JP6992037B2 - Anti-reflection film and its manufacturing method, and method for measuring reflected light characteristics of anti-reflection film - Google Patents

Description

The present invention relates to an antireflection film having an antireflection layer on a transparent film and a method for producing the same. The present invention also relates to a method for measuring the reflected light characteristics of an antireflection film in-line.

An antireflection film is used on the visible side surface of an image display device such as a liquid crystal display or an organic EL display for the purpose of preventing deterioration of image quality due to reflection of external light or reflection of an image, improvement of contrast, and the like. The antireflection film includes an antireflection layer made of a laminate of a plurality of thin films having different refractive indexes on the transparent film.

As one form of the antireflection film, a polarizing plate with an antireflection layer can be mentioned. The polarizing plate with an antireflection layer is formed by attaching an antireflection film to the surface of the polarizing plate or by attaching an antireflection film as a protective film to the surface of the polarizing element. Further, a method of forming a polarizing plate with an antireflection layer by forming an antireflection layer on the polarizing plate is also known (for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 8-136730

The antireflection layer utilizes the multiple reflection interference of the thin film to reduce the reflectance of visible light. Therefore, when the refractive index and the film thickness of the thin film fluctuate, the reflected light characteristics such as the reflectance and the reflected light hue change. Even when the film thickness conditions of the thin film are strictly controlled and kept constant in the formation of the antireflection layer, the film thickness of the thin film and the film thickness due to variations in the characteristics of the raw materials and changes in the film formation environment over time, etc. The refractive index and the like fluctuate slightly. The effect of such slight fluctuations on the reflected light characteristics is small. Therefore, in general, the quality of the antireflection film is controlled by forming a film under certain conditions and then visually checking the reflected light characteristics with an inspection device such as a spectrophotometer offline after the film formation. ..

In recent years, as the definition of a display has been improved, the required characteristics for an antireflection film have been increasing, and there is a demand for an antireflection film having a lower reflectance and less coloring of reflected light. Attempts have also been made to neutralize the emitted light from the panel by adjusting the hue of the reflected light. For example, when the light emitted from the panel is yellowish, neutralization is performed by using an antireflection film in which the reflected light is bluish.

As the required characteristics increase, it is required to more strictly control the reflected light characteristics of the antireflection film. Therefore, the antireflection film may deviate from the quality standard due to the change in the reflected light characteristics due to a slight change in the manufacturing conditions. Therefore, in the process of manufacturing the antireflection film, it is necessary to control the film forming conditions more strictly, suppress the fluctuation of the refractive index and the film thickness of the thin film, and keep the reflected light characteristics constant.

In film production, in-line measurement is performed in the manufacturing process, and the measurement result is fed back to the previous process to maintain the quality of the film at a constant level. However, the film thickness of the thin film constituting the antireflection layer is several nm to several tens of nm, and it is not easy to directly measure the film thickness. In particular, it is extremely difficult to measure the film thickness of each thin film in a laminated body of a plurality of thin films. Further, in film manufacturing, a product is cut out at the start of manufacturing (line start) or in the middle of a process, the cut product is inspected offline, and the result is fed back to the manufacturing process. However, since the thin film such as the antireflection layer is formed by a vacuum process such as sputtering, vacuum vapor deposition, or CVD, it is not possible to sample the product at the start of the line or in the middle of the process.

As an in-line inspection in the manufacturing process of the antireflection film, it is conceivable to measure the reflected light characteristics in-line and feed back the measurement results to the film forming conditions of the thin film. However, in measuring the reflected light characteristics in-line of the antireflection film, the influence of backside reflection becomes a problem.

Generally, the antireflection film is designed so that the visible light reflectance of the antireflection layer forming surface is 1% or less, whereas it is visible on the back surface side of the transparent film (the interface between the transparent film and air). The light reflectance is about 4%. In the offline inspection after forming the antireflection layer, it is relatively easy to eliminate the influence of the back surface reflection and measure the reflected light characteristic on the front surface side. On the other hand, in the in-line inspection of the antireflection film, it is not easy to eliminate backside reflection because the film running in the air or vacuum is irradiated with light for measurement. When backside reflection is involved, most of the reflected light detected by in-line inspection is reflected light from the back side, and it is detected even if the characteristics of the reflected light from the antireflection layer forming surface (reflection hue, etc.) change. The reflected light hardly changes. Therefore, it is not easy to accurately measure the reflected light characteristics from the antireflection layer forming surface side in-line.

Patent Document 1 proposes a method of measuring the reflectance by arranging a polarizing element (photon) on the antireflection layer forming surface side of the polarizing plate when forming the antireflection layer on the surface of the polarizing plate. There is. If the polarizing plate with an antireflection layer and the analyzer are arranged so that the absorption axis directions of both are orthogonal to each other, the reflected light on the back surface side of the polarizing plate with an antireflection layer is absorbed by the detector, so that the back surface is reflected. It is possible to measure the reflected light characteristics on the surface side by eliminating the influence of.

However, this method cannot be applied except when the antireflection layer is formed on the polarizing plate. The polarizing plate has a structure in which a transparent film is laminated on both sides of the polarizing element, and is more expensive than the transparent film alone. Therefore, in the method of forming the antireflection layer on the polarizing plate, manufacturing due to process loss occurs when a nonstandard portion occurs at the initial stage of formation of the antireflection layer (before the start of control of the film forming condition by in-line reflected light detection). The increase in cost tends to be remarkable. In addition, the characteristics of the polarizing plate may deteriorate due to the film formation environment of the antireflection layer. For example, when a polarizing plate is introduced into a sputtering film forming apparatus, the polarizing element may be deteriorated by being exposed to a high temperature environment or high output plasma.

Therefore, from the viewpoint of improving productivity and reducing costs, there is a need for a method of accurately measuring reflected light characteristics by eliminating the influence of backside reflection in forming an antireflection layer on a transparent film that does not contain a stator. ing. The present invention more accurately detects changes in reflected light characteristics in-line in the process of forming an antireflection layer on a transparent film, and reflects the detection results in film formation conditions to achieve highly uniform reflection. The purpose is to obtain a preventive film. Another object of the present invention is to provide a method for measuring the reflected light characteristics of an antireflection film in-line.

As a result of the examination in view of the above, by using a laminated body in which a light-absorbing film base material is detachably attached to the back surface side of the transparent film via an adhesive layer, the back surface reflection is reduced and the antireflection layer is formed. It has been found that changes in reflected light characteristics due to slight fluctuations in refractive index, film thickness, etc. can be detected.

