阅读说明：本技术 反射薄膜、液晶显示装置及反射薄膜的制造方法 (Reflective film, liquid crystal display device, and method for manufacturing reflective film ) 是由 保住敏之 嶋田那由太 于 2020-03-31 设计创作，主要内容包括：一种反射薄膜,其具有基材、底涂层、金属蒸镀层、和表面涂层,金属蒸镀层包含银或以银为主要成分的银合金,表面涂层包含硫化合物,表面涂层中的硫化合物的硫元素浓度在表面涂层的厚度方向上在金属蒸镀层侧高于金属蒸镀层相反侧。(A reflective film comprising a substrate, an undercoat layer, a metal deposition layer, and a top coat layer, wherein the metal deposition layer contains silver or a silver alloy containing silver as a main component, the top coat layer contains a sulfur compound, and the sulfur element concentration of the sulfur compound in the top coat layer is higher on the metal deposition layer side than on the opposite side to the metal deposition layer in the thickness direction of the top coat layer.)

1. A reflective film having a substrate, a primer layer provided on the substrate, a metal deposition layer provided on the primer layer, and a surface coating layer provided on the metal deposition layer,

the metal evaporation layer contains silver or a silver alloy containing silver as a main component,

the surface coating comprises a sulfur compound and a sulfur compound,

the elemental sulfur concentration of the sulfur compound in the surface coating is: the concentration on the metal vapor deposition layer side in the thickness direction of the surface coating layer is higher than the concentration on the opposite side of the metal vapor deposition layer.

2. The reflective film according to claim 1,

the sulfur compound is contained in the surface coating in the following manner: when the sulfur element concentration of the surface coating layer in the thickness direction of the surface coating layer is measured from the metal deposition layer side opposite to the surface coating layer toward the metal deposition layer side by X-ray photoelectron spectroscopy (XPS), a maximum concentration peak of the sulfur element concentration appears on the metal deposition layer side in the thickness direction of the surface coating layer.

3. The reflective film according to claim 2,

the maximum concentration peak value of the sulfur element concentration is 0.5-30.0 atomic%.

4. The reflective film according to any one of claims 1 to 3,

the primer layer comprises a melamine resin.

5. The reflective film according to any one of claims 1 to 4,

the topcoat layer comprises a melamine resin.

6. The reflective film according to any one of claims 1 to 5,

the content of the sulfur compound in the surface coating layer is 0.5-20% by mass in terms of resin solid content.

7. The reflective film according to any one of claims 1 to 6,

a resin film layer is provided on the surface coating layer via an adhesive layer.

8. A liquid crystal display device comprising a light source, a light guide plate, the reflective film according to any one of claims 1 to 7, and a liquid crystal panel.

9. A method of manufacturing a reflective film, comprising: an undercoat layer forming step of forming an undercoat layer on a substrate; a vapor deposition step of forming a metal vapor deposition layer on the undercoat layer; a surface coating layer forming step of applying a resin solution of a resin composition for a surface coating layer on the metal vapor deposition layer to form a surface coating layer; a low-temperature drying step of drying at 80 to 150 ℃; and a resin film layer forming step of providing a resin film layer to which an adhesive is applied on the surface coating layer,

the metal evaporation layer contains silver or a silver alloy containing silver as a main component,

the resin composition for surface coating comprises a sulfur compound,

the surface coating forming process comprises the following steps: and applying a resin solution of the resin composition for surface coating on the metal deposition layer, whereby the sulfur compound in the resin solution reacts with the silver or silver alloy containing silver as a main component in the metal deposition layer, and the sulfur compound is unevenly distributed so that the sulfur element concentration of the sulfur compound in the surface coating layer is higher on the metal deposition layer side than on the opposite side of the metal deposition layer in the thickness direction of the surface coating layer.

Technical Field

The invention relates to a reflective film, a liquid crystal display device and a method for manufacturing the reflective film. More specifically, the present invention relates to a reflective film, a liquid crystal display device, and a method for producing a reflective film, which are less likely to cause appearance defects such as thermal wrinkles or streaks, have excellent adhesion between a metal deposition layer and a surface coating layer, are less likely to cause defects such as peeling even when an impact is applied in a step such as dicing, and have excellent durability.

Background

Conventionally, a reflective film has been used as a backlight of a liquid crystal display device. In order to impart high brightness and durability to the reflective film, high adhesion of the metal vapor-deposited layer to the surface coating layer is required. Patent document 1 discloses a laminate film in which a melamine resin is blended to form a resin constituting an undercoat layer and a surface coating layer, thereby achieving adhesion between a metal deposition layer and the surface coating layer and preventing corrosion of the metal deposition layer.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2009-286100

Disclosure of Invention

However, the laminated film described in patent document 1 has room for improvement in adhesion between the metal deposition layer and the surface coating layer. In particular, the conventional laminated film (reflective sheet, reflective film) may have the following problems: peeling off the metal deposition layer and the surface coating due to impact applied in subsequent processes such as slicing; when the adhesive is dried at a high temperature to cure the adhesive, appearance defects such as thermal wrinkles and streaks are generated in the production of a reflective film by roll-to-roll.

The present invention has been made in view of the above-described conventional inventions, and an object thereof is to provide a reflective film, a liquid crystal display device, and a method for producing a reflective film, which are less likely to cause appearance defects such as thermal wrinkles or streaks, which are excellent in adhesion between a metal deposition layer and a surface coating layer, which are less likely to cause defects such as peeling when an impact is applied in a step such as dicing, and which exhibit excellent durability.

