JP5424116B2 - Method for simultaneously forming both sides of optical element sheet and optical element sheet forming apparatus - Google Patents

Description

  The present invention relates to a method for simultaneously forming both sides of an optical element sheet, in which a plurality of optical elements are formed simultaneously on the front and back surfaces of a base film, and an optical element sheet forming apparatus.

  The optical element in the present invention includes a lens, a prism, a mirror element, a diffraction element, a diffraction mirror, a grism, a Fresnel lens, a lenticular sheet, a lens sheet, a microlens array, and the like. Includes black ink. In the present invention, a plurality of these optical elements are formed on both sides of the base film, and the formed product is called an optical element sheet. The optical elements formed on the front surface and the back surface of the base film need not be the same type of optical elements. For example, a lens may be formed on one surface and a diaphragm formed on the other surface.

  Optical elements such as lenses are formed in a matrix on an optical element sheet, and are separated after completion and used as individual optical elements. On the other hand, lenticular sheets and the like are not individually separated on the optical element sheet, but are used after being cut into a predetermined size after completion. It is included.

  In the present invention, a plurality of such optical elements are simultaneously formed on both sides of the base film. Here, the optical element forming method includes “molding”, “molding”, and “printing”. Collectively called “formation”. “Molding” refers to a process in which a solid workpiece is softened by heating or pressurization and is brought into close contact with the transfer surface of the mold to transfer it. “Molding” is a process in which a liquid workpiece is placed in the mold. It is a process in which it is poured into a film, cured by heating or UV light irradiation, and transferred. “Printing” refers to a process in which a printing material (ink) is attached to a roll-shaped plate and the printing material is transferred to a base film.

  Such an optical element sheet forming method can form a large number of optical elements continuously, and in recent years, a strobe lens for a mobile phone or a digital camera, a diffusion lens for LED illumination, or a lens sheet for a backlight of a liquid crystal display device. It has come to be used for forming various optical elements.

  As a method for forming an optical element sheet, Patent Document 1 discloses that a lens sheet, in particular, a prism sheet, a lenticular lens sheet, and a Fresnel lens sheet are continuously formed on one side of a base film by transferring an energy ray curable resin using a roll die. In particular, a method for forming the lens sheet is proposed, which eliminates the warp of the lens sheet by temperature control before and during curing.

  In Patent Document 2, an ultraviolet curable resin is applied to one surface of a base film, and this is introduced between a roll mold for forming a lenticular lens array and a pressure roll, pressurized, cured by ultraviolet irradiation, and lenticular. After forming a lens array, a second ultraviolet curable resin is applied to the other surface of the base film, and this is introduced between a roll mold for forming a convex portion and a pressure roll, and pressurized. It discloses a method of forming a transmissive rear screen by forming a convex part by curing by irradiation and applying a light-shielding ink to the top surface of the convex part.

  Further, Patent Document 2 provides an alignment mark forming mold portion in a blank portion of a lenticular lens array forming roll mold to form an alignment mark at the same time as forming the lenticular lens array, while a convex portion forming roll. Alignment of optical elements formed on both sides of the sheet by forming the same alignment mark on the mold and aligning the marks on the convex mold roll mold with the alignment marks formed on the resin layer We are proposing a technology to do this.

JP 2009-292060 A JP 2007-264184 A

  Since the alignment technique of Patent Document 2 has not been specifically described, it is not clear, but the alignment mark of the convex mold forming roll mold matches the alignment mark formed on the resin layer. It is considered that the rotational phase of the convex part forming roll mold is adjusted, and this adjustment is considered to be performed in the initial stage of formation.

  However, when performing optical element formation on the other side following optical element formation on one side of the base film, if there is a temperature change in the base film between these two steps, expansion and contraction in the length direction occurs. Vertical misalignment occurs when the optical element on the other side is formed. Since the optical element is formed on the base film by continuously conveying the base film, the length change of the base film is accumulated, and if left as it is, a very large value is obtained.

