JP7139202B2 - Decorative film and its manufacturing method - Google Patents

Description

The present invention relates to a decorative film and its manufacturing method.

BACKGROUND ART As a method for decorating the appearance of a resin molded article, a metal molded article, or the like, a method of laminating a decorative film on the surface of the molded article is known. Molded articles decorated with decorative films are used in various applications such as interior and exterior materials for cars, housings for home electric appliances and mobile phones, and building materials such as window frames and door frames. Decorative films used in such various applications are usually printed for the purpose of imparting decorativeness and displaying information. In order to enable clear printing, the decorative film includes, for example, a decorative resin layer that conforms to the surface of the molded product, and an ink-receiving layer laminated on the surface of the resin layer. consists of On the other hand, molded products used for the above various applications may have curved surfaces from the viewpoint of design, and may have uneven surfaces due to the presence of wiring or the like. Therefore, the resin layer must easily follow the surface of the molded product, and the ink receiving layer must also follow the resin layer. As a result, attention has been paid to the adhesion between the resin layer and the ink-receiving layer.

Japanese Patent Application Laid-Open No. 2002-100003 discloses a decorative film that focuses on the adhesiveness between the resin layer and the ink-receiving layer. This decorative film has a substrate layer (resin layer) and an ink-containing pattern layer (printed ink-receiving layer). Further, the substrate layer contains acrylic resin and cellulose ester resin in a predetermined ratio.

However, there is still room for improvement in the adhesion between the resin layer and the ink receiving layer. Insufficient adhesion greatly affects the printability of the ink-receiving layer. In this respect, Patent Document 1 assumes that the pattern layer contains ink, and improvement of printability and the like are not a direct problem. However, printability is also an issue when the decorative film is to be printable.

JP 2017-185641 A

A main problem to be solved by the present invention is to provide a decorative film having an ink-receiving layer that has excellent adhesion to a resin layer and preferably excellent printability, and a method for producing the same.

Means for solving the above problems are as follows.
(Means according to claim 1)
having a resin layer and an ink-receiving layer,
The ink-receiving layer contains cellulose nanofibers, glycerin, sorbitol, and a polyvinylacetamide-based compound ,
The resin layer is made of one or more resins selected from acrylic resins, polycarbonates, polycarbonates, ABS resins, and polyolefins,
The thickness of the resin layer is 12 to 250 μm, and the thickness of the ink receiving layer is 0.008 to 4.2 times the thickness of the resin layer.
A decorative film characterized by:

(Means according to claim 2)
In the ink-receiving layer, the content of glycerin is 1.0 to 10.0% by mass, the content of sorbitol is 1.0 to 10.0% by mass, and the content of polyvinylacetamide-based compound is 1.0 to 10.0%. % by mass,
The decorative film according to claim 1.

(Means according to claim 3)
The total content of glycerin, sorbitol, and polyvinylacetamide-based compound in the ink-receiving layer is 8.0 to 12.0% by mass.
The decorative film according to claim 1 or 2.

(Means according to claim 4)
The ink-receiving layer contains a polyamide epichlorohydrin-based compound,
The content ratio of the polyamide epichlorohydrin-based compound to the polyvinylacetamide-based compound is 1.0 to 200% by mass,
The decorative film according to any one of claims 1 to 3.

(Means according to claim 5 )
The cellulose nanofibers have an average fiber diameter of 4 to 500 nm,
The decorative film according to any one of claims 1-4 .

(Means according to claim 6 )
A coating solution is obtained by adding glycerin, sorbitol, and a polyvinylacetamide-based compound to a cellulose nanofiber dispersion,
This coating liquid is applied to the resin layer and dried to obtain ,
The resin layer is made of one or more resins selected from acrylic resins, polycarbonates, polycarbonates, ABS resins, and polyolefins,
The thickness of the resin layer is 12 to 250 μm, and the thickness of the ink receiving layer is 0.008 to 4.2 times the thickness of the resin layer.
A method for producing a decorative film, characterized by:

(Means according to claim 7 )
Corona treatment or easy adhesion treatment on one or both sides of the resin layer,
and defoaming the coating liquid prior to coating the coating liquid,
The method for manufacturing the decorative film according to claim 6 .

According to the present invention, there is provided a decorative film having an ink-receiving layer that has excellent adhesion to a resin layer and preferably excellent printability, and a method for producing the same.

FIG. 4 is a schematic cross-sectional view of a molded article decorated with a decorative film;

Next, the form for implementing this invention is demonstrated. In addition, this form is an example of the present invention. Various modifications can be made to this embodiment without departing from the gist of the invention.

As shown in FIG. 1, the decorative film 1 of this embodiment has a resin film layer 2 and an ink receiving layer 3 which are resin layers. Also, the ink receiving layer 3 contains cellulose nanofibers (CNF), glycerin, sorbitol, and a polyvinylacetamide-based compound. For the decorative film 1, for example, glycerin, sorbitol, and a polyvinylacetamide-based compound are added to a cellulose nanofiber (CNF) dispersion to obtain a coating liquid, and the resin film layer 2 is coated with the coating liquid. It can be obtained by processing and drying. A detailed description will be given below.

(resin film layer)
The resin film layer 2 of this embodiment is a resin layer and is formed of a film that follows the surface of the molded product 6 .

The resin film layer 2 can be formed from various resins in consideration of three-dimensional moldability, compatibility with the molded product 6, and the like. However, the resin film layer 2 is preferably made of one or more resins selected from acrylic resins, polycarbonates, easily moldable polyesters, polycarbonates, ABS resins, and polyolefins.

