JP2009244482A - Optical function member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical function member that has superior bonding strength between a light guide member and a lens sheet, and position precision of a lens, and reduces variations in projection amount and projection direction of light. <P>SOLUTION: The optical function member 10 has a light guide film 11 for propagating light made incident from a light source provided on a side face and the lens sheet 12 having a plurality of unit lenses 14 disposed on a surface and controlling the projection angle of projection light projected from the light guide film 11, those light guide film and lens sheet being united together with a viscous adhesive layer 15 interposed. Each of the unit lenses 14 has one or a plurality of peak portions 14a, having a vertical angle of less than 180°, at its tip, and the light guide film 11 and lens sheet 12 are bonded together while peak portions 14a of the unit lenses 14 sink into the viscous adhesive layer 15. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical functional member used for illumination light path control in a backlight unit such as a liquid crystal display or a surface light source device used in an illumination device.

  In an LCD backlight or lighting device, a surface light source device having a light source provided at an edge portion and a flat light guide member (also referred to as a light guide plate or a light guide film) that converts light from the light source into surface light emission Is used. As the surface light source device, there is known a surface light source device including a lens sheet and a light diffusion sheet in order to uniformly and efficiently emit light from the light source from the flat plate surface of the light guide member. Usually, a lens sheet or a light diffusing sheet is placed on the light guide member so that light incident on the light guide member is turned in a direction perpendicular to the sheet.

  In recent years, in order to reduce the number of optical components such as the lens sheet and the light diffusion sheet, or to reduce the thickness of the surface light source device, a configuration in which a light turning function is added to the light guide member has been devised.

  For example, in Patent Document 1, as shown in FIG. 10A, a light source 50 having a light emitting diode 50a, a light guide 51, and a lens having a plurality of lenses 54 formed in an array on a support film 53. A surface light source device including a sheet 52 and a reflective film 56 is disclosed. In Patent Document 1, the light guide 51 and the lens sheet 52 are integrated by attaching the flat top 54 a of each lens 54 to the light guide 51. In such a configuration, as shown in FIG. 10B, the light propagating through the light guide 51 is turned upward via the lens 54.

  In Patent Document 2, as shown in FIG. 11, a lens sheet 62 including a light source 60, a light guide 61, and a plurality of microprisms 64 bonded to the surface of the base material layer 63 through an adhesive layer 66. The flat light incident surface 64a of the microprism 64 is bonded to the light guide 61 with the adhesive layer 65 interposed therebetween. Even in such a configuration, the light propagating in the light guide 61 is turned upward via the microprism 64 as shown in the figure.

Patent Document 3 discloses a configuration in which a light guide plate, a polarization functional layer that selectively transmits specific polarized light, and a lens sheet for controlling the emission angle of emitted light are integrally formed. ing. In Patent Document 3, a plurality of convex portions are arranged on the surface of the lens sheet in a one-dimensional array or a two-dimensional array, and the top portion of the convex portions is bonded to the light exit surface of the light guide plate.
Japanese Patent No. 3826145 US Pat. No. 5,396,350 JP 2006-244803 A

  As a method for integrating the flat light guide member and the lens sheet, for example, a method in which an adhesive is applied to the flat surface at the tip of each lens arranged on the lens sheet surface and bonded to the light guide member, A method is used in which an adhesive is applied to the light guide member, and a flat portion at the tip of each lens is placed and bonded. As a bonding method, for example, as described in Patent Document 1, a film-shaped light guide member (hereinafter referred to as a light guide film) is used to continuously roll a light guide film and a lens sheet. Attempts have been made to create by a roll-to-roll process in which the paper is fed out and wound after being bonded together. In this roll-to-roll process, for example, as shown in FIG. 12, a lens 54 is bonded (contacted) to the light guide film 51, and then transported to the transport roll 70 and pressed by the transport roll 70. The lens 54 is fixed to the surface of the light guide film 51.

