CN115298579A

CN115298579A - Optical filter and method for manufacturing the same

Info

Publication number: CN115298579A
Application number: CN202180021232.3A
Authority: CN
Inventors: 菅将吾
Original assignee: Tomoegawa Paper Co Ltd
Current assignee: Tomoegawa Co Ltd
Priority date: 2020-03-31
Filing date: 2021-03-30
Publication date: 2022-11-04
Also published as: WO2021200890A1; JPWO2021200890A1; KR20220160543A

Abstract

The invention provides an optical filter which has a high aperture ratio, excellent viewing angle control function and easy manufacture. The optical filter of the present invention is an optical filter comprising an opaquely processed film having a film portion with a total light transmittance of 10% or less in the thickness direction and regularly arranged in the thickness direction so as to penetrate through the opaquely processed filmHas at least a thickness F of a film processed from opacity _T Diameter H of the through hole _D Aspect ratio (F) shown _T /H _D ) The surface has a surface area of 1 or more and has at least a surface area having an aperture ratio (a ratio of the area of the through hole region to the entire surface area) of more than 40%.

Description

Optical filter and method for manufacturing the same

Technical Field

The present invention relates to an optical filter and a method for manufacturing the same.

Background

When various display devices such as liquid crystal display devices (LCDs) and organic electroluminescence elements (organic ELs) are used, a privacy filter (privacy filter) has been developed to make information displayed on the display devices less visible to others.

Such a privacy filter has a function of transmitting light from the front of the filter and blocking light from a direction in which the filter is inclined. As a specific structure for realizing such a function, for example, a structure in which a plurality of holes are provided in the thickness direction of a light-blocking film is known.

For example, patent document 1 discloses a view angle limiting film made of a metal selected from the group consisting of transition metals having atomic numbers of 24 to 48, oxides thereof, and sulfides thereof, and having a film thickness of 1 to 100 μm and through-holes arranged in a honeycomb shape and having a pore diameter of 1 to 100 μm.

Patent document 2 discloses a privacy filter provided on a display surface, the privacy filter including a resin film which is a porous body formed with a plurality of straight holes that linearly penetrate in a thickness direction, and in which wall surfaces of the plurality of straight holes are colored.

Documents of the prior art

Patent literature

Patent document 1: japanese patent laid-open No. 2008-65183

Patent document 2: japanese patent laid-open No. 2014-142636

Disclosure of Invention

Problems to be solved by the invention

However, the viewing angle controlling function of the viewing angle restricting film of patent document 1 is insufficient. For example, in the example of patent document 1, the light transmittance value from the direction inclined by 60 ° from the normal direction is about 10%, but in this case, the function of preventing peeking is not sufficient. In addition, the viewing angle limiting film of patent document 1 has a difficulty in productivity and manufacturing cost.

In addition, the privacy filter of patent document 2 cannot improve the aperture ratio. For example, in the embodiment of patent document 2, the aperture ratio is only 40% at the maximum, but when this privacy filter is used in various display devices, it is necessary to increase the output of a light source such as a backlight in order to increase the luminance in the front direction. In addition, the privacy filter of patent document 2 has a difficulty in productivity and manufacturing cost. Further, in the privacy filter of patent document 2, if the straight hole density is increased in order to obtain a sufficient aperture ratio, the straight holes come into contact with each other, which causes a problem that the resin film is fragile in addition to the reduction of the viewing angle control function, and thus the manufacturing itself becomes difficult.

Accordingly, an object of the present invention is to provide an optical filter having a high aperture ratio, excellent viewing angle control function, and easy manufacturing.

Means for solving the problems

The present inventors have made intensive studies and found that the above problems can be solved by an optical filter including a film having a specific structure. Namely, the present invention is as follows.

The present invention is an optical filter comprising an opaquely processed film, wherein the opaquely processed film has a film portion having a total light transmittance of 10% or less in a thickness direction and a plurality of through holes regularly arranged in the thickness direction and penetrating the opaquely processed film, and at least has a thickness F of the opaquely processed film _T A diameter H of the through hole _D Aspect ratio (F) shown _T /H _D ) The surface is 1 or more, and at least has a surface having an aperture ratio (a ratio of the area of the through hole region to the entire surface) of more than 40%.

