JP5729908B2 - Structured optical film and backlight using the same - Google Patents

Description

  The present invention relates to a structured optical film used for, for example, a backlight of a liquid crystal display device, and makes it difficult to visually recognize an optical defect while preventing a decrease in front luminance, and uses a structured optical film having a wide viewing angle and the same. It relates to the backlight.

  In recent years, color liquid crystal display devices have been used in various fields such as monitors for notebook personal computers or desktop personal computers or liquid crystal televisions. This type of liquid crystal display device includes a liquid crystal cell and a backlight, and the backlight has a light source structure directly below the liquid crystal cell via a diffusion plate or a light source. An edge light type structure provided on the side surface of the light plate is known.

  The color liquid crystal display device is superior in that it consumes less power than PDP and CRT. However, in a color liquid crystal display device, the front luminance tends to be low. Therefore, it is required to increase the front luminance with low power consumption by increasing the optical efficiency using the above-described backlight.

  Such a backlight is generally composed of a light source, a diffusion plate, a light guide plate, a structured optical film, and the like.

  Among these, the structured optical film is disposed on the light exit surface of the diffusion plate or the light guide plate, and collects the light emitted from the diffusion plate or the light guide plate to the front by a refracting function, thereby improving the front luminance. Fulfill.

  In general, the structured optical film includes a lens portion in which a plurality of structures having a triangular cross section are regularly arranged, and is formed by the apex angle of the triangular structure, that is, the oblique sides of the structure. It is considered that an angle of 90 ° is optimal for increasing the front luminance. It is considered that the radius of curvature of the top of the lens unit is 0, that is, it is desirable that the tip has a sharp shape (Patent Document 1).

JP 09-197109 A (Embodiment of the Invention)

  Since the structured optical film described above has a sharp tip at the structure, the tip of the structure is likely to have fine defects due to vibration during handling or use. Since optical defects such as lowering occur, handling of the structured optical film requires great care so that the yield does not decrease.

  Furthermore, regarding optical members other than the structured optical film described above, and members such as a diffusion plate and a light guide plate, fine defects may be introduced in the manufacturing process and the backlight assembly process, and members having such defects are included. The included backlight similarly has an adverse effect on the optical characteristics, and thus has a problem that the commercial value is lost.

  Further, it is preferable that the liquid crystal display device can be comfortably visually recognized without being darkened not only in the front direction but also in an oblique direction with respect to the device, and a wide viewing angle is desired. Yes.

  Accordingly, an object of the present invention is to provide a structured optical film having a wide viewing angle and a backlight using the same, while making it difficult to visually recognize optical defects while preventing a decrease in front luminance.

  As a result of diligent studies to solve these problems, the present inventors made a structured optical film having a special structured surface, while exhibiting the function of improving the front luminance, while preventing optical defects. It has been found that a structured optical film can be made difficult to visually recognize and has a wide viewing angle, and the present invention has been achieved.

That is, the structured optical film of the present invention has a structured surface, and the structured surface is constituted by a plurality of convex rows arranged in parallel, and the adjacent convex rows are arranged in parallel. Separated by valleys, each convex row has a peak, the peak height varies along its ridgeline, the peak height variation is periodic, and the average period is 1000-5000 μm. With respect to the period of the peak height fluctuation, when there is a phase difference in the period for each convex row and the fluctuation range of the peak height that fluctuates along the ridge line is ΔH, 1 μm ≦ | [Delta] H | 40% of the maximum peak height on ≦ ridge, satisfy the relationship, the structured surface is made up of a convex row of the two kinds different Do that the average height along the ridgeline of the peak The peak height variation of convex rows with low average height Is larger than the fluctuation range of the peak height of the convex row having a high average height, the pitch between adjacent peaks is different from the pitch before and after the peak, and the pitch between the adjacent valleys is Hp _max is the maximum height on the ridge line when cut in a direction perpendicular to the flow direction of the peak ridge line of the convex row at any point of the structured optical film, which varies along the flow direction . When the minimum height is Hp _min , the relationship of Hp _max −Hp _min ≧ 11 μm is satisfied.

  Moreover, the structured optical film of the present invention is preferably characterized in that the pitch between peaks is formed by alternately repeating two types of pitches.

  In addition, the structured optical film of the present invention is preferably characterized in that the difference between two types of pitches between peaks is 2 μm or more, and one pitch is 10 to 200 μm.

  Moreover, the structured optical film of the present invention is preferably composed of two types of convex rows having different average heights along the ridgeline of the peak, and has a convex shape with a low average height. The fluctuation range of the peak height of the row is larger than the fluctuation range of the peak height of the convex row having a high average height.