As the resin film layer 2, it is preferable to use a uniaxially oriented film. If the resin film layer 2 is non-oriented or biaxially oriented (crystals are oriented in both directions), the decoration (molding) of the decorative film 1 may be difficult.

The stretching of the resin film layer 2 can be performed by, for example, a roll method, a tenter method, a tube method, or the like.

The thickness of the resin film layer 2 is preferably 12-250 μm, more preferably 25-125 μm, and particularly preferably 40-100 μm. If the thickness of the resin film layer 2 is less than 12 μm, the resin film layer 2 may thermally shrink when the coating liquid for forming the ink-receiving layer 3 is formed into a film, resulting in abnormal appearance.

On the other hand, if the thickness of the resin film layer 2 exceeds 250 μm, wrinkles and cracks are formed in the decorative film 1 (decrease in appearance) due to the difference in heat shrinkage between the resin film layer 2 and the ink-receiving layer 3 . There is a risk.

The resin film layer 2 may be a single layer or multiple layers. However, even when a plurality of layers are used, the total thickness is preferably within the above range.

One side or both sides of the resin film layer 2 are preferably subjected to corona treatment or easy adhesion treatment prior to application of the coating liquid. By performing these treatments, the interlaminar strength between the ink receiving layer 3 and the resin film layer 2 is strengthened, and the adhesion between the two is improved.

Incidentally, corona treatment is a surface treatment technique for modifying the surface of a treated substrate by irradiating it with corona discharge. The easy-adhesion treatment is a surface treatment technique in which the surface of the substrate to be treated is coated with a resin to improve the adhesiveness between the surface of the substrate to be treated and the coating liquid (film-formed layer).

(Ink receiving layer)
The ink-receiving layer 3 contains cellulose nanofibers (CNF, cellulose fine fibers), glycerin, sorbitol, and a polyvinylacetamide-based compound. Preferably, it further contains a polyamide epichlorohydrin compound. Moreover, more preferably, it further contains an alginate.

The ink-receiving layer 3 preferably has a thickness of 2 to 50 μm, more preferably 5 to 35 μm, particularly preferably 10 to 25 μm. If the thickness of the ink-receiving layer 3 is less than 2 μm, the desired strength may not be obtained.

On the other hand, if the thickness of the ink-receiving layer 3 exceeds 50 μm, a large-scale apparatus is required for drying the coating liquid for forming the ink-receiving layer 3, which may complicate the manufacturing process.

The thickness of the ink-receiving layer 3 is a value measured in accordance with JIS P8118 (2014) "Paper and paperboard-Testing methods for thickness, density and specific volume".

When the thickness of the resin film layer 2 is 12 to 250 μm, the thickness of the ink receiving layer 3 is preferably 0.008 to 4.2 times the thickness of the resin film layer 2, and the thickness is 0.02 μm. It is more preferably to 3.0 times, and particularly preferably 0.04 to 2.1 times. If the thickness of the ink-receiving layer 3 is set within the above range in relation to the thickness of the resin film layer 2, the effects described above regarding the thickness of the resin film layer 2 can be reliably achieved.

The ink-receiving layer 3 preferably has a basis weight of 5.0 to 100.0 g/m ² , more preferably 10.0 to 80.0 g/m ² , and more preferably 20.0 to 60.0 g/m 2 . m ² is particularly preferred. If the basis weight of the ink-receiving layer 3 is less than 5.0 g/m ² , the desired strength may not be obtained.

On the other hand, if the basis weight of the ink-receiving layer 3 exceeds 100.0 g/m ² , a large-scale apparatus is required for the drying process, which may complicate the manufacturing process.

The basis weight of the ink-receiving layer is a value measured in accordance with JIS P8124 (2011) “Paper and paperboard—Method for measuring basis weight”.

The ink-receiving layer 3 may be provided on the entire surface of the resin film layer 2 or may be provided only on a part thereof. Further, even if the ink receiving layer 3 is provided on the resin film layer 2 via other layers such as an anchor coat layer, it is provided directly on the resin film layer 2 without other layers. may Furthermore, the ink-receiving layer 3 may also function as a protective layer having wear resistance and slipperiness. Of course, as shown in FIG. 1, a protective layer 4 may be separately provided on the surface of the resin film layer 2 .

The ink-receiving layer 3 may or may not be transparent.

(cellulose nanofiber)
Cellulose nanofibers can be obtained by defibrating (refining) cellulose fibers (raw material fibers).

As raw material fibers, for example, plant-derived fibers, animal-derived fibers, microorganism-derived fibers, and the like can be used. These fibers can be used singly or in combination as required. However, as the raw material fiber, it is preferable to use plant-derived fiber (plant fiber), and it is more preferable to use pulp fiber, which is a type of plant fiber. When the raw material fibers are pulp fibers, it is easy to adjust the physical properties of the cellulose nanofibers.

Examples of plant fibers include wood pulp made from broad-leaved trees and conifers, non-wood pulp made from straw, bagasse, etc., and waste paper pulp (DIP) made from recycled waste paper and waste paper. can be done. These vegetable fibers can be used singly or in combination.

As wood pulp, for example, chemical pulp such as hardwood kraft pulp (LKP) and softwood kraft pulp (NKP), mechanical pulp (TMP), waste paper pulp (DIP), and the like can be used. These wood pulps can be used singly or in combination. However, since it is easily integrated with the resin film layer 2 and has excellent dimensional stability after being integrated with the resin film layer 2 (improved adhesion), it is more preferable to use chemical pulp as the wood pulp. preferable.