As a result of intensive studies, the present inventors have found that a metal vapor deposition layer is formed by including silver or a silver alloy containing silver as a main component and a surface coating layer is formed by including a sulfur compound, and that the silver or the silver alloy in the metal vapor deposition layer reacts with the sulfur compound by setting the sulfur element concentration of the sulfur compound in the surface coating layer higher on the metal vapor deposition layer side than on the opposite side of the metal vapor deposition layer in the thickness direction of the surface coating layer, thereby enabling the metal vapor deposition layer and the surface coating layer to be more firmly bonded to each other, and have completed the present invention.

A reflective film according to an aspect of the present invention to solve the above problems includes a substrate, an undercoat layer provided on the substrate, a metal vapor deposition layer provided on the undercoat layer, and a surface coating layer provided on the metal vapor deposition layer, wherein the metal vapor deposition layer contains silver or a silver alloy containing silver as a main component, the surface coating layer contains a sulfur compound, and a sulfur element concentration of the sulfur compound in the surface coating layer is higher on the metal vapor deposition layer side than on the opposite side to the metal vapor deposition layer in a thickness direction of the surface coating layer.

In addition, a liquid crystal display device according to an aspect of the present invention to solve the above problems includes a light source, a light guide plate, the above reflective film, and a liquid crystal panel.

Further, a method for manufacturing a reflective film according to an aspect of the present invention to solve the above problems includes: an undercoat layer forming step of forming an undercoat layer on a substrate; a vapor deposition step of forming a metal vapor deposition layer on the undercoat layer; a surface coating layer forming step of applying a resin solution of a resin composition for a surface coating layer on the metal vapor deposition layer to form a surface coating layer; a low-temperature drying step of drying at 80 to 150 ℃; and a resin thin film layer forming step of providing a resin thin film layer provided with an adhesive on the surface coating layer, wherein the metal vapor deposition layer contains silver or a silver alloy containing silver as a main component, the resin composition for surface coating layer contains a sulfur compound, and the surface coating layer forming step is a step of: the surface coating resin composition is applied to the metal vapor deposition layer in a resin solution, whereby the sulfur compound in the resin solution reacts with the silver or a silver alloy containing silver as a main component in the metal vapor deposition layer, and the sulfur compound is unevenly distributed so that the sulfur element concentration of the sulfur compound in the surface coating layer is higher on the metal vapor deposition layer side than on the opposite side of the metal vapor deposition layer in the thickness direction of the surface coating layer.

Drawings

Fig. 1 is a schematic cross-sectional view for explaining the structure of a reflective film according to an embodiment of the present invention.

Fig. 2 is a graph showing the measurement result of the sulfur element concentration by X-ray photoelectron spectroscopy (XPS) of the reflective film of the specific example (example 6) according to the embodiment of the present invention.

Fig. 3 is an enlarged view of the diagram shown in fig. 2.

Fig. 4 is a graph showing the measurement result of the sulfur element concentration by X-ray photoelectron spectroscopy (XPS) of the reflective film of the specific example (example 3) according to the embodiment of the present invention.

Fig. 5 is an enlarged view of the diagram shown in fig. 4.

Fig. 6 is a graph showing the measurement result of the sulfur element concentration by X-ray photoelectron spectroscopy (XPS) of the reflective film of the specific example (example 4) according to the embodiment of the present invention.

Fig. 7 is an enlarged view of the diagram shown in fig. 6.

Fig. 8 is a schematic cross-sectional view for explaining a liquid crystal display device including a reflective film according to an embodiment of the present invention.

Detailed Description

< reflective film >

Fig. 1 is a schematic cross-sectional view for explaining the structure of a reflective film 1 according to an embodiment of the present invention. The reflective film 1 of the present embodiment has a substrate 2, an undercoat layer 3 provided on the substrate 2, a metal deposition layer 4 provided on the undercoat layer 3, and a surface coating layer 5 provided on the metal deposition layer 4. The metal vapor deposition layer 4 contains silver or a silver alloy containing silver as a main component. The surface coating 5 contains a sulfur compound. The elemental sulfur concentration of the sulfur compound in the surface coating layer 5 is higher on the metal deposition layer 4 side than on the opposite side of the metal deposition layer 4 in the thickness direction of the surface coating layer 5. In the reflective film 1, the metal deposition layer 4 and the surface coating layer 5 have excellent adhesion. Therefore, the reflective film 1 is less likely to cause defects such as peeling when an impact is applied in a step such as dicing, and exhibits excellent durability. The temperature required for drying the reflective film 1 may be, for example, a low temperature of about 80 to 150 ℃. Therefore, the reflective film 1 is less likely to cause appearance defects such as thermal wrinkles and streaks during production. Each configuration will be described below.

(substrate 2)

As the substrate 2, a resin film commonly used for the reflective film 1 of a liquid crystal display device can be used. For example, the substrate 2 may be a polyethylene terephthalate (PET) film, an olefin film, a Polycarbonate (PC) film, a polyether sulfone (PES) film, or the like. The substrate 2 may be a transparent film or a white film such as a white PET (foamed PET) film.

The thickness of the substrate 2 is not particularly limited. For example, the thickness of the substrate 2 is preferably 20 μm or more. The thickness of the substrate 2 is preferably 400 μm or less. When the thickness of the substrate 2 is within the above range, the obtained reflection film 1 can exhibit appropriate rigidity and strength.

