KR20120120935A - Light-guide plate and method for manufacturing a light-guide plate - Google Patents

Abstract

Provided is a method of manufacturing a light guide plate that can easily and inexpensively form a fine pattern of a diffusion layer.
The manufacturing method of a light guide plate is a manufacturing method of the light guide plate 100 in which a light source is arrange | positioned at the cross section in order to comprise a surface light source device. The diffusion layer 3 is coated by applying a coating liquid 2 containing the light-diffusion fine particles 21 and the light-transmitting binder 22 in the state of fine droplets on the back surface or the surface or both surfaces of the light guide plate substrate 1, thereby coating the light diffusion layer 3. The fine particles 21 are the aggregates 210, and the ratio between the planar area occupied by the aggregates 210 in the coated surface of the light guide plate substrate 1 and the coating area of the coating liquid 2 is 0.1% or more and 70% or less. .

Description

Light guide plate and manufacturing method of light guide plate {LIGHT-GUIDE PLATE AND METHOD FOR MANUFACTURING A LIGHT-GUIDE PLATE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface light source device for irradiating light from the back of a liquid crystal display panel or a signboard, a so-called light guide plate for a backlight device, and a manufacturing method of the light guide plate. It relates to a method for producing.

The backlight device which irradiates light from the back surface of a liquid crystal display panel, a signboard, etc., has a direct type | mold which arrange | positions a light source in planar form, and forms surface uniform light emission by a diffuser plate, and the edge which arrange | positioned the line light source in the end surface of the light guide plate. A light guide plate type called a light or side light is known.

In recent years, it is desired to be thinner, lighter, and energy-saving. As such a backlight device, a light guide plate system is attracting attention. In particular, LED (Light Emitting Diode) has attracted attention from the viewpoint of high brightness, long life, and energy saving, instead of a conventional fluorescent lamp or cold cathode tube as a light source.

The light guide plate for backlight devices disperse | distributes a diffuser inside a light guide plate, or forms a light-diffusion layer or a diffusion pattern in at least one of a surface and a back surface. The light guide plate receives light from the cold cathode tube or the LED array light source formed in the end face in the light guide plate and emits the light toward the exit side to form a surface light source device.

As a light guide plate type backlight device used for such a transmissive liquid crystal display panel, a signboard, etc., the technique which forms gradation distribution is known (refer patent document 1). The gradation distribution increases the light diffusion capability of the diffusion layer as it moves away from the light source so that the brightness of the emission surface of the backlight device becomes uniform.

As a method of forming a gradation distribution by a diffusion layer and a diffusion pattern, the method of transferring an uneven | corrugated pattern by injection molding or press molding using a metal mold | die is known. The desired gradation pattern is previously formed in the said metal mold | die. Moreover, the method (refer patent document 2) of dot printing of the light-diffusion ink by the screen printing method, etc. are also known.

Japanese Laid-Open Patent Publication No. 57-128383 Japanese Patent Publication No. 3734547

As for the diffusion layer formed in the light-guide plate base material, it is necessary to refine | miniaturize and pit the individual diffusion parts so that the pattern of the said diffusion layer may not be outstanding. In recent years, the display device has been required to be thinned. However, when the light guide plate is made thin, the pattern of the diffusion layer is easily visible. Therefore, the pattern of the said diffusion layer needs to be refine | miniaturized and peach pitch further.

However, in injection molding, press molding using a plate or a metal mold, and the screen printing method, it is difficult to sufficiently refine the pattern of the diffusion layer. In addition, when the design pattern is inadequate, not only redesign, but also expensive plate, mold, and screen plate are made again, leading to an increase in cost.

An object of the present invention is to provide a light guide plate and a method of manufacturing the light guide plate which can form a fine pattern of the diffusion layer simply and inexpensively.

The manufacturing method of the light guide plate which concerns on this invention is a manufacturing method of the light guide plate by which a light source is arrange | positioned at the cross section in order to comprise a surface light source device, and is apply | coated which contains light-diffusion microparticles | fine-particles and a translucent binder on the back surface or the surface, or both surfaces of a light guide plate base material. The diffusion layer is coated by applying the liquid in the state of fine droplets, and the light-diffusion fine particles are aggregated, and the ratio of the planar area occupied by the aggregate in the coating surface of the light guide plate substrate to the coating area of the coating liquid is 0.1% or more 70 It is made into% or less. Thereby, if a coating liquid is apply | coated to the light-guide plate base material, even if it does not manufacture a plate and a metal mold | die conventionally, the diffusion layer excellent in the light-diffusion ability of a fine pattern can be formed simply and inexpensively.

When coating the diffusion layer, it is preferable that the portion close to the light source lowers the coating density of the light diffusing fine particles, and the portion far from the light source increases the coating density of the light diffusing fine particles. Thereby, if a coating liquid is apply | coated to the light-guide plate base material, even if it does not manufacture a plate and a metal mold | die conventionally, the diffusion layer excellent in the light-diffusion ability of a fine pattern can be formed simply and inexpensively.

It is preferable to apply | coat the said coating liquid to the back surface, the surface, or both surfaces of the said light-guide plate base material by the spray coating method which sprays the said coating liquid from a nozzle. Since the spray coating method only scans a light and small nozzle in the X-Y direction, the objective is achieved by inexpensive equipment. That is, the spray coating method is applied to a large light guide plate by inexpensive installation.

By arranging a plurality of nozzles in parallel and scanning the plurality of nozzles in substantially parallel, it is preferable to change the coating density of the light-diffusion fine particles in one or two dimensions.

It is preferable that the space | interval from the said nozzle to the coating surface in the said light-guide plate base material is 70 mm or more and 300 mm or less.

The said spray coating method scans which moves the said nozzle in the direction substantially parallel to the 1st side of the said light-guide plate base material on the coating surface of the said light-guide plate base material, while spraying the said coating liquid from a nozzle. It is preferable to apply | coat the said coating liquid to the whole surface or one part of the said coating surface by repeating at predetermined | prescribed feed pitch in the direction orthogonal to.

A step of repeating a scan for moving the nozzle in a direction substantially parallel to the first side of the light guide plate substrate at a predetermined feed pitch in a direction orthogonal to the first side is partially performed on the coated surface of the light guide plate substrate. It is preferable to change the coating density of the light-diffusion fine particles one-dimensionally by repeating with.

It is preferable to change the coating density of the light-diffusion fine particles one-dimensionally by changing the conveyance pitch of the nozzle and applying the coating liquid to the entire surface or part of the coated surface of the light guide plate substrate.

It is preferable to change the coating density of the light-diffusion fine particles one-dimensionally by varying the scanning speed of the nozzle for each scan of the nozzle and applying the coating liquid to the entire surface or part of the coated surface of the light guide plate substrate. .

The application density per unit time of the coating liquid from the nozzle is changed for each scan of the nozzle, and the coating liquid is applied to the entire surface or part of the coated surface of the light guide plate substrate, thereby applying the one-dimensional coating density of the light-diffusion fine particles. It is preferable to change to.

The light guide plate according to the present invention is a light guide plate in which a light source is disposed on one end surface in order to constitute a surface light source device. The said light-diffusion microparticles | fine-particles are coat | coated, and the ratio of the planar area which the said aggregate in the coating surface of the said light-guide plate base material occupies, and the application area of the said coating liquid is 0.1% or more and 70% or less, It is characterized by the above-mentioned. Thereby, if a coating liquid is apply | coated to the light-guide plate base material, even if it does not manufacture a plate and a metal mold | die conventionally, the diffusion layer excellent in the light-diffusion ability of a fine pattern can be formed simply and inexpensively.

It is preferable to apply | coat the said coating liquid to the back surface, the surface, or both surfaces of the said light-guide plate base material by the spray coating method which sprays the said coating liquid from a nozzle. Since the spray coating method only scans a light and small nozzle in the X-Y direction, the objective is achieved by inexpensive equipment. That is, the spray coating method is applied to a large light guide plate by inexpensive installation.

It is preferable that the number of the light-diffusion microparticles contained in one said aggregate is 10 or more and 10,000 or less.

As it moves away from the light source, the ratio of the planar area occupied by the agglomerate in the coating surface of the light guide plate substrate to the coating area of the coating liquid, or the coating area ratio of the coating area of the coating liquid and the area of the coating surface of the light guide plate substrate. It is desirable to increase this.

According to the present invention, it is possible to provide a light guide plate and a manufacturing method of the light guide plate which can form a fine pattern of the diffusion layer simply and inexpensively.

