TWI832894B - Resin film and method of manufacturing resin film - Google Patents

Abstract

The present invention is mainly based on the viewpoint of controlling the surface shape and aims to provide a resin film suitable for use as a light guide plate and a manufacturing method thereof. The above problem can be solved by a resin film in which the ratio of the area occupied by the inclined region having an inclination angle of 0.3 degrees or more is 10% or less of the surface, and a melt extrusion method for melt extruding the resin material of the resin film. The manufacturing method of the resin film is solved in the following steps.

Description

Resin film and manufacturing method of resin film

The present invention relates to a resin film, and in particular to a resin film suitable for use as a light guide plate and a manufacturing method thereof.

Liquid crystal display devices such as tablet computers and smartphones generally use a light guide plate that transmits light for illumination while diffusing it (for example, Patent Documents 1 and 2, etc.). When the side surface of the light guide plate is irradiated with light from a light source, the light transmitted inside the light guide plate is emitted from the light exit surface, and the emitted illumination light is used for illumination.

In the light guide plate, the illumination light needs to be emitted effectively and evenly from the light exit surface. That is, the light guide plate is not only responsible for diffusing the illumination light, but also responsible for ultimately emitting the light. Therefore, generally, the surface shape of the light-emitting surface of a light guide plate made of resin, that is, the surface with the largest area in the film, is controlled so that the illuminating light can be effectively and evenly emitted. [Prior technical literature] [Patent Document]

[Patent Document 1] Japanese Patent Application Publication No. 2000-258633 [Patent Document 2] Japanese Patent Application Publication No. 2004-200093

[Problem to be solved by the invention]

As mentioned above, the surface shape of the light guide plate needs to be controlled, but the surface shape of the light guide plate may not be easy to control. For example, in the step of producing a final product of a light guide plate from a resin film, depending on the state of the resin film used as a material, especially the state of its surface, it may be difficult to produce a light guide plate with a desired surface shape.

The present invention was completed in view of the above-mentioned circumstances. That is, the present invention is mainly based on the viewpoint of controlling the surface shape, and provides a resin film suitable for use as a light guide plate, a manufacturing method thereof, and the like. [Means to solve the problem]

The present invention relates to the following resin films and their manufacturing methods.

(1) A resin film in which the ratio of the area occupied by the inclined region having an inclination angle of 0.3 degrees or more in the surface is 10% or less. (2) The resin film according to the above (1), wherein the ratio of the area occupied by the inclined region in the surface is 0.01% or more. (3) The resin film according to the above (1) or (2), wherein the proportion of the area occupied by the inclined region having an inclination angle of 0.2 degrees or more in the surface is 30% or less. (4) The resin film according to any one of (1) to (3) above, wherein the proportion of the area occupied by the inclined region having an inclination angle of 0.15 degrees or more in the surface is 45% or less. (5) The resin film according to any one of (1) to (4) above, wherein the surface has a surface roughness Sa value based on ISO 25178 of 5.0 nm or less. (6) The resin film according to the above (5), wherein the surface roughness Sa of the surface is 1.0 nm or more. (7) The resin film according to any one of the above (1) to (6), wherein the dYI value based on ASTM E313-05 is 0.8 or less. (8) The resin film according to any one of the above (1) to (7), wherein the resin film is produced by a melt extrusion method. (9) The resin film according to the above (8), wherein the melt extrusion method includes a melt extrusion step of melt extruding the resin material of the resin film. (10) The resin film according to any one of the above (1) to (7), which contains polycarbonate (PC), acrylic resin, polyethylene terephthalate (PET), and triacetyl Cellulose (TAC), polyethylene naphthalate (PEN), polyimide (PI), cyclic olefin polymer (COP), cyclic olefin copolymer (COC), norbornene-containing resin, polyether At least one of polyamide, cellophane, and aromatic polyamide. (11) The resin film according to the above (10), wherein the acrylic resin contains polymethyl methacrylate (PMMA). (12) A light guide plate having a surface corresponding to the surface of the resin film described in any one of (1) to (11) above as a light-emitting surface. (13) The method for producing a resin film according to any one of (1) to (11) above, which includes a melt extrusion step of melt extruding the resin material of the resin film. (14) The method for producing a resin film according to the above (13), which uses a roller with an uneven surface formed in the melt extrusion step so that the area occupied by the inclined region having an inclination angle of 0.3 degrees or more The proportion is less than 5%. [Effects of the invention]

According to the present invention, it is possible to provide a resin film that can accurately control the surface shape when used in manufacturing a light guide plate, a manufacturing method thereof, and the like.

