JP2009163906A - Brightness improvement device for backlight and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brightness improvement device without fear of brightness unevenness due to scratch caused by a light diffusion sheet and a lens sheet rubbing each other at transportation, or without fear of brightness unevenness since a brightness improvement sheet hardly gets wrinkled even if a great environmental change such as in humidity takes place, and suitable for a large-screen display device, easy to manufacture, and obtained at low cost. <P>SOLUTION: The method of manufacturing the brightness improvement device for the backlight equipped with a light-diffusion sheet and a lens sheet comprises: a light-reflecting layer laminating step of providing a light-reflecting adhesive layer on the light-diffusion sheet; and a pressing step of pressing the lens sheet against the light-diffusion sheet so that a tip of each lens part of the lens sheet penetrates the light-reflecting adhesive layer to reach the light-diffusion sheet. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a backlight luminance improving apparatus. For example, the present invention relates to a backlight luminance improving apparatus used for a backlight of a liquid crystal display device or a signboard.

  As a backlight of a liquid crystal display device, for example, a direct surface light source including a back light source and a diffusion sheet is known. That is, in the liquid crystal display device, since the brightness in front of the observer is important, it has been proposed to provide a lens sheet for improving the luminance in front of the backlight.

For example, a method using a prism sheet has been proposed (Japanese Patent Laid-Open No. 62-144102). In addition, it has been proposed to use a plurality of sheets (JP-A-9-197109) for the purpose of further improving the luminance and controlling the left and right and upper and lower viewing angles separately. As a backlight, a so-called edge light type surface light source using a light guide plate that transmits light from a light source provided at an end portion in a planar direction has also been proposed (Japanese Patent Laid-Open No. Hei 8-221003). Yes. A backlight assembly for use in an electro-optic display having a modulator that can send an image to a viewer at a remote location, comprising: (a) a light generator; and (b) the light generator. An opening device disposed close to the modulation device; and (c) a first collimation device disposed between the opening device and the modulation device, wherein the opening device is close to the opening device. A flat light input surface and a flat light output surface having a larger surface area away from and parallel to the light input surface, the light rays being transmitted through the first collimator by total reflection. A first collimating device that exits the light output surface in a substantially parallel pattern; and (d) a second parallel device having a light input surface disposed between the first collimating device and the modulator. The light input surface is the first collimating device Proposing a backlight assembly comprising: a second collimator that receives the substantially collimated beam from a light source and transmits the beam through refraction and directs the beam in a pattern parallel to the modulator ( No. 9-505212). An illumination device comprising: (a) a light source; and (b) a light directing assembly disposed in close proximity to the light source and including at least one microprism, the microprism being emitted from the light source. An incident surface that receives the reflected light, an exit surface that is distal to and parallel to the entrance surface, and is disposed between and adjacent to the entrance surface and the exit surface. A light directing assembly that includes at least one side wall that forms an obtuse angle with respect to the incident surface and that is arranged to totally reflect light received by the incident surface; (C) An illuminating device including at least one light shielding means for blocking light from passing through the side wall has also been proposed (Japanese Patent Publication No. 2000-507736).
JP 62-144102 A JP-A-9-197109 JP-A-8-2221013 JP-T 9-505412 Special Table 2000-507736

  By the way, in a direct type surface light source composed of a back light source, a light diffusion sheet, a brightness enhancement sheet, and the like, a plurality of sheets such as a light diffusion sheet and a brightness enhancement sheet are used. For this reason, the handling at the time of assembling a backlight is complicated.

  Further, the two sheets rub against each other due to vibrations when the backlight or the liquid crystal display device is transported. As a result, it has been found that there is a problem of scratches and uneven brightness.

  Further, it has been found that when the brightness enhancement sheet is thin, wrinkles are generated on the brightness enhancement sheet due to environmental changes such as temperature and humidity. It has been found that such wrinkles have a problem that causes uneven brightness.

  In addition, such a problem can be improved if it is the structure which bonded together the light-guide plate and the brightness enhancement sheet like the said patent document 3, etc., for example. However, in recent years, liquid crystal display devices have become larger in size. The edge light type surface light source is not suitable for increasing the screen size as compared to the direct type surface light source. Therefore, it has been difficult to employ an edge light type backlight as disclosed in Patent Document 3 on a large screen, for example, a screen size of 32 inches diagonal or more.

