HK1113595A - Multi-layer coated products and curtain coating process for same - Google Patents

Description

Multi-layer coated product and curtain coating method thereof

Technical Field

The present invention relates to a coated product suitable for printing on, comprising at least two different coatings which impart to said coated product very distinct characteristics, namely good mechanical properties and good ink absorption. The invention also relates to a wet-on-wet single pass (one pass) multi-layer curtain coating process for making coated products suitable for surface printing. The invention also relates to the use of a coated product as defined above, suitable for printing on.

Background

In the production of printing papers, the speed of the production processes using pigmented coating compositions, for example doctor blade, bar, air knife or reverse roll coating processes, is generally above 200m/min, even above 1000 m/min. However, the above coating methods (other than air knife coating) do not match the profile of the original substrate, which means that any irregular substrate surface will result in uneven coating thickness and thus irregular coating results during printing. Curtain coating methods are well known in the photographic art as coating methods applied to the surface of a moving support with one or more liquid layers. Curtain coating methods are based on free-flow coating onto the surface to be coated from a coating head located on the surface. The coating head is defined to take the properties of the coating flow in order to obtain as uniform a coating height as possible during the straight and transverse movements of the machine. In the photographic industry, the application of multi-layer photographic emulsions to underlayers or slide-coating techniques have been widely used. Curtain coating processes are still under development and are used in the paper industry. International patent application WO 2004/063464a discloses a method of making a paper sheet having an iridescent appearance comprising a layer formed from iridescent pigment mixed with hollow plastic microspheres. International patent application WO 02/084029a2 discloses another method of making multilayer coated paper and coated paperboard particularly suitable for printing, packaging and labeling purposes. In the method, at least two curtain layers selected from an aqueous emulsion or an aqueous suspension are formed into a composite free-falling curtain, and a continuous web of base paper or substrate is coated with the composite curtain.

The applicant has found that one drawback of these coating bases is: when good printing properties are to be maintained, they cannot simultaneously produce high optical properties, which is a low cost requirement. There is a great need for coated products suitable for surface printing which can give high optical properties, such as a glossy and/or iridescent appearance, a matte appearance, a pigmented appearance, etc., while at the same time having good mechanical properties, such as good adhesion to the substrate, and which are also cost-effective. In particular, there is a need for coated substrates suitable for surface printing that produce a dual optical effect while maintaining good printing characteristics.

It is therefore an object of the present invention to provide a coated product suitable for surface printing, comprising at least two different coatings which impart high optical properties to said product, while having good mechanical and ink absorption properties.

The applicant has verified that: if a coated product having at least two separate coating layers with different properties is produced by a wet-on-wet single pass curtain coating process for the base layer, the coated product suitable for printing will have high dual optical properties, such as a combination of high gloss and high iridescent effect, and can be produced at low cost.

Disclosure of Invention

The invention relates to a coated product suitable for surface printing, comprising a substrate and at least two different coatings with different properties, one coating being close to the substrate, called low-coat layer, which can be used for ink absorption (print drying time) and other printing requirements (e.g. printed optical density), and the other different coating being remote from the substrate, called top-coat layer, which is used to create the optical properties of the product surface.

The invention therefore provides a coated product suitable for printing on, comprising a substrate and at least two different coatings having different properties, characterized in that the product comprises one coating, preferably pigmented, adjacent to the substrate, having printing properties and possibly optical properties, and another coating, remote from the substrate, imparting optical effect properties, both coatings having a dry coating weight of from 0.1 to 12g/m²Within the range of (1).

The coated products according to the invention have good surface quality (uniform coating), absorption, porosity, adhesion to the substrate, and special optical properties, such as gloss, metallic effect and iridescence depending on the pigment arrangement.

The coated product according to the invention comprises a coating layer adjacent to the substrate layer which imparts printing properties to the product and which adheres to the substrate layer with good surface wetting properties.

In particular, the coating (preferably pigmented) adjacent to the substrate is referred to as a low coat, and can be used to adhere the coating to the substrate, as well as to absorb ink (which affects print dry time), and other printing requirements, such as optical density of the print, etc.

According to a particular embodiment of the invention, said coating layer adjacent to the underlayer (called low coating layer) may further have optical properties, such as gloss, etc.

According to the invention, the coated product comprises a coating layer remote from the substrate, called top coat, which imparts to the surface of the product special optical properties, such as a glossy appearance, an iridescent effect and/or a metallic effect.

In particular, the low-coat layer of the present invention is a coating component consisting of a coating pigment and a binder, and the dry coating weight thereof is in the range of 0.1 to 12g/m². Preferably, the pigment in the colored low coating is selected from: calcium carbonate, clay, kaolin, talc, titanium dioxide, silica, alumina, boehmite alumina, barium sulfate, zinc oxide, gypsum, and mixtures thereof.

Preferably, the top coat of the coated product comprises optical pigments selected from: plastic pigments with gloss characteristics and light interference color changing pigments, such as metallic effect pigments or iridescent effect pigments.

By "optical variable pigments", it is meant that the present disclosure includes pigments that are capable of exhibiting different visual effects depending on the angle of observation, and in particular, known variations of such pigments, including reflections, shades or shadows, depending on the angle of observation. As light-interference color-changing pigments, these pigments can produce the following effects: metallic, iridescent, sparkling, shiny or multicolored appearance.

The top coat may also include other pigments such as amorphous silica or calcium carbonate that may improve its properties such as: print quality, ink absorption, or other optical characteristics. In general, these pigments are used in small amounts.

Preferably, the optical pigment is selected from: plastic pigments with gloss properties, metallic pigments or pigments with iridescent effect, the content of the optical pigments being 50-98% of the dry weight of the coating of the total top coat, calculated on a dry weight basis. More preferably, the optical pigment is present in an amount of 70% to 90% by dry weight of the coating of the top coat.

According to the invention, the different coatings of the coated product may comprise a binder. Preferably, the binder is selected from: styrene copolymers, such as styrene-butadiene, styrene-acrylate, styrene-maleic anhydride, polyvinyl alcohol, polyvinylpyrrolidone, carboxymethylcellulose, starch, protein, polyvinyl acetate, polyurethane, polyester or acrylic acid, and mixtures thereof.

According to the invention, the low-coat layer and the top-coat layer each have a thickness of 0.1 to 12g/m²Dry coating weight of (c). Preferably, the top coat has a thickness of 0.1 to 5g/m²More preferably 0.1 to 2.5g/m²Dry weight of (d). Preferably, the low coating has a thickness of 0.1 to 7g/m²More preferably 0.1 to 3g/m²Dry weight of (d).

