JPH11281805A - Lens sheet and its manufacture method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To mitigate the deformation of a lens shape owing to the polymerizing contraction of active energy line hardening composition and to obtain a lens sheet provided with a superior optical characteristic without the occurrence of optical defect such as a dot-shaped pattern by forming a mitigating layer having specified thickness on a transparent base material with respect to the lens sheet where multiple lens units are formed on one surface of the transparent base material. SOLUTION: A lens part 2 formed on one surface of the transparent base material 3 is formed of an active energy line hardening resin and the mitigating layer 1 is formed between the material 3 and the part 2. The layer 1 is arranged between the material 3 and the valley parts 4 of the lens units and integrally formed with the part 2 by the hardening resin being the same as that of the part 2 normally. The layer 1 is formed within the range of 1-1,000 μm in thickness so that the occurrence of the dot-shaped pattern owing to the polymerizing contraction at the time of hardening the active energy line hardening composition is restricted. The thickness of the layer 1 is favorably within the range of 1-500 μm and the thinner one is preferable at the time of forming the fine lens units.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight or the like used for a liquid crystal display device or the like, in which the front luminance is reduced.
The present invention relates to a lens sheet used for improvement and a method for manufacturing the same, and more particularly to an excellent lens sheet free from optical defects such as spotted patterns and a method for manufacturing such a lens sheet.

[0002]

2. Description of the Related Art In recent years, the power consumption of a liquid crystal display device has been increasing in a portable notebook personal computer equipped with a color liquid crystal display device and a battery driven product such as a portable liquid crystal TV or a video integrated liquid crystal TV using a color liquid crystal panel. Are obstacles to extending battery life. Above all, the power consumption of backlights used in liquid crystal display devices is high, and keeping this power consumption as low as possible is an important issue in extending battery drive time and increasing the practical value of the above products. ing. However, if the brightness of the backlight is reduced by suppressing the power consumption of the backlight, the liquid crystal display becomes difficult to see, which is not preferable. Therefore, in Japanese Utility Model Laid-Open No. 3-69184, etc., in order to suppress the power consumption without sacrificing the luminance of the backlight by improving the optical efficiency of the backlight, a lens unit such as a prism array is provided on the surface. There has been proposed a backlight in which a lens sheet formed with a large number of lenses is placed on the exit surface side of a light guide.

[0003]

Such a lens sheet is disclosed in, for example, JP-A-5-196808 and JP-A-6-196808.
As proposed in, for example, JP-A-59129, a lens portion is formed using an active energy ray-curable composition such as an ultraviolet-curable composition from the viewpoint of accurate transferability and productivity of a lens pattern. Things are being used. For example, a lens portion made of a cured product of an active energy ray-curable composition is integrally formed on a transparent substrate such as a transparent resin film or a transparent resin sheet.

However, in a lens sheet in which a lens portion is formed by such an active energy ray-curable resin, the lens shape is delicate due to polymerization shrinkage generated when the active energy ray-curable composition is cured and shaped. A spot-like pattern, which is considered to be the cause of such deformation, is generated, and the spot-like pattern becomes an optical defect, and has a problem of deteriorating the optical characteristics of the backlight.

Accordingly, an object of the present invention is to suppress the deformation of the lens shape due to the polymerization shrinkage of the active energy ray-curable composition during the production of a lens sheet, and to obtain excellent optical properties free from optical defects such as spot-like patterns. Another object of the present invention is to provide a lens sheet having the same and a method for manufacturing such a lens sheet.

[0006]

In order to solve the above-mentioned conventional problems, the present inventors have studied the configuration and manufacturing method of a lens sheet, and have specified thicknesses on a transparent substrate. It has been found that by providing a relaxation layer, deformation of the lens shape due to polymerization shrinkage of the active energy ray-curable composition can be reduced.

