Optical film forming device and optical film forming method

Abstract

An optical film forming apparatus (8) configured to form a light guide plate (1) having a light incident portion (2) and a surface-emitting portion (3), both upper surfaces (2a, 3a) of which are flat surfaces arranged parallel to each other, and an inclined surface (4) is formed between the upper surfaces (2a, 3a), and wherein a lower surface (1s) of the light guide plate (1) is formed as a continuous flat surface, opposite and parallel to the two upper surfaces (2a, 3a), thereby enabling the light incident portion (2) to be formed as a thick portion and the surface-emitting portion (3) to be formed as a thin portion, the optical film forming apparatus (8) comprising: an extrusion unit (9) having an extruder (20) which melts and kneads a resin material to produce a molten resin, and a T-die (21) which discharges a sheet-shaped molten resin from a discharge slit (18) connected to a manifold (25a) via a clearance passage (25b) defined as a clearance (H) between a first slit surface (18a) of a first lip (26a) and a second slit surface (18b) of a second lip (26b) which are oppositely parallel to each other, a molding roller unit (10) having a main roller (15) configured to rotate about a rotation axis (15r) arranged in a direction crossing an extrusion direction (Fp) to convey the discharged molten resin in the extrusion direction (Fp) while the discharged molten resin solidifies, and a pressing roller (16), and wherein the main roller (15) and the pressing roller (16) each have a cylindrical transfer surface (15s, 16s); a thicker-portion forming groove (19) formed in one or both of the main roller (15) and the press roller (16) by continuously pressing down from a lateral side of the transfer surface (15s, 16s) along a circumferential direction, having a groove bottom surface (19a) and two inclined surfaces (19b, 19c) inclined from respective sides of the groove bottom surface (19a) toward the transfer surface (15s, 16s), and configured to continuously form a thick portion (14b) thicker than another portion in the extrusion direction (Fp) in a part of the molten resin; and a position adjustment mechanism (12) configured to adjust a position of the discharge slot (18) with respect to the thicker portion forming groove (19), wherein a necking portion (13p) caused by a necking phenomenon is continuously formed in the extrusion direction (Fp) in the molten resin discharged from the discharge slot (18), and the necking portion (13p) is positioned by adjusting the position of the discharge slot (18) with respect to the thicker portion forming groove (19) by the position adjusting mechanism (12) to be opposite to the thicker portion forming groove (19), thereby making it possible to form a semi-finished product of the light guide plate (1) in a width direction of the sheet-shaped molten resin.

Description

Technical area

[0001] The present invention relates to a technique for molding, for example, an optical film used for a light guide plate, etc., by extrusion molding. In the embodiments, the light guide plate is formed as a reduced-thickness film for optical use (also referred to as a thin film). State of the art

[0002] For example, in the technical field of mobile devices such as mobile phones and smartphones, with the trend toward thinner device bodies, thinner backlight units are required. The backlight unit is formed from, for example, a light guide plate, a diffusion film, a prism film, etc. The light guide plate is made of transparent resin with a high refractive index. To reduce the thickness of the backlight unit, a reduced-thickness light guide plate, i.e., a thin light guide plate, must be formed. To meet the above-described need, a technique of molding a thin optical film using resin has been proposed (see, for example, Patent Literature 1).

[0003] Injection molding and extrusion molding are commonly used to form thin films. In this case, extrusion molding is a technique that offers superior production efficiency to injection molding. Therefore, a thin resin film should preferably be formed using an extrusion molding technique. List of referencesPatent literature

[0004] Patent Literature 1: JP 2014-502568 A

[0005] US 2016 / 0009011 A1 describes a device for producing light guide plates. The device comprises: a feed unit with a slot-shaped outlet opening, an extrusion unit with a conveyor roller for conveying the raw material and an extrusion roller for extruding the raw material, and a cutting unit for cutting the light guide plate fed out of the extrusion unit. An elongated recess is arranged on a roller body of the extrusion roller, which extends toward the interior of the extrusion roller to produce a light guide plate of varying thickness.

[0006] DE 23 05 115 A describes an extrusion system for producing a material web. The system comprises an extruder into which thermoplastic starting material flows, an extruder barrel in which the material is heated, and a slot die into which the heated material is pressed. The extruders are supported for movement transversely to the slot die.

[0007] JP H08-118458 A relates to an extrusion laminator. The extrusion laminator includes edge detection means, roll positioning means, slit length adjustment means, and Teflon tape position adjustment means, all of which are controlled by a controller. The position of a base material roll can be adjusted in parallel with adjustment work.

[0008] JP 2002-192 598 A relates to a T-die for extrusion molding. The T-die for extrusion molding comprises a pair of cover plates slidably arranged in a manifold of a mold body, a mold land, and a lip land that are adjustable in a mold width by approaching and separating a mold body. Summary of the inventionTechnical problem

[0009] In a conventional extrusion molding technique, in the case of continuously molding a thin film having flat front and back surfaces and a constant thickness (hereinafter referred to as a standard thickness), for example, a technique of continuously molding a thin film by thinly spreading and discharging a molten resin extruded from an extruder into a film shape through a flow passage of a T-die, and compressing and solidifying the discharged film-shaped molten resin by a pair of rollers has been known. In this technique, the flow passage of the T-die is designed such that the flow volume of the molten resin becomes uniform in the width direction of the T-die when the molten resin is thinly spread into a film shape.

[0010] Meanwhile, the continuous thin film forming technique is not exclusively applied to the formation of a thin film with flat front and back surfaces, but also to the formation of a patterned film with a recess-projection pattern in which recesses and projections are regularly arranged side by side entirely on one or both of the front and back surfaces. In this case, a projection-recess pattern corresponding to the inverse recess-projection pattern of the patterned film is provided on the surfaces of the pair of rollers. At this time, similar to the formation of a thin film with flat front and back surfaces, a sheet-shaped molten resin with a uniform volume in the width direction is discharged from the T-mold.When the sheet-shaped molten resin touches the pair of rollers, the molten resin overflowing from the pattern's protrusions will creep into the pattern's recesses, thereby equalizing the resin volume. Therefore, the average thickness of the formed patterned sheet will be the standard thickness.

