KR102545860B1 - Antireflective film and manufacturing method thereof, and method of measuring reflected light characteristics of antireflective film - Google Patents

Abstract

The method of the present invention is a laminate preparation step of preparing a laminate 40 to which the film base material 20 is peelably attached to the second main surface of the transparent film 10 via the adhesive layer 30, An antireflection layer forming step of forming an antireflection layer 50 composed of two or more thin films on the first main surface of the transparent film, and after forming at least one layer of the thin film constituting the antireflection layer into a film, the first main surface side of the laminate It has an in-line inspection process of irradiating visible light from and detecting the reflected light. The adhesive layer 30 is a diffused pressure-sensitive adhesive layer having a haze of 40% or more. The antireflection layer forming step and the inline inspection step are continuously performed while conveying the layered product 40 in one direction. Uniformity is improved by adjusting the film formation conditions of the thin film in the antireflection layer forming step according to the detection result of the reflected light in the inline inspection step.

Description

Antireflection film, method for manufacturing the same, and method for measuring reflective light properties of the antireflection film

The present invention relates to an antireflection film comprising an antireflection layer on a transparent film and a manufacturing method thereof. Further, the present invention relates to a method for in-line measuring the reflected light characteristics of an antireflection film.

BACKGROUND ART An antireflection film is used for the purpose of preventing deterioration in image quality due to reflection of external light or reflection of an image, improvement of contrast, and the like, on the surface of an image display device such as a liquid crystal display or an organic EL display. The antireflection film includes an antireflection layer composed of a plurality of thin film laminates having different refractive indices on a transparent film.

As one form of the antireflection film, a polarizing plate with an antireflection layer is exemplified. A polarizing plate with an antireflection layer is formed by bonding an antireflection film to the surface of the polarizing plate or by bonding an antireflection film to the surface of a polarizer as a protective film. Moreover, the method of forming the polarizing plate with an antireflection layer by forming an antireflection layer on a polarizing plate is also known (patent document 1, for example).

Japanese Unexamined Patent Publication No. 8-136730

The antireflection layer reduces the reflectance of visible light by utilizing multiple reflection interference of the thin film. Therefore, when the refractive index or film thickness of the thin film fluctuates, reflected light characteristics such as reflectance and reflected light color change. In the formation of the antireflection layer, even when the film formation conditions of the thin film are strictly managed and kept constant, the film thickness, refractive index, etc. do. The influence of such a slight fluctuation on the specular characteristics is small. Therefore, in general, quality control of the antireflection film is performed by performing film formation under certain conditions and confirming the reflected light characteristics offline after film formation with the naked eye or an inspection device such as a spectrophotometer.

[0003] In recent years, as high resolution of displays progresses, the required properties for antireflection films are increasing, and antireflection films with lower reflectance and less coloration of reflected light are required. In addition, attempts have been made to neutralize the light emitted from the panel by adjusting the hue of the reflected light. For example, when the light emitted from the panel is yellow, the neutralization is performed by using an antireflection film in which the reflected light is blue.

With such an increase in required properties, more strict management of the reflected light properties of antireflection films is required. Therefore, there are cases in which the antireflection film deviate from the quality standard due to a change in reflected light characteristics resulting from slight fluctuations in manufacturing conditions. Therefore, in the manufacturing process of the antireflection film, it is necessary to control the film formation conditions more strictly to suppress fluctuations in the refractive index and film thickness of the thin film and to keep the reflected light characteristics constant.

In film production, in-line measurement is performed during the production process, and the quality of the film is kept constant by feeding back the measurement result to the preceding process. 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 very difficult to measure the film thickness of each thin film in a plurality of thin film laminates. Therefore, it is conceivable to measure reflected light characteristics in-line at the time of film formation of a thin film, and to feed back the measurement result to the film formation conditions of the thin film. In the in-line measurement of reflected light characteristics, it is necessary to eliminate the influence of the back surface reflection.

In general, an antireflection film is designed so that the antireflection layer formation surface has a visible light reflectance of 1% or less, whereas the visible light reflectance on the back side of the transparent film (interface between the transparent film and air) is about 4%. In the off-line inspection after forming the antireflection layer, it is possible to measure the reflected light characteristics on the front side while excluding the influence of the back side reflection. On the other hand, most of the reflected light detected by in-line inspection in the manufacturing process of the antireflection film is reflected light from the back surface, and even if the characteristics (reflected color, etc.) of the reflected light from the antireflection layer formation surface change, the detected reflected light hardly changes. I never do that. Therefore, it is not easy to accurately measure the reflected light characteristics from the antireflection layer formation surface side in-line.

