JP7016757B2 - How to manufacture the light guide plate - Google Patents

Description

The present invention relates to a method for manufacturing a light guide plate used for lighting an image display device such as an LCD or PDP, an advertisement, or an exhibition window.

As one aspect of the light guide plate, it is known that the light received from the end face is reflected and refracted by a plurality of concave lens shapes (hereinafter referred to as recesses) formed on the surface and emitted to the outside. However, if the surface on which the recess is formed is the outermost surface, there is a concern that the optical characteristics may be impaired due to adhesion of dirt, scratches, or the like. Further, when laminated with another layer, there is a problem that interference fringes or the like occur due to the thin air layer entering the flat surface portion (region other than the recess) on the surface where the recess is formed.

On the other hand, Patent Document 1 discloses a method of sealing air with a sealing member for a minute reflective portion composed of a partially spherical concave portion. In the specification, examples of the sealing member include a thin film adhesive, a hot melt adhesive, a blocking resin sheet, and a cured body obtained by adhering a semi-cured body to a light guide member and curing it.

Further, in Patent Document 2, when an optical film having an uneven surface is bonded, a part of the convex portion is fixed by using a pressure-sensitive adhesive layer cured by irradiating heat or active energy rays before bonding. How to do it is shown.

Patent No. 6027331 Patent No. 5517776

However, in the method disclosed in the above patent document, the adhesiveness between the light guide member and the sealing member is not sufficient, and the optical characteristics of the light guide plate may not be sufficiently exhibited.

Therefore, the present invention manufactures a light guide plate using a light guide plate sealing member, which can improve the adhesiveness with the light guide member after being cured and can sufficiently exert the optical characteristics of the light guide plate. The challenge is to provide a method.

The present inventors have conducted diligent research and found that the above problems can be solved by including a step using a specific sealing member for a light guide plate, and completed the present invention. That is, the present invention is as follows.

The present invention
A guide having an end surface forming a side surface and an emission surface which is a main surface on which light incident from the end surface is bent and emitted, and having a plurality of recesses on a non-emission surface which is a surface opposite to the emission surface. It is a method of manufacturing a light guide plate provided with an optical member.
For a light guide plate having a coated base material and a sealing layer in a state where at least one of a gas, a liquid, or a vacuum having a refractive index different from the refractive index of the light guide member is sealed inside the recess. A laminated heating step in which the sealing member is laminated on the surface of the non-emitting surface so that the sealing layer is in contact with the sealing layer and the sealing layer is heated.
A curing step of curing the sealing layer after the laminated heating step is included.
The sealing layer contains at least an active energy ray-curable resin and contains.
The sealing member is characterized in that the tensile shear strength based on JIS K-6850 when the sealing layer and the acrylic film are bonded at 25 ° C. is 0.1 MPa or less. The method.
The present invention
As a step prior to the laminated heating step,
A coating step of applying an active energy ray-curable composition containing at least an active energy ray-curable resin to the coating substrate, and a coating step.
Further comprising a sealing member forming step including a partially curing step of irradiating the active energy ray-curable composition with active energy rays and partially curing the active energy ray-curable composition to form the sealing layer. Is preferable.
The present invention
It is preferable that the laminated heating step and the curing step are performed by a roll-to-roll method.

According to the present invention, a light guide plate using a light guide plate sealing member capable of improving the adhesiveness with the light guide member after being cured and sufficiently exerting the optical characteristics of the light guide plate. A manufacturing method is provided.

It is a schematic diagram which shows the structure of the sealing member for a light guide plate, the light guide plate, and the light guide member. It is a schematic diagram which shows the progress of light in a light guide member. It is the top view and the cross-sectional view which illustrated the shape of the concave part. It is a schematic diagram which shows the distribution example of the concave structure in a light guide member. It is a schematic diagram which shows the apparatus used for optical characteristic contrast measurement.

The light guide plate sealing member is a member used in the manufacture of the light guide plate together with the light guide member. This light guide member has an emission surface which is a main surface in which light incident from an end surface is bent and emitted, and has a structure having a plurality of recesses in a non-emission surface which is a surface opposite to the emission surface. .. Further, the sealing member for the light guide plate is a solid content of an active energy ray-curable composition containing a coating base material, a specific resin provided on the coating base material, and, if necessary, a photopolymerization initiator. With a sealing layer formed by. More specifically, the sealing layer of the light guide plate sealing member is in a state of having a cured portion and an uncured portion (partially cured state) or in a completely uncured state (uncured state). It is a layer formed by the solid content of the active energy ray-curable composition. The light guide plate sealing member seals at least one of gas, liquid, and vacuum (encapsulated object) having a refractive index different from that of the light guide member inside the concave portion of the light guide member. The sealing layer is laminated on the surface of the non-emitting surface so as to be in contact with the light guide member. Then, by curing the sealing layer (for example, by a photopolymerization reaction), a cured sealing layer can be formed and the object to be sealed can be sealed.

