TW201920557A - Laminate for protecting polarizing film and method for producing same - Google Patents

Abstract

Provided is a laminated body for protecting a polarizing film, in which a photocurable resin layer comprising a radical polymerizable compound is laminated on a substrate film, wherein the laminated body for protecting a polarizing film is characterized in that: the thickness of the photocurable resin layer is 9 [mu]m or less; the boric acid permeation in terms of boron atoms of the photocurable resin layer is 2.25 g/m2.day or less; the adhesion force between the substrate film and the photocurable resin layer is 0.005-0.06 N/mm; and the root-mean-square surface roughness (rms) of the photocurable resin layer on the substrate film side, after the substrate film is separated from the photocurable resin layer, is 300 nm or less. There are thereby provided: a laminated body for protecting a polarizing film, the laminated body having exceptional surface smoothness and exceptional humidity and heat resistance even when the thickness of the photocurable resin layer is 9 [mu]m or less; and a method for manufacturing said laminated body.

Description

   Laminate for polarizing film protection and manufacturing method thereof   

The present invention relates to a laminated body for protecting a polarizing film formed by laminating a photocurable resin on a base film, and a method for producing the laminated body.

A polarizing plate having a function of transmitting and shielding light is a basic constituent element of a liquid crystal display (LCD) at the same time as a liquid crystal that changes a polarization state of the light. Many polarizing plates have a structure in which a protective film such as a cellulose triacetate (TAC) film is bonded to the surface of a polarizing film. As a polarizing film constituting a polarizing plate, the mainstream is a iodine dye (I ₃ ^- or I ₅ ^- etc.) or a dichroic organic substance adsorbed on a stretched film in which a polyvinyl alcohol (PVA) film is uniaxially stretched and aligned. Dyes and other dichroic pigments. Such a polarizing film is generally obtained by uniaxially stretching a PVA film containing a dichroic pigment in advance, simultaneously adsorbing a dichroic dye with a uniaxial stretching of the PVA film, or adsorbing a dichroic pigment after uniaxially stretching the PVA film. Sex pigments are continuously produced.

LCDs are used in a wide range of applications such as small devices such as computers and watches, notebook computers, LCD screens, LCD color projectors, LCD TVs, car navigation systems, smart phones, and measuring instruments used indoors and outdoors; however, in recent years In particular, with the expansion to mobile applications such as small smartphones, thinning of polarizing plates is strongly required. Also, in mobile applications, durability is required due to the wide range of use locations.

One of the methods for reducing the thickness of a polarizing plate is to reduce the thickness of a protective film. In recent years, there has been proposed a polarizing plate that forms a photocurable resin layer instead of the protective film (for example, refer to Patent Documents 1 to 4).

    [Prior technical literature]         [Patent Literature]    

[Patent Document 1] Japanese Patent Laid-Open No. 2011-221185

[Patent Document 2] Japanese Patent Laid-Open No. 2004-245924

[Patent Document 3] Japanese Patent Publication No. 2013-513832

[Patent Document 4] Japanese Patent Laid-Open No. 2008-20891

However, in the polarizing plate having a photocurable resin layer described in Patent Documents 1 to 4, the polarizing performance is deteriorated when used under high temperature and high humidity conditions. As described in the method described in Patent Document 1 or 2, if a composition containing a radical polymerizable compound or the like is directly applied to the surface of a polarizing film, the surface smoothness of the photocurable resin layer is likely to be deteriorated. External interference causes the polarization performance of the polarizer to deteriorate. Furthermore, the solvent contained in the composition containing a radically polymerizable compound etc. will attack the polarizing film and deteriorate the polarizing performance, or the adhesive force between the polarizing film and the light-curing resin layer is reduced. When the polarizing plate is cut to a panel size and the like, the photo-curable resin layer is peeled during handling. In addition, when a composition containing a radical polymerizable compound or the like is directly coated on the surface of the polarizing film, the polarizing film may be deteriorated, and it is not possible to sufficiently irradiate ultraviolet rays or electron beams, and it is difficult to increase the crosslinking density. On the other hand, Patent Document 3 or 4 proposes a method of forming a photocurable resin layer on a base film such as a release PET film, and then bonding the photocurable resin layer to the polarizing film using an adhesive. However, if the releasability between the base film and the photocurable resin layer is not good, the surface smoothness of the photocurable resin layer is deteriorated, and the polarizing performance of the polarizing plate is deteriorated due to external interference. In addition, when used under high-temperature and high-humidity conditions, the polarizing property is also deteriorated, and improvement is required.

The present invention has been made in order to solve the above-mentioned problems, and it is therefore to provide a laminated body for protecting a polarizing film for obtaining a polarizing plate with excellent surface smoothness and a thickness of a photocurable resin layer of 9 μm or less and excellent in heat and humidity resistance, and a manufacturing method thereof Method for the purpose.

The inventors of the present case have accumulated a number of studies in order to achieve the above-mentioned purpose. It has been found that the thickness of the photocurable resin layer is 9 μm or less in length, and the boric acid penetration is 2.25 g / m ² The light-hardening resin layer is bonded to the polarizing film, and a polarizing plate with excellent moisture and heat resistance can also be obtained. The adhesion between the base film and the light-hardening resin layer is 0.005 to 0.06 N / mm, and light with excellent surface smoothness can be obtained. The resin layer is hardened, and the present invention is further repeated based on these findings.

That is, the present invention relates to:

[1] A laminated body for protecting a polarizing film, which is a laminated body for protecting a polarizing film obtained by laminating a photocurable resin containing a radical polymerizable compound on a base film, wherein the thickness of the photocurable resin layer is 9 μm Hereinafter, the boric acid penetration of the photocurable resin layer is 2.25 g / m ² or less in terms of boron atoms, and the adhesion between the substrate film and the photocurable resin layer is 0.005 to 0.06 N / mm. The root-mean-square surface roughness (rms) of the photocurable resin layer on the substrate film side after the substrate film is peeled off is 300 nm or less.

