JP6955470B2 - Sealing member for light guide plate and manufacturing method of light guide plate using it - Google Patents

Description

The present invention relates to a light guide plate sealing member 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, and a method for manufacturing the light guide plate using the sealing member.

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 formed on the surface (hereinafter referred to as recesses) 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 dirt adhesion or scratches. Further, when laminated with another layer, there is a problem that interference fringes or the like occur due to a thin air layer entering the flat surface portion (region other than the recess) of the surface on which the recess is formed.

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

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 an adhesive coating 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 above method, 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 provides a light guide plate sealing member capable of improving the adhesiveness with the light guide member after curing and sufficiently exerting the optical characteristics of the light guide plate, and a light guide plate seal. An object of the present invention is to provide a method for manufacturing a light guide plate using a stop member.

The present inventors have conducted diligent research and found that the above problems can be solved by using a specific sealing member for a light guide plate, and have 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. A sealing member for a light guide plate used in manufacturing a light guide plate provided with an optical member.
The sealing member for the light guide plate is
At least with a sealing layer and a substrate,
A gas having a refractive index different from that of the light guide member inside the recess by laminating the sealing layer on the surface of the non-emitting surface and then curing the sealing layer. Used for the purpose of sealing at least either liquid or vacuum,
The sealing layer contains a (meth) acrylic graft polymer having a radically polymerizable group and a photopolymerization initiator.
It is a sealing member for a light guide plate, characterized in that the glass transition temperature (Tg) of the (meth) acrylic graft polymer is 45 ° C. to 150 ° C.
In the present invention, the weight average molecular weight of the (meth) acrylic graft polymer is preferably 10,000 or more.
In the present invention, the radically polymerizable group is preferably a (meth) acryloyl group.
In the present invention, the (meth) acrylic graft polymer preferably has a (meth) acryloyl group equivalent of 300 (g / eq) or more.
In the present invention, it is preferable that a radically polymerizable group is present at the side chain terminal of the graft polymer.
Further, the present invention provides a light guide member having an emission surface which is a main surface in which light incident from an 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 to be provided.
The light guide plate according to any one of claims 1 to 5, in which at least one of gas, liquid, and vacuum having a refractive index different from that of the light guide member is sealed inside the recess. A laminating step of laminating the sealing layer of the light guide plate sealing member on the surface of the non-exiting surface of the sealing member.
A method for manufacturing a light guide plate, which comprises a curing step of curing the sealing layer by a photopolymerization reaction after the laminating step.

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

It is a schematic diagram which shows the structure of the sealing member for a light guide plate, a light guide plate, and a 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 recess structure in a light guide member. It is sectional drawing which showed the recess and the cured body of the sealing member for a light guide plate which covers a recess, and the schematic diagram which showed the measurement part of the surface roughness. It is explanatory drawing of the optical characteristic measurement of a light guide plate and a light guide member. It is a schematic diagram which shows the apparatus used for optical characteristic measurement.

The sealing member for a light guide plate according to the present invention is a member used for manufacturing a light guide plate together with a light guide member. More specifically, the light guide member has an exit surface which is a main surface on which light incident from an end surface is bent and emitted, and has a plurality of recesses on a non-emission surface which is a surface opposite to the exit surface. It has a structure. Further, the sealing member for a light guide plate according to the present invention is usually an active energy ray-curable material containing a coating base material, a polymer having a specific polymerizable group provided on the coating base material, and a photopolymerization initiator. It has a sealing layer obtained by drying the composition. In other words, the sealing layer of the light guide plate sealing member is a layer formed of the solid content of the active energy ray-curable composition, which is at least partially uncured. 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 recess of the light guide member. The sealing layer is laminated on the light guide member so as to be laminated on the surface of the non-exiting surface. Then, by curing the sealing layer by a photopolymerization reaction, it becomes possible to form a cured sealing layer.

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 2-3. Manufacturing method of sealing member for light guide plate 3. Light guide plate 3-1. Light guide member 3-2. Cured body of sealing member for light guide plate 3-3. Manufacturing method of light guide plate 3-4. Characteristics 3-4-1.90 ° Peeling strength 3-4-2. Arithmetic mean roughness (Ra) average value 3-4-3. Optical characteristics (C)
4. 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. 1A, the light guide plate sealing member (10) is 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 a seal made of the solid content of the active energy ray-curable composition, which is provided on the coated base material (12) and is at least partially uncured. It is a member having a stop layer (11).
The light guide plate sealing member (10) may have a multi-layer structure, but in the light guide plate sealing member (10), the surface of the light guide plate sealing member (10) is opposite to the light emitting surface of the light guide plate. The sealing layer (11) in which the layer in contact with the surface is a composition (active energy ray-curable composition) containing at least a (meth) acrylic graft polymer having a radically polymerizable group and a photopolymerization initiator. It is necessary to be.

