KR102317707B1 - Reflective multi-layer film - Google Patents

Abstract

The present invention relates to a multilayer reflective film comprising a structure in which a first resin layer and a second resin layer are alternately laminated, and including a first reflection peak in a near-infrared region and a second reflection peak in a visible region. Since the multilayer reflective film has two reflection peaks, the reflectance of the film can be easily adjusted, and it has the effect of blocking infrared rays. In addition, since it reflects different colors depending on the angle, the visual effect is excellent, and it can be usefully used in various fields such as industrial, packaging, display, and window.

Description

Multilayer reflective film {REFLECTIVE MULTI-LAYER FILM}

The present invention relates to a multilayer reflective film, and more particularly, to a multilayer reflective film that reflects visible light and infrared wavelength regions, respectively.

Films that characterize light reflection using a multi-layer structure have been continuously developed, ranging from simple films that reflect a specific wavelength to films that reflect the entire range of visible light, infrared reflecting films, and reflective polarizing films. , is widely used for packaging, displays, windows, etc.

The multilayer reflective film uses the reflection and interference effect of light occurring in each layer, and the prior art uses a method of selectively reflecting a specific wavelength by alternately stacking resin layers having different refractive indices to reflect a specific wavelength. Yes (Japanese Patent Laid-Open No. 1997-506837).

However, the conventional method of realizing color using only one wavelength is inconvenient to use two materials having a large difference in refractive index to add a sense of color or to implement color by stacking a large amount of film layers. . In addition, each layer has a disadvantage in that it is difficult to adjust the reflectance because the refractive index difference is limited.

Accordingly, there is a need to present a multilayer film capable of implementing the convenience of adjusting reflectance through a film reflecting two or more wavelengths.

Japanese Patent Laid-Open No. 1997-506837 (December 20, 1994)

An object of the present invention is to provide a multilayer reflective film having two reflection peaks that reflect a visible light wavelength region and an infrared wavelength region.

According to an embodiment, a multilayer reflective film including a structure in which a first resin layer and a second resin layer are alternately stacked, and a first reflection peak in a near-infrared region and a second reflection peak in a visible light region, is provided

In the multilayer reflective film according to the embodiment, two resin layers having different refractive indices are alternately laminated through co-extrusion, and the multilayer reflective film may reflect a visible light wavelength region and an infrared wavelength region, respectively. Since the multilayer reflective film has two reflection peaks, the reflectivity of the film can be easily adjusted, and colors can be realized by reflecting light in a visible wavelength region, and also have an infrared blocking function. In addition, since light of different wavelengths is reflected according to the angle at which the light is reflected, various colors can be implemented depending on the viewing field, and the visual effect is also excellent.

1 is a graph showing reflectance according to wavelength of a multilayer laminated film according to an embodiment.
FIG. 2 is a graph illustrating a change in a thickness ratio of a second resin layer to a first resin layer according to a refractive index of the second resin layer in the multilayer laminated film according to an exemplary embodiment.
3 is a graph showing reflectance according to a thickness ratio of a second resin layer to a first resin layer in the multilayer laminated film according to an embodiment.
4 is a graph illustrating a change in reflectance of a first reflection peak after heat treatment of the multilayer laminated film according to an embodiment at 150° C. for 30 minutes.

The above object, features and advantages of the present invention will be easily understood through the following preferred embodiments in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. In describing each figure, like reference numerals have been used for like elements. In the accompanying drawings, the dimensions of the structures are enlarged than the actual size for clarity of the present invention. Terms such as first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component. The singular expression includes the plural expression unless the context clearly dictates otherwise.

In the present application, terms such as “comprise” or “have” are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one or more other features It is to be understood that it does not preclude the possibility of the presence or addition of numbers, steps, operations, components, parts, or combinations thereof. In addition, the reference to a number as a range in the specification is merely because it is easy to replace each separate number falling within the range individually, and each separate number includes all numerical values in a similar range.

Hereinafter, the present invention will be described in more detail.

