Method for manufacturing retardation film piece and method for manufacturing optical laminate

Abstract

Provided is a method for manufacturing a retardation film piece, the method involving: preparing a long retardation film; and, in the longitudinal direction, repeatedly punching the long retardation film in the width direction into one retardation film piece for each of N columns from a first column to an Nth column extending in the longitudinal direction. The long retardation film is a stretched resin film. N is an integer of 2 or greater. Punching of the retardation film piece is carried out using punching blades for the first to Nth columns, the punching blades being prepared for each of the columns. Preparation of the long retardation film includes selecting a long retardation film that satisfies the following conditions: (i) the angle of the slow axes of the first and Nth columns in relation to the width direction is from Xa° to Xb°, inclusive; and (ii) when the blade angle of the punching blade for the first column is denoted by Y1° and the blade angle of the punching blade for the Nth column is denoted by Yn°, the relationship of Y1 = Yn = (Xa + Xb) / 2 holds true. Moreover, when N≥3, the punching blades for the first to Nth columns have blade angles that decrease toward the center column.

Description

Method for producing retardation film piece and method for producing optical laminate

[0001] The present invention relates to a method for producing a retardation film piece and a method for producing an optical laminate.

[0002] Image display devices typified by liquid crystal display devices and electroluminescence (EL) display devices (for example, organic EL display devices) have been rapidly spreading. In image display devices, optical members such as a polarizing member and a retardation member are generally used to realize image display and improve image display performance (see, for example, Patent Document 1).

[0003] In recent years, new applications of image display devices have been developed. For example, goggles with a display (VR goggles) for realizing Virtual Reality (VR) have begun to be commercialized. Since the use of VR goggles in various situations is under consideration, higher definition and the like are desired.

[0004] Japanese Patent Application Laid-Open No. 2021-103286

[0005] In view of the above, a main object of the present invention is to provide a retardation film piece that can contribute to the production of display systems such as high-definition VR goggles.

[0006] [1] According to one aspect of the present invention, a method for manufacturing a phase difference film piece, comprising: preparing a long phase difference film; and repeatedly punching out one phase difference film piece for every N rows from the first row to the Nth row extending in the longitudinal direction in the width direction of the long phase difference film, wherein the long phase difference film is a stretched film of a resin film, N is an integer of 2 or more, and the punching out of the phase difference film piece is performed using punching blades prepared for each row from the first row to the Nth row, and the long A method for manufacturing a phase difference film is provided, wherein preparing the phase difference film includes selecting a long phase difference film that satisfies the following (i) and (ii): (i) the angle of the slow axis in the first and Nth columns with respect to the width direction is Xa° or more and Xb° or less; (ii) when the cutting angle of the punching blade for the first column is Y1° and the cutting angle of the punching blade for the Nth column is Yn°, the relationship Y1 = Yn = (Xa + Xb) / 2 holds; when N ≥ 3, the punching blades for the first to Nth columns have cutting angles that decrease toward the central column. [2] In the manufacturing method described in [1] above, preparing the long phase difference film may include selecting a plurality of long phase difference films that satisfy the above (i) and (ii). [3] In the manufacturing method described in [1] or [2] above, Xa and Xb may satisfy the relationship Xb - Xa ≤ 1.0. [4] In the manufacturing method described in any of [1] to [3] above, Y1 and Yn may be 1.0 or more and 1.5 or less. [5] In the manufacturing method described in any of [1] to [4] above, Xa may be 0.8 or more and 1.2 or less, Xb may be 1.5 or more and 2.0 or less, and Xa and Xb may satisfy the relationship Xb - Xa ≤ 0.8. [6] In the manufacturing method described in any of [1] to [5] above, N may be an integer from 3 to 10 or more. [7] In the manufacturing method described in any of [1] to [6] above, the elongated phase difference film may be a transversely uniaxially oriented film or a biaxially oriented film of a resin film.[8] According to another aspect of the present invention, a method for manufacturing an optical laminate is provided, comprising a polarizing member including an absorbing polarizing film, a λ / 4 phase difference member A disposed on the first main surface side of the polarizing member, and a λ / 4 phase difference member B disposed on the second main surface side of the polarizing member, the method comprising: obtaining a λ / 4 phase difference film piece A by the method for manufacturing a phase difference film piece described in any of [1] to [7] above, and bonding the λ / 4 phase difference film piece A to the polarizing member as the λ / 4 phase difference member A. [9] The manufacturing method described in [8] above may further include punching out a λ / 4 phase difference film piece B from a long phase difference film that was not selected in the preparation of the long phase difference film in the method for manufacturing a phase difference film piece described in any of [1] to [7] above, and bonding the λ / 4 phase difference film piece B to the polarizing member as the λ / 4 phase difference member B.

[0007] According to the method for manufacturing a phase difference film piece according to an embodiment of the present invention, a phase difference film piece with suppressed axial angle variation can be efficiently obtained, and as a result, it can contribute to the manufacture of high-definition display systems (e.g., VR goggles, etc.).

[0008] This is a schematic diagram illustrating Boeing. (a) to (c) are schematic diagrams illustrating an example of Boeing. (a) and (b) are schematic diagrams illustrating an example of Boeing. (a) to (c) are schematic diagrams illustrating the relationship between punching out a phase difference film piece and the axis angle. (a) to (c) are schematic diagrams illustrating the relationship between punching out a phase difference film piece and the axis angle. This is a schematic diagram illustrating the punching out of a phase difference film piece in a method for manufacturing a phase difference film piece according to one embodiment of the present invention. This is a schematic diagram showing the general configuration of an example of a display system in which a phase difference film piece obtained by a method for manufacturing a phase difference film piece according to an embodiment of the present invention can be used. This is a schematic cross-sectional view illustrating the configuration of an optical laminate obtained by a method for manufacturing an optical laminate according to an embodiment of the present invention.

