KR101749842B1 - Lens sheet manufacturing method - Google Patents

Abstract

Provided is a manufacturing method by extrusion molding of a lens sheet having a thick resin sheet and a high aspect ratio of a wavy lens. A thermoplastic resin (A) and a thermoplastic resin (B) having a smaller MFR (measured in accordance with ISO 1133 at 230 캜 under a load of 37.3 N) than the thermoplastic resin (A) are extruded to obtain a thermoplastic resin (A Layered sheet having a volume per unit length of y (y is a positive number) and having a first layer as a surface layer and a second layer composed of a thermoplastic resin (B) adjacently to each other in a molten state, A first step obtained by folding die; And a negative mold having a plurality of grooves whose volume per unit length satisfies the following formula (1) and x (x is a positive number) are brought into close contact with the surface of the first layer of the molten double-layer sheet obtained in the first step , a second step of forming a wavy lens of n (n is a natural number); Wherein the lens sheet is formed by extrusion molding.
0.7? Y / nx? 2.0 (1)

Description

[0001] LENS SHEET MANUFACTURING METHOD [0002]

The present invention relates to a method of manufacturing a lens sheet including a plurality of corrugated lenses arranged in parallel on a surface of a resin sheet. More particularly, the present invention relates to a method of manufacturing a lens sheet, Of the lens sheet having a high aspect ratio can be preferably manufactured.

A lens sheet having a plurality of corrugated lenses arranged in parallel on the surface of a resin sheet is known. As the shape of the corrugated lens, for example, a plate-shaped lens or a delta prism lens having a vertex angle of 90 degrees can be mentioned (see Patent Documents 1 to 4). In such a lens sheet, it is generally required to increase the aspect ratio of the corrugated lens (that is, (the height of the corrugated lens) / (the pitch of the corrugated lens)).

Examples of the production method of the lens sheet include a method of extruding or injection molding a thermoplastic resin, and a method of photo-curing a UV curable resin. Among them, a method of extruding a thermoplastic resin is excellent in terms of continuous productivity.

As a method of producing a lens sheet having a corrugated lens on both sides by extrusion molding of a thermoplastic resin, there is known a method in which a thermoplastic resin having a low viscosity is arranged so as to sandwich a thermoplastic resin having a high viscosity to perform multilayer extrusion molding. By manufacturing the lens sheet in this manner, it is possible to suppress the resin sagging of the molten sheet when manufacturing the lens sheet having the wavy lens having a high aspect ratio, and the production stability is improved (refer to Patent Document 5).

Further, there is known a method of transferring the shape of a pattern member to a sheet in a molten state by extrusion molding using a pattern roll having a heat buffering member disposed between the core and the pattern member as a mold, and a prism lens having an aspect ratio of 0.5 Is arranged on a resin sheet having a thickness of 1 mm (see Patent Document 6).

As one of applications of the lens sheet, there is a light guide plate used for a liquid crystal display device or the like. In these applications, the size of the apparatus has been recently increased, and accordingly, in order to secure the strength of the light guide plate, it is required to increase the thickness of the resin sheet.

According to the examination by the present inventors, in the method described in Patent Document 5, when the resin sheet is made thick, the negative rate (that is, the height of the wavy lens of the lens sheet / the depth of the groove of the negative mold) The aspect ratio tends to be lowered, and it has been found that there is room for improvement.

In the method described in Patent Document 6, heat is efficiently transferred to the resin sheet by the heat buffering member. Therefore, when the thickness of the resin sheet is large, cooling and hardening of the formed concavo- The wave-like lens tends to be deformed, which is a problem.

Japanese Unexamined Patent Publication No. 2-190835 Japanese Laid-Open Patent Publication No. 2009-37803 Japanese Laid-Open Patent Publication No. 2009-265380 Japanese Laid-Open Patent Publication No. 2009-283383 Japanese Patent Application Laid-Open No. 4-299329 Japanese Laid-Open Patent Publication No. 2003-53834

It is an object of the present invention 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 which has a high resin sheet thickness, a high aspect ratio of the wavy lens, And to provide a method which can industrially easily manufacture a lens sheet.

According to the present invention, the above object is solved by the invention including the following aspects.

