JP2016065966A - Optical film having difference in reflectance between front and back sides - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical film having a difference in reflectance between front and back sides, without laminating a functional layer as a film.SOLUTION: An optical film has a plurality of through holes penetrating in a thickness direction, with a central axis extends linearly. The ratio (a/b) of the opening diameter a of the through hole in one principal plane and the opening diameter b of the through hole in the other principal plane is less than 80%. An aperture of the opening diameter a in the other principal plane is 20 μm or less.SELECTED DRAWING: Figure 2

Description

  The present invention relates to optical films having different reflectances on the front and back sides.

  The constituent materials of each display, such as tablet PCs and smartphones, and optical films used for the addition of visibility functions are required to be lighter by thinning, to further improve characteristics and to add new functions ( For example, Patent Documents 1 to 3). As a means for adding a function, measures for laminating a functional layer such as an inorganic material on a film substrate have been implemented (for example, Patent Documents 4 to 8).

  However, by laminating these functional layers, there are problems such as an increase in film thickness and a decrease in flexibility. Therefore, studies on the surface processing technology of the base material have been carried out as a solution to these problems.

Japanese Patent Laid-Open No. 06-130228 JP 2000-080240 A JP 2002-196113 A JP 2005-352121 A JP 2010-117714 A JP 2012-208448 A JP 2012-181292 A JP2012-052170A

  An object of this invention is to provide the optical film from which a reflectance differs in front and back, without laminating | stacking a functional layer as a film.

  The optical film of the present invention has a plurality of through-holes having a central axis extending linearly and penetrating in the thickness direction. The ratio (a / b) between the opening diameter a of the through hole on one main surface and the opening diameter b of the through hole on the other main surface is less than 80%. The hole diameter of the opening diameter a in the one main surface is 20 μm or less.

  The optical member of the present invention includes the optical film of the present invention.

  The composition of this invention contains the ground material of the said optical film of this invention.

  In the optical film of the present invention, the reflectance of the front and back is different for a single substrate without laminating a functional layer as a film. Moreover, the optical film of the present invention can improve visibility (for example, widen the viewing angle).

It is a top view which shows typically an example of the optical film of this invention. It is sectional drawing which shows the cross section BB of the optical film shown in FIG. It is sectional drawing of the optical film of one embodiment of this invention. It is a schematic diagram for demonstrating the outline of ion beam irradiation. It is process drawing which shows typically an example of process (II) in the manufacturing method of the resin film used for the optical film of this invention. It is a figure which shows the relationship between the aperture ratio and reflectance of the optical film of an Example and a comparative example. It is a figure which shows the relationship between a reflectance and each parameter in the optical film which has an asymmetrical through-hole of an Example and a comparative example.

  The optical film of the present invention has a through-hole having an asymmetric structure in which the central axis (the axis of the through-hole) is linearly penetrated in the thickness direction, and the hole diameters on the front surface and the back surface are different by a predetermined ratio (hereinafter, simply “asymmetric through-hole”). ”). As the optical film of the present invention, it is preferable to use a non-porous resin film except for the through holes.

  An example of the optical film is shown in FIGS. FIG. 2 shows a cross section BB of the optical film 11 shown in FIG. The optical film 11 is formed with a large number of through holes 12 penetrating in the thickness direction. The optical film 11 is non-porous except for the through holes 12. The axis of the through hole is linear.

  The hole diameter of the through hole is the diameter of the circle when the cross-sectional shape (for example, the opening shape) of the opening diameter a (or b) on one main surface is regarded as a circle, in other words, one main surface. The diameter of a circle having the same area as the cross-sectional area (for example, the opening area) of the opening having the opening diameter a (or b) in FIG. Moreover, the following opening diameter a and opening diameter b mean the average value of the said diameter unless there is particular description.

  In the optical film, the ratio a / b between the opening diameter a of the through hole on one main surface and the opening diameter b of the through hole on the other main surface is less than 80%, preferably 75% or less, and preferably 60% or less. Is more preferable. The diameter of the through hole a is normally 20 μm or less, preferably 10 μm or less, and more preferably 5 μm or less. By using a film having an asymmetrical through hole in which the ratio of the hole diameter is in a specific range, the difference in reflectance between the front and back of the film is increased. Since the film can maintain an appropriate mechanical strength, the hole diameter of the through hole a is usually 20 μm or less. The lower limit of the diameter (opening diameter) and a / b of the through hole a is a main surface having a through hole with an opening diameter a (hereinafter also referred to as “opening diameter a surface”) and a main surface having a through hole with an opening diameter b. The reflectance is not particularly limited as long as the reflectance of (the “aperture diameter b surface” hereinafter) is different and the pore diameter ratio a / b is in the above range. The lower limit of the pore diameter a is, for example, 0.05 μm.