[2] A polarizing plate in which the light-curable resin layer of the laminated body for protecting a polarizing film according to [1] is adhered to at least one side of a polarizing film via an adhesive layer.

[3] A method for producing a laminated body for polarizing film protection as described in [1], which is a method for producing a laminated body for polarizing film protection obtained by laminating a photocurable resin containing a radical polymerizable compound on a base film. It is characterized in that it includes a step of applying a solution containing a radical polymerizable compound and a solvent to a substrate film; a step of heating the substrate film after application to volatilize the solvent; and irradiating ultraviolet rays and electron beams. At least one of the steps; the water contact angle of the coating surface of the substrate film is 40 to 100 degrees.

[4] The method for manufacturing a laminated body for protecting a polarizing film according to [3], wherein the detection intensity of silicon on the coating surface of the base film is 10 cps / mA or less.

According to the present invention, a laminated body for protecting a polarizing film that can obtain a polarizing plate having excellent surface smoothness and a thickness of a photocurable resin layer of 9 μm or less and excellent in moisture and heat resistance, and a method for producing the same can be provided.

1‧‧‧Light-hardened resin layer

2‧‧‧ Permeability container

3‧‧‧ pure water

4‧‧‧ airtight container

8 mass% boric acid aqueous solution at 5‧‧‧60 ° C

6‧‧‧ sample water

FIG. 1 is a schematic diagram related to a method for measuring the penetration of boric acid in terms of boric acid.

    [Form of Implementing Invention]    

The present invention will be described in detail below.

    <Laminated body for polarizing film protection>    

The laminated system for protecting a polarizing film of the present invention is a laminated body for protecting a polarizing film formed by laminating a light-curable resin layer containing a radical polymerizable compound with a thickness of 9 μm or less on a base film, which is characterized by boric acid in the photo-curable resin layer. The transmittance is 2.25 g / m ² or less in terms of boron atom. The degree of boric acid transmission through the light-hardening resin layer is 2.25 g / m ² or less in terms of boron atoms. When bonded to a polarizing film, a polarizing plate with excellent moisture and heat resistance that can maintain initial polarization performance can be obtained. If the boric acid penetration exceeds 2.25 g / m ² in terms of boron atom, ‧day, the moisture and heat resistance of the polarizing plate cannot be sufficiently improved. From this point of view, the boric acid penetration of the light-hardening resin layer is preferably 1.50 g / m ² or less in terms of boron atoms, more preferably 0.50 g / m ² or less, and even more preferably 0.20 g / m ² Below ‧day, especially preferred is below 0.10g / m ² ‧day. On the other hand, the lower limit of the boron atomic conversion of boric acid conversion of the photocurable resin layer is not particularly limited. When the boron atomic conversion of boric acid conversion is too low, the softness of the photocurable resin layer tends to be lost. The transmittance in terms of boron atom is preferably 0.02 g / m ² ‧day or more, and more preferably 0.03 g / m ² ‧day or more. In addition, the boric acid penetration in terms of boron atom can be obtained by the method described in the examples described later.

In the present invention, the photocurable resin layer system contains a radical polymerizable compound and the like. By using a radical polymerizable compound, it is possible to reduce the boric acid penetration of the boron atom conversion of the obtained photocurable resin layer. As the radical polymerizable compound, a compound having an acrylofluorenyl group in the molecule is preferably used. The radical polymerizable compound may be used singly or in combination of two or more kinds. Moreover, as a photopolymerization initiator for irradiating at least one of ultraviolet rays and an electron beam to harden it, a radical polymerization initiator is preferably used. As the radical polymerization initiator, a compound that can promote the reaction of a radical polymerizable compound by irradiating an active energy ray can be used. Examples of such a radical polymerization initiator include carbonyl compounds such as acetophenones, benzophenones, Michler's ketones, and benzoin; tetramethylmethanilamine monosulfide, thioxanthine Sulfur compounds such as ketones, etc., are preferably carbonyl compounds. These radical polymerization initiators may be used individually by 1 type, and may use 2 or more types together.

In the present invention, the thickness of the photocurable resin layer is 9 μm or less. When the thickness exceeds 9 μm, a polarizing plate with a conventional protective film laminated cannot be sufficiently thinned. From this viewpoint, the thickness of the photocurable resin layer is preferably 8 μm or less, more preferably 7 μm or less, and even more preferably 6 μm or less. On the other hand, the lower limit of the thickness of the photocurable resin layer is not particularly limited. If the boron acid penetration of the boron atom conversion is to be achieved with a thinner photocurable resin layer, the softness of the photocurable resin layer tends to be lost. Therefore, it is preferably 0.1 μm or more, more preferably 0.5 μm or more, and even more preferably 1 μm or more.

The substrate film used in the laminated body for polarizing film protection of the present invention is preferably one having excellent surface uniformity. Polycarbonate film, cellulose triacetate film, norbornene film, polypropylene film, polyester can be used. Film, polystyrene film, etc. The surface of the substrate film on the photocurable resin layer side may be subjected to a release treatment. By using a substrate film having excellent surface uniformity, the root-mean-square surface roughness (rms) of the photocurable resin layer on the substrate film side after the substrate film is peeled from the photocurable resin layer tends to be 300 nm or less.

In the present invention, the adhesion between the photocurable resin layer and the substrate film is 0.005 to 0.06 N / mm. After the light-hardening resin layer is bonded to the polarizing film to obtain a polarizing plate, the base film needs to be peeled off from the light-hardening resin layer. Therefore, the adhesion between the light-hardening resin layer and the base film is preferably 0.05 N / mm or less. It is preferably 0.04 N / mm or less, and even more preferably 0.03 N / mm or less. In addition, by strengthening the release treatment of the base film used, the adhesion between the photocurable resin layer and the base film can be made 0.06 N / mm or less. When the adhesion between the photocurable resin layer and the base film is too low, when the laminated body for polarizing film protection such as when the photocurable resin layer and the polarizing film are bonded, the base film is likely to peel off from the photocurable resin layer. It is not easy to handle. Therefore, the adhesion between the light-hardening resin layer and the substrate film is preferably 0.010 N / mm or more, more preferably 0.013 N / mm or more, and still more preferably 0.015 N / mm or more.