(undercoat layer 3)

The primer layer 3 is provided on the substrate 2 in order to strongly adhere the metal deposition layer 4 to the substrate 2. The undercoat layer 3 is provided to protect the metal vapor-deposited layer 4 containing silver or an alloy containing silver from corrosion by moisture, oxygen, or the like.

The raw material of the undercoat layer 3 is not particularly limited. For example, the undercoat layer 3 is an acrylic resin, a urethane resin, a polyester resin, a silicone resin, a melamine resin, an epoxy resin, or the like. Of these, the undercoat layer 3 preferably contains a melamine resin, and more preferably contains a melamine resin and a polyester resin. By containing the melamine resin, the metal vapor-deposited layer 4 of the reflective film 1 containing silver or a silver alloy containing silver as a main component is less likely to be corroded, and is likely to exhibit excellent corrosion resistance.

The melamine resin content in the undercoat layer 3 is preferably 5 mass% or more, and more preferably 10 mass% or more, in the resin solid content. The melamine resin may be 100 mass% in the resin solid content. When the content of the melamine resin is in the above range, the metal vapor-deposited layer 4 of the reflective film 1 containing silver or a silver alloy containing silver as a main component is less likely to be corroded, and is likely to exhibit excellent corrosion resistance.

The thickness of the undercoat layer 3 is not particularly limited. For example, the thickness of the undercoat layer 3 is preferably 10nm or more, and more preferably 50nm or more. The thickness of the undercoat layer 3 is preferably 1000nm or less, and more preferably 500nm or less. When the thickness of the primer layer 3 is within the above range, the metal vapor-deposited layer 4 in the primer layer 3 is easily and firmly adhered to the substrate 2. In addition, the undercoat layer 3 easily protects the metal evaporation layer 4 containing silver or an alloy containing silver from corrosion by moisture, oxygen, or the like.

The method for providing the undercoat layer 3 on the substrate 2 is not particularly limited. For example, a so-called wet coating method such as a gravure coating method, a reverse coating method, a die coating method, or the like can be used as the undercoat layer 3.

(Metal deposition layer 4)

The metal deposition layer 4 is provided on the undercoat layer 3. The metal vapor deposition layer 4 of the present embodiment contains silver or a silver alloy containing silver as a main component.

The other metals constituting the silver alloy are not particularly limited. Examples of the other metals include copper, bismuth, gold, platinum, zinc, tin, titanium, nickel, magnesium, and lead. The ratio of the other metal contained in the silver alloy is preferably 0.1 (unit: atomic%) or more, and preferably 10 (unit: atomic%) or less.

The thickness of the metal deposition layer 4 is not particularly limited. For example, the thickness of the metal deposition layer 4 is preferably 60nm or more, and more preferably 80nm or more. The thickness of the metal deposition layer 4 is preferably 200nm or less, and more preferably 150nm or less. By setting the thickness of the metal deposition layer 4 within the above range, the obtained reflective film 1 can be produced at an appropriate cost and exhibit an appropriate reflectance.

The method of laminating the metal deposition layer 4 is not particularly limited. For example, the metal deposition layer 4 may be provided on the undercoat layer 3 by a so-called dry coating method such as a vacuum deposition method, a sputtering method, an ion plating method, or the like.

(surface coating 5)

The surface coating layer 5 is provided for protecting the metal deposition layer 4 or preventing corrosion of silver (including silver alloy) contained in the metal deposition layer 4. The surface coating 5 contains a sulfur compound. The surface coating 5 may be provided in a plurality of layers.

The raw material of the surface coating layer 5 is not particularly limited as long as it contains a sulfur compound. For example, in the surface coating layer 5, the other sulfur compounds include acrylic resin, urethane resin, polyester resin, silicone resin, melamine resin, epoxy resin, and the like. Of these, the surface coating layer 5 preferably contains a melamine resin, and more preferably contains a melamine resin and an acrylic resin. By containing the melamine resin, the metal vapor-deposited layer 4 containing silver or a silver alloy containing silver as a main component in the reflective film 1 is less likely to be corroded, and is likely to exhibit excellent corrosion resistance.

The melamine resin content in the top coat layer 5 is preferably 5 mass% or more, and more preferably 10 mass% or more, in the resin solid content. The melamine resin may be 100 mass% in the resin solid content. When the content of the melamine resin is in the above range, the metal vapor-deposited layer 4 containing silver or a silver alloy containing silver as a main component in the reflective film 1 is less likely to be corroded, and is likely to exhibit excellent corrosion resistance.

The sulfur compound is not particularly limited. Examples of the sulfur compound include a mercaptopropionic acid derivative-based sulfur compound such as pentaerythritol tetrathiopropionate (PETP), a thioglycolic acid derivative-based sulfur compound such as pentaerythritol tetrathioglycolate (PETG), and a thiol-based silane coupling agent. The sulfur compounds may be used in combination.

The content of the sulfur compound is not particularly limited. For example, the content of the sulfur compound is preferably 0.5 mass% or more, and more preferably 1 mass% or more, in the resin solid content constituting the surface coating layer 5. The content of the sulfur compound is preferably 20 mass% or less, and more preferably 10 mass% or less, in the solid content of the resin constituting the surface coating layer 5. When the content of the sulfur compound is within the above range, the reflective film 1 can be produced at a suitable cost and the adhesion between the metal deposition layer 4 and the surface coating layer 5 is excellent. Therefore, the obtained reflective film 1 is less likely to cause defects such as peeling when an impact is applied in a step such as dicing, and exhibits more excellent durability.