BRIEF DESCRIPTION OF THE DRAWINGS In the manufacturing method of the light-guide plate which concerns on this invention, it is a schematic diagram which shows the state which spray-coated a coating liquid to the coating surface of a light-guide plate base material.
It is a side view which shows the state in which the coating liquid was apply | coated to the light guide plate base material by the spray coating method.
FIG. 2B is a plan view showing a state in which the coating liquid is applied to the light guide plate substrate by the spray coating method. FIG.
It is a side view which shows the state in which the coating liquid was apply | coated to the light-guide plate base material by the spray coating method.
3B is a plan view showing a state in which the coating liquid is applied to the light guide plate substrate by the spray coating method.
4: A is a side view which shows the state which light-diffusion microparticles lined up individually.
4B is a plan view illustrating a state in which the light diffusing fine particles are individually lined up.
Fig. 5 is a schematic diagram showing how the luminance distribution of the surface light source device is measured.
6 is a diagram showing a distribution in the X direction of the relative luminance of the light guide plate on which the coating liquid is uniformly coated by changing the feed pitch.
It is a figure which shows roughly the trace of the nozzle at the time of apply | coating a coating liquid by the spray coating method.
FIG. 7B is a diagram showing the distribution in the X direction of the coating density of the light-diffusion fine particles applied by the trajectory of the nozzle shown in FIG. 7A.
It is a figure which prescribed | regulated the scanning direction and the conveyance direction of the nozzle at the time of apply | coating a coating liquid by the spray coating method.
It is a figure which shows the conditions of the coating method used for the manufacturing method of the light guide plate of this invention in detail.
It is a figure which shows the trace of the nozzle by the coating method shown in FIG. 8B, and the distribution of the X direction of the application | coating density of light-diffusion microparticles | fine-particles.
FIG. 9B is a diagram showing the X-direction distribution of the locus of the nozzle by the coating method shown in FIG. 8B and the coating density of the light-diffusion fine particles. FIG.
FIG. 9C is a diagram illustrating the X-direction distribution of the locus of the nozzle by the coating method shown in FIG. 8B and the coating density of the light-diffusion fine particles. FIG.
FIG. 9D is a diagram showing the X-direction distribution of the locus of the nozzle by the coating method shown in FIG. 8B and the coating density of the light-diffusion fine particles. FIG.
FIG. 9E is a diagram showing the X-direction distribution of the locus of the nozzle by the coating method shown in FIG. 8B and the coating density of the light-diffusion fine particles. FIG.
FIG. 9F is a diagram showing the X-direction distribution of the locus of the nozzle by the coating method shown in FIG. 8B and the coating density of the light-diffusion fine particles. FIG.
It is a figure which shows distribution of the X direction of the application | coating density of light-diffusion microparticles | fine-particles when the coating liquid is apply | coated uniformly to the light guide plate base material.
FIG. 10B is a diagram showing a distribution in the X direction of luminance measured by providing a light source at the left end of the light guide plate substrate of FIG. 10A. FIG.
It is a figure which shows the distribution of the X direction of the target coating density of light-diffusion microparticles | fine-particles.
10D is a diagram illustrating a distribution in the X direction of target coating densities of different light-diffusion fine particles.
FIG. 11: is a figure which shows typically the two-dimensional gradation distribution which assumed the installation of the line light source in four sides of the light guide plate.
It is a schematic diagram which shows a mode which spray-coating a coating liquid to the coating surface of a light-guide plate base material with a some nozzle.
13 is a schematic view showing each step of the method for manufacturing a light guide plate according to the present invention.
14A is a side view schematically showing a light guide plate on which a coating liquid is applied in the form of water droplets.
14B is a plan view schematically illustrating the light guide plate on which the coating liquid is applied in the form of a droplet.
15A is a side view schematically showing a light guide plate coated with a coating liquid on the entire surface of the coated surface.
FIG. 15B is a plan view schematically illustrating the light guide plate on which the coating liquid is applied to the entire surface of the coating surface. FIG.
16A is a micrograph of the coating surface of the light guide plate substrate.
It is a microscope picture of the coating surface of a light guide plate base material.

First, the process which overwrote the technical idea of this invention is demonstrated, and the detail of each embodiment is demonstrated after that.

Screen printing, offset printing, etc. are mentioned as a technique of forming a diffusion layer in a light-guide plate base material. First of all, it is necessary to manufacture a pattern that becomes a master such as a printing plate or a mold. For example, screen printing plates produce patterns that are optically designed precisely by laser drawing or inkjet printers. Next, the photograph of the pattern which appeared on the silk which apply | coated the photosensitive emulsion is selected, and it washes | cleans. As a result, a diffusion layer is formed on the light guide plate.

In these processes, refinement | miniaturization has a limit, respectively. For example, it is necessary to clear the problems such as the limitation of the line width of the laser drawing, the photosensitivity of the emulsion, and the sticking at the time of cleaning. In addition, even if the plate is formed, it causes problems in the printing process or performance, such as print defects accompanied by miniaturization or fluctuations in product performance due to variation in transfer rate. Therefore, improvement of printing technique is also required at the same time. In addition, when the design pattern or the manufactured plate was defective, the expensive master plate is made again. In order to avoid these problems, a diffusion layer formation method that does not require a master plate is essentially suitable.

On the other hand, in a large light guide plate, the gradation pattern may be formed in a diffused layer from a viewpoint of making uniform the brightness of a light emission surface. That is, the vicinity of the light source is a pattern of low light diffusing ability, and is a method of forming a pattern of high light diffusing ability as it moves away from the light source. In order to reduce the light diffusing ability, for example, a method of performing geometric patterning such as reducing the pitch or area of the pattern and a method of physically lowering the light diffusing ability of the diffusing layer itself, such as lowering the concentration of the diffusing material or the reflecting material, are mentioned. have. However, the change of the concentration of the diffusing material and the reflecting material significantly lowers the productivity. Therefore, it is common to adjust to the area density, pitch, and height of an application part. However, precise patterning printing is a barrier for the above reason, making it difficult to enlarge the light guide plate.

Accordingly, in view of these problems, the present invention has been made to provide a light guide plate and a method of manufacturing a light guide plate that can form a fine pattern diffusion layer easily and inexpensively without producing a plate or a mold.

That is, the light guide plate and the manufacturing method of the light guide plate which concern on this invention were made into the following structures and processes.

≪ Embodiment 1 >

Embodiment 1 of this invention is demonstrated below. The light guide plate which concerns on this invention is one of the structural members of the backlight apparatus which irradiates light from the back surface, such as a liquid crystal display panel and a signboard. The light source is disposed on the cross section of the light guide plate.

As shown in FIGS. 1 and 2, the light guide plate is formed in a fine droplet state of the coating liquid 2 containing the light-diffusion fine particles 21 and the light-transmitting binder 22 on the back surface, the surface, or both surfaces of the light guide plate substrate 1. The diffusion layer 3 is coated by coating with. The light-diffusion fine particles 21 become aggregates 210.

Specifically, first, the light guide plate substrate 1 is prepared. As the light guide plate substrate 1, a general transparent resin substrate such as polymethyl methacrylate (PMMA) resin, polystyrene resin, polycarbonate resin is preferably used. In particular, as a large light-guide plate board | substrate, the polymethylmethacrylate resin board | substrate which is the most excellent in transparency is more preferable. Moreover, it is preferable that the curvature of the light-guide plate base material 1 is within ± 1.61 * 10 <^-4> (1 / mm) by curvature (curvature of the most curved part).

Next, the coating liquid 2 which contains the light-diffusion microparticles 21 and the translucent binder 22 in the back surface or surface of the light-guide plate base material 1, or both surfaces (it is only a surface in this embodiment and is called a coating surface). ) Is applied. In addition, the coating layer 2 was apply | coated so that the application | coating part and an uncoated part may be randomly arrange | positioned, as shown to FIG. 2A, b. However, in the example shown in FIGS. 2A and 2B, the island-like coating portions are randomly arranged. As shown in FIGS. 3A and 3B, the island-free uncoated portions may be randomly disposed.

Here, the light guide plate used for the surface light source device is a light guide plate which is incident on the light guide plate while repeating the total reflection at the interface of the gas phase and the solid phase (hereinafter may be referred to as a contribution interface) by using light incident at an angle below the critical angle. It propagates light away from the light source. Thereby, light is taken out by inhibiting total reflection of the interface to which light is to be taken out. Therefore, of course, the diffusion layer is formed in the portion to be emitted, but in the portion not to emit light, a technique of leaving the interface as it is is required. That is, of course, a technique for forming a diffusion layer, but intentionally leaves a contribution interface is required. As a diffusion layer formation method corresponding to this request, the spray coating method which sprays a coating liquid with the blowing of gas is preferable.

Generally, the coating apparatus which does not use a plate aims at apply | coating the whole surface uniformly. Therefore, it is difficult to intentionally make an uncoated portion. The uncoated portion also occurs due to blur due to lack of coating liquid, but the control of the blur is very unstable. In addition, sometimes an unapplied part, such as a pinhole, may generate | occur | produce as an unsatisfactory situation, but it is inherently out of control. On the other hand, since the spray coating method sprays the coating liquid in the state of fine droplets, there is an excellent feature that the coating unit and the uncoated portion of the micro unit are essentially contained.

Therefore, in this embodiment, the coating liquid 2 is apply | coated to the light guide plate base material 1 by the spray coat method. That is, as a coating apparatus, it is preferable that it is excellent in flow stability and there is no possibility of clogging of a nozzle. Moreover, as a coating apparatus, the coating liquid 2 can be sprayed in a uniform fine droplet state, and the coating efficiency is high, which hardly scatters the coating liquid 2 out of the planar region of the light guide plate substrate 1. It is preferable. Therefore, the spray coater 4 is used as a coating apparatus. However, the diffusion layer formation method is not limited to the spray coating method, In short, what is necessary is just the spray coating method which can apply | coat the coating liquid 2 to the light-guide plate base material 1 in a fine droplet state.

The spray coater 4 pumps gas to the nozzle 5 and blows it out. And the spray coater 4 sprays the light guide plate base material 1 with the coating liquid 2 conveyed to the nozzle 5 by the pump etc. from the storage tank 6 to the gas which blows out. The flow rates of the gas and the coating liquid 2 which are pressurized to the nozzle 5 are controlled by the flow control units 7 and 8, respectively.