One form of the antireflection film of the present invention is a reflective film with a film substrate, wherein one surface of the transparent film is provided with an antireflection layer, and the film substrate is detachably attached to the other surface via an adhesive layer. It is a preventive film.

For the antireflection film with a film substrate, a laminate in which the film substrate is detachably attached via an adhesive layer is prepared on the second main surface of the transparent film (laminate preparation step), and the laminate is prepared. It is obtained by forming an antireflection layer composed of two or more thin films on the first main surface of the transparent film of the body (antireflection layer forming step). In the formation of the antireflection layer, after forming at least one thin film, visible light is irradiated from the first main surface side of the laminated body, and the reflected light is detected in-line (in-line inspection step). The formation of the antireflection layer and the in-line inspection are continuously performed while transporting the laminate in one direction. It is preferable that the film forming conditions of the thin film are adjusted according to the detection result of the reflected light in the in-line inspection. As a result, the reflected light characteristics of the antireflection film can be kept uniform and the quality stability can be improved.

The laminate of the film substrate and the adhesive layer preferably has a visible light transmittance of 3% or less. When light is incident on the laminate of the film substrate and the adhesive layer from the adhesive layer side, the backside reflectance of visible light is preferably 1.0% or less. By using a light-absorbing film as the film base material, the back surface reflectance can be reduced. As the film base material, a film having a release layer may be used. When a film substrate having a release layer is used, the release layer forming surface is attached to the adhesive layer. In the film substrate, the difference n ₁ −n ₂ between the refractive index n ₁ of the release layer and the refractive index n ₂ of the layer immediately below the release layer is preferably −0.25 to 0.25. Backside reflection can also be reduced by using a light-scattering pressure-sensitive adhesive as an adhesive layer for temporarily adhering the transparent film and the film substrate.

After forming the antireflection layer on the transparent film, the film substrate is peeled off (peeling step). After that, another optical film such as a polarizing plate is bonded onto the second main surface of the transparent film, and the antireflection film is put into practical use.

By forming the antireflection layer on the laminated body in which the back surface reflection is reduced, the detection accuracy and the reproducibility of the reflected light in the in-line inspection are improved. Further, by feeding back the detection result of the reflected light in-line to the film forming conditions of the thin film, an antireflection film having excellent uniformity of the reflected light characteristics can be obtained.

It is sectional drawing which shows typically one form of the antireflection film with a film base material. It is sectional drawing which shows typically an example of the layer structure of a film base material. It is a conceptual diagram which shows the structural example of the film forming apparatus of the antireflection layer. (A) is a cross-sectional view schematically showing a structural example of a laminate used for forming an antireflection film, and (B) is an antireflection film with a film substrate having an antireflection layer formed on the laminate. It is sectional drawing which shows the structural example schematically. (C1) and (C2) are cross-sectional views schematically showing a configuration example of an antireflection film after peeling the film substrate. (D1) and (D2) are sectional views schematically showing a configuration example of an antireflection film to which another film is bonded. (A) and (B) are sectional views schematically showing a structural example of a polarizing plate with an antireflection layer.

[Structure of antireflection film]
FIG. 1A is a cross-sectional view schematically showing the configuration of the antireflection film according to the embodiment. The antireflection film 101 of FIG. 1A includes an antireflection layer 50 on the first main surface of the transparent film 10. A film base material 20 is detachably attached to the second main surface of the transparent film 10 via an adhesive layer 30. The antireflection layer is a laminated body of two or more thin films. In FIG. 1A, an antireflection layer 50 composed of a laminated body of four thin films 51, 52, 53, 54 is shown.

(Transparent film)
As the transparent film 10, a flexible transparent film is used. The transparent film 10 may have a functional layer (not shown) such as a hard coat layer or an easy-adhesive layer on the film surface (antireflection layer forming surface). The hard coat layer can be provided on the surface of the film by a method of forming a cured film of an appropriate ultraviolet curable resin such as acrylic or silicone.

The visible light transmittance of the transparent film is preferably 80% or more, more preferably 90% or more. The thickness of the transparent film 10 is not particularly limited, but is preferably in the range of about 10 μm to 300 μm.

Examples of the resin material constituting the transparent film include polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN); cellulose-based polymers such as diacetyl cellulose and triacetyl cellulose; polymethyl methacrylate and the like. Acrylic polymers; styrene polymers such as polystyrene and acrylonitrile / styrene copolymers; cyclic polyolefins such as polynorbornene; polycarbonate and the like.

The surface of the transparent film is subjected to surface modification treatment such as corona treatment, plasma treatment, frame treatment, ozone treatment, primer treatment, glow treatment, saponification treatment, and treatment with a coupling agent for the purpose of improving adhesion. May be broken.

(Film base material)
In the production of the antireflection film, the laminated body 40 in which the film base material 20 is detachably attached to the second main surface (non-forming surface of the antireflection layer 50) of the transparent film 10 via the adhesive layer 30. Is used. In the present invention, by bonding the film base material 20 to the transparent film 10, it is possible to reduce backside reflection when light is incident from the transparent film side.

The backside reflectance of visible light when light is incident on the laminate of the film substrate and the adhesive layer from the adhesive layer side is preferably 1.0% or less, and preferably 0.7% or less. More preferably, it is more preferably 0.5% or less, and particularly preferably 0.3% or less. The visible light reflectance is measured according to JIS R3106: 1998. As the film base material 20, a light-absorbing film, a light-scattering film having fine irregularities on the surface, or the like is preferably used. A light-absorbing film is preferably used as the film base material 20 in order to further reduce backside reflection.

The visible light transmittance of the laminate of the film base material 20 and the adhesive layer 30 is preferably 40% or less, more preferably 20% or less, still more preferably 10% or less. When a transparent material is used as the adhesive layer 30, the visible light transmittance of the film substrate 20 is preferably 40% or less, more preferably 20% or less, still more preferably 10% or less. ..

Assuming that the visible light transmittance of the laminate of the film base material and the adhesive layer is T (%) and the refractive index of the film base material is n, the back surface reflectance (of the film base material) when light is incident from the adhesive layer side. The ratio of light reflected at the air interface and re-emitted from the adhesive layer) can be calculated as follows.
Backside reflectance (%) = (T ^2/100 ) × (n-1) ² / (n + 1) ²

If the visible light transmittance T is 40% or less, even if the reflection due to the difference in refractive index at the interface between the film substrate and air is about 6% (when the refractive index of the film substrate is about 1.6). The backside refractive index with respect to the incident light from the transparent film side is 1% or less.