Hereinafter, the following items will be described in order.
1. 1. Configuration of sealing member for light guide plate and light guide plate
1-1. Configuration of sealing member for light guide plate 1-2. Structure of light guide plate 2. Sealing member for light guide plate 2-1. Sealing layer 2-2. Coating base material 3. Light guide plate 3-1. Light guide member 3-2. Sealing member for light guide plate Hardened body 3-3. Characteristics 3-3-1.90 ° Peeling strength 3-3-2. Optical characteristics (C)
4. Manufacturing method 4-1. Manufacturing method of sealing member for light guide plate 4-2. Manufacturing method of light guide plate 5. Applications for planar light source devices or lighting devices

1. 1. Configuration of the light guide plate sealing member and the light guide plate First, the configuration of the light guide plate sealing member and the light guide plate of the present invention will be described with reference to FIG.

1-1. Configuration of the light guide plate sealing member As shown in FIG. 1 (a), the light guide plate sealing member (10) has a coating base material (12) and a sealing layer laminated on the coating base material (12). (11) and at least.
More specifically, the sealing member (10) for the light guide plate is made of the solid content of the active energy ray-curable composition, which is provided on the coated substrate (12) and is at least partially uncured. It is a member having a stop layer (11).

1-2. Configuration of the light guide plate As shown in FIG. 1 (b), the light guide plate (100) is laminated on the surface of the light guide member (120) provided with the recess (121) and the recess. It is composed of a cured body (110) for a sealing member for a light guide plate that seals (121).
As will be described later, the light guide plate sealing member (10) of FIG. 1 (a) is bonded to the light guide member and then undergoes a curing step to cure the solid content of the active energy ray-curable composition. As shown in FIG. 1 (b), the cured body (110) is a sealing member for a light guide plate. As described above, the light guide plate sealing member (10) and the light guide plate sealing member cured body (110) are substantially different only in their cured form, and have various configurations {for example, raw materials (for example, raw materials (for example). Solids)} may be interchangeable.

2. 2. Sealing member for light guide plate 2-1. Sealing layer The sealing layer of the sealing member for the light guide plate is formed of a composition containing an active energy ray-curable resin (active energy ray-curable composition) in which at least a part thereof is uncured.

The active energy ray-curable resin refers to a resin that can be cured through an electron beam or, preferably, a cross-linking reaction or the like by irradiation with an active energy ray such as ultraviolet rays. The active energy ray-curable resin is not particularly limited as long as it exhibits the above-mentioned properties, but is preferably a resin containing an ethylenically unsaturated double bond. More specifically, the active energy ray-curable resin is a monomer or oligomer having a polymerizable group {for example, a monofunctional monomer having one (meth) acrylate group (for example, ethyl (meth) acrylate, N-vinylpyrrolidone, etc.). ) And polyfunctional monomers having two or more (meth) acrylate groups (eg, hexanediol (meth) acrylate, etc.)}, urethane (meth) acrylate, polyester (meth) acrylate, epoxy (meth) acrylate, polyether (meth). ) Acrylate, (meth) acrylic polymer (meth) acrylate and the like. It should be noted that these can be used alone or in combination of two or more. Further, (meth) acrylate indicates either methacrylate or acrylate, and similarly (meth) acrylic indicates methacrylic or acrylic.

When ultraviolet rays are used as the active energy rays, it is preferable that the active energy ray-curable composition contains a photopolymerization initiator. As the photopolymerization initiator, radical polymerization initiators such as acetophenone-based, benzophenone-based, thioxanthone-based, benzoin, and benzoin methyl ether can be used alone or in combination as appropriate.

Here, the sealing layer needs to have a tensile shear strength of 0.1 MPa or less based on JIS K-6850 when the sealing layer and the acrylic film are bonded to each other at 25 ° C. as a sealing member for a light guide plate. be. The tensile shear strength can be adjusted by changing the molecular weight, polar group, functional group equivalent, and partially cured state of the active energy ray-curable resin. In order to change the partially cured state, for example, the conditions for irradiation with active energy rays (irradiation intensity and irradiation time) may be changed.

The effect of the present invention by using the sealing layer having such properties is presumed as follows.

