JP2013168288A - Light guide plate, planar light source device, transmission type image display device, and method for manufacturing light guide plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light guide plate that can reduce non-uniformity of linear luminance in a coupling part between inkjet heads.SOLUTION: In a light guide plate 1 in which a light distribution pattern composed of a plurality of light reflection dots 12a, 12b on at least one of the faces of a light guide plate base material is formed by using a printing device in which two or more of inkjet heads 5a, 5b are aligned in an alignment direction of a plurality of nozzles 51, the neighboring inkjet heads 5a, 5b are located so that a part of the plurality of nozzles 51 may be superimposed in a direction crossing the alignment direction, and in a region Ro in the light distribution pattern which is a region formed by the superimposed part of the neighboring inkjet heads, there exist in mixture the light reflection dots 12a formed by one of the inkjet heads 5a and the light reflection dots 12b formed by the other inkjet head 5b.

Description

  The present invention relates to a light guide plate, a surface light source device, a transmissive image display device, and a method of manufacturing a light guide plate.

  In general, a transmissive image display device such as a liquid crystal display device has a surface light source device that supplies planar light as a backlight using a light guide plate. As a method of the surface light source device, there are a direct type in which a light source is provided on the back side of the light guide plate and an edge light method in which a light source is provided along the side surface of the light guide plate. The edge light system is advantageous from the viewpoint of reducing the thickness of the image display device.

  In the edge light type surface light source device, light incident from the side surface of the light guide plate is reflected and diffused by the action of a light distribution pattern (for example, a light distribution pattern made of light reflecting dots) provided on the back side of the light guide plate. The light having an angle component equal to or greater than the critical angle is emitted from the emission surface of the light guide plate, thereby supplying planar light. In order to make the luminance of the light emitting surface uniform, the light guide plates described in Patent Documents 1 and 2 are provided with gradation in which the density of the light distribution pattern is increased from coarse to dense as the distance from the light source increases.

  Patent Document 1 also discloses a method of forming this kind of dot-like light distribution pattern by droplet discharge (for example, ink jet printing). For example, in an inkjet printing method, printing may be performed by arranging a plurality of inkjet heads in order to shorten the printing tact.

JP 2004-240294 A JP 2008-27609 A

  However, when printing is performed with a plurality of inkjet heads arranged, due to the mounting accuracy and position adjustment accuracy, linear luminance unevenness (straight irregularity) occurs at the connection portion between the inkjet heads. In this regard, much time and labor are required to adjust the position of the inkjet head with higher accuracy.

  Therefore, the present invention provides a light guide plate, a surface light source device, a transmissive image display device, and a method of manufacturing the light guide plate that can reduce the linear luminance non-uniformity at the connection portion between the inkjet heads. For the purpose.

  As a result of intensive studies, the inventors of the present application have arranged adjacent ink jet heads so that part of the nozzles overlap each other, and in the region of the light distribution pattern formed by the overlapping parts, the ink jet heads are formed by one ink jet head. It has been found that by mixing the light reflecting dots and the light reflecting dots formed by the other inkjet head, it is possible to reduce the linear luminance non-uniformity at the connecting portion between the inkjet heads. This prevents the portion where the distance between the light reflecting dots is increased or decreased due to the mounting accuracy and position adjustment accuracy between the inkjet heads from being aligned in a narrow range in the scanning direction of the inkjet head. This is thought to be due to the fact that he was able to.

  Therefore, the light guide plate of the present invention includes at least two of the inkjet heads in which a plurality of nozzles are arranged, and uses a printing apparatus in which the inkjet heads are arranged in the arrangement direction of the plurality of nozzles. In a light guide plate in which a light distribution pattern composed of a plurality of light reflecting dots is formed on one surface, adjacent inkjet heads in a printing apparatus are arranged so that a part of the plurality of nozzles overlap in a direction intersecting the arrangement direction. In the light distribution pattern, the region formed by the overlapping portion of the adjacent inkjet heads has a light reflection dot formed by one inkjet head and a light reflection formed by the other inkjet head. Dot is mixed.

