JP2023068672A - Method of manufacturing film with through-hole, and circularly polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a film with a through-hole, which reduces discoloration around the through-hole, and to provide a circularly polarizing plate.

SOLUTION: A circularly polarizing plate provided herein comprises a polarizer having a protective film provided on at least one surface thereof and a liquid crystal retardation plate, and has a through-hole with a diameter of 2.5 mm or less. The maximum width of a retardation shift area Q around the through-hole is 0 to 30 μm, and an annular area with a width of 30 μm around the through-hole has a polarizing function.

SELECTED DRAWING: Figure 9

COPYRIGHT: (C)2023,JPO&INPIT

Description

TECHNICAL FIELD The present invention relates to a method for producing a film with through holes and a circularly polarizing plate.

In recent years, the diameter of camera holes in image display devices such as smartphones has been reduced. Methods for forming small-diameter through holes in a polarizing plate include laser processing and end mill processing.

JP 2017-151162 A JP 2017-083878 A JP 2020-149034 A JP 2020-149033 A

With laser processing, it is easy to reduce the diameter of the through-hole, but the polarizer is modified by the heat of the laser, etc., and a depolarizing portion that does not have polarization performance is always formed around the through-hole. There's a problem.

On the other hand, it was found that in end milling, a depolarized portion is difficult to form around the through-hole, but a discolored portion may be formed around the through-hole when the diameter of the through-hole becomes small.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for manufacturing a film with through holes and a circularly polarizing plate that can reduce discoloration around the through holes.

In the method for producing a film with through holes according to one aspect of the present invention, the axis of an end mill is arranged in parallel with the thickness direction of a film laminate, and the end mill is moved in the thickness direction of the laminate. A1 step of forming a hole in the laminate by relatively moving a distance less than the thickness;
After the A1 step, an A2 step of relatively moving an end mill along the inner peripheral surface of the hole to expand the inner diameter of the hole is provided. Each said film includes a liquid crystal retarder. In this method, the step A is repeated two or more times to form through-holes in the laminate.

A distance of the relative movement in each A1 step may be 1.5 mm or less.

In the above method, after repeating the A step twice or more to form a through hole in the laminate, the entire inner peripheral surface of the through hole is further cut with an end mill to a thickness of 0.01 to 0.10 mm. can further include:

In the A1 step and the A2 step, the end mill can be rotated so that the scraps of the laminate are discharged toward the stem side of the end mill.

In the A1 step and the A2 step, dry ice snow can be jetted obliquely to the axis of the end mill and in a direction from the handle of the end mill toward the cutting edge.

Each said film may further comprise a polarizer.

The film can be a film for an image display device.

A circularly polarizing plate according to one aspect of the present invention is a circularly polarizing plate comprising a polarizer having a protective film on at least one surface and a liquid crystal retardation plate in this order,
having a through hole with a diameter of 2.5 mm or less,
The maximum width of the retardation region Q around the through hole is 30 μm or less.

An annular region having a width of 30 μm from the perimeter of the through hole can have a polarizing function.

A laminate according to one aspect of the present invention is a laminate of the circularly polarizing plates.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the film with a through-hole which can reduce the discoloration around a through-hole, and a circularly-polarizing plate are provided.

FIG. 1 is an end view showing an example of a laminate 200 of films 100. FIG. FIG. 2 is a single plane view showing an example of the liquid crystal retardation plate 10. As shown in FIG. FIG. 3 is an end view showing an example of the film 100. As shown in FIG. 4A to 4C are end views showing an example of the polarizing plate 30. FIG. FIG. 5 is an end view showing an example of the retardation film 70. As shown in FIG. FIGS. 6A to 6D are schematic perspective views sequentially showing steps A1, A2, A1, and A2 performed on the laminate 200 of the films 100. FIG. (a) of FIG. 7 is a schematic perspective view showing a state in which the through holes 200HT are formed in the laminate 200, and (b) of FIG. It is a perspective view. 8(a) and 8(b) are side views showing the relationship between the direction of rotation of the end mill and the direction of discharge of machining waste, and the direction of blowing dry ice snow. FIG. 9 is an enlarged view around the through-hole 100HT of the film.

An embodiment of the present invention will be described with reference to the drawings.

