JP2014096204A - Optical sheet for light guide plate and manufacturing method of optical sheet for light guide plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical sheet for a light guide plate which can form desired reflect pattern easily and certainly.SOLUTION: An optical sheet for a light guide plate comprises a laser coloring layer developing by laser radiation, and the laser coloring layer contains a synthetic resin of a matrix and a coloring agent dispersing in the synthetic resin. It is preferable that a synthetic resin layer layered over the laser coloring layer is provided. It is preferable that at least one of the synthetic resin constructing the laser coloring layer and the synthetic resin constructing the synthetic resin layer is transparent. It is preferable that the laser coloring layer and/or the synthetic resin layer are provided two or more layers. It is preferable that a main component of the synthetic resin constructing the laser coloring layer and the synthetic resin constructing the synthetic resin layer is an acrylic resin.

Description

  The present invention relates to an optical sheet for a light guide plate and a method for producing the optical sheet for a light guide plate.

  Liquid crystal display devices are widely used as display devices for screens of televisions, personal computers, and the like, and are broadly classified into direct-view types in which a user directly views a display screen and projection types in which an image projected on a screen is viewed. Direct-view liquid crystal display devices include a transmissive type that transmits light from the backlight, a reflective type that does not have a backlight and uses reflected light such as natural light and room light, and a reflective type in bright places and a transmissive type in dark places. There is a transflective type. On the other hand, the projection type liquid crystal display device includes a front type that projects an image on a front screen and a rear type that captures the screen in a display cabinet and projects the image. Nowadays, a direct-view type liquid crystal display device among them is generally used as a mainstream.

  In the transmissive liquid crystal display device, a backlight system that illuminates a liquid crystal layer from the back is widespread, and backlight units such as an edge light type (side light type) and a direct type are provided on the lower surface side of the liquid crystal layer. In general, as shown in FIG. 5, the edge light type backlight unit 40 includes a lamp 41 as a light source, and a rectangular plate-shaped light guide plate 42 that is disposed so that an end thereof is along the lamp 41. A plurality of optical sheets 43 stacked on the surface side of the light guide plate 42 are provided. As the lamp 41 as the light source, an LED (light emitting diode), a cold cathode tube, or the like is used, but an LED is generally used from the viewpoint of miniaturization and energy saving. The optical sheet 43 has optical functions such as diffusion and refraction with respect to transmitted light. (1) A prism that is disposed on the surface side of the light guide plate 42 and has a refraction function toward the normal direction side. A sheet 45, (2) a light diffusion sheet 44 disposed on the back side of the prism sheet 45 and mainly having a light diffusion function is used.

  Although not shown, in consideration of the light guide characteristics of the light guide plate 42 and the optical function of the optical sheet provided in the optical sheet 43, more optical sheets 43 such as a light diffusion sheet and a prism sheet are provided. There is also a backlight unit.

  The function of the backlight unit 40 will be described. First, a light beam incident on the light guide plate 42 from the lamp 41 is reflected by a reflection pattern portion or a reflection sheet (not shown) on the back surface of the light guide plate 42 and each side surface. 42 is emitted from the surface. The light beam emitted from the light guide plate 42 enters the light diffusion sheet 44, is diffused, and is emitted from the surface. Light rays emitted from the surface of the light diffusion sheet 44 enter the prism sheet 45, are refracted in the normal direction by the prism portions of the plurality of protrusions formed on the surface, and are emitted from the surface. Thereafter, the light beam emitted from the surface of the prism sheet 45 illuminates the entire upper surface of the liquid crystal layer (not shown).

  The light guide plate 42 is provided with a reflection pattern portion on the back surface by means of printing or the like that scatters light from the light source (lamp 41) introduced from the side surface of the light guide plate 42 efficiently and uniformly on the surface side of the backlight unit 40. . This reflection pattern part is comprised by the fine dot pattern etc. which reflect and scatter light, for example. Moreover, as a formation method of a reflective pattern part, the method of printing the composition which mixed the pigment etc. in the binder solution on the back surface of the light-guide plate 42 is used, for example. In addition, a method of cutting a groove or the like on the back surface of the light guide plate with a laser or the like to improve the light diffusion effect is also used (see JP 2009-43708 A).