The nozzle 5 is preferably a swirl flow (spiral flow) type. In the swirl flow nozzle, the spray fluid is vortexed to narrow the spray angle. Therefore, the light-diffusion fine particles 21 tend to aggregate. In addition, since the flow velocity in the normal direction when the light diffusing fine particles 21 arrive at the light guide plate substrate 1 is low, the light diffusing fine particles 21 can be attached to the light guide plate substrate 1 without disrupting the aggregation of the light diffusing fine particles 21.

The nozzle 5 is configured to be movable in the X direction and the Y direction. The nozzle 5 is comprised in the structure which can spray the coating liquid 2 to the whole planar area (however, one part may be sufficient) of the light-guide plate base material 1. The nozzle 5 is further configured to be movable in the vertical direction. Thus, it is preferable that the nozzle 5 is set as the structure which can change the space | interval of the nozzle 5 and the light guide plate base material 1. In addition, the drive mechanism in the X * Y direction of the nozzle 5 and the drive mechanism in the up-down direction are not specifically limited. However, in this embodiment, although the nozzle 5 was set as the structure which can move to an X-Y direction and an up-down direction, the stage (not shown) which supports the light-guide plate base material 1 can move to an X-Y direction and an up-down direction It is good also as a structure.

As a gas, dry air, dry nitrogen, etc. can be used, for example. When using a flammable solvent, it is preferable to use dry nitrogen, in order to prevent complexation by static electricity or the like. In addition, in order to promote aggregation of the light-diffusion fine particles 21 as described later, the gas serving as the carrier may be heated to, for example, 30 ° C or more and 120 ° C or less before spraying.

The coating liquid 2 is a mixture containing the light-diffusion fine particles 21 and the translucent binder 22 as mentioned above. The light diffusing fine particles 21 are members that transmit and diffuse light. As the light diffusing fine particles 21, inorganic fine particles such as silica, calcium carbonate, barium sulfate, titanium oxide, aluminum oxide, and organic fine particles such as silicon beads, PMMA beads, MS beads, styrene beads can be used.

When apply | coating the coating liquid 2 to the surface (light emitting surface) of the light-guide plate base material 1, it is preferable to use the transparent glass microparticles and transparent resin microparticles which permeate | transmit and scatter as the light-diffusion microparticles | fine-particles 21. When apply | coating the coating liquid 2 to the back surface (light reflection surface) of the light-guide plate base material 1, it is preferable to use the white particle which reflects and scatters as a light-diffusion microparticle 21, and a pigment.

The shape of the light-diffusion fine particles 21 may be spherical, spherical, flaky, indefinite, or the like, and is not particularly limited.

As for the average particle diameter of the light-diffusion microparticles | fine-particles 21, 1 micrometer or more and 50 micrometers or less are preferable. When the said average particle diameter is smaller than the lower limit mentioned above, there exists a possibility that the ability to diffuse light may be lacking, or diffused light may color. When the average particle diameter is larger than the above-mentioned upper limit, the nozzle may be easily clogged when the nozzle is used, or the diffused light by the light-diffusion fine particles 21 may become bright and visible at a portion having a small coating density. In particular, the average particle diameter is preferably 1 µm or more and 20 µm or less.

As a ratio which the light-diffusion microparticles | fine-particles 21 occupy with respect to the coating liquid 2, 1 wt% or more and 20 wt% or less are preferable. When the said ratio is out of the range mentioned above, generation | occurrence | production of the aggregate of the light-diffusion microparticles | fine-particles 21 may not occur easily. When the said ratio is lower than the lower limit mentioned above, a high aspect ratio may be hard to be obtained and the light-diffusion ability may be lacking.

The light-transmitting binder 22 is a member which adheres the light-diffusion fine particles 21 to the light guide plate base material 1. As the light-transmissive binder 22, a solvent type adhesive agent, a thermosetting resin, an ultraviolet curable resin, etc. can be used, for example. As the light-transmissive binder 22, as described later, a resin component that does not adhere during solvent dilution but exhibits adhesion after drying the solvent may be used, for example, an acrylic pressure sensitive adhesive. However, it is also within the scope of the present invention to disperse the non-reactive polymer in a solvent and apply a spray, and to dry the solvent on the light guide plate substrate to function the light-diffusion fine particles as an adhesive.

When the length of the light guide plate in the light guide direction is 600 mm or less, it is preferable that the difference between the refractive index of the light transmissive binder 22 and the refractive index of the light diffusing fine particles 21 is -0.1 or less or 0.1 or more. This is because the light diffusion effect is exerted by both the unevenness of the surface and the refractive index difference, and the light can be taken out efficiently in the plane direction at a relatively short light guiding distance. When the length of the light guide plate in the light guide direction is 300 mm or more, it is preferable that the difference between the refractive index of the light-transmitting binder 22 and the refractive index of the light diffusing fine particles 21 is -0.1 or more and 0.1 or less. The light diffusion effect is mainly exerted only by the surface irregularities, and the light can be taken out gradually, and the light guide distance is relatively long. You may mainly use the light-diffusion microparticles | fine-particles 21 with a small refractive index difference, and the light-diffusion microparticles | fine-particles 21 with a large refractive index difference may be mainly used in the position away from a light source. The diffusion effect of light in the light guiding direction can be changed more dynamically, so that a long light guiding distance and high light extraction efficiency can be achieved.

As for the viscosity of the translucent binder 22, 1 mPa * s or more and 100 mPa * s or less are preferable. When the said viscosity is smaller than the lower limit mentioned above, leveling will likely occur in the light guide plate base material 1, and light-diffusion ability will fall. When the said viscosity is larger than the upper limit mentioned above, application | coating nonuniformity will generate easily. Especially preferably, they are 1 mPa * s or more and 20 mPa * s or less.

It is preferable that the difference between the refractive index of the translucent binder 22 and the refractive index of the light guide plate substrate 1 is within ± 0.1. Since the refractive reflection at the interface between the light-transmitting binder 22 and the light guide plate substrate 1 does not have to be considered, the optical design is simple.

By the way, when only a light transmissive binder is apply | coated using a spray coater, the light transmissive binder apply | coated to the light-guide plate base material produces a leveling phenomenon. It is difficult to form an average pitch (hereinafter sometimes referred to as an aspect ratio) of surface irregularities, in particular, uneven height ÷ unevenness sufficient to cause light diffusion by the leveling phenomenon, that is, sufficient to inhibit total reflection, and become flattened. There is a possibility. If the light-transmitting binder is repeatedly applied several times, the coating liquids in the state of fine droplets may be in close contact with each other from the surface tension, and may also be flattened.

In order to improve these, the method of apply | coating a high viscosity translucent binder, and the method of adding (mixing) light-diffusion microparticles | fine-particles to a translucent binder, and forming an unevenness | corrugation can be considered. However, high viscosity of the light transmissive binder tends to cause uneven coating upon spraying. Moreover, when apply | coating the coating liquid which added the light-diffusion microparticles | fine-particles of large diameter to a light-transmissive binder, there exists a possibility that the light-diffusion microparticles may settle in the clogging of the nozzle of a spray coater, or a light-transmissive binder.

Therefore, in this embodiment, the light transmitting binder was diluted to about 1.1 to 10 times with a solvent. For example, the light-diffusion fine particles of 1 micrometer or more and 20 micrometers or less are added to the low-viscosity light-transmitting binder diluted to 1 mPa * s or more and 20 mPa * s, and are provided from the nozzle to the light-guide plate base material. By re-aggregating the light-diffusion fine particles 21 of the sprayed coating liquid 2, the diffusion layer 3 with high light-diffusion ability is obtained (refer FIG. 2A, b and FIG. 3A, b).

That is, the coating liquid 2 sprayed from the nozzle 5 is in a dispersed state while the content of the solvent is large. When the solvent is dried, it reaggregates with one light-diffusion fine particle 21 as a nucleus by surface tension. At this time, the light-diffusion fine particles 21 become aggregates 210 or more. The aggregate 210 is attached to the light guide plate base material 1. In addition, it is not preferable if the solvent remains in a large amount because it causes leveling after deposition. Therefore, you may promote aggregation by using hot air.

If the speed at the time of reaching the light guide plate substrate 1 is high, the grape cluster is broken as shown in Figs. 4A and 4B, so that the light diffusing fine particles 21 are lined up individually, resulting in a decrease in the light diffusing ability. These can be eliminated by adjusting the space | interval T (FIG. 1) from the nozzle 5 to the light-guide plate base material 1. FIG. For example, as the space | interval T from the nozzle 5 to the light-guide plate base material 1, it is preferable to set it as 70 mm or more and 300 mm or less. If the said interval T is shorter than the lower limit mentioned above, drying of a solvent will become inadequate. Therefore, generation | occurrence | production of the aggregate of the light-diffusion microparticles | fine-particles 21 hardly arises, and each light-diffusion microparticles | fine-particles 21 settle in the translucent binder 22, and light diffusion ability may fall remarkably. Moreover, since the arrival speed of the light guide plate base material 1 to the coating surface is fast, aggregates tend to collapse. When the said space | interval T is longer than the above-mentioned upper limit, the flow velocity will become remarkably low until the coating liquid 2 reaches the coating surface of the light guide plate base material 1. Therefore, the coating liquid 2 does not reach the coating surface of the said light guide plate base material 1, but the quantity which spreads outwards increases.