When a pressure-sensitive adhesive is used in forming the cured sealing layer (111), there is a concern that the embedding of the pressure-sensitive adhesive changes in the recesses due to aging and pressure during manufacturing and use, and the optical characteristics change. With hot melt adhesives, there is a concern that they will remelt at high temperatures and their optical properties will deteriorate. Since the blocking resin sheet has slight adhesiveness, it is difficult to handle.

Here, when a UV curable resin in an uncured state is used in the formation of the sealed layer cured body (111), it is resistant to external pressure and heat by being cured after being bonded to the light guide member. A light guide plate can be obtained.

However, when a general semi-cured resin is used, foreign matter tends to adhere due to its tackiness at room temperature, and it becomes difficult to remove the foreign matter, so that defects are likely to occur, resulting in induction. It turned out that the optical characteristics of the light plate are difficult to be exhibited.

Further, when a pressure-sensitive adhesive containing a cyclic ether group-containing monomer is used and the sealed layer cured product (111) is formed by irradiating with active energy rays before bonding to the light guide member, the cyclic ether group is formed even after the irradiation is stopped. There is a risk that the cationic polymerization reaction will continue. As described above, it has been found that the characteristics of the adhesive layer change with the passage of time from the irradiation with the active energy ray to the bonding with the member.

On the other hand, according to the sealing member for a light guide plate according to the present invention, the sealing layer has improved tackiness at room temperature. As a result, it is possible to prevent the adhesion of foreign matter, facilitate the removal of foreign matter, prevent the occurrence of defects, and further enhance the effect of preventing the sealing layer from being embedded in the recess of the light guide plate. When the cured body (110) of the sealing member for the light guide plate is formed, the optical characteristics of the light guide member can be fully exhibited. Furthermore, it is possible to improve the appearance quality and the yield. Further, as a result of improving the tackiness, it becomes easy to position (correct the positional deviation) of the sealing member for the light guide plate before the curing process.

In the production of the light guide plate, the active energy ray-curable composition has high adhesiveness of the sealing member for the light guide plate to the light guide member, an effect of suppressing embedding of the light guide member in the recess, and smoothness of the concave lid surface. Various additives such as an ultraviolet absorber, a leveling agent, an antistatic agent, and the like may be contained as long as the above is not impaired. This makes it possible to impart ultraviolet absorption characteristics, antistatic characteristics, and the like to the sealing layer.

The film thickness of the sealing layer according to the present invention is preferably 50 μm or less, more preferably 25 μm or less, and further preferably 10 μm or less. The lower limit of the film thickness of the sealing layer is not particularly limited, but is preferably 0.1 μm, for example.

2-2. Coating base material The coating base material plays a role of protecting the light guide member together with the cured sealing layer in the light guide plate, and functions as a part of the light guide plate. Therefore, it is preferable that the coating base material has transparency. , It is preferable that it has the same refractive index as the light guide member and the cured body of the sealing layer.

The thickness of the coated substrate is not particularly limited, but is preferably 25 μm to 5,000 μm, more preferably 50 μm to 1,000 μm, still more preferably 80 μm to 500 μm, from the viewpoint of ease of manufacture and the role of protecting the light guide member. ..

3. 3. Light guide plate The light guide plate obtained by the manufacturing method according to the present invention will be described in detail below. The configuration shown here is merely an example, and the present invention is not limited thereto.

3-1. Light guide member As the light guide member according to the present invention, known light guide members can be used. The light guide member receives the light emitted from the light source at the light incident end surface (101) (side surface side) of the light guide plate (100) of FIG. 1 (b) (the light becomes incident light). Light can be emitted to the emission surface (102) side through the inside.

The light guide member can be composed of a transparent member such as a plate or a film, or a laminate of these members. The material of the light guide member may be any transparent member, and examples thereof include transparent resin and glass, but transparent resin is preferable, and thermoplastic resin having high transparency is more preferable. Examples of the highly transparent thermoplastic resin include polyolefin resins, vinyl resins, acrylic resins, polyamide resins, polyester resins, polycarbonate resins, polyurethane resins, and polyether resins. Of these, polycarbonate resins, acrylic resins, and urethane resins having no wavelength absorption region in the visible light region are preferable from the viewpoint of transparency.

As shown in FIG. 2, the light incident on the light guide member from the light source (200) installed on the side surface of the light guide member (120) is repeatedly totally reflected on the inner surface of the light guide member (120). Go inside. The light guide member (120) is provided with a plurality of recesses (121) as shown in FIG. 1 (c) that change the reflection angle when the light is totally reflected, and the light is reflected by the recesses (121). The light whose angle has been changed is emitted to the outside from the emission surface (102).