  For example, when the sheet material is polyethylene terephthalate (PET), the linear expansion coefficient is about 70 ppm / ° C., but if the temperature changes by 1 ° C. during transfer formation between one side and the other side, the length is 70 μm per meter. It becomes a change. In addition, when 100 m is fed in this state, the accumulated length changes to 7 mm, and the optical elements on the one surface and the other surface are misaligned and cannot be used.

  When the sheet material is non-alkali glass with a thickness of about 100 μm, the amount of vertical misalignment is 300 μm when it is fed under the same conditions, although the linear expansion coefficient is as small as about 3 ppm / ° C. It is not an acceptable value.

  The present inventor has come up with the idea of simultaneously forming optical elements on the front surface and the back surface in view of the above-described problem of the forming method in which the optical elements are sequentially formed on the front surface and the back surface as in Patent Document 2. Thus, if it forms simultaneously on the surface and a back surface, the problem of vertical shift will be eliminated completely.

  Furthermore, this simultaneous double-sided formation method requires only initial adjustment with respect to the thickness and lateral deviation of the optical element, and no adjustment is required at the formation stage. If the thickness of the optical element sheet (the thickness of the base film and the thickness of the formed optical elements on the front and back sides) is set accurately, the distance between the roll molds for the front surface and the back surface that are opposed to each other is set. The thickness of the optical element sheet formed between the molds is always constant.

  In addition, the lateral position of the roll dies for the front surface and the back surface, which are also opposed to each other, may be set accurately. The interval between the molds and the horizontal position may be adjusted by measuring with a measuring instrument from above both molds before starting the formation. Alternatively, a small amount of test formation may be performed, and the completed optical element sheet may be measured and adjusted.

  Thus, although the simultaneous double-sided formation method of the optical element sheet is an excellent formation method, it has been found that there is a problem in terms of warpage of the formed optical element sheet. That is, the optical elements formed on the front surface and the back surface are not exactly the same shape, and are different in shape and size. Therefore, since the degree of expansion / contraction of the optical element on the front surface and the back surface before the optical element is cured is different, it is considered that the formed optical element sheet is warped. Of course, the temperature management of Patent Document 1 is also important for the solution of the warp, but it cannot be solved only by the temperature management.

  In view of such a problem, the present invention provides a method for simultaneously forming both sides of an optical element sheet that can eliminate the warp of the optical element sheet formed when simultaneously forming a plurality of optical elements on the front and back surfaces of a base film, and the optical An object is to provide an element sheet forming apparatus.

The above objective is accomplished by the following method and apparatus .
1. The first roll mold and the second roll mold are arranged to face each other at a predetermined interval in the horizontal direction, a base film is supplied between both roll molds, and the ultraviolet curable resin is used as the first roll mold or the A plurality of optical elements are simultaneously molded, molded or printed on both surfaces of the base film by supplying each roll mold to the second roll mold, and the optical element sheet formed by both roll molds is vertically lowered. The simultaneous double-sided formation method of the optical element sheet | seat characterized by continuing the conveyance of the perpendicular direction by the distance more than the distance until it conveys and the said resin hardens | cures completely.
2. Simultaneous duplex formation of an optical element sheet according to the 1, wherein the benzalkonium curing the resin by ultraviolet rays.
3. A base film supply unit;
A first roll mold and a second roll mold, which are arranged opposite to each other in a horizontal direction at a predetermined interval, and simultaneously mold, mold or print optical elements on both surfaces of the base film supplied from the base film supply unit;
And having at least one pair of transport rollers disposed vertically below the first roll mold and the second roll mold,
Supplying an ultraviolet curable resin to the first roll mold or the second roll mold;
The optical element sheet forming apparatus, wherein a distance from the first roll mold and the second roll mold to the pair of conveying rollers is equal to or more than a distance until the resin is completely cured.
4). The optical element sheet forming apparatus according to 3, wherein the benzalkonium curing the resin by ultraviolet rays.
5. 3 or 4 above, wherein the conveying roller pair is a grooved roller having a groove in the circumferential direction corresponding to the optical element forming portion or a grooved roller having a recess corresponding to the optical element forming portion. The optical element sheet forming apparatus according to the description.