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) of 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), it is a cured body (110) of 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 the cured form, and have various configurations {for example, raw materials (for example, raw materials (for example). Solids)} can be read interchangeably.

2. Sealing member for light guide plate 2-1. Encapsulation layer The encapsulation layer of the encapsulation member for a light guide plate is a composition containing a (meth) acrylic graft polymer having a radically polymerizable group and a photopolymerization initiator, which is at least partially uncured. It is formed by an active energy ray-curable composition). The active energy ray-curable composition refers to a composition containing an electron beam or a resin that can be cured through a cross-linking reaction or the like by irradiation with an active ray such as ultraviolet rays.

The (meth) acrylic graft polymer has a polymer of a monomer component containing acrylic acid or a derivative thereof as a main chain, and further has a polymer chain as a side chain.

The (meth) acrylic graft polymer is not particularly limited as long as it contains a radically polymerizable group. For example, as side chains, (meth) acrylic, polyurethane, (meth) acrylic urethane, polyester, epoxy, silicone, (meth) acrylic silicone, phenol, vinyl chloride, alkyd, melamine. , A polymer having a polymer chain such as a cellulose type can be exemplified. The (meth) acrylic graft polymer may be used alone or in combination of two or more.

The radically polymerizable group is not particularly limited as long as it is a radically polymerizable group, and examples of the radically polymerizable group include a (meth) acryloyl group, a vinyl group, an allyl group, and a styryl group, and the (meth) acryloyl group. Is preferable.

In particular, when a (meth) acryloyl group is provided as a radically polymerizable group, the (meth) acryloyl group equivalent of the (meth) acrylic graft polymer is preferably 300 (g / eq) or more, preferably 500 (g / eq). ) Or more, and more preferably 700 (g / eq) or more. The upper limit of the (meth) acryloyl group equivalent of the (meth) acrylic graft polymer is not particularly limited, but is preferably 2,000 (g / eq), for example. The (meth) acryloyl group equivalent is a theoretical value, but in some cases, it may be obtained by a known method.

Further, such a radically polymerizable group may be located at the side chain of the graft polymer or at the end of the main chain, but is preferably present at the end of the side chain.

The glass transition temperature (hereinafter referred to as Tg) of the (meth) acrylic graft polymer is 45 ° C to 150 ° C. The lower limit of Tg of the (meth) acrylic graft polymer is preferably 50 ° C, 60 ° C, 70 ° C, 80 ° C, 90 ° C, 100 ° C, or 105 ° C, and the upper limit is 145 ° C. , 140 ° C, 135 ° C, 130 ° C, 125 ° C, 120 ° C, 115 ° C. The lower limit value and the upper limit value may be freely combined. Although this Tg is a theoretical value, it may be obtained by a known method in some cases.

The weight average molecular weight of the (meth) acrylic graft polymer is preferably 10,000 or more, more preferably 30,000 or more, and further preferably 80,000 or more. The upper limit of the weight average molecular weight of the (meth) acrylic graft polymer is not particularly limited, but is preferably 5,000,000, for example.

Such a (meth) acrylic graft polymer can be produced according to a known method, and its structure can be freely designed as appropriate by changing various monomers and synthetic conditions.

The active energy ray-curable composition may contain a resin other than the (meth) acrylic graft polymer as long as the effects of the present invention are not impaired.

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.

In the production of the light guide plate, the active energy ray-curable composition has high adhesiveness to the light guide member of the light guide plate sealing 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, and an antistatic agent 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.

The sealing member for a light guide plate according to the present invention uses a composition containing a (meth) acrylic graft polymer having a radically polymerizable group having a Tg of 45 ° C. to 150 ° C. and a photopolymerization initiator. There is. Therefore, not only has high adhesive strength to the light guide member, but also the tackiness at room temperature is improved as compared with the conventional UV curable resin and the like, and it is possible to prevent the adhesion of foreign substances and the occurrence of defects. When the cured body of the sealing member for the light plate is formed, the optical characteristics of the light guide member can be fully exhibited.

Further, as a result of the improved tackiness, positioning (correction of misalignment) of the light guide plate sealing member becomes easy before the curing step (detailed later).