As the material of the film base material 20, polyesters, cellulose-based polymers, acrylic polymers, styrene-based polymers, amide-based polymers, polyolefins, cyclic polyolefins, polycarbonates and the like are used. A light-absorbing film substrate can be obtained by adding a black pigment such as carbon black to these resin materials or by providing a colored layer with black ink or the like on the surface of the base film. The colored layer may be provided on only one side of the base film, or may be provided on both sides. When a light-absorbing film having a colored layer is used as the film base material 20, the colored layer is provided at least on the surface of the base film on the transparent film 10 side from the viewpoint of suppressing light reflection at the interface on the transparent film 10 side. It is preferable that the film is used. The thickness of the colored layer is, for example, about 0.5 μm to 10 μm.

As shown in FIGS. 3 (C1) and 3 (C2), the film base material 20 is peeled off and removed when the antireflection film is put into practical use. That is, the film base material 20 is a process material that is not included in the final product. Therefore, the film base material is preferably as inexpensive as possible, and a general-purpose film such as polyethylene terephthalate is preferably used. The thickness of the film base material 20 is not particularly limited. If the thickness of the film base material is small, the continuous film formation length when the antireflection layer 50 is formed on the laminated body 40 can be lengthened, and the productivity of the antireflection film can be improved. Therefore, it is preferable that the thickness of the film base material 20 is as small as possible within a range that does not impair the film forming property and the handleability. The thickness of the film substrate is preferably 5 μm to 200 μm, more preferably 10 μm to 130 μm, and even more preferably 15 μm to 110 μm.

FIG. 1B is a cross-sectional view schematically showing an example of the layer structure of the film base material 20. The film base material 20 shown in FIG. 1B includes a release layer 21 on the base film 25. The release layer 21 can be formed, for example, by applying a release agent to the surface of the base film 25. As the mold release agent, a mold release material such as silicone-based, fluorine-based, long-chain alkyl-based, fatty acid amide-based, or a solution containing silica powder or the like is used. When a film base material provided with a release layer is used, it is preferable that the release layer 21 is arranged on the surface to be attached to the adhesive layer 30. Since the release layer is present on the surface to be adhered to the adhesive layer, the adhesive force between the transparent film 10 and the film base material 20 is reduced, so that the film base material from the antireflection film after the antireflection layer is formed is formed. Peeling removal can be easily performed.

It is preferable that the difference in refractive index between the release layer 21 of the film substrate 20 and the layer immediately below the release layer 21 is small. Specifically, the difference n ₁ −n ₂ between the refractive index n ₁ of the release layer 21 and the refractive index n ₂ of the layer immediately below the release layer is preferably −0.3 to 0.25, and −0. 25 to 0.25 is more preferable, -0.25 to 0.15 is further preferable, and -0.25 to 0.1 is particularly preferable. The refractive index is a value at a wavelength of 590 nm. The layer directly below the release layer is a layer adjacent to the release layer 21. When the release layer 21 is formed directly on the base film 25, the base film 25 corresponds to the layer directly below the release layer. When a colored layer, an oligomer encapsulating layer, or the like is provided between the base film and the release layer, the layer adjacent to the release layer corresponds to the layer directly under the release layer among these layers. ..

For example, when the release layer is provided directly on the PET base film (when the PET base film is the layer directly below the release layer), the refractive index of the release layer is 1.35 to 1.8. It is preferable, 1.4 to 1.75 is more preferable.

The reflected light related to the film substrate when light is incident on the laminate of the antireflection film and the film substrate from the antireflection layer side is mainly the difference in refractive index on the back surface side (air interface) of the film substrate. However, the reflected light caused by the difference in refractive index at the interface between the release layer and the layer immediately below it (base film, etc.) may also affect the measurement of the reflectance. By setting the refractive index difference n ₁ to n ₂ at this interface in the above range, the reflectance of the film substrate can be further reduced.

Further, if the difference in refractive index at the interface between the film base material 20 and the adhesive layer 30 described later is reduced to reduce the reflected light at this interface, the reflected light with respect to the incident light from the adhesive layer side is further reduced. can. In order to reduce the difference in refractive index at these interfaces, the refractive index n ₁ of the release layer 21 is an intermediate value between the refractive index n ₂ of the layer immediately below it and the refractive index n ₃ of the adhesive layer 30. It is preferable to have. That is, it is preferable that n ₂ <n ₁ <n ₃ or n ₃ <n ₁ <n ₂ .

(Adhesive layer)
The transparent film 10 and the film base material 20 are bonded to each other via the adhesive layer 30. The material of the adhesive layer 30 is not particularly limited, but an adhesive is preferably used in order to attach the film base material 20 so that it can be peeled off. As the pressure-sensitive adhesive, for example, an acrylic pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, a sea cone-based pressure-sensitive adhesive, or the like can be used. Of these, an acrylic pressure-sensitive adhesive containing an acrylic polymer as a main component is preferably used.

The adhesive layer 30 may be transparent or opaque. If a light-absorbing film is used as the film base material 20 and the light-absorbing adhesive layer 30 is used, the visible light transmittance of the laminate of the film base material 20 and the adhesive layer 30 is lowered, and the back surface reflection is further enhanced. Can be reduced. On the other hand, as shown in FIG. 3 (D1), when the adhesive layer 30 is used for bonding with another film 71 after peeling the film base material 20 from the antireflection film, a light-transmitting adhesive layer should be used. Is preferable. The light-transmitting adhesive layer preferably has a visible light transmittance of 80% or more, more preferably 85% or more, and further preferably 90% or more.

The adhesive layer 30 may have a light scattering property. By giving the adhesive layer light scattering property, the light transmitted through the transparent film 10 can be scattered by the adhesive layer, and the back surface reflection can be further reduced. Examples of the adhesive layer having light scattering properties include a light scattering adhesive in which particles are dispersed in the adhesive. When the adhesive layer is a light-scattering adhesive, the larger the haze of the light-scattering adhesive, the less the backside reflection tends to be. Therefore, the haze of the light scattering pressure-sensitive adhesive layer is preferably 40% or more, more preferably 50% or more, further preferably 70% or more, and particularly preferably 90% or more.