(film laminate)
First, as shown in FIG. 1, a laminate 200 of films 100 is prepared. Each film 100 may be a single layer film or a laminated film. The thickness of the laminate 200 can be 3 mm or more, 4 mm or more, 5 mm or more, 6 mm or more, can be 20 mm or less, can be 15 mm or less, or can be 10 mm or less. Both surfaces of the laminate 200 may have protective films 140 such as PET. The thickness of each film 100 can be 30-500 μm.

(the film)
Each film 100 includes a liquid crystal retarder. An example of a liquid crystal retardation plate is shown in FIG. The liquid crystal retardation plate 10 has a cured product layer (hereinafter sometimes referred to as a liquid crystal retardation layer) 14 of an oriented polymerizable liquid crystal compound, and may further have an alignment layer 12 in contact with the cured product layer 14. can.

A polymerizable liquid crystal compound is a liquid crystal compound having a polymerizable functional group (preferably a photopolymerizable functional group).

A photopolymerizable functional group is a group that can participate in a polymerization reaction by an active radical generated from a photopolymerization initiator, an acid, or the like. Photopolymerizable functional groups include vinyl group, vinyloxy group, 1-chlorovinyl group, isopropenyl group, 4-vinylphenyl group, acryloyloxy group, methacryloyloxy group, oxiranyl group and oxetanyl group.

The type of polymerizable liquid crystal compound is not particularly limited, and rod-like liquid crystal compounds, discotic liquid crystal compounds, and mixtures thereof can be used. The liquid crystallinity of the liquid crystal compound may be either thermotropic liquid crystal or lyotropic liquid crystal, but thermotropic liquid crystal is preferred in that it enables precise film thickness control. The phase-ordered structure of the thermotropic liquid crystal may be nematic liquid crystal or smectic liquid crystal. A photopolymerization initiator or the like can be appropriately used for the polymerization.

The liquid crystal retardation plate may have forward wavelength dispersion in which the in-plane retardation decreases as the wavelength increases, or may have reverse wavelength dispersion in which the in-plane retardation increases as the wavelength increases. good.

The thickness of the cured product layer 14 of the polymerizable liquid crystal compound can be, for example, 0.5 to 10 μm, 0.5 to 8 μm, or 1 to 5 μm.

The alignment layer 12 is used to orient the polymerizable liquid crystal compound during the production of the cured product layer 14 of the polymerizable liquid crystal compound. The alignment layer 12 is not particularly limited, and may be a rubbing film of a resin such as PVA, or a photo-alignment film obtained by polymerizing a photopolymerizable resin film with polarized light or the like. The thickness of the alignment layer 12 can be, for example, 10-5000 nm, 10-1000 nm, 10-500 nm, 10-300 nm.

Examples of the polymerizable liquid crystal compound, subcomponents such as a polymerization initiator to be blended as necessary in the cured product layer of the polymerizable liquid crystal compound, materials for the alignment layer, and methods for producing these are known, for example, It is disclosed in JP 2017-167517, JP 5463666, JP 2016-121339, JP 2018-087152, JP 6700468, JP 2020-074021. Examples of the vertical alignment layer when the liquid crystal retardation plate is a positive C plate are disclosed in documents such as JP-A-2016-028284.

There is no particular limitation on the order of stacking the alignment layer 12 and the cured product layer 14 . Further, if the liquid crystal retardation plate 10 has at least a cured product layer of an aligned polymerizable liquid crystal compound, the liquid crystal retardation plate 10 does not have an alignment layer, for example, the liquid crystal retardation plate 10 is obtained by removing the alignment layer. can also Further, the liquid crystal retardation plate 10 may have layers other than the cured product layer and the alignment layer.

Examples of liquid crystal retardation plates are λ/4 plates, λ/2 plates, positive C plates, and the like. A λ/4 plate can have an in-plane retardation of 50 to 200 nm at a wavelength of 550 nm. Each retardation plate may independently have forward wavelength dispersion or reverse wavelength dispersion.

Although the thickness of the liquid crystal retardation plate 10 is not limited, it can be, for example, 0.5 to 15 μm, 0.5 to 10 μm, and 1 to 8 μm.