[0009] Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these embodiments. While the drawings may schematically represent the width, thickness, shape, etc., of each part compared to the embodiments for clarity, they are merely examples and do not limit the interpretation of the present invention.

[0010] (Definitions of Terms and Symbols) The definitions of terms and symbols used herein are as follows: (1) Refractive Index (nx, ny, nz) "nx" is the refractive index in the direction in which the refractive index in the plane is maximum (i.e., in the direction of the slow phase axis), "ny" is the refractive index in the direction perpendicular to the slow phase axis in the plane (i.e., in the direction of the fast phase axis), and "nz" is the refractive index in the thickness direction. (2) In-Plane Phase Difference (Re) "Re(λ)" is the in-plane phase difference measured with light of wavelength λnm at 23°C. For example, "Re(550)" is the in-plane phase difference measured with light of wavelength 550nm at 23°C. Re(λ) can be calculated by the formula: Re(λ) = (nx - ny) × d, where d (nm) is the thickness of the layer (film). (3) Phase Difference in the Thickness Direction (Rth) "Rth(λ)" is the phase difference in the thickness direction measured with light of wavelength λnm at 23°C. For example, "Rth(550)" is the phase difference in the thickness direction measured with light of a wavelength of 550 nm at 23°C. Rth(λ) is obtained by the formula: Rth(λ) = (nx - nz) × d, where d (nm) is the thickness of the layer (film). (4) Nz coefficient The Nz coefficient is obtained by Nz = Rth / Re. (5) Angle When an angle is referred to in this specification, unless otherwise specified, the angle includes both clockwise and counterclockwise with respect to the reference direction. Therefore, for example, "45°" means ±45°. Also in this specification, "approximately parallel" includes the range of 0° ± 10°, preferably within the range of 0° ± 5°. "Approximately orthogonal" includes the range of 90° ± 10°, preferably within the range of 90° ± 5°.

[0011] A. Method for Manufacturing Phase Difference Film Pieces According to one aspect of the present invention, a method for manufacturing phase difference film pieces is provided. The method for manufacturing phase difference film pieces according to an embodiment of the present invention includes: Step I: preparing a long phase difference film; and Step II: repeatedly punching out one phase difference film piece for every N rows from the 1st row to the Nth row extending in the longitudinal direction in the width direction of the long phase difference film. In Step II, N is an integer of 2 or more, and the punching out of the phase difference film pieces is performed using punching blades for the 1st row to the Nth row, which are prepared for each row. In the above method for manufacturing phase difference film pieces, the long phase difference film is typically a stretched film of a resin film. As shown in Figure 1, when a long resin film 3 is stretched using a tenter stretching device 1, deformation occurs in the center of the width direction that is delayed or preceded by the ends, so-called bowing, which can result in differences in physical properties such as a difference in the angle of the orientation axis A between the center and the ends in the width direction (in the illustrated example, the center is delayed). The degree and shape of the deformation of the above-mentioned phase difference film can vary depending on subtle differences in the film forming material, stretching conditions, etc. For example, the degree of deformation may differ as shown in Figures 2(a) to 2(c), and the deformation may be asymmetrical as shown in Figures 3(a) and 3(b). Therefore, when punching out multiple phase difference film pieces 110 having a predetermined axial angle in the width direction from a long phase difference film 100, if a punching blade with a constant blade angle is used for multiple long phase difference films, there is a problem that variations will occur in the axial angle of the resulting phase difference film pieces (see, for example, Figures 4(a) to 4(c)). The above problem can be solved by adjusting the blade angle of each punching blade according to the degree and shape of the deformation of each long phase difference film 100 to be punched out, as shown in Figures 5(a) to 5(c), but this complicates production management. In contrast, in the method for manufacturing a phase difference film piece according to an embodiment of the present invention, the long phase difference film to be punched and the punching blade are appropriately selected so that the lagging axis angle at the widthwise end of the long phase difference film and the blade angle of the punching blade have a predetermined relationship.This allows for the efficient production of phase difference film pieces with reduced axial angle variation without having to adjust the blade angle of each punching die for each elongated phase difference film according to the degree and shape of the Boeing. The axial angle of a phase difference film piece is the angle between the reference direction and the slow phase axis direction in the phase difference film piece. The reference direction of the phase difference film piece can be set to any direction. The slow phase axis direction of the phase difference film piece can be measured at the center position of the phase difference film piece (e.g., the center of gravity). The punching die has a shape corresponding to the phase difference film piece. The blade angle of the punching die is the angle between the direction corresponding to the reference direction of the phase difference film piece in the punching die and the width direction of the elongated phase difference film. Unless otherwise specified, "width direction" refers to the width direction of the elongated phase difference film and is perpendicular to the elongated direction. Below, an embodiment in which multiple rectangular phase difference film pieces having a slow phase axis in a direction parallel to the short side direction in the width direction are punched out from an elongated phase difference film will be specifically described. In this embodiment, the reference direction of the phase difference film piece is set to the short-side direction, and the target value of the axial angle (the angle between the short-side direction and the slow-phase direction) is set to 0°. Therefore, the blade angle of the punching blade is the angle between the short-side direction of the punching blade and the width direction of the elongated phase difference film. However, the present invention is not limited to the above embodiment. For example, the axial angle of the phase difference film piece may be an angle other than 0°. Also, for example, the shape of the phase difference film piece may be any shape such as a rectangle, square, ellipse, or circle.

