Light control film

Abstract

This specification aims to disclose a light-controlled film, specifically a light-controlled film in which the luminance characteristics are controlled according to a particular purpose. [Solution] The light control film may include a louver film having a first surface in which light-absorbing and light-transmitting portions are alternately arranged, and a light-transmitting portion on the opposite side of the first surface, and the line aperture ratio and area aperture ratio may be adjusted. According to the disclosure herein, the brightness characteristics of the light control film can be controlled according to the purpose.

Description

Technical Field

[0001] This specification discloses a light control film.

Background Art

[0002] A light control film is an optical film configured to be able to adjust its transmittance. Various light control films are known. A typical light control film includes a transmissive film having a plurality of parallel grooves, and these grooves are formed of a light-absorbing material. Such a type of film is also called a louver film.

[0003] The light control film can be disposed in proximity to a display surface, an image surface, or other surfaces. An image can be displayed at normal incidence (i.e., a 0° viewing angle) when an observer observes the image through the light control film from a direction perpendicular to the film surface. As the viewing angle increases, the amount of light passing through the light control film decreases until a viewing cutoff angle is reached where the light is blocked by the light-absorbing material and the image is no longer visible. This can provide privacy to the observer by blocking observation by others outside the typical viewing angle range.

Summary of the Invention

Problems to be Solved by the Invention

[0004] This specification discloses a light control film. The purpose of this specification is to disclose a light control film in which the luminance characteristics are controlled according to the purpose.

Means for Solving the Problems

[0005] The light control film of the present disclosure includes a louver film having a first surface with an absorbing portion and a light-transmitting portion alternately arranged and a second surface having a light-transmitting portion on the side opposite to the first surface, and satisfies the following formula 1: [Formula 1] AR1 / AR2 < 1.45 In Equation 1, AR1 is defined by Equation 2 below, and AR2 is defined by Equation 3 below: [Formula 2] AR1 = (AB) / A × 100 [Formula 3] AR2 = (pL) / p × 100 In equations 2 and 3, A is p × h, B is (U + L) × h / 2, p is the pitch of the light-absorbing portion, h is the height of the light-absorbing portion, U is the width of the second surface side of the light-absorbing portion, and L is the width of the first surface side of the light-absorbing portion.

[0006] The triangle Con in equation 4 below may be less than 15%: [Formula 4] △Con=Con2-Con1 In Equation 4, Con1 is the central brightness of the light control film, and Con2 is the peak brightness, which is the maximum brightness value at angles within the range of -88° to 88° (Horizontal Cross Section). The central brightness and peak brightness represent the relative brightness to the central brightness of the film laminate configuration excluding the louver film.

[0007] The ratio AR1 / AR2 in Equation 1 may be 1 or greater.

[0008] The light-absorbing portion has a first wall angle (θ1) and a second wall angle (θ2), and the sum of the first wall angle (θ1) and the second wall angle (θ2) (θ) may be in the range of 2° to 8°.

[0009] The height of the absorbent portion may be within the range of 80 μm to 170 μm.

[0010] The AR2 in Equation 1 may be in the range of 33% to 96%.

[0011] The AR1 in Equation 1 may be within the range of 33% to 96%.

[0012] The second surface of the louver film does not necessarily need to have a light-absorbing area.

[0013] It may further include a first base film adhered to the first surface of the louver film via an adhesive layer.

[0014] It may further include a second base film directly contacting the second surface of the louver film.

Advantages of the Invention

[0015] This specification discloses a light control film. According to the disclosure of this specification, the luminance characteristics of the light control film can be controlled according to the purpose.

Brief Description of the Drawings

[0016] [Figure 1] It is a side view of an exemplary louver film. [Figure 2] It is a front view of an exemplary louver film. [Figure 3] It is a drawing for explaining the wall surface angle of the light absorption part. [Figure 4] It is a side view of an exemplary light control film. [Figure 5] It is a drawing showing the luminance measurement results of the light control film of Example 1. [Figure 6] It is a drawing showing the luminance measurement results of the light control film of Example 2. [Figure 7] It is a drawing showing the luminance measurement results of the light control film of Comparative Example 1. [Figure 8] It is a drawing showing the luminance measurement results of the light control film of Comparative Example 2.

Modes for Carrying Out the Invention

[0017] Among the physical properties mentioned in this specification, for those physical properties where the measurement temperature affects the results, unless otherwise specified, they are the results measured at room temperature.