  However, when the reflective pattern portion is formed by printing, it is difficult to form a fine reflective pattern portion, and there may be a case where sufficient brightness cannot be obtained due to unevenness or missing in the reflective pattern portion. On the other hand, when it is formed by processing a physical shape such as a groove, a certain thickness is required for the light guide plate in order to perform cutting, and there is a limit to reducing the thickness of the backlight unit.

JP 2009-43708 A

  The present invention has been made based on the above-described circumstances, and an object thereof is to provide an optical sheet for a light guide plate capable of easily and reliably forming a desired reflection pattern.

The invention made to solve the above problems is
It has a laser coloring layer that develops color by laser irradiation.
The laser color-developing layer is an optical sheet for a light guide plate containing a matrix synthetic resin and a color former dispersed in the synthetic resin.

  Since the optical sheet for the light guide plate can cause the laser coloring layer to develop color by laser irradiation, a fine reflection pattern can be accurately formed on the laser coloring layer. Therefore, by using the optical sheet for a light guide plate in which such a fine reflection pattern is formed as the light guide plate of the backlight unit, the reflectivity and thinness of the light guide plate can be improved.

  The optical sheet for a light guide plate preferably includes a synthetic resin layer laminated on the laser coloring layer. By laminating the synthetic resin layer on the laser coloring layer in this way, a highly shape-stable part that is unlikely to shrink even when irradiated with a laser can be formed near the laminated surface of the laser coloring layer. . Therefore, the optical sheet for a light guide plate can easily and reliably form a fine reflection pattern in the vicinity of the laminated surface, and can protect the reflection pattern with a synthetic resin layer. Moreover, the intensity | strength of the light-guide plate obtained using the said optical sheet for light-guide plates can also be improved.

  In the optical sheet for a light guide plate, it is preferable that at least one of the synthetic resin constituting the laser coloring layer and the synthetic resin constituting the synthetic resin layer is transparent. In this way, by using at least one of the laser coloring layer and the synthetic resin layer as a transparent resin layer, and using the transparent resin layer as a layer into which light from the light source in the light guide plate is introduced, the optical sheet for the light guide plate is used. The light transmittance of the obtained light guide plate can be improved.

  The optical sheet for a light guide plate preferably includes two or more of the laser coloring layer and / or the synthetic resin layer. By providing a plurality of laser color developing layers and / or synthetic resin layers in this manner, it is possible to improve the protection of the reflection pattern of the optical sheet for the light guide plate, the sheet strength, and the like. In particular, when a plurality of laser coloring layers are provided, a plurality of reflection patterns can be formed in the optical sheet for the light guide plate, so that the luminance of the light guide plate obtained using the optical sheet for the light guide plate is uniformized. The effect can be enhanced.

  In the optical sheet for the light guide plate, it is preferable that the synthetic resin constituting the laser coloring layer and the main component of the synthetic resin constituting the synthetic resin layer are acrylic resins. Thus, by making the laser color developing layer and the synthetic resin layer made of an acrylic resin, the transparency of the light guide plate optical sheet can be improved, and as a result, the light guide plate optical sheet can be obtained. The luminance uniformity performance of the light guide plate can be enhanced.

  In the optical sheet for a light guide plate, the content of the color former in the laser color development layer is preferably 2.5% by mass or less. Thus, by setting the content of the color former in the above range, the laser marking property, transparency, strength, and the like of the light guide plate optical sheet can be improved.

  In the optical sheet for a light guide plate, the thickness of the laser coloring layer is preferably 550 μm or less. Thus, by setting the thickness of the laser coloring layer within the above range, the thickness of the light guide plate obtained using the optical sheet for the light guide plate can be reduced, and as a result, the liquid crystal display device can be made thinner. Can be planned.

  Since the optical sheet for a light guide plate has the functions described above, it can be suitably used for a backlight unit of a liquid crystal display device.