[0012] In step I, a long phase difference film is prepared. In this specification, "long" means an elongated shape in which the length is sufficiently longer than the width, and for example, includes an elongated shape in which the length is 10 times or more, preferably 20 times or more, than the width. The length in the longitudinal direction of the long phase difference film may be, for example, 100 m or more or 500 m or more, or for example, 2000 m or less or 1000 m or less. The length in the width direction of the long phase difference film may be, for example, 500 mm or more or 900 mm or more, or for example, 1500 mm or less or 1200 mm or less. The long phase difference film may be wound in a roll shape.

[0013] A long phase difference film can have any suitable optical properties depending on the application. For example, a long phase difference film exhibits a refractive index characteristic of nx > ny ≥ nz. Here, "ny = nz" includes not only the case where ny and nz are exactly equal, but also the case where they are substantially equal. Therefore, there may be cases where ny < nz. The Nz coefficient of the long phase difference film is preferably 0.9 to 3, more preferably 0.9 to 2.5, even more preferably 0.9 to 1.5, and particularly preferably 0.9 to 1.3.

[0014] The in-plane phase difference Re(550) of the elongated phase difference film is, for example, 100 nm to 190 nm, but may also be 110 nm to 180 nm, 130 nm to 160 nm, or 135 nm to 155 nm. Preferably, the elongated phase difference film exhibits an inverse dispersion wavelength characteristic in which the phase difference value increases with the wavelength of the measured light. The Re(450) / Re(550) of the elongated phase difference film is, for example, 0.75 or more and less than 1, and may also be 0.8 or more and 0.95 or less.

[0015] The elongated phase difference film is composed of a stretched film of any suitable resin film. Examples of resins included in the resin film include polycarbonate resins, polyester carbonate resins, polyester resins, polyvinyl acetal resins, polyarylate resins, cyclic olefin resins, cellulose resins, polyvinyl alcohol resins, polyamide resins, polyimide resins, polyether resins, polystyrene resins, and acrylic resins. These resins may be used individually or in combination. Methods of combination include, for example, blending and copolymerization. When the elongated phase difference film exhibits inverse dispersion wavelength characteristics, a resin film containing a polycarbonate resin or a polyester carbonate resin (hereinafter sometimes simply referred to as a polycarbonate resin) can be suitably used.

[0016] As the polycarbonate resin described above, any suitable polycarbonate resin can be used as long as the effects of the present invention are obtained. For example, the polycarbonate resin contains structural units derived from fluorene-based dihydroxy compounds, structural units derived from isosorbide-based dihydroxy compounds, and structural units derived from at least one dihydroxy compound selected from the group consisting of alicyclic diols, alicyclic dimethanol, di, tri, or polyethylene glycol, and alkylene glycol or spiroglycol. Preferably, the polycarbonate resin contains structural units derived from fluorene-based dihydroxy compounds, structural units derived from isosorbide-based dihydroxy compounds, structural units derived from alicyclic dimethanol, and / or structural units derived from di, tri, or polyethylene glycol; more preferably, it contains structural units derived from fluorene-based dihydroxy compounds, structural units derived from isosorbide-based dihydroxy compounds, and structural units derived from di, tri, or polyethylene glycol. The polycarbonate resin may optionally contain structural units derived from other dihydroxy compounds. Details of polycarbonate resins suitably used in long phase difference films are described, for example, in Japanese Patent Publication No. 2014-10291, Japanese Patent Publication No. 2014-26266, Japanese Patent Publication No. 2015-212816, Japanese Patent Publication No. 2015-212817, and Japanese Patent Publication No. 2015-212818, and the descriptions in these publications are incorporated herein by reference.

[0017] The stretching of the resin film may be, for example, transverse uniaxial stretching or biaxial stretching. Biaxial stretching may be simultaneous biaxial stretching or sequential biaxial stretching. Simultaneous biaxial stretching is preferred. Stretching conditions such as stretching ratio and stretching temperature can be appropriately set according to the forming material of the resin film, the desired optical properties, etc. In one embodiment, a long phase difference film may be a polycarbonate resin film that has been preheated for, for example, 20 to 30 seconds at 135°C to 170°C, preferably 145°C to 160°C using a tenter stretching device, and then transverse uniaxial or biaxial stretched at 135°C to 150°C, preferably 135°C to 145°C, with stretching ratios of, for example, 1 to 5 times, preferably 1 to 3 times, in the longitudinal direction (MD) and for example, 1 to 5 times, preferably 1.5 to 4 times, more preferably 2 to 3 times, in the width direction (TD). By stretching a polycarbonate resin film under these conditions, a phase difference film having the above optical properties (specifically, a phase difference film having a refractive index characteristic of nx > ny ≥ nz and Re(550) in the range of 100 nm to 190 nm) can be suitably obtained.

[0018] The above-mentioned elongated phase difference film has orientation axes at different angles in the width direction at its center and ends, according to Boeing. Specifically, the slow phase axis of the elongated phase difference film extends in the width direction, and the center in the width direction may have a curved shape that is convex or concave.