  The opening shape of the through hole is not particularly limited, and may be, for example, circular or indefinite. In the optical film 11 shown in FIG.1 and FIG.2, the opening shape of the through-hole 12 is circular.

  The axis of the through hole is usually in a direction perpendicular to the main surface of the optical film. As long as the through hole penetrates in the thickness direction of the optical film (by the through hole, ventilation in the thickness direction of the optical film is ensured), the axis of the through hole is inclined from the direction perpendicular to the main surface. (Figure 3). The inclination is not particularly limited as long as the effect of the present invention is not hindered, and the direction of the axis may be randomly different (FIG. 3).

The optical film has a plurality of through-holes, and the through-holes are typically independent of each other, but two or more through-holes may be combined as long as the effects of the present invention are not hindered. For example, when the axis of the through hole is in a direction perpendicular to the main surface of the optical film, the openings on the main surface having through holes with an opening diameter a are independent from each other due to the difference in the hole diameters on the front and back surfaces. The openings on the main surface having through holes with an opening diameter b may be joined together. The through hole can be formed by ion beam irradiation and etching, for example.

  By using ion beam irradiation and etching using a resin film as a material, a large number of through holes having the same opening diameter and axial direction can be formed in the resin film. In addition, when at least a part of the resin film includes a part in which the direction of the axis is different at random, the part can be formed by performing ion beam irradiation in a random direction, and in the part, two or more through holes are formed in the film. They may be combined (FIG. 3).

  The material constituting the resin film having the asymmetrical through hole is not particularly limited as long as it is a material in which the through hole is formed by ion beam irradiation and etching. As said material, the resin film comprised from resin which can be etched with an alkaline solution or an acidic solution is preferable, for example. Specifically, at least one resin selected from the group consisting of polyethylene terephthalate (PET), polycarbonate (PC), polyimide (PI), polyethylene naphthalate (PEN), and polyvinylidene fluoride (PVdF) is preferable. In view of excellent surface smoothness, the resin film is more preferably composed of PET. These resins are decomposed by an etching treatment liquid containing an alkaline substance and / or an oxidizing agent. PI is decomposed by an etching treatment liquid containing sodium hypochlorite as a main component. Other resins are decomposed by an etching treatment liquid containing sodium hydroxide as a main component. Examples of the alkaline substance include potassium hydroxide and sodium hydroxide. Examples of the oxidizing agent include chlorous acid and its salt, hypochlorous acid and its salt, hydrogen peroxide, potassium permanganate and the like. The resin film may contain a material other than resin. Examples of materials other than the resin include arbitrary additives such as light stabilizers and antioxidants, oligomer components derived from resin raw materials, metal oxides (for example, white pigments: alumina, titanium oxide, etc.), and the like. .

  The resin film having the asymmetric through hole can be produced by the following production method.

  The step (I) of irradiating a polymer film (resin film as a material as described above) with an ion beam, and the ion collision of the polymer film after the ion beam irradiation are performed by chemical etching. Forming a through hole extending along the trajectory of the film in the film (II). In the step (II), the masking layer is disposed on one main surface of the polymer film, so that the etching from the other main surface of the polymer film is compared with the etching of the portion from the one main surface. It can be obtained by performing chemical etching with a large degree of etching of the part. The manufacturing method may include any step other than steps (I) and (II) as long as a film having an asymmetrical through hole is obtained.

[Step (I)]
In step (I), the polymer film is irradiated with an ion beam. The ion beam is composed of accelerated ions. By irradiation with an ion beam, a polymer film in which ions in the beam collide is formed. The method for irradiating the ion beam is not limited. For example, after the polymer film 1 is accommodated in the chamber and the pressure in the chamber is lowered (for example, after a high vacuum atmosphere is set in order to suppress the attenuation of the energy of the irradiated ions 2), the ions 2 are removed from the beam line. The polymer film 1 is irradiated. A specific gas may be added to the chamber, or the polymer film 1 may be accommodated in the chamber, but the pressure in the chamber may not be reduced, and for example, ion beam irradiation may be performed at atmospheric pressure.

When the polymer film is irradiated with the ion beam, as shown in FIG.
Collide with the polymer film 1, and the collided ions 2 leave a trajectory 3 (the trajectory of such ion collision is also referred to as “ion track”) inside the film 1. The ions 2 usually penetrate the polymer film 1.

  A roll around which the belt-shaped polymer film 1 is wound may be prepared, and the polymer film 1 may be continuously irradiated with an ion beam while the polymer film 1 is fed from the roll. In the chamber described above, the roll (feeding roll) and a winding roll for winding the polymer film 1 after irradiation with the ion beam are disposed, and the chamber is set in an arbitrary atmosphere such as reduced pressure or high vacuum. The film may be continuously irradiated with an ion beam while the belt-shaped polymer film 1 is fed out, and the polymer film 1 after the beam irradiation may be wound on a winding roll.

