Optical Filters and Their Manufacturing Methods

Abstract

This invention provides an optical filter with high aperture ratio, excellent viewing angle control, and ease of manufacture. The optical filter of this invention comprises an opaque processed film. The opaque processed film has a portion with a total light transmittance of less than 10% in the thickness direction and a plurality of through holes regularly arranged in the thickness direction of the opaque processed film, and has at least a thickness F of the opaque processed film. T Relative to the diameter H of the through hole D The aspect ratio (F) represents T / H D A surface with an aperture ratio of 1 or higher, and having at least an aperture ratio (the proportion of the area of ​​the through-hole region to the total surface area) of more than 40%.

Description

Technical Field

[0001] This invention relates to optical filters and their manufacturing methods. Background Technology

[0002] When using various display devices such as liquid crystal display (LCD) and organic electroluminescent elements (OLED), privacy filters have been developed to prevent others from seeing the information displayed on the display device.

[0003] Such a privacy filter has the function of allowing light from the front of the filter to pass through while blocking light from the angle of the filter. As a specific structure for achieving this function, a structure in which multiple holes are provided in the thickness direction of the light-blocking film is known.

[0004] For example, Patent Document 1 discloses a viewing angle limiting film composed of a metal selected from the group consisting of transition metals, their oxides and sulfides with atomic numbers 24 to 48, having a film thickness of 1 μm to 100 μm and through holes with a diameter of 1 μm to 100 μm arranged in a honeycomb pattern.

[0005] In addition, Patent Document 2 discloses a privacy filter disposed on the surface of a display. The privacy filter has a resin film, which is a porous body with a plurality of straight holes extending in a straight line along the thickness direction, and the walls of the plurality of straight holes are colored.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2008-65183

[0009] Patent Document 2: Japanese Patent Application Publication No. 2014-142636 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] However, the viewing angle control function of the viewing angle limiting film in Patent Document 1 is insufficient. For example, in the embodiment of Patent Document 1, the light transmittance value from a direction tilted at 60° from the normal direction is shown to be about 10%, but this is not sufficient to prevent peeping. In addition, the viewing angle limiting film in Patent Document 1 also presents challenges in terms of productivity and manufacturing cost.

[0012] Furthermore, the privacy filter in Patent Document 2 cannot increase the aperture ratio. For example, in the embodiment of Patent Document 2, the maximum aperture ratio is only 40%. However, when using this privacy filter in various display devices, the output of light sources such as backlights must be increased to increase the brightness in the front direction. In addition, the privacy filter in Patent Document 2 also faces difficulties in terms of productivity and manufacturing cost. Moreover, for the privacy filter in Patent Document 2, if the density of straight holes is increased to obtain a sufficient aperture ratio, the straight holes will come into contact with each other. This not only reduces the viewing angle control function but also causes problems such as the resin film becoming fragile, making manufacturing itself difficult.

[0013] Therefore, the objective of this invention is to provide an optical filter that has a high aperture ratio, excellent viewing angle control, and is easy to manufacture.

[0014] Methods for solving problems

[0015] The inventors conducted in-depth research and discovered that the above-mentioned problems can be solved by using an optical filter comprising a film with a specific structure. That is, the present invention is as follows.

[0016] This invention relates to an optical filter comprising an opaque processed film. The opaque processed film is characterized by having a portion having a total light transmittance of 10% or less in the thickness direction and a plurality of through-holes regularly arranged throughout the thickness direction of the opaque processed film, and having at least a thickness F of the opaque processed film. T Relative to the diameter H of the aforementioned through hole D The aspect ratio (F) represents T / H D The surface has an aperture ratio of 1 or higher, and has at least an aperture ratio (the proportion of the area of ​​the aforementioned through-hole region to the total surface area) of more than 40%.

[0017] The above diameter H D Preferably, it is below 100μm.

[0018] The thickness F of the aforementioned opaque processed film T Preferably larger than 100μm.

[0019] The aforementioned film is preferably a resin film that has light absorption capability in at least a portion of the wavelength region of 360 nm to 830 nm and contains dyes or pigments.

[0020] The aforementioned opaque processed film may have an adhesive layer on at least one of its surfaces as needed.

[0021] The aforementioned opaque processed film may have a protective film on at least one of its surfaces as needed.