In the present invention, the root-mean-square surface roughness (rms) of the photocurable resin layer on the substrate film side after the substrate film is peeled from the photocurable resin layer is 300 nm or less. The root-mean-square roughness (rms) of the photocurable resin layer on the substrate film side is preferably 250 nm or less, more preferably 200 nm or less, and still more preferably 150 nm or less. In order to make the root-mean-square roughness (rms) of the photocurable resin layer on the base film side be 300 nm or less, it is important to include a radical polymerizable compound and The solvent solution does not spring up; and the peelability of the base film and the photocurable resin layer is good; for example, as described later, the solubility parameter of the solvent used for the radical polymerizable compound or the water contact angle of the coating surface of the base film is adjusted Department is valid. The lower limit of the root-mean-square surface roughness (rms) of the photocurable resin layer on the substrate film side is not particularly limited, and it is not easy to have an extremely smooth surface, but it is, for example, 20 nm or more.

    <Manufacturing method of laminated body for polarizing film protection>    

As for the manufacturing method of the laminated body for polarizing film protection of this invention, it is preferable to have the process of apply | coating the solution containing a radically polymerizable compound and a solvent to a base film, and heating a base film after coating. The step of volatilizing the solvent; and the step of irradiating at least one of ultraviolet rays and electron beams; and the water contact angle of the coating surface of the substrate film is 40 to 100 degrees. By including a solvent in this solution, the surface smoothness of the photocurable resin layer having a thickness of 9 μm or less is good.

    [Coating step]    

In the step of applying a solution containing a radically polymerizable compound and a solvent to the substrate film, any appropriate method can be adopted. Examples of the method for applying a solution containing a radically polymerizable compound and a solvent to a substrate film include die coating, roll coating, air knife coating, gravure roller coating, doctor blade coating, doctor blade coating, and curtain coating. , Spray coating, wire rod coating, rod coating, dipping, brush coating and other methods. Among these, in order to make the thickness of the obtained photocurable resin layer 9 μm or less, gravure roll coating is preferred.

    [Solvent evaporation step]    

For the step of heating the substrate film after the solution is applied to volatilize the solvent, any appropriate method can be adopted. The solution-coated substrate film can be heated on a heat roller or in a floating dryer. The preferred temperature of the hot roll or hot air can be determined according to the boiling point of the solvent used, and is preferably in the range of 60 ° C to 120 ° C. The solvent is preferably volatilized until the residual amount of the solvent becomes 10% or less.

    [Irradiation procedure]    

In the step of irradiating at least one of ultraviolet rays and electron beams, the solution applied on the substrate film may be directly irradiated with at least one of ultraviolet rays and electron beams after drying, or may be irradiated from the substrate film side. From the viewpoints of curing speed, availability of an irradiation device, and price, it is more preferable to have a step of irradiating ultraviolet rays.

The aforementioned ultraviolet rays or electron beams can be irradiated using a known device. When using ultraviolet rays, high-pressure mercury lamps, ultra-high-pressure mercury lamps, carbon arc lamps, metal halide lamps, xenon lamps, chemical lamps, LEDs, etc., which can emit light in a wavelength range below 450 nm can be used. When an electron beam (EB) is used, the acceleration voltage is preferably in the range of 0.1 to 10 MeV, and the irradiation dose is preferably in the range of 1 to 500 kGy.

The integrated light quantity of ultraviolet or electron beam is not particularly limited, it is preferably in the range of 10 ~ 20,000mJ / cm ^2, and more preferably in the range of 30 ~ 5,000mJ / cm ² in. If the amount of integrated light of ultraviolet rays or electron beams is too small, the hardening of the radical polymerizable compound will be poor, and the boron atom conversion of the photocurable resin layer will increase, or the mechanical strength of the photocurable resin layer will decrease. On the other hand, if the amount of accumulated light of ultraviolet rays or electron beams is too much, the laminated body for polarizing film protection generates excessive heat, which causes deterioration of the photocurable resin layer or the base film.

In order to increase the crosslinking density of the photo-curable resin layer during or after the irradiation with ultraviolet rays or electron beams, heating can also be performed as needed to promote the curing of the photo-curable resin layer. In view of this heating temperature, from the viewpoint of the curing speed or the effect on the light-curable resin layer and the base film, it is preferably in the range of 40 to 130 ° C, and more preferably in the range of 50 to 100 ° C. When the temperature is lower than 40 ° C, it is difficult to promote the curing of the photocurable resin layer; when the temperature exceeds 130 ° C, the substrate film is easily deformed, and a smooth photocurable resin layer cannot be obtained. The above method can sufficiently increase the crosslink density of the photocurable resin layer on the substrate film, and can appropriately reduce the boric acid penetration of boron atom conversion.

In the method for manufacturing a laminated body for protecting a polarizing film of the present invention, the water contact angle of the solution-coated surface of the base film is preferably 40 to 100 degrees. When the water contact angle of the solution coating surface of the base film is large, the solution is easy to bounce off when the solution is coated on the base film, and it is not easy to uniformly apply the solution. Furthermore, even if the solution can be applied uniformly, there is still a problem that the surface of the photocurable resin layer on the substrate film side after the substrate film is peeled off by the photocurable resin layer is not easily smooth. On the other hand, when the water contact angle is small, the adhesion force between the base film and the photo-curable resin layer becomes strong, and it is difficult to peel the base film from the photo-curable resin layer or the substrate after the base film is peeled from the photo-curable resin layer. The surface smoothness of the photocurable resin layer on the material film side is deteriorated. Based on these viewpoints, the water contact angle of the solution-coated surface of the substrate film is preferably 45 to 95 degrees, more preferably 50 to 90 degrees, and even more preferably 55 to 85 degrees. In order to adjust the water contact angle of the solution-coated surface of the base film to the above range, it is effective to adjust the strength of the hydrophilization treatment such as corona treatment.