The above diameter H _D Preference is given toIs 100 μm or less.

Thickness F of the above-mentioned opaque processed film _T Preferably more than 100 μm.

The film portion is preferably a resin film having light absorbing ability in at least a part of a wavelength region of 360nm to 830nm and containing a dye or a pigment.

The opaque processed film may be provided with an adhesive layer on at least one surface thereof as required.

The opacity processing film may be provided with a protective film on at least one surface thereof as required.

The processed film having opacity may be provided with an antireflection film on at least one surface thereof as required.

Further, the present invention is a method for manufacturing an optical filter including an opaque processed film, including a laser irradiation step of: irradiating one surface of an opaque film having a total light transmittance of 10% or less in the thickness direction with a laser beam to form a processed film having at least a thickness F of the processed film _T A diameter H of the through hole _D Aspect ratio (F) _T /H _D ) The surface of the film is 1 or more, and at least the surface of the processed film has an opening ratio (a ratio of an area of the through hole region to the entire surface) of more than 40%.

Effects of the invention

According to the present invention, it is possible to provide an optical filter having a high aperture ratio, excellent viewing angle control function, and easy manufacturing.

Drawings

Fig. 1 is a conceptual diagram of a cross section of an opacity process film.

Fig. 2 is a conceptual diagram of the surface of an opacity process film.

Fig. 3 is a conceptual diagram of a cross section of an optical filter.

Fig. 4 is a conceptual diagram of a cross section of an optical filter.

Fig. 5 is a schematic diagram showing a method of measuring the incident light angle dependence of the optical filter.

Detailed Description

The structure, physical properties, use, production method and the like of the optical filter of the present invention will be explained.

In the following description, when the upper limit value and the lower limit value are described separately, all combinations of the upper limit value and the lower limit value are described in the present specification.

Structure of optical filter

The optical filter comprises an opaque processed film. The optical filter may or may not have another layer on the surface of the opacity processing film (fig. 1).

Opacity processing film

The processed opaque film is also a substrate, and has a film portion for forming a thick portion of the processed opaque film and a plurality of through holes (processed holes) provided so as to penetrate through the processed opaque film in the thickness direction.

Thickness F of the opaque working film _T The average particle diameter is not particularly limited, but is preferably more than 10 μm, more preferably more than 50 μm, and still more preferably more than 100. Mu.m. By setting the range as described above, visibility when the optical filter is viewed from an oblique direction can be sufficiently reduced. Further, the thickness F of the opaque processed film _T The upper limit of (b) is not particularly limited, but is preferably 1000 μm or less from the viewpoint of processability and the like.

The shape of the opaque processed film may be appropriately changed depending on the application.

< membrane part >

The total light transmittance of the film portion in the thickness direction is 10% or less, preferably 5% or less, more preferably 3% or less, still more preferably 1% or less, and particularly preferably 0%. By setting the range as described above, visibility when the optical filter is viewed from an oblique direction can be sufficiently reduced.

The method for measuring the total light transmittance is not particularly limited, and the measurement can be performed by a known method. For example, the measurement can be carried out in accordance with JIS K7375 "method for calculating total light transmittance and total light reflectance of plastics".

The total light transmittance of the film portion can be adjusted by changing the material of the film portion and the thickness of the film portion.

The thickness of the film portion is equal to the thickness of the opaque processed film.

The material constituting the film portion is not particularly limited as long as it has the above-mentioned total light transmittance. The film portion may be a woven or nonwoven fabric made of natural fibers (e.g., pulp, wool, cotton, etc.), synthetic fibers (e.g., rayon, polyester, polypropylene, etc.), or inorganic fibers (e.g., metal, glass, ceramic, rock wool, etc.), or a metal film (e.g., aluminum, iron, copper, silver, nickel, chromium, etc.). From the viewpoint of processing suitability and the like, the film portion is preferably a resin film containing a colored material as necessary. The amount of the colored material to be blended is not particularly limited, and may be blended so as to achieve the above-mentioned total light transmittance. In addition, the film portion may be coated with a colored material on the surface of the film as necessary. The film portion may be a film portion in which a plurality of layers are stacked.

