JP7147121B2 - Protective film, laminate, polarizing plate, and image display device - Google Patents

Description

TECHNICAL FIELD The present invention relates to protective films, laminates, polarizing plates, and image display devices.

In recent years, thin displays using liquid crystals and organic light-emitting diodes have been developed. In particular, the development of mobile devices called smartphones and tablets is progressing. In such an image display device such as a mobile device, a polarizing plate is usually provided on the observer side rather than the display element.

A polarizing plate is composed of a polarizer and protective films provided on both sides of the polarizer, and a triacetylcellulose base material (TAC base material) is usually used as the protective film. A polarizer and a TAC substrate are often adhered via an ultraviolet curable adhesive or a water-based adhesive (see Patent Document 1, for example).

JP 2016-66047 A

With the development of thin displays in recent years, there is a demand for thin polarizing plates. However, the thickness of the TAC substrate as a protective film used in the polarizing plate is large, and the TAC substrate usually contains an additive (for example, an ultraviolet absorber) that exhibits a desired function. If the TAC base material is simply made thinner, it becomes difficult to obtain the desired function (for example, ultraviolet absorption function) accordingly.

Therefore, it is possible to reduce the thickness of the protective film for the polarizing plate by not providing a base material such as a TAC base material, and it is possible to exhibit the desired function by adding an additive. The use of a substrate-less protective film composed of a light-transmitting functional layer is being studied. A substrate-less protective film can be formed by forming a light-transmissive functional layer on one surface of a release film and peeling the release film from the light-transmissive functional layer.

At present, substrate-less protective films are required to have a low haze value from the viewpoint of transparency in addition to being thin, but the current situation is that such a protective film has not yet been obtained. be.

The present invention has been made to solve the above problems. That is, an object of the present invention is to provide a protective film that is thin and has a low haze value, a laminate, a polarizing plate, and an image display device comprising the same.

According to one aspect of the present invention, there is provided a substrate-less protective film comprising a light-transmitting functional layer, wherein the surface of the light-transmitting functional layer forms the surface of the protective film, and the light-transmitting functional layer The root mean square roughness Rq _0.25 measured with a cutoff value of 0.25 mm and the root mean square roughness Rq _2.5 measured with a cutoff value of 2.5 mm are both 0.035 μm or less. A protective film is provided.

In the protective film, the maximum height Ry measured at a cutoff value of 0.25 mm on the surface of the light-transmitting functional layer was _0.25 , and the maximum height Ry _2.5 measured at a cutoff value of 2.5 mm. are both 0.05 μm or more and 0.25 μm or less, and the difference between the maximum height Ry _2.5 and the maximum height Ry _0.25 (Ry _2.5 −Ry _0.25 ) is 0.100 μm It may be below.

In the protective film, the difference (Rq _2.5 −Rq _0.25 ) between the root mean square roughness Rq _2.5 and the root mean square roughness Rq _0.25 may be 0.010 μm or less. .

In the protective film, a ten-point average roughness Rz _2.5 measured with a cutoff value of 2.5 mm on the surface of the light-transmitting functional layer and a ten-point average roughness measured with a cutoff value of 0.25 mm The difference from Rz _0.25 (Rz _2.5 −Rz _0.25 ) may be 0.050 μm or less.

In the protective film, the protective film may have a moisture permeability of 100 g/(m ² ·24 h) or less.

In the above protective film, the film thickness of the protective film may be 5 μm or more and 40 μm or less, and the tensile strength at break of the protective film may be 8 N/10 mm or more.

In the protective film, the light-transmitting functional layer may have a multilayer structure in which two or more light-transmitting functional layers are laminated.

According to another aspect of the present invention, there is provided a laminate comprising the above protective film and a peelable release film provided directly on the surface of the light transmissive functional layer of the protective film.

In the laminate, the laminate is irradiated with light having a wavelength of 200 nm or more and 500 nm or less from the release film side so that the integrated light amount becomes 1000 mJ/cm ² , and the release film is removed from the light-transmitting functional layer, The release film may have a peel strength of 20 mN/25 mm or more and 200 mN/25 mm or less when peeled in a direction of 180° at a peel rate of 300 mm/min under an environment of 25° C. and a relative humidity of 60%.

According to another aspect of the present invention, the protective film or the laminate, and a polarizer provided on the side opposite to the surface side of the light-transmissive functional layer of the protective film or the laminate. , a polarizer is provided.

According to another aspect of the invention, there is provided an image display device comprising the protective film or the polarizing plate.

According to the protective film of one aspect of the present invention, it is possible to provide a thin protective film having a low haze value. Moreover, according to another aspect of the present invention, it is possible to provide a laminate, a polarizing plate, and an image display device each having such a protective film.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram of the protective film which concerns on embodiment. It is a figure explaining Rq'. It is a schematic block diagram of the laminated body which concerns on embodiment. It is the figure which showed the mode at the time of measuring the peel strength of the peeling film in the laminated body which concerns on embodiment. It is the figure which showed typically the manufacturing process of the protective film which concerns on embodiment. It is the figure which showed typically the manufacturing process of the protective film which concerns on embodiment. 1 is a schematic configuration diagram of a polarizing plate according to an embodiment; FIG. 1 is a schematic configuration diagram of an image display device according to an embodiment; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION A laminate, a polarizing plate, and an image display device according to embodiments of the present invention will be described below with reference to the drawings. As used herein, the terms "film", "sheet" and the like are not to be distinguished from each other based solely on the difference in designation. Therefore, for example, the term "film" is used to include members that are also called sheets. In addition, the term "light transmissive" as used herein means a property of transmitting light. Including being 90% or more. Transparency does not necessarily have to be transparent, and may be translucent. FIG. 1 is a schematic configuration diagram of a laminate according to this embodiment, FIG. 2 is a diagram for explaining Rq′, and FIG. 3 is a schematic configuration diagram of a laminate according to this embodiment. FIG. 4 is a diagram showing how the peel strength of the release film in the laminate according to this embodiment is measured. 5 and 6 are diagrams schematically showing the manufacturing process of the protective film according to the embodiment.

<<<protective film>>>
The protective film 10 shown in FIG. 1 is a substrate-less protective film provided with a light-transmitting functional layer 11 . A surface 10A of the protective film 10 is composed of a surface 11A of the light transmissive functional layer 11 . The “protective film” used herein has a function of protecting a material to be protected (for example, a polarizer) and does not peel off even when the material to be protected is used. In other words, the protective film is used during the manufacture of the protected material, but is different from the process film that is peeled off when the protected material is used. In this embodiment, the protective film 10 has the function of protecting the polarizer. Further, the term "substrate" as used herein means a film or sheet made of a thermoplastic resin or glass that serves as a support for forming the light-transmissive functional layer. Examples of the substrate include cellulose acylate substrates such as triacetyl cellulose, cycloolefin polymer substrates, polycarbonate substrates, acrylic substrates, polyester substrates such as polyethylene terephthalate substrates, and glass substrates. In addition, since the release film to be described later is to be peeled off from the protective film 10 in the end, it does not constitute a part of the protective film 10 . Furthermore, the "light-transmitting functional layer" in this specification is a layer that has light-transmitting properties and is intended to exhibit some function in the protective film. Specifically, the light-transmissive functional layer includes, for example, a hard coat layer, a core layer, and the like.

In the protective film 10, the root-mean-square roughness Rq measured with a cutoff value of 0.25 mm on the surface 11A of the light-transmitting functional layer 11 was _0.25 , and the root-mean-square roughness measured with a cutoff value of 2.5 mm. Rq _2.5 is 0.035 μm or less. If both Rq _0.25 and Rq _2.5 of the surface 11A are 0.035 μm or less, the surface 11A becomes extremely flat, and thus the protective film 10 having a low haze value can be provided.

The root-square roughness Rq is a value obtained by squaring and averaging the elevation values of the peaks and troughs of the roughness curve of the evaluation length, dividing by the evaluation length and taking the square root to obtain a uniform elevation. Here, since Rq is the square of the roughness curve, the difference due to unevenness appears more sensitively than the arithmetic mean roughness Ra. On the other hand, since Rq is obtained by squaring the value of each altitude, it is greatly affected by the cutoff value (evaluation length) and needle feed speed. Therefore, Rq is measured with cutoff values of 0.25 mm and 2.5 mm. When Rq is measured with a cut-off value of 0.25 mm, the measurement is performed in a microscopic range, so the influence of the high-frequency component of the unevenness existing on the surface 11A of the light-transmitting functional layer 11 appears. On the other hand, when Rq is measured with a cutoff value of 2.5 mm, it is measured in a macroscopic range to some extent. The influence of frequency components appears.

上記式中、ｆ（ｘ）は粗さ曲線を表し、Ｌは評価長さを表す。 The root-mean-square roughness Rq is obtained by calculating Rq' (see FIG. 2) obtained by the following formula at a plurality of evaluation lengths and calculating their arithmetic mean value.

In the above formula, f(x) represents the roughness curve and L represents the evaluation length.

Both Rq _0.25 and Rq _2.5 can be measured using a surface roughness tester under the following measurement conditions. Surfcoders SE-3400, SE-3500 and SE-500 (all manufactured by Kosaka Laboratory) can be used as the surface roughness measuring instrument. Rq is a parameter defined in JIS B0601:2001, but not defined in JIS B0601:1994. Surfcoders SE-3400 and SE-3500 comply with JIS B0601:1994, but do not comply with JIS B0601:2001. , Rq can be measured with the surfcoder SE-3400 or SE-3500. Also, since the surfcoder 500 complies with JIS B0601:2001, the surfcoder 500 can also measure Rq.