The solubility parameter (SP value) of the solvent containing the solution of the radically polymerizable compound and the solvent is preferably 8 to 10 (cal / cm ³ ) ^1/2 . If the solubility parameter of the solvent is too small or too large, when the solution is coated on the substrate film, the solution is easy to pop open, and it is not easy to uniformly apply the solution. From this point of view, the solubility parameter of the solvent is preferably in the range of 8.2 to 9.8 (cal / cm ³ ) ^1/2 , more preferably in the range of 8.4 to 9.6 (cal / cm ³ ) ^1/2 , and particularly preferably 8.6 to 9.4. (cal / cm ³ ) ^1/2 range. Solubility parameters are documented in the literature (as an example, the Polymer Materials Handbook: Edited by the Polymer Society, Solvent Handbook; edited by Terasa Asahara, DWVAN KREVELEN, PROPERTIES OF POLYMERS Third edition, p214 ~ 220 (1990), etc.).

In the manufacturing method of the laminated body for polarizing film protection of this invention, it is preferable that the detection intensity of the silicon of the coating surface of a base film is 10 cps / mA or less. In general, by applying a silicon-containing release agent or the like to the surface of a base film, the peelability of the formed photocurable resin layer can be made better. However, there is a problem that a silicon-containing release agent or the like is transferred to a solution containing a radically polymerizable compound and a solvent, resulting in a change in the physical properties of the obtained photocurable resin layer or contamination of equipment for manufacturing a laminated body for protecting a polarizing film. Therefore, it is preferable to use a base film that is subjected to a release treatment without using a silicon-containing release agent. The measurement of silicon on the coated surface of the base film can be performed using an X-ray analysis microscope as described in Examples described later.

    <Polarizer>    

The polarizing plate obtained according to the present invention is obtained by bonding a photocurable resin layer to at least one side of a polarizing film through an adhesive layer. Thereby, a polarizing plate excellent in moist heat resistance and surface smoothness can be obtained. The polarizing film used to make the polarizing plate can be uniaxially stretched to a PVA film pre-containing dichroic pigment, and simultaneously adsorb the dichroic pigment with the uniaxial stretching of the PVA film, or uniaxially to the PVA film. It is manufactured by adsorbing a dichroic dye or the like after stretching.

By bonding the light-hardening resin layer in the laminated body for protecting a polarizing film of the present invention to a polarizing film, it is possible to produce a polarizing plate that is thin and lightweight, and has superior humidity and heat resistance. The manufacturing method of the polarizing plate is not particularly limited, and it can be manufactured by a manufacturing method having, for example, the following steps: At least one side of the polarizing film is bonded to the photocurable resin in the laminated body for polarizing film protection of the present invention through an adhesive layer. A step of laminating (adhesion step); and a step of hardening the adhesive layer by irradiating at least one of ultraviolet rays or electron beams after the lamination step (next step); further, peeling off the substrate film after the next step Step (peeling step).

    [Laminating step]    

In the bonding step, the photocurable resin layer in the polarizing film protection laminate of the present invention is bonded to at least one side of the polarizing film via an adhesive layer. This laminating method is not particularly limited, and is based on simpler lamination, and is preferably a method of laminating a polarizing film after applying an adhesive to the photocurable resin layer of the laminated body for polarizing film protection of the present invention. Furthermore, an adhesive may be applied to the photocurable resin layer of another laminated body for polarizing film protection, and then laminated on the other side of the polarizing film. The method of applying the adhesive is not particularly limited, and examples thereof include die coating, roll coating, air knife coating, gravure roll coating, doctor roll coating, doctor blade coating, curtain coating, spray coating, wire rod coating, rod coating, and brush Coating and other methods.

The paste obtained in the pasting step may be pressed with a roller or the like. In this case, examples of the material of the roller include metal and rubber.

The adhesive used is not particularly limited as long as it is capable of adhering a polarizing film and a photocurable resin layer, and a solvent-free photocurable adhesive is preferably used.

In addition, in order to further improve the adhesion between the polarizing film and the light-hardening resin layer, the surface of the light-hardening resin layer may be modified by a known corona treatment, plasma treatment, UV treatment, flame treatment, or the like, as required.

    [Next steps]    

In the subsequent step, the uncured adhesive layer is cured by irradiating at least one of ultraviolet rays or electron beams. Irradiation with ultraviolet rays or electron beams can be performed using a known device. Integrated light quantity of ultraviolet or electron beam is not particularly limited, it is preferably in the range of 10 ~ 20,000mJ / cm ^2, and more preferably in the range of 30 ~ 5,000mJ / cm ² in. If the amount of accumulated light is too small, the adhesion between the polarizing film and the photocurable resin layer is insufficient. On the other hand, if the cumulative amount of light is too large, excessive heat is generated, and the adhesive layer, the polarizing film, and the photocurable resin layer are deteriorated. In addition, from the viewpoints of curing speed, availability of irradiation equipment, and price, it is more preferable to use ultraviolet rays.

During or after irradiation with ultraviolet rays or electron beams, the hardening of the adhesive layer can also be promoted by heating as required. This heating temperature is based on viewpoints such as the hardening rate and the degree of deterioration of the polarizing film, etc., and is preferably in the range of 40 to 130 ° C, and more preferably in the range of 50 to 100 ° C. When the temperature is lower than 40 ° C, it is difficult to promote the hardening of the adhesive layer; when the temperature is higher than 130 ° C, the polarizing film or the substrate film is easily deteriorated or deformed, and it is difficult to obtain a polarizing plate with excellent polarization performance or smoothness.

    [Stripping step]    

By peeling the base film after the subsequent step, a polarizing plate in which the photocurable resin layer is disposed on at least one side of the polarizing film through the adhesive layer can be obtained.

    [Example]    

The present invention will be described more specifically based on the following examples, but the present invention is not limited at all by these examples. In addition, various evaluation methods or measurement methods used in the following examples and comparative examples are shown below.