The material used for the resin film is not particularly limited as long as it is a polycarbonate resin, (meth) acrylic resin, polystyrene resin, polyolefin resin, polyester resin, or the like.

Examples of the colored material include dyes and pigments. More specifically, there are dyes and pigments having light absorbing ability in at least a part of a wavelength region of 360nm to 830 nm. Specific examples of the dye include a phenylazo dye, an anthraquinone dye, a heterocyclic azo dye, and a benzodifuranone dye. Specific examples of the pigment include carbon black, calcium carbonate, barium sulfate, iron oxide, chromium oxide, titanium dioxide, and azo pigments.

< through hole >

The shape of the through-hole in the surface of the opaque processed film is usually circular (including elliptical), but may be other than circular (for example, polygonal, elongated, etc.).

The diameter of the through-holes on one surface of the processed opaque film may be the same as or different from the diameter of the through-holes on the other surface of the processed opaque film (see fig. 1 a) or fig. 1B). For example, the through-hole may be columnar or tapered like a frustum. In the case where the through-hole has a tapered shape, the diameter H of the through-hole having a larger diameter _D1 Diameter H of through hole with small diameter _D2 Ratio of (H) _D1 /H _D2 ) The content is not particularly limited, but is preferably 3 or less, and more preferably 2 or less. H _D1 /H _D2 May be 1 or more than 1, may be 1.05 or more, may be 1.1 or more, or may be 1.2 or more. When the through-hole of the opaque processed film is formed by laser processing, the diameter of the through-hole on the surface on the laser irradiation side is generally increased, and the diameter of the through-hole on the surface opposite to the laser irradiation side is generally decreased.

Diameter H of through hole _D The diameter of any 100 through holes was measured on any surface of the opaque processed film, and calculated as a number average value. Further, the diameter H of the through hole on one surface and the diameter H of the through hole on the other surface can be calculated _D (mean diameter), the diameter of the through-hole on the side having the larger mean diameter is defined as the diameter H _D1 The diameter of the through-hole on the side with a smaller number average is H _D2 . When the shape of the through-hole on the surface of the opaque processed film is other than a circle, the diameter of the through-hole indicates the equivalent circle diameter of the through-hole.

Diameter H of through-hole on any surface of opaque processed film _D (diameter H) _D1 And diameter H _D2 ) The lower limit of (B) is not particularly limited, but is preferably 5 μm or more, more preferably 10 μm or more. Further, the diameter H of the through hole _D (diameter H) _D1 And diameter H _D2 ) The upper limit of (B) is not particularly limited, but is preferably 500 μm or less, more preferably 250 μm or less, and particularly preferably 100 μm or less.

The processed film has at least a thickness F of the processed film _T Diameter H of the through hole _D Aspect ratio (F) shown _T /H _D ) A surface of 1 or more (preferably 1.2 or more, more preferably 1.5 or more). As an example, the thickness F of the opaque processed film _T Diameter H of through hole with relatively small diameter _D2 Aspect ratio (F) _T /H _D2 ) Is 1.0 or more, preferably 1.2 or more, and more preferably 1.5 or more. By adjusting the aspect ratio (F) _T /H _D2 ) With such a range, the viewing angle control function of the optical filter can be improved.

Shape and diameter H of through hole _D The irradiation conditions (beam diameter, output, irradiation time, etc.) of the laser beam in the laser irradiation step described later can be adjusted and changed according to the material of the film portion.

The through holes are regularly arranged in the opaque processed film. The through holes are arranged regularly, that is, adjacent through holes are arranged in the film plane at a certain interval (pitch) of a certain degree. More specifically, the regular arrangement may be such that a plurality of rows each including a plurality of through holes repeatedly provided at a predetermined pitch are formed, and the plurality of rows are repeatedly formed at a specific pitch.

When the through holes are arranged randomly, a desired viewing angle control function may not be obtained in some cases, for example, when 2 through holes are in contact with each other to form a large through hole or when a distance from an adjacent through hole is large in a part of the area to be separated from each other in the production of an opaque processed film.

