KR20070020509A - Belt over compliant roller with molding roller - Google Patents

Abstract

The present invention relates to an apparatus and method for producing a solid film. Viscous material 163 is introduced into the nip between pattern roller 165 and belt 167. The nip between the pattern roller 165 and the belt 167 is facilitated by the flexible roller 169. Therefore, the film which has individual optical elements and the flat back surface can be manufactured.

Description

Forming method of pattern sheet {BELT OVER COMPLIANT ROLLER WITH MOLDING ROLLER}

Exemplary embodiments of the invention relate to a method of making a thermoplastic film having an optical element on one side of the film and a flat surface on the other side of the film.

Films with a patterned surface have been produced for a variety of applications. For example, the photo paper may include a film having a matte or glossy finish. Such a matte finish or gloss finish may provide a desirable effect on the photograph as seen by the everyday viewer. Gloss or matte finish requires a photo paper manufacturing process with some tolerance (ie, some degree of precision). As the tolerances of the manufacturing process become higher, the manufacturing process is generally more complex and expensive. In other words, the tolerance required to produce a pattern film for photo paper may be significantly lower than the tolerance required to produce a light management film for liquid crystal displays.

Light handling films may be used for a variety of applications. For example, a light direct film may be used as part of a liquid crystal display (LCD). It may be important to increase the power efficiency of LCDs (or other similar displays). Liquid crystal displays are often included in battery operated mobile devices (eg, cell phones, laptop computers, digital cameras, etc.). It is desirable for this mobile device to maximize the operating time of its battery. While battery technology is advancing, one way to increase the battery life of a mobile device is to reduce the device's power consumption without compromising quality. By making the liquid crystal display device more efficient, the battery life of the mobile device can be extended, which is a great benefit to the user.

The optics of the light handling film are very special and detailed compared to the gloss of the photograph or the optics of the mat.

Thus, the precision of the manufacturing process for producing a gloss or matte finish on photo paper may be inadequate for the purpose of manufacturing the light handling film. For example, the manufacturing process used to make other pattern films may not properly reproduce the optical elements of the light handling film or may not provide a uniform thickness of the film that may be necessary to make the light handling film suitable for use. have. The inadequacies of these existing manufacturing processes are important considerations in the manufacture of light handling films.

Summary of the Invention

Exemplary embodiments of the present invention relate to a device comprising a hard surface and a compliant surface. The hard side includes the optical element shaping pattern. The flexible and rigid sides form a nip and the nip is configured to form a solid film from the viscous material inserted into the nip.

Another exemplary embodiment relates to a flexible compression belt that includes an endless belt. The endless belt includes at least one elastomer layer and at least one metal layer. The outer side of the belt has an average roughness of less than 50 nanometers and a Shore hardness of type 70 to 100 A.

Another exemplary embodiment relates to a method of forming a pattern sheet. The method includes supplying a melt curtain of thermoplastic polymer and leading the curtain into a forming nip between the forming roller and the flexible compression belt. Flexible compression belts include endless belts. The endless belt includes at least one elastomer layer. The outer side of the belt has an average roughness of less than 50 nanometers and a Shore hardness of type 70 to 100 A.

Another exemplary embodiment relates to a method of forming a pattern sheet. The method includes feeding a molten curtain of thermoplastic polymer and directing the curtain into a forming nip between the forming roller and the compression belt. The compression belt includes a contact belt in contact with the molten curtain and a cushioning belt in contact with the metal belt on the opposite side from the melt curtain. The cushioning belt has a Shore hardness of 70 to 100 A type.

According to an exemplary embodiment of the present invention, the production method makes it possible to produce heat treated films that can be used for various applications. For example, by using the manufacturing method according to the invention, the heat treatment film can be made into a precise replica of a special optical element. The duplication of this particular optical element takes into account a film that can significantly increase the efficiency of a liquid crystal display. Thus, this increase in efficiency can extend the battery life of mobile devices (eg, mobile phones, laptop computers, digital cameras, etc.). The manufacturing method of an exemplary embodiment will make it possible to manufacture thin films into individual optical elements having a uniform thickness. Light handling films that do not have individual optical elements and uniform thicknesses will not be effective in increasing the efficiency of the display device.