    [Boric acid penetration in terms of boron atom of photocurable resin layer]    

The light-hardening resin layer obtained in each of the following examples or comparative examples was mounted in a moisture-permeable container (fastened type, based on JIS Z-0208) containing pure water, and immersed in an 8 mass% boric acid aqueous solution at 60 ° C. . Then, the ICP luminescence analysis method (Shimadzu MULTI-type ICP luminescence analyzer ICPE-9000, manufactured by Shimadzu Corporation) was used to analyze the sample water (pure water) in the water vapor permeability container before the test and the water vapor permeability after immersion for 24 hours. The boron concentration of the sample water in the cup was calculated from the increase in boron concentration according to the following formula (1): the boric acid penetration (A) (see Fig. 1).

A = ((a ₂₄ -a ₀ ) × 10 ^-6 × M) / S (1)

A: Boric acid penetration in terms of boron atom [g / m ² ‧day]

a ₂₄ : boron concentration in sample water after 24 hours [ppm]

a ₀ : boron concentration of the sample water (pure water) before the start of the test [ppm]

M: weight of sample water [g]

S: The area where the light-hardening resin layer is in contact with the aqueous boric acid solution (penetration area of the water permeability container) [m ² ]

    [Adhesion between substrate film and photocurable resin layer]    

After the laminated bodies for polarizing film protection obtained in each of the following examples or comparative examples were allowed to stand under the conditions of 23 ° C and 50% RH for 24 hours, 5 pieces of 250 mm × 25 mm were cut out of the laminated bodies for polarizing film protection. Long thin film sheet. Next, for each film sheet, the base film and the photocurable resin layer were peeled in accordance with a T-type peel test according to JIS K6854-3: 1999, and the average value of five measurements of the obtained peel force was used as the adhesion force. In this test, the peeling speed was set to 30 mm / minute. In addition, when the adhesion between the base film and the photo-curable resin layer is too high and the base film or the photo-curable resin layer is damaged, it is evaluated as "material failure".

    [Root-Mean-Square Roughness (rms) of the Photocurable Resin Layer on the Base Film Side]    

The base film of the laminated body for polarizing film protection obtained in each of the following Examples or Comparative Examples was peeled off to expose the surface of the photocurable resin layer on the base film side. Thereafter, the surface shape of the photocurable resin layer on the base film side was measured using a white interference microscope (manufactured by Zygo), and the root-mean-square surface roughness (rms) was calculated (the calculation range was 2.0 mm × 2.7 mm).

    [Water contact angle]    

A 200 mm × 15 mm long thin film sheet was cut from the substrate film used in the following examples or comparative examples, and the solution coating of this thin film sheet was measured in accordance with JIS R3257: 1999 (Test method for wettability of the substrate glass surface). Water contact angle on the surface. That is, a water droplet of 4 μL or less is left to stand on a horizontally arranged film sheet, and the shape of the water droplet is measured. The radius r (mm) of the surface where the water droplet contacts the film sheet, and the height h (mm) ), And the water contact angle θ (degrees) is obtained by the following formula (2).

θ = 2tan ^-1 (h / r) (2)

The measurement was performed five times, and the average value was used as the water contact angle of the base film. The measurement was performed under the conditions of 25 ° C and 50% RH.

    [Silicon on the coating surface of the base film]    

A 50 mm square film was cut from the base film used in the following examples or comparative examples, and an X-ray analysis microscope (XGT-5200 manufactured by Horiba, Ltd. was used. The X-ray irradiation diameter was 100 μm and the current was 1 mA. The X-ray tube The voltage was 30 kV, and the measurement time was 400 seconds.)

    [Total transmittance and polarization of polarizing plate]    

From the central portion in the width direction (TD) of the polarizing plate obtained in the following examples or comparative examples, two rectangular samples having a length direction (MD) of the polarizing plate of 2 cm and a width direction (TD) of 3 cm were taken. For each sample, the light transmittance at a 45 ° inclination from the longitudinal direction and the light transmittance at a -45 ° inclination were measured, and the average of all of them was taken as the total transmittance (%) of the polarizing plate. . In addition, the light transmittance T ∥ (%) when the two samples were in a parallel Nicols state were measured in the same manner as in the case of the total light transmittance (%), and the two samples were orthogonal. The light transmittance T ⊥ (%) in the Nicols state was determined by the following formula (3). In addition, the transmittance was measured using a spectrophotometer with an integrating sphere ("V7100" manufactured by JASCO Corporation) in accordance with JIS Z 8722 (method for measuring the color of an object), and visible light with a C light source and a 2 ° field of view Visual sensitivity correction of the area.

Polarization = ((T ∥-T ⊥) / (T ∥ + T ⊥)) ^1/2 × 100 (3)

In addition, the initial total light transmittance before the moist heat resistance test was set to T ₀ .

    [Damp and heat resistance of polarizing plate]    

From the central portion of the width direction (TD) of the polarizing plate obtained in the following examples or comparative examples, two rectangular samples having a length direction (MD) of the polarizing plate of 4 cm and a width direction (TD) of 3 cm were taken. Each was fixed to a metal frame, and the initial total light transmittance (T ₀ ) and the degree of polarization were obtained according to the above method. A 60 ° C, 90% RH thermo-hygrostat (HUMIDIC CHAMBER IG400, manufactured by Yamato Scientific Co., Ltd.) was placed, and a 48-hour humidity and heat resistance test was performed. The total light transmittance after the humidity and heat resistance test (T ₄₈ ). Polarization. From the above T ₀ and T ₄₈ , the change amount (ΔT) of the total light transmittance was obtained by the following formula (4), and this was used as an index of the moisture and heat resistance of the polarizing plate.