Preferably, the coated product of the present invention may be a high gloss coated product, and the top coat layer contains a plastic pigment with gloss characteristics to give the product a high gloss appearance. Thus, the coated product suitable for surface printing comprises a base layer and at least two different coating layers having respectively different properties, i.e. a pigmented low coating layer adjacent to the base layer, having the printing properties as described above, and a top coating layer comprising plastic pigments, giving the product a high gloss appearance, the low coating layer and the top coating layer each having a weight of from 0.1 to 12g/m²Range of dry coating weights. According to a preferred synthetic example of the invention, the plastic pigments with lustrous properties are hollow plastic microspheres, which are based in particular on styrene-acrylic polymers. According to a particular embodiment of the invention, the microspheres have an average diameter comprised between 0.2 μm and 1.3 μm.

More preferably, the top coat comprising hollow plastic microspheres provides the coated product with a high gloss appearance, and the top coat is applied dryThe weight return is 0.1 to 5g/m²。

Preferably, said coated product for surface printing comprises a base layer and at least two coating layers having respectively different characteristics, i.e. comprising a coating layer (called low coat) close to the base layer, preferably pigmented, giving the product printing characteristics, and a coating layer (called top coat) remote from the base layer, comprising optical interference colour change pigments, giving the product surface special optical effect characteristics, said low coat and top coat having from 0.1 to 12g/m²Range of dry coating weights.

More preferably, the optical interference color changing pigment is an iridescent effect pigment. The pigment is based on the principle of light diffraction to produce an iridescent effect, the reflection of light causing a change in hue depending on the angle of observation, separating white light into colors covering the entire rainbow spectrum. Thus, the coated product is a highly iridescent product suitable for surface printing, wherein the top coat comprises iridescent pigments, which alone provide the product with a highly iridescent appearance.

More preferably, the top coat comprising iridescent pigments provides a highly iridescent appearance to the product, the top coat being applied in a dry weight range of 0.1 to 5g/m²。

Among the iridescent substances frequently used, in particular, the following can be made: nacreous layer extract, coated titanium oxide mica pigment, and interference multilayer plastic pigment.

More preferably, the coated product according to the invention may be an iridescent coated product with high gloss suitable for surface printing, wherein the low coating layer further comprises a plastic pigment with gloss properties and a top coating layer comprising iridescent pigments.

According to a particular embodiment of the invention, the coated product comprises a low-coat layer with a colour having printing properties, such as ink absorption (print dry time), adjacent to the substrate, the low-coat layer with a colourThe layer further comprises hollow plastic microspheres having optical properties; and a top coat comprising iridescent pigments having special optical effect characteristics; the low coating layer and the top coating layer are both 0.1 to 12g/m²Range of dry coating weights. In this particular embodiment, the low and top coats preferably have a dry coatweight of 0.1 to 3g/m²More preferably 0.1 to 2g/m²The range of (1).

According to this particular embodiment of the invention, when the low-coat layer of the coated product comprises plastic pigments with gloss properties, the iridescent effect of the final coated product is improved without altering the printability of the product.

Once coated, the coated product, in particular for the purpose of developing the gloss optical properties of the plastic pigments, can then be calendered in a calender comprising a steel roll, a rubber roll or a cotton roll, as well as mixtures of these rolls. Pressure is applied over a series of multi-clips. Alternatively, the rolls of the calender are heatable.

In particular, the top coat of said coated product comprises plastic pigments with gloss characteristics, exhibiting a gloss value after calendering greater than or equal to 90, calculated according to ISO2813 standard at 75 degrees.

According to a preferred aspect of the invention, the substrate layer may be any fibrous material, such as a material prepared from cellulose (natural) fibers and/or synthetic fibers. In a presently preferred form, this aspect of the invention is embodied in a sheet-based paper. However, the invention can also be applied to substrates made of other materials, for example plastics made of certain polyolefins. These are included in so-called "synthetic papers", for example, manufactured plastic sheets (e.g., polyethylene) that mimic natural cellulosic paper, having printability, stiffness, handling, and other properties similar to those of natural cellulosic paper; and a particularly manufactured class of printable polyethylene sheets for use in the graphic arts and related packaging and stationery. Synthetic papers are available, such as those sold under the trademark Polyart ® by Arjobex, Inc., UK. The aforementioned printable polyethylene sheet is, for example, a product of the trade mark "PRIPLAK ®" from PRIPLAK company, france. These products are transparent, translucent or opaque, with a variety of surface textures.

The multi-layer curtain is coated on a continuous substrate layer, which is uncoated or pre-coated. The weight per square meter of the substrate layer is directly dependent on the application of the end use product. There is generally no restriction on the grammage (per square meter) of the substrate used, while the term paper (paper) as used in this specification should be understood to encompass heavier weight papers, such papers also commonly being referred to as "board". However, the grammage of the base layer before coating is preferably in the range of 45 to 300g/m²In the meantime.

According to a particular embodiment of the invention, the substrate layer may be pre-coated on at least one of its surfaces with one or several commonly used colored pre-coats. Preferably, the precipitation of the pigmented pre-coat is by means of a customary coating process, for example a knife, bar, air knife or reverse roll coating process, or by means of a curtain coating process. Optionally, the pre-coated base layer may be calendered to improve the surface smoothness on the applied coating.

According to a particular embodiment of the invention, the substrate layer is a base paper in which the grammage of the paper substrate before coating is equal to or less than 150g/m²Preferably the grammage is equal to or less than 80g/m²。

In a preferred example, the base layer is a precoated paper in which the paper base layer is double-coated with a coating composition containing a pigment and a binder, and the precoating amount of the surface is 40g/m or less²Is preferably equal to or less than 20g/m². In the case of the desired final high gloss product, the pre-coated paper substrate is preferably calendered. In particular, binders for precoatingCan be selected from: styrene copolymers, such as styrene-butadiene, styrene-acrylate, styrene-maleic anhydride, polyvinyl alcohol, polyvinylpyrrolidone, carboxymethylcellulose, starch, protein, polyvinyl acetate, polyurethane, polyester or acrylic acid, and mixtures thereof. Preferably, the pre-coated pigment is selected from: calcium carbonate, clay, kaolin, talc, titanium dioxide, silica, alumina, boehmite alumina, barium sulfate, zinc oxide, gypsum, and mixtures thereof.

The present invention therefore provides a coated paper (web or sheet) suitable for surface printing, in particular a high gloss paper and/or a high iridescent appearance paper. In particular, the present invention also provides a paper having a combination of high gloss and high iridescent appearance.

It is another object of the present invention to provide a multi-layer curtain coating process for making a coated product suitable for surface printing as described above.

Thus, described herein are: a multi-layer curtain coating process for manufacturing a coated product suitable for surface printing, wherein at least two different coatings having different properties are applied simultaneously by a single pass wet-on-wet curtain coating process.

According to a first aspect, the present invention provides a multi-layer curtain coating process for manufacturing a coated product suitable for surface printing, said coated product comprising a substrate and at least two different coating layers having different properties, said coating layers being applied simultaneously in a single pass on the coated substrate.