1 is a schematic side view of a light handling film system in accordance with an exemplary embodiment of the present invention;

2 is a partially enlarged side view of a portion of a backlight and light treatment film system according to an embodiment of the present invention;

3 and 4 are schematic side views of a light handling film system according to an exemplary embodiment of the present invention;

5 is a schematic diagram showing an optical element on a light handling film according to an exemplary embodiment of the present invention;

6 is a schematic view of an extrusion roll forming system having a flexible belt system in accordance with an exemplary embodiment of the present invention;

7 is a schematic diagram of a belt system having timing protrusions in accordance with an exemplary embodiment of the present invention;

8 is a schematic diagram of a belt system having a three-dimensional pattern on an outer metal layer in accordance with an exemplary embodiment of the present invention;

9 is a schematic diagram of an extrusion roll forming system having a flexible belt system and a flexible reciprocating lint-free fabric cleaner in accordance with an exemplary embodiment of the present invention;

10 is a schematic diagram of an extrusion roll forming system having a flexible belt system and an abrasive roll in accordance with an exemplary embodiment of the present invention;

11 is a schematic diagram of an extrusion roll forming system having a flexible belt system and an electrostatic discharge system in accordance with an exemplary embodiment of the present invention;

12 is a schematic diagram of an extrusion roll forming system having a flexible belt system including a metal belt and an elastomeric belt in accordance with an exemplary embodiment of the present invention, wherein the metal belt and the elastomeric belt surround different belt rollers;

13 is a view of a portion of a heat treated film showing land and ridges in accordance with an exemplary embodiment of the present invention.

1 and 2 schematically illustrate one form of a light handling film system according to an exemplary embodiment of the present invention. The light handling film system 1 may include a light handling film 2 that redistributes much of the light emitted by the backlight BL (or other light source) in a direction more perpendicular to the surface of the film. The film 2 may be used to redistribute light within the desired viewing angle from most of the light sources for lighting applications. For example, the film 2 may be used in conjunction with a display D (eg, in liquid crystal displays used in laptop computers, word processors, avionics displays, cellular phones, and PDAs) to make the display brighter. The liquid crystal display can be a transmissive liquid crystal display as shown schematically in the embodiments of FIGS. 1 and 2, a reflective liquid crystal display as shown schematically in the embodiment of FIG. 3, or as shown schematically in the embodiment of FIG. 4. It may be of any type, including a transflective liquid crystal display.

The reflective liquid crystal display D shown in the embodiment of FIG. 3 has a back reflector 40 adjacent to the rear side to reflect the ambient light incident on the rear of the display to the outside of the display to increase the brightness of the display. It may also include. The light handling film 2 according to an exemplary embodiment of the invention is in a direction more perpendicular to the plane of the film in order to reflect the ambient light (or light from the front light) back by the rear reflector within the desired viewing angle. It is disposed adjacent the top of the liquid crystal display to face into the display, increasing the brightness of the display. The light handling film 2 may be attached, laminated or otherwise maintained in place relative to the top of the liquid crystal display.

The transflective liquid crystal display D shown in the example of FIG. 4 reflects the ambient light incident on the front of the display to the rear of the display to increase the brightness of the display in the lighting environment, and also transmits the light from the backlight to the trans reflector. And a transreflector T disposed between the display and the backlight BL for transmitting to the outside of the display to illuminate the display in a dark environment. In this exemplary embodiment, the light reflecting film 2 is from a backlight more perpendicular to the plane of the ambient light and / or film to allow the light output distribution to allow movement through the display to increase the brightness of the display. In order to process or redistribute the light, it may be placed proximate to the top of the display or proximate to the bottom of the display, or both, as schematically shown in FIG. 4.

The light handling film 2 is a discrete optical element 5 having a distinct shape on the light exit face 6 of the film in order to deflect the incident light distribution such that the distribution of light incident on the film is in a direction more perpendicular to the surface of the film. It may also comprise a thin transparent film or substrate 8 having a pattern of. 5 shows an example of the light handling film 2.

