WO2008048870A2 - Film optique et son procédé de fabrication - Google Patents

Film optique et son procédé de fabrication Download PDF

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Publication number
WO2008048870A2
WO2008048870A2 PCT/US2007/081184 US2007081184W WO2008048870A2 WO 2008048870 A2 WO2008048870 A2 WO 2008048870A2 US 2007081184 W US2007081184 W US 2007081184W WO 2008048870 A2 WO2008048870 A2 WO 2008048870A2
Authority
WO
WIPO (PCT)
Prior art keywords
film
optical film
precursor
prism
protruding ribs
Prior art date
Application number
PCT/US2007/081184
Other languages
English (en)
Other versions
WO2008048870A3 (fr
Inventor
Ken Egashira
Tsuyoshi Tanaka
Original Assignee
3M Innovative Properties Company
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 3M Innovative Properties Company filed Critical 3M Innovative Properties Company
Publication of WO2008048870A2 publication Critical patent/WO2008048870A2/fr
Publication of WO2008048870A3 publication Critical patent/WO2008048870A3/fr

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0033—Means for improving the coupling-out of light from the light guide
    • G02B6/005—Means for improving the coupling-out of light from the light guide provided by one optical element, or plurality thereof, placed on the light output side of the light guide
    • G02B6/0053—Prismatic sheet or layer; Brightness enhancement element, sheet or layer
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
    • B29D11/00—Producing optical elements, e.g. lenses or prisms
    • B29D11/0074—Production of other optical elements not provided for in B29D11/00009- B29D11/0073
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/04—Prisms
    • G02B5/045—Prism arrays
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0065—Manufacturing aspects; Material aspects

Definitions

  • the present invention relates to an optical film. More specifically, the present invention relates to an optical film with a light control function, particularly a lens function, and a production method thereof.
  • the optical film of the present invention can be advantageously used as a decorative film, a graphic film, an ornamental film of a lamp cover, or the like.
  • an optical film having a light control function is laminated on a display surface so as to enhance the visual effect on the display surface of an electronic device such as television and personal computer, and other devices.
  • an optical film with prism ribs disposed on the entire surface called a lens film, a prism film, a prism sheet or the like.
  • Such an optical film is usually produced from a thermoforming or ultraviolet-curable resin such as polycarbonate resin and acrylic resin, but these resins are hard at an ordinary temperature and disadvantageously unable to cope with a complicated shape, for example, a three-dimensional curved surface.
  • a film cannot be used outdoors because of its poor weather resistance, and can be hardly colored as needed.
  • Japanese Unexamined Patent Publication (Kokai) No. 11-149001 describes a prism sheet for surface light sources and a backlight shown in Fig. 1.
  • the prism sheet 110 is formed of a thermosetting polyurethane resin and, as shown, comprises a smooth surface 114 and many prism ribs 112 formed on the opposite side and having a cross-section in a triangular shape.
  • the backlight consists of the prism sheet 110, a light source 132 and a scattering light guide 130.
  • This prism sheet is formed of polyurethane resin and therefore, expected to have flexibility, but since a shaping method of coating and curing a urethane- based liquid composition on a mold having formed thereon prism ribs is employed, the prism sheet can be produced only by single cavity molding and the currently increasing demand for a mass-production system (continuous production of a prism sheet and taking-up in the roll form) cannot be satisfied. Furthermore, an isocyanate monomer must be directly used in the urethane-based liquid composition and this requires taking elaborate care in handling.
  • the present invention can be used to solve one or a combination of those problems in conventional techniques.
  • the present invention can provide an optical film capable of bringing about remarkably high visual effect, decorative effect and the like that is unable or difficult to produce by conventional lens films or prism films, as well as excellent light control effect.
  • the present invention can also be used to provide an optical film which can be dispensed without a starting material requiring careful handling or adversely effecting the environment, can be easily and continuously produced in a good yield, can ensure that the final product can be taken up in the roll form, or a combination thereof.
  • the present invention can be used to provide a method where the above- described optical film excellent in the light control effect, visual effect, decorative effect and the like can be continuously produced by simple and easy means and, preferably, the production process can be implemented in the roll-to-roll form.
  • an optical film is provided with a light control function, comprising a plurality of fine prismatic protruding ribs comprising a two-component reaction-curable non-yellowing transparent polyurethane resin and arranged in a predetermined pattern on one surface of the optical film.
  • the prismatic protruding ribs can be derived from a plurality of fine grooved ribs arranged on the surface of a pattern transfer backing film abutted against a starting material on the way of shaping the optical film, which are corresponding to the protruding ribs and have a cross-section in the inverted prism shape.
  • a method for producing an optical film with a light control function having on one surface thereof a plurality of fine prismatic protruding ribs arranged in a predetermined pattern.
  • the method comprises: producing a pattern transfer backing film having on one surface thereof a plurality of fine grooved ribs corresponding to the protruding ribs and having a cross-section in the inverted prism shape, abuttedly casting a starting material of a polyurethane resin on the grooved rib-holding surface of the pattern transfer backing film, thereby forming a precursor of the optical film, and heating and curing the optical film precursor as it is, or heating the precursor to a semi-cured state, stacking a flat support film on the back surface of the precursor, and allowing the stack to stand in that state, thereby curing the precursor.
  • a method for producing an optical film with a light control function having on one surface thereof a plurality of fine prismatic protruding ribs arranged in a predetermined pattern.