More specifically, this is a process for manufacturing a coated product suitable for surface printing, having optical properties, comprising simultaneous curtain coating of at least two different coatings with different properties in a wet-on-wet single pass:

a coating layer (called a low-coat layer) adjacent to the base layer, preferably pigmented, having printing properties and possibly optical properties; and

a different coating layer remote from the base layer (referred to as a top coating layer) comprising optical pigments which impart optical effect characteristics;

wherein, for each of said specific coatings, said base layer is applied in a dry weight range of 0.1 to 12g/m²。

The applicant has surprisingly found that: compared with the coating product with the same formula and different processes, the coating product with at least two separated coatings with different characteristics, which is obtained by applying a single-pass wet-on-wet coating method by using a curtain coater, has obvious advantages in the aspects of enhancing the optical characteristics, good adhesion between the coating and the base layer, raw materials, process cost and the like; the product of comparison is a curtain coating process or other coating process in two separate lanes, or a process that combines two different desired properties in a single layer.

Indeed, the simultaneous application of at least two separate coatings having different properties in a wet-on-wet single pass process with a sliding or slot curtain coating head makes the coated product suitable for printing and has high optical properties, such as gloss and/or iridescent appearance, matte appearance, color, low dry weight and low cost.

In particular, the low coating may be able to meet ink absorption (print dry time) and other printing requirements, such as printed optical density, while the top coating may enhance optical properties, such as gloss, tint, matte, optical effects, such as iridescent, metallic optical effects.

Indeed, the low coating according to the invention provides the printing properties of the product and provides the adhesion between the coating and the substrate.

According to a special embodiment of the curtain coating method according to the invention, the top coat comprises plastic pigments with gloss properties (e.g. hollow plastic microspheres) and separately provides the coated product with a glossy appearance. This can be achieved by simultaneously coating two coatings with different properties in a single pass with a curtain coater, which has significant advantages over products coated in a single pass with a combined "property" layer. In one particular embodiment, the low coat may be used to absorb ink (print dry time) while the top coat may be used to create a glossy appearance.

According to another embodiment of the curtain coating method according to the invention the top coat comprises iridescent effect pigments and alone provides a high iridescent appearance to the coated product.

In addition, it has also been surprisingly found that: when the low coat comprising plastic pigments with gloss properties and the top coat comprising optical interference color-changing pigments are applied simultaneously on a moving substrate by a wet-on-wet single pass curtain coating process, each coat has a low dry coating weight and the optical effect properties of the product surface are indeed improved without affecting the printability of the product. The term "improved" is understood here to mean that a high optical effect is produced on the surface of the product by means of the special coating in question. Indeed, according to a particular embodiment of the multilayer wet-on-wet single pass curtain coating method according to the present invention, a coated product having a particularly high gloss iridescent appearance suitable for surface printing is provided, wherein the low coating layer (preferably pigmented and having printing properties) further comprises plastic pigments having gloss properties and the top coating layer comprises iridescent effect pigments for creating iridescent optical effects.

According to this particular embodiment of the invention, the wet-on-wet single pass curtain coating process described provides two high value requirements for the coated product, namely high gloss and iridescent surface effects.

According to a particular embodiment of the method according to the invention, the low-coat layer and the top-coat layer each have a thickness of 0.1 to 5g/m²Range of dry coating weights. According to another particular embodiment, the top coat preferably has a dry coating weight ranging from 0.1 to 2.5g/m²And low-coat preferred coatingThe dry weight range is 0.1 to 5g/m². According to another particular embodiment of the method according to the invention, the more preferred dry coating weight range of the top coat and the low coat is 0.1 to 2g/m²。

According to one embodiment of the invention, the method also comprises a drying step of the coating of the coated product, so that the coated product obtained can be calendered. According to a particular embodiment of the method for producing gloss according to the invention, the coated product is calendered by means of a multi-nip calender comprising a steel or rubber or cotton roll, or a mixture of these rolls.

According to the invention, the coated product may also comprise one or more coating layers below the low-coat layer, which coating layers may have special properties, such as wetting of the substrate, adhesion of the substrate, ink absorption or gloss enhancement, or common properties, such as printing properties or colour.

The invention also provides a coated product (roll or sheet) suitable for printing on obtained according to said method, in particular a high gloss and/or iridescent product.

The invention also relates to the use of the coated product defined above for coating paper made from cellulose and/or synthetic fibres, and for coating cardboard or plastic articles (sheets or rolls) and making them printable.

The invention will be more clearly understood from the following non-limiting examples.

1. Examples of coating Components with printing and gloss "functionality

Examples of coating samples uniformly coated on the paper base layer are summarized in table 3, and examples of printing and gloss "functionality" are summarized in table 4.

Coating composition

Coating compositions having two different functionalities (printing and optical properties) were coated on a paper substrate in a single pass wet-on-wet curtain coating process as described in examples 1-6 below.

The Comparative Mix (Comparative Mix) is a Comparative coating composition (Mix 1) that contains two functionalities and is coated as a single layer on a paper substrate.

Both the low coat (Mix 2) and the top coat (Mix 3) are coating components according to the invention, which have printing properties and gloss properties, respectively.

Comparative mixture (Mix 1): calcium carbonate pigment (82.3kg) was dispersed in water (34.1 kg). Amorphous silica (0.79kg) was then dispersed in the mixture for 0.5 hours. Then, a plastic pigment (33.1kg) was added to the mixture and stirred for 0.25 hour. Thereafter, polyvinyl alcohol (binder) (3.4kg) was added to the mixture, and stirred for 10 minutes. A latex binder (15.3kg) was added. The rheology modifier (0.5kg) was then added to the mixture and stirred for 0.5 hours. Finally, an alkyl acetylene glycol surfactant (510g) was added and the mixture was stirred for 0.5 hour.

Low coat (Mix 2): calcium carbonate pigment (64.2kg) was dispersed in water (35.1 kg). Amorphous silica (1.16kg) was then dispersed in the mixture for 0.5 hour. Latex binder (16.9kg) was then added. A polyvinyl alcohol binder (2.34kg) was further added, and the mixture was stirred for 10 minutes. The rheology modifier (0.34kg) was then added to the mixture and stirred for an additional 10 minutes. Alkyl acetylene glycol surfactant (240g) was then added and the mixture stirred for 0.5 hours.

Top coat (Mix 3): the plastic pigment (102kg) was added to water (5.4kg) and the mixture was agitated for 0.25 hours. Latex binder (12.6kg) was then added and the mixture stirred for 0.25 hours. Alkyl acetylene glycol surfactant (300g) was then added and the mixture stirred for 0.25 hours.

TABLE 1 mixture parameters

Parameters of the mixture	Comparison mixture (Mix 1)	Low coat (Mix 2)	Top coating (Mix 3)
				Solid content (%)	50	50.6	35.35
Viscosity (cps)/T deg.C	495/26.5℃	385/28℃	88/20℃
				Density (g/cm)3)	1.323	1.375	1.028
Surface tension (dyne/cm)	37.4	42.1	29.1

Paper base (for examples 1 to 6)

The paper base is a pre-coated 150g/m paper base formed from a virgin paper base²Of paper substrate, which is double-coated and calendered (steel or steel)A clip). The precoating component comprises 75 parts of calcium carbonate, 15 parts of clay and 10 parts of latex adhesive at 14g/m²And (4) coating. The relevant physical data are recorded in table 2 below.