Therefore, the problem to be solved by the present invention is to solve the above problems.
In particular, the light diffusion sheet and the lens sheet do not rub against each other during transportation, causing scratches on the sheet and causing uneven brightness, and improving brightness even if environmental changes such as temperature and humidity occur. Providing a brightness enhancement device for backlights that does not easily wrinkle on the sheet and does not cause uneven brightness, and is suitable for large-screen display devices that are easy to manufacture and can be obtained at low cost. It is to be.

The above issues are
A method for manufacturing a brightness enhancement device for a backlight comprising a light diffusion sheet and a lens sheet,
A light-reflective adhesive layer laminating step of providing a light-reflective adhesive layer on the light diffusion sheet;
A pressing step of pressing the lens sheet against the light diffusing sheet so that the tip of the lens portion of the lens sheet reaches the light diffusing sheet through the light reflective adhesive layer. This is solved by a method for manufacturing a backlight brightness enhancement apparatus.

In particular, a method for manufacturing a backlight brightness enhancement device comprising a light diffusion sheet and a lens sheet,
A light-reflective adhesive layer laminating step of providing a light-reflective adhesive layer on the light diffusion sheet;
The lens sheet is pressed against the light diffusing sheet so that the front end of the lens part of the lens sheet reaches the light diffusing sheet through the light reflective adhesive layer. And the light diffusing sheet, and a pressing step that is a pressing that leaves an air layer in a region surrounded by the side surface of the lens portion of the lens sheet and the light-reflective adhesive layer. This is solved by the manufacturing method of the brightness enhancement device for the backlight.

  A method for manufacturing a backlight brightness improving apparatus as described above, wherein a lens sheet having a lens portion having a flat surface is used at the tip. Solved by the method.

  Also, a method for manufacturing the backlight brightness improving apparatus described above, wherein a light reflecting adhesive having an action of swelling the light diffusing sheet and / or the lens portion is used. It is solved by the manufacturing method of the improvement device.

In addition, a brightness enhancement device for a backlight including a light diffusion sheet and a lens sheet,
A light reflective adhesive layer is provided on the light diffusion sheet,
The tip of the lens portion of the lens sheet that has passed through the light reflective adhesive layer reaches the light diffusion sheet,
The light diffusion sheet and the lens sheet are solved by a backlight brightness improving apparatus, wherein the light reflecting sheet and the lens sheet are bonded together by the light reflective adhesive layer.

In particular, a backlight brightness enhancement device including a light diffusion sheet and a lens sheet,
A light reflective adhesive layer is provided on the light diffusion sheet,
The tip of the lens portion of the lens sheet that has passed through the light reflective adhesive layer reaches the light diffusion sheet,
The light diffusion sheet and the lens sheet are bonded by the light reflective adhesive layer,
The problem is solved by a backlight luminance improving apparatus, wherein an air layer exists in a region surrounded by a side surface of the lens portion of the lens sheet and the light-reflective adhesive layer.

  In addition, the above-described backlight brightness improving apparatus is solved by the backlight brightness improving apparatus using a lens sheet having a lens portion having a flat surface at the tip.

  Also, a method for manufacturing the backlight brightness improving apparatus described above, wherein a light reflecting adhesive having an action of swelling the light diffusing sheet and / or the lens portion is used. Solved by the enhancement device.

  The backlight brightness improving apparatus of the present invention has a configuration in which a light diffusion sheet and a lens sheet are bonded (integrated) with a light-reflecting adhesive.

  Therefore, even when an external force such as vibration or shaking is applied during transportation, the sheets do not rub against each other and are not damaged. For this reason, the brightness nonuniformity resulting from a damage is not caused. In addition, the sheet is less likely to wrinkle even if environmental changes such as temperature and humidity occur. For this reason, it is difficult to cause uneven brightness due to the occurrence of wrinkles.

  Furthermore, since the light diffusion sheet and the lens sheet are integrated, it can be easily incorporated into the backlight. A backlight device can be obtained at low cost.