(1) A thermoplastic resin composition comprising a thermoplastic resin (A) and a thermoplastic resin (B) having a smaller MFR (measured at 230 ° C under a load of 37.3 N in accordance with ISO 1133) than the thermoplastic resin (A) A multilayer sheet in a molten state comprising a resin (A) and having a volume per unit length of y (y is a positive number) and a first layer as a surface layer and a second layer as a thermoplastic resin (B) In a multi-manifold die; And

A negative mold having a plurality of grooves each having a volume per unit length satisfying the following formula (1) and x (x being a positive number) is brought into close contact with the surface of the first layer of the molten double-layer sheet obtained in the first step, a second step of forming a wavy lens of n (n is a natural number);

Wherein the lens sheet is formed by extrusion molding.

0.7? Y / nx? 2.0 (1)

[2] The extrusion-producing method of the 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, it is possible to provide a lens sheet, for example, a resin sheet having a thickness of 2.5 to 15 mm and a wavy lens having a high resin-sheet thickness and a high aspect ratio of a wavy lens, A lens sheet of 0.3 to 1.0 can be industrially easily produced.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view showing the relationship between the ratio of the central portion of the corrugated lens of Examples 1 to 5 and Comparative Examples 3 and 4 to y / nx. Fig.
2 is a schematic view of an extrusion molding machine for producing lens sheets of Examples and Comparative Examples.

[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, the value of MFR (A) / MFR (B) exceeds 1 when the MFR of the thermoplastic resin (A) is taken as MFR (A) and the MFR of the thermoplastic resin (B) is taken as MFR (B). 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 wavy lens becomes high. It is preferable that the value of MFR (A) / MFR (B) is 40 or less from the viewpoint of enhancing the uniformity of the thickness of the obtained lens sheet. In the present specification, the MFR is a value measured under the conditions of 230 占 폚 and a load of 37.3 N in accordance with ISO1133.

The MFR (A) is preferably in a range higher than that of the thermoplastic resin used in the conventional extrusion molding, from the viewpoint of filling the thermoplastic resin (A) in the grooves of the mold metal mold as little as possible. For example, a range of 7 to 50 g / 10 min is preferable, a range of 7 to 30 g / 10 min is more preferable, a range of 10 to 25 g / 10 min is more preferable, a range of 10 to 20 g / 10 minutes is particularly preferred. If the MFR (A) is less than 7 g / 10 min, the resulting lens sheet may have a reduced porosity. If it is more than 50 g / 10 min, the extrusion amount of the thermoplastic resin (A) may become unstable during extrusion molding .

In the present specification, a description connecting two numerical values with " ~ " means the two numerical values and the range therebetween.

The 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, more preferably in the range of 0.5 to 3 g / 10 min Range is more preferable. When the MFR (B) is less than 0.2 g / 10 min, the pressure of the molten resin in the extrusion molding machine becomes excessively high and the extrusion molding machine may be damaged. When the MFR (B) is larger than 5 g / 10 min, .

[First Step]

In the first step, the thermoplastic resin (A) and the thermoplastic resin (B) are extruded to form a first layer which is a surface layer made of a thermoplastic resin (A) and a second layer which is a thermoplastic resin (B) Thereby obtaining a double-layered sheet in a molten state.

The conditions for the extrusion molding of the thermoplastic resin (A) and the thermoplastic resin (B) are not particularly limited. Usually, the thermoplastic resin (A) and the thermoplastic resin (B) are each melted in a cylinder of an extrusion molding machine, laminated in an extrusion die, and then subjected to extrusion molding to obtain a melted double-layered sheet. The extrusion die uses a multi-manifold die having a plurality of manifolds therein in view of making uniform the thickness of each layer.

When a multi-layer sheet is produced in the multi-manifold die used in the present invention, the thermoplastic resin constituting each layer is supplied as a separate flow path inside the die, and the resin constituting each layer is separately expanded in the width direction of the plate And then joined and extruded near the discharge port of the die. Therefore, in the multi-manifold die, even if the fluidity of the resin is different, the thickness of each layer can be made uniform in the width direction of the plate.

The temperature (molding temperature) at which the thermoplastic resin (A) and the thermoplastic resin (B) are melted in the extrusion molding is usually 130 to 180 Deg.] C. The molding temperatures of the thermoplastic resin (A) and the thermoplastic resin (B) may be different from each other. In the formation of the corrugated lens in the second step, it is preferable that the molding temperature of the thermoplastic resin (A) is made higher than the molding temperature of the thermoplastic resin (B) from the viewpoint of increasing the fluidity of the thermoplastic resin (A) desirable.