When measuring Rq _0.25 with the Surfcoder SE-3400, the measurement of Rq _0.25 shall be performed under the following measurement conditions 1 in principle. If the unevenness becomes too large to measure, the following measurement condition 3 shall be used. Similarly, when measuring Rq _2.5 with the Surfcoder SE-3400, the measurement of Rq _2.5 is, in principle, performed under the following measurement conditions 2, but the longitudinal magnification of the following measurement conditions 2 is 10 If the measurement is impossible at 10,000 times because the unevenness of the surface becomes too large, the following measurement condition 4 shall be used. Also, Rq _0.25 and Rq _2.5 may be measured with a surface roughness measuring instrument conforming to JIS B0601:2001.
1) Stylus of surface roughness detector (product name “Surfcorder SE-3400”, manufactured by Kosaka Laboratory, 2 μm standard)
・ Tip curvature radius 2 μm, apex angle 90 degrees, material diamond 2-1) Measurement condition 1
・Reference length (cutoff value λc of roughness curve): 0.25 mm
・ Evaluation length (reference length (cutoff value λc) × 5): 1.25 mm
・Feeding speed of stylus: 0.1mm/s
・ Spare length: (cutoff value λc) × 2
・Longitudinal magnification: 100,000 times ・Horizontal magnification: 50 times ・Skid: Not used (no contact with the measurement surface)
・Cutoff filter type: Gaussian ・JIS mode: JIS1994
2-2) Measurement condition 2
・Reference length (cutoff value λc of roughness curve): 2.5 mm
・ Evaluation length (reference length (cutoff value λc) × 5): 12.5 mm
・Feeding speed of stylus: 0.5mm/s
・ Spare length: (cutoff value λc) × 2
・Longitudinal magnification: 100,000 times ・Horizontal magnification: 50 times ・Skid: Not used (no contact with the measurement surface)
・Cutoff filter type: Gaussian ・JIS mode: JIS1994
2-3) Measurement condition 3
・Reference length (cutoff value λc of roughness curve): 0.25 mm
・ Evaluation length (reference length (cutoff value λc) × 5): 1.25 mm
・Feeding speed of stylus: 0.1mm/s
・ Spare length: (cutoff value λc) × 2
・Longitudinal magnification: 10,000 times ・Horizontal magnification: 50 times ・Skid: Not used (no contact with the measurement surface)
・Cutoff filter type: Gaussian ・JIS mode: JIS1994
2-4) Measurement condition 4
・Reference length (cutoff value λc of roughness curve): 2.5 mm
・ Evaluation length (reference length (cutoff value λc) × 5): 12.5 mm
・Feeding speed of stylus: 0.5mm/s
・ Spare length: (cutoff value λc) × 2
・Longitudinal magnification: 10,000 times ・Horizontal magnification: 50 times ・Skid: Not used (no contact with the measurement surface)
・Cutoff filter type: Gaussian ・JIS mode: JIS1994

The lower limits of Rq _0.25 and Rq _2.5 are both 0.010 μm or more from the viewpoint of suppressing sticking between the protective films 10 when the protective film 10 is wound in a roll. It is more preferably 0.015 μm or more, and the upper limit is preferably 0.030 μm or less from the viewpoint of suppressing an increase in haze value.

In the protective film 10, the difference between Rq _2.5 and Rq _0.25 (Rq _2.5 −Rq _0.25 ) is preferably 0.010 μm or less. If this difference is 0.010 μm or less, the haze value of the protective film 10 does not become too high due to the unevenness of the surface 11A, and the deterioration of the transparency of the protective film 10 can be suppressed. More preferably, this difference is 0.008 μm or less.

In the protective film 10, the maximum height Ry measured with a cutoff value of 0.25 mm on the surface 11A of the light-transmitting functional layer 11 was _0.25 , and the maximum height Ry measured with a cutoff value of 2.5 mm was 2.5 mm _{. 5} is 0.05 μm or more and 0.25 μm or less, and the difference between the maximum height Ry _2.5 and the maximum height Ry _0.25 (Ry _2.5 −Ry _0.25 ) is 0.100 μm or less It is preferable that If both Ry _0.25 and Ry _2.5 of the surface 11A are 0.05 μm or more, it is not extremely smooth, so when the protective film 10 is wound in a roll, the protective film 10 can be stuck to each other. can suppress sticking. In addition, both Ry _0.25 and Ry _2.5 of the surface 11A are 0.25 μm or less, and the difference between Ry _2.5 and Ry _0.25 (Ry _2.5 −Ry _0.25 ) However, if the thickness is 0.100 μm or less, the haze value of the protective film does not become too high due to the unevenness of the surface 11A, and the deterioration of the transparency of the protective film 10 can be suppressed.

The maximum height Ry is defined as N Ry′ obtained by dividing the roughness curve of the evaluation length N times the sampling length equal to the cutoff value into N equal parts and obtaining the maximum height Ry′ for each section. is the arithmetic mean of In the above Rq, since Rq' itself is an average value, if there is an extremely large convex portion on the surface of the light-transmitting functional layer, it will be flattened. On the other hand, although Ry is the arithmetic mean value of Ry', Ry' itself is not the mean value. appears. Therefore, Ry is measured in addition to Rq. Also, since Ry is the arithmetic average value of the maximum height Ry' for each section, it is greatly affected by the cutoff value (evaluation length) and needle feeding speed. Therefore, Ry is measured with cutoff values of 0.25 mm and 2.5 mm. Furthermore, in order to define the smoothness of the surface 11A, the difference between Ry _2.5 and Ry _0.25 (Ry _2.5 −Ry _0.25 ) is calculated.

Both Ry _0.25 and Ry _2.5 are measured using a surface roughness measuring instrument in accordance with JIS B0601: 1994 under the same measurement conditions as those for Rq _0.25 and Rq _2.5 . It can be measured according to the measurement conditions.

The lower limits of Ry _0.25 and Ry _2.5 are both 0.08 μm or more from the viewpoint of suppressing sticking between protective films 10 when the protective film 10 is wound in a roll. More preferably, the upper limit is 0.20 μm or less for each from the viewpoint of suppressing an increase in haze value. In addition, the difference between Ry _2.5 and Ry _0.25 (Ry _2.5 −Ry _0.25 ) is such that the haze value of the protective film does not become too high due to the unevenness of the surface 11A, and the transparency of the protective film 10 is maintained. From the viewpoint of suppressing the decrease, it is more preferably 0.10 μm or less.

In the protective film 10, the ten-point average roughness Rz _2.5 measured with a cutoff value of 2.5 mm on the surface 11A of the light-transmitting functional layer 11 and the ten-point average roughness measured with a cutoff value of 0.25 mm It is preferable that the difference (Rz _2.5 −Rz _0.25 ) of height Rz _0.25 is 0.050 μm or less. If this difference is 0.050 μm or less, the haze value of the protective film 10 does not become too high due to the unevenness of the surface 11A, and the deterioration of the transparency of the protective film 10 can be suppressed. This difference is more preferably 0.030 μm or less.

The ten-point average roughness Rz is obtained by dividing the roughness curve of the evaluation length N times the sampling length equal to the cutoff value into N equal parts, and the average altitude of valley bottoms of the first to fifth depths. Since Rz is the average of the heights and depths of the first to fifth ranks, it is greatly affected by the cutoff value (evaluation length) and needle feed speed. Therefore, Rz is measured with cutoff values of 0.25 mm and 2.5 mm. In addition, the difference (Rz _2.5 −Rz _0.25 ) between Rz _2.5 and Rz _0.25 is calculated to define the smoothness of the surface 11A.

Both Rz _0.25 and Rz _2.5 are measured using a surface roughness measuring instrument in accordance with JIS B0601: 1994 under the same measurement conditions as those for Rq _0.25 and Rq _2.5 . It can be measured according to the measurement conditions.

In the protective film 10, the surface 11A of the light transmissive functional layer 11 preferably has an arithmetic mean roughness Ra of 0.010 μm or more and 0.020 μm or less. If the Ra is 0.010 μm or more, it is not too smooth, so that the protective film 10 can be prevented from sticking to each other when the protective film 10 is wound into a roll, and the Ra is 0.020 μm or less. If so, the haze value of the protective film 10 does not become too high due to the unevenness of the surface 11A, and the deterioration of the transparency of the protective film 10 can be suppressed. The lower limit of Ra is more preferably 0.012 μm or more, and the upper limit of Ra is more preferably 0.018 μm or less.

The arithmetic average roughness Ra is a value obtained by integrating the absolute values of the elevations of the peaks and valleys of the roughness curve of the evaluation length and dividing them by the evaluation length to obtain a uniform elevation. Since Ra takes the absolute value of each altitude, it is less affected by the cutoff value (evaluation length) and needle feed speed. Therefore, Ra may be measured with cutoff values of 0.25 mm and 2.5 mm, respectively, but Ra may be measured using either cutoff of 0.25 mm and 2.5 mm. .

The above Ra can be measured using a surface roughness measuring instrument in accordance with JIS B0601:1994 under the same measurement conditions as those for Rq _0.25 and Rq _2.5 .

From the viewpoint of thinning the protective film 10, the thickness of the protective film 10 is preferably less than 40 μm. The thickness of the protective film 10 is obtained by photographing the cross section of the protective film 10 using a scanning electron microscope (SEM), measuring the thickness of the protective film 10 at 20 points in the image of the cross section, and calculating the thickness at the 20 points. Average value. From the viewpoint of thinning the protective film 10, the thickness of the protective film 10 is more preferably less than 21 μm, even more preferably less than 15 μm, and most preferably less than 10 μm.

The protective film 10 preferably has a haze value (total haze value) of less than 0.5%. By setting the haze value of the protective film 10 to less than 0.5%, a low haze value can be achieved, and whitening of the screen can be suppressed when the protective film 10 is used in a mobile terminal. The haze value can be measured using a haze meter (product name "HM-150", manufactured by Murakami Color Research Laboratory) in accordance with JIS K7136:2000. The haze value of the protective film 10 is a value obtained when the release film described later is peeled off and the protective film 10 alone is measured, and is the arithmetic mean value of three measurements. The haze value of protective film 10 is measured by allowing light to enter protective film 10 from the core layer 12 side. The upper limit of the haze value of the protective film 10 is more preferably 0.3% or less, and even more preferably 0.2% or less.

The protective film 10 preferably has a total light transmittance of 90% or more. By setting the total light transmittance of protective film 10 to 90% or more, protective film 10 having excellent light transmittance can be provided. The total light transmittance can be measured using a haze meter (product name “HM-150”, manufactured by Murakami Color Research Laboratory) in accordance with JIS K7361:1997. The total light transmittance of the protective film 10 is the value when the release film described later is peeled off and the protective film 10 alone is measured. do. The total light transmittance of the protective film 10 is measured by making light enter the protective film 10 from the core layer 12 side. More preferably, the lower limit of the total structural transmittance of the protective film 10 is 91% or more.

The protective film 10 preferably has a transmittance of 7% or less for light with a wavelength of 380 nm. By setting the transmittance of light in this wavelength region in the protective film 10 to 7% or less, when the protective film 10 is used in mobile terminals such as smartphones and tablet terminals, the polarizer is exposed to ultraviolet rays and deteriorates. can be suppressed. The light transmittance can be measured using a spectrophotometer (product name “UV-2450” manufactured by Shimadzu Corporation). The light transmittance of the protective film 10 at a wavelength of 380 nm is the value when the release film described later is peeled off and the protective film 10 alone is measured, and the arithmetic mean of the values obtained by three measurements. value. The transmittance of the protective film 10 for light with a full wavelength of 380 nm is measured by making the light enter the protective film 10 from the core layer 12 side. More preferably, the upper limit of the transmittance of light with a wavelength of 380 nm of the protective film 10 is 5% or less.