Examples of the particles contained in the light scattering pressure-sensitive adhesive include inorganic fine particles and polymer fine particles. The particles are preferably polymer fine particles. Examples of the material of the polymer fine particles include silicone resin, polymethyl methacrylate resin, polystyrene resin, polyurethane resin, melamine resin and the like. Since these resins have excellent dispersibility in the pressure-sensitive adhesive and have an appropriate difference in refractive index from the pressure-sensitive adhesive such as an acrylic pressure-sensitive adhesive, a light-scattering pressure-sensitive adhesive layer having excellent diffusion performance can be obtained. The shape of the particles is not particularly limited, and examples thereof include a true spherical shape, a flat shape, and an indefinite shape. The particles may be used alone or in combination of two or more.

The volume average particle size of the particles is preferably 1 μm to 10 μm, and more preferably 1.5 μm to 5 μm. By setting the volume average particle size in the above range, excellent light scattering performance can be imparted. The volume average particle size can be measured by using, for example, an ultracentrifugal automatic particle size distribution measuring device. The content of the particles in the light scattering pressure-sensitive adhesive layer is preferably 0.3% by weight to 50% by weight, more preferably 3% by weight to 48% by weight. By setting the blending amount of the particles in the above range, a light scattering adhesive layer having excellent light scattering performance can be obtained.

(Anti-reflective layer)
An antireflection layer 50 is formed on the first main surface of the laminate 40 to which the film base material 20 is attached via the adhesive layer 30 on the second main surface of the transparent film 10. The antireflection layer 50 is composed of two or more thin films. Generally, in the antireflection layer, the optical film thickness (product of refractive index and thickness) of the thin film is adjusted so that the inverted phases of the incident light and the reflected light cancel each other out. By forming the antireflection layer as a multi-layered laminate of two or more thin films having different refractive indexes, the reflectance can be reduced in a wide wavelength range of visible light.

Examples of the material of the thin film constituting the antireflection layer 50 include metal oxides, nitrides, and fluorides. For example, as a low refractive index material having a refractive index of about 1.35 to 1.55, silicon oxide, magnesium fluoride, etc., and as a high refractive index material having a refractive index of 1.80 to 2.40, titanium oxide, niobium oxide, oxidation, etc. Examples thereof include zirconium, tin-doped indium oxide (ITO), antimonated tin oxide (ATO) and the like. Further, in addition to the low refractive index layer and the high refractive index layer, as a medium refractive index layer having a refractive index of about 1.50 to 1.85, for example, titanium oxide or a mixture of the low refractive index material and the high refractive index material ( A thin film made of a mixture of titanium oxide and silicon oxide, etc.) may be formed.

The laminated structure of the antireflection layer 50 is a two-layer structure consisting of a high refractive index layer having an optical film thickness of about 240 nm to 260 nm and a low refractive index layer having an optical film thickness of about 120 nm to 140 nm from the transparent film 10 side; the optical film. A three-layer structure consisting of a medium refractive index layer having a thickness of 170 nm to 180 nm, a high refractive index layer having an optical thickness of 60 nm to 70 nm, and a low refractive index layer having an optical film thickness of 135 nm to 145 nm; an optical film thickness of 25 nm to 55 nm. A high refractive index layer having an optical thickness of about 35 nm to 55 nm, a high refractive index layer having an optical film thickness of about 80 nm to 240 nm, and a low refractive index layer having an optical film thickness of about 120 nm to 150 nm. 4-layer configuration: a low refractive index layer with an optical film thickness of about 15 nm to 30 nm, a high refractive index layer with an optical film thickness of about 20 nm to 40 nm, a low refractive index layer with an optical film thickness of about 20 nm to 40 nm, and an optical film thickness of 240 nm. Examples thereof include a five-layer structure consisting of a high refractive index layer having an optical thickness of about 290 nm and a low refractive index layer having an optical film thickness of about 100 nm to 200 nm. The range of the refractive index and the film thickness of the thin film constituting the antireflection layer is not limited to the above examples. Further, the antireflection layer 50 may be a laminated body of six or more thin films.

[Method of forming antireflection layer]
The method for forming the thin film constituting the antireflection layer is not particularly limited, and either a wet coating method or a dry coating method may be used. Dry coating methods such as vacuum deposition, CVD, sputtering, and electron beam steaming are preferable because they can form a thin film with a uniform film thickness and it is easy to adjust the film thickness at the nanometer level. And electron beam deposition is preferred.

The formation of the antireflection layer is continuously carried out while transporting the laminated body 40 in one direction. For example, when the antireflection layer is formed by sputtering, continuous film formation is performed using a take-up sputtering device.

After forming at least one thin film constituting the antireflection layer, visible light is irradiated from the first main surface side (thin film forming surface side) of the laminated body 40, and the reflected light is detected to perform in-line inspection. Will be implemented. By recording the result of this in-line inspection, it is possible to improve the efficiency of processes such as bonding the antireflection film to another optical film and forming an image display device. For example, if the portion determined to be out of specification by the in-line inspection is not supplied to the next process, the yield of the final product can be improved and the frequency of rework can be reduced. Further, by adjusting the film forming conditions of the thin film based on the detection result of the reflected light in-line, an antireflection film having excellent uniformity of the reflected light characteristics can be obtained.

In the following, as an example of forming an antireflection layer 50 composed of four thin films 51, 52, 53, 54 on the transparent film 10 by a sputtering method, the detection result of in-line reflected light is used as a film forming condition. A method of manufacturing an antireflection film will be described while reflecting the effect.

FIG. 2 is a conceptual diagram showing a configuration example of a film forming apparatus for reflecting the detection result of reflected light in-line in the film forming conditions of the antireflection layer. The film forming apparatus of FIG. 2 includes two film forming rolls 281,282. A plurality of film forming chambers 210, 220, 230, 240 separated by partition walls are provided along the circumferential direction of each film forming roll 281,282. A cathode is provided in each film forming chamber, and each cathode 214, 224, 234, 244 is connected to a power supply 216, 226, 236, 246. Targets 213,223,233,243 are arranged on the cathodes 214, 224, 234 and 244 so as to face the film forming rolls 281,282. A gas introduction pipe is connected to each of the film forming chambers 210, 220, 230, 240, and valves 219, 229, 239, 249 are provided upstream of the gas introduction pipe.

