JP2018077355A - Multilayer optical film and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer optical film in which a peelable seal is pasted and which hardly causes display unevenness even if the seal is peeled.SOLUTION: A multilayer optical film 1 of the present invention includes: an optical film 2 including an optical anisotropy film; and a protective peeling film 3 pasted on the surface of the optical film 2 via an adhesive layer 4 in a peelable manner. The shear stress of the adhesive layer 4 is equal to or less than 22 N/cm, and a seal 5 is passed on the surface of the protective peeling film 3 in a peelable manner.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a laminated optical film and the like.

2. Description of the Related Art Conventionally, various optical films have been used as constituent members for image display devices such as liquid crystal display devices and projectors, and polarization filters for photographing devices such as polarized sunglasses and cameras.
For example, as an optical film used as a constituent member of a liquid crystal display device, a laminated body having a retardation film, a polarizing film and a protective film is generally used. Such an optical film is also called a polarizing plate.
By the way, a liquid crystal display device is obtained by assembling various components such as an optical film, a liquid crystal cell, a backlight, a casing including a bezel, and a power cord. Normally, not all of these constituent members are manufactured by the manufacturer of the liquid crystal display device, but the manufacture of each constituent member and the liquid crystal display device is divided. In other words, a liquid crystal display manufacturer (finished product manufacturer) purchases each component from an optical film manufacturer or a backlight manufacturer (parts manufacturer), and assembles the components to assemble the liquid crystal display. Often manufactures equipment.
Various measures have been taken to prevent the finished product and parts from being damaged during storage and transportation. For example, a protective release film is attached to an optical film assembled as a liquid crystal display device or an optical film as a pre-assembled part in order to protect the surface. This protective release film is often attached by a manufacturer of a finished product or a manufacturer of a part. In addition, such a peeling film for protection is also called a product protective film, and is affixed to the surface of the optical film so as to be easily peelable so as to be easily peeled by human power.

  Furthermore, the seal | sticker with which various information was comprised may be further affixed on the surface of such a peeling film for protection. Examples of information included in the seal include various symbols and numbers such as an optical mechanical reading symbol such as a barcode and a two-dimensional code, and a storage number. The information provided in the seal is used in the manufacturing process, and the seal is finally peeled off from the surface of the protective release film.

  However, after peeling off the seal from the surface of the protective release film, when the protective release film is further peeled off and the liquid crystal display device is driven, display unevenness (such as cloudiness) appears on the screen as a trace of the seal. Whitening) may occur.

  An object of the present invention is to provide a laminated optical film and an image display device in which display unevenness hardly occurs even when a peelable seal is attached.

As described above, the present inventors have found a problem that display unevenness occurs on the screen when the protective release film is peeled off after the seal is peeled off.
As for the cause of this problem, the following has been found.
First, when the protective release film with the seal attached was peeled from the screen without peeling off only the seal, the display unevenness did not occur. From this, it was presumed that peeling only the seal first was the cause of the display unevenness. Next, even when the protective peeling film was peeled off from the screen immediately after peeling off the seal, display unevenness did not occur. However, when the seal was peeled and left for a predetermined time, and then the protective release film was peeled off, display unevenness occurred. From these studies, the present inventors have found that the pressure-sensitive adhesive layer used for attaching the protective release film to the screen has an influence on the occurrence of display unevenness, and completed the present invention.

The laminated optical film of the present invention has an optical film having an optical anisotropic film, and a protective release film that is detachably attached to the surface of the optical film via an adhesive layer. The shear stress of the pressure-sensitive adhesive layer is 22 N / cm ² or less.

In a preferred laminated optical film of the present invention, the pressure-sensitive adhesive layer has a shear stress of 3 N / cm ² or more.
In a preferred laminated optical film of the present invention, a peelable seal is attached to the surface of the protective release film.
In a preferred laminated optical film of the present invention, the optical film has the optical anisotropic film and a protective film laminated on the surface of the optical anisotropic film.
In a preferred laminated optical film of the present invention, the optically anisotropic film includes a retardation film.

According to another aspect of the present invention, an image display device is provided.
The image display device of the present invention has the laminated optical film.

In the laminated optical film of the present invention, even when a seal is attached to the surface of the protective release film, the seal is peeled off, and further the protective release film is peeled off, display unevenness hardly occurs.
Such a laminated optical film can be suitably used as an optical member of an image display device.

The schematic perspective view which looked at the lamination optical film of the present invention from the surface side. However, the layer configuration of the optical film or the like is not shown. Sectional drawing of the laminated optical film which concerns on 1st Embodiment (sectional drawing cut | disconnected by the II-II line | wire of FIG. 1). Sectional drawing of the laminated optical film which concerns on 2nd Embodiment. Sectional drawing of the laminated optical film which concerns on 3rd Embodiment. Sectional drawing of the laminated optical film which concerns on 4th Embodiment. Sectional drawing of the laminated optical film which concerns on 5th Embodiment. The schematic perspective view which looked at the laminated optical film of 6th Embodiment from the surface side. However, the layer configuration of the optical film or the like is not shown. Sectional drawing cut | disconnected by the VIII-VIII line of FIG. The schematic perspective view which looked at the image display device of the present invention from the surface side. Sectional drawing of the image display apparatus cut | disconnected by the XX line of FIG. However, the layer configuration of the optical film or the like is not shown. The expanded sectional view of the XI-XI part of FIG. The reference side view for demonstrating the effect | action of the laminated optical film of this invention. The reference side view which shows the procedure of the measuring method of the shear stress of an adhesive layer. The photograph of the surface of the laminated optical film of the comparative example 1.

