JP6046737B2 - Lens sheet manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing a lens sheet comprising a plurality of parallel-shaped lenses arranged in parallel on the surface of a resin sheet, and in particular, the present invention relates to an aspect of a saddle-shaped lens in which the resin sheet is particularly thick. The present invention relates to a method for suitably producing a lens sheet having a high ratio.

  2. Description of the Related Art A lens sheet having a plurality of bowl-shaped lenses arranged in parallel on the surface of a resin sheet is known. Examples of the shape of the bowl-shaped lens include a semi-cylindrical lens and a triangular prism prism lens having an apex angle of 90 degrees (see Patent Documents 1 to 4). In such a lens sheet, it is usually required to increase the aspect ratio of the bowl-shaped lens (that is, (the height of the bowl-shaped lens) / (the pitch of the bowl-shaped lens)).

  As a manufacturing method of said lens sheet, the method of carrying out extrusion molding or injection molding of a thermoplastic resin, and the method of carrying out photocuring shaping | molding of ultraviolet curable resin are mentioned. Among them, the method of extruding a thermoplastic resin is excellent from the viewpoint of continuous productivity.

As a method of manufacturing a lens sheet having a bowl-shaped lens on both sides by extrusion molding of a thermoplastic resin, there is a method of multilayer extrusion molding by placing a thermoplastic resin having a high viscosity between low-viscosity thermoplastic resins. Are known. By manufacturing a lens sheet by such a method, it is said that the resin dripping of the molten sheet when manufacturing a lens sheet having a bowl-shaped lens having a high aspect ratio can be suppressed, and production stability is improved (see Patent Document 5). ).
In addition, a method of transferring the shape of the pattern member to a melted sheet that has been extrusion-molded using a pattern roll in which a heat buffer member is arranged between the core and the pattern member as a shaping mold is known, An example of manufacturing a lens sheet in which prism lenses having an aspect ratio of 0.5 are arranged on a resin sheet having a thickness of 1 mm is disclosed (see Patent Document 6).

  Incidentally, one of the uses of the lens sheet is a light guide plate used in a liquid crystal display device or the like. In recent years, the size of the apparatus has been increased in such applications, and accordingly, it is required to increase the thickness of the resin sheet in order to ensure the strength of the light guide plate.

According to the study by the present inventors, in the method described in Patent Document 5, when the resin sheet is thickened, the shaping rate (that is, the height of the bowl-shaped lens of the lens sheet / the depth of the groove of the shaping mold) ) Decreased, and the aspect ratio of the saddle-shaped lens tended to decrease, and it was found that there was room for improvement.
Further, in the method described in Patent Document 6, since heat is efficiently transmitted to the resin sheet by the heat buffer member, when the thickness of the resin sheet is thick, the cooling and curing of the formed uneven pattern does not proceed quickly, and the pattern roll There is a tendency for the hook-shaped lens to be deformed after being peeled off, which is a problem.

JP-A-2-190835 JP 2009-37803 A JP 2009-265380 A JP 2009-283383 A JP-A-4-299329 JP 2003-53834 A

  An object of the present invention is to provide a method for producing a lens sheet by extrusion molding using a thermoplastic resin, which is suitable for a large light guide plate and the like, and has a thick resin sheet, a high aspect ratio of a bowl-shaped lens, and an extrusion width. It is an object of the present invention to provide a method capable of industrially easily manufacturing a lens sheet that is uniform in direction.

According to the present invention, the above object is solved by the invention including the following aspects.
[1] A thermoplastic resin (A) and a thermoplastic resin (B) having a smaller MFR (measured in accordance with ISO 1133 at 230 ° C. and a load of 37.3 N) than the thermoplastic resin (A). Extruded and made of a thermoplastic resin (A), the volume per unit length is y (y is a positive number), and the first layer as the surface layer and the thermoplastic resin (B) A first step of obtaining a melted multilayer sheet adjacent to the second layer by a multi-manifold die; and a volume per unit length satisfying the following formula (1) (x is a positive number) N) (n is a natural number) in the shape of a mold, which has a plurality of grooves, which are in contact with the surface of the first layer of the molten multilayer sheet obtained in the first step. A second step of forming a lens;
A method for extrusion production of a lens sheet.
0.7 ≦ y / nx ≦ 2.0 (1)
[2] The method for extruding a lens sheet according to [1], wherein y, n, and x satisfy the following formula (2).
1.05 ≦ y / nx ≦ 1.4 (2)

  According to the present invention, a lens sheet having a thick resin sheet and a high aspect ratio of a bowl-shaped lens suitable for a large light guide plate or the like, for example, a resin sheet having a thickness of 2.5 to 15 mm, bowl-shaped A lens sheet having a lens aspect ratio of 0.3 to 1.0 can be easily produced industrially.