The invention made to solve the above problems is
A method for producing an optical sheet for a light guide plate, comprising a step of extruding a material containing a thermoplastic synthetic resin and a color former.

  The method for producing the optical sheet for a light guide plate can form a laser coloring layer that develops color by laser irradiation by extruding a material containing a thermoplastic synthetic resin and a coloring agent. Therefore, the optical sheet for light guide plates which has a laser coloring layer easily and reliably can be manufactured using the conventional resin film manufacturing apparatus. Moreover, the optical sheet for a light guide plate obtained by the method for producing an optical sheet for a light guide plate is excellent in laser marking properties, and can form a fine and uniform reflection pattern on a laser coloring layer. Therefore, a light guide plate that is thin and has a high luminance uniformity effect can be obtained.

  The content of the color former in the laser coloring layer means a mass ratio with respect to the synthetic resin which is a matrix of the laser coloring layer. The “thickness” means an average thickness measured according to JIS-K-7130.

  As described above, the optical sheet for a light guide plate of the present invention can easily and reliably form a desired reflection pattern. Therefore, by using the optical sheet for a light guide plate in which a fine reflection pattern is formed as a light guide plate of a backlight unit, the reflectivity and thinness of the light guide plate can be improved. As a result, the brightness of the liquid crystal display device Uniformity and thinning can be promoted.

It is a typical sectional view showing the optical sheet for light guide plates concerning one embodiment of the present invention. It is typical sectional drawing which shows the optical sheet for light guide plates which concerns on the form different from the optical sheet for light guide plates of FIG. It is typical sectional drawing which shows the optical sheet for light guide plates which concerns on the form different from the optical sheet for light guide plates of FIG.1 and FIG.2. It is typical sectional drawing which shows an example of the light-guide plate obtained by forming a reflective pattern in the optical sheet for light-guide plates of FIG.1 and FIG.2. It is a typical perspective view which shows a general edge light type backlight unit.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. First, an optical sheet for a light guide plate according to a first embodiment of the present invention will be described with reference to FIG.

[First embodiment]
The optical sheet 1 for a light guide plate in FIG. 1 has a two-layer structure including a laser coloring layer 2 and a synthetic resin layer 3 laminated on one surface of the laser coloring layer 2. The optical sheet 1 for the light guide plate in FIG. 1 is a light guide plate that guides the light source introduced into the laser color developing layer 2 to the surface side (upward in the drawing) when the light source is disposed on the side of the laser color developing layer 2. Can be formed.

<Laser coloring layer 2>
The laser coloring layer 2 contains a matrix synthetic resin and a color former dispersed in the synthetic resin, and the portion irradiated with the laser develops color.

  The matrix synthetic resin constituting the laser coloring layer 2 is preferably a synthetic resin that transmits light, and examples thereof include acrylic resins, polycarbonate resins, polystyrene resins, and polyvinyl chloride resins. Among these, acrylic resins that are excellent in transparency and hardly cause discoloration even when a laser passes are particularly preferable.

  The acrylic resin is a resin having a skeleton derived from acrylic acid or methacrylic acid. Examples of acrylic resins include, but are not limited to, poly (meth) acrylic acid esters such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymers, and methyl methacrylate- (meth) acrylic acid esters. Copolymer, methyl methacrylate-acrylic ester- (meth) acrylic acid copolymer, (meth) methyl acrylate-styrene copolymer, polymer having an alicyclic hydrocarbon group (for example, methyl methacrylate- Cyclohexyl methacrylate copolymer, methyl methacrylate- (meth) acrylate norbornyl copolymer), and the like. Among these acrylic resins, poly (meth) acrylic acid C1-6 alkyl such as poly (meth) methyl acrylate is preferable, and methyl methacrylate resin is more preferable.

