KR20140049549A - Method for manufacturing optical sheet - Google Patents

Abstract

The present invention provides a method for manufacturing an optical sheet and an apparatus for producing an optical sheet by suppressing generation of lines on the printing surface when printing a dot pattern on the back surface of the optical sheet. The ink 54 is sprayed from the nozzle 51 onto the original plate 60 of the light guide plate. At this time, the non-printed surface of the original plate 60 is suction-absorbed to eliminate warpage, the gap distance D, which is the distance between the nozzle 51 and the original plate 60, is adjusted to 2.8 mm or less, and ink is sprayed to form a dot pattern. Print

Description

Manufacturing method of optical sheet {METHOD FOR MANUFACTURING OPTICAL SHEET}

The present invention relates to an optical sheet, a manufacturing method and a manufacturing apparatus thereof, and a surface light source device and a transmissive image display device using the optical sheet.

As the backlight used as the surface light source device of a liquid crystal display (transmissive image display device), what is called a direct type | mold or an edge light type is known. Among these, the direct type surface light source device arranges light sources, such as a cold cathode tube and LED, on the back side of a light guide plate, and emits the light incident from the back surface of the light guide plate to the front side.

On the other hand, the edge light type surface light source device arranges light sources, such as a cold cathode tube and LED, in the side surface of the light guide plate which is a transparent plate, and emits the light incident from the side surface of the light guide plate to the front side. As a conventional backlight, many direct-type surface light source devices have been used from the viewpoint of increasing the luminance. However, in recent years, the use of a thin and high brightness LED light source is increasing, but with the thinning of a liquid crystal display, the use ratio of the edge light type surface light source device is increasing.

 In the light guide plate of the edge light type surface light source device, dot printing is performed on the rear surface so that the light incident from the side surface is diffusely reflected on the rear surface and emitted from the front surface. As a method of performing dot printing on the back surface of a light guide plate, the method by screen printing is known (for example, refer patent document 1). However, when dot printing is performed by screen printing, it is necessary to prepare individual plates for each pattern. For this reason, there is a problem that the degree of freedom is low in screen printing.

On the other hand, dot pattern printing using inkjet is known as a method other than screen printing (for example, refer patent document 2). By using the inkjet, it is not necessary to prepare a large number of plates, and thus the degree of freedom can be increased so that even if the printing pattern is diversified, it is possible to cope.

Japanese Patent Laid-Open No. 7-49421 Japanese Patent Publication No. 2006-136867

By the way, high precision, for example, 150 dpi or more has been required for the surface light source device using this kind of light guide plate.

In addition, liquid crystal display displays have recently been applied to televisions and the like, so that the light guide plate needs to be enlarged and thinned. In manufacturing the light guide plate, the light guide plate original plate is ideally a plate without warping, but in practice, warpage and bending occur due to moisture absorption during storage, uneven heating, and the like. With the increase in size and thickness of the light guide plate, it is assumed that the influence of this warpage becomes remarkable.

 However, about the light guide plate disclosed in the said patent document 2, the request for high precision and the request for the improvement of the curvature of the light guide plate original plate were not high. For this reason, in the light guide plate using the dot pattern printing disclosed in the patent document 2, when the dot pattern printing is performed, streaks appear on the printing surface due to the unevenness of the distance between dots and the disturbance of the dot shape. There was a case. Thus, when a line shows on a printing surface, there existed a problem that the quality deteriorated, such as a liquid crystal display using an optical sheet.

 Then, the subject of this invention is manufacturing method of the optical sheet which can aim at the quality improvement of the product using an optical sheet by suppressing generation | occurrence | production of the line | wire in a printing surface, when performing dot pattern printing on the back surface of an optical sheet. And providing a manufacturing apparatus.

The present invention is an optical sheet which emits light incident from a light incident surface from a light exit surface intersecting the light incident surface, wherein a dot pattern is formed by ejecting ink from a nozzle to the back surface of the original plate of the optical sheet. As a method of manufacturing a printed optical sheet, a non-printed surface of a disc is suction-absorbed to eliminate warpage of the disc, the distance between the nozzle and the disc is adjusted to 2.8 mm or less, and ink is sprayed to print a dot pattern.

