JP7795488B2 - Manufacturing method of optical film piece and management method of long optical film - Google Patents

Description

The present invention relates to a method for manufacturing optical film pieces used in display systems such as goggles with displays, and a method for managing long optical films.

Image display devices, such as liquid crystal display devices and electroluminescence (EL) display devices (e.g., organic EL display devices), are rapidly becoming popular. Image display devices generally use optical components such as polarizing components and phase difference components to display images and improve their performance (see, for example, Patent Document 1).

In recent years, new applications for image display devices have been developed. For example, goggles with displays (VR goggles) that enable virtual reality (VR) have begun to be commercialized. Because VR goggles are being considered for use in a variety of situations, there is a demand for higher resolution.

Japanese Patent Application Laid-Open No. 2021-103286

The primary objective of the present invention is to provide optical components suitable for manufacturing display systems such as goggles with high-definition displays.

[1] A method for manufacturing an optical film piece according to an embodiment of the present invention includes the steps of preparing a first long optical film including a phase difference member, and slitting the first long optical film along its longitudinal direction to obtain a plurality of second long optical films, wherein the width of the first long optical film is 10 times or more the width of the optical film piece, and the width of the second long optical film is 1.1 times or more and 3.0 times or less the width of the optical film piece.
[2] In the above [1], the manufacturing method may further include a step of continuously punching out the optical film pieces while transporting the second long optical film in the lengthwise direction.
[3] In the above [1] or [2], the second long optical film may have an in-plane retardation variation in the long direction of 1.5 nm or less.
[4] In any one of the above [1] to [3], the manufacturing method may further include a step of classifying the plurality of second long optical films into two or more groups based on the in-plane retardation.
[5] In the above [4], the classifying step may include classifying the plurality of second long optical films into two or more groups each having a predetermined in-plane retardation width.
[6] In the above [4] or [5], the in-plane retardation may be measured before and/or after the slit.
[7] In any one of the above [4] to [6], the in-plane retardation may be measured at two or more locations on the leading end of the second long optical film.
[8] In the above [7], the in-plane retardation may be further measured at two or more locations on an end of the second long optical film.
[9] In any one of the above [1] to [8], the length of the first long optical film may be 100 m or more and 2000 m or less.
[10] In any of [1] to [9] above, the step of preparing the first long optical film may include selecting, as the first long optical film, a long optical film having an in-plane retardation variation in the width direction of 5 nm or less and an in-plane retardation variation in the longitudinal direction of 1.5 nm or less.
[11] A method for managing a long optical film according to an embodiment of the present invention includes the steps of preparing a first long optical film including a retardation member, slitting the first long optical film along its longitudinal direction to obtain a plurality of second long optical films, and classifying the plurality of second long optical films into two or more groups based on their in-plane retardation.
[12] In the above [11], the classifying step may include classifying the plurality of second long optical films into two or more groups each having a predetermined in-plane retardation width.

The method for manufacturing an optical film piece according to an embodiment of the present invention makes it possible to obtain an optical film piece with small variations in in-plane retardation. By using such an optical film piece, it is possible to suitably manufacture display systems such as goggles with high-definition displays.

1 is a schematic diagram illustrating a general configuration of a display system to which an optical film piece obtained by a method for producing an optical film piece according to an embodiment of the present invention can be applied. 2(a) and 2(b) are each a schematic cross-sectional view illustrating an example of the configuration of a first long optical film. 3 is a schematic diagram illustrating an example of step II of the method for producing an optical film piece according to an embodiment of the present invention. FIG. FIG. 3 is a schematic diagram illustrating an example of step III of the method for producing an optical film piece according to an embodiment of the present invention. FIG. 5( a ) is a schematic diagram illustrating an example of step IV of the method for producing an optical film piece according to an embodiment of the present invention, and FIG. 5( b ) is a schematic diagram of FIG. 5( a ) viewed from above.

Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these embodiments. Furthermore, to clarify the explanation, the drawings may show the width, thickness, shape, etc. of each part more schematically than in the embodiments, but this is merely an example and does not limit the interpretation of the present invention. In this specification, "elongated" means an elongated shape in which the length is sufficiently longer than the width, and includes, for example, an elongated shape in which the length is 10 times or more, preferably 20 times or more, the width.

(Definition of terms and symbols)
The definitions of terms and symbols used in this specification are as follows.
(1) Refractive index (nx, ny, nz)
"nx" is the refractive index in the direction in which the in-plane refractive index is greatest (i.e., the slow axis direction), "ny" is the refractive index in the direction perpendicular to the slow axis in the plane (i.e., the fast axis direction), and "nz" is the refractive index in the thickness direction.
(2) In-plane phase difference (Re)
"Re(λ)" is the in-plane retardation measured with light having a wavelength of λ nm at 23° C. For example, "Re(550)" is the in-plane retardation measured with light having a wavelength of 550 nm at 23° C. Re(λ) is calculated by the formula: Re(λ)=(nx-ny)×d, where d (nm) is the thickness of the layer (film).
(3) Retardation in the thickness direction (Rth)
"Rth(λ)" is the retardation in the thickness direction measured with light having a wavelength of λ nm at 23° C. For example, "Rth(550)" is the retardation in the thickness direction measured with light having a wavelength of 550 nm at 23° C. Rth(λ) is calculated 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 calculated 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 angles relative to a reference direction. Thus, for example, "45°" means ±45°. Furthermore, in this specification, "substantially parallel" includes the case of 0°±10°, for example, within the range of 0°±5°, preferably 0°±3°, and more preferably 0°±1°, and "substantially perpendicular" includes the case of 90°±10°, for example, within the range of 90°±5°, preferably 90°±3°, and more preferably 90°±1°.