  In the present specification, an ordinal number such as “first” or “second” may be added in front of a term. This ordinal number is added to distinguish the terms, and the superiority or inferiority of the terms. It has no special meaning. Furthermore, in this specification, a numerical value connected by “to” means a numerical range including numerical values before and after “to” as a lower limit value and an upper limit value. When a plurality of lower limit values and a plurality of upper limit values are separately described, arbitrary lower limit values and upper limit values can be selected and connected by “˜”. It should be noted that the dimensions such as thickness and length shown in each figure and the relative proportions between the members are different from the actual ones.

[Laminated optical film]
The laminated optical film of the present invention includes an optical film and a protective release film that is detachably attached to the surface of the optical film via an adhesive layer.
The optical film includes an optically anisotropic film and a protective film laminated on the surface side of the optically anisotropic film.
In the present invention, an adhesive layer having a shear stress of 22 N / cm ² or less is used as an adhesive layer for attaching the protective release film to the optical film.

FIG. 1 is a perspective view of the laminated optical film of the first embodiment, and FIG. 2 is a sectional view thereof.
1 and 2, the laminated optical film 1 has an optical film 2 and a protective release film 3.
As shown in FIG. 2, the optical film 2 includes a protective film 21, a polarizing film 22, and a retardation film 23 in order from the surface side. These films (the protective film 21 and the polarizing film 22, and the polarizing film 22 and the retardation film 23) cannot be peeled off via an appropriate adhesive or adhesive (adhesive or adhesive not shown). It is glued to. When these films are materials that can be self-adhered to each other, the protective film 21 and the polarizing film 22, and the polarizing film 22 and the retardation film 23 can be directly used without using an adhesive or the like. It may be adhered to the surface so as not to be peeled off.
An adhesive layer 4 is provided on the back surface of the protective release film 3. The protective release film 3 is attached to the surface of the protective film 21 of the optical film 2 through the pressure-sensitive adhesive layer 4 so as to be peelable. The surface of the protective release film 3 constitutes the surface of the laminated optical film 1.
Here, the term “non-separable adhesion” means that the two bonded films have such adhesive strength that they cannot be peeled off manually, or the two films are peeled off so that the material destruction of the film occurs. It means that it is bonded with strength. The phrase “attached so as to be peelable” means that two films are attached with an adhesive strength that can be peeled by human power.

3 to 6 are cross-sectional views of the laminated optical films of the second to fifth embodiments. In addition, also in the laminated optical film of these embodiments, the perspective view seen from the surface side is the same as FIG.
The second embodiment is different from the first embodiment in that a surface treatment layer 24 is provided on the surface of the protective film 21. That is, as shown in FIG. 3, the optical film 2 of the second embodiment includes a surface treatment layer 24, a protective film 21, a polarizing film 22, and a retardation film 23 in order from the surface side. The surface treatment layer 24 is also bonded to the protective film 21 so as not to be peeled off. In the present embodiment, the surface of the surface treatment layer 24 constitutes the surface of the optical film 2, and thus the protective release film 3 is detachably attached to the surface of the surface treatment layer 24. Yes.
Examples of the surface treatment layer 24 include an antiglare layer and a hard coat layer.

The third embodiment is that the optically anisotropic film is composed of a polarizing film and two retardation films, and the optically anisotropic film is composed of a polarizing film and one retardation film. Is different.
That is, as shown in FIG. 4, the optical film 2 of the third embodiment has a protective film 21, a polarizing film 22, a first retardation film 231, and a second retardation film 232 in order from the surface side. And having. These films are bonded via an adhesive or a pressure sensitive adhesive (adhesive or pressure sensitive adhesive is not shown). These retardation films 231 and 232 are usually films having different birefringence.

The fourth embodiment is different from the first embodiment in that a protective film is also provided on the back side.
That is, as shown in FIG. 5, the optical film 2 of 4th Embodiment is the 1st protective film 211, the polarizing film 22, the retardation film 23, and the 2nd protective film 212 in order from the surface side. Have. These films are bonded so as not to be peeled off via an adhesive or the like (adhesive or the like is not shown). These protective films 211 and 212 may be films having the same material and thickness, or may be films having different materials or thicknesses.

The fifth embodiment is different from the first embodiment in that a protective release film is detachably attached to the back side of the optical film.
That is, as shown in FIG. 6, the laminated optical film 1 of 4th Embodiment is the 1st protective peeling film 31, the 1st adhesive layer 41, and the optical film 2 (for example, from the surface side) A protective film 21, a polarizing film 22 and a retardation film 23), a second pressure-sensitive adhesive layer 42, and a second protective release film 32.
The first protective release film 31 is detachably attached to the surface of the optical film 2 via the first pressure-sensitive adhesive layer 41, and the second protective release film 32 is a second pressure-sensitive adhesive layer. Via 42, it is affixed on the back surface of the optical film 2 so that peeling is possible. When two protective release films are provided as in this embodiment, the protective release films 31 and 32 may be the same material and thickness, or may be different materials or thicknesses. . In addition, at least one of the first pressure-sensitive adhesive layer 41 and the second pressure-sensitive adhesive layer 42 may be a pressure-sensitive adhesive layer having a shear stress of 22 N / cm ² or less, preferably the first pressure-sensitive adhesive layer 41. Both the second pressure-sensitive adhesive layer 42 has a shear stress of 22 N / cm ² or less.

In addition, although not shown, the above embodiments may be appropriately combined. For example, you may provide the 2nd peeling film for protection of 5th Embodiment in the laminated optical film of the layer structure of 2nd Embodiment, 3rd Embodiment, or 4th Embodiment.
In addition, the laminated optical film of each of the above embodiments includes a polarizing film and a retardation film as an optically anisotropic film. For example, the optically anisotropic film is composed only of a polarizing film or a retardation film. May be.

