infrared rays to the extent that the printing surface temperature became 70 ° C. The image was printed without blurring and normal density was obtained. Next, the adhesive layer for transfer was printed and formed on the image by a screen printing method using liquid silicone without performing the curing treatment in the drying oven after printing. Subsequently, the water transfer paper B covering the image with this adhesive layer was pressed and attached to the surface of the silicone rubber base material. When water was applied from the back surface, the permeated water dissolved the water-soluble layer, so that the released image was transferred to the silicone rubber substrate together with the adhesive layer. This was placed in a drying oven set at 130 ° C. for 1 hour for curing. Adhesive strength to the silicone rubber substrate of the same image as in Example 1 was obtained. However, if the water transfer paper B was placed in a drying oven to cure the image before printing and forming the liquid silicone adhesive layer for transfer on the image, when the substrate was stretched, several cracks were formed in the image. Entered. It can be inferred that this is a result of the decrease in the adhesive force with the substrate with respect to the lateral breaking resistance of the silica hybrid ink image layer.

Comparative Example 1

The flatbed type UV printer VersaUV LEF2-200 (trademark, Roland DG) and EUV ink (trademark, Roland DG) were applied to the 2 mm thick silicone rubber sheet substrate used in Example 1 with the corona discharge surface modification treatment. Company) was installed to print a four-color image. Since it is an ultraviolet curable ink, it was not cured in a drying oven after printing.
EUV ink has higher flexibility than UV ink, but the wear resistance test results on the nails were also insufficient. However, as in Example 1, the silicone rubber sheet base material was stretched and deformed 10 times. Most of them fell off when the grid tape was peeled off. It seems that sufficient adhesive strength with the base material cannot be obtained. The result was the same even if the surface modification treatment was replaced with the itro treatment.

The present invention provides a method for forming an inkjet printing layer that strongly adheres to silicone rubber using a silica hybrid ink, and is used in various industries such as the medical industry, tableware industry, container industry, and exercise equipment industry using silicone rubber material. Can be widely used for decorating durable products.

Claims (6)

Using an organic solvent containing an organic / inorganic hybrid composition to obtain a silica hybrid cured film after drying and curing as ink, an image is taken with an inkjet printer while keeping the surface of the surface-modified silicone rubber substrate at a certain temperature or higher. Printing and forming layers,
A method for forming a silica hybrid ink image layer on a silicone rubber substrate. After using an organic solvent containing an organic / inorganic hybrid composition to obtain a silica hybrid cured film after drying and curing as an ink, an image layer is printed and formed on a transfer sheet whose surface is kept at a certain temperature or higher by an inkjet printer. To transfer the image by covering the image layer with liquid silicone to form a silicone rubber film layer that acts as an adhesive layer between the image layer and the silicone rubber base material to be transferred.
A method for forming a silica hybrid ink image layer on a silicone rubber substrate. Covering the image layer formed on the silicone rubber base material with liquid silicone to form a silicone rubber film layer,
The method for forming a silica hybrid ink image layer according to any one of claims 1 or 2 on a silicone rubber substrate. The organic polymer of the organic / inorganic hybrid composition contains a thermosetting unsaturated polyester resin, a polyvinyl butyral resin, an epoxy resin alone, or two or more kinds of resins.
A method for forming a silica hybrid ink image layer according to any one of claims 1 to 3 on a silicone rubber substrate. Silicone on the front side or at least one side of the image layer made of a silica hybrid cured film containing a thermosetting unsaturated polyester resin, a polyvinyl butyral resin, an epoxy resin alone, or two or more kinds of resins as an organic polymer. An image printed matter characterized by the fact that rubber is adhered. The image printed matter according to claim 5, wherein silica having a single particle size in the range of 1 to 100 nm is dispersed in the silica hybrid cured film at a concentration of 10% by weight to 50% by weight.