  According to the present invention described above, when simultaneously forming a plurality of optical elements on the front and back surfaces of a base film, a method for simultaneously forming both sides of an optical element sheet that can eliminate the warp of the formed optical element sheet, and the optical element sheet A forming apparatus can be provided.

The schematic diagram which shows the optical element sheet | seat formation apparatus of this invention. The schematic diagram which expanded and showed the roll metal mold | die 3 or 4. FIG. The perspective view which shows the conveyance roller pair of this invention.

  Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing an optical element sheet forming apparatus of the present invention.

  In FIG. 1, a base film F is wound around a base film supply roller 1 and is drawn out as shown by an arrow. In the conveyance path of the base film F, the conveyance roller pair 2, the front surface forming roll die 3 and the back surface forming roll die 4 that are arranged opposite to each other in the horizontal direction, the upstream side of the surface forming roll die 3, and the base film F An ultraviolet curable resin supply unit 5 for supplying an ultraviolet curable resin between the base film F and an ultraviolet curable resin supply unit 6 for supplying an ultraviolet curable resin between the upstream side of the back surface forming roll mold 4 and the base film F, and a pair of conveying rollers. 7, a pair of conveying rollers 8 and a pair of conveying rollers 9 are arranged, and finally the spacer sheet S supplied from the spacer sheet supply roller 10 is sandwiched between the molded optical element sheets, and both are wound around the molded product roller 11. .

  On the peripheral surfaces of the surface molding roll mold 3 and the back molding roll mold 4, optical element molds (marked in the figure) to be formed as shown in FIG. 2 are formed in a matrix, Each is provided with a heater, and is configured to keep the temperature of the ultraviolet curable resin constant.

  The ultraviolet curable resin supplied between the surface molding roll mold 3 and the back molding roll mold 4 and the base film F is composed of ultraviolet irradiation lamps UV1, UV2, UV3, UV4, UV5, which are arranged on both sides of the conveyance path. It is irradiated and cured with UV6, UV7, and UV8.

  In the example of FIG. 1, as shown in an enlarged view, a convex lens La is formed on the front side and a concave lens Lb is formed on the back side.

  Here, the front surface forming roll mold 3 and the back surface forming roll mold 4, the conveying roller pair 7, and the conveying roller pair 8 are arranged so as to face each other in the horizontal direction and are sequentially arranged in the vertical direction. These peripheral speeds are all driven at a constant speed.

  The surface forming roll mold 3 and the back surface forming roll mold 4 are accurately adjusted in the interval, the vertical direction (circumferential direction), and the horizontal direction (axial direction) between the molds before the start of formation. By this adjustment, the optical elements formed on the front and back sides can be formed without shifting.

  In FIG. 1, the rollers on the side opposite to the spacer sheet of the conveying roller pairs 7 and 8 and the conveying roller pair 9 are preferably rollers that do not contact the optical element but contact the portion between the optical elements. FIG. 3 shows such a roller. FIG. 3A shows a grooved roller having a structure in which a groove is formed in the circumferential direction and an optical element forming portion enters the groove. FIG. 3B shows an optical element. The hollow with a hollow in which the hollow corresponding to the formation part was formed in the matrix form in the surrounding surface is shown. In FIG. 1, a conveyance roller indicated by a double circle is a portion that employs the grooved roller or the recessed roller.

  An optical element that gradually cures on the base film F by sandwiching the optical element sheet using a pair of conveyance rollers that do not contact the optical element but contacts a portion between the optical elements and conveying the sheet in the vertical direction. Since the sheet is tensioned by the weight and the conveying force of the conveying roller pair, the sheet can be cured without warping.