The thickness of the surface coating 5 is not particularly limited. For example, the thickness of the surface coating layer 5 is preferably 20nm or more, and more preferably 50nm or more. The thickness of the surface coating layer 5 is preferably 5000nm or less, and more preferably 2000nm or less. When the thickness of the surface coating 5 is within the above range, the obtained reflective film 1 exhibits appropriate rigidity and is less likely to bend. In addition, the surface coating layer 5 easily protects the metal evaporation layer 4 containing silver or an alloy containing silver from corrosion by moisture, oxygen, or the like.

The method of providing the surface coating 5 on the metal deposition layer 4 is not particularly limited. To exemplify this, the surface coating 5 may be prepared by the following method: a resin solution of a resin composition for the top coat layer 5 containing the above-mentioned sulfur compound and an appropriate resin is prepared, and the resin solution is applied to the metal deposition layer 4 by a so-called wet coating method such as a gravure coating method, a reverse coating method, or a die coating method.

In the reflective film 1 of the present embodiment, the surface coating layer 5 is formed on the metal deposition layer 4 by a wet coating method. In the obtained reflective film 1, the sulfur element concentration of the sulfur compound in the surface coating layer 5 is higher on the metal deposition layer 4 side than on the opposite side of the metal deposition layer 4 in the thickness direction of the surface coating layer 5. This is because the sulfur compound contained in the surface coating layer 5 reacts with silver contained in the metal deposition layer 4 or a silver alloy containing silver as a main component to be strongly bonded, and therefore the sulfur compound is present in a large amount in the vicinity of the adhesion surface with the metal deposition layer 4. In fig. 1, reference numeral 51 shows a region containing a large amount of sulfur compounds.

Fig. 2 is a graph showing the measurement results of the sulfur element concentration by X-ray photoelectron spectroscopy (XPS) of the reflective film of the specific example of the present embodiment (example 6 described later, containing 1.0 mass% of a thiol-based silane coupling agent as a sulfur compound). Fig. 3 is an enlarged view of the diagram shown in fig. 2. Fig. 4 is a graph showing the measurement results of the sulfur element concentration by X-ray photoelectron spectroscopy (XPS) of the reflection film of a specific example of the present embodiment (example 3 described later, containing 5.0 mass% of pentaerythritol tetrathiopropionate (PETP) as a sulfur compound). Fig. 5 is an enlarged view of the diagram shown in fig. 4. Fig. 6 is a graph showing the measurement results of the sulfur element concentration by X-ray photoelectron spectroscopy (XPS) of the reflection film of the specific example of the present embodiment (example 4 described later, containing 10.0 mass% of pentaerythritol tetrathiopropionate (PETP) as a sulfur compound). Fig. 7 is an enlarged view of the diagram shown in fig. 6.

As shown in fig. 2 to 7, in the reflective film of the present embodiment, when the sulfur element concentration of the surface coating layer in the thickness direction of the surface coating layer is measured from the opposite side of the metal deposition layer of the surface coating layer toward the metal deposition layer side by XPS, the maximum concentration peak of the sulfur element concentration is shown on the metal deposition layer side in the thickness direction of the surface coating layer. As shown in fig. 2, the depth of the maximum concentration peak is a depth (depth of about 20nm) at which the concentration of carbon element decreases from 100 atomic% and the concentration of silver element increases from 0 atomic%, and the maximum concentration peak is 1.0 atomic%. As shown in fig. 4, the depth indicating the maximum concentration peak is a depth (depth of about 25nm) at which the concentration of carbon element decreases from 100 atomic% and the concentration of silver element increases from 0 atomic%, and the maximum concentration peak is 3.0 atomic%. As shown in fig. 6, the depth indicating the maximum concentration peak is a depth (depth of about 35nm) at which the concentration of carbon element decreases from 100 atomic% and the concentration of silver element increases from 0 atomic%, and the maximum concentration peak at this time is 5.0 atomic%. Namely, it is known that: the sulfur compound contained in the surface coating layer has a peak of sulfur element concentration in the vicinity of the surface of adhesion to the metal deposition layer, and therefore is unevenly distributed so as to have a high concentration in the vicinity of the surface of adhesion to the metal deposition layer. Therefore, in the reflective film in which the sulfur compound is strongly bonded to silver or an alloy containing silver as a main component, the adhesion between the metal deposition layer and the surface coating layer is excellent. Therefore, the reflective film is less likely to cause defects such as peeling when an impact is applied in a step such as dicing, and exhibits more excellent durability.

The measurement conditions of XPS are not particularly limited. For example, XPS measurement was performed by subjecting the surface of a sample to sputter etching for 30 seconds using a multifunction scanning X-ray photoelectron spectroscopy apparatus (model: PHI5000 Versa Probe2, ULVAC-PHI) with an attached Ar ion gun (2kV), and photoelectrons of C1S (carbon), S2p (nitrogen), and Ag3d (silver) were detected by irradiation with AlK alpha rays to calculate the ratio of 3 elements. The detection time of C1S (carbon), S2p (nitrogen), and Ag3d (silver) can be measured under the condition of about 60 seconds, respectively.

The maximum concentration peak of the sulfur element concentration of the sulfur compound in the surface coating layer measured by XPS is preferably 0.5 atomic% or more, and more preferably 1.0 atomic% or more. The maximum concentration peak is preferably 30.0 atomic% or less, and more preferably 10.0 atomic% or less. By making the maximum concentration peak within the above range, the adhesion of the metal vapor-deposited layer to the surface coating layer in the reflective film is more excellent. Therefore, the reflective film is less likely to cause defects such as peeling when an impact is applied in a step such as dicing, and exhibits more excellent durability.