It is a figure which shows the relationship between the shaping rate of the center part of the bowl-shaped lens of Examples 1-5 and Comparative Examples 3 and 4, and y / nx. It is the schematic of the extrusion machine which manufactured the lens sheet of the Example and the comparative example.

[Thermoplastic resin]
The MFR of the thermoplastic resin (B) used in the production method of the present invention is smaller than the MFR of the thermoplastic resin (A). That is, when the MFR of the thermoplastic resin (A) is MFR (A) and the MFR of the thermoplastic resin (B) is MFR (B), the value of MFR (A) / MFR (B) exceeds 1. The value of MFR (A) / MFR (B) is preferably in the range of 1.5 to 40, more preferably in the range of 2 to 30, and still more preferably in the range of 3 to 20. When the value of MFR (A) / MFR (B) exceeds 1, the aspect ratio of the bowl-shaped lens can be increased. From the viewpoint of increasing the uniformity of the thickness of the obtained lens sheet, the value of MFR (A) / MFR (B) is preferably 40 or less. In the present specification, MFR is a value measured under conditions of 230 ° C. and a load of 37.3 N according to ISO1133.

MFR (A) is preferably in a higher range than the thermoplastic resin used in conventional extrusion molding from the viewpoint of filling the thermoplastic resin (A) into the grooves of the shaping mold as much as possible. For example, a range of 7 to 50 g / 10 minutes is preferable, a range of 7 to 30 g / 10 minutes is more preferable, a range of 10 to 25 g / 10 minutes is further preferable, and a range of 10 to 20 g / 10 minutes is particularly preferable. If the MFR (A) is smaller than 7 g / 10 minutes, the shaping rate of the obtained lens sheet may be reduced. If it is larger than 50 g / 10 minutes, the extrusion amount of the thermoplastic resin (A) at the time of extrusion molding is unstable. It may become.
In the present specification, the description of connecting two numerical values with “to” means the two numerical values and the range between them.

  MFR (B) is preferably in the range of 0.2 to 5 g / 10 min, more preferably in the range of 0.4 to 4 g / 10 min, and 0.5 to 3 g / 10 from the viewpoint of the operational stability of extrusion molding. More preferred is a range of minutes. If the MFR (B) is smaller than 0.2 g / 10 minutes, the pressure of the molten resin in the extruder becomes too high, and the extruder may be damaged. If the MFR (B) is larger than 5 g / 10 minutes, the thickness of the lens sheet obtained Samurai may increase.

[First step]
In the first step, the thermoplastic resin (A) and the thermoplastic resin (B) are extruded and formed from the thermoplastic resin (A) and the surface layer, the first layer, and the thermoplastic resin (B). A molten multilayer sheet comprising the second layer adjacently is obtained.

There are no particular restrictions on the conditions for extrusion molding of the thermoplastic resin (A) and the thermoplastic resin (B). Usually, the thermoplastic resin (A) and the thermoplastic resin (B) are each melted in a cylinder of an extruder, laminated in an extrusion die, and then extruded to obtain a molten multilayer sheet. As the extrusion die, a multi-manifold die having a plurality of manifolds is used from the viewpoint of making the thickness of each layer uniform.
When manufacturing a multilayer sheet with the multi-manifold die used in the present application, the thermoplastic resin constituting each layer is supplied to separate flow paths inside the die, and the resin constituting each layer is spread separately in the width direction of the plate. After that, they are merged and extruded near the discharge port of the die. Therefore, in the multi-manifold die, the thickness of each layer can be made uniform in the width direction of the plate even if the fluidity of the resin is different.