According to an embodiment, a multilayer reflective film including a structure in which a first resin layer and a second resin layer are alternately stacked, and a first reflection peak in a near-infrared region and a second reflection peak in a visible light region, is provided

The first reflection peak may appear in a near-infrared region, and the near-infrared region may have a wavelength range of 750 nm to 1,500 nm. Specifically, the first reflection peak may appear in a wavelength range of 780 nm to 930 nm, 810 nm to 900 nm, or 840 nm to 870 nm. The first reflection peak is reflected in the near-infrared wavelength region, and the color due to the reflection is not implemented. However, if necessary, it is possible to implement a color through the first reflection peak.

In addition, the multilayer reflective film may have an infrared blocking function through reflection in the infrared wavelength range region. Specifically, the multilayer reflective film has an infrared blocking rate of 27% to 50%, 29% to 48%, or 32% to 46% in the 900 nm to 1200 nm region. Furthermore, by additionally applying or including an adhesive containing a UV curing agent to the multilayer reflective film, it is possible to simultaneously implement an infrared blocking function as well as an ultraviolet blocking effect.

Also, the second reflection peak may appear in a visible ray region, and the visible ray region may have a wavelength range of 350 nm to 740 nm. Specifically, the second reflection peak may appear in a wavelength range of 350 nm to 500 nm, 370 nm to 480 nm, 380 nm to 470 nm, or 390 nm to 460 nm. The second reflection peak may selectively reflect light, and may implement various colors according to an observation angle. Specifically, when observed from a frontal angle, a blue or green wavelength region is mainly reflected and appears, and as the observation angle increases, it gradually moves to a lower wavelength band to exhibit a color reflecting blue to purple. More specifically, the multilayer reflective film according to an embodiment may implement a blue-violet reflection color, and may implement a yellow or yellow-green transmission color.

The resin constituting the first resin layer is not particularly limited, but polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polycyclohexane terephthalate, polyethylene naphthalate, polyethylene, polypropylene, polymethylpentene, etc. One or more first resins selected from the group consisting of polyolefin resins, polyamide resins such as nylon 6 or nylon 66, aramid resins, fluororesins such as vinylidene fluoride resins, and acrylic resins may be used, specifically polyethylene terephthalate can be used, and it is preferable to use a material whose refractive index changes by stretching during the process.

The resin constituting the second resin layer is not particularly limited, but is made of copolymerized polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polymethyl methacrylate, polylactide and polyethylene terephthalate. One or more second resins selected from the group can be used, and more specifically, polymethmethyl acrylate or copolymerized polyethylene terephthalate can be used. desirable.

The copolymerized polyethylene terephthalate is ethylene glycol (EG) as a glycol component, neopentyl glycol (NPG), cyclonucleic acid dimethanol (CHDM), dicarboxylic acid (CHDA), polyspiroglycol petephthalate (SPG), dimethylnaphthalenedicarboxyl The rate (NDC) may include, but is not limited to, copolymerized ones. Specifically, it is preferable that ethylene glycol (EG) and neopentyl glycol (NPG) are copolymerized. The neopentyl glycol content of the glycol component may be copolymerized in an amount of 10 mol% to 30 mol%. More specifically, the neopentyl glycol content may be copolymerized in an amount of 15 mol% to 25 mol% with respect to the glycol component.

The refractive index of the second resin layer varies according to the content of the neopentyl glycol, and the thickness ratio of the second resin layer to the first resin layer also varies. More specifically, as shown in Table 1 below, when the content of neopentyl glycol (NPG) with respect to the glycol component is in the range of 15 mol% to 25 mol%, the refractive index of the second resin layer is 1.58 to 1.62 range, wherein the thickness ratio of the second resin layer to the first resin layer having a refractive index of 1.654 is 0.65 to 0.90. As a result, the reflectivity of the multilayer reflective film can be easily adjusted by adjusting the thickness ratio of the second resin layer to the first resin layer according to the content of neopentyl glycol.