Further, the structured optical film of the present invention preferably has a maximum height on the ridge line when cut in a direction perpendicular to the flow direction of the peak ridge line of the convex row at an arbitrary position of the structured optical film. Is Hp _max and the minimum height is Hp _min , the relationship of Hp _max −Hp _min ≧ 3 μm is satisfied.

  Further, the backlight of the present invention includes at least a light source, an optical plate disposed adjacent to the light source, for guiding or diffusing, and a structured optical film disposed on the light emitting side of the optical plate. The structured optical film is a structured optical film of the present invention.

  The structured optical film of the present invention has a structured surface, and the structured surface is constituted by a plurality of convex rows generally arranged in parallel, and adjacent convex rows are formed by valleys. The convex rows are separated, each having a peak, the peak height varies along its ridgeline, the peak height variation is periodic, and the average period is 1000-5000 μm Since the pitch between adjacent peaks is different from the pitch before and after that, and the pitch between adjacent valleys varies along the flow direction of the valleys, the function of improving the front brightness, which could not be achieved conventionally. It is possible to make it difficult to visually recognize optical defects and to have a wide viewing angle.

The perspective view which shows embodiment of the structured optical film of this invention The perspective view which shows embodiment of the structured optical film of this invention The top view which shows embodiment of the structured optical film of this invention Side view showing an embodiment of the structured optical film of the present invention Sectional drawing which shows embodiment of the structured optical film of this invention The perspective view which shows embodiment of the backlight of this invention

  The structured optical film of the present invention has a structured surface, and the structured surface is constituted by a plurality of convex rows that are generally arranged in parallel, and adjacent convex rows are valleys. The convex rows each have a peak, the peak height varies along its ridgeline, the peak height variation is periodic, and the average period is 1000-5000 μm. The pitch between adjacent peaks is different from the pitch before and after that, and the pitch between adjacent valleys varies along the flow direction of the valleys. The backlight of the present invention uses the structured optical film of the present invention. Hereinafter, embodiments of the structured optical film of the present invention will be described.

  1 and 2 are perspective views showing one embodiment of the structured optical film of the present invention. The structured optical film 1 shown in FIGS. 1 and 2 has a structured surface 2, and the structured surface 2 is constituted by a plurality of convex rows 3 that are generally arranged in parallel. , Adjacent convex rows 3 are separated by valleys 4, each of which has a peak 5, the height of peak 5 varies along its ridgeline, and the height of peak 5 The fluctuation is periodic, the average period is 1000 to 5000 μm, the pitch 6 between the adjacent peaks 5 is different from the pitch 6 before and after that, and the pitch 7 between the adjacent valleys 4 is that of the valley 4. It fluctuates along the flow direction.

  Moreover, about the structured optical film of this invention, the shape observed from the plane direction is shown in FIG. The structured optical film 1 of the present invention is different from 6 ′, which is the pitch before and after the pitch 5 between adjacent peaks 5 as described above, and the pitch 7 between adjacent valleys 4 is the above-described valley 4. Fluctuate along the flow direction (fluctuated as 7, 7 ′, 7 ″ in FIG. 3).

  Moreover, about the structured optical film of this invention, the shape observed from the side surface direction is shown in FIG. In the structured optical film 1 of the present invention, as described above, the height of the peak 5 varies along the ridgeline, and the height variation of the peak 5 is periodic, and the average period is 1000 to 5000 μm. is there. Similarly, the height of the valley 4 varies.

  In addition, as shown in FIG. 4, the average height of the valley in the present invention refers to the length p from the surface facing the structured surface of the layer having the structured surface to the average surface of the ridge line of the valley, and the peak Is the length q from the average surface of the peak ridgeline of the structured surface to the average height of the valleys.

  In addition, as shown in FIG. 4, the peak height in the present invention refers to the actual length a from the average height of the valley at an arbitrary point to the peak ridge line, and the valley height is an arbitrary height. It refers to the actual length b from the surface facing the structured surface of the layer having the structured surface of the point to the valley.

  In the structured optical film of the present invention, the height of the peak of the convex row thus fluctuates along the ridge line, the pitch between adjacent peaks is different from the pitch before and after the peak, or between the adjacent valleys. Since a special structured surface in which the pitch fluctuates along the valley flow direction is provided, a structured optical film in which optical defects are difficult to visually recognize without lowering the front luminance can be obtained. Here, the “optical defect” refers to a defect such as a decrease in luminance caused by the presence of scratches or foreign matters having a diameter of about 10 to 100 μm. Further, by providing such a structured surface, it is possible to improve the luminance not only in the front direction but also in a direction slightly deviating from the front direction as compared with the conventional structured optical film. Moreover, since such a structured optical film makes it difficult to visually recognize optical defects, excessive care during manufacture and use is not necessary, and the handleability is good.