There is no restriction | limiting, such as a ketone system, alcohol system, ester type, as a solvent. However, in order to stabilize the reaggregation of the light-diffusion fine particles 21, it is preferable that a solvent is 60 degreeC or more and 200 degrees C or less. Moreover, it is preferable that solvent is specific gravity 0.8 or more and 1.3 or less from a viewpoint of sedimentation prevention. If the boiling point or specific gravity is higher than the above upper limit, drying of the solvent becomes insufficient. Therefore, generation | occurrence | production of the aggregate of the light-diffusion microparticles | fine-particles 21 may not occur easily. When the said boiling point and specific gravity are lower than the above-mentioned lower limit, there are many things with comparatively low viscosity. For this reason, there are cases where problems such as precipitation of the light diffusing fine particles 21 are likely to occur. As for the said boiling point, 120 degreeC or more and 170 degrees C or less are preferable. Moreover, as for the said boiling point, 130 degreeC or more and 160 degrees C or less are more preferable.

As for the mixing ratio of the mixture of the light-diffusion fine particles 21 and the translucent binder 22 with respect to a solvent, 2 wt% or more and 50 wt% or less are preferable. When the said mixing ratio is more than the upper limit mentioned above, production | generation of the aggregate 210 of the light-diffusion microparticles | fine-particles 21 may be difficult to occur, or coating property may be inferior. Production of the aggregate of the light-diffusion fine particles 21 is not particularly remarkable at least in the above-mentioned lower limit than the above-mentioned lower limit, and there is a case that the increase in cost due to the increase in the amount of the solvent used is problematic. As for the said mixing ratio, 3 wt% or more and 30 wt% or less are more preferable.

Next, the light guide plate base material 1 which spray-coated the coating liquid 2 dries the said solvent by natural air drying, hot air, etc. In the case where the light-transmissive binder 22 is made of an ultraviolet curable resin, ultraviolet rays are irradiated at a subsequent step to cure the light-transmissive binder 22. As a result, as shown in FIG. 2A, B and FIG. 3A, b, the one light-diffusion microparticle 21 is used as the nucleus, and the some light-diffusion microparticles | fine-particles 21 become the aggregate 210 beyond grapevine. The aggregate 210 is attached to the coated surface of the light guide plate substrate 1. This aggregate 210 has a high aspect ratio and forms the diffusion layer 3 of a fine pattern. Therefore, if the coating liquid 2 is applied to the light guide plate substrate 1 without producing a plate or a mold as in the related art, the diffusion layer 3 having excellent light diffusing ability of a fine pattern can be formed simply and inexpensively. . In addition, even if the coating liquid 2 is applied to the light guide plate base material 1 by the spray coating method, the light-diffusion fine particles 21 are hardly flattened because they adhere in an aggregated state. Therefore, the coating liquid 2 can be repeatedly applied to the light guide plate base material 1 by the spray coating method.

Here, the ratio R of the planar area which the aggregate in the coating surface of the light-guide plate base material 1 occupies, and the application area of the coating liquid 2 becomes 0.1% or more and 70% or less. When the said ratio R is less than the lower limit mentioned above, the light-diffusion ability of the light guide plate 100 may be insufficient. When the said ratio R is larger than the above-mentioned upper limit, the light-diffusion ability of the light guide plate 100 will become large too much, and when the light guide length L (FIG. 5) is long, the amount of emitted light in the position far from a light source may be insufficient. .

The light guide plate 100 manufactured as mentioned above coats the diffusion layer 3 by apply | coating the coating liquid 2 containing the light-diffusion microparticles | fine-particles 21 and the translucent binder 22 to the surface of the light-guide plate base material 1 It is. The light diffusing fine particles 21 are formed of an aggregate 210. The ratio R between the planar area occupied by the aggregate 210 in the coated surface of the light guide plate substrate 1 and the coating area of the coating liquid 2 is 0.1% or more and 70% or less. As illustrated in FIG. 5, the light guide plate 100 includes, for example, a line light source 9 such as an LED array provided at one end, a diffuse reflection film 10 provided on the rear surface side, and a diffusion film provided on the front surface side. The surface light source device is constituted by (11). The aggregate 210 of the some light-diffusion microparticles | fine-particles 21 has a high aspect ratio and forms the diffused layer 3 of a fine pattern. Therefore, if the coating liquid 2 is applied to the light guide plate substrate 1 without producing a plate or a mold as in the related art, the diffusion layer 3 having excellent light diffusing ability of a fine pattern can be formed simply and inexpensively. . In addition, you may apply the light-transmitting binder which does not contain the light-diffusion microparticles | fine-particles 21 between the light-guide plate base material 1 and the diffused layer 3 to the whole area | region of the upper surface of the light-guide plate base material 1 with uniform thickness. The light transmitting binder functions as an antistatic layer, a hard coat layer, or the like.

It is preferable that the coating area ratio S of the coating area (planar area of a diffusion layer) of the coating liquid 2, and the area of the coating surface of the light-guide plate base material 1 is 5% or more and 95% or less. When the said coating area ratio S is less than the lower limit mentioned above, the light-diffusion ability of the light guide plate 100 may be insufficient. When the said coating area ratio S is larger than the upper limit mentioned above, absorption of the light by the translucent binder 22 will not be ignored, and brightness may be insufficient.

It is preferable that the number of the light-diffusion fine particles 21 contained in one aggregate 210 is 10 or more and 10,000 or less. When the number is less than the above lower limit, the light diffusion capability of the light guide plate 100 may be insufficient. When the said number is larger than the above-mentioned upper limit, it is easy to produce a nonuniformity, a rough feeling, and an appearance defect, such as a bright point.

However, in the coating surface of the light-guide plate base material 1, in addition to the aggregate in which the number of light-diffusion microparticles | fine-particles 21 is 10 or more and 10,000 or less, with monodisperse light-diffusion microparticles | fine-particles 21 and less than 10 light-diffusion microparticles | fine-particles 21, The aggregate 210 which consists of may exist. In this case, it is preferable that the aggregate 210 which consists of monodisperse light-diffusion microparticles | fine-particles 21 and less than 10 light-diffusion microparticles | fine-particles 21 is less than 20% of the total number of light-diffusion microparticles | fine-particles.

In addition, the number of the light-diffusion microparticles | fine-particles 21 contained in the aggregate 210 can be counted by observation, such as an optical microscope or a laser microscope about 300-1000 times. Moreover, after taking out the aggregate 210 and removing the translucent binder 22, it can count by observation, such as an optical microscope.

In the case where the light diffusing ability is insufficient in one coating, the coating may be repeated. Even if it apply | coats repeatedly and the aggregates of the light-diffusion microparticles | fine-particles 21 adhere and integrate, the high aspect ratio of the said aggregate 210 is maintained. Therefore, there is an advantage that the light diffusing ability is high and it is difficult to cause appearance defects.

It is preferable that the difference of the refractive index of an aggregate and the refractive index of a translucent binder is 0.001 or more and 0.5 or less. The light diffusing ability varies depending on the refractive index difference of the material which is substantially different from the refractive index of the transparent material, the volume of the material, the volume concentration of the material, the shape of the material (shape and irregular shape such as a sphere), the fine irregularities on the surface, and the like. When the said refractive index difference is smaller than the above-mentioned lower limit, refractive scattering property is small and it is difficult to obtain a roughness equalization effect. When the said refractive index difference is larger than the above-mentioned upper limit, the reflection in an interface (convex interface) increases, and it is hard to obtain the roughness equalization effect, for example, when comparatively long light guide lengths, such as 300 mm or more.

It is preferable that the arithmetic mean surface roughness of the fine unevenness in the aggregate 210 is 0.01 µm or more and 10 µm or less. When the said arithmetic mean surface roughness is smaller than the above-mentioned lower limit, reflection scattering property is small and it becomes easy to become dark overall. When the arithmetic mean surface roughness is larger than the above-mentioned upper limit, the reflection scattering element is physically large and the illuminance uniformity effect is difficult to be obtained, such as locally bright in the vicinity of the light source.

&Lt; Embodiment 2 &gt;

Embodiment 2 of this invention is described below. The light guide plate of this embodiment and the manufacturing method of the light guide plate are substantially the same as the manufacturing method of the light guide plate and light guide plate of Embodiment 1, but as it moves away from a light source so that the brightness of a light guide plate may become substantially uniform, in the coating surface of a light-guide plate base material The ratio (R) of the planar area occupied by the aggregate and the coating area of the coating liquid or the coating area of the coating liquid and the area of the coated surface of the light guide plate substrate was increased. That is, as it moved away from a light source, the application density of light-diffusion microparticles | fine-particles was made high.

With the recent increase in the size of the display device, the size of the backlight is also required. That is, it is necessary to lengthen the light guide length L (FIG. 5). In order to make the brightness of the light exit surface of the light guide plate uniform, it is necessary to reduce the light diffusing ability of the diffusion layer in the vicinity of the light source, particularly in the light guide plate, and increase the light diffusing ability as the light guide plate moves away from the light source. For this reason, it is necessary to significantly increase the light diffusion capability of the diffusion layer at the position farthest from the light source in the light guide plate. If the patterning of the diffusion layer is inappropriate or the pattern design is inferior, even if the printing accuracy is inferior, only the end portion near the light source in the light guide plate is bright and the center part is dark, that is, the essential performance as the light guide plate is not satisfied, or the light output There is a problem that luminance unevenness of the surface occurs. From these viewpoints, it is necessary to precisely form a pattern arrangement in which the pattern of the diffusion layer is made finer, and the diffusion portion becomes coarser as it gets closer to the light source and becomes denser as it moves away from the light source. In addition, "near light source" means the site | part located closest to the light source in the effective light output part of a light guide plate. That is, the "near light source" means the edge part of the side in which a light source is installed. The "distance from the light source" means the site | part away from the light source in the effective light output part of a light guide plate. That is, "the position farthest from a light source" means the edge part of the side which opposes the edge part of the side in which the light source 9 is provided in the case of the light guide plate shown in FIG.