  It is also suitable for increasing the screen size.

  Further, since the light-reflective adhesive is used, a backlight brightness enhancement device can be obtained very simply and at a low cost.

  The present invention is a method for manufacturing a backlight brightness enhancement device. In particular, it is a method for manufacturing a backlight brightness enhancement device (brightness enhancement sheet) including a light diffusion sheet and a lens sheet (for example, a lenticular lens sheet). And it has the light-reflective adhesive layer lamination process which provides a light-reflective adhesive layer on a light-diffusion sheet. Also, a pressing step of pressing the lens sheet against the light diffusing sheet so that the tip of the lens part (for example, lenticular lens part) of the lens sheet reaches the light diffusing sheet through the light reflective adhesive layer. Have As a result, the light diffusion sheet and the lens sheet are sequentially arranged and integrated (adhered / integrated) from the light source side, and the tip of the lens portion of the lens sheet is optically connected to the light diffusion sheet. A backlight brightness enhancement device (brightness enhancement sheet) is obtained in which the light that has passed through is incident on the lens unit side. Preferably, the pressing step is performed such that the lens portion of the lens sheet and the light diffusion sheet are connected and an air layer remains in a region surrounded by the side surface of the lens portion of the lens sheet and the light-reflective adhesive layer. Process. And as one preferable aspect, the lens part has a flat surface at the tip (light diffusion sheet side). Moreover, as one preferable aspect, the light-reflective adhesive has an action of swelling the light diffusion sheet. Or it has the effect | action which swells a lens part. Accordingly, the optical connection between the tip of the lens portion of the lens sheet and the light diffusion sheet facilitates securing a light transmitting portion (opening portion) having a desired area.

  The backlight brightness improving apparatus obtained as described above includes a light diffusion sheet and a lens sheet. A lens sheet (for example, a lenticular lens sheet) has a lens part (for example, a lenticular lens part) on the incident surface side (light diffusion sheet side). Each sheet is provided on the light diffusion sheet and bonded and integrated by a light reflective adhesive layer. In particular, the tip of the lens portion of the lens sheet and the light diffusion sheet are bonded and integrated so as to be optically connected. Preferably, an air layer exists in a region surrounded by the side surface of the lens portion of the lens sheet and the light reflective adhesive layer.

Hereinafter, further details will be described.
FIG. 1 is a schematic view of a backlight brightness enhancement device (backlight brightness enhancement sheet) according to the present invention.

  The light emitted from the light source 1 enters a diffusion sheet (light diffusion sheet; light source side diffusion sheet) 2 positioned on the light source side. The incident light is diffused by the diffusion sheet 2 and the in-plane luminance is made uniform.

  Part of the light diffused by the diffusion sheet 2 is a contact portion between the lens portion (lenticular lens portion) 4 of the lens sheet (lenticular lens sheet) 3 and the diffusion sheet 2 (interface portion: opening portion: translucent portion). 5 is incident.

  The light that has entered the opening 5 at an angle (small incident angle) that is nearly perpendicular to the sheet surface of the lenticular lens sheet 3 (the sheet upper surface in FIG. 1) travels straight through the lens unit 4 as it is. The light is emitted at an angle close to vertical (small emission angle). Light that has entered the opening 5 at a large incident angle with respect to the sheet surface travels straight through the lens unit 4 and is then reflected by the slope of the lens unit 4 (a parabolic surface in FIG. 1), and an angle that is nearly perpendicular to the sheet surface. It emits at (small exit angle). Therefore, the light incident on the opening 5 of the lenticular lens sheet 3 is collected in the front (upper surface in FIG. 1) direction.

  On the other hand, a part of the light diffused by the diffusion sheet 2 is reflected by the reflective layer (light reflective adhesive layer) 6 other than the opening 5. The light reflected by the reflective layer 6 is reflected and diffused in the diffusion sheet 2. This reflected / diffused light again enters the opening 5 of the lenticular lens sheet 3. Then, the light is condensed and emitted in the front direction. The remaining reflected / diffused light that has not entered the opening 5 of the lenticular lens sheet 3 goes through the same process. Hereinafter, the phenomenon in which light is reflected by the reflective layer 6 and is emitted from the opening 5 of the lenticular lens sheet 3 may be referred to as light reuse.