  Further, the light guide plate manufacturing method of the present invention includes a light guide plate base using a printing apparatus that includes two or more inkjet heads in which a plurality of nozzles are arranged and in which the ink jet heads are arranged in the arrangement direction of the plurality of nozzles. In a method for manufacturing a light guide plate in which a light distribution pattern composed of a plurality of light reflecting dots is formed on at least one surface of a material, adjacent inkjet heads in a printing apparatus are arranged such that some of a plurality of nozzles intersect in the arrangement direction. It is arranged so as to overlap in the direction, and is an area in the light distribution pattern, which is formed by the overlapping part of the adjacent inkjet heads, by the light reflecting dots formed by one inkjet head and the other inkjet head. Light distribution pattern on the light guide plate base material so that the light reflection dots to be formed are mixed To print.

  According to the light guide plate and the method for manufacturing the light guide plate, the adjacent inkjet heads are arranged so that the nozzles partially overlap each other, and one of the light distribution patterns formed by the overlapping portions has one of them. Since the light reflecting dots formed by the inkjet head and the light reflecting dots formed by the other inkjet head are mixed, the distance between the light reflecting dots is caused by the mounting accuracy and the position adjustment accuracy between the inkjet heads. It is possible to prevent the portions that become larger or the portions that become smaller from being aligned in a narrow range in the scanning direction of the inkjet head. Therefore, it is possible to reduce the linear luminance non-uniformity at the connection portion between the inkjet heads.

  It is preferable that the light reflecting dots in the region in the above-described light distribution pattern are formed by ink ejected from one of the nozzles of one and the other ink jet heads. According to this, it is possible to prevent irregularities (variations) in the shape and size of the light reflecting dots due to a slight deviation between the nozzle positions of the two inkjet heads.

  In addition, in the region in the light distribution pattern described above, the light reflecting dots formed by one inkjet head and the light reflecting dots formed by the other inkjet head are regularly arranged in a direction intersecting the arrangement direction. It may be arranged irregularly in a direction crossing the arrangement direction. According to this, the portion where the distance between the light reflecting dots is increased or decreased due to the mounting accuracy and the position adjustment accuracy between the inkjet heads is not aligned in the scanning direction of the inkjet head. Further, it is possible to reduce the non-uniformity of the linear luminance at the connecting portion between the inkjet heads.

  The surface light source device of the present invention is an edge light type surface light source device, and includes the above-described light guide plate and a light source that supplies light to the side surface of the light guide plate. According to this surface light source device, since the above-described light guide plate is provided, it is possible to reduce unevenness in luminance of the edge light type surface light source device.

  A transmissive image display device of the present invention includes the above-described surface light source device and a transmissive image display unit disposed to face the emission surface of the surface light source device. According to this transmissive image display device, since the surface light source device having the above-described light guide plate is provided, it is possible to reduce nonuniform luminance of the transmissive image display device.

  According to the present invention, it is possible to easily reduce the linear luminance non-uniformity at the connection portion between the inkjet heads. Further, it is possible to reduce non-uniform luminance of the edge light type surface light source device using the light guide plate and the transmissive image display device using the edge light type surface light source device.

It is sectional drawing which shows a transmissive image display apparatus provided with one Embodiment of the light-guide plate which concerns on this invention. It is a top view at the time of seeing the light-guide plate of this embodiment from the back side. It is a perspective view which shows one Embodiment of the manufacturing method of the light-guide plate which concerns on this invention. It is a schematic diagram which shows a part of manufacturing method of the conventional light-guide plate, and the light distribution pattern of the conventional light-guide plate. It is a schematic diagram which shows a manufacturing method of the light guide plate of this embodiment, and a part of light distribution pattern of the light guide plate of this embodiment. It is a schematic diagram which shows a manufacturing method of the light-guide plate which concerns on the modification of this invention, and a part of light distribution pattern of the light-guide plate which concerns on the modification of this invention. It is a schematic diagram which shows a manufacturing method of the light-guide plate which concerns on the modification of this invention, and a part of light distribution pattern of the light-guide plate which concerns on the modification of this invention. It is a schematic diagram which shows a manufacturing method of the light-guide plate which concerns on the modification of this invention, and a part of light distribution pattern of the light-guide plate which concerns on the modification of this invention. It is a schematic diagram which shows a manufacturing method of the light-guide plate which concerns on the modification of this invention, and a part of light distribution pattern of the light-guide plate which concerns on the modification of this invention. It is a schematic diagram which shows a manufacturing method of the light-guide plate which concerns on the modification of this invention, and a part of light distribution pattern of the light-guide plate which concerns on the modification of this invention. It is a schematic diagram which shows a part of light distribution pattern of the light-guide plate which concerns on the modification of this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