(Film structure)
An example of the film 100 including the liquid crystal retardation plate 10 is a circular polarizer. FIG. 3 is a schematic cross-sectional view of film 100 according to one embodiment. This film 100 has, in turn, a polarizer 30 , an adhesive or adhesive layer 24 , and a retardation film 70 comprising a liquid crystal retardation plate 10 .

(Polarizing plate (linear polarizing plate) 30)
Polarizing plate 30 includes a polarizer. An example of a polarizer is a stretched polyvinyl alcohol-based resin containing a dichroic dye such as iodine. In this case, the polarizing plate 30 can have a configuration of a first protective film 32, a polarizer 36, and a second protective film 38, as shown in FIG. 4(a). At least one of the polarizers 36 needs to have a protective film. Examples of first protective film 32 and second protective film 38 are triacetyl cellulose films and cycloolefin polymer films.

The thickness of the polarizer 36 when it is stretched PVA is usually 5 to 60 μm. The thickness of the protective film is usually 10-100 μm.

Another example of the polarizer 36 includes an oriented cured polymerizable liquid crystal compound and a dichroic dye, and the dichroic dye is dispersed and oriented in the cured liquid crystal compound. An example of the polarizing plate 30 in this case is shown in FIGS. 4(b) and 4(c). In FIG. 4(b), the polarizing plate 30 has a first protective film 32, an alignment layer 34, a polarizer 36, and a second protective film 38 in order. In FIG. 4C, the polarizing plate 30 has a first protective film 32, a polarizer 36, an alignment layer 34, and a second protective film 38 in order. At least one of the polarizers should have a protective film.

The thickness of the polarizer 36 in the case of a liquid crystal type is usually 10 μm or less, preferably 0.5 μm or more and 8 μm or less, more preferably 1 μm or more and 5 μm or less.

As for the polymerizable liquid crystal compound, those described in the section of the retardation plate can be used. As the polymerizable liquid crystal compound used for the polarizer, a smectic liquid crystal compound is preferable to a nematic liquid crystal compound, and a high-order smectic liquid crystal compound is more preferable. Among them, high-order smectic liquid crystal compounds forming smectic B phase, smectic D phase, smectic E phase, smectic F phase, smectic G phase, smectic H phase, smectic I phase, smectic J phase, smectic K phase or smectic L phase. Higher order smectic liquid crystal compounds forming a smectic B phase, a smectic F phase or a smectic I phase are more preferred. A photopolymerization initiator or the like can be appropriately used for the polymerization.

A dichroic dye is a dye that has different absorbances in the long-axis direction and the short-axis direction of the molecule.

As dichroic dyes, those having a maximum absorption wavelength (λMAX) in the range of 300 to 700 nm are preferred. Such dichroic dyes include, for example, acridine dyes, oxazine dyes, cyanine dyes, naphthalene dyes, azo dyes and anthraquinone dyes, with azo dyes being preferred. The azo dyes include monoazo dyes, bisazo dyes, trisazo dyes, tetrakis azo dyes and stilbenazo dyes, preferably bisazo dyes and trisazo dyes. The dichroic dyes may be used alone or in combination, but it is preferable to combine three or more dichroic dyes, more preferably three or more azo dyes.

The orientation layer 34 is a layer for orienting the liquid crystalline compound of the polarizer 36 when manufacturing the polarizer 36 and is in contact with the polarizer 36 . The material of the alignment layer 34 is not particularly limited, and a rubbed layer of a resin such as PVA, or a photo-alignment film obtained by aligning a polymer layer having a photo-alignment group by irradiating polarized light or the like may be used. Although the thickness of the alignment layer 34 is not limited, the thickness of the alignment layer is usually in the range of 10-10000 nm, preferably in the range of 10-1000 nm, more preferably in the range of 50-200 nm.

Materials for the alignment layer, the polymerizable liquid crystal compound, and the dichroic dye are not particularly limited, and known materials can be used. Examples and manufacturing methods of these materials are, for example, JP-A-2017-167517, JP-A-2013-37353, JP-A-2013-33249, JP-A-2017-83843, WO2020/122117, WO2020. /179864.