[0011] On the other hand, in the case of forming a thin film with flat front and back surfaces and with the standard thickness as the contour of a given shape, for example, it is impossible to make a part of the surface of the thin film stereoscopically protrude (thicken) while maintaining the standard thickness.

[0012] In this case, only a recessed groove pattern corresponding to the inverted protrusion (stereoscopically protruding part of the surface) of the thin film is provided on the surfaces of the pair of rollers. In other words, a protrusion corresponding to a recessed groove is not provided on the surfaces of the pair of rollers. Furthermore, similar to the formation of a thin film with flat front and back surfaces, a film-shaped molten resin with a uniform volume in the width direction is discharged from the T-mold.

[0013] When the sheet-shaped molten resin contacts the pair of rollers, the creeping effect of the molten resin is insufficient for the molten resin to creep into the entire recessed groove of the pattern. This makes it impossible to sufficiently ensure the resin volume required for the stereoscopic protrusion (thickening). As a result, due to, for example, a "sink mark" that occurs when the molten resin solidifies, the thin sheet cannot be accurately formed with the contour of a predetermined shape in some cases.

[0014] The present invention aims to provide an optical film molding technique of accurately molding an optical film having a contour of a predetermined shape by extrusion molding. Solution to the problem

[0015] To achieve the object, the present invention comprises an optical film forming apparatus according to the features of claim 1 and an optical film forming method according to the features of claim 5. Advantageous effects of the invention

[0016] According to the present invention, an optical film molding technique of accurately molding an optical film having a contour of a predetermined shape by extrusion molding can be realized. Short description of the drawings Fig. 1 is a perspective view showing the external structure of an optical film molding apparatus according to an embodiment. Fig. 2 is a perspective view showing the external structure of a T-shape. Fig. 3 is a sectional view showing the internal structure of the T-shape. Fig. 4 is a schematic view showing a state where a necking portion is arranged to oppose a thicker portion forming groove. Fig. 5 is a schematic view showing a state where the necking portion is arranged to be opposed to the thicker portion forming groove by a margin. Fig. 6 is a sectional view showing a separating section of a semi-finished product. Fig. 7 is a sectional view showing an operation mode of a finished product as a light guide plate. Fig. 8 is a sectional view showing the structure of a press roller according to a modification. Fig. 9 is a sectional view showing a result of comparison between a case where the necking portion is opposed to the thicker portion forming groove (sample of the present invention) and a case where the necking portion is not opposed to the thicker portion forming groove (conventional sample). Way of carrying out the invention "An embodiment" "Regarding general description of optical film forming device"

[0017] An optical film molding apparatus according to the present embodiment is configured to form a light guide plate. The light guide plate is used, for example, as a structure of a backlight unit of a mobile device such as a mobile phone or a smartphone. The light guide plate can be formed from a transparent resin with a high refractive index. Resins such as acrylic resin (PMMA), polycarbonate resin (PC), and cycloolefin resin (COP) can be used as the transparent resin.

[0018] As in Fig. As shown in Fig. 7, a thin light guide plate 1 for optical use includes a light incident portion 2 and a surface-emitting portion 3. The light incident portion 2 is thicker than the surface-emitting portion 3. Here, along with the trend of the thin backlight unit, the surface-emitting portion 3 must be thin. On the other hand, it is technically difficult to make a light source 7 (for example, an LED), which will be described later, as thin as the surface-emitting portion 3. Therefore, in order to admit all the light from the light source 7 while further reducing the thickness of the surface-emitting portion 3, the light incident portion 2 must be at least as thick as the light source 7.

[0019] An upper surface 2a of the light incident portion 2 and an upper surface 3a of the surface-emitting portion 3 are formed as smooth and flat surfaces. Both of the upper surfaces 2a and 3a are arranged parallel to each other. On the other hand, a lower surface 1s of the light guide plate 1 is formed continuously from the light incident portion 2 to the surface-emitting portion 3. The lower surface 1s of the light guide plate 1 is formed as a smooth and flat surface. The lower surface 1s of the light guide plate 1 is parallel to both of the upper surfaces 2a and 3a.

[0020] In the light incident portion 2, a smooth and inclined surface 4 is formed between the upper surface 2a and the upper surface 3a. A boundary portion 5 between the inclined surface 4 and the upper surface 2a of the light incident portion 2 is angled. In other words, the boundary portion 5 between the inclined surface 4 and the upper surface 2a of the light incident portion 2 is not rounded. In short, the angle at the boundary portion 5 changes steeply from the upper surface 2a of the light incident portion 2 to the inclined surface 4.

[0021] The light guide plate 1 is integrally formed from the light incidence portion 2 to the surface-emitting portion 3. A light incidence surface 2b is formed in the light incidence portion 2. The light incidence surface 2b extends in a direction orthogonal to the upper surfaces 2a and 3a. The light incidence surface 2b has, for example, a rectangular shape. The light incidence surface 2b is formed to be directly opposite to the surface-emitting portion 3 from the light incidence portion 2. A light-scattering component 6, such as a diffusion film or a prism film, is mounted, for example, on the upper surface 3a of the surface-emitting portion 3.

[0022] Here, the light guide plate 1 with the light-diffusing component 6 is installed in the mobile device. The light source 7 (for example, an LED) is arranged to face the light-incident surface 2b. The backlight unit is thereby formed in the mobile device. In this structure, the light emitted from the light source 7 is guided from the light-incident surface 2b to the light-incident portion 2. The light guided to the light-incident portion 2 is guided along the inclined surface 4 and propagates to the surface-emitting portion 3 without leakage. The light that has propagated to the surface-emitting portion 3 is plane-diffusive by the light-diffusing component 6. As a result, uniform light can be plane-generated from the surface-emitting portion 3.

[0023] As in Fig. 1 to 3, an optical film forming apparatus 8 includes an extrusion unit 9, a forming roll unit 10, a thicker portion forming mechanism 11, and a position adjusting mechanism 12.

[0024] The extrusion unit 9 is designed to discharge a film- or sheet-shaped molten resin 13a.

[0025] In the forming roller unit 10, the discharged sheet-shaped molten resin 13a changes into a molten resin 13b whose surface is solidified alone. For example, in the case of amorphous resin, the temperature is adjusted to a temperature lower than a glass transition point. Thereafter, an optical film or sheet 13c, which is solidified and fully flexible, is conveyed in the direction of arrow Fp.