[0022] The aforementioned opaque processed film may have an anti-reflective film on at least one of its surfaces as needed.

[0023] Furthermore, this invention relates to a method for manufacturing an optical filter, specifically a method for manufacturing an optical filter comprising an opaque processed film. The method is characterized by a laser irradiation step: irradiating a surface of an opaque film with a total light transmittance of 10% or less in the thickness direction with a laser; and fabricating a plurality of through-holes penetrating the thickness direction of the opaque film in a regularly arranged manner to form the opaque processed film, which has a thickness F of at least the aforementioned opaque processed film. T Relative to the diameter H of the aforementioned through hole D Aspect Ratio (F) T / H D A surface with an aperture ratio of 1 or higher, and a surface having an aperture ratio (the proportion of the area of ​​the through-hole region in the total surface area) of at least 40%.

[0024] Invention Effects

[0025] According to the present invention, an optical filter with high aperture ratio, excellent viewing angle control function, and easy manufacturing can be provided. Attached Figure Description

[0026] Figure 1 This is a conceptual diagram of the cross-section of an opaque processed film.

[0027] Figure 2 This is a conceptual diagram of the surface of an opaque processed film.

[0028] Figure 3 This is a conceptual diagram of the cross-section of an optical filter.

[0029] Figure 4 This is a conceptual diagram of the cross-section of an optical filter.

[0030] Figure 5 This is a schematic diagram illustrating the method for determining the incident light angle dependence of an optical filter. Detailed Implementation

[0031] The structure, properties, applications, and manufacturing methods of the optical filter of the present invention will be described.

[0032] In the following description, where the upper limit and lower limit are described separately, all combinations of the upper limit and lower limit are described in this specification.

[0033] <<<Structure of Optical Filters>>>

[0034] Optical filters contain an opaque processing film. Furthermore, optical filters may or may not have other layers on the surface of the opaque processing film. Figure 1 ).

[0035] <<Opaque Processed Film>>

[0036] The opaque processed film is also a substrate, having a film portion forming the wall thickness of the opaque processed film and a plurality of through holes (processing holes) arranged in a manner that penetrates the thickness direction of the opaque processed film.

[0037] The thickness F of the opaque processing film T There are no particular limitations, but a thickness exceeding 10 μm is preferred, more preferably exceeding 50 μm, and even more preferably exceeding 100 μm. By setting it within this range, the visual discernibility of the optical filter when viewed from an oblique direction can be sufficiently reduced. Additionally, the thickness F of the opaque processing film... T There is no specific upper limit for the value, but from the perspective of processing suitability, it is preferable to set it to below 1000μm.

[0038] The shape of opaque processed films can be appropriately modified according to their application.

[0039] <Membranous Part>

[0040] The total light transmittance of the film in the thickness direction is 10% or less, preferably 5% or less, more preferably 3% or less, more preferably 1% or less, and particularly preferably 0%. By setting it to such a range, the visual discernibility of the optical filter when viewed from an oblique direction can be sufficiently reduced.

[0041] There are no particular limitations on the method for measuring total light transmittance; any known method can be used. For example, it can be measured according to JIS K7375 "Plastics - Calculation of total light transmittance and total light reflectance".

[0042] The total light transmittance of the membrane can be adjusted by changing the membrane material and the membrane thickness.

[0043] The thickness of the film portion is equal to the thickness of the opaque processed film.

[0044] The material constituting the membrane is not particularly limited as long as it has the aforementioned total light transmittance. The membrane can also be a woven or non-woven fabric or a metal film (e.g., aluminum, iron, copper, silver, nickel, chromium, etc.) 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.). From the viewpoint of processability, the membrane is preferably a resin film incorporating a colored material as needed. It should be noted that the amount of such colored material is not particularly limited, as long as it is incorporated in a manner that achieves the aforementioned total light transmittance. Furthermore, the membrane can also be coated with a colored material on its surface as needed. The membrane can also be a membrane with multiple layers stacked together.

[0045] The materials used in the above-mentioned resin films are not particularly limited, as long as they are polycarbonate resin, (meth)acrylic resin, polystyrene resin, polyolefin resin, polyester resin, etc.

