Hard coat film, polarizing plate using same, and optical member

Abstract

To provide a hard coat film which has ultraviolet-cut performance and in which an ultraviolet absorber does not segregate on a surface of a hard coat layer, and to provide a polarizing plate using the hard coat film and an optical member such as a display device.SOLUTION: Provided is a hard coat film having a hard coat layer on a transparent support, the hard coat layer being a cured film of a composition containing 100 pts.mass of an acrylate compound, 1.5-25 pts.mass of an ultraviolet absorber, and 0.1-15 pts.mass of a photopolymerization initiator, a proportion of the ultraviolet absorber existing in a region within 30% of a thickness of the hard coat layer from a surface of the hard coat layer being 50 mass% or less, and a light transmittance at a wavelength of 380 nm being 10% or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a hard-coated film, a polarizing plate using the same, and an optical member using the same. [Background technology]

[0002] Polarizing plates are used in display devices such as smartphones, tablets, laptop computers, and monitor televisions, and the outermost surface of the polarizing plate is a hard coat film (HC film) as described in Patent Document 1. The hard coat film has a hard coat layer (HC layer) made of a cured film of a resin composition formed on one surface of a transparent support.

[0003] Hard coat films are provided for the purpose of improving scratch resistance, so they are required to have surface hardness and durability, but they are also required to have UV protection, in consideration of the fact that devices vulnerable to UV rays, such as OLEDs (organic emitting diodes), are used as light sources for display devices. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6577768 Summary of the Invention [Problem to be solved by the invention]

[0005] One way to impart UV blocking properties to a hard coat film is to add a UV absorber to the adhesive used to bond the light source (OLED) and polarizer (Figure 6). However, due to low compatibility between the adhesive components and the UV absorber, the amount of UV absorber added to the adhesive is low, and even if the amount added is increased, the UV absorber aggregates within the adhesive, making it difficult to achieve the desired UV blocking properties.

[0006] Another method is to add a UV absorber to the hard coat layer to impart UV blocking properties to the hard coat film, but this can cause problems because the UV absorber segregates onto the surface when the hard coat layer is cured.The outermost surface of a display device is generally protected by a cover glass, but the UV absorber that segregates onto the surface of the hard coat layer dissolves into the adhesive used to attach the cover glass, inhibiting the UV curing of the adhesive and causing poor adhesion of the cover glass.

[0007] Therefore, an object of the present invention is to provide a hard-coated film that has ultraviolet blocking properties and does not have an ultraviolet absorber segregated on the surface of the hard-coat layer, and to provide optical components such as polarizing plates and display devices that use the hard-coated film. [Means for solving the problem]

[0008] The hard coat film according to the present invention is a hard coat film having a hard coat layer provided on a transparent support, wherein the hard coat layer is a cured film of a composition containing 100 parts by mass of an acrylate compound, 1.5 to 25 parts by mass of an ultraviolet absorber, and 0.1 to 15 parts by mass of a photopolymerization initiator, and the proportion of the ultraviolet absorber present in a portion within 30% of the thickness of the hard coat layer from the surface of the hard coat layer is 50% by mass or less, and the transmittance of light with a wavelength of 380 nm is 10% or less.

[0009] The polarizing plate according to the present invention uses the above hard coat film.

[0010] The optical member according to the present invention uses the above polarizing plate. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a hard-coated film that has ultraviolet blocking properties and in which an ultraviolet absorber does not segregate on the surface of the hard-coat layer.The present invention also provides optical components such as polarizing plates and display devices that use the hard-coated film. [Brief explanation of the drawings]

[0012] [Figure 1] Schematic cross-sectional view of a hard coat film according to an embodiment. [Figure 2] FIG. 1 is a diagram showing an example of a layer configuration of a display device according to an embodiment; [Figure 3] Enlarged cross-section of hard coat film [Figure 4] Graph showing the relationship between the depth of the hard coat layer and the ratio of the amount of ultraviolet absorber (I1230 / I1720) in the acrylate compound [Figure 5] Graph showing the total abundance ratio of ultraviolet absorbers versus the depth of the hard coat layer [Figure 6] FIG. 1 is a diagram showing an example of a layer structure of a conventional display device. DETAILED DESCRIPTION OF THE INVENTION

[0013] FIG. 1 is a schematic cross-sectional view of a hard coat film according to an embodiment, FIG. 2 is a diagram showing an example of the layer structure of a display device according to an embodiment, and FIG. 3 is a partially enlarged view of the cross-section of the hard coat film.