[0018] The term "room temperature" refers to a natural temperature that is not artificially heated or cooled, meaning a temperature within the range of 10°C to 30°C, such as approximately 23°C or 25°C.

[0019] In this specification, the unit of temperature is Celsius (°C) unless otherwise specified.

[0020] Of the physical properties mentioned herein, those whose results are affected by the measurement pressure are those measured under normal pressure unless otherwise specified.

[0021] The term "normal pressure" refers to the natural pressure that has not been artificially pressurized or depressurized, and usually means around 740 mmHg to 780 mmHg, which is the level of atmospheric pressure.

[0022] In this specification, if a physical property is affected by the measured humidity, the physical property is defined as a property measured at natural humidity that has not been artificially adjusted under normal temperature and pressure conditions.

[0023] In this specification, unless otherwise specified, the term "transmittance" means the actual transmittance measured at a specific wavelength or wavelength band (measured transmittance).

[0024] In this specification, the term “angle of incidence” means the angle between the incident light and the normal to the surface on which the incident light enters.

[0025] This specification discloses a light-controlled film.

[0026] The light control film may include at least a louver film. The significance of the louver film is well known.

[0027] Figure 1 is a side view of a typical louver film (1000). Figure 2 is a front view of the first surface (1001) of the louver film (1000) in Figure 1.

[0028] As illustrated, the louver film has a first surface (1001) on which alternating light-absorbing areas (A) and light-transmitting areas (T) can be observed when viewed from the front, and a second surface (1002) on the opposite side of the first surface. Light-transmitting areas (T) are present on the second surface (1002). There are cases where light-absorbing areas (A) are not present on the second surface (1002). Even when observing the louver film on the second surface due to the light-transmitting areas (T), the light-absorbing areas (A) can still be observed. In other words, the absence of light-absorbing areas (A) on the second surface (1002) means that when the louver film is observed from the side, as shown in Figure 1, the light-absorbing areas (A) are not in contact with the second surface (1002).

[0029] The louver film disclosed herein can be formed such that AR1 / AR2 in the following formula 1 are within a predetermined range. [Formula 1] AR1 / AR2 AR1 in Equation 1 is defined by Equation 2 below, and this AR1 is called the area aperture ratio. AR2 in Equation 2 is defined by Equation 3 below, and this AR2 is called the line aperture ratio. [Formula 2] AR1 = (AB) / A × 100 [Formula 3] AR2 = (pL) / p × 100 In equations 2 and 3, A is p × h, B is (U + L) × h / 2, p is the pitch of the absorbent portion, h is the height of the absorbent portion, U is the width of the second surface side of the absorbent portion, and L is the width of the first surface side of the absorbent portion.

[0030] The pitch p is the distance between the starting point of one absorbent area and another absorbent area adjacent to it, when the louver film is observed from the side. p, h, L, and U are shown illustratively in Figure 1.

[0031] The upper limit of AR1 / AR2 in Equation 1 may be approximately 1.45, 1.4, 1.35, 1.3, 1.25, 1.2, or 1.15, and the lower limit may be approximately 1, 1.05, 1.1, 1.15, 1.2, 1.25, or 1.3. AR1 / AR2 may be within the range of any upper limit arbitrarily selected from the upper limits listed above; or it may be within the range of any upper limit arbitrarily selected from the upper limits listed above, and above or above any lower limit arbitrarily selected from the lower limits listed above. Within such a range, the desired brightness characteristics can be ensured for the light-controlled film.

[0032] The lower limit of AR2 (line aperture ratio) in Equation 1 may be approximately 33%, 35%, 40%, 45%, or 50%, and its upper limit may be approximately 96%, 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, or 55%. AR2 may be less than or equal to any of the upper limits listed above, and greater than or equal to any of the lower limits listed above. Within this range, the desired brightness characteristics can be ensured for the light-controlled film.

[0033] The lower limit of AR1 (area aperture ratio) in Equation 1 may be approximately 33%, 35%, 40%, 45%, 50%, 55%, 60%, or 65%, and its upper limit may be approximately 96%, 95%, 90%, 85%, 80%, 75%, or 70%. AR1 may be less than or equal to any of the upper limits listed above, and greater than or equal to any of the lower limits listed above. Within this range, the desired brightness characteristics can be ensured for the light-control film.

[0034] AR1 and AR2 and the ratio of AR 1 / To satisfy AR2, the ranges of p, h, L, and U in the louver film can be adjusted.