[0026] The thicker portion forming mechanism 11 is configured to continuously form a thick portion 14b, which is thicker than the other portion, in the molten resins 13a and 13b in the extrusion direction Fb.

[0027] The position adjustment mechanism 12 is designed to adjust the position of the extrusion unit 9 with respect to the forming roller unit 10.

[0028] Here, the extrusion direction Fp indicates, for example, a direction along a series of extrusion paths continuous from the extrusion unit 9 to the molding roller unit 10. The series of extrusion paths indicates a series of process passes through which the molten resin 13a discharged from the extrusion unit 9 in the gravitational direction (vertical direction) is sent out through the molding roller unit 10. “Forming roller unit 10”

[0029] The molding roll unit 10 includes a main roll (second roll) 15, a press roll (first roll) 16, and a feed roll (third roll) 17. The three rolls 15, 16, and 17 are configured as temperature-controlled rolls. The three rolls 15, 16, and 17 are maintained at a predetermined constant temperature. The set temperature indicates a temperature at which the molten resins 13a and 13b are not melted but solidified and retain their flexibility. For example, in the case of polycarbonate resin (PC), the temperature is set to 100°C to 140°C.

[0030] The main roller (second roller) 15 has a cylindrical transfer surface 15s. The transfer surface 15s is highly polished. The transfer surface 15s is configured to guide the sheet-shaped molten resin 13a, which is discharged from a discharge slot 18, which will be described later, in the extrusion direction Fp.

[0031] The press roller (first roller) 16 has a cylindrical transfer surface 16s. The transfer surface 16s is highly polished. The transfer surface 16s is designed to press the molten resin 13a against the transfer surface 15s of the main roller 15.

[0032] The feed roller (third roller) 17 has a cylindrical feed surface 17s. The feed surface 17s is not necessarily mirror-polished. The feed surface 17s is configured to extrude the optical film 13c in the extrusion direction Fp.

[0033] The three rollers 15, 16, and 17 are configured to rotate about individual rotation axes 15r, 16r, and 17r, respectively. The three rotation axes 15r, 16r, and 17r are arranged parallel to each other in the horizontal direction. In other words, the three rotation axes 15r, 16r, and 17r are arranged in a direction (horizontal direction) that crosses (orthogonally crosses) the direction of gravity (vertical direction). The rotation direction of the main roller 15 is set to be opposite to the rotation direction of the other two rollers 16 and 17.

[0034] In this structure, the sheet-shaped molten resin 13a discharged from the extrusion unit 9 in the gravitational direction (vertical direction) passes (at a contact point) between the main roller 15 and the pressing roller 16. As the molten resin 13a, which has passed the contact point, is conveyed along the transfer surface 15s of the main roller 15, the molten resin 13a becomes the molten resin 13b whose surface alone is solidified. After the molten resin 13b passes (at a contact point) between the main roller 15 and the feed roller 17, the molten resin 13b becomes the optical film 13c, which is solidified and fully flexible. The optical film 13c is thereby conveyed in the direction of arrow Fp. At this time, the thickness of the optical film 13c is determined as a semi-finished product, which results in the thin light guide plate 1.

[0035] As an example of the best operating mode, the drawing shows a mode where the three rollers 15, 16, and 17 are arranged side by side in the horizontal direction. Alternatively, as a relatively preferred mode, for example, the main roller 15 may be centered and the side rollers (the press roller 16 and the feed roller 17) may be arranged obliquely. However, a vertical arrangement of the three rollers 15, 16, and 17 in the gravitational direction (vertical direction) cannot be said to be the best operating mode.

[0036] In the vertical arrangement mode, the resin from the extrusion unit 9 is discharged to the contact point between the main roller 15 and the pressing roller 16. At this time, before reaching the contact point between the main roller 15 and the pressing roller 16, the discharged resin is pulled down and suspended by the action of gravity. Therefore, the resin contacts the lower roller (e.g., the pressing roller 16) first, and solidification begins relatively early. As a result, the transfer (molding) accuracy between the main roller 15 and the pressing roller 16 may not be consistently maintained. “Thick-section forming mechanism 11”

[0037] The thicker section forming mechanism 11 is formed in one or both of the main roller 15 and the press roller 16. Preferably, the thicker section forming mechanism 11 should be formed in the main roller 15. Therefore, the drawing shows the thicker section forming mechanism 11 formed in the main roller 15 as an example. The thicker section forming mechanism 11 has an annular thicker section forming groove 19 in the circumferential direction of the main roller 15. The thicker section forming groove 19 is provided on the transfer surface 15s of the main roller 15.

[0038] On the transfer surface 15s, the thicker-portion forming groove 19 is formed to be continuously recessed from the other surface in the circumferential direction. The thicker-portion forming groove 19 is applied to a mode where a portion (thick portion 14b) thicker than the other portion is continuously formed in the extrusion direction Fp in a semi-finished product (for example, the optical film 13c) having a constant thickness (standard thickness).

[0039] In the present embodiment, a mode of molding a semi-finished product (thin light guide plate 1) is assumed. In this case, it is only necessary to form a thicker portion forming groove 19 (thicker portion forming mechanism 11) on one side of the main roller 15 in the width direction. As a result, the thick portion 14b, which is thicker than the other portion, can be continuously formed in the extrusion direction Fp in the molten resins 13a and 13b that have passed between the main roller 15 and the press roller 16. “Extrusion Unit 9”

[0040] The extrusion unit 9 includes an extruder 20 and a T-die 21. The extruder 20 and the T-die 21 are connected by a connecting pipe 22. The extruder 20, the connecting pipe 22, and the T-die 21 are heated to a predetermined temperature in advance and maintained at the predetermined temperature. The predetermined temperature is higher than the predetermined temperatures of the three rollers 15, 16, and 17. For example, in the case of polycarbonate resin (PC), the temperature is set to approximately 260°C.

[0041] The extruder 20 includes a barrel and a hopper, which are not shown in the drawing. One or more screws (not shown) are rotatably inserted into the barrel. Here, a single-screw extruder 20 is provided in a mode where one screw is inserted into the barrel. A twin-screw extruder 20 is provided in a mode where a plurality of (for example, two) screws are inserted into the barrel.