△ T = T ₄₈ -T ₀ (4)

    [Example 1]         <Production of laminated body for polarizing film protection>    

HITALOID 7975 (manufactured by Hitachi Chemical Co., Ltd., resin content 32% by mass, solvent toluene, and solvent SP value 8.9 was measured in a sample tube as a solution containing the radical polymerizable compound and a solvent. ) 31.25 g and 0.4 g of 1-hydroxycyclohexylphenyl ketone (IRGACURE 184 manufactured by BASF) were stirred and mixed uniformly for 24 hours to obtain a solution. Thereafter, LAYHIPAR F (manufactured by Nakai Industry Co., Ltd., water contact angle 68.9 degrees, silicon detection strength 5.25 cps / mA) was cut into a size 300 mm × 150 mm as a base film, and a rod was used. The applicator applied the solution to the release-treated surface, heated it at 70 ° C for 1 minute to volatilize the solvent, and then used an ultraviolet irradiation device (using a metal halide lamp of GS YUASA Co., Ltd., with an irradiation intensity of 300 mW / cm ² ). Ultraviolet rays were irradiated so that the accumulated light amount reached 300 mJ / cm ² to obtain a laminated body for polarizing film protection having a light-curing resin layer having a thickness of 5.9 μm on the base film. The cumulative light amount was measured using a UV measuring device (GS YUASA Co., Ltd.).

    <Evaluation of laminated body for polarizing film protection>    

With respect to the obtained laminated body for protecting a polarizing film, the boric acid conversion of the boron atom conversion of the photocurable resin layer, the adhesion force of the base film and the photocurable resin layer, and the Evaluation of root mean square roughness (rms). The results are shown in Tables 1 and 2.

    <Production of Polarizing Film>    

A long-sized PVA film (including PVA, glycerol, and a surfactant, having a thickness of 30 μm and a width of 65 cm, contains 12 parts by mass of glycerol relative to 100 parts by mass of PVA; and 100 parts by mass of PVA, a surfactant The content of PVA film is 0.03 parts by mass. PVA is a saponified product of a homopolymer of vinyl acetate with a degree of polymerization of 2,400 and a degree of saponification of 99.9 mol%. The film is continuously rolled out from the film roll, subjected to swelling treatment, and dyed. Treatment, cross-linking treatment, stretching treatment, fixing treatment, and drying treatment to form a polarizing film.

That is, for the swelling treatment, the PVA film was immersed in water at 30 ° C. for 1 minute, and during this period, uniaxial stretching was performed at a stretching ratio of 2 times in the longitudinal direction. Then, the dyeing treatment was performed by immersing in an aqueous solution (iodine concentration: 0.02% by mass, potassium iodide concentration: 0.4% by mass, 30 ° C) containing an iodine-based pigment for 1 minute, and the stretching was performed in the lengthwise direction at 1.2 times during this period. Uniaxial stretching. Further, the crosslinking treatment was immersed in an aqueous boric acid solution (boric acid concentration: 2.6% by mass, 30 ° C.) for 2 minutes, and during this period, uniaxial stretching was performed at a stretching ratio of 1.1 times in the longitudinal direction. Next, the stretching treatment was performed in a boric acid aqueous solution (boric acid concentration: 2.8% by mass, potassium iodide concentration: 5% by mass, 57 ° C) at a stretching ratio of 2.4 times in the longitudinal direction (total stretching ratio) 6.3 times). The fixing treatment was performed by immersing in a boric acid aqueous solution (boric acid concentration: 1.5% by mass, potassium iodide concentration: 5% by mass, 22 ° C) for 10 seconds. After that, it was dried and dried at 60 ° C for 1 minute to obtain a polarizing film.

    <Preparation of Adhesive>    

In a sample tube, weigh 2 g of 3-ethyl-3-hydroxymethyloxetane (OXT-101 manufactured by Toa Synthesis Co., Ltd.), 3 ', 4'-epoxycyclohexylmethyl 3,4- 8 g of epoxycyclohexane carboxylate (Celloxide 2021P, manufactured by DAICEL Co., Ltd.), 50% by mass solution of propylene carbonate with diphenyl [4- (phenylthio) phenyl] fluorene hexafluorophosphate (San -Apro Co., Ltd. CPI-100P) 0.8g, stirred for 24 hours and uniformly mixed to obtain an adhesive for adhering a polarizing film and a photocurable resin layer.

    <Production of Polarizing Plate>    

The laminated body for polarizing film protection was cut into two pieces having a size of 140 mm × 120 mm, and the above-mentioned adhesive was applied to the photocurable resin layer of the first laminated body for polarizing film protection with a bar coater. Next, a polarizing film cut into a length direction (MD) of 120 mm and a width direction (TD) of 100 mm was laminated thereon via the above-mentioned adhesive. After that, the same adhesive as described above was applied to the light-curing resin surface of the second polarizing film-protecting laminate by using a bar coater, and then laminated on the other surface of the polarizing film. The laminate having the substrate film / light-curable resin layer / adhesive agent / polarizing film / adhesive agent / light-curable resin layer / base film layer thus obtained is pressed by a laminator, The partial thickness of the agent was adjusted to 1 μm. Thereafter, the substrate was irradiated with ultraviolet rays to harden the adhesive, and then the substrate film on both sides was peeled off to obtain a polarizing plate.

    <Evaluation of Polarizer>    

For the obtained polarizing plate, the initial polarizing performance (initial total light transmittance (T ₀ ), degree of polarization) of the polarizing plate and the polarizing performance (total transmittance after moist-heat resistance test) of the polarizing plate after the moist-heat resistance test were performed according to the aforementioned method. Evaluation of luminosity (T ₄₈ ), degree of polarization, and total light transmittance (ΔT)). The results are shown in Table 2.

    [Example 2]    

A laminated body for polarizing film protection and a polarizing plate were obtained in the same manner as in Example 1 except that the thickness of the obtained photocurable resin layer was 1.4 μm. For the obtained laminated body for protecting a polarizing film and a polarizing plate, the boric acid conversion of the boron atom conversion of the photocuring resin layer, the adhesion between the base film and the photocuring resin layer, and the uniformity of the photocuring resin layer on the base film side were performed. Square root surface roughness (rms), initial polarizing performance of the polarizer (initial total light transmittance (T ₀ ), degree of polarization), and polarizing performance after polarizing plate's humidity and heat resistance test (total transmittance after humidity and heat resistance test) Evaluation of luminosity (T ₄₈ ), degree of polarization, and total light transmittance (ΔT)). The results are shown in Tables 1 and 2.