The sixth embodiment is different from the above embodiments in that the seal is detachably attached to the surface of the protective release film.
That is, as shown in FIGS. 7 and 8, the laminated optical film 1 of the sixth embodiment includes a protective release film 3, an adhesive layer 4, and an optical film 2 (for example, a protective film 21, a polarizing film 22, and A phase difference film 23), and a seal 5 is detachably attached to the surface of the protective release film 3. In FIG. 7, except for the seal 5, for convenience, the same laminated optical film 1 as the layer configuration shown in FIG. 2 (layer configuration of the first embodiment) is shown. But you may affix the said seal | sticker 5 on the surface of the peeling film for protection of the laminated optical film 1 of the layer structure shown in FIG. 3 thru | or FIG.
The seal 5 includes a base material 51 and an adhesive layer 52 provided on the back surface of the base material 51. Hereinafter, in order to distinguish from the adhesive layer 4 provided on the back surface of the protective release film 3, the adhesive layer 52 provided on the back surface of the base material 51 of the seal 5 is referred to as "seal adhesive layer").
In this embodiment, the seal 5 is detachably attached to the surface of the protective release film 3 via the seal adhesive layer 52.

<Polarizing film>
The polarizing film 22 shown in each figure is an optically anisotropic film showing absorption dichroism. The polarizing film has an absorption axis and a transmission axis in its plane. The polarizing film has a property of selectively transmitting linearly polarized light having a vibration direction parallel to the direction in which the transmission axis extends.
As the polarizing film, a conventionally known film can be used, and typically, a polarizing film obtained by adsorbing a dichroic substance to a hydrophilic polymer film and stretching (hereinafter referred to as “adsorptive polarizing film”). And a polarizing film obtained by applying a coating liquid containing an organic dye to an arbitrary film and drying (hereinafter referred to as “coating-type polarizing film”). In the present invention, it is preferable to use an adsorptive polarizing film.
The hydrophilic polymer film is not particularly limited. For example, a polyvinyl alcohol (PVA) film, a partially formalized polyvinyl alcohol film, a polyethylene terephthalate (PET) film, an ethylene / vinyl acetate copolymer film, and these parts. A saponified film etc. are mentioned. Among these, a polyvinyl alcohol film is preferable because it is particularly excellent in dyeability with iodine. As the dichroic substance, conventionally known substances can be used, and examples thereof include iodine and organic dyes. Of these, iodine is preferable.
The adsorptive polarizing film can be obtained, for example, by swelling a hydrophilic polymer film, dyeing the film with a dichroic substance, crosslinking the dyed film, and stretching.
Examples of the coating-type polarizing film include polarizing films disclosed in JP 2010-039154 A, JP 2011-016920 A, JP 2011-016922 A, JP 2011-034061 A, and the like. .
The thickness of a polarizing film is not specifically limited, For example, they are 2 micrometers-100 micrometers.

<Phase difference film>
The retardation films 23, 231, and 232 shown in each figure are optically anisotropic films having birefringence, and are films that give a predetermined retardation to transmitted light. Typical examples of the retardation film include a half-wave plate and a quarter-wave plate.
A conventionally well-known thing can be used as a phase difference film.
For example, as a retardation film, a birefringent film containing a thermoplastic resin, a liquid crystal monomer oriented film, a cross-linked polymerized oriented film, a liquid crystal polymer oriented film, and a liquid crystal polymer oriented layer laminated Etc. Although the thickness of a phase difference film is not specifically limited, For example, they are 5 micrometers-100 micrometers.
Examples of the thermoplastic resin include polyolefin resin, cycloolefin resin, polyvinyl chloride resin, cellulose resin, styrene resin, acrylonitrile / butadiene / styrene resin, acrylonitrile / styrene resin, polymethyl methacrylate, polyacetic acid General-purpose plastics such as vinyl and polyvinylidene chloride resins; general-purpose engineering plastics such as polyamide-based resins, polyacetal-based resins, polycarbonate-based resins, modified polyphenylene ether-based resins, polybutylene terephthalate-based resins, and polyethylene terephthalate-based resins; polyphenylene sulfide-based resins , Polysulfone resin, polyethersulfone resin, polyetheretherketone resin, polyarylate resin, liquid crystalline resin, polyamideimide resin, Polyimide-based resins, super engineering plastics such as polytetrafluoroethylene-based resin.

<Protective film>
The protective films 21, 211, and 212 shown in each figure are provided to protect the surface of an optically anisotropic film such as a polarizing film or a retardation film.
A protective film will not be specifically limited if it is a transparent film, A conventionally well-known film can be used.
For example, as the protective film, a transparent film having optical isotropy is used.
The protective film is not particularly limited from the viewpoint of the forming material, and a conventionally known resin film can be used. Examples of protective film materials include cellulose resin films such as cellulose acetates such as triacetyl cellulose (TAC); cycloolefin resin films such as norbornene resins; olefin resin films such as polyethylene and polypropylene; polyesters Resin film; (meth) acrylic resin film; and the like. In the present specification, (meth) acryl means acryl and / or methacryl.
The thickness of a protective film is not specifically limited, For example, they are 10 micrometers-120 micrometers, Preferably they are 20 micrometers-60 micrometers.

Moreover, surface treatment may be given to the surface of the protective film.
A conventionally well-known thing can be employ | adopted as said surface treatment. For example, examples of the surface treatment include an antiglare treatment, a sticking prevention treatment, and a hard coat layer formation treatment.

<Protective release film and adhesive layer>
The protective release films 3, 31, and 32 shown in the drawings are provided to protect the surface of the optical film 2. Accordingly, the protective release film is finally peeled off from the optical film and removed.
The protective release film is not particularly limited as long as it can appropriately protect the optical film. Usually, a resin film is used as the protective release film. The material of the resin film is not particularly limited, and polyester resins such as polyethylene terephthalate and polylactic acid; olefin resins such as polyethylene, polypropylene, and cyclic olefin; polystyrene resins such as polystyrene and styrene-butadiene copolymer; polyamide One type selected from thermoplastic resins such as vinyl resins, or a mixture of two or more types.
Although the thickness of the peeling film for protection is not specifically limited, For example, they are 20 micrometers-100 micrometers, Preferably they are 20 micrometers-80 micrometers.