[0042] The hopper is configured to introduce a resin material into the cylinder. Here, for example, a pelletized resin material is introduced from the hopper. The input resin material is melted and kneaded by the rotating screw within the cylinder. The melted and kneaded resin material is conveyed in a molten state to the distal end of the cylinder. The connecting pipe 22 is provided at the distal end of the cylinder.

[0043] The molten resin conveyed to the distal end of the cylinder is supplied to the T-mold 21 through the connecting pipe 22. In other words, the molten resin is produced in the extruder 20. The produced molten resin is supplied to the T-mold 21 through the connecting pipe 22. A heating device 23, which heats the T-mold and keeps the T-mold warm (see Fig. 3) is provided in the T-mold 21. The T-mold 21 is maintained at a predetermined constant temperature by the heater 23. Therefore, the molten resin supplied to the T-mold 21 does not solidify but is maintained in a constant molten state. Since the temperature for maintaining the T-mold 21 at a constant temperature is determined according to the type and application of the molten resin, a numerical limitation thereof will not be specifically described.

[0044] The T-mold 21 is configured to distribute and discharge the supplied molten resin into a sheet shape. The T-mold 21 includes, for example, a manifold 25a communicating with the connecting pipe 22 and a clearance passage 25b extending from the manifold 25a (see Fig. 3). The manifold 25a extends in a direction that crosses the extrusion direction Fp (that is, the width direction of the slit 18, which will be described later). The gap passage 25b extends planarly in the width direction of the manifold 25a. One end of the gap passage 25b is connected to the manifold 25a. The other end of the gap passage 25b is connected to the slit 18.

[0045] The T-shape 21 includes a T-shape body 21a, a fixed lip 21b, and a movable lip 21c. The fixed lip 21b and the movable lip 21c can be detachably attached to the T-shape body 21a by fastening bolts 24. In a state where the fixed lip 21b and the movable lip 21c are attached to the T-shape body 21a, the manifold 25a and the clearance passage 25b are formed in the T-shape 21. “Discharge slot 18”

[0046] The T-mold 21 includes the discharge slot 18 (hereinafter referred to as a slot). The slot 18 is configured to discharge the sheet-shaped molten resin 13a. The slot 18 has two slot surfaces (first slot surface 18a and second slot surface 18b) that are parallel and opposite to each other. The two slot surfaces (first slot surface 18a and second slot surface 18b) are formed as flat surfaces without recesses and projections.

[0047] Here, the slit 18 is defined as a gap (also referred to as a lip gap H) between the first slit surface 18a and the second slit surface 18b. The slit 18 is formed in a region over the entire length (flow passage length L (see Fig. 3)) of the first and second slit surfaces 18a and 18b in the extrusion direction Fp. Further, the slit 18 is provided with a discharge opening 18c at its distal end.

[0048] More specifically, the discharge port 18c is provided at the distal end of the T-shape 21. The distal end of the T-shape 21 indicates the lowest portion, which corresponds to the lowest position in the direction of gravity. The discharge port 18c is formed on the end surface of the lowest portion (the lower end surfaces of the first and second slit surfaces 18a and 18b). Further, the T-shape 21 is provided with two lips (first lip 26a and second lip 26b) at its distal end. The first lip 26a and the second lip 26b are opposed to each other with a space formed therebetween. The first lip 26a is provided in the movable lip 21c. The second lip 26b is provided in the fixed lip 21b.

[0049] The first and second slot surfaces 18a and 18b are provided on the opposite surfaces of the first and second lips 26a and 26b, respectively. That is, the first slot 18a is provided on the opposite surface of the first lip 26a. The second slot surface 18b is provided on the opposite surface of the second lip 26b. Thus, the slot 18 is formed over a gap area (lip gap H) between the first slot surface 18a and the second slot surface 18b.

[0050] In this structure, the discharge opening 18c may be defined as a thin rectangular opening extending in a direction crossing the extrusion direction Fp (i.e., the width direction of the slit 18) along the lower end faces of the first and second slit surfaces 18a and 18b. In this case, the molten resin 13a discharged from the T-mold 21 (the slit 18 and the discharge opening 18c) falls down in a long and thin rectangular shape as a whole. At this time, as described later, due to a necking phenomenon, necking portions 13p are continuously formed in the extrusion direction Fp at both edge portions (both side portions) of the molten resin 13a.

[0051] The T-shape 21 includes a lip gap adjustment mechanism 27 configured to adjust the gap (lip gap H) between the two lips 26a and 26b (first and second slot surfaces 18a and 18b). The lip gap adjustment mechanism 27 includes a plurality of lip adjustment bolts 28. The lip adjustment bolts 28 are arranged parallel to each other and are equally spaced from each other. The lip adjustment bolts 28 are rotatably supported on the T-shape 21. An adjustment portion 28a is provided at the proximal end of the lip adjustment bolt 28. A pressing portion 28b is provided at the distal end of the lip adjustment bolt 28. The pressing portion 28b is configured to make contact with one of the two lips 26a and 26b.

[0052] The drawing shows the lip adjustment bolt 28 in which the pressing portion 28b makes contact with the first lip 26a as an example. Here, the adjustment portion 28a is rotated. The pressing portion 28b is moved forward. A pressing force is applied from the pressing portion 28b to the first lip 26a. The first lip 26a is elastically deformed. The first lip 26a is thereby brought close to the second lip 26b. As a result, the lip gap H can be narrowed.

[0053] Conversely, the adjusting section 28a is rotated in the opposite direction. The pressing section 28b is retracted. The pressing force from the pressing section 28b to the first lip 26a is released. The original shape of the first lip 26a is restored by an elastic force or spring force. The first lip 26a is thereby separated from the second lip 26b. As a result, the lip gap H can be widened. “Position adjustment mechanism 12”

[0054] As in Fig. As shown in Figures 1 to 2 and 4, the position adjustment mechanism 12 is configured to move the extrusion unit 9 and the forming roller unit 10 relatively along the rotation axes 15r, 16r, and 17r. The position of the slot 18 relative to the forming roller unit 10 can thereby be adjusted. In this case, the following three variations can be adopted as the operating mode of the position adjustment mechanism 12.