  Moreover, the structured optical film of the present invention has periodicity in peak height fluctuation along the ridgeline, and the average period is 1000 to 5000 μm, so that it is not only in the front direction but also in the direction away from the front direction. In contrast, light can be emitted efficiently. As a result, the luminance can be improved even in a direction away from the front direction, and a wide viewing angle can be achieved. Further, when the average period is within such a range, it is possible to make it difficult to visually recognize the optical defect without reducing the front luminance more than necessary. The average period is more preferably 1000 to 2000 μm.

  The pitch between the valleys of the convex rows varies along the flow direction of the valleys. When the pitch between adjacent valleys varies along the flow direction of the valleys, the optical defect can be made difficult to visually recognize. It is preferable that the pitch between the valleys varies randomly within a range of 2 to 30% of the maximum height of the peak from the viewpoint of making it difficult to visually recognize an optical defect without lowering the front luminance more than necessary. Specifically, it is preferable to vary randomly within a range of 10 to 200 μm.

  The apex angle of the valleys of the convex rows is preferably in the range of 80 to 105 °.

  Next, the pitch between adjacent peaks in the convex row is different between the pitch and the front and rear pitches. By adopting a configuration in which the pitch between the peaks is different from the front and rear pitches, it is possible to make it difficult to visually recognize the optical defect. Further, from the viewpoint of sufficiently suppressing the decrease in front luminance, it is preferable that two types of pitches are alternately repeated.

  The pitch between the peaks is different from the pitch before and after, but one pitch is preferably in the range of 10 to 200 μm, more preferably 10 to 80 μm.

  Further, the difference between the pitch between the peaks and the pitch before and after the peak is preferably different by 2 μm or more, more preferably within a range of 2 to 10 μm. In addition, it is more preferable that the above-described difference is provided in the relationship between the pitch between the peaks in the range of 10 to 200 μm and the pitch before and after the peak.

  Further, the peak height of the convex row varies along its ridgeline. By changing the height of the peak along the ridge line and making the pitch between adjacent peaks different from the pitch before and after the peak, it is possible to make it difficult to visually recognize the optical defect.

  The average height of the peaks in the convex row is not unclear because it depends on the apex angle of the peaks and the pitch of the valleys, but is preferably 5 to 100 μm from the viewpoint of improving the front luminance. More preferably, it is ˜40 μm.

  Further, when the above-described peak height fluctuation region is ΔH, 1 μm ≦ | ΔH | ≦ maximum peak height on the ridge line from the viewpoint of suppressing scratches during handling and making optical defects less likely to occur. It is preferable to satisfy the 40% relationship. In particular, 1 μm ≦ | ΔH | ≦ more preferably satisfies the relationship of 25% of the maximum height of the peak on the ridgeline.

  In addition, regarding the period of the peak height fluctuation, it is preferable that a phase difference exists in the period for each convex row. The period of peak height variation along the ridge line does not coincide at any point in the flow direction of the ridge line for each convex row, and the presence of a phase difference allows the structured optical film The points to be grounded with respect to the member facing the structured surface will be dispersed, and the damage to the film will be alleviated.

  The structured surface is composed of a plurality of convex rows that are generally arranged in parallel, and the convex rows are two types having different average heights along the ridgeline of the peak. It is preferable to be made of a material from the viewpoint of making it difficult to visually recognize optical defects.

  In particular, if the fluctuation range of the peak height of the convex row with the low average height is larger than the fluctuation range of the peak height of the convex row with the high average height, the average height is low. The height of an arbitrary peak of a convex row may exceed the height of an arbitrary peak of a convex row having a high average particle diameter, and a structured optical film having such a structured surface is a facing member This is preferable in that it can suppress scratches and the like during handling.

  Further, in the two types of convex rows having different average heights along the peak ridgeline, the peak height variation along the ridgeline has a constant average period as described above. Thereby, the high brightness | luminance to a front direction can be maintained further.

Further, the structured optical film of the present invention is on a ridge line when cut in a direction perpendicular to the flow direction of the ridge line of the peak of the convex row as shown in FIG. 5 at an arbitrary position of the structured optical film. When the maximum height is Hp _max and the minimum height is Hp _min , the relationship of Hp _max −Hp _min ≧ 3 μm is preferably satisfied, and further the relationship of Hp _max −Hp _min ≧ 5 μm is more preferable. By satisfying such a relationship, it is difficult to visually recognize the optical defect.