Physical properties of the second resin layer Thickness ratio of the second resin layer (d2) to the first resin layer (d1) NPG content mol% refractive index 30% reflectance 40% reflectance 50% reflectance 60% reflectance 23 1.590 0.870 0.821 0.727 0.670 20 1.601 0.877 0.827 0.731 0.674 17 1.611 0.884 0.832 0.737 0.679 15 1.619 0.889 0.835 0.739 0.680

In the multilayer reflective film according to an embodiment, the refractive index of the first resin layer may be 1.55 to 1.75, and the refractive index of the second resin layer may be 1.45 to 1.70. More specifically, the refractive index of the first resin layer may be 1.60 to 1.70, and the refractive index of the second resin layer may be 1.50 to 1.65, 1.55 to 1.62, or 1.58 to 1.62. In this case, it is preferable that the refractive index difference between the first resin layer and the second resin layer is 0.04 or more.

In the multilayer reflective film according to an embodiment, the value of the f-ratio expressed by Equation 1 below may be 0.01 to less than 0.5 or more than 0.5 to 0.99, and more specifically, the value of the f-ratio is 0.2 to 0.4 or 0.6 to 0.8. By having the value of the f-ratio in the above range, the multilayer reflective film according to an exemplary embodiment may realize two reflection peaks.

[Equation 1]

f-ratio = D ₁ / (D ₁ + D ₂ )

In the above formula, D ₁ and D ₂ are optical thicknesses of the first resin layer and the second resin layer, respectively, and represent D ₁ = n ₁ xd ₁ and D ₂ = n ₂ xd ₂ . Here, n ₁ and n ₂ are the refractive indices of the first resin layer and the second resin layer, and d ₁ and d ₂ are the physical thicknesses of the first resin layer and the second resin layer.

In the multilayer reflective film according to an embodiment, a thickness ratio of the second resin layer to the first resin layer is 0.55 to 0.90, 0.60 to 0.90, or 0.65 to 0.90. In addition, the thickness ratio of the first resin layer to the second resin layer is 0.55 to 0.90, 0.60 to 0.90, or 0.65 to 0.90.

The first resin layer and the second resin layer of the multilayer reflective film may be biaxially stretched 2.5 times to 5.0 times in the MD direction and 3.0 times to 6.0 times in the TD direction, and more specifically, 3.1 times to 3.4 times in the MD direction and It can be biaxially stretched 4.0 to 5.0 times in the TD direction. Through the stretching, a difference in refractive index between the first resin layer and the second resin layer may be further increased.

In the multilayer reflective film according to an embodiment, a total of 145 to 900 layers or a total of 150 to 900 layers of the first resin layer and the second resin layer may be laminated, and on one or both surfaces of the outermost layer of the multilayer reflective film. It may have a 1st resin layer. More specifically, 150 to 800 layers, 150 to 700 layers, 150 to 600 layers, 150 to 500 layers, 150 to 400 layers, 150 to 300 layers, or 150 to 200 layers may be laminated. However, the present invention is not limited thereto.

The multilayer reflective film may have a thickness of 15 μm to 360 μm, and more specifically 15 μm to 300 μm, 15 μm to 250 μm, 15 μm to 200 μm, 15 μm to 150 μm, 15 μm to 135 μm, 15 μm to 120 μm, 15 μm to 100 μm, 15 μm to 80 μm, 20 μm to 60 μm, 25 μm to 50 μm, 30 μm to 45 μm or 35 μm to 40 μm. does not

The thickness of the first resin layer and the second resin layer can be appropriately adjusted according to the purpose and purpose of the film, and more specifically, the first resin layer and the second resin layer are 80 nm to 400 nm, 80 nm to 300 nm, respectively. , 80 nm to 250 nm, 80 nm to 200 nm, 90 nm to 175 nm, 100 nm to 170 nm, 110 nm to 165 nm, 120 nm to 160 nm, 130 nm to 155 nm, 140 nm to 150 nm or 135 It may have a monolayer thickness of nm to 145 nm, but is not limited thereto.