[Form of carrying out the invention]

The present invention will be described in detail below. In addition, the present invention is not limited to the following embodiments, and can be implemented with any modification within the scope having the effects of the invention.

In the surface of the resin film of the present invention, the shape is controlled as described in detail later, and the surface of the resin film has high smoothness. In addition, the surface of the film mentioned in the description of this case refers to the surface with the largest area in the film, excluding the extremely small side surfaces. Furthermore, the light guide plate of the present invention is derived from the resin film by at least further roughening the surface of the resin film. The present invention further includes a method of manufacturing the above-mentioned resin film.

[Resin film] The resin film of the present invention has a highly smooth surface and is particularly suitable as a material for plate-shaped members that require more controlled surface shape, such as light guide plates.

＜Shape of resin film＞ In the resin film, the surface shape is controlled so that the proportion of the area occupied by the inclined region having an inclination angle of 0.3 degrees or more is 10% or less. Here, if the area occupied by the sloped region on the surface of the resin film is regarded as the slope, then the slope is considered to be the sloped region when the region on the surface of the resin film with a slope angle of 0.3 degrees or more is regarded as the sloped region. The proportion of the total surface area of the resin film to the entire surface of the resin film.

In order to calculate the slope of the film surface, the surface shape of the film was measured. Devices for measuring surface shape include contact surface roughness meters or non-contact surface roughness meters (such as white interference microscopes, confocal microscopes, atomic force microscopes, etc.). Among these, a scanning white interference microscope is preferred from the viewpoint of simplicity of measurement. Specific examples of such a scanning white interference microscope include VS-1550 (Hitachi High-Tech Science Co., Ltd.).

In order to calculate the tilt rate using a scanning white interference microscope or the like, first, the tilt angle θ of each point on the surface of the film is determined. The method of calculating the tilt angle θ is as follows. When one of the two orthogonal directions on the measurement surface of the film is set as the x-axis and the other is set as the y-axis, the slope in the x-axis direction relative to the x-axis and the slope relative to the x-axis at a point on the film surface are determined. The slope of the y-axis in the y-axis direction. Let the value of the slope in the x-axis direction be tanθx (hereinafter also referred to as Sx), and the value of the slope in the y-axis direction be tanθy (hereinafter also referred to as Sy). These values are expressed by the following formulas (1) and (2) Figure it out. In formulas (1) and (2), Z1 is the height (Z-axis value) of the pixel A that is the object of measurement of the tilt angle θ on the film as shown in Figure 1(a), Z2 and Z3 are respectively The height (Z-axis value) of pixel B adjacent to pixel A on the x-axis direction side, and the height (Z-axis value) of pixel C adjacent to pixel A on the y-axis direction side, Δx and Δy respectively It is the size of 1 pixel in the x-axis and y-axis directions.

Furthermore, the value tanθxy (hereinafter also referred to as the slope St) of the inclination angle of the pixel A in the xy direction is calculated according to the following equation (3): see FIGS. 1(b) and (c)). The value of tanθxy (slope St: St ² = (Sx ² +Sy ² )) calculated in this way is converted into the value of the inclination angle θ according to the following equation (4). Based on this calculation, the values of the inclination angle θi of multiple points on the film surface are calculated, and the inclination angle data is obtained.