The adhesive layers 4, 41, 42 shown in each figure are laminated on the back surface of the protective release films 3, 31, 32 in order to attach the protective release films 3, 31, 32 to the optical film 2. Yes.
The protective release film attached via the pressure-sensitive adhesive layer can be peeled off from the surface of the optical film (the surface of the protective film). That is, when the protective release film is peeled off, the protective release film is peeled off along with the pressure-sensitive adhesive layer.
As the adhesive layers 4, 41, 42, those having a shear stress of 22 N / cm ² or less are used. By sticking the protective release film through such a pressure-sensitive adhesive layer, the optically anisotropic film can be prevented from being displaced after the seal attached to the protective release film is peeled off.
Shear stress of the pressure-sensitive adhesive layer is preferably at most 20 N / cm ² or less, more preferably at 18N / cm ² or less, further preferably 15N / cm ² or less.
The lower limit of the shear stress of the pressure-sensitive adhesive layer is not particularly limited, but if it is too small, the pressure-sensitive adhesive layer is too soft, and after peeling the protective release film from the optical film, a part of the pressure-sensitive adhesive layer is on the surface of the optical film. May remain. From such a viewpoint, shear stress of the adhesive layer, 3N / cm ² or more is preferable, 5N / cm ² or more is more preferable, 6N / cm ² or more is more preferable.
However, the shear stress of the pressure-sensitive adhesive layer can be measured using a precision universal testing machine (trade name “AUTOGRAPH” manufactured by Shimadzu Corporation). Specifically, a pressure-sensitive adhesive layer to be measured is provided on the back surface of the protective release film, and the pressure-sensitive adhesive layer is attached to the surface of the optical film so that the adhesion area is vertical × horizontal = 1 cm × 1 cm. The maximum load (N / cm ² ) when the release film for a film is pulled parallel to the surface at 23 ° C. at a pulling speed of 0.06 mm / min is shear stress.

The pressure-sensitive adhesive layer is one that adheres to the surface of the optical film with peelable adhesive strength.
Although it does not specifically limit as adhesive strength with respect to the optical film of an adhesive layer, For example, about 0.2N / 25mm-20N / 25mm is illustrated, Preferably, about 2N / 25mm-15N / 25mm is illustrated.
However, according to JIS Z 0237, the said adhesive strength cuts the protective peeling film provided with the adhesive layer into length x width = 100 mm x 25 mm, produces a test piece, and the test piece is used as an adhesive layer. Then, the test piece is measured in a peel test under conditions of a peel angle of 90 degrees, a peel speed of 300 mm / min, and a temperature of 23 ° C.

The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is not particularly limited as long as a pressure-sensitive adhesive layer having a shear stress of 22 N / cm ² or less can be formed, and a conventionally known pressure-sensitive adhesive can be used. Examples of the adhesive include acrylic adhesive, silicone adhesive, polyoxyalkylene adhesive, urethane adhesive, rubber adhesive, polyester adhesive, polyamide adhesive, epoxy adhesive, and vinyl. Examples include alkyl ether adhesives and fluorine adhesives. These pressure-sensitive adhesives can be used alone or in combination of two or more.
Examples of the acrylic pressure-sensitive adhesive include an acrylic pressure-sensitive adhesive having an acrylic polymer having a main skeleton of an alkyl (meth) acrylate monomer unit as a base polymer. The average carbon number of the alkyl group of the alkyl (meth) acrylate constituting the main skeleton of the acrylic polymer is preferably about 1 to 18, and specific examples of such alkyl (meth) acrylate include methyl (meth) acrylate, ethyl ( Examples include (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, lauryl (meth) acrylate, and the like. Used in combination. Of these, alkyl (meth) acrylates having 1 to 12 carbon atoms in the alkyl group are preferred.
Examples of the silicone-based pressure-sensitive adhesive include peroxide cross-linked silicone pressure-sensitive adhesive (peroxide-curing type silicone pressure-sensitive adhesive) and addition reaction type silicone-based pressure-sensitive adhesive.
The thickness of the pressure-sensitive adhesive layer is not particularly limited and is, for example, 2 μm to 30 μm, preferably 5 μm to 25 μm.
In addition, since the shear stress of the pressure-sensitive adhesive layer also changes depending on the surface state of the protective release film to which the pressure-sensitive adhesive layer adheres, an appropriate pressure-sensitive adhesive should be used in consideration of the material of the surface of the protective release film. By selecting, the adhesive layer which has the said shear stress can be comprised.

<Seal>
The seal 5 shown in each drawing is attached to the surface of the protective release film 3 as necessary. The seal includes various types of information used by the manufacturer of the laminated optical film and the manufacturer of the image display device in the manufacturing process of the product. Examples of the information include a management number such as a product lot number, product specifications, and shipping destination information. The information is provided in the seal, for example, in place of display of numbers and symbols or stored in an optical mechanical reading symbol such as a barcode or a two-dimensional code or an IC chip. Such a seal is also called a label or the like.
In the example shown in FIG. 7, various types of information are stored as bar codes and numbers, and the bar codes and the like are printed on the sticker 5.
As shown in FIG. 8, the seal 5 includes a base material 51 and a seal adhesive layer 52. The seal 5 is detachably attached to any part of the surface of the protective release film 3 via the seal adhesive layer 52.
The size of the seal may be the same as the size of the protective release film, but usually the size of the seal is smaller than that of the protective release film. That is, the surface area of the seal is smaller than the surface area of the protective release film. In specific dimensions, the seal is, for example, length × width = 1 cm to 10 cm × 1 cm to 10 cm.