  In extrusion molding, the temperature (molding temperature) at which the thermoplastic resin (A) and the thermoplastic resin (B) are melted is usually 130, for example, more than the deflection temperature under load of the thermoplastic resin (A) and the thermoplastic resin (B). It is preferable to increase the temperature by ~ 180 ° C. The molding temperature of the thermoplastic resin (A) and the thermoplastic resin (B) may be different. In the formation of the bowl-shaped lens in the second step, from the viewpoint of increasing the fluidity of the thermoplastic resin (A) and increasing the shaping rate, the molding temperature of the thermoplastic resin (A) is changed to the molding temperature of the thermoplastic resin (B). Higher than that.

  The multi-manifold die usually has a heater for heating each thermoplastic resin. The heater of the multi-manifold die may be different for each thermoplastic resin, and in that case, the temperature (molding temperature) of the heater of each thermoplastic resin can be changed. The temperature of the heater that is in contact with the thermoplastic resin (A) that is the first layer may be higher than the temperature of the heater that is in contact with the thermoplastic resin (B) of the multi-manifold die, usually by a temperature difference of 5 to 40 ° C. Preferably, the temperature difference is more preferably 10 to 35 ° C., more preferably 15 to 30 ° C. Warpage of the lens sheet obtained by setting the temperature difference to 40 ° C. or less is less likely to occur.

  Although there is no restriction | limiting in particular in the extrusion amount of a thermoplastic resin (A), For example, it can be set as 5-100 kg / hour.

  Although there is no restriction | limiting in particular in the extrusion amount of a thermoplastic resin (B), For example, it can be set as 50-400 kg / hour.

  The ratio of the extrusion amount of the thermoplastic resin (A) and the thermoplastic resin (B) can be, for example, 1: 2 to 1:50.

  Although there is no restriction | limiting in particular in the extrusion speed of a multilayer sheet | seat of a molten state, For example, it can be set as 0.1-10 m / min.

  The volume y per unit length of the first layer can be adjusted by the extrusion amount of each thermoplastic resin to be used and the thickness of the multilayered sheet in a molten state adjusted by the width of the discharge port of the multi-manifold die.

  In extrusion molding, one or both of the thermoplastic resin (A) and the thermoplastic resin (B) may be added to an antioxidant, a thermal deterioration inhibitor, an ultraviolet absorber, a light stabilizer, a lubricant, a release agent, if necessary. Molding agents, antistatic agents, polymer processing aids, flame retardants, dyes and pigments, light diffusing agents, impact resistance modifiers, phosphors, and the like may be added.

  The thickness of the multilayer sheet in the molten state obtained in this step is usually preferably in the range of 2 to 20 mm, and more preferably in the range of 2.5 to 10 mm. If the thickness is less than 2 mm, the strength of the resin sheet may be insufficient. If the thickness is more than 20 mm, the cooling and curing of the formed concavo-convex pattern does not proceed quickly, and the bowl-shaped lens is deformed after peeling from the shaping mold. Tend.

  The thickness ratio between the first layer and the second layer of the molten multilayer sheet obtained in this step can be, for example, 1: 2 to 1:50.

  In this specification, the volume per unit length of the first layer is defined as y. The first layer is a surface layer of the molten multilayer sheet, and is in close contact with the shaping mold in the second step. As a result, the first layer becomes at least a part of the n bowl-shaped lenses formed in the second step.

  The second layer may be a surface layer of a multilayer sheet in a molten state, or may be covered with another layer. That is, the multilayer sheet in the molten state may include layers other than the first layer and the second layer. Such another layer may be made of the thermoplastic resin (A) or the thermoplastic resin (B), or may be made of another thermoplastic resin. From the viewpoint of suppressing the warp of the obtained lens sheet, a third layer made of a thermoplastic resin (A) is used as another layer, and a three-layer composite arranged in the order of the first layer / second layer / third layer is used. A layer sheet is preferable. When producing such a three-layered multilayer sheet, the extrusion amount of the third layer is preferably in the range of 0.9 to 1.1 times the extrusion amount of the first layer. It is more preferable to make it equal to the extrusion amount.

[Second step]
In the second step, the shaping mold having a plurality of grooves whose volume per unit length is x satisfying the formula (1) is obtained from the first layer of the multilayered sheet in the molten state obtained in the first step. N pieces of saddle-shaped lenses are formed in close contact with the surface. At this time, it is preferable that a pressing die is closely attached to the other surface of the molten multilayer sheet.