A. Overview of the Display System FIG. 1 is a schematic diagram showing the overall configuration of a display system to which an optical film piece obtained by a manufacturing method for an optical film piece according to an embodiment of the present invention can be applied. FIG. 1 also shows the layout and shape of each component of a display system 2. The display system 2 includes a display element 12, a reflective polarizing element 14, a first lens unit 16, a half mirror 18, a first phase difference element 20, a second phase difference element 22, and a second lens unit 24. The reflective polarizing element 14 is disposed in front of the display surface 12a of the display element 12 and can reflect light emitted from the display element 12. The first lens unit 16 is disposed on the optical path between the display element 12 and the reflective polarizing element 14, and the half mirror 18 is disposed between the display element 12 and the first lens unit 16. The first phase difference element 20 is disposed on the optical path between the display element 12 and the half mirror 18, and the second phase difference element 22 is disposed on the optical path between the half mirror 18 and the reflective polarizing element 14. Although not shown, from the viewpoint of improving visibility, an absorptive polarizing element may be disposed between the reflective polarizing element 14 and the second lens portion 24. In this case, the reflection axis of the reflective polarizing element 14 and the absorption axis of the absorptive polarizing element may be disposed approximately parallel to each other, and the transmission axis of the reflective polarizing element 14 and the transmission axis of the absorptive polarizing element may be disposed approximately parallel to each other.

The components arranged in front of the half mirror (in the illustrated example, the half mirror 18, first lens section 16, second phase difference member 22, reflective polarizing member 14, and second lens section 24) may be collectively referred to as the lens section (lens section 4).

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, for example, a polarizing member (typically, a polarizing film) that may be included in the display element 12, and is converted into first linearly polarized light.

The first phase difference member 20 includes a first λ/4 member that can convert first linearly polarized light incident on the first phase difference member 20 into first circularly polarized light. If the first phase difference member does not include any member 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.

The half mirror 18 transmits light emitted from the display element 12 and reflects light reflected by the reflective polarizing element 14 back toward the reflective polarizing element 14. The half mirror 18 is integral with the first lens portion 16.

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 member 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.

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

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

Light that passes through the reflective polarizing element 14 passes through the second lens portion 24 and enters the user's eye 26.

For example, the absorption axis of the polarizing element included in the display element 12 and the reflection axis of the reflective polarizing element 14 may be arranged approximately parallel to each other or approximately perpendicular to each other. The angle between the absorption axis of the polarizing element included in the display element 12 and the slow axis of the first λ/4 element included in the first phase difference element 20 is, for example, 40° to 50°, or may be 42° to 48°, or may be approximately 45°. The angle between the absorption axis of the polarizing element included in the display element 12 and the slow axis of the second λ/4 element included in the second phase difference element 22 is, for example, 40° to 50°, or may be 42° to 48°, or may be approximately 45°. The first λ/4 element and the second λ/4 element are preferably arranged so that their slow axis directions are approximately parallel or approximately perpendicular to each other.

The in-plane retardation Re(550) of the first λ/4 member is, for example, 100 nm to 190 nm, or alternatively, 110 nm to 180 nm, 130 nm to 160 nm, or 135 nm to 155 nm. The first λ/4 member preferably exhibits inverse dispersion wavelength characteristics in which the retardation value increases according to the wavelength of the measurement light. The Re(450)/Re(550) of the first λ/4 member may be, for example, 0.75 or greater but less than 1, or 0.8 or greater but 0.95 or less.

The in-plane retardation Re(550) of the second λ/4 member is, for example, 100 nm to 190 nm, or alternatively, 110 nm to 180 nm, 130 nm to 160 nm, or 135 nm to 155 nm. The second λ/4 member preferably exhibits inverse dispersion wavelength characteristics in which the retardation value increases according to the wavelength of the measurement light. The Re(450)/Re(550) of the second λ/4 member may be, for example, 0.75 or greater but less than 1, or 0.8 or greater but 0.95 or less.

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 λ/4 element and the second λ/4 element in that order, then reflects off the reflective polarizing element 14 and then reflects again off the half mirror 18, passing through the second λ/4 element two more times, and then passes through the reflective polarizing element 14 and emits forward, where it is perceived by the viewer. Therefore, if the in-plane phase difference of the first λ/4 element or the second λ/4 element is large, polarization may be disrupted, causing light leakage, resulting in the light that should be reflected being mixed with the light that should be perceived (resulting in a blurred image). To prevent this problem and achieve high-resolution image display, it is desirable to have high precision in the in-plane phase difference of the first λ/4 element and the second λ/4 element. It is also desirable that the in-plane phase difference of the first λ/4 element and the second λ/4 element be highly consistent.