The base material of the seal is not particularly limited, and a conventionally known one can be used. Examples of the substrate include resin film, paper, synthetic paper, foamed resin film, and laminated films thereof.
The thickness of the base material is not particularly limited, and is, for example, 30 μm to 100 μm.
Moreover, the seal adhesive layer is laminated | stacked on the back surface of a base material, in order to affix a seal | sticker on the peeling film for protection.
The seal attached through the seal adhesive layer can be peeled off from the surface of the protective release film. That is, when the seal is peeled off, the seal is separated between the seal adhesive layer and the surface of the protective release film, and the seal is peeled off together with the seal adhesive layer.
It does not specifically limit as an adhesive which comprises the said sealing adhesive layer, A conventionally well-known adhesive can be used.
It does not specifically limit as adhesive strength with respect to the peeling film for protection of a seal | sticker. However, if the adhesive strength of the seal pressure-sensitive adhesive layer is too small, the seal may drop off. If it is too large, the seal is difficult to peel off easily. From this viewpoint, the adhesive strength of the seal to the protective release film is, for example, 1 N / 25 mm to 20 N / 25 mm, and preferably 3 N / 25 mm to 15 N / 25 mm.
However, according to JIS Z 0237, the adhesive strength is determined by cutting a seal provided with a seal pressure-sensitive adhesive layer into a length × width = 100 mm × 25 mm to produce a test piece. Then, the test piece is measured in a peel test under the conditions of a peel angle of 90 degrees, a peel speed of 300 mm / min, and a temperature of 23 ° C.
According to the present invention, display unevenness of the laminated optical film can be effectively prevented not only when a seal having a relatively low adhesive strength is used but also when a seal having a relatively high adhesive strength is used.

[Image display device]
The laminated optical film 1 of the present invention is used as, for example, a constituent member of an image display device.
9 is a perspective view of the image display device, FIG. 10 is a cross-sectional view thereof, and FIG. 11 is an enlarged cross-sectional view of a part thereof.
9 to 11, the image display device 10 is a liquid crystal display device including a liquid crystal panel 7, for example.
As shown in FIGS. 10 and 11, the liquid crystal panel 7 includes a liquid crystal cell 71, a viewing side polarizing plate 72 disposed on the viewing side of the liquid crystal cell 71, and a viewing side opposite to the viewing side of the liquid crystal cell 71. And an anti-viewing-side polarizing plate 73 arranged.
The liquid crystal cell 71 is filled with a liquid crystal 713 between a pair of glass plates 711 and 712. As the viewing side polarizing plate 72, the laminated optical film 1 of the present invention is used. That is, the viewing side polarizing plate 72 (laminated optical film 1) is the retardation film 23, the polarizing film 22, the protective film 21, the adhesive layer 4, and the protective release film in order from the side close to the liquid crystal cell 71. 3.
The counter-viewing polarizing plate 73 includes a retardation film 733, a polarizing film 732, and a protective film 731 in order from the side close to the liquid crystal cell 71. The viewing-side polarizing plate 72 and the anti-viewing-side polarizing plate 73 are bonded to the liquid crystal cell 71 via an appropriate adhesive or pressure-sensitive adhesive (not shown). In addition, the polarizing film 732 of the non-viewing side polarizing plate 73 and the polarizing film 22 of the viewing side polarizing plate 72 are disposed so that their absorption axes are orthogonal to each other (so-called crossed Nicols).
The seal 5 is detachably attached to the surface of the protective release film 3 of the viewing-side polarizing plate 72 (laminated optical film 1 of the present invention) via a seal adhesive layer 52. However, the protective release film is not attached to the anti-viewing side polarizing plate 73.
A light source 81 (backlight or the like) is provided behind the counter-viewing side polarizing plate 73. The liquid crystal panel 7 and the light source 81 are disposed in a housing 82 having a bezel 82a.

In addition to the polarizing plate and the liquid crystal cell, the liquid crystal panel 7 includes a color filter, an alignment film, an electrode, a spacer, an electronic circuit, and the like, which are not illustrated. In addition to the light source and the liquid crystal panel, a control device, a light guide plate, wiring, and the like are provided in the housing, but these are not shown.
Furthermore, the liquid crystal display device of the illustrated example is a transmissive type in which the light source 81 is disposed on the non-viewing surface side of the liquid crystal panel 7, but is not limited thereto, and may be a reflective type or a transflective type (see FIG. Not shown).
The reflection type liquid crystal display device is a type in which a light source is arranged on the viewing surface side of the liquid crystal panel or a light source is arranged on the side surface side of the liquid crystal panel, and the image is displayed by reflecting light with a reflection plate. The transflective liquid crystal display device is a type having both the transmissive type and the reflective type.

The seal 5 attached to the surface of the protective release film 3 of the liquid crystal display device (image display device 10) is peeled off, for example, by a manufacturer of the image display device before shipping the product.
The protective release film 3 of the liquid crystal display device (image display device 10) is peeled off by, for example, a product purchaser. By peeling off the protective release film 3, the protective film 21 of the viewing side polarizing plate 72 (laminated optical film 1) appears. The surface of the protective film 21 becomes a screen so that an image can be visually recognized.