  FIG. 1 is a cross-sectional view showing a transmissive image display device including an embodiment of a light guide plate according to the present invention. The transmissive image display device 100 shown in FIG. 1 is mainly composed of a surface light source device 20 and a transmissive image display unit 30. The surface light source device 20 is an edge light type surface light source device including a light guide plate 1 having a light guide plate base material 11 and a light source 3 that is provided on the side of the light guide plate 1 and supplies light to the light guide plate 1. .

The light guide plate substrate 11 has a substantially rectangular parallelepiped shape, having an emission surface S1, the opposite side of the back S2 of the exit surface S1, and four end surfaces S3 ₁ to S3 ₄ intersecting the emitting surface S1 and the back surface S2 . In the present embodiment, the four end surfaces S3 _{1 to} S3 ₄ are substantially orthogonal to the emission surface S1 and the back surface S2.

  The light guide plate substrate 11 is made of a translucent material, and is preferably a poly (meth) acrylic acid alkyl resin sheet, a polystyrene sheet, or a polycarbonate resin sheet, and among these, a polymethyl methacrylate resin sheet (PMMA resin) Sheet) is preferred. The light guide plate substrate 11 may include diffusing particles. The surface (light exit surface S1) opposite to the surface (back surface S2) on which the light reflecting dots 12 of the light guide plate substrate 11 are formed may be a flat surface as in the present embodiment, but has an uneven shape. You may do it. In addition, it is preferable that the thickness of the light-guide plate base material 11 is 1.0 mm or more and 4.5 mm or less.

  The back surface S2 of the light guide plate substrate 11 may be a surface on which substantially the entire back surface S2 has been subjected to a liquid repellent treatment. The liquid repellent treatment applied to the back surface S2 is a liquid repellent treatment so that the contact angle when water drops are dropped on the back surface S2 is 80 degrees to 130 degrees, preferably the contact angle is 85 degrees to 120 degrees, more preferably The liquid repellent treatment is such that the contact angle is 90 to 110 degrees. In the present embodiment, the contact angle is a static contact angle.

  A plurality of light reflecting dots 12 are formed on the back surface S2 side of the light guide plate substrate 11. That is, the light guide plate 1 further includes a plurality of light reflecting dots 12 provided on the back surface S2 side. The maximum thickness of each light reflecting dot 12 is, for example, 20 μm or less.

  As shown in FIG. 2, the plurality of light reflecting dots 12 are arranged on the back surface S2 so as to be separated from each other. FIG. 2 is a plan view when the light guide plate is viewed from the back side. In FIG. 2, the light source 3 is also shown for convenience of explanation. As shown in FIG. 2, the light reflecting dots 12 are small on the light incident side near the light source 3 and increase as the distance from the light source 3 increases. Since the light reflecting dots 12 are formed at lattice points regularly arranged two-dimensionally over the entire surface of the back surface S2, the coverage of the light reflecting dots 12 is low on the light incident part side close to the light source 3, and the light source 3 It gets higher as you leave. The light reflecting dots 12 are preferably not connected to each other, but may actually be connected. In FIG. 2, the size and number of the light reflecting dots 12 are changed for convenience of explanation. As will be described later, the number and arrangement pattern of the light reflecting dots 12 are efficient for uniform planar light. To be emitted from the emission surface S1.

The light source 3 is disposed on the side of a pair of end faces S3 ₁ and S3 ₂ facing each other. The light source 3 may be a linear light source such as a cold cathode fluorescent lamp (CCFL), but is preferably a point light source such as an LED. In this case, as shown in FIG. 2, a plurality of point light sources are arranged along two sides facing each other among the four sides of the translucent resin sheet 11 constituting, for example, the rectangular back surface S2. It is particularly advantageous to combine light-reflecting dots 12 formed by inkjet ink, which will be described later, and LEDs in order to obtain light with a natural color tone.

  As shown in FIG. 1, the transmissive image display unit 30 is disposed to face the light guide plate 1 on the light exit surface S1 side of the light guide plate 1. The transmissive image display unit 30 is, for example, a liquid crystal display unit having a liquid crystal cell.