The first protective film 32 and the second protective film 38 are layers that protect the liquid crystal polarizer 36, suppress the diffusion of the dichroic dye in the polarizer 36 to the outside, and protect the polarizer 36 from the outside. It can have a function such as suppression of diffusion of oxygen or the like to. The first protective film 32 and the second protective film 38 may be cured polyvinyl alcohol-based resins. The first protective film 32 and the second protective film 38 may be made of the same material or different materials.

Examples of cured products of polyvinyl alcohol-based resins include cured products of polyvinyl alcohol-based resins and cross-linking agents, and cured products of polyvinyl alcohol-based resins having polymerizable functional groups.

Examples of polyvinyl alcohol-based resins include partially saponified polyvinyl alcohol, fully saponified polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, methylol group-modified polyvinyl alcohol, and amino group-modified polyvinyl alcohol. It is a modified polyvinyl alcohol resin.

The degree of saponification of the polyvinyl alcohol resin is usually about 85 mol% or more and 100 mol% or less, preferably 90 mol% or more, may be 95 mol% or more, or may be 98 mol% or more. good.

The average degree of polymerization of the polyvinyl alcohol resin is usually 1000 or more and 5000 or less, preferably 1500 or more and 3000 or less, and may be 2000 or less or 1500 or less.

The content of the polyvinyl alcohol-based resin in the uncured product of the polyvinyl alcohol-based resin is preferably 85% by mass or more, more preferably 90% by mass or more, and still more preferably 95% by mass, based on the mass of the solid content of the uncured product. % by mass or more, and may be 100% by mass.

Examples of cross-linking agents are amine compounds, aldehyde compounds, methylol compounds, water-soluble epoxy resins, isocyanate compounds, polyvalent metal salts. In particular, aldehyde compounds such as glyoxal, methylol compounds such as methylolmelamine, and water-soluble epoxy resins are suitable. The water-soluble epoxy resin is, for example, a polyamide epoxy resin obtained by reacting epichlorohydrin with a polyamide polyamine which is a reaction product of a polyalkylene polyamine such as diethylenetriamine and triethylenetetramine and a dicarboxylic acid such as adipic acid. can be done.

When the polyvinyl alcohol-based resin has a polymerizable functional group, a cured product can be obtained by heating or the like without using a cross-linking agent. Examples of polymerizable functional groups are vinyl, vinyloxy, 1-chlorovinyl, isopropenyl, 4-vinylphenyl, acryloyloxy, methacryloyloxy, oxiranyl and oxetanyl groups.

The cured product of the polyvinyl alcohol resin can be obtained by dissolving the polyvinyl alcohol resin and, if necessary, additives and the like in a solvent, applying the solution on a substrate, and drying.

The thickness of the first protective film 32 and the second protective film 38 can be 1 to 100 μm.

(Adhesive or adhesive layer 24)
In FIG. 3, adhesive or adhesive layer 24 secures polarizing plate 30 and retardation film 70 . The adhesive or adhesive layer 24 is not particularly limited.

Examples of adhesives include rubber-based adhesives, acrylic-based adhesives, silicone-based adhesives, urethane-based adhesives, vinyl alkyl ether-based adhesives, polyvinyl alcohol-based adhesives, polyvinylpyrrolidone-based adhesives, and polyacrylamide-based adhesives. , cellulose-based adhesives, and the like. Among these, the acrylic pressure-sensitive adhesive is preferable from the viewpoint of transparency, weather resistance, heat resistance, and the like.

An example of the adhesive is an active energy ray-curable adhesive such as UV, and specifically, it can be an epoxy resin-based UV-curable adhesive.

The thickness of the adhesive or adhesive layer 24 can be 0.5-50 μm.

As used herein, the adhesive is also called a pressure-sensitive adhesive. On the other hand, an adhesive refers to an adhesive other than a pressure-sensitive adhesive (pressure-sensitive adhesive), and is clearly distinguished from a pressure-sensitive adhesive.

(Retardation film 70)
The retardation film 70 may be a single retardation plate or a laminate of a plurality of retardation plates. At least one retardation plate in the retardation film 70 is the liquid crystal retardation plate 10 described above. In the retardation film 70 , all the retardation plates in the retardation film 70 may be liquid crystal retardation plates 10 . An example of a retardation plate that is not a liquid crystal retardation plate is a stretched film of thermoplastic resin such as COP.