[0035] For example, the lower limit of h, which is the height of the light-absorbing portion (A) in the louver film, may be approximately 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, or 150 μm, and the upper limit may be approximately 170 μm, 160 μm, 150 μm, 140 μm, 130 μm, 120 μm, 110 μm, or 100 μm. The height may be less than or equal to any of the upper limits listed above, and greater than or equal to any of the lower limits listed above. Within such a range, AR1, AR2, and their ratio AR1 / AR2 can be effectively controlled.

[0036] For example, in a louver film (1000), the lower limit of the pitch p of the light-absorbing portion (A) may be approximately 20 μm, 25 μm, 30 μm, or 35 μm, and the upper limit may be approximately 60 μm, 55 μm, 50 μm, 45 μm, or 40 μm. The pitch may be less than or equal to any of the upper limits listed above, and greater than or equal to any of the lower limits listed above. Within such a range, AR1, AR2 and their ratio AR 1 / AR2 can be controlled effectively.

[0037] In the louver film (1000), the lower limit of the width U on the second surface (1002) side of the light-absorbing portion (A) may be approximately 0 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, or 6 μm, and the upper limit may be approximately 10 μm, 9.5 μm, 9 μm, 8.5 μm, 8 μm, 7.5 μm, 7 μm, 6.5 μm, 6 μm, 5.5 μm, 5 μm, 4.5 μm, 4 μm, 3.5 μm, 3 μm, 2.5 μm, 2 μm, 1.5 μm, 1 μm, or 0.5 μm. In the above, a width U of 0 μm refers to the case where the cross-section of the absorbent portion is formed in a triangular shape, and the upper part of the triangle is formed on the second surface (1002) side. The width U may be less than or equal to any upper limit arbitrarily selected from the upper limits listed above, and greater than or equal to any lower limit arbitrarily selected from the lower limits listed above. Within such a range, AR1, AR2 and their ratio AR1 / AR2 can be effectively controlled.

[0038] In the louver film (1000), the lower limit of the width L on the first surface (1001) side of the light-absorbing portion (A) may be approximately 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, or 18 μm, and the upper limit may be approximately 22 μm, 20 μm, 18 μm, 16 μm, 14 μm, 12 μm, or 10 μm. The width L may be less than or equal to any of the upper limits listed above, and greater than or equal to any of the lower limits listed above. Within such a range, AR1, AR2 and their ratio AR1 / AR2 can be effectively controlled.

[0039] To satisfy the aforementioned value, the wall angle of the light-absorbing section (A) can be adjusted. The wall angle is the angle formed between the surface normal of the louver film and the side wall of the light-absorbing section, which is shown as θ1 and θ2 in Figure 3.

[0040] On the side surface of the louver film, the light-absorbing portion may have a first wall angle (θ1) and a second wall angle (θ2). The lower limit of the sum of the first wall angle (θ1) and the second wall angle (θ2) (θ=θ1+θ2) may be approximately 2°, 2.5°, 3°, 3.5°, 4°, 4.5°, 5°, 5.5°, or 6°, and the upper limit may be approximately 8°, 7.5°, 7°, 6.5°, 6°, 5.5°, 5°, 4.5°, or 4°. The sum (θ=θ1+θ2) may be less than or equal to any of the upper limits listed above, and greater than or equal to any of the lower limits listed above. Within such a range, AR1, AR2, and their ratio AR1 / AR2 can be effectively controlled.

[0041] In a light-controlled film including a louver film realized in this form, ΔCon in the following Equation 4 may be within a predetermined range. [Formula 4] ΔCon = Con2 - Con1 In Equation 4, Con1 is the central luminance of the light-controlled film. The central luminance is the luminance measured at the front (0 degrees) of the light-controlled film. In Equation 4, Con2 is the peak luminance, which is the maximum luminance value among the luminance measured at angles in the range of -88° to 88° in the Horizontal Cross Section.

[0042] In Equation 4, luminances Con1 and Con2 are relative luminances, respectively, with the central luminance measured for the laminated film structure excluding the louver film in the light control film as the reference.

[0043] The upper limit of ΔCon may be approximately 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7.5%, 7%, 6.5%, 6%, 5.5%, 5%, 4.5%, 4%, 3.5%, 3%, or 2.5%, and its lower limit may be approximately 0%, 0.5%, 1%, 1.5%, 2%, or 2.5%. ΔCon may be within the range of any upper limit arbitrarily selected from the upper limits listed above; or it may be within the range of any upper limit arbitrarily selected from the upper limits listed above, and greater than or equal to any lower limit arbitrarily selected from the lower limits listed above.