  The distance in the vertical direction from the front surface forming roll mold 3 and the back surface forming roll mold 4 to the conveying roller pair 8 is set to be equal to or longer than the distance until the resin is completely cured. Although this distance depends on the resin material used and the size of the optical element to be formed, it is generally 3 m or more.

  In the above description, the roll mold is precisely manufactured, and it is assumed that there is no shaft eccentricity or roll shape deviation, but it is difficult to eliminate these eccentricity and deviation at all. In the case where the eccentricity of the optical elements on the front surface and the back surface becomes a problem, such as in the case of forming a lens, these influences become large. In this case, the shaft eccentricity and roll shape of both roll molds are measured in advance, the measured values are stored, and the speed of both roll molds is corrected using the stored eccentricity measured values and roll shape measured values. You just have to do it. At this time, since the rotational position information of both roll molds is required, the surface forming roll mold 3 and the back forming roll mold 4 are marked and measured, or a rotary encoder is provided on the shaft. Rotational position information is obtained.

  In the embodiments of the present invention described above, an ultraviolet curable resin is used as a material for forming the optical element. However, the ultraviolet curable resin is appropriately selected according to the performance of the optical element such as urethane acrylate, epoxy acrylate, or unsaturated acid polyester. it can. Further, instead of the ultraviolet curable resin, an energy ray curable resin such as visible light or an electron beam, or a thermosetting resin such as diethylene glycol diallyl carbonate or siloxanyl methacrylate may be used.

  As the ultraviolet irradiation lamp, a high pressure mercury lamp, a metal halide lamp, or the like can be used, and an LED type ultraviolet irradiation lamp developed in recent years can also be used.

  As described above, in the present invention, optical elements of various forms can be formed as optical elements in addition to lenses, and the forming method is “molding”, “molding”, and “printing”. Can do.

  The above-mentioned embodiment is “molding”, but in the case of “molding”, the resin is heated and softened, poured into a roll mold, and molded by heating and pressing. In the case of “printing”, the roll mold is an intaglio, and ink is put into the depressions of the mold and transferred to the base film by pressing. Of course, different methods can be used for the front side and the back side.

DESCRIPTION OF SYMBOLS 1 Base film supply roller 2, 7, 8, 9 Conveyance roller pair 3 Front surface forming roll metal mold 4 Back surface forming roll metal mold 5, 6 UV curable resin supply part 10 Spacer sheet supply roller 11 Molded product roller F Base film S Spacer sheet UV1-UV8 UV irradiation lamp

Claims (5)

The first roll mold and the second roll mold are arranged to face each other at a predetermined interval in the horizontal direction, a base film is supplied between both roll molds, and the ultraviolet curable resin is used as the first roll mold or the A plurality of optical elements are simultaneously molded, molded or printed on both surfaces of the base film by supplying each roll mold to the second roll mold, and the optical element sheet formed by both roll molds is vertically lowered. The simultaneous double-sided formation method of the optical element sheet | seat characterized by continuing the conveyance of the perpendicular direction by the distance more than the distance until it conveys and the said resin hardens | cures completely. Simultaneous duplex formation of an optical element sheet according to claim 1, wherein the benzalkonium curing the resin by ultraviolet rays. A base film supply unit;
A first roll mold and a second roll mold, which are arranged opposite to each other in a horizontal direction at a predetermined interval, and simultaneously mold, mold or print optical elements on both surfaces of the base film supplied from the base film supply unit;
And having at least one pair of transport rollers disposed vertically below the first roll mold and the second roll mold,
Supplying an ultraviolet curable resin to the first roll mold or the second roll mold;
The optical element sheet forming apparatus, wherein a distance from the first roll mold and the second roll mold to the pair of conveying rollers is equal to or more than a distance until the resin is completely cured. The optical element sheet forming apparatus according to claim 3, wherein the benzalkonium curing the resin by ultraviolet rays.   5. The conveying roller pair is a grooved roller having a circumferential groove corresponding to the optical element forming portion or a hollow roller having a recess corresponding to the optical element forming portion. 2. An optical element sheet forming apparatus according to 1.

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