The hardwood kraft pulp (LKP) may be bleached hardwood kraft pulp, unbleached hardwood kraft pulp, or semi-bleached hardwood kraft pulp. Softwood kraft pulp (NKP) may be softwood bleached kraft pulp, softwood unbleached kraft pulp, or softwood semi-bleached kraft pulp. Waste paper pulp (DIP) may be magazine waste paper pulp (MDIP), newsprint waste paper pulp (NDIP), corrugated waste paper pulp (WP), or other waste paper pulp.

If necessary, the raw material fibers can be subjected to pretreatment such as beating prior to defibration. This pretreatment can be carried out by physical or chemical methods, preferably by physical and chemical methods. Pretreatment by a physical method or a chemical method prior to defibration can significantly reduce the number of fibrillation steps and the energy required for fibrillation.

Beating is preferably employed as the pretreatment by a physical method. If the raw material fibers are beaten, the raw material fibers are trimmed and thus the problem of the fibers being entangled and aggregated can be solved. From this point of view, the beating is preferably carried out until the freeness of the raw material fibers is 120 ml or less, more preferably 110 ml or less, and particularly preferably 100 ml or less.

The freeness is a value measured according to JIS P8121-2 (2012).

Beating can be performed using, for example, a refiner, a beater, or the like.

Examples of chemical pretreatments include hydrolysis of polysaccharides with acid (acid treatment), hydrolysis of polysaccharides with enzymes (enzyme treatment), swelling of polysaccharides with alkali (alkali treatment), and oxidation of polysaccharides with an oxidizing agent ( oxidation treatment), reduction of polysaccharides with a reducing agent (reduction treatment), and the like can be employed. However, if the enzymatic treatment is performed and then the beating treatment is performed, the adhesion of the obtained ink-receiving layer 3 to the resin film layer 2 is improved. In addition, the enzymatic treatment shortens the cellulose fibers, which suppresses print bleeding and improves printability. Therefore, the use of pigments can be reduced or eliminated.

Physical and chemical pretreatments can be performed simultaneously or separately.

As the pretreatment, in addition to the above, for example, chemical treatment such as phosphite esterification treatment, phosphoric acid esterification treatment, acetylation treatment, and cyanoethylation treatment can be performed.

The raw material fibers are defibrated (refined) after being subjected to pretreatment such as beating. By this fibrillation, the raw material fibers are microfibrillated into CNF (cellulose nanofibers).

The fibrillation of the raw material fibers is performed by, for example, one of various devices such as a high-pressure homogenizer, a homogenizer such as a high-pressure homogenizer, a grinder, a millstone friction machine such as a grinder, a refiner such as a conical refiner, a disc refiner, etc. or Two or more means can be selected and used. However, the defibration of the raw material fibers is preferably carried out using an apparatus and method for fibrillation with a water stream, particularly a high-pressure water stream. According to this apparatus and method, the obtained CNF has very high dimensional uniformity and dispersion uniformity. On the other hand, for example, if a grinder that grinds between rotating grindstones is used, it is difficult to defibrate the fibers uniformly, and some unfrayed fiber clumps remain, resulting in the desired effect (improving printability). improvement, etc.) may not be obtained. In this regard, a test was conducted in which pulp fibers were defibrated by a method of defibrating with a high-pressure water stream and by a method of grinding between rotating grindstones, and the obtained fibers were observed under a microscope. As a result, it was found that the fiber obtained by the method of defibrating with a high-pressure water jet has a more uniform fiber width.

As an apparatus for defibrating with a high-pressure water stream, for example, Star Burst (registered trademark) manufactured by Sugino Machine Co., Ltd., Nanovater \Nanovater (registered trademark) manufactured by Yoshida Kikai Kogyo Co., Ltd., and the like exist. As a grinder, for example, Mascolloider (registered trademark) manufactured by Masuko Sangyo Co., Ltd. is available.

Next, a method of defibrating with a high-pressure water stream will be described.
Defibrillation by high-pressure water jet is carried out by pressurizing the raw material fiber dispersion with a pressure booster to, for example, 30 MPa or more, preferably 100 MPa or more, more preferably 150 MPa or more, and particularly preferably 220 MPa or more (high pressure conditions), and the pore diameter is 50 μm or more. and the pressure difference is reduced to, for example, 30 MPa or more, preferably 80 MPa or more, more preferably 90 MPa or more (reduced pressure conditions). The raw material fibers are defibrated by the cleavage phenomenon caused by this pressure difference. If the pressure under the high pressure condition is low or if the pressure difference from the high pressure condition to the reduced pressure condition is small, the defibration efficiency may decrease, and it may be necessary to repeat blowing to obtain the desired fiber diameter.

A high-pressure homogenizer is preferably used as a device for fibrillating with a high-pressure water stream. A high-pressure homogenizer is a homogenizer capable of discharging a dispersion liquid of raw material fibers at a pressure of, for example, 10 MPa or more, preferably 100 MPa or more. When the raw material fibers are treated with a high-pressure homogenizer, the raw material fibers collide with each other, pressure difference, micro-cavitation, etc., and defibration occurs effectively. Therefore, the number of defibration times can be reduced, and the production efficiency of CNF can be improved. If the raw material fibers are sufficiently softened by the pretreatment, they can be defibrated effectively with a high-pressure homogenizer. Therefore, the number of defibration times can be reduced, and productivity can be improved.