  The polymer film 1 made of the resin has a feature that the chemical etching of the portion where the ions 2 collide smoothly proceeds, but the chemical etching of the other portion hardly proceeds. It becomes easy to control the chemical etching of the portion corresponding to the locus 3 in FIG. For this reason, the freedom degree of control of the shape of the pore as a resin film which has an asymmetrical through-hole can be made higher.

  The polymer film 1 that irradiates the ion beam is, for example, a non-porous film. In this case, the resin film in which the portions other than the pores formed by the steps (I) and (II) are non-porous unless a further step of providing holes in the film other than the steps (I) and (II) is performed. Can be obtained. When the said further process is implemented, the resin film which has the pore formed by process (I) and (II) and the hole formed by the said further process is obtained.

  Although the kind of ion 2 irradiated and collided to the polymer film 1 is not limited, since a chemical reaction with the resin constituting the polymer film 1 is suppressed, an ion having a larger mass number than neon is preferable. Specifically, at least one ion selected from the group consisting of argon ions, krypton ions, and xenon ions is preferable.

  The state of the locus 3 formed on the polymer film 1 after the beam irradiation also changes depending on the type and energy of the ions 2 irradiated on the film. For example, in the case of argon ions, krypton ions, and xenon ions, the length of the trajectory 3 formed on the polymer film 1 becomes longer as the ions having the smaller atomic number have the same energy. The change in the state of the locus 3 accompanying the change in the ion species and the change in the ion energy affects the shape of the pores formed after the chemical etching in the step (II). For this reason, it is possible to further increase the degree of freedom in controlling the shape of the pores as the resin film having asymmetric through-holes by using the selection of the ion species and the energy thereof together.

  When ion 2 is an argon ion, its energy is typically 100-1000 MeV. When ion 2 is a krypton ion, its energy is typically 100-1000 MeV. When ion 2 is a xenon ion, its energy is typically 100-1000 MeV. The energy of the ions 2 irradiated to the polymer film 1 can be adjusted according to the ion species and the type of resin constituting the polymer film.

  The ion source of the ion 2 irradiated to the polymer film 1 is not limited. For example, the ions 2 emitted from the ion source are accelerated by an ion accelerator and then irradiated onto the polymer film 1 through a beam line. Examples of the ion accelerator include a cyclotron such as an AVF cyclotron.

The pressure of the beam line serving as the path of the ions 2 is preferably a high vacuum of about 10 ⁻⁵ to 10 ⁻³ Pa from the viewpoint of suppressing energy attenuation of the ions 2 in the beam line. When the pressure of the chamber in which the polymer film 1 for irradiating the ions 2 is accommodated does not reach a high vacuum, the pressure difference between the beam line and the chamber may be maintained by a partition wall that transmits the ions 2. The partition is made of, for example, a titanium film or an aluminum film.

  The ion 2 is irradiated to the said film from the direction perpendicular | vertical to the main surface of the polymer film 1, for example. In this case, since the locus 3 extends perpendicularly to the main surface of the film 1, a resin film in which pores extending in a direction perpendicular to the main surface of the film 1 are formed is obtained by subsequent chemical etching. The ions 2 may be irradiated to the film from a direction oblique to the main surface of the polymer film 1. In this case, a resin film in which pores extending in an oblique direction with respect to the main surface of the film 1 are formed by subsequent chemical etching. The direction in which the polymer film 1 is irradiated with the ions 2 can be controlled by a known means.

  For example, the ions 2 are applied to the film 1 so that tracks of the plurality of ions 2 are parallel to each other. In this case, a resin film in which a plurality of pores extending in parallel with each other is formed by subsequent chemical etching. The film 1 may be irradiated with the ions 2 such that the tracks of the plurality of ions 2 are not parallel to each other (for example, are random to each other).

The ion 2 may be applied to the polymer film 1 from two or more beam lines.
Step (I) may be performed in a state where the masking layer is disposed on the main surface of the polymer film 1, for example, the one main surface.

[Step (II)]
In the step (II), the portion of the polymer film 1 that has been irradiated with the ion beam in the step (I) is subjected to chemical etching so that the pores extending along the trajectory 3 of the collision of the ions 2 Form on film 1.

  A collision locus (ion track) 3 remains on the polymer film 1 after irradiation with the ion beam. In the locus 3, the polymer chain constituting the polymer film 1 is damaged due to collision with the ions 2. Damaged polymer chains are more easily decomposed and removed by chemical etching than polymer chains that do not collide with ions 2. Therefore, by chemically etching the polymer film 1 after irradiation with the ion beam, the portion of the locus 3 in the polymer film 1 is selectively removed, and pores extending along the locus 3 of the collision of the ions 2 are formed. A resin film is obtained.