In the image display device having the laminated optical film of the present invention, display unevenness hardly occurs on the screen. This is presumed to be based on the following action.
As shown in FIG. 12, when the seal is peeled off, the surface of the protective release film (optical film) is pulled by the seal adhesive layer. At this time, the thickness of the protective release film does not change, but the pressure-sensitive adhesive layer slightly changes, so that the internal stress remains in the pressure-sensitive adhesive layer after the seal is peeled off. This stress acts on the polarizing film and the retardation film with the passage of time, and axial misalignment of these films occurs. Due to the misalignment of the polarizing film and / or the retardation film, unexpected light leakage occurs from the screen of the image display device, which causes display unevenness. In particular, since the retardation film causes light leakage due to slight axial misalignment, the adverse effect due to the peeling of the seal is great for the laminated optical film having the retardation film.
In this regard, as in the present invention, by using an adhesive layer having a shear stress of 22 N / cm ² or less, even when the adhesive layer is deformed when the seal is peeled off, it is easy to return to the original state immediately, Internal stress hardly remains in the agent layer. For this reason, even if it leaves for a long time after peeling a seal | sticker, stress does not act on optically anisotropic films, such as a phase difference film and a polarizing film, and the axial shift of an optically anisotropic film can be prevented. For this reason, by using the laminated optical film of the present invention, it is possible to provide an image display device in which display unevenness hardly occurs even when a sticker for management of the manufacturer is attached.

In addition, as a method of preventing display unevenness of the laminated optical film having the protective release film in a state where the seal is affixed, (a) the protective release film is released from the surface of the optical film immediately after the seal is released, (B) The protective release film is peeled off from the surface of the optical film with a seal. (C) After the seal is peeled off, the protective release film is peeled off from the surface of the optical film in less than 24 hours. It is valid. This is clear from Reference Examples 1 to 3 below.
Although these three methods can prevent the occurrence of display unevenness, the methods (a) and (c) described above require the protective release film to be peeled off within a predetermined time after peeling off the seal. The above constraints are imposed. For example, when the manufacturer peels off the seal and the purchaser peels off the protective release film, it often takes a relatively long time between the former and the latter. In some cases, the protective release film cannot be peeled off. In addition, the method (b) has a usage constraint that the seal and the protective release film must be peeled off simultaneously.
In this regard, when the pressure-sensitive adhesive layer having a shear stress of 22 N / cm ² or less is used, display unevenness can be prevented without being restricted in time and use as described above. Needless to say, even if a seal or the like is peeled off by any of the above methods (a) to (c) while using an adhesive layer having a shear stress of 22 N / cm ² or less, display unevenness can be prevented.

  Hereinafter, the present invention will be further described with reference to Examples and Comparative Examples. However, the present invention is not limited to the following examples.

[Materials Used in Examples and Comparative Examples]
・ Protective release film with adhesive layer (1)
A polyethylene terephthalate film having a thickness of 50 μm (trade name “RP296C” manufactured by Nitto Denko Corporation) was used. A pressure-sensitive adhesive layer having a thickness of 12 μm is laminated on the back surface of the film. The pressure-sensitive adhesive layer was an acrylic pressure-sensitive adhesive.
・ Protective release film with adhesive layer (2)
A polyethylene terephthalate film (trade name “RP108C” manufactured by Nitto Denko Corporation) having a thickness of 50 μm was used. A pressure-sensitive adhesive layer having a thickness of 12 μm is laminated on the back surface of the film. The pressure-sensitive adhesive layer was an acrylic pressure-sensitive adhesive.

・ Protective film (3)
A triacetyl cellulose (TAC) film (trade name “TD60UL” manufactured by Fuji Film Co., Ltd.) having a thickness of 60 μm was used.
・ Protective film (4)
A film in which an antiglare layer having a thickness of 5 μm was provided on the surface of a triacetylcellulose (TAC) film having a thickness of 60 μm (trade name “TD60UL” manufactured by Fuji Film Co., Ltd.) was used.
・ Protective film (5)
A film in which a low-reflection layer having a thickness of 6 μm was provided on the surface of a triacetylcellulose (TAC) film having a thickness of 60 μm (trade name “TD60UL” manufactured by Fuji Film Co., Ltd.) was used.
・ Protective film (6)
A transparent protective film having a thickness of 40 μm described in [0126] of JP-A-2016-151696 was used.
・ Protective film (7)
A polyethylene terephthalate film having a thickness of 80 μm (trade name “SRF-80” manufactured by Toyobo Co., Ltd.) was used.

・ Adhesive (8)
An active energy ray curable adhesive was used.
This active energy ray-curable adhesive is prepared by mixing each component in accordance with the description in Example 1 of Table 1 of JP-A No. 2006-184151, and further KAYACURE-DETX-S (2,4-diethylthioxanthone; Nippon Kayaku) 1) and Irgacure 907 (2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one; manufactured by BASF) are each 1. Prepared by adding 5 g and 3 g and stirring.
・ Adhesive (9)
A water-based adhesive was used.
This aqueous adhesive was prepared as follows. Polyvinyl alcohol resin containing acetoacetyl groups (average polymerization degree 1200, saponification degree 98.5%, acetoacetylation degree 5 mol%) 100 parts by weight, methylol melamine 50 parts by weight, 30 ° C. temperature condition Then, it was dissolved in pure water to obtain an aqueous solution having a solid concentration of 3.7% by weight. An adhesive solution was prepared by adding 18 parts by weight of an aqueous colloidal alumina solution (average particle size 15 nm, solid content concentration 10% by weight, positive charge) to 100 parts by weight of this aqueous solution. The viscosity of the adhesive solution was 9.6 mPa · s, the pH was in the range of 4 to 4.5, and the compounding amount of the alumina colloid was 74 parts by weight with respect to 100 parts by weight of the polyvinyl alcohol resin.

・ Polarizing film with retardation film (10)
A retardation film having a thickness of 52 μm (trade name “ZB12-50135” manufactured by Nippon Zeon Co., Ltd.) is laminated on the back surface of a polarizing film having a thickness of 60 μm (trade name “PE6000” manufactured by Kuraray Co., Ltd.). It was used.

・ Seal (11)
A commercially available cellophane adhesive tape (trade name “Cello Tape (registered trademark)” manufactured by Nichiban Co., Ltd.) was cut into length × width = 20 mm × 40 mm and used as a seal (11).
・ Seal (12)
A commercially available masking adhesive tape (trade name “Masking Tape No. 720” manufactured by Nitto Denko Corporation) was cut into length × width = 20 mm × 40 mm and used as a seal (12).