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 base material 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. ..

2-3. Method for manufacturing the sealing member for the light guide plate The method for manufacturing the sealing member for the 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): Drying step; After coating, the active energy ray-curable composition is dried to form a sealing layer (arbitrary step).

First, regarding the step (A1), the active energy ray-curable composition contains a (meth) acrylic graft polymer having a radically polymerizable group and a photopolymerization initiator. The (meth) acrylic graft polymer, photopolymerization initiator, and any other additives are as described above.

The proportions of the (meth) acrylic graft polymer, the photopolymerization initiator and any of the 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, in terms of solid content mass ratio, the (meth) acrylic graft polymer is 50% by mass to 99% by mass (more preferably 70% by mass to 99% by mass, still more preferably 90% by mass to 99% by mass). The photopolymerization initiator may be 0.5% by mass to 10% by mass, and various additives may be 49.5% by mass or less. 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 coating 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 obtain a desired sealed layer cured product after curing.
From the above, by applying the active energy ray-curable composition on the base material, it is possible to obtain a light guide plate sealing member having a sealing layer formed on the coated base material.

Subsequently, the drying in the step (A2) is an optional step, and from the viewpoint of workability, the solvent usually contained in the active energy ray-curable composition is volatilized in whole or in part to form a solid separation layer (sealing layer). This is the process of forming. 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.
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, it is not necessary to provide such a drying step. good.
From the above, by drying the active energy ray-curable composition, a sealing member for a light guide plate in which a sealing layer is formed on a coated base material can be obtained.

Further, the sealing layer of the present invention may contain a non-solid content as long as the effect of the present invention is not impaired (that is, it does not necessarily have to be completely dried).

3. 3. Light guide plate The light guide plate manufactured by using the light guide plate sealing member 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 exit 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 a transparent member, and examples thereof include transparent resin and glass. A transparent resin is preferable, and a highly transparent thermoplastic resin is more preferable. Examples of the highly transparent thermoplastic resin include polyolefin-based resins, vinyl-based resins, acrylic-based resins, polyamide-based resins, polyester-based resins, polycarbonate resins, polyurethane-based resins, and polyether-based 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 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 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 exit 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 recess is not particularly limited, and examples thereof include FIGS. 3 (a) to 3 (g).

Further, the arrangement of the recesses (121) is not particularly limited, and may be arranged randomly or regularly. 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. 4B, when the light source (200) is also installed on another side of the light guide member, the uniformity of light in the exit surface can be improved. The arrangement and distribution density can be adjusted as appropriate.

3-2. Cured body of sealing member for light guide plate The cured body of sealing member for light guide plate is at least one of gas, liquid, and vacuum (sealed) inside the recess of the light guide member when the sealing member for light guide plate is laminated. The thing) is sealed. By doing so, it is possible to prevent dust from adhering to the recesses 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 of the sealing member is uncured. Is laminated (bonded) on the surface of the light guide member and inside the recess of the light guide member in a state where at least one of gas, liquid, and vacuum is sealed. Next, by curing this sealing layer, the light guide plate sealing member becomes a light guide plate sealing member cured body having a sealing layer cured body.

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 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 the light guide plate of the present invention, it is possible to prevent the formation of an air layer and prevent interference fringes.

3-3. Method for manufacturing a light guide plate Next, a specific method for manufacturing a light guide plate using the light guide plate sealing member according to the present invention will be described in detail.

The method for manufacturing the light guide plate is not particularly limited, and examples thereof include a method including the following steps (A3) and (A4).
Step (A3): Laminating step; In a state where the object to be sealed (at least one of gas, liquid or vacuum) is sealed inside the concave portion of the light guide member, the light guide member is guided to the surface of the non-exiting surface of the light guide member. The sealing layer of the light plate sealing member is laminated.
Step (A4): Curing step; After the laminating step, the sealing layer is cured by a photopolymerization reaction to obtain a cured sealing layer.

First, regarding the step (A3), the material to be sealed (at least one of gas, liquid, and vacuum) is sealed inside the concave portion of the light guide member, and the light guide member is guided to the surface of the non-exiting surface of the light guide member. As a method of laminating the sealing layer of the light plate sealing member, a known method may be used, and examples thereof include a so-called thermal lamination method of heating the light guide sealing member.