  Since the ions 2 normally penetrate the polymer film 1, through holes are formed as pores by chemically etching all the portions of the polymer film 1 after the beam irradiation where the ions 2 collide. Unless the step of changing the state of the film 1 is further performed, the portions other than the pores in the obtained resin film are basically the same as the polymer film 1 before the ion beam irradiation. Portions other than the pores can be non-porous, for example.

In step (II), chemical etching is performed with a masking layer disposed on one main surface of the polymer film 1. For this reason, in this chemical etching, the degree of etching from the other main surface is smaller than the etching from the one main surface where the masking layer is disposed in the etching of the portion of the polymer film 1 where the ions 2 collide. growing. That is, in step (II), chemical etching is performed in which etching from both main surfaces of the film proceeds asymmetrically (hereinafter also simply referred to as “asymmetric etching”). On the other hand, in the conventional method, etching from both main surfaces of the polymer film proceeds uniformly (symmetrically) (
Hereinafter, it is also simply referred to as “symmetrical etching”). More specifically, “the degree of etching is large” means, for example, that the etching amount per unit time is large for the part, that is, the etching rate is high for the part.

  In the step (II), the masking layer that is hard to be chemically etched compared to the portion of the polymer film 1 where the ions 2 collide is disposed on one main surface of the polymer film 1, so that You may perform the chemical etching (asymmetrical etching) which advances the etching of the said part from the other main surface of the polymer film 1, suppressing the etching of a part. Such etching can be performed, for example, by selecting the type and thickness of the masking layer, disposing the masking layer, selecting etching conditions, and the like.

  Although the kind of masking layer is not specifically limited, It is preferable that it is a layer comprised from the material which is hard to carry out chemical etching compared with the part which the ion 2 in the polymer film 1 collided. More specifically, “not easily etched” means, for example, that the amount etched per unit time is small, that is, the etching rate is small. Whether or not chemical etching is difficult can be determined based on the conditions of asymmetric etching (type of etching processing solution, etching temperature, etching time, etc.) actually performed in step (II). As will be described later, when the asymmetric etching is performed a plurality of times in the step (II) while changing the type and / or arrangement surface of the masking layer, each etching may be determined based on the etching conditions.

  A masking layer is comprised from at least 1 sort (s) chosen from the group which consists of polyolefin (for example, polyethylene etc.), polystyrene, polyvinyl chloride, polyvinyl alcohol, and metal foil, for example. These resins are difficult to be chemically etched and are not easily damaged by ion beam irradiation.

  In the step (I), when the polymer film 1 on which the masking layer is disposed is irradiated with an ion beam, an ion track is also formed on the masking layer. Considering this, it is preferable that the material constituting the masking layer is a material in which the polymer chain is hardly damaged even by irradiation with an ion beam.

  The masking layer may be disposed on at least a part of one main surface of the polymer film 1 corresponding to a region where asymmetric etching is performed, and, if necessary, on the entire one main surface of the polymer film 1. You may arrange.

  The arrangement method of the masking layer on the main surface of the polymer film 1 is not limited as long as the masking layer does not peel off from the main surface during the asymmetric etching. The masking layer is disposed on the main surface of the polymer film 1 with an adhesive, for example. That is, in the step (II), the chemical etching (asymmetric etching) may be performed in a state where the masking layer is bonded to the one main surface with an adhesive. The arrangement of the masking layer with the pressure-sensitive adhesive can be performed relatively easily. Further, by selecting the type of pressure-sensitive adhesive (for example, silicone pressure-sensitive adhesive, acrylic pressure-sensitive adhesive, etc.), the masking layer can be easily peeled off from the polymer film 1 after asymmetric etching.

  In step (II), asymmetric etching may be performed a plurality of times. Further, as long as at least one asymmetric etching is performed, symmetric etching may be performed. For example, the masking layer may be peeled off from the polymer film 1 in the course of etching to switch from asymmetric etching to symmetric etching.

By performing asymmetric etching a plurality of times in step (II), the degree of freedom in controlling the shape of the pores to be formed, typically the cross-sectional shape thereof, becomes higher. Moreover, the degree of freedom in controlling the shape of the pores to be formed is further increased by using the replacement of the main surface on which the masking layer is disposed and / or the change of the etching conditions. In FIG. 5, the example of process (II) and the shape (cross-sectional shape) of the pore formed in the said example are shown.

