JP2015194599A - Optical sheet, optical waveguide, electronic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical sheet having superior optical transmission properties.SOLUTION: An optical sheet 100 includes a layer of high refractive index region 101 having a relatively high refractive index, and a layer of low refractive index region 102 having a relatively low refractive index compared with the high refractive index region 101. The optical sheet contains a refractive index regulating agent having a glass transition temperature in a range of 50 to 300°C, inclusive, as calculated by the Bicerano method. A polystyrene-equivalent weight average molecular weight of the refractive index regulating agent, as measured by gel permeation chromatography, shall preferably be in a range of 5,000 to 200,000, inclusive.

Description

  The present invention relates to an optical sheet, an optical waveguide, and an electronic device.

In recent years, in the field of optical communication, development of a high-performance optical waveguide has been advanced as a basic element constituting an optical communication component. Such an optical waveguide includes a core layer provided on a support substrate and an upper clad layer formed so as to cover the core layer.
In the conventional optical waveguide, the surface of the core layer made of a material with a high refractive index is covered with an upper clad layer made of a material with a low refractive index, thereby suppressing optical transmission defects generated in the core layer. .

  Patent Document 1 describes a technique for improving such a light transmission defect. Patent Document 1 describes a technique for reducing optical transmission defects in the thickness direction by changing the refractive index from the inside of the core layer toward the surface.

In the optical waveguide described in Patent Document 1, the core layer is formed by sequentially laminating solutions having different refractive indexes on a supporting substrate by repeating a series of steps of coating, drying and curing. In this way, it is described that a core layer whose refractive index changes from the inside toward the surface can be formed (paragraph 0029, Example 1).
And on such a core layer, only the adoption of a low refractive index material is described (paragraph 0034). Therefore, since the technique described in Patent Document 1 is trying to obtain the effect of reducing optical transmission defects by the optical confinement effect using the refractive index change of the core layer in the thickness direction, I can say that. In addition, in the technique described in Patent Document 1, it is described that the effect of reducing optical transmission defects cannot be obtained when a laminated body of core layers is collectively formed and heat-treated. (Comparative Example 3).

JP 2006-23374 A

  In recent years, optical waveguides are required to have a function capable of high-capacity and high-speed communication. For this reason, the optical waveguide is required to further improve the optical transmission characteristics. However, the optical waveguide of Patent Document 1 still has room for improvement in terms of optical transmission characteristics.

According to the present invention,
An optical sheet comprising a layered high refractive index region having a relatively high refractive index and a layered low refractive index region having a refractive index relatively lower than that of the high refractive index region,
There is provided an optical sheet containing a refractive index adjusting agent having a glass transition temperature calculated by the Bicerano method of 50 ° C. or higher and 300 ° C. or lower.

Moreover, according to the present invention,
An optical waveguide including the optical sheet is provided.

Furthermore, according to the present invention,
An electronic device including the optical waveguide is provided.

  According to the present invention, for example, an optical sheet excellent in light transmission characteristics can be provided.

It is a perspective view which shows an example of the structure of the optical sheet of 1st Embodiment which concerns on this invention. It is a figure which shows typically an example of refractive index distribution about the cross section in the XX line of the optical sheet shown in FIG. It is a figure which shows typically an example of D1 / D2 of the refractive index distribution in the layer thickness direction of the optical sheet of 1st Embodiment. It is a perspective view which shows an example of the structure of the optical sheet of 2nd Embodiment which concerns on this invention. It is a figure which shows typically an example of refractive index distribution about the cross section in the XX line of the optical sheet shown in FIG. It is a figure which shows typically an example of refractive index distribution about the cross section in the XX line of the optical sheet 200 shown in FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate.

(First embodiment)
<Optical sheet>
First, the optical sheet of the first embodiment according to the present invention will be described.
FIG. 1 is a perspective view showing an example of the structure of the optical sheet 100 according to the first embodiment of the present invention. FIG. 2 is a diagram schematically illustrating an example of a refractive index distribution with respect to a cross section taken along line XX of the optical sheet 100 illustrated in FIG. 1. (A) of FIG. 2 shows sectional drawing in the XX line of the optical sheet 100 shown in FIG. FIG. 2B shows a refractive index on the center line C1 that vertically passes through the center in the width direction of the optical sheet 100 when the horizontal axis represents the refractive index and the vertical axis represents the distance in the layer thickness direction. It is a figure which shows an example of distribution T typically.

  The optical sheet 100 includes a layered high refractive index region 101 having a relatively high refractive index and a layered low refractive index region 102 having a refractive index relatively lower than that of the high refractive index region 101. And the glass transition temperature computed by the Bicerano method is 50 degreeC or more and 300 degrees C or less, More preferably, the refractive index regulator which is 85 degreeC or more and 250 degrees C or less is included.

When the glass transition temperature of the refractive index adjusting agent calculated by the Bicerano method is within the above range, even if the optical sheet 100 is left for a long time under high temperature and high humidity, the diffusion of the refractive index adjusting agent can be suppressed, and the optical sheet It can be suppressed that the refractive index distribution T in the layer thickness direction of 100 changes and the optical transmission characteristics deteriorate. That is, when the glass transition temperature of the refractive index modifier calculated by the Bicerano method is within the above range, the reliability of the optical sheet 100 under high temperature and high humidity can be further improved.
The “Bicerrano method” is described in, for example, Prediction of Polymer Properties (Plastics Engineering, 65) Joseph Bicerano (Author). The glass transition temperature can be calculated by the Bicerano method using MDL Polymer (MDL Information Systems, Inc.).