TABLE 2

Bottom layer	Dispersed surface energy (Dynes/cm)	Bendtsen roughness (ml/min)	Bekk smoothness (sec)	PPS roughness (mum)	Contact angle (°) bromonaphthalene	Angle of contact (degree) water
							150g/m2Of the precoated paper	39	3	4135	0.62	81.7	29.8

COMPARATIVE EXAMPLE 1 (PRIOR ART)

Example 1 is an example of the preparation of a comparative mixture (Mix 1) where both printing and gloss "functionality" are represented in a single layer.

Mix 1 (comparative mixture) was curtain coated onto a paper substrate at a roll speed of 600m/min, with a dry coating weight of up to 8g/m². Thereby obtaining a uniform coated sample.

The coated samples of the present invention will be summarized in examples 2 to 6.

Example 2: mix 2 (low coating) at a flow rate of 230l/h (dry coating weight of 7 g/m)²) The coating on the paper base results in a stable curtain. Mix 3 (topcoat) was applied at a flow rate of 50l/h (dry coating weight 1.1 g/m)²) Coating on the paper substrate results in another curtain. The combined curtain from the two mixtures (flow rate 280l/h) was stable. A uniform coating sample was obtained on the bottom layer.

Example 3: mix 2 (low coating) at a flow rate of 230l/h (dry coating weight of 7 g/m)²) The coating on the paper base results in a stable curtain. Mix 3 (topcoat) was applied at a flow rate of 100l/h (dry coating weight 2.2 g/m)²) Coating on the paper substrate results in another curtain. The combined curtain from the two mixtures (flow rate 330l/h) was stable. A uniform coating sample was obtained on the bottom layer.

Example 4: mix 2 (low coating) at a flow rate of 230l/h (dry coating weight of 7 g/m)²) The coating on the paper base results in a stable curtain. Mix 3 (topcoat) was applied at a flow rate of 150l/h (dry coating weight 3.3 g/m)²) Coating on the paper substrate results in another curtain. The combined curtain from the two mixtures (flow rate 380l/h) was stable. A uniform coating sample was obtained on the bottom layer.

Example 5: mix 2 (low coating) at a flow rate of 230l/h (dry coating weight of 7 g/m)²) The coating on the paper base results in a stable curtain. Mix 3 (topcoat) was applied at a flow rate of 200l/h (dry coating weight 4.3 g/m)²) Coating on the paper substrate results in another curtain. The combined curtain from the two mixtures (flow rate 430l/h) was stable. A uniform coating sample was obtained on the bottom layer.

Example 6: mix 2 (low coating) at a flow rate of 230l/h (dry coating weight of 7 g/m)²) The coating on the paper base results in a stable curtain. Mix 3 (topcoat) was applied at a flow rate of 250l/h (dry coating weight 5.4 g/m)²) Coated on a paper substrate to obtain anotherAnd (5) curtain. The combined curtain from the two mixtures (flow rate 480l/h) was stable. A uniform coating sample was obtained on the bottom layer.

The data on examples 1 to 6 and their uniform coating samples are summarized in table 3, wherein the dry coating weights mentioned for the low coating and top coating are expressed as "low + dry top coating weight".

TABLE 3 coating evaluation

Example No. 2	Coating step	Flow rate (l/h)		Winding speed (m/min)	Dry coating weight (g/m)2) Low + top	Remarks for note
							Mixture undercoating	Mixture top coat
		1	1-layer 1-track comparison mixture						245(Mix 1)		600	8	Uniform coating
2	2-layer 1-pass Low/Top coat			230(Mix 2)	50(Mix 3)	600	7+1.1	Uniform coating
		3	2-layer 1-pass Low/Top coat						230(Mix 2)	100(Mix 3)	600	7+2.2	Uniform coating
4	2-layer 1-pass Low/Top coat			230(Mix 2)	150(Mix 3)	600	7+3.2	Uniform coating
		5	2-layer 1-pass Low/Top coat						230(Mix 2)	200(Mix 3)	600	7+4.3	Uniform coating
6	2-layer 1-pass Low/Top coat			230(Mix 2)	250(Mix 3)	600	7+5.4	Uniform coating

Physical properties of the medium

The samples in examples 1 to 4 were calendered at 1200pli (pounds per linear inch) at 45 ℃ and 50m/min to increase the gloss of the appearance. As shown in Table 4, the 2-layer 1-lane coated product had a higher gloss than the 1-layer 1-lane product. With a larger proportion of plastic pigment, the gloss value increases with increasing dry coating weight of the top coat. The adhesion of the 2-layer 1-pass coating (examples 2 to 4) to the base layer was also significantly improved compared to the 1-layer 1-pass coating (comparative example 1).

TABLE 4 gloss data

Example No. 2	Number of layers	Number of tracks	Calendering	Gloss (75 °) BYKGardener	Gloss (60 °) BYKGardener	Gloss (20 °) BYKGardener	Adhesion test
								1	1	1	Is that	78	41.2	3.9	3
2	2	1	Is that	97	73.2	11.2	1
								3	2	1	Is that	103	88.1	15.2	1
4	2	1	Is that	105	98.0	20.8	1

Thus, it can be clearly seen that: the advantage of separating the coating into coatings of different functionalities is that the glossy appearance of the coated product is enhanced. The print performance of the samples obtained from all examples was also better than that of the comparative mixture (comparative example 1).

Microscopic analysis

The invention is given below in the microscope cross-section of example 2 (fig. 1), of example 3 (fig. 2) and of example 4 (fig. 3).

As shown in fig. 1, 2 and 3, the hollow spheres used to enhance gloss are clearly visible on top of the coating after the calendering process.

Examples of coating Components for obtaining coated products with printing Properties and glossy iridescent appearance Properties

Examples of uniformly coated samples on the paper substrate are summarized in table 7, and examples of print and "functionality" of the glossy iridescent appearance are summarized in table 8.

Coating composition

Coating compositions having different characteristics (printing, gloss and iridescent properties) were coated on a paper substrate in a single pass wet-on-wet curtain coating process as described in the examples below.

The comparative mixture (Mix 4) is a comparative coating component that contains all functionalities and is coated as a single layer on the paper substrate.

Both the low coat (Mix 5) and the top coat (Mix 6 or Mix 7) are coating components according to the invention, which have printing properties, gloss properties and iridescent properties, respectively.

Comparative mixture (Mix 4): amorphous silica (4.08kg) was dispersed in water (61.63kg) for 0.5 hour. Then, plastic pigment (55.44kg) was added and stirred. Iridescent pigment (12.58kg) was then added to the mixture. Polyvinyl alcohol (binder) (66kg, 12% solution) was added. Alkyl acetylene glycol surfactant (0.264kg) was then added and the mixture stirred for 0.5 hours.