  The apex angle of the peak of the convex row is preferably in the range of 80 to 105 °. Further, the shape of the convex row may be a triangular column having a sharp peak, or a shape having a slight R at the end of the triangular column.

  In addition, the structured optical film of the present invention improves the luminance in the front direction as described above, but when incorporated in a liquid crystal display device or the like, not only the front direction but also an oblique direction with respect to the front direction. In contrast, the brightness is high and the viewing angle is wide. For example, depending on the specific configuration of the backlight device, when the luminance in the normal direction is set to 100% with respect to the lens layer surface of the structured optical film, it is inclined by 50 degrees from the normal direction. The brightness at the tilted position is 40% or more. When the luminance is 40% or more, it is difficult to give the viewer a sense of incongruity, such as when the image suddenly becomes dark when viewed from an oblique direction with respect to the front direction.

  As the structure of the structured optical film of the present invention, a layer having a structured surface is laminated on a support even if it is composed of a single layer having the structured surface described above. There may be.

  As the support, a highly transparent material such as a glass plate or a plastic film can be used. As the glass plate, it is possible to use a glass plate made of oxide glass such as silicate glass, phosphate glass, borate glass, etc., especially silicate glass, alkali silicate glass, soda lime glass, A silicate glass such as potash lime glass, lead glass, barium glass, borosilicate glass or the like is preferably used as a plate glass. As the plastic film, for example, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyethylene, polypropylene, polystyrene, triacetyl cellulose, acrylic, polyvinyl chloride, norbornene compound, etc. can be used. Polyethylene terephthalate film is preferably used because of its excellent mechanical strength and dimensional stability. It is preferable to use a support that has been subjected to an easy adhesion treatment such as a plasma treatment, a corona discharge treatment, a far-ultraviolet irradiation treatment, or an undercoat easy adhesion layer.

  Although it does not specifically limit as thickness of a support body, Although it can select suitably with respect to the material applied, Generally it is 25-300 micrometers, Preferably it is 50-300 micrometers.

  The layer having the structured surface of the present invention is made of a polymer resin. Examples of the polymer resin include an ionizing radiation curable resin, a thermosetting resin, and a thermoplastic resin.

  As the ionizing radiation curable resin, a photopolymerizable prepolymer that can be crosslinked and cured by irradiation with ionizing radiation (ultraviolet ray or electron beam) can be used. An acrylic prepolymer having at least one acryloyl group and having a three-dimensional network structure by crosslinking and curing is particularly preferably used. As the acrylic prepolymer, urethane acrylate, polyester acrylate, epoxy acrylate, melamine acrylate, polyfluoroalkyl acrylate, silicone acrylate and the like can be used. Furthermore, these acrylic prepolymers can be used alone, but it is preferable to add a photopolymerizable monomer in order to improve the cross-linking curability and the hardness of the lens layer.

  As photopolymerizable monomers, monofunctional acrylic monomers such as 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, butoxyethyl acrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, diethylene glycol One kind of bifunctional acrylic monomer such as diacrylate, polyethylene glycol diacrylate, hydroxypivalate ester neopentyl glycol diacrylate, etc., or polyfunctional acrylic monomer such as dipentaerythritol hexaacrylate, trimethylpropane triacrylate, pentaerythritol triacrylate or the like Two or more are used.

  In addition to the above-described photopolymerizable prepolymer and photopolymerizable monomer, it is preferable to use additives such as a photopolymerization initiator and a photopolymerization accelerator when curing by ultraviolet irradiation.

  Examples of the photopolymerization initiator include acetophenone, benzophenone, Michler's ketone, benzoin, benzylmethyl ketal, benzoylbenzoate, α-acyloxime ester, thioxanthone and the like.

  Further, the photopolymerization accelerator is capable of reducing the polymerization obstacle due to air at the time of curing and increasing the curing speed. For example, p-dimethylaminobenzoic acid isoamyl ester, p-dimethylaminobenzoic acid ethyl ester, etc. Can be mentioned.

  Thermosetting resins include silicone resins, phenolic resins, urea resins, melamine resins, furan resins, unsaturated polyester resins, epoxy resins, diallyl phthalate resins, guanamine resins, ketone resins, Examples include amino alkyd resins, urethane resins, acrylic resins, and polycarbonate resins. These can be used alone, but it is desirable to add a curing agent in order to further improve the crosslinkability and the hardness of the crosslinked cured coating film.

  As the curing agent, a compound such as polyisocyanate, amino resin, epoxy resin, or carboxylic acid can be appropriately used in accordance with a suitable resin.