In the above configuration, the light output from the light source 3 enters the light guide plate base 11 from the end faces S3 ₁ and S3 ₂ . The light incident on the light guide plate substrate 11 is mainly reflected from the exit surface S1 by being irregularly reflected by the light reflecting dots 12. The light emitted from the emission surface S <b> 1 is supplied to the transmissive image display unit 30. The number and arrangement pattern of the light reflecting dots 12 are adjusted so that uniform planar light is efficiently emitted from the emission surface S1.

  Next, a method for manufacturing the light guide plate 1 will be described.

  The manufacturing apparatus 200 for the light guide plate 1 shown in FIG. 3 includes a transport means 40 for transporting the light guide plate base material 11, an inkjet head unit 5, and a UV lamp 7. You may install the inspection apparatus 9 as needed. The inkjet head unit 5, the UV lamp 7, and the inspection device 9 are arranged in this order from the upstream side in the movement direction A of the light guide plate substrate 11.

  The light guide plate substrate 11 is conveyed continuously or intermittently along the direction A by the conveying means 40. The light guide plate substrate 11 may be cut in advance according to the size of the light guide plate to be manufactured, or the light reflecting dots 12 are formed on the long light guide plate substrate 11, and then the light guide plate substrate 11. May be cut. The transport unit 40 in the present embodiment is a table shuttle, but the transport unit is not limited to this, and may be, for example, a belt conveyor, a roller, or air floating transfer.

  On the surface S0 of the light guide plate substrate 11, droplet-shaped inkjet ink is pattern-printed in a dot shape by the inkjet head unit 5 supported by the support unit 41. At this time, the pattern printing is performed so that the droplet-shaped inkjet inks dropped on the surface S0 are separated from each other.

  The inkjet head unit 5 has a surface S0 (back surface S2) of the light guide plate substrate 11 over the entire width direction (direction perpendicular to A) of the region where the light reflecting dots 12 are formed on the surface S0 of the light guide plate substrate 11. ) And a plurality of nozzles in one row or two rows fixed in alignment. Droplet-like ink ejected from the plurality of nozzles by the ink jet method is simultaneously printed all over the entire width direction of the light guide plate substrate 11. Preferably, ink is printed while continuously moving the light guide plate substrate 11 at a constant speed. Alternatively, printing is performed in a state where the light guide plate base material 11 is stopped, and the light guide plate base material 11 is moved to the next printing position and then stopped, and is configured from a plurality of rows of dots. Ink can also be efficiently printed with a pattern.

  The moving speed of the light guide plate substrate 11 is adjusted so that ink is printed appropriately. In the case of this embodiment, as shown in FIGS. 3 to 5, the inkjet head unit 5 includes a plurality of inkjet heads 5 a to 5 c each having a plurality of nozzles 51. The plurality of inkjet heads 5a to 5c are arranged in a direction orthogonal to the direction A in which the light guide plate base material 11 is conveyed, and are connected via a fixing member 52 so that the ends of the inkjet heads 5a to 5c overlap in the conveyance direction A. Yes. 4 and 5 show only the adjacent inkjet heads 5a and 5b in order to clarify the characteristics of the present invention.

  In the case of the present embodiment, the ink can be collectively printed over the entire width direction of the light guide plate substrate 11 with the plurality of nozzles of the inkjet head unit 5 fixed. Thereby, the productivity of the light guide plate 1 is dramatically improved as compared with the case where ink is sequentially printed while moving the movable nozzle along the width direction of the light guide plate substrate 11.

  In particular, when manufacturing a large-sized light guide plate 1 having a short side length of 200 mm or more and 1000 mm or less of the light guide plate substrate 11, the effect of improving the productivity by the method of the present embodiment is great. Furthermore, according to the ink jet method, even the light reflecting dots 12 having a maximum diameter of 100 μm or less can be easily and accurately formed. When the light guide plate substrate 11 is thin, the light reflecting dots 12 may be seen through from the exit surface S1 side, but this can be prevented by making the light reflecting dots 12 small.