  Examples of the shape of the shaping die and the pressing die include a belt shape and a roll shape.

  In forming n bowl-shaped lenses, the total volume per unit length of the grooves of the shaping mold required is nx. The value of y / nx in formula (1) is in the range of 0.7 to 2.0 from the viewpoint of realizing a high shaping rate, preferably in the range of 1.05 to 1.4, and 1.2 to 1 A range of .3 is more preferred.

The number n of hook-shaped lenses of the lens sheet of the present invention is determined as (width of lens sheet to be manufactured) / (pitch of hook-shaped lenses). The number n of such bowl-shaped lenses, the volume y per unit length of the first layer of the molten multilayer sheet determined in the first step, and the volume per unit length of the grooves of the shaping mold With x, the value of y / nx can be adjusted to a desired range. Specifically, when the molten multilayer sheet is produced in the first step, r is the total extrusion amount per unit time of all thermoplastic resins used, and the thermoplastic resin (A) per unit time. When the extrusion amount is r ₁ , the value of y / nx can be adjusted by adjusting the ratio r ₁ / r, and y / nx increases as r ₁ / r increases.

  The value of y / nx determines how much of the volume in the groove of the shaping mold is satisfied by the first layer. That is, when the value of y / nx exceeds 1, only the thermoplastic resin (A) fills the groove, and in the obtained lens sheet, the first layer is part of the bowl-shaped lens and the resin sheet, and the second layer Can form a resin sheet. On the other hand, if the value of y / nx is less than 1, the entire amount of the thermoplastic resin (A) and a part of the thermoplastic resin (B) are filled in the groove, and the first layer of the lens sheet obtained is a bowl-shaped lens. The second layer can form a part of a bowl-shaped lens and a resin sheet. If the value of y / nx is 1, only the thermoplastic resin (A) fills the inside of the groove, and the obtained lens sheet can form only a bowl-shaped lens and the second layer can form only a resin sheet. . As described above, the manufacturing method of the present invention achieves the object by adjusting the ratio of forming the hook-shaped lens in the first layer and the ratio of forming the first layer in the hook-shaped lens.

The temperature of the shaping mold is preferably in the range of the deflection temperature under load of the thermoplastic resin (A) ± 10 ° C. from the viewpoint of filling the shaping mold with the thermoplastic resin (A) as much as possible. If the temperature of the shaping mold is less than 10 ° C below the deflection temperature under load of the thermoplastic resin (A), the resin will not be sufficiently filled in the shaping mold. The resin is not smoothly released from the mold, and a trouble that the resin sheet is wound around the roll occurs or a surface defect called a release mark is generated.
From the viewpoint of sufficiently cooling the thermoplastic resin (B), the temperature of the pressing mold is in the range of (the deflection temperature under load of the thermoplastic resin (B) —20 ° C.) to (the deflection temperature under load of the thermoplastic resin (B)). Is preferred.
In addition, the deflection temperature under load of the thermoplastic resin (A) and the thermoplastic resin (B) is measured according to ISO75-2.

  From the viewpoint of increasing the aspect ratio of the bowl-shaped lens of the obtained lens sheet, the pitch of the shaping mold to be used is usually preferably in the range of 0.05 to 1.0 mm, more preferably in the range of 0.1 to 0.8 mm. preferable.

  In the present invention, the sheet molded product obtained after the second step is usually cut in a direction perpendicular to the extrusion direction, and the length is adjusted to obtain a lens sheet. Further, the width may be adjusted by appropriately cutting both ends in the extrusion width direction parallel to the extrusion direction.

  Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

The shaping molds used are as follows.
The surface shape of the shaping mold was transferred using a two-component curable silicone resin, the cross-sectional shape was observed with a microscope, and the groove pitch and depth were measured. As a result, the cross-sectional shape of the groove of the shaping mold roll was a semi-elliptical shape having a pitch of 0.4 mm and a depth of 0.231 mm.
Further, the area of the semi-elliptical groove was calculated from the pitch and depth of the obtained groove, and the volume per unit length x (m ³ / m) was further calculated. As a result, x was 0.14 × 10 ⁻⁶ m ³ / m.