  As described above, the backlight brightness enhancement device (brightness enhancement sheet) of the present invention diffuses light by the diffusion sheet 2 to make the in-plane brightness uniform, and further by the lenticular lens sheet 3 disposed on the exit surface side. Since condensing is performed in the front direction, high front luminance can be realized.

  In addition, if a reflection plate (reflection sheet: reflection device: not shown) is provided on the back surface of the light source 1, the light from the light source 1 can be used effectively. Further, in the reuse of light, the light reaching the light source 1 side without being diffusely reflected on the emission side in the diffusion sheet 2 can be used effectively. Therefore, it is preferable to provide a reflector.

  The cross-sectional shape of the lens unit (lenticular lens unit) 4 may be any shape as long as it emits light incident at various angles from the opening 5 in the front direction. From another viewpoint, it has a reflection surface that condenses light only on the opening 5 when parallel light is incident on the brightness enhancement sheet, that is, the lenticular lens sheet 3 from the exit surface side in a direction perpendicular to the sheet surface. Any shape is acceptable. For example, the substantially parabolic shape shown in FIG. 1 or the trapezoid shown in FIG. Also, as shown in FIGS. 3 and 4, a curved shape (the cross section is a curved shape) and a straight shape (the cross section is a straight shape) can be appropriately combined.

  The opening 5 in the lens unit 4 is preferably formed in the vicinity of the focal point of the parabola, more specifically, about 0.8 to 2.5 times the distance from the apex of the lens unit 4 to the focal point. That is, when such a shape is used, the luminance in the front direction can be more effectively improved. When the cross-sectional shape of the lens portion (lenticular lens portion) 4 is deformed or becomes unclear due to the bonding, the vertex of the lens portion 4 is substituted with a virtual vertex obtained from the shape of the lens slope. The

  It is preferable that the angle at the position closest to the incident surface side of the lens inclined surface (side surface) in contact with the interface of the air portion (air layer) 7 between the lens portions 4 is not less than the critical angle with respect to the light passing through the center of the opening 5. It was good. This is because total reflection is likely to occur on the lens slope, and the light utilization efficiency is increased. For the same reason, the material constituting the lens unit 4 is preferably a material having a refractive index of 1.5 or more.

  The height of the lens part (lenticular lens part) 4 (height (distance) from the interface between the diffusion sheet 2 and the reflective layer 6 to the valley position between the lens parts 4) is determined by the luminance in the front direction and the viewing angle. Decide in consideration. For example, about 0.5 to 3 times the lens unit 4 pitch is preferable. This is because if the height is lower than this, the effect of improving the luminance in the front direction may be insufficient. Conversely, if the height is higher than this, the viewing angle becomes excessively narrow, and molding becomes difficult.

  There may be noticeable brightness unevenness due to molding of the lens unit 4 or unevenness of the adhesive surface, particularly brightness unevenness in an oblique direction. This will be described with reference to FIG. In FIG. 5, light is incident obliquely on the end (A in FIG. 5) of the opening 5 of a certain lens unit 4, and passes through the vicinity of the lens valley (B in FIG. 5) on the opposite side of the same lens unit 4. It is the schematic which shows the path | route of the light to do. It is assumed that the light beam L passing through the points A and B is incident at a critical angle on the exit surface of the brightness enhancement sheet. When the height of the lens unit 4 is excessively low (indicated by a broken line in FIG. 5), the amount of light passing through the critical angle increases, so that the light totally reflected on the exit surface is reflected by the lens unit 4 or the reflective layer 6. After being reflected and scattered by the light, the light is emitted to the observation side, so that it does not contribute to the improvement of luminance in the front direction. On the contrary, when the height of the lens unit 4 is excessively high (indicated by a dotted line in FIG. 5), there is no light incident at a critical angle or more, so that the luminance in the front direction is improved, but the viewing angle is excessive. Narrow. The viewing angle characteristic is a so-called cut-off characteristic in which there is almost no emission at an angle larger than the light ray L ′ passing through the points A and B ′ in FIG. 5. For this reason, the variation in the width of the opening 5 in the molding and bonding process of the lens unit 4 directly affects the variation in the cut-off angle. As a result, the brightness unevenness in the vicinity of the cutoff angle becomes remarkable. Accordingly, the height of the lens unit 4 is preferably set to about 0.8 to 1.5 times the height of the point B in FIG. 5 (the point B where the light beam passes at a critical angle).