The tensile breaking strength of the protective film 10 is preferably 8 N/10 mm or more in order to obtain excellent toughness. The tensile breaking strength of the protective film 10 is measured by pulling the protective film at a test speed of 100 mm / min with a width of 25 mm and a distance between chucks of 80 mm using a Tensilon universal tester in accordance with JIS-K7161-1:2014. The stress applied to the protective film when the protective film breaks is taken as the tensile breaking strength. The tensile strength at break of the protective film 10 is the value when the release film described later is peeled off and the protective film 10 alone is measured, and the arithmetic mean value of the values obtained by three measurements. . The tensile breaking strength of the protective film 10 is preferably 10 N/10 mm or more.

The moisture permeability of the protective film 10 is preferably 100 g/(m ² ·24 h) or less. If the moisture permeability of the protective film 10 is 100 g/(m ² · 24 h) or less, when the protective film 10 is placed in a moist and hot environment, moisture does not easily pass through the protective film, and deterioration of the polarizer is prevented. can be suppressed. The term “moisture permeability” as used herein refers to a protective film measured under an atmosphere of 40° C. and 90% relative humidity by a method conforming to the moisture permeability test method (cup method) described in JIS Z0208-1976. It means the amount of water vapor passing through in 24 hours (g/(m ² ·24h)). In addition, the moisture permeability of the protective film 10 is the value when the release film described later is peeled off and the protective film 10 alone is measured, and the arithmetic mean value of the values obtained by three measurements. do. More preferably, the upper limit of the moisture permeability of the protective film 10 is 80 g/(m ² ·24 h) or less.

The protective film 10 may be cut into a desired size, or may be in the form of a roll. When the protective film 10 is cut to a desired size, the size of the protective film is not particularly limited. It is appropriately determined according to the size of the display surface of the image display device. Specifically, the size of the protective film 10 may be, for example, 1 inch or more and 500 inches or less.

<<Light transmissive functional layer>>
The light-transmitting functional layer may have a single-layer structure, or may have a multi-layer structure in which two or more light-transmitting functional layers are laminated. The light-transmissive functional layer 11 shown in FIG. 1 has a multi-layer structure in which the light-transmissive functional layer 11 consists of two layers. Specifically, it is composed of a core layer 12 and a hard coat layer 13 provided on one surface of the core layer 12 . In FIG. 1 , the surface of the hard coat layer 13 is the surface 11A of the light-transmitting functional layer 11 . In addition, when the light-transmitting functional layer has a multi-layer structure of two or more layers, the interface between each light-transmitting functional layer may not necessarily be clear. If the interfaces between layers are not clear, it can be determined that the light-transmitting functional layer is composed of two or more layers having different functions by analyzing the components of each layer. When the light-transmitting functional layer has a multi-layered structure of two or more layers, the functions of each layer may be the same or different.

The film thickness of the light-transmissive functional layer 11 is preferably 5 μm or more and 40 μm or less. If the film thickness of the light-transmitting functional layer 11 is 5 μm or more, the breaking strength and moisture permeability can be optimized. , and an increase in manufacturing cost can be suppressed. The film thickness of the light-transmissive functional layer 11 is measured by the same method as for the film thickness of the protective film 10 . When the light-transmitting functional layer has a multi-layer structure, the "film thickness of the light-transmitting functional layer" means the total thickness of each light-transmitting functional layer. The lower limit of the film thickness of the light-transmitting functional layer 11 is more preferably 8 μm or more, and the upper limit of the film thickness of the light-transmitting functional layer 11 is more preferably 30 μm or less.

<Core layer>
The core layer 12 is a layer that imparts toughness instead of the substrate in the protective film 10 and is the thickest layer in the protective film 10 . In addition, the core layer 12 has a function of providing the protective film 10 with the above-described transmittance performance and moisture permeability within a desired range. Specifically, the film thickness of the core layer 12 is preferably 5 μm or more and 40 μm or less. By setting the film thickness of the core layer 12 within this range, it is possible to suppress a significant decrease in the strength of the core layer 12, and to easily perform the coating of the core layer composition for forming the core layer 12. Further, deterioration of workability (in particular, chipping resistance) due to the core layer 12 being too thick does not occur. The film thickness of the core layer 12 is measured by the same method as for the protective film 10 . The upper limit of the film thickness of the core layer 12 is more preferably 30 μm or less, even more preferably 20 μm or less, and most preferably 10 μm or less.

The core layer 12 preferably contains a resin made of a polymer of an ionizing radiation-polymerizable compound. The reason why it is preferable to use a resin composed of a polymer of an ionizing radiation polymerizable compound as the resin forming the core layer 12 is that a solvent-drying type resin such as a thermoplastic resin is used instead of this resin. This is because, if the core layer is formed by pressing, the core layer becomes too soft and the hardness of the protective film becomes low.

The core layer 12 may be a layer composed only of the above resins, but may contain additives to exhibit desired functions. The additive is not particularly limited, but since mobile devices are often used outdoors and the polarizer is easily exposed to ultraviolet rays and deteriorates, the additive absorbs the ultraviolet rays and suppresses the deterioration of the polarizer due to the ultraviolet rays. Ultraviolet absorbers (UVA) are preferred. In addition, the core layer 12 may contain inorganic particles such as silica particles, talc, or organic fibers as additives in order to increase dimensional stability and breaking strength. Cellulose nanofibers can be suitably used as organic fibers. When the core layer 12 contains an additive such as an ultraviolet absorber, the resin functions as a binder resin.

(resin)
The resin contained in the core layer 12 is, as described above, a resin composed of a polymer of an ionizing radiation-polymerizable compound. The ionizing radiation polymerizable compound has at least one ionizing radiation polymerizable functional group. As used herein, the term "ionizing radiation-polymerizable functional group" refers to a functional group capable of undergoing a polymerization reaction upon exposure to ionizing radiation. Examples of ionizing radiation-polymerizable functional groups include ethylenically unsaturated groups such as (meth)acryloyl groups, vinyl groups, and allyl groups. In addition, the "(meth)acryloyl group" in this specification is meant to include both "acryloyl group" and "methacryloyl group". Examples of the ionizing radiation irradiated when polymerizing the ionizing radiation-polymerizable compound include visible light, ultraviolet rays, X-rays, electron beams, α rays, β rays, and γ rays.

When obtaining a core layer having excellent toughness and moderate flexibility, it is preferable to use, for example, an ionizing radiation-polymerizable oligomer or an ionizing radiation-polymerizable prepolymer as the ionizing radiation-polymerizable compound. Ionizing radiation polymerizable oligomers or ionizing radiation polymerizable prepolymers include urethane (meth)acrylates, polyester (meth)acrylates, epoxy (meth)acrylates, melamine (meth)acrylates, polyfluoroalkyl (meth)acrylates, silicone (meth)acrylates, and silicone (meth)acrylates. ) oligomers or prepolymers such as acrylates. These ionizing radiation-polymerizable oligomers or ionizing radiation-polymerizable prepolymers may be used singly or in combination of two or more.

The weight average molecular weight of the ionizing radiation-polymerizable oligomer or ionizing radiation-polymerizable prepolymer is preferably 1,000 or more and 20,000 or less. The lower limit of the weight average molecular weight of the ionizing radiation-polymerizable oligomer or ionizing radiation-polymerizable prepolymer is more preferably 3000 or more, and the upper limit is more preferably 12000 or less, and even more preferably 10000 or less. As used herein, the "weight average molecular weight" is a value obtained by dissolving in a solvent such as tetrahydrofuran (THF) and converting to polystyrene by a conventionally known gel permeation chromatography (GPC) method.

In order to adjust the hardness and viscosity of the composition, the resin of the core layer 12 is formed from a cured mixture containing an ionizing radiation-polymerizable oligomer or an ionizing radiation-polymerizable prepolymer and a monofunctional ionizing radiation-polymerizable monomer. You may A monofunctional ionizing radiation-polymerizable monomer is a compound having one ionizing radiation-polymerizable functional group in the molecule. Examples of monofunctional ionizing radiation polymerizable monomers include hydroxyethyl acrylate (HEA), glycidyl methacrylate, methoxypolyethylene glycol (meth)acrylate, isostearyl (meth)acrylate, 2-acryloyloxyethyl succinate and the like.

(Ultraviolet absorber)
The ultraviolet absorber has a function of absorbing ultraviolet rays. Although the ultraviolet absorber is not particularly limited, examples of the ultraviolet absorber include triazine-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, and benzotriazole-based ultraviolet absorbers.

Examples of the triazine-based ultraviolet absorber include 2-(2-hydroxy-4-[1-octyloxycarbonylethoxy]phenyl)-4,6-bis(4-phenylphenyl)-1,3,5-triazine , 2-[4-[(2-hydroxy-3-dodecyloxypropyl)oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 2 ,4-bis[2-hydroxy-4-butoxyphenyl]-6-(2,4-dibutoxyphenyl)-1,3,5-triazine, 2-[4-[(2-hydroxy-3-tridecyl oxypropyl)oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, and 2-[4-[(2-hydroxy-3-(2 '-ethyl)hexyl)oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine and the like.

Examples of commercially available triazine-based ultraviolet absorbers include TINUVIN460 (manufactured by BASF Japan) and LA-46 (manufactured by ADEKA).

Examples of the benzophenone-based ultraviolet absorbers include 2-hydroxybenzophenone, 2,4-dihydroxybenzophenone, 2,2′-dihydroxy-4,4′-dimethoxybenzophenone, 2,2′,4,4′-tetrahydroxy Benzophenone, 2-hydroxy-4-methoxybenzophenone, hydroxymethoxybenzophenone sulfonic acid and its trihydrate, sodium hydroxymethoxybenzophenone sulfonate and the like. Examples of commercially available benzophenone-based UV absorbers include CHMASSORB81/FL (manufactured by BASF).

Examples of the benzotriazole-based ultraviolet absorbers include 2-ethylhexyl-3-[3-tert-butyl-4-hydroxy-5-(5-chloro-2H-benzotriazol-2-yl)phenyl]propionate, 2 -(2H-benzotriazol-2-yl)-6-(linear and branched dodecyl)-4-methylphenol, 2-[5-chloro(2H)-benzotriazol-2-yl]-4-methyl- 6-(tert-butyl)phenol, 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2′-hydroxy-3′,5′-di-tert-butylphenyl)benzotriazole, 2-(2′-hydroxy-3′-tert-butyl-5′-methylphenyl)benzotriazole, 2- (2′-hydroxy-3′,5′-di-tert-butylphenyl)-5-chlorobenzotriazole, 2-(2′-hydroxy-3′-(3″,4″,5″, 6''-tetrahydrophthalimidomethyl)-5'-methylphenyl)benzotriazole, 2,2-methylenebis(4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol--yl ) phenol), and 2-(2′-hydroxy-3′-tert-butyl-5′-methylphenyl)-5-chlorobenzotriazole.