  The color former dispersed in the synthetic resin is a pigment that changes color by laser irradiation. As this color former, a well-known organic substance or inorganic substance used as a laser marking agent can be used. Specifically, for example, yellow iron oxide, inorganic lead compound, manganese violet, cobalt violet, mercury, cobalt, copper, bismuth, nickel and other metal compounds, pearlescent pigments, silicon compounds, mica, kaolins, silica sand, A diatomaceous earth, a talc, etc. can be mentioned, Among these, 1 type (s) or 2 or more types can be used. However, since the optical sheet 1 for a light guide plate is intended to form a reflection pattern that reflects a light beam by laser irradiation, it is preferable that a coloring portion formed by the laser irradiation has a light reflection color. Therefore, it is preferable to use a color former that develops white color by laser irradiation in the optical sheet 1 for the light guide plate. Conversely, a color former that is carbonized by laser irradiation and changes to black that absorbs light is not suitable for the present invention. Is appropriate. Examples of such a color former that develops white color include titanium black, cordierite, and mica.

As the cordierite, in addition to the inorganic compound represented by the composition formula MG ₂ Al ₃ (AlSi ₅ O ₁₈ ), one in which a part of Mg is substituted with Fe can be used. Moreover, you may use the thing containing a water | moisture content.

  As the mica, natural mica such as mascobite, phlogopite, biotite and sericite, and synthetic mica such as fluorine phlogopite and tetrasilica mica can be used.

  The content of the color former in the laser coloring layer 2 is preferably 0.0001% by mass to 2.5% by mass, and more preferably 0.1% by mass to 1% by mass. When the content of the color former is less than the above range, a sufficient color development effect cannot be obtained at the time of laser irradiation, and a desired reflection pattern may not be formed. On the contrary, when the content of the color former exceeds the above range, the transparency and mechanical strength of the laser color development layer 2 may be lowered.

  The thickness of the laser coloring layer 2 is preferably from 100 μm to 550 μm, and more preferably from 200 μm to 400 μm. If the thickness of the laser coloring layer 2 is less than the above range, it may be difficult to form a reflection pattern, and the light source incident from the side surface may not be sufficiently diffused over the entire surface. On the other hand, when the thickness of the laser coloring layer 2 exceeds the above range, the thickness of the optical sheet 1 for the light guide plate is increased, which may contradict the thinning of the liquid crystal display device.

  The total light transmittance of the laser coloring layer 2 is preferably 85% or more, and more preferably 90% or more. When the total light transmittance of the laser coloring layer 2 is less than the lower limit, the light loss of the light guide plate obtained using the optical sheet 1 for the light guide plate is increased, and the luminance of the backlight unit using the light guide plate is lowered. There is a risk. The total light transmittance is a value measured according to JIS-K-7361.

<Synthetic resin layer 3>
The synthetic resin layer 3 is made of synthetic resin. As this synthetic resin, the same synthetic resin as that of the laser coloring layer 2 can be used, and examples thereof include acrylic resins, polycarbonate resins, polystyrene resins, and polyvinyl chloride resins. Among these, an acrylic resin that hardly changes color even when a laser passes is particularly preferable.

  The synthetic resin layer 3 preferably has light reflectivity. By making the synthetic resin layer 3 light-reflective, when a light beam is incident from the side surface of the laser coloring layer 2 on the light guide plate in which the reflection pattern is formed on the laser coloring layer 2, it is reflected by the reflection pattern of the laser coloring layer 2. It was possible to reflect the light rays that did not exist on the surface side.

  Examples of a method of imparting light reflectivity to the synthetic resin layer 3 include a method of coloring the synthetic resin layer 3 to a light reflecting color. The light reflection color is not particularly limited as long as it can reflect light rays, and examples thereof include white and silver glossy colors. As a specific method for coloring the synthetic resin layer 3 to a light reflection color, for example, a method of adding a pigment having a light reflection color can be used. As this pigment, for example, white pigments such as calcium carbonate, titanium oxide, zinc oxide, lead carbonate, and barium sulfate, aluminum powder, and the like can be used.