As the high-pressure homogenizer, it is preferable to use a homogenizer that causes the dispersion liquid of the raw material fibers to face and collide in a straight line. As such an apparatus, for example, there is a counter-impingement type high-pressure homogenizer (Microfluidizer/MICROFLUIDIZER (registered trademark), wet jet mill). In this device, two upstream flow paths are formed so that the pressurized raw fiber dispersion liquids face and collide at the junction. Further, the raw fiber dispersion collides at the confluence portion, and the collided raw fiber dispersion flows out from the downstream channel. The downstream channel is provided perpendicular to the upstream channel, and the upstream channel and the downstream channel form a T-shaped channel. When this device is used, the energy of the device is maximally converted into collision energy, so the raw material fibers can be defibrated more efficiently.

The fibrillation of the raw material fibers is performed so that the average fiber diameter, average fiber length, water retention, crystallinity, peak value of pseudo particle size distribution, and pulp viscosity of the obtained CNF are the desired values or evaluations as shown below. It is preferable to go to However, it is more preferable to defibrate until the raw material fibers have a predetermined fiber diameter (average fiber diameter). By defibrating until the raw material fibers have a predetermined fiber diameter, the water retention of CNF can be kept low. As a result, the coatability of the coating liquid can be improved. An improvement in coatability leads to an improvement in adhesion between the resin film layer 2 and the ink-receiving layer 3 .

(Average fiber diameter (width))
The average fiber diameter (average diameter of single fibers) of CNF is, for example, 4 to 500 nm, preferably 6 to 300 nm, more preferably 10 to 100 nm. When the average fiber diameter of the CNF is less than 4 nm, the ink receiving layer 3 becomes denser and thus the strength of the ink receiving layer 3 increases, and cracks may easily occur in the ink receiving layer 3 during drying. Moreover, when the strength of the ink receiving layer 3 increases, the adhesion to the resin film layer 2 may decrease.

On the other hand, if the CNF has an average fiber size of more than 500 nm, the voids in the ink-receiving layer 3 will be too open, allowing the ink to permeate too much, and the ink will not stay on the surface of the ink-receiving layer 3, possibly deteriorating the printability. .

The average fiber diameter of CNF can be adjusted by, for example, selection of raw material fibers, pretreatment, fibrillation, and the like.

The method for measuring the average fiber diameter of CNF is as follows.
First, 100 ml of an aqueous dispersion of CNF with a solid content concentration of 0.01 to 0.1% by mass is filtered through a Teflon (registered trademark) membrane filter, and the solvent is replaced with 100 ml of ethanol once and 20 ml of t-butanol three times. . It is then freeze-dried and coated with osmium to form a sample. This sample is observed with an electron microscope SEM image at a magnification of either 5,000, 10,000 or 30,000 times depending on the width of the constituent fibers. Specifically, two diagonal lines are drawn on the observation image, and three straight lines passing through the intersections of the diagonal lines are arbitrarily drawn. Furthermore, the width of a total of 100 fibers intersecting with these three straight lines is visually measured. Then, the median diameter of the measured value is taken as the average fiber diameter.

(average fiber length)
The average fiber length (single fiber length) of CNF is, for example, 1 to 5,000 μm, preferably 10 to 3,000 μm, more preferably 100 to 1,000 μm. When the average fiber length of CNF is less than 1 μm, the ink-receiving layer 3 becomes dense, and appropriate voids are not formed in the ink-receiving layer 3, which may deteriorate ink absorbability and reduce printability. Also, if the ink-receiving layer 3 is too dense, the adhesion to the resin film layer 2 may deteriorate.

On the other hand, if the average fiber length of the CNF exceeds 5,000 μm, the surface of the ink-receiving layer 3 is likely to be uneven due to the fibers, making it impossible to completely prevent printing unevenness and bleeding, resulting in a decrease in printability. there is a possibility. Further, unevenness on the surface of the ink-receiving layer 3 tends to lead to deterioration in adhesion to the resin film layer 2 .

The average fiber length of CNF can be adjusted by, for example, selection of raw material fibers, pretreatment, fibrillation, and the like.

The average fiber length is measured by visually measuring the length of each fiber in the same manner as the average fiber diameter. Let the median length of the measured value be the average fiber length.

(water retention)
The water retention of CNF is, for example, 300-500%, preferably 350-480%, more preferably 380-450%. If the water retention of CNF is less than 300%, the fibrillating property of the cellulose fibers is deteriorated, which may make it difficult to form an appropriate ink-receiving layer 3 .

On the other hand, when the CNF water retention exceeds 500%, the water retention of the CNF itself increases, the drying property of the ink-receiving layer 3 deteriorates, and the productivity deteriorates.

The water retention of CNF can be adjusted by, for example, selection of raw material fibers, pretreatment, fibrillation, and the like.

The water retention rate of CNF is determined by JAPAN TAPPI No. 26 (2000).

(peak value)
The peak value in the pseudo-particle size distribution curve of CNF is preferably one peak. When there is one peak, CNF has high uniformity in fiber length and fiber diameter, and is excellent in drying properties.

The peak value of CNF is, for example, 5-25 μm, preferably 7-23 μm, more preferably 10-20 μm.

The CNF peak value can be adjusted by, for example, selection of raw material fibers, pretreatment, fibrillation, and the like.

The peak value of CNF is the value measured according to ISO-13320 (2009). More specifically, first, the volume-based particle size distribution of the CNF aqueous dispersion is examined using a particle size distribution analyzer (laser diffraction/scattering particle size distribution analyzer manufactured by Seishin Enterprise Co., Ltd.). Next, the median diameter of CNF is measured from this distribution. Let this median diameter be a peak value.