[0055] In the operating mode of the first variation, the extrusion unit 9 is moved along the rotation axes 15r, 16r, and 17r. In the operating mode of the second variation, the forming roller unit 10 is moved along the rotation axes 15r, 16r, and 17r. In the operating mode of the third variation, both the extrusion unit 9 and the forming roller unit 10 are moved simultaneously along the rotation axes 15r, 16r, and 17r.

[0056] The drawing shows the operating mode of the position adjustment mechanism 12 according to the first variation as an example. In this operating mode, the position adjustment mechanism 12 includes a moving device and a supporting unit.

[0057] The movement device is configured to move the extrusion unit 9 along the rotation axes 15r, 16r, and 17r. The movement device comprises a movement body and a movement mechanism. For example, the extruder 20 provided in the extrusion unit 9 can be used as the movement body. The movement mechanism is configured to move the extruder (movement body) 20 in predetermined directions S1 and S2. Furthermore, the movement mechanism comprises, for example, two guide rails 29, a plurality of rollers 30, and a control device (not shown).

[0058] The two guide rails 29 are arranged in parallel along the rotation axes 15r, 16r, and 17r. The rollers 30 are rotatably provided in the extruder (moving body) 20. The rollers 30 are configured to roll along the guide rails 29. The control device is configured to control the rotation state (e.g., the rotation direction, the rotation speed, and the rotation number) of the rollers 30. A servo motor (not shown) that rotates the rollers 30 is mounted on the control device.

[0059] According to the moving device, the rollers 30 are driven and controlled by the control device. The rollers 30 can thereby roll along the guide rails 29. As a result, the extruder (moving body) 20 can be advanced and retracted in the directions of arrows S1 and S2 in accordance with the rotational movement of the rollers 30. That is, by advancing the extruder (moving body) 20 in the direction of arrow S1, it is possible to bring the extruder (moving body) 20 close to the molding roll unit 10 along the rotational axes 15r, 16r, and 17r. Conversely, by retracting the extruder (moving body) 20 in the direction of arrow S2, it is possible to separate the extruder (moving body) 20 from the molding roll unit 10 along the rotational axes 15r, 16r, and 17r.

[0060] The support unit comprises a support body and a connecting mechanism. The connecting mechanism is designed to connect the support body to the extruder (moving body) 20. For example, the connecting pipe 22 provided in the extrusion unit 9 can be used as the connecting mechanism.

[0061] The support body is configured to support the slot 18. For example, the T-shape 21 provided in the extrusion unit 9 can be used as the support body. The T-shape 21 is provided with the slot 18. In other words, the slot 18 is supported by the T-shape 21. Here, the direction and position of the T-shape (support body) 21 are adjusted in a predetermined direction.

[0062] In the direction adjustment of the T-shape (support body) 21, for example, the direction of the long and thin rectangular discharge opening 18c is adjusted to be parallel to the rotation axes 15r, 16r, and 17r. The slit 18 is thereby supported parallel to the rotation axes 15r, 16r, and 17r. As a result, the sheet-shaped molten resin 13a can be discharged from the slit 18 parallel to the rotation axes 15r, 16r, and 17r.

[0063] During the position adjustment of the T-die (support body) 21, the position of the discharge port 18c (slit 18) is adjusted to match the position between the main roller 15 and the press roller 16. In other words, the discharge port 18c (slit 18) is positioned directly above the position between the main roller 15 and the press roller 16. In this way, the discharge port 18c (slit 18) is formed parallel to the rotation axes 15r, 16r, and 17r and has a gap (lip gap H) of a constant size in the direction crossing the extrusion direction Fp. Consequently, the molten resin 13a can be supplied between the main roller 15 and the press roller 16, which rotate respectively.

[0064] In this structure, the T-mold (supporting body) supporting the slit 18 is connected to the extruder (moving body) 20 via the connecting pipe (connecting mechanism) 22. Here, the rollers 30 are rolled along the guide rails 29 by, for example, the control device (servo motor). The extruder (moving body) 20 is advanced or retreated in the directions of arrows S1 and S2. At this time, the forward and backward movements are transmitted to the T-mold (supporting body) 21 via the connecting pipe (connecting mechanism) 22. In this way, the T-mold (supporting body) 21 can be moved in accordance with the movement (advancement and retreat) of the extruder (moving body) 20. As a result, the slot 18 can be moved parallel to the rotation axes 15r, 16r and 17r, directly over the position between the main roller 15 and the press roller 16.

[0065] The position adjustment mechanism (not shown) according to the second variation and the third variation for moving the molding roller unit 10 along the rotation axes 15r, 16r, and 17r includes a moving mechanism (not shown) that moves the molding roller unit 10 along the rotation axes 15r, 16r, and 17r. Similar to the moving mechanism of the position adjustment mechanism 12 according to the first variation, this moving mechanism can move the molding roller unit 10 along the rotation axes 15r, 16r, and 17r, for example, by rolling rollers provided in the molding roller unit 10 along guide rails. “Position adjustment of neck sections 13p”

[0066] The necking portions 13p are continuously formed in the extrusion direction Fp in the sheet-shaped molten resin 13a discharged from the T-die 21 (slit 18 and discharge port 18c). The necking portions 13p are formed at both edge portions (both side portions) of the molten resin 13a by a necking phenomenon.

[0067] The necking phenomenon is a phenomenon in which the sheet-shaped molten resin 13a discharged from the T-die 21 is contracted and narrowed in the direction crossing the extrusion direction Fp (i.e., the width direction of the slit 18), in other words, in the width direction of the sheet-shaped molten resin 13a. The necking of the sheet-shaped molten resin 13a at this time occurs primarily at both end portions in the width direction, decreases toward the inside, and does not occur at the inside of specific positions. Consequently, the thickness of the sheet-shaped resin 13a is large in the width direction at both end portions, the thickness decreases from both end portions to the specific positions corresponding to the end portions, and the thickness is a constant thickness (standard thickness) at the inside of the specific positions.

[0068] It is considered that this necking phenomenon is caused by the action of the resultant force of the surface tension of the sheet-shaped molten resin 13a discharged from the T-die 21, the melt elasticity characteristics, and the tensile force of the sheet-shaped molten resin 13a in the extrusion direction Fp, and although the degree of contraction varies depending on the type of resin, this necking phenomenon always occurs.