That is, a lens sheet according to the present invention is a lens sheet in which a lens portion composed of a large number of lens units is formed on at least one surface of a transparent substrate with an active energy ray-curable resin. Thickness 1
A large number of lens units are formed via a relaxation layer of １０００1000 μm. Further, the method for producing a lens sheet according to the present invention includes a step of injecting the active energy ray-curable composition between the transparent substrate and the lens pattern forming surface of the lens in which the lens pattern is formed; A step of making the thickness of the active energy ray-curable composition uniform with a nip roll arranged on the side, a step of irradiating the active energy ray through a transparent substrate to cure and shape the active energy ray-curable composition, a lens A method for producing a lens sheet comprising a step of releasing from a mold, wherein a nip pressure of a nip roll is adjusted by a pressure mechanism to make the thickness of the active energy ray-curable composition uniform and form a relaxation layer. Things.

According to the present invention, the thickness of the active energy ray-curable composition is made uniform by adjusting the nip pressure of a nip roll by a pressure mechanism, and a relaxation layer is formed on a transparent substrate. It is possible to provide a lens sheet having excellent optical properties free from optical defects such as spot-like patterns, which can alleviate the deformation of the lens shape due to polymerization shrinkage during curing of the curable composition by the formed relaxation layer. it can.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a lens sheet 2 according to the present invention has a lens portion 2 having a large number of lens units formed on at least one surface of a transparent substrate 3 made of an active energy ray-curable resin. The relaxation layer 1 is formed between the transparent substrate 3 and the lens portion 2. The relaxation layer 1 is provided between the transparent substrate 3 and the valley portion 4 of the lens unit, and is usually integrally formed of the same active energy ray curable resin as the lens portion 2. This relaxation layer 1 has a thickness of 1 to
By forming the active energy ray-curable composition in a range of 1000 μm, it is possible to suppress the occurrence of a spot-like pattern due to polymerization shrinkage during curing of the active energy ray-curable composition. When the thickness of the relaxation layer 1 is less than 1 μm, the deformation of the lens shape due to polymerization shrinkage in the relaxation layer tends to be unable to be sufficiently relaxed. Conversely, when the thickness exceeds 1000 μm, the thickness unevenness of the relaxation layer is controlled. And the optical characteristics tend to deteriorate due to uneven thickness. The thickness of the relaxation layer 1 is preferably 1 to 500.
In the case of forming a fine lens unit of about several tens of μm such as a prism sheet for a backlight of a liquid crystal display device, a thinner one is preferable.
To 100 μm, more preferably 1 to 50 μm, and more preferably 1.5 to 10 μm.

In the present invention, the shape of the lens portion 2 of the lens sheet may be, depending on the purpose, a prism surface in which a large number of prism rows are formed in parallel, a Fresnel lens surface in which linear or circular Fresnel lenses are formed, and a cross section. Various lens surfaces such as a lenticular lens surface and a wavy lens surface in which a large number of semicircular or semielliptical lenticular lenses are formed in parallel are formed. These lens portions 2 may have the same or different lens shapes on both surfaces of the transparent substrate 3. In the lens sheet of the present invention, it is preferable that the thickness of the lens portion 2 is about 10 to 500 μm, and the pitch of the lens unit is about 10 μm to 500 μm. Further, when the lens unit is a prism array, the apex angle of the prism array is preferably in the range of 50 to 150 °. Generally, in a backlight of a liquid crystal display device, when the prism surface is disposed on the liquid crystal panel side, an apex angle is in a range of about 80 to 100 °, preferably in a range of 90 to 100 °. is there.
On the other hand, when the prism surface is disposed on the light guide side, the angle is in the range of about 50 to 75 °, preferably 55 °.
It is in the range of ゜ 70 °. The lens portion 2 made of the active energy ray-curable resin preferably has a high refractive index from the viewpoint of improving the brightness of the backlight, and specifically,
Its refractive index is 1.55 or more, more preferably 1.6 or more.

The transparent substrate 3 constituting the lens sheet of the present invention is not particularly limited as long as it is a material that transmits active energy rays such as ultraviolet rays and electron beams, and a flexible glass plate or the like may be used. Although it is possible, a transparent resin sheet or film of a polyester resin, an acrylic resin, a polycarbonate resin, a vinyl chloride resin, a polymethacrylimide resin, or the like is preferable. In particular, it is made of a polyester resin such as polymethyl methacrylate, a mixture of polymethyl acrylate and polyvinylidene fluoride resin having a lower refractive index than the refractive index of the lens portion 2 and a low surface reflectance, a polycarbonate resin, and a polyethylene terephthalate. Are preferred. Although the thickness of the transparent substrate 3 varies depending on the use, a thickness in the range of about 50 μm to 500 μm is used. In addition, the transparent base material 3 is subjected to an adhesion improving treatment such as an anchor coat treatment on its surface in order to improve the adhesion between the lens part 2 made of the active energy ray-curable resin and the transparent base material 3. Is preferred.