[Example 1]
MCD coater (cell shape: honeycomb, number of gravure rolls: 1000 lines / inch, rotation speed 140% / line speed) on the surface of the polarizing film (10) with retardation film (surface of the polarizing film) ), The adhesive (8) was applied in a thickness of 1 μm, and the back surface of the protective film (3) was bonded thereon. Then, after irradiating visible light with the active energy ray irradiation apparatus from both surfaces of the laminated body bonded together and hardening the adhesive (8), an optical film is produced by drying with hot air at 70 ° C. for 3 minutes. did. The active energy ray irradiation apparatus is an apparatus that irradiates visible light (gallium-encapsulated metal halide lamp) as active energy rays. Light HAMMER 10 (bulb: V bulb, peak illuminance: 1600 mW / cm ² , manufactured by Fusion UV Systems, Inc., Integrated irradiation amount: 1000 / mJ / cm ² (wavelength 380 to 440 nm)) was used.
A laminated optical film having a layer structure as shown in FIG. 2 was produced by attaching the protective release film (1) to the surface of the protective film (3) of the optical film via an adhesive layer. In addition, the magnitude | size of this laminated optical film was made into square shape of length x width = 50mmx50mm.

[Examples 2 to 10 and Comparative Examples 1 to 5]
A laminated optical film was produced in the same manner as in Example 1 except that the protective release film, protective release film or adhesive having an adhesive layer was changed as shown in Table 1.
In Table 1, the film (1) is a protective release film (1) having the pressure-sensitive adhesive layer, and the film (2) is a protective release film (2) having the pressure-sensitive adhesive layer. 3) is the protective film (3), film (4) is the protective film (4), film (5) is the protective film (5), and film (6) is the protective film ( 6), the film (7) represents the protective film (7), and the film (10) represents the polarizing film with a retardation film (10).
In addition, about Example 10, the adhesive agent (9) which is a water-system adhesive agent was used. That is, about Example 10, after laminating | stacking the said film while dripping an adhesive agent (9) on the bonding part of the polarizing film surface of a polarizing film with a retardation film, and a protective film, it is 4 minutes at 70 degreeC. Hot air dried.

[Measurement of shear stress]
About each Example and the comparative example, in order to measure the shear stress of the adhesive layer of a protective peeling film, the maximum load was measured in the following procedures.
The protective release film (1) having the pressure-sensitive adhesive layer used in Example 1 is cut into length × width = 100 mm × 10 mm, and the adhesive area (contact area) of the pressure-sensitive adhesive layer is 1 cm ² (one side is 1 cm square), the protective release film (1) is protected at 23 ° C. at a pulling rate of 0.06 mm / min as shown in FIG. The film was pulled parallel to the surface of the film, and the maximum load (N / cm ² ) at that time was measured using a precision universal testing machine (trade name “AUTOGRAPH” manufactured by Shimadzu Corporation). This maximum load is the shear stress of the pressure-sensitive adhesive layer.
For Examples 2 to 10 and Comparative Examples 1 to 5, the shear stress of each pressure-sensitive adhesive layer was measured in the same manner using the protective release film and the protective film having the pressure-sensitive adhesive layer used in each case.
The results are shown in Table 1.

[Production of image display device and display characteristic test]
A seal (11) was affixed to a part of the surface of the protective release film (1) of the laminated optical film of Example 1. The viewing side polarizing plate was removed from the liquid crystal panel of the liquid crystal display device used for general purposes, and the laminated optical film to which the seal (11) was attached was incorporated into the viewing side polarizing plate of the liquid crystal panel.
Thus, a test liquid crystal display device as shown in FIGS. 9 to 11 was obtained.
Next, the seal (11) attached to the surface of the protective release film (1) of the liquid crystal display device was peeled off with a finger and then left at 23 ° C. and 60% RH for 24 hours. Thereafter, the protective release film (1) was peeled off with a finger to expose the screen of the liquid crystal panel (the surface of the protective film (3)), the liquid crystal display device was turned on, and the state of the screen was visually confirmed. As a result, display unevenness was not recognized.
The laminated optical films of Examples 2 to 10 were incorporated into the liquid crystal display device in the same manner as in Example 1, peeled off the seal, left for 24 hours, and the state of the screen after peeling off the protective release film. It was confirmed visually. As a result, no display unevenness was observed in any of the examples. In Example 6, the seal (12) was used instead of the seal (11).
The laminated optical films of Comparative Examples 1 to 5 were also incorporated into the liquid crystal display device in the same manner as in Example 1, peeled off the seal, allowed to stand for 24 hours, and the state of the screen after peeling off the protective release film. It was confirmed visually. As a result, in any of the comparative examples, display unevenness such as a seal trace was confirmed on the screen. This display unevenness looked cloudy and white. FIG. 14 is a photograph of the area around the place where the sticker is attached in the screen of Comparative Example 1.

[Reference Example 1]
In the same manner as in [Production of image display device], a test liquid crystal display device was produced using the laminated optical film of Example 1. After the seal (11) attached to the surface of the protective release film (1) of the liquid crystal display device is peeled off with a finger, the protective release film (1) is immediately peeled off with the finger, and the liquid crystal panel The screen (the surface of the protective film) was exposed, the liquid crystal display device was turned on, and the state of the screen was visually confirmed. As a result, display unevenness was not recognized.
Similarly, for the liquid crystal display device using the laminated optical film of Comparative Example 1, when the protective release film (2) was peeled off immediately after the seal (11) was peeled off, no display unevenness was observed.