Calcium carbonate pigment (82.3kg) was dispersed and stirred for 0.25 hour. Thereafter, the mixture was added and stirred for 10 minutes. A latex binder (15.3kg) was added. The rheology modifier (0.5kg) was then added to the mixture and stirred for 0.5 hours.

Low coat (Mix 5): amorphous silica (4.1kg) was dispersed in water (64.4kg) for 0.5 hour. Thereafter, plastic pigment (91.4kg, 35% solids) was added. Polyvinyl alcohol (binder) (40kg, 10% solids) was then added. The mixture was stirred for 0.5 hour. Alkyl acetylene glycol surfactant (0.20%) was added. The mixture was then stirred for 0.5 hour.

Top coat (Mix 6): amorphous silica (0.83kg) was dispersed in water (155.2kg) for 0.5 hour. Iridescent pigment (155.2kg) was then added. Polyvinyl alcohol (binder) (32kg, 10% solution) was then added and the mixture was stirred for 0.5 hours. Further, an alkyl acetylene glycol surfactant (0.25%) was added, and the mixture was stirred for 0.5 hour.

Top coat (Mix 7): amorphous silica (0.153kg) was dispersed in water (89.75kg) for 0.5 hour. Iridescent pigment (12.60kg) was then added. Polyvinyl alcohol (binder) (22.5kg, 10% solution) was then added and the mixture stirred for 0.5 hours. Further, an alkyl acetylene glycol surfactant (0.25%) was added, and the mixture was stirred for 0.5 hour.

TABLE 5 mixture parameters

Parameters of the mixture	Comparison mixture (Mix 4)	Low coat (Mix 5)	Top coating (Mix 6)	Top coating (Mix 7)
					Solid content (%)	22.43	19.26	7.18	12.3
Viscosity (cps)/T deg.C	225	234/19℃	32/19℃	46/11℃
					pH/T℃	7.9/27.3℃	8.5/25.6℃	7.8/14.7℃	7.7/11℃
Density (g/cm)3)	1.077	1.0279	1.051	1.083
					Surface tension (dyne/cm)	31.3	30	28	27

Paper base (for examples 7 to 21)

The paper base is a pre-coated 150g/m paper base formed from a virgin paper base²The paper base is double coated and calendered (steel or steel nip). The precoating component comprises 75 parts of calcium carbonate, 15 parts of clay and 10 parts of latex adhesive at 14g/m²And (4) coating. The relevant physical data are recorded in table 2 below.

TABLE 6

Bottom layer	Surface energy (Dynes/cm)	Bendtsen roughness (ml/min)	Bekk smoothness (sec)	PPS roughness (mum)
					150g/m2Paper base	38.5	15	241	2.56

COMPARATIVE EXAMPLE 7 (Prior Art)

Example 7 is an example of the preparation of a comparative mixture (Mix 4) where the printing, gloss and iridescence "functionalities" are all combined in one layer.

Mix 4 (comparative mixture) was curtain coated onto a paper substrate at a roll speed of 600m/min, reaching a dry coating weight of 5.0g/m². Thereby obtaining a uniform coated sample.

In examples 8 to 10, the different coatings were applied simultaneously (2 layers in lane 1), wherein the dry coating weight of the low coating (Mix 5) was 2g/m²While the dry coating weight of the top coat (Mix 6) was varied.

Example 8 (invention): mix5 was fed at a flow rate of 180l/h (dry coating weight 2.0 g/m)²) Coating on paper substrate resulted in a stable curtain. At a flow rate of 120l/h (dry coating weight 0.5 g/m)²) Mix6 was applied to obtain a curtain. By mixing of the twoThe object-bound curtain (flow rate 300l/h) was stable. A uniform coating sample was obtained on the bottom layer.

Example 9 (invention): mix5 was fed at a flow rate of 180l/h (dry coating weight 2.0 g/m)²) Coating on paper substrate resulted in a stable curtain. Followed by a flow rate of 200l/h (dry coating weight 0.8 g/m)²) Mix6 was applied to obtain a curtain. The combined curtain (flow rate 380l/h) from the two mixtures was stable. Thus, a uniform coated sample was obtained.

Example 10 (invention): mix5 was fed at a flow rate of 180l/h (dry coating weight 2.0 g/m)²) Coating on paper substrate resulted in a stable curtain. At a flow rate of 250l/h (dry coating weight 1.2 g/m)²) Mix6 was applied to obtain a curtain. The combined curtain (flow rate 430l/h) from the two mixtures was stable. Thus, a uniform coated sample was obtained.

In the following comparative examples 11 to 16, the different coatings were applied separately (2 layers in 2 passes), wherein the low coating (Mix 5) was applied to the paper substrate first and then the top coating was applied in a separate second pass.

Example 11 (comparative example): mix5 was first coated as a low coat on a paper substrate in one pass in a curtain coating process and dried. Mix6 was then applied as a top coat to the paper substrate in another pass in a curtain coating process with a dry coating weight of 0.5g/m². A stable curtain was formed at a flow rate of 260 l/h. This corresponds to about 1.1g/m²Dry coating weight of (c). The coated samples were very poor and non-uniform.

Example 12 (comparative example): mix5 was first coated as a low coat on a paper substrate in one pass in a curtain coating process and dried. Mix6 was then coated as a top coat on the paper substrate in another pass in a curtain coating process. A more stable curtain was formed at an increased flow rate of 400 l/m. This corresponds to 1.68g/m²Dry coating weight of (c). The coated sample was still poor and non-uniform.

Example 13 (comparative example)Examples): mix5 was first coated as a low coat on a paper substrate in a curtain coating process in one pass and dried. Mix6 containing 0.5% sodium alginate as a top coat was then coated on the paper substrate in another pass in a curtain coating process with a dry coating weight of 0.5g/m². A stable curtain was formed at a reduced flow rate of 140 l/m. This corresponds to 0.6g/m²Dry coating weight of (c). However, the coated sample was still poor with signs of "skip" on the bottom layer.

Example 14 (comparative example): mix5 was first coated as a low coat on a paper substrate in a curtain coating process in one pass and dried. Mix6 containing 0.25% rheology modifier was then coated as a top coat on the paper substrate in another pass in a curtain coating process at a flow rate of 200 l/h. This corresponds to 0.8g/m²Dry coating weight of (c). Thereby forming a stable curtain of Mix 6. However, the coated sample was poor with signs of "skip" on the bottom layer.

Example 15 (comparative example): mix5 was first coated as a low coat on a paper substrate in one pass in a curtain coating process and dried. Mix6 containing 0.25% rheology modifier was then coated as a top coat on the paper substrate in another pass in a curtain coating process at a flow rate of 300 l/h. This corresponds to 1.2g/m²Dry coating weight of (c). Thereby forming a stable curtain of Mix 6. However, the coated sample was poor with signs of "skip" on the bottom layer.