  The pitch of the lens parts 4 in the lens sheet 3 is preferably 30 μm to 300 μm. That is, when it is smaller than 30 μm, it is difficult to manufacture. On the contrary, when it is larger than 300 μm, the moire pattern that the pixel pitch of the liquid crystal screen and the lens pitch interfere with each other becomes conspicuous.

  The width of the opening 5 was preferably 20% to 50% of the pitch of the lens unit 4. That is, when the lens pitch is less than 20%, molding becomes difficult. On the other hand, when it exceeds 50%, the effect of improving the luminance in the front direction becomes insufficient. The width of the opening 5 may be different between the center portion and the end portion of the sheet. That is, when the width of the opening 5 at the end is made larger than the width of the opening 5 at the center, the viewing angle at the end is widened, and when the screen is viewed from the front, the end is prevented from becoming dark. Because it was made.

  On the exit surface of the lenticular lens sheet 3, a diffusion layer that does not adversely affect the luminance improvement in the front direction may be provided to prevent scratches and moire. Further, in order to further adjust the viewing angle characteristics, fine surface irregularities may be provided. You may provide an output surface lens row | line | column (for example, prism row | line | column) in the same arrangement direction as the arrangement direction of the lenticular lens part 4. FIG. In addition, in order to adjust the horizontal and vertical viewing angle characteristics, respectively, an exit surface lens array may be provided in the arrangement direction intersecting with the arrangement direction of the lenticular lens portions 4.

  There is no particular limitation on the thickness of the lenticular lens sheet 3. However, it was preferable that the height of the lens part 4 is 1.5 times or more. That is, when the value is smaller than the above value, tearing may occur along the lens array. For this reason, attention is required when handling the brightness enhancement sheet. That is, a problem was observed in durability.

  The light-reflective adhesive layer 6 laminated on the diffusion sheet 2 is obtained by applying a paint in which a white pigment such as titanium oxide, zinc oxide, calcium carbonate, or a metal powder and an adhesive resin are dispersed in a solvent. Can be configured. The light reflective adhesive layer 6 only needs to have a thickness that sufficiently reflects light. For example, when a white pigment is used, the thickness of the light reflective adhesive layer 6 is preferably 5 μm or more. However, when the light-reflective adhesive layer 6 is excessively thick, the area ratio of the lens slope contacting the air interface becomes small. As a result, it has become difficult to reflect light rays using total reflection. Therefore, it is preferable that the light reflective adhesive layer 6 has a thickness of 20 μm or less. The adhesive resin constituting the light-reflective adhesive layer 6 is, for example, a thermosetting resin such as an epoxy adhesive, a solvent-type adhesive such as an organic solvent in which an acrylic resin is dissolved, or an ultraviolet light such as a urethane acrylate. A curable resin can be used.

  The emission surface side (upper surface side in FIG. 1) of the diffusion sheet 2 is preferably flat in consideration of bonding. In addition, in order to prevent scratches due to handling before bonding and to improve adhesive strength, unevenness finer than the lens pitch of the lens sheet 3 may be provided on the exit surface side.

  The incident surface side of the diffusion sheet 2 may be flat, or a fine uneven shape or a lens array may be formed. When the back light source 1 is a linear light source or a light source in which point light sources are arranged in a line, a lens parallel to the longitudinal direction of the arrangement of the linear light sources or point light sources is disposed on the incident surface side of the diffusion sheet 2. A row is preferably provided (see FIG. 10). This is because the in-plane luminance is made uniform.

The diffusion sheet 2 can be composed of a synthetic resin sheet mixed with a light diffusing agent, for example.
Here, the light diffusing agent is used for the following reason. If the light diffusing power of the diffusion sheet 2 is only its surface shape, the light reflected by the light-reflective adhesive layer 6 is not sufficiently diffused and reflected by the diffusion sheet 2 to the emission side, and the light reuse efficiency is improved. It is because it does not rise.