  • the method comprises: producing a pattern transfer backing film having on one surface thereof a plurality of fine grooved ribs corresponding to the protruding ribs and having a cross-section in the inverted prism shape, abuttedly casting a starting material of a polyurethane resin on a flat support film to form a precursor of the optical film, heating the optical film precursor to a semi-cured state, stacking the pattern transfer backing film on the back surface of the optical film precursor still in a semi-cured state, and allowing the stack in which the optical film precursor is interposed between the backing film and the support film, to stand in that state, thereby curing the precursor.
  • the optical film of the present invention can bring about remarkably high visual effect, decorative effect and the like that cannot be produced, or is at least difficult to produce, by conventional products at the same time in addition to the light control effect, particularly lens action, peculiar to the conventional lens film or prism film.
  • the optical film of the present invention can bring about excellent weather resistance heretofore difficult to achieve by conventional products, can easily cope with a product having a complicated shape such as three-dimensional curved surface without generating defects such as ruptured wrinkle, and ensures good handleability.
  • the optical film of the present invention can be easily colored, and this contributes to the enhancement of decorative effect.
  • an optical film capable of being lightly colored and at the same time, having transparency can be provided.
  • the optical film of the present invention not only a material requiring careful handling or adversely affecting the environment needs not be used as the starting material but also simple and continuous production can be implemented with a good yield.
  • the optical film of the present invention is continuously produced, the final product can be taken up in the roll form.
  • the optical film of the present invention can be advantageously used in various technical fields by utilizing its various excellent properties.
  • the optical film of the present invention is advantageously usable as a decorative film by laminating on a windowpane, a show window glass pane or a plated or pained surface of articles, a graphic film by laminating on a car body of automobiles or other vehicles, or a light control sheet by laminating on a lamp cover of a head lamp or the like.
  • the optical film of the present invention excellent in the light control effect, visual effect, decorative effect and the like can be continuously produced by simple and easy means.
  • This optical film ensures that not only the final product can be taken up in the roll form but also a production process fundamentally in the roll-to-roll form can be implemented by using each starting material in the form of a roll.
  • Fig. 1 is a cross-sectional view of a conventional backlight with a prism sheet for a surface light source.
  • Fig. 2 is a perspective view showing one preferred embodiment of the optical film of the present invention.
  • Fig. 3 is an enlarged cross-sectional view showing a part of the optical film shown in Fig. 2.
  • Fig. 4 is a cross-sectional view showing a film structure containing the optical film shown in Figs. 2 and 3.
  • Fig. 5 is a cross-sectional view showing another preferred embodiment of the optical film of the present invention.
  • Fig. 6 is a cross-sectional view showing still another preferred embodiment of the optical film of the present invention.
  • Fig. 7 is a cross-sectional view showing yet still another preferred embodiment of the optical film of the present invention.
  • Fig. 8 is a view schematically showing the production process of the pattern transfer backing film for use in practicing the present invention.
  • Fig. 9 is a view schematically showing one preferred production process of the optical film of the present invention.
  • Fig. 10 is a perspective view of a cylinder with protruding ribs, used for the production of a pattern transfer backing film in Example 1.
  • optical film and the production method therefor of the present invention each can be advantageously implemented in various modes. Preferred embodiments of the present invention are described below, but it should be understood that the present invention is not limited to the following embodiments.
  • the optical film of the present invention comprises at least: (1) a transparent substrate comprising a polyurethane resin, and (2) a plurality of fine prismatic protruding ribs arranged in a predetermined pattern on one surface of the substrate and integrated with the substrate, and, if desired, may have an additional layer or may be subjected to an additional treatment.
  • prismatic protruding rib as used herein means a protruding rib in various shapes having a prismatic cross-section.
  • the peak (edge) of the protruding rib is not particularly limited in its angle as long as a predetermined function can be realized, and the sharply peaked portion may be rounded. That is, r (roundness) may be imparted to the peak.
  • the prismatic protruding rib typically includes a linear triangular prism, a pseudo triangular prism in which either one or both of the prism apex angle of a linear triangular prism and an angle between two adjacent triangles are rounded, a prism having a shape resulting from removing a part of the triangular prism or pseudo triangular prism, a semi cylindrical prism, a triangular or quadrangular pyramidal prism, and a combination thereof.
  • Fig. 2 is a perspective view showing one preferred embodiment of the optical film of the present invention.
  • Fig. 3 is an enlarged cross-sectional view showing a part of the optical film shown in Fig. 2.
  • the optical film 10 comprises, as shown, a transparent substrate 1 and protruding ribs 11 arranged in an integral and stripe-like manner on one surface of the substrate, each having a triangular cross-sectional shape.
  • stripe-like protruding ribs 11 are gaplessly arranged at the same pitch, but, if desired, protruding ribs 11 may be arranged with a spacing from each other and by this arrangement, a different light control effect can be obtained.
  • the optical film 10 has a protruding rib- holding surface 10a on one surface thereof and a smooth surface 10b on the side opposite the protruding rib-holding surface 10a.
  • the substrate 1 may be colored, if desired.
  • the protruding rib 11 is transparent similarly to the substrate 1 and sharp at the peak P and has an obliquely inclined plane 10a, so that when arbitrary light (for example, light from a light source, or outdoor light) enters from the upper or lower side of the optical film 10, the light can be controlled to a desired form by the light control function of the protruding rib 11 and then output.