B. Method for Manufacturing Optical Film Pieces B-1. Overview of the Method for Manufacturing Optical Film Pieces The method for manufacturing optical film pieces according to an embodiment of the present invention includes the following steps:
Step I of preparing a first long optical film including a retardation member;
and step II of slitting the first long optical film along the longitudinal direction to obtain a plurality of second long optical films,
the width of the first long optical film is 10 times or more the width of the optical film piece;
The width of the second long optical film is 1.1 times or more and 3.0 times or less the width of the optical film piece.
In one embodiment, the method for manufacturing the optical film piece further includes step III of classifying the plurality of second long optical films into two or more groups based on the in-plane retardation.
In one embodiment, the method for producing the optical film pieces further includes a step IV of continuously punching out the optical film pieces while transporting the second long optical film in the lengthwise direction.
Since wide-width retardation members generally have variations in in-plane retardation in the width direction, there may be a large difference in in-plane retardation between optical film pieces punched at the widthwise end and those punched at the widthwise center. If optical film pieces with such variations in in-plane retardation are applied to the manufacture of the display system described in Section A, it is difficult to stably manufacture a high-definition display system. In contrast, according to a method for manufacturing an optical film piece according to an embodiment of the present invention, a wide, elongated optical film is slit along the longitudinal direction to form a narrow, elongated optical film. This allows a elongated optical film with reduced variations in in-plane retardation in the width direction to be subjected to the punching process, resulting in efficient production of optical film pieces with reduced variations in in-plane retardation.

The optical film piece obtained by the manufacturing method according to an embodiment of the present invention can have any suitable shape. In one embodiment, the optical film piece is approximately circular. In this specification, the term "approximately circular shape" includes a circle or an ellipse, and also includes a shape that is visually recognized as being close to a circle or an ellipse. For example, the approximately circular shape may be a circle, an ellipse, or a shape with irregularities formed on the periphery thereof, or a shape with part of the periphery formed by straight lines.

The ratio of the major axis to the minor axis of the optical film piece (minor axis/major axis) can be, for example, 0.8 or more and 1 or less, or, for example, 0.9 or more and 1 or less. The major axis of the optical film piece is, for example, 40 mm or more and 60 mm or less, or, for example, 42 mm or more and 50 mm or less. The major axis and minor axis of the optical film piece refer to the maximum and minimum values of the distance between parallel lines of the optical film piece, respectively.

Each step will be explained in detail below, with reference to Figures 2 to 5.

B-2. Process I
In step I, a first long optical film including a retardation member is prepared. The retardation member is, for example, the second retardation member 22 in the display system 2 described in section A, and includes a λ/4 member as the second λ/4 member. The first long optical film may be wound into a roll. Hereinafter, the first long optical film wound into a roll may be referred to as a "parent roll."

In one embodiment, the variation in in-plane retardation (e.g., Re(590)) in the longitudinal direction of the first long optical film is, for example, 3 nm or less, preferably 1.5 nm or less. The variation in in-plane retardation in the width direction of the first long optical film is, for example, 5 nm or less, preferably 3 nm or less, and, for example, 0.5 nm or more. The effects of the present invention can be suitably achieved by producing an optical film piece from a first long optical film having a small variation in in-plane retardation, via the production of a second long optical film. The variation in in-plane retardation in the longitudinal direction can be determined by measuring the in-plane retardation at any position in the width direction of the long optical film (e.g., the center in the width direction) over a predetermined length in the longitudinal direction (e.g., approximately 50 m or more, or the entire length), and calculating the difference between the maximum and minimum values. Furthermore, the variation in in-plane retardation in the width direction can be determined by measuring the in-plane retardation at multiple locations at predetermined intervals in the width direction (for example, intervals of about 30 mm to about 350 mm) at any position in the longitudinal direction of the long optical film, and calculating the difference between the maximum and minimum values.

Figures 2(a) and 2(b) are schematic cross-sectional views illustrating an example of the configuration of a first long optical film. The first long optical film 30a shown in Figure 2(a) includes, in this order, an adhesive layer 32, a λ/4 member 22a, and a protective member 34. In the optical film 30a configured as shown in Figure 2(a), the retardation member (second retardation member in the display system 2) 22 is made of a λ/4 member (second λ/4 member in the display system 2) 22a. The first long optical film 30b shown in Figure 2(b) includes, in this order, an adhesive layer 32, a λ/4 member 22a, a member (so-called positive C plate) 22b whose refractive index characteristics can exhibit the relationship nz > nx = ny, and a protective member 34. In the optical film 30b shown in FIG. 2(b), the retardation member (second retardation member in the display system 2) 22 includes a λ/4 member (second λ/4 member in the display system 2) 22a and a positive C plate 22b. In other words, the retardation member 22 has a laminated structure of the λ/4 member 22a and the positive C plate 22b. Unlike the configuration shown in FIG. 2(b), in the retardation member 22, the λ/4 member 22a may be located closer to the protective member 34 than the positive C plate 22b. In the illustrated example, the surface of the pressure-sensitive adhesive layer 32 of each of the first long optical films 30a and 30b is protected by a release liner 36. The optical film piece ultimately obtained from the long optical films 30a and 30b can be bonded to the first lens unit 16 via the pressure-sensitive adhesive layer 32 during the production of the display system 2.

The width of the first long optical film is 10 times or more, preferably 15 to 25 times, and more preferably 15 to 20 times, the width of the optical film piece to be produced. In this specification, the width of the optical film piece may be the punching width (the length indicated by arrow _X1 in FIG. 5 ) when punching the optical film piece from the second long optical film or the major axis of the optical film piece, and is preferably the punching width. In one embodiment, the width of the first long optical film is, for example, 500 mm to 1500 mm, or, for example, 900 mm to 1200 mm.

The length of the first long optical film is, for example, 100 m or more and 2000 m or less, or, for example, 500 m or more and 1000 m or less.