  However, when the light guide film and the lens sheet are integrated, as shown in FIGS. 13A to 13D, the adhesive layer at the portion sandwiched between the flat surface of the light guide film 51 and the flat portion at the tip of the lens 54. The thickness of the lens changes due to the pressure during pressure bonding, and the relative position of the lens 54 and the light guide film 51 changes, or the adhesive 55 protrudes from the joint between the two. When the protrusion of the adhesive 55 is remarkable, the amount of the intervening adhesive becomes insufficient, the bonding strength is reduced, and, as shown in FIGS. The amount of emission and the direction of emission vary. Further, in general, in order to obtain a high bonding strength, an adhesive of a thermosetting type having a low viscosity and a high fluidity that can obtain a throwing effect is often used in order to obtain a high bonding strength. It takes 1 hour or more to complete curing. In this case, when the above roll-to-roll process is used for integration, the adhesive layer is pressed by a transport roll, a take-up roll or the like in a state where the adhesive layer is not sufficiently cured. In addition to the protrusion of the lens and the change in the relative position in the thickness direction (change in the thickness of the adhesive layer), the lens sheet also shifts in the sheet surface direction. As described above, in the optical sheet in which the light guide member and the lens sheet are integrated, the in-plane variation of the bonding strength due to the fluidity of the adhesive and the low positional accuracy of the lens, and the light emission amount associated therewith, and There is a problem of variation in the emission direction, and development of an optical sheet capable of solving these problems is desired.

  Accordingly, an object of the present invention is to provide an optical functional member that is excellent in in-plane uniformity of the bonding strength between the light guide member and the lens sheet and the positional accuracy of the lens, and can reduce variations in the amount and direction of light emission. There is.

  According to a first aspect of the present invention, a flat light guide member for propagating light incident from a light source provided on a side surface and a plurality of unit lenses arranged on the surface are emitted from the light guide member. A lens sheet for controlling the emission angle of the emitted light, and these are optical function members formed integrally through an adhesive layer, and the unit lens is disposed at the tip thereof. The light guide member and the lens sheet are bonded with one or more apexes having an apex angle of less than 180 °, with the apex of the unit lens biting into the adhesive layer. This is an optical functional member.

  According to a second aspect of the present invention, in the optical functional member according to the first aspect, the unit lens has a plurality of apexes having apex angles of less than 180 ° at the tip, and the unit lens tip The difference in height between the topmost portion and the concave portion is larger than the thickness of the adhesive layer.

  According to a third aspect of the present invention, in the optical functional member according to the second aspect, the volume of the portion that bites into the adhesive layer at the top portion having the topmost portion, the concave portion, and the adhesive layer The top part which has the said top part bites into the said adhesive layer so that the volume of the space formed by these may become equal.

  According to a fourth aspect of the present invention, in the optical functional member according to any one of the first to third aspects, a triangular prism is arranged in parallel at the top of the unit lens.

  According to a fifth aspect of the present invention, in the optical functional member according to any one of the first to fourth aspects, the topmost part of the one or more unit lenses is in contact with the light guide member. Features.

  According to a sixth aspect of the present invention, in the optical functional member according to any one of the first to fifth aspects, the adhesive layer is made of a photocurable adhesive.

  According to a seventh aspect of the present invention, in the optical functional member according to any one of the first to sixth aspects, a refractive index after curing of the adhesive layer is equal to a refractive index of the unit lens. It is characterized by.

  According to an eighth aspect of the present invention, in the optical functional member according to any one of the first to seventh aspects, a refractive index after curing of the adhesive layer is equal to a refractive index of the light guide member. It is characterized by that.