The unwinding roll 251 in the preparation chamber 250 is set with a wound body of the laminated body 40 of the transparent film 10 and the film base material 20. The laminate 40 unwound from the unwinding roll is conveyed onto the first film forming roll 281 and is sequentially guided to the first film forming chamber 210 and the second film forming chamber 220. In the first film forming chamber 210, the thin film 51 is formed on the first main surface of the transparent film 10, and in the second film forming chamber 220, the thin film 52 is formed on the thin film 51. The laminate 45 on which the thin films 51 and 52 are formed is conveyed onto the second film forming roll 282, and the thin film 53 and the thin film 54 are sequentially formed in the third film forming chamber 230 and the fourth film forming chamber 240. .. The antireflection film 101 in which the antireflection layer 50 composed of four thin films is formed on the transparent film 10 of the laminated body 40 is guided to the winding chamber 260 and wound by the winding roll 261 to form the antireflection film. A wound body is obtained.

In the winding chamber 260, a light irradiation unit 291 and a light detection unit 293 are arranged so as to face the antireflection layer 50 forming surface of the antireflection film 101. The light emitted from the light irradiation unit may be white light or monochromatic light as long as it contains visible light. The light irradiation may be continuous or intermittent. The reflected light of the light irradiated from the light irradiation unit 291 to the antireflection film 101 is detected by the light detection unit 293. The reflected light detected by the photodetector 293 is converted into an electric signal by the light receiving element, and calculation is performed by the calculation unit 273 as necessary. In the calculation unit, the spectrum of the detected reflected light is calculated, and conversion to a specific color system (for example, XYZ color system, L ^* a ^* b ^* color system, Yab color system) is performed. ..

Further, the calculation unit 273 determines the difference between the detected reflected light reflection characteristic and the target reflected light characteristic, and changes the film forming conditions of the thin film when the difference exceeds the threshold value. To send a signal to the control unit. The control unit 275 adjusts the film forming conditions of the thin film so that the characteristics of the reflected light (reflectance, hue, etc.) are within a predetermined range.

The film forming conditions to be adjusted include the amount of gas introduced into the film forming chamber, the film transport speed, the amount of input power, and the like. For example, in the film forming apparatus shown in FIG. 2, the control unit 275 determines the rotation speeds of the unwinding roll 251 and the winding roll 261 and the film forming rolls 281,282, and the input power amount of the power supplies 216, 226, 236, 246. Further, by adjusting the opening degree of the valves 219, 229, 239, 249 of the gas introduction pipe, the film forming conditions of the thin film in each film forming chamber can be adjusted. The change in the characteristics of the reflected light is mainly due to the fluctuation in the film thickness of the thin film. Therefore, it is preferable to adjust the film thickness conditions of the thin film so that the film thickness of the thin film approaches the set value. The adjustment of the film forming conditions is performed, for example, by PID control. Further, the refractive index can be changed by adjusting the production conditions so as to change the composition of the thin film. For example, in reactive sputtering, by changing the amount of oxygen introduced into the film forming chamber, the oxygen content in the metal oxide changes, and the refractive index of the thin film changes accordingly.

In order to determine the difference from the target reflected light characteristic, it is necessary to determine the reference reflected light characteristic in advance. The standard reflected light characteristics are appropriately determined according to the product specifications and the like. As an example, a method based on the center of the standard range of the product and a method based on the reflected light spectrum calculated by optical calculation from the set film thickness and the refractive index of each layer (see Examples described later) can be mentioned. Further, the reflected light spectrum of the product measured offline may be used as a reference.

Optical calculation and offline calculation or measurement of the reference spectrum of reflected light are preferably performed with the backside reflection excluded. By eliminating backside reflection and setting the standard, the target reflected light characteristics can be matched with the product standard, and the difference between the standard value and the in-line measurement result can be accurately evaluated.

The antireflection film 101 after forming all the thin films constituting the antireflection layer 50 on the transparent film 10 of the laminated body 40 preferably has a luminance Y of 0.5% or less in the Yab color system. The Y value in the Yab table system is the same as the Y value in the XYZ table system. In the present invention, the Y value of the reflected light can be reduced by reducing the back surface reflection by using the light-absorbing film base material 20. By reducing the reflection Y value, the difference between the reference spectrum and the in-line measured value can be detected with high sensitivity, and the detection sensitivity of the difference in hue tends to be improved.

When the backside reflection is large and the detection sensitivity is dull, in order to keep the product within the standard stably, the control range of the in-line measured value is controlled in consideration of the difference that may occur between the in-line measured value and the true value. Need to be narrowed. Therefore, the control range of manufacturing conditions becomes narrow, and it may be difficult to adjust the film forming conditions of the thin film. In addition, due to the narrow control range of in-line measurement, products that are originally within the standard are often judged to be out of the standard, and the yield of the product tends to decrease.

On the other hand, according to the present invention, by suppressing the back surface reflection, the detection sensitivity of the difference between the reference value and the in-line measured value is enhanced, and the control range in the manufacturing process can be expanded. Therefore, in addition to facilitating process control based on in-line measurement results, product yield can be improved.

Further, by suppressing the back surface reflection and reducing the reflection Y value, the difference in chromaticity from the reference spectrum tends to be small. Therefore, in-line hue management becomes easy. The chromaticity difference Δab between the reflected light of the antireflection film 101 after forming all the thin films constituting the antireflection layer 50 on the transparent film 10 of the laminated body 40 and the reference spectrum of the antireflection film excluding backside reflection is , 7.5 or less is preferable. The chromaticity difference Δab is a distance on the ab chromaticity diagram of the Yab color system, and is calculated by the following formula from the chromaticity a ₀ and b ₀ of the reference spectrum and the chromaticity a and b of the measurement target. ..
Δab = {(aa ₀ ) ² + (bb ₀ ) ² } ^1/2

The mode in which the in-line detection of the reflected light is performed after the film formation of all the thin films 51, 52, 53, 54 has been described above, but the in-line detection of the reflected light can be performed only after the formation of at least one thin film. It may be done at any stage. For example, after the thin films 51 and 52 were formed on the first film forming roll 281 and before the laminated body 45 was guided onto the second film forming roll 282, the laminated body 45 was irradiated from the light irradiation unit 297. In-line detection of the reflected light may be performed by detecting the reflected light of the light by the light detection unit 299. Further, in-line detection of reflected light may be performed at two or more points. For example, in the form shown in FIG. 2, after the two-layer thin films 51 and 52 are formed, the light detection unit 299 detects the reflected light from the laminated body 45, and further forms the two-layer thin films 53 and 54 on the two-layer thin films 51 and 52. Later, the light detection unit 293 may detect the reflected light from the antireflection film 101. If the in-line measurement is performed at two or more points in this way, it becomes easy to determine the film forming chamber to which the film forming conditions should be adjusted, and more precise control becomes possible. Further, in-line detection may be performed at a plurality of locations in the width direction, and the film forming conditions may be adjusted so that the reflected light characteristics in the width direction become uniform. For example, the film forming conditions in the width direction can be adjusted by changing the amount of gas introduced in the width direction.