Subsequently, regarding the step (A4), a known method may be used as a method of curing the sealing layer by a photopolymerization reaction after the laminating step to obtain a cured sealing layer, and examples thereof include a method of irradiating with ultraviolet rays. ..
The ultraviolet irradiation can be performed by irradiating the ultraviolet rays from the ultraviolet irradiation device. 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 an emission distribution at a wavelength of 400 nm or less can be used. When a composition containing a (meth) acrylic compound as an active energy ray-curable composition 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 taken into consideration in consideration of the absorption wavelength indicated by a general polymerization initiator. However, it is preferably used as an ultraviolet light source.

The finished 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.

3-4. Characteristics Next, the characteristics of the light guide plate according to the present invention will be described based on the cured body of the sealing member for the light guide plate obtained after curing.

3-4-1. 90 ° peel strength The 90 ° peel strength (according to JIS K6854) at the interface between the cured sealing layer of the cured body of the sealing member for the light guide plate and the light guide member according to the present invention is defined as 0. It can be 2N / 25mm or more. If it is less than 0.2 N / 25 mm, there is a concern that peeling or floating may occur.

3-4-2. Average value of arithmetic mean roughness (Ra) As shown in FIG. 5, the maximum rectangular shape (the area is maximum) of the sealed layer cured body (113) in the concave surface shape of the light guide member (120) according to the present invention. Rectangle shape), the arithmetic mean roughness (Ra, hereafter Ra) on the lines (117 and 118) that pass through the center point (114) of the rectangle shape and are parallel to each side of the rectangle. The average value of (referred to as) can be 0.50 μm or less.

A part of the region of the surface (113) facing the concave portion of the sealing layer cured body (111) covering the front surface of the concave portion (121) usually enters the concave portion, and unevenness is generated on the surface. This unevenness tends to reduce the optical characteristics of the light guide plate.

However, in the light guide plate of the present invention, the cured body of the sealing layer contains at least a specific (meth) acrylic graft polymer, so that the average value of Ra in the surface region is 0.50 μm or less. , It is possible to prevent the optical characteristics of the light guide plate from deteriorating. The average value of Ra is more preferably 0.10 μm or less, and further preferably 0.02 μm or less.

Subsequently, the method for measuring Ra will be described in detail below.

5 (a) and 5 (b) are cross-sectional views of the recess (121) and the cured body of the sealing member for the light guide plate (110) covering the recess, and FIG. 5 (c) shows the surface roughness. It is a schematic diagram which showed the measurement point. Here, in FIG. 5, for ease of explanation, the surface shape of the recessed portion of the light guide member will be described as being circular.

The surface (113) of the sealed layer cured body (111) in the concave surface shape of the light guide member is closer to the inner side of the concave peripheral length than the central portion with respect to the concave surface shape (circular shape in this case) of the light guide member. In addition, since embedding (entry) of the cured sealing layer is not a little likely to occur, in the measurement of Ra according to the present invention, the measurement is performed excluding the portion where this embedding is likely to occur.

That is, in the maximum rectangular shape of the sealing layer cured body (113) in the concave surface shape of the light guide member, the side (114) that passes through the center point (114) of the rectangular shape and has the rectangular shape in the rectangular shape. 115) Lines parallel to the {short side (115)} and the side (116) {long side (116)} adjacent to the certain side are drawn in order, line 1 (117) and line 2 (118). And. Then, when Ra is measured within the range of the line 1 (117) and the line 2 (118) and the respective values are set to Ra1 and Ra2 in order, the average value of all the values is the average value of Ra in the present invention. Then, the smoothness of the concave lid surface is evaluated.

Here, the measuring device is not particularly limited, and a known measuring device can be used. For example, a method using a contact type profile measuring device or a non-contact type confocal laser microscope can be mentioned, and the measurement may be performed based on the measuring method specified in ISO4287: 1997.

Further, in the above description, for the sake of simplicity, the surface shape of the concave portion of the light guide member is assumed to be circular, but even when the surface shape of the concave portion of the light guide member is not circular, the surface shape of the concave portion of the light guide member is within the shape. The same measurement is performed by using a line that passes through the center point of the rectangular shape and is parallel to each side of the rectangular shape with respect to the maximum rectangular shape of the sealed layer cured product (113). Ra can be obtained by the method.

3-4-3. Optical characteristics (C)
Hereinafter, the optical characteristics will be described in detail. As shown in FIG. 6, light is incident from the light source at 0 ° in the normal direction with respect to the emission surface (the surface on the side described as the emission light) of the light guide plate (100) or the light guide member (120). The direction perpendicular to the end face of the light guide plate or the light guide member 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 exit surface. At this time, based on the above-defined angle, the brightness integral 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 integrated luminance value of the light emitted from the non-emitting surface, which is the surface opposite to the emitting 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-light emitting surface is based on the brightness of the light emitted from the non-exiting 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 exit 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 capacity as a planar light source device or a lighting device will be insufficient.