[0019] In step II, one phase difference film piece is punched out from the elongated phase difference film in the width direction, for every N rows from the first to the Nth row extending in the elongated direction. N is an integer of 2 or more, preferably an integer from 3 to 10, and may be an integer from 4 to 8. In other words, the number of phase difference film pieces punched out in the width direction of the elongated phase difference film is 2 or more, preferably 3 to 10, and may be 4 to 8. For example, in the embodiment shown in Figure 6, in a plan view, five rows from the first to the fifth row are set from the left end to the right end of the elongated phase difference film 100, and one phase difference film piece 110 is punched out from each row in the width direction. The width lengths of the first to Nth rows are not limited to the range in which one phase difference film piece can be punched out in each row, and may be the same or different from each other. The width length of each row may be, for example, 0.1 to 0.3 times the width length of the elongated phase difference film. Furthermore, in a long-length phase difference film, adjacent rows may partially overlap. For example, if the first and second rows partially overlap, the punching margin of the first row can be used to punch out phase difference film pieces in the second row, and the punching margin of the second row can be used to punch out phase difference film pieces in the first row.

[0020] The above-mentioned phase difference film pieces are punched out using punching blades prepared for each row, from the first row to the Nth row. Each of the punching blades for the first to Nth rows is set to a predetermined blade angle.

[0021] In process I, a long phase difference film satisfying the following (i) and (ii) is selected as the long phase difference film to be used in process II. Preferably, a plurality of long phase difference films are selected from the viewpoint of suitably obtaining the effects of the present invention. (i) The angles θ1 and θn of the slow axis with respect to the width direction in the first and Nth rows are between Xa° and Xb°. (ii) When the cutting angle of the punching blade for the first row is Y1° and the cutting angle of the punching blade for the Nth row is Yn°, the relationship Y1 = Yn = (Xa + Xb) / 2 holds. Typically, the angles θ1 and θn and Y1 and Yn are angles that rotate in opposite directions with respect to the width direction. For example, if angles θ1 and Y1 are clockwise angles with respect to the width direction, angles θn and Yn may be counterclockwise angles with respect to the width direction. Furthermore, the above-mentioned "Y1 = Yn = (Xa + Xb) / 2" includes not only the case where Y1, Yn, and (Xa + Xb) / 2 are exactly equal to each other, but also the case where they are substantially equal. For example, Y1 and Y2 may be values ​​obtained by rounding down, rounding up, rounding to the nearest integer, etc., of (Xa + Xb) / 2 to a convenient number (for example, to the nearest 0.05°, 0.1°, or 0.2°). In one embodiment, the difference between Y1 or Yn and (Xa + Xb) / 2 may be, for example, 0° to 0.2°, preferably 0 to 0.1°. The difference between Y1 and Yn may be, for example, 0° to 0.2°, preferably 0 to 0.1°. In other words, the relationship "Y1 = Yn = (Xa + Xb) / 2" allows the difference between Y1 and Yn, the difference between Y1 and (Xa + Xb) / 2, and the difference between Yn and (Xa + Xb) / 2 to be between 0 and 0.2.

[0022] If (i) and (ii) above are satisfied, the axial angle of the phase difference film piece punched out in the first column and the axial angle of the phase difference film piece punched out in the Nth column can both be less than or equal to |Xa - Xb| / 2.

[0023] The blade angles Y1° and Yn° can be appropriately set, respectively, taking into account the shape and degree of bowing in the elongated phase difference film. For example, the blade angles Y1° and Yn° can be set by (a) measuring the lagging axis angles (e.g., lagging axis angles with respect to the width direction) in the first and Nth columns for a plurality of elongated phase difference films manufactured under predetermined conditions, (b) calculating the median lagging axis angles in the first column and the median lagging axis angles in the Nth column, and (c) setting the blade angles so that a phase difference film piece with the desired axis angle is obtained by taking the average of the median lagging axis angles in the first column and the median lagging axis angles in the Nth column as the lagging axis angle in those columns. In this case, the blade angles Y1° and Yn° will be approximately equal angles in the clockwise or counterclockwise direction with respect to the width direction. With respect to (c) above, the blade angles Y1° and Yn° do not need to correspond strictly to the average of the median values ​​of the lagging axis angles, and can be rounded to a convenient number (the same applies to the blade angles of the punching blades for the columns between the first and Nth columns, as described later). For example, if the average of the median values ​​of the lagging axis angles is 1.35°, Y1 and Yn may be 1.3°, 1.4°, 1.5°, etc. The difference between the average of the median values ​​of the lagging axis angles and Y1 and Yn may be, for example, 0° to 0.2°. The median value of the lagging axis angle in each column can be determined, for example, by measuring 20 or more, preferably 32 or more, elongated phase difference films.

[0024] Furthermore, in long phase difference films with bowing, generally, the change in the orientation axis angle is small in the center in the width direction, and the change in the orientation axis angle increases towards the ends. Therefore, when N≧3, it is preferable that the blade angle of the punching blade for the first to the Nth row decreases from the end rows to the central rows. The blade angle of the punching blade for the central row may be, for example, within the range of 0°±0.5°, or for example, within the range of 0°±0.3°. By setting the blade angle of the punching blade for the rows between the first and Nth rows as described above, variations in the axis angle of the phase difference film pieces punched in these rows can also be suppressed.

[0025] For example, the blade angle of a punching blade for a row between the first and the Nth row can be set by measuring the lagging axis angle in each row for a plurality of elongated phase difference films manufactured under predetermined conditions, calculating the median value of the lagging axis angles in each row, and setting the blade angle such that a phase difference film piece with the desired axis angle can be obtained when the median value is used as the lagging axis angle in each row. Alternatively, for example, the blade angle of a punching blade for a row between the first and the Nth row can be set so that the blade angles of the punching blades for rows 1 through N change symmetrically around the central row. In this case, the difference in blade angles between adjacent rows may be constant (i.e., arithmetic) or not.