In general, in the case of forming a low-precision dot pattern, even when the distance between the nozzle and the original plate is far from each other, a line (a phenomenon in which the printing dots are formed in a straight line) rarely occurs in the printed pattern. The gap distance was taken large to avoid. However, when forming a high precision dot pattern, when a gap distance is large, a line may generate | occur | produce in a printed pattern, and this line | wire has a problem that the quality of a product falls. In this regard, in the manufacturing method of the optical sheet according to the present invention, when performing dot pattern printing, the distance between the nozzle and the disc is adjusted to 2.8 mm or less by suction-absorbing the non-printed surface of the disc to eliminate warpage. By suction-absorbing the non-printed surface of the original plate and eliminating warpage, the distance between the nozzle and the original plate is adjusted to 2.8 mm or less, so that generation of lines on the printing surface of dot pattern printing in the optical sheet can be suppressed. Therefore, quality improvement of the product using an optical sheet can be aimed at. On the other hand, the more preferable distance of a nozzle and a disc at the time of dot pattern printing is 1.8 mm or less, and a more preferable range is 1.0 mm or less.

Here, it can be set as the aspect in which the distance of a nozzle and an original when printing a dot pattern is adjusted to 2.8 mm or less.

The disc used for optical sheets, such as a light-guide plate, does not become completely planar, and a little curvature arises in many cases. If the distance between the inkjet nozzle and the original plate becomes too long under the influence of the warpage, streaks may be generated on the printing surface. In this regard, when dot pattern printing is performed, suction of the non-printed surface of the original plate is sucked to eliminate warpage, and the distance between the nozzle and the original plate is adjusted to 2.8 mm or less, thereby more stably suppressing the generation of lines on the printed surface. can do. As a result, the quality improvement of the product using an optical sheet can be aimed at further.

Moreover, it can be set as the aspect whose disc is 4.5 mm or less in thickness.

Thus, it is suitable that the thickness of a disc is adjusted to 4.5 mm or less. Moreover, it is more suitable that the thickness of a disc is adjusted to 2.0 mm or less.

Moreover, when printing a dot pattern, an original plate is mounted on the table, and it can be set as the aspect that the distance of a nozzle and a table becomes below the distance which added the thickness of an original plate to 2.8 mm.

In this way, by adding the thickness of the original, the distance between the nozzle and the original can be managed by the distance between the table and the nozzle on which the original is placed.

It can also be set as the optical sheet manufactured by the manufacturing method of an optical sheet, and can also be set as the surface light source device provided with the light source arrange | positioned at the side of the light-incidence surface of this optical sheet. In addition, it is also possible to provide a transmissive image display device comprising the surface light source device and provided with a transmissive image display unit disposed to face the light exit surface of the optical sheet and irradiated with light emitted from the light source to display an image.

The present invention is an optical sheet which emits light incident from a light incident surface from a light exit surface intersecting the light incident surface, wherein a dot pattern is formed by ejecting ink from a nozzle to the back surface of the original plate of the optical sheet. A device for manufacturing a printed optical sheet, which suction-absorbs the non-printed surface of a disc to eliminate warpage of the disc, and the distance between the nozzle and the table on which the disc is placed is adjusted to be 2.8 mm or less plus the thickness of the disc. And the optical sheet manufacturing apparatus which prints a dot pattern by spraying ink.

 According to the manufacturing method and the manufacturing apparatus of the optical sheet which concerns on this invention, when the dot pattern printing is performed on the back surface of an optical sheet, the generation | occurrence | production of the line in a printing surface can be suppressed, and the quality of the product using an optical sheet can be aimed at. Can be.

1 is an exploded side cross-sectional view schematically showing a transmissive image display device using a light guide plate according to an embodiment.
2 is a plan view schematically showing a transmissive image display device using the light guide plate according to the embodiment.
3 is a perspective view illustrating a light guide plate manufacturing apparatus according to an embodiment.
It is a side view which shows typically the relationship of the inkjet nozzle and the original plate of a light guide plate at the time of dot pattern printing.
5 is a plan view showing a conveyance belt on which the light guide plate is placed when dot pattern printing is performed.
FIG. 6: (a), (b) is a figure which shows another arrangement pattern of a printing dot.

EMBODIMENT OF THE INVENTION Hereinafter, preferred embodiment of this invention is described with reference to drawings. In addition, in each embodiment, the same code | symbol may be attached | subjected to the same element and the overlapping description may be abbreviate | omitted. In addition, the dimension ratio of drawing does not necessarily correspond with what is demonstrated for convenience of illustration.