  The thickness of the synthetic resin layer 3 is preferably 1 μm or more and 400 μm or less, and more preferably 10 μm or more and 200 μm or less. When the thickness of the synthetic resin layer 3 is less than the above range, the reflection pattern formed on the laser coloring layer 2 may not be sufficiently protected, and the strength of the light guide plate optical sheet 1 may be reduced. There is. On the other hand, when the thickness of the laser coloring layer 2 exceeds the above range, the thickness of the optical sheet 1 for the light guide plate is increased, which may contradict the thinning of the liquid crystal display device.

  For the laser coloring layer 2 and the synthetic resin layer 3, a dispersant, a fluidity adjusting agent, a flame retardant, a lubricant, a mold release agent, an antioxidant, an ultraviolet absorber, a reinforcing agent, a colorant, and the like as necessary. Can be added as appropriate.

<Optical sheet 1 for light guide plate>
As thickness of the said optical sheet 1 for light-guide plates, 250 micrometers or more and 600 micrometers or less are preferable, and 350 micrometers or more and 550 micrometers or less are more preferable. When the thickness of the light guide plate optical sheet 1 is less than the above range, the strength and handleability of the light guide plate optical sheet 1 may be reduced, or curling may occur during laser irradiation. On the other hand, when the thickness of the optical sheet 1 for the light guide plate exceeds the above range, there is a risk that the liquid crystal display device is thinned.

<Usage method of optical sheet 1 for light guide plate>
As shown in FIG. 4A, the optical sheet 1 for the light guide plate has a dense reflective pattern 4 that efficiently and uniformly scatters light incident from the side surface of the laser coloring layer 2 on the surface side. The light guide plate 100 that can be suitably used for a backlight unit of a liquid crystal display device can be obtained by forming the back surface of the substrate by laser irradiation.

  The laser for irradiating the laser coloring layer 2 is not particularly limited, and for example, a carbon dioxide laser, a carbon monoxide laser, a semiconductor laser, a YAG (yttrium, aluminum, garnet) laser or the like can be used. Among these, a carbon dioxide laser having a wavelength of 9.3 to 10.6 μm is suitable for forming a fine dot pattern.

  As the carbon dioxide laser, a lateral atmospheric pressure excitation (TEA) type, a continuous oscillation type, a pulse oscillation type, or the like can be used.

  Examples of the reflection pattern 4 formed on the laser coloring layer 2 include a pattern made of fine dots. The dots are formed by irradiating the laser coloring layer 2 with a laser to cause the color former to develop color. The shape of the dot is not limited to a dot shape, and may be a linear shape, an elliptical shape, a rectangular shape, or the like. Alternatively, the laser coloring layer 2 may have a three-dimensional shape having a height in the thickness direction. As the size of the dots, for example, the maximum width is preferably 1 mm or less. Further, it is preferable that the size and density of the dots are formed so as to increase as the distance from the side surface on the side where the light source is disposed. By forming the reflection pattern 4 composed of such dots, the luminance of the exit surface of the light guide plate 100 can be made uniform. As a result, the luminance of the liquid crystal display device using the light guide plate 100 can be made uniform.

  In the light guide plate 100 in which the reflection pattern 4 is formed on the laser coloring layer 2 of the optical sheet 1 for the light guide plate, a light source is arranged on the side surface of the laser coloring layer 2, and the light beam of the light source is introduced into the laser coloring layer 2. The light can be emitted from the surface of the layer 2 (the surface on which the synthetic resin layer 3 is not laminated).

<Advantages of optical sheet 1 for light guide plate>
Since the optical sheet 1 for the light guide plate can color the laser coloring layer 2 by laser irradiation, it can be accurately formed on the laser coloring layer 2 even with a fine reflection pattern. When the light guide plate optical sheet 1 having such a fine reflection pattern is used as the light guide plate of the backlight unit, the light beam introduced into the light guide plate can be accurately reflected by the reflection pattern. For this reason, the light guide plate using the optical sheet 1 for the light guide plate has a uniform luminance compared to the light guide plate on which the reflection pattern is formed by conventional printing, and the reflection pattern by processing of the conventional physical shape. Compared to the light guide plate on which is formed, the thickness can be reduced.