Relaxing layer 1 and lens portion 2 of lens sheet
Is not particularly limited as long as it is cured with active energy rays such as ultraviolet rays and electron beams. For example, polyesters, epoxy resins, polyester (meth) (Meth) acrylate resins such as acrylate, epoxy (meth) acrylate, and urethane (meth) acrylate are exemplified. Among them, (meth) acrylate resins are particularly preferable from the viewpoint of their optical characteristics and the like. As the active energy ray-curable composition used for such a cured resin, polyhydric acrylate and / or polyhydric methacrylate (hereinafter, referred to as polyhydric (meth) acrylate) in terms of handleability, curability, and the like. , Monoacrylate and / or monomethacrylate (hereinafter, referred to as mono (meth) acrylate), and a photopolymerization initiator using active energy rays as a main component are preferable. Representative polyvalent (meth) acrylates include polyol poly (meth) acrylate, polyester poly (meth) acrylate, epoxy poly (meth) acrylate, urethane poly (meth) acrylate, and the like. These can be used alone or
Used as a mixture of more than one species. Also, thing (meta)
As the acrylate, mono-alcohol mono (meth)
Acrylic acid esters and mono (meth) acrylic acid esters of polyols may be mentioned. In the latter case, it is thought that the effect is caused by free hydroxyl groups. When using, it is better not to use a large amount. Also, since (meth) acrylic acid and its metal salt have high polarity, it is better not to use a large amount when using a metal type.

Next, a method for manufacturing a lens sheet according to the present invention will be described with reference to FIG.

Reference numeral 5 in the figure denotes a lens type having a lens pattern in which a large number of lens units are engraved, such as a metal type made of metal such as aluminum, brass, steel, or the like, silicon resin, polyurethane resin, epoxy resin, ABS resin. , A resin mold made of synthetic resin such as fluororesin, polymethylpentene resin,
An electroforming mold manufactured by Ni electroforming is used. In particular, in the case of a roll type as shown in FIG. 2, it is desirable to use a metal type from the viewpoint of heat resistance and strength. In the present invention, the shape is not limited to the roll type, and may be a flat type flat plate. In the case of a roll mold, as shown in FIG. 3, a thin plate mold 13 on which a lens pattern is formed may be wound around a cylindrical roll 14 and fixed. In order to form the relaxation layer 1 uniformly, a cylindrical stepped lens mold 18 in which a thin plate stepped lens mold 18 having a thick portion formed at the end as shown in FIG. It is preferable to use a lens mold. It is preferable to apply plating such as copper or nickel to the surface of such a lens mold in order to prevent various types of corrosion. Further, in order to make the cutting material particles uniform and fine, it is also possible to form a thick plating of copper, nickel or the like and form a lens pattern on the plating layer portion.

A transparent substrate 7 is supplied to the lens mold 5 along the lens pattern forming surface, and an active energy ray-curable composition 8 is filled between the lens mold 5 and the transparent substrate 7 in a resin tank 10. Continuously supplied from. A nip roll 6 for setting the thickness of the supplied active energy ray-curable composition 8 to be uniform is provided outside the transparent substrate 7. As the nip roll 6, a metal roll, a rubber roll, or the like is used. Further, in order to make the thickness of the active energy ray-curable composition 8 uniform, it is preferable that the nip roll 6 is processed with high accuracy in terms of roundness, surface roughness, and the like. In the case of a rubber roll, Rubber hardness is 6
Those having a high hardness of 0 degree or more are preferable. The nip roll 6 needs to accurately adjust the thickness of the active energy ray-curable composition 8, and is operated by a pressure mechanism 9. As the pressure mechanism 9, a hydraulic cylinder, a pneumatic cylinder, various screw mechanisms and the like can be used, but a pneumatic cylinder is preferable from the viewpoint of simplicity of the mechanism. The air pressure is controlled by a pressure regulating valve or the like.