The obtained lens sheet was evaluated by the following method.
(1) Height of bowl-shaped lens A cross section perpendicular to the extrusion direction of the lens sheet was observed with a microscope, and a distance parallel to the thickness direction from the top to the valley of the bowl-shaped lens was measured. The height measured at the center in the extrusion width direction is the height of the bowl-shaped lens at the center, and the end measured at a distance of 600 mm from the center in the extrusion width direction to the end in one extrusion width direction. The height of the bowl-shaped lens.
(2) Thickness of resin sheet A cross section perpendicular to the extrusion direction of the lens sheet was observed with a microscope, and the distance from the trough of the bowl-shaped lens to the surface of the third layer was measured.
(3) Calculation of y / nx The extrusion amount Q (kg / hour) of the thermoplastic resin (A), the extrusion speed v (m / min) of the lens sheet, the specific gravity ρ (g / cm ³ ) of the thermoplastic resin (A) ) To calculate the volume y (m ³ / m) per unit length of the first layer from the following formula.
y = Q / (60000 × ρ × v) (m ³ / m)
Y / nx was calculated from the calculated y, the number n of the formed bowl-shaped lenses, and the calculated x (m ³ / m).
(4) Pitch of bowl-shaped lens A cross section perpendicular to the extrusion direction of the lens sheet was observed with a microscope, and the distance from the top of the bowl-shaped lens to the top of the adjacent bowl-shaped lens was measured.
(5) Aspect ratio of bowl-shaped lens The aspect ratio was obtained by dividing the height of the bowl-shaped lens at the center measured in (1) above by the pitch of the bowl-shaped lens measured in (4).
(6) Forming rate (%)
The percentage of the height of the saddle-shaped lens at the center and the end measured in the above (1) with respect to the depth of the groove of the shaping mold was determined and used as the shaping ratio (%) of the center and the end.
(7) Thickness of the third layer The thickness of the third layer was measured by observing a cross section perpendicular to the extrusion direction of the sheet with a microscope. The thickness measured at the central portion in the extrusion width direction is the thickness of the third layer in the central portion, and the end portion is measured at a location 600 mm away from the central portion in the extrusion width direction to the end portion in one extrusion width direction. The thickness of the third layer.

FIG. 2 is a schematic view of the extruder 1 used in Examples and Comparative Examples. The extrusion molding machine 1 includes an extrusion screw section (not shown), a multilayer extrusion T-type multi-manifold die 2, a pressing mold roll 31, a shaping mold roll 32, and cooling rolls 33 and 34. On the surface of the shaping mold roll 32, 3250 grooves extending along the outer periphery of the roll are provided.
The surfaces of the pressing die roll 31 and the cooling rolls 33 and 34 are smooth. The molten belt-like resin is discharged downward from the molten resin discharge portion of the multilayer extrusion T-type multi-manifold die 2. The pressing mold roll 31 and the shaping mold roll 32 face each other so as to sandwich the molten resin and are arranged in parallel and horizontally with each other. The cooling rolls 33 and 34 are arranged in parallel with the pressing mold roll 31 and the shaping mold roll 32 so that the respective rotation axes are located on the same plane.

In the examples and comparative examples, the following acrylic resin (a) and acrylic resin (b) were used.
Acrylic resin (a): manufactured by Kuraray Co., Ltd., “Parapet GH”, MFR = 10 (catalog value measured at 230 ° C., load 37.3 N according to ISO 1133), deflection temperature under load = 95 ° C. (ISO 75-2) According to the above, with annealing, catalog value measured at a load of 1.82 MPa), specific gravity 1.19.
Acrylic resin (b): “Parapet EH” manufactured by Kuraray Co., Ltd., MFR = 1.3 g / 10 min (catalog value measured at 230 ° C. under a load of 37.3 N in accordance with ISO 1133), deflection temperature under load = 93 ° C (measuring condition: according to ISO 75-2, with annealing, catalog value measured at a load of 1.82 MPa), specific gravity 1.19.