  In addition, since the optical sheet 1 for the light guide plate includes the synthetic resin layer 3 laminated on the laser coloring layer 2, the vicinity of the laminated surface of the laser coloring layer 2 is less likely to shrink even when irradiated with laser. It becomes a highly stable part. Therefore, the light guide plate optical sheet 1 can easily and reliably form a fine reflection pattern in the vicinity of the laminated surface, and can protect the reflection pattern with the synthetic resin layer 3. Moreover, the intensity | strength of the light guide plate obtained using the said optical sheet 1 for light guide plates can be improved.

<The manufacturing method of the optical sheet 1 for light-guide plates>
Next, an embodiment of a method for producing the optical sheet 1 for the light guide plate will be described below.

The manufacturing method of the optical sheet 1 for a light guide plate in the present embodiment is as follows:
(1) a first step of preparing a forming material for the laser coloring layer 2 containing a thermoplastic synthetic resin and a coloring agent; and (2) extruding the forming material for the laser coloring layer 2 together with the forming material for the synthetic resin layer 3. A second step of forming the optical sheet 1 for the light guide plate.

<(1) First step>
In the first step, a material for forming the laser coloring layer 2 is prepared by adding a coloring agent to a thermoplastic synthetic resin.

  The forming material of the laser coloring layer 2 contains a thermoplastic synthetic resin that is a matrix of the laser coloring layer 2 and a coloring agent that is dispersed in the thermoplastic resin. As a method for adjusting the forming material, for example, a method of adding a color former to a molten thermoplastic synthetic resin and stirring it can be used.

<(2) Second step>
In the second step, the optical sheet 1 for the light guide plate is formed by extruding the forming material of the laser coloring layer 2 together with the forming material of the synthetic resin layer 3.

  Specifically, the forming material for the laser color forming layer 2 and the forming material for the synthetic resin layer 3 (thermoplastic synthetic resin) are coextruded by an extruder to form the light guide plate optical sheet 1. As this co-extrusion method, a known method can be used, and examples thereof include a T-die method and an inflation method. The temperature of the forming material at the time of extrusion is preferably 150 ° C. or higher and 350 ° C. or lower, and more preferably 200 ° C. or higher and 300 ° C. or lower. When the optical sheet 1 for the light guide plate is formed by the T-die method, a T-die having an inner portion and an outlet divided into two or more layers is attached to the tip of a known single-screw extruder or biaxial extruder, and the forming material is It can be coextruded into a sheet and wound to obtain a roll sheet. Under the present circumstances, it is also possible to set it as a uniaxial stretching process by adjusting the temperature of a winding roll suitably, and adding extending | stretching to an extrusion direction. It is also possible to add steps such as sequential biaxial stretching and simultaneous biaxial stretching by adding a step of stretching the sheet in a direction perpendicular to the extrusion direction.

[Second Embodiment]
The optical sheet 11 for a light guide plate in FIG. 2 has a two-layer structure including a laser coloring layer 2 and a synthetic resin layer 3 laminated on one surface of the laser coloring layer 2. The light guide plate optical sheet 11 shown in FIG. 2 has a light guide plate that guides the light source introduced into the synthetic resin layer 3 to the surface side (upward in the drawing) when the light source is disposed on the side of the synthetic resin layer 3. Can be formed.

  The laser coloring layer 2 is the same as the light guide plate optical sheet 1 of the first embodiment. However, the thickness of the laser coloring layer 2 is preferably from 30 μm to 400 μm, and more preferably from 50 μm to 200 μm. When the thickness of the laser coloring layer 2 is less than the above range, it may be difficult to form a reflection pattern. On the other hand, when the thickness of the laser coloring layer 2 exceeds the above range, the thickness of the optical sheet 11 for the light guide plate is increased, which may contradict the thinning of the liquid crystal display device.