  • the protruding rib 11 of the optical film 10 may have various prismatic cross-sectional shapes according to the desired light control effect.
  • the protruding rib 11 may have a nearly equilateral triangular cross-section.
  • the protruding rib 11 may have a saw blade-shaped cross-section, in other words, a right triangular cross-section.
  • the angle of the peak P (apex angle) of each protruding rib is not particularly limited and is usually 150° or less, preferably from about 50 to 120°, more preferably from about 70 to 100°. Even if the apex angle is too small, there arises no problem, but if the apex angle is excessively large, the effect of, for example, enhancing the stereoscopic appearance by parallax images is disadvantageously reduced.
  • the r of the apex angle may be arbitrarily varied.
  • the r is usually from about 1 to 30, preferably from about 3 to 15.
  • the size of the protruding rib may be varied over a wide range according to the size or usage of the optical film or the like.
  • the length of the protruding rib is, when a lengthy optical film is cut into a predetermined length and used with an unchanged width, corresponds to the width of the optical film and is usually from about 100 to 1,500 mm, preferably from about 200 to 1,000 mm. Accordingly, in the case of using the optical film by cutting it in the longitudinal direction, the length of the protruding rib becomes smaller than the above- described range according to the cutting ratio.
  • the protruding rib is a triangular or quadrangular pyramidal prism
  • the optical film is cut at every pitch of the prisms and a plurality of protruding ribs running in different directions are present.
  • the length of the base of a protruding rib having a triangular cross-section is usually from about 10 to 500 ⁇ m, preferably from about 24 to 250 ⁇ m.
  • the height of the protruding rib is usually from about 1 to 300 ⁇ m, preferably from about 5 to 150 ⁇ m.
  • the protruding ribs may be gaplessly and continuously arranged or may be regularly arranged with a predetermined spacing. If desired, the protruding ribs may be randomly arranged. Accordingly, in arranging the protruding ribs, the distance (pitch) between peaks of adjacent protruding ribs may be varied over a wide range.
  • the pitch of the protruding ribs is usually 1 mm or less, preferably from about 10 to 500 ⁇ m, more preferably from about 25 to 250 ⁇ m. If the pitch is too large, the presence of pitch is highly visible and this may become an obstacle to enhancing the appearance.
  • the fine prismatic protruding ribs on the substrate surface are usually not formed by machining but are formed by transferring a fine structure pattern previously formed on a backing film, onto one surface of the substrate on the way of shaping the optical film. More specifically, the prismatic protruding ribs are derived from a plurality of fine grooved ribs arranged on the surface of a pattern transfer backing film abutted against a starting material on the way of shaping the optical film, which are corresponding to the protruding ribs and have a cross-section in the inverted prism shape.
  • Fig. 4 is a view for explaining this transfer technique and shows a state where the optical film 10 after shaping is sandwiched between a backing film 20 and a laminate film (preferably a flat support film) 30. That is, in the present invention, it is essential to use a pattern transfer backing film 20.
  • the backing film 20 has, as shown, a plurality of fine grooved ribs corresponding to the protruding ribs 11 and having a cross-section in the inverted prism shape.
  • a backing film 11 taken up in the roll form is unrolled, and a starting material (film- forming material) of the optical film is cast on the grooved rib-holding surface 20a of the backing film and abuttedly cured.
  • the curing process of the film- forming material may be implemented through various routes. For example, the film-forming material on the backing film 11 may be completely cured by using an oven or the like.
  • the film-forming material for forming the optical film 10 may be cured between the pattern transfer backing film 20 and a laminate film (preferably a flat support film) 30 disposed with a spacing to oppose the grooved rib-holding surface 20a of the backing film 20 and thereby shaped into a film form.
  • the curing process is preferably performed in two steps of semi-curing and complete curing subsequent thereto.
  • the film-forming material cast on the backing film 11 as described above is semi-cured by an oven or the like and after stacking a laminate film 30 on the side opposite the backing film 11 , completely cured by allowing to stand while keeping the stacked state.
  • the stack of a laminate film 30, an optical film 10 and a backing film 11 may be subjected as it is to the complete curing step, but in the present invention, advantageously, the stack can be taken up in the roll state and by allowing it to stand, the complete curing step can be effected.
  • the laminate film 30 may be omitted depending on the curing mechanism of the optical film 10.
  • the method of implementing the curing step in two steps of semi-curing and complete curing subsequent thereto may be changed as follows.
  • a film-forming material is cast on a laminate film (preferably a flat support film), semi-cured by an oven or the like and after stacking thereon a pattern transfer backing film so that the grooved rib-holding surface of the film can abut the film- forming material, completely cured by allowing to stand while keeping the stacked state.
  • the optical film may be formed from an arbitrary polyurethane resin.
  • the polyurethane resin is preferably transparent, free of yellowing and colorable in an arbitrary color tone.
  • the polyurethane resin preferably has weather resistance and high stretch ability to an extent of allowing for lamination to a three- dimensional curved surface at an ordinary temperature without causing troubles such as rupture and wrinkling, and ensures that the lengthy optical film formed can be taken up in the roll form.
  • the polyurethane resin capable of satisfying these requirements is a solventless-type, organic solvent-based or aqueous reaction-curable polyurethane pre-solution, particularly, a two-component reaction-curable polyurethane pre-solution.
  • a pre-solution is coated on the backing film and dried by heating in a hot air oven or the like, whereby the pre-solution can be cured.