Examples of the concave (121) shape of the light guide member according to the present invention that changes the light reflection angle include a concave lens shape and the like. These structures may be used alone or in combination of a plurality of structures. The shape of the concave portion is not particularly limited, and examples thereof include FIGS. 3A to 3G.

Further, the arrangement of the recesses (121) is not particularly limited, and may be randomly arranged or regularly arranged. For example, as shown in FIG. 4A, the light guide plate can be arranged so that the distribution density of the recesses increases as the distance from the side closer to the light source (200) increases. Further, as shown in FIG. 4 (b), when the light source (200) is also installed on another side of the light guide member, the uniformity of the light in the exit surface can be improved, so that the recessed portion described above can be used. The arrangement and distribution density can be adjusted as appropriate.

3-2. Cured body of sealing member for light guide plate When stacking the sealing member for light guide plate, the cured body of the sealing member for light guide plate is at least one of gas, liquid or vacuum (sealed) inside the recess of the light guide member. The thing) is sealed. By doing so, it is possible to prevent dust from adhering to the concave portion and deterioration of the optical characteristics of the light guide plate due to scratches.

More specifically, when the cured body of the sealing member for the light guide plate is formed, as described above, the sealing layer is a layer made of the active energy ray-curable composition in a state where at least a part thereof is uncured. Is laminated (bonded) on the concave surface side surface of the light guide member in a state where at least one of gas, liquid, and vacuum is sealed inside the concave portion of the light guide member. Next, by curing this sealing layer, the sealing member for the light guide plate becomes a cured body for the light guide plate having a cured body for the sealing layer.

Further, when another layer (for example, a polarizing plate or a retardation plate) is laminated on the concave surface side surface of the light guide member having the concave portion, if the bonding and sealing is not performed, the light guide member other than the concave portion is used. A thin air layer may enter between the concave surface and the other layer, which may cause interference fringes. By passing through the cured body of the sealing member for a light guide plate of the present invention, it is possible to prevent the formation of an air layer and prevent interference fringes.

3-3. Characteristics 3-3-1.90 ° peel strength The 90 ° peel strength (according to JIS K6854) at the interface between the sealed layer cured body (111) of the light guide plate sealing member cured body (110) and the light guide member is , 0.2N / 25mm or more. If it is less than 0.2 N / 25 mm, there is a concern that peeling or floating may occur.

3-3-2. Optical characteristics (C)
Hereinafter, the optical characteristics will be described in detail. As shown in FIG. 5, the normal direction of the light guide plate (100) or the light guide member (120) with respect to the emission surface is 0 °, and the light is incident from the light source perpendicular to the end surface of the light guide plate or the light guide member. The normal direction is defined as 90 °.

The light emitted from the light source enters from the end surface of the light guide plate or the light guide member, travels inside the light guide plate or the light guide member, is reflected and diffused by the concave portion of the light guide member, and is emitted from the emission surface. .. At this time, based on the angle specified above, the integrated luminance value of the light emitted in the range of −70 ° to 70 ° is La, and the light emitted in the range of 110 ° to 250 ° (light guide plate or guide). Let Lb be the luminance integrated value of the light emitted from the non-emitted surface, which is the surface opposite to the emitted surface of the optical member. That is, La represents the luminance integral value of the exit surface, and Lb represents the luminance integral value of the non-exit surface. Further, a value (La-Lb) / Lb indicating how much the difference between the brightness of the light emitted from the light emitting surface and the brightness of the light emitted from the non-lighting surface is based on the brightness of the light emitted from the non-emitting surface is set. , Defined as optical characteristic (C).

In the present invention, when the optical characteristic of the light guide plate is (Cx) and the optical characteristic of only the light guide member (Cy) is set, the optical characteristic ratio (Cx / Cy), which is the ratio between them, is 0.3 or more. Can be.

That is, when (Cx / Cy) is less than 0.3, the brightness emitted from the emission surface is low and the brightness emitted to the non-exit surface is high as compared with the original design of the light guide member. Therefore, there is a risk that the capability as a planar light source device or lighting device will be insufficient.

4. Manufacturing method 4-1. Method for manufacturing a sealing member for a light guide plate The method for manufacturing a sealing member for a light guide plate is not particularly limited, and examples thereof include a method including the following steps (A1) and (A2).
Step (A1): Coating step; The active energy ray-curable composition is coated on the coating substrate.
Step (A2): Sealing member forming step; A drying step of drying the active energy ray-curable composition after coating, if necessary, and / or, if necessary, activity on the active energy ray-curable composition. A partial curing step of irradiating with energy rays is performed to form a sealing layer.