Based on the tilt angle data thus obtained, the proportion of the tilt area in which the absolute value of the tilt angle θi is 0.3 degrees or more is calculated as the tilt rate. That is, since it is a region having an inclination angle θi with an absolute value of 0.3 degrees or more, the ratio of the total area of the portion considered to be an inclination region to the total surface area of the film is calculated based on the above-mentioned inclination rate. Here, the total area of the inclined region is the sum of the total surface area of the inclined region (the area of the inclined surface) with respect to the convex region and the total surface area of the inclined region (the area of the inclined surface) with respect to the concave region. For example, in the surface of the resin film 10 illustrated in FIG. 2 , the areas other than the convex areas 12 are flat areas 10A. If the inclination angle α is 0.3 degrees or more, the total area of the surface of the convex areas 12 on the side of the inclined surface 12A is It is calculated as the area of the inclined area; if the inclination angle β is less than 0.3 degrees, the surface of the convex area 12 on the side of the inclined surface 12B does not belong to the inclined area. Furthermore, although not shown in FIG. 2 , the inclination angle and the inclination area of the concave area are also determined in the same manner as in the convex area 12 . That is, an area in which the inclination angle of the angle between the extended surface S and the inclined surface of the concave area (not shown) is 0.3 degrees or more is also recognized as an inclined area.

Furthermore, the sum of the total surface area of the convex areas exemplified by the convex area 12, the total surface area of the concave areas not shown, and the area of the flat area exemplified by 10A is calculated as the total surface area of the resin film. Furthermore, the total area of the inclined regions included in the convex regions and the concave regions was calculated, and the ratio of the total area of the inclined regions (total area of the inclined regions) to the total surface area of the resin film was calculated as the slope rate.

In the resin film, as mentioned above, the predetermined slope value is 10% or less. The slope value is preferably 9% or less, more preferably 5% or less, and still more preferably 2% or less. On the other hand, the value of the slope of the resin film is, for example, 0.01% or more; however, since disadvantages caused by high smoothness are basically not seen, the lower limit of the slope may be a value less than 0.01%.

The inclination rate when the threshold value of the inclination angle is set to be less than the above-mentioned value of 0.3 degrees is also discussed. For example, when the threshold value of the inclination angle is 0.2 degrees and the inclination rate is specified as described above, the ratio of the area occupied by the inclination region having an inclination angle of 0.2 degrees or more is preferably 30% or less, more preferably The best is less than 26%, the best is less than 10%, and the best is less than 5%. Furthermore, in the resin film when the threshold value of the inclination angle is 0.15 degrees and the inclination rate is specified as described above, the proportion of the area occupied by the inclination region having an inclination angle of 0.15 degrees or more is preferably 45% or less, and more preferably The best is less than 44%, the best is less than 20%, and the best is less than 12%.

On the surface of the resin film, the value of the surface roughness Sa according to ISO 25178 is preferably 5.0 nm or less, more preferably 4.5 nm or less, still more preferably 3.5 nm or less, and particularly preferably 3.0 nm or less.

As mentioned above, the sloped region occupies a smaller area and preferably has a smaller surface roughness Sa. This means that the surface smoothness of the resin film is higher. Moreover, such a resin film having a smooth surface can be used to form a predetermined pattern of concave and convex shapes on the surface through further processing. In addition, both sides of the resin film, that is, both surfaces preferably have the above-mentioned shape, but only one of the surfaces may have the above-mentioned shape.

The resin film of the present invention is particularly suitable as a material for a light guide plate having uneven surfaces. The reason for this is that, as will be described in detail later, in the resin film of the present invention, the emission of light from the surface can be suppressed to a minimum even when light is irradiated from the end portion (side surface) and conducted. This is because as long as the light guide plate is formed of a resin film as a material, the ideal light emission as a light guide plate can be reliably achieved by providing the concave and convex shape suitable for causing the transmitted light to be emitted from the light emitting surface as originally designed. Performance reasons.

Thus, in the present invention, by controlling the surface shape of the resin film based on the proportion of the area occupied by the inclined region having a specific inclination angle, preferably further based on the control of the surface shape of the surface roughness Sa, Can suppress the emission of light from the surface. In contrast, based on other parameters, such as Ra (line thickness) specified in JIS B 0601:2013, it is difficult to suppress the emission of light from the surface of the resin film. That is, even if the above-mentioned Ra value is adjusted to evaluate a resin film with a small Ra value, the emission of light from the surface of the resin film may not be suppressed, and no correlation is seen between the Ra value and the suppression of light emission. In this way, it was confirmed that the control of the surface shape based on the ratio of the area occupied by the inclined region, preferably further based on the value of the surface roughness Sa, is particularly suitable for suppressing the emission of light from the surface.