  The nozzles of the inkjet head unit 5 are connected to the ink supply unit 50 via a conduit 55. The ink supply unit 50 includes, for example, an ink tank in which ink is stored and a pump for sending out ink. The plurality of conduits 55 may be connected to a single ink tank, or may be connected to a plurality of ink tanks.

  The inkjet ink used for inkjet printing to form the light reflecting dots 12 may be an ultraviolet curable ink containing a pigment, a photopolymerizable component, and a photopolymerization initiator, or an aqueous ink or A solvent-based ink or the like may be used. Note that the inkjet ink does not necessarily contain a pigment.

  The pigment is preferably at least one of calcium carbonate particles, barium sulfate particles and titanium dioxide particles. The 50% cumulative particle diameter D50 of each of the calcium carbonate particles, barium sulfate particles and titanium dioxide particles is 50 to 3000 nm, more preferably 100 to 1500 nm, and still more preferably 150 to 600 nm. Calcium carbonate particles, barium sulfate particles, and titanium dioxide particles having a cumulative 50% particle diameter D50 in the range of 50 to 3000 nm can be obtained by appropriately selecting from commercially available products based on the particle size distribution. The content ratio of the pigment in the ink is usually about 0.5 to 15.0% by mass based on the total mass of the ink. An ink using a pigment which is at least one of calcium carbonate particles, barium sulfate particles and titanium dioxide particles is an ink using an inorganic substance. In consideration of the storage stability of the ink using such an inorganic substance, that is, the inorganic pigment sedimentation property, it is more preferable as the ink to use calcium carbonate particles having the smallest specific gravity among the three particles as the pigment.

  The viscosity of the inkjet ink at 50 ± 10 ° C. is preferably 5.0 to 15.0 mPa · s, more preferably 8.0 to 12.0 mPa · s. The viscosity of inkjet ink can be adjusted with the weight average molecular weight and / or content rate of aliphatic urethane (meth) acrylate, for example. When the weight average molecular weight and the content ratio of the aliphatic urethane (meth) acrylate are increased, the viscosity of the ink tends to increase.

The surface tension of the inkjet ink at 25.0 ° C. is preferably 25.0 to 45.0 mJ / m ² , more preferably 25.0 to 37.0 mJ / m ² . The surface tension of the ink-jet ink can be adjusted, for example, by blending a surfactant such as silicon and fluorine into the ink.

  The printed ink is cured in the region 70 by the UV lamp 7 supported by the support portion 42. Thereby, the light reflecting dots 12 made of the cured ink are formed.

  Thereafter, the light guide plate 1 is obtained through a process of inspecting the state of the formed light reflecting dots 12 by the inspection device 9 supported by the support portion 43. The light guide plate 1 is cut into a desired size as necessary. As in this embodiment, the light guide plate does not necessarily have to be continuously inspected by the inspection device provided on the downstream side of the inkjet head unit, and the light guide plate may be inspected offline by a separately prepared inspection device. it can. Alternatively, the inspection of the light guide plate by the inspection device may be omitted.

  Usually, the print pattern of the ink to be the light reflecting dots 12 is designed to have a desired pattern such that uniform planar light is efficiently emitted from the emission surface S1. In this case, since the arrangement pattern of the plurality of light reflecting dots 12 is substantially a desired pattern, the light supplied from the light source 3 to the translucent resin sheet 11 can be efficiently extracted from the light emitting surface S1. As a result, light can be emitted from the light exit surface S1 of the light guide plate 1 with higher luminance. Moreover, since the arrangement pattern of the light reflecting dots 12 is a desired pattern as described above, light can be emitted almost uniformly from the light emitting surface S1.

  Since the surface light source device 20 includes the light guide plate 1, it can emit light with higher luminance. Further, since the transmissive image display device 100 is illuminated with light having higher luminance emitted from the surface light source device 20, it is possible to display an image with good display quality such that the contrast can be displayed more clearly.

  Here, as shown in FIG. 4, when a plurality of inkjet heads 5 a and 5 b are arranged and printed, a linear luminance is generated in the connection portion C between the inkjet heads 5 a and 5 b due to the mounting accuracy and the position adjustment accuracy. Non-uniformity (straight unevenness) occurs.