  As thermoplastic resins, ABS resin, norbornene resin, silicone resin, nylon resin, polyacetal resin, polycarbonate resin, modified polyphenylene ether resin, polybutylene terephthalate, polyethylene terephthalate, sulfone resin, imide resin, fluorine resin Resin, styrene resin, acrylic resin, vinyl chloride resin, vinyl acetate resin, vinyl chloride-vinyl acetate copolymer resin, polyester resin, urethane resin, nylon resin, rubber resin, polyvinyl ether, polyvinyl Examples include alcohol, polyvinyl butyral, polyvinyl pyrrolidone, and polyethylene glycol.

  Of these thermosetting resins or thermoplastic resins, acrylic resin thermosetting resins or thermoplastics are used from the viewpoint of obtaining coating strength when forming a layer having a structured surface and good transparency. It is preferable to use a resin. Moreover, these thermosetting resins or thermoplastic resins can also be used as thermosetting resins or composite resins in which a plurality of types of thermoplastic resins are combined.

  As the polymer resin, a resin other than the above-mentioned resin can be used in combination, but as the content ratio of the above-described polymer resin and the other resin, from the viewpoint of accurately producing the structure of the present invention, As will be described later, when a prism sheet is produced by the Photo-Polymer method (2P method), the ionizing radiation curable resin is preferably contained in an amount of 30% by weight or more in the total polymer resin component. On the other hand, when a prism sheet is produced by the Thermal-Transformation method (2T method) or other embossing methods, it is preferable that 30% by weight or more of the thermosetting resin or thermoplastic resin is contained in the total polymer resin component.

  In addition to the polymer resin described above, the layer having a structured surface may be fine particles, lubricants, fluorescent whitening agents, antistatic agents, flame retardants, antibacterial agents, as long as the effects of the present invention are not impaired. Various additives such as fungicides, ultraviolet absorbers, light stabilizers, antioxidants, plasticizers, leveling agents, flow regulators, antifoaming agents, dispersants, mold release agents, crosslinking agents, etc. may be included. it can.

  The thickness of the layer having the structured surface is, in the case of forming the structured optical film of the present invention as a single layer having the structured surface, from the viewpoint of obtaining sufficient coating strength and smoothness of the layer, It is preferable to set it as 25-300 micrometers. On the other hand, when a structured optical film is formed by forming a layer having a structured surface on a support, the thickness is preferably 3 to 10 μm. The thickness of the layer having a structured surface here refers to the thickness of only the resin portion where the structure is not formed (portion p in FIG. 4).

  As a method for producing a structured optical film having a layer having a structured surface according to the present invention, it can be formed by a transfer shaping technique such as 2P method, 2T method or other embossing method. For example, a polymer resin or the like constituting a layer having a structured surface as described above is filled in a mold having a shape complementary to the surface shape of the layer having the required structured surface, and the shape pattern is transferred. After the shaping, the polymer resin or the like is cured and peeled from the mold to obtain a structured optical film having a layer having a structured surface on which the structure is shaped. On the other hand, when a support is used, a polymer resin or the like is filled in the mold, the support is overlaid thereon, the polymer resin or the like is cured, and the support is removed from the mold. A structured optical film comprising a layer having a structured surface on which a structure is shaped is obtained. When forming a layered structure having a structured surface by the 2P method, an ionizing radiation curable resin is used to form a layered structure having a structured surface by the 2T method or other embossing methods. In some cases, a thermosetting resin or a thermoplastic resin is used.

  Of the above-described transfer shaping techniques, the structured optical film can be produced in a relatively short time, and since heating and cooling are unnecessary, it is preferable to adopt the 2P method from the viewpoint of suppressing the deformation of the component due to heat. . On the other hand, it is preferable to adopt the 2T method from the viewpoint that the degree of freedom of material selectivity of the constituent members is high and the process cost can be reduced.

  In addition, the embossing method formed at room temperature results in a gentler corner than the uneven shape of the plate (embossing roll) due to the elasticity of the polymer resin at the time of formation, and the uneven shape of the desired size Therefore, the 2P method and the 2T method are more preferable in that a desired uneven shape can be accurately formed.

  As a method for curing the polymer resin, when the polymer resin is an ionizing radiation curable resin, it can be cured by irradiating with ionizing radiation. Further, when the polymer resin is a thermosetting resin, it can be cured by applying heat. Here, as the ionizing radiation, for example, ultra-high pressure mercury lamps, high-pressure mercury lamps, low-pressure mercury lamps, carbon arcs, metal halide lamps, etc. emitted from 100 to 400 nm, preferably 200 to 400 nm wavelength region, scanning type / curtain type An electron beam emitted from an electron beam accelerator having a wavelength region of 100 nm or less can be used. The heating temperature of the thermosetting resin is designed in consideration of the type of resin and the thickness of the layer having a structured surface, but is usually in the range of 80 to 200 ° C.