Example 16 (comparative example): mix5 was first coated as a low coat on a paper substrate in one pass in a curtain coating process and dried. Mix6 containing 0.25% rheology modifier was then coated as a top coat on the paper substrate in another pass in a curtain coating process at a flow rate of 400 l/h. This corresponds to 1.6g/m²Dry coating weight of (c). Thereby forming a stable curtain of Mix 6. However, the coated sample was poor with signs of "skip" on the bottom layer.

In the following examples 17 to 21, the different coatings were applied simultaneously (2 layers in each caseLane 1), wherein the dry coating weight of the low-coat layer Mix 5) is 2g/m²While the dry coating weight of the top coat (Mix 7) was varied.

Example 17 (invention): mix5 was fed at a flow rate of 180l/h (dry coating weight 2.0 g/m)²) Coating on paper substrate resulted in a stable curtain. At a flow rate of 50l/h (dry coating weight of about 0.35 g/m)²) Mix7 was applied to obtain a curtain. The combined curtain (flow rate 230l/h) from the two mixtures was stable. Thus, a uniform coated sample was obtained.

Example 18 (invention): mix5 was fed at a flow rate of 180l/h (dry coating weight 2.0 g/m)²) Coating on paper substrate resulted in a stable curtain. At a flow rate of 100l/h (dry coating weight of about 0.69 g/m)²) Mix7 was applied to obtain a curtain. The combined curtain (flow rate 280l/h) from the two mixtures was stable. Thus, a uniform coated sample was obtained.

Example 19 (invention): mix5 was fed at a flow rate of 180l/h (dry coating weight 2.0 g/m)²) Coating on paper substrate resulted in a stable curtain. At a flow rate of 150l/h (dry coating weight of about 1.04 g/m)²) Mix7 was applied to obtain a curtain. The combined curtain (flow rate 330l/h) from the two mixtures was stable. Thus, a uniform coated sample was obtained.

Example 20 (invention): mix5 was fed at a flow rate of 180l/h (dry coating weight 2.0 g/m)²) Coating on paper substrate resulted in a stable curtain. At a flow rate of 200l/h (dry coating weight of about 1.38 g/m)²) Mix7 was applied to obtain a curtain. The combined curtain (flow rate 380l/h) from the two mixtures was stable. Thus, a uniform coated sample was obtained.

Example 21 (invention): mix5 was fed at a flow rate of 180l/h (dry coating weight 2.0 g/m)²) Coating on paper substrate resulted in a stable curtain. At a flow rate of 300l/h (dry coating weight of about 2.07 g/m)²) Mix7 was applied to obtain a curtain. The combined curtain (flow rate 480l/h) from the two mixtures was stable. Thus, a uniform coated sample was obtained.

A vacuum box (under the catch tray) was used in the coating trials to help minimize air entrainment effects during the coating of the curtain.

TABLE 7 evaluation of coating

Example No. 2	Coating step	Flow rate (l/h)		Winding speed (m/min)	Dry coating weight (g/m)2)	Wet thickness (μm)	Remarks for note
								Mixture undercoating	Mixture top coat
		7	1-layer 1-track contrast Mix 4							370		600	5.0	20.8	Uniform coating
8	2-layer 1-pass Low/Top coat			180(Mix 5)	120(Mix 6)	600	2.5(2.0+0.5)	10.1/6.7	Uniform coating

9	2-layer 1-pass Low/Top coat	180(Mix 5)	200(Mix 6)	600	2.8(2.0+0.8)	10.1/11.2	Uniform coating
								10	2-layer 1-pass Low/Top coat	180(Mix 5)	250(Mix 6)	600	3.2(2.0+1.2)	10.1/14.0	Uniform coating
11	2-layer 2-track top coat		260(Mix 6)	600	1.1	14.6	The curtain is formed at a minimum flow rate of 260 l/h. Poor uniform coating
								12	2-layer 2-track top coat		400(Mix 6)	600	1.68	22.4	The curtain was formed at an increased flow rate of 400 l/h. Poor uniform coating
13	2-layer 2-coat top coat containing 0.5% sodium alginate		140(Mix 6)	600	0.6	7.9	The curtain is formed at a minimum flow rate of 140 l/h. Poor uniform coating
								14	2-layer 2-pass top coat containing 0.25% rheology modifier		200(Mix 6)	600	0.81	11.2	Forming a curtain. Poor uniform coating
15	2-layer 2-pass top coat containing 0.25% rheology modifier		300(Mix 6)	600	1.22	16.8	Forming a curtain. Poor uniform coating
								16	2-layer 2-pass top coat containing 0.25% rheology modifier		400(Mix 6)	600	1.63	22.4	Forming a curtain. Poor uniform coating
17	2-layer 1-pass Low/Top coat	180(Mix 5)	50(Mix 7)	600	2.35(2.0+0.35)	10.1/2.8	Uniform coating
								18	2-layer 1-pass Low/Top coat	180(Mix 5)	100(Mix 7)	600	2.69(2.0+0.69)	10.1/5.6	Uniform coating
19	2-layer 1-pass Low/Top coat	180(Mix 5)	150(Mix 7)	600	3.04(2.0+1.04)	10.1/8.4	Uniform coating

	Layer(s)
								20	2-layer 1-pass Low/Top coat	180(Mix 5)	200(Mix 7)	600	3.38(2.0+1.38)	10.1/11.2	Uniform coating
21	2-layer 1-pass Low/Top coat	180(Mix 5)	300(Mix 7)	600	4.07(2.0+2.07)	10.1/16.8	Uniform coating

The use of a coating with printing and gloss properties (as a low coating) and a coating with iridescent properties (as a top coating) with a sliding curtain coating head applied to a paper substrate using a wet-on-wet single pass process gives the coated product a highly glossy iridescent appearance, with lower dry coating weight and lower cost.

With the stated "low coat" (coating dry weight of 2.0 g/m)²) Applying a thin iridescent topcoat (dry coating weight in the range of 0.35 g/m)²To 2.07g/m²) Creating a highly uniform coated sample and maintaining the iridescent pigments on the surface of the coating layer oriented parallel to the underlying surface, all as described herein, in order to effectively create an iridescent appearance.

The top coat (Mix 7) of example 17 was prepared at a flow rate of 50l/h to give a uniform coating profile. A clear iridescent appearance was observed, averaging 0.35g/m². The flow rate was increased to 300l/h in small amounts, and a uniformly coated sample was obtained. An increased iridescent appearance was observed relative to higher coating weights.

For the formation of iridescent top coats, applying two "functional" coats separately resulted in poor coating uniformity. The top coat Mix6 will form a stable curtain only at a flow rate of 260 l/h. However, an uneven coating sample and a "skip" coating obtained on the media can be observed in the curtain impact zone. The reason for this missed coating may be due to air entrainment effects and curtain instability at the applied roll speed. The flow rate can also be increased to 400l/h to stabilize the resulting curtain, but the coated sample is still poor. This particular top coat cannot be applied in one pass using a curtain coating module. Even if the viscosity of the top coat mixture was increased with 0.5% sodium alginate as a thickener (Brookfield viscosity 204cps, 21 ℃), the coating quality could not be improved (example 13). The addition of 0.25% rheology modifier increased the high shear and high extensional viscosity of the mixture, although a stable curtain could be formed, which still did not improve the coating samples at flow rates of 200 to 400 l/h.