In Patent Document 1, when forming an antireflection layer on the surface of a polarizing plate, a method of arranging a polarizer (analyzer) on the antireflection layer formation side of the polarizing plate and measuring the reflectance is proposed. If the polarizer with antireflection layer and the analyzer are arranged so that their absorption axis directions are orthogonal to each other, the reflected light from the back side of the polarizer with antireflection layer is absorbed by the analyzer. can be measured

However, this method cannot be applied except when forming an antireflection layer on a polarizing plate. A polarizing plate has a structure in which transparent films are laminated on both sides of a polarizer, and is more expensive than a transparent film alone. Therefore, in the method of forming an antireflection layer on a polarizing plate, an increase in manufacturing cost due to process loss occurs when an out-of-standard portion occurs in the early stage of formation of the antireflection layer (before control of film formation conditions by in-line reflected light detection) or the like. It is easy to become conspicuous. In addition, the properties 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 sputter film forming apparatus, the polarizer may deteriorate due to exposure to a high-temperature environment or high-output plasma.

Therefore, from the viewpoint of productivity improvement or cost reduction, in forming an antireflection layer on a transparent film not containing a polarizer, there is a need for a method of accurately measuring reflected light characteristics by excluding the influence of backside reflection. An object of the present invention is to more accurately detect a change in reflected light characteristics in-line in a step of forming an antireflection layer on a transparent film, and to reflect the detection result to film formation conditions, thereby obtaining an antireflection film excellent in uniformity. to be Another object of the present invention is to provide a method for in-line measurement of reflected light characteristics of an antireflection film.

As a result of examination in view of the above, by using a laminate in which a film base material is peelably attached to the back side of a transparent film via an adhesive layer, the back surface reflection is reduced, and the refractive index of the antireflection layer, the film thickness, etc. It was discovered that a change in reflected light characteristics resulting from slight fluctuations could be detected.

One embodiment of the antireflection film of the present invention is an antireflection film having a film base material in which an antireflection layer is provided on one surface of a transparent film and the film base material is peelably adhered to the other surface via an adhesive layer.

The antireflection film on which the film substrate is formed is prepared by preparing a laminate in which the film substrate is peelably adhered to the second main surface of the transparent film via an adhesive layer (laminate preparation step), and the transparent film of the laminate is prepared. It is obtained by forming an antireflection layer composed of two or more thin films on one principal surface (antireflection layer forming step). In formation of the antireflection layer, after forming at least one layer of the thin film, visible light is irradiated from the side of the first main surface of the laminate, and the reflected light is detected in-line (in-line inspection step). Formation of the antireflection layer and inline inspection are performed continuously while conveying the laminate in one direction. It is preferable that film formation conditions of the thin film are adjusted according to the detection result of the reflected light in the inline inspection. In this way, the reflected light characteristics of the antireflection film can be maintained uniformly, and the stability of quality can be improved.

It is preferable that the adhesive layer used for sticking a transparent film and a film base material is a diffusion pressure-sensitive adhesive layer having a haze of 40% or more. By using the high-haze diffusing pressure-sensitive adhesive layer as the adhesive layer, incident light from the first main surface side of the transparent film is diffused in the adhesive layer, so light reflection on the back surface side of the transparent film is reduced.

After forming the antireflection layer on the transparent film, the film substrate is peeled off (peeling step). Then, another optical film, such as a polarizing plate, is bonded on the 2nd main surface of a transparent film, and an antireflection film is provided for practical use.

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

1 is a cross-sectional view schematically showing one embodiment of an antireflection film having a film substrate.
2 is a conceptual diagram showing a configuration example of an antireflection layer film forming apparatus.
Fig. 3 (A) is a cross-sectional view schematically showing a structural example of a laminate used for forming an antireflection film, and (B) is a structural example of an antireflection film formed with a film substrate having an antireflection layer formed on the laminate. It is a cross-sectional view schematically showing. (C1) and (C2) are cross-sectional views schematically showing structural examples of the antireflection film after peeling the film substrate. (D1) and (D2) are cross-sectional views schematically showing structural examples of antireflection films to which other films are bonded.
4(A) and (B) are cross-sectional views schematically showing a configuration example of a polarizing plate with an antireflection layer.