[0014] The hard coat film 1 has a hard coat layer 3 provided on one surface of a transparent support 2. As shown in FIG. 2, the hard coat film 1 can be used in combination with a polarizer to form a polarizing plate 10. The polarizing plate 10 is formed by laminating a polarizer and a hard coat film 1 on one surface of a transparent support, each laminated with an adhesive. The polarizing plate 10 is used in optical components such as a display device 100. The display device 100 has a cover glass attached to one surface of the polarizing plate 10 with an adhesive, and a light source (in this embodiment, an OLED device) attached to the other surface with an adhesive. Examples of the display device 100 include smartphones, tablets, laptop computers, and monitor televisions. The layer configurations of the display device 100, polarizing plate 10, and hard coat film 1 shown in FIG. 2 are merely examples and may be modified as appropriate.

[0015] (transparent support) The transparent support 2 is a film that serves as the base of the hard coat film 1. The transparent support 2 is not particularly limited as long as it is a film made of a material that has excellent transparency and transmittance to visible light, but for example, a film made of any of the following materials can be used: triacetyl cellulose (TAC), polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), cycloolefin polymer (COP), and polyimide (PI).

[0016] The thickness of the transparent support 2 is preferably 11 to 50 μm. If the thickness of the transparent support 2 is less than 11 μm, the transparent support 2 becomes too thin, resulting in a decrease in the hardness of the hard coat layer 3 and the strength of the hard coat film 1. On the other hand, if the thickness of the transparent support 2 exceeds 50 μm, the hard coat film 1 becomes too thick, which will not contribute to reducing the thickness of display devices such as displays using the hard coat film 1.

[0017] (Hard coat layer) The hard coat layer 3 is a functional layer that coats the flexible transparent support 2 and imparts hardness to the hard coat film 1. The hard coat layer 3 can be formed by applying and curing a coating liquid containing an active energy ray-curable resin, an ultraviolet absorber, and a photopolymerization initiator.

[0018] The hard coat layer 3 according to this embodiment contains an ultraviolet absorber. This allows the hard coat layer 3 to absorb ultraviolet light, thereby protecting the display device 100 from ultraviolet light, even when a device vulnerable to ultraviolet light, such as an organic emitting diode (OLED), is used as the light source of the display device. Furthermore, the amount of ultraviolet absorber segregated near the surface of the hard coat layer 3 is reduced, and the proportion of the ultraviolet absorber present in a portion within 30% of the thickness of the hard coat layer 3 from the surface of the hard coat layer 3 is 50% by mass or less. A UV-curable adhesive is applied to bond the cover glass for protecting the display device to the hard coat layer 3 (see FIG. 2 ). Therefore, if the content of the ultraviolet absorber near the surface of the hard coat layer 3 is high, the UV absorber may dissolve in the adhesive, inhibiting UV curing of the adhesive and potentially causing poor adhesion of the cover glass. This embodiment prevents the UV absorber segregated on the surface of the hard coat layer 3 from dissolving in the adhesive applied to the surface of the hard coat layer 3. The hard coat layer 3 may also contain a styrene filler to exhibit antiglare properties.

[0019] The thickness of the hard coat layer 3 is preferably 4 to 15 μm. If the thickness of the hard coat layer 3 is less than 4 μm, the hardness of the hard coat layer 3 will be insufficient. On the other hand, if the thickness of the hard coat layer 3 exceeds 15 μm, the thickness of the hard coat film 1 will be too large, which will not contribute to making the optical member using the hard coat film 1 thinner.