The thickness of the resin film is not particularly limited, but is preferably 50 to 3000 μm (3.0 mm), more preferably 70 to 2000 μm, still more preferably 100 to 1000 μm, and particularly preferably 100 to 700 μm.

＜Material of resin film＞ The material of the resin film is not particularly limited, but preferably contains thermoplastic resin. Examples of the thermoplastic resin include polycarbonate (PC) resin, acrylic resin including polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), triacetyl cellulose (TAC), Polyethylene naphthalate (PEN), polyimide (PI), cyclic olefin polymer (COP), cyclic olefin copolymer (COC), norbornene-containing resin, polyether ethylene, cellophane, Various resins such as aromatic polyamide. Among these options, it is preferable that the resin film contains at least polycarbonate resin.

Regarding the types of polycarbonate resins mentioned above, as long as the main chain of the molecule contains -[O-R-OCO]-units containing carbonate bonds (R includes an aliphatic group, an aromatic group, or both an aliphatic group and an aromatic group). (which may further have a linear structure or a branched structure) is not particularly limited, but is preferably a polycarbonate having a bisphenol skeleton, and particularly preferably a polycarbonate having a bisphenol A skeleton or a bisphenol C skeleton. . A mixture or copolymer of bisphenol A and bisphenol C can also be used as the polycarbonate resin. By using bisphenol C-based polycarbonate resins, such as polycarbonate resins containing only bisphenol C, polycarbonate resins containing a mixture or copolymer of bisphenol C and bisphenol A, the hardness of the resin film can be increased.

The thermoplastic resin forming the resin film, such as polycarbonate resin, preferably has a viscosity average molecular weight of 10,000 to 40,000, more preferably 15,000 to 32,000, and still more preferably 15,000 to 28,000.

In addition, the resin film may contain additives as components other than the thermoplastic resin. For example, it is at least one additive selected from the group consisting of a heat stabilizer, an antioxidant, a flame retardant, a flame retardant auxiliary, an ultraviolet absorber, a release agent, and a coloring agent. In addition, antistatic agents, fluorescent whitening agents, anti-fogging agents, fluidity improvers, plasticizers, dispersants, antibacterial agents, etc. can also be added to the resin film.

In the resin film, the thermoplastic resin content is preferably 80 mass% or more, more preferably 90 mass% or more, and particularly preferably 95 mass% or more. Moreover, among the thermoplastic resins of the resin film, the polycarbonate resin preferably contains 80 mass% or more, more preferably 90 mass% or more, and particularly preferably 95 mass% or more. In addition, the resin film is preferably formed with a uniform composition, and preferably does not contain particles such as translucent fine particles or is non-uniform.

＜Properties and conditions of resin films＞ In the resin film, the dYI value according to ASTM E313-05 is preferably 0.8 or less, more preferably 0.7 or less, and still more preferably 0.6 or less. In this way, by lowering the dYI value, yellowing of the film end surface when the resin film guides light can be suppressed, and a resin film particularly suitable as a light guide product can be realized. Furthermore, in order to reduce the dYI value of the resin film, it is better to perform the manufacturing steps of the resin film, such as the melting of the resin particles of the material, in an inert gas environment. Nitrogen is preferably used as the inert gas.

In a resin film, it is preferable to suppress the emission of light from the surface (light-emitting surface) in a state where light is transmitted from the side. Specifically, the brightness value of the surface (light-emitting surface) measured under the following conditions is preferably 70 (Cd/m ² ) or less. That is, the end (side) of a resin film sample of 12 cm (length) × 12 cm (width) × 0.47 mm (thickness) is illuminated with LEDs arranged to be in contact with the end. The brightness value when the brightness of the film surface is measured with a luminance meter (LS-110 manufactured by KONICA MINOLTA) at an angle of 20 degrees to the film surface while transmitting light.

The brightness value measured under the above conditions is preferably 60 (Cd/m ² ) or less, still more preferably 50 (Cd/m ² ) or less, and particularly preferably 40 (Cd/m ² ) or less. Furthermore, as for the evaluation method of the brightness value, it is more preferable to set the light guide direction of the light from the above-mentioned LED to the MD direction (the direction of resin flow when the resin film is formed) and the TD direction (the direction perpendicular to the MD direction), and Furthermore, the measurement surface was defined as the front surface and the back surface, and the same sample was measured in four ways, and the maximum brightness value was evaluated.