In the obtained reflection film 1, a resin film layer 7 is preferably provided on the surface coating layer 5 via an adhesive layer 6.

The material constituting the adhesive layer 6 is not particularly limited. For example, the material of the adhesive layer 6 is a liquid-curable adhesive, a two-component solvent-based adhesive, a one-component solvent-free adhesive, or the like. As the two-component curing adhesive, an acrylic adhesive may be used, as the two-component solvent adhesive, a polyester adhesive, an aromatic polyester adhesive, an aliphatic polyester adhesive, a polyester/polyurethane adhesive, a polyether/polyurethane adhesive may be used, and as the one-component solvent-free adhesive (moisture curing adhesive), a polyether/polyurethane adhesive may be used.

The resin film layer 7 is not particularly limited. For example, the resin film layer 7 may be a polyethylene terephthalate (PET) film, an olefin film, a Polycarbonate (PC) film, a polyether sulfone (PES) film, or the like. In order to impart excellent reflectivity, the substrate 2 is preferably a white film such as a white PET (foamed PET) film. The resin thin film layer 7 may be a resin thin film (e.g., Al-deposited PET) on which metal deposition is performed.

The thickness of the resin film layer 7 is not particularly limited. For example, the thickness of the resin thin film layer 7 is preferably 20 μm or more. The thickness of the resin film layer 7 is preferably 400 μm or less. By setting the thickness of the resin film layer 7 within the above range, the obtained reflection film 1 can exhibit appropriate rigidity and strength.

The thickness of the adhesive layer 6 provided on the resin film layer 7 is not particularly limited. For example, the thickness of the adhesive layer 6 is preferably 3 μm or more. The thickness of the adhesive layer 6 is preferably 10 μm or less. By setting the thickness of the adhesive layer 6 within the above range, the resin film layer 7 of the obtained reflection film 1 can be firmly adhered to the surface coating layer 5.

The method for providing the adhesive layer 6 on the resin film is not particularly limited. For example, the adhesive layer 6 may be provided on the resin film by a reverse coater, a gravure coater (direct, reverse, offset), a bar reverse coater, a roll coater, a die coater, a wire bar coater, a bar coater, or the like.

The resin film layer 7 provided with the adhesive layer 6 is laminated on the topcoat 5 and pressure-bonded under a predetermined temperature condition (for example, 40 ℃ C., 3 days) to be adhered to the topcoat 5 via the adhesive layer 6. The obtained reflective film 1 can be provided with various functions such as excellent weather resistance and abrasion resistance. Further, such a reflective film is less likely to cause defects such as peeling when an impact is applied in a step such as dicing, and exhibits more excellent durability.

As described above, in the reflective film 1 of the present embodiment, silver contained in the metal deposition layer 4 or a silver alloy containing silver as a main component reacts with the sulfur compound contained in the surface coating layer 5 to be firmly bonded. As a result, the reflective film 1 has excellent adhesion between the metal deposition layer 4 and the surface coating layer 5. Therefore, the reflective film 1 is less likely to cause defects such as peeling when an impact is applied in a step such as dicing, and exhibits excellent durability.

< liquid crystal display device >

The liquid crystal display device according to one embodiment of the present invention includes a light source, a light guide plate, the reflection film 1 described in detail in the above embodiments, and a liquid crystal panel. The reflective film 1 used in the liquid crystal display device is excellent in adhesion between the metal deposition layer 4 and the surface coating layer 5 as described above. Therefore, the reflective film 1 is less likely to cause defects such as peeling when an impact is applied in a step such as dicing, and exhibits excellent durability. Therefore, the liquid crystal display device can maintain the quality such as high brightness and high durability for a long time. The following description is made separately.

Fig. 8 is a schematic cross-sectional view for explaining a liquid crystal display device 8 including a reflection film 1 according to an embodiment of the present invention. The liquid crystal display device 8 includes a backlight unit and a liquid crystal panel 9. The backlight unit includes a reflective film 1, a light guide plate 10, a light source 11 disposed on an end surface of the light guide plate 10, and a diffusion prism 12. The liquid crystal display device 8 may be suitably provided with a member which can be provided in a known liquid crystal display device, such as a polarizing plate and a diffusion sheet, which are not shown.

(light source 11)

The light source 11 is not particularly limited. For example, the light source 11 is preferably a white light source. In the present embodiment, the white light includes not only light uniformly containing wavelength components in a visible light region (wavelengths 380 to 780nm), but also light which looks white to the naked eye even though the wavelength components are not uniformly contained. That is, the white light may include light in a specific wavelength band such as red light, green light, and blue light as a reference color. The light source 11 is preferably a white LED (W-LED).

(light guide plate 10)

The light guide plate 10 is not particularly limited. For example, the light guide plate 10 may be a light guide plate 10 having a lens pattern formed on the back surface side thereof, or a light guide plate 10 having a prism shape or the like formed on the back surface side or the visible side thereof, so that light from the lateral direction can be deflected in the thickness direction.

(diffusion prism 12)

The diffusion prism 12 is not particularly limited. For example, the diffusion prism 12 may be any member that can diffuse the light deflected by the light guide plate 10 toward the liquid crystal panel 9. In the case where the light guide plate 10 can sufficiently diffuse light toward the liquid crystal panel 9, the diffusion prism 12 may be omitted as appropriate.