  Therefore, in the present embodiment, as shown in FIG. 5, in the adjacent inkjet heads 5a and 5b, a part of the plurality of nozzles 51 is overlapped in the transport direction A (scanning direction, direction intersecting the nozzle arrangement direction). Is arranged. And in the overlap area | region Ro of the light distribution pattern formed of this overlapping part, the light reflection dot 12a formed by the inkjet head 5a and the light reflection dot 12b formed by the inkjet head 5b are mixed, Print the light distribution pattern.

  Specifically, in the overlapping region Ro of the light distribution pattern, the row of the light reflecting dots 12a and the row of the light reflecting dots 12b along the carrying direction A cross in the carrying direction A (nozzle arrangement direction). The light distribution pattern is printed so as to be alternately arranged. That is, in the present embodiment, the light reflecting dots 12a and 12b are regularly arranged in the transport direction A in the overlapping region Ro of the light distribution pattern. Note that the rows of the light reflecting dots 12a and the rows of the light reflecting dots 12b may be alternately arranged one by one as shown in FIG. 5, or may be alternately arranged in units of a plurality of columns.

  Thus, according to the light guide plate 1 and the method of manufacturing the light guide plate 1 of the present embodiment, as shown in FIG. The light reflecting dots 12a formed by one inkjet head 5a and the other are disposed in the overlapping region Ro of the light distribution pattern formed by the overlapping portions. Since the light reflection dots 12b formed by the inkjet head 5b are mixed, the distance between the light reflection dots 12a and 12b is increased due to the mounting accuracy and the position adjustment accuracy between the inkjet heads 5a and 5b. Or smaller portions are aligned in the transport direction A (scanning direction of the ink jet heads 5a and 5b). It is possible to prevent the Bukoto. Accordingly, it is possible to reduce the linear luminance non-uniformity at the connection portion C between the inkjet heads 5a and 5b.

  By the way, when the light reflecting dots in the overlap region Ro of the light distribution pattern are formed by the ink ejected from both nozzles of the adjacent inkjet heads 5a and 5b, it is caused by the mounting accuracy and the position adjustment system of the inkjet head. As a result, the size of the light reflecting dots may increase, or the shape of the light reflecting dots may be distorted. However, according to the present embodiment, the light reflecting dots in the overlapping region Ro of the light distribution pattern are formed by ink ejected from one of the nozzles of the one inkjet head 5a and the other inkjet head 5b. Therefore, it is possible to prevent irregularities (variations) in the shape and size of the light reflecting dots due to slight deviations in the nozzle positions of the two inkjet heads 5a and 5b.

  The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, in the present embodiment, in the overlap region Ro of the light distribution pattern, the rows of the light reflecting dots 12a and the rows of the light reflecting dots 12b along the carrying direction A are alternately arranged in a direction intersecting the carrying direction A. As shown in FIG. 6, in the overlapping region Ro of the light distribution pattern, the row of the light reflection dots 12a and the light reflection dots 12b along the direction intersecting the transport direction A are formed as shown in FIG. The light distribution pattern may be printed so that the columns are alternately arranged in the transport direction A. Also in this modified example, the light reflecting dots 12a and 12b are regularly arranged in the transport direction A in the overlapping region Ro of the light distribution pattern. In addition, the row | line | column of the light reflection dot 12a and the row | line | column of the light reflection dot 12b may be alternately arrange | positioned for every 1 row as shown in FIG.

  Further, as shown in FIG. 7, in the overlapping region Ro of the light distribution pattern, the light reflecting dots 12 a and the light reflecting dots 12 b are alternately arranged in the transport direction A and in a direction intersecting the transport direction A. Alternatively, the light distribution pattern may be printed so as to be alternately arranged. Also in this modified example, the light reflecting dots 12a and 12b are regularly arranged in the transport direction A in the overlapping region Ro of the light distribution pattern. The light reflecting dots 12a and the light reflecting dots 12b may be alternately arranged one by one as shown in FIG. 7, or may be alternately arranged in a plurality of units.

  Further, as shown in FIG. 8, in the overlap region Ro of the light distribution pattern, the light reflecting dots 12a and the light reflecting dots 12b are irregularly arranged in the transport direction A and intersect the transport direction A. The light distribution pattern may be printed so as to be irregularly arranged in the direction.