  The synthetic resin layer 3 is the same as the light guide plate optical sheet 1 of the first embodiment. However, the thickness of the synthetic resin layer 3 is preferably 100 μm or more and 500 μm or less, and more preferably 200 μm or more and 400 μm or less. When the thickness of the synthetic resin layer 3 is less than the above range, the reflection pattern formed on the laser coloring layer 2 may not be sufficiently protected, and the strength of the optical sheet 11 for the light guide plate may be reduced. There is. Moreover, there is a possibility that the light incident from the side surface cannot be sufficiently diffused over the entire surface. On the other hand, when the thickness of the laser coloring layer 2 exceeds the above range, the thickness of the optical sheet 11 for the light guide plate is increased, which may contradict the thinning of the liquid crystal display device.

  Moreover, it is preferable that the synthetic resin layer 3 is transparent so that light can be easily transmitted. The total light transmittance of the synthetic resin layer 3 in the optical sheet 11 for the light guide plate is preferably 85% or more, and more preferably 90% or more. When the total light transmittance of the synthetic resin layer 3 is less than the lower limit, the light loss of the light guide plate obtained using the optical sheet 1 for the light guide plate is increased, and the luminance of the backlight unit using the light guide plate is reduced. There is a risk.

  As shown in FIG. 4B, the light guide plate optical sheet 11 has a dense reflective pattern 4 that efficiently and uniformly scatters light incident from the side surface of the synthetic resin layer 3 on the surface side. The light guide plate 101 that can be suitably used for the backlight unit of the liquid crystal display device can be obtained by forming the surface of the substrate by laser irradiation (the laminated surface side of the synthetic resin layer 3). Further, as shown in FIG. 4C, the light guide plate 102 can be obtained by forming the reflection pattern 4 on the back surface side of the laser coloring layer 2.

  The light guide plate optical sheet 11 has the same advantages as the light guide plate optical sheet 1 of the first embodiment. That is, since the laser coloring layer 2 can be colored by laser irradiation, a light guide plate in which a fine reflection pattern is accurately formed can be obtained. This light guide plate can achieve uniform brightness and can be made thinner than a light guide plate in which a reflection pattern is formed by processing a conventional physical shape.

  In addition, the manufacturing method of the said optical sheet 11 for light guide plates can be made to be the same as that of the optical sheet 1 for light guide plates of said 1st embodiment.

[Third embodiment]
The optical sheet 21 for a light guide plate in FIG. 3 has a three-layer structure including a laser coloring layer 12 and two synthetic resin layers 13 laminated on both surfaces of the laser coloring layer 12.

  Since the laser coloring layer 12 and the synthetic resin layer 13 are the same as the laser coloring layer 2 and the synthetic resin layer 3 of the light guide plate optical sheet 1 of the first embodiment, the description thereof is omitted.

  The light guide plate optical sheet 21 is formed by forming a precise reflection pattern on the laser color forming layer 12 by laser irradiation that efficiently and uniformly scatters light incident from the side surface of the light guide plate optical sheet 21 to the surface side. A light guide plate for a backlight unit of a liquid crystal display device can be obtained.

  The reflection pattern can be formed along one surface of the laser coloring layer 12 where the synthetic resin layer 13 is laminated.

  The light guide plate in which a reflection pattern is formed on the laser color developing layer 12 of the optical sheet 21 for the light guide plate can introduce light from the light source from the side surface of the laser color developing layer 12. It is also possible to introduce light from the light source from the side of either layer. However, when light is introduced from the synthetic resin layer 13, if the light is introduced from the synthetic resin layer 13 having a large distance to the reflection pattern, the attenuation of the light may increase and the luminance may decrease. It is preferable to make it enter from the synthetic resin layer 13 with small distance. In addition, when light is incident from the synthetic resin layer 13 laminated on the surface of the laser coloring layer 12, the synthetic resin layer 13 laminated on the back surface of the laser coloring layer 12 preferably has the above-described light reflectivity.