In this embodiment, the coating liquid 2 is applied to the light guide plate base material 1 by the spray coating method in the same manner as in the first embodiment. At this time, a plurality of light-diffusion fine particles 21 are aggregated to grape grapes or more with one light-diffusion fine particles 21 as a nucleus. The aggregated aggregate 210 as described above is a pattern arrangement of gradation distribution that becomes denser as it moves away from the light source.

Here, the PMMA board | substrate of thickness 5mm and light guide length 600mm was repeated the scanning of the nozzle to a Y direction by the constant feed pitch in the X direction, and tried uniform coating. And the LED array light source 9 was installed in the left end of the light guide plate 100 which apply | coated the coating liquid 2 by changing a conveyance pitch on the conditions shown in FIG. The coating surface of the light guide plate base material 1 was made into the emission surface side. The diffuse reflection film 10 was installed in the back surface of a coating surface. The diffusion film 11 was installed in the front surface of a coating surface. Thus, the side light type backlight was produced. As shown in FIG. 5 from above of this side light type backlight, it measured using the surface luminance measuring device 12. As shown in FIG. In this case, the side arrange | positioned in the Y direction in the light-guide plate base material 1 turns into the 1st side said by this invention.

The coating width by scanning of the nozzle 5 once in a Y direction is about 50 mm. The central portion has a distribution similar to the Gaussian distribution such that the coating density of the light diffusing fine particles 21 is high and gradually decreases as it goes outward. In the case of a rough pitch such that the feed pitch in the X direction exceeds 10 mm, nonuniformity occurs in the coating density of the light-diffusion fine particles 21, and light and light nonuniformity occurs in the luminance distribution as shown in FIG. By setting the feed pitch to 10 mm, coating without unevenness due to the feed pitch is possible.

As shown in FIG. 6, the further away from the light source 9, the lower the relative luminance. The light diffusion performance of the light guide plate 100 coated with the coating liquid 2 is proportional to the coating density of the light diffusing fine particles 21 on the surface of the light guide plate substrate 1. Therefore, what is necessary is just to spray-coat the said coating liquid 2 so that the application density of the light-diffusion microparticles | fine-particles 21 may be low on a light source side, and high on the far side of a light source. The method is described below.

7A and 7B repeat the scan for moving the nozzle 5 in the Y direction at a predetermined feed pitch in the X direction and light diffusion around the central portion of the light guide plate substrate 1 in one dimension. It shows the state of the gradation distribution which makes the application | coating density of the microparticles | fine-particles 21 high, and makes the coating density of the light-diffusion microparticles | fine-particles 21 low on both sides (namely, cross section A, B side) of the said central part.

This light guide plate base material 1 assumes the light guide plate base material which installs line light sources, such as an LED array, in both end surfaces A and B. As shown in FIG. In the example of FIGS. 7A and 7B, the coating amount of the coating liquid 2 is kept constant, and the nozzle 5 is scanned at a constant speed in the Y direction. From the end surface A side, the conveyance pitch of the nozzle 5 to the X direction starts from 10 mm so that there may be no unevenness. The coating liquid 2 is applied around the central portion of the light guide plate substrate 1 so that the conveying pitch is gradually narrowed. This realizes a complete gradation distribution without discontinuities.

In realizing the gradation distribution, the spray coating method has a very high degree of freedom. 8A and 8B summarize each parameter and various coating methods when applying the coating liquid 2. Here, the case where the light guide plate of the both ends light source type which installs line light sources, such as an LED array, in the left and right end surface A, B of the light-guide plate base material 1 is considered.

In the case of both-end light source types, in order to make the in-plane luminance distribution constant, the ratio R or the coating area ratio S are increased as the distance from the light source increases. That is, the application | coating density of the light-diffusion fine particles 21 in the both ends of the light-guide plate base material 1 is made low, and the application | coating density of the light-diffusion fine particles 21 is made high around the center part. Other conditions are set such that the light-diffusion fine particles 21 are preferably aggregates 210 and adhered to the light guide plate substrate 1. In addition, in this embodiment, the X direction was made into the longitudinal direction of the light guide plate base material 1, ie, the light guide direction, and the Y direction was made into the width dimension direction of the light guide plate base material 1.

In the table of FIG. 8B, as each parameter, the scanning direction of the nozzle 5, the scanning speed of the nozzle 5, the feed pitch of the nozzle 5, the coating amount per unit time of the coating liquid 2, and the like can be considered. . Any one or more of these parameters are controlled, and the other parameters are made constant.

Specifically, the coating method 1 shown in FIG. 8B applies the coating liquid 2 as follows. In the said coating method (1), the side arrange | positioned in the Y direction in the light-guide plate base material 1 becomes a 1st side said by this invention.

First, all parameters are made constant and the coating liquid 2 is apply | coated uniformly to the whole or one part of the transparent light-guide plate base material 1 (FIG. 9A). Next, the coating liquid 2 is applied repeatedly in the same manner around the central portion. That is, all parameters are made constant and application | coating of the coating liquid 2 is repeated around a center part.

Thereby, as it moves away from a light source, the said ratio R or coating area ratio S is made high. That is, the application | coating density of the light-diffusion fine particles 21 in the both ends near the light source of the light-guide plate base material 1 is made low, and the application | coating density of the light-diffusion fine particles 21 around the center part far from a light source is made high. Although this situation is shown in FIG. 9A, a finite step cannot necessarily be avoided at the boundary which overlaps. Therefore, it is preferable to make the coating amount of the coating liquid 2 as small as possible, and to make the scanning speed of the nozzle 5 as fast as possible. That is, it is preferable to apply | coat the coating liquid 2 so that the application density of the light-diffusion microparticles | fine-particles 21 in one uniform coating may be made as little as possible, and the number of overlap application | coatings may be increased.

In addition, about such multilayer overlap application | coating, you may perform overlap application | coating, changing suitably, changing the application amount of the coating liquid 2, the scanning speed of the nozzle 5, the conveyance pitch of the nozzle 5, etc ..

The coating method (2) shown to FIG. 8B is the coating method which changed only the feed pitch to X direction continuously, and made another parameter constant. The said coating method (2) also turns into the 1st edge | part mentioned by this invention in the side arrange | positioned in the Y direction in the light-guide plate base material 1.

The application density of the light-diffusion fine particles 21 to be applied increases and decreases in inverse proportion to the conveyance pitch of the nozzle 5. Therefore, the feed pitch is continuously increased or decreased so as to be inversely proportional to the desired gradient distribution function (Fig. 9B). That is, the feed pitch of the nozzle 5 is made wide at the both ends of the light guide plate base material 1, and the feed pitch of the nozzle 5 is made narrow at the center part periphery.

Thereby, as it moves away from a light source, the said ratio R or coating area ratio S is made high. That is, the application | coating density of the light-diffusion fine particles 21 in the both ends near the light source of the light-guide plate base material 1 is made low, and the application | coating density of the light-diffusion fine particles 21 around the center part far from a light source is made high. In this coating method (2), even if it does not apply | coat the coating liquid (2) repeatedly, desired gradation distribution is obtained and productivity is high. In addition, since it is a complete gradation distribution in which no discontinuity points occur, a high quality surface light source device without luminance unevenness is obtained.

The coating method 3 shown in FIG. 8B is a coating method in which only the scanning speed is changed for each scan of the nozzle 5 and other parameters are fixed. The said coating method (3) also turns into the 1st edge | part mentioned in this invention in the side arrange | positioned in the Y direction in the light-guide plate base material 1.

The coating density of the light-diffusion fine particles 21 is inversely proportional to the scanning speed of the nozzle 5. Therefore, as shown in FIG. 9C, the scanning speed for every scan of the nozzle 5 is continuously changed so that it may become an inverse relationship of a desired gradation distribution. That is, both ends of the light guide plate substrate 1 make the scanning speed of the nozzle 5 fast and slow around the central portion.

Thereby, as it moves away from a light source, the said ratio R or coating area ratio S is made high. That is, the application | coating density of the light-diffusion fine particles 21 in the both ends near the light source of the light-guide plate base material 1 is made low, and the application | coating density of the light-diffusion fine particles 21 around the center part far from a light source is made high. This coating method (3) is also preferable in both surfaces of productivity and a luminance nonuniformity grade.

The coating method 4 shown to FIG. 8B is a coating method which changed only the application | coating flow volume of the coating liquid 2 for every scan of the nozzle 5, and made another parameter constant. The said coating method (4) also turns into the 1st edge | part mentioned by this invention in the side arrange | positioned in the Y direction in the light-guide plate base material 1.

That is, as the nozzle 5 is transferred from the end face A side to the center part at a predetermined pitch, the coating amount of the coating liquid 2 is increased, and the coating liquid 2 is transferred from the center part to the end face B side where the light source is installed. ), The coating amount is reduced (FIG. 9D).

Thereby, as it moves away from a light source, the said ratio R or coating area ratio S is made high. That is, the application | coating density of the light-diffusion fine particles 21 in the both ends near the light source of the light-guide plate base material 1 is made low, and the application | coating density of the light-diffusion fine particles 21 around the center part far from a light source is made high. In the spray coating method which can set the coating amount setting of the coating liquid 2 quickly, easily, and with high reproducibility, during coating, this coating method (4) is also preferable on both surfaces of productivity and a luminance nonuniformity grade.