  • the polyurethane pre-solution which can be advantageously used is, for example, a combination of a polyol and a polyisocyanate.
  • Preferred examples of the polyol include acryl polyol and polyester polyol, and preferred examples of the polyisocyanate include isophorone diisocyanate (IPDI).
  • a combination of an isophorone diisocyanate and a polyol prepared by mixing a low molecular weight polycaprolactone diol and a polycarbonate diol can be advantageously used.
  • the polyurethane resin obtained from this polyurethane pre-solution can satisfy all of flexibility at an ordinary temperature, high elongation at break at a high temperature of 8O 0 C, outdoor weather resistance and the like.
  • a polyurethane film may be formed even by using a one-component drying type or ultraviolet (UV)-curable type polyurethane pre-solution, but a film capable of satisfying the requirements of outdoor weather resistance and flexibility at the same time in a high level cannot be obtained.
  • the polyurethane pre-solution may contain arbitrary additives, if desired, in addition to the above-described main ingredients.
  • appropriate additives include a coloring agent, a light stabilizer such as ultraviolet absorbent, and a curing catalyst such as di-n-butyltin dinaphthalate (DBTDL).
  • DBTDL di-n-butyltin dinaphthalate
  • the optical film may be used in various thicknesses (thickness of the substrate portion excluding the protruding rib) according to the intended use, but the thickness is usually from about 5 to 500 ⁇ m, preferably from about 100 to 250 ⁇ m, more preferably from 150 to 200 ⁇ m. If the thickness of the substrate is less than 5 ⁇ m, sufficiently high weather resistance and the like may not be imparted to the optical film, whereas if it exceeds 500 ⁇ m, the thickness of the film becomes conspicuous and this causes reduction in the appearance performance.
  • a plastic film or the like generally used as a carrier film when forming a plastic film by the casting method may be used.
  • Suitable examples of the backing film include, but are not limited to, a polyethylene terephthalate (PET) film, a polyethylene naphthalate (PEN) film, a polypropylene (PP) film, a polyethylene (PE) film, a thermoplastic olefin (TPO) film, a fluororesin film, an acryl film, a polycarbonate film and a silicone film.
  • PET polyethylene terephthalate
  • PEN polyethylene naphthalate
  • PP polypropylene
  • PE polyethylene
  • TPO thermoplastic olefin
  • the backing film may be used in various thicknesses according to the size of the grooved ribs (corresponding to the protruding ribs) to be previously imparted, the conditions of transferring protruding ribs, and the like, but the thickness is usually from about 30 to 1,000 ⁇ m, preferably from about 50 to 500 ⁇ m.
  • the grooved ribs have a shape and a size corresponding to those of the protruding ribs which should be imparted to the target optical film.
  • the backing film not only has a function of imparting protruding ribs but also can improve the handleability of the optical film and can be separated from the optical film at the use of the optical film.
  • the backing film has a function of imparting excellent surface gloss to the protruding rib-holding surface of the obtained optical film.
  • the coating can be cured by heating in an oven or with use of other heating means.
  • the obtained stack may be allowed to stand at an ordinary temperature, thereby completely curing the coating.
  • the stack can be taken up in the roll state and allowed to stand, whereby the coating can be completely cured.
  • the laminate film can be formed from various plastic materials, similarly to the backing film. Suitable examples of the laminate film include, but are not limited to, a polyethylene terephthalate (PET) film, a polyethylene naphthalate (PEN) film, a polypropylene (PP) film, a polyethylene (PE) film, a thermoplastic olefin (TPO) film, a fluororesin film, an acryl film, a polycarbonate film and a silicone film.
  • PET polyethylene terephthalate
  • PEN polyethylene naphthalate
  • PP polypropylene
  • PET polyethylene
  • TPO thermoplastic olefin
  • a polypropylene (PP) film, a polyethylene (PE) film, a thermoplastic olefin (TPO) film, a fluororesin film, a polyethylene terephthalate (PET) film or the like subjected to a surface release treatment can be advantageously used.
  • the laminate film may be used in various thicknesses, but the thickness is usually from about 4 to 1,000 ⁇ m, preferably from about 25 to 200 ⁇ m.
  • the present invention is not limited only to the optical film itself, but, as special embodiments thereof, a two-layer stacked structure of the optical film and the backing film, and a three-layer stacked structure of the laminate film, the optical film and the backing film are also included in the scope of the present invention.
  • the optical film of the present invention may further have an adhesive layer on the smooth surface opposite the surface having the prismatic protruding ribs.
  • an adhesive layer By laminating and compounding an adhesive layer, the obtained optical film can be laminated on a three- dimensional curved surface at an ordinary temperature and used outdoors without causing heat cracking.
  • the adhesive layer various adhesives may be used. Suitable examples of the adhesive include an acryl-based adhesive, a polyurethane-based adhesive and a polyester-based adhesive.
  • the thickness of the adhesive layer may be varied over a wide range but is usually from about 10 to 500 ⁇ m, preferably from about 20 to 100 ⁇ m.
  • the adhesive layer is advantageously formed from an acryl-based adhesive.
  • the acryl-based adhesive is excellent in the transparency and weather resistance, so that the optical effect and durability of the optical film can be unimpaired and the optical film can be pressure-fixed and laminated on an arbitrary substrate such as three-dimensional curved surface by utilizing its flexibility.