  The light guide plate optical sheet 21 has the same effect as the light guide plate optical sheet 1 of the first embodiment. That is, the light guide plate optical sheet 21 can color the laser coloring layer 12 by laser irradiation, and therefore can be accurately formed on the laser coloring layer 12 even with a fine reflection pattern. When the light guide plate optical sheet 21 having such a fine reflection pattern is used as the light guide plate of the backlight unit, the light beam introduced into the light guide plate can be accurately reflected by the reflection pattern. For this reason, the light guide plate using the optical sheet 21 for the light guide plate is more uniform in luminance than the light guide plate in which the reflection pattern is formed by conventional printing, and the reflection pattern is obtained by processing the conventional physical shape. Compared to the light guide plate on which is formed, the thickness can be reduced.

  The optical sheet 21 for the light guide plate is also provided with a synthetic resin layer 13 on both sides of the laser coloring layer 12 and thus has higher dimensional stability. For this reason, the occurrence of curling, heat shrinkage, and the like during laser irradiation can be suppressed, and the accuracy of the position and shape of the reflection pattern can be kept high. As a result, a high luminance uniformity effect can be obtained.

  In addition, the said optical sheet 21 for light-guide plates can be manufactured by coextruding the formation material of each layer similarly to the optical sheet 1 for light-guide plates of said 1st embodiment.

<Other embodiments>
The optical sheet for a light guide plate of the present invention is not limited to the above-described embodiment, and may be the following embodiment.

  In the above-described embodiment, the optical sheet for a light guide plate having a multilayer structure has been described. However, an optical sheet for a light guide plate composed of a single layer of a laser coloring layer is also within the scope of the present invention.

  Conversely, the optical sheet for a light guide plate of the present invention may include two or more laser coloring layers. Also, three or more synthetic resin layers may be laminated. A plurality of these layers can be stacked as long as the transmittance is not reduced.

  In the manufacturing method of the optical sheet for a light guide plate described above, a sheet is formed by extrusion. However, the optical sheet for a light guide plate in the present invention can be manufactured by other methods. As a method for forming the optical sheet for the light guide plate other than the extrusion, one layer is formed by, for example, a solution casting method (solution casting method), a calendering method, a compression molding method, etc. Examples of the layer coating method include a roll coater, a bar coater, a blade coater, a spin coater, a gravure coater, a flow coater, an air knife, and a spray. It is also possible to use a method in which each layer is formed independently and then laminated with an adhesive or the like.

  As described above, since the optical sheet for a light guide plate of the present invention can form a desired reflection pattern easily and reliably, it is possible to obtain a thin light guide plate having an excellent luminance uniformity effect, and a liquid crystal display device It can use suitably for the backlight unit of. The optical sheet for a light guide plate can be manufactured by a known manufacturing method.

1, 11, 21 Optical sheet for light guide plate 2 Laser coloring layer 3 Synthetic resin layer 4 Reflective pattern 12 Laser coloring layer 13 Synthetic resin layer 100, 101, 102 Light guiding plate

Claims (9)

It has a laser coloring layer that develops color by laser irradiation.
The optical sheet for a light guide plate, wherein the laser coloring layer contains a matrix synthetic resin and a color former dispersed in the synthetic resin.   The optical sheet for a light guide plate according to claim 1, further comprising a synthetic resin layer laminated on the laser coloring layer.   The optical sheet for a light guide plate according to claim 2, wherein at least one of a synthetic resin constituting the laser coloring layer and a synthetic resin constituting the synthetic resin layer is transparent.   4. The optical sheet for a light guide plate according to claim 2, comprising two or more laser coloring layers and / or synthetic resin layers. 5.   5. The optical sheet for a light guide plate according to claim 2, wherein a main component of the synthetic resin constituting the laser coloring layer and the synthetic resin constituting the synthetic resin layer is an acrylic resin.   The optical sheet for a light guide plate according to any one of claims 1 to 5, wherein the content of the color former in the laser color development layer is 2.5% by mass or less.   The optical sheet for a light guide plate according to any one of claims 1 to 6, wherein a thickness of the laser coloring layer is 550 µm or less.   The optical sheet for a light guide plate according to any one of claims 1 to 7, which is used in a backlight unit of a liquid crystal display device. A method for producing an optical sheet for a light guide plate, comprising: extruding a material containing a thermoplastic synthetic resin and a color former.

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