[0026] In one embodiment, the cutting angles of the punching blades for the first to Nth rows can be set by measuring the lagging axis angle in each row with respect to a plurality of elongated phase difference films, calculating the median value of the lagging axis angles in each row, and setting the cutting angles so that a phase difference film piece having the desired axis angle is obtained by taking the average of the median values ​​of the lagging axis angles in two rows located symmetrically to the central row (the central first row when N is odd, and the central second row when N is even) as the lagging axis angle in these rows. As a specific example, when N=7, the cutting angles of the punching blades for the first and seventh columns may be set to the average of the median values ​​of the lagging axis angles in the first and seventh columns, the cutting angles of the punching blades for the second and sixth columns may be set to the average of the median values ​​of the lagging axis angles in the second and sixth columns, the cutting angles of the punching blades for the third and fifth columns may be set to the average of the median values ​​of the lagging axis angles in the third and fifth columns, and the cutting angle of the punching blade for the fourth column may be set to the median value of the lagging axis angles in the fourth column. As another specific example, when N=6, the cutting angles of the punching blades for the first and sixth columns may be set to the average of the median values ​​of the lagging axis angles in the first and sixth columns, the cutting angles of the punching blades for the second and fifth columns may be set to the average of the median values ​​of the lagging axis angles in the second and fifth columns, and the cutting angles of the punching blades for the third and fourth columns may be set to the average of the median values ​​of the lagging axis angles in the third and fourth columns. However, the cutting angle of the punching blade for the central column may be, for example, within the range of 0°±0.5° or, for example, within the range of 0°±0.3°. According to the above embodiment, the cutting angles of the punching blades for the first to Nth columns may change symmetrically around the central column.

[0027] The lagging axis angle in each row of a long phase difference film can be measured at a position corresponding to the center position (e.g., the centroid) of the punched-out phase difference film piece (the position marked with an "x" in Figure 6). The lagging axis angle in each row may be measured at any point along the longitudinal direction of the long phase difference film. Alternatively, the average of measurements taken at multiple points along the longitudinal direction may be adopted as the lagging axis angle for each row. In one embodiment, the lagging axis angle in each row can be measured in the start and / or end regions of the long phase difference film, and the measurement taken in the start region, the measurement taken in the end region, or their average value can be adopted as the lagging axis angle for each row. Here, the start region and the end region may be the regions in the long phase difference film where the first and last phase difference film pieces are punched out, respectively.

[0028] Within each elongated phase difference film, the shape and degree of boeing do not change significantly in the longitudinal direction and remain approximately constant. Therefore, even if the punching of N phase difference film pieces in the width direction is repeated in the longitudinal direction without changing the blade angle of the punching blades for each row from the first row to the Nth row, the axial angle of the phase difference film pieces punched in each row does not change significantly and remains approximately constant. Thus, according to the above method for manufacturing phase difference film pieces, in step II, for a plurality of elongated phase difference films selected in step I, by repeatedly punching phase difference film pieces in the longitudinal direction without adjusting the blade angle of the punching blades for each row of each elongated phase difference film to be punched, phase difference film pieces with suppressed axial angle variations can be efficiently obtained.

[0029] Xa and Xb can be appropriately set according to the allowable variation in the axial angle of the phase difference film piece, the blade angles Y1° and Yn°, etc. Specifically, the difference between Xa and Xb can be set according to the allowable variation in the axial angle of the phase difference film piece, and Xa and Xb can be set according to the difference between Xa and Xb and the blade angles Y1° and Yn°. For example, if the allowable variation in the axial angle of the phase difference film piece is within the range of a set angle ± A°, Xa and Xb can be set to satisfy the relationship Xb - Xa ≤ A, preferably A × 0.5 ≤ Xb - Xa ≤ A × 0.9.

[0030] The blade angles Y1° and Yn° may vary depending on the shape and degree of bowing in the elongated phase difference film. The blade angles Y1° and Yn° may be, for example, 0.5° or more, 0.8° or more, or 1.0° or more, and may also be, for example, 3.0° or less, 2.0° or less, or 1.5° or less.

[0031] The difference between Xa and Xb (Xb-Xa) can be set according to the allowable variation in the axial angle of the phase difference film piece. Xb-Xa can be, for example, 1.2 or less, 1.0 or less, or 0.8 or less, or for example, 0.3 or more. When Xb-Xa is within the above range, phase difference film pieces can be manufactured with high production efficiency while suppressing the variation in axial angle to, for example, 1.2° or less, 1.0° or less, or 0.8° or less.

[0032] In one embodiment, Xb-Xa may be 0.8 or less, Xa may be 0.8 to 1.2, and Xb may be 1.5 to 2.0. When Xa and Xb are within the above ranges and the above relationship is satisfied, phase difference film pieces with axis angle variations suppressed to within ±1.0° can be efficiently obtained without adjusting the blade angle of the punching blade for each row for each long phase difference film to be punched.

[0033] In one embodiment, Xb-Xa may be 1.3 or less, Xa may be 0.5 to 1.2, and Xb may be 1.5 to 2.5. When Xa and Xb are within the above ranges and the above relationship is satisfied, phase difference film pieces can be efficiently obtained in which the variation in axis angle is suppressed to, for example, within ±1.5° without adjusting the blade angle of the punching blade for each row for each long phase difference film to be punched.