The multi-manifold die usually has a heater for heating each thermoplastic resin. The heater included in the multi-manifold die may be different for each thermoplastic resin, and in this case, the temperature (molding temperature) of the heater of each thermoplastic resin can be changed. The temperature of the heater to which the thermoplastic resin (A) as the first layer is contacted is preferably higher than the temperature of the heater to which the thermoplastic resin (B) of the multi-manifold die touches, usually at a temperature difference of 5 to 40 DEG C, More preferably at a temperature difference of -35 DEG C, and more preferably at a temperature difference of 15 DEG C to 30 DEG C. When the temperature difference is 40 DEG C or less, warpage of the obtained lens sheet is less likely to occur.

The amount of extrusion of the thermoplastic resin (A) is not particularly limited, but may be, for example, 5 to 100 kg / hr.

The amount of extrusion of the thermoplastic resin (B) is not particularly limited, but may be, for example, 50 to 400 kg / hr.

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

The extrusion speed of the double-layer sheet in a molten state is not particularly limited, but may be, for example, 0.1 to 10 m / min.

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

An antioxidant, an ultraviolet absorber, a photostabilizer, a lubricant, a release agent, an antistatic agent, and a polymer processing aid (hereinafter referred to as " antioxidant ") may be added to one or both of the thermoplastic resin (A) and the thermoplastic resin , A flame retardant, a salt pigment, a light diffusing agent, an impact resistance modifier, a phosphor, or 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, 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 thicker than 20 mm, cooling and curing of the concavo-convex pattern formed thereon does not progress rapidly, and the wavy lens tends to be deformed after being peeled off from the mold .

The ratio of the thickness of the first layer to the thickness of the second layer of the multi-layered sheet in a molten state obtained in this step can be, for example, from 1: 2 to 1:50.

In the present specification, the volume per unit length of the first layer is defined as y. The first layer is a surface layer of a multi-layered sheet in a molten state, and is in close contact with the negative mold in the second step. As a result, the first layer becomes at least a part of the n-number of wavy 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 multi-layered sheet in a molten state may include layers other than the first layer and the second layer. The other layer may be made of a thermoplastic resin (A) or a thermoplastic resin (B), or may be made of another thermoplastic resin. From the viewpoint of suppressing the warpage of the obtained lens sheet, it is preferable to use a third layer made of a thermoplastic resin (A) as a separate layer and a three-layered two-layered sheet arranged in the order of first layer / second layer / third layer . In the case of producing such a three-layered double-layered 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, Is more preferable.

[Second Step]

In the second step, a negative mold having a plurality of grooves having a volume x satisfying the formula (1) per unit length is brought into close contact with the surface of the first layer of the molten double-layer sheet obtained in the first step, Thereby forming a corrugated lens. At this time, it is preferable to adhere the pressing mold to the other surface of the double-layered sheet in a molten state.

The shapes of the mold and the press mold include, for example, a belt shape and a roll shape.

In forming the n-number of corrugated lenses, the sum of the volumes per unit length of the grooves of the negative mold required is nx. The value of y / nx in the formula (1) is in the range of 0.7 to 2.0, preferably in the range of 1.05 to 1.4, and more preferably in the range of 1.2 to 1.3, from the viewpoint of realizing a high negative ratio.

The number n of wavy lenses of the lens sheet of the present invention is determined as (width of lens sheet to be manufactured) / (pitch of wavy lens). The number n of wavy lenses, the volume y per unit length of the first layer of the multilayered sheet in the molten state determined in the first step, and the volume x per unit length of the groove of the negative mold, Can be adjusted to a desired range. Specifically, when the total amount of extruded amounts of the entire thermoplastic resins to be used per unit time is r and the extruded amount per unit time of the thermoplastic resin (A) is r ₁ when the multilayer sheet in a molten state is produced in the first step, by adjusting the ratio r ₁ / r, y / nx can adjust the value of a, r Therefore, y / nx becomes larger as increasing the ₁ / r.