[0069] The neck-in portions 13p indicate both edge portions (both side portions) from both end portions in the width direction to the specific positions corresponding to the end portions, and indicate portions with a thickness greater than the constant thickness (standard thickness) of the sheet-shaped molten resin 13a located at the inside of the specific positions. In other words, the neck-in portions 13p are formed at both edge portions (both side portions) of the sheet-shaped molten resin 13a in the direction crossing the extrusion direction Fp. A thickness W1 of the neck-in portions 13p is greater than a thickness W2 of the portion (central portion or intermediate portion) that is not both edge portions (both side portions) (see Fig. 4).

[0070] Because the 13p neck sections have a thickness greater than the standard (constant) thickness, the 13p neck sections were not traditionally used as a semi-finished or finished product. The 13p neck sections were separated and then disposed of or recycled.

[0071] Here, the position adjustment mechanism 12 is configured to adjust the position of the slit 18 (discharge opening 18c) and thereby position the necking portion 13p to be opposite to the thicker portion forming groove 19. The thicker portion forming groove 19 is continuously formed in the circumferential direction along one side of the main roller 15 (transfer surface 15s).

[0072] The thicker-portion forming groove 19 includes a groove bottom surface 19a and two inclined surfaces (first inclined surface 19b and second inclined surface 19c). The bottom surface 19a is formed, for example, parallel to a horizontal direction E (the direction along the rotation axis 15r). The first and second inclined surfaces 19b and 19c are inclined from both sides of the groove bottom surface 19a toward the transfer surface 15s. The first and second inclined surfaces 19b and 19c have diverging gradients (inclination angles θ1 and θ2).

[0073] In this case, the portion formed by the first inclined surface 19b corresponds to the inclined surface 4 of the thin light guide plate 1 (see Fig. 7). It is necessary to set the inclined surface 4 at an optimal angle for propagating the light emitted from the light source 7 to the surface light-emitting portion 3 without leakage. Therefore, the inclination angle θ1 of the first inclined surface 19b is set in the range of 0° < θ1 < 30°.

[0074] Further, when the necking portion 13p and the thicker-portion forming groove 19 are aligned with each other, a rising portion 13d of the necking portion 13p should preferably be opposite to the first inclined surface 19b of the thicker-portion forming groove 19. The rising portion 13d is positioned near a boundary region between both edge portions (both side portions) in which the necking portions 13p are formed and the other portion (middle portion or intermediate portion).

[0075] On the other hand, the second inclined surface 19c functions as a stopper wall that holds the molten resin 13a in the thicker-section mold groove 19. Therefore, the inclination angle θ2 of the second inclined surface 19c is not particularly numerically limited. The inclination angle θ2 can be any angle as long as the molten resin 13a does not flow out of the thicker-section mold groove 19.

[0076] Even with the same resin, if the molecular weight is high, the viscosity becomes high, and the level of contraction of the sheet-shaped molten resin 13a due to the necking-in phenomenon becomes low. In this case, it is conceivable that the volume of the molten resin in the rising portion 13d of the necking-in portion 13p may be insufficient for the thicker-portion forming groove 19. As a countermeasure against this, for example, a groove with a depth of approximately 0.1 mm may be provided at a position corresponding to the rising portion 13d on the first slit surface 18a or the second slit surface 18b of the discharge slit 18, and the volume of the molten resin discharged from the discharge slit 18 can thereby be increased only in that range. “Optical film forming process”

[0077] As in Fig. 1 to 2 and 4, a molten resin is extruded from the extruder 20. By an extrusion pressure caused at this time, the molten resin is supplied from the connecting pipe 22 to the T-die 21. The molten resin supplied to the T-die 21 passes through the slit 18. At this time, the sheet-shaped molten resin 13a is discharged from the slit 18. The neck-in portions 13p are formed at both edge portions (both side portions) of the discharged molten resin 13a. The neck-in portion 13p is positioned by the position adjustment mechanism 12 to oppose the thicker-portion mold groove 19. During positioning, it is possible to position the necking portion 13p to be opposite to the thicker-portion forming groove 19 while taking into account the expansion amount of the connecting pipe 22 due to thermal expansion. The initial adjustment is thus completed.In this process, it is necessary to release the molten resin 13 experimentally.

[0078] Here, a different process can be used instead of the initial adjustment process described above. In this process, for example, the structural position of the necking portion 13p and the expansion amount of the connecting pipe 22 due to thermal expansion are predicted. Based on the predicted values, the necking portion 13p is positioned by the position adjustment mechanism 12 to be opposite to the thicker-portion mold groove 19. The initial adjustment is thus completed. In this process, it is not necessary to experimentally discharge the molten resin 13.

[0079] After the initial setting is completed, the sheet-shaped molten resin 13a is discharged from the slit 18. The discharged molten resin 13a passes (at the contact point) between the main roller 15 and the press roller 16, while the discharged molten resin 13a is compressed therebetween. At this time, the thick portion 14b, which conforms to the contour of the thicker portion forming groove 19, is formed in the molten resin 13a. The thick portion 14b is thicker than the other portions and is continuously formed in the extrusion direction Fp. Subsequently, in a separation process (see Fig. 6), the thick portion 14b is separated along a predetermined dividing line 31. As a result, a semi-finished product leading to the thin light guide plate 1 is formed.

[0080] Next, in the semi-finished product, an excess portion 32, which is opposite to and opposite to the thick portion 14b, is cut off along a predetermined cutting line 33. Further, the semi-finished product is cut out at a predetermined interval in the extrusion direction Fp. The thin light guide plate 1, which is integrally formed from the light incident portion 2 to the surface-emitting portion 3 (see Fig. 7), is thereby formed.

[0081] Subsequently, in the thin light guide plate 1, various surface treatments are applied to a thin portion 14a, which is to be the surface-emitting portion 3. The thin light guide plate 1 as a finished product is thereby completed. Thereafter, the light-scattering component 6 (for example, a diffusion film, a prism film, etc.) is mounted on the upper surface 3a of the surface-emitting portion 3. The backlight unit of the mobile device (see Fig. 7) is thereby completed. “Advantageous effects of the embodiment”

[0082] According to the present embodiment, the extruder (moving body) 20 is advanced or retracted in the directions of arrows S1 and S2 (directions parallel to the rotation axes 15r, 16r, and 17r). At this time, the forward and backward movements are transmitted via the connecting pipe (connecting mechanism) 22 and move the T-die (support body) 21. Consequently, in the sheet-shaped molten resin 13a discharged from the T-die 21 (slit 18 and discharge port 18c), the necking portion 13p is positioned to oppose the thicker portion forming groove 19. The contour of the thick portion 14b of the semi-finished product (the light incident portion 2 of the light guide plate 1) can thereby be accurately formed. As a result, the optical film used in the semi-finished product (thin light guide plate 1) can be accurately extruded and formed in accordance with the predetermined shape.