4. Applications of planar light source device or lighting device A light guide plate manufactured by using the light guide plate sealing member according to the present invention is provided by providing one or more light sources at the side positions (end faces) of the light guide plate. It can be used as a planar light source 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 reflecting member and / or a diffusing member can be provided on one surface of the light guide plate. The reflecting member and the diffusing 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.

[Manufacturing Example 1]
Preparation of compound 1:
In the flask, 500 g of deionized water and 1.5 g of disodium hydrogen phosphate as a suspension aid were added, 10.012 g (1 mol) of methyl methacrylate and 142.15 g (1 mol) of glycidyl methacrylate. , 2.5 g of 2-ethylhexyl thioglycolate and 3 g of azobisisobutyronitrile were added, and then the in-flask solution was stirred while substituting nitrogen in the flask to obtain mixed solution 1. After that, the temperature of the mixed solution 1 was raised to 60 ° C. while continuing the stirring, and the mixture was stirred while maintaining the temperature of the mixed solution 1. One hour after the temperature of the mixed solution 1 reached 60 ° C., 0.15 g of ADEKA PLRONIC F-68 (manufactured by ADEKA) was added to prepare the mixed solution 2, and then the temperature of the mixed solution 2 was further increased to 60. The mixture was stirred for 1 hour while being maintained at ° C. Subsequently, the temperature of the mixed solution 2 was raised to 80 ° C. while continuing the stirring, and the mixture was stirred for 5 hours while maintaining the temperature of the mixed solution 2.
The obtained product was washed with water using 3 times the total amount of deionized water four times, and the water content was dried to obtain a polymer.
Next, 30 g of the obtained polymer and 70 g of methylisobutylbutyl ketone were added into a new flask, and the solution in the flask was stirred to obtain a mixed solution 3, and then the mixed solution 3 was kept stirred. The temperature of the flask was raised to 80 ° C. After the temperature of the mixed solution 3 reaches 80 ° C., a mixed solution containing 0.02 g of hydroquinone monomethyl ether, 0.05 g of triphenylphosphine and 5 g of methyl isobutyl ketone is added to prepare a mixed solution 4 and further. The mixture was stirred for 1 hour while maintaining the temperature of the mixed solution 4 at 80 ° C.
Then, while maintaining the temperature of the mixed solution 4 at 80 ° C., stirring is continued, and a mixed solution consisting of 20 g of acrylic acid and 10 g of methyl isobutyl ketone is added into the flask to prepare the mixed solution 5, and the mixed solution 5 is continued. While maintaining the temperature at 80 ° C., the inside of the flask was replaced with nitrogen, and the mixture was stirred for 30 hours to synthesize a (meth) acrylic graft polymer (compound 1) solution having an acryloyl group in the side chain.

[Manufacturing Example 2]
Synthesis of compound 2:
In the flask, 500 g of methyl isobutyl ketone and 100.12 g (1 mol) of methyl methacrylate were added, 142.15 g (1 mol) of glycidyl methacrylate, 1.5 g of 2-ethylhexyl thioglycolate, and azobisisobuty. After adding a monomer mixed solution containing 3 g of ronitrile, the in-flask solution was stirred while replacing nitrogen in the flask to obtain a mixed solution 6, and then the temperature of the mixed solution 6 was set to 85 while continuing stirring. The temperature was raised to ° C., the temperature of the mixed solution 6 was maintained, and then the mixture was stirred for 5 hours.
Subsequently, while the stirring was continued, the temperature of the mixed solution 6 in the flask was lowered to 80 ° C. and stirred to maintain the temperature of the mixed solution 6. After the temperature of the mixed solution 6 reaches 80 ° C., a mixed solution containing 0.15 g of hydroquinone monomethyl ether, 0.4 g of triphenylphosphine and 40 g of methyl isobutyl ketone is added to prepare a mixed solution 7. The mixture was stirred for 1 hour while maintaining the temperature of the mixed solution 7 at 80 ° C.
Then, while maintaining the temperature of the mixed solution 7 at 80 ° C., stirring is continued, and a mixed solution consisting of 160 g of acrylic acid and 80 g of methyl isobutyl ketone is added into the flask to prepare a mixed solution 8, and the mixing is continued. While maintaining the temperature of the solution 8 at 80 ° C., the inside of the flask was replaced with nitrogen and stirred for 30 hours to synthesize a (meth) acrylic graft polymer (compound 2) solution having an acryloyl group in the side chain.