The regular arrangement method is not particularly limited, and examples thereof include a method of arranging in parallel (see fig. 2 a), a method of arranging in a staggered manner (60 ° staggered manner, angle staggered manner) (preferably a method of arranging in a 60 ° staggered manner (see fig. 2B)), and the like.

The distance (or pitch) P between the center points of adjacent through holes is suitably determined according to the diameter H of the through holes _D But is preferably H _D1 Is 2.0 times or less, more preferably 1.5 times or less, and still more preferably 1.2 times or less. The lower limit of P is not particularly limited, but preferably exceeds H _D1 Is regularly arranged in a manner of 1.0 times.

The processed opaque film has at least a surface having an aperture ratio (a ratio of an area occupied by the through holes in the surface of the processed opaque film) of more than 40% (preferably more than 50%, and more preferably more than 60%). The upper limit of the aperture ratio is not particularly limited, but is preferably 90% or less, and more preferably 80% or less. For example, the diameter H of the through hole _D Is diameter H _D1 The surface of (2) may be set to have an aperture ratio of more than 40%, more than 50%, or more than 60% (and 90% or less or 80% or less). By setting the aperture ratio in such a range, the light transmittance in the thickness direction of the film can be made sufficient. The aperture ratio can be changed by changing the distance P between the center points of the adjacent through holes and the diameter H of the through hole _D To adjust.

The through-holes are usually provided so that the hole axes are perpendicular to the surface of the opaque processed film (so that the hole axes are along the thickness direction of the opaque processed film), but the hole axes may be inclined from this as long as the effects of the present invention are not hindered.

Other layers

Examples of the other layer include a protective film, an antireflection film, and an adhesive layer. In addition, other layers (for example, a transparent film for improving the strength of the optical filter) may be further provided within a range not to hinder the effect of the present invention.

The optical filter may have only 1 other layer or may have a plurality of other layers.

< adhesive layer >

The adhesive layer is a layer provided as a layer for bonding layers forming the optical filter or a layer for bonding the optical filter and an object to be bonded.

Examples of the adhesive constituting the adhesive layer include an acrylic adhesive, a silicone adhesive, a urethane adhesive, and a rubber adhesive.

< protective film >

The protective film is a layer for protecting the outermost layer of the optical filter before use. The protective film is usually removed when the optical filter is used.

The protective film is not particularly limited, and a film subjected to a peeling treatment (e.g., a silicone treatment), paper, or the like can be used.

< antireflection film >

The antireflection film is a layer for preventing reflection of light incident on the optical filter from the outside and improving visibility of a display screen on which the optical filter is disposed.

The antireflection film generally has a structure in which an antireflection layer is formed on a resin film (for example, a polyester film or the like). As a method for forming the antireflection layer, a method of alternately laminating a material having a high refractive index and a material having a low refractive index and forming a multilayer (multi-coat) layer is exemplified. By forming such an antireflection layer, reflection on the surface can be suppressed, and a good antireflection effect can be obtained. Usually, the anti-reflection layer is formed by mixing SiO ₂ Low refractive index material and TiO ₂ 、ZrO ₂ The high refractive index material is formed by a vapor phase method, a sol-gel method, or the like, in which films are alternately formed by vapor deposition or the like.

The thickness of the antireflection film can be designed as appropriate and freely, but the antireflection film preferably has sufficient light transmittance. The term "having sufficient light transmittance" means that the total light transmittance is 80% or more.

The antireflection film is generally laminated on an opaque processed film via an adhesive layer.

Here, the other layer may or may not have through holes continuous with the through holes provided in the opaque processed film.

Specifically, fig. 3 shows an embodiment in which the optical filter has a protective film, an adhesive layer, and an antireflection film as other layers, and the other layers do not have through holes. Fig. 4 shows an embodiment in which the optical filter has a protective film, an adhesive layer, and an antireflection film as other layers, and the other layers have through holes continuous with the through holes provided in the opaque processed film. The form of the other layer may be appropriately selected in consideration of the use, ease of production, and the like.

When the optical filter includes another layer having a through hole continuous with the through hole provided in the opaque processed film, another layer having no through hole may be further provided. The optical filter may include another layer having a through hole discontinuous from the through hole provided in the opaque processed film.