  The diffusion sheet 2 is composed of a plurality of layers, the exit surface side (upper surface side in FIG. 1) is a layer having a relatively small diffusion force, and the incident surface side (lower surface side in FIG. 1) is a layer having a relatively large diffusion force. This is a preferred example. For example, the light emission surface side is a transparent layer and the light incident surface side is a diffusing agent-containing layer. In this case, the probability that the reused light enters the opening 5 of the lens sheet 3 is increased, and the light utilization efficiency is increased. In addition, it is preferable that the thickness of the layer having a small diffusing power is about 0.5 times or more of the lens pitch.

  This point will be described with reference to FIGS. FIG. 6 shows an outline of a light path reflected by the light-reflective adhesive layer 6 in the vicinity of the interface between the light-reflective adhesive layer 6 and the diffusion sheet 2 (a diffusion sheet having no transparent layer). is there. The light incident on the light-reflective adhesive layer 6 is reflected and once travels toward the diffusion sheet 2, then diffuses and reflects within the diffusion sheet 2, becomes diffused light, and enters the lenticular lens sheet 3 again. . The phenomenon in which light is reflected by the light-reflective adhesive layer 6 and is emitted from the opening (translucent portion) 5 of the lenticular lens sheet 3 may be referred to as light reuse. However, not all of the reflected light necessarily enters the opening (translucent portion) 5. For example, part of the reflected light is repeatedly reflected between the light reflective adhesive layer 6 and the diffusion sheet 2. Here, the reflection efficiency in the light-reflective adhesive layer 6 and the diffusion sheet 2 is not actually 100%, and light loss occurs. 7 shows a light-reflective adhesive layer 6 and a diffusion sheet (a diffusion sheet provided with a transparent layer containing a diffusing agent on the incident surface side but not including a diffusing agent on the outgoing surface side). The outline of the path | route of the light reflected by the light reflective adhesive layer 6 in the interface vicinity is shown. In this case, the light incident on the light-reflective adhesive layer 6 is reflected and once travels toward the diffusion sheet 2, then passes through the transparent layer, and is diffused and reflected in the diffusion sheet 2 toward the emission surface. For this reason, the possibility of reflection at a position away from the light reflective adhesive layer 6 in the lens arrangement direction is increased. Accordingly, since the components that are repeatedly reflected in the diffusion sheet 2 can be reduced, the light use efficiency is increased. In addition, it is preferable that the thickness of the layer having small (or no) diffusing power is about 0.5 to 10 times the lens pitch. If it is smaller than 0.5 times, the effect of the present invention may not be sufficiently exhibited. On the contrary, even if it is a large case exceeding 10 times, the effect is not exhibited remarkably, but rather, it obstructs the reduction in thickness and weight of the backlight.

  Other embodiments of the preferred diffusion sheet 2 include the following. For example, having a diffusion layer containing a high concentration diffusing agent on the incident surface side and having a diffusion layer containing a low concentration diffusing agent on the exit surface side, or a difference in refractive index from the base material on the incident surface side Having a diffusion layer containing a large diffusing agent and having a diffusion layer containing a diffusing agent having a small refractive index difference from the base material on the exit surface side, or from the vicinity of the entrance surface toward the exit surface, Examples thereof include those having a diffusion layer whose concentration is changed (decreased) stepwise or continuously.

  In the present invention, the contact portion between the lenticular lens portion 4 and the light source side diffusion sheet 2 is the opening portion (translucent portion) 5. However, even if the lenticular lens portion 4 having a rounded tip at the tip of the lens portion 4 and the light source side diffusion sheet 2 having a flat exit surface are pressed against each other, the width of the contact portion is very small and the width of the opening portion is small. It may not be obtained sufficiently. Such problems can be improved by the following.