  • the adherend is a spherical body
  • the optical film can be firmly laminated on the surface of the spherical body without causing wrinkling or lifting.
  • a release liner is preferably stacked on the adhesive layer.
  • a smooth PET film-based liner may be used as the release liner, but other commonly employed release liners may also be used.
  • the optical film of the present invention may be colored.
  • a coloring agent such as pigment or dye
  • an optical film with a beautiful appearance attributable to the coloration can be easily produced.
  • Suitable examples of the coloring agent include various dyes or pigments and other coloring agents such as phthalocyanine-based blue pigment, azo-based red pigment, aluminum flake and mica powder.
  • a coloring agent When blending a coloring agent at the stage of a urethane pre-solution, various means may be used.
  • a pigment As the coloring agent, a mill base prepared by previously dispersing and stabilizing a pigment in a binder such as acrylic resin is used as the starting material, and in the case of using a dye, a dye solution prepared by dissolving a dye in a solvent is used as the starting material.
  • the operation required is only to add such a starting material to the urethane pre-solution and mix the solution with stirring.
  • the urethane film obtained by blending an appropriate amount of a pigment or dye having high transparency is light-transparent and allows for distribution of the colored transmitted light by the effect of the lens pattern, so that a novel good-looking appearance can be provided.
  • the optical film of the present invention is preferably provided in the state of being taken up in the roll form.
  • the optical film is preferably provided as a lengthy film roll, the storability or handleability can be remarkably improved.
  • the backlight film or laminate film is used in the roll form, the production can be facilitated and the production space can be reduced.
  • the optical film of the present invention can be used for various applications according to the profile, size, pattern or the like of the prismatic protruding ribs or further according to the presence or absence of coloration.
  • the optical film can be advantageously used as a decorative film by laminating on a windowpane, a show window glass pane or a plated or pained surface of articles, a graphic film by laminating on a car body of automobiles or other vehicles, or a light control sheet by laminating on a lamp cover of a head lamp or the like of automobiles.
  • the optical film of the present invention can exhibit excellent weather resistance in all of these uses and the effect thereof is proved in the outdoor exposure test for 2 years by the present inventors. That is, the optical film of the present invention can be stably used without causing any change in the appearance during long-term outdoor use.
  • a colorless optical film having a protruding rib pattern shown in Fig. 5 can be used by laminating on the inner surface of a lamp cover of an automobile lamp.
  • the optical film can function as a fine prism unproducible when the lamp cover is formed by ejection molding.
  • a colorless optical film having a protruding rib pattern with a rounded apex angle shown in Fig. 7 can be used.
  • the optical film of the present invention is effective, for example, for a building material surface or a transparent substrate such as automotive glass surface or polycarbonate-made motorcycle window screen. Particularly, by the partial lamination, depth feeling and design property can be brought about. These effects can be similarly obtained also on a reflective substrate such as mirror and plated surface.
  • the present invention also provides a method for producing the optical film of the present invention comprising a plurality of fine prismatic protruding ribs.
  • the production method of the present invention may be implemented through various steps, but the method can be preferably performed by the following series production process A, B or C.
  • (3b) a step of heating the optical film precursor to a semi-cured state, (4) a step of stacking a laminate film on the back surface of the optical film precursor still in a semi-cured state, and
  • the production processes A, B and C each may be variously modified within the scope of the present invention and, for example, may comprise a step where the pattern transfer backing film produced in the step (1), the optical film produced in the step (3 a) or step (5), or a stack containing such a film is taken up in the roll form and stored. Accordingly, in the step (2), the pattern transfer backing film is preferably used by unrolling it. Similarly, also in the step (4), the laminate film is preferably used by unrolling it.
  • the production processes A, B and C each preferably further comprises, subsequently to the production step of an optical film, a step of forming an adhesive layer on the smooth surface opposite the protruding rib-holding surface of the optical film. Furthermore, the adhesive layer is preferably covered with a release liner. The adhesive layer and the release liner are as described above.
  • the pattern transfer backing film may be produced according to various techniques, but in practicing the present invention, considering the integration with later production steps, the film formation is preferably performed by using a metal tool having on the surface thereof a plurality of fine protruding ribs corresponding to the grooved ribs of the backing film and having a prismatic cross-section.
  • the metal tool is preferably a metal-made cylinder having on the surface thereof protruding ribs formed by machining.
  • Fig. 8 is a view schematically showing the production process of the pattern transfer backing film for use in practicing the present invention.
  • a 200 ⁇ m-thick polypropylene (PP) film is used as the backing film, and an SUS-made cylinder 53 with protruding ribs is used for imparting grooves having a cross- section in the inverted prism shape to the backing film.
  • PP polypropylene
  • SUS-made cylinder 53 with protruding ribs is used for imparting grooves having a cross- section in the inverted prism shape to the backing film.
  • protruding ribs corresponding to the protruding ribs of the final objective optical film and having the same shape and the same size are imparted in the same pattern.
  • a PP raw material 51 is prepared in a hopper 52 and melt-extruded into a gap between a pair of laminate rollers (cylinder 53 + guide roller 54) disposed below.
  • the PP raw material 51 is formed into a film when passing between laminate rollers and the protruding rib pattern of the cylinder 53 is transferred to the film surface.
  • the obtained backing film 20 having a grooved rib-holding surface 20a as one surface is taken up on a roller 55.