(liquid crystal panel 9)

The driving display mode of the liquid crystal panel 9 is not particularly limited. For example, the driving display mode may be a Twisted Nematic (TN), Super Twisted Nematic (STN), Vertical Alignment (VA), in-plane switching (IPS), Optically Compensated Bend (OCB), or the like.

The liquid crystal display device 8 of the present embodiment includes the above-described reflective film 1 as a backlight unit. The reflective film 1 is excellent in adhesion between the metal deposition layer 4 and the surface coating layer 5 as described above. Therefore, the reflective film 1 is less likely to cause defects such as peeling when an impact is applied in a step such as dicing, and exhibits excellent durability. Therefore, the liquid crystal display device 8 can maintain the quality such as high brightness and high durability for a long period of time.

< method for producing reflective film >

The method for manufacturing a reflective film according to an embodiment of the present invention includes: an undercoat layer forming step of forming an undercoat layer on a substrate; a vapor deposition step of providing a metal vapor deposition layer on the undercoat layer; a surface coating layer forming step of applying a resin solution of a resin composition for a surface coating layer on the metal vapor deposition layer to form a surface coating layer; a low-temperature drying step of drying at 80 to 150 ℃; and a resin film layer forming step of providing a resin film layer provided with an adhesive on the surface coating layer. The metal vapor deposition layer contains silver or a silver alloy containing silver as a main component. The resin composition for surface coating contains a sulfur compound. The surface coating layer forming process comprises the following steps: the resin solution of the resin composition for surface coating is applied on the metal deposition layer, so that the sulfur compound in the resin solution reacts with the silver or the silver alloy containing silver as a main component in the metal deposition layer, and the sulfur compound is unevenly distributed in such a manner that the sulfur element concentration of the sulfur compound in the surface coating layer is higher on the metal deposition layer side than on the opposite side of the metal deposition layer in the thickness direction of the surface coating layer. The respective steps will be explained below. In the following description, the above-described features that have been described in the embodiments of the reflective film will be appropriately omitted.

(undercoat layer Forming step)

The undercoat layer forming step is a step of providing an undercoat layer on the substrate.

The method for providing the undercoat layer on the substrate is not particularly limited. For example, a so-called wet coating method such as a gravure coating method, a reverse coating method, a die coating method, or the like can be used as the undercoat layer.

(vapor deposition Process)

The deposition step is a step of providing a metal deposition layer on the undercoat layer. The method of stacking the metal deposition layers is not particularly limited. For example, the metal vapor-deposited layer can be provided on the undercoat layer by a so-called dry coating method such as a vacuum vapor deposition method, a sputtering method, or an ion plating method.

(surface coating layer formation step)

The surface coating layer forming step is a step of providing a surface coating layer on the metal deposition layer. The method for providing the surface coating layer on the metal deposition layer is not particularly limited. To exemplify an example, the surface coating can be prepared by the following method: a resin solution of the resin composition for surface coating containing the above sulfur compound and an appropriate resin is prepared, and the resin solution is applied to the metal deposition layer by a so-called wet coating method such as a gravure coating method, a reverse coating method, or a die coating method.

According to the method for manufacturing a reflective film of the present embodiment, the surface coating layer is formed on the metal deposition layer by a wet coating method. At this time, the sulfur compound in the resin solution reacts with silver or a silver alloy containing silver as a main component in the metal deposition layer. Thus, the sulfur compound is unevenly distributed so that the sulfur element concentration of the sulfur compound in the surface coating layer is higher on the metal deposition layer side than on the opposite side of the metal deposition layer in the thickness direction of the surface coating layer.

The uneven distribution of the sulfur compound in the surface coating layer can be confirmed by measuring the sulfur element concentration by X-ray photoelectron spectroscopy (XPS). That is, as described in the related section of the embodiment of the reflective film, in the reflective film manufactured by the method for manufacturing a reflective film according to the present embodiment, when the sulfur element concentration of the surface coating layer in the thickness direction of the surface coating layer is measured from the opposite side of the metal deposition layer of the surface coating layer toward the metal deposition layer side by XPS, the maximum concentration peak of the sulfur element concentration appears on the metal deposition layer side in the thickness direction of the surface coating layer. Thus, the sulfur compound contained in the surface coating layer has a peak of the sulfur element concentration in the vicinity of the surface of adhesion to the metal deposition layer, and therefore, it is found that the sulfur compound is unevenly distributed so as to have a high concentration in the vicinity of the surface of adhesion to the metal deposition layer. Thus, in the reflective film in which the sulfur compound is strongly bonded to silver or an alloy containing silver as a main component, the adhesion between the metal deposition layer and the surface coating layer is excellent. Therefore, the reflective film is less likely to cause defects such as peeling when an impact is applied in a step such as dicing, and exhibits more excellent durability.

(Low temperature drying Process)

The low-temperature drying step is a step of drying at 80 to 150 ℃. In the low-temperature drying step, the resin solution of the surface coating layer is dried, and the metal deposition layer is bonded to the surface coating layer. In the method for producing a reflective film according to the present embodiment, the sulfur compound in the resin solution for forming the surface coating layer reacts with silver in the metal deposition layer or a silver alloy containing silver as a main component to be strongly bonded. Therefore, the drying conditions in the low-temperature drying step may be temperature conditions (80 to 150 ℃ C., preferably 100 to 130 ℃ C.) that can dry the resin solution of the surface coating layer. Even under such mild drying conditions, the metal deposition layer and the surface coating layer can be firmly adhered to each other.