[0034] B. Display System Figure 7 is a schematic diagram showing the general configuration of an example of a display system in which a phase difference film piece obtained by the method for manufacturing a phase difference film piece described in Section A can be used. Figure 7 schematically illustrates the arrangement and shape of each component of the display system 2. The display system 2 comprises a display element 12, a reflective polarizing member 14, a first lens portion 16, a half mirror 18, a first phase difference member 20, a second phase difference member 22, and a second lens portion 24. The reflective polarizing member 14 is positioned in front of the display element 12 on the display surface 12a side and can reflect light emitted from the display element 12. The first lens portion 16 is positioned in the optical path between the display element 12 and the reflective polarizing member 14, and the half mirror 18 is positioned between the display element 12 and the first lens portion 16. The first phase difference member 20 is positioned in the optical path between the display element 12 and the half mirror 18, and the second phase difference member 22 is positioned in the optical path between the half mirror 18 and the reflective polarizing member 14.

[0035] The display element 12 is, for example, a liquid crystal display or an organic EL display, and has a display surface 12a for displaying an image. The light emitted from the display surface 12a passes through a polarizing member (typically a polarizing film) that may be included in the display element 12, and is emitted as first linearly polarized light.

[0036] The first phase difference member 20 includes a first λ / 4 member capable of converting a first linearly polarized light incident on the first phase difference member 20 into a first circularly polarized light. If the first phase difference member does not include any members other than the first λ / 4 member, the first phase difference member may correspond to the first λ / 4 member. The first phase difference member 20 may be provided integrally with the display element 12.

[0037] The half mirror 18 transmits light emitted from the display element 12 and reflects the light reflected by the reflective polarizing member 14 back towards the reflective polarizing member 14. The half mirror 18 is integrally provided with the first lens portion 16.

[0038] The second phase difference member 22 includes a second λ / 4 member that can transmit light reflected by the reflective polarizing member 14 and the half mirror 18 through the reflective polarizing member 14. If the second phase difference member does not include any members other than the second λ / 4 member, the second phase difference member may correspond to the second λ / 4 member. The second phase difference member 22 may be provided integrally with the first lens portion 16.

[0039] The first circularly polarized light emitted from the first λ / 4 member included in the first phase difference member 20 passes through the half mirror 18 and the first lens portion 16 and is converted into a second linearly polarized light by the second λ / 4 member included in the second phase difference member 22. The second linearly polarized light emitted from the second λ / 4 member is reflected toward the half mirror 18 without passing through the reflective polarizing member 14. At this time, the polarization direction of the second linearly polarized light incident on the reflective polarizing member 14 is in the same direction as the reflection axis of the reflective polarizing member. Therefore, the second linearly polarized light incident on the reflective polarizing member is reflected by the reflective polarizing member.

[0040] The second linearly polarized light reflected by the reflective polarizing member 14 is converted into a second circularly polarized light by the second λ / 4 member included in the second phase difference member 22. The second circularly polarized light emitted from the second λ / 4 member passes through the first lens portion 16 and is reflected by the half mirror 18. The second circularly polarized light reflected by the half mirror 18 passes through the first lens portion 16 and is converted into a third linearly polarized light by the second λ / 4 member included in the second phase difference member 22. The third linearly polarized light is transmitted through the reflective polarizing member. At this time, the polarization direction of the third linearly polarized light incident on the reflective polarizing member 14 is in the same direction as the transmission axis of the reflective polarizing member. Therefore, the third linearly polarized light incident on the reflective polarizing member 14 is transmitted through the reflective polarizing member.

[0041] Light that has passed through the reflective polarizing member 14 passes through the second lens portion 24 and enters the user's eye 26.

[0042] Although not shown in the figure, the display system 2 may include an absorptive polarizing member (typically, an absorptive polarizing film) in front of the reflective polarizing member 14. The reflection axis of the reflective polarizing member and the absorption axis of the absorptive polarizing member may be arranged substantially parallel to each other, and the transmission axis of the reflective polarizing member and the transmission axis of the absorptive polarizing member may be arranged substantially parallel to each other. Accordingly, the third linearly polarized light transmitted through the reflective polarizing member can pass through the absorptive polarizing member as it is.

[0043] For example, the absorption axis of the polarizing member that may be included in the display element 12 and the reflection axis of the reflective polarizing member 14 may be arranged substantially parallel to each other or substantially orthogonal to each other. The angle between the absorption axis of the polarizing member that may be included in the display element 12 and the slow axis of the first λ / 4 member included in the first retardation member 20 is, for example, 40° to 50°, may be 42° to 48°, or may be approximately 45°. The angle between the absorption axis of the polarizing member that may be included in the display element 12 and the slow axis of the second λ / 4 member included in the second retardation member 22 is, for example, 40° to 50°, may be 42° to 48°, or may be approximately 45°.

[0044] The in-plane retardation Re (550) of the first λ / 4 member is, for example, 100 nm to 190 nm, may be 110 nm to 180 nm, may be 130 nm to 160 nm, or may be 135 nm to 155 nm. Preferably, the first λ / 4 member exhibits reverse dispersion wavelength characteristics in which the retardation value increases with the wavelength of the measurement light. Re (450) / Re (550) of the first λ / 4 member is, for example, 0.75 or more and less than 1, and may be 0.8 or more and 0.95 or less.

[0045] The in-plane retardation Re (550) of the second λ / 4 member is, for example, 100 nm to 190 nm, may be 110 nm to 180 nm, may be 130 nm to 160 nm, or may be 135 nm to 155 nm. Preferably, the second λ / 4 member exhibits reverse dispersion wavelength characteristics in which the retardation value increases with the wavelength of the measurement light. Re (450) / Re (550) of the second λ / 4 member is, for example, 0.75 or more and less than 1, and may be 0.8 or more and 0.95 or less.