[Composition of antireflection film]

1 is a cross-sectional view schematically showing the configuration of an antireflection film according to an embodiment. The antireflection film 101 of FIG. 1 includes an antireflection layer 50 on the first main surface of the transparent film 10 . On the 2nd main surface of the transparent film 10, the film base material 20 is attached via the adhesive layer 30 so that exfoliation is possible. The antireflection layer is a laminate of two or more thin films. In Fig. 1, an antireflection layer 50 composed of a laminate of four layers of thin films 51, 52, 53 and 54 is shown.

(transparency 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 easily bonding layer on the film surface (antireflection layer formation surface). The hard coat layer can be formed by, for example, a method of forming a cured film of an appropriate ultraviolet curable resin such as acrylic resin or silicone resin on the surface of the film.

The visible light transmittance of the transparent film is preferably 80% or more, more preferably 90% or more. Although the thickness of the transparent film 10 is not specifically limited, the range of about 10 micrometers - 300 micrometers is preferable.

Examples of the resin material constituting the transparent film include polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN); cellulosic polymers such as diacetyl cellulose and triacetyl cellulose; acrylic polymers such as polymethyl methacrylate; Styrene-type polymers, such as polystyrene and an acrylonitrile-styrene copolymer; cyclic polyolefins such as polynorbornene; Polycarbonate etc. are mentioned.

The surface of the transparent film may be subjected to a surface modification treatment such as corona treatment, plasma treatment, flame treatment, ozone treatment, priming treatment, gloss treatment, saponification treatment, treatment with a coupling agent, etc. for the purpose of improving adhesion.

(adhesive layer)

The transparent film 10 and the film substrate 20 are bonded together via the adhesive layer 30 . Although the material of the adhesive layer 30 is not specifically limited, In order to attach the film base material 20 so that exfoliation is possible, an adhesive is used preferably. As the pressure-sensitive adhesive, for example, an acrylic pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, a silicone pressure-sensitive adhesive, and the like can be used. Among them, an acrylic adhesive containing an acrylic polymer as a main component is preferably used.

The adhesive layer 30 is a light scattering adhesive layer. By using the light-scattering adhesive, the light transmitted through the transparent film 10 is scattered by the adhesive layer 30, and backside reflection can be reduced. As the haze of the adhesive layer 30 (light scattering pressure-sensitive adhesive layer) increases, light scattering in the adhesive layer increases, and backside reflection tends to decrease. Therefore, the haze of the adhesive layer 30 (light scattering adhesive layer) is preferably 40% or more, more preferably 50% or more, still more preferably 70% or more, and particularly preferably 90% or more.

The composition of the light scattering adhesive layer is not particularly limited as long as the haze is within the above range. As a light scattering adhesive, what disperse|distributed particle|grains in the adhesive is mentioned, for example. Examples of the particles included in the light scattering 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, and melamine resin. Since these resins are excellent in dispersibility to the pressure-sensitive adhesive and have an appropriate refractive index difference with the pressure-sensitive adhesive such as an acrylic pressure-sensitive adhesive, a light scattering pressure-sensitive adhesive layer having excellent diffusion performance is obtained. The shape of the particles is not particularly limited, and examples thereof include a spherical shape, a flat shape, and an irregular shape. Particles may be used alone or in combination of two or more.

The volume average particle diameter of the particles is preferably 1 μm to 10 μm, more preferably 1.5 μm to 5 μm. By setting the volume average particle diameter within the above range, excellent light scattering performance can be provided. The volume average particle diameter can be measured using, for example, an ultracentrifugal automatic particle size distribution analyzer. 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 compounding amount of the particles within the above range, a light scattering pressure-sensitive adhesive layer having excellent light scattering performance can be obtained.

(film substrate)

In the manufacture of the antireflection film, the film substrate 20 is attached to the second main surface (surface on which the antireflection layer 50 is not formed) of the transparent film 10 so as to be peelable with the adhesive layer 30 interposed therebetween. A sieve 40 is used. By temporarily attaching the film base material 20 to the surface of the adhesive layer 30, the exposed surface of the adhesive layer 30 is covered, contamination of the adhesive layer due to contact with the outside, adhesion of the adhesive (diffusion adhesive) to the film forming device, etc. can prevent

As the film substrate 20, a resin film is used. The material of the film substrate 20 may be transparent or opaque, and polyesters, cellulose polymers, acrylic polymers, styrenic polymers, amide polymers, polyolefins, cyclic polyolefins, polycarbonates and the like are used.