The other layer having the through hole continuous to the through hole provided in the opaque processed film can be produced by providing the through hole by irradiating the film portion with laser light in a state where the film portion and the other layer are laminated (performing a pre-lamination step described later).

Use of optical filter

The optical filter has an excellent viewing angle control function, and thus can be applied to various applications. For example, an optical filter is mounted on the outermost surface or inside of a display device such as a Liquid Crystal Display (LCD) or an organic electroluminescent element (organic EL), and thus can be used as a privacy filter for preventing peeking from others. In addition, the optical filter can be applied to lighting fixtures and building materials.

Method for manufacturing optical filter

An example of a method for manufacturing an optical filter will be described below.

The method for manufacturing the optical filter at least comprises a laser irradiation step: an opaque film having a total light transmittance of 10% or less in the thickness direction is irradiated with a laser beam to form an opaque processed film. In the laser irradiation step, laser light is irradiated from one surface of the opaque film, and a through hole penetrating the opaque film in the thickness direction is provided. In this case, a plurality of through holes are provided in a regular array.

The portion where the through-hole is not provided serves as a film portion of the opaque processed film. Therefore, the material and the like of the opaque film are the same as those of the film portion.

The laser irradiation machine may use any of a flat laser and a galvanometer laser. When a flat laser is used, the opaque film can be provided with regularly arranged through holes by repeating ON/OFF of laser irradiation while moving the position of a stage ON which the opaque film is provided. When a galvanometer laser is used, the opaque film can be provided with through holes regularly arranged by repeating ON/OFF of laser irradiation while moving the galvanometer laser.

The laser light irradiation is usually performed so as to be perpendicular to the surface of the opaque film, but the laser light irradiation may be performed from a direction inclined at a predetermined angle (for example, 5 ° or less) with respect to the perpendicular direction within a range not to impair the effect of the present invention.

The conditions for laser irradiation are not particularly limited as long as they are appropriately adjusted according to the material and thickness of the opaque film, the shape and diameter of the through-holes, and the like, and for example, the conditions are such that the processing energy per through-hole is 0.5mJ or more and 20.0mJ or less, and the number of shots per through-hole is 1 or more and 100 or less.

The type of laser used is not particularly limited, and may be CO ₂ Lasers, YAG lasers, excimer lasers, and the like.

In the laser irradiation step, the other surface of the opaque film may be irradiated with laser light.

When the optical filter includes another layer, a pre-lamination step of laminating another layer on the opaque film and then performing a laser irradiation step and/or a post-lamination step of laminating another layer on the opaque processed film after the laser irradiation step may be performed. When the pre-lamination step is performed, an optical filter in which another layer having a through hole continuous with the through hole provided in the opaque processed film is laminated as shown in fig. 4 can be manufactured. When the post-lamination step is performed, an optical filter in which other layers having no through-hole are laminated as shown in fig. 3 can be manufactured.

In the case where the optical filter does not include another layer, the lamination step may be omitted.

Examples

The present invention will be described below based on examples and comparative examples, but the present invention is not limited to the contents of the examples.

< manufacture of optical Filter >

[ example 1]

As a resin film having a high light-shielding property in the thickness direction, a black PET film (trade name: lumirrorX30#125, manufactured by Toray corporation, total light transmittance: 0%) having a thickness of 125 μm was prepared.

Next, the black PET film was irradiated with CO so that the interval between the adjacent holes became 75 μm and the positional relationship thereof became 60 ℃ in a staggered manner ₂ The laser thus performs the hole opening processing. The laser beam was irradiated and the processing was performed under the condition that the aperture of the surface irradiated with the laser beam was 65 μm, thereby obtaining the optical filter 1 of example 1.

[ example 2]

Processing was performed in the same manner as in example 1 except that the arrangement was changed so that the interval between adjacent holes became 100 μm, and the irradiation condition of the laser beam was changed so that the hole diameter of the surface irradiated with the laser beam became 75 μm, to obtain an optical filter 2 of example 2.

[ example 3]

An optical filter 3 of example 3 was obtained by processing in the same manner as in example 1 except that the resin film having high light-shielding property used was changed to a black PET film (trade name: lumirrorX30#100, manufactured by Toray corporation, total light transmittance: 0%) having a thickness of 100. Mu.m.