(Process for Forming resin film layer)

The resin film layer forming step is a step of providing a resin film layer to which an adhesive is applied on the surface coating layer. The method for providing the adhesive layer on the resin film is not particularly limited. For example, the adhesive layer may be provided on the resin film by a reverse coater, a gravure coater (direct, reverse, offset), a bar reverse coater, a roll coater, a die coater, a wire bar coater, a bar coater, or the like.

The resin film layer provided with the adhesive layer is laminated on the surface coating layer and pressure-bonded thereto, whereby the resin film layer is adhered to the surface coating layer via the adhesive layer.

The reflective film of the present embodiment can be produced by a roll-to-roll method. In the case of such a production by the roll-to-roll method, since the drying conditions of the reflective film can be kept from being excessively severe, appearance defects such as thermal wrinkles and streaks are less likely to occur in the low-temperature drying step. Therefore, the method for manufacturing a reflective film of the present embodiment is excellent in manufacturing efficiency.

The obtained long reflective film may be punched (cut) in accordance with a desired size and shape. Since the reflective film of the present embodiment has excellent adhesion between the metal deposition layer and the surface coating layer, even when a strong impact is applied in a step of dicing or the like, the cut edge portions are less likely to be peeled off. As a result, the reflective film is less likely to have poor appearance and exhibits excellent durability.

One embodiment of the present invention is explained above. The present invention is not particularly limited to the above embodiments. The above embodiments mainly describe the invention having the following configurations.

(1) A reflective film comprising a substrate, an undercoat layer provided on the substrate, a metal deposition layer provided on the undercoat layer, and a top coat layer provided on the metal deposition layer, wherein the metal deposition layer contains silver or a silver alloy containing silver as a main component, the top coat layer contains a sulfur compound, and the sulfur compound in the top coat layer has a sulfur element concentration of: the concentration of the surface coating layer on the side of the metal deposition layer in the thickness direction is higher than the concentration of the surface coating layer on the opposite side of the metal deposition layer.

With this configuration, the metal vapor-deposited layer in the reflective film has excellent adhesion to the surface coating layer. Therefore, the reflective film is less likely to cause defects such as peeling when an impact is applied in a step such as dicing, and exhibits excellent durability. The temperature required for drying the reflective film may be, for example, a low temperature of about 80 to 150 ℃. Therefore, poor appearance such as thermal wrinkles and streaks are less likely to occur in the production of the reflective film.

(2) The reflective film according to (1), wherein the sulfur compound is contained in the surface coating layer in such a manner that: when the sulfur element concentration of the surface coating layer in the thickness direction of the surface coating layer is measured from the opposite side of the metal deposition layer of the surface coating layer toward the metal deposition layer side by X-ray photoelectron spectroscopy (XPS), a maximum concentration peak of the sulfur element concentration appears on the metal deposition layer side in the thickness direction of the surface coating layer.

With this configuration, the adhesion between the metal vapor-deposited layer and the surface coating layer in the reflective film is further improved. Therefore, the reflective film is less likely to cause defects such as peeling when an impact is applied in a step such as dicing, and exhibits more excellent durability.

(3) The reflective film according to the item (2), wherein a maximum concentration peak of the sulfur element concentration is 0.5 to 30.0 atomic%.

With this configuration, the adhesion between the metal vapor-deposited layer and the surface coating layer in the reflective film is further improved. Therefore, the reflective film is less likely to cause defects such as peeling when an impact is applied in a step such as dicing, and exhibits more excellent durability.

(4) The reflective film according to any one of (1) to (3), wherein the undercoat layer contains a melamine resin.

With such a configuration, the metal vapor-deposited layer containing silver or a silver alloy containing silver as a main component in the reflective film is less likely to be corroded, and is likely to exhibit excellent corrosion resistance.

(5) The reflective film according to any one of (1) to (4), wherein the surface coating layer contains a melamine resin.

With such a configuration, the metal vapor-deposited layer containing silver or a silver alloy containing silver as a main component in the reflective film is less likely to be corroded, and is likely to exhibit excellent corrosion resistance.

(6) The reflective film according to any one of (1) to (5), wherein the content of the sulfur compound in the surface coating layer is 0.5 to 20% by mass in terms of resin solids.

With this configuration, the adhesion between the metal vapor-deposited layer and the surface coating layer in the reflective film is further improved. Therefore, the reflective film is less likely to cause defects such as peeling when an impact is applied in a step such as dicing, and exhibits more excellent durability.

(7) The reflection film according to any one of (1) to (6), wherein a resin thin film layer is provided on the surface coating layer via an adhesive layer.

With such a configuration, the reflective film can be provided with various functions such as excellent weather resistance and abrasion resistance. Further, such a reflective film is less likely to cause defects such as peeling when an impact is applied in a step such as dicing, and exhibits more excellent durability.

(8) A liquid crystal display device comprising a light source, a light guide plate, the reflective film according to any one of (1) to (7), and a liquid crystal panel.

With this configuration, the adhesion between the metal vapor-deposited layer and the surface coating layer in the reflective film used in the liquid crystal display device is excellent. Therefore, the reflective film is less likely to cause defects such as peeling when an impact is applied in a step such as dicing, and exhibits excellent durability. Therefore, the liquid crystal display device can maintain the quality such as high brightness and high durability for a long time.