In this invention, dot pattern printing in the manufacturing method of the light-guide plate which is an optical sheet is mainly characteristic in the surface light source device used for transmissive image display apparatuses, such as a liquid crystal display device. In this embodiment, first, the structure of the liquid crystal display device including the light guide plate will be described, and then dot pattern printing in the manufacturing method of the light guide plate will be described.

1 is an exploded side cross-sectional view schematically showing a liquid crystal display using a light guide plate according to a first embodiment of the present invention, and FIG. 2 is a rear view thereof. As shown in FIG. 1, the liquid crystal display device 1 which is a transmissive image display apparatus is provided with the transmissive image display part 10 and the surface light source device 20. As shown in FIG. The surface light source device 20 is disposed on the back side of the transmissive image display unit 10 and irradiates light from the back side of the transmissive image display unit 10. In the following description, as shown in FIG. 1, the arrangement direction of the surface light source device 20 and the transmissive image display part 10 is called Z direction (plate thickness direction), and it is the two directions orthogonal to a Z direction, and orthogonal to each other. The two directions are referred to as the X direction and the Y direction.

The transmissive image display part 10 is equipped with the liquid crystal cell 11 and the linear polarizing plate 12, and the linear polarizing plate 12 is arrange | positioned at the both sides of the liquid crystal cell 11. As shown in FIG. The liquid crystal cell 11 and the linear polarizing plate 12 can use what is used by a known liquid crystal display device. As the liquid crystal cell 11, well-known liquid crystal cells, such as TFT type and STN type, can be illustrated.

The surface light source device 20 includes a light guide plate 30 which is an optical sheet and an LED light source 22. The light guide plate 30 is formed of a light transmitting resin that transmits light and has a plate shape. The light transmitting resin is a resin that transmits light. In addition, the light guide plate 30 may be a sheet form or a film form may be sufficient as it. In addition, it is preferable that the thickness T of the light guide plate 30 is 1.0 mm or more and 4.5 mm or less.

The light guide plate 30 is provided with a plate-shaped member made of a light transmitting resin. The refractive index of translucent resin exists in the range of 1.49-1.59, for example. As translucent resin used for the light guide plate 30, methacryl resin is mainly used. As resin used for the light guide plate 30, other resin may be used and styrene resin may be used. As the light transmitting resin, an acrylic resin, a styrene resin, a polycarbonate resin, a cyclic olefin resin, an MS resin (copolymer of acryl and styrene) and the like can be used. Furthermore, additives, such as a light diffusing agent, an ultraviolet absorber, a heat stabilizer, and a photopolymerization stabilizer, can also be added to the light guide plate 30.

In addition, the light guide plate 30 forms a rectangular parallelepiped, and is provided with the surface 31 and the back surface 32 which are a pair of main surfaces which oppose a Z-axis direction (thickness direction), as shown in FIG. have. In addition, the light guide plate 30 includes a pair of side surfaces 33 facing the X-axis direction and a pair of side surfaces 34 facing the Y-axis direction. The surface 31 and the back surface 32 are formed in a direction intersecting the side surfaces 33 and 34, that is, in a direction orthogonal to the side surfaces 33 and 34. These surfaces 31, the back surface 32, and the side surfaces 33 and 34 all have a rectangular shape.

Among these, the surface 31 may be a flat surface or a surface provided with irregularities. In the case of providing the unevenness to the surface 31, for example, it protrudes in the Z-axis direction, and a plurality of protrusions along the X-axis direction thereof are spaced apart in the Y-axis direction and parallel to each other. Can be arranged. As a shape of a protrusion part, the surface can be made into the shape which becomes a prism shape, and the cross-sectional shape at the time of cutting a protrusion part in the direction orthogonal to a longitudinal direction can be made into the shape which becomes a semi-circle shape and a semi-ellipse shape. Moreover, it is preferable to make it so that the cross-sectional shape at the time of cut | disconnecting in a direction orthogonal to a longitudinal direction may be the same shape. On the other hand, the direction in which the protrusion extends is preferably parallel to the incidence direction when light emitted from the light source is incident from the side surface of the light guide plate.