The active energy ray-curable composition 8 supplied between the lens mold 5 and the transparent substrate 7 needs to be maintained at a constant viscosity in order to form a uniform relaxation layer. The viscosity range depends on the thickness of the relaxation layer to be formed, but is generally preferably in the range of 20 to 3000 mPa · S, and more preferably 100 to 3000 mPa · S.
The range is 1000 mPa · S. When the viscosity of the active energy ray-curable composition 8 is less than 20 mPa · S,
In order to form the relaxation layer, it is necessary to set the nip pressure extremely low or to extremely increase the molding speed.
However, when the nip pressure is extremely low, the pressure mechanism 9 tends to be unable to operate stably, which tends to cause uneven thickness of the relief layer. Further, when the molding speed is extremely increased, the irradiation amount of the active energy ray is insufficient, and the curing of the active energy ray-curable composition tends to be insufficient. On the other hand, the viscosity of the active energy ray-curable composition 8 is 3000
If mPa · S is exceeded, the curable composition 8 will not sufficiently spread to the details of the lens-type lens pattern, and it will be difficult to transfer the lens shape accurately, or defects due to the incorporation of bubbles will easily occur, There is a tendency that productivity is deteriorated due to an extremely low molding speed. In order to maintain the viscosity of the active energy ray-curable composition 8 constant as described above, a sheath heater, a hot water jacket, or the like is provided outside or inside the resin tank 10 so that the temperature of the curable composition 8 can be controlled. It is preferable to install heat source equipment.

After the active energy ray-curable composition 8 is supplied between the lens mold 5 and the transparent substrate 7, the active energy ray-curable composition 8 is sandwiched between the lens mold 5 and the transparent substrate 7. In this state, the active energy ray emitting light source 12 irradiates an active energy ray through the transparent substrate 7 to polymerize and cure the active energy ray-curable composition 8 and transfer the lens pattern formed on the lens mold 5. The active energy ray irradiation device 12 includes a chemical lamp for chemical reaction, a low-pressure mercury lamp, a high-pressure mercury lamp, a metal halide lamp,
A visible light halogen lamp or the like is used. It is preferable that the irradiation amount of the active energy ray is set so that the integrated energy at a wavelength of 200 to 600 nm is 0.1 to 50 J / cm ² . The active energy ray irradiation atmosphere may be air or an inert gas atmosphere such as nitrogen or argon. Next, the lens sheet in which the transparent base 7 and the lens portion formed of the active energy ray-curable resin are integrated is released from the lens mold 5.

The thickness of the active energy ray-curable composition 8 is adjusted by adjusting the pressure of the nip roll 6 and the viscosity of the active energy ray-curable composition 8 by the above-described manufacturing method. Is made uniform and the active energy ray is irradiated in a state in which the relaxation layer is formed, so that the deformation of the lens shape due to polymerization shrinkage during polymerization and curing of the active energy ray-curable composition 8 can be relaxed by the relaxation layer.

[0019]

The present invention will be described below in more detail with reference to examples.

Embodiment 1 As shown in FIG. 3, a thickness of 1.0 mm, 400 mm × 6
A pitch of 50 mm is applied to the surface of 90 mm JIS brass thin sheet.
A thin lens mold 13 was prepared by engraving a prism pattern in which a number of prism rows each having a vertical angle of 90 ° were formed in parallel. The lens mold 13 was subjected to electroless nickel plating. Next, in order to fix the thin plate lens mold 13, the diameter 2
A stainless steel cylindrical roll 14 having a length of 20 mm and a length of 450 mm was prepared. A thin lens mold 13 was wound around the circumference of the cylindrical roll 14 and fixed with screws to obtain a cylindrical lens mold 5.