However, in the cross section A side, the amount of application of the coating liquid 2 is excessive, and the aggregate 210 of the light-diffusion fine particles 21 is allowed to settle in the light-transmitting binder 22. As the nozzle 5 is transferred to the center part, the application amount of the coating liquid 2 is made an appropriate amount. In addition, as the nozzle 5 is transferred from the center portion to the cross-section B side, the coating amount of the coating liquid 2 is excessively again, and the aggregate 210 of the light-diffusion fine particles 21 is allowed to settle in the transparent binder 22. By coating in this way, the same effect can be obtained.

The coating method 5 shown in FIG. 8B is a coating method which repeats the scan which moves the nozzle 5 to an X direction at a predetermined feed pitch in a Y direction. Specifically, the scanning speed is continuously changed during the scanning of the nozzle 5, and the other parameters are made constant. In the coating method (5), the side disposed in the X direction in the light guide plate substrate 1 is the first side in the present invention.

In detail, the scanning speed of the nozzle 5 to the X direction is changed continuously so that it may become an inverse function relationship of a desired gradation distribution function. That is, in the scanning of the nozzle 5 in the X direction, the scanning speed of the nozzle 5 is rapidly increased at both ends of the light guide plate substrate 1 and is slowed around the center portion (FIG. 9E).

Thereby, as it moves away from a light source, the said ratio R or coating area ratio S is made high. That is, the application | coating density of the light-diffusion fine particles 21 in the both ends near the light source of the light-guide plate base material 1 is made low, and the application | coating density of the light-diffusion fine particles 21 around the center part far from a light source is made high. This coating method (5) is also preferable in both surfaces of productivity and a brightness nonuniformity grade.

The coating method 6 shown in FIG. 8B is also a coating method which repeats the scan which moves the nozzle 5 to a X direction at a predetermined feed pitch in a Y direction. Specifically, the coating amount of the coating liquid 2 is continuously changed during the scanning of the nozzle 5, and other parameters are made constant. The said coating method (6) also turns into the 1st edge | part mentioned in this invention in the side arrange | positioned in the X direction in the light-guide plate base material 1.

In detail, in the scanning of the nozzle 5 in the X direction, the coating amount of the coating liquid 2 is small at both ends of the light guide plate substrate 1 and is ejected a lot around the central portion (FIG. 9F).

Thereby, as it moves away from a light source, the said ratio R or coating area ratio S is made high. That is, the application | coating density of the light-diffusion fine particles 21 in the both ends near the light source of the light-guide plate base material 1 is made low, and the application | coating density of the light-diffusion fine particles 21 around the center part far from a light source is made high. This coating method (6) is also preferable in both surfaces of productivity and a brightness nonuniformity grade. Moreover, when the application amount of a coating liquid can be changed at high speed, desired gradation distribution can be implement | achieved easily by this coating method (6).

However, at both ends of the light guide plate substrate 1, the coating amount of the coating liquid 2 is excessively set so that the aggregate 210 of the light-diffusion fine particles 21 is settled in the light-transmitting binder 22, and in the center portion, the coating liquid 2 is applied. Even if the application amount of is set to an appropriate amount, the same effect can be obtained.

It explains in more detail quantitatively. First, the light-diffusion fine particles 21 and the light-transmitting binder 22, and the coating liquid 2 which contains a solvent as needed further, the light guide plate by the conveyance pitch which brightness unevenness generate | occur | produces, for example, the conveyance pitch of 10 mm. Uniform coating is performed on the base material 1. The light guide plate uniformly coated in this manner is produced by varying the coating amount of the coating liquid 2, the scanning speed of the nozzle 5, and the like (three types of α to γ in the illustrated example). FIG. 10A shows the coating density of the light diffusing fine particles 21 of the manufactured light guide plates α to γ. About each light guide plate (alpha)-(gamma), when a line light source, such as an LED array, is provided in the left end, and luminance distribution is measured like FIG. 5, it will become as shown to FIG. 10B. Based on this, the application | coating density of the light-diffusion microparticles | fine-particles 21 which give in-plane uniform brightness | luminance becomes as shown to FIG. 10C, when it is a light guide plate of the left and right light sources. Moreover, in the case of the light guide plate of a left end light source, it becomes as shown to FIG. 10D.

In order to realize the application density of such light-diffusion microparticles | fine-particles 21, the six types of coating methods (1)-(6) shown to FIG. 8B are used preferably, respectively. The scanning speed in the X direction of the coating liquid (2) coating amount F (X, Y), the nozzle (5) scan speed V _Y (X), the nozzle 5 in the Y direction of the V _X (X), the nozzle ( 5) the feed pitch ΔX (X) in the X direction and the feed pitch ΔY (X) in the Y direction of the nozzle 5. What is necessary is just to coat the coating methods (1)-(6) shown to FIG. 8B as follows. However, the X coordinate at the left end of FIG. 8A is X ₀ , and the coating amount of the coating liquid 2 at the left end is F ₀ , V _Y0 , ΔX ₀ , and the target coating density of the light diffusing fine particles 21 at the left end, respectively. If the C _0, the target density of the coating C (X) of the light-diffusing particles 21 in the position X in Figure 10c or Figure 10d is, if the coating is determined with the parameters as follows. At this time, in order to prevent coating unevenness, in all cases, it is necessary to set the conveyance pitch of the longest nozzle to be 10 mm mentioned above.

Coating method (1) ： F, V _Y , ΔX and the number of overlapping coatings are appropriately selected and performed.

Coating method (2): ΔX (X) = ΔX ₀ × C ₀ / C (X ₀ + ΣΔX), F and V _Y are constant

Coating method (3): V _Y (X) = V _{Y 0} × C ₀ / C (X ₀ + ΣΔX), F and ΔX are constant

Coating method (4): F (X) = F ₀ × C (X ₀ + ΣΔX) / C ₀ , V _Y and ΔX are constant

Coating method _{(5): V X (X} ) = V X0 × C 0 / C (X), F is constant and ΔY

Coating method (6): F (X) = F ₀ × C (X) / C ₀ , V _X and ΔY are constant

Moreover, you may use together the coating methods (1)-(6) as needed.

Using such coating methods (1)-(6), a diffusion layer is coated by apply | coating the coating liquid containing light-diffusion microparticles | fine-particles and a translucent binder to the surface of the light-guide plate base material 1. The light diffusing fine particles become aggregates. The ratio of the planar area occupied by the aggregate in the coating surface of the light guide plate substrate 1 to the coating area of the coating liquid is 0.1% or more and 70% or less. Therefore, also in this embodiment, the aggregate of some light-diffusion microparticles | fine-particles has a high aspect ratio and forms the diffused layer of a fine pattern. Therefore, if a coating liquid is applied to the light guide plate substrate 1 without producing a plate or a mold as in the related art, a diffusion layer having excellent light diffusing ability of a fine pattern can be formed simply and inexpensively.

In addition, the spray coating method can be applied to the surface or the back surface of the light guide plate substrate 1 and further to both surfaces without any problem. For example, 1-dimensional gradation distribution with respect to the X direction is implement | achieved by the said coating methods (1)-(6) about a surface, and Y-direction is performed by the said coating methods (1)-(6) about a back surface. It is also possible to realize a one-dimensional gradation distribution with respect to the light guide plate of the three-sided light source type and the four-sided light source type.

In general, in order to realize a gradation distribution with high light emission efficiency, a wide diffuse reflecting capability range, that is, a coating density range of the light diffusing fine particles 21 is required. It is generally difficult to increase or decrease the coating density of the light diffusing fine particles 21 to achieve light diffusion performance of 5 to 10 times or more. In such a case, gradation distribution is realized by the coating methods (1) to (6) so that the coating density of the light-diffusion fine particles 21 is uniformly spray-coated on the back surface and the light diffusion performance of the insufficient amount is compensated for on the surface. do. Thereby, it may be easy to manufacture the gradation light guide plate of high brightness luminous efficiency uniformly. This invention can be effectively applied also in such a case.

In addition, the spray coating method can be easily applied to a large light guide plate of 50 inches or more, for example. Injection molding, press molding, dot printing, etc. all require large precision molds and screen plates, and large equipment is required, and investment costs are high. Moreover, also in the inkjet printing method, a large amount of investment is required in order to respond to large board | substrate. With the spray coating method, only a light and small nozzle is scanned in the X-Y direction. Therefore, the objective is achieved by inexpensive facilities. That is, the spray coating method of this invention is applied to a large light guide plate by inexpensive installation. It is especially preferable for the light-guide plate whose light-guide length L is 900 mm or more. In this case, it is preferable that the ratio of the illuminance in the vicinity of the light source and the illuminance at the position furthest from the light source is 0.8 or more and 1.2 or less.

Moreover, when the thing which contained the diffuser in the light-guide plate base material itself is used, the coating density of the light-diffusion microparticles | fine-particles apply | coated to a surface can be reduced and apply | coated as a whole. Therefore, it is beneficial in some cases. For example, as described above, light diffusion performance is insufficient only by surface coating. For example, in the case of a thick and short light guide plate, while the light guide light incident from the light source does not sufficiently collide with the diffuse reflection surface, the opposite end surface may be reached and not sufficiently surface-emitted. In that case, by slightly dispersing the diffuser in the light guide plate, it is possible to effectively emit light. This invention is used suitably also for such a use.