Each of the individual optical elements 5 may have a width and length several times smaller than the width and length of the film, and may be formed by recesses or protrusions on the exit face of the film. These individual optical elements 5 may comprise at least one inclined plane for refracting incident light in a direction perpendicular to the light exit plane. The optical element 5 may have an aspect ratio (height to width) greater than 0.5. The optical element 5 may have a depth of at least 15 micrometers. The example of FIG. 5 shows one pattern of the individual optical elements 5 on the film 2. These optical elements may take many different shapes. The entirety of US Patent Application Publication No. US 2001/0053075 A1, entitled “Light Handling Films and Film Systems,” is hereby incorporated by reference. This application shows a number of variations of the optical device. However, those skilled in the art will recognize other variations of the optical elements of the light processing system encompassed by embodiments of the present invention.

As shown in the example of FIG. 2, the light entrance face 7 of the film 2 may have an optical coating 25 (eg, a totally reflective coating, a reflective polarizer, a delayed coating or a polarizer). Further, in this example, a mat or diffused fabric may be provided on the light entrance face 7 according to the desired visual appearance. The matte finish produces a flatter image without high axial gain. The combination of the flat and curved surfaces of the individual optical elements 5 of the embodiment of the present invention redirects some of the rays impinging in different directions so that no additional diffuser or matte finish is required at the entrance face of the film. It may be configured to generate a flat image. In addition, the individual optical elements 5 of the light handling film 2 may overlap each other in staggered, interlocked and / or intersecting forms to form an optical structure having an appropriate surface area range.

The backlight BL may be substantially flat or curved. The backlight BL may be a single layer or a multilayer, and may have different thicknesses and shapes. The backlight BL may be flexible or rigid, and may be made of various composites. In addition, the backlight may be hollow, filled with liquid or air, may be solid, or may have holes or ridges.

The light source 26 may be of any suitable shape (e.g., arc lamps, colored, filtered or painted incandescent bulbs, lens end bulbs, line lights, halogen lamps, light emitting diodes (LEDs), chips from LEDs, neon lights). Light bulbs, cold cathode fluorescent lamps, optical fiber light pipes from remote power sources, lasers or laser diodes, or any other suitable light source. The light source 26 may also be a plurality of color LEDs, or a combination of a plurality of color radiation sources to provide a desired color or white light output distribution. For example, using a plurality of color lights, such as LEDs of different colors (e.g. red, blue, green) or a single LED with a plurality of curl chips, white light or any other by varying the intensity of each individual color light. It is also possible to form a color light output distribution.

The rear reflector 40 provides a backlight (as shown schematically in the example of FIGS. 1 and 2) to improve the light output efficiency of the backlight by reflecting light emitted from the side back through the backlight and emitting through the opposite side. It may be attached or positioned relative to one side of the BL). Also, in order to change the path of the light such that the internal threshold angle is exceeded and some of the light is emitted from one or both sides of the backlight, a pattern 50 of optical deformities is shown schematically in the example of FIGS. 1 and 2. Likewise, it may be provided on one or both sides of the backlight.

Thermoplastic films with woven sides are used for applications ranging from packaging to optical films. The fabric may be produced in a casting nip consisting of a compression roller and a pattern roller. Depending on the pattern transferred to the thermoplastic film, it may be difficult to achieve a uniform degree of replication across the width of the film. It may also be difficult to achieve this uniform degree of replication and to have a flat backside in the film.

Rubber compression rollers may be used to provide a relatively uniform pressure across the casting nip. Because their shell can be modified to accommodate any thickness non-uniformity of the molten curtain. This thickness non-uniformity may be due to the presence of thick edges from neck-in or from other sources of non-uniform flow from the extrusion die. However, the rubber sheath may not have a surface with a roughness low enough to produce a glossy (ie flat) back side.

The example of FIG. 6 is a schematic diagram of an extrusion roll forming system having a belt system that meets requirements in accordance with an exemplary embodiment of the present invention. Melt extrusion from a slit die may also be performed using a T die or a coat hanger die. Extrusion die 161 maintains and / or converts the material (eg, polymer, polycarbonate, etc.) in a viscous state. Qualitative material 162 (eg, molten polymer) is injected into the nip between pattern roller 165 and belt 167. The viscous material may be a thermoplastic polymer. The viscous material may have a viscosity of 10 Pa.S to 100 Pa.S immediately before entering the nip. The residence time of the viscous material (when converted to solid phase) is 20 to 40 milliseconds. The nip pressure may be 1.4 × ^{10 8} dyne / cm to 2.63 × 10 ⁸ dyne / cm. The material may have a glass transition temperature of less than 200 ° C. However, once the substance enters the nip it needs to be solid. In an exemplary embodiment, the temperature gradient between the point just before the nip and the point just after the belt exits the nip is at least 148 ° C. Belt 167 is reinforced with belt roller 169. In addition, the belt roller 171 is used to maintain sufficient tension on the belt 167.