[0046] As examples of the aforementioned colored materials, dyes and pigments can be listed. More specifically, dyes and pigments that have light absorption capabilities in at least a portion of the wavelength region from 360 nm to 830 nm can be listed. Specific examples of dyes include benzoazo dyes, anthraquinone dyes, heterocyclic azo dyes, and benzodifuranone dyes. Specific examples of pigments include carbon black, calcium carbonate, barium sulfate, iron oxide, chromium oxide, titanium dioxide, and azo pigments.

[0047] <Through Hole>

[0048] The shape of the through holes on the surface of the opaque processed film is usually circular (including elliptical), but it can also be other shapes (e.g., polygonal, elongated, etc.).

[0049] The diameter of a through-hole on one surface of an opaque processed film can be the same as the diameter of a through-hole on the other surface of the opaque processed film (see reference). Figure 1 (A) can also be different (see reference) Figure 1 (B)). For example, a through hole can be cylindrical or tapered, like a frustum. In the case of a tapered through hole, the diameter H of the larger through hole... D1 The diameter H of the through hole with a smaller diameter D2 The ratio (H) D1 / H D2 There is no particular limitation, but 3 or less is preferred, and 2 or less is more preferred. D1 / H D2It can be 1 or higher, 1.05 or higher, 1.1 or higher, or 1.2 or higher. In the case of forming through holes in an opaque processed film by laser processing, the diameter of the through hole on the laser-irradiated side is usually larger, and the diameter of the through hole on the opposite side of the laser-irradiated side is smaller.

[0050] Diameter H of the through hole D The diameter is calculated by measuring the diameter of any 100 through holes on any surface of an opaque processed film and using the average value. Additionally, the diameter H of the through holes on one surface and the other surface can be calculated. D (Numerical mean of diameters), the diameter of the through hole on the side with the larger numerical mean of diameters is set as diameter H. D1 Let H be the diameter of the through hole on the side with the smaller mean diameter. D2 It should be noted that when the shape of the through hole on the surface of the opaque processed film is not circular, the diameter of the through hole represents the equivalent circle diameter of the through hole.

[0051] The diameter H of the through hole on any surface of the opaque processed film D (diameter H) D1 and diameter H D2 The lower limit value of the diameter of the through hole is not particularly limited, but it is preferably 5 μm or more, and more preferably 10 μm or more. Additionally, the diameter H of the through hole... D (diameter H) D1 and diameter H D2 There is no particular limitation on the upper limit of ), but it is preferably 500 μm or less, more preferably 250 μm or less, and particularly preferably 100 μm or less.

[0052] Here, the opaque processed film has at least a thickness F of the opaque processed film. T Relative to the diameter H of the through hole D The aspect ratio (F) represents T / H D The surface thickness F is 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 The diameter H of the through hole with a smaller diameter D2 Aspect Ratio (F) T / H D2 The aspect ratio (F) is 1.0 or higher, preferably 1.2 or higher, and more preferably 1.5 or higher. T / H D2 This range is set to enable excellent viewing angle control of the optical filter.

[0053] The shape and diameter H of the through hole DThe laser irradiation conditions (beam diameter, output, irradiation time, etc.) in the laser irradiation process described later can be changed according to the material of the film.

[0054] Through-holes are arranged regularly in an opaque processed film. Regular arrangement of through-holes means that adjacent through-holes are arranged sequentially with a certain interval (spacing) between them in the film plane. More specifically, regular arrangement can refer to forming multiple columns consisting of multiple through-holes repeatedly arranged at a specified interval, with these columns being repeatedly formed at specific intervals.

[0055] When through holes are randomly arranged, during the manufacturing of opaque processed films, two through holes may come into contact to form a large through hole, or the distance between two through holes and adjacent through holes may be large and separated in some areas, which sometimes makes it impossible to obtain the desired viewing angle control function.

[0056] There are no particular limitations on the configuration method for rules; examples of parallel configurations can be cited (see [reference]). Figure 2 (A)) A method configured as an interlaced type (60° interlaced type, angular interlaced type) (preferably configured as a 60° interlaced type) (refer to) Figure 2 (B))) etc.