[0020] The active energy ray-curable resin is preferably an acrylate compound having an aromatic ring, and preferably contains a high molecular weight compound having a weight average molecular weight of 1,000 to 100,000 and a low molecular weight compound having a weight average molecular weight of less than 1,000. Here, the high molecular weight compound is a component added to suppress curling and impart toughness. The mass ratio of the high molecular weight compound to the low molecular weight compound is preferably 50:50 to 90:10. When the mass ratio of the high molecular weight compound to the low molecular weight compound is within this range, the UV absorber is less likely to segregate on the surface of the hard coat layer 3. On the other hand, when the mass ratio of the low molecular weight compound to the high molecular weight compound is greater than 50:50, the UV absorber is more likely to segregate on the surface of the hard coat layer 3. This is because the UV absorber and the low molecular weight compound are separated due to the difference in molecular weight.

[0021] The UV absorber is a component that imparts UV-blocking properties to the hard coat layer 3 itself. If the UV absorber segregates on the surface of the hard coat layer 3, it will dissolve in the adhesive applied to the hard coat layer 3. Therefore, the hard coat layer 3 in this embodiment is configured so that the UV absorber does not segregate on the surface of the hard coat layer 3. More specifically, the UV absorber present in a portion X within 30% of the thickness (depth 30%) of the hard coat layer 3, based on the surface of the hard coat layer 3 (the surface opposite the transparent support 2; hereinafter, this may be referred to as a depth of 0%), is preferably 50% by mass or less of the total UV absorber present in the hard coat layer 3. If the UV absorber present within 30% of the depth from the surface of the hard coat layer 3 exceeds 50% by mass, the UV absorber will dissolve in the adhesive applied to the hard coat layer 3, inhibiting UV curing of the adhesive. The amount of UV absorber added is preferably 1.5 to 25 parts by mass per 100 parts by mass of the total acrylate compound. If the amount of the ultraviolet absorber is less than 1.5 parts by mass, the ultraviolet blocking performance will be insufficient, and if it exceeds 25 parts by mass, the curability of the hard coat layer 3 will decrease and sufficient hardness will not be obtained.

[0022] The amount of the photopolymerization initiator added is preferably 0.1 to 15 parts by mass per 100 parts by mass of the total of the acrylate compounds. If the amount of the photopolymerization initiator added is less than 0.1 part by mass, the curability of the hard coat layer 3 decreases, making it impossible to obtain sufficient surface hardness. If the amount of the photopolymerization initiator added is more than 15 parts by mass, the curability of the hard coat layer 3 becomes too strong, impairing the adhesion between the hard coat layer 3 and the transparent support 2.

[0023] The hard coat film 1 according to this embodiment preferably has a transmittance of 10% or less at a wavelength of 380 nm. When this is satisfied, the light source of a display device, such as an OLED, which is vulnerable to ultraviolet light, can be prevented from being deteriorated by external ultraviolet light.

[0024] The amount of the ultraviolet absorber added to the hard coat layer 3 is 1.5 to 25 parts by mass per 100 parts by mass of the total of the acrylate compounds, so the hard coat film 1 has excellent ultraviolet blocking performance and surface hardness.

[0025] Furthermore, the amount of the ultraviolet absorber present in portion X of the hard coat layer 3 is 50 mass % or less of the total amount of the ultraviolet absorber present in the hard coat layer 3. Therefore, it is possible to prevent the ultraviolet absorber from dissolving in the adhesive applied onto the hard coat layer 3.

[0026] Furthermore, the mass ratio of the high molecular weight compound to the low molecular weight compound contained in the acrylate compound is 50:50 to 90:10, so segregation of the ultraviolet absorber on the surface of the hard coat layer 3 can be suppressed.

[0027] The photopolymerization initiator is added in an amount of 0.1 to 15 parts by mass per 100 parts by mass of the total of the acrylate compounds, thereby providing the hard coat layer 3 with sufficient surface hardness and preventing the hard coat layer 3 from having too strong a curing property, which would impair the adhesion between the hard coat layer 3 and the transparent support 2. [Example]

[0028] Examples of specific implementations of the present invention will be described below.