Examples of commercially available benzotriazole-based ultraviolet absorbers include KEMIISORB71D, KEMIISORB79 (both manufactured by Chemipro Kasei), JF-80, JAST-500 (both manufactured by Johoku Kagaku), and ULS-1933D. (manufactured by Ippo), RUVA-93 (manufactured by Otsuka Chemical Co., Ltd.), and the like.

As the ultraviolet absorber, a triazine-based ultraviolet absorber is particularly preferably used. TINUVIN400 is particularly preferably used from the viewpoint of properties and the like.

Although the content of the ultraviolet absorber is not particularly limited, it is preferably 1 part by mass or more and 6 parts by mass or less with respect to 100 parts by mass of the resin solid content of the core layer. When the content of the ultraviolet absorbent in the core layer is within this range, the ultraviolet absorbent can be sufficiently contained in the core layer, and significant coloration and strength reduction of the core layer can be suppressed. A more preferable lower limit for the content of the ultraviolet absorber is 2 parts by mass or more, and a more preferable upper limit is 5 parts by mass or less.

The core layer 12 may optionally contain other components such as lubricants, plasticizers, fillers, fillers, antistatic agents, anti-blocking agents, cross-linking agents, light stabilizers, colorants such as dyes and pigments. may be contained.

<Hard coat layer>
The hard coat layer 13 is a layer having a hardness of "H" or higher in a pencil hardness test specified by JIS K5600-5-4:1999. Since the hardness of the protective film 10 can be improved by setting the pencil hardness to "H" or higher, the durability can be improved. The pencil hardness of the protective film 10 is measured by using an ultraviolet curable adhesive and applying the protective film 10 to, for example, a polyethylene terephthalate base material (for example, Cosmoshine A4300 with a thickness of 100 μm or Cosmoshine A4100 with a thickness of 100 μm manufactured by Toyobo Co., Ltd.). ) is a value measured in a state of being adhered to a substrate such as Moreover, when measuring the pencil hardness, the pencil is moved at a speed of 1 mm/sec while a load of 750 g is applied to the pencil. In addition, when measuring the pencil hardness, a plurality of pencils with different hardness are used, but the pencil hardness test is performed 5 times for each pencil, and the surface of the protective film is measured under a fluorescent light at least 4 times out of 5 times. When no scratches were visually observed on the surface of the protective film when observed through transmission, it is judged that the surface of the protective film was not scratched by the pencil with this hardness. From the viewpoint of the toughness of the light transmissive functional layer 11 and the prevention of curling, the upper limit of the pencil hardness of the surface of the hard coat layer 13 is preferably about 4H.

The hard coat layer 13 can be composed of a resin made of at least a cured product (polymer) of an ionizing radiation polymerizable compound. The hard coat layer 13 may contain inorganic particles and a leveling agent in addition to the resin. When the hard coat layer 13 contains inorganic particles, the resin functions as a binder resin.

(resin)
The resin contained in the hard coat layer 13 includes a cured ionizing radiation polymerizable compound as described above. The resin may contain a solvent-drying type resin in addition to the cured product of the ionizing radiation polymerizable compound.

Examples of the ionizing radiation-polymerizable compound include ionizing radiation-polymerizable monomers, ionizing radiation-polymerizable oligomers, and ionizing radiation-polymerizable prepolymers, and these can be appropriately adjusted and used. As the ionizing radiation-polymerizable compound, a combination of an ionizing radiation-polymerizable monomer and an ionizing radiation-polymerizable oligomer or ionizing radiation-polymerizable prepolymer is preferable.

(Ionizing radiation polymerizable monomer)
As the ionizing radiation-polymerizable monomer, a polyfunctional monomer having two or more ionizing radiation-polymerizable functional groups (that is, bifunctional) is preferable.

Examples of ionizing radiation-polymerizable monomers include ionizing radiation-polymerizable monomers into which modifying groups such as alkylene oxide-modified, urethane-modified, epoxy-modified, and alkoxy-modified are introduced. Among these, alkylene oxide-modified (meth)acrylates are preferable from the viewpoint of obtaining a protective film having good releasability from a release film, tackiness, and high mechanical strength. Alkylene oxides include methylene oxide, ethylene oxide, propylene oxide, butylene oxide and the like.

Among these, ethylene oxide-modified (EO-modified) acrylate and propylene oxide-modified (PO-modified) acrylate are more preferable from the viewpoint of obtaining good peelability and scratch resistance. Furthermore, among these, PO-modified acrylates are particularly preferable because they have a good balance between releasability and scratch resistance.

(ionizing radiation polymerizable oligomer)
Ionizing radiation polymerizable oligomers include oligomers such as urethane (meth)acrylate, polyester (meth)acrylate, epoxy (meth)acrylate, melamine (meth)acrylate, polyfluoroalkyl (meth)acrylate, and silicone (meth)acrylate. mentioned.

(Ionizing radiation polymerizable prepolymer)
The weight average molecular weight of the ionizing radiation polymerizable prepolymer is preferably 10,000 or more and 80,000 or less, more preferably 10,000 or more and 40,000 or less. If the weight-average molecular weight exceeds 80,000, the coating aptitude is lowered due to the high viscosity, and the appearance of the resulting protective film may be deteriorated. Ionizing radiation polymerizable prepolymers include prepolymers such as urethane (meth)acrylate, polyester (meth)acrylate, epoxy (meth)acrylate, melamine (meth)acrylate, polyfluoroalkyl (meth)acrylate, and silicone (meth)acrylate. etc.

Among these, the urethane acrylate prepolymer is preferable from the viewpoint of improving the interlayer adhesion with the core layer 12 .

A suitable combination of the ionizing radiation-polymerizable monomer and the ionizing radiation-polymerizable prepolymer is that the ionizing radiation-polymerizable monomer is an EO-modified acrylate and the ionizing radiation-polymerizable prepolymer is a urethane acrylate prepolymer.

The ionizing radiation-polymerizable monomer and the ionizing radiation-polymerizable prepolymer are preferably contained at a ratio of 90:10 to 70:30. By containing the ionizing radiation-polymerizable monomer and the ionizing radiation-polymerizable prepolymer in this range, the flexibility and toughness can be improved without lowering the hardness.

<Inorganic particles>
Inorganic particles are components for improving the mechanical strength and pencil strength of the light transmissive functional layer 11. Examples of inorganic particles include silica (SiO ₂ ) particles, alumina particles, titania particles, tin oxide particles, Inorganic oxide particles such as antimony-doped tin oxide (abbreviation: ATO) particles and zinc oxide particles are included. Among these, silica particles are preferred from the viewpoint of further increasing hardness, and among silica particles, irregularly shaped silica particles are more preferred. When spherical silica particles are used, the smaller the particle size of the spherical silica particles, the higher the hardness of the light-transmitting functional layer. In contrast, irregularly shaped silica particles are not as small as the smallest commercially available spherical silica particles, but can achieve hardness equivalent to this spherical silica.

The average primary particle size of the irregularly shaped silica particles is preferably 1 nm or more and 100 nm or less. Even if the average primary particle size of the irregularly shaped silica particles is within this range, hardness equivalent to that of spherical silica having an average primary particle size of 1 nm or more and 45 nm or less can be achieved. The average particle size of the irregularly shaped silica particles was obtained by randomly extracting 10 irregularly shaped silica particles from a screen obtained by imaging the cross section of the hard coat layer at a magnification of 200,000 with a transmission electron microscope (TEM). After calculating, the arithmetic mean value is taken as the average particle size. The particle diameter of each irregularly shaped silica particle is the average value of the longest diameter and the shortest diameter in the cross section of the particle.

The content of the inorganic particles in the hard coat layer 13 is preferably 20% by mass or more and 70% by mass or less. If the content of the inorganic particles is less than 20% by mass, it becomes difficult to ensure sufficient hardness. Adhesion to the binder resin is deteriorated, and the hardness of the hard coat layer is lowered.

As the inorganic particles, it is preferable to use inorganic particles (reactive inorganic particles) having ionizing radiation-polymerizable functional groups on their surfaces. Such inorganic particles having ionizing radiation-polymerizable functional groups on their surfaces can be produced by surface-treating inorganic particles with a silane coupling agent or the like. Methods for treating the surface of inorganic particles with a silane coupling agent include a dry method in which the silane coupling agent is sprayed onto the inorganic particles, and a wet method in which the inorganic particles are dispersed in a solvent and then the silane coupling agent is added for reaction. etc.

<Leveling agent>
A leveling agent means an additive that smoothes the surface by preventing defects such as cissing, dents, pinholes, and peeling caused by non-uniform surface tension of the hard coat layer. The leveling agent is not particularly limited, but examples thereof include compounds having a polyether group, polyurethane group, epoxy group, carboxyl group, acrylate group, methacrylate group, carbinol group or hydroxyl group. The leveling agent may have a polyether group, a polyurethane group, an epoxy group, a carboxyl group, an acrylate group, a methacrylate group, a carbinol group, or a hydroxyl group at the end (one end, both ends) of the main chain. It may be present in the chain, or may be present in the end of the main chain or in the side chain. The leveling agent is not particularly limited as long as it is a compound having a polyether group, polyurethane group, epoxy group, carboxyl group, acrylate group, methacrylate group, carbinol group or hydroxyl group. /fluorine mixed leveling agents, acrylic, methacrylic and aromatic leveling agents.

If the leveling agent containing silicon atoms is added in a large amount, the recoating property may be deteriorated and coating defects such as repelling may increase. Commercially available fluorine-based leveling agents include, for example, F-568, F-556, F-554 and F-553 (all manufactured by DIC).

The content of the leveling agent is 100 parts by mass of the ionizing radiation polymerizable compound in the curable composition for forming the hard coat layer 13 (hereinafter, this composition is referred to as the "hard coat layer composition"). On the other hand, it is preferably 0.01 parts by mass or more and 5 parts by mass or less. By setting the content of the leveling agent within this range, it is possible to obtain a surface of the hard coat layer 13 with more excellent flatness.

Protective film 10 may be incorporated in a laminate comprising a release film releasably provided directly on surface 10A of protective film 10 . However, when the protective film 10 is used, the release film is peeled off from the surface 11A of the light transmissive functional layer 11 .

<<<Laminate>>>
A laminate 20 shown in FIG. 3 includes a protective film 10 and a release film 30 that is detachably provided directly on the surface 10A of the protective film 10 (the surface 11A of the light-transmitting functional layer 11). As used herein, "directly provided" means that the release film is in direct contact with the surface of the protective film.