Example 1
Acrylic resin (a) and acrylic resin (b) are charged into an extruder, the acrylic resin (a) is heated to 260 ° C., the acrylic resin (b) is heated to 245 ° C., and the length in the extrusion width direction in which the molten resin is discharged. Is laminated in the order of acrylic resin (a), acrylic resin (b) and acrylic resin (a) in a multilayer extrusion T-type multi-manifold die having a length of about 1500 mm, and acrylic resin (a) is laminated in the first layer, acrylic resin ( A molten multilayer sheet having the second layer b) and the third layer acrylic resin (a) was extruded. The extrusion rate of acrylic resin (a) (first layer and third layer) was 20 kg / hour, and the extrusion rate of acrylic resin (b) (second layer) was 200 kg / hour.
Next, the molten multilayer sheet is supplied between a pressing mold roll 31 and a shaping mold roll 32 which are arranged parallel to each other with a distance of 3 mm to shape the lens shape, and then the cooling roll 33. , 34, and a sheet molded product having a plurality of bowl-shaped lenses arranged on the surface was obtained. The width of the sheet molded product was approximately 1.4 (m).
The surface temperature of the pressing mold roll 31 is 80 ° C., the surface temperature of the shaping mold roll 32 is 100 ° C., the surface temperature of the cooling roll 33 is 100 ° C., the surface temperature of the cooling roll 34 is 70 ° C., and the extrusion speed of the lens sheet. Was 0.8 m / min.
The value of y / nx was 0.750.

  The obtained sheet molded product was cut at a length of 1.3 m perpendicular to the extrusion direction. Moreover, the both ends of the extrusion width direction parallel to the extrusion direction were cut at equal widths to obtain a lens sheet having a width of 1.3 m.

  The pitch of the bowl-shaped lens of the lens sheet obtained as described above is 0.4 mm, the thickness of the resin sheet is 2.8 mm, the height of the bowl-shaped lens at the center is 0.16 mm, and the bowl-shaped lens at the end. The height of the lens was 0.159 mm, the aspect ratio of the saddle-shaped lens was 0.400, and the shaping ratio of the central portion and the end portion was 69%. The thickness of the third layer at the center was 0.136 mm, and the thickness of the third layer at the end was 0.135 mm.

Example 2
Examples except that the extrusion rate of the acrylic resin (a) (the first layer and the third layer) was 28.8 kg / hour and the extrusion rate of the acrylic resin (b) (the second layer) was 182.3 kg / hour, respectively. A lens sheet was produced in the same manner as in Example 1. As a result, y / nx was 1.081. The pitch of the bowl-shaped lens of the lens sheet obtained as described above is 0.4 mm, the thickness of the resin sheet is 2.8 mm, the height of the bowl-shaped lens at the center is 0.164 mm, and the bowl-shaped lens at the end. The height of the lens was 0.162 mm, the aspect ratio of the bowl-shaped lens was 0.410, the shaping ratio at the center was 71%, and the shaping ratio at the end was 70%. The thickness of the third layer at the center was 0.196 mm, and the thickness of the third layer at the end was 0.194 mm.

Example 3
Except for the extrusion rate of acrylic resin (a) (first layer and third layer) being 32 kg / hour and the extrusion rate of acrylic resin (b) (second layer) being 176 kg / hour, the same as in Example 1. A lens sheet was manufactured. As a result, y / nx was 1.230. The pitch of the bowl-shaped lenses of the lens sheet obtained as described above is 0.4 mm, the thickness of the resin sheet is 2.8 mm, the height of the bowl-shaped lenses at the center and the end is 0.177 mm, and the bowl-shaped lenses The aspect ratio was 0.443, and the forming ratio of the central portion and the end portion was 77%. The thickness of the third layer at the center was 0.223 mm, and the thickness of the third layer at the end was 0.222 mm.

Example 4
Examples except that the extrusion rate of the acrylic resin (a) (first layer and third layer) was 36.8 kg / hr and the extrusion rate of the acrylic resin (b) (second layer) was 164.4 kg / hr, respectively. A lens sheet was produced in the same manner as in Example 1. As a result, y / nx was 1.379. The pitch of the bowl-shaped lens of the lens sheet obtained as described above is 0.4 mm, the thickness of the resin sheet is 2.8 mm, the height of the bowl-shaped lens at the center is 0.164 mm, and the bowl-shaped lens at the end. The height of the lens was 0.166 mm, the aspect ratio of the bowl-shaped lens was 0.410, the shaping ratio at the center was 71%, and the shaping ratio at the end was 72%. The thickness of the third layer at the center and at the end was 0.25 mm.