[0057] The appropriate distance (or spacing) P between the center points of adjacent through holes is based on the diameter H of the through holes. D However, H is preferred over H. D1 The value of P is less than 2.0 times, more preferably less than 1.5 times, and even more preferably less than 1.2 times. The lower limit of P is not particularly limited, but it is preferably greater than H. D1 Configured in a regular manner at 1.0 times the standard.

[0058] The opaque processed film has a surface with an aperture ratio (the proportion of the area occupied by through holes in the surface of the opaque processed film) of more than 40% (preferably more than 50%, more preferably more than 60%). It should be noted that the upper limit of the aperture ratio is not particularly limited, but is preferably 90% or less, more preferably 80% or less. As an example, in the case of the diameter H of the aforementioned through holes... D For diameter H D1 The aperture ratio can be set to be greater than 40%, greater than 50%, or greater than 60% (and less than 90% or less than 80%). By setting the aperture ratio within such a range, sufficient light transmittance in the thickness direction of the membrane can be achieved. The aperture ratio can be adjusted by changing the distance P between the center points of adjacent through holes and the diameter H of the through holes. D To adjust.

[0059] Through holes are typically arranged with the hole axis perpendicular to the surface of the opaque processed film (with the hole axis along the thickness direction of the opaque processed film), but the hole axis may also be inclined to the opposite direction without hindering the effects of the present invention.

[0060] <<Other Layers>>

[0061] Other layers include protective films, anti-reflective films, and adhesive layers. Furthermore, other layers (e.g., transparent films for improving the intensity of optical filters) may be further provided without hindering the effects of the present invention.

[0062] Optical filters can have only one other layer or multiple other layers.

[0063] <Adhesive layer>

[0064] An adhesive layer is a layer provided for bonding the various layers that form an optical filter or for bonding the optical filter to an object to be bonded.

[0065] Examples of adhesives that form the adhesive layer include acrylic adhesives, silicone adhesives, urethane adhesives, and rubber-based adhesives.

[0066] <Protective film>

[0067] The protective film is the outermost layer of the optical filter used to protect it before use. The protective film is usually removed when the optical filter is used.

[0068] As a protective film, there are no particular limitations; films, papers, etc., that have undergone peeling treatment (e.g., silicone treatment) can be used.

[0069] Anti-reflective film

[0070] Anti-reflective coating is a layer used to prevent the reflection of light incident from the outside onto an optical filter and to improve the visual legibility of a display screen equipped with an optical filter.

[0071] Anti-reflective films typically have a structure in which an anti-reflective layer is formed on a resin film (such as a polyester film). One method for forming the anti-reflective layer is to alternately layer materials with high and low refractive indices, creating multiple layers (multiple coatings). By forming such an anti-reflective layer, surface reflection can be suppressed, resulting in a good anti-reflective effect. Generally, this anti-reflective layer is formed by alternating film formation methods such as vapor deposition (e.g., using low-refractive-index materials like SiO2) and high-refractive-index materials like TiO2 and ZrO2), such as vapor deposition or sol-gel methods.

[0072] The thickness of the anti-reflective film can be designed with appropriate freedom, but it is preferable that the anti-reflective film has sufficient light transmittance. Sufficient light transmittance means that the total light transmittance is above 80%.

[0073] Anti-reflective films are typically laminated onto opaque processed films through an adhesive layer.

[0074] Here, other layers may or may not have through holes that are continuous with the through holes provided in the opaque processed film.

[0075] As a specific example Figure 3 The diagram shows an optical filter with a protective film, an adhesive layer, and an anti-reflective film as other layers, none of which have through-holes. Additionally, Figure 4 The diagram shows an optical filter having a protective film, an adhesive layer, and an anti-reflective film as other layers, with the other layers having through holes continuous with the through holes provided in the opaque processed film. The shapes of the other layers can be appropriately selected considering their application, ease of manufacture, etc.

[0076] It should be noted that, in cases where the optical filter includes other layers having through holes that are continuous with the through holes provided in the opaque processing film, other layers without through holes may also be provided. Alternatively, the optical filter may also include other layers having through holes that are discontinuous with the through holes provided in the opaque processing film.

[0077] Other layers having through holes that are continuous with the through holes provided in the opaque processed film can be manufactured by laser irradiating the film portion while the film portion and other layers are stacked (performing the pre-stacking process described later).