[Manufacturing Example 3]
Synthesis of compound 3:
The same method as in Production Example 2 was carried out except that the amount of methyl methacrylate added to the flask was 10.12 g (0.1 mol) and the amount of glycidyl methacrylate was 270.09 g (1.9 mol), and acryloyl was added to the side chain. A (meth) acrylic graft polymer (compound 3) solution having a group was synthesized.

[Manufacturing of light guide member]
A coating layer is formed on a sheet of PMMA having a size of 130 mm × 90 mm and a thickness of 0.2 mm with a UV-curable acrylic resin (containing a photopolymerization initiator) to a thickness of 10 μm, and a convex lens having a diameter of about 40 μm and a height of about 10 μm. By irradiating UV light from the surface opposite to the coating layer of the PMMA sheet and curing it while pressing with a mold having a dot shape of the mold (convex lens density: about 100 pieces / mm ^2). , 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 having a concave lens-shaped dot shape having a size (diameter) of about 40 μm and a depth of about 8 μm at ^{a density of about 100 pieces / mm 2.} It was confirmed that the light guide member was obtained.

[Example 1]
Using a wire bar, the main material, Acryt 8KX-212 (manufactured by Taisei Fine Chemical Co., Ltd.), was applied to the coated base material {Sumitomo Chemical's acrylic film technoloy (100 μm thickness)} with 95 parts by weight of solid content and IRUGACURE. An active energy ray-curable composition (P1) for producing a sealing layer composed of 5 parts by weight of 184 (manufactured by BASF Japan Ltd.) and propylene glycol monomethyl ether was applied. The content of propylene glycol monomethyl ether was adjusted so that the solid content ratio was 30%, and the coating thickness of the active energy ray-curable composition (P1) was adjusted so that the film thickness after drying was 7 μm. The coating film was dried in a clean oven set to a drying furnace temperature of 100 ° C. to obtain a sealing member for a light guide plate.

After temporarily fixing the surface of the light guide plate sealing member on the sealing layer side by laminating the surface of the light guide member having a recess, the pressure is 3.0 J / cm ² with a high-pressure mercury lamp. Light irradiation was performed to sufficiently cure the unreacted acryloyl group remaining in the sealing layer to obtain a light guide plate of Example 1.
Table 1 shows the names, main structures, weight average molecular weights, (meth) acryloyl group equivalents, and Tg (° C.) of the main materials used in Example 1.

[Examples 2 and 3]
Example 1 except that the Acryt 8KX-212 described in Example 1 is changed to the above-mentioned compound 1 or compound 2 in order, and the organic solvent is changed to one having solubility in each resin. The light guide plates of Examples 2 and 3 were obtained in order by the same manufacturing method as above.
Table 1 shows the names, main structures, weight average molecular weights, (meth) acryloyl group equivalents, and Tg (° C.) of the main materials used in Examples 2 and 3.

[Comparative Examples 1 to 3]
The same manufacturing method as in Example 1 except that the Acryt 8KX-212 described in Example 1 is sequentially changed to the above compounds 3, 8UH-4005 (manufactured by Taisei Fine Chemical Co., Ltd.) or Aronix M305 (manufactured by Toagosei Co., Ltd.). , In order, the light guide plates of Comparative Examples 1 to 3 were obtained.
Table 1 shows the names, main structures, weight average molecular weights, (meth) acryloyl group equivalents, and Tg (° C.) of the main materials used in Comparative Examples 1 to 3.

[Comparative Example 4]
A clean oven in which the active energy ray-curable composition for producing a sealing layer prepared in the same manner as in Comparative Example 3 was applied after adjusting the film thickness after drying to 7 μm, and the temperature inside the drying oven was set to 100 ° C. Inside, the coating film was dried. Subsequently, a high-pressure mercury lamp was used to ^{irradiate light at 0.2 J / cm 2} , and the sealing layer was brought into a state where at least a part of it was uncured to obtain a sealing member for a light guide plate. After that, similarly to Examples 1 to 3 and Comparative Examples 1 to 3, the surface of the light guide plate sealing member on the sealing layer side and the surface of the light guide member having the recesses are temporarily fixed by laminating. ^{After that, light irradiation of 3.0 J / cm 2} was performed with a high-pressure mercury lamp to completely cure the unreacted acryloyl group remaining in the sealing layer to obtain a light guide plate of Comparative Example 4.
The main material, main structure, and Tg (° C.) of the main structure used in Comparative Example 4 are shown in Table 1. Further, in Comparative Example 4, the weight average molecular weight and the (meth) acryloyl group equivalent could not be measured.