As shown in FIG. 4, an NBR rubber roll 6 having a rubber hardness of 80 ° was arranged close to the cylindrical lens mold 5. A polyester film 7 having a thickness of 125 μm, which is slightly wider than the cylindrical lens mold 5, is supplied between the cylindrical lens mold 5 and the rubber roll 6 along the cylindrical lens mold 5. Polyester film 7 between the cylindrical lens mold 5 and
Nipped. At this time, the operating pressure of the pneumatic cylinder 9 was 0.1 MPa. As the pneumatic cylinder 9, an SMC air cylinder having an air tube diameter of 32 mm was used. Further, an ultraviolet irradiation device 12 was provided below the cylindrical lens mold 5. UV irradiation device 12 is 120 W / c
It has an ultraviolet intensity of 9.6 kW, a UV irradiation lamp manufactured by Western Quartz, a cold mirror type parallel light reflector, and a power supply. The ultraviolet curable composition 8 was previously mixed with a refractive index adjusting component, a catalyst, and the like, and then charged into the resin tank 10. In the resin tank 10, all parts in contact with the ultraviolet curable composition 8 were SUS304. In addition, it has a warm water jacket layer for controlling the liquid temperature of the ultraviolet curable composition 8, supplies warm water adjusted to 40 ° C. by the temperature controller 15 to the warm water jacket layer, and The liquid temperature of the ultraviolet curable composition 8 was kept at 40 ° C. ± 1 ° C. Further, the inside of the resin tank 10 was evacuated by the vacuum pump 16 to remove bubbles generated at the time of charging.

The UV-curable composition 8 was as follows, and the viscosity was adjusted to 300 mPa · S / 25 ° C.

50 parts by weight of phenoxyethyl acrylate (Biscoat # 192 manufactured by Osaka Organic Chemical Industry Co., Ltd.) 50 parts by weight of bisphenol A-diepoxy-acrylate (Epoxyester 3000A manufactured by Kyoeisha Yushi Kagaku Kogyo Co., Ltd.) 2-hydroxy-2-methyl-1- Phenyl-propan-1-one (Darocur 1173 manufactured by Ciba Geigy) 1.5 parts by weight After the inside of the resin tank 10 was returned to normal pressure and the tank was sealed,
By applying air pressure of 0.02 MPa in the resin tank 10 and opening a valve at the lower part of the resin tank 10, the ultraviolet curable composition 8 is passed through a temperature-controlled pipe 17,
The temperature of the supply nozzle 11 and the rubber roll 6
It was supplied onto a polyester film 7 that was nipped between the cylindrical lens mold 5 and the mold. As the supply nozzle 11, an AV101 valve manufactured by Iwata Engineering Co., Ltd. equipped with a MN-18-G13 needle was used. While rotating the cylindrical lens mold 5 at a speed of 3.5 m / min with a Mitsubishi Electric 0.2 kW geared motor (reduction ratio 1/200),
In a state where the ultraviolet curable composition 8 is sandwiched between the cylindrical lens mold 5 and the polyester film 7, the ultraviolet irradiation device 12
UV irradiation was performed to polymerize and cure the UV-curable composition 8 to transfer the prism pattern of the cylindrical lens mold 5.
Thereafter, the mold was released from the cylindrical lens mold 5 to obtain a lens sheet.

A lens section of the obtained prism sheet is scanned with a scanning electron microscope (JSM-840A, 20 manufactured by JEOL Ltd.).
As a result, a relaxation layer having a thickness of 2 μm was formed between the polyester film 7 and the prism valleys, and almost no deformation was observed in the prism shape due to polymerization shrinkage. Further, the obtained prism sheet is placed via a diffusion film on the emission surface of an acrylic resin light guide in which a cold cathode tube is arranged on the side surface, with the prism surface facing upward, and the other side surface and The back was covered with a reflection sheet, and the cold cathode tube was turned on to check the appearance. As a result, generation of optical defects such as spotted patterns was not observed, and the optical characteristics were excellent.