In an exemplary embodiment, pattern roller 165 includes a pattern for replicating a special optical element on an optical film that is output from the nip. In an exemplary embodiment, the pattern roller 165 is rigid and the pattern on the pattern roller 165 is precise. The belt 167 is relatively flexible compared to the pattern roller 165. However, although belt 167 is flexible when pressure is applied to the nip, it has sufficient hardness and flexibility to create a flat surface on one side of the solid film output from the nip. In an exemplary embodiment, the belt 167 has a 90 Shore A to 50 Shore D durometer hardness. Film output from the nip may proceed along the belt 167 for a while after moving to a solid state (or quasi-solid state). In an exemplary embodiment, the belt 167 includes a metal and an elastomeric material, and the roller 169 may be a metal or an elastomeric material. As a variant, those skilled in the art will appreciate that the flexible portion of the belt produces a film with a uniform thickness and a properly smooth surface on one side, while the other side of the film has a pattern that is properly replicated from the pattern roller 165. It will be appreciated that there are other materials that can be used for 167 and belt roller 169.

Belt 167 may be a continuous metal belt designed to form a smooth finish from one side of the film output from the nip. In an exemplary embodiment, the outer surface of the belt 167 has an average roughness of less than 50 nanometers. In another exemplary embodiment, the belt 167 has a roughness of 15 to 30 nanometers. Belt 167 may have between 70 and 100 Type A Shore Hardness. In some exemplary embodiments, belt 167 is made entirely of metal, while in other exemplary embodiments, belt 167 is made of a compound of metal and elastomeric material. The belt 167 may be a circumference of 0.75 to 10 meters, or may have a width of 0.5 to 2 meters. In an exemplary embodiment, the elastomeric material may be external to the belt. The elastomeric material may comprise from 1 to 10 weight percent of the polymer with a surface energy of 22 to 35 dyne (dyne / cm 2) per square centimeter shown to facilitate release of the extruded polymer.

In an exemplary embodiment of the present invention, the belt 167 may be heated before entering the nip. Using heat may help the belt to reduce the land area (described in detail below) of the optical element formed in the light handling film. Also, as the film enters the nip, because the belt 167 is heated, the heat treated film may be temporarily held attached to the belt. Those skilled in the art will appreciate that the heat provided to the belt 167 may be achieved by a number of different methods. For example, heat may be provided to the belt by conduction or induction. In an exemplary embodiment, the belt only contacts material in the nip. In an exemplary embodiment, a release agent is provided on the belt that easily detaches the output film from the belt after exiting the nip. In an exemplary embodiment, the belt 167 is hotter in the nip than the pattern roller 169.

In an exemplary embodiment, as shown in FIG. 7, the belt system 141 may include a timing protrusion 145 on the belt 143. This timing protrusion 145 may assist the manufacturing machinery in adjusting the movement of the roller within the belt 143 in the nip. Those skilled in the art will appreciate that the timing protrusion 145 may be disposed inside or outside the belt 143.

In the example embodiment shown in FIG. 8, the belt 151 may include a three-dimensional pattern 153. This three-dimensional pattern may be a light diffusion layer for an output optical film. In applications such as light handling films for displays, the light diffusing layer may serve to increase the viewing angle of the LCD. Increasing the viewing angle layer is a desirable feature in many products, such as LCD TVs.

The example of FIG. 9 is similar to the example of FIG. 6. However, in FIG. 9, a reciprocating, smooth, lint-free weave cleaner 181 is disposed on the surface belt 167. This cleaner may provide a mechanism for cleaning the belt in front of the belt entering the nip. In the exemplary embodiment shown in the example of FIG. 10, a polishing roller 191 is included. This polishing roller 191 forms a nip between the belt 167. The polishing roller 191 may facilitate polishing of the belt 167 so that a sufficiently flat surface can be formed at the film output from the nip between the pattern roller 165 and the belt 167.