[ example 4]

The resin film having high light-shielding property used was processed in the same manner as in example 2 except that the resin film was changed to a black PET film (trade name: lumirrorX30#250, manufactured by Toray corporation, total light transmittance: 0%) having a thickness of 250 μm, and the irradiation conditions of the laser beam were changed so that the pore diameter of the surface irradiated with the laser beam became 80 μm, to obtain an optical filter 4 of example 4.

[ example 5]

As a resin film having a high light-shielding property in the thickness direction, a black PET film (product name: lumirrorX30#50, manufactured by Toray corporation, total light transmittance: 0%) having a thickness of 50 μm was prepared.

Next, the black PET film was irradiated with excimer laser light so that the adjacent holes were staggered at an interval of 35 μm and the positional relationship was 60 °, to thereby form holes. The laser beam was irradiated and processed under the condition that the aperture of the surface irradiated with the laser beam became 25 μm, thereby obtaining the optical filter 5 of example 5.

Comparative example 1

An optical filter a of comparative example 1 was obtained by processing in the same manner as in example 1, except that the resin film having high light-shielding properties used was changed to a black PET film (LumirrorX 30#25, manufactured by toray corporation) having a thickness of 25 μm.

Comparative example 2

An optical filter b of comparative example 2 was obtained by processing in the same manner as in example 1, except that the arrangement was changed so that the interval between the adjacent holes was 125 μm.

< Structure of optical Filter >

Table 1 summarizes the thickness of the black PET film, the processing conditions, and the shape obtained by the processing in the optical filters of the examples and comparative examples.

In this case, the machining hole diameters were measured as 100 diameters of the recessed regions as through holes by microscopic observation on the laser irradiation surface and the back surface thereof, respectively, and the number of diameters was averaged.

The aspect ratio is calculated by "(machining aperture (back surface))/(black PET film thickness)", and the aperture ratio is calculated by applying these numerical values to the following equation (1) when "machining aperture (laser irradiated surface)" is D and "machining pitch" is P.

[ number 1]

[ Table 1]

< evaluation >

(evaluation of light-blocking Property)

The evaluation of the light blocking properties of the optical filters of the examples and comparative examples was performed using a goniometer (manufactured by Genecia corporation) as shown in fig. 5, which can arbitrarily change the light projecting angle of the light source and the light receiving angle of the detector. As shown in fig. 5, a sample 3 of the optical filter of the example and the comparative example was disposed between the light source 1 and the detector 2 (here, the light source 1 and the detector 2 were fixed, respectively). In this evaluation, the case where the irradiation light I from the light source 1 is incident from the normal direction of the optical filter is assumed as an incident angle of 0 °, and the optical filter is disposed so as to be rotatable in an arbitrary direction with the straight line V on the surface of the optical filter as a rotation axis.

Since the optical filter in this embodiment is isotropic, the axis of rotation can be arbitrarily set.

Next, the optical filters of the examples and comparative examples were disposed at 3 angles of 0 °, 15 °, and 30 ° with respect to the normal direction of the optical filter, and the amount of light transmitted in the linear direction (linear transmitted light amount) of light at each incident light angle was measured. The measurement of the amount of linearly transmitted light is obtained by measuring the wavelength in the visible light region using a visibility filter. Then, the ratio of the amount of the linearly transmitted light to the amount of the linearly transmitted light (the amount of incident light ) directly irradiated from the light source 1 to the detector 2 without passing through the optical filter is defined as a linear transmittance (%).

The evaluation results of the light-blocking properties of the optical filters of the examples and comparative examples are shown in table 2.

[ evaluation standards ]

Evaluation criteria for each evaluation of the examples of the present invention are as follows.