When used as a polarizing plate, the retardation film 70 preferably contains at least a λ/4 plate.

FIG. 5 shows an example in which the retardation film 70 has a plurality of retardation plates. This retardation film 70 has a λ/2 plate 50, an adhesive or adhesive layer 26, and a λ/4 plate 60 in order from the polarizing plate 30 side. Further, the retardation film may have a structure having a λ/4 plate, an adhesive or adhesive layer, and a positive C plate.

The thickness of each retardation plate can be, for example, 0.5 to 15 μm, 0.5 to 10 μm, and 1 to 8 μm.

An adhesive layer or adhesive layer 26 secures the two retarders. Examples of adhesive or adhesive layer 26 are as described for adhesive or adhesive layer 24 above. The thickness of the adhesive or adhesive layer 26 can be 0.5-50 μm.

(temporary protective layer 80)
The film 100 can further include a temporary protective layer 80 on the polarizing plate 30 (viewing side), as shown in FIG. The temporary protective layer 80 can have a base material such as PET and an adhesive layer, and can be easily removed from the film 100 by hand or the like after the film 100 is attached to an EL panel or the like and before the image display device is used. can be peeled off.

The film 100 may have an adhesive layer 21 for attachment on the image display panel side of the retardation film 70 . The above-described adhesive layer can also be used. Furthermore, in this case, a peelable separator 22 may be provided on the adhesive layer 21 .

(Other Lamination Forms of Optical Laminate)
The laminate of films according to the embodiment of the present invention is not limited to the laminate structure described above. For example, another layer such as a retardation plate may be provided between the polarizing plate 30 and the temporary protective layer 80 .

An example of the application of the above film is an antireflection film, which is attached to an image display device such as an organic EL panel. The above film can be a film for an image display device.

(Manufacturing method of film with through holes)
Next, a method for manufacturing a film with through holes will be described.
(A process)
A process has A1 process and A2 process performed after the said A1 process.

(A1 process)
In step A1, as shown in FIG. 6A, the end mill 300 is placed on the film laminate 200 with the axis of the end mill 300 arranged parallel to the thickness direction of the film laminate 200. A hole 200H1 is formed in the laminate 200 by relatively moving the laminate 200 in the thickness direction of the laminate 200 by a distance L that is less than the thickness TH of the laminate 200 .

The axial length (relative movement distance) L of the hole 200H1 formed in each A1 step can be 1.5 mm or less, preferably 1.3 mm or less, and may be 1.1 mm or less. The lower limit of the axial length L can be 0.05 mm or more, preferably 0.1 mm or more.

The inner diameter D1 of the hole portion 200H1 formed in the A1 step, in other words, the diameter of the blade portion of the end mill 300 may be 1.4 mm or less, 1.3 mm or less, or 1.0 mm or more. It may be 1.1 mm or more.

The relative feed speed of the end mill 300 with respect to the laminate in the A1 process can be 300-1500 mm/min.

(A2 process)
Subsequently, as shown in FIG. 6B, after the A1 step, the end mill 300 is relatively moved along the inner peripheral surface of the hole 200H1 formed in the A1 step to expand the inner diameter of the hole 200H1. The inner diameter D2 after expansion can be 1.1 mm or more. The amount of expansion of the inner diameter in the A2 stroke can be, for example, 0.10 to 0.78 mm.

The relative movement between the laminate 200 and the end mill 300 may be spiral as shown in FIGS. 6(b) and 6(d). You can repeat the outward movement and the circular movement again.

(Repetition of combination of A1 step and A2 step)
Subsequently, this combination of steps A1 and A2 is repeated two or more times. As a result, first, as shown in FIG. 6(c), a hole portion 200H2 having an inner diameter D1 is formed by the A1 step, and then, as shown in FIG. 6(d), the hole portion 200H2 is formed by the A2 step. A hole portion 200H2 having an enlarged inner diameter and having an inner diameter D2 is formed. In this manner, the axial length of the hole portion 200Hn gradually increases, and finally, as shown in FIG. 7A, the through hole 200HT with the inner diameter D2 is formed. The number of repetitions is determined so that the through hole 200HT is formed by the relative movement distance L in the axial direction and the thickness TH of the laminate 200 .