By using a material having a low visible light reflectance as the film base material 20, backside reflection when light is irradiated from the side of the first principal surface can be further reduced. In order to further reduce the back surface reflection, the back surface reflectance of visible light of the film base material when light is incident from the first main surface is preferably 1.0% or less, more preferably 0.7% or less, and still more preferably 0.5% or less. , 0.3% or less is particularly preferred. In addition, the visible light reflectance is measured according to JIS R3106:1998.

Examples of low-reflectance film substrates include light-absorbing films and light-scattering films having fine irregularities on the surface. In particular, when a light-absorptive film is used, the backside reflection reduction effect is easily obtained. In order to further reduce backside reflection by using a light-absorbing film substrate, the visible light transmittance of the film substrate 20 is preferably 40% or less, more preferably 20% or less, and even more preferably 10% or less. .

For example, a light-absorbing film substrate is obtained by adding a black pigment such as carbon black to a resin material of a film substrate or by forming a colored layer using black ink or the like on the surface of the film substrate. The colored layer may be formed only on one surface of the film substrate or may be formed on both surfaces. When a light-absorbing film having a colored layer is used as the film substrate 20, from the viewpoint of suppressing light reflection at the interface on the transparent film 10 side, at least the surface of the film substrate on the transparent film 10 side It is preferable that a colored layer is formed thereon. The thickness of the colored layer is, for example, about 0.5 µm to 10 µm.

As shown in FIG. 3(C1) and FIG. 3(C2), the film base material 20 is peeled and removed at the time of practical use of an antireflection film. That is, the film substrate 20 is a process material not included in the final product. Therefore, it is preferable that the film base material is as inexpensive as possible, and a general-purpose film such as polyethylene terephthalate is preferably used. The thickness of the film substrate 20 is not particularly limited. When the thickness of the film substrate is thin, the continuous film formation length at the time of forming the antireflection layer 50 on the layered product 40 can be lengthened, and the productivity of the antireflection film can be improved. Therefore, it is preferable that the thickness of the film substrate 20 is as thin as possible within a range that does not impair film formability or handling properties. The thickness of the film substrate is preferably from 5 μm to 200 μm, more preferably from 10 μm to 130 μm, still more preferably from 15 μm to 110 μm.

(Laminate)

As described above, when the laminate 40 in which the adhesive layer 30 made of the diffusion adhesive and the film substrate 20 are formed on the second main surface of the transparent film 10 is irradiated with light from the first main surface side of the transparent film The backside reflection of is small. Table 1 shows a measurement example of the back surface reflectance of the laminate. In Samples 1 to 5, a triacetyl cellulose film having a thickness of 40 μm in which an acrylic hard coat layer was formed on the first main surface was used as the transparent film 10, and a transparent PET film having a thickness of 38 μm was used as the film substrate 20 did The haze rate of the pressure-sensitive adhesive layer was changed by using an acrylic pressure-sensitive adhesive having a thickness of 20 µm as the adhesive layer 30 and changing the particle size and content of particles to be dispersed in the pressure-sensitive adhesive.

The back surface reflectance of Example 1 using the particle-free transparent adhesive was 4%, which was substantially the same as the back surface reflectance of the transparent film 10 alone. When the haze of the pressure-sensitive adhesive layer was raised to 40%, the back surface reflectance decreased to 1%, and when the haze was raised to 60%, the back surface reflectance was less than 0.5%. As described above, the surface reflectance of the antireflection film is 1% or less. In order to reduce the influence of back surface reflection and accurately detect the reflected light characteristics from the surface, it is necessary to set the back surface reflectance of the laminate 40 to a value equal to or less than the surface reflectance, that is, 1% or less. The back surface reflectance is preferably 0.7% or less, more preferably 0.5% or less, still more preferably 0.3% or less. From the result of Table 1, it turns out that the back surface reflectance of the laminated body 40 can be adjusted to the said range by raising the haze of the adhesive layer 30.

(antireflection layer)

An antireflection layer 50 is formed on the first main surface of the layered product 40 to which the film substrate 20 is stuck on the second main surface of the transparent film 10 with the adhesive layer 30 interposed therebetween. The antireflection layer 50 is composed of two or more layers of thin films. In general, the optical film thickness (product of refractive index and thickness) of the antireflection layer is adjusted so that the inverted phases of incident light and reflected light cancel each other out. By making the antireflection layer a multilayer laminate of two or more thin films having different refractive indices, 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, silicon oxide, magnesium fluoride, etc. as a low refractive index material with a refractive index of about 1.35 to 1.55, titanium oxide, niobium oxide, zirconium oxide, tin-doped indium oxide (ITO), antimony-doped oxide as a high refractive index material with a refractive index of about 1.80 to 2.40 Annotation (ATO) etc. are mentioned. 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 above-mentioned low refractive index material and high refractive index material (a mixture of titanium oxide and silicon oxide, etc.) You may form the thin film which consists of.