It is preferable that no whitening of the surface is observed in the state where light is guided to the resin film. For example, the end (side) of a resin film sample with a size of 12 cm (length) × 12 cm (width) × 0.47 mm (thickness) is illuminated by an LED arranged so as to be connected to the end. It is better if there is no whitening on the surface of the film when light is transmitted.

[Light guide plate] ＜Shape of light guide plate＞ In a light guide plate made of a resin film, a predetermined shape suitable for the purpose of the light guide plate, such as a hemispherical concave and convex shape, a hemispherical shape, etc. is formed on the light exit surface corresponding to the surface of the resin film. As described above, in the resin film of the present invention, since the emission of light from the surface is suppressed to a minimum, as long as a predetermined surface shape is formed in the light guide plate made of the resin film, light can be easily emitted as originally designed. . Therefore, the light guide plate of the present invention has the characteristic of reliably controlling the light guide performance.

＜Material of light guide plate＞ The material of the light guide plate is not particularly limited. Since it is formed using a resin film, it is preferably made of the same material as the above-mentioned resin film.

[Manufacturing method of resin film] The resin film of the present invention is preferably produced by melt extrusion. This is because surface smoothness can be easily and reliably achieved. In this way, extrusion molding using the melt extrusion method is performed, for example, according to the following steps. It involves melting and kneading granular, flake or powdery resin materials with an extruder, extruding them through a T-shaped die, etc., and then cooling and solidifying the resulting semi-melted flakes with rollers to form flakes. steps.

Furthermore, as mentioned above, when producing a resin film by a production method including a melt extrusion step, it is preferable to adjust the surface shape of the roller, which is generally a metallic roller, that presses the resin material in the melt extrusion step in advance. This is because a resin film having a highly smooth surface can be produced reliably. Specifically, it is preferable to use a roller having a surface on which an uneven shape is formed so that the area of the inclined region having an inclination angle of 0.3 degrees or more accounts for the inclination defined similarly to the inclination of the resin film. The proportion of area is less than 5%. In the roller surface used in the melt extrusion step, the above-mentioned slope ratio is more preferably 4% or less, still more preferably 1% or less, and particularly preferably 0.5% or less. In the roller surface, the ratio of the area of the inclined region having an inclination angle of 0.2 degrees or more is preferably 25% or less, more preferably 21% or less, still more preferably 10% or less, and particularly preferably 5% or less. Moreover, in the roller surface, the ratio of the area of the inclined region having an inclination angle of 0.15 degrees or more is preferably 42.5% or less, more preferably 42% or less, still more preferably 20% or less, and particularly preferably 12%. the following.

On the surface of the roll used in the melt extrusion step, the surface roughness Sa according to ISO 25178 is preferably 7.0 nm or less, more preferably 5.0 nm or less, still more preferably 4.0 nm or less, and particularly preferably Below 3.0nm. In addition, as will be described in detail later, the surface shape of the roller can be measured by measuring the surface shape of the roller copy mold formed by hardening the resin on the roller surface, and is approximately equal to the surface shape.

The method for producing a resin film will be described with reference to Fig. 3 schematically illustrating the melt extrusion step. The manufacturing device 20 used for manufacturing a resin film includes a die 22 for accommodating and extruding a resin material, a rectangular extrusion port 24 formed in the die 22, a first roller 30, a second roller 32, and a third roller 34. It is preferable that the first to third rollers 30, 32 and 34 are made of metal.

The first and second rollers 30 and 32 are disposed below the extrusion port 24 and are disposed to sandwich the pre-molding resin material 40 extruded from the extrusion port 24 . The third roller 34 is arranged on the side of the second roller 32 . The first to third rollers 30, 32 and 34 rotate in the directions indicated by arrows in Figure 3, and the resin material 40 is mainly shaped by the second roller 32 and stretched at the same time to become an unfinished resin film. 42. Then, the unfinished resin film 42 is subjected to cutting and final processing to form a resin film.