(pulp viscosity)
The pulp viscosity of CNF is, for example, 1.5-7.0 cps, preferably 1.8-6.8 cps, more preferably 2.0-6.5 cps.

The pulp viscosity of CNF can be adjusted by, for example, selection of raw material fibers, pretreatment, fibrillation, and the like.

The pulp viscosity of CNF is a value measured according to JIS-P8215 (1998). A higher pulp viscosity means a higher degree of polymerization of cellulose.

(CNF dispersion)
CNF obtained by fibrillation is dispersed in an aqueous medium to form a dispersion. It is particularly preferred that the aqueous medium is entirely water (aqueous solution). However, the aqueous medium may be another liquid partially compatible with water. As other liquids, for example, lower alcohols having 3 or less carbon atoms can be used.

The dispersion liquid is preferably adjusted so that the main component, preferably 1.0% by mass or more, is CNF. Moreover, the solid content concentration of the dispersion liquid is preferably 1.0% by mass or more because it is easy to handle.

The B-type viscosity of the dispersion when the concentration of CNF is 2 mass % (w/w) is preferably 100 to 50,000 cps, and more preferably 3,000 cps or less from the viewpoint of coatability.

The B-type viscosity of CNF is a value measured in accordance with JIS-Z8803 (2011) "Method for measuring the viscosity of a liquid" for a CNF dispersion having a solid concentration of 1%. The B-type viscosity is the resistance torque when the dispersion is stirred, and means that the higher the viscosity, the greater the energy required for stirring.

Additives (chemicals such as glycerin) shown below are added to the CNF dispersion thus obtained. In this embodiment, by adding an additive, the ink-receiving layer 3 having excellent adhesion (integrity) with the resin film layer 2 can be obtained. In addition, the decorative film 1 with excellent dimensional stability and good appearance can be obtained in a state in which the ink receiving layer 3 and the resin film layer 2 are integrated. Moreover, there is no possibility that the process of manufacturing the decorative film 1 will be complicated. Hereinafter, each additive will be described in order.

(glycerin)
Glycerin (glycerol) is a trihydric alcohol. Glycerin is obtained together with fatty acids, for example, by hydrolysis of fats and oils. As used herein, glycerin also includes derivatives of glycerin.

When glycerin is added to the ink-receiving layer 3, the flexibility of the ink-receiving layer 3 is improved, and the adhesion with the resin film layer 2 following the molded article 6 is improved. In addition, shrinkage wrinkles and cracks during drying of the coating liquid are reduced, the appearance of the decorative film 1 is improved, and the transparency is improved.

As glycerin, it is preferable to use glycerin that is not chemically modified. The use of chemically unmodified glycerin improves CNF dispersibility and homogenizes the ink-receiving layer 3 . In addition, the flexibility of the ink-receiving layer 3 is further improved by using chemically unmodified glycerin. This is because chemically unmodified glycerin is difficult to crystallize.

The amount (content ratio) of glycerin to be added is preferably 1.0 to 10.0% by mass, more preferably 2.0 to 7.0% by mass, of the total mass of the ink-receiving layer 3 (the total amount of the coating liquid). is more preferable, and 3.0 to 6.0% by mass is particularly preferable. If the amount added is less than 1.0% by mass, the flexibility of the ink-receiving layer 3 may not be sufficient. If the amount added is less than 1.0% by mass, shrinkage wrinkles and cracks may occur during drying of the coating liquid.

On the other hand, if the amount of glycerin added exceeds 10.0% by mass, the strength of the ink-receiving layer 3 may be lost, and the ink-receiving layer 3 may be broken or cracked during printing, resulting in poor printability. Further, if the amount of glycerin added exceeds 10.0% by mass, there is a possibility that minute particles may be generated in the ink receiving layer 3 due to aggregation of glycerin. The occurrence of this smiling face leads to deterioration in the transparency and printability of the ink receiving layer 3 .

(sorbitol)
Sorbitol is a type of sugar alcohol of glucose. As used herein, sorbitol also includes derivatives of sorbitol.

Addition of sorbitol to the ink-receiving layer 3 improves the fluidity of the coating liquid and also improves the compatibility with other additives. As a result, the ink-receiving layer 3 is homogenized, printability is improved, and the appearance of the decorative film 1 is improved. Furthermore, the transparency of the decorative film 1 is also improved. Further, when sorbitol is added, the strength of the ink-receiving layer 3 is improved, which also improves the printability.

As sorbitol, it is preferable to use sorbitol that is not chemically modified. Use of chemically unmodified sorbitol improves compatibility with other additives having hydroxyl groups.

The amount (content ratio) of sorbitol added is preferably 1.0 to 10.0% by mass, more preferably 2.0 to 7.0% by mass, of the total mass of the ink-receiving layer 3 (the total amount of the coating liquid). is more preferable, and 3.0 to 6.0% by mass is particularly preferable. If the amount added is less than 1.0% by mass, the fluidity of the CNF dispersion may be reduced, resulting in difficulty in coating. As a result, the appearance of the decorative film 1 may deteriorate, and the transparency may deteriorate.

On the other hand, if the amount of sorbitol added exceeds 10.0% by mass, the ink-receiving layer 3 becomes brittle, which may lead to deterioration in printability and cracking.