As the laminate configuration of the antireflection layer 50, from the side of the transparent film 10, 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 are two layers. composition ; a three-layer configuration of a medium refractive index layer with an optical film thickness of about 170 nm to 180 nm, a high refractive index layer with an optical film thickness of about 60 nm to 70 nm, and a low refractive index layer with an optical film thickness of about 135 nm to 145 nm; A high refractive index layer having an optical film thickness of about 25 nm to 55 nm, a low refractive index layer having an optical film 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 an optical film thickness of 120 nm 4-layer configuration of a low refractive index layer of about 150 nm; A low refractive index layer having an optical film thickness of about 15 nm to 30 nm, a high refractive index layer having an optical film thickness of about 20 nm to 40 nm, a low refractive index layer having an optical film thickness of about 20 nm to 40 nm, and an optical film thickness of 240 nm A five-layer structure of a high refractive index layer of about -290 nm and a low refractive index layer of about 100 nm to 200 nm in optical film thickness, and the like are exemplified. The range of the refractive index or 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 laminate of six or more thin films.

[Method of Forming Antireflection Layer]

The film formation method of the thin film constituting the antireflection layer is not particularly limited, and may be either a wet coating method or a dry coating method. Dry coating methods such as vacuum deposition, CVD, sputtering, and electron beam deposition are preferable in that a thin film having a uniform film thickness can be formed and the film thickness of a nanometer-level thin film can be easily adjusted, and among them, sputtering and Electron beam deposition is preferred.

Formation of the antireflection layer is performed continuously while conveying the layered product 40 in one direction. For example, when the antireflection layer is formed by sputtering, continuous film formation is performed using a winding-type sputtering apparatus.

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

In the following, a case in which the antireflection layer 50 composed of four layers of thin films 51, 52, 53, and 54 is formed on the transparent film 10 by the sputtering method is taken as an example, and the reflected light detection result in line A method for manufacturing the antireflection film while reflecting the film formation conditions will be described.

2 is a conceptual diagram showing an example of a configuration of a film forming apparatus for reflecting in-line reflected light detection results to film forming conditions of an antireflection layer. The film forming apparatus of FIG. 2 includes two film forming rolls 281 and 282 . Along the circumferential direction of each of the film-forming rolls 281 and 282, a plurality of film-forming chambers 210, 220, 230, and 240 partitioned off by partition walls are provided. A cathode is formed in each film formation chamber, and each cathode 214 , 224 , 234 , 244 is connected to a power source 216 , 226 , 236 , 246 . On the cathodes 214 , 224 , 234 , and 244 , targets 213 , 223 , 233 , and 243 are disposed so as to face the film forming rolls 281 and 282 . A gas inlet pipe is connected to each of the film formation chambers 210, 220, 230, and 240, and valves 219, 229, 239, and 249 are provided upstream of the gas inlet pipe.

The winding body of the laminated body 40 of the transparent film 10 and the film base material 20 is set on the unwinding roll 251 in the preparation room 250. The layered product 40 unwound from the unwinding roll is conveyed onto the first film forming roll 281 and guided to the first film forming room 210 and the second film forming room 220 in this order. In the first film formation chamber 210, a thin film 51 is formed on the first main surface of the transparent film 10, and in the second film formation chamber 220, a 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) is sequentially formed. The antireflection film 101 in which the antireflection layer 50 composed of four layers of thin films is formed on the transparent film 10 of the laminate 40 is guided to a take-up chamber 260 and wound up by a take-up roll 261. Thus, a rolled body of the antireflection film is obtained.

Inside the take-up chamber 260, the light irradiation part 291 and the light detection part 293 are arrange|positioned so that it may face the surface on which the antireflection layer 50 of the antireflection film 101 is formed. The light irradiated from the light irradiation unit may be white light or monochromatic light as long as it includes visible light. 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 electrical signal by the light receiving element, and calculation is performed by the arithmetic unit 273 as necessary. In the calculation unit, spectrum calculation of the detected reflected light and conversion to a specific color system (for example, XYZ color system, L*a*b* color system, Yab color system) are performed.