Example 5
Example 1 except that the extrusion rate of the acrylic resin (a) (first layer and third layer) was 51.5 kg / hour and the extrusion rate of the acrylic resin (b) (second layer) was 137 kg / hour, respectively. Similarly, a lens sheet was manufactured. As a result, y / nx was 1.930. The pitch of the bowl-shaped lens of the lens sheet obtained as described above is 0.4 mm, the thickness of the resin sheet is 2.8 mm, the height of the bowl-shaped lens at the center is 0.156 mm, and the bowl-shaped lens at the end. The height of the lens was 0.157 mm, the aspect ratio of the bowl-shaped lens was 0.390, and the shaping ratio at the center and the end was 68%. The thickness of the third layer at the center was 0.35 mm, and the thickness of the third layer at the end was 0.348 mm.

Comparative Example 1
Acrylic resin (b) was charged into an extruder and heated to 245 ° C., and a molten sheet was extruded from a T-type multi-manifold die at an extrusion rate of 240 kg / hour. Next, the molten sheet is supplied between a pressing mold roll 31 and a shaping mold roll 32 which are arranged parallel to each other at a distance of 3 mm to shape the lens shape, and then the cooling rolls 33 and 34 are used. A lens sheet having a plurality of bowl-shaped lenses arranged on the surface was manufactured. The surface temperature of the pressing mold roll 31 is 80 ° C., the surface temperature of the shaping mold roll 32 is 100 ° C., the surface temperature of the cooling roll 33 is 100 ° C., the surface temperature of the cooling roll 34 is 70 ° C., and the extrusion speed of the lens sheet. Was 0.8 m / min.
The pitch of the bowl-shaped lenses of the lens sheet obtained as described above is 0.4 mm, the thickness of the resin sheet is 2.9 mm, the height of the bowl-shaped lenses at the center and the end is 0.100 mm, and the bowl-shaped lenses The aspect ratio was 0.250, and the forming ratio of the central portion and the end portion was 43%.

Comparative Example 2
The lens was the same as in Comparative Example 1 except that the amount of the acrylic resin (b) extruded was 160 kg / hr and the pressing mold roll 31 and the shaping mold roll 32 were spaced apart by 2 mm and arranged parallel to each other. Sheet 4 was produced.
The pitch of the bowl-shaped lenses of the lens sheet obtained as described above is 0.4 mm, the thickness of the resin sheet is 1.9 mm, the height of the bowl-shaped lenses at the center and the end is 0.150 mm, and the bowl-shaped lenses The aspect ratio was 0.375, and the forming ratio of the central portion and the end portion was 65%.

Comparative Example 3
Examples except that the extrusion rate of the acrylic resin (a) (first layer and third layer) was 5.9 kg / hour and the extrusion rate of the acrylic resin (b) (second layer) was 228.2 kg / hour, respectively. A lens sheet was produced in the same manner as in Example 1. As a result, y / nx was 0.221. The pitch of the bowl-shaped lens of the lens sheet obtained as described above is 0.4 mm, the thickness of the resin sheet is 2.9 mm, the height of the bowl-shaped lens in the center is 0.115 mm, and the bowl-shaped lens at the end. The height of the lens was 0.113 mm, the aspect ratio of the bowl-shaped lens was 0.288, the shaping ratio at the center was 50%, and the shaping ratio at the end was 49%. The thickness of the third layer at the center and end was 0.040 mm.

Comparative Example 4
Examples except that the extrusion rate of the acrylic resin (a) (the first layer and the third layer) was 88.2 kg / hour and the extrusion rate of the acrylic resin (b) (the second layer) was 63.5 kg / hour, respectively. A lens sheet was produced in the same manner as in Example 1. As a result, y / nx was 3.309. The pitch of the bowl-shaped lenses of the lens sheet obtained as described above is 0.4 mm, the thickness of the resin sheet is 2.9 mm, the height of the bowl-shaped lenses at the center and the end is 0.112 mm, and the bowl-shaped lenses The aspect ratio was 0.280, and the forming ratio of the central portion and the end portion was 48%. The thickness of the third layer at the center was 0.600 mm, and the thickness of the third layer at the end was 0.597 mm.