Moreover, the surface 31 functions as a surface which can emit surface light. The surface 31 is disposed on the transmissive image display portion 10 side, and the back surface 32 is disposed on the side opposite to the transmissive image display portion 10. On the front side of the light guide plate 30, various films 41 are disposed between the light guide plate 30 and the transmissive image display unit 10. Furthermore, the reflection sheet 42 which reflects the light in the light guide plate 30 to the surface 31 side is arrange | positioned in the position which faces the back surface 32. As shown in FIG. As various films 41, a diffusion film, a prism film, a brightness enhancement film, etc. are mentioned.

The LED light source 22 is disposed on the side of the light guide plate 30 so as to face the side surface 33 extending in the Y-axis direction of the light guide plate 30. The side surface 33 in the light guide plate 30 becomes an incidence surface that enters light emitted from the LED light source 22. The plurality of LED light sources 22 are disposed discretely along the longitudinal direction (Y-axis direction) of the side surface 33. Light incident from the side surface 33 in the light guide plate 30 is emitted from the surface 31. The surface of the light guide plate 30 serves as an emission surface for emitting light incident from the side surface 33.

The spacing of the LED light sources 22 is usually 5 mm to 20 mm. The LED light source 22 is disposed along the opposite side surface 33 along the Y axis. Instead of this aspect, it may be arrange | positioned along each of the four sides of the light-guide plate 30, and may be arrange | positioned along the side surface 34 which opposes along the X-axis. Alternatively, the side surfaces 33 and 34 may be disposed along any one side. The light source is not limited to the LED light source but may be another light source. Furthermore, the structure in which linear light sources, such as a cold cathode tube, are arrange | positioned may be sufficient as a light source.

The LED light source 22 is comprised by white LED, for example, and arrange | positions several LED in one location, and comprises one light source unit. In addition, as one light source unit, LEDs of three different colors of red, green, and blue may be arranged in close proximity to each other. Here, when the light source unit which has a some LED is arrange | positioned discretely along the arrangement direction mentioned above, it is preferable that LED of a different color is arrange | positioned as close as possible.

As an LED light source, what has various light output distribution can be used, but it is suitable that the light intensity of the LED light source is normal in the normal direction (X-axis direction), and has an light output distribution whose half value width of a light intensity distribution is 40 degree | times or more and 80 degrees or less. In addition, examples of the type of the LED light source include Lambertian type, shell type, side emission type, and the like.

The size at the time of planarizing the light guide plate 30 is set to be suitable for the screen size of the transmissive image display unit 10 as a target. Specifically, the length of two orthogonal sides is usually 250 mm x 440 mm or more (diagonal length L is 506 mm or more). Furthermore, the thing of the large size of 500 mm x 800 mm or more (diagonal length L is 943 mm or more) may be used. Alternatively, the planar shape of the light guide plate 30 is rectangular, but may be other shapes such as square. In addition, the thickness T of the original plate (transparent resin sheet) of the light guide plate 30 may be 4.5 mm or less, for example, 2.0 mm or 1.0 mm.

Here, a rectangle of 250 mm x 440 mm or more means a rectangle of which one side is 250 mm or more and the other side is 440 mm or more. In addition, the rectangle of 500 mm x 800 mm or more means the rectangle whose one side is 500 mm or more and the other side is 800 mm or more.

In addition, the original plate 60 of the light guide plate 30 may satisfy the following expression (1).

Where L is the diagonal length of the disc (mm) and T is the thickness of the disc (mm). On the other hand, the diagonal length L is 500 mm or more.

In addition, a plurality of printing dots 35 are formed on the back surface 32 of the light guide plate 30. The printing dot 35 is formed by dot pattern printing using inkjet. The printing dot 35 is formed so that the diameter closer to the LED light source 22 on the back surface 32 is smaller and gradually increases as it moves away from the LED light source 22.

In addition to the form shown in FIG. 2, about the printing dot 35, as shown to FIG. 6 (a), for example, the some printing dot 35 of substantially the same size is substantially the same on the back side of the light guide plate 30. As shown in FIG. It can also be set as the sun arrange | positioned at grid form at intervals. In the case where the printing dots 35 are arranged in a lattice form, they may be a square lattice, a triangular lattice, a cubic lattice, a hexagonal lattice, a basket lattice, or the like. Alternatively, as shown in Fig. 6B, a plurality of printing dots 35 of approximately the same size can be arranged at random. In addition, the aspect in which the size of the printing dot 35 changes suitably in these aspects can also be taken.