[0046] The reflective polarizing member 14 transmits polarized light parallel to its transmission axis (typically linearly polarized light) while maintaining the polarization state thereof, and can reflect light in other polarization states (typically light in a polarization state orthogonal to the transmission axis). The reflective polarizing member is typically constituted by a film having a multilayer structure (which may be referred to as a reflective polarizing film). In this case, the thickness of the reflective polarizing member is, for example, 10 μm to 150 μm, preferably 20 μm to 100 μm, and more preferably 30 μm to 60 μm. Commercially available reflective polarizing films include, for example, those manufactured by 3M Company under the trade names "DBEF" and "APF", and those manufactured by Nitto Denko Corporation under the trade name "APCF".

[0047] The orthogonal transmittance (Tc) of the reflective polarizing member (reflective polarizing film) can be, for example, 0.001% to 3%. The single-piece transmittance (Ts) of the reflective polarizing member (reflective polarizing film) is, for example, 43% to 49%, preferably 45% to 47%. The degree of polarization (P) of the reflective polarizing member (reflective polarizing film) can be, for example, 92% to 99.99%.

[0048] The polarizing member that may be included in the display element 12 and the absorptive polarizing member that may be disposed in front of the reflective polarizing member 14 typically may include a resin film containing a dichroic substance as an absorptive polarizing film. The orthogonal transmittance (Tc) of the polarizing member or the absorptive polarizing member is preferably 0.5% or less, more preferably 0.1% or less, and still more preferably 0.05% or less. The single-piece transmittance (Ts) of the polarizing member or the absorptive polarizing member is, for example, 41.0% to 45.0%, preferably 42.0% or more. The degree of polarization (P) of the polarizing member or the absorptive polarizing member is, for example, 99.0% to 99.997%, preferably 99.9% or more.

[0049] The above orthogonal transmittance, single-element transmittance, and polarization degree can be measured, for example, using a UV-Vis spectrophotometer. The polarization degree P can be calculated using a UV-Vis spectrophotometer to measure the single-element transmittance Ts, parallel transmittance Tp, and orthogonal transmittance Tc, and then calculated from the obtained Tp and Tc using the following formula. Note that Ts, Tp, and Tc are Y values ​​measured using a 2-degree field of view (C light source) according to JIS Z8701 and corrected for luminous efficiency. Polarization degree P (%) = {(Tp - Tc) / (Tp + Tc)} １／２ ×100

[0050] As described above, in the display system 2, linearly polarized light emitted forward from the display surface 12a of the display element 12 passes through the first phase difference member 20 and the second phase difference member 22 in that order, then passes through the second phase difference member 22 two more times due to reflection by the reflective polarizing member 14 and re-reflection by the half mirror 18, and then passes through the reflective polarizing member 14 and is emitted forward, making it visible to the viewer. Therefore, if the axis angles of the first λ / 4 member and the second λ / 4 member deviate from the set angle, the polarization state of the light will be disrupted, and problems such as light that should be reflected being visible and light that should be transmitted being re-reflected may occur (as a result, the accuracy of the image may decrease). In order to prevent such problems, it is desirable that the axis angles of the first λ / 4 member and the second λ / 4 member be strictly controlled.

[0051] In the phase difference film piece obtained by the manufacturing method of the phase difference film piece described in Section A, variations in the axis angle are suppressed. Therefore, the phase difference film piece obtained by the above manufacturing method can be preferably used as the first λ / 4 member and the second λ / 4 member in the display system 2.

[0052] In the above-described display system 2, if the display element 12 is an organic EL display, a third λ / 4 member may be placed behind the polarizing member that emits the first linearly polarized light, that is, on the opposite side from the side where the first phase difference member 20 is placed, for the purpose of preventing reflection. In this case, in the manufacture of the display system 2, an optical laminate 50 having a first λ / 4 member 21, a polarizing member 10, and a third λ / 4 member 23 in this order may be used, as shown in Figure 8. In the optical laminate 50, the first λ / 4 member 21 is placed on the first main surface side (front side) of the polarizing member 10 via an adhesive layer 32. The third λ / 4 member 23 is placed on the second main surface side (rear side) of the polarizing member 10 via an adhesive layer 34. The optical laminate 50 further has an adhesive layer 36 on the side of the third λ / 4 member 23 opposite to the side where the polarizing member 10 is placed. The optical laminate 50 can be bonded to adjacent members via an adhesive layer 36, thereby integrating it with the organic EL display 12. The polarizing member 10 may be an absorptive polarizing member. The adhesive layers 32 and 34 may be adhesive layers or tack layers. The optical laminate 50 may further have any suitable members (e.g., other phase difference members, protective members) depending on the purpose.

[0053] The same description as for the first and second λ / 4 members may be applied to the third λ / 4 member described above. The third λ / 4 member 23 may be positioned such that its slow axis forms an angle with the absorption axis of the polarizing member 10 of, for example, 40° to 50°, 42° to 48°, or about 45°. On the other hand, unlike the first and second λ / 4 members, the third λ / 4 member 23 is not required to have precise control of its axial angle with the polarizing member 10. Therefore, the optical laminate may be obtained by a manufacturing method that includes obtaining a λ / 4 phase difference film piece by the method for manufacturing a phase difference film piece described in Section A (Step A), and laminating the λ / 4 phase difference film piece with the polarizing member as the first λ / 4 member (Step B). In the above manufacturing method, the λ / 4 phase difference film piece may be laminated with the polarizing member as the first λ / 4 member and the third λ / 4 member.