(Polyvinylacetamide-based compound)
Addition of a polyvinylacetamide-based compound improves compatibility between additives. As a result, the appearance of the decorative film 1 is improved, and the fixability of the dye ink is improved (improved printability). In addition, when a polyvinylacetamide-based compound is added, the shear stress of the CNF dispersion is reduced, the thickness of the ink-receiving layer 3 is easily made uniform, and the adhesion to the resin film layer 2 and transparency are improved. leads to

Poly-N-vinylacetamide having a weight average molecular weight of 5,000 to 2,000,000 (more preferably 7,000 to 18,000) is preferably used as the polyvinylacetamide compound. Poly-N-vinylacetamide is a hydrophilic/alcoholophilic polymer containing N-vinylacetamide as a main monomer.

The amount (content ratio) of the polyvinylacetamide-based compound added is preferably 1.0 to 10.0% by mass, more preferably 1.0 to 7.0% by mass, of the total mass of the ink-receiving layer 3 (the total amount of the coating liquid). is more preferable, and 1.0 to 5.0% by mass is particularly preferable. If the amount added is less than 1.0% by mass, the compatibility between the additives may not be sufficiently improved, and agglomerates may occur.

On the other hand, when the added amount of the polyvinylacetamide-based compound exceeds 10.0% by mass, the shear stress of the CNF dispersion is lowered, and the thickness of the ink-receiving layer 3 may not be uniform.

The compounding ratio of each chemical solution (additive) is, as described above, 1.0 to 10.0% by mass of glycerin, 1.0 to 10.0% by mass of sorbitol, and 1.0 to 10.0% by mass of polyvinylacetamide-based compound. is preferable, but the total content (total content) of glycerin, sorbitol, and polyvinylacetamide-based compound is preferably 8.0 to 12.0% by mass, and 8.5 to 11.5% by mass. %, and particularly preferably 8.5 to 11.0% by mass. If the total content is less than 8.0% by mass, the appearance of the ink-receiving layer 3 may not be good.

On the other hand, if the total content exceeds 12.0% by mass, the ink-receiving layer 3 may become uneven and the ink colorability may vary (reduced printability).

(polyamide epichlorohydrin compound)
In addition to the above, when a polyamide epichlorohydrin compound is added to the ink-receiving layer 3 (coating liquid), the wet strength of the ink-receiving layer 3 is improved, and it becomes easier to follow the resin film layer 2 (improved adhesion ).

The content ratio (content) of the polyamide epichlorohydrin-based compound is preferably 0.1 to 2.0% by mass with respect to the total mass of the ink-receiving layer 3 (the total amount of the coating liquid). It is more preferably 3 to 2.0% by mass, particularly preferably 0.5 to 2.0% by mass. If the content of the polyamide epichlorohydrin-based compound is less than 0.1% by mass, it may be insufficient to improve the wet strength of the ink-receiving layer 3 .

On the other hand, if the content of the polyamide epichlorohydrin compound exceeds 2.0% by mass, the additive may aggregate.

Further, the content ratio (content) of the polyamide epichlorohydrin compound is preferably 1.0 to 200% by mass with respect to the content ratio of the polyvinylacetamide compound described above, and 1.5 to 150% by mass. is more preferable, and 2.0 to 100% by mass is particularly preferable. When the content of the polyamide epichlorohydrin-based compound is less than 1.0% by mass, there is a tendency that uneven printing and ink bleeding during printing become worse.

On the other hand, if the content of the polyamide epichlorohydrin-based compound exceeds 200% by mass, aggregates are generated in the ink-receiving layer coating solution, which tends to deteriorate the coatability.

(Alginate)
Alginic acid is a sticky acidic polysaccharide obtained from brown algae. Alginate is its salt. Addition of alginate to the ink-receiving layer 3 improves the strength of the ink-receiving layer 3 . Since the resin film layer 2 deforms following the molded product 6 , improvement in the strength of the ink receiving layer 3 contributes to improvement in adhesion to the resin film layer 2 .

At least one of sodium alginate and potassium alginate is preferably used as the alginate. When these alginates are used, the strength of the ink-receiving layer 3 is further improved due to the film-forming property of the alginate itself.

The content ratio (content) of the alginate is preferably 1.0 to 6.0% by mass, more preferably 2.0 to 6.0%, based on the total mass of the ink-receiving layer 3 (the total amount of the coating liquid). % by mass is more preferable, and 3.0 to 6.0% by mass is particularly preferable. If the alginate content is less than 1.0% by mass, it may not be sufficient to improve the strength of the ink-receiving layer 3 .

On the other hand, if the alginate content exceeds 6.0% by mass, the flexibility of the ink-receiving layer 3 is lost, the adhesion to the resin film layer 2 is reduced, and shrinkage wrinkles may occur. be.

(Other additives)
The ink-receiving layer 3 (coating liquid) may optionally contain, for example, an antioxidant, a corrosion inhibitor, a light stabilizer, an ultraviolet absorber, a heat stabilizer, a polymerization inhibitor, an inorganic or organic filler, and a metal powder. , dyes, antistatic agents, plasticizers, flame retardants, lubricants, anti-settling agents, dispersants, anti-separation agents, fragrances, deodorants and the like can be added. A pigment may be added to the ink-receiving layer 3, but the ink-receiving layer 3 of this embodiment has sufficient printability without adding a pigment.

(coating/drying)
The ink-receiving layer 3 is formed by applying a coating liquid containing each raw material such as CNF, glycerin, sorbitol, and polyvinylacetamide-based compounds described above to one or both sides of the resin film layer 2 and drying it. can be done.

The coating liquid for forming the ink-receiving layer 3 preferably has a solid content concentration of 0.5 to 2.0 mass % from the viewpoint of coating properties. For the same reason, the coating liquid preferably has a B-type viscosity of 500 to 3500 cps. As a method of adjusting the solid content concentration and B-type viscosity of the coating liquid to the above range, a method of adding water etc. to dilute when adding an additive, a method of adding other additives to adjust the viscosity, etc. exists.