  In the example shown in FIG. 5, a masking layer 4 is disposed on one main surface of the polymer film 1 after irradiation with an ion beam (FIG. 5A), and chemical etching is performed in this state. As a result, etching proceeds along the locus 3 formed by irradiation of the ion beam from the other surface where the masking layer is not disposed, and through holes extending along the locus 3 are formed as the pores 5. (FIG. 5B). As shown in FIG. 5B, etching does not proceed from the main surface on which the masking layer 4 is disposed, and no pores are formed. Due to the relationship Vt >> Vb between the etching rate Vt in the direction along the locus 3 and the etching rate Vb in the direction perpendicular to the direction in which the locus 3 extends, the cross section of the formed through-hole has a conical shape and is etched. As a result of the further progress, the front end opens on the one main surface of the film 1. And the opening diameter in said one main surface of the said through-hole and the opening diameter in the other main surface are mutually different, and the opening diameter in said other main surface used as the origin of etching is larger. That is, in the example shown in FIG. 5, a resin film 6 having a through-hole having a conical cross-sectional shape, the opening diameter of which is different between both main surfaces of the polymer film 1 is obtained. (FIG. 5C). The ratio a / b between the opening diameter a of the through hole in the one main surface and the opening diameter b of the through hole in the other main surface is less than 80%, and depending on the etching conditions in the step (II), This ratio can be set to a smaller value (for example, 75% or less, 70% or less, or 60% or less).

  In the manufacturing method, in the step (II), the hole diameter is changed in the film thickness direction of the polymer film, and the opening diameter a on one main surface of the polymer film and the opening on the other main surface. It is possible to form an asymmetrical through hole in which the ratio a / b to the diameter b is less than 80%. The central axis of the through hole is usually along the locus 3.

  In the example shown in FIG. 5, since asymmetric etching has already been performed once, chemical etching may be further advanced from the state where the masking layer 4 shown in FIG. Thereby, for example, the ratio of the opening diameter of the through hole 5 or the opening diameter of the through hole 5 on one main surface of the polymer film 1 to the opening diameter of the through hole 5 on the other main surface can be controlled. In FIG. 5, the width (pore diameter) of the pores 5 is exaggerated over the length for easy understanding.

  The opening diameter of the through hole formed in the step (II) is not particularly limited, and can be controlled by, for example, etching conditions such as etching temperature, etching time, and composition of the etching treatment solution. The lower limit of the opening diameter can be set to 0.01 μm, for example.

  When the polymer film 1 on which the ion beam irradiation is performed in the step (I) is non-porous, for example, the resin film 6 in which all the through holes have an opening diameter of 10 μm or less can be used. Or it can also be set as the resin film 6 whose average (average opening diameter) of opening diameter is 10 micrometers or less.

The density of the through holes to be formed (the number of holes per square centimeter) can be controlled by, for example, ion beam irradiation conditions (ion species, ion energy, ion collision density (irradiation density), etc.), and is not particularly limited. For example, it may be 10 holes / cm ² to 1 × 10 ⁸ holes / cm ² , and if the number of holes is too large, the mechanical strength of the film such as expansion of the holes due to the bonding of adjacent holes decreases. If the amount is too small, the difference in reflectance between the front surface and the back surface of the film is unlikely to be large, so about 5.0 × 10 ³ pieces / cm ^{2 to} 7.0 × 10 ⁷ pieces / cm ² is preferable.

  The etching process liquid used for chemical etching is not specifically limited. The etching treatment liquid is, for example, an alkaline solution, an acidic solution, or an alkaline solution or an acidic solution to which at least one selected from an oxidizing agent, an organic solvent, and a surfactant is added. Examples of the alkaline solution include a solution containing a base such as sodium hydroxide and potassium hydroxide (typically an aqueous solution). Examples of the acidic solution include a solution (typically an aqueous solution) containing an acid such as nitric acid and sulfuric acid. Examples of the oxidizing agent include potassium dichromate, potassium permanganate, sodium hypochlorite and the like. Examples of the organic solvent include methanol, ethanol, 2-propanol, ethylene glycol, amino alcohol, N-methylpyrrolidone, N, N-dimethylformamide and the like. Examples of the surfactant include alkylbenzene sulfonate and alkyl sulfate.

  Except for asymmetric etching using a masking layer, a specific etching method may follow a known method. For example, the polymer film after the beam irradiation in which the masking layer is disposed may be immersed in the etching treatment liquid at a predetermined temperature for a predetermined time. The etching temperature may be 40 to 150 ° C., for example. The etching time may be, for example, 10 seconds to 60 minutes.

  After the etching is completed, the film is taken out, washed and dried, and then the masking layer is peeled off. The method of taking out the film, washing, drying, peeling, etc. is not particularly limited. Thereby, a resin film having an asymmetric through hole is obtained.

  In the resin film, the direction in which the through hole extends (the direction of the central axis) can be a direction perpendicular to the main surface of the film (the normal direction of the film) or a tilted direction. The angle including vertical can be controlled by the irradiation angle of the ion beam to the polymer film.

  The optical film of the present invention is not particularly limited, and may be used as a single layer as a film, or may be used as a laminate, but it is a single layer from the viewpoint of reducing the thickness of the film and using it as a thin film. It is preferable to use it. In the optical film of the present invention, the through hole is not filled with resin or the like.