Comparative Example 5
A lens sheet was produced in the same manner as in Comparative Example 1 except that the acrylic resin (a) was used instead of the acrylic resin (b), and the resin was heated to 260 ° C. and extruded. The molten sheet extruded from the T-type multi-manifold die frequently broke and could not be stably manufactured. Further, the obtained lens sheet was not practical because the shape of the bowl-shaped lens was uneven.

Comparative Example 6
A lens sheet was produced in the same manner as in Example 3 except that the multilayer extrusion T-type multi-manifold die was changed to a multilayer extrusion T-type feed block die. As a result, y / nx was 1.230. The pitch of the bowl-shaped lens of the lens sheet obtained as described above is 0.4 mm, the thickness of the resin sheet is 2.8 mm, the height of the bowl-shaped lens at the center is 0.165 mm, and the bowl-shaped lens at the end. The height of the lens was 0.114 mm, the aspect ratio of the bowl-shaped lens was 0.413, the shaping ratio at the center was 71%, and the shaping ratio at the end was 49%. The thickness of the third layer at the center was 0.230 mm, and the thickness of the third layer at the end was 0.088 mm.

  Table 1 shows the y / nx values of the lens sheets obtained in Examples and Comparative Examples, and the height, aspect ratio, shaping ratio, and the like of the saddle-shaped lens.

FIG. 1 shows the relationship between the shaping ratio of the central portion of the bowl-shaped lens and y / nx in the lens sheets obtained in Examples 1 to 5 and Comparative Examples 3 and 4.
E1 to E5 in FIG. 1 indicate Example 1, Example 2, Example 3, Example 4, and Example 5 in order, and C3 and C4 indicate Comparative Example 3 and Comparative Example 4, respectively. .
From FIG. 1 and Table 1, it can be seen that the lens sheets obtained in Examples 1 to 5 have a higher shaping rate and a higher aspect ratio of the bowl-shaped lens than the lens sheets obtained in Comparative Examples 3 and 4.
Further, from Comparative Examples 1 and 2, the lens sheet produced only with the acrylic resin (b) has a low shaping ratio and a low aspect ratio of the bowl-shaped lens, and the tendency is particularly large when the resin sheet is thick. I understand.
Further, it can be seen from Comparative Example 5 that a lens sheet produced only with the acrylic resin (a) cannot be stably produced, and the shape of the lens becomes non-uniform.
Further, it can be seen from Comparative Example 6 that the lens sheet that did not use the multi-manifold die has a difference in the thickness of the layer made of the acrylic resin (a) in the extrusion width direction, and the shaping rate becomes non-uniform.
From the above results, according to the method for manufacturing a lens sheet of the present invention, a lens having a high aspect ratio and a high aspect ratio can be realized even when the resin sheet is as thick as 3.0 mm. It can be seen that a sheet is obtained.

1: Extruder 2: Multi-layer extrusion T die 31: Pressing die roll 32: Shaping die roll 33, 34: Cooling roll 4: Lens sheet

Claims (2)

A thermoplastic resin (A), a thermoplastic resin (B) having a smaller MFR (measured in accordance with ISO 1133 at 230 ° C. and a load of 37.3 N) than the thermoplastic resin (A), and the thermoplastic resin (A) is extruded and made of a thermoplastic resin (A), the volume per unit length is y (y is a positive number), and the surface layer is a first layer, and the thermoplastic resin. a second layer of (B), the first step sequentially comprising a multilayer sheet of the molten state and a third layer of thermoplastic resin (a) obtained by the multi-manifold die; and,
The molten multi-layer sheet obtained in the first step is a molding die having a plurality of grooves whose volume per unit length is x (x is a positive number) satisfying the following formula (1): A second step of forming n (n is a natural number) bowl-shaped lenses in close contact with the surface of the first layer;
A method for extrusion production of a lens sheet.
0.7 ≦ y / nx ≦ 2.0 (1) The method for extruding a lens sheet according to claim 1, wherein y, n, and x satisfy the following formula (2).
1.05 ≦ y / nx ≦ 1.4 (2)

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