[0083] Meanwhile, if the moving direction of the T-shape (support body) 21 is different from the connecting direction of the connecting pipe (connecting mechanism) 22 with respect to the T-shape (support body) 21, it is necessary to perform the movement of the T-shape (support body) 21 taking into account the expansion amount of the connecting pipe (connecting mechanism) 22 due to thermal expansion, separately from the movement of the T-shape (support body) 21, for positioning the necking portion 13p to be opposite to the thicker-portion forming groove 19.

[0084] Therefore, according to the present embodiment, the movement direction of the T-shape (support body) 21 and the connection direction of the connecting pipe (connecting mechanism) 22 with respect to the T-shape (support body) 21 are set to the same direction (for example, the direction parallel to the rotation axes 15r, 16r, and 17r). Consequently, by simply moving the T-shape (support body) 21 in one direction, it is possible to position the necking portion 13p to oppose the thicker-portion forming groove 19 while taking into account the expansion amount of the connecting pipe 22 due to thermal expansion.

[0085] According to the present embodiment, a semi-finished product leading to the thin light guide plate 1 is formed in the direction crossing the extrusion direction Fp (i.e., the width direction of the slit 18), in other words, in the width direction of the sheet-shaped molten resin 13a discharged from the T-mold 21. Therefore, the size of the T-mold (support body) 21 can be reduced. As a result, the structure of the position adjustment mechanism 12 can be simplified, and the entire device can be made compact.

[0086] According to the present embodiment, in the contour of the semi-finished product (the thin light guide plate 1), the upper surface 2a of the light incidence portion 2 can be formed as a flat surface without recesses and protrusions. Consequently, the light emitted from the light source 7 (for example, an LED) can be absorbed by the light incidence surface 2b without leakage and can be smoothly guided to the light incidence portion 2. As a result, the semi-finished product (the thin light guide plate 1) with excellent light guiding efficiency can be realized.

[0087] According to the present embodiment, the boundary portion 5 between the inclined surface 4 and the upper surface 2a of the light incident portion 2 can be formed angularly in the contour of the semi-finished product (thin light guide plate 1). In other words, the boundary portion 5 between the inclined surface 4 and the upper surface 2a of the light incident portion 2 can be formed so as not to be rounded. In short, the angle at the boundary portion 5 can be sharply changed from the upper surface 2a of the light incident portion 2 to the inclined surface 4. Therefore, the light guided to the light incident portion 2 can propagate to the surface-emitting portion 3 without leakage along the inclined surface 4. As a result, uniform light can be generated from the surface-emitting portion 3 in a planar manner. “Verification test for effects of the embodiment”

[0088] An inventive mode in which the necking portion 13p is positioned to oppose the thicker-portion forming groove 19 and a conventional mode in which the necking portion 13p is not positioned to oppose the thicker-portion forming groove 19 are prepared. Subsequently, a common test device (i.e., the optical film forming device 8) is prepared for both modes.

[0089] The specifications of the test device are as follows. Extruder: co-rotating twin-screw kneading extruder, nominal screw diameter 28mm T-shape: width 330mm, lip gap 0.8mm Three rollers: diameter 180mm, long side length 400mm Main roller: groove with depth of 0.15mm on one side Extrusion volume (flow rate) of molten resin: 20kg / h, polycarbonate material

[0090] Thickness of the finished product (light guide plate): Thickness of thick section (light incidence section) 0.35mm, Thickness of thin section (surface emitting section) 0.2mm

[0091] Fig. 9 shows a test result. That is, a cross-sectional photographic image of a semi-finished product obtained according to the invention mode (sample of the present invention) and a cross-sectional photographic image of a semi-finished product obtained according to the conventional mode (conventional sample) are shown. An optical product contour is shown between both cross-sectional photographic images. According to the test result, in a product region with the product contour, a "dip" appears in the semi-finished product of the conventional mode, whereas a "dip" does not appear in the semi-finished product of the invention mode. The result verifies the advantageous effects described above. "Modification"

[0092] In the above-described embodiment, it is assumed that the press roll (first roll) 16 of the forming roll unit 10 has an outer periphery or outer surface that is not elastically deformed. Instead, the press roll 16 with an elastically deformable outer periphery may be used. As shown in Fig. As shown in Fig. 8, the press roller 16 of the present modification includes an outer cylinder 34, an inner cylinder 35, and a temperature control medium 36. The outer cylinder 34 is disposed outside the inner cylinder 35. The temperature control medium 36 fills or circulates between the outer cylinder 34 and the inner cylinder 35 without any space therebetween. The outer cylinder 34 and the inner cylinder 35 are provided concentrically with respect to the rotation axis 16r of the press roller 16.

[0093] The inner cylinder 35 has rigidity. The inner cylinder 35 is less likely to be elastically deformed. The inner cylinder 35 is formed of a metal material. On the other hand, the outer cylinder 34 has elasticity. The outer cylinder 34 is designed to be elastically deformed. The outer cylinder 34 is formed of a metal material. In this case, the outer cylinder 34 is thinner than the inner cylinder 35. Since the outer cylinder 34 is made thin, the outer cylinder 34 is more likely to be elastically deformed.

[0094] According to this structure, when the sheet-shaped molten resin 13a discharged from the slit 18 of the T-die 21 is pressed against the transfer surface 15s of the main roller (second roller) 15, the outer cylinder 34 is elastically deformed along the transfer surface 15s. Therefore, the molten resin 13a can be brought into close contact with the thicker-portion forming groove 19 of the main roller 15 without any gap. As a result, the molten resin 13a can be evenly pressed across the entire width of the transfer surface 15s of the main roller 15.