Subsequently, dot pattern printing in the manufacturing method of the light guide plate 30 will be described. Dot pattern printing is performed using inkjet. When dot pattern printing using inkjet is performed, ink is ejected from an inkjet nozzle onto the original plate at the time of manufacturing the light guide plate 30 to print a dot pattern.

3 is a perspective view illustrating a light guide plate manufacturing apparatus according to an embodiment. When performing dot pattern printing, the light-guide plate manufacturing apparatus (production apparatus of an optical sheet) 200 as shown in FIG. 3 is used. The light guide plate manufacturing apparatus 200 shown in FIG. 3 is provided with the conveying means 70 and the inkjet head 50 which convey the translucent resin sheet 60 (original board of the light guide plate 30). Moreover, the manufacturing apparatus 200 is equipped with the UV lamp and inspection apparatus which are not shown in the downstream of the inkjet head 50 in the moving direction A of the original plate 60. As shown in FIG.

The conveying means 70 carries the conveyance belt 71 which mounts and conveys the translucent resin sheet 60, and the pair of conveyance rollers 72 which move the conveyance belt 71 (only one is shown in FIG. 3). And a suction box 73 for sucking the light-transmissive resin sheet 60 placed on the conveyance belt 71.

The conveyance belt 71 is installed on a pair of conveyance rollers 72 and extends in the horizontal direction (shown in the direction A). The conveyance roller 72 on the drive side is rotationally driven by a motor (not shown) to move the conveyance belt 71. The non-printing surface 60b (see FIG. 4), which is the surface on the opposite side to the printing surface 60a, with the printing surface 60a of the original plate 60 facing upward, is disposed against the conveying belt (table) 71. .

The suction box 73 forms a box shape, and is arrange | positioned between the conveyance belts 71 and 71 spaced apart in the up-down direction. The suction box 73 is arranged in multiple numbers along the movement direction A. As shown in FIG. The suction box 73 is connected to exhaust means, such as a vacuum pump, for example, and it is set as the structure which can depressurize the inside of a box.

It is a side view which shows typically the relationship of the inkjet nozzle and the original plate of a light guide plate at the time of dot pattern printing. The inkjet head 50 is provided with a plurality of inkjet nozzles 51. It is a figure which shows the conveyance belt which mounts a light guide plate when dot pattern printing is performed. The suction box 73 has the top plate 73a on which the conveyance belt 71 is mounted. The outer surface of this top plate 73a forms a flat surface, and comprises the surface which slides the conveyance belt 71. FIG. And the translucent resin sheet 60 is mounted on the conveyance belt 71. That is, the conveyance belt 71 functions as a table on which the original plate 60 is placed.

A plurality of openings 73b and 71a are provided in the top plate 73a and the conveyance belt 71 of the suction box 73. The interval between the openings 73b and 71a is, for example, about 5 cm. The shapes of the openings 73b and 71a may be shapes other than circular. When the conveyance belt 71 is arrange | positioned at a predetermined position, the opening part 71a of the conveyance belt 71 and the opening part 73b of the ceiling plate 73a will match. And when the inside of the suction box 73 is depressurized by operating a vacuum pump part, the non-printing surface 60b of the conveyed original board 60 will be adsorb | sucked on the conveyance belt 71, and curvature will be excluded. The distance between the conveyance belt 71 (table) and the inkjet nozzle 51 on which the original plate 60 is placed is adjusted to be equal to or less than the distance obtained by adding the thickness T of the original plate 60 to 2.8 mm.

On the other hand, in the light guide plate manufacturing apparatus 200, the original plate 60 can be conveyed continuously or intermittently. In addition, the table on which the original plate 60 is mounted is not limited to the conveyance belt 71, Other conveyance trays etc. may be sufficient. In addition, the light guide plate manufacturing apparatus 200 may be the structure which is not equipped with the conveying means. The disc 60 may be placed on a table, and suction of the non-printed surface 60b of the disc 60 may be performed by suction to remove the warpage of the disc 60.

When manufacturing the light guide plate 30, first, a liquid repellent treatment may be performed on the surface of the original plate 60, which will be the back surface 32 of the original plate 60 (translucent resin sheet included in the light guide plate 30).