Although FIG. 2 shows an example in which the antireflection layer 50 is composed of four thin films, the number of thin films constituting the antireflection layer is not particularly limited as long as it is two or more layers as described above. Further, an appropriate film forming apparatus can be used depending on the number of thin films. The number of film forming chambers provided around one film forming roll may be one or three or more. The number of film forming rolls may be one or three or more.

As described above, the method for forming the thin film is not limited to the sputtering method, and various dry coating methods and wet coating methods may be adopted. Even when the thin film is formed by a method other than sputtering, an antireflection film having excellent uniformity of reflected light characteristics can be obtained by adjusting the thin film formation conditions based on the in-line detection result of the reflected light.

When the antireflection film having the antireflection layer formed on the first main surface of the transparent film is irradiated with light, most of the reflected light is due to the backside reflection on the second main surface side, and the first It is difficult to accurately detect the reflected light on the main surface side (reflection layer forming surface). On the other hand, by attaching the light-absorbing film base material 20 to the second main surface side of the transparent film 10, backside reflection is suppressed. In this embodiment, most of the reflected light detected by the photodetector 293 is the reflected light from the first main surface side (reflection layer forming surface side), so that the reflected light from the first main surface side. Small changes in characteristics can be detected inline. By adjusting the film forming conditions of the thin film based on this detection result, it is possible to manufacture an antireflection film having excellent uniformity of reflected light characteristics.

In this way, by attaching a light-absorbing film base material to the transparent film before forming the antireflection layer to be inspected, backside reflection is suppressed and the reflected light characteristics are accurately measured in-line. can. When forming an antireflection layer by vacuum film formation such as a sputtering method, it is not possible to extract the product during film formation and inspect it, or to bond or peel the film on the same line as the film formation line. Therefore, the method of the present invention is particularly useful.

As described above, since an inexpensive general-purpose film is used as the film base material 20, the laminate of the transparent film and the film base material is cheaper than the polarizing plate. Therefore, as compared with the case of using a polarizing plate as in Patent Document 1, even if a nonstandard portion occurs at the initial stage of formation of the antireflection layer (before the start of control of the film forming condition by in-line reflected light detection), the process loss. The impact on the manufacturing cost is small.

Further, by forming the antireflection layer on the laminate 40 of the transparent film 10 and the film base material 20, the continuous film length of the antireflection layer is longer than that in the case of forming the antireflection layer on the polarizing plate. Can be increased. In general, the unwinding roll 251 and the winding roll 261 have an upper limit of the weight and diameter of the film winding body that can be set on the gantry. The smaller the film thickness, the larger the length of the film at which the weight and diameter of the wound body reach the specified upper limit, and therefore the longer the continuous film formation length becomes. In general, the polarizing plate has a structure in which transparent protective films are provided on both sides of the polarizing element and is composed of three films, whereas the above-mentioned laminated body 40 can be composed of two films. .. Therefore, the laminated body 40 can be designed to have a smaller thickness than the polarizing plate, and the continuous film formation length can be increased. As a result, the operating rate of the film forming apparatus is improved, and the productivity can be increased.

[Practical form of antireflection film]
In the present invention, for the purpose of measuring the reflected light characteristics of the antireflection film in-line, a laminate (FIG. 3 (A)) in which the film base material 20 is attached to the second main surface side of the transparent film 10 is used. Be done. The antireflection layer 50 is formed on the transparent film 10 (FIG. 3B), and after the reflected light characteristics of the antireflection film 101 with a film substrate are measured, the film substrate 20 becomes unnecessary. .. Therefore, when the antireflection film is put into practical use, it is preferable that the film base material 20 is peeled off and removed from the transparent film 10.

When removing the peeling off of the film base material, for example, as shown in FIG. 3 (C1), only the film base material 20 is peeled off and removed with the adhesive layer 30 attached to the transparent film 10. For example, as shown in FIG. 1B, if a film base material 20 having a release layer 21 on the adhesive layer forming surface side of the base film 25 is used, the film base material 20 is left on the transparent film 10 with the adhesive layer 30 left. Only can be peeled off. After removing the film substrate, another film 71 is attached to the second main surface of the transparent film 10 via the adhesive layer 30.

When removing the film base material, as shown in FIG. 3 (C2), the adhesive layer 30 may be peeled off and removed from the transparent film 10 together with the film base material 20. After removing the film substrate, another film 72 is attached to the second main surface of the transparent film 10 via the other adhesive layer 33.

As described above, the film base material 20 is provided to improve the detection accuracy of the reflected light characteristics during the formation of the antireflection layer and in-line after the formation of the antireflection layer, and is peeled off and removed after the inspection is completed. Ru. The film base material is peeled off and removed in both the case where only the film base material 20 is peeled off while the adhesive layer 30 is left on the transparent film 10 and the case where the adhesive layer 30 is also peeled off from the transparent film 10 together with the film base material 20. The latter antireflection film is put into practical use by laminating it with another film. In order to improve the work efficiency of bonding the antireflection film to another film, it is preferable that the bonding is performed in-line using a roll laminator or the like. Therefore, it is preferable that the peeling work of the film base material 20 performed between the in-line inspection of the reflected light characteristics and the bonding with another film is also performed in-line.

In order to stably remove the film base material 20 from the transparent film 10 after forming the antireflection layer 50 in-line, it is preferable that the peeling force of the film base material 20 from the transparent film 10 is small. Specifically, the peeling force of the transparent film and the film substrate in the 180 ° peeling test (peeling speed: 10 m / min) is preferably 2N / 50 mm or less, more preferably 1.5N / 50 mm or less, and 1N / 50 mm. The following is more preferable. The peeling force can be reduced by adjusting the composition of the adhesive layer 30 or by providing a release layer on the surface of the film substrate.