In the laminate 20, as shown in FIG. 4A, after irradiating the laminate 20 with light having a wavelength of 200 nm or more and 500 nm or less from the release film 30 side so that the integrated light amount becomes 1000 mJ/cm ² . As shown in FIG. 4B, the release film 30 was peeled off from the light-transmitting functional layer 11 in an environment of 25° C. and 60% relative humidity at a peel speed of 300 m/min in a direction of 180°. In this case, the peel strength of the release film 30 is preferably 20 mN/25 mm or more and 200 mN/25 mm or less. If the peel strength of the release film 30 after irradiation with the light is 20 mN / 25 mm or more, peeling can be suppressed during roll winding or in a subsequent process, and if it is 200 mN / 25 mm or less, the release film When the release film 30 is peeled off, it is possible to suppress the so-called break-up phenomenon in which the release film 30 is torn, and breakage of the release film 30 . The peel strength of the release film 30 is the arithmetic mean value of the values measured three times. The lower limit of the peel strength of the release film 30 is more preferably 30 mN / 25 mm or more from the viewpoint of suppressing peeling during roll winding or in a post-process, and the upper limit is the separation phenomenon or breakage of the release film 30. from the viewpoint of suppressing, it is preferably 180 mN/25 mm or less. In the above description, the reason why the light is irradiated so that the integrated amount of light is 1000 mJ/cm ² is that the photo-curing adhesive used for attaching the laminate 20 to the polarizer 41 described below is cured. This is because this level of light is necessary.

<< release film >>
The release film 30 functions as a base material when the protective film 10 is formed, but is peeled off from the surface 11A of the light-transmitting functional layer 11 when the protective film 10 is used.

Root mean square measured with a cutoff value of 0.25 mm for the surface 30A of the release film 30 that was in contact with the light-transmitting functional layer 11 after the release film 30 was peeled off by irradiating the laminate 20 with the light. Roughness Rq _0.25 , root mean square roughness Rq _2.5 measured with a cutoff value of 2.5 mm, difference between Rq _2.5 and Rq _0.25 (Rq _2.5 - Rq _0.25 ), the maximum height Ry _0.25 measured with a cutoff value of 0.25 mm, the maximum height Ry _2.5 measured with a cutoff value of 2.5 mm, the above Ry _2.5 and the above Ry _0.25 Difference (Ry _2.5 −Ry _0.25 ), ten point average roughness Rz _2.5 measured with a cutoff value of 2.5 mm and ten point average roughness Rz ₀ measured with a cutoff value of 0.25 mm The difference (Rz _2.5 -Rz _0.25 ) of _.25 and the arithmetic mean roughness Ra of the surface 11A of the light transmissive functional layer 11 are the above Rq _0.25 , the above Rq _2.5 , the above Rq 2.5 _{. 5} and the above Rq _0.25 (Rq _2.5 −Rq _0.25 ), the above Ry _0.25 , the above Ry _2.5 , the above Ry _2.5 and the above Ry _0.25 difference (Ry 2.5 ) _{. 5} −Ry _0.25 ), the difference between the above Rz _2.5 and the above Rz _0.25 (Rz _2.5 −Rz _0.25 ), which is the same as the above Ra, so the description will be omitted here. . The Rq of _2.5 , etc. of the surface 30A of the release film 30 that was in contact with the light-transmitting functional layer 11 is measured by the same method as the Rq of _0.25 , etc. of the surface 11A of the light-transmitting functional layer 11. shall be

As for the release film 30, both the above Rq _0.25 and the above Rq _2.5 on the surface 11A of the light transmissive functional layer 11 after peeling the release film 30 from the light transmissive functional layer 11 are 0.035 μm. The film is not particularly limited as long as it satisfies the following conditions. For example, a resin film having an untreated surface on at least one side is preferably used. In this case, the untreated surface of the resin film is used as surface 30A. A resin film having an untreated surface on at least one side has excellent releasability from the light-transmitting functional layer and is inexpensive, so that the manufacturing cost of the laminate of the present embodiment can be kept low. For example, when a release film coated with a silicon-containing Si-based release agent or the like is used as the release film, the release property of the release film is good, while the light-transmitting function When the layer is transferred, the component of the release agent may be transferred to the light-transmitting functional layer side, and the unevenness of the surface of the light-transmitting functional layer may become large. On the other hand, when a resin film having an untreated surface on at least one side is used as the release film 30, there is no component transferred to the light-transmitting functional layer 11 when the release film 30 is peeled off. The unevenness of the surface of the layer is reduced. As used herein, "a resin film having at least one untreated surface" means a resin film having at least one untreated surface. Therefore, the untreated surface of the resin film having an untreated surface on at least one side does not contain a release agent for enhancing the releasability.

Although the thickness of the release film 30 is not particularly limited, it is preferably 25 μm or more and 100 μm or less. If the thickness of the release film 30 is 25 μm or more, the effect of curing shrinkage of the light-transmitting functional layer is less likely to appear when the light-transmitting functional layer is cured with light, and wrinkles are less likely to occur in the release film. Moreover, if the thickness of the release film 30 is 100 μm or less, the manufacturing cost can be suppressed. The thickness of the release film 30 means the arithmetic mean value of the thickness of the release film 30 measured at 10 points using a thickness measuring device (product name “Digimatic Indicator IDF-130” manufactured by Mitutoyo Corporation). shall be More preferably, the lower limit of the release film 30 is 30 μm or more, and the upper limit of the release film 30 is 80 μm or less.

Examples of the release film 30 include cellulose acylate films such as triacetyl cellulose, cycloolefin polymer films, polycarbonate films, acrylic films, and polyester films such as polyethylene terephthalate.

<<Method for producing protective film and laminate>>
Protective film 10 and laminate 20 can be produced, for example, as follows. First, the laminate 20 is formed. Specifically, after preparing the release film 30, as shown in FIG. The composition is applied and dried to form a coating film 15 of the hard coat layer.

The hard coat layer composition contains an ionizing radiation-polymerizable compound, and may optionally contain the inorganic particles, the leveling agent, the solvent, and the polymerization initiator. Further, the hard coat layer composition may contain conventionally known dispersants, surfactants, Silane coupling agents, thickeners, anti-coloring agents, coloring agents (pigments, dyes), antifoaming agents, flame retardants, UV absorbers, adhesion promoters, polymerization inhibitors, antioxidants, surface modifiers, A lubricant or the like may be added.

<Solvent>
Examples of solvents include alcohols (methanol, ethanol, propanol, isopropanol, n-butanol, s-butanol, t-butanol, benzyl alcohol, PGME, ethylene glycol, etc.), ketones (acetone, methyl ethyl ketone (MEK), cyclohexanone , methyl isobutyl ketone, diacetone alcohol, cycloheptanone, diethyl ketone, etc.), ethers (1,4-dioxane, dioxolane, diisopropyl ether dioxane, tetrahydrofuran, etc.), aliphatic hydrocarbons (hexane, etc.), alicyclic Hydrocarbons (cyclohexane, etc.), aromatic hydrocarbons (toluene, xylene, etc.), halogenated carbons (dichloromethane, dichloroethane, etc.), esters (methyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, lactic acid ethyl, etc.), cellosolves (methyl cellosolve, ethyl cellosolve, butyl cellosolve, etc.), cellosolve acetates, sulfoxides (dimethyl sulfoxide, etc.), amides (dimethylformamide, dimethylacetamide, etc.), or mixtures thereof.

<Polymerization initiator>
The polymerization initiator is a component that is decomposed by light or heat to generate radicals to initiate or advance polymerization (crosslinking) of the ionizing radiation-polymerizable compound. Polymerization initiators used in the composition for the light-transmitting functional layer include photopolymerization initiators (for example, photoradical polymerization initiators, photocationic polymerization initiators, and photoanion polymerization initiators).

Examples of the radical photopolymerization initiator include benzophenone-based compounds, acetophenone-based compounds, acylphosphine oxide-based compounds, titanocene-based compounds, oxime ester-based compounds, benzoin ether-based compounds, and thioxanthone.

Commercially available photoradical polymerization initiators include, for example, IRGACURE184, IRGACURE369, IRGACURE379, IRGACURE651, IRGACURE819, IRGACURE907, IRGACURE2959, IRGACURE OXE01, Lucirin TPO (all manufactured by BASF Japan), NCI-930 ( ADEKA), SPEEDCURE EMK (manufactured by Nihon SibelHegner), benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether (all manufactured by Tokyo Chemical Industry Co., Ltd.), and the like.

Examples of the photocationic polymerization initiator include aromatic diazonium salts, aromatic iodonium salts, aromatic sulfonium salts and the like. Commercially available photo cationic polymerization initiators include, for example, Adeka Optomer SP-150 and Adeka Optomer SP-170 (both manufactured by ADEKA).

The content of the polymerization initiator in the hard coat layer composition is preferably 0.5 parts by mass or more and 10.0 parts by mass or less with respect to 100 parts by mass of the ionizing radiation-polymerizable compound. By setting the content of the polymerization initiator within this range, the hard coat performance can be sufficiently maintained, and curing inhibition can be suppressed.

Examples of the method for applying the hard coat layer composition include known coating methods such as spin coating, dipping, spraying, slide coating, bar coating, roll coating, gravure coating, and die coating.

Next, as shown in FIG. 5B, the coating film 15 is irradiated with ionizing radiation such as ultraviolet rays to polymerize (crosslink) the ionizing radiation polymerizable compound, thereby curing the coating film 15 to form a hard coat layer. form 13. Here, if nitrogen purge is performed during curing, the hard coat layer hardens excessively, so it is preferable to harden the hard coat layer without performing nitrogen purge.

When ultraviolet rays are used as the ionizing radiation for curing the hard coat layer composition, ultraviolet rays emitted from ultra-high pressure mercury lamps, high pressure mercury lamps, low pressure mercury lamps, carbon arcs, xenon arcs, metal halide lamps, etc. can be used. As the wavelength of ultraviolet rays, a wavelength range of 190 to 380 nm can be used. Specific examples of the electron beam source include various electron beam accelerators such as Cockcroftwald type, Vandegraft type, resonance transformer type, insulating core transformer type, linear type, dynamitron type, and high frequency type.

After forming the hard coat layer 13 on the release film 30, as shown in FIG. A core layer composition as a functional layer composition is applied and dried to form a coating film 16 of the core layer composition. The core layer composition contains the ionizing radiation-polymerizable compound as described above, and may also contain the UV absorber, the leveling agent, the solvent, and the polymerization initiator, if necessary. The solvent and polymerization initiator to be contained in the core layer composition are the same as the solvent and polymerization initiator described in the section of the hard coat layer composition, and therefore the description thereof is omitted here.