According to the value of y / nx, it is determined how much the first layer fills the volume in the groove of the mold metal mold. That is, when the value of y / nx exceeds 1, only the thermoplastic resin (A) fills the grooves, and the resulting lens sheet has a structure in which the first layer is a part of the corrugated lens and the resin sheet, Can be formed. On the other hand, if the value of y / nx is less than 1, the total amount of the thermoplastic resin (A) in the groove and a part of the thermoplastic resin (B) are filled, The two layers can form a part of the corrugated lens and the resin sheet. When the value of y / nx is 1, only the thermoplastic resin (A) is filled in the grooves, and the obtained lens sheet can form only the first layer of the wavy lens and the second layer of the resin sheet. As described above, the manufacturing method of the present invention achieves the object by adjusting the ratio of forming the wavy lens in the first layer and the ratio of the first layer in the wavy lens.

From the viewpoint of filling the thermoplastic resin (A) into the mold metal mold as far as possible without gaps, the temperature of the mold metal mold is preferably within the range of the deflection temperature of the thermoplastic resin (A) ± 10 ° C. If the temperature of the negative mold is lower than 10 占 폚 below the load deflection temperature of the thermoplastic resin (A), filling of the resin with respect to the negative mold becomes insufficient, and if the temperature exceeds 10 占 폚, release of the resin from the negative mold is smoothly carried out The resin sheet is wound around the roll, or a surface defect called a release mark is generated.

The temperature of the press mold is preferably in the range of (the deflection temperature of the thermoplastic resin (B) - 20 deg. C) to (the deflection temperature of the thermoplastic resin (B)) from the viewpoint of sufficiently cooling the thermoplastic resin (B).

The load deflection temperature of the thermoplastic resin (A) and the thermoplastic resin (B) is measured according to ISO 75-2.

From the viewpoint of raising the aspect ratio of the corrugated lens of the obtained lens sheet, the pitch of the used metal 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.

In the present invention, the sheet formed article obtained after the second step is cut in the direction perpendicular to the normal extrusion direction, and the length is adjusted to obtain a lens sheet. Further, both ends in the extrusion width direction parallel to the extrusion direction may be suitably cut to adjust the width.

Example

EXAMPLES 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 used mold is as follows.

The surface shape of the negative mold was transferred using a two-liquid curable silicone resin, and the cross-sectional shape thereof was observed with a microscope to measure the pitch and depth of the groove. As a result, the cross-sectional shape of the groove of the negative mold roll was semi-elliptical with 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 the depth of the obtained groove, and the volume x (m 3 / m) per unit length 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 wave lens

A section perpendicular to the extrusion direction of the lens sheet was observed with a microscope and the distance parallel to the thickness direction from the top of the wavy lens to the valley was measured. The height measured at the center in the extrusion width direction was taken as the height of the corrugated lens at the center and the height measured at the position 600 mm away from the center in the extrusion width direction to one end in the extrusion width direction was defined as the height of the corrugated lens at the end .

(2) Thickness of Resin Sheet

A section perpendicular to the extrusion direction of the lens sheet was observed with a microscope and the distance from the valley portion of the corrugated lens to the surface of the third layer was measured.

(3) Calculation of y / nx

(G / cm < 3 >) of the thermoplastic resin (A), the extrusion rate Q (kg / hour) of the thermoplastic resin The volume per unit length y (m < 3 > / m) was calculated.

y = Q / (60000 x? v) (m3 / m)

Y / nx was calculated from the calculated y, the number n of formed wavy lenses, and the calculated x (m 3 / m).

(4) The pitch of the wavy lens

A section perpendicular to the extrusion direction of the lens sheet was observed with a microscope and the distance from the top of the wavy lens to the top of the adjacent wavy lens was measured.

(5) The aspect ratio of the wavy lens

The height of the corrugated lens at the center measured in (1) above was divided by the pitch of the corrugated lens measured at (4) to obtain an aspect ratio.

(6) Poor (%)

The percentage of the height of the corrugated lens at the center portion and the end portion measured in the above (1) with respect to the depth of the groove of the negative mold was obtained, and the percentage of the central portion and the end portion was determined as a percentage.

(7) Thickness of the third layer

A section perpendicular to the extrusion direction of the sheet was observed with a microscope and measured. The thickness measured at the center in the extrusion width direction was taken as the thickness of the third layer at the center and the thickness measured at the position 600 mm away from the center in the extrusion width direction to one end in the extrusion width direction was the thickness of the third layer at the end .