(9) A method of manufacturing a reflective film, comprising: an undercoat layer forming step of forming an undercoat layer on a substrate; a vapor deposition step of forming a metal vapor deposition layer on the undercoat layer; a surface coating layer forming step of applying a resin solution of a resin composition for a surface coating layer on the metal vapor deposition layer to form a surface coating layer; a low-temperature drying step of drying at 80 to 150 ℃; and a resin thin film layer forming step of providing a resin thin film layer provided with an adhesive on the surface coating layer, wherein the metal vapor deposition layer contains silver or a silver alloy containing silver as a main component, the resin composition for surface coating layer contains a sulfur compound, and the surface coating layer forming step is a step of: the surface coating resin composition is applied to the metal deposition layer in a resin solution, whereby the sulfur compound in the resin solution reacts with the silver or a silver alloy containing silver as a main component in the metal deposition layer, and the sulfur compound is unevenly distributed so that the sulfur element concentration of the sulfur compound in the surface coating layer is higher on the metal deposition layer side than on the opposite side of the metal deposition layer in the thickness direction of the surface coating layer.

With this configuration, the obtained reflective film has excellent adhesion between the metal vapor-deposited layer and the surface coating layer. Therefore, the reflective film is less likely to cause defects such as peeling when an impact is applied in a step such as dicing, and exhibits excellent durability. The temperature required for drying the reflective film may be, for example, a low temperature of about 80 to 150 ℃. Therefore, poor appearance such as thermal wrinkles and streaks are less likely to occur in the production of the reflective film.

Examples

The present invention will be described more specifically with reference to examples. The present invention is not limited to these examples in any way. Unless otherwise specified, "%" represents "% by mass".

(example 1)

A polyester resin solution (comprising 70% of a polyester resin (more specifically, polyester polyol), 20% of an isocyanate, and 10% of a melamine resin) was applied to a substrate (thickness: 25 μm) which was a polyethylene terephthalate (PET) film by a wire bar coater. The uncured resin layer was cured at 100 ℃ for 1 minute to form an undercoat layer having a thickness of 100nm (undercoat layer formation step). On the undercoat layer, silver was vacuum-deposited by a resistance heating type deposition machine to form an Ag film (metal deposition layer) having a thickness of 100nm (metal deposition layer forming step). An acrylic resin solution (containing 69% of an acrylic resin (specifically, an acrylic polyol), 20% of isocyanate, 10% of a melamine resin and 1% of PETP) was applied to the metal vapor-deposited layer by a wire bar coater to form a surface coating layer having a thickness of 1.5 μm (surface coating layer forming step). Then, the film was dried at 130 ℃ for 1 minute (low-temperature drying step), thereby producing a reflective film.

(examples 2 to 5)

A reflective film was produced in the same manner as in example 1, except that the raw materials and conditions described in table 1 were changed. In this case, the amount of the acrylic resin and isocyanate blended was reduced while keeping the ratio of these in the same state as in example 1, and the concentration of PETP was adjusted to table 1. The concentration of melamine resin was fixed at 10%.

(examples 6 to 13)

A reflective film was produced in the same manner as in example 1, except that the raw materials and conditions described in table 1 were changed. The sulfur compound used was a thiol silane coupling agent. At this time, the ratio of the acrylic resin to the isocyanate was adjusted so that the concentration of the thiol silane coupling agent became table 1 while keeping the same ratio as in example 1. The concentration of melamine resin was fixed at 10%.

Comparative example 1

A reflective film was produced in the same manner as in example 1, except that the raw materials and conditions described in table 1 were changed. In this case, the acrylic resin was 70%, the isocyanate was 20%, and the melamine resin was 10%, and no sulfur compound was used.

[ TABLE 1 ]

The obtained reflective film was evaluated for the checkerboard peeling test, initial adhesion, adhesion after heat resistance test, and adhesion after wet heat resistance test by the following evaluation methods. The results are shown in Table 1.

< checkerboard peeling test >

100 checkerboards (10X 10) were prepared with a width of 1mm, and the number of the checkerboards that were not peeled off was examined by attaching a commercially available adhesive tape to the 100 checkerboards and peeling them off.

< adhesion >

A resin film layer (PET, specifically toshibine a4300) to which an adhesive (polyester polyol + isocyanate) was applied was separately prepared from the reflective film immediately after the preparation, the reflective film after the holding at 90 ℃ for 500 hours (after the heat resistance test), and the reflective film after the holding at 60 ℃ for 95% humidity for 500 hours (after the heat resistance test), and a resin film layer having a thickness of 50 μm was formed on the top coat layer via the adhesive (thickness 5 μm), followed by drying (curing at 40 ℃ x 72 hours after conditions of 100 ℃ x 1 minutes) (resin film layer forming step). Then, the resin film layer and the reflective film were held and stretched in the 180 ℃ direction, and the degree of peeling was checked in 5 stages of 1 to 5. "1" indicates the easiest peeling, and "5" indicates the difficulty in peeling.

As shown in table 1, the reflective films of examples 1 to 13 of the present invention had excellent adhesion between the metal vapor-deposited layer and the surface coating layer, and were difficult to peel. On the other hand, the reflection film of comparative example 1 containing no sulfur compound was not different from the reflection film of the present invention in the checkerboard peeling test, but was easily peeled in a severer test, i.e., a peeling test after dry lamination.

Description of the symbols

1 reflective film

2 base material

3 base coat

4 metal vapor deposition layer

5 surface coating

51 zone containing more sulfur compounds

6 adhesive layer

7 resin film layer

8 liquid crystal display device

9 liquid crystal panel

10 light guide plate

11 light source

12 diffusion prism