B-2-1. λ/4 Member As described in Section A regarding the second λ/4 member, the in-plane retardation Re(550) of the λ/4 member 22a is, for example, 100 nm to 190 nm, or may be 110 nm to 180 nm, 130 nm to 160 nm, or 135 nm to 155 nm. The λ/4 member preferably exhibits inverse dispersion wavelength characteristics in which the retardation value increases according to the wavelength of the measurement light. The Re(450)/Re(550) of the λ/4 member may be, for example, 0.75 or more and less than 1, or 0.8 or more and 0.95 or less.

The refractive index characteristics of a λ/4 member preferably satisfy the relationship nx > ny ≥ nz. Here, "ny = nz" does not only include the case where ny and nz are completely equal, but also includes the case where they are substantially equal. Therefore, there may be cases where ny < nz, as long as the effects of the present invention are not impaired. The Nz coefficient of a λ/4 member is preferably 0.9 to 3, more preferably 0.9 to 2.5, even more preferably 0.9 to 1.5, and especially preferably 0.9 to 1.3.

In one embodiment, the λ/4 member is a stretched resin film, for example, a stretched film obtained by stretching a long resin film in the width direction.

Resins contained in the resin film include polycarbonate-based resins, polyester carbonate-based resins, polyester-based resins, polyvinyl acetal-based resins, polyarylate-based resins, cyclic olefin-based resins, cellulose-based resins, polyvinyl alcohol-based resins, polyamide-based resins, polyimide-based resins, polyether-based resins, polystyrene-based resins, and acrylic-based resins. These resins may be used alone or in combination. Methods for combining them include blending and copolymerization. When the λ/4 component exhibits reverse dispersion wavelength characteristics, a resin film containing a polycarbonate-based resin or polyester carbonate-based resin (hereinafter sometimes simply referred to as polycarbonate-based resin) can be suitably used.

Any suitable polycarbonate-based resin can be used as the polycarbonate-based resin. For example, the polycarbonate-based resin contains structural units derived from a fluorene-based dihydroxy compound, structural units derived from an isosorbide-based dihydroxy compound, and structural units derived from at least one dihydroxy compound selected from the group consisting of alicyclic diols, alicyclic dimethanols, di-, tri-, or polyethylene glycols, and alkylene glycols or spiroglycols. Preferably, the polycarbonate-based resin contains structural units derived from a fluorene-based dihydroxy compound, structural units derived from an isosorbide-based dihydroxy compound, structural units derived from an alicyclic dimethanol, and/or structural units derived from di-, tri-, or polyethylene glycol; more preferably, it contains structural units derived from a fluorene-based dihydroxy compound, structural units derived from an isosorbide-based dihydroxy compound, and structural units derived from di-, tri-, or polyethylene glycol. The polycarbonate-based resin may also contain structural units derived from other dihydroxy compounds as needed. Details of polycarbonate resins suitable for use in λ/4 members and methods for forming λ/4 members are described, for example, in JP 2014-10291 A, JP 2014-26266 A, JP 2015-212816 A, JP 2015-212817 A, and JP 2015-212818 A, the disclosures of which are incorporated herein by reference.

The thickness of the λ/4 member, which is a stretched resin film, is, for example, 10 μm to 100 μm, preferably 10 μm to 70 μm, and more preferably 20 μm to 60 μm.

In one embodiment, the λ/4 component is a layer of solidified alignment of a liquid crystal compound. A solidified alignment layer of a liquid crystal compound is a layer in which the liquid crystal compound is oriented in a predetermined direction within the layer, and this alignment state is fixed. The term "solidified alignment layer" encompasses a solidified alignment layer obtained by curing a liquid crystal monomer, as described below. In a λ/4 component, rod-shaped liquid crystal compounds are typically aligned in the slow axis direction of the λ/4 component (homogeneous alignment). Examples of rod-shaped liquid crystal compounds include liquid crystal polymers and liquid crystal monomers. The liquid crystal compound is preferably polymerizable. If the liquid crystal compound is polymerizable, the alignment state of the liquid crystal compound can be fixed by aligning the liquid crystal compound and then polymerizing it.

The above-mentioned liquid crystal compound alignment solidified layer (liquid crystal alignment solidified layer) can be formed by performing an alignment treatment on the surface of a predetermined substrate, applying a coating liquid containing a liquid crystal compound to the surface to align the liquid crystal compound in a direction corresponding to the alignment treatment, and fixing the alignment state. Any appropriate alignment treatment can be used. Specific examples include mechanical alignment treatment, physical alignment treatment, and chemical alignment treatment. Specific examples of mechanical alignment treatment include rubbing treatment and stretching treatment. Specific examples of physical alignment treatment include magnetic field alignment treatment and electric field alignment treatment. Specific examples of chemical alignment treatment include oblique vapor deposition and photoalignment treatment. Any appropriate treatment conditions can be used for the various alignment treatments depending on the purpose.

Liquid crystal compounds are aligned by treating them at a temperature that allows them to exhibit a liquid crystal phase, depending on the type of liquid crystal compound. By performing this temperature treatment, the liquid crystal compounds assume a liquid crystal state and are aligned in accordance with the alignment treatment direction on the substrate surface.

In one embodiment, the alignment state is fixed by cooling the liquid crystal compound aligned as described above. If the liquid crystal compound is polymerizable or crosslinkable, the alignment state is fixed by subjecting the liquid crystal compound aligned as described above to a polymerization treatment or crosslinking treatment.