Example 2 As shown in FIG. 5, a thickness of 1.0 mm, 450 mm × 6
A thin plate stepped lens in which a large number of prism rows with a pitch of 50 μm and an apex angle of 90 ° are stamped in parallel on a thin plate of three types of JIS brass with a size of 90 mm and a portion excluding 10 mm from both ends reduced by 0.03 mm from both ends. The mold 18 was prepared. The lens mold 18 was subjected to electroless nickel plating to prevent various types of corrosion. Next, in order to fix the lens mold 18,
A stainless steel cylindrical roll 14 having a diameter of 220 mm and a length of 450 mm was prepared, and a lens mold 18 was wound around the circumference of the cylindrical roll 14 and fixed with screws to obtain a cylindrical stepped lens mold 5.

As shown in FIG. 4, a metal roll 6 (obtained by cutting a SUS400 round bar and subjected to hard chrome plating) was disposed close to a cylindrical stepped lens mold 5. Lens mold 5 with cylindrical step and metal roll 6
Thickness 1 slightly wider than the cylindrical stepped lens mold 5 between
A 25 μm polyester film 7 was supplied along the cylindrical lens mold 5, and the polyester film 7 was interposed between the metal roll 6 and the cylindrical stepped lens mold 5 by the same pneumatic cylinder 9 connected to the metal roll 6 as in Example 1. Nipped. The operating pressure of the pneumatic cylinder 9 at this time is 0.3MP.
was a. Further, the same ultraviolet irradiation device 12 as in Example 1 was installed below the lens mold 5 with a cylindrical step. The ultraviolet-curable composition 8 is prepared by previously mixing a refractive index adjusting component, a catalyst, and the like, and then putting the mixture into the same resin tank 10 as in Example 1, and setting the liquid temperature of the ultraviolet-curable composition 8 to 40 ° C. ± 1. It was kept at ° C. Further, the inside of the resin tank 10 was evacuated by the vacuum pump 16 to remove bubbles generated at the time of charging.

The UV curable composition 8 was as follows, and the viscosity was adjusted to 300 mPa · S / 25 ° C.

Phenoxyethyl acrylate 50 parts by weight (Biscoat # 192 manufactured by Osaka Organic Chemical Industry Co., Ltd.) Bisphenol A-diepoxy-acrylate 50 parts by weight (Epoxyester 3000A manufactured by Kyoeisha Yushi Kagaku Kogyo Co., Ltd.) 2-hydroxy-2-methyl-1- Phenyl-propan-1-one (Darocur 1173 manufactured by Ciba Geigy) 1.5 parts by weight After the inside of the resin tank 10 was returned to normal pressure and the tank was sealed,
By applying air pressure of 0.02 MPa in the resin tank 10 and opening a valve at the lower part of the resin tank 10, the ultraviolet curable composition 8 is passed through a temperature-controlled pipe 17,
Similarly, the temperature was controlled and supplied from the same supply nozzle 11 as in Example 1 onto the polyester film 7 which was nipped between the metal roll 6 and the lens mold 5 with a cylindrical step. While the lens mold 5 having a cylindrical step was rotated at a speed of 3.5 m / min with a 0.2 kW geared motor (reduction ratio 1/200) manufactured by Mitsubishi Electric, the ultraviolet curable composition 8 was used to rotate the lens mold 5 having a cylindrical step.
Ultraviolet rays were irradiated from an ultraviolet irradiation device 12 in a state sandwiched between the film and the polyester film 7 to polymerize and cure the ultraviolet curable composition 8 to transfer the prism pattern of the lens mold 5 with a cylindrical step. Thereafter, the mold was released from the lens mold 5 with a cylindrical step to obtain a lens sheet.

The lens section of the obtained prism sheet was scanned with a scanning electron microscope (JSM-840A, 20 manufactured by JEOL Ltd.).
As a result, a relaxation layer having a thickness of 2 μm was formed between the polyester film 7 and the prism valleys, and almost no deformation was observed in the prism shape due to polymerization shrinkage. Further, the obtained prism sheet is placed via a diffusion film on the emission surface of an acrylic resin light guide in which a cold cathode tube is arranged on the side surface, with the prism surface facing upward, and the other side surface and The back was covered with a reflection sheet, and the cold cathode tube was turned on to check the appearance. As a result, generation of optical defects such as spotted patterns was not observed, and the optical characteristics were excellent.