Incidentally, the coating area ratio S1 in the vicinity of the light source is 5% or more and 50% or less, and the coating area ratio S2 at the position farthest from the light source is 20% or more and 95% or less, and S2> S1. It is preferable.

Moreover, the coating surface of the light-guide plate base material 1 in the position farthest from the light source is (2π / 360) x 60 rad gross | gloss value GS1 of 40 to 90 or less of the coating surface of the light-guide plate base material in the vicinity of a light source. The (2π / 360) x 60 rad gross value GS2 is 10 or more and 60 or less, and GS2> GS1 may be sufficient as it.

Moreover, the haze value H1 of the surface direction in the vicinity of a light source is 5% or more and 30% or less, and the haze value H2 in the position which is furthest from a light source is 10% or more and 40% or less, and H2> H1. It may be.

<Embodiment 3>

Embodiment 3 of this invention is demonstrated below. Although the manufacturing method of the light-guide plate and light-guide plate of this embodiment is substantially the same as the manufacturing method of the light-guide plate and light-guide plate of Embodiment 2, it differs in the point which makes light-diffusion fine particle into two-dimensional gradation distribution. Therefore, only different parts are demonstrated in detail.

FIG. 11 schematically shows a two-dimensional gradation distribution assuming that a linear light source is provided on four sides of the light guide plate 100. That is, M in FIG. 11 has shown the part which the coating density of light-diffusion microparticles | fine-particles are substantially equal by the line | wire. N in FIG. 11 showed distribution of the X direction of the coating density of light-diffusion microparticles | fine-particles. P in FIG. 11 showed distribution in the Y direction of the coating density of light-diffusion microparticles | fine-particles. If this target gradation distribution can be represented by C (X, Y), it can manufacture by using coating method (1)-(6) individually or in combination.

Application | coating of the coating method (1) becomes possible by carrying out overlap application | coating sequentially along the line of (a) in FIG. In order to prevent a luminance nonuniformity and a brightness | luminance level difference in the boundary of overlapping application | coating, a sufficient number of overlapping application | coating is required.

Application of the coating method (3) becomes possible by continuously changing a scanning speed during one scan of a nozzle to a Y direction. That is, what is necessary is just to scan the scanning speed of the nozzle to a Y direction by the following formula | equation.

V _Y (X, Y) = V _Y0 × C ₀ / C (X ₀ + ΣΔX, Y), F and ΔX are constant

Application of the coating method (4) becomes possible by continuously changing the application amount of a coating liquid during one scan of the nozzle to a Y direction. That is, during the scanning of the nozzle in the Y direction, the coating amount of the coating liquid may be ejected according to the following formula.

F (X, Y) = F ₀ × C (X ₀ + ΣΔX, Y) / C ₀ , V _Y and ΔX are constant

By combining the coating methods (5) and (6), a two-dimensional gradation distribution can also be realized. That is, what is necessary is just to scan a nozzle to a X direction according to the following formula | equation.

_{V X (X, Y) =} V X0 × C 0 / C (X, Y), F is constant and ΔY

F (X, Y) = F ₀ × C (X, Y) / C ₀ , V _X and ΔY are constant

In addition, by applying the coating method (2), two-dimensional gradation distribution can also be realized by changing the scanning speed of a nozzle and the application amount of a coating liquid during scanning of a nozzle in a Y direction.

The two-dimensional gradation distribution herein is not limited to that of a four-sided light source, but may be an orthogonal two-sided light source or a three-sided light source. This is the same also in the one-dimensional gradation distribution mentioned above.

In the manufacturing method of the light guide plate in above-mentioned Embodiment 1, 2, when productivity is considered, it takes time to coat the coating surface of the light-guide plate base material of a large area only with one nozzle. Therefore, it is not necessarily advantageous measures. 12 arrange | positions the some nozzle 5 in parallel at equal intervals, for example in a Y direction, ie, a direction orthogonal to a scanning direction. The plurality of nozzles 5 are scanned in the X direction. However, the structure which arrange | positions the some nozzle 5 in parallel at equal intervals in the X direction, and scans the said some nozzle 5 in the Y direction may be sufficient. By using the multi nozzle in this manner, the application time can be significantly shortened. The space | interval of the adjacent nozzles 5 and 5 needs a sufficiently wide space | interval which does not interfere with each other at the time of application | coating, or may arrange | position differently by shifting adjacent nozzles to an X direction depending on a case.

These several nozzles 5 are controlled individually or in common, and spray-coat a coating liquid to the light guide plate base material 1.

In the case of 1-dimensional gradation distribution, the nozzle 5 arrange | positioned in parallel by applying the coating method (5) or (6), for example, is scanned once in a X direction. At this time, each nozzle 5 is made into the same flow volume. Next, it scans in the X direction by the coating method (5) or (6), shift | deviating to a Y direction by a sufficiently small Y-direction feed pitch which does not produce a luminance nonuniformity, for example, 10 mm. This can be uniformly applied to the entire surface by scanning the nozzle intervals.

In the case of two-dimensional gradation distribution, it becomes possible by controlling the application amount of the coating liquid 2 from each nozzle 5 independently for every scan so that it may correspond to the application | coating density distribution of light-diffusion microparticles | fine-particles in a Y direction.

FIG. 13: shows the start-up and manufacturing process at the time of spray-coating using the coating liquid of the light-diffusion fine particle which a translucent binder is an ultraviolet curable type, and also used the solvent. First, after spray-coating the coating liquid 2 to the light guide plate base material 1, the solvent is dried by warm air or the like. Subsequently, ultraviolet light is irradiated to cure the light transmitting binder, and the light diffusing fine particles are permanently bonded to the surface of the light guide plate substrate.

In many cases, the light guide plate with desired luminance uniformity is rarely obtained by one gradation distribution design. However, according to the present invention, as shown in Fig. 13, the luminance distribution is measured and evaluated immediately, and when the desired uniformity is not obtained, fine adjustment is made to each parameter and coating is performed again. If this is repeated as necessary, the gradation distribution of light-diffusion fine particles can be realized easily and in a short time.

As described above, according to the present invention, the one-dimensional gradation distribution diagram and the two-dimensional gradation distribution diagram of the light-diffusion fine particles can be started and produced immediately from the design without requiring a mold or a printing plate. In particular, the gradation distribution of the light-diffusing fine particles of the uniform brightness uniformly capable of emitting the light of the light source efficiently and uniformly forward is different depending on the size, shape, plate thickness, light source position, etc. of the light guide plate. The method of the invention is such a variety of varieties and is preferably applied to a variety of production.

In the first embodiment, the aggregate 210 of the light diffusing fine particles 21 is attached to the light guide plate substrate 1 at random. In the second embodiment, as the distance from the light source 9 increases, the ratio (R) or the coating liquid of the planar area occupied by the aggregate 210 in the coated surface of the light guide plate substrate 1 and the coating liquid 2 is applied. The coating area ratio S of the application area of (2) and the area of the coating surface of the light-guide plate base material 1 is made high. However, when the ratio of the planar area occupied by the aggregate 210 on the coated surface of the light guide plate substrate to the application area of the coating liquid 2 satisfies the requirement of 0.1% or more and 70% or less, aggregates of the light-diffusion fine particles 21 ( 210 may be attached to the light guide plate substrate 1 substantially uniformly. That is, the value of the ratio S2 / S1 of the coating area ratio S1 in the vicinity of the light source 9 and the coating area ratio S2 in the position which is furthest from the light source 9 is 80% or more and 120% It is comprised so that it may be as follows.

In the said Embodiment 2, although the ratio of the planar area which the aggregate 210 in the coating surface of the light-guide plate base material 1 occupies, and the coating area of the coating liquid 2 is made into 0.1% or more and 70% or less, it is limited to this. It is not. In other words, the portion close to the light source may have a low coating density of the light diffusing fine particles, and the portion far from the light source may have a high coating density of the light diffusing fine particles.

In the first to third embodiments, the light-diffusion fine particles 21 are aggregated, but the present invention is not limited thereto. That is, the light-diffusion fine particles 21 do not need to be aggregated. At this time, in order to obtain preferable light-diffusion performance, spray application conditions, such as light-diffusion microparticles | fine-particles, a light-transmitting binder, a solvent, and the space | interval of a light guide plate base material and a nozzle, are controlled and selected suitably. At this time, for example, the coating liquid 2 may be applied in the form of a droplet (FIG. 14). Moreover, in order to enlarge light-diffusion performance, you may cover the whole surface with the coating liquid 2 (FIG. 15). Incidentally, FIGS. 16A and B are micrographs of a state in which a coating liquid of MS fine particles, an ultraviolet curable light transmitting binder, and a solvent is spray-coated onto a PMMA substrate and cured. In FIG. 16A and B, the part expressed like a bubble is light-diffusion microparticles | fine-particles. Since the light-diffusion fine particles adhering to the coated surface of the light guide plate substrate 1 each become a diffusion portion, a fine diffusion portion can be easily formed. Moreover, since light-diffusion microparticles | fine-particles are apply | coated randomly, it can suppress generation | occurrence | production of moire.

Example

&Lt; Example 1 &gt;

An acrylic resin sheet having a length (length in the light guide direction) 1200 mm, a width of 1000 mm, and a thickness of 8 mm is placed on the surface plate (stage) as a light guide plate substrate, and the nozzle of the spray coater is placed from above the acrylic resin sheet. The coating liquid was sprayed by. The coating liquid is a mixed solution diluted so as to have a solid content of 5 wt% with a resin fine particle (refractive index 1.56, an average particle diameter of 3 μmφ) as light-diffusing fine particles, an acrylic ultraviolet curable resin as a light transmitting binder, and a ketone solvent as a diluting solvent. Nitrogen gas was entrained with this coating liquid, and it ejected.