As the degree of liquid repellent treatment, the contact angle when water droplets are dropped on the surface of the liquid repellent treated plate 60 is 80 to 130 degrees, preferably 85 to 120 degrees, more preferably 90 to 110 degrees. By setting the contact angle to 80 degrees or more, the connection of the reflective dots (print dots) 35 and 35 can be prevented, and the reflective dots 35 can be provided more densely. In addition, by setting the contact angle to 130 degrees or less, it is possible to maintain high adhesion between the reflective dot 35 and the original plate 60.

Examples of the liquid repellent treatment include treatment using a surface modifier as a liquid repellent treatment agent, treatment by various energy rays, treatment by chemisorption, treatment by graft polymerization on the material surface, and the like.

The treatment using the surface modifier is a treatment to form a liquid repellent layer in which a small amount of the surface modifier is added on the surface of the master 60. Examples of the surface modifier as the liquid repellent treatment agent include vinyl polymers having a perfluoroalkyl group (Rf group) in the side chain, Rf group-containing silicone, and the like. The liquid repellent layer may be formed by applying a surface modifier to a surface of a paper towel or the like, or applying the surface modifier to the surface by spraying or inkjet printing.

The treatment by various energy rays is a treatment which makes the surface have liquid repellency by energy rays. Examples of energy rays are plasma, electron beam, ion beam, and the like. Examples of the liquid repellent treatment in the case of using the plasma treatment include, after roughening the surface by plasma etching, to form, for example, a liquid repellent monomolecular film on the roughened surface, fluorination of the surface by fluorine-based gas plasma, Forming a film composed of a liquid-repellent compound on the surface by plasma CVD, forming a liquid-repellent thin film on the surface by plasma polymerization, or the like.

Examples of the treatment by surface roughening include imparting concave-convex shapes to the surface of the original plate 60 by hot pressing, etching with chemicals, blasting treatment, and the like.

In the treatment by chemical adsorption, the terminal of the adsorption molecule is preferably modified with fluorine. In particular, as the terminal substituent, a CF ₃ group is preferable from the viewpoint of liquid repellency.

In the example of such a process, it is preferable at the point that surface fluorination can be performed easily and uniformly by fluorine-type gas plasma.

The conveyance belt 71 is movable in the horizontal direction shown by the arrow A by the motor which is not shown in figure. The ink 54 jetted from the inkjet nozzle 51 is made of an ultraviolet curable resin, and is impacted on the original plate 60, and then gradually widens in a circular shape. Furthermore, the light guide plate manufacturing apparatus 200 is equipped with the ultraviolet irradiation device which is not shown in figure. A pigment may or may not be added to ink.

The pigment is preferably at least one of calcium carbonate particles, barium sulfate particles and titanium dioxide particles. The cumulative 50% 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 even more preferably 300 to 600 nm. Calcium carbonate particles, barium sulfate particles, and titanium dioxide particles having a cumulative 50% particle diameter (D50) in a range of 50 to 3000 nm can be obtained by selecting appropriately from a commercially available product based on the particle size distribution. The content rate of the pigment in the ink is usually about 0.5 to 15.0 mass% based on the total mass of the ink. The 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.

The photopolymerizable component has photopolymerizable functional groups, such as a vinyl group, Preferably it is comprised by the photopolymerizable monomer and / or photopolymerizable oligomer which does not have a hydroxyl group. The content rate of the photopolymerizable monomer which does not have a hydroxyl group becomes like this. Preferably it is 65-75 mass% based on the total mass of an ink. The content rate of the photopolymerizable oligomer which does not have a hydroxyl group becomes like this. Preferably it is 10-20 mass% based on the total mass of an ink.

The photopolymerizable monomer which does not have a hydroxyl group is, for example, 1,4-butanediol diacrylate (for example, manufactured by Sarmer Japan Co., Ltd., SR213), 1,6-hexanediol diacrylate (for example, Sartomer Japan Co., Ltd., SR238F), 1,3-butylene diacrylate (for example, Satomer Japan Co., Ltd. product, SR212), 1,9-nonanediol diacrylate (for example, Shin-Nakamura Chemical Co., Ltd.) Co., Ltd., A-NOD-N), and propoxylated (2) neopentyl glycol diacrylate (for example, Satomer Japan Co., Ltd. product, SR9003).