As shown in the exemplary embodiment of FIG. 11, an electrostatic discharge system may be disposed near the belt 167. This electrostatic discharge system 201 removes charge on the belt before the belt enters the nip. The discharge of static electricity will improve the quality of the film output from the system, thereby obtaining the desired effect.

In the example embodiment shown in FIG. 12, a metal belt 211 may be used with the elisatomer belt 213 in the nip between the belt roller 169 and the pattern roller 165. The combination of the elastomeric belt 213 and the metal belt 211 may be ideal for providing adequate flexibility and flatness in terms of flexibility of the nip.

FIG. 13 is a view of a portion of a light handling film, illustrating land and ridges in accordance with an exemplary embodiment of the present invention. FIG. Each optical element 219 includes a land portion 215 and a ridge 217. The ridge 217 and the surface forming it serve to provide optical power and to redirect the light. In contrast, the land portion 215 does not add light output to the system and does not redirect the light. Thus, a light handling film that requires significant turn of light will have only ridges 217 without lands 215. However, due to manufacturing tolerances, it may be impractical (eg, expensive) to use manufacturing processes and materials that produce very small land portions. Therefore, with respect to the light handling film, the ratio of the raised portion 217 to the land portion 215 needs to be higher than a predetermined level.

In an exemplary embodiment, the land portion 215 is less than 5 microns wide. In an exemplary embodiment, the land portion 215 is less than 3 microns wide. In an exemplary embodiment, the width of the land portions is less than 1 micrometer. In an exemplary embodiment, the total surface area of the land portions of the solid film is less than about 20% of the surface area of the light handling film, while the total surface area of the ridges of the solid film is at least 80% of the surface area of the light handling film. In an exemplary embodiment, the total surface area of the land portions of the solid film is less than about 6% of the surface area of the solid film, while the total surface area of the ridges of the solid film is at least about 93% of the surface area of the solid film. In an exemplary embodiment, the total surface area of the land portions of the solid film is less than about 3% of the surface area of the solid film, while the total surface area of the ridges of the solid film is at least about 96% of the surface area of the solid film. Those skilled in the art will appreciate that the surface area of the ridge is the amount of light active area parallel to the solid film.

Those skilled in the art will appreciate that careful selection of materials and manufacturing processes is required to reduce the land area of the light handling film. In addition, the flat surface 221 is maintained on the opposite side of the film while reducing the area of the land portion 215. In addition, care must be taken to maintain a uniform thickness of the film.

The metal layer of the belt of the belt system should be thin enough to provide sufficient flexibility to accommodate any thickness non-uniformity of the metal curtain. Preferably, the metal layer has a thickness of 50 to 2,000 micrometers. If the thickness is 35 micrometers or less, the metal layer may be weakened, shortening the life of the product. If the thickness of the metal layer is at least 2,500 micrometers, the flexibility may be less and it may be difficult to maintain a uniform pressure across the nip. Preferred materials for the metal layer include stainless steel, nickel, high phosphorescent nickel, chromium, alloys or any other suitable metal. The sleeve is preferably free of seams in order to prevent any defects on the back side of the film being regenerated into the film.

The elastomer layer of the belt may comprise a polymeric material. The elastomer layer provides a flexible face, thereby making it possible to maintain a relatively uniform nip pressure despite the thickness variation across the width of the belt curtain. The elastomer layer should be between 3 millimeters and 20 millimeters to provide adequate elasticity without sacrificing heat transfer properties. The cover may be made of silicone rubber, neoprene rubber, EPDM, Viton, Hypalon, polyurethane or any other material having suitable hardness and durability. However, one skilled in the art will recognize other materials.

The belt system may be durable to withstand the high temperatures and high nip pressures formed in the extrusion cast nip. The sleeve may be capable of being polished with an optical finish and has sufficient release properties for the material being extruded. The sleeve may resist accumulation of residues associated with extrusion of the plastic at high temperatures and may be easily cleaned when an unacceptable level of residue adheres to its surface. It may be desirable to have an apparatus for cleaning the surface of this roller during fabrication.