[0044] When ΔCon is controlled within this range, the visibility or brightness of the display can be maintained uniformly according to the left and right position, thereby improving image quality.

[0045] Louver films can be manufactured by known methods, provided that the above conditions are met. Typically, a louver film can be manufactured by forming a louver film body (light-transmitting part) with grooves formed by a so-called nano-imprinting process using a transparent resin material, and then filling the grooves of the body with a light-absorbing material to form a light-absorbing part.

[0046] There are no special restrictions on the type of transparent resin material that can be used as described above; common materials applicable during the manufacture of louver films can be used. Typically, the body is formed by applying a material that can be polymerized by light, such as ultraviolet light. Examples of such polymerizable materials include materials selected from known (meth)acrylate monomers, (meth)acrylate oligomers, and mixtures thereof. A monomer or oligomer is any substance that can be converted into a polymer by polymerization. (Meth)acrylate refers to both acrylate compounds and methacrylate compounds. Examples of materials may include (meth)acrylated urethane oligomers, (meth)acrylated epoxy oligomers, (meth)acrylated polyester oligomers, (meth)acrylated phenol oligomers, (meth)acrylated acrylic oligomers, and mixtures thereof.

[0047] Suitable and known materials that can be used as light-absorbing materials include, but are not limited to, carbon-based pigments and / or dyes.

[0048] The light control film may include other components that are further required for the louver film.

[0049] For example, the light control film may further include a first base film on the first surface of the louver film. Such a first base film may be bonded to the first surface via an adhesive layer or the like.

[0050] For example, the light control film may further include a second base film on the second surface of the louver film. Such a second base film may be in direct contact with the second surface.

[0051] Figure 4 is an example that includes a second base film (3000) in direct contact with the second surface of the louver film (1000) and a first base film (6000) bonded to the first surface via an adhesive layer (5000).

[0052] Any known film can be used as the first and second base film without any special limitations. Examples of applicable base films include, but are not limited to, acrylic films such as PMMA (polymethyl methacrylate) film, polyester films such as PC (polycarbonate) film and PET (polyethylene terephthalate) film, polyurethane films, TAC (triacetylcellulose) film, or polyurethane films.

[0053] There are no special restrictions on the type of adhesive used to bond the aforementioned base film to the louver film; for example, known optical adhesives such as acrylic, epoxy, or silicone adhesives can be used.

[0054] Such light-controlling films can be used in a variety of applications, including displays. [Examples]

[0055] The following examples will specifically describe light control films and the like, but the range of bandpass filters and the like is not limited by the following examples.

[0056] Example 1 A light-controlling film with the shape shown in Figure 4 was fabricated. First, an ultraviolet-curable transparent resin material was applied to a second base film (3000), and grooves for forming light-absorbing parts (A) were formed by a nanoimprint process to create a translucent body. Then, a light-absorbing material was filled into the grooves to form the light-absorbing parts (A), and the first base film (6000) was bonded to it via an adhesive layer (5000) to produce a light-controlling film.

[0057] In the above, a PET (polyethylene terephthalate) film with a thickness of approximately 150 μm was used as the first base film (6000), and a PET (polyethylene terephthalate) film with a thickness of approximately 150 μm was used as the second base film (3000). The thicknesses of the first and second base films may be within the range of 80 μm to 150 μm, respectively. An acrylic adhesive was used as the adhesive layer (5000).

[0058] Furthermore, the louver film (1000) was formed to a thickness of approximately 200 μm. The thickness of the louver film can also be controlled within a range of, for example, 100 μm to 200 μm. For the light-transmitting portion of the louver film (1000), an acrylic UV-curable resin was used as the material (UV-curable transparent resin material), and for the light-absorbing material, an acrylic UV-curable resin with dispersed carbon black pigment was used.

[0059] The refractive index of the light-transmitting portion of the louver film (1000) was approximately 1.50 to 1.56 at a wavelength of 589 nm, while the refractive index of the light-absorbing portion was approximately 1.48 to 1.51 at a wavelength of 589 nm.

[0060] The pitch p of the light-absorbing section (A) of the louver film, the height h of the light-absorbing section (A), the width L of the first surface side of the light-absorbing section, the width U of the second surface side of the light-absorbing section, and the wall angle (sum of θ1 and θ2 in Figure 3) were adjusted as shown in Table 1 below.