In addition, among the first to third rollers 30 , 32 and 34 , the second roller 32 that has the greatest influence on the surface shape of the resin material 40 presses the front surface of the resin film 42 (the surface shown in FIG. 3 ). Therefore, it is preferable to perform a step of smoothing the resin film in advance before manufacturing it so as to sufficiently reduce the slope of the surface of the second roller 32 below the extrusion port 24 of the die 22 and downstream. [Example]

The present invention will be described in more detail below with reference to Examples. However, the present invention is not limited to the following examples, and can be arbitrarily modified and implemented within the scope that does not deviate from the gist of the present invention.

＜Creation of roller copy mold＞ In order to measure the surface shape of the metal roller, a transparent copy mold of the surface of the metal roller was made using UV curable resin GLX18-73N manufactured by Gluelabo Co., Ltd. That is, the resin was hardened on the surface of the metal roller to obtain a copy mold, and the surface shape of the transparent copy mold was measured and judged to be equal to the surface shape of the metal roller.

＜Measurement method of surface slope of film and roller transfer mold＞ The measurement of the slope of the surface of the film and the roller transfer mold, that is, the ratio of the sum of the sloped areas with a slope angle of 0.3 degrees or more to the total surface area of the film, is based on the following (i) acquisition of the surface shape, and (ii) consisting of the determination of area ratio.

(i) Obtaining surface shape (using machine) White interference microscope: Scanning white interference microscope VS-1550 (Hitachi High-Tech Science Co., Ltd.) Measurement software: VS-Measure (optical conditions) Camera: Sony XCL-C30　1/3 Camera speed: 1.0X Objective lens: 50XDI Lens barrel: 1X Zoom lens: 1X Light source: 530white (Measurement conditions) Measuring device: piezoelectric Measurement mode: Wave Scan speed: 4um/sec Field of view size: 640×480 Scanning range(um) Start: 10 Stop: -10 Effective number of pixels: 70% Average times: 1 Measurement was performed based on the above conditions to obtain surface shape data of the film. The area of the field of view obtained at this time is 94 μm×71 μm, the value of Δx in the above formula (1) is 0.147 μm, and the value of Δy in the above formula (2) is 0.148 μm.

(ii) Determination of tilt angle Analysis software: VS-Viewer For the film surface shape data obtained by the method (i) above, use the analysis software VS-Viewer to analyze and measure according to the following operations, and measure the proportion of the area occupied by an inclination angle of 0.3 degrees or more in the plane. Operation 1. Open the surface shape data file that is the object of measurement of the tilt angle. Regarding the result of operation 1 of the following embodiment 1, the screen displayed on the screen of the device is shown in Figure 6 through the analysis software VS-Viewer. On the screen displaying the actual surface shape data in Figure 6, the horizontal axis represents the length (μm) of the Display) the height difference within the measurement area. In Figure 6, the portion shown in dark color (the portion shown in red in the basic application) in the area where the X-axis value is about 0 (μm) to 20 (μm) indicates that the height from the reference plane is 11.7 μm. The relatively high film surface area on the left and right; the part shown in dark color (the part shown in blue in the basic application) in the area with an X-axis value of about 70 (μm) to 95 (μm) represents the distance The height of the reference plane is a relatively low film surface area of about 10.5 μm. Operation 2. Perform surface correction by selecting 4 times with an approximate surface shape based on surface correction. Operation 3. Set the cutoff value to 1μm in the ripple analysis, perform object expansion for boundary processing, select "Interpolate Edge" from the set mode, and output the ripple image. The results of each operation so far are shown in Figure 7(A) as shown in Figure 7(A) by using the analysis software VS-Viewer to display the screen of the device according to Embodiment 1. FIG. 7(A) shows the ripple image to be output as a result of each operation up to the above-mentioned operation 3, that is, the ripple image in which the reference plane of the height difference is changed from FIG. 6 . Regarding the ripple image in Figure 7(A), the film surface area that is about 0.009 μm lower than the reference plane in the measurement area has an X-axis value of about 55 (μm) to 75 (μm) and a Y-axis value of 25 ( The range of about 0.005 μm (μm) to 35 (μm) is represented by a dark color (shown in blue in the basic application); the film surface area within the measurement area that is about 0.005 μm higher than the reference plane is shown in other dark colors (shown in the basic application). Basic applications are shown in red). In addition, the time point when the ripple image in FIG. 7(A) is actually displayed on the screen is just after the following operation 4 is performed. Operation 4. Perform angle/normal analysis in the resulting ripple image according to the following conditions. The area ratio recorded in the output histogram is used as the ratio of the area occupied by a tilt angle of 0.3 degrees or more. Analysis: angle Direction:XY Area threshold: 0.3deg Output: Histogram As for the results of each operation in operation 4, the ripple image of Example 1 showing the results of the angle/normal analysis displayed on the screen of the device is shown in FIG. 7(B) through the analysis software VS-Viewer. 7(B) shows the relationship between the tilt angle of each pixel and the frequency obtained based on the above analysis. The horizontal axis represents the tilt angle (angle: deg), and the vertical axis represents the frequency of the pixel having each tilt angle. As shown in FIG. 7(B) , the results of the angle/normal analysis related to Example 1 are expressed as the ratio of the threshold value of the tilt area having a tilt angle of 0.3000 degrees (deg) or more to the entire area of the film to be measured. The value of the slope rate (expressed as an area ratio in Figure 7(B)) was calculated to be 0.0013%.