  According to the optical functional member of the present invention, the unit lens has one or more apexes having apex angles of less than 180 ° at the tip, and the apex is bitten into the adhesive layer. Since the light guide member and the lens sheet are bonded, the top part bites into the surface and can ensure a high bonding strength above a certain level regardless of the fluidity of the adhesive layer. A uniform bonding strength can be obtained. In particular, by using a material having a plurality of top portions, the contact area with the adhesive layer can be increased, and the bonding strength can be further improved. In addition, it is possible to ensure a high bonding strength of a certain level or more, and further to make the bonding strength uniform in the surface. Change and lens displacement are less likely to occur. For this reason, since the positional accuracy of the lens is improved, variation in the light emission amount and the light emission direction can be reduced, and more uniform surface light emission can be realized.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional view showing an optical functional member (optical sheet) 10 according to an embodiment of the present invention. The optical sheet 10 includes a light guide film 11 and a lens sheet 12, which are integrally formed with an adhesive layer 15 interposed therebetween.
The lens sheet 12 is for controlling the emission angle of the emitted light emitted from the light guide film, and includes a base film 13 and a plurality of unit lenses 14 arranged on the surface of the base film 13. Has been.

  The lens sheet 12 is for controlling the emission angle of the emitted light emitted from the light emitting surface 11 a of the light guide film 11, and a base film 13 and a plurality arranged on the surface of the base film 13. Unit lens 14.

  As shown in FIG. 1, the unit lens 14 has a top portion 14 a having an apex angle of less than 180 ° at the tip portion, and the top portion 14 a is arranged to bite into the adhesive layer 15. Thus, while the top part 14a of the unit lens 14 bites into the adhesive layer 15, regardless of the fluidity of the adhesive, it is possible to ensure a high bonding strength of a certain level or more and the lens sheet surface. A uniform bonding strength can be obtained. Thereby, when the lens sheet 12 and the light guide film 11 are integrated, it is possible to make it difficult to cause a change in the relative position in the thickness direction and a displacement of the lens. Specifically, when the optical sheet 10 is produced by a roll-to-roll process in which the light guide film 11 and the lens sheet 12 are continuously fed out and wound after being bonded, Due to the influence of the curvature, force is applied to the adhesive part, so if the progress of curing is insufficient, the relative position of the lens and the light guide film in the thickness direction may change, or the lens may be displaced in the film surface direction. Although there is a problem that occurs, it is possible to improve the positional accuracy of the lens by using the unit lens 14 having the top part 14a and causing the top part 14a to bite into the adhesive layer 15. Can be eliminated. Further, as a result of improving the positional accuracy of the lens, it is possible to reduce variations in the light emission amount and the light emission direction, and to realize more uniform surface light emission.

  As shown in FIG. 1, it is preferable that the tip of the top portion 14 a of the unit lens 14 is in contact with the light guide film 11 through the adhesive layer 15. The lens array is guided through the adhesive layer 15 by designing the shape of the top portion 14a and / or the thickness of the adhesive layer 15 so that the tip of the top portion 14a and the light guide film 11 are in contact with each other. When the optical film 11 is pressed and pasted, the bite stops when the tip of the top portion 14a reaches the light guide film, so that the relative position between the lens 14 and the light guide film 11 is stabilized, and the positional accuracy in the thickness direction is increased. Can be further improved.

  The shape of the unit lens is not particularly limited as long as it has at least one apex having an apex angle of less than 180 ° at the tip. Instead of the unit lens 14 shown in FIG. 1, for example, a unit lens 24 having three apexes 24a to 24c as shown in FIG. 2 can be used. With such a configuration, the contact area with the adhesive layer 15 is increased as compared with the unit lens 14 shown in FIG. 1, so that the bonding strength can be further improved.

  Also when using the unit lens 24, it is preferable that the top 24a is in contact with the light guide film 11 as shown in the figure. Further, in the unit lens 24, it is preferable that the height difference h from the lens bottom surface between the top 24 a and the recess 24 d is set to be larger than the thickness of the adhesive layer 15. Thereby, the adhesive 24 pushed out by the top 24a biting into the adhesive layer 15 can be absorbed in the space formed by the two recesses 24d and the adhesive layer 15, The sticking out of the adhesive can be suppressed, and the stability of bonding strength and positional accuracy can be obtained. In particular, the shape of the top 24 so that the volume of the portion of the top 24a biting into the adhesive layer 15 and the volume of the space formed by the two recesses 24d and the adhesive layer 15 are equal. And / or it is preferable to design the thickness of the adhesive layer so that the extruded adhesive can be completely absorbed into the space.