The multilayer reflective film may further include a protective layer, and the protective layer may be formed on one or both surfaces of the multilayer reflective film. The protective layer may be at least one selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, and polymethyl methacrylate.

In addition, the protective layer may have a thickness of 1 μm to 30 μm, 1 μm to 25 μm, 1 μm to 20 μm, or 1 μm to 15 μm. By setting the thickness of the protective layer in the above range, it is possible to protect the multilayer reflective film without disturbing the optical characteristics generated by the multilayer reflective film.

In the multilayer reflective film according to an embodiment, a maximum reflectance of the first reflection peak may be 30% to 95%, and a maximum reflectance of the second reflection peak may be 35% to 90%. More specifically, the maximum reflectance of the first reflection peak may be 35% to 75% or 40% to 70%, and the maximum reflectance of the second reflection peak may be 30% to 70% or 35% to 65% have. When having a reflectance in the above range, the multilayer reflective film may implement a color of a desired transparency.

In addition, a ratio of the maximum reflectance of the second reflection peak to the maximum reflectance of the first reflection peak may be 0.3 to 3.0, more specifically, 0.4 to 0.8 or 0.35 to 0.75.

When the multilayer reflective film according to an embodiment is heat-treated at 150° C. for 30 minutes, the maximum reflectance of the first reflection peak may be reduced by 15% to 30% or 20% to 25%.

In the multilayer reflective film according to an embodiment, a first resin layer and a second resin layer are alternately laminated by co-extruding the first resin and the second resin, and a film having a multilayer structure is formed in-line. Since it can be manufactured in one process, it is possible to lower the production cost with a simple procedure.

Hereinafter, the present invention will be described in more detail by way of Examples. However, the following examples are only for illustrating the present invention, and the scope of the present invention is not limited thereto.

Example 1

Polyethylene terephthalate (PET) was used as the first resin and polymethyl methacrylate (PMMA) was used as the second resin, and each resin layer was extruded by controlling the extrusion amount with different extruders. The extruded first resin layer and the second resin layer were introduced into a feedblock through respective inflow paths.

At this time, each resin layer passed through different areas of the pre-designed multi-layer diaphragm inflow path to have a desired thickness, and specifically, the f-ratio of each resin layer was maintained at an average of 0.3.

The first resin layer and the second resin layer introduced into the feed block were alternately laminated, and the outermost layer of the film was configured to be the first resin layer. Then, 3.1 times in the MD direction and 4.5 times in the TD direction were biaxially stretched to obtain a multilayer reflective film.

Examples 2 to 12

It was carried out under the same conditions as in Example 1, but by changing the component and f-ratio of the second resin, multilayer reflective films having different thicknesses were obtained, and copolymerized polyethylene terephthalate (Co-PET) of Examples 7 to 15 was obtained. ), a copolymer of ethylene glycol (EG) and neopentyl glycol (NPG) was used. Specific components and conditions are as shown in Table 2 below.

Comparative Examples 1 to 6

It was carried out under the same conditions as in Example 1, but by changing the component and f-ratio of the second resin, multilayer reflective films having different thicknesses were obtained, and copolymerized polyethylene terephthalate (Co-PET) of Comparative Examples 4 to 6 was obtained. ) was used as a glycol component copolymerized with ethylene glycol (EG) and cyclohexanedimethanol (CHDM). Specific components and conditions are as shown in Table 2 below.