  • Fig. 9 is a view schematically showing one preferred production process of the optical film of the present invention.
  • the backing film 20 is a 200 ⁇ m-thick PP film produced by the method described above by referring to Fig. 8.
  • a method of semi-curing a polyurethane pre-solution in an oven and then completely curing the solution by allowing it to stand at an ordinary temperature is employed, but in another method, the solution may be completely cured or cured nearly to a completely cured state in the oven.
  • a coating of a starting material (polyurethane pre-solution) of a polyurethane resin is stacked on the grooved rib-holding surface 20a of the pattern transfer backing film 20 produced above.
  • a notch bar coat method is used for this stacking step.
  • a polyurethane pre-solution for example, a two-component reaction-curable polyurethane solution
  • the polyurethane pre-solution is coated on the grooved rib-holding surface 20a having an elevation difference of the backing film 20 and therefore, a pre-solution having a large solid content is suitable.
  • a pre-solution capable of being coated to a thickness exceeding 50 ⁇ m as a dry thickness is usually preferred.
  • the backing film 20 is unrolled from the roller 55 and guided between a pair of rollers 64 through a notch bar coater.
  • the gap between laminate rollers 64 is previously set to an optimal value by taking account of the total amount of the thickness of the backing film 20 and the thickness of the finally obtained optical film.
  • a necessary amount of the polyurethane pre-solution 61 is delivered from the vessel 62 by a pre-solution supply roller 63 and coated on the grooved rib-holding surface 20a of the baking film 20 on passing thereabove. That is, the polyurethane pre-solution 61 is cast on the backing film 20 while abutting against the film.
  • the thus-coated polyurethane pre-solution 61 is controlled in the thickness during passing between laminate rollers 64 and while being held as an optical film precursor (coating in the uncured state) on the backing film 20, guided into a hot air oven 65 in the post stage.
  • the coating of the polyurethane pre-solution 61 is heated and cured inside the hot air oven 65.
  • the coating is not completely cured and the heating is finished in the semi-cured state.
  • various designs may be applied to the hot air oven 65.
  • the hot air oven 65 may be divided into four heating zones (70 o C/80°C/80 o C/80°C) and the heating may be performed for about 5 minutes.
  • the solvent dissipates, but the coating is unreacted and accordingly, still nearly uncured (such an unreacted and uncured state is referred to as "semi-cure").
  • a laminate film 30 is withdrawn from a roller 66.
  • the laminate film 30 used here is an untreated biaxially stretched PET film (thickness: 50 ⁇ m).
  • the backing film 20 from the hot air oven 65 and the laminate film 30 from the roller 66 are guided between a pair of laminate roller 67 in the form of sandwiching the semi-cured coating in the middle of these films and stacked.
  • a three-layer structure 40 comprising an optical film 10 on the way of curing as well as a backing film 20 and a laminate film 30 sandwiching the optical film as described above by referring to Fig. 4 is obtained.
  • the three-layer structure 40 is turned in the direction by a guide roller 68, taken up on a take-up roller (not shown) and left standing in the taken-up state.
  • a curing reaction of urethane proceeds by the standing for about 3 days and the optical film 10 on the way of curing can be completely cured.
  • optical film 10 can also be provided in the form of a lengthy film roll having an unbroken continuous protruding rib pattern.
  • a pattern transfer backing film was produced from polypropylene (PP) according to the method described above by referring to Fig. 8.
  • PP polypropylene
  • an SUS- made cylinder 53 with protruding ribs as shown in Fig. 10 was used.
  • the protruding rib patterns of the cylinder 53 are corresponding to protruding rib patterns of the optical films described above by referring to Figs. 5 to 7, respectively, and formed by arraying regions A, B and C having three kinds of protruding rib patterns each in a width of 100 mm. That is, the protruding rib pattern of the region A corresponds to the protruding rib pattern of Fig.
  • a PP raw material (trade name: "NOVATEC PP MA3 U57264", produced by Japan Polypropylene Corp.) was melt-extruded and laminate-shaped by a backing film producing apparatus shown in Fig. 8. Three kinds of protruding rib patterns of the cylinder 53 with protruding ribs are transferred to the PP film, and a PP film having a width of about 380 mm and a thickness of 200 ⁇ m, in which three kinds of grooved rib patterns are formed on one surface, was obtained. The PP film was taken up on a roller and stored.
  • composition ratio by weight (solid content: 77.4%)
  • a polyurethane pre-solution having the composition shown above was notch bar coated with a gap of about 120 ⁇ m. Subsequently, the coating of the polyurethane pre- solution held on the PP film, still in the semi-cured state, was guided into a hot air oven.
  • the hot air oven 65 used in these Examples was consisting of four heating zones (70 o C/80°C/80 o C/80°C). The coating of the polyurethane pre-solution was heated in the hot air oven for a residence time of about 5 minutes. The solvent was dissipated by the heating, but the coating was not completely cured.
  • a separately prepared untreated biaxially stretched PET film (thickness: 50 ⁇ m) was laminated on the semi-cured polyurethane coating supported by the PP film.
  • the obtained stack was taken up on a take-up roller and left standing in that state. During standing at an ordinary temperature over about 3 days, a curing reaction of urethane proceeded and the semi-cured polyurethane coating sandwiched between the PP film and the PET film was completely cured.
  • the obtained polyurethane film was transparent, had a beautiful appearance and could be separated from the PP film and PET film without resistance.