[0029] In Examples 1 to 12 and Comparative Examples 1 to 7, a 25 μm-thick triacetyl cellulose film was used as the transparent support. The hard coat layer-forming composition was prepared by mixing a high molecular weight acrylate compound and a low molecular weight acrylate compound (NK Ester A-TMM-3L, manufactured by Shin-Nakamura Chemical Co., Ltd.), an ultraviolet absorber (Tinuvin® 477, manufactured by BASF Japan Ltd.), and a photopolymerization initiator (Omnirad® 184, manufactured by IGM Resins) in the ratios shown in Table 1. The blending amounts of the materials in Table 1 are in parts by mass relative to 100 parts by mass of the total acrylate compounds.

[0030] The hard coat layer-forming composition was applied to one side of the transparent support by bar coating and dried, and then the coating film was cured by irradiating ultraviolet light using a high-pressure mercury lamp in an environment with an oxygen concentration of 500 ppm or less to obtain a hard coat film. The amount of the hard coat layer-forming composition applied was adjusted so that the thickness of the cured film would be 8 μm.

[0031] [Table 1]

[0032] For each of the hard coat films produced in Examples 1 to 12 and Comparative Examples 1 to 7, the transmittance at a wavelength of 380 nm, adhesion to the cover glass, total abundance ratio of the ultraviolet absorber in portion X, pencil hardness, and adhesion were evaluated.

[0033] (transmittance) The transmittance at a wavelength of 380 nm of the hard coat films produced in Examples 1 to 12 and Comparative Examples 1 to 7 was measured using a spectrophotometer (U-4100 manufactured by Hitachi High-Technologies Corporation) under conditions of a C light source and a 2-degree visual field. A transmittance of 10% or less was rated as good, and a transmittance of more than 10% was rated as poor.

[0034] (adhesion to cover glass) A photoelastic resin (SVR1150 manufactured by Dexerials Corporation) was applied to the surface of the hard-coated film produced in Examples 1 to 12 and Comparative Examples 1 to 7 to a thickness of 0.1 to 0.2 mm, and a soda lime glass simulating a cover glass was attached thereto. The photoelastic resin was cured by UV irradiation from a high-pressure mercury lamp. The hard-coated film was pulled from the soda lime glass, and peeling was evaluated as ×, while no peeling was evaluated as ○.

[0035] (Total abundance ratio of ultraviolet absorbers in part X) The total abundance ratio of the ultraviolet absorber was calculated by the following procedure.

[0036] <Step 1> A specific example will be described using Example 1. The hard coat film produced in Example 1 was embedded in a photocurable resin and cut with a microtome to prepare a cross-sectional sample.

[0037] Microscopic Raman spectroscopy was performed on the cross-section of the cross-section sample, and the 1230 cm was measured at nine measurement points (depths of 0, 1, . . . , 8 μm) every 1 μm from the surface of the hard coat layer (depth 0%, depth 0 μm) to the back surface (depth 100%, depth 8 μm). -1 Peak intensity I 1230 , and 1720 cm -1 Peak intensity I 1720 was measured. 1230 is an intrinsic value derived from the ultraviolet absorber, and I 1720 is an intrinsic value derived from the carbonyl group of the acrylate compound. From this measurement result, the ratio of the amount of ultraviolet absorber in the acrylate compound (I 1230 / I 1720 The ratio of the amount of ultraviolet absorber to the depth (I 1230 / I 1720 ) are shown in the "Measured Values" row of Table 2.