Any suitable liquid crystal polymer and/or liquid crystal monomer can be used as the liquid crystal compound. The liquid crystal polymer and liquid crystal monomer can be used alone or in combination. Specific examples of liquid crystal compounds and methods for producing a liquid crystal alignment solidified layer are described in, for example, JP 2006-163343 A, JP 2006-178389 A, and WO 2018/123551 A. The disclosures of these publications are incorporated herein by reference.

The thickness of the λ/4 member composed of the liquid crystal alignment solidification layer is, for example, 1 μm to 10 μm, preferably 1 μm to 8 μm, more preferably 1 μm to 6 μm, and even more preferably 1 μm to 4 μm.

B-2-2. Positive C Plate The thickness direction retardation Rth(550) of the positive C plate 22b is preferably −50 nm to −300 nm, more preferably −70 nm to −250 nm, even more preferably −90 nm to −200 nm, and particularly preferably −100 nm to −180 nm. Here, "nx = ny" includes not only the case where nx and ny are strictly equal, but also the case where nx and ny are substantially equal. The in-plane retardation Re(550) of the positive C plate is, for example, less than 10 nm.

The positive C plate can be made of any suitable material, but is preferably composed of a film containing a liquid crystal material fixed in homeotropic alignment. The liquid crystal material (liquid crystal compound) that can be homeotropically aligned may be a liquid crystal monomer or a liquid crystal polymer. Specific examples of such liquid crystal compounds and methods for forming a positive C plate include the liquid crystal compounds and methods for forming the retardation layer described in paragraphs [0020] to [0028] of JP 2002-333642 A. In this case, the thickness of the positive C plate is preferably 0.5 μm to 5 μm.

B-2-3. Protective Member The protective member 34 typically includes a substrate. The substrate may be composed of any appropriate film. Examples of materials that form the main component of the film constituting the substrate include cellulose-based resins such as triacetyl cellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, polysulfone-based, polystyrene-based, cycloolefin-based resins such as polynorbornene, polyolefin-based, (meth)acrylic, and acetate-based resins. The thickness of the substrate is preferably 5 μm to 80 μm, more preferably 10 μm to 40 μm, and even more preferably 15 μm to 35 μm.

The protective member preferably has a substrate and a surface treatment layer formed on the substrate. A protective member having a surface treatment layer can be positioned so that the surface treatment layer is located on the front side. The surface treatment layer can have any appropriate function. For example, from the perspective of improving visibility, the surface treatment layer preferably has an anti-reflection function. The surface treatment layer may also include a hard coat layer. The thickness of the surface treatment layer is preferably 1 μm to 20 μm, more preferably 2 μm to 15 μm, and even more preferably 3 μm to 10 μm.

When the protective member has a substrate and a surface treatment layer formed thereon, a second protective member may be further provided to protect the surface treatment layer. The second protective member can be a film similar to the substrate described above.

B-2-4. Pressure-sensitive adhesive layer The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 32 typically contains a (meth)acrylic polymer, a urethane polymer, a silicone polymer, or a rubber polymer as a base polymer. Preferably, the pressure-sensitive adhesive is a (meth)acrylic pressure-sensitive adhesive containing a (meth)acrylic polymer as a main component. The thickness of the pressure-sensitive adhesive layer is, for example, 12 μm or more, preferably 15 μm or more, and, for example, 100 μm or less, preferably 80 μm or less.

B-2-5. Release Liner The release liner 36 typically comprises a substrate and a release-treated layer (e.g., a silicone-treated layer) provided on the surface of the substrate facing the PSA layer 32. The substrate is formed from a resin such as a polyolefin resin, a polyester resin, a (meth)acrylic resin, a polyamide resin, a polyimide resin, a polyvinyl chloride resin, a polyvinylidene chloride resin, a cellulose resin, a polystyrene resin, or a polycarbonate resin.

B-2-6. Manufacturing Method The first long optical film is produced by any appropriate method. For example, the first long optical film can be obtained by a manufacturing method including forming each of the above-mentioned components into a long shape and sequentially laminating the components, if necessary, via an adhesive layer, and then winding it up into a roll as needed. The lamination is preferably performed by roll-to-roll. Here, "roll-to-roll" refers to laminating rolled films while transporting them with their longitudinal directions aligned. A pressure-sensitive adhesive layer or an adhesive layer is used as the adhesive layer.

In one embodiment, from the long optical films produced as described above, one having a variation in in-plane retardation in the long direction and/or width direction within the above-mentioned specified range (specifically, a variation in in-plane retardation in the width direction of, for example, 5 nm or less, and a variation in in-plane retardation in the long direction of, for example, 3 nm or less, or 1.5 nm or less) can be selected and used as the first long optical film.

B-3. Process II
In step II, as shown in Fig. 3, the first long optical film 30 prepared in step I is slit in the longitudinal direction to obtain a plurality of second long optical films 40. Slitting can be performed not only in the longitudinal direction but also in the width direction, thereby obtaining a plurality of second long optical films each having a predetermined width and length.

In one embodiment, the second long optical film 40 is wound into a roll and then subjected to the next process (hereinafter, the roll of the second long optical film may be referred to as a "child roll").