The active energy ray-curable composition contains an active energy ray-curable resin and, if necessary, further contains a photopolymerization initiator. The active energy ray-curable resin, photopolymerization initiator, and any other additives are as described above.

The proportions of the active energy ray-curable resin, the photopolymerization initiator and any of various additives in the active energy ray-curable composition differ depending on the type of each material, and it is difficult to unambiguously define them. As an example, the mass ratio of the solid content may be 50% by mass to 99% by mass for the monomer, 0.5% by mass to 10% by mass for the photopolymerization initiator, and 50% by mass or less for various additives. Further, the active energy ray-curable composition may appropriately contain a known solvent (for example, an organic solvent such as benzene), if necessary. Further, in this case, the solid content concentration of the active energy ray-curable composition can be freely designed according to the production conditions.

In order to apply the prepared active energy ray-curable composition onto the coated substrate, it is preferable to use a coating method such as a roll coating method or a gravure coating method in consideration of continuous productivity. By the coating method, the active energy ray-curable composition can be applied so as to form a thin layer. The coating thickness of the active energy ray-curable composition may be designed so as to be a desired sealed layer cured product (111) after curing.

The drying step in the step (A2) is an optional step of volatilizing all or part of the solvent usually contained in the active energy ray-curable composition from the viewpoint of workability to form a solid separation layer (sealing layer). Such drying conditions can be appropriately carried out according to a known method, and are not particularly limited, but for example, drying may be performed at 40 ° C. to 200 ° C. for 10 seconds to 600 seconds.

By drying the active energy ray-curable composition, a sealing member for a light guide plate having a sealing layer formed on a coated substrate can be obtained. If the sealing layer is naturally formed due to a high solid content ratio in the active energy ray-curable composition, a long standing time after the coating step, or the like, such a drying step is provided. It doesn't have to be. Further, the sealing layer may contain non-solid content as long as it does not impair the effect of the present invention (that is, it does not necessarily have to be completely dried).

The partial curing step in the step (A2) is a preferable arbitrary step performed according to the active energy ray-curable resin or the like used. The partial curing step is a step of irradiating the active energy ray-curable resin with active energy rays after the coating step to partially cure the active energy ray-curable composition in order to obtain the predetermined properties of the present invention, in other words. If so, it is a step of preliminarily irradiating with active energy rays to polymerize a part of the active energy ray-curable resin. It is preferable that this partial curing step is performed after the drying step.

When the active energy ray is ultraviolet rays, the ultraviolet light source used is not particularly limited, and for example, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, a metal halide lamp, or the like having a emission distribution having a wavelength of 400 nm or less can be used. When a composition containing an acrylic compound as an active energy ray curing component is used, a high-pressure mercury lamp or a metal halide lamp having a large amount of light of 400 nm or less is preferably used as an ultraviolet light source in consideration of the absorption wavelength exhibited by a general polymerization initiator. Be done.

4-2. Manufacturing method of light guide plate In the light guide plate, a sealing member for a light guide plate provided with a sealing layer in an uncured or partially cured state is laminated (bonded) on the concave surface side surface of the light guide member, and the sealing layer is formed. Obtained by curing the uncured portion.

More specifically, the sealing layer is brought into contact with the surface of the non-emitting surface in a state where the material to be sealed (at least one of gas, liquid or vacuum) is contained in the recess of the light guide member. It goes through a laminated heating step of laminating the sealing members for the light guide plate and heating the sealing layer, and a curing step of curing the sealing layer and sealing the object to be sealed after the laminated heating step. Therefore, the light guide plate can be manufactured.

In the laminated heating step, a known method may be used, and heating may be performed after laminating the light guide plate sealing member on the light guide member, or heating may be performed at the same time as laminating the light guide plate sealing member on the light guide member. Or may be heated before laminating the light guide plate sealing member on the light guide member.

Specific means used in the laminating heating step include high-pressure laminating and ultrasonic laminating, which are methods of laminating so that heat energy is generated on the contact surface between the light guide plate sealing member and the light guide member. Although exemplary, the so-called thermal laminating method is preferred. By performing such thermal laminating and the like to heat the sealing layer, it is possible to develop tackiness in the sealing layer, prevent misalignment and the like, and improve adhesiveness. In addition, in order to sufficiently develop the tackiness of the sealing layer and suppress dimensional changes and softening of the resin, the temperature is maintained at 40 ° C. to 200 ° C. (for example, the thermal conditions of the thermal laminating are set. 40 ° C to 200 ° C) is preferable. The temperature may be 45 ° C. or higher, 50 ° C. or higher, 55 ° C. or higher, or the like.