[Flatening the tip of the lens (lenticular lens)]
As shown in FIG. 8, a flat portion is formed at the tip of the lenticular lens portion 4. And the flat surface of a front-end | tip is joined to the diffusion sheet 2, and it bonds together. Thereby, the width of the opening 5 can be easily increased. In addition, the width of the flat portion can be matched with the width of the opening (translucent portion) 5, and variations in the width of the opening 5 can be suppressed. In addition, when the flat surface was provided in the front-end | tip, it was thought that a flat surface and a diffusion sheet did not adhere | attach but the light-reflective adhesive layer 6 remained between. However, when the size of the pigment particles of the light reflective adhesive layer 6 is 5 μm or less, there is no problem when the lenticular lens sheet 3 is pressed with sufficient pressure.

[Use of a light-reflective adhesive having an action of swelling the diffusion sheet]
As an adhesive that constitutes the light-reflective adhesive layer 6, in particular, a solvent that can swell the diffusion sheet 2 is used as a solvent contained in the adhesive. That is, when the light-reflective adhesive having such an action is applied to the emission surface side of the diffusion sheet 2 and left for a predetermined time (for example, 1 to 30 minutes), the emission surface of the diffusion sheet 2 The side surface swells. As a result, the exit surface side surface of the diffusion sheet 2 becomes soft. Therefore, when the lenticular lens sheet 3 is pressed with a sufficient pressure under such a state, as shown in FIG. 9, the tip convex portion of the lens portion 4 is fitted into the exit surface side surface of the diffusion sheet 2, thereby transmitting the light. The width of the portion (opening) 5 can be easily increased.

[Use of a light-reflective adhesive having an action of swelling the lens part]
As an adhesive that constitutes the light-reflective adhesive layer 6, particularly a solvent contained in the adhesive, one that has an action of swelling the lens portion 4 (lens sheet 3) is used. That is, after the light reflective adhesive having such an action is applied to the light exit surface side of the diffusion sheet 2, the tip of the lens unit 4 is immediately aligned toward the light reflective adhesive layer 6 side for a predetermined time. If the lenticular lens sheet 3 is pressed with sufficient pressure in this state, as shown in FIG. The distal end portion becomes relatively flat, and the width of the light transmitting portion (opening portion) 5 can be easily increased.

  The lens sheet 3 can be manufactured by a known manufacturing method. For example, it can be produced by an extrusion method or a transfer method using an ultraviolet curable resin.

  In the above description, the lenticular lens sheet 3 is bonded to the diffusion sheet 2. However, even if the lenticular lens sheet 3 is once bonded to the base material sheet and overlapped with the diffusion sheet 2, similarly, The reuse effect is demonstrated.

Hereinafter, the present invention will be described with reference to more specific examples, but the present invention is naturally not limited to the following examples.
[Example]
First, a lenticular lens sheet 3 was prepared.
The physical characteristics of the lenticular lens sheet 3 are as shown in Table 1 below. Further, the front end side of the lens portion 4 provided on the incident surface side of the lenticular lens sheet 3 is formed with a flat surface.
Table-1
Lens unit 4 pitch 0.080 mm
Optical refractive index in the lens unit 4 1.55
Side surface shape (cross-sectional shape) of the lens unit 4 y = (83.33 / 2) x ² parabolic shape (where y is the height of the lens unit 4 and x is the distance in the width direction of the lens unit 4) (The origin is the apex of the lens unit 4.)
Distance from the apex of the lens unit 4 to the flat surface (opening) 5 0.006 mm
Width of flat surface (opening) 5 0.024 mm (opening ratio: 30%)
End height of the lens part 4 (height (distance) from the flat surface to the position of the valley point between the lens parts 4)
0.067mm
End angle of the lens part 4 (angle of tangent at the valley point between the lens parts 4)
73.3 °
On the exit surface side of the lenticular lens sheet 3, a diffusion layer having the characteristics shown in Table 2 below is provided.
Table-2
Haze 78%
View half-value angle α 4.1 °
Field of view 1/3 value angle β 6.0 °
Field of view 1/10 value angle γ 12.9 °

  Further, a diffusion sheet 2 having a refractive index of 1.55 mixed with a light diffusing agent was prepared.