The films 71 and 72 to be bonded to the second main surface of the transparent film 10 after the film base material 20 is peeled off are not particularly limited, and a transparent release film or the like may be bonded. For example, when an antireflection film having an antireflection layer provided on a transparent film is shipped as a product, the light-absorbing film base material 20 used at the time of forming the antireflection layer is replaced with a transparent release film. It is possible to measure the transmittance and inspect the presence or absence of foreign matter. Further, by using the transparent release film, the design of the product is enhanced.

In practical use of the antireflection film, an optical film is attached to the second main surface of the transparent film 10. Examples of the optical film include a polarizing element, a polarizing element protective film, an optical compensation film (phase difference film), and a combination thereof. As an example of a practical form, a polarizing plate with an antireflection layer can be obtained by laminating an antireflection film and an optical film containing a polarizing element. In this way, in the form in which the antireflection layer is formed on the transparent film and then bonded to the polarizing element or the like, the polarizing element is not exposed to the high temperature environment for forming the antireflection layer or the high output plasma. A polarizing plate with an antireflection layer can be obtained. Therefore, it is possible to suppress problems such as deterioration of the stator and increase the yield.

4 (A) and 4 (B) are cross-sectional views schematically showing a configuration example of a polarizing plate with an antireflection layer. In the polarizing plate 121 with an antireflection layer shown in FIG. 4A, one surface of the polarizing element 79 is bonded to the second main surface of the transparent film 10 via the adhesive layer 36. A transparent protective film 74 is attached to the other surface of the polarizing element 79 via an adhesive layer 38, and a release film 22 is temporarily attached to the surface of the transparent protective film 74 via an adhesive layer 39. ing.

The polarizing element 79 includes a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, an ethylene / vinyl acetate copolymerization system partially saponified film, and a dichroic property such as iodine or a dichroic dye. Examples thereof include a uniaxially stretched film by adsorbing a substance, a polyene-based oriented film such as a dehydrated product of polyvinyl alcohol and a dehydrogenated product of polyvinyl chloride.

Above all, from the viewpoint of having a high degree of polarization, a polyvinyl alcohol-based film such as polyvinyl alcohol or partially formalized polyvinyl alcohol was adsorbed with a dichroic substance such as iodine or a dichroic dye and oriented in a predetermined direction. Polyvinyl alcohol (PVA) -based modulators are preferred. For example, a PVA-based polarizing element can be obtained by subjecting a polyvinyl alcohol-based film to iodine dyeing and stretching. As the PVA-based polarizing element, a thin polarizing element having a thickness of 10 μm or less can also be used. Examples of the thin polarizing element are described in JP-A No. 51-06644, JP-A-2000-338329, WO2010 / 100917 Pamphlet, Patent No. 46910205, Patent No. 4751481 and the like. The thin polarizing film that is used can be mentioned. Such a thin polarizing element can be obtained, for example, by a production method including a step of stretching a PVA-based resin layer and a stretching resin base material in a laminated state, and a step of iodine dyeing.

As the transparent protective film 74, the same material as described above is preferably used as the material of the transparent film 10. The material of the transparent protective film 74 and the material of the transparent film 10 may be the same or different.

Adhesives used for the adhesive layers 36 and 38 include acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyvinyl alcohols, polyvinyl ethers, vinyl acetate / vinyl chloride copolymers, modified polyolefins, epoxy polymers, and fluorine-based adhesives. A polymer, a rubber-based polymer, or the like as a base polymer can be appropriately selected and used. A polyvinyl alcohol-based adhesive is preferably used for bonding the PVA-based polarizing element.

In the form shown in FIG. 4B, a polarizing plate in which transparent protective films 73 and 74 are bonded to both surfaces of a polarizing element 79 via adhesive layers 36 and 38, and an antireflection film are interposed via an adhesive layer 35. It is a polarizing plate 122 with an antireflection layer bonded together. A release film 22 is temporarily attached to the surface of the transparent protective film 74 via an adhesive layer 39.

As the adhesive layer 35 used for bonding the transparent protective film 73 and the transparent film 10, a pressure-sensitive adhesive such as an acrylic pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, or a sea cone-based pressure-sensitive adhesive is preferable. The adhesive layer 30 (adhesive) used for the temporary attachment of the transparent film 10 and the film base material 20 can also be used as it is (see FIGS. 3 (B) and 3 (C1)).

The antireflection film is preferably used for forming an image display device. When the antireflection film is attached to the outermost surface of the image display device, it is susceptible to contamination (fingerprints, hand stains, dust, etc.) from the external environment. For the purpose of preventing contamination from the external environment and imparting easy removal of contamination, an antifouling layer made of a fluorine group-containing silane compound or a fluorine group-containing organic compound is provided on the surface of the antireflection layer. It may be provided.

[Evaluation of reflected light characteristics by optical simulation]
In the following examples and comparative examples, the spectrum of the reflected light of the laminate in which various film substrates are bonded via the adhesive layer on the side opposite to the antireflection layer forming surface of the antireflection film is calculated by optical simulation. did. As the antireflection film, a triacetyl cellulose (TAC) film (refractive index 1.49) having a thickness of 80 μm is provided with an acrylic hard coat layer (refractive index 1.51) having a thickness of 8 μm on the surface of the hard coat layer. In addition, a titanium oxide layer with a film thickness of 12 nm (refractive index 2.35), a silicon oxide layer with a film thickness of 28 nm (refractive index 1.46), a titanium oxide layer with a film thickness of 100 nm (refractive index 2.35), and a film thickness. A configuration including an antireflection layer composed of four layers of an 85 nm silicon oxide layer (refractive index 1.46) was adopted.

<Example 1>
A black film with a thickness of 38 μm (visible light transmittance 3%, refractive index 1.65) is attached to the antireflection layer non-formed surface side of the antireflection film via an adhesive layer (refractive index 1.48) with a thickness of 20 μm. Combined configuration.

<Example 2>
The release layer side of a 38 μm-thick black film (visible light transmittance 3%, refractive index 1.65) having a silicone release layer (refractive index 1.46) of 80 nm on the surface is an adhesive layer (refraction) with a thickness of 20 μm. A configuration in which the antireflection film is bonded to the non-formating surface of the antireflection layer via a refractive index of 1.48).

<Comparative Example 1>
A configuration in which a black translucent film having a visible light transmittance of 50% is used instead of the black film of Example 1.