As the curing step, a method of irradiating the sealing layer with active energy rays (for example, ultraviolet rays) may be used. The light source is as described above.

Further, it is preferable that the stacking heating step and the curing step are performed by a roll-to-roll method.

The completed light guide plate has the same transparency and refractive index as the light guide member, for example, an acrylic plate or the like, and the thickness of the light guide member can be increased.

5. Applications of planar light source device or lighting device The light guide plate using the light guide plate sealing member according to the present invention is a planar light source by providing one or more light sources at the position (end face) of the side surface of the light guide plate. It can be used as a device or a lighting device. A known light source can be used, and the light source is not particularly limited, but an LED light source is preferable from the viewpoint of size saving and power consumption.

Further, when the planar light source device is used as a backlight, a reflection member and / or a diffusion member can be provided on one surface of the light guide plate. The reflective member and the diffuser member are not particularly limited, and known members may be used.

The planar light source device or lighting device is used as a transmissive display device which is a display device, a planar light source device for an edge type display device in a reflective display device, and a lighting device.

Hereinafter, the present invention will be described based on Examples and Comparative Examples, but the present invention is not limited to the contents of the Examples.

<Preparation of raw materials>
An active energy ray-curable composition used as a raw material for the sealing layer of the sealing member for the light guide plate was prepared based on the following procedure.

(Active energy ray-curable composition 1)
94.5 parts by mass of compound 1 obtained by the following procedure, 5.5 parts by mass of IRGACURE184 (manufactured by BASF Japan) as an initiator, and toluene are blended so that the solid content ratio is 40%. The active energy ray-curable composition 1 was obtained.

-Synthesis of compound 1:
196.29 g (1 mol) of tricyclodecanedimethanol and 22.828 g (0.2 mol) of ε-caprolactone were placed in a flask, the temperature was raised to 120 ° C., and 50 ppm of monobutyltin oxide was added as a catalyst. Then, the reaction was carried out under a nitrogen stream until the remaining ε-caprolactone was 1% or less by gas chromatography to obtain a diol (1).

444.56 g (2 mol) of isophorone diisocyanate was charged in another flask, and 424.57 g (1 mol) of diol (1) was added at a reaction temperature of 70 ° C. when the remaining isocyanate group became 5.7%. 232.24 g (2 mol) of 2-hydroxyethyl acrylate and 0.35 g of dibutyltin laurylate were added, and the reaction was carried out until the remaining isocyanate group became 0.1% to obtain urethane acrylate (compound 1) as a monomer. ..

(Active energy ray-curable composition 2)
95 parts by mass of Acryt 8KX-212 (manufactured by Taisei Fine Chemical Co., Ltd.), 5 parts by mass of IRUGACURE 184 (manufactured by BASF Japan), and propylene glycol monomethyl ether are blended so that the solid content ratio is 30%. An active energy ray-curable composition 2 was obtained.

(Active energy ray-curable composition 3)
The active energy ray-curable composition 3 was obtained in the same manner as in the preparation of the active energy ray-curable composition 1 except that the compound 1 was changed to pentaerythritol triacrylate.

(Active energy ray-curable composition 4)
The active energy ray-curable composition 4 was obtained in the same manner as in the preparation of the active energy ray-curable composition 1 except that the compound 1 was changed to ethylene diol dimethacrylate.

<Manufacturing of light guide plate of Example 1>
(Sealing member forming process)
Using a wire bar, the active energy ray-curable composition 1 was applied to the coated substrate {acrylic film technoloy manufactured by Sumitomo Chemical Co., Ltd. (thickness 100 μm)}.

The coating thickness of the active energy ray-curable composition 1 was adjusted so that the film thickness after drying was 2 μm. A sealing member for a light guide plate is formed by drying the coating film in a clean oven set to a drying oven temperature of 100 ° C. and forming a sealing layer on one side of the coating substrate on which unreacted acryloyl groups remain. Obtained.

(Laminate heating process, curing process)
After thermal laminating the surface of the light guide plate sealing member on the sealing layer side and the surface of the light guide member on the concave portion side obtained by the following procedure under the condition of a temperature of 100 ° C., the integrated light intensity is 3000 mJ / By irradiating ultraviolet rays with a high-pressure mercury lamp under the condition of cm ² , the unreacted acryloyl group remaining in the sealing layer was completely cured to obtain a light guide plate of Example 1.