However, when the top coat mixture is applied in a wet-on-wet process in combination with the low coat mixture, a uniform coated product can be obtained. The low-coat mixture combines with the effective rheology of the top-coat mixture to make it possible to obtain such a uniformly coated sample.

Colorimetric data

The color data for examples 7, 9, 10, 17 and 19 were determined for a (L, a, b) system with a fixed-45 ° illumination angle, the measured angle range being-75 ° to 75 °.

The comparative sample (comparative example 7) showed a more yellow color at a measurement angle of 45 °. The green effect of iridescence becomes more pronounced upon moving to the 2-ply 1-lane product. Thus, example 9 has a density of 0.8g/m²Iridescent top coat (Mix 6) over the low coat. Example 10 has a density of 1.2g/m²An iridescent top coat (Mix 6) having enhanced iridescence. Application of Mix7 as a top coat produced a wider color gamut (yellow-green) as seen in examples 17 and 19.

Physical properties of the medium

The samples were calendered (steel/composite) at 1200pli (45 ℃, 50m/min) to increase their gloss and iridescent appearance. As shown in table 8, the 2-layer 1-lane product had a higher gloss (gloss values may be affected by poor coating uniformity) than the product when the top coat was applied in a separate layer. The amount of top coat applied is increased and the gloss value is reduced because of the particle size of the iridescent pigment (5 to 25 μm), but the iridescent appearance becomes more pronounced.

TABLE 8 gloss data

Example No. 2	Number of layers	Number of tracks	Calendering	Gloss (75 °) BYKGardener
					7	1	1	Is that	70
8	2	1	Is that	75.1
					9	2	1	Is that	68.4
10	2	1	Is that	62.7
					11	2	2	Is that	49.8
13	2	2	Is that	60.0
					14	2	2	Is that	29.3
15	2	2	Is that	26.6
					17	2	1	Is that	79.2
18	2	1	Is that	78.4
					19	2	1	Is that	74.0
20	2	1	Is that	64.1
					21	2	1	Is that	50.5

The print performance of the samples obtained from all examples was better than that of the comparative sample (comparative example). Drying times and collection rates were similarly improved.

Microscopic (SEM) analysis

The invention is given below in the microscope cross-sections of comparative example 7 (fig. 4 and 4a), example 9 (fig. 5 and 5a), example 19 (fig. 6) and example 21 (fig. 7).

As shown in fig. 5a, 6 and 7, the iridescent pigment plate of the 2-layer-1-lane iridescent paper is clearly visible on the paper surface. In contrast, the iridescent pigments of the 1-ply-1-way iridescent papers are all masked in the coating (fig. 4 and 4 a).

Test method

Adhesion test: a layer of adhesive tape (Scotch ®) (1 cm. times.10 cm) was firmly attached to the coated paper, and the tape was then pulled off the paper surface by hand. The coating deposited on the blanket was then evaluated for coating weight and rated on a 1 to5 scale accordingly. Grade 1 means that there is no coating on the blanket (excellent adhesion), and grade 5 means that the coating can be completely pulled off by the blanket (poor adhesion).

Viscosity: measured using a Brookfield RVT viscometer. The selected shaft speed was 100 rpm. For the mixtures of examples 1 to 6, the axis size was Sp 3; for the mixtures of examples 7 to 21, the axis size was Sp2 or Sp 3. During the viscosity measurement, the temperature of the mixture was recorded.

Density: measured using a 100mL densitometer. During the density measurement, the temperature was recorded.

pH: the measurement was carried out using a HI 9024 microcomputer pH meter (Hanna instruments Co.). During the pH measurement, the temperature was recorded.

Solids content (%): measured using a CEM Labwave 9000 microwave moisture/solids analyser.

Contact angle: measured using a FibroDAT 1100.

Surface tension: the measurement was carried out using a DCA 132(Wilhelmy plate) instrument with platinum plates.

Paper gloss: measured at fixed angles of 20 °, 60 °, 75 ° using a gloss meter (BYK Gardner gmbh, germany).

Paper smoothness: measured using a Bekk smoothness tester and a Parker surface printing tester (Messmer Instrument Co., Ltd.) (pps roughness).

Air permeability: measured using a Bendtsen tester (Lorentzen & Wettre Co.).

Rheological property: the flow data was measured with parallel plates at 25+/-1 ℃ in a 40 μm gap using a CV0120 high resolution rheometer (Bohlin instruments). The shear rate is in the range of 10 to 100000s^-1。

Effective extensional viscosity: the measurements were carried out on a Paar automatic high shear viscometer HVA 6, the instrument having capillary lengths of 10mm and 5mm and a capillary diameter of 0.6 mm.

Scanning Electron Microscope (SEM): hitachi S-4000 electron microscope.

Mixture preparation and coating method

All parts are calculated as wet weights. All formulations were mixed using a great GM disperser. Stirring to ensure good mixing but avoid excessive air entrainment. The curtain coating head used was of the slide type with a width of 49cm and a die slit of 300. mu.m. The curtain coating head was equipped with edge guides running water from each side and also with a vacuum aspirator to remove water at the bottom of the edge guides. The catch tray also acts as an obstacle, a mechanical barrier to limit air entrainment in the impact zone. Optionally, a vacuum pump (0.3bar) may be applied to reduce the penetration in the impingement zoneThe movement of the roller blind can also limit the occurrence of air entrainment. The curtain height of the roll is 150 mm. The amount of coating per coated sample is determined by the volumetric flow rate of a known pump that delivers the mixture to the curtain coating head and is determined by the roll speed, density and solids content% of the mixture, and the width of the curtain. The coating weight for gravimetric determination can be determined by: placing in an oven for 1m²Coated and uncoated substrate samples were left at 150 ℃ for 10 minutes and the difference in weight of the two samples was determined. As is well known to those skilled in the art, each layer can be accurately calculated based on the coating speed, the width of the coating head, the flow rate of each mixture or each layer into the coating head, the solids content, and the density of the mixture given herein.

Each mixture was deaerated, superior to the product coated with the deaerator.

Raw materials for formulation

Plastic pigment: hollow plastic microspheres with dual peaks of distribution, with particle sizes of 1.3 μm and 0.2 μm, 35% solids. These pigments may also act as opacifying agents and gloss enhancers in calendering.

Amorphous silica: silica powder having an average particle size of 5 to 6 μm. Dispersed in water for 0.5 hours to form a mixture.

Iridescent pigments: iridescent "interference" pigment plates with particle sizes in the range of 5-25 μm.

Polyvinyl alcohol binder: the polyvinyl alcohol was 88% water soluble. The viscosity of the 4% solution at 25 ℃ is 40 cps. A polyvinyl alcohol binder was used as a 10% solution obtained by heating polyvinyl alcohol particles in water at 95 ℃ for 0.5 hour.