[Reference Example 2]
In the same manner as in [Production of image display device], a test liquid crystal display device was produced using the laminated optical film of Example 1. For this liquid crystal display device, the protective release film (1) with the seal (11) attached was peeled off with a finger. That is, the protective release film (1) with the seal (11) is peeled off with a finger, the screen of the liquid crystal panel (the surface of the protective film) is exposed, the liquid crystal display device is turned on, and the state of the screen is visually observed. confirmed. As a result, display unevenness was not recognized.
Similarly, in the liquid crystal display device using the laminated optical film of Comparative Example 1, when the protective release film (2) was peeled off with the seal (11), display unevenness was not recognized.

[Reference Example 3]
In the same manner as in [Production of image display device], a test liquid crystal display device was produced using the laminated optical film of Example 1. The seal (11) affixed to the surface of the protective release film (1) of this liquid crystal display device was peeled off with a finger and then left at 23 ° C. and 60% RH for 23 hours. Immediately after that, peel off the protective release film (1) with your finger to expose the screen of the liquid crystal panel (the surface of the protective film (3)), turn on the liquid crystal display, and visually check the state of the screen did. As a result, display unevenness was not recognized.
Similarly, for the liquid crystal display device using the laminated optical film of Comparative Example 1, the seal (11) was peeled off, and the protective release film (2) was pulled immediately after being left for 23 hours at 23 ° C. and 60% RH. When peeled off, no display unevenness was observed.

DESCRIPTION OF SYMBOLS 1 Laminated optical film 2 Optical film 21,211,212 Protective film 22 Polarizing film (optical anisotropic film)
23,231,232 retardation film (optically anisotropic film)
3 Protective Release Film 4 Protective Release Film Adhesive Layer 5 Seal 52 Seal Adhesive Layer 10 Image Display Device

The fifth embodiment is different from the first embodiment in that a protective release film is detachably attached to the back side of the optical film.
That is, as shown in FIG. 6, the laminated optical film 1 of the fifth embodiment is, in order from the surface side, the first protective release film 31, the first pressure-sensitive adhesive layer 41, and the optical film 2 (for example, A protective film 21, a polarizing film 22 and a retardation film 23), a second pressure-sensitive adhesive layer 42, and a second protective release film 32.
The first protective release film 31 is detachably attached to the surface of the optical film 2 via the first pressure-sensitive adhesive layer 41, and the second protective release film 32 is a second pressure-sensitive adhesive layer. Via 42, it is affixed on the back surface of the optical film 2 so that peeling is possible. When two protective release films are provided as in this embodiment, the protective release films 31 and 32 may be the same material and thickness, or may be different materials or thicknesses. . In addition, at least one of the first pressure-sensitive adhesive layer 41 and the second pressure-sensitive adhesive layer 42 may be a pressure-sensitive adhesive layer having a shear stress of 22 N / cm ² or less, preferably the first pressure-sensitive adhesive layer 41. Both the second pressure-sensitive adhesive layer 42 has a shear stress of 22 N / cm ² or less.

The sixth embodiment is different from the above embodiments in that the seal is detachably attached to the surface of the protective release film.
That is, as shown in FIGS. 7 and 8, the laminated optical film 1 of the sixth embodiment includes a protective release film 3, an adhesive layer 4, and an optical film 2 (for example, a protective film 21, a polarizing film 22, and A phase difference film 23), and a seal 5 is detachably attached to the surface of the protective release film 3. In FIG. 8 , except for the seal 5, for convenience, the same laminated optical film 1 as the layer configuration shown in FIG. 2 (layer configuration of the first embodiment) is shown. But you may affix the said seal | sticker 5 on the surface of the peeling film for protection of the laminated optical film 1 of the layer structure shown in FIG. 3 thru | or FIG.
The seal 5 includes a base material 51 and an adhesive layer 52 provided on the back surface of the base material 51. Hereinafter, in order to distinguish from the adhesive layer 4 provided on the back surface of the protective release film 3, the adhesive layer 52 provided on the back surface of the base material 51 of the seal 5 is referred to as "seal adhesive layer".
In this embodiment, the seal 5 is detachably attached to the surface of the protective release film 3 via the seal adhesive layer 52.

[Examples 2 to 10 and Comparative Examples 1 to 5]
Protective release film having an adhesive layer, the coercive Mamorufu Irumu or adhesives, except that was changed as shown in Table 1, to prepare a laminated optical film in the same manner as in Example 1.
In Table 1, the film (1) is a protective release film (1) having the pressure-sensitive adhesive layer, and the film (2) is a protective release film (2) having the pressure-sensitive adhesive layer. 3) is the protective film (3), film (4) is the protective film (4), film (5) is the protective film (5), and film (6) is the protective film ( 6), the film (7) represents the protective film (7), and the film (10) represents the polarizing film with a retardation film (10).
In addition, about Example 10, the adhesive agent (9) which is a water-system adhesive agent was used. That is, about Example 10, after laminating | stacking the said film while dripping an adhesive agent (9) on the bonding part of the polarizing film surface of a polarizing film with a retardation film, and a protective film, it is 4 minutes at 70 degreeC. Hot air dried.

Claims (6)

An optical film having an optically anisotropic film;
A protective release film attached to the surface of the optical film so as to be peelable through an adhesive layer;
A laminated optical film, wherein the pressure-sensitive adhesive layer has a shear stress of 22 N / cm ² or less. The laminated optical film according to claim 1, wherein the pressure-sensitive adhesive layer has a shear stress of 3 N / cm ² or more.   The laminated optical film according to claim 1, wherein a peelable seal is attached to a surface of the protective release film.   The laminated optical film according to any one of claims 1 to 3, wherein the optical film includes the optically anisotropic film and a protective film laminated on a surface of the optically anisotropic film.   The laminated optical film according to claim 1, wherein the optically anisotropic film includes a retardation film.   An image display device comprising the laminated optical film according to claim 1.