2 is a schematic view of an extrusion molding machine 1 used in Examples and Comparative Examples. The extrusion molding machine 1 is composed of an extrusion screw portion not shown and a multilayer extrusion T-type multi-manifold die 2, a press mold roll 31, a mold die roll 32 and cooling rolls 33 and 34. On the surface of the mold roll 32, 3250 grooves extending along the outer periphery of the roll are formed.

The surfaces of the press roll 31 and cooling rolls 33 and 34 are smooth. The molten resin is discharged downward from the molten resin discharge portion of the multi-layer extruded T-shaped multi-manifold die 2. The pressurizing mold roll 31 and the mold mold roll 32 are arranged horizontally so as to face each other so as to sandwich the molten resin. The cooling rolls 33 and 34 are arranged so as to be parallel to the pressurizing mold roll 31 and the mold roll 32 such that their respective rotating shafts 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): "Parapet GH" manufactured by Kuraray Co., Ltd., MFR = 10 (catalog value measured at 230 ° C under load of 37.3 N in accordance with ISO1133), load deflection temperature = 95 ° C 2, with annealed, catalog value measured at load 1.82 MPa), specific gravity 1.19.

Acrylic resin (b): "Parapett EH" manufactured by Kuraray Co., Ltd., MFR = 1.3 g / 10 min (catalog value measured at 230 ° C. under load of 37.3 N in accordance with ISO 1133), load deflection temperature = 93 ° C (measurement conditions: according to ISO 75-2, annealed, catalog value measured at load of 1.82 MPa), specific gravity 1.19.

Example 1

The acrylic resin (a) and the acrylic resin (b) were heated to 260 ° C. and 245 ° C., respectively, in the extrusion molding machine, and the length in the extrusion width direction through which the molten resin was discharged was about The acrylic resin (a), the acrylic resin (b) and the acrylic resin (a) were laminated in this order in the multi-layer extruded T-shaped multi-manifold die having a thickness of 1,500 mm, layered sheet having the first layer (b) as the second layer and the acrylic resin (a) as the third layer was extruded. The extrusion rates of the acrylic resin (a) (first layer and third layer) were respectively 20 kg / hr and the extrusion amount of the acrylic resin (b) (second layer) was 200 kg / hr.

Subsequently, the molten two-layered sheet was fed between the press mold 31 and the mold mold roll 32 arranged at a distance of 3 mm apart from each other to form a lens shape, and then the cooling rolls 33, To obtain a sheet molded article having a plurality of corrugated lenses arranged on its surface. The sheet molded article had a width of about 1.4 (m).

The surface temperature of the pressing mold roll 31 is 80 DEG C, the surface temperature of the mold die roll 32 is 100 DEG C, the surface temperature of the cooling roll 33 is 100 DEG C, the surface temperature of the cooling roll 34 is 70 DEG C, 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 into a length of 1.3 m perpendicular to the extrusion direction. Further, both ends in the extrusion width direction parallel to the extrusion direction were cut by an equal width, and the width was 1.3 m, thereby forming a lens sheet.

The pitch of the wavy lens of the lens sheet thus obtained was 0.4 mm, the thickness of the resin sheet was 2.8 mm, the height of the wavy lens at the center was 0.16 mm, the height of the wavy lens at the end was 0.159 mm, The aspect ratio was 0.400, and the ratio of the central portion and the end portion was 69%. The thickness of the third layer at the center portion was 0.136 mm and the thickness of the third layer at the end portion was 0.135 mm.

Example 2

The same procedures as in Example 1 were carried out except that the extrusion amount of the acrylic resin (a) (first layer and third layer) was 28.8 kg / hour, and the extrusion amount of the acrylic resin (b) (second layer) was 182.3 kg / To prepare a lens sheet. As a result, y / nx became 1.081. The pitch of the wavy lens of the lens sheet thus obtained was 0.4 mm, the thickness of the resin sheet was 2.8 mm, the height of the wavy lens at the center was 0.164 mm, the height of the wavy lens at the end was 0.162 mm, The spectral ratio was 0.410, the central porosity was 71%, and the edge porosity was 70%. The thickness of the third layer at the center portion was 0.196 mm and the thickness of the third layer at the end portion was 0.194 mm.