The width of the second long optical film is equal to or greater than the width of the optical film piece to be produced, and is, for example, 1.1 times or more, preferably 1.2 times or more, and for example, 3.0 times or less, preferably 2.0 times or less, more preferably 1.5 times or less, of the width of the optical film piece to be produced. The variation in the in-plane retardation (e.g., Re(590)) in the width direction of the second long optical film having the above width can be, for example, 3 nm or less, preferably 1.5 nm or less. The variation in the in-plane retardation (e.g., Re(590)) in the longitudinal direction of the second long optical film can be, for example, 3 nm or less, preferably 1.5 nm or less. Such a second long optical film can significantly reduce the variation in the in-plane retardation in the optical film piece obtained from one second long optical film.
In one embodiment, the width of the second long optical film is, for example, 40 mm or more and 200 mm or less, or, for example, 45 mm or more and 150 mm or less, or, for example, 50 mm or more and 120 mm or less.
In one embodiment, the number of divisions of the film by slits along the longitudinal direction (meaning the number of divisions of the first long optical film in the width direction) is, for example, 6 or more, preferably 10 or more and 25 or less, and preferably 15 or more and 20 or less.

The length of the second long optical film is, for example, 50 m or more and 1000 m or less, 50 m or more and 300 m or less, or 100 m or more and 150 m or less.

B-4. Process III
In step III, as shown in Fig. 4, a plurality of second long optical films 40 are classified into two or more groups based on their in-plane retardation (substantially the in-plane retardation of a λ/4 member). Specifically, prior to step III, the in-plane retardation (e.g., Re(590)) is measured for each of the plurality of second long optical films, and the plurality of second long optical films are classified into N groups based on the measured in-plane retardation so that the variation in the in-plane retardation within each group is smaller than the variation in the overall in-plane retardation. In the illustrated example, the second long optical films are classified into two groups, group A and group B, but N may be any integer of 2 or greater, for example, 3 or greater. From the viewpoint of optimally obtaining the effects of the present invention, N is preferably 2 to 4, more preferably 2 or 3.

The in-plane retardation is measured, for example, after slitting, at two or more locations (e.g., two locations) at the leading edge and/or the trailing edge of the second long optical film. For a long optical film with small variation in in-plane retardation in the longitudinal direction, even if the film has a length of 50 m or more, the in-plane retardation throughout the film can be roughly determined by measuring the leading edge and/or the trailing edge. In one embodiment, the in-plane retardation is measured at two or more locations in the width direction of the leading edge of the film (e.g., two or more locations within 500 mm of the leading edge (e.g., multiple locations spaced at a predetermined interval in the width direction)), as indicated by the "x" marks in the second long optical film 40 in the top left row of Figure 4. If necessary, the in-plane retardation can also be measured at two or more locations in the width direction of the trailing edge (e.g., two or more locations within 500 mm of the trailing edge (e.g., multiple locations spaced at a predetermined interval in the width direction)). The average of these measurements can be used as the in-plane retardation of the second long optical film.

For example, the in-plane retardation is measured on the first long optical film before slitting. In this case, the first long optical film before slitting is divided along the intended slit lines, and the in-plane retardation at the locations corresponding to the leading and/or trailing ends of the divisions is measured in the same manner as above, and this can be used as the in-plane retardation of the second long optical film corresponding to the divisions obtained after slitting.

The classification can be performed, for example, by classifying the plurality of second long optical films into groups each having a predetermined in-plane retardation width based on the in-plane retardation measured as described above. The classification width of the in-plane retardation of each group can be, for example, 2 nm or less, preferably 1 nm or more and 1.5 nm or less, and more preferably 1 nm or more and 1.3 nm or less.
In one embodiment, the classification is performed by classifying by a predetermined in-plane retardation width from a preset reference value. As a specific example, when classifying with a classification width of 2 nm (±1 nm) using an Re(590) of 146 nm as a reference value, for example, it can be sequentially classified into a group having an Re(590) of 145 nm or more and less than 147 nm, a group having an Re(590) of 143 nm or more and less than 145 nm, a group having an Re(590) of 147 nm or more and less than 149 nm, a group having an Re(590) of 141 nm or more and less than 143 nm, and a group having an Re(590) of 149 nm or more and less than 151 nm.
In another embodiment, the classification is performed by classifying the films in order of the measured in-plane retardation value from the largest to the smallest, in in-plane retardation steps of a predetermined in-plane retardation width. The classification width of the in-plane retardation (e.g., Re(590)) can be, for example, 2 nm or less, preferably 1 nm or more to 1.5 nm or less, and more preferably 1 nm or more to 1.3 nm or less.
The variation in in-plane retardation among the second long optical films in each group classified as described above is smaller than the variation in in-plane retardation among all the second long optical films before classification.

B-5. Process IV
In step IV, as shown in FIG. 5( a), optical film pieces 50 are continuously punched out while the second long optical film 40 is being transported in the longitudinal direction. For example, the second long optical film may be laminated to a surface protective film using a roll-to-roll method, and then punched out into optical film pieces. The punched optical film pieces are subjected to quality inspection, etc., as necessary, and then used to assemble the display system 2.

FIG. 5( b) is a schematic diagram of FIG. 5( a) viewed from above. As described above, the width _X2 of the second long optical film 40 is, for example, 1.1 to 3.0 times, preferably 1.2 to 2.0 times, and more preferably 1.2 to 1.5 times the punched width _X1 of the optical film piece 50. Therefore, the number of optical film pieces punched in the width direction of the second long optical film is typically one or two, preferably one. A wide parent roll is produced, slit along the longitudinal direction to produce narrow child rolls, and one or two, preferably only one, optical film pieces are punched in the width direction from each child roll, thereby obtaining optical film pieces with reduced variation in in-plane retardation. Furthermore, by classifying child rolls with similar in-plane retardation into the same group, optical film pieces obtained from child rolls belonging to the same group have the characteristic of high uniformity in in-plane retardation.