-Manufacturing of light guide member A coating layer with a thickness of 10 μm is formed on a sheet of PMMA with a size of 130 mm × 90 mm and a thickness of 0.2 mm with a UV curable acrylic resin (containing a photopolymerization initiator), and the height is about 40 μm in diameter. While pressing with a mold having a convex lens type dot shape with a thickness of about 10 μm (convex lens density: about 100 pieces / mm ² ), UV light is irradiated from the surface opposite to the coating layer of the PMMA sheet. By curing the light, a light guide member having a recess used in the present invention was produced. The surface of the obtained light guide member is observed with a laser microscope, and has recesses in which concave lens-shaped dot shapes having a size (diameter) of about 40 μm and a depth of about 8 μm exist at a density of about 100 pieces / mm ² . It was confirmed that the light guide member was obtained.

<Manufacturing of light guide plate of Example 2>
The light guide plate of Example 2 was manufactured in the same manner as in Example 1 except that the thermal laminating temperature in the laminating heating step was set to 40 ° C.

<Manufacturing of light guide plate of Example 3>
In the sealing member forming step, after the coating film is dried, the active energy ray-curable composition 1 is obtained by irradiating ultraviolet rays with a high-pressure mercury lamp under the condition of an integrated light amount of 200 mJ / cm ² in an atmospheric atmosphere. The light guide plate of Example 3 was manufactured in the same manner as in Example 1 except that it was partially cured.

<Manufacturing of light guide plate of Example 4>
The light guide plate of Example 4 was produced in the same manner as in Example 1 except that the active energy ray-curable composition 2 was used as the active energy ray-curable composition.

<Manufacturing of light guide plate of Example 5>
The light guide plate of Example 5 was produced in the same manner as in Example 3 except that the active energy ray-curable composition 3 was used as the active energy ray-curable composition.

<Manufacturing of light guide plate of Comparative Example 1>
The light guide plate of Comparative Example 1 was produced in the same manner as in Example 1 except that the active energy ray-curable composition 3 was used as the active energy ray-curable composition.

<Manufacturing of light guide plate of Comparative Example 2>
The light guide plate of Comparative Example 2 was produced in the same manner as in Example 3 except that the active energy ray-curable composition 4 was used as the active energy ray-curable composition.

<Manufacturing of light guide plate of Comparative Example 3>
The light guide plate of Comparative Example 3 was manufactured in the same manner as in Example 1 except that the laminating was performed at room temperature (25 ° C.) without performing thermal laminating in the laminating heating step.

Table 1 shows the conditions used in each Example and Comparative Example, and the tensile shear strength of the light guide plate sealing member. The tensile shear strength of the light guide plate sealing member is a numerical value measured by the method based on JIS K-6850 described above. In addition, the sheets in which the tensile shear strength could not be measured because the sealing layer and the acrylic film did not adhere to each other are shown in Table 1 with *.

<Evaluation>
The foreign matter removing property, adhesiveness, and optical characteristics of each light guide plate were evaluated based on the following procedure. The results are shown in Table 1.

(Foreign matter removal property)
After adhering the paper dust to the surface of the sealing layer, the paper dust can be removed by air blow etc. and no traces are left on the surface of the sealing layer. It was marked as x.

(Adhesiveness)
Those having a 90 ° peeling force of 0.2 N / 25 mm or more after the curing step were evaluated as ◯, and those having a 90 ° peeling force of less than 0.2 N / 25 mm were evaluated as x.

(optical properties)
5 (a) and 5 (b) show schematic views of an example of a measuring device used for evaluating the optical characteristics of the light guide plate. With this measuring device, the optical characteristics of the light guide plates obtained in each of the examples and comparative examples were evaluated by the following methods.
First, as shown in FIG. 5A, an LED light source (200) is attached to the light incident end surface (101) of the light guide plates (100) of Examples and Comparative Examples, and a black felt sheet is used to suppress the reflected light from the back surface. (140, black felt sheet FU-714 manufactured by Waki Sangyo Co., Ltd., thickness 2 mm) was installed on the non-light emitting surface (lower surface of the light guide plate (100) in FIG. 5 (a)) of Examples and Comparative Examples, respectively.
Subsequently, using a luminance meter (300) (GP-5 manufactured by Murakami Color Technology Research Institute), the traveling direction of the incident light in the light guide plate (100) (direction from left to right in FIG. 5A). Is 90 °, and the normal direction with respect to the light guide plate emission surface (direction from bottom to top in FIG. 5A) is 0 °, and the specified angle is used as a reference in the range of −70 ° to 70 °. The luminance integrated value (La) of the light emitted to the emitting surface was measured. As for the emission direction, when the emission surface normal direction is defined as 0 °, the direction of the light incident end surface (101) as viewed from the luminance meter (300) is − (minus), and the opposite direction is + (plus). did.