[0061] Example 2 and Comparative Examples 1 and 2 A light-control film was manufactured in the same manner as in Example 1, except that the pitch p of the light-absorbing section (A), the height h of the light-absorbing section (A), the first surface width L of the light-absorbing section, the second surface width U of the light-absorbing section, and the wall angle (sum of θ1 and θ2 in Figure 3) were adjusted as shown in Table 1 below. In Table 1 below, the units for pitch p, height h, width L and U are μm, and the unit for wall angle is degrees.

[0062] [Table 1]

[0063] Test Example 1 The luminance characteristics of the light-controlled films in the examples and comparative examples were evaluated. Luminance was evaluated using the device (lighttools simulation program). The calculated AR1 (area aperture ratio) and AR2 (line aperture ratio), as well as the central luminance Con1 and peak luminance Con2 for each light-controlled film, are summarized in Table 2 below.

[0064] The relative luminance in Table 2 below is relative to the reference luminance. In this case, the reference luminance is the luminance measured similarly for a laminate in which the first base film (6000) and the second base film (3000) are laminated with adhesive (5000) without the louver film.

[0065] In Table 2 below, luminance Con1 is the central luminance of the light-controlled film, and is the luminance measured in a direction parallel to the surface normal direction of the light-controlled film.

[0066] In Table 2 below, luminance Con2 is the maximum value of the luminance measured at angles within the range of -88° to 88°, which is within the Horizontal Cross Section range, where angles 88° and -88° are measured relative to Center (0°).

[0067] In Table 2 below, "relative" in parentheses means that the luminance is relative luminance, and "absolute" means that the luminance is absolute luminance.

[0068] [Table 2]

[0069] The results in Tables 1 and 2 show that in the examples where AR1 / AR2 is less than 1.45, the central brightness (Con1) is high and △Con remains low, thus confirming that excellent image quality can be achieved. However, in the comparative examples where AR1 / AR2 exceeds 1.45, both the central brightness and △Con are low, suggesting that a decrease in image quality may occur. [Explanation of symbols]

[0070] 1000: Louver film 1001: First surface of the louver film 1002: Second surface of the louver film 3000: Second base film 6000: First base film 5000: Adhesive layer

Claims

1. The louver film includes a first surface in which light-absorbing and light-transmitting portions are arranged alternately, and a second surface having a light-transmitting portion on the opposite side of the first surface. A light-controlling film characterized by satisfying the following formula 1: [Formula 1] AR １ / AR ２ <1.45 In Equation 1, AR １ AR is defined in the following equation 2, ２ It is defined by the following equation 3: [Formula 2] AR １ =(A-B) / A×100 [Formula 3] AR ２ =(p-L) / p×100 In equations 2 and 3, A is p × h, B is (U + L) × h / 2, p is the pitch of the light-absorbing portion, h is the height of the light-absorbing portion, U is the width of the second surface side of the light-absorbing portion, and L is the width of the first surface side of the light-absorbing portion.

2. The light-controlling film according to claim 1, characterized in that ΔCon in the following formula 4 is less than 15%: [Formula 4] △Con=Con2-Con1 In Equation 4, Con1 is the central brightness of the light-controlling film, and Con2 is the peak brightness, which is the maximum brightness value at angles within the range of -88° to 88° (Horizontal Cross Section). The central brightness and peak brightness represent the relative brightness to the central brightness of the film laminate configuration excluding the louver film.

3. AR in Equation 1 １ / AR ２ The light control film according to claim 1, characterized in that the value is 1 or more.

4. The light-absorbing portion has a first wall angle (θ1) and a second wall angle (θ2), and the sum of the first wall angle (θ1) and the second wall angle (θ2) (θ) is in the range of 2° to 8°, characterized in that the light-controlling film according to claim 1.

5. The light-controlling film according to claim 1, characterized in that the height of the light-absorbing portion is in the range of 80 μm to 170 μm.

6. AR of Formula 1 ２ The light control film according to claim 1, wherein ２ is in the range of 33% to 96%.

7. AR in Equation 1 １ The light control film according to claim 1, characterized in that the percentage is in the range of 33% to 96%.

8. The light control film according to claim 1, characterized in that there is no light-absorbing portion on the second surface of the louver film.

9. The light control film according to claim 1, further comprising a first base film bonded to the first surface of a louver film via an adhesive layer.

10. The light control film according to claim 1, further comprising a second base film that is in direct contact with the second surface of the louver film.

Images