The photopolymerizable oligomer which does not have a hydroxyl group, Preferably, it contains aliphatic urethane (meth) acrylate (For example, Satomer Japan Co., Ltd. product, CN985B88, CN991). Aliphatic urethane (meth) acrylate is a photopolymerizable oligomer which has the polyurethane oligomer chain formed from aliphatic polyisocyanate and aliphatic polyol, and the acrylate group or methacrylate group couple | bonded with this. The glass transition temperature of aliphatic urethane (meth) acrylate becomes like this. Preferably it is 40 degreeC or more.

A photoinitiator can be suitably selected from the thing normally used in the field of ultraviolet curable resin. The content rate in the ink of a photoinitiator is about 0.5-10.0 mass% normally.

The inkjet ink may contain components other than a pigment, a photopolymerizable component, and a photoinitiator in the range which does not deviate from the meaning of this invention.

When dot pattern printing is performed, first, the non-printing surface 60b of the original plate 60 is suction-absorbed to eliminate warpage, and a predetermined amount of ink 54 is sprayed from the inkjet nozzle 51 onto the original plate 60 to dot pattern printing. Generates section 55. Thereafter, the table 52 is moved by the motor to convey the original plate 53 until the dot pattern printing unit 55 comes to the position where the ultraviolet irradiation device is installed. Subsequently, ultraviolet rays are irradiated to the dot pattern printing unit 55 in the original plate 53 by an ultraviolet irradiation device to cure the ink to produce the printing dots 35 shown in FIG. 2.

Here, in the present embodiment, the inkjet nozzle 51 and the original plate 53 are removed by suction-adsorbing the non-printing surface 60b of the original plate 60 when discharging the ink 54 from the inkjet nozzle 51 to eliminate warping. ) Distance is set to 2.8mm. In the case of forming a low-precision dot pattern, even when the distance between the inkjet nozzle 51 and the original plate 53 (hereinafter referred to as the "gap distance") D is large, there is almost no streak in the printed pattern, so the inkjet In order to avoid the contact of the nozzle 51 and the original plate 53, the gap distance D was taken large.

However, when forming a high precision dot pattern, when a gap distance D is large, a line may generate | occur | produce in a printed pattern, and the quality of a product falls by this line. In this regard, the distance between the inkjet nozzle 51 and the original plate 60 at the time of performing dot pattern printing is adjusted to 2.8 mm. By adjusting the distance of the inkjet nozzle 51 and the original plate 60 to 2.8 mm, the generation | occurrence | production of the line | wire in the printing surface of the dot pattern printing performed to the light guide plate 30 can be suppressed. Therefore, the quality of the surface light source device 20 and the liquid crystal display device 1 using the light guide plate 30 can be improved.

The gap distance D for suppressing the generation | occurrence | production of the line | wire in the printing surface of the dot pattern printing performed on the light-guide plate 30 becomes 2.8 mm or less. Further, by setting the gap distance D to 1.8 mm or less, it is possible to suppress the generation of streaks more suitably. Although the gap distance D is preferably smaller, the lower limit of the gap distance D is such that the contact between the inkjet nozzle 51 and the original plate 53 at the time of performing dot pattern printing can be avoided. You can do Specifically, the gap distance D can be made 0.4 mm or more or 0.5 mm or more. From these viewpoints, the gap distance needs to be 0.4 mm or more and 2.8 mm or less, preferably 0.5 mm or more and 1.8 mm or less, and more preferably 0.5 mm or more and 1.0 mm or less.

( Example )

Hereinafter, the experiment about the line generation situation in the optical sheet printing surface was done. In this experiment, the gap distance D was changed suitably, the some optical sheet was manufactured, and the line generation situation was evaluated visually about these optical sheets, respectively. The set gap distance D was made into 0.5 mm, 1.3 mm, 2.3 mm, 4.0 mm, and 9.0 mm.

In addition, as a common condition, the original (optical sheet) used the thing of a 40 inch panel. In addition, the ink viscosity of the used ink was 18.6 mPa * s, and the quantity of the ink liquid was 30 pL. Furthermore, the dot diameter in the dot pattern was about 130 micrometers. In addition, the scanning (conveying) speed | rate at the time of conveying an original board was 400 mm / s, and the resolution was 150 dpi. In addition, ultraviolet irradiation was performed 1.5 seconds after the ink landed on the original plate. UV accumulated light quantity at the time of ultraviolet irradiation was 0.25 J / cm <^2> .