[0078] <<<Applications of Optical Filters>>>

[0079] Optical filters offer excellent viewing angle control, making them suitable for a wide range of applications. For instance, by mounting optical filters on the outermost surface or inside display devices such as liquid crystal displays (LCDs) and organic light-emitting diodes (OLEDs), they can be used as privacy filters to prevent peeping from others. Furthermore, optical filters can also be applied to lighting fixtures and building materials.

[0080] <<<Methods for Manufacturing Optical Filters>>>

[0081] The following is an example of a method for manufacturing an optical filter.

[0082] The manufacturing method of the optical filter includes at least a laser irradiation step: an opaque film with a total light transmittance of less than 10% in the thickness direction is laser-irradiated to form an opaque processed film. In the laser irradiation step, a laser is irradiated from one surface of the opaque film to create through holes penetrating the thickness direction of the opaque film. At this time, multiple through holes are arranged in a regular pattern.

[0083] The portion without through holes becomes the film portion of the opaque processed film. Therefore, the material and other properties of the opaque film are the same as those of the film portion described above.

[0084] The laser irradiation machine can use either a flat panel laser or a galvanometer laser. When using a flat panel laser, by repeatedly switching the laser irradiation ON / OFF while moving the stage on which the opaque film is mounted, regularly arranged through-holes can be created on the opaque film. When using a galvanometer laser, by repeatedly switching the laser irradiation ON / OFF while moving the galvanometer laser, regularly arranged through-holes can be created on the opaque film.

[0085] Laser irradiation is usually performed in a direction perpendicular to the surface of the opaque film, but without hindering the effects of the present invention, laser irradiation may also be performed from a direction tilted at a specified angle (e.g., less than 5°) relative to the vertical direction.

[0086] The laser irradiation conditions can be adjusted appropriately according to the material and thickness of the opaque film, the shape or diameter of the through holes, etc. There are no special limitations. For example, the processing energy of each through hole can be set to 0.5mJ or more and 20.0mJ or less, and the emission number of each through hole can be set to 1 or more and 100 or less.

[0087] There are no particular restrictions on the type of laser used; it can be a CO2 laser, a YAG laser, an excimer laser, etc.

[0088] It should be noted that during the laser irradiation process, laser irradiation can also be performed from another surface of the opaque film.

[0089] When the optical filter includes other layers, it is sufficient to perform a pre-lamination process where the other layers are laminated on the opaque film before the laser irradiation process, and / or a post-lamination process where the other layers are laminated on the opaque processing film after the laser irradiation process. With the pre-lamination process performed, it is possible to manufacture... Figure 4 The illustrated optical filter consists of layers with through-holes continuous with those provided in the opaque processing film. By performing a post-lamination process, it is possible to manufacture optical filters such as... Figure 3 The optical filter shown is stacked with other layers that do not have through holes.

[0090] If the optical filter does not contain other layers, the lamination process can be omitted.

[0091] Example

[0092] The present invention will now be described based on embodiments and comparative examples, but the present invention is not limited to the contents of the embodiments.

[0093] <Manufacturing of Optical Filters>

[0094] [Example 1]

[0095] As a resin film with high light-blocking properties in the thickness direction, a black PET film with a thickness of 125μm (manufactured by Toray Industries, trade name: LumirrorX30#125, total light transmittance: 0%) was prepared.

[0096] Next, the black PET film was irradiated with a CO2 laser to create openings, with adjacent holes spaced 75 μm apart and staggered at 60° intervals. The laser irradiation was performed on a surface with an aperture of 65 μm, thus obtaining the optical filter 1 of Example 1.

[0097] [Example 2]

[0098] The arrangement of adjacent holes was changed so that the spacing between them was 100 μm, and the laser irradiation conditions were changed so that the aperture of the surface irradiated by the laser was 75 μm. Otherwise, the optical filter 2 of Example 2 was obtained by processing in the same way as in Example 1.

[0099] [Example 3]

[0100] The high-shielding resin film used was replaced with a 100μm thick black PET film (manufactured by Toray Industries, trade name: LumirrorX30#100, total light transmittance: 0%). Otherwise, the optical filter 3 of Example 3 was obtained by processing in the same way as in Example 1.