  In the optical film of the present invention, the ratio of the aperture ratio between the main surface having a through hole having an opening diameter a (opening diameter a surface) and the main surface having a through hole having an opening diameter b (opening diameter b surface) is 65% or less is preferable, 63% or less is more preferable, and 60% or less is more preferable from the point which can make the difference of the reflectance of a table | surface and a back larger. The method for measuring the aperture ratio is as described in the examples described later.

  Furthermore, since the thickness of an optical film has favorable reflectance, about 1-100 micrometers is preferable, about 5-90 micrometers is more preferable, About 5-80 micrometers is further more preferable. Moreover, since it is a thin film, the problem that a flexibility falls is not produced.

  It is preferable that the optical film of the present invention has a different reflectance of light having a wavelength region of 300 to 800 nm, and the difference in reflectance between the front surface and the back surface is large. The reflectance of the front surface and the back surface is preferably 2% or more, and more preferably 3% or more. The method of measuring the reflectance is as described in the examples described later. Since the optical film of the present invention has different reflectivities on the front and back surfaces, it does not require processes such as laminating films having different reflectivities, and in the case of a film having holes, positioning the holes. It is advantageous. The method of measuring the reflectance is as described in the examples described later.

The optical film of this invention is not specifically limited, It can utilize for an optical use. Such applications include, for example, electronic paper, personal computer monitors, notebook computers, copy machines, mobile phones, watches, digital cameras, personal digital assistants (PDAs), portable game machines, video cameras, televisions, microwave ovens, back monitors. It can be used for various displays such as car navigation system monitors, car audio, nursing care monitors, medical monitors, polarizing plates, optical lenses, illumination members, etc. The optical film of the present invention can be used for liquid crystal display devices, etc. It can be used as various functional films such as a polarizing plate protective film, a retardation film, a viewing angle widening film, and various functional films used in an organic EL display.

  As other embodiment of this invention, an optical member provided with the optical film of this invention is mentioned. It can become an optical member by joining the optical film of this invention with another member. At this time, other members are not particularly limited.

  As other embodiment of this invention, the composition containing the ground material obtained by grind | pulverizing the optical film of this invention is mentioned.

  The method for pulverizing the optical film is not particularly limited, and examples thereof include a method of cutting with a cutter as necessary and then pulverizing with a pulverizer. There are no particular restrictions on the type of pulverizer. Use a shear crusher such as a biaxial rotary shear crusher or a uniaxial rotary shear crusher, an impact crusher such as a hammer mill or impact crusher, or a shredder. Can do. The size of the pulverized product is not particularly limited.

  Since such a composition includes a pulverized product of a film having a large difference in reflectance between the front surface and the back surface, the paint is used for the purpose of improving the reflectance, obtaining a random reflectance, or obtaining a play color effect. It can be used for cosmetics.

  The present invention includes embodiments in which the above-described configurations are variously combined within the technical scope of the present invention as long as the effects of the present invention are exhibited.

  EXAMPLES Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples at all, and many variations are within the technical idea of the present invention. This is possible by those with ordinary knowledge.

  About each physical property of the film of an Example and a comparative example, it measured with the following method.

[Pore diameter]
Both main surfaces (front surface and back surface) of the surface of the film of each example and comparative example were imaged by SEM (manufactured by JEOL (JEOL Ltd., JSM-6510LV)) and arbitrarily selected from the obtained SEM images The hole diameters (diameters) of the 10 through holes were measured from the image, and the average value was taken as the hole diameter of the through holes.

[Pore density]
The hole density (number of holes per square centimeter) of the film was calculated by visually counting the number of holes in the SEM image used in the above-mentioned measurement of the hole diameter for each sample, and converting it per square centimeter.

[Aperture ratio]
The opening ratio of the resin film was evaluated for the main surfaces of both sides (the front surface and the back surface) of the resin film. Specifically, first, the main surface is made of SEM (JEOL (JEOL Ltd.), JS
M-6510LV), and the number of through holes (number of holes) existing on the obtained SEM image was visually counted. Next, for the counted holes, the area of the through holes (hole area) obtained from the hole diameter (average hole diameter) measured by the above method was calculated, and the number of holes, the hole area (μm ² ), and the area of the SEM image (μm ² ) Was calculated from the following formula.
Opening ratio (%) = {(hole area × number of holes) / area of SEM image} × 100
In the SEM image shooting, the field of view range was set so that the outline of the hole included in the image was not lost as much as possible. In the said range, the hole connected to the adjacent hole and the hole existing over the boundary of the image were excluded from evaluation in the evaluation of the hole diameter, the number of holes and the hole density.