division first resin layer 2nd resin layer f-ratio Thickness (nm) refractive index Number of layers (layers ) first resin layer 2nd resin layer first resin layer 2nd resin layer Comparative Example 1 PET PMMA 0.5 72 80 1.654 1.493 145 Comparative Example 2 PET PMMA 0.5 80 88 1.654 1.493 145 Comparative Example 3 PET PMMA 0.5 96 106 1.654 1.493 145 Comparative Example 4 PET Co-PET (EG+CHDM)
(CHDM 29 mol%) 0.7 72 32 1.654 1.608 145 Comparative Example 5 PET Co-PET (EG+CHDM)
(CHDM 29 mol%) 0.7 80 35 1.654 1.608 145 Comparative Example 6 PET Co-PET (EG+CHDM)
(CHDM 29 mol%) 0.7 96 43 1.654 1.608 145 Example 1 PET PMMA 0.3 146 370 1.654 1.493 145 Example 2 PET PMMA 0.4 146 242 1.654 1.493 145 Example 3 PET PMMA 0.3 146 106 1.654 1.493 145 Example 4 PET PMMA 0.7 146 71 1.654 1.493 145 Example 5 PET PMMA 0.7 146 69 1.654 1.493 145 Example 6 PET PMMA 0.7 146 70 1.654 1.493 145 Example 7 PET Co-PET
(EG+NPG)
(NPG 17 mol%) 0.3 146 305 1.654 1.611 145 Example 8 PET Co-PET (EG+NPG)
(NPG 17 mol%) 0.4 146 208 1.654 1.611 145 Example 9 PET Co-PET (EG+NPG)
(NPG 17mol%) 0.6 146 100 1.654 1.611 145 Example 10 PET Co-PET (EG+NPG)
(NPG 17mol%) 0.7 146 65 1.654 1.611 145 Example 11 PET Co-PET (EG+NPG)
(NPG 17mol%) 0.7 146 64 1.654 1.611 145 Example 12 PET Co-PET
(EG+NPG)
(NPG 15mol%) 0.7 146 69 1.654 1.619 145 Example 13 PET Co-PET (EG+NPG)
(NPG 20mol%) 0.7 146 60 1.654 1.601 145 Example 14 PET Co-PET (EG+NPG)
(NPG 23mol%) 0.7 146 54 1.654 1.590 145 Example 15 PET Co-PET
(EG+NPG)
(NPG 17mol%) 0.7 146 65 1.654 1.611 870

The multilayer reflective films of Examples and Comparative Examples prepared as described above were evaluated as follows.

Experimental example: physical property measurement test

(1) Reflectance measurement

(1-1) Measurement of reflectance

After the multilayer reflective film was cut to 10 cm wide x 10 cm long, reflectance was measured in D65 light using Hunterab's UltrascanPro equipment.

(1-2) Measurement of reflectance difference after heat treatment

After cutting the multilayer reflective film to 10 cm wide x 10 cm long, it was left at 150° C. for 30 minutes through a heat chamber equipped with a hot air fan, left at room temperature for more than 5 minutes, and then left in the same manner as in (1-1) above. The reflectance was measured in D65 light using Hunterab's UltrascanPro equipment.

(2) Infrared blocking rate measurement

After cutting the multilayer reflective films prepared in Examples 1 to 12 and Comparative Examples 1 to 6 to 10 cm in width x 10 cm in length, foreign substances on the film surface were removed and equipment: Abbe refractometer, manufacturer: ATAGO, Model : Measured using 4T1240, and infrared cut off (IRC) in the 900 nm to 1200 nm region was measured.

(3) Visual color measurement

After cutting the multilayer reflective film prepared in Examples 1 to 12 and Comparative Examples 1 to 6 to a width of 10 cm x a length of 10 cm, foreign substances attached to the film surface were removed, The color of the film was measured with the naked eye.

The results of the above experimental examples are shown in Table 3 below.