    [Example 3]    

Except as the base film, LAYHIPAR N1 (manufactured by Nakai Industry Co., Ltd., water contact angle of 84 degrees, silicon detection strength of 5.89 cps / mA) was used as the PET film; and the thickness of the obtained photocurable resin layer was 5.5. Except for μm, a laminated body for polarizing film protection and a polarizing plate were obtained in the same manner as in Example 1. For the obtained laminated body for protecting a polarizing film and a polarizing plate, the boric acid conversion of the boron atom conversion of the photocuring resin layer, the adhesion between the base film and the photocuring resin layer, and the uniformity of the photocuring resin layer on the base film side were performed. Square root surface roughness (rms), initial polarizing performance of the polarizer (initial total light transmittance (T ₀ ), degree of polarization), and polarizing performance after polarizing plate's humidity and heat resistance test (total transmittance after humidity and heat resistance test) Evaluation of luminosity (T ₄₈ ), degree of polarization, and total light transmittance (ΔT)). The results are shown in Tables 1 and 2.

    [Example 4]    

Except as the base film, Purex AN15 (manufactured by TEIJIN DUPONT FILM Co., Ltd., water contact angle of 82.7 degrees, silicon detection strength of 6.12 cps / mA) was used as the PET film; and the thickness of the obtained photocurable resin layer was Except for 5.6 μm, a laminated body for polarizing film protection and a polarizing plate were obtained in the same manner as in Example 1. For the obtained laminated body for protecting a polarizing film and a polarizing plate, the boric acid conversion of the boron atom conversion of the photocuring resin layer, the adhesion between the base film and the photocuring resin layer, and the uniformity of the photocuring resin layer on the base film side were performed. Square root surface roughness (rms), initial polarizing performance of the polarizer (initial total light transmittance (T ₀ ), degree of polarization), and polarizing performance after polarizing plate's humidity and heat resistance test (total transmittance after humidity and heat resistance test) Evaluation of luminosity (T ₄₈ ), degree of polarization, and total light transmittance (ΔT)). The results are shown in Tables 1 and 2.

    [Example 5]    

In a sample tube, 5 g of dimethylol tricyclodecane diacrylate (LIGHT ACRYLATE DCP-A, manufactured by Kyoeisha Chemical Co., Ltd.), which is a radical polymerizable compound, was weighed in different amounts to ginseng (2-hydroxyethyl). 5 g of cyanurate triacrylate (M-315, manufactured by Toa Synthesis Co., Ltd.), 0.4 g of 1-hydroxycyclohexylphenyl ketone (IRGACURE 184, manufactured by BASF) as a photopolymerization initiator, and acetic acid as a solvent Any amount of ethyl ester (manufactured by Wako Pure Chemical Industries, Ltd., SP value 9.1) was stirred for 24 hours and uniformly mixed to obtain a solution. Thereafter, a laminated body for polarizing film protection and a polarizing plate were obtained in the same manner as in Example 1 except that the thickness of the obtained photocurable resin layer was 5.1 μm. For the obtained laminated body for protecting a polarizing film and a polarizing plate, the boric acid conversion of the boron atom conversion of the photocuring resin layer, the adhesion between the base film and the photocuring resin layer, and the uniformity of the photocuring resin layer on the base film side were performed. Square root surface roughness (rms), initial polarizing performance of the polarizer (initial total light transmittance (T ₀ ), degree of polarization), and polarizing performance after polarizing plate's humidity and heat resistance test (total transmittance after humidity and heat resistance test) Evaluation of luminosity (T ₄₈ ), degree of polarization, and total light transmittance (ΔT)). The results are shown in Tables 1 and 2.

    [Comparative Example 1]    

16.67 g of HITALOID 7975D (manufactured by Hitachi Chemical Co., Ltd., 60% by mass of resin, methyl isobutyl ketone, and solvent SP value of 8.4) as a radical polymerizable compound was measured in a sample tube. 0.4 g of 1-hydroxycyclohexylphenyl ketone (IRGACURE 184 manufactured by BASF) as a polymerization initiator was stirred for 24 hours and uniformly mixed to obtain a solution. Thereafter, a laminated body for polarizing film protection and a polarizing plate were obtained in the same manner as in Example 1 except that the thickness of the obtained photocurable resin layer was 6.0 μm. For the obtained laminated body for protecting a polarizing film and a polarizing plate, the boric acid conversion of the boron atom conversion of the photocuring resin layer, the adhesion between the base film and the photocuring resin layer, and the uniformity of the photocuring resin layer on the base film side were performed. Square root surface roughness (rms), initial polarizing performance of the polarizer (initial total light transmittance (T ₀ ), degree of polarization), and polarizing performance after polarizing plate's humidity and heat resistance test (total transmittance after humidity and heat resistance test) Evaluation of luminosity (T ₄₈ ), degree of polarization, and total light transmittance (ΔT)). The results are shown in Tables 1 and 2.

    [Comparative Example 2]    

In a sample tube, 10 g of 3 ', 4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate (Celloxide 2021P, manufactured by DAICEL Co., Ltd.) was weighed as a radical polymerizable compound, and polymerized as a polymer. A starting solution containing 50% by mass of a solution of diphenyl [4- (phenylthio) phenyl] fluorene hexafluorophosphate and a solvent of propylene carbonate (CPI-100P manufactured by San-Apro Co., Ltd.) 0.8 g , Stir for 24 hours and mix uniformly to obtain a solution. Thereafter, a laminated body for polarizing film protection and a polarizing plate were obtained in the same manner as in Example 1 except that the thickness of the obtained photocurable resin layer was 6.1 μm. For the obtained laminated body for protecting a polarizing film and a polarizing plate, the boric acid conversion of the boron atom conversion of the photocuring resin layer, the adhesion between the base film and the photocuring resin layer, and the uniformity of the photocuring resin layer on the base film side were performed. Square root surface roughness (rms), initial polarizing performance of the polarizer (initial total light transmittance (T ₀ ), degree of polarization), and polarizing performance after polarizing plate's damp heat resistance test (total transmittance after damp heat resistance test Evaluation of luminosity (T ₄₈ ), degree of polarization, and total light transmittance (ΔT)). The results are shown in Tables 1 and 2.