[optical properties]
For the front and back of each sample, the reflectance (% R) is assigned to an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, trade name: V-560, double beam method, detector: photomultiplier tube). It measured with the apparatus which attached the integrating sphere apparatus (The JASCO Corporation make, brand name: ISV-469). The measurement wavelength region was 300 to 800 nm. The reflectance is a relative value when the light reflectance is 100 when a barium sulfate plate is used as the standard reflecting plate. Moreover, the reflectance described in the table was calculated as an average value of the reflectance in the measurement wavelength region of 300 to 800 nm.

[Example 1]
A non-porous commercially available PET film (it4ip, Track etched membrane, thickness 50 μm) in which a plurality of through holes penetrating in the thickness direction was formed was prepared. This film is a film produced by irradiating a non-porous PET film with an ion beam and chemically etching the irradiated film. Observation of the surface and cross-section of this film by SEM confirmed the following:
(1) The through hole is a straight hole having a diameter of 0.25 μm;
(2) There are through-holes extending in the direction perpendicular to the main surface of the film; (3) The hole density of the film is 2.0 × 10 ⁶ holes / cm ² .

  Next, a polyethylene film (thickness: 55 μm) was attached to one main surface of the porous PET film with an acrylic adhesive as a masking layer. This was immersed in an etching treatment liquid maintained at 80 ° C. (aqueous solution having a potassium hydroxide concentration of 20 mass%) for 23 minutes. After completion of the etching, the film was taken out, immersed and washed with RO water, and dried in a drying oven at 50 ° C. Thereafter, the masking layer was peeled off to obtain an optical film in which asymmetric through holes were formed.

  The hole diameter, the aperture ratio, and the reflectance were measured for both surfaces (the front surface and the back surface) of the obtained optical film. Moreover, the hole diameter ratio and the opening ratio were calculated based on the measurement results. The results are shown in Table 1 below. A surface having a smaller hole diameter than that of the other main surface represents a masking surface.

[Example 2]
An optical film in which asymmetric through-holes were formed was obtained in the same manner as in Example 1 except that the etching time after applying the masking layer to one main surface of the porous PET film was 20 minutes. The hole diameter, the aperture ratio, and the reflectance were measured for both surfaces (the front surface and the back surface) of the obtained optical film. Moreover, the hole diameter ratio and the opening ratio were calculated based on the measurement results. The results are shown in Table 1 below. A surface having a smaller hole diameter than that of the other main surface represents a masking surface.

[Example 3]
An optical film in which asymmetric through holes were formed was obtained in the same manner as in Example 1 except that the etching time after applying the masking layer to one main surface of the porous PET film was 10 minutes. The hole diameter, the aperture ratio, and the reflectance were measured for both surfaces (the front surface and the back surface) of the obtained optical film. Moreover, the hole diameter ratio and the opening ratio were calculated based on the measurement results. The results are shown in Table 1 below. A surface having a smaller hole diameter than that of the other main surface represents a masking surface.

[Comparative Example 1]
A non-porous commercially available PET film (it4ip, Track etched membrane, thickness 50 μm) in which a plurality of through holes penetrating in the thickness direction was formed was prepared. This film is a film produced by irradiating a non-porous PET film with an ion beam and chemically etching the irradiated film. Observation of the surface and cross-section of this film from SEM confirmed the following:
(1) The through hole is a straight hole having a diameter of 0.25 μm;
(2) There are through-holes extending in the direction perpendicular to the main surface of the film; (3) The hole density of the film is 2.0 × 10 ⁶ holes / cm ² .

  Next, the porous PET film was immersed in an etching treatment liquid (aqueous solution having a potassium hydroxide concentration of 20% by mass) maintained at 80 ° C. for 20 minutes. After completion of the etching, the film was taken out, immersed and washed with RO water, and dried in a drying oven at 50 ° C. Then, the optical film in which the vertical through-hole was formed was obtained.

  The hole diameter, the aperture ratio, and the reflectance were measured for both surfaces (the front surface and the back surface) of the obtained optical film. Moreover, the hole diameter ratio and the opening ratio were calculated based on the measurement results. The results are shown in Table 1 below. A surface having a smaller hole diameter than that of the other main surface represents a masking surface.

[Comparative Example 2]
A non-porous commercially available PET film (it4ip, Track etched membrane, thickness 50 μm) in which a plurality of through holes penetrating in the thickness direction was formed was prepared. This film is a film produced by irradiating a non-porous PET film with an ion beam and chemically etching the irradiated film. Observation of the surface and cross-section of this film from SEM confirmed the following:
(1) The through hole is a straight hole having a diameter of 0.25 μm;
(2) There are through-holes extending in the direction perpendicular to the main surface of the film; (3) The hole density of the film is 2.0 × 10 ⁶ holes / cm ² .