Example 3

Was the same as Example 1 except that the extrusion amount of the acrylic resin (a) (the first layer and the third layer) was 32 kg / hour, and the extrusion amount of the acrylic resin (b) (the second layer) was 176 kg / To prepare a lens sheet. As a result, y / nx became 1.230. The pitch of the corrugated lens of the lens sheet thus obtained was 0.4 mm, the thickness of the resin sheet was 2.8 mm, the height of the corrugated lens at the center and the corners was 0.177 mm, the aspect ratio of the corrugated lens was 0.443, Of the population was 77%. The thickness of the third layer at the center portion was 0.223 mm and the thickness of the third layer at the end portion was 0.222 mm.

Example 4

Was the same as in Example 1 except that the extrusion amount of the acrylic resin (a) (the first layer and the third layer) was 36.8 kg / hour, and the extrusion amount of the acrylic resin (b) (the second layer) was 164.4 kg / To prepare a lens sheet. As a result, y / nx became 1.379. The pitch of the corrugated lens of the lens sheet thus obtained was 0.4 mm, the thickness of the resin sheet was 2.8 mm, the height of the corrugated lens at the center was 0.164 mm, the height of corrugated lenses at the corners was 0.166 mm, The spectral ratio was 0.410, the central porosity was 71%, and the edge porosity was 72%. The thickness of the third layer at the center and at the end was 0.25 mm.

Example 5

Was the same as Example 1 except that the extrusion amount of the acrylic resin (a) (the first layer and the third layer) was 51.5 kg / hour, and the extrusion amount of the acrylic resin (b) (the second layer) was 137 kg / To prepare a lens sheet. As a result, y / nx became 1.930. The pitch of the wavy lens of the lens sheet thus obtained was 0.4 mm, the thickness of the resin sheet was 2.8 mm, the height of the wavy lens at the center was 0.156 mm, the height of the wavy lens at the end was 0.157 mm, The aspect ratio was 0.390, and the ratio of the central portion and the end portion was 68%. The thickness of the third layer at the center portion was 0.35 mm and the thickness of the third layer at the end portion was 0.348 mm.

Comparative Example 1

The acrylic resin (b) was placed in an extrusion molding machine, heated at 245 DEG C, and extruded from the T-type multi manifold die at an extrusion amount of 240 kg / hour. Subsequently, the sheets in the melted state were fed between the press mold 31 and the mold mold roll 32 arranged parallel to each other with a space of 3 mm therebetween to form a lens shape. Subsequently, the sheet was supplied to the cooling rolls 33 and 34 And a lens sheet in which a plurality of corrugated lenses were arranged on the surface was manufactured. The surface temperature of the pressing mold roll 31 is 80 DEG C, the surface temperature of the mold die roll 32 is 100 DEG C, the surface temperature of the cooling roll 33 is 100 DEG C, the surface temperature of the cooling roll 34 is 70 DEG C, The extrusion speed of the lens sheet was 0.8 m / min.

The pitch of the corrugated lens of the lens sheet thus obtained was 0.4 mm, the thickness of the resin sheet was 2.9 mm, the height of the corrugated lens at the center and the corners was 0.100 mm, the aspect ratio of the corrugated lens was 0.250, Of the population was 43%.

Comparative Example 2

Except that the extruded amount of the acrylic resin (b) was set to 160 kg / hr, and the molten resin was placed parallel to each other with a distance of 2 mm between the press mold roll 31 and the mold mold roll 32, To prepare a sheet (4).

The pitch of the corrugated lens of the lens sheet thus obtained was 0.4 mm, the thickness of the resin sheet was 1.9 mm, the height of the corrugated lens at the center portion and the corners was 0.150 mm, the aspect ratio of the corrugated lens was 0.375, Of the population was 65%.

Comparative Example 3

Was the same as Example 1 except that the extrusion amount of the acrylic resin (a) (first layer and third layer) was changed to 5.9 kg / hour and the extrusion amount of the acrylic resin (b) (second layer) was changed to 228.2 kg / To prepare a lens sheet. As a result, y / nx became 0.221. The pitch of the wavy lens of the lens sheet thus obtained was 0.4 mm, the thickness of the resin sheet was 2.9 mm, the height of the wavy lens at the center was 0.115 mm, the height of the wavy lens at the end was 0.113 mm, The aspect ratio was 0.288, the central part was 50% and the end part was 49%. The thickness of the third layer at the center portion and the end portion was 0.040 mm.