[0101] [Example 4]

[0102] The high-shielding resin film used was changed to a black PET film with a thickness of 250μm (manufactured by Toray Industries, trade name: LumirrorX30#250, total light transmittance: 0%). The laser irradiation conditions were further changed so that the aperture of the surface irradiated by the laser was 80μm. Otherwise, the optical filter 4 of Example 4 was obtained by processing in the same way as in Example 2.

[0103] [Example 5]

[0104] As a resin film with high light-blocking properties in the thickness direction, a black PET film with a thickness of 50 μm (manufactured by Toray Industries, trade name: LumirrorX30#50, total light transmittance: 0%) was prepared.

[0105] Next, the black PET film was irradiated with an excimer laser to create openings, with adjacent holes spaced 35 μm apart and arranged in a staggered 60° configuration. The laser irradiation was performed with the aperture of the irradiated surface being 25 μm, thus obtaining the optical filter 5 of Example 5.

[0106] [Comparative Example 1]

[0107] Except for changing the high-shielding resin film used to a 25μm thick black PET film (manufactured by Toray Industries, Lumirror X30#25), the optical filter a of Comparative Example 1 was obtained by processing in the same way as in Example 1.

[0108] [Comparative Example 2]

[0109] Except for changing the arrangement so that adjacent holes are spaced 125 μm apart, the optical filter b of Comparative Example 2 was obtained by processing in the same way as in Example 1.

[0110] <Structure of Optical Filters>

[0111] Table 1 summarizes the thickness of the black PET film, processing conditions, and the shape obtained by processing in the optical filters of the above embodiments and comparative examples.

[0112] At this point, regarding the machining aperture, the diameter of 100 diameters of the recessed area serving as the through hole is measured by microscopic observation on both the laser-irradiated surface and its back side, and is taken as its average.

[0113] In addition, the aspect ratio is calculated by “(processing aperture (back side)) / (black PET film thickness)”. The aperture ratio is calculated by applying these values ​​to the following mathematical formula (1) when “processing aperture (laser irradiation surface)” is set to D and “processing spacing” is set to P.

[0114] [Number 1]

[0115]

[0116] [Table 1]

[0117]

[0118] <Evaluation>

[0119] (Evaluation of light blocking properties)

[0120] use Figure 5 A variable-angle photometer goniometer (manufactured by Genecia) capable of arbitrarily changing the projection angle of the light source and the receiving angle of the detector, as shown, was used to evaluate the light blocking performance of the optical filters in the examples and comparative examples. Figure 5 As shown, sample 3 of the optical filter of the embodiment and comparative example is placed between light source 1 and detector 2 (here, light source 1 and detector 2 are fixed respectively). In this evaluation, the case where the illumination light I from light source 1 is incident from the normal direction of the optical filter is set as an incident angle of 0°, and the optical filter is configured to be able to rotate in any direction about the straight line V on the surface of the optical filter as the rotation axis.

[0121] It should be noted that since the optical filter in this embodiment is isotropic, the axis of rotation can be set arbitrarily.

[0122] Next, the optical filters of the configured embodiments and comparative examples were arranged at three angles relative to the optical filter normal direction: 0°, 15°, and 30°. The amount of light transmitted in the straight line (linear transmitted light amount) at each incident light angle was measured. It should be noted that the linear transmitted light amount was measured by using a visibility filter to determine the wavelength of the visible light region. Then, the ratio of the linear transmitted light amount to the linear transmitted light amount (incident light amount, incident light amount) that directly illuminates the detector 2 from the light source 1 without passing through the optical filter was set as the linear transmittance (%).

[0123] The evaluation results of the light blocking performance of the optical filters of each embodiment and comparative example are shown in Table 2.

[0124] [Evaluation Criteria]

[0125] The evaluation criteria for each evaluation in the embodiments of the present invention are as follows.

[0126] Linear transmittance at 0° (%)

[0127] ◎: Excellent transmittance from the front (25 or higher)

[0128] 〇: Excellent transmittance in the front direction, 15 or higher and less than 25.

[0129] ×: Transmittance in the front direction is insufficient, less than 15.