Next, as shown in FIG. 6(B), the coating film 16 is irradiated with ionizing radiation such as ultraviolet rays to polymerize (crosslink) the ionizing radiation polymerizable compound to cure the coating film 16, thereby forming a core layer. form 12; Thereby, the laminate 20 shown in FIG. 3 can be obtained.

In the above description, the coating film 15 is completely cured (fully cured) to form the hard coat layer 13, and then the coating film 16 is completely cured (fully cured) to form the core layer 12. is semi-cured (half-cured), the coating film 16 may be formed on the coating film 15, and then the coating films 15 and 16 may be completely cured (fully cured). "Complete curing" as used herein means that curing does not substantially progress even if further light is irradiated, and "semi-curing" means that curing substantially progresses when ionizing radiation is irradiated. means that

After obtaining the laminate 20, the release film 30 is peeled off from the laminate 20 as shown in FIG. 6(C). Thereby, the protective film 10 having the light transmissive functional layer 11 shown in FIG. 1 can be obtained.

In the present embodiment, both the above Rq _0.25 and the above Rq _2.5 at the surface 11A of the light transmissive functional layer 11 are 0.035 μm or less, so that the surface 11A of the light transmissive functional layer 11 is A uniform and flat protective film 10 having a low haze value can be obtained. Furthermore, since the protective film 10 does not have a substrate, a thin protective film 10 can be obtained. This makes it possible to provide a protective film 10 that is thin and has a low haze value.

<<<polarizing plate>>>
The protective film 10 and the laminate 20 can be incorporated into a polarizing plate and used. FIG. 7 is a schematic configuration diagram of a polarizing plate according to this embodiment. As shown in FIG. 7, the polarizing plate 40 includes a polarizer 41, a laminate 20 bonded to one surface of the polarizer 41 via an adhesive layer 42 made of a cured product of a photocurable adhesive, A protective film 44 such as a triacetylcellulose film (TAC film) or a cycloolefin polymer film is attached to the other surface of the polarizer 41 via an adhesive layer 43 made of a cured photocurable adhesive. there is The polarizer 41 is arranged on the back surface 11B side of the light transmissive functional layer 11 of the protective film 10 opposite to the surface 11A. The adhesive layer 42 is arranged on the surface of the core layer 12 opposite to the surface on the hard coat layer 13 side. Although the polarizing plate 40 shown in FIG. 7 includes the release film 30 , the polarizing plate may be a polarizing plate in which the release film 30 is peeled off from the light-transmissive functional layer 11 .

The polarizer 41 may be a polyvinyl alcohol resin film dyed with iodine or a dichroic dye and uniaxially stretched. As the polyvinyl alcohol-based resin, a saponified polyvinyl acetate-based resin can be used. Polyvinyl acetate-based resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate with other monomers copolymerizable therewith. Other monomers copolymerizable with vinyl acetate include, for example, unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

The polyvinyl alcohol-based resin may be modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used.

<<Photo-curing adhesive>>
The photocurable adhesive for bonding the polarizer 41 and the laminate 20 and the polarizer 41 and the protective film 44 together is an adhesive composition containing a photopolymerizable compound that is irradiated with light having a wavelength of 200 nm or more and 500 nm or less. means an adhesive in the form of A conventionally known UV curable adhesive can be used as the photocurable adhesive.

<<<Manufacturing method of polarizing plate>>>
The polarizing plate 40 can be produced, for example, as follows. First, the laminate 20 and one surface of the polarizer 41 are laminated via a photocurable adhesive so that the core layer 12 of the laminate 20 is in contact with the photocurable adhesive. On the other hand, the other surface of the polarizer 41 and the protective film 44 are laminated via an ultraviolet curable adhesive.

Next, the laminate 20 is irradiated with light having a wavelength of 200 nm or more and 500 nm or less so that the integrated amount of light becomes 1000 mJ/cm ² , and the photocurable adhesive is cured. and a polarizer 41 are bonded together by adhesive layers 42 and 43 . Thereby, the polarizing plate 40 with the release film 30 shown in FIG. 7 is obtained.

Such a polarizing plate 40 can be used by incorporating it into an image display device, for example, as a polarizing plate with the release film 30 peeled off from the polarizing plate 40 . FIG. 8 is a schematic configuration diagram of an image display device according to this embodiment.

<<<Image display device>>>
As shown in FIG. 8 , the image display device 50 mainly includes a display panel 60 for displaying images, a backlight device 70 arranged on the back side of the display panel 60 , and an image display device 70 for viewing from the display panel 60 . The touch panel 80 is arranged on the user's side, and the optically transparent adhesive layer 110 is interposed between the display panel 60 and the touch panel 80 . In this embodiment, since the display panel 60 is a liquid crystal display panel, the image display device 50 includes the backlight device 70. However, depending on the type of display panel (display element), the backlight device 70 may not be provided. It's good.

<<Display Panel>>
As shown in FIG. 8, the display panel 60 includes a polarizing plate 61, a light-transmitting adhesive layer 62, a display element 63, a light-transmitting adhesive layer 64, a light-transmitting adhesive layer 64, a light-transmitting adhesive layer 64, It has a structure in which the polarizing plates 65 are laminated in order. The display panel 60 may include the display element 63 and the polarizing plate 65, and may not include the polarizing plate 61 and the like.

The polarizing plate 61 has a protective film 66, a polarizer 67, and a protective film 68 in this order. The protective films 66, 68 are made of triacetyl cellulose film (TAC film) or cycloolefin polymer film. Since the polarizer 67 is the same as the polarizer 41, description thereof will be omitted here.

The polarizing plate 65 is obtained by peeling the release film 30 from the polarizing plate 40, and other than that, the polarizing plate 65 is the same as the polarizing plate 40, so the description is omitted here.

The display element 63 is a liquid crystal display element. However, the display element 63 is not limited to a liquid crystal display element, and may be, for example, a display element using an organic light emitting diode (OLED), an inorganic light emitting diode, and/or a quantum dot light emitting diode (QLED). A liquid crystal display element has a liquid crystal layer, an alignment film, an electrode layer, a color filter, and the like arranged between two glass substrates.

<<Backlight Device>>
The backlight device 70 illuminates the display panel 60 from the rear side of the display panel 60 . A known backlight device can be used as the backlight device 70, and the backlight device 70 may be either an edge light type backlight device or a direct type backlight device.

<<Touch Panel>>
The touch panel 80 includes a sensor section 90 and a cover glass 100 arranged closer to the observer than the sensor section 90 . The touch panel 80 may include the sensor section 90 and may not include the cover glass 100 .

<Sensor part>
The sensor unit 90 is a portion that functions as a sensor of the touch panel 80 . Although the sensor unit 90 is not particularly limited, for example, a sensor used in a projected capacitive method can be used. The sensor unit 90 shown in FIG. 8 is composed of a base film 91 provided with a patterned conductive layer 92 and a base film 91 provided with a patterned conductive layer 93, and a light-transmitting adhesive layer 94. It has a structure in which it is laminated through

<Base film>
The base film 91 has at least a light transmissive base. Examples of light-transmitting substrates include polyolefin substrates, polycarbonate substrates, polyacrylate substrates, polyester substrates, aromatic polyetherketone substrates, polyethersulfone substrates, polyamide substrates, or glass substrates. etc.

The base film 91 includes a hard coat layer, a high refractive index layer, and a low refractive index layer provided on one surface of the light transmissive base, and a hard coat layer provided on the other surface of the light transmissive base. It may further include a coat layer.

<Conductive layer>
Although the shape of the conductive layers 92 and 93 is not particularly limited, examples thereof include a square shape and a stripe shape. The conductive layers 92 and 93 are connected to terminal portions (not shown) via extraction patterns (not shown). Although the conductive layers 92 and 93 are made of a transparent conductive material in this example, the conductive layers can be made of mesh-like conductive wires. Examples of transparent conductive materials include tin-doped indium oxide (ITO), antimony-doped tin oxide (ATO), zinc oxide, indium oxide ₍ In2O3), aluminum _- doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), oxide metal oxides such as tin, zinc oxide-tin oxide system, indium oxide-tin oxide system, and zinc oxide-indium oxide-magnesium oxide system; Materials for the conductive wire include light-shielding metallic materials such as silver, copper, aluminum, and alloys thereof.

The film thickness of the conductive layers 92 and 93 is appropriately set according to the specification of electric resistance and the like, and is preferably, for example, 10 nm or more and 50 nm or less.

The method of forming the conductive layers 92 and 93 is not particularly limited, and sputtering, vacuum deposition, ion plating, CVD, coating, printing, and the like can be used. Examples of methods for patterning the conductive layer include photolithography.

When the conductive layer is composed of a mesh-like conductor wire, the width of the conductor wire is preferably 1 μm or more and 20 μm or less, more preferably 2 μm or more and 15 μm or less. As a result, the influence of the conducting wire on the image viewed by the observer can be reduced to a negligible level.

When the conductive layer is composed of mesh-like conductors, the conductor layer has, for example, rectangular openings formed by the conductors. The aperture ratio of the conductive layer is appropriately set according to the characteristics of image light emitted from the display device, and is, for example, within the range of 80% or more and 90% or less. In addition, the arrangement pitch of the openings is appropriately set within the range of 100 μm or more and 1000 μm or less according to the desired opening ratio and width of the conductor.

<<adhesion layer>>
The adhesive layer 110 is interposed between the display panel 60 and the touch panel 80 and adhered to both the display panel 60 and the touch panel 80 . Thereby, the display panel 60 and the touch panel 80 are fixed. The adhesive layer 110 is composed of a cured liquid ionizing radiation curable adhesive (for example, OCR: optically clear resin) containing an ionizing radiation polymerizable compound.

The film thickness of the adhesive layer 110 is preferably 10 μm or more and 50 μm or less. If the thickness of the adhesive layer is less than 10 μm, noise may occur in the display panel because it is too thin. The thickness of the adhesive layer is determined by photographing a cross section of the adhesive layer using a scanning electron microscope (SEM), measuring the thickness of the protective film at 20 locations in the image of the cross section, and calculating the arithmetic mean value of the thickness at 20 locations. and

EXAMPLES In order to describe the present invention in detail, examples are given below, but the present invention is not limited to these descriptions. In addition, the following "solid content 100% conversion value" is a value when the solid content in the solvent-diluted product is 100%.