<Evaluation>
For each of the configurations of Examples and Comparative Examples, the reflected light spectrum when white light was incident from the antireflection layer side was calculated. In addition, the reflected light spectrum (reference spectrum) of the antireflection film was calculated when the backside reflection was set to zero. From the obtained anti-light spectrum, the luminance Y (%) and the chromaticity a and b in the Yab color system were calculated, and the chromaticity difference Δab between the reflected light of each Example and the comparative example and the reference spectrum was obtained. .. Table 1 shows the laminated structure of the transparent film, the adhesive layer and the film substrate, and the reflected light characteristics in Examples and Comparative Examples.

[Evaluation of peeling force and in-line peeling property]
In the following, a film substrate was bonded to a TAC film (manufactured by Fujifilm; Fujitac TD80UL) having a thickness of 80 μm via an adhesive layer to prepare an evaluation sample, and the peeling force was evaluated.

<Sample 1>
Using a roll laminator, a protective film material (manufactured by Nitto Denko; E-MASK RP300) in which a light peeling adhesive layer having a thickness of 20 μm was formed on a PET film having a thickness of 38 μm was attached to the TAC film.

<Sample 2>
Similar to the preparation of Sample 1, a protective film material was bonded onto the TAC film, and then heat-treated at 100 ° C. for 2 hours.

<Sample 3>
Using a roll laminator, a transparent adhesive sheet with a thickness of 20 μm (an acrylic adhesive sheet for polarizing plates manufactured by Nitto Denko) is attached onto a TAC film, and a PET film with a thickness of 38 μm whose surface is mold-released (PET film). The mold release treated surface of Mitsubishi resin; Diafoil MRF38) was bonded.

<Evaluation>
Samples 1 and 2 were subjected to a peeling test at the interface between the TAC film and the adhesive layer, and Sample 3 was subjected to a peeling test at the interface between the PET film and the adhesive layer.
(Peel test)
Samples 1 to 3 were cut into strips having a width of 50 mm, and the peeling force was measured by a 180 ° peel test (test speed: 10 m / min).
(In-line peelability test)
Using a roll laminator, the in-line peelability of the film substrate of Samples 1 to 3 was evaluated, and those that could be peeled without problems were regarded as "good", and those in which tension abnormality occurred during running of the film were regarded as "bad". did.
The results are shown in Table 2.

As shown in Table 1, by lowering the transmittance of the film substrate, the backside reflectance is reduced, and the Y value of the reflected light is reduced accordingly, and the chromaticity difference Δab from the reference spectrum is also increased. It turns out that it becomes smaller. In Example 2 in which the film substrate provided with the release layer on the base film was used, the Y value and the chromaticity difference tended to increase as compared with Example 1 due to the increase in the reflective interface. Backside reflection can be reduced by adjusting the refractive index of the release layer.

As shown in Table 2, by reducing the peeling force between the transparent film and the film substrate, in-line peeling tends to be easy. From this result, if the peeling force is reduced by using a lightly peelable adhesive material as the material of the adhesive layer or by using a film base material having a release layer, the film base material can be used after the antireflection layer is formed. It can be seen that the workability when reattaching to the film can be improved and the productivity can be improved.

10 Transparent film 20 Film base material 21 Release layer 25 Base film 30, 33, 35, 36, 38, 39 Adhesive layer 40 Laminated body 50 Antireflection layer 51, 52, 53, 54 Thin film 73, 74 Transparent protective film 79 Polarized Child 100, 101, 103 Anti-reflection film 111, 112 Anti-reflection film (optical film with anti-reflection layer)
121,122 Antireflection film (polarizing plate with antireflection layer)

Claims (10)

A method for producing an antireflection film, which comprises an antireflection layer composed of two or more thin films having different refractive indexes on the first main surface of the transparent film.
A laminate preparation step of preparing a laminate in which a film substrate is detachably attached to a second main surface of a transparent film via an adhesive layer;
An antireflection layer forming step of forming an antireflection layer composed of two or more thin films having different refractive indexes on the first main surface of the transparent film of the laminate; and at least of the thin films constituting the antireflection layer. It has an in-line inspection step of irradiating visible light from the formation surface side of the thin film after forming one layer and detecting the reflected light.
The laminate of the film substrate and the adhesive layer has a visible light transmittance of 3% or less.
The adhesive layer is a light scattering adhesive layer having a haze of 50% or more.
A method for producing an antireflection film, wherein the antireflection layer forming step and the in-line inspection step are continuously carried out while transporting the laminated body in one direction. The reflection according to claim 1, wherein in the in-line inspection step, after all of the plurality of thin films constituting the antireflection layer are formed, visible light is irradiated from the formation surface side of the thin film and the reflected light is detected. Manufacturing method of preventive film. The method for producing an antireflection film according to claim 1 or 2, wherein the film forming conditions of the thin film in the antireflection layer forming step are adjusted according to the detection result of the reflected light in the in-line inspection step. One of claims 1 to 3, wherein the back surface reflectance of visible light is 1.0% or less when light is incident on the laminate of the film substrate and the adhesive layer from the adhesive layer side. The method for manufacturing an antireflection film according to. The method for producing an antireflection film according to any one of claims 1 to 4 , wherein the peeling force between the transparent film and the film substrate in a 180 ° peeling test is 2N / 50 mm or less. The method for producing an antireflection film according to any one of claims 1 to 5 , further comprising a peeling step of peeling the film substrate from the transparent film after the in-line inspection step. The method for producing an antireflection film according to claim 6, wherein an optical film is bonded onto the second main surface of the transparent film after the peeling step. The method for manufacturing an antireflection film according to claim 7 , wherein the optical film is an optical film containing a polarizing element. An antireflection layer composed of two or more thin films having different refractive indexes is provided on one surface of the transparent film, and a film base material is detachably attached to the second main surface of the transparent film via an adhesive layer. And
The laminate of the film substrate and the adhesive layer has a visible light transmittance of 3% or less .
The adhesive layer is an antireflection film having a haze of 50% or more, which is a light scattering adhesive layer . A method for measuring the reflected light characteristics of an antireflection film having an antireflection layer composed of two or more thin films having different refractive indexes on the first main surface of the transparent film.
Visible light reflected from the first main surface is detected while the film substrate is detachably attached to the second main surface of the transparent film via an adhesive layer. ,
The laminate of the film substrate and the adhesive layer has a visible light transmittance of 3% or less.
The adhesive layer is a light scattering adhesive layer having a haze of 50% or more.
The detection of the reflected light is a method for measuring reflected light characteristics, which is continuously carried out while transporting the antireflection film in one direction.

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