"straight line transmittance at 0 ° (-)") "

Very good: excellent in permeability in the front direction of 25 or more

Good: excellent permeability in the front direction of 15 or more and less than 25

X: permeability in the front direction is not sufficiently less than 15

"straight line transmittance at 15 ° (-)") "

Excellent: light-shielding property in the 15 DEG direction is very excellent and less than 3

Good component: excellent light-shielding property in 15 DEG direction of 3 or more and less than 10

X: light-shielding property in the 15 DEG direction is not sufficiently less than 10

"straight line transmittance at 30 ° (%)") "

Very good: the light-shielding property in the 30 DEG direction is very excellent and less than 3

Good: excellent light-shielding property in the 30 DEG direction of 3 to less than 10

X: light-intercepting property in the 30 DEG direction is not sufficiently less than 10

[ Table 2]

From examples 1 to 5 of table 2, it was confirmed that the optical filter of the present invention is an optical filter having excellent light blocking properties in oblique directions (15 ° and 30 °) in addition to having excellent linear transmittance in the front direction.

Among the optical filters described above, the optical filters of examples 1, 3, and 5 having a processing pitch of 75 μm or less are particularly excellent in the in-line transmittance in the front direction, and when these optical filters are mounted on the front surface or inside of a display device, for example, an effect of suppressing the power consumption of the backlight is expected as compared with the case of using an optical filter having low transmittance in the front direction.

The optical filters of examples 1, 2, and 4, in which the thickness of the black PET film is 125 μm or more, are particularly excellent in light blocking properties from the 15 ° direction, and when these optical filters are mounted on the surface or inside of a display device, for example, the possibility that others may be expected to peep at the display device is extremely low.

The optical filter of example 5 was different from the other examples in that the processing of the optical filter was carried out using an excimer laser. Thereby, CO is used with others ₂ The laser processing has a disadvantage that the processing cost is higher than that of the laser processing, but the processing aperture can be reduced. Therefore, even when a black PET film of another film of 50 μm or more was used, it was confirmed that the optical filter could have a sufficient aspect ratio and thus had excellent performance.

The optical filter of comparative example 1 was obtained by processing a black PET film having a thickness of 25 μm. Therefore, the aspect ratio of the machined hole showed a small value of less than 1, and as a result, it was confirmed that the light blocking property from the oblique direction of the obtained optical filter was insufficient.

The optical filter of comparative example 2 was processed by enlarging the processing pitch to 125 μm. Therefore, the aperture ratio showed a small value of 40% or less, and as a result, it was confirmed that the transmittance in the front direction of the obtained optical filter was insufficient.

The preferred embodiments of the present invention have been described above with reference to the drawings, but the present invention is not limited to the above embodiments. That is, other modes and various modifications that can be conceived by those skilled in the art within the scope of the invention described in the claims are also understood to fall within the technical scope of the present invention.

Claims

1. An optical filter comprising an opaque processed film characterized in that,

the processed film has a film part having a total light transmittance of 10% or less in the thickness direction, a plurality of through holes regularly arranged in the thickness direction and penetrating the processed film, and at least the processed film has a thickness F _T Relative to the diameter H of the through hole _D Aspect ratio shown as F _T /H _D The surface is 1 or more, and at least the surface has an aperture ratio, that is, a ratio of the area of the through hole region to the entire surface is more than 40%.

2. The optical filter of claim 1,

at least having said diameter H _D The surface was 100 μm or less.

3. The optical filter according to claim 1 or 2,

thickness F of the opaque working film _T Over 100 μm.

4. The optical filter according to any one of claims 1 to 3,

the film part is a resin film which has light absorption capability in at least a part of a wavelength region of 360nm to 830nm and contains a dye or a pigment.

5. The optical filter according to any one of claims 1 to 4,

an adhesive layer is provided on at least one surface of the opaque processed film.

6. The optical filter according to any one of claims 1 to 5,

a protective film is provided on at least one surface of the opacity process film.

7. The optical filter according to any one of claims 1 to 6,

an antireflection film is provided on at least one surface of the opacity processing film.

8. A method for manufacturing an optical filter comprising an opaque processed film, characterized in that,

the method comprises a laser irradiation process: irradiating one surface of an opaque film having a total light transmittance of 10% or less in the thickness direction with a laser beam to form a plurality of through holes in the thickness direction of the opaque film in a regularly arranged manner,

at least having a thickness F of the opaque working film _T Diameter H of the through hole _D Aspect ratio of (i) F _T /H _D Is a surface of 1 or more in number,

the surface having at least the surface of the processed opaque film has an opening ratio, that is, a ratio of the area of the through-hole region to the entire surface of more than 40%.