<Composition for core layer>
A core layer composition 1 was obtained by blending each component so as to have the composition shown below.
(Core layer composition 1)
・ Urethane acrylate (product name “UV-3310B”, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., weight average molecular weight 5000, bifunctional): 40 parts by mass ・ Polymerization initiator (product name “Irgacure 184”, manufactured by BASF Japan): 4 mass Part Leveling agent (product name "F568", manufactured by DIC): 0.1 part by mass (converted to 100% solid content)
· Ultraviolet absorber (product name "TINUVIN400", manufactured by BASF Japan): 3 parts by mass · Methyl isobutyl ketone (MIBK): 60 parts by mass

<Composition for hard coat layer>
First, each component was blended so as to have the composition shown below to obtain a composition for a hard coat layer.
(Composition 1 for hard coat layer)
・ Reactive modified silica (inorganic particles, product name “ELCOM V8803”, manufactured by JGC Catalysts & Chemicals Co., Ltd.): 30 parts by mass ・ Alkoxylated pentaerythritol acrylate (product name “ATM-10P”, manufactured by Shin-Nakamura Chemical Co., tetrafunctional) : 56 parts by mass Urethane acrylate prepolymer (product name "UN-350", manufactured by Negami Kogyo Co., Ltd., weight average molecular weight 12500, bifunctional): 14 parts by mass Polymerization initiator (product name "Irgacure 184", BASF Japan product): 4 parts by mass Leveling agent (product name “F568”, manufactured by DIC): 0.1 parts by mass (converted to 100% solid content)
・Methyl isobutyl ketone (MIBK): 150 parts by mass

(Composition 2 for hard coat layer)
・ Reactive modified silica (inorganic particles, product name “ELCOM V8803”, manufactured by JGC Catalysts & Chemicals Co., Ltd.): 10 parts by mass ・ Alkoxylated pentaerythritol acrylate (product name “ATM-10P”, manufactured by Shin-Nakamura Chemical Co., tetrafunctional) : 76 parts by mass ・Urethane acrylate prepolymer (product name “UN-350”, manufactured by Negami Kogyo Co., Ltd., weight average molecular weight 12500, bifunctional): 14 parts by mass ・Polymerization initiator (product name “Irgacure 184”, BASF Japan product): 4 parts by mass Leveling agent (product name “F568”, manufactured by DIC): 0.1 parts by mass (converted to 100% solid content)
・Methyl isobutyl ketone (MIBK): 150 mass

<Ultraviolet curable adhesive composition>
An ultraviolet curable adhesive composition 1 was obtained by blending each component so as to have the composition shown below.
(Ultraviolet curable adhesive composition 1)
・ Hydroxyacrylamide (product name “HEAA”, manufactured by KJ Chemicals): 40 parts by mass ・ Tripropylene glycol diacrylate (product name “M-220”, manufactured by Toagosei Co., Ltd.): 20 parts by mass ・ Acryloylmorpholine (product name “ ACMO", manufactured by KJ Chemicals): 40 parts by mass Polymerization initiator (product name "Irgacure 819", manufactured by BASF Japan): 1.4 parts by mass

<Example 1>
First, a polyethylene terephthalate film (product name: “Lumirror (registered trademark) U413”, manufactured by Toray Industries, Inc.) having a size of 20 cm × 30 cm and a thickness of 50 μm with one side treated for easy adhesion as a release film was prepared. Hard coat layer composition 1 was applied to the untreated side of the terephthalate film to form a coating film. Next, dry air at 50°C is passed through the formed coating film at a flow rate of 0.5 m/s for 15 seconds, and then dry air at 70°C is passed at a flow rate of 10 m/s for 30 seconds to dry. By evaporating the solvent in the coating film, the coating film is cured by irradiating the coating film with ultraviolet light so that the integrated light amount becomes 200 mJ / cm ² , so that the film thickness as a light-transmitting functional layer is 2.5 μm. A hard coat layer was formed.

After forming the hard coat layer, the core layer composition 1 was applied on the hard coat layer to form a coating film. Next, dry air at 50°C is passed through the formed coating film at a flow rate of 0.5 m/s for 15 seconds, and then dry air at 70°C is passed at a flow rate of 10 m/s for 30 seconds to dry. A core layer having a thickness of 12.5 μm was formed by curing the coating film by irradiating the coating film with ultraviolet rays so that the cumulative light amount was 300 mJ/cm ² . As a result, a protective film in which a hard coat layer having a thickness of 2.5 μm and a core layer having a thickness of 12.5 μm are laminated, and a polyethylene terephthalate film provided directly on one surface of the protective film and the hard coat layer. A laminate was obtained. The thicknesses of the polyethylene terephthalate film, the core layer, and the hard coat layer are determined by photographing a cross-section of the protective film using a scanning electron microscope (SEM), measuring the thickness of the protective film at 20 locations in the cross-sectional image, and measuring the thickness of the protective film. Arithmetic mean value of thickness at 20 points was used. In Example 2 and Comparative Examples 1 and 2, the same method as in Example 1 was used to measure the thickness of the film and the thickness of each layer.

<Example 2>
In Example 2, a protective film and a laminate were obtained in the same manner as in Example 1, except that Composition 2 for hard coat layer was used instead of Composition 1 for hard coat layer.

<Comparative Example 1>
In Comparative Example 1, a 38 μm-thick polyethylene terephthalate film (product name “Toyobo Ester Film E5000”, manufactured by Toyobo) was used instead of the polyethylene terephthalate film (product name “Lumirror (registered trademark) U413” manufactured by Toray Industries, Inc.). A protective film and a laminate were obtained in the same manner as in Example 1 except that the was used.

<Comparative Example 2>
In Comparative Example 2, instead of the polyethylene terephthalate film (product name “Lumirror (registered trademark) U413”, manufactured by Toray Industries, Inc.), a polyethylene terephthalate film having a thickness of 50 μm (product name “Diafoil T100-50S”, Mitsubishi Plastics Co., Ltd. A protective film and a laminate were obtained in the same manner as in Example 1, except that the product was used.

<Rq, Ry, Rz, and Ra measurement>
In the protective films according to Examples and Comparative Examples, Rq _0.25 , Ry _0.25 , Rz _0.25 , and Ra _0.25 were measured with a cutoff value of 0.25 mm on the surface of the hard coat layer, Rq _2.5 , Ry _2.5 , Rz _2.5 and Ra _2.5 were measured with a cutoff value of 2.5 mm. Specifically, first, a transparent adhesive layer having a thickness of 50 μm (refractive index: 1.55, It was laminated to an acrylic plate (product name: "Comoglas DFA502K", manufactured by Kuraray Co., Ltd.) having a size of 10 cm x 10 cm and a thickness of 2 mm via a product name "PDC-SI" manufactured by Panac Co., Ltd.). Thereafter, the polyethylene terephthalate film was peeled off from the hard coat layer to expose the surface of the hard coat layer. Then, Rq _0.25 , Ry _0.25 , Rz _0.25 , and Ra _0.25 were measured with a cutoff value of 0.25 mm on the surface of the hard coat layer, and Rq was measured with a cutoff value of 2.5 mm. _2.5 , _Ry2.5 , _Rz2.5 , and _Ra2.5 were measured. The definition of Rq shall be as described in this specification, and the definition of Ry, Rz and Ra shall comply with JIS B0601:1994. Rq _0.25 , Rq _2.5 , Ry _0.25 , Ry _2.5 , Rz _0.25 , Rz _2.5 , Ra _0.25 and Ra _2.25 are surface roughness measuring instruments (product name "Surfcorder SE-3400" (manufactured by Kosaka Laboratory Ltd.) was used for measurement under the following measurement conditions. Measurements of Rq _0.25 , Ry _0.25 , Rz _0.25 and Ra _0.25 are, in principle, carried out under measurement condition 1 below. When the unevenness of the surface became too large to make the measurement, the following measurement condition 3 was used. Specifically, the following measurement conditions 1 were used as the measurement conditions for the protective films according to Examples 1 and 2, and the following measurement conditions 3 were used as the measurement conditions for the protective film according to Comparative Example 1. Similarly, the measurements of Rq _2.5 , Ry _2.5 , Rz _2.5 and Ra _2.5 are in principle carried out under measurement conditions 2 below, but the longitudinal magnification of measurement conditions 2 below is When 100,000-fold magnification made the surface irregularities too large for measurement, the following measurement condition 4 was used. Specifically, the following measurement conditions 2 were used as the measurement conditions for the protective films according to Examples 1 and 2, and the following measurement conditions 4 were used as the measurement conditions for the protective film according to Comparative Example 1. In addition, as Reference Example 1, Rq _0.25 etc. of the untreated side of the polyethylene terephthalate film used in Example 1 was similarly measured under the following measurement conditions 1, and Rq _2.5 etc. was similarly measured under the following measurement conditions 2. As Reference Example 2, Rq _0.25 , etc. of the hard coat layer side surface of the polyethylene terephthalate film used in Comparative Example 1 was similarly measured under the following measurement conditions 1, and Rq _2.5 , etc. was similarly measured under the following measurement conditions 2. As Example 3, Rq _0.25 and the like of the hard coat layer side of the polyethylene terephthalate film used in Comparative Example 2 were measured under measurement conditions 3 below, and Rq _2.5 and the like were similarly measured under measurement conditions 4 below. In addition, Rq, Ry, Rz and Ra were each taken as the arithmetic mean value of the value obtained by measuring 3 times.
1) Stylus of surface roughness detector (product name “Surfcorder SE-3400”, manufactured by Kosaka Laboratory, 2 μm standard)
・ Tip curvature radius 2 μm, apex angle 90 degrees, material diamond 2-1) Measurement condition 1
・Reference length (cutoff value λc of roughness curve): 0.25 mm
・ Evaluation length (reference length (cutoff value λc) × 5): 1.25 mm
・Feeding speed of stylus: 0.1mm/s
・ Spare length: (cutoff value λc) × 2
・Longitudinal magnification: 100,000 times ・Horizontal magnification: 50 times ・Skid: Not used (no contact with the measurement surface)
・Cutoff filter type: Gaussian ・JIS mode: JIS1994
2-2) Measurement condition 2
・Reference length (cutoff value λc of roughness curve): 2.5 mm
・ Evaluation length (reference length (cutoff value λc) × 5): 12.5 mm
・Feeding speed of stylus: 0.5mm/s
・ Spare length: (cutoff value λc) × 2
・Longitudinal magnification: 100,000 times ・Horizontal magnification: 50 times ・Skid: Not used (no contact with the measurement surface)
・Cutoff filter type: Gaussian ・JIS mode: JIS1994
2-3) Measurement condition 3
・Reference length (cutoff value λc of roughness curve): 0.25 mm
・ Evaluation length (reference length (cutoff value λc) × 5): 1.25 mm
・Feeding speed of stylus: 0.1mm/s
・ Spare length: (cutoff value λc) × 2
・Longitudinal magnification: 10,000 times ・Horizontal magnification: 50 times ・Skid: Not used (no contact with the measurement surface)
・Cutoff filter type: Gaussian ・JIS mode: JIS1994
2-4) Measurement condition 4
・Reference length (cutoff value λc of roughness curve): 2.5 mm
・ Evaluation length (reference length (cutoff value λc) × 5): 12.5 mm
・Feeding speed of stylus: 0.5mm/s
・ Spare length: (cutoff value λc) × 2
・Longitudinal magnification: 10,000 times ・Horizontal magnification: 50 times ・Skid: Not used (no contact with the measurement surface)
・Cutoff filter type: Gaussian ・JIS mode: JIS1994

<Haze measurement>
The haze values (total haze values) of the protective films of Examples and Comparative Examples were measured. The haze value was measured in accordance with JIS K7136:2000 by using a haze meter (product name "HM-150", manufactured by Murakami Color Research Laboratory) and allowing light to enter the protective film from the core layer side. . When measuring the haze value, the polyethylene terephthalate film was peeled off from each of the laminates according to Examples and Comparative Examples, and the haze value was measured in the state of a single protective film. The haze value was taken as the arithmetic mean value of the values obtained by measuring 3 times.