  In addition, as shown in FIG. 9, in the overlapping region Ro of the light distribution pattern, the light reflecting dots 12a and the light reflecting dots 12b are regularly arranged in the transport direction A and intersect with the transport direction A. In addition, the light distribution pattern may be printed so as to be regularly arranged.

  Further, in the above-described embodiment and modification, the ink jet head 5a forms the same light reflecting dot 12a and the ink jet head 5b forms the same light reflecting dot 12b. However, as shown in FIG. In addition, the features of the present invention can be applied to a form in which the inkjet head 5a forms different light reflecting dots 12a and 13a and the inkjet head 5b forms different light reflecting dots 12b and 13b. For example, in FIG. 10, the inkjet head 5 a alternately forms a row of light reflecting dots 12 a and a row of light reflecting dots 13 a along the transport direction A in a direction intersecting the transport direction A. 5b alternately forms a row of light reflecting dots 12b and a row of light reflecting dots 13b along the carrying direction A in a direction intersecting the carrying direction A. Also in this case, in the overlapping region Ro of the light distribution pattern, the light reflecting dots 12a, the light reflecting dots 13a, the light reflecting dots 12b, and the light reflecting dots 13b are regularly (or alternatively) in the transport direction A. The light distribution pattern may be printed so that the light distribution pattern is arranged irregularly and regularly (or irregularly) in a direction intersecting the conveyance direction A. This technique can also be achieved by arranging two or more inkjet heads side by side or using an inkjet head having two or more nozzle rows.

  Further, in the above-described embodiment and the modification, the light distribution pattern by the light reflecting dots 12a and 12b (and 13a and 13b) having one kind of size is exemplified. However, as shown in FIG. The light reflecting dots having the following sizes may be arranged in an irregular order, and the light reflecting dots having three or more kinds of sizes may be arranged in an irregular order.

  As described above, when the light reflecting dots having two or more kinds of sizes are arranged in an irregular order, the gradation change due to the light reflecting dots can be reduced. As a result, it is possible to reduce unevenness in luminance in a region where the coverage of the light distribution pattern is low, such as the light incident part side near the light source. In particular, there is an effect in individual regions where the concealment rate by a plurality of light reflecting dots is 50% or less.

Further, in the present embodiment, the example in which the light source 3 is arranged respectively on the end surface S3 _1, S3 ₂ opposed sides to each other. However, the light source 3 should just be arrange | positioned at the side of the at least 1 end surface which cross | intersects the light-projection surface S1 (or back surface S2) of the translucent resin sheet 11. FIG.

The light guide plate 1 according to the embodiment of the present invention was prototyped as an example, and a comparative evaluation with the light guide plate of the comparative example was performed. The light guide plates of Examples and Comparative Examples are as follows.
Example 1

  A PMMA resin sheet having a size of 600 mm × 345 mm was prepared as a translucent resin sheet, and a light guide plate was produced using an ultraviolet curable inkjet ink that did not contain a pigment.

Specifically, the masking film was peeled from the PMMA resin sheet, and the light distribution pattern shown in FIG. 5 was ink jet printed on the peeled surface with an ultraviolet curable ink jet ink. As the ink jet head, one having a distance between nozzles of about 84.5 μm was used. Further, the mounting accuracy and the position adjustment accuracy when a plurality of inkjet heads are connected and arranged are about 15 μm. Next, the printed inkjet ink was irradiated with ultraviolet rays to photocur the ink. Specifically, after ultraviolet curable inkjet ink was pattern-printed on a PMMA resin sheet, the ink was photocured by irradiation with ultraviolet rays after 6 seconds. As a result, the light guide plate of Example 1 in which a uniform light distribution pattern with a coverage of 48% was formed was obtained.
(Example 2)

A light guide plate of Example 2 was obtained in the same manner as Example 1 except that the light distribution pattern shown in FIG. 6 was formed.
(Example 3)

A light guide plate of Example 3 was obtained in the same manner as Example 1 except that the light distribution pattern shown in FIG. 7 was formed.
Example 4

A light guide plate of Example 4 was obtained in the same manner as Example 1 except that the light distribution pattern shown in FIG. 8 was formed.
(Example 5)

A light guide plate of Example 5 was obtained in the same manner as Example 1 except that the light distribution pattern shown in FIG. 9 was formed.
(Example 6)

A light guide plate of Example 6 was obtained in the same manner as Example 1 except that the light distribution pattern shown in FIG. 10 was formed.
(Comparative Example 1)

  A light guide plate of Comparative Example 1 was obtained in the same manner as Example 1 except that the light distribution pattern shown in FIG. 4 was formed.