  Further, instead of the unit lens 14 shown in FIG. 1, for example, a unit lens 34 having a stripe shape in which the apex 34a is formed by arranging triangular prisms in parallel as shown in FIG. 3 may be used. Even when the unit lens 34 is used, it is preferable that the topmost portion is in contact with the light guide film 11. Further, when the unit lens 34 having such a shape is used, when the lens sheet 12 is bonded to the light guide film via the adhesive layer 15, the triangular prism of each unit lens 34 is illustrated as illustrated. It is preferable that the ridge line is bonded so that it coincides with the bonding direction of the lens sheet 12. As a result, it is possible to perform good bonding without taking in air into the concave portion of the top 34a.

  The adhesive which comprises the adhesive layer 15 contains the adhesive and the adhesive which has adhesiveness and adhesiveness other than the adhesive also called a pressure sensitive adhesive. Adhesives include (meth) acrylate and oxetane monomer / oligomer adhesives, urea resin, melamine resin, phenol resin, resorcinol resin, epoxy, polyurethane resin, vinyl acetate resin, Resin adhesives such as polyvinyl alcohol resin, acrylic resin and cellulose resin, chloroprene, nitrile rubber, styrene butadiene rubber, styrene block copolymer thermoplastic elastomer, butyl rubber, natural rubber, recycled rubber , Rubber adhesives such as chlorinated rubber and silicone rubber, and natural adhesives such as glue and starch. In addition, as the adhesive, (meth) acrylate, oxetane, styrene butadiene rubber, butyl rubber, natural rubber, silicone rubber, polyisoprene, polybutene, polyvinyl ether, acrylic resin, polyester, etc. Is mentioned. As the adhesive, for example, a mixture of the above-mentioned adhesive and pressure-sensitive adhesive can be used.

  By using the above adhesive, pressure-sensitive adhesive, or adhesive, the adhesive layer 15 is cured by applying pressure such as pressure bonding at normal temperature or heating, or ultraviolet light, and the light guide film 11 is cured. And the lens sheet 12 are bonded together. As the adhesive layer 15, it is preferable to use a photocurable adhesive having a faster curing speed than thermosetting. Thereby, for example, in the case of producing by a roll-to-roll process, it is quickly cured by light irradiation immediately after the light guide film 11 and the lens sheet 12 are bonded. The lens array can be fixed by being sufficiently cured. Therefore, the positional deviation of the lens in the film surface direction can be further suppressed.

  Further, by making the refractive index after curing of the adhesive layer 15 equal to the refractive index of the unit lens 14 and / or the light guide film 11, the reflection of light at the interface can be reduced, and the loss of emitted light can be reduced. It is preferable in that it can be reduced.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Example 1
As shown in FIG. 4, a lens sheet was prepared in which a plurality of unit lenses having a cross-sectional shape combining a trapezoidal shape (upper side 45 μm, lower side 10 μm, height 25 μm) and a triangle (base side 4 μm, height 3 μm) were prepared. . 3μm of adhesive layer is coated on a 700μm thick light guide film, pasted with a lens sheet using a laminating roller and UV cured to create an optical sheet 30mm long and 5mm wide did.
FIG. 5 shows the luminance distribution in the length direction of the front surface (light emitting surface) of the light guide film when light is incident from the edge of the light guide film. In addition, in a graph, a horizontal axis shows the distance of the length direction from the light source side edge part of a light guide film.

(Example 2)
A lens sheet in which a plurality of unit lenses having the cross-sectional shape shown in FIG. 3μm of adhesive layer is coated on a 700μm thick light guide film, pasted with a lens sheet using a laminating roller and UV cured to create an optical sheet 30mm long and 5mm wide did.
FIG. 7 shows the luminance distribution in the length direction of the front surface (light emitting surface) of the light guide film when light is incident from the edge of the light guide film.