[0038] <Step 2> The measurement results at each measurement point are plotted against the depth of the hard coat layer on the horizontal axis and the UV absorber amount ratio (I 1230 / I 1720) on the vertical axis, the graph shown in Figure 4 was obtained. Based on the measurement results obtained, the relationship between the depth and the ultraviolet absorber amount ratio (I 1230 / I 1720 The following approximate formula (1) was obtained, which represents the relationship between the coefficient of determination and R 2 =0.95. Approximate formula (1) y=-0.0002x 2 +0.0141x+1.0139

[0039] <Step 3> Next, based on the approximate formula (1), the ultraviolet absorber amount ratio (I 1230 / I 1720 ) calculated values ​​A0, A1, . . ., A 100 was calculated. A m is the value of y obtained by substituting the depth m% (m is an integer between 0 and 100) for x in the approximate formula (1). The ratio of the amount of ultraviolet absorber in the acrylate compound (I 1230 / I 1720 ) calculated value A m The calculated value A from the approximate formula in Table 2 m In step 3, the calculated depth values ​​A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, A21, A22, A23, A24, A25, A26, A27, A28, A29, A30, A31, A32, A33, A34, A35, A36, A37, A38, A39, A40, A41, A42, A43, A44, A45, A46, A47, A48, A49, A50, A51, A52, A53, A54, A55, A56, A57, A58, A59, A60, A61, A62, A63, 100 However, for simplicity, Table 2 shows only the calculated depth values ​​corresponding to each measurement point.

[0040] <Step 4> Next, the calculated values ​​A0, A1, . . ., A calculated in step 3 100 The UV absorber amount ratio (I 1230 / I 1720 ) the sum of B0, B1, . . ., B 100 Specifically, the total value B m was calculated based on the following formula (2). (Formula 2) JPEG2025168897000003.jpg3249

[0041] <Step 5> Next, the sums B0, B1, . . ., B calculated in step 4 are 100 The total of B0, B1, B2, B3, B4, B5, B6, B7, B8, B9, B10, B11, B12, B13, B14, B15, B16, B17, B18, B19, B20, B21, B22, B23, B24, B25, B26, B27, B28, B29, B30, B31, B32, B3 100 The total abundance ratio of ultraviolet absorbers C0, C1, . . ., C 100 Specifically, the total abundance ratio C of the ultraviolet absorber m was calculated based on the following formula (3). (Formula 3) JPEG2025168897000004.jpg3580

[0042] <Step 6> Next, the total abundance ratios of the UV absorbers C0, C1, . . . , C calculated in step 6 are 100 The values ​​were plotted on a graph with the depth of the hard coat layer on the horizontal axis and the total abundance ratio of the ultraviolet absorber on the vertical axis to obtain the graph shown in FIG.

[0043] For each sample of Examples 2 to 12 and Comparative Examples 1 to 7, the above steps 1 to 5 were carried out to determine the total abundance ratio C of the ultraviolet absorber contained in the portion X from the surface (depth 0%, depth 0 μm) to a depth of 30% of the hard coat layer. 30 was calculated.

[0044] When the total content ratio of the ultraviolet absorber contained in the portion X from the surface (depth 0%, depth 0 μm) to a depth of 30% of the hard coat layer was 50% or less, the result was judged to be good, and when the content was not good, the result was judged to be bad. In the graph of FIG. 5, when data exists in the shaded area, the result is considered to be good.

[0045] [Table 2]

[0046] (Pencil hardness) A scratch test was performed on the hard coat layer surface using a pencil (Uni, manufactured by Mitsubishi Pencil Co., Ltd.) and a Clemens scratch tester (HA-301, manufactured by Tester Sangyo Co., Ltd.) under conditions of a load of 500 g and a scratching speed of 0.5 mm / sec. The scratch test was performed on five samples, and if two or more samples had scratches on the hard coat layer surface, they were rated as "poor," if fewer than two, they were rated as "good." If the maximum hardness was 2H or more (not considered poor), they were rated as "○," and if it was H or less, they were rated as "×."

[0047] (adhesion) The hard coat layer was cut into 100 squares, and the adhesion of the hard coat layer to the transparent support was examined in accordance with JIS K 5400. A case in which 10 or fewer squares peeled off (90 or more squares remaining) was evaluated as ◯, and a case in which 11 or more squares peeled off (89 or fewer squares remaining) was evaluated as ×.