In this evaluation, in the television unit using LEDs as light sources, the light guide plates of Examples 1 to 6 and Comparative Example 1 were incorporated in place of the diffusion film, the prism film, the DBEF, and the light guide plate, respectively. Then, these television units were turned on, and stripes (non-uniformity of linear brightness) were visually evaluated (no diffusion film, prism film, and DBEF film). Moreover, the stripe unevenness when using a diffusion film was also visually evaluated (with film). These evaluation results are shown in Table 1.

  According to this evaluation result, adjacent inkjet heads are arranged so that part of the nozzles overlap, and in the overlapping region of the light distribution pattern formed by the overlapping parts, the light reflecting dots formed by one inkjet head and It has been found that by mixing the light reflecting dots formed by the other ink jet head, it is possible to reduce the uneven stripes (nonuniformity of the linear luminance) at the connection portion between the ink jet heads.

DESCRIPTION OF SYMBOLS 1 ... Light guide plate, 3 ... Light source, 11 ... Light guide plate base material, 12 ... Light reflection dot, 20 ... Surface light source device, 30 ... Transmission type image display part, 100 ... Transmission type image display apparatus (liquid crystal display device), S0 ... Surface (one surface treated with liquid repellency), S1 ... Emission surface, S2 ... Back (one surface treated with liquid repellency), S3 _{1 to} S3 ₄ ... End faces, 5a, 5b ... Adjacent inkjet heads, 51 ... Nozzles, 12a ... light reflecting dots formed by one ink jet head, 12b ... light reflecting dots formed by the other ink jet head, Ro ... overlapping regions of the light distribution pattern.

Claims (8)

A plurality of light sources are provided on at least one surface of the light guide plate base material using a printing apparatus that includes two or more ink jet heads in which a plurality of nozzles are arranged, and the ink jet heads are arranged in the arrangement direction of the plurality of nozzles. In the light guide plate in which the light distribution pattern consisting of reflective dots is formed,
Adjacent inkjet heads in the printing apparatus are arranged such that some of the plurality of nozzles overlap in a direction intersecting the arrangement direction,
A light reflection dot formed by one ink jet head and a light reflection dot formed by the other ink jet head are regions in the light distribution pattern, which are formed by overlapping portions of the adjacent ink jet heads. Are mixed,
Light guide plate.   The light guide plate according to claim 1, wherein the light reflecting dots in the region of the light distribution pattern are formed by ink ejected from one of the nozzles of the one and the other ink jet heads.   In the region of the light distribution pattern, light reflecting dots formed by one inkjet head and light reflecting dots formed by the other inkjet head are regularly arranged in a direction crossing the arrangement direction. The light guide plate according to claim 1 or 2.   In the region of the light distribution pattern, light reflecting dots formed by one inkjet head and light reflecting dots formed by the other inkjet head are irregularly arranged in a direction intersecting the arrangement direction. The light guide plate according to claim 1 or 2. A plurality of light sources are provided on at least one surface of the light guide plate base material using a printing apparatus that includes two or more ink jet heads in which a plurality of nozzles are arranged, and the ink jet heads are arranged in the arrangement direction of the plurality of nozzles. In a method of manufacturing a light guide plate in which a light distribution pattern composed of reflective dots is formed,
Adjacent inkjet heads in the printing apparatus are arranged so that some of the plurality of nozzles overlap in a direction intersecting the arrangement direction,
A light reflection dot formed by one ink jet head and a light reflection dot formed by the other ink jet head are regions in the light distribution pattern, which are formed by overlapping portions of the adjacent ink jet heads. And the light distribution pattern is printed on the light guide plate base material,
Manufacturing method of light guide plate.   A light guide plate manufactured by the method for manufacturing a light guide plate according to claim 5. The light guide plate according to any one of claims 1 to 4 and claim 6,
A light source for supplying light to a side surface of the light guide plate;
An edge light type surface light source device. A surface light source device according to claim 7;
A transmissive image display unit disposed opposite to the emission surface of the surface light source device;
A transmissive image display device.