<Total light transmittance measurement>
The total light transmittance of the protective films of Examples and Comparative Examples was measured. The total light transmittance is measured in accordance with JIS K-7361: 1997, using a haze meter (product name "HM-150", manufactured by Murakami Color Research Laboratory), and allowing light to enter the protective film from the core layer side. was measured by When measuring the total light transmittance, the polyethylene terephthalate film was peeled off from each of the laminates according to Examples and Comparative Examples, and the total light transmittance was measured with the protective film alone. The total light transmittance was the arithmetic mean value of the values obtained by measuring 3 times.

<Pencil hardness measurement>
The pencil hardness of the surface of the protective films according to Examples and Comparative Examples was measured. Specifically, first, in the laminate formed to obtain the protective film, the UV-curable adhesive composition 1 is applied to the surface of the core layer of the laminate opposite to the hard coat layer side. to form a coating film. Next, on the formed coating film, a polyethylene terephthalate film having a thickness of 100 μm and one side of which has been subjected to an easy-adhesion treatment (product name “Cosmo Shine A4100”, manufactured by Toyobo Co., Ltd.) is laminated for easy-adhesion treatment, and the above-mentioned ultraviolet rays are applied. After irradiation, the polyethylene terephthalate film in contact with the hard coat layer was peeled off. As a result, a protective film attached to the polyethylene terephthalate film was obtained. Then, the pencil hardness of the surface of the protective film (the surface of the hard coat layer) was measured. Then, using a test pencil specified by JIS S6006, a pencil hardness test specified by JIS K5600-5-4: 1999 was performed on the surface of the hard coat layer, and the highest hardness without scratches was taken as the pencil hardness. . When measuring the pencil hardness, the pencil was moved at a speed of 1 mm/sec while a load of 750 g was applied to the pencil. In addition, when measuring the pencil hardness, a plurality of pencils with different hardness are used, but the pencil hardness test is performed 5 times for each pencil, and the surface of the protective film is measured under a fluorescent light at least 4 times out of 5 times. When no scratches were visually observed on the surface of the protective film when observed through transmission, it was judged that the surface of the protective film was not scratched by the pencil with this hardness.

<Moisture permeability measurement>
The moisture permeability of the protective films according to Examples and Comparative Examples was measured. Specifically, a protective film is measured using a weight measuring device (product name “analytical balance HR-202i”, manufactured by A&D) by a method based on the moisture permeability test method (cup method) described in JIS Z0208-1976. was placed in an atmosphere with a temperature of 40° C. and a relative humidity of 90%, and the amount of water vapor passing through in 24 hours was measured. When measuring the moisture permeability, the polyethylene terephthalate film was peeled off from each laminate according to Examples and Comparative Examples, and the moisture permeability was measured in the state of a single protective film.

<Tensile breaking strength measurement>
The tensile breaking strength of the protective films according to Examples and Comparative Examples was measured. In accordance with JIS-K7161-1:2014, using a Tensilon universal testing machine (product name "ORIENTEC STA-1150", manufactured by Orientec), the width is 10 mm, the distance between chucks is 80 mm, and the test speed is 100 mm / min. was pulled, and the stress applied to the protective film when it broke was measured, and this stress was taken as the tensile strength at break. When measuring the tensile strength at break, the polyethylene terephthalate film was peeled off from each laminate according to Examples and Comparative Examples, and the tensile strength at break was measured in the state of a single protective film. The tensile strength at break was the arithmetic mean value of the values obtained by measuring three times.

<Scratch resistance>
A scratch resistance test was performed on the protective films according to Examples and Comparative Examples. Specifically, first, a transparent adhesive layer having a thickness of 50 μm (refractive index: 1.55, It was laminated to an acrylic plate (product name: "Comoglas DFA502K", manufactured by Kuraray Co., Ltd.) having a size of 10 cm x 10 cm and a thickness of 2 mm via a product name "PDC-SI" manufactured by Panac Co., Ltd.). Thereafter, the polyethylene terephthalate film was peeled off from the hard coat layer to expose the surface of the hard coat layer. Then, the surface of the hard coat layer was subjected to a scratch resistance test in which #0000 steel wool (product name “Bonstar”, manufactured by Nippon Steel Wool Co., Ltd.) was rubbed back and forth 10 times while applying a load of 500 g/cm ² . The surface of the hard coat layer was visually observed to see if there were any scratches. The evaluation results were as follows.
◯: No scratches were observed.
Δ: Some scratches were observed, but the level was practically acceptable.
x: Scratches were clearly confirmed.

<Peel strength measurement>
In the laminates according to Examples and Comparative Examples, the peel strength of the polyethylene terephthalate film was measured after the laminates were irradiated with ultraviolet rays. First, a sample of each laminate was prepared by cutting out a sample having a size of 25 mm×150 mm. Then, the sample was irradiated with light having a wavelength of 200 nm or more and 500 nm or less from the side of the polyethylene terephthalate film so that the integrated light amount was 1000 mJ/cm ² . After that, the surface of the core layer side of the sample irradiated with ultraviolet rays was attached to a glass plate using double-sided tape "751B" manufactured by Teraoka Seisakusho. Then, in an environment of 25 ° C. and a relative humidity of 60%, using a Tensilon universal tester (product name “ORIENTEC STA-1150” manufactured by Orientec), the hard coat layer was peeled off in the direction of 180 ° at a peel speed of 300 m / min. The polyethylene terephthalate film was peeled off from the tape, and the peel strength at that time was measured.

The results are shown in Tables 1 and 2 below.

In the protective films according to Comparative Examples 1 and 2, either Rq _0.25 or Rq _2.5 of the surface of the hard coat layer exceeded 0.035 μm, so the haze value was high. As can be seen from the results of Rq _0.25 and Rq _2.5 for the polyethylene terephthalate films according to Reference Examples 2 and 3, the surface of the polyethylene terephthalate film as the release film was rough. It is believed that this is because the surface of the hard coat layer in contact was also roughened.

On the other hand, in the protective films of Examples 1 and 2, Rq _0.25 and Rq _2.5 of the surface of the hard coat layer were both 0.035 μm or less, so the haze values were low. As can be seen from the results of Rq _0.25 and Rq _2.5 for the polyethylene terephthalate film according to Reference Example 1, the surface of the polyethylene terephthalate film as the release film was smooth, so that it was in contact with the polyethylene terephthalate film. It is considered that this is because the surface of the hard coat layer, which had been exposed, also became smooth.

DESCRIPTION OF SYMBOLS 10... Protective film 10A... Surface 11... Optically transparent functional layer 11A... Surface 12... Core layer 13... Hard coat layer 20... Laminate 30... Release film 40... Polarizing plate 41... Polarizer 50... Image display device 60... Display panel 62 ... display element

Claims (10)

A substrate-less protective film comprising a light-transmitting functional layer,
The surface of the light-transmitting functional layer forms the surface of the protective film,
The light-transmitting functional layer includes a core layer containing a resin , and a hard coat layer provided on one surface of the core layer and containing a resin,
the resin of the hard coat layer contains a polymer of an ionizing radiation polymerizable compound,
The surface of the hard coat layer forms the surface of the light-transmitting functional layer,
A root mean square roughness Rq of _0.25 measured with a cutoff value of 0.25 mm and a root mean square roughness Rq of _2.5 measured with a cutoff value of 2.5 mm on the surface of the light-transmitting functional layer are Both are 0.035 μm or less ,
The maximum height Ry of _0.25 measured with a cutoff value of 0.25 mm and the maximum height Ry _2.5 measured with a cutoff value of 2.5 mm on the surface of the light-transmitting functional layer were both 0.25. 05 μm or more and 0.25 μm or less, and the difference between the maximum height Ry _2.5 and the maximum height Ry _0.25 (Ry _2.5 −Ry _0.25 ) is 0.100 μm or less,
A protective film having a haze value of 0.2% or less . The protection according to claim 1, wherein the difference (Rq _2.5 −Rq _0.25 ) between the root mean square roughness Rq _2.5 and the root mean square roughness Rq _0.25 is 0.010 μm or less. the film. Ten-point average roughness Rz _2.5 measured with a cutoff value of 2.5 mm on the surface of the light-transmitting functional layer and ten-point average roughness Rz _0.25 measured with a cutoff value of 0.25 mm 3. The protective film according to claim 1, wherein the difference (Rz _2.5 −Rz _0.25 ) is 0.050 μm or less. The protective film according to any one of claims 1 to 3 , wherein the protective film has a moisture permeability of 100 g/( ^m2 ·24h) or less. The protective film according to any one of claims 1 to 4 , wherein the protective film has a thickness of 5 µm or more and 40 µm or less, and a tensile strength at break of 8 N/10 mm or more. The protective film according to any one of claims 1 to 5 , wherein the light-transmitting functional layer has a multilayer structure in which two or more light-transmitting functional layers are laminated. A protective film according to any one of claims 1 to 6 ;
and a peelable release film provided directly on the surface of the light-transmitting functional layer of the protective film. Light with a wavelength of 200 nm or more and 500 nm or less was irradiated to the laminate from the release film side so that the integrated light amount was 1000 mJ/cm ² , and the release film was removed from the light-transmitting functional layer at 25 ° C. and relative. The laminate according to claim 7 , wherein the release film has a peel strength of 20 mN/25 mm or more and 200 mN/25 mm or less when peeled in a direction of 180° at a peel speed of 300 mm/min in an environment with a humidity of 60%. body. The protective film according to any one of claims 1 to 6 or the laminate according to claim 7 or 8 ,
a polarizer provided on the side opposite to the surface side of the light-transmissive functional layer of the protective film or the laminate;
A polarizing plate. An image display device comprising the protective film according to any one of claims 1 to 6 or the polarizing plate according to claim 9 .

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