[0048] Table 3 shows the evaluation results of the hard coat layer thickness, transmittance at a wavelength of 380 nm, adhesion to the cover glass, total abundance ratio of the ultraviolet absorber in portion X, pencil hardness, and adhesion of the hard coat films produced in Examples 1 to 12 and Comparative Examples 1 to 7.

[0049] [Table 3]

[0050] In all of the hard-coated films according to Examples 1 to 12, the amount of UV absorber added was 1.5 to 25 parts by mass relative to 100 parts by mass of the total acrylate compounds. Therefore, they had excellent UV-blocking performance and surface hardness. Furthermore, the mass ratio of the high-molecular-weight compound to the low-molecular-weight compound contained in the acrylate compounds was 50:50 to 90:10, which prevented the UV absorber from segregating on the surface of the hard-coat layer and ensured that the total proportion of the UV absorber in portion X of the hard-coat layer was 50% or less. Therefore, the UV absorber was prevented from dissolving in the photoelastic resin applied to the hard-coat layer, and the adhesion between the hard-coat layer and the cover glass was not impaired. Furthermore, the photopolymerization initiator was added in an amount of 0.1 to 15 parts by mass relative to 100 parts by mass of the total acrylate compounds. As a result, the hard-coat layer exhibited excellent surface hardness (pencil hardness), and the adhesion between the hard-coat layer and the transparent support was not impaired due to excessive hardness.

[0051] In the hard coat films according to Comparative Examples 1 and 2, the content of the high molecular weight compound was less than 50 parts by mass, so the UV absorber segregated on the surface of the hard coat layer, and as a result, the UV absorber dissolved in the photoelastic resin applied to the hard coat layer, impairing adhesion to the cover glass.

[0052] The hard coat films according to Comparative Examples 3 and 4 contained less than 1.5 parts by mass of the ultraviolet absorber, and therefore had high transmittance at a wavelength of 380 nm and low ultraviolet blocking performance.

[0053] In the hard coat film according to Comparative Example 5, the amount of the ultraviolet absorber exceeded 25 parts by mass, and therefore the pencil hardness of the hard coat layer was low and the surface hardness was poor.

[0054] In the hard coat film of Comparative Example 6, the amount of the photopolymerization initiator was less than 0.1 parts by mass, and therefore the curability of the hard coat layer was reduced, and sufficient surface hardness was not obtained.

[0055] In the hard coat film of Comparative Example 7, the amount of photopolymerization initiator exceeded 15 parts by mass, and therefore the hard coat layer had too strong curing properties, resulting in poor adhesion between the hard coat layer and the transparent support. [Industrial Applicability]

[0056] The hard coat film according to the present invention can be used for optical components such as polarizing plates and display devices. [Explanation of symbols]

[0057] 1. Hard coated film 2 Transparent support 3 Hard coat layer 10 Polarizing plate 100 Hard Coat Film

Claims

1. A hard coat film having a hard coat layer provided on a transparent support, the hard coat layer is a cured film of a composition containing 100 parts by mass of an acrylate compound, 1.5 to 25 parts by mass of an ultraviolet absorber, and 0.1 to 15 parts by mass of a photopolymerization initiator; the proportion of the ultraviolet absorber present in a portion of the hard coat layer within 30% of the thickness of the hard coat layer from the surface of the hard coat layer is 50% by mass or less, A hard coat film having a transmittance of 10% or less for light with a wavelength of 380 nm.

2. The acrylate compound is a high molecular weight compound having a weight average molecular weight of 1,000 to 100,000; and a low molecular weight compound having a weight average molecular weight of less than 1000, 2. The hard coat film according to claim 1, wherein the mass ratio of the high molecular weight compound to the low molecular weight compound is 50:50 to 90:

10.

3. 2. The hard coat film according to claim 1, wherein the transparent support is a film made of any one of triacetyl cellulose, polymethyl methacrylate, polyethylene terephthalate, cycloolefin polymer, and polyimide.

4. A polarizing plate using the hard coat film according to any one of claims 1 to 3.

5. An optical member using the polarizing plate according to claim 4.

Images