Parts list

1: light handling film system 2: light handling film 5: optical element

6: light exit surface 7: light entrance surface 25: optical coating

26 light source 30 light diffuser layer 40 rear reflector

141: belt system having timing protrusion

143: belt 145: timing protrusion 151: belt having a three-dimensional pattern

153: three-dimensional pattern 161: extrusion die 163: molten polymer

165: pattern roller 167: belt 169: belt roller

171: belt roller 181: reciprocating flat lint-free weave cleaner

191: polishing roll 201: electrostatic discharge system 211: melt belt

213: elastomer belt 215: land portion 217: ridge

219: Optical element BL: Backlight D: Display R: Light ray

Claims (28)

In the method of forming a pattern sheet, Providing a molten curtain of thermoplastic polymer, Entering the curtain into a forming nip between a forming roller and a flexible compression roller, the compression roller having a flat belt overlapping its surface, wherein the belt entering step is provided with heat; doing Method of forming a pattern sheet. The method of claim 1, The thermoplastic polymer has a glass transition temperature of less than 200 ° C. Method of forming a pattern sheet. The method of claim 1, The thermoplastic polymer has a viscosity of less than 100 Pa · s when entering the thermoplastic polymer nip. Method of forming a pattern sheet. The method of claim 1, The thermoplastic polymer has a viscosity of 10 Pa.S to 100 Pa.S before entering between the forming roller and the flexible compression roller. Method of forming a pattern sheet. The method of claim 1, The temperature gradient between the point immediately before the belt enters the nip and the point immediately after the belt enters the nip is at least 148 ° C. Method of forming a pattern sheet. The method of claim 1, The residence time of the thermoplastic polymer in the nip is 20 to 40 milliseconds Method of forming a pattern sheet. The method of claim 1, The thermoplastic polymer is solid when advancing out of the nip Method of forming a pattern sheet. The method of claim 1, The nip compression is 1.4 × 10 ⁸ dyne.cm to 2.63 × 10 ⁸ dyne / cm Method of forming a pattern sheet. The method of claim 1, The flexible compression roll has a hardness of 90 Shore A to 50 Shore D Durometer Method of forming a pattern sheet. The method of claim 1, The belt comprises a material consisting of alloy steel or stainless steel Method of forming a pattern sheet. The method of claim 1, The belt has an average roughness of less than 50 nanometers Method of forming a pattern sheet. The method of claim 1, The belt has an average roughness of 15 nanometers to 30 nanometers. Method of forming a pattern sheet. The method of claim 1, Cleaning the belt with a reciprocating flexible lint-free woven cleaner Method of forming a pattern sheet. The method of claim 1, The heat is provided by convection conduction Method of forming a pattern sheet. The method of claim 1, The heat is provided by induction Method of forming a pattern sheet. The method of claim 1, The heat is provided by radiation Method of forming a pattern sheet. The method of claim 1, The heat is provided by conduction Method of forming a pattern sheet. The method of claim 1, The thermoplastic polymer comprises a polycarbonate Method of forming a pattern sheet. The method of claim 1, The belt and the thermoplastic polymer are in contact only in the nip Method of forming a pattern sheet. The method of claim 1, The release agent is provided to the belt Method of forming a pattern sheet. The method of claim 1, The belt is provided with an electrostatic discharge prior to entering the nip Method of forming a pattern sheet. The method of claim 1, The forming roller has a gap having at least one curved surface and at least one flat surface. Method of forming a pattern sheet. The method of claim 1, The forming roller has a clearance having an aspect ratio (ratio of height to width) of 0.4 or more. Method of forming a pattern sheet. The method of claim 1, The forming roller has a clearance having a depth of 10 micrometers or more. Method of forming a pattern sheet. The method of claim 1, The forming roller has a clearance having a depth of 15 micrometers to 30 micrometers. Method of forming a pattern sheet. The method of claim 1, The metal belt is at a higher temperature than the compression roller at a point just before entering the nip. Method of forming a pattern sheet. The method of claim 26, The temperature of the metal belt is 30 to 110 ℃ higher than the compression roller Method of forming a pattern sheet. The method of claim 1, The metal belt has a thickness of 0.5 mm to 4 mm Method of forming a pattern sheet.

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