The method for measuring the ratio (inclination rate) of the tilted area having a tilt angle different from the above-mentioned 0.3 degrees to the total surface area of the surface of the measurement object is based on the above-mentioned method. That is, the method of measuring the inclination rate of the inclination area having inclination angles of 0.15 degrees and 0.2 degrees is the same as the above except that 0.15 degrees and 0.2 degrees are used respectively instead of 0.3 degrees as the threshold value of the inclination angle. The method of determination is the same.

<Measurement method of Sa on film and roll copy mold surfaces> Based on ISO25178, the arithmetic mean height (Sa) in the range of 70 μm×70 μm was measured using a white interference microscope (VS-1550, Hitachi High-Tech Science Co., Ltd.).

＜Measurement of dYI value＞ The dYI value based on ASTM E313-05 is determined as follows. A 15% by weight methylene chloride solution of the polycarbonate resin was placed in a glass sample tank, and the light from the D65 light source was allowed to penetrate the 50 mm methylene chloride solution layer and receive light at the light-receiving part. The calculated penetration at this time was rate as dYI value. This measurement uses a spectrophotometer SD-6000 manufactured by Nippon Denshoku Industries Co., Ltd. This measurement is performed after adding only solvent to a 50mm-long glass sample tank and performing a baseline measurement. The dYI value is calibrated according to the type of sample tank and solvent.

＜Measurement of luminance＞ Measure with a luminance meter (LS-110 manufactured by KONICA MINOLTA) at an angle of approximately 20 degrees to the plane of the film, and conduct the light from the LED from the end to a sample film (thickness 0.47mm) cut into a 12cm square. The brightness of the film surface. The light guide direction was set as the MD direction (the direction of resin flow when the resin film is formed) and the TD direction (the direction perpendicular to the MD direction), and the measurement surfaces were further set as the front and back surfaces, and four methods were used for each sample. Measurement was performed, and the maximum value was used as the brightness value (Cd/m ² ).

＜Whitening on the film surface＞ The whitening of the film surface when the LED light is transmitted from the end to the above-mentioned sample film cut into 12 cm squares is evaluated based on the following standards. Particularly good: almost no whitishness visible on the surface. Good: Faintly visible surface whitishness. Slightly bad: visible surface whitishness. Bad : Strongly visible surface whitishness.

[Example 1] A resin film was produced as follows. Aromatic polycarbonate resin pellets (Iupilon (registered trademark) HL-3000 manufactured by Mitsubishi Engineering-Plastics Co., Ltd. (PC resin with a mass average molecular weight of approximately 19,000 having a bisphenol A skeleton) were dried at 120 °C for 3 hours. After drying, the pellets are melted and extruded using a single-screw extruder with a T-die lip and a screw diameter of 90 mm to form a resin film. In this melt extrusion step, Roller A having a shape shown in the following Table 1 was used. Roller A and rolls B to D used in other examples or comparative examples were metal mirror rolls with chromium (Cr) plating on the surface, and their surface shapes were The shapes of the roller copy molds shown in Table 1 are almost the same. In addition, the pellets were melted in a single-screw extruder under a nitrogen atmosphere. Through this nitrogen blowing, the dYI value of the resin film can be reduced.