The coating liquid for forming the ink-receiving layer 3 is preferably defoamed. As a method for defoaming the coating liquid, for example, a method of stirring with a stirrer with blades or the like, followed by natural defoaming (still standing), or stirring vacuum defoaming, or the like can be employed.

The method of applying the coating liquid to the resin film layer 2 may be a continuous method or a batch method. As a continuous method, for example, the coating liquid is continuously supplied to a coating device, and the coating liquid is thinly applied onto the resin film layer 2 by a discharge means such as a die attached to the coating device (a thin layer). ) extrusion, or a coating method using a roll coater, knife coater, roll knife coater, reverse coater, gravure coater, or the like can be employed.

As a batch method, for example, a method of casting a coating liquid on the resin film layer 2 and forming a thin layer using an applicator, Meyer bar, knife coater, or the like can be adopted.

The coating solution applied to the resin film layer 2 can be dried by, for example, blowing dry air. Drying of the coating liquid may be performed in a single drying step or in combination of a plurality of drying steps.

(decorative film)
The decorative film 1 obtained by forming the ink-receiving layer 3 on the surface of the resin film layer 2 that deforms following the surface of the molded product 6 preferably has a thickness of 50 to 300 μm, more preferably 55 to 55 μm. It is more preferably 280 μm, particularly preferably 57-250 μm. If the thickness of the decorative film is less than 50 µm, the tensile strength may be insufficient.

On the other hand, when the thickness of the decorative film exceeds 300 μm, the tensile elongation is high and processing may become difficult.

(others)
Various types of information such as character information, codes, and multicolor graphics can be printed on the decorative film 1 of the present embodiment by, for example, a printing device such as an inkjet printer. As a printing method, for example, gravure printing, flexographic printing, letterpress rotary printing, etc. can be adopted.

In addition to the resin film layer 2 and the ink receiving layer 3, the decorative film 1 of the present embodiment includes, for example, a protective layer 4 such as a hard coat layer, an adhesive layer 5, an ultraviolet blocking layer, an anchor coat layer, a primer coat layer, and the present embodiment. In addition to the ink-receiving layer, it may have a layer such as a printed layer, non-woven fabric, paper, or the like. The protective layer 4 is provided, for example, on the opposite side of the ink-receiving layer 3 with the resin film layer 2 interposed therebetween, so as to achieve scratch resistance and durability against fingerprints.

The decorative film 1 of this embodiment may be used so that the ink-receiving layer 3 is in contact with the molded article 6 (inside) or outside.

The decorative film 1 of this embodiment can be used for in-mold decoration performed by injection molding, injection press molding, or the like, and for out-mold decoration for decorating the molded product 6 afterward. However, since the decorative film 1 of the present embodiment is provided with the ink-receiving layer 3 mainly composed of a composition other than resin on the surface of the resin film 2 having heat-decorating properties, it is suitable for out-mold decoration. Are suitable.

As a molding method for out-mold decoration, for example, methods such as overlay molding, hot stamping, out-mold transfer, out-mold attachment, hydraulic transfer, and labeling can be employed.

The decorative film 1 of this embodiment can decorate the surface of products (molded products 6) such as automobile outer panels, automobile parts, electrical appliances, electronic parts, and building materials.

Next, examples of the present invention will be described. In addition, in the following tables, "% by mass" means absolute dry mass ratio.

A decorative film (test piece) having a resin film layer and an ink-receiving layer was produced, and a test was conducted to evaluate the printability and processability of each test piece. Details are as follows.

The resin film layer was formed of a resin film having thermal decorating properties (other than Comparative Example 1) or a resin film having no thermal decorating properties (Comparative Example 1). An acrylic resin film (thickness: 100 μm) was used as the resin film having thermal decorating properties. A biaxially stretched PET film (thickness: 100 μm) was used as the resin film having no thermal decorating property.

The ink receiving layer was formed by the following method.
First, hardwood bleached kraft pulp (LBKP) for papermaking was made into a 2.0% by mass aqueous dispersion. This aqueous dispersion was beaten using a refiner until the freeness reached 100 ml or less, and further fined (fibrillated) using a high-pressure homogenizer. Thus, CNF (average fiber length 1.5 μm, average fiber diameter 39 nm, water retention 280%, peak value 20 μm, pulp viscosity 3.3 cps) was obtained.

Next, an additive was added to the CNF dispersion (aqueous solution) obtained as described above to obtain a coating liquid. Table 1 shows the types and blending ratios of the additives. The following additives were used.
Glycerin: Product name “purified glycerin” (manufactured by Sakamoto Pharmaceutical Co., Ltd.)
Sorbitol: Product name “Sorbit KK (60%)” (manufactured by MC Food Specialties Co., Ltd.)
Polyvinylacetamide compound: product name “GE191-053” (manufactured by Showa Denko KK)
Polyamide epichlorohydrin compound: trade name "WS4024" (manufactured by Seiko PMC Co., Ltd.)

The resulting coating liquid was applied to one surface of the resin film layer. This coating was performed using a comma coater. Table 1 shows the evaluation of the decorative film (test piece) having an ink-receiving layer formed by coating. In addition, the "mass" in a table|surface is an absolute dry mass ratio. Moreover, the evaluation criteria in the table are as follows.