[0095] In this case, a portion of the outer cylinder 34 in contact with the molten resin 13a should preferably be mirror-polished. The lower surface 1s of the semi-finished product (thin light guide plate 1) can thereby be formed as a smooth and flat surface. The lower surface 1s of the semi-finished product (thin light guide plate 1) can be parallel to the upper surface 2a of the light incident portion 2 and the upper surface 3a of the surface-emitting portion 3. As a result, the optical characteristics of the thin light guide plate 1 as a semi-finished product can be maintained constant. Since structures and advantageous effects other than those described above are similar to those of the above-described embodiment, a detailed description thereof will be omitted. "Modification"

[0096] In the above-described embodiment, at the time of the initial adjustment, for example, in the case of further performing the position adjustment of the necking portion 13p after the initial adjustment as shown in Fig.As shown in Fig. 5, a slit 18 (discharge opening 18c) of the T-mold 21 may be defined by a rim 37. The rim 37 may be set to partially cover the slit 18 (discharge opening 18c). As a result, the discharge area of ​​the molten resin 13a can be narrowed or widened, and can be adjusted according to the intended purpose and use. Thus, for example, the neck-in portion 13p and the thicker-portion forming groove 19 can be aligned with each other with high accuracy. As a result, an optical film with high quality and accuracy can be formed. Since structures and advantageous effects other than those described above are similar to those of the above-described embodiment, a detailed description thereof will be omitted. List of reference symbols

[0097] 8...optical film forming device, 9...extrusion unit, 10...forming roller unit, 11...thick section forming mechanism, 12...position adjusting mechanism, 13a and 13b...molten resin, 13p...necking section, 15...main roller (second roller), 16...pressing roller (first roller), 17...feeding roller (third roller), 18...discharge slot, 19...thick section forming groove, 20...extruder and 21...T-die.

Claims

[1] An optical film forming apparatus (8) configured to form a light guide plate (1) having a light incident portion (2) and a surface-emitting portion (3), both upper surfaces (2a, 3a) of which are flat surfaces arranged parallel to each other, and an inclined surface (4) is formed between the upper surfaces (2a, 3a), and wherein a lower surface (1s) of the light guide plate (1) is formed as a continuous flat surface oppositely parallel to the two upper surfaces (2a, 3a), thereby enabling the light incident portion (2) to be formed as a thick portion and the surface-emitting portion (3) to be formed as a thin portion, the optical film forming apparatus (8) comprising: an extrusion unit (9) having an extruder (20) which melts and kneads a resin material to produce a molten resin, and a T-die (21) which discharges a sheet-shaped molten resin from a discharge slit (18) connected to a manifold (25a) via a clearance passage (25b) defined as a clearance (H) between a first slit surface (18a) of a first lip (26a) and a second slit surface (18b) of a second lip (26b) which are oppositely parallel to each other, a molding roller unit (10) having a main roller (15) configured to rotate about a rotation axis (15r) arranged in a direction crossing an extrusion direction (Fp) to convey the discharged molten resin in the extrusion direction (Fp) while the discharged molten resin solidifies, and a pressing roller (16), and wherein the main roller (15) and the pressing roller (16) each have a cylindrical transfer surface (15s, 16s); a thicker-portion forming groove (19) formed in one or both of the main roller (15) and the press roller (16) by continuously pressing down from a lateral side of the transfer surface (15s, 16s) along a circumferential direction, having a groove bottom surface (19a) and two inclined surfaces (19b, 19c) inclined from respective sides of the groove bottom surface (19a) toward the transfer surface (15s, 16s), and configured to continuously form a thick portion (14b) thicker than another portion in the extrusion direction (Fp) in a part of the molten resin; and a position adjustment mechanism (12) configured to adjust a position of the discharge slot (18) with respect to the thicker portion forming groove (19), wherein a necking portion (13p) caused by a necking phenomenon is continuously formed in the extrusion direction (Fp) in the molten resin discharged from the discharge slot (18), and the necking portion (13p) is positioned by adjusting the position of the discharge slot (18) with respect to the thicker portion forming groove (19) by the position adjusting mechanism (12) to be opposite to the thicker portion forming groove (19), thereby making it possible to form a semi-finished product of the light guide plate (1) in a width direction of the sheet-shaped molten resin. [2] The optical film forming apparatus (8) according to claim 1, wherein the position adjusting mechanism (12) comprises: a movement device (20, 29, 30) designed to move the extrusion unit (9) along the rotation axis (15r); and the movement device (20, 29, 30) moves the discharge slot (18) parallel along the rotation axis (15r) by moving the extrusion unit (9). [3] Optical film forming apparatus (8) according to claim 1, wherein the position adjustment mechanism (12) comprises a movement mechanism (29, 30) configured to move the forming roller unit (10) along the rotation axis (15r), and the position adjusting mechanism (12) moves the forming roller unit (10) through the moving mechanism (29, 30), thereby moving the thicker portion forming groove (19) in parallel along the rotation axis (15r). [4] Optical film forming apparatus (8) according to claim 1, wherein the position adjustment mechanism (12) has an edge limiter (37) designed to cover a part of the dispensing slot (18), and the position adjustment mechanism (12) limits the discharge slot (18) by the edge limitation (37), thereby adjusting a discharge area of ​​the molten resin. [5] An optical film forming method using the optical film forming apparatus (8) according to any one of claims 1 to 4, comprising: Discharge of the film-shaped molten resin from the discharge slot (18) of the extrusion unit (9); Conveying the discharged molten resin in the extrusion direction (Fp) while the discharged molten resin is solidified by the molding roller unit (10); forming the thick portion (14b) which is thicker than another portion continuously in the extrusion direction (Fp) in the part of the molten resin through the thicker portion forming groove (19); and Adjusting the position of the discharge slot (18) with respect to the thicker section forming groove (19) by the position adjusting mechanism (12), wherein the necking portion (13p) caused by the necking phenomenon is continuously formed in the discharged molten resin in the extrusion direction (Fp), and the necking portion (13p) is positioned by adjusting the position of the discharge slot (18) with respect to the thicker portion forming groove (19) by the position adjusting mechanism (12) to be opposite to the thicker portion forming groove (19). [6] The optical film forming method according to claim 5, further comprising: Separating the thick portion (14b) along the thick portion (14b); and Cutting off an excess portion (32) which is opposite and opposite to the thick portion (14b).

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