Latex binder: styrene butadiene emulsion with a particle size of 140 nm.

A surfactant: nonionic alkyl benzene ethoxy ether can reduce dynamic surface tension.

Rheology modifier: an anionic water-oil emulsion of acrylate/acrylic acid copolymer.

Print evaluation

The printing was performed at a Heidelburg GTO52 printing pressure.

The drying time of the PIRA ink (BASF Flashdri 3000 tube stabilized ink) was measured in the press room.

IGT sample detection (Pick-Test).

Claims (38)

1. A coated product for surface printing comprising a substrate and at least two different coatings having different properties, characterized in that:

said product comprising a low-coat layer adjacent to a substrate, the layer having printing properties and possibly optical properties, the layer preferably being pigmented; and

a different top coat layer remote from the base layer, the layer comprising an optical pigment having an optical effect characteristic,

the coating dry weight of each coating is 0.1-12g/m²Within the range of (1).

2. The coated product according to claim 1, characterized in that: the top coat layer contains optical pigment selected from plastic pigment with gloss characteristic or optical interference color-changing pigment.

3. The coated product according to claim 1 or 2, characterized in that: the low-coat layer comprises a coating pigment and a binder that imparts printing characteristics.

4. The coated product according to claim 3, characterized in that: the coating pigment of the low coating is selected from the following: calcium carbonate, clay, kaolin, talc, titanium dioxide, silica, alumina, boehmite alumina, barium sulfate, zinc oxide, gypsum, and mixtures thereof.

5. The coated product according to any one of claims 1 to 4, characterized in that: the top coat comprises a plastic pigment with gloss characteristics.

6. The coated product according to any one of claims 1 to 4, characterized in that: the top coat layer contains an optical interference color changing pigment.

7. The coated product according to claim 2, characterized in that: the optical interference color-changing pigment is selected from metallic effect pigment or iridescent effect pigment.

8. The coated product according to claim 3, characterized in that: the colored basecoat further comprises a plastic pigment that imparts optical properties.

9. The coated product according to claim 8, characterized in that: the low coating layer comprises plastic pigments with gloss characteristics and the top coating layer comprises light interference color changing pigments.

10. The coated product according to claim 9, characterized in that: the optical interference color-changing pigment is iridescent effect pigment.

11. The coated product according to claim 9, characterized in that: the optical interference color-changing pigment is a metal effect pigment.

12. The coated product according to claim 7 or 10, characterized in that: the iridescent effect pigment is selected from the group consisting of nacreous layer extract, coated titanium oxide mica pigment, and interference multilayer plastic pigment.

13. The coated product according to any of the preceding claims, wherein: the bottom layer is a fibrous bottom layer or a plastic bottom layer.

14. The coated product according to claim 13, characterized in that: the fibrous substrate is a material based on cellulose fibres.

15. The coated product according to claim 14, characterized in that: the bottom layer is paper or paperboard.

16. The coated product according to claim 15, characterized in that: the grammage of the paper bottom layer is equal to or less than 150g/m²Preferably the grammage is equal to or less than 80g/m²In the case of a pre-coated paper substrate, the grammage referred to herein is the grammage prior to coating.

17. The coated product according to claim 13, characterized in that: the bottom layer is selected from:

a) an uncoated or initial base layer;

b) a pre-coated or pre-prepared base layer;

c) pre-coated and then calendered.

18. The coated product according to any of the preceding claims, characterized in that: the low coating has a thickness of 0.1 to 7g/m²And said top coat has a dry coating weight of 0.1 to 5g/m²Dry coating weight of (c).

19. The coated product according to claim 5, characterized in that: the low coating has a thickness of 7g/m²And said top coat has a dry coating weight of 0.1 to 5g/m²Dry coating weight of (c).

20. The coated product according to claim 9, characterized in that: the low coating has a thickness of 0.1 to 5g/m²And said top coat has a dry coating weight of 0.1 to 2.5g/m²Dry coating weight of (c).

21. The coated product according to any of the preceding claims, characterized in that: the different coatings of the coated product comprise a binder.

22. The coated product of claim 21, wherein: the binder is selected from the group consisting of styrene copolymers such as styrene-butadiene, styrene-acrylate, styrene-maleic anhydride, polyvinyl alcohol, polyvinyl pyrrolidone, carboxymethyl cellulose, starch, protein, polyvinyl acetate, polyurethane, polyester or acrylic acid, and mixtures thereof.

23. The coated product according to claim 5, characterized in that: the top-coated product comprises a plastic pigment with gloss properties, the gloss value after calendering being equal to or greater than 90, the gloss value being determined at 75 degrees according to the ISO2813 standard.

24. A method for manufacturing a coated product having optical properties suitable for surface printing, comprising: simultaneous curtain coating of at least two different coatings with different properties in a wet-on-wet single pass, on a substrate:

a low-coat layer, preferably pigmented, having printing properties and possibly optical properties; and

a different topcoat layer comprising optical pigments that impart optical effect characteristics;

wherein said base layer is applied in a dry weight range of 0.1 to 12g/m for each of said specialized coatings²。

25. The method of claim 24, wherein: the coating method also comprises a drying step.

26. The method according to claim 24 or 25, characterized in that: the bottom layer is a material based on cellulose fibres.

27. The method according to claim 24 or 25, characterized in that: the bottom layer is a plastic film or a plastic sheet.

28. Method according to one of claims 24 to 27, characterized in that: the low-coat layer comprises a coating pigment and a binder that imparts printing characteristics.

29. The method of claim 28, wherein: the low-coat coating pigment is selected from the group consisting of calcium carbonate, clay, kaolin, talc, titanium dioxide, silica, alumina, boehmite alumina, barium sulfate, zinc oxide, gypsum, and mixtures thereof.

30. Method according to one of claims 24 to 29, characterized in that: the top coat layer contains optical pigment selected from plastic pigment with gloss characteristic or optical interference color-changing pigment.

31. The method of claim 30, wherein: the top coat comprises plastic pigment with gloss characteristic.

32. The method of claim 31, wherein: in order to exploit the glossy optical properties of the plastic pigments of the top coat, the coated products are obtained after drying and then calendered.

33. The method of claim 30, wherein: the top coat layer contains an optical interference color changing pigment.

34. The method of claim 33, wherein: the optical interference color-changing pigment is selected from metal effect pigments or iridescent effect pigments.

35. Method according to one of claims 24 to 30, characterized in that: the colored basecoat further comprises a plastic pigment that imparts optical properties.

36. The method of claim 35, wherein: the optical interference color-changing pigment is iridescent effect pigment.

37. The method according to one of claims 24 to 36, wherein: the low coating has a thickness of 0.1 to 7g/m²And said top coat has a dry coating weight of 0.1 to 5g/m²Dry coating weight of (c).

38. The method according to one of claims 24 to 37, wherein: also included is drying the obtained coated product.