  Next, the porous PET film was immersed in an etching treatment liquid (aqueous solution having a potassium hydroxide concentration of 20% by mass) maintained at 80 ° C. for 23 minutes. After completion of the etching, the film was taken out, immersed and washed with RO water, and dried in a drying oven at 50 ° C. Then, the optical film in which the vertical through-hole was formed was obtained.

  The hole diameter, the aperture ratio, and the reflectance were measured for both surfaces (the front surface and the back surface) of the obtained optical film. Moreover, the hole diameter ratio and the opening ratio were calculated based on the measurement results. The results are shown in Table 1 below. A surface having a smaller hole diameter than that of the other main surface represents a masking surface.

[Comparative Example 3]
A non-porous commercially available PET film (it4ip, Track etched membrane, thickness 50 μm) in which a plurality of through holes penetrating in the thickness direction was formed was prepared. This film is a film produced by irradiating a non-porous PET film with an ion beam and chemically etching the irradiated film. Observation of the surface and cross-section of this film by SEM confirmed the following:
(1) The through hole is a straight hole having a diameter of 0.25 μm;
(2) There are through-holes extending in the direction perpendicular to the main surface of the film; (3) The hole density of the film is 2.0 × 10 ⁶ holes / cm ² .

Next, a polyethylene film (thickness: 55 μm) was attached to one main surface of the porous PET film with an acrylic adhesive as a masking layer. This was immersed in an etching treatment liquid (aqueous solution having a potassium hydroxide concentration of 20% by mass) maintained at 80 ° C. for 5 minutes. After completion of the etching, the film was taken out, immersed and washed with RO water, and dried in a drying oven at 50 ° C. Thereafter, the masking layer was peeled off to obtain an optical film in which asymmetric through holes were formed.

  The hole diameter, the aperture ratio, and the reflectance were measured for both surfaces (the front surface and the back surface) of the obtained optical film. Moreover, the hole diameter ratio and the opening ratio were calculated based on the measurement results. The results are shown in Table 1 below. A surface having a smaller hole diameter than that of the other main surface represents a masking surface.

6 and Table 1, when comparing Example 1 of the asymmetric structure film and Comparative Examples 1 and 2 of the film of the symmetric structure, the reflectance of the film of Example 1 is higher on both sides, In addition, the film of Example 1 had a significant difference in reflectance between the front and back sides. Further, in Table 1 and FIG. 7, when the reflectances of the example having the asymmetric structure and the reflectance of the comparative example 3 are compared, the reflectance of the front and back is also different in the comparative example 3, but the difference is 1%. It was.
As described above, since the reflectance of the optical film of the present invention is different between the front and back surfaces, the optical film can be used for two uses on the front and back surfaces.

  The optical film of the present invention is an electronic paper, a personal computer monitor, a notebook computer, a copy machine, a mobile phone, a clock, a digital camera, a personal digital assistant (PDA), a portable game machine, a video camera, a TV, a microwave oven, a back monitor, a car. It can be used for various displays such as navigation system monitors, car audio systems, nursing care monitors, medical monitors, polarizing plates, optical lenses, illumination members, and the like. Moreover, the composition containing the ground material obtained by grind | pulverizing the optical film of this invention can be utilized for a coating material, cosmetics, etc.

DESCRIPTION OF SYMBOLS 1 Polymer film 2 Ion 3 (Ion 2 collision in polymer film 1) locus 4 Masking layer 5 Pore (through hole)
6 resin film having through hole 4a one side 4b other side 11 optical film 12 through hole 16 hole a opening diameter on one side b opening diameter on the other side

Claims (8)

An optical film having a plurality of through-holes with a central axis extending linearly and penetrating in the thickness direction,
The ratio (a / b) between the opening diameter a of the through hole on one main surface and the opening diameter b of the through hole on the other main surface is less than 80%,
An optical film having a hole diameter of an opening diameter a on the one main surface of 20 μm or less.   The optical film according to claim 1, wherein the reflectance of light having a wavelength region of 300 to 800 nm is different between the front and back sides of the resin film. Pore density optical film according to 1 × 10 ³ / cm ² or more 1 × 10 ¹⁰ pieces / cm ² or less according to claim 1 or 2.   The optical film according to any one of claims 1 to 3, wherein a ratio of an aperture ratio between a main surface having a through hole having an opening diameter a and a main surface having a through hole having an opening diameter b is 65% or less.   The optical film according to claim 1, wherein the optical film is a resin film made of a resin that can be etched with an alkaline solution or an acidic solution.   The optical film according to claim 5, wherein the resin film is composed of at least one resin selected from the group consisting of polyethylene terephthalate, polycarbonate, polyimide, polyethylene naphthalate, and polyvinylidene fluoride.   An optical member provided with the optical film of any one of Claims 1-6.   The composition containing the ground material of the optical film of any one of Claims 1-6.

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