[0130] Linear transmittance at 15° (%)

[0131] ◎: Excellent light blocking performance at 15°, less than 3

[0132] 〇: Excellent light blocking performance at 15° direction (3 or higher and less than 10)

[0133] ×: Insufficient light blocking properties in the 15° direction less than 10

[0134] Linear transmittance at 30° (%)

[0135] ◎: Excellent light blocking performance at 30°, less than 3

[0136] 〇: Excellent light blocking performance at 30° direction (3 or higher and less than 10)

[0137] ×: Insufficient light blocking properties in the 30° direction less than 10

[0138] [Table 2]

[0139]

[0140] Based on Examples 1 to 5 in Table 2, it was confirmed that the optical filter of the present invention is an optical filter that not only has excellent linear transmittance in the front direction, but also excellent light blocking performance in the tilt direction (15° and 30°).

[0141] Among the optical filters described above, the optical filters of Examples 1, 3, and 5, which have a processing pitch of 75 μm or less, have particularly excellent linear transmittance in the front direction. For example, when these optical filters are mounted on the surface or inside a display device, compared with the case of using an optical filter with low transmittance in the front direction, it is expected to suppress the power consumption of the backlight.

[0142] In addition, the optical filters of Examples 1, 2 and 4, which have a black PET film thickness of 125 μm or more, have particularly excellent light blocking properties from a 15° direction. For example, when these optical filters are mounted on the surface or inside a display device, the possibility of the display being spied on by others can be expected to be extremely low.

[0143] The optical filter in Example 5 differs from other examples in that it was fabricated using an excimer laser. While this increases processing costs compared to other methods using CO2 lasers, it allows for a smaller processing aperture. Therefore, even when using a black PET film with a thickness of 50 μm or similar thin film, a sufficiently high aspect ratio is achieved, confirming the ability to fabricate an optical filter with excellent performance.

[0144] The optical filter of Comparative Example 1 was obtained by processing a black PET film with a thickness of 25 μm. As a result, the aspect ratio of the processed holes showed a small value of less than 1, which confirmed that the light blocking performance of the obtained optical filter from the tilt direction was insufficient.

[0145] The optical filter of Comparative Example 2 was fabricated by increasing the processing pitch to 125 μm. As a result, the aperture ratio showed a small value of less than 40%, which confirmed that the transmittance of the obtained optical filter in the front direction was insufficient.

[0146] The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to the above-described embodiments. That is, other embodiments or various modifications that can be conceived by those skilled in the art within the scope of the invention as 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 opaque processed film has a portion of film with a total light transmittance of less than 10% in the thickness direction and a plurality of through holes arranged regularly in the thickness direction of the opaque processed film, and has at least a thickness F of the opaque processed film. T Relative to the diameter H of the through hole D The aspect ratio represented is F. T / H D A surface with a value of 1 or higher, and having at least an aperture ratio, i.e., the area of ​​the through-hole region relative to the total surface area, exceeding 40%.

2. The optical filter according to claim 1, characterized in that, At least having the diameter H D For surfaces smaller than 100 μm.

3. The optical filter according to claim 1 or 2, characterized in that, The thickness F of the opaque processed film T More than 100μm.

4. The optical filter according to claim 1 or 2, characterized in that, The film portion is a resin film containing dyes or pigments that has light absorption capability in at least a portion of the wavelength region of 360nm to 830nm.

5. The optical filter according to claim 1 or 2, characterized in that, An adhesive layer is provided on at least one surface of the opaque processed film.

6. The optical filter according to claim 1 or 2, characterized in that, A protective film is provided on at least one surface of the opaque processed film.

7. The optical filter according to claim 1 or 2, characterized in that, An anti-reflective film is provided on at least one surface of the opaque processed film.

8. A method for manufacturing an optical filter, comprising an opaque processing film, characterized in that, The process includes a laser irradiation step: irradiating a surface of an opaque film with a total light transmittance of less than 10% in the thickness direction with a laser, and creating multiple through-holes penetrating the thickness direction of the opaque film in a regularly arranged manner to produce an opaque processed film. At least the thickness F of the opaque processed film T Relative to the diameter H of the through hole D The aspect ratio, i.e., F T / H D Surfaces with a value of 1 or higher A surface having at least the aperture ratio of the surface having the opaque processed film, i.e., the area of ​​the through-hole region, which accounts for more than 40% of the total surface area.

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