[0054] In one embodiment, the method for manufacturing the optical laminate may further include step C, which involves punching out phase difference film pieces (λ / 4 phase difference film pieces) from a long phase difference film that was not selected in step I of the method for manufacturing phase difference film pieces described in Section A. In this embodiment, the λ / 4 phase difference film piece obtained in step A can be bonded to the polarizing member as a first λ / 4 member, and the λ / 4 phase difference film piece obtained in step C can be bonded to the polarizing member as a third λ / 4 member.

[0055] The present invention will be specifically described below with reference to examples, but the present invention is not limited in any way by these examples.

[0056] [Example 1] Multiple elongated phase difference films were prepared as follows, and rectangular phase difference film pieces were punched out so that the slow phase axis direction was parallel to the short side direction. <1> Elongated polyester carbonate resin films were manufactured in the same manner as in Manufacturing Example 1 of Japanese Patent Application Publication No. 2023-134317. Multiple elongated phase difference films capable of functioning as λ / 4 members were manufactured by uniaxially stretching the obtained elongated polyester carbonate resin films at a predetermined stretching temperature and stretching ratio. <2> For 20 or more elongated phase difference films manufactured in <1> above, the slow phase axis angle with respect to the width direction of each row was measured with N=5, and the median value was determined. <3> Based on the average of the median of the lagging axis angle of the first column and the median of the lagging axis angle of the fifth column, the average of the median of the lagging axis angle of the second column and the median of the lagging axis angle of the fourth column, and the median of the lagging axis angle of the third column, the cutting angles of the punching blades for the first, second, third, fourth, and fifth columns were set to -1.3°, -0.7°, 0°, 0.7°, and 1.3°, respectively (Y1=Y5=1.3). <4> From the elongated phase difference films produced in <1> above, elongated phase difference films were selected in which the lagging axis angles of the first and fifth columns were between 1.0° and 1.7° clockwise or counterclockwise with respect to the width direction (Xa=1.0, Xb=1.7). The ratio of the number of selected elongated phase difference films to the number of elongated phase difference films produced in <1> above was approximately 80%. <5> The elongated phase difference film selected in <4> above was punched continuously in the elongated direction using the punching blades for the first to fifth rows without adjusting the blade angle. The axial angle (angle between the short side direction and the slow axis) of the phase difference film pieces obtained in this manner was measured, and the Cpk for the production of phase difference film pieces with an axial angle variation within ±1.0° was 1.33 or higher.

[0057] The present invention is not limited to the embodiments described above, and various modifications are possible. For example, the configurations shown in the embodiments above can be replaced with configurations that are substantially the same, configurations that produce the same effects, or configurations that can achieve the same purpose.

[0058] The method for manufacturing a phase difference film piece according to an embodiment of the present invention can be suitably used, for example, in the manufacture of display systems such as VR goggles.

[0059] 2 Display system, 12 Display element, 14 Reflective polarizing member, 16 First lens section, 18 Half mirror, 20 First phase difference member, 22 Second phase difference member, 24 Second lens section, 100 Long phase difference film, 110 Phase difference film piece

Claims

1. A method for manufacturing a phase difference film piece, comprising: preparing a long phase difference film; and repeatedly punching out one phase difference film piece for every N rows from the first to the Nth row extending in the longitudinal direction in the width direction of the long phase difference film, wherein the long phase difference film is a stretched film of a resin film, N is an integer of 2 or more, the punching out of the phase difference film piece is performed using punching blades prepared for each row from the first to the Nth row, and the preparation of the long phase difference film includes selecting a long phase difference film that satisfies the following (i) and (ii): (i) the angle of the slow axis in the first and Nth rows with respect to the width direction is Xa° or more and Xb° or less; (ii) When the cutting angle of the punching blade for the first row is Y1° and the cutting angle of the punching blade for the Nth row is Yn°, the relationship Y1 = Yn = (Xa + Xb) / 2 holds; when N ≥ 3, the punching blades for the first row to the Nth row have cutting angles that decrease toward the central row, a method for manufacturing a phase difference film piece.

2. The manufacturing method according to claim 1, wherein preparing the elongated phase difference film includes selecting a plurality of elongated phase difference films that satisfy (i) and (ii).

3. The manufacturing method according to claim 1, wherein Xa and Xb satisfy the relationship Xb - Xa ≤ 1.

0.

4. The manufacturing method according to claim 1, wherein Y1 and Yn are 1.0 or more and 1.5 or less.

5. The manufacturing method according to claim 1, wherein Xa is 0.8 or more and 1.2 or less, Xb is 1.5 or more and 2.0 or less, and Xa and Xb satisfy the relationship Xb - Xa ≤ 0.

8.

6. The manufacturing method according to claim 1, wherein N is an integer between 3 and 10.

7. The manufacturing method according to claim 1, wherein the elongated phase difference film is a transversely uniaxially oriented or biaxially oriented resin film.

8. A method for manufacturing an optical laminate comprising a polarizing member including an absorption polarizing film, a λ / 4 phase difference member A disposed on the first main surface side of the polarizing member, and a λ / 4 phase difference member B disposed on the second main surface side of the polarizing member, the method comprising: obtaining a λ / 4 phase difference film piece A by the method for manufacturing a phase difference film piece described in claim 1; and bonding the λ / 4 phase difference film piece A to the polarizing member as the λ / 4 phase difference member A.

9. The manufacturing method according to claim 8, further comprising punching out a λ / 4 phase difference film piece B from a long phase difference film that was not selected in the preparation of the long phase difference film in the manufacturing method of the phase difference film piece according to claim 1, and bonding the λ / 4 phase difference film piece B as the λ / 4 phase difference member B with the polarizing member.

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