Further, in the calculation unit 273, a difference between the reflection characteristic of the detected reflected light and the target reflected light characteristic is determined, and when the difference exceeds a threshold value, a signal is sent to the control unit to change the film formation conditions of the thin film. do. The control unit 275 adjusts the film formation conditions of the thin film so that the characteristics of the reflected light (reflectance, color, etc.) fall within a predetermined range.

Examples of the film formation conditions to be adjusted include the amount of gas introduced into the film formation chamber, the transport speed of the film, and the amount of power input. For example, in the film forming apparatus shown in FIG. 2 , the control unit 275 controls the rotation speed of the unwinding roll 251, the winding roll 261, and the film forming rolls 281 and 282, the power sources 216, 226, 236, 246) and the opening degree of the valves 219, 229, 239, and 249 of the gas inlet pipe, it is possible to adjust the thin film formation conditions in each film formation chamber. Changes in the characteristics of the reflected light mainly originate from fluctuations in the film thickness of the thin film. Therefore, it is preferable to adjust the film formation conditions of the thin film so that the film thickness of the thin film approaches the set value. Adjustment of film formation conditions is performed by, for example, PID control. In addition, the refractive index can be changed by adjusting the manufacturing 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 formation chamber, the oxygen content in the metal oxide changes, and the refractive index of the thin film changes accordingly.

In the above, the mode in which in-line detection of reflected light is performed after all the thin films 51, 52, 53, and 54 have been formed has been described, but in-line detection of reflected light is performed at any stage after forming at least one thin film layer. It can be. For example, after the thin films 51 and 52 are formed on the first film-forming roll 281, while the laminate 45 is guided onto the second film-forming roll 282, the laminate from the light irradiation unit 297 In-line detection of the reflected light may be performed by detecting the reflected light of the light irradiated to the sieve 45 by the photodetector 299 . In addition, inline detection of the reflected light may be performed at two or more points. For example, in the form shown in FIG. 2 , after forming the two layers of thin films 51 and 52, the light detection unit 299 detects the reflected light from the laminate 45, and furthermore, the two layers are formed thereon. After the thin films 53 and 54 are formed, the light reflected from the antireflection film 101 may be detected by the photodetector 293 . In this way, when inline measurement is performed at two or more points, it is easy to determine the film formation room in which the film formation conditions must be adjusted, and more precise control is possible. Furthermore, inline detection may be performed at a plurality of points in the width direction, and film formation conditions may be adjusted so that reflected light characteristics in the width direction become uniform. For example, the deposition conditions in the width direction can be adjusted by changing the gas introduction amount in the width direction.

2 shows an example in which the antireflection layer 50 is composed of four layers of thin films, however, as described above, the number of thin films constituting the antireflection layer is not particularly limited as long as it is two or more layers. In addition, an appropriate film forming apparatus can be used according to 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 employed. Even when the thin film is formed by a method other than sputtering, an antireflection film having excellent uniformity in reflected light characteristics can be obtained by adjusting the conditions for forming the thin film based on the result of inline detection of the reflected light.

When light is irradiated to the antireflection film in which the antireflection layer is formed on the first main surface of the transparent film, most of the reflected light is due to backside reflection on the second main surface side, and the reflected light on the first main surface side (surface where the antireflection layer is formed) is accurately reflected. It is difficult to detect. In contrast, back surface reflection is suppressed by providing a light scattering pressure-sensitive adhesive layer on the second main surface side of the transparent film 10 . In this embodiment, since most of the reflected light detected by the photodetector 293 is the reflected light from the first principal surface side (the antireflection layer formation surface side), slight changes in the reflected light characteristics from the first principal surface side can be detected in-line. can By adjusting the film formation conditions of the thin film based on this detection result, an antireflection film having excellent uniformity in reflected light characteristics can be manufactured.