Next, as shown in FIG. 5 (b), the light guide plates (100) of Examples and Comparative Examples are arranged upside down from FIG. 5 (a), and the black felt sheet (140) is emitted. It was installed in the same manner as in FIG. 5 (a) except that it was installed on the surface ((the lower surface of the light guide plate (100) in FIG. 5 (b)). The specified angle is the angle in FIG. 5 (a). Was the standard.
Similarly, the luminance integral value (Lb) of the light emitted to the non-emitting surface was measured in the range of 110 ° to 250 ° with the above-mentioned specified angle as a reference. As for the emission direction, the normal direction of the non-emission surface is set to 180 ° based on the above-mentioned specified angle reference, the direction of the light incident end surface (101) is − (minus) when viewed from the luminance meter (300), and the opposite direction is defined as − (minus). It was set as + (plus).
From the above, a value (La-Lb) / Lb indicating how much the difference between the brightness of the light emitted from the light emitting surface and the brightness of the light emitted from the non-lighting surface is based on the brightness of the light emitted from the non-exiting surface. Let Lb be the optical characteristic (C), and the optical characteristic (Cx) of the light guide plate obtained in Examples and Comparative Examples and the optical characteristic of the light guide member (120) not provided with the cured body of the sealing member for the light guide plate. The optical characteristic ratio of the light guide plate and the light guide member was evaluated by the value of the ratio (Cx / Cy) to (Cy).
When the optical characteristic ratio was 0.3 or more, it was evaluated as ◯, and when it was less than 0.3, it was evaluated as x. Further, the case where the light guide member and the light guide plate sealing member did not stick to each other and the light guide plate including the light guide plate sealing member could not be obtained was defined as −.

As shown in Table 1, in the embodiment of the present invention, the seal for the light guide plate is capable of improving the adhesiveness with the light guide member after being cured and sufficiently exerting the optical characteristics of the light guide plate. It was possible to obtain a light guide plate using a stop member.

On the other hand, in Comparative Examples 1 and 2, the tensile shear strength of the sealing member for the light guide plate is 0.1 MPa or more, and since it has tackiness at room temperature, it is difficult to remove foreign matter, and the light guide plate can be used as a light guide plate. Sufficient optical characteristics could not be obtained. It is considered that this is because the surface of the sealing layer of the sealing member for the light guide plate is so soft that it has a tack property, and the sealing layer is embedded in the recess.

Further, in Comparative Example 3, as in Example 1, it is a sealing member for a light guide plate which does not have tackiness at room temperature, and has good foreign matter removing property. However, in the general laminating at room temperature (25 ° C.), since it does not have tackiness, it does not adhere to the light guide member, and it is not possible to obtain a light guide plate using the light guide plate sealing member.

Claims (3)

A guide having an end surface forming a side surface and an emission surface which is a main surface on which light incident from the end surface is bent and emitted, and having a plurality of recesses on a non-emission surface which is a surface opposite to the emission surface. It is a method of manufacturing a light guide plate provided with an optical member.
For a light guide plate having a coated base material and a sealing layer in a state where at least one of a gas, a liquid, or a vacuum having a refractive index different from the refractive index of the light guide member is sealed inside the recess. A laminated heating step in which the sealing member is laminated on the surface of the non-emitting surface so that the sealing layer is in contact with the sealing layer and the sealing layer is heated.
A curing step of curing the sealing layer after the laminated heating step is included.
The sealing layer contains at least an active energy ray-curable resin and contains.
The sealing member is characterized in that the tensile shear strength based on JIS K-6850 when the sealing layer and the acrylic film are bonded at 25 ° C. is 0.1 MPa or less. Method. As a step prior to the laminated heating step,
A coating step of applying an active energy ray-curable composition containing at least an active energy ray-curable resin to the coating substrate, and a coating step.
Further comprising a sealing member forming step including a partially curing step of irradiating the active energy ray-curable composition with active energy rays and partially curing the active energy ray-curable composition to form the sealing layer. The method for manufacturing a light guide plate according to claim 1. The method for manufacturing a light guide plate according to claim 1 or 2, wherein the laminated heating step and the curing step are performed by a roll-to-roll method.

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