  A light reflective adhesive layer 6 was provided on the exit surface side of the diffusion sheet 2. The light-reflective adhesive layer 6 is coated with a coating containing a titanium oxide having a particle size of 2 to 10 μm (reflective material), a urethane acrylate-based ultraviolet curable resin (adhesive), and an acrylic monomer having a thickness of 10 μm. It is composed of

  Thereafter, the lens portion 4 of the lenticular lens sheet 3 is opposed to the reflective adhesive layer 6 and pressed so that the flat surface 5 at the tip of the lens portion 4 penetrates the light reflective adhesive layer 6. Reached. That is, the flat surface 5 at the tip of the lens unit 4 is bonded to the emission surface of the light diffusion sheet 2 so that light is transmitted from the light diffusion sheet 2 to the lens unit 4 through the flat surface 5. The above pressing was such that an air layer remained in a region surrounded by the side surface of the lens portion 4 and the light reflective adhesive layer 6.

  In addition, since the side surface of the lens portion 4 of the lenticular lens sheet 3 is bonded to the reflective adhesive layer 6, the lenticular lens sheet 3 and the diffusion sheet 2 are integrated.

  A light source was disposed on the back of the backlight brightness enhancement sheet obtained as described above, and a reflection sheet having a reflectance of 80% was disposed on the back of the light source, thereby obtaining a backlight.

  And since the viewing angle characteristic of the brightness improvement sheet | seat for backlights obtained as mentioned above was investigated, the result is shown in FIG.

  In FIG. 11, a case where the lenticular lens sheet 4 having the above structure is not bonded (comparative example) is indicated by a dotted line. According to this, it can be seen that the brightness enhancement sheet for backlight according to the present invention has a front brightness about 1.6 times that of the comparative example, and is excellent in viewing angle characteristics.

  Further, as can be seen from the above description, the brightness enhancement sheet for backlight of the present invention can be obtained very easily and at low cost.

Schematic of the brightness enhancement device for backlight of the present invention Schematic of another example of the brightness enhancement device for backlight of the present invention Schematic of another shape example of the lens part Schematic of another shape example of the lens part Schematic showing the path of light incident on the end of the opening of the lens Schematic showing the path of light incident on the reflective layer (light reflective adhesive layer) Schematic showing the path of light incident on the reflective layer (light reflective adhesive layer) Schematic of another example of the brightness enhancement device for backlight of the present invention Schematic of another example of the brightness enhancement device for backlight of the present invention Schematic of another example of the brightness enhancement device for backlight of the present invention Illustration of viewing angle characteristics

Explanation of symbols

1 Light source 2 Diffusion sheet (light diffusion sheet; light source side diffusion sheet)
3 Lens sheet (lenticular lens sheet)
4 Lens part (lenticular lens part)
5 Contact part (interface part: opening: translucent part)
6 Reflective layer (light reflective adhesive layer)
7 Air part (air layer)

Patent applicant Kuraray Co., Ltd.
Representative Katsumi Udaka

Claims (5)

A method for manufacturing a brightness enhancement device for a backlight comprising a light diffusion sheet and a lens sheet,
A light-reflective adhesive layer laminating step of providing a light-reflective adhesive layer on the light diffusion sheet;
A pressing step of pressing the lens sheet against the light diffusing sheet so that the tip of the lens portion of the lens sheet reaches the light diffusing sheet through the light reflective adhesive layer. A method for manufacturing a backlight brightness enhancement device. The pressing step is a step in which the lens portion of the lens sheet and the light diffusion sheet are connected and pressed to such an extent that an air layer remains in a region surrounded by the side surface of the lens portion of the lens sheet and the light-reflective adhesive layer. The method for manufacturing a backlight brightness improving apparatus according to claim 1, wherein: 3. The method for manufacturing a backlight brightness improving apparatus according to claim 1, wherein a lens sheet having a lens portion having a flat surface is used at the tip. 4. The method for manufacturing a backlight brightness improving apparatus according to claim 1, wherein a light-reflective adhesive having an action of swelling the light diffusion sheet and / or the lens portion is used. A brightness enhancement device for a backlight comprising a light diffusion sheet and a lens sheet,
A light reflective adhesive layer is provided on the light diffusion sheet,
The tip of the lens portion of the lens sheet that has passed through the light reflective adhesive layer reaches the light diffusion sheet,
The backlight brightness improving apparatus, wherein the light diffusion sheet and the lens sheet are bonded together by the light reflective adhesive layer.

Images