The optical film piece obtained by the manufacturing method according to an embodiment of the present invention has a high degree of uniformity in in-plane retardation, and therefore can be used as a component of the second retardation member 22, contributing to the efficient production of high-definition display systems 2. Another advantage is that it is easy to match the in-plane retardation between the first λ/4 member and the second λ/4 member, which is important for achieving high definition.

C. Method for Managing Long Optical Film A method for managing a long optical film according to an embodiment of the present invention includes:
A step A of preparing a first long optical film including a retardation member;
a step B of slitting the first long optical film along the longitudinal direction to obtain a plurality of second long optical films;
and step C of classifying the plurality of second long optical films into two or more groups based on the in-plane retardation.
The same explanations as for Step I, Step II, and Step III described in Section B can be applied to Step A, Step B, and Step C, respectively.
According to the above-mentioned management method, after producing a wide, long optical film, the film is slit along the longitudinal direction to divide it into a plurality of narrow, long optical films. Furthermore, by grouping the plurality of narrow, long optical films based on their in-plane retardation, it is possible to reduce the variation in the in-plane retardation in the width direction and obtain a group of long optical films having in-plane retardations that are similar to each other. Therefore, by managing the narrow, long optical films in groups and subjecting them to the subsequent punching process, it is possible to obtain a group of optical film pieces having a desired in-plane retardation and small variation in the in-plane retardation.

The present invention will be explained in more detail below using examples, but the present invention is not limited to these examples in any way. The test and evaluation methods used in the examples are as follows. "Parts" means "parts by weight" unless otherwise specified, and "%" means "% by weight" unless otherwise specified.

(1) Thickness Thicknesses of 10 μm or less were measured using a scanning electron microscope (manufactured by JEOL Ltd., product name "JSM-7100F"), and thicknesses of more than 10 μm were measured using a digital micrometer (manufactured by Anritsu Corporation, product name "KC-351C").
(2) In-plane phase difference Re(λ)
The in-plane retardation was measured at 23±2° C. and 65±15% RH using KOBRA (manufactured by Oji Measurement Co., Ltd.).

[Fabrication of λ/4 Member A]
A batch polymerization apparatus consisting of two vertical reactors equipped with stirring blades and a reflux condenser controlled to 100°C was charged with 29.60 parts by weight (0.046 mol) of bis[9-(2-phenoxycarbonylethyl)fluoren-9-yl]methane, 29.21 parts by weight (0.200 mol) of isosorbide (ISB), 42.28 parts by weight (0.139 mol) of spiroglycol (SPG), 63.77 parts by weight (0.298 mol) of diphenyl carbonate (DPC), and 1.19 × 10 ^-2 parts by weight (6.78 × 10 ^-5 mol) of calcium acetate monohydrate as a catalyst. The atmosphere inside the reactor was purged with nitrogen under reduced pressure, and then the reactor was heated with a heat medium. Stirring was started when the internal temperature reached 100°C. The internal temperature reached 220°C 40 minutes after the start of the temperature increase, and while maintaining this temperature, pressure reduction was initiated. The pressure was reduced to 13.3 kPa 90 minutes after reaching 220°C. Phenol vapor by-produced during the polymerization reaction was introduced into a reflux condenser at 100°C, and a small amount of monomer components contained in the phenol vapor was returned to the reactor. Uncondensed phenol vapor was introduced into a condenser at 45°C and recovered. Nitrogen was introduced into the first reactor, and the pressure was temporarily restored to atmospheric pressure. The oligomerized reaction liquid in the first reactor was then transferred to the second reactor. Next, temperature increase and pressure reduction were initiated in the second reactor, and the internal temperature reached 240°C and the pressure reached 0.2 kPa in 50 minutes. Polymerization was then allowed to proceed until the predetermined stirring power was reached. When the predetermined power was reached, nitrogen was introduced into the reactor to restore the pressure, and the resulting polyester carbonate resin was extruded into water, and strands were cut to obtain pellets.
The obtained polyester carbonate resin (pellets) was vacuum-dried at 80°C for 5 hours, and then a long resin film having a thickness of 130 μm was produced using a film-forming device equipped with a single-screw extruder (manufactured by Toshiba Machine Co., Ltd., cylinder set temperature: 250°C), a T-die (width 200 mm, set temperature: 250°C), a chill roll (set temperature: 120-130°C), and a winder. The obtained long resin film was stretched in the width direction at a stretching temperature of 140°C and a stretch ratio of 2.7 times, and wound into a roll. This resulted in a λ/4 member A having a thickness of 47 μm. The Re (590) at the center of the width direction of the λ/4 member A was 147 nm.

[Preparation of Positive C Plate A]
A liquid crystal coating solution was prepared by dissolving 20 parts by weight of a side-chain liquid crystal polymer represented by the following chemical formula (1) (the numbers 65 and 35 in the formula indicate the mole percent of the monomer unit, and are conveniently expressed as a block polymer; weight-average molecular weight 5000), 80 parts by weight of a polymerizable liquid crystal exhibiting a nematic liquid crystal phase (manufactured by BASF: trade name Paliocolor LC242), and 5 parts by weight of a photopolymerization initiator (manufactured by Ciba Specialty Chemicals: trade name Irgacure 907) in 200 parts by weight of cyclopentanone. The coating solution was then applied to a PET substrate that had been subjected to a vertical alignment treatment using a bar coater, and the liquid crystal was aligned by heating and drying at 80°C for 4 minutes. The liquid crystal layer was irradiated with ultraviolet light to harden the liquid crystal layer, forming a positive C plate with a thickness of 4 μm and an Rth(550) of -100 nm on the substrate.