  Since the structured optical film of the present invention has a special structured surface in this way, it is possible to make it difficult to visually recognize optical defects without lowering the front luminance. Therefore, the handleability at the time of manufacture and use is also good without reducing the yield.

  Next, an embodiment of the backlight of the present invention will be described. A cross-sectional view showing one embodiment of the backlight of the present invention is shown in FIG. The backlight 10 of the present invention of FIG. 6 is an edge light type backlight, and includes a light source 11, a light guide plate 12, and a structured optical film 1 placed thereon. As shown in the figure, a light diffusion sheet 13 or the like may be provided adjacent to the structured optical film 1 as necessary.

  In addition, as the backlight of the present invention, FIG. 6 illustrates an edge light type backlight, but the backlight of the present invention has a light source disposed below the diffusion plate, and a light diffusion sheet for lower use on the upper side. The present invention can also be applied to a direct type backlight provided with a structured optical film, an upper diffusion sheet, and the like.

  As described above, the backlight of the present invention is provided with the structured optical film in which it is difficult to visually recognize optical defects without lowering the front luminance, which could not be achieved in the past. Optical defects attached to other members can be made difficult to visually recognize, and the other members also have excellent handleability. In addition, since the structured optical film having a wide viewing angle is provided, a liquid crystal display device using the backlight can have a wide viewing angle and high visibility.

  The following examples further illustrate the present invention. “Parts” and “%” are based on weight unless otherwise specified.

1. Preparation of structured optical film [Example 1]
A copper plate having a smooth surface and a thickness of 4 mm was cut using a 90 ° bit made of diamond to produce a mold. To the mold, 50 parts by weight of acrylic monomer (methyl methacrylate: Wako Pure Chemical Industries), 45 parts of polyfunctional acrylic monomer (NK ester A-TMPT-3EO: Shin-Nakamura Chemical Co., Ltd.), photopolymerization initiator ( (Irgacure 184: Ciba Japan Co., Ltd.) 5 parts of the mixture is dropped, covered with a 100 μm thick polyester film (Cosmo Shine A4300: Toyobo Co., Ltd.), and the resin is spread evenly with a roller so that no bubbles remain. The resin and the polyester film were adhered.

In this state, a 1500 mJ / cm ² ultraviolet ray was irradiated from the polyester film side with a metal halide lamp to cure the ultraviolet curable resin, and then the polyester film was peeled off to faithfully transfer the shape of the mold. 1 structured optical film was prepared.

<Structured optical film of Example 1>
・ Peak apex angle: 90 °
・ Peak pitch: repetition of 40 μm and 36 μm (repetition of 6 and 6 ′ in FIG. 3)
Constitution of convex rows: repetition of convex rows with a high average height and convex rows with a low average height (repetition of m and n in FIG. 5)
-Average height Hb of peaks of convex rows having a high average height: 23 μm
(Average height q in FIG. 4)
・ Fluctuation range ΔHb of the peak height of the convex row having a high average height: ± 3 μm
(Vertical fluctuation range of actual length a in FIG. 4)
・ Maximum peak height of convex rows with high average height: 26 μm
-Average height Hs of peaks of convex rows with low average height: 22 μm
(Average height q in FIG. 4)
・ Fluctuation range ΔHs of peak height of convex rows with low average height: ± 4 μm
(Vertical fluctuation range of actual length a in FIG. 4)
・ Maximum height of peaks of convex rows with low average height: 26 μm
・ Average period of peak height fluctuation: 1000 μm
(S in FIG. 4)
・ Hp _max −Hp _min = 8 μm
・ Pitch between valleys: Fluctuates randomly within a range of 29 to 48 μm along the flow direction of the valleys

[Example 2]
A structured optical film of Example 2 below was produced in the same manner as in Example 1 except that the copper plate was cut under a cutting condition different from that of Example 1.