In this way, when the step A, which is a combination of the steps A1 and A2, is repeated for the thick laminate 200 to form the through-holes 200HT, discoloration around the through-holes in each obtained film is suppressed. be. Although the reason for this is not clear, it is possible to reduce the cutting depth with an end mill, which improves the discharge of cutting debris from the hole during cutting and suppresses damage to the liquid crystal retardation layer due to heat generation. is thought to be a factor.

(B process)
In the B process, after forming the through hole 200HT by repeating the A process, as shown in FIG. The cutting thickness in the B step can be 0.01 mm or more and can be 0.10 mm or less.

In step B, the direction of movement of the end mill 300 relative to the inner peripheral surface of the through hole 200HT may be spiral or concentric, as in step A1.

The shape of the end mill 300 is not particularly limited, but as shown in FIGS. 8A and 8B, the end mill 300 has a columnar shape having a blade portion 300b and a handle (shank) portion 300a and extending in the axial direction of rotation. A portion 300z is provided. The end mill 300 is preferably provided with blades 300c on the outer peripheral surface and the bottom surface of the blade portion 300b. The length (Z-axis direction) of the blade portion 300b of the end mill 300 is preferably longer than the thickness of the laminate 200, for example, 8 mm or more.

The outer diameter of the blade of the end mill 300 used in the A1 and A2 processes may be 1.3 mm or less, may be 1.0 mm or more, or may be 1.1 mm or more. Although it is preferable to use the same end mill in the A1 step and the A2 step, different end mills may be used.

In the A1 process, the A2 process, and the B process, the rotating direction of the end mill 300 is preferably the direction in which the chips are discharged toward the handle 300a of the end mill. As a result, cutting chips are discharged from the hole 200Hn more smoothly, and discoloration around the through hole can be further suppressed.

For example, as shown in (a) of FIG. 8, the end mill has a right-handed blade right-handed twist, that is, the blade 300c rotates clockwise when viewed from the handle 300a side toward the tip (bottom surface) of the blade 300b from the handle 300a. and the flank 300d is provided closer to the tip of the blade portion 300b than the blade 300c, when the end mill 300 is rotated clockwise when viewed from the handle portion 300a, the milling waste is discharged. The direction is the direction from the tip of the blade portion 300b toward the handle portion 300a.

As shown in (b) of FIG. 8, the end mill 300 has a left-handed left-handed twist, that is, the blade 300c spirals counterclockwise when viewed from the handle 300a side toward the tip of the blade 300b from the handle 300a. and the flank 300d is provided closer to the tip of the blade portion 300b than the blade 300c, when the end mill 300 is rotated counterclockwise as viewed from the handle portion 300a, the direction of discharge of the milling chips is , from the tip of the blade portion 300b toward the handle portion 300a.

In the A1 process, A2 process, and B process, as shown in FIG. 8, dry ice snow (particles) can be jetted to the blade portion 300b of the end mill 300. As shown in FIG. Here, it is preferable to jet the dry ice snow obliquely to the axis of the end mill 300 and in a direction from the handle portion 300a of the end mill toward the blade portion 300b.

As a result, it is possible to continuously remove debris adhering to the blade portion 300b during cutting, which has the effect of suppressing heat generation during cutting and further suppressing discoloration.

For example, as shown in FIG. 8, when dry ice snow is blown onto the blade portion 300b of the end mill 300 through a nozzle 420 connected to a dry ice snow supply means, the injection direction EJ (the axial direction of the nozzle 420) can be easily controlled. is suitable. The angle (acute angle) α between the axis of the end mill 300 and the injection direction EJ can be 5 to 85°, preferably 10 to 65°. The nozzle 420 preferably moves following the end mill 300 even when the end mill 300 moves. The opening of the nozzle 420 may be circular, and the diameter of the opening of the nozzle 420 may be 1-10 mm.

Although the average particle size of the dry ice snow to be impinged is not particularly limited, it is preferably 100 μm or more from the viewpoint of efficiently removing processing waste. In addition, from the viewpoint of suppressing scratches on the laminate, the thickness is preferably 1000 μm or less. The average particle size of dry ice particles can be measured with a laser Doppler anemometer. The speed of the impinging dry ice particles can be from 5 m/sec to 100 m/sec.