[Creating parent roll]
A positive C plate A was bonded to the λ/4 component A via a UV-curable adhesive (thickness 1 μm after curing), and the substrate was peeled off to obtain a retardation component A having a configuration of [λ/4 component A/positive C plate A]. An acrylic adhesive (thickness 50 μm) and a release liner were bonded to the surface of the λ/4 component A side of the retardation component A. In addition, an acrylic resin film with a hard coat layer was bonded as a protective member to the surface of the positive C plate A side of the retardation component A via an acrylic adhesive (thickness 23 μm) so that the acrylic resin film side faced the positive C plate A side. All of the above bonding operations were performed by roll-to-roll.
As a result, a roll-shaped optical film (parent roll) having a structure of [release liner/adhesive layer/λ/4 member A/positive C plate A/protective member] was obtained. The length of the parent roll was 1000 m and the width was 1120 mm.

[Production of child roll 1]
The optical film was unwound from the parent roll, slit at predetermined intervals along the longitudinal direction, and wound into a roll to obtain a child roll 1 including three rolls.
[Child Roll Production 2]
Child rolls 2 to 6 having various lengths and widths were obtained in the same manner as in Child Roll Preparation 1, except that the rolls were slit in the longitudinal direction and/or width direction at different intervals.

[Evaluation of in-plane retardation variation]
For each of the child rolls 1 to 6 and the parent roll, Re(590) was measured at multiple locations spaced approximately 60 mm apart in the width direction along the entire length, and the difference between the maximum and minimum average values of the measured values at each measurement location was taken as the variation in in-plane retardation in the width direction. The results are shown in Table 1. In the table, the variation in in-plane retardation for child rolls 1 to 6 is the average value of the variation in in-plane retardation in the width direction for each of the child rolls 1 to 6. The "number of divisions in the width direction" is the number of divisions in the width direction by slits along the longitudinal direction (the number of blocks after division). For each of the child rolls 1 to 6 and the parent roll, the variation in in-plane retardation in the longitudinal direction at each measurement location was 1.5 nm or less.

As shown in Table 1, narrow, long optical films have smaller variations in in-plane retardation in the width direction than wide, long optical films. Long optical films with such small variations in in-plane retardation in the width direction (e.g., variations of 1.5 nm or less, 1.2 nm or less, or 1 nm or less) can be obtained by slitting a wide, long optical film along the length direction. Furthermore, by continuously punching out such long optical films with small variations in in-plane retardation in the width direction, optical film pieces with excellent uniformity in in-plane retardation can be obtained with high production efficiency.

The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, the configuration shown in the above-described embodiment can be replaced with a configuration that is substantially the same as the configuration shown in the above-described embodiment, a configuration that provides the same effects, or a configuration that can achieve the same purpose.

The manufacturing method for an optical film piece according to an embodiment of the present invention can be suitably used, for example, in the manufacture of displays such as VR goggles.

2 Display system 4 Lens section 12 Display element 14 Reflective polarizing member 16 First lens section 18 Half mirror 20 First phase difference member 22 Second phase difference member 22a Second λ/4 member 22b Positive C plate 24 Second lens section 30 First long optical film (parent roll)
40 Second long optical film (child roll)

Claims (9)

A method for manufacturing an optical film piece, comprising:
A step of preparing a first long optical film including a retardation member;
slitting the first long optical film along its longitudinal direction to obtain a plurality of second long optical films;
and classifying the plurality of second long optical films into two or more groups based on in-plane retardation ,
the classifying step includes classifying the plurality of second long optical films into two or more groups by a predetermined width of in-plane retardation,
the width of the first long optical film is 10 times or more the width of the optical film piece;
The manufacturing method, wherein the width of the second long optical film is 1.1 times or more and 3.0 times or less the width of the optical film piece. The manufacturing method described in claim 1 further includes a step of continuously punching out the optical film pieces while transporting the second long optical film in the long direction. The manufacturing method described in claim 1, wherein the variation in in-plane retardation in the length direction of the second long optical film is 1.5 nm or less. The manufacturing method according to claim 1 , wherein the in-plane retardation is measured before and/or after the slit. The manufacturing method according to claim 4 , wherein the in-plane retardation is measured at two or more points on the leading end of the second long optical film. The manufacturing method according to claim 5 , wherein the in-plane retardation is further measured at two or more locations on an end of the second long optical film. The manufacturing method described in claim 1, wherein the length of the first long optical film is 100 m or more and 2000 m or less. The manufacturing method described in claim 1, wherein the step of preparing the first long optical film includes selecting, as the first long optical film, a long optical film having an in-plane retardation variation of 5 nm or less in the width direction and an in-plane retardation variation of 1.5 nm or less in the length direction. A step of preparing a first long optical film including a retardation member;
slitting the first long optical film along its longitudinal direction to obtain a plurality of second long optical films;
and classifying the plurality of second long optical films into two or more groups based on in-plane retardation,
The classifying step includes classifying the plurality of second long optical films into two or more groups each having a predetermined in-plane retardation width.
A method for managing long optical films.