In this way, before forming the antireflection layer to be inspected, by attaching the film base material to the transparent film through the light scattering adhesive layer, backside reflection is suppressed and reflected light characteristics can be accurately measured inline. As described above, since an inexpensive general-purpose film is used as the film substrate 20, a laminate of a transparent film and a film substrate is less expensive than a polarizing plate. Therefore, compared to the case of using a polarizing plate as in Patent Literature 1, even if an out-of-standard part occurs in the early stage of formation of the antireflection layer (before start of film formation condition control by in-line reflected light detection), the effect of process loss on manufacturing cost this is small

In addition, by forming the antireflection layer on the laminate 40 of the transparent film 10 and the film substrate 20, the length of continuous film formation of the antireflection layer can be increased compared to the case where the antireflection layer is formed on the polarizing plate. . Generally, the unwinding roll 251 and the winding roll 261 have upper limits of the weight and diameter of the film wound body that can be set on the frame. Since the length of the film which the weight and diameter of a winding object reach|attain the prescribed upper limit is so long that the film thickness of a film is thin, the continuous film-forming length becomes long. In general, a polarizing plate has a structure in which a transparent protective film is formed on both sides of a polarizer and is composed of three films, whereas the laminate 40 can be composed of two films. Therefore, the layered product 40 can be designed to be thinner than the polarizing plate, and the length of continuous film formation can be increased. As a result, the operation rate of the film forming apparatus is improved, and productivity can be increased.

[Practical form of antireflection film]

In the present invention, for the purpose of in-line measurement of the reflected light characteristics of an antireflection film, a laminate (FIG. 3(A)) in which a film substrate 20 is attached to the second main surface side of a transparent film 10 is used. After the antireflection layer 50 is formed on the transparent film 10 (FIG. 3(B)) and the reflection property of the antireflection film 101 on which the film substrate is formed is measured, the film substrate 20 becomes unnecessary. Therefore, when providing an antireflection film for practical use, it is preferable that the film substrate 20 be peeled off from the transparent film 10.

In the case of peeling removal of the film substrate, only the film substrate 20 is peeled and removed in a state where the adhesive layer 30 is attached to the transparent film 10, as shown in FIG. 3 (C1), for example. For example, if the release treatment is performed on the side of the adhesive layer 30 formed side of the film substrate 20, only the film substrate 20 can be peeled off while leaving the adhesive layer 30 on the transparent film 10. After removing the film substrate, another film 71 is bonded to the second main surface of the transparent film 10 via the adhesive layer 30 .

At the time of removal of the film substrate, as shown in FIG. 3(C2), the adhesive layer 30 may also be peeled off from the transparent film 10 together with the film substrate 20. After removing the film substrate, another film 72 is bonded to the second main surface of the transparent film 10 via another adhesive layer 33 .

After peeling of the film base material 20, the films 71 and 72 bonded to the 2nd main surface of the transparent film 10 are not specifically limited. For example, a polarizer, a polarizer protective film, an optical compensation film (retardation film), or an optical film comprising a combination thereof is bonded to an antireflection film to obtain an optical film with an antireflection layer. As an example of a practical mode, a polarizing plate with an antireflection layer is obtained by bonding together with an optical film containing an antireflection film and a polarizer. In this way, in the form of bonding with a polarizer or the like after forming an antireflection layer on a transparent film, a polarizing plate with an antireflection layer can be obtained without exposing the polarizer to a high-temperature environment or high-output plasma for forming the antireflection layer. . Therefore, problems, such as deterioration of a polarizer, can be suppressed and a yield can be raised.

4(A) and (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 polarizer 79 is bonded to the second main surface of the transparent film 10 via the adhesive layer 36. A transparent protective film 74 is bonded to the other surface of the polarizer 79 via an adhesive layer 38, and a release film 22 is attached to the surface of the transparent protective film 74 via an adhesive layer 39. This is attached.

As the polarizer 79, a dichroic substance such as iodine or a dichroic dye is adsorbed to a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, or an ethylene-vinyl acetate copolymer-based partially saponified film. Polyene type oriented films, such as what uniaxially stretched, and the dehydration process material of polyvinyl alcohol, and the dehydrochlorination process material of polyvinyl chloride, etc. are mentioned.

Among them, from the viewpoint of having a high degree of polarization, a polyvinyl alcohol-based film such as polyvinyl alcohol or partially formalized polyvinyl alcohol is oriented in a predetermined direction by adsorbing a dichroic substance such as iodine or a dichroic dye to a polyvinyl alcohol-based film. A vinyl alcohol (PVA)-based polarizer is preferred. For example, a PVA type polarizer is obtained by performing iodine dyeing and extending|stretching to a polyvinyl alcohol type film. As the PVA-based polarizer, a thin polarizer having a thickness of 10 µm or less may be used. As a thin polarizer, for example, Japanese Unexamined Patent Publication No. 51-069644, Japanese Unexamined Patent Publication No. 2000-338329, WO2010 / 100917 pamphlet, Japanese Patent No. 4691205 specification, Japanese Patent No. 4751481 is described in the specification, etc. A thin polarizing film is exemplified. Such a thin polarizer is obtained by a manufacturing method including, for example, a process of stretching a PVA-based resin layer and a resin substrate for stretching in a laminated body state, and a process of dyeing with iodine.