Comparative Example 1 Using the same apparatus as in Example 1, the molding conditions were such that the operating pressure of the pneumatic cylinder 9 was 0.1 MPa and the ultraviolet curable composition 8 had the following composition. Except for the above, a lens sheet was obtained in the same manner as in Example 1. The UV-curable composition 8 had a viscosity of 15 mPa ·
S / 25 ° C.

90 parts by weight of phenoxyethyl acrylate (Biscoat # 192 manufactured by Osaka Organic Chemical Industry Co., Ltd.) 10 parts by weight of bisphenol A-diepoxy-acrylate (Epoxyester 3000A manufactured by Kyoeisha Yushi Kagaku Kogyo Co., Ltd.) 2-hydroxy-2-methyl-1- 1.5 parts by weight of phenyl-propan-1-one (Darocur 1173 manufactured by Ciba-Geigy) The cross section of the lens of the obtained prism sheet was confirmed with a scanning electron microscope (JSM-840A, manufactured by JEOL Ltd., 2000 times). No relaxation layer was formed between the film 7 and the prism valley, and it was found that the prism surface was slightly deformed into a concave shape. Further, the obtained prism sheet is placed via a diffusion film on the emission surface of an acrylic resin light guide in which a cold cathode tube is arranged on the side surface, with the prism surface facing upward, and the other side surface and The back was covered with a reflection sheet, and the cold cathode tube was turned on to check the appearance. As a result, an optical defect having a spot-like pattern was observed, and the optical characteristics were poor.

[0032]

According to the present invention, there is provided a lens sheet in which a large number of lens units are formed on at least one surface of a transparent substrate with an active energy ray-curable resin, and a relaxation layer having a specific thickness is formed on the transparent substrate. Thereby, a lens sheet having excellent optical characteristics without occurrence of optical defects such as spotted patterns can be provided by alleviating deformation of the lens shape due to polymerization shrinkage of the active energy ray-curable composition.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a lens sheet of the present invention.

FIG. 2 is a schematic diagram showing a manufacturing process of the present invention.

FIG. 3 is a schematic view showing a cylindrical lens mold of the present invention.

FIG. 4 is a schematic diagram showing a specific manufacturing process of the present invention.

FIG. 5 is a schematic view showing a cylindrical stepped lens mold of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Relaxation layer 2 Lens part 3 Transparent base material 4 Lens trough 5 Cylindrical lens type 6 Nip roll 7 Transparent base material 8 Active energy ray curable composition 9 Pressure mechanism 10 Resin tank 11 Supply nozzle 12 Active energy ray irradiation device 13 Thin plate lens Mold 14 Cylindrical roll 15 Temperature controller 16 Vacuum pump 17 Piping 18 Lens type with thin plate step

Continuation of the front page (51) Int.Cl. ⁶ Identification symbol FI // B29K 105: 32 (72) Inventor Yukichi Konami 4-160 Sunadabashi, Higashi-ku, Nagoya City, Aichi Prefecture Mitsubishi Rayon Co., Ltd. Product Development Laboratory

Claims (4)

[Claims] 1. A lens sheet in which a lens portion composed of a large number of lens units is formed on at least one surface of a transparent base material by an active energy ray-curable resin, wherein the transparent base material has a thickness of 1 to 1000 μm. A lens sheet comprising a plurality of lens units formed through a relaxation layer. 2. The lens sheet according to claim 1, wherein the relaxation layer is made of an active energy ray-curable resin, and is integrated with the lens portion. 3. A step of injecting an active energy ray-curable composition between a lens pattern forming surface of a lens having a lens pattern formed thereon and a transparent substrate, wherein a nip roll disposed on an outer surface side of the transparent substrate is used. From the step of making the thickness of the active energy ray-curable composition uniform, the step of irradiating the active energy ray through a transparent substrate to cure the active energy ray-curable composition, and the step of releasing from the lens mold A method for producing a lens sheet, comprising: adjusting the nip pressure of a nip roll by a pressure mechanism to uniform the thickness of the active energy ray-curable composition to form a relaxation layer. 4. The method for manufacturing a lens sheet according to claim 3, wherein the lens mold has a cylindrical shape, and a step portion thicker than other portions is formed near an end of the cylinder.