    [Comparative Example 3]    

Except as the base film, Purex A31 (manufactured by TEIJIN DUPONT FILM Co., Ltd., with a water contact angle of 110.6 degrees and a silicon detection strength of 19.24 cps / mA) was used as the PET film; and the thickness of the obtained photocurable resin layer was Except for 5.7 μm, a laminated body for protecting a polarizing film was obtained in the same manner as in Example 1. However, since the solution is spread away when applied to a PET film, a photo-curable resin layer with a uniform film surface cannot be obtained. Therefore, it is impossible to perform boric acid conversion in terms of boron atom conversion of the obtained photocurable resin layer, adhesion between the substrate film and the photocurable resin layer, and root-mean-square surface roughness (rms) of the photocurable resin layer on the substrate film side. , The initial polarizing performance of the polarizing plate (initial total light transmittance (T ₀ ), degree of polarization) and the polarizing performance after the polarizing plate's humidity and heat resistance test (the total light transmittance after the humidity and heat resistance test (T ₄₈ ), polarized light) And the total light transmittance (ΔT)). The results are shown in Tables 1 and 2.

    [Comparative Example 4]    

Except as the base film, Purex A71 (manufactured by TEIJIN DUPONT FILM Co., Ltd., with a water contact angle of 108.2 degrees and a silicon detection strength of 18.55 cps / mA) was used as the PET film; and the thickness of the obtained light-hardening resin layer was Except for 5.8 μm, a laminated body for protecting a polarizing film and a polarizing plate were obtained in the same manner as in Example 1. For the obtained laminated body for protecting a polarizing film and a polarizing plate, the boric acid conversion of the boron atom conversion of the photocuring resin layer, the adhesion between the base film and the photocuring resin layer, and the uniformity of the photocuring resin layer on the base film side Evaluation of square root surface roughness (rms). Because the root-mean-square roughness of the light-hardening resin layer on the substrate film side is extremely large, it is judged as not applicable, and the initial polarization performance (initial total light transmittance (T ₀ ), polarization degree) and polarization of the polarizing plate are discontinued. Evaluation of the polarizing performance (total light transmittance (T ₄₈ ), polarization degree, and total light transmittance change (ΔT) after the moist heat resistance test) of the board after the moist heat resistance test. The results are shown in Tables 1 and 2.

    [Comparative Example 5]    

Except for the substrate film, which uses corona treatment on Purex A71 (manufactured by TEIJIN DUPONT FILM Co., Ltd., the detection strength of silicon is 18.55 cps / mA) to release the PET film to make the water contact angle 33.3 degrees A laminated body for polarizing film protection and a polarizing plate were obtained in the same manner as in Example 1. For the obtained laminated body for protecting a polarizing film and a polarizing plate, the boric acid conversion of the boron atom conversion of the photocuring resin layer, the adhesion between the base film and the photocuring resin layer, and the uniformity of the photocuring resin layer on the base film side were performed. Evaluation of square root surface roughness (rms). Because the root-mean-square roughness of the light-hardening resin layer on the substrate film side is extremely large, it is judged as not applicable, and the initial polarization performance (initial total light transmittance (T ₀ ), polarization degree) and polarization of the polarizing plate are discontinued. Evaluation of the polarizing performance (total light transmittance (T ₄₈ ), polarization degree, and total light transmittance change (ΔT) after the moist heat resistance test) of the board after the moist heat resistance test. The results are shown in Tables 1 and 2.

    [Comparative Example 6]    

Except for using TN-100 (manufactured by Toyobo Co., Ltd., the detection strength of silicon is 7.11 cps / mA) as the base film to corona treat the PET film with a water contact angle of 31.1 degrees. A laminated body for protecting a polarizing film was obtained in the same manner as in Example 1. However, the adhesion between the substrate film and the photo-curable resin layer was strong, and the photo-curable resin layer was damaged in material. Therefore, it is impossible to perform boric acid conversion of the boron atom conversion of the photo-hardening resin layer, the root-mean-square surface roughness (rms) of the photo-hardening resin layer on the substrate film side, and the initial polarization performance (initial total light transmittance) (T ₀ ), polarization degree) and polarization performance (total light transmittance (T ₄₈ ) after humidity and heat resistance test), polarization degree, total light transmittance change (△ T) ) 'S evaluation. The results are shown in Tables 1 and 2.

Claims (4)

A laminated body for protecting a polarizing film, which is a laminated body for protecting a polarizing film obtained by laminating a photocurable resin containing a radical polymerizable compound on a base film, wherein the thickness of the photocurable resin layer is 9 μm or less. The boric acid penetration of the light-curing resin layer is 2.25 g / m ² or less in terms of boron atoms. The adhesion between the substrate film and the light-curing resin layer is 0.005 to 0.06 N / mm. The substrate is peeled from the light-curing resin layer. The root-mean-square surface roughness (rms) of the photocurable resin layer on the substrate film side after the film is 300 nm or less.     A polarizing plate in which the light-curable resin layer of the laminated body for polarizing film protection according to claim 1 is bonded to at least one side of the polarizing film via an adhesive layer.         A method for producing a laminated body for polarizing film protection as claimed in claim 1, which is a method for producing a laminated body for polarizing film protection obtained by laminating a light-curable resin containing a radical polymerizable compound on a base film, which is characterized by The method comprises the steps of: applying a solution containing a radically polymerizable compound and a solvent to a substrate film; heating the substrate film after the application to volatilize the solvent; and irradiating at least one of ultraviolet rays and an electron beam. The water contact angle of the coating surface of the substrate film is 40 to 100 degrees.         For example, the method for manufacturing a laminated body for protecting a polarizing film of claim 3, wherein the detection intensity of silicon on the coating surface of the base film is 10 cps / mA or less.