As a result, in the case where the gap distances D were 0.5 mm, 1.3 mm, and 2.3 mm, string generation was almost not seen. Moreover, when the gap distance D was 5.0 mm, the ink in adjacent dots stuck together, and the result was a line | wire generate | occur | produced. In the case where the gap distance D was 9.0 mm, ink scattered to the non-printed area, resulting in a large generation of streaks.

When the printed surface of the light guide plate was visually seen, the gap distance (D) was almost invisible at 2.3 mm, and the lines were clearly seen at 4.0 mm, but the gap distance (D) was about 2.8 mm. do. In addition, the string was almost completely invisible when the gap distance D was 1.3 mm. From this result, it is thought that the line will be almost completely invisible with the gap distance D. Therefore, the gap distance D of this invention was prescribed | regulated to 2.8 mm, and the more preferable gap distance D was defined to 1.8 mm.

The manufacturing method of the optical sheet of this invention, the optical sheet, and the manufacturing apparatus of an optical sheet can suppress the generation | occurrence | production of the line | wire in a printing surface, when performing dot pattern printing on the back surface of an optical sheet. According to the present invention, the quality of a product (a surface light source device and a transmissive image display device) using an optical sheet can be improved.

1: Liquid crystal display device 10: Transmissive image display part
11: liquid crystal cell 12: linear polarizer
20: surface light source device 22: LED light source
30: Light guide plate 31: surface
32: back 33, 34: side
35: printing dot 41: various films
42: reflective sheet 50: inkjet head
51: inkjet nozzle 52: table
53: Disc 54: Ink
55: dot pattern printing unit 60: original (translucent resin sheet)
60a: print side 60b: non-print side
70: conveying means 71: conveying belt
71a: opening 72: conveying roller
73: suction box 73a: ceiling panel
73b: opening
200: light guide plate manufacturing apparatus (manufacturing apparatus of optical sheet)
D: gap distance L: diagonal length of the disc
T: Diagonal length of the disc A: Direction of movement of the disc

Claims (9)

An optical sheet which emits light incident from the light incident surface from a light exiting surface intersecting the light incident surface, wherein a dot pattern is printed by spraying ink from an inkjet nozzle onto the back surface of the original plate of the optical sheet. As a method of manufacturing the optical sheet,
By suction adsorption of the non-printing surface of the disc to eliminate the warpage of the disc,
Adjust the distance between the nozzle and the disc to 2.8mm or less,
The manufacturing method of the optical sheet which sprays the said ink and prints the said dot pattern. The method of claim 1,
The manufacturing method of the optical sheet whose thickness of the said disc is 4.5 mm or less. 3. The method according to claim 1 or 2,
The manufacturing method of the optical sheet whose diagonal length L of the said disk is 500 mm or more. 4. The method according to any one of claims 1 to 3,
Diagonal length (L) and thickness (T) of the original plate satisfies the following formula (1).
[Equation 1]
L / T≤0.01
Where L is the diagonal length of the disc (mm) and T is the thickness of the disc (mm). 5. The method according to any one of claims 1 to 4,
When the dot pattern is printed, the original plate is placed on a table,
The manufacturing method of the optical sheet whose distance of the said nozzle and the said table is below the distance which added the thickness of the said original plate to 2.8 mm. The optical sheet manufactured by the manufacturing method of the optical sheet in any one of Claims 1-5. The optical sheet according to claim 6,
And a light source disposed to face the light incident surface of the optical sheet. The surface light source device of Claim 7 is provided,
And a transmissive image display unit disposed opposite to the light exit surface of the optical sheet and configured to display an image by irradiating light emitted from the light source. The optical sheet which emits light incident from the light incident surface from the light exit surface intersecting the light incident surface, wherein the dot pattern is printed by ejecting ink from the nozzle to the back surface of the original plate of the optical sheet. An apparatus for manufacturing an optical sheet,
The suction of the non-printed surface of the disc is sucked to eliminate warpage of the disc, and the distance between the nozzle and the table on which the disc is placed is adjusted to be 2.8 mm or less plus the thickness of the disc,
An optical sheet manufacturing apparatus for printing the dot pattern by ejecting the ink.

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