The carrier gas for dry ice is not particularly limited, and can be, for example, nitrogen, air, or carbon dioxide gas.

(Polarizing plate film obtained)
In the laminate 200 with through holes obtained by the above method, each film 100 has through holes 100HT as shown in FIG.

The diameter of the through-hole 100HT may be 2.5 mm or less, 2.0 mm or less, 1.8 mm or less, 1.7 mm or less, or 1.5 mm or more. The shape of the through-hole 100HT is not limited to a perfect circle, and may be an elongated hole, an ellipse, or the like. The diameter of the non-perfect circle can be defined as the maximum diameter.

When the film 100 is a circularly polarizing plate having a polarizer and a liquid crystal retardation plate (λ/4 plate, etc.), the maximum width W of the retardation region Q formed around the through hole 100HT is 30 μm or less. is. The width W is the radial width of the ring-shaped region Q, as shown in FIG.

The retardation shift region Q corresponds to the discolored portion described above, a circularly polarizing plate is placed on the aluminum film so that the polarizer is above the retardation plate, and a polarizing microscope is used to observe in reflection mode. , In the image observed around the through-hole of the circularly polarizing plate from the direction perpendicular to the thickness of the circularly polarizing plate, the brightness is brighter than the light shielding portion P of the crossed Nicols around it, and the region (phase difference shift area Q). This change in color (brightness) means that the reflected light from the aluminum film could not be blocked due to the retardation of the retardation layer.

Specifically, the phase difference shift region Q can be identified based on visible light image data around the through hole. First, the average lightness (brightness) Mx of the pixels of the light shielding portion (crossed Nicols portion) P which is 500 to 1000 μm away from the periphery of the through hole is used as a reference value. If there is a pixel region around the through-hole (the region less than 500 μm from the perimeter of the through-hole) having a lightness (brightness) 1.2 times or more that of Mx, the region inside the pixel is It is recognized as the phase difference shift region Q. A pixel region having a lightness (brightness) 1.2 times or more as large as Mx is present around the through-hole at an angle of 180 degrees or more with respect to the center of the through-hole so as to surround the through-hole. Alternatively, the maximum lightness (brightness) of pixels in the region surrounding the through-hole may be 1.5 times or more of Mx.

Image data can be obtained, for example, with the following equipment and conditions. BX51 manufactured by Olympus Corporation can be used as a polarizing microscope. The reflective light source can be U-LH100-3, a 12V 100W halogen lamphouse. The magnification of the objective lens can be 5x. The lightness (brightness) of an image depends on the amount of exposure and the exposure time. The amount of exposure and the exposure time can be appropriately selected according to the device or the like used so that the discolored portion can be easily identified. For example, when using the Olympus BX51, the exposure can be changed by adjusting the knobs on the microscope. The exposure dose can be 50-100%, where the maximum exposure dose is 100% and the minimum exposure dose is 0%. The exposure time can be 25-125 ms.

In the image data, the average lightness (brightness) of the light shielding portion P is preferably within the range of 48-58 (average 52) in the gradation of 0-255. The lightness of the pixels of the image data can be obtained from the RGB data, and for example, the lightness can be obtained using WINDOWS (registered trademark) paint software.

An annular region with a radial width of 30 μm around the through-hole has a polarizing function, ie can block visible light. Specifically, another linear polarizing plate is added to this circular polarizing plate so that the absorption axis of the polarizer of the circular polarizing plate and the absorption axis of the linear polarizing plate are crossed Nicols, and the circularly polarized light When stacked on the polarizer side of the plate, the 30 μm-wide annular region around the through hole can block visible light to the same extent as the surrounding region (light blocking portion P). Note that when the through-hole is formed by a laser, the annular region with a width of 30 μm around the through-hole does not have a polarizing function and does not block visible light. Moreover, it is preferable to peel off the temporary protective layer and the separator in the circularly polarizing plate in advance at the time of this measurement.