  • a polyurethane film having a thickness of about 100 ⁇ m and having on one surface thereof fine protruding rib patterns (fine lens patterns) corresponding to three kinds of protruding rib patterns of the cylinder 53 was obtained as a lengthy roll. Also, it was confirmed that three kinds of protruding rib patterns of the cylinder 53 were faithfully transferred to one surface of the polyurethane film. Furthermore, the above-described procedure was repeated by omitting the lamination of a biaxially stretched PET film.
  • a PET film (produced by Toyobo Co., Ltd.) subjected to a release treatment was prepared, and an acryl-based pressure-sensitive adhesive (trade name: "RD2737", produced by 3M) was coated on one surface thereof to a thickness of 35 ⁇ m and dried. Subsequently, the smooth surface (surface opposite the fine lens pattern-holding surface) of the polyurethane film produced in Examples 1, 2 and 3 was stacked on the pressure-sensitive adhesive layer surface. The obtained film stack was cut into 30 mm (width) x 90 mm (length) and used as the test film.
  • a transparent acrylic resin-made hemispherical body having a diameter of 150 mm and a thickness of 1.0 mm was prepared.
  • the test film was laminated on the surface of this hemispherical body by hand so that the fine lens pattern- holding surface of the test film could become the outer surface.
  • the test film could follow the spherical surface without causing wrinkles and could be easily laminated. Also, by virtue of the effect of light refraction due to the fine lens pattern on the surface, a uniform beautiful appearance could be obtained.
  • a plating-like acrylic resin-made hemispherical body having the same shape and the same size was prepared in place of the acrylic resin-made hemispherical body, and the above- described lamination test was repeated.
  • the test film could follow the spherical surface without causing wrinkles and could be easily laminated.
  • a strikingly beautiful appearance different from that of the transparent acrylic resin-made hemispherical body could be obtained.
  • the above-described lamination test was repeated by using a commercially available brightness-increasing film (substrate: thickness of 125 ⁇ m and made of PET, prism part: height of 30 ⁇ m, pitch of 50 ⁇ m, apex angle of 90° and made of acrylic resin, trade name: "BEFII90/50", produced by 3M) in place of the test film.
  • This prism film was hard and therefore, did not follow the spherical surface, failing in lamination on both hemispherical bodies.
  • a polyurethane film with a fine lens pattern was produced by repeating the procedure of Example 1 except that in this example, for producing a colored polyurethane film, a blue pigment was added at a ratio (by weight) of 1 per 100 of the polyurethane pre-solution shown in Table 1 (Example 1).
  • the blue pigment used in this example was a mill base obtained by dispersing a phthalocyanine-based blue pigment (trade name: "TX Blue", produced by NOF
  • a red dye was added at a ratio (by weight) of 2.5 per 100 of the polyurethane pre-solution shown in Table 1 (Example 1).
  • the red dye used in this example was a 20% solution obtained by dissolving a red dye (trade name: "Zapon Red 335", produced by BASF) in cyclohexane.
  • a deeply red colored polyurethane film having a fine lens pattern on one surface and having a thickness of about 100 ⁇ m was obtained as a lengthy roll.
  • the lamination performance of a polyurethane film on a spherical adherend was tested according to the method described in Test Example 1 by using, as the test film, the colored polyurethane films with a fine lens pattern produced in Example 4.
  • test film was laminated by hand on each of the transparent acrylic resin-made hemispherical body and the plating-like acrylic resin-made hemispherical body and subjected to the lamination performance test. Similarly to the transparent test film in Test Example 1, the test film could follow the spherical surface of each acrylic resin-made hemispherical body without causing wrinkles and could be easily laminated. Also, by virtue of the effect of light refraction due to the fine lens pattern on the surface and the effect of coloration, a strikingly beautiful appearance different from that when using the transparent test film could be obtained.
  • an unclouded light-transparent colored lens film is obtained by blending a small amount of a pigment or dye having high transparency and the light transmitted through or reflected on the hemispherical body used as the adherend is colored and refracted, as a result, a beautiful appearance with high novelty is obtained.
  • the weather resistance was tested by using, as the test film, the polyurethane films with a fine lens pattern produced in Examples 1, 2 and 3.
  • a PET film (produced by Toyobo Co., Ltd.) subjected to a release treatment was prepared, and an acryl-based pressure-sensitive adhesive (trade name: "RD2737", produced by 3M) was coated on one surface thereof to a thickness of 35 ⁇ m and dried. Subsequently, the smooth surface (surface opposite the fine lens pattern-holding surface) of the polyurethane film produced in Examples 1, 2 and 3 was stacked on the pressure-sensitive adhesive layer surface. The obtained film stack was cut into 30 mm (width) x 90 mm (length) and used as the test film.
  • test film was laminated by hand on a separately prepared panel for automobile outer plate painting test so that the fine lens pattern-holding surface of the test film could became the outer surface.
  • the test panel was disposed in an outdoor test ground to face south at an angle of 30° from the horizon and left standing over 2 years. Thereafter, the appearance and characteristics of the test film were evaluated with an eye, as a result, despite exposure to wind, rain or sunlight over a long period of time, troubles such as discoloration, deformation or delustering were not generated and the test film was still a fine lens film having light transparency and light refraction effect unchanged from those in the initial stage, thereby confirming its durability for long-term outdoor use.