The light guide plates obtained in the above Examples and Comparative Examples were evaluated.

[90 ° peel strength at the interface between the cured sealing layer and the light guide member]
The light guide plate obtained in each of the above Examples and Comparative Examples is cut into a width of 25 mm, and the light guide plate is guided by pulling the cured body of the sealing member for the light guide plate while fixing the light guide member by a method conforming to JIS K6854. The 90 ° peel strength at the interface between the cured body of the sealing layer and the cured body of the sealing member for the light plate was measured.

[Average value of arithmetic mean roughness (Ra) of the cured sealed layer (surface roughness)]
The light guide plates obtained in each of the above Examples and Comparative Examples were peeled off at the interface between the cured sealing layer and the light guide member, and a vacuum vapor deposition apparatus (Sanyu) was placed on the exposed surface of the cured sealing layer. Gold particles were vacuum-deposited to a thickness of 15 nm using an Electronics SC-701AT). For this sample, the surface of the sample was observed using a confocal laser microscope (OLS3000 manufactured by Olympus), and the center point of the rectangle having the largest area among the rectangles in the surface shape of the recesses of the light guide member. The average value of Ra of each line segment passing through and parallel to each side of the rectangle was calculated.

[Optical characteristic ratio of light guide plate and light guide member]
7 (a) and 7 (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 Examples and Comparative Examples were evaluated by the following methods.
First, as shown in FIG. 7A, a black felt sheet is applied to the light incident end surface (101) of the light guide plates (100) of Examples and Comparative Examples with the LED light source (200) in order 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) of FIG. 7 (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. 7A). 90 ° and 0 ° in the normal direction with respect to the light guide plate exit surface (direction from bottom to top in FIG. 7A), in the range of −70 ° to 70 ° with respect to the specified angle. The luminance integrated value (La) of the light emitted to the exit surface was measured. As for the emission direction, when the normal direction of the emission surface 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). bottom.

Next, as shown in FIG. 7 (b), the light guide plates (100) of Examples and Comparative Examples are arranged upside down from FIG. 7 (a), and the black felt sheet (140) is emitted. It was installed in the same manner as in FIG. 7 (a) except that it was installed on the surface ((the lower surface of the light guide plate (100) in FIG. 7 (b)). The specified angle is the angle in FIG. 7 (a). Was used as 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 reference to the above-mentioned specified angle. 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) / 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-light emitting 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).

[Tack-free property of sealing member for light guide plate (tensile shear adhesive strength)]
The tensile shear adhesive strength between the light guide plate sealing layer and the coated base material of the light guide plate sealing members obtained in each of the above Examples and Comparative Examples was measured by a method in accordance with JIS K6850. This was defined as the tack-free property of the sealing member for the light guide plate.

Table 2 shows the evaluation results of Examples and Comparative Examples obtained from the above. The evaluation criteria in Table 2 are as follows.
"90 ° peel strength at the interface between the cured sealing layer and the light guide member"
○ 0.5N / 25mm or more △ 0.2N / 25mm or more and less than 0.5N / 25mm × less than 0.2N / 25mm "Average value (surface roughness) of arithmetic average roughness (Ra) of sealed layer cured product"
○ Less than 0.10 μm △ 0.10 μm or more and less than 0.50 μm × 0.50 μm or more “Optical characteristic ratio of light guide plate and light guide member”
○ 0.8 or more △ 0.3 or more and less than 0.8 x less than 0.3 "Tack-free property of sealing member for light guide plate (tensile shear adhesive strength)"
○ 0.01 MPa or more x less than 0.01 MPa

As shown in Table 2, in Examples 1 to 3 of the present invention, the light guide plate of the present invention in which the light guide plate sealing member having sufficient tack-free property is sealed with the light guide member and cured is sealed. The cured stop layer has sufficient peeling strength with respect to the light guide member and sufficient smoothness with respect to the concave lid surface of the light guide member, and even if it is a light guide plate, it can be used as a light guide member. On the other hand, there is little deterioration in optical characteristics. In particular, Example 1 showed excellent evaluation results in all the evaluation items shown in Table 2.