Specifically, the polarizing function of a 30 μm-wide annular region around the through-hole can be evaluated based on the visible light image data of the transmitted image around the through-hole. First, another linear polarizing plate is attached to the circular polarizing plate so that the absorption axis of the polarizer of the circular polarizing plate and the absorption axis of the linear polarizing plate are crossed Nicols, and the polarizer of the circular polarizing plate Overlap on the side. The average lightness (brightness) Mx2 of the pixels in the light shielding portion (crossed Nicol portion) P 500 to 1000 μm away from the periphery of the through hole is used as a reference value. If the average brightness of the 30-μm-wide annular region around the through-hole is less than 1.2 times that of Mx2, it can be said that the 30-μm-wide annular region around the through-hole has a polarizing function. The average brightness in a 30 μm-wide annular region around the through-hole may be 1.1 times or less of Mx2. The lower limit is not particularly limited. The average brightness in a 30 μm-wide annular region around the through-hole can be 0.8 times or more that of Mx2.

In the above image data, the average lightness (brightness) of the light shielding portion P is preferably in the range of 48 to 58 (average 52) in the gradation of 0 to 255. Similarly, the average lightness (brightness) of the 30 μm-wide annular region around the through-hole is preferably in the range of 48-58 (average 52) in the 0-255 gradation.

(Example 1)
(Prepare film)
A film 100 having the following configuration was prepared. The thickness of the film 100 was 200 μm.

PET temporary protective layer/triacetylcellulose layer/iodine-dyed polyvinyl alcohol layer (polarizer)/triacetylcellulose layer/acrylic adhesive layer/liquid crystal retardation plate (λ/2 plate)/acrylic adhesive layer/liquid crystal position Retardation Plate (λ/4 Plate)/Adhesive Layer/Separator Layer 35 sheets of the above films were laminated to obtain a laminate having a thickness of 7 mm.

(Formation of through holes)
With an end mill having a blade outer diameter of 1.1 mm and a blade length of 10 mm, A1 step is performed with a distance L of 1.5 mm, A2 step is performed with an inner diameter D2 of 2.0 mm, A including A1 and A2 steps The process was repeated 5 times to form through-holes with an inner diameter of 2.0 mm in the laminate.

(Examples 2-5)
It was the same as Example 1 except that the inner diameters in the A2 process were 1.8 mm, 1.7 mm, 1.6 mm and 1.5 mm.

(Comparative Examples 1 to 5)
It was the same as Examples 1 to 5 except that the distance L in the A1 step was set to 10 mm and the A step was performed only once.

(evaluation)
(Measurement of width of discolored area)
Place the circularly polarizing plate on the aluminum film so that the polarizer is above the retardation plate, and use a polarizing microscope to observe the circularly polarizing plate from the direction perpendicular to the thickness of the circularly polarizing plate in the reflection mode. Image data was obtained by observing the periphery of the through hole, the presence or absence of the phase difference shift region Q was determined according to the above-described criteria, and the maximum width W of the phase difference shift region Q and the like were measured. At the time of image taking, the knob was adjusted so that the exposure amount was 70 to 100%. Also, the exposure time was set to 40 to 60 ms.

(Presence or absence of depolarization part)
For the circularly polarizing plate from which the PET temporary protective layer has been peeled, another linearly polarizing plate is applied so that the absorption axis of the polarizer of the circularly polarizing plate and the absorption axis of the linearly polarizing plate are crossed Nicols, and circular Arranged on the polarizer side of the polarizing plate, image data was acquired with a microscope, and judgment was made according to the above-mentioned criteria. determined to be functional.

Table 1 shows the results.

In Examples, it was confirmed that discoloration around the through-holes could be suppressed.

DESCRIPTION OF SYMBOLS 200... Laminate 10... Liquid crystal retardation plate 36... Polarizer 80... Temporary protective layer 300... End mill 300a... Handle portion 300b... Blade portion 100... Film (circularly polarizing plate) 200H1, 200H2... Hole 200HT... Through hole 140... Protective film 200H1, 200H2... Hole 200HT... Through hole D1, D2... Inside diameter L... Distance Q... Area W... Width.

Claims (2)

A circularly polarizing plate comprising a polarizer having a protective film on at least one surface and a liquid crystal retardation plate,
having a through hole with a diameter of 2.5 mm or less,
the maximum width of the retardation region Q around the through hole is 0 to 30 μm or less,
A circularly polarizing plate, wherein an annular region having a width of 30 μm from the periphery of the through hole has a polarizing function. A laminate of circularly polarizing plates according to claim 1 .

Images