<Structured optical film of Example 2>
・ Peak apex angle: 90 °
・ Peak pitch: 54 μm, 48 μm, 44 μm repeat ・ Construction of convex rows: convex rows with the highest average height, convex rows with the second highest average height, and average height Repetition with the lowest convex row ・ Average height of peak of convex row with the highest average height Hb: 30 μm
・ Fluctuation range ΔHb of the peak height of the convex row having the highest average height: ± 3 μm
・ Maximum peak height of convex rows with the highest average height: 33 μm
The average height Hm of the peak of the convex row having the second highest average height Hm: 28.5 μm
・ Fluctuation range ΔHm of peak height of convex row having the second highest average height: ± 4.5 μm
The maximum height of the peak of the convex row having the second highest average height: 33 μm
-Average height Hs of peak of convex row having the lowest average height: 27.5 μm
・ Fluctuation range ΔHs of peak height of convex row having the lowest average height: ± 5.5 μm
・ Maximum peak height of the convex row with the lowest average height: 33 μm
・ Average period of peak height fluctuation: 1500μm
・ Hp _max −Hp _min = 11 μm
・ Pitch between valleys: Fluctuates randomly within the range of 38-60 μm along the flow direction of the valleys

[Example 3]
A structured optical film of Example 3 below was produced in the same manner as in Example 1 except that the copper plate was cut under a cutting condition different from that of Example 1.

<Structured optical film of Example 3>
-Peak apex angle: 90 °
・ Peak pitch: 40 μm, 36 μm repeat ・ Convex row configuration: repeat of convex row with high average height and convex row with low average height ・ Convex shape with high average height Average height Hb of rows: 23 μm
・ Fluctuation range ΔHb of the peak height of the convex row having a high average height: ± 3 μm
・ Maximum peak height of convex rows with high average height: 26 μm
-Average height Hm of convex rows with low average height: 22 μm
・ Fluctuation range ΔHm of the peak height of the convex row with a low average height: ± 4 μm
・ Maximum height of peaks of convex rows with low average height: 26 μm
・ Average period of peak height fluctuation: 1500μm
・ Hp _max −Hp _min = 8 μm
・ Pitch between valleys: Fluctuates randomly within the range of 30 to 46 μm along the flow direction of the valleys

[Example 4]
A structured optical film of Example 4 below was produced in the same manner as in Example 1 except that the copper plate was cut under a cutting condition different from that of Example 1.

<Structured optical film of Example 4>
・ Peak apex angle: 90 °
・ Pitch between peaks: 50 μm, 46 μm repeat ・ Construction of convex rows: repeat of convex rows with high average height and convex rows with low average height ・ Convex rows with high average height The average height Hb of the column peak: 25 μm
・ Fluctuation range ΔHb of the peak height of the convex row having a high average height: ± 4 μm
・ Maximum peak height of convex rows with high average height: 29 μm
-Average height Hs of peaks of convex rows having a low average height: 23 μm
・ Fluctuation range ΔHs of peak height of convex rows with low average height: ± 6 μm
・ Maximum height of peaks of convex rows with low average height: 29 μm
-Average period of peak height fluctuation: 2000 μm
・ Hp _max −Hp _min = 12 μm
・ Pitch between valleys: Fluctuates randomly within the range of 38 to 58 μm along the flow direction of the valleys.

[Example 5]
The structured optical film of Example 5 was produced in the same manner as in Example 4 except that the average period of peak height fluctuation of the molded product was changed to 6000 μm among the cutting conditions of the copper plate of Example 4. .

[Comparative Example 1]
A structured optical film of Comparative Example 1 below was produced in the same manner as in Example 1 except that the copper plate was cut under cutting conditions different from those in Example 1.

<Structured optical film of Comparative Example 1>
・ Peak apex angle: 90 °
・ Peak pitch: 40μm
-Peak height of convex rows: 20 μm
-Peak height fluctuation range: None-Peak height fluctuation: None

[Comparative Example 2]
A structured optical film of Comparative Example 2 below was produced in the same manner as in Example 1 except that the copper plate was cut under cutting conditions different from those in Example 1.

<Structured optical film of Comparative Example 2>
・ Peak apex angle: 90 °
・ Pitch between peaks: 50 μm
-Peak height of convex rows: 25 μm
-Peak height fluctuation range: ± 4 μm
・ Average period of peak height fluctuation: 1000 μm

2. Evaluation (1) Visibility of optical defect (fine defect) of light guide plate and diffusion film On a shaped light guide plate having a thickness of 0.7 mm with a cylindrical foreign substance (defect) having a diameter of 15 μm and a height of 30 μm attached to the surface, Diffusion film with 100 μm thickness (light-up MXE: Kimotosha) with white spot-like scratches (defects) with a diameter of 30 μm, structured optical films prepared in Examples 1 to 5 and Comparative Examples 1 and 2, and thickness A 15-inch edge-light type backlight (backlights of Examples 1 to 5 and Comparative Examples 1 and 2 and two linear lamps) having a 100 μm diffusion film (Light Up TL2: Kimoto Co., Inc.) in sequence is prepared. did. And the backlight of Examples 1-5 and Comparative Examples 1 and 2 was turned on, and it was observed whether the optical defect by the fine defect of a light-guide plate and a diffusion film can be confirmed visually. “○” indicates that it could not be confirmed visually, “△” indicates that it was slightly visible but “×” indicates that it could be confirmed visually. Those that could be clearly confirmed visually were designated as “XX”. The evaluation results are shown in Table 1.