(Comparative Example 1)
A lens sheet was prepared in which a plurality of unit lenses having a trapezoidal shape with a cross section of an upper side of 45 μm, a lower side of 10 μm, and a height of 25 μm were arranged. An adhesive sheet of 3 μm was coated on a 700 μm thick light guide film, bonded to a lens sheet using a bonding roller, and thermally cured to create an optical sheet having a length of 30 mm and a width of 5 mm. .
FIG. 8 shows the luminance distribution in the length direction of the front surface of the light guide film (light emitting surface) when light is incident from the edge of the light guide film.

Moreover, the result of putting together about the uniformity of the surface emission of Example 1, Example 2, and the comparative example 1 and joining strength is shown in FIG.
From the results of FIGS. 5 and 7 to 9, it can be seen that Examples 1 and 2 have less luminance variation than Comparative Example 1 and can provide excellent luminance uniformity.
Regarding the bonding strength, in Comparative Example 1, in-plane variation in bonding strength occurred due to the fluidity of the adhesive layer, whereas in Examples 1 and 2, the bonding strength was caused by the effect of the top biting in. Can be made uniform in the plane. Furthermore, in Example 2, since it has a some top part, the joint strength could be improved more.

It is sectional drawing which shows the optical function member concerning one Embodiment of this invention. It is sectional drawing which shows the modification of a unit lens. It is sectional drawing which shows the other modification of a unit lens. 3 is a cross-sectional view showing a unit lens of Example 1. FIG. It is a graph which shows the luminance distribution of the length direction of the light guide film front surface (light emission surface) of Example 1. FIG. 6 is a cross-sectional view showing a unit lens of Example 2. FIG. It is a graph which shows the luminance distribution of the length direction of the light guide film front surface (light emission surface) of Example 2. FIG. It is a graph which shows the luminance distribution of the length direction of the light guide film front surface (light-emitting surface) of the comparative example 1. It is a graph which shows the result of the uniformity of surface light emission of Example 1, 2, and the comparative example 1, and joining strength. (A) is sectional drawing which shows the example of the conventional optical function member, (b) is a figure for demonstrating propagation of the light in the surface light source device shown in FIG. It is sectional drawing which shows the other example of the conventional optical function member. It is a figure for demonstrating the manufacturing method of the conventional optical function member. It is FIG. (1) for demonstrating the malfunction of the conventional optical function member. It is FIG. (2) for demonstrating the malfunction of the conventional optical function member.

Explanation of symbols

10 Optical sheet (optical functional member)
11 Light guide film (light guide member)
12 Lens sheet 13 Base film 14 Unit lens 14a Top 15 Adhesive layer

Claims (8)

A flat light guide member for propagating light incident from a light source provided on the side surface, and a plurality of unit lenses arranged on the surface, control the emission angle of the outgoing light emitted from the light guide member. And an optical functional member integrally formed through an adhesive layer,
The unit lens has one or more apexes having apex angles of less than 180 ° at the tip thereof,
The optical function member, wherein the light guide member and the lens sheet are bonded in a state in which a top portion of the unit lens bites into the adhesive layer. The unit lens has a plurality of apexes having apex angles of less than 180 ° at the tip thereof,
2. The optical function member according to claim 1, wherein a difference in height between the topmost portion and the concave portion of the front end portion of the unit lens is larger than a thickness of the adhesive layer.   The top portion having the topmost portion so that the volume of the portion that bites into the adhesive layer of the top portion having the topmost portion is equal to the volume of the space formed by the concave portion and the adhesive layer. The optical functional member according to claim 2, wherein the optical functional member bites into the adhesive layer.   The optical function member according to any one of claims 1 to 3, wherein the top portion of the unit lens has a shape in which triangular prisms are arranged in parallel.   5. The optical functional member according to claim 1, wherein an uppermost portion of the one or more unit lenses is in contact with the light guide member.   The optical functional member according to any one of claims 1 to 5, wherein the adhesive layer is made of a photocurable adhesive.   The optical function member according to claim 1, wherein a refractive index after curing of the adhesive layer is equal to a refractive index of the unit lens. The optical function member according to any one of claims 1 to 7, wherein a refractive index after curing of the adhesive layer is equal to a refractive index of the light guide member.

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