At this time, in order to apply | coat a coating liquid to the whole surface, it sprayed, moving a nozzle in the plane direction (namely, X, Y direction) of a light-guide plate base material. Specifically, the coating amount is changed in the longitudinal direction (that is, the X direction) of the light guide plate substrate, and once to 8 at the feeding pitch of the nozzle 10 to 40 mm depending on the place so as to be most applied at the center portion in the X direction. Multiple overlapping applications were performed. Incidentally, the distance between the light guide plate substrate 1 and the nozzle 5 is 100 to 200 mm, the coating amount of the coating liquid 2 is 0.5 to 4.0 gr / min, and the scanning speed of the nozzle 5 is 200 to 400 mm. It was / sec.

As a result, the surface state by coating became gloss 15 in the gross 85 and the 600-mm-long position in the light source vicinity.

Subsequently, a light source in which white LEDs were arranged in a line at both ends of the light guide plate substrate was provided, and a light diffusion film was laminated on the back diffusion side of the light guide plate substrate and a coating surface serving as the surface side to produce a side light type backlight. It was.

As a result of visual observation of the side light type backlight at a position 2 m away from the front face, the luminance was uniform throughout the entire surface, and luminance unevenness such as a bright point was not noticeable.

<Example 2>

On the surface plate (stage), the transparent PMMA light-guide plate base material of the same size as Example 1 was put, and the coating liquid was apply | coated with the nozzle from the upper side like FIG. At this time, by the coating method (1) shown in FIG. 8B, uniform application | coating was performed first by making a scanning direction into the Y direction, and making it into the X direction feed pitch of 10 mm pitch. The coating liquid is crosslinked particles of MS resin (average particle diameter 3 µm, solids equivalent concentration excluding 10% solvent) as light-diffusion fine particles, urethane-based ultraviolet curable resin as a light-transmissive binder, and PGMAC (propylene glycol monomethyl ether acetate) as a diluting solvent. It is a mixed solution diluted so that it may become 20 weight% of solid content with. Nitrogen gas was entrained with this coating liquid, and it ejected.

The distance between the light guide plate substrate and the nozzle was 150 mm, the coating amount of the coating liquid was 1 ml / min in terms of solution, and the scanning speed of the nozzle was 150 mm / min. In this case, the coating width was about 50 mm.

Under this condition, the coating liquid was applied to the entire surface of the light guide plate substrate while transferring the scan in the Y direction of the nozzle at intervals of 10 mm in the X direction. However, at the beginning of coating on one end face (lower end face in the sheet in Fig. 5) arranged in the X direction, air scanning was started 20 mm before the light guide plate substrate. Moreover, the light guide plate base material was also scanned to the place exceeding 20 mm also in the last application | coating on the other end surface (upper end surface in the surface of FIG. 5) arrange | positioned in the X direction. Coating was carried out from 20 mm in front of the light guide plate base material on one end face (left end face in the sheet of FIG. 5) arranged in the Y direction. Further, the light guide plate substrate was coated over 20 mm on the other end face (right end face in the ground in Fig. 5) arranged in the Y direction, and the coating nonuniformity in the direction change part of the nozzle was prevented from entering the base body. .

In order to manufacture the light guide plate of a both ends light source type, 8 steps of overlap | coating was performed like FIG. 9A. The side light type backlight was produced like Example 1, with the coating surface of this light guide plate being an emission side. As a result of the appearance inspection and the luminance distribution of the side light type backlight, the luminance step of eight stages was visually recognized, but a sufficiently acceptable uniform light guide plate was obtained.

<Example 3>

Although coating was started under the same conditions as in Example 2, in the coating method (3), a method of semi-continuously changing the scanning speed in the Y direction by the X-direction feed pitch was used. In the coating conditions of Example 2, the coating distribution of the light-diffusion fine particles on the light-guide plate base material 1 of the uniform coating in which the X-direction feed pitch is 10 mm is C ₀ and the scanning speed in the Y direction of the nozzle 5 is 150 mm / min. the V _Y0, and a constant feed pitch ΔX = 10 ㎜ in the X direction of the nozzles 5 and made to change in sequence as follows for n scanning speed V _Y (X) on the light guide plate of th base material (1). All other variables were coated uniformly.

V _Y (X) = V _{Y 0} × C ₀ / C (X ₀ + ΣΔX)

As a result of the appearance inspection and the luminance distribution measurement using the coated light source as both ends, a high quality light guide plate was obtained at which no luminance unevenness or luminance step was observed and the luminance uniformity accuracy was very high.

In addition, this invention is not limited to the said embodiment and Example, It can change suitably in the range which does not deviate from the meaning.

Industrial availability

The manufacturing method of the light guide plate and light guide plate of this invention can be used as a surface light source device which irradiates light from the back surface, such as a liquid crystal display panel and a signboard, a light guide plate for what is called a backlight device, and a light guide plate.

1: light guide plate base material
2: coating liquid
3: diffusion layer
4: spray coater
5: nozzle
6: reservoir
7: flow control
9: light source
10: Diffuse Reflective Film
11: diffusion film
12: surface luminance meter
21: light diffusing fine particles
22: light transmitting binder
100: light guide plate
210: aggregate

Claims (14)

In order to form a surface light source device, as a manufacturing method of the light guide plate in which a light source is arrange | positioned at the end surface,
The diffusion layer is coated by applying a coating liquid containing light-diffusing fine particles and a light-transmitting binder in the form of fine droplets on the back surface, the surface, or both surfaces of the light-guide plate substrate, wherein the light-diffusion fine particles are formed into an aggregate and the coated surface of the light-guide plate substrate A ratio of the planar area occupied by the agglomerates to and the coating area of the coating liquid is 0.1% or more and 70% or less. The method of claim 1,
When coating the diffusion layer, a portion close to the light source lowers the coating density of the light diffusing fine particles, and a portion far from the light source increases the coating density of the light diffusing fine particles. The method of claim 1,
The said coating liquid is apply | coated to the back surface, the surface, or both surfaces of the said light-guide plate base material by the spray coating method which sprays the said coating liquid from a nozzle, The manufacturing method of the light-guide plate characterized by the above-mentioned. The method of claim 3, wherein
A method of manufacturing a light guide plate, wherein a plurality of nozzles are arranged in parallel and the plurality of nozzles are scanned in substantially parallel to change the coating density of the light-diffusion fine particles in one or two dimensions. The method according to claim 3 or 4,
The interval from the nozzle to the coating surface in the light guide plate base material is 70 mm or more and 300 mm or less. The method according to claim 3 or 4,
The said spray coating method scans which moves the said nozzle in the direction substantially parallel to the 1st side of the said light-guide plate base material on the coating surface of the said light-guide plate base material, while spraying the said coating liquid from a nozzle. The coating liquid is applied to the entire surface or part of the coating surface by repeating at a predetermined feed pitch in a direction perpendicular to the direction. The method according to claim 3 or 4,
A step of repeating a scan for moving the nozzle in a direction substantially parallel to the first side of the light guide plate substrate at a predetermined feed pitch in a direction orthogonal to the first side is partially performed on the coated surface of the light guide plate substrate. The method of manufacturing a light guide plate characterized by changing the coating density of the light-diffusion fine particles one-dimensionally by repeating. The method according to claim 3 or 4,
The coating density of the light-diffusion fine particles is changed in one dimension by changing the feed pitch of the nozzle and applying the coating liquid to the entire surface or part of the coated surface of the light guide plate substrate. . The method according to claim 3 or 4,
The coating density of the light-diffusion fine particles is changed in one dimension by changing the scanning speed of the nozzle for each scan of the nozzle and applying the coating liquid to the entire surface or part of the coated surface of the light guide plate substrate. The manufacturing method of the light guide plate. The method according to claim 3 or 4,
The application density per unit time of the coating liquid from the nozzle is changed for each scan of the nozzle, and the coating liquid is applied to the entire surface or part of the coated surface of the light guide plate substrate, thereby applying the one-dimensional coating density of the light-diffusion fine particles. The manufacturing method of the light guide plate characterized by the above-mentioned. As a light guide plate in which a light source is arrange | positioned at the cross section, in order to comprise a surface light source device,
The diffusion layer is coated by applying a coating liquid containing light-diffusing fine particles and a light-transmitting binder to the back surface, the surface, or both surfaces of the light guide plate substrate,
The light-diffusion fine particles become an aggregate, and a ratio between the planar area occupied by the aggregate in the coated surface of the light guide plate substrate and the coating area of the coating liquid is 0.1% or more and 70% or less. The method of claim 11,
The said coating liquid is apply | coated to the back surface, the surface, or both surfaces of the said light-guide plate base material by the spray coating method which sprays the said coating liquid from a nozzle, The light guide plate characterized by the above-mentioned. 13. The method according to claim 11 or 12,
The number of light-diffusion fine particles contained in one said aggregate is 10 or more and 10,000 or less, The light guide plate characterized by the above-mentioned. 13. The method according to claim 11 or 12,
As it moves away from the light source, the ratio of the planar area occupied by the agglomerate in the coating surface of the light guide plate substrate to the coating area of the coating liquid, or the coating area ratio of the coating area of the coating liquid to the coating surface of the light guide plate substrate. The light guide plate characterized by the above-mentioned.

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