  • BEF film 1 an optical film obtained by shaping a uniform wave pattern on the surface of a transparent polycarbonate substrate; substrate: thickness of 180 ⁇ m, wave pattern: height of 70 ⁇ m, pitch of 100 ⁇ m and apex angle of about 90°, trade name: "WAVE W818", produced by 3M), and
  • BEF film 2 (substrate: thickness of 125 ⁇ m and made of PET, prism part: height of 30 ⁇ m, pitch of 50 ⁇ m, apex angle of 90° and made of ultraviolet curable acrylic resin, trade name: "Accentrim (registered trademark)", produced by
  • test Example 2 in order to test the lamination performance of a polyurethane film on a spherical adherend, the method described in Test Example 1 was repeated. However, in this example, an exposure test was performed by allowing the test film laminated on each of the acrylic resin-made hemispherical bodies to stand outdoors over 1 year. In all of the test films, separation, discoloration, deformation of prism, and chipping were not generated, and the light refraction effect, transparency and beautiful appearance were maintained.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Health & Medical Sciences (AREA)
  • Ophthalmology & Optometry (AREA)
  • Mechanical Engineering (AREA)
  • Optical Elements Other Than Lenses (AREA)
  • Casting Or Compression Moulding Of Plastics Or The Like (AREA)
  • Laminated Bodies (AREA)
  • Moulding By Coating Moulds (AREA)

Abstract

L'invention concerne un film optique capable d'entraîner des caractéristiques remarquablement élevées en terme d'effet visuel, d'effet décoratif et d'autre effet similaire, ainsi que d'excellentes caractéristiques en terme d'effet de contrôle de lumière, qui ne peut pas être fabriqué, ou qui est difficile à fabriquer par les films de lentille ou les films prisme classiques. Le film optique comporte une pluralité de fines nervures saillantes prismatiques agencées selon un modèle prédéterminé sur une surface du film optique, et comportant une résine de polyuréthanne transparente à deux composants, ne jaunissant pas et durcissant par réaction. Les nervures saillantes prismatiques proviennent d'une pluralité de fines nervures cannelées agencées sur la surface d'un film de renfort de transfert de modèle mis en butée contre un matériau de départ sur le trajet de mise en forme du film optique. Lesdites nervures cannelées correspondent aux nervures saillantes, et présentent une section transversale sous la forme d'un prisme inversé.
PCT/US2007/081184 2006-10-13 2007-10-12 Film optique et son procédé de fabrication WO2008048870A2 (fr)

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JP2006280259A JP2008096820A (ja) 2006-10-13 2006-10-13 光学フィルム及びその製造方法
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Cited By (3)

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JP2021067735A (ja) * 2019-10-18 2021-04-30 大塚テクノ株式会社 反射防止構造体
CN113133300A (zh) * 2021-04-15 2021-07-16 维沃移动通信(重庆)有限公司 纹理加工工艺、盖体和电子设备
WO2022222285A1 (fr) * 2021-04-22 2022-10-27 庄煌 Structure de face réfléchissante tridimensionnelle

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TW201116858A (en) * 2009-07-06 2011-05-16 Sumitomo Chemical Co Light diffusion plate and method for generating array pattern of optical elements on light diffusion plate
JP2011221131A (ja) * 2010-04-06 2011-11-04 Dainippon Printing Co Ltd 光学部材用保護フィルム、光学部材積層体および光学部材積層体の製造方法
JP2012194308A (ja) * 2011-03-16 2012-10-11 Dic Corp プリズムシート及びその製造方法
JP5724527B2 (ja) * 2011-03-29 2015-05-27 大日本印刷株式会社 導光板積層体およびその製造方法
US20150309227A1 (en) * 2012-11-20 2015-10-29 Sumitomo Chemical Company, Limited Light-modulating member

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US20040075897A1 (en) * 1998-08-05 2004-04-22 Mitsubishi Rayon Co., Ltd. Lens sheet and method of manufacturing the same
US20040190102A1 (en) * 2000-08-18 2004-09-30 Mullen Patrick W. Differentially-cured materials and process for forming same
WO2005098485A1 (fr) * 2004-04-09 2005-10-20 Kimoto Co., Ltd. Feuille de régulation de lumière et source lumineuse de surface utilisant celle-ci
WO2006022270A1 (fr) * 2004-08-24 2006-03-02 Zeon Corporation Rétroéclairage directement sous-jacent

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Publication number Priority date Publication date Assignee Title
US20040075897A1 (en) * 1998-08-05 2004-04-22 Mitsubishi Rayon Co., Ltd. Lens sheet and method of manufacturing the same
US20040190102A1 (en) * 2000-08-18 2004-09-30 Mullen Patrick W. Differentially-cured materials and process for forming same
WO2005098485A1 (fr) * 2004-04-09 2005-10-20 Kimoto Co., Ltd. Feuille de régulation de lumière et source lumineuse de surface utilisant celle-ci
WO2006022270A1 (fr) * 2004-08-24 2006-03-02 Zeon Corporation Rétroéclairage directement sous-jacent

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2021067735A (ja) * 2019-10-18 2021-04-30 大塚テクノ株式会社 反射防止構造体
CN113133300A (zh) * 2021-04-15 2021-07-16 维沃移动通信(重庆)有限公司 纹理加工工艺、盖体和电子设备
WO2022222285A1 (fr) * 2021-04-22 2022-10-27 庄煌 Structure de face réfléchissante tridimensionnelle

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