As the transparent protective film 74, the same material as that described above as the material of the transparent film 10 is preferably used. In addition, 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 alcohol, polyvinyl ethers, vinyl acetate/vinyl chloride copolymers, modified polyolefins, and epoxy polymers. , a fluorine-based polymer, a rubber-based polymer, or the like can be appropriately selected and used as a base polymer. For adhesion of the PVA-based polarizer, a polyvinyl alcohol-based adhesive is preferably used.

In the form shown in FIG. 4(B), a polarizing plate in which transparent protective films 73 and 74 are bonded to both sides of a polarizer 79 via adhesive layers 36 and 38, and an antireflection film, the adhesive layer 35 It is the polarizing plate 122 with the antireflection layer bonded through it. 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, an adhesive such as an acrylic adhesive, a rubber adhesive, or a silicone adhesive is preferable. The adhesive layer 30 (diffusion adhesive) used for temporary attachment of the transparent film 10 and the film substrate 20 can also be used as it is (see Figs. 3(B) and (C1)).

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

10: transparent film
20: film substrate
30: adhesive layer (diffusion adhesive layer)
33, 35, 36, 38, 39: adhesive layer
40: laminate
50: antireflection layer
51, 52, 53, 54: thin film
73, 74: transparent protective film
79: polarizer
100, 101, 103: antireflection film
111, 112: antireflection film (optical film with an antireflection layer)
121, 122: antireflection film (polarizing plate with an antireflection layer)

Claims (10)

A method for producing an antireflection film comprising an antireflection layer on a first main surface of a transparent film, comprising:
Laminate preparation process which prepares the laminated body to which the film base material was adhered on the 2nd main surface of a transparent film so that exfoliation was possible via an adhesive layer;
an antireflection layer forming step of forming an antireflection layer composed of two or more thin films on a first main surface of the transparent film of the laminate; and
After forming at least one layer of the thin film constituting the antireflection layer, an inline inspection step of irradiating visible light from the side on which the thin film is formed and detecting the reflected light;
The adhesive layer is a diffusion pressure-sensitive adhesive layer having a haze of 40% or more,
The method for manufacturing an antireflection film, wherein the antireflection layer forming step and the inline inspection step are performed continuously while conveying the laminate in one direction. According to claim 1,
In the in-line inspection step, after forming all of the plurality of thin films constituting the antireflection layer, visible light is irradiated from the side on which the thin films are formed, and the reflected light is detected. According to claim 1 or 2,
The method for manufacturing an antireflection film, wherein film formation conditions of the thin film in the antireflection layer forming step are adjusted according to the detection result of the reflected light in the inline inspection step. According to claim 1 or 2,
After the in-line inspection step, further comprising a peeling step of peeling the film substrate from the transparent film, the manufacturing method of the antireflection film. According to claim 4,
In the peeling step, the film substrate is peeled off in a state where the adhesive layer is attached to the transparent film. According to claim 4,
In the peeling step, the adhesive layer is peeled from the transparent film together with the film substrate. According to claim 4,
The manufacturing method of the antireflection film in which an optical film is bonded on the 2nd main surface of the said transparent film after the said peeling process. According to claim 7,
The method of manufacturing an antireflection film, wherein the optical film is an optical film including a polarizer. An antireflection layer composed of two or more thin films is provided on the first main surface of the transparent film, and a film substrate is attached to the second main surface of the transparent film so as to be peelable via an adhesive layer,
The antireflection film wherein the adhesive layer is a diffusion pressure-sensitive adhesive layer having a haze of 40% or more. A method for measuring reflected light characteristics of an antireflection film having an antireflection layer comprising two or more thin films on a first main surface of the transparent film, the method comprising:
On the second main surface of the transparent film, in a state where the film base material is peelably attached via the adhesive layer, reflected light of visible light irradiated from the side of the first main surface is detected,
The adhesive layer is a diffusion pressure-sensitive adhesive layer having a haze of 40% or more,
The method for measuring reflected light characteristics, wherein the detection of the reflected light is carried out continuously while conveying the antireflection film in one direction.

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