Regarding the 90 ° peel strength at the interface between the cured sealing layer and the light guide member, Examples 1 to 3 are graft polymers having a (meth) acrylic polymer as a main structure, which are shown in Table 1. As described above, Examples 2 and 3 have a higher (meth) acryloyl group equivalent and a higher Tg of the main structure as compared with Example 1. Therefore, it is considered that the 90 ° peel strength is higher than that of Examples 2 and 3.

Further, regarding the average value of Ra of the cured sealed layer, Examples 2 and 3 are graft polymers having a (meth) acrylic polymer as a main structure as described above, and the (meth) in Table 1 shows. ) The acryloyl group equivalent is also the same value, but the weight average molecular weight is higher in Example 2 than in Example 3. Therefore, it is considered that the sealing member for the light guide plate of Example 2 is more resistant to deformation due to pressure than that of Example 3, so that the average value of Ra of the cured sealing layer is lower.

Comparative Example 1 is a graft polymer having a (meth) acrylic polymer as a main structure as in Examples 1 to 3, but as shown in Table 1, Comparative Example 1 is (as opposed to Examples 1 to 3). Meta) Acryloyl group equivalent is low and Tg is low. Therefore, as shown in Table 2, it is considered that the cohesive force of the resin after curing is low and the peel strength is lowered.

Comparative Example 2 is a graft polymer having a urethane polymer as a main structure, and as shown in Table 1, although the weight average molecular weight and the (meth) acryloyl group equivalent are higher than those of other Examples and Comparative Examples. , Tg is low. Therefore, as shown in Table 2, the sealing member for the light guide plate has a tack property, the average value of Ra of the cured sealing layer is high, and the optical characteristic ratio when the light guide plate is used with respect to the light guide member. Is thought to have deteriorated.

In Comparative Example 3, since the main structure is an acrylic monomer, the light guide plate sealing member exhibits tackiness even at room temperature and is vulnerable to deformation due to pressure, so that the average value of the sealed layer cured product Ra is high. It is probable that the height became higher and the optical characteristic ratio when the light guide plate was used was worse than that of the light guide member.

In Comparative Example 4, since the sealing member for the light guide plate in which the acrylic monomer is semi-cured by light irradiation is used, the Tg is high as shown in Table 1. It is considered that this reduced the 90 ° peel strength at the interface between the cured sealing layer and the light guide member.

10 Sealing member for light guide plate 11 Sealing layer 12 Coating base material 100 Light guide plate 101 Light incident end surface 102 Exit surface 110 Sealing member for light guide plate Hardened body 111 Sealing layer Hardened body 120 Light guide member 121 Recess 140 Black felt sheet 200 LED light source 300 Luminance meter

Claims (6)

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. A sealing member for a light guide plate used in manufacturing a light guide plate provided with an optical member.
The sealing member for the light guide plate is
At least with a sealing layer and a substrate,
A gas having a refractive index different from that of the light guide member inside the recess by laminating the sealing layer on the surface of the non-emitting surface and then curing the sealing layer. Used for the purpose of sealing at least either liquid or vacuum,
The sealing layer contains a (meth) acrylic graft polymer having a radically polymerizable group and a photopolymerization initiator.
A sealing member for a light guide plate, characterized in that the glass transition temperature (Tg) of the (meth) acrylic graft polymer is 45 ° C. to 150 ° C. The sealing member for a light guide plate according to claim 1, wherein the (meth) acrylic graft polymer has a weight average molecular weight of 10,000 or more. The sealing member for a light guide plate according to claim 1 or 2, wherein the radically polymerizable group is a (meth) acryloyl group. The sealing member for a light guide plate according to claim 3, wherein the (meth) acrylic graft polymer has a (meth) acryloyl group equivalent of 300 (g / eq) or more. The sealing member for a light guide plate according to any one of claims 1 to 4, wherein the radically polymerizable group is present at the end of the side chain of the graft polymer. A method for manufacturing a light guide plate having an exit surface which is a main surface on which light incident from an end surface is bent and emitted, and a light guide member having a plurality of recesses on a non-emission surface which is a surface opposite to the exit surface. And
The light guide plate according to any one of claims 1 to 5, in which at least one of gas, liquid, and vacuum having a refractive index different from that of the light guide member is sealed inside the recess. A laminating step of laminating the sealing layer of the light guide plate sealing member on the surface of the non-exiting surface of the sealing member.
A method for producing a light guide plate, which comprises a curing step of curing the sealing layer by a photopolymerization reaction after the laminating step.

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