division first reflection peak second reflection peak Infrared blocking rate (%) Reflectance of the first reflection peak body color
[Reflection/Transmission] before heat treatment after heat treatment Comparative Example 1 478 nm - 8.6 95 70 yellowish green Purplish Blue Comparative Example 2 531 nm - 8.3 91 69 Blue Green Yellowish Pink Comparative Example 3 640 nm - 8.2 93 70 Purplish Blue Yellow Comparative Example 4 485 nm - 8.3 80 64 yellowish green Purplish Blue Comparative Example 5 535 nm - 8.9 75 59 Blue Green Yellowish Pink Comparative Example 6 478 nm - 8.6 82 64 Purplish Blue Yellow Example 1 800 nm 460 nm 35.8 63 49 Purplish Blue Yellow Example 2 950 nm 470 nm 46.1 62 44 Purplish Blue Yellow Example 3 975 nm 478 nm 46.2 61 41 Purplish Blue Yellow Example 4 975 nm 475 nm 46.1 80 61 Purplish Blue Yellow Example 5 1050 nm 530 nm 38.3 79 60 Blue Green Yellowish Pink Example 6 1200 nm 610 nm 32.2 73 54 Yellow Green Purplish Blue Example 7 900 nm 440 nm 45.1 74 54 Purplish Blue Yellow Example 8 920 nm 445 nm 45.2 65 49 Purplish Blue Yellow Example 9 920 nm 443 nm 45.2 75 55 Purplish Blue Yellow Example 10 940 nm 450 nm 44.1 62 44 Purplish Blue Yellow Example 11 1050 nm 540 nm 38.2 63 43 Blue Green Yellowish Pink Example 12 940 nm 450 nm 44.6 54 32 Purplish Blue Yellow Example 13 940 nm 455 nm 44.9 77 53 Purplish Blue Yellow Example 14 940 nm 450 nm 43.7 82 59 Purplish Blue Yellow Example 15 1250 nm 620 nm 32.0 95 75 yellowish green Purplish Blue

As shown in Table 3, Examples 1 to 15 including the first reflection peak and the second reflection peak exhibited a significantly superior infrared blocking effect compared to Comparative Examples 1 to 6 having only the first reflection peak.

Claims (12)

Including a structure in which the first resin layer and the second resin layer are alternately laminated in a total of 145 to 900 layers,
a first reflection peak in the near-infrared region and a second reflection peak in the visible region;
In the 900 nm to 1200 nm region, the infrared blocking rate is 27% to 50%,
In the case of heat treatment at 150° C. for 30 minutes, the maximum reflectance of the first reflection peak decreases by 15% to 30%,
The reflectance of the first reflection peak before the heat treatment is 54% to 95%, and the reflectance of the first reflection peak after the heat treatment is 32% to 75%,
The first resin layer comprises at least one first resin selected from the group consisting of a polyester resin, a polyolefin resin, a polyamide resin, a fluororesin, and an acrylic resin,
The second resin layer is at least one second resin selected from the group consisting of copolymerized polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polymethyl methacrylate, polylactide and polyethylene terephthalate. including,
The refractive index of the first resin layer is 1.55 to 1.75, and the refractive index of the second resin layer is 1.45 to 1.70,
wherein the first resin layer and the second resin layer each have a monolayer thickness of 54 nm to 400 nm. delete delete According to claim 1,
A multilayer reflective film, wherein the value of the f-ratio represented by the following formula (1) is 0.01 to less than 0.5 or more than 0.5 to 0.99:
[Equation 1]
f-ratio = D ₁ / (D ₁ + D ₂ )
In the above formula, D ₁ and D ₂ represent the optical thickness of the first resin layer and the second resin layer, respectively. According to claim 1,
The thickness ratio of the second resin layer to the first resin layer is 0.55 to 0.90. According to claim 1,
The thickness ratio of the first resin layer to the second resin layer is 0.55 to 0.90. According to claim 1,
wherein the first resin layer and the second resin layer are biaxially stretched 2.5 times to 5.0 times in the MD direction and 3.0 times to 6.0 times in the TD direction, respectively. According to claim 1,
The multilayer reflective film is a multilayer reflective film in which the first resin layer and the second resin layer are stacked in total of 150 to 900 layers, and the outermost layer is the first resin layer. According to claim 1,
wherein the multilayer reflective film has a thickness of 15 μm to 360 μm. delete According to claim 1,
The maximum reflectance of the first reflection peak is 30% to 95%,
wherein the maximum reflectance of the second reflection peak is 35% to 90%. According to claim 1,
The ratio of the maximum reflectance of the second reflection peak to the maximum reflectance of the first reflection peak is 0.3 to 3.0.

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