Comparative Example 4

Was the same as Example 1 except that the extrusion amount of the acrylic resin (a) (the first layer and the third layer) was 88.2 kg / hour, and the extrusion amount of the acrylic resin (b) (the second layer) was 63.5 kg / To prepare a lens sheet. As a result, y / nx became 3.309. The pitch of the corrugated lens of the lens sheet thus obtained was 0.4 mm, the thickness of the resin sheet was 2.9 mm, the height of the corrugated lens at the center portion and the corners was 0.112 mm, the aspect ratio of the corrugated lens was 0.280, Of the population 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 acrylic resin (a) was used instead of acrylic resin (b) and extruded by heating at 260 캜. Sheets in a molten state extruded from the T-shaped multi-manifold die frequently break, failing to stably manufacture. Further, the obtained lens sheet was not uniform in shape of the wavy lens and was not practical.

Comparative Example 6

Lens sheet was produced in the same manner as in Example 3 except that the multi-layer extruded T-shaped multi-manifold die was replaced with a multi-layer extruded T-shaped feed block die. As a result, y / nx became 1.230. The pitch of the wavy lens of the lens sheet thus obtained was 0.4 mm, the thickness of the resin sheet was 2.8 mm, the height of the wavy lens at the center was 0.165 mm, the height of the wavy lens at the end was 0.114 mm, The aspect ratio was 0.413, the central part was 71% and the end part was 49%. The thickness of the third layer at the center portion was 0.230 mm and the thickness of the third layer at the end portion was 0.088 mm.

Table 1 shows the values of y / nx of the lens sheet obtained in Examples and Comparative Examples and the height, aspect ratio, negative ratio and the like of the corrugated lens.

Fig. 1 shows the relationship between the ratio of the central portion of the corrugated lens and y / nx in the lens sheet obtained in Examples 1 to 5 and Comparative Examples 3 and 4. Fig.

E1 to E5 in Fig. 1 are shown for Example 1, Example 2, Example 3, Example 4 and Example 5 in order, and C3 and C4 for Comparative Example 3 and Comparative Example 4, respectively .

From Fig. 1 and Table 1, it can be seen that the lens sheet obtained in Examples 1 to 5 has a higher aspect ratio and a wavy-surface lens aspect ratio than the lens sheet obtained in Comparative Examples 3 and 4.

It can also be seen from the comparative examples 1 and 2 that the lens sheet made of only the acrylic resin (b) has a low aspect ratio and a low aspect ratio of the wavy lens, and particularly a large thickness of the resin sheet.

Further, it can be seen from the comparative example 5 that the lens sheet made only of the acrylic resin (a) can not be stably produced, and the shape of the lens is also uneven.

From the comparative example 6, it can be seen that the thickness of the layer made of the acrylic resin (a) in the lens sheet not using the multi-manifold die is different in the extrusion width direction, and the percentage of the unevenness is uneven.

From the above results, it can be seen that, according to the production method of the lens sheet of the present invention, even when the thickness of the resin sheet is as large as 3.0 mm, a high aspect ratio can be realized and a lens sheet having a wavy- .

1: extrusion molding machine
2: Multilayer extruded T-die
31: Press mold roll
32: CUTTING MOLD ROLL
33, 34: cooling roll
4: Lens sheet

Claims (2)

A thermoplastic resin composition is obtained by extruding a thermoplastic resin (A) and a thermoplastic resin (A) having a smaller MFR (measured in accordance with ISO 1133 at 230 캜 under a load of 37.3 N) than the thermoplastic resin (A) Molding,
A thermoplastic resin composition comprising a thermoplastic resin (A) and having a volume per unit length of y (y is a positive number), a first layer as a surface layer, a second layer as a thermoplastic resin (B) A first step of obtaining a multi-layered sheet in a molten state having a third layer sequentially in a multi-manifold die; And
A negative mold having a plurality of grooves each having a volume x (x is a positive number) satisfying the following formula (1) is adhered to the surface of the first layer of the molten double-layer sheet obtained in the first step, a second step of forming a wavy lens of n (n is a natural number);
Wherein the lens sheet is formed by extrusion molding.
0.7? Y / nx? 2.0 (1) The method 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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