[Examples 2 to 12] As shown in Table 1, the polycarbonate resin system used the above-mentioned Iupilon (registered trademark) HL-3000 and Iupilon (registered trademark) S-3000 manufactured by Mitsubishi Engineering-Plastics Co., Ltd. (having a bisphenol A skeleton with a viscosity average molecular weight of approximately 39,000 PC resin), or Iupilon (registered trademark) E-2000 (a PC resin having a bisphenol A skeleton and a weight average molecular weight of approximately 36,000) manufactured by Mitsubishi Engineering-Plastics Co., Ltd. Furthermore, a resin film was formed in the same manner as in Example 1, except that at least one of the type of polycarbonate resin, the type of roller used in the melt extrusion step, and the presence or absence of nitrogen blowing was different from Example 1.

[Comparative Examples 1 to 4] Comparative Examples 1 to 4 are as shown in Table 1, except that the type of roller used in the melt extrusion step is different from each Example, and Comparative Example 2 and the following are different from Example 1 in that nitrogen gas flushing is not used. Except for this, a resin film was formed in the same manner as in Example 1.

For the resin film produced in this way, the surface shape is measured, predetermined parameter values are calculated, and the properties of the resin film are measured. The results are summarized in Table 1. In addition, if we compare Figure 4 showing the surface of the resin film of Example 3 in a state where light is guided from the end (side surface) with Figure 5 showing the surface of the resin film of Comparative Example 1, in Example 3, the light Almost no light was emitted from the surface and the surface was dark (Fig. 4). In contrast, in Comparative Example 1, in which the entire film surface was brighter, it was confirmed that light was emitted from the surface (Fig. 5).

10:Resin film 12: Inclined area 32: 2nd roller (metal roller)

[Fig. 1] is a diagram showing a method of calculating the inclination angle of the film surface. [Fig. 2] Fig. 2 is an enlarged cross-sectional view schematically showing the surface of the resin film. [Fig. 3] is a perspective view schematically showing the manufacturing steps of the resin film. [Fig. 4] is an image of the surface of the resin film of Example. [Fig. 5] is an image of the surface of the resin film of a comparative example. [Fig. 6] A graph showing measurement data of the surface shape of the film of Example 1. [Fig. [Fig. 7(A)] is a diagram showing the ripple image obtained in Example 1 displayed on the screen of the analysis device; [Fig. 7(B)] is a diagram showing each pixel obtained based on the analysis related to Example 1 Plot of tilt angle versus frequency.

Claims (12)

A resin film in which the ratio of the area occupied by the inclined region having an inclination angle of 0.3 degrees or more in the surface is 10% or less and contains 95 mass % or more of polycarbonate resin. The resin film according to claim 1, wherein the ratio of the area occupied by the inclined region in the surface is 0.01% or more. The resin film according to claim 1 or 2, wherein the proportion of the area occupied by the inclined region having an inclination angle of 0.2 degrees or more in the surface is 30% or less. The resin film according to claim 1, wherein the proportion of the area occupied by the inclined region having an inclination angle of 0.15 degrees or more in the surface is 45% or less. The resin film according to Claim 1, wherein the surface roughness Sa value based on ISO 25178 is 5.0 nm or less. The resin film according to claim 5, wherein the surface roughness Sa of the surface is 1.0 nm or more. The resin film according to claim 1, wherein the resin film is based on ASTM E313- The dYI value of 05 is below 0.8. The resin film according to claim 1, wherein the resin film is produced by a melt extrusion method. The resin film according to claim 8, wherein the melt extrusion method includes a melt extrusion step of melt extruding the resin material of the resin film. A light guide plate having a surface corresponding to the surface of the resin film described in any one of claims 1 to 9 as a light emitting surface. The method for producing a resin film according to any one of claims 1 to 9, which includes a melt extrusion step of melt extruding the resin material of the resin film. The method for manufacturing a resin film according to claim 11, wherein a roller having an uneven surface is used in the melt extrusion step so that the ratio of the area occupied by the inclined region having an inclination angle of 0.3 degrees or more is 5 %the following.