(decorative)
The test piece (decorative film) was set on the substrate (molded product) in the out-mold pasting molding machine, and the heating and vacuum pressure were adjusted to carry out the decorative molding. At this time, the moldability of the test piece was visually evaluated according to the following criteria.
◯: There is no floating, and it is easy to three-dimensionally mold.
Δ: There is partial floating, and there is some difficulty in practical use.
x: There is floating and cannot be used practically.

(exterior)
The surface of the base material decorated using the test piece was visually evaluated according to the following criteria.
A: No cracks or wrinkles after three-dimensional molding.
◯: Very fine wrinkles are partially observed, but no cracks are observed.
Δ: There are linear cracks and wrinkles, and there is some difficulty in practical use (maximum crack length is less than 5 mm).
x: There are linear cracks and wrinkles, and it cannot be practically used (the maximum crack length is 5 mm or more).

(Print density)
A printer/EP-803A (manufactured by Seiko Epson Corporation) was used to print dye ink on the test piece. The print mode was set to "superfine paper, standard". The rest of the test piece was printed with pigment ink using a printer PX-045A (manufactured by Seiko Epson Corporation). The print mode was set to "superfine paper, standard".
For the printed matter obtained by the above printing, 4 colors (black, cyan, magenta, yellow), the print density of the total part (100% solid part was measured with FD-7 (manufactured by Konica Minolta Co., Ltd.), 4 colors ) was measured.

(Print unevenness)
A printer/EP-803A (manufactured by Seiko Epson Corporation) was used to perform solid printing with dye ink. The print mode was set to "superfine paper, standard". The solid printed portion other than the character portion was visually observed, and the density unevenness was evaluated according to the following criteria. It should be noted that those with evaluation criteria of 3 or higher are recognized as being practical.
5: Suitable as a decorative film with almost no shading unevenness.
4: Density unevenness is observed, but it is hardly conspicuous and has no practical problem.
3: There is unevenness in density, and it is somewhat difficult to put into practical use.
2: There is unevenness in density, and it is not practical.
1: The density unevenness is severe and not practical.

(Print bleeding)
Broken lines and characters were printed with dye ink using a printer/EP-803A (manufactured by Seiko Epson Corporation). The print mode was set to "superfine paper, standard". The dashed line portion and characters were magnified 100 times with a microscope, and bleeding was evaluated according to the following criteria. It should be noted that those with evaluation criteria of 3 or higher are recognized as being practical.
5: Almost no ink bleeding, suitable as a decorative film.
4: Ink bleeding is observed, but it is hardly conspicuous and has no practical problem.
3: There is ink bleeding, and there is some difficulty in practical use.
2: There is ink bleeding, and the practicality is poor.
1: Severe ink bleeding, not practical.

(dryness)
Ruled lines were printed with dye ink using a printer/PX-045A (manufactured by Seiko Epson Corporation). The print mode was set to "superfine paper, standard". Immediately after printing, the ruled line portion was wiped off with a cloth, and the dryness was evaluated according to the following criteria. It should be noted that those with evaluation criteria of 3 or higher are recognized as being practical.
5: Almost no contamination on the printed part, suitable as a decorative film.
4: Stain is observed in the printed portion, but it is hardly conspicuous and poses no practical problem.
3: The printed portion is stained, and it is somewhat difficult to put it to practical use.
2: The printed portion is stained, and it is poor for practical use.
1: Severe stains on the printed portion, not practical at all.

INDUSTRIAL APPLICABILITY The present invention can be used as a decorative film and its manufacturing method.

REFERENCE SIGNS LIST 1 decorative film 2 resin film layer 3 ink receiving layer 4 protective layer 5 adhesive layer 6 molded article

Claims (7)

having a resin layer and an ink-receiving layer,
The ink-receiving layer contains cellulose nanofibers, glycerin, sorbitol, and a polyvinylacetamide-based compound ,
The resin layer is made of one or more resins selected from acrylic resins, polycarbonates, polycarbonates, ABS resins, and polyolefins,
The thickness of the resin layer is 12 to 250 μm, and the thickness of the ink receiving layer is 0.008 to 4.2 times the thickness of the resin layer.
A decorative film characterized by: In the ink-receiving layer, the content of glycerin is 1.0 to 10.0% by mass, the content of sorbitol is 1.0 to 10.0% by mass, and the content of polyvinylacetamide-based compound is 1.0 to 10.0%. % by mass,
The decorative film according to claim 1. The total content of glycerin, sorbitol, and polyvinylacetamide-based compound in the ink-receiving layer is 8.0 to 12.0% by mass.
The decorative film according to claim 1 or 2. The ink-receiving layer contains a polyamide epichlorohydrin-based compound,
The content ratio of the polyamide epichlorohydrin-based compound to the polyvinylacetamide-based compound is 1.0 to 200% by mass,
The decorative film according to any one of claims 1 to 3. The cellulose nanofibers have an average fiber diameter of 4 to 500 nm,
The decorative film according to any one of claims 1-4 . A coating solution is obtained by adding glycerin, sorbitol, and a polyvinylacetamide-based compound to a cellulose nanofiber dispersion,
This coating liquid is applied to the resin layer and dried to obtain ,
The resin layer is made of one or more resins selected from acrylic resins, polycarbonates, polycarbonates, ABS resins, and polyolefins,
The thickness of the resin layer is 12 to 250 μm, and the thickness of the ink receiving layer is 0.008 to 4.2 times the thickness of the resin layer.
A method for producing a decorative film, characterized by: Corona treatment or easy adhesion treatment on one or both sides of the resin layer,
and defoaming the coating liquid prior to coating the coating liquid,
The method for manufacturing the decorative film according to claim 6 .

Images