(2) Front luminance (1) The front luminance of the backlights of Examples 1 to 5 and Comparative Examples 1 and 2 produced during the evaluation of the visibility of optical defects of the light guide plate was measured. The evaluation results are shown in Table 1.

(3) Viewing angle characteristics Luminance in the front direction (normal direction relative to the lens layer surface of the structured optical film) measured in (2) using the backlights of Examples 1 to 5 and Comparative Examples 1 and 2. The ratio of the luminance at an angle inclined by 50 degrees from the normal direction was measured with respect to 100%. The evaluation results are shown in Table 1.

  As shown in Table 1, the backlights of Examples 1-5 using the structured optical films of Examples 1-5 are those in which the structured optical film used has a structured surface. Consists of a plurality of convex rows whose faces are generally aligned in parallel, adjacent convex rows are separated by valleys, each convex row having a peak, and the peak height variation Is periodic, the average period is in the range of 1000 to 5000 μm, the pitch between adjacent peaks is different from the pitch before and after that, and the pitch between adjacent valleys varies along the flow direction. Therefore, it is possible to make it difficult to visually recognize an optical defect due to a fine defect attached to the light guide plate or the diffusion film while preventing a decrease in front luminance, and a wide viewing angle.

  In addition, the backlight of Example 1 using the structured optical film of Example 1 was formed by alternately repeating the pitch between the two types of peaks, so that the reduction in front luminance was suppressed as much as possible. Optical defects due to fine defects adhering to the optical plate and the diffusion film can be made difficult to visually recognize.

  In addition, the backlights of Examples 1 to 4 using the structured optical films of Examples 1 to 4 were in the range of 1000 to 2000 μm in the average period of peak height fluctuations in the convex rows. In addition, optical defects due to fine defects adhering to the diffusion film were invisible to the naked eye.

  On the other hand, the backlight of Comparative Example 1 using the structured optical film of Comparative Example 1 was such that the height of the peak of the convex row of the structured optical film used did not vary along the ridgeline, The scratches on the light guide plate can be clearly confirmed visually, and the scratches on the diffusion film can also be visually confirmed.

  Further, in the backlight of Comparative Example 2 using the structured optical film of Comparative Example 2, the pitch between the peaks of the convex rows of the structured optical film used was not different from the pitch before and after that. The scratches on the light guide plate can be visually confirmed, and the scratches on the diffusion film can be visually confirmed.

DESCRIPTION OF SYMBOLS 1 ... Structured optical film 2 ... Structured surface 3 ... Convex row 4 ... Valley 5 ... Peak 6 ... Between adjacent peaks ································································································ Backlight 11 of the present invention

Claims (4)

A structured optical film having a structured surface,
The structured surface is comprised of a plurality of convex rows generally aligned in parallel;
Adjacent convex rows are separated by valleys;
The convex rows each have a peak;
The peak height varies along its ridgeline, the peak height variation is periodic, and the average period is 1000 to 5000 μm,
Regarding the period of the peak height fluctuation, there is a phase difference in the period for each convex row,
When the fluctuation range of the peak height that fluctuates along the ridge line is ΔH, the following relationship is satisfied:
1 μm ≦ | ΔH | ≦ 40% of maximum height of peak on ridgeline
The structured surface is made consists convex rows of the two kinds different Do that the average height along the ridgeline of the peak, the average height of the variation range of the peak height lower convex column Is larger than the peak height fluctuation range of the convex row with a high average height,
The pitch between adjacent peaks is different from the pitch before and after that,
And the pitch between the adjacent valleys varies along the direction of flow of the valleys ,
The maximum height on the ridge line when cut in a direction perpendicular to the flow direction of the peak ridge line of the convex row at an arbitrary position of the structured optical film is Hp _max and the minimum height is Hp _min . A structured optical film characterized by satisfying the following relationship:
Hp _max −Hp _min ≧ 11 μm   The structured optical film according to claim 1, wherein the pitch between the peaks is formed by alternately repeating two kinds of pitches. The difference between the two types of pitches between the peaks is 2 μm or more,
The structured optical film according to claim 2, wherein one pitch is 10 to 200 μm. In the backlight, comprising at least a light source, an optical plate arranged adjacent to the light source, for guiding or diffusing, and a structured optical film arranged on a light emitting side of the optical plate, the structured optical A backlight, wherein the film is the structured optical film according to any one of claims 1 to 3 .