The optical sheet 100 has a refractive index change region 107 in which the refractive index continuously decreases along the layer thickness direction in at least a part of the portion from the center line A1 in the layer thickness direction toward the one surface 105. It is preferable that the refractive index adjusting agent described above is present in the refractive index changing region 107.
Note that the refractive index continuously decreases along the layer thickness direction is a state where the curve of the refractive index distribution T in the layer thickness direction is rounded and the curve is differentiable.

  As shown in FIG. 2, the optical sheet 100 further includes a layered low refractive index region 103 having a refractive index relatively lower than that of the high refractive index region 101, and the other surface 109 from the center line A1 in the layer thickness direction. It is preferable that the refractive index changing region 111 in which the refractive index continuously decreases along the layer thickness direction is provided at least at a part of the portion toward the surface.

Here, “a layered high refractive index region 101 having a relatively high refractive index” refers to a region having refractive index changing regions 107 and 111 in which the refractive index continuously decreases along the layer thickness direction. The high refractive index region 101 may include a flat portion where the refractive index does not substantially change in the vicinity of the maximum value W of the refractive index. Even in this case, the optical waveguide of the present invention exhibits the effects and effects as described above. Here, the flat portion where the refractive index is not substantially changed refers to a region where the refractive index variation is less than 0.001.
Further, “the layered low refractive index regions 102 and 103 having a refractive index relatively lower than that of the high refractive index region 101” has a refractive index relatively lower than that of the high refractive index region 101 and is refracted from the maximum value W. An area where the rate is 0.01 or more is low. The low refractive index regions 102 and 103 may include flat portions 113 and 115 in which the refractive index does not substantially change. Here, the flat portion where the refractive index is not substantially changed refers to a region where the refractive index variation is less than 0.001.

When the optical sheet 100 further includes the refractive index changing region 111, the refractive index distribution T includes the maximum value W in the high refractive index region 101 and the center line A1 in the layer thickness direction as shown in FIG. However, it is preferable that the shape is symmetrical.
Hereinafter, the refractive index distribution T including the high refractive index region 101 having the maximum value W and the refractive index changing regions 107 and 111 and the low refractive index regions 102 and 103 having the regions 113 and 115 having relatively low refractive indexes will be described. This is referred to as a GI (graded index) refractive index distribution T.

  The optical sheet 100 according to the present embodiment may have a GI-type refractive index distribution T in the thickness direction in a part of the width direction, or may have a GI-type refractive index distribution T in the entire width direction. It may be. Moreover, it is preferable that the optical sheet 100 according to the present embodiment maintains the substantially same GI-type refractive index distribution T in the thickness direction in the entire longitudinal direction.

Hereinafter, effects obtained by the optical sheet 100 according to the present embodiment having the GI type refractive index distribution T will be described.
According to the optical sheet 100 according to the present embodiment, high light transmission characteristics can be realized.
In the conventional optical sheet represented by the above-mentioned Patent Document 1, the upper cladding layer is formed adjacent to the upper portion of the core layer. The refractive index distribution of the upper cladding layer has a uniform refractive index. In this specification, such a refractive index distribution is referred to as “step index type (hereinafter referred to as SI type)”. The SI type refractive index distribution means that the refractive index is substantially constant in each of the core layer and the cladding layer, and the refractive index is discontinuous at the boundary between the core layer and the cladding layer. It has been found by the present inventors that the upper clad layer having the SI type refractive index profile has insufficient optical transmission characteristics.

  On the other hand, as described above, the optical sheet 100 having the GI type refractive index distribution T has the refractive index change regions 107 and 111 in which the refractive index continuously decreases along the layer thickness direction. The optical transmission characteristics of the refractive index changing regions 107 and 111 are very excellent.

  Further, in the GI type refractive index distribution T, as described above, the refractive index continuously decreases as the distance from the center increases. For this reason, due to the property that the speed of light is inversely proportional to the refractive index, the speed of light increases with distance from the center, and a difference in propagation time for each optical path is less likely to occur. For this reason, the transmission waveform does not easily collapse, and for example, even when the transmission light includes a pulse signal, it is possible to suppress blunting of the pulse signal (spreading of the pulse signal). As a result, the quality of optical communication can be further improved.

The average thickness of the optical sheet 100 according to this embodiment is not particularly limited, but is preferably 3 μm or more and 600 μm or less, more preferably 15 μm or more and 300 μm or less, and further preferably 20 μm or more and 200 μm or less.
The average thickness of the high refractive index region 101 is not particularly limited, but is preferably 1 μm or more and 200 μm or less, more preferably 5 μm or more and 100 μm or less, and further preferably 10 μm or more and 70 μm or less. As a result, when the optical sheet 100 is used as an optical waveguide while preventing the optical sheet 100 from becoming unnecessarily large (thickened), the function as the core portion is suitably exhibited.

The average thickness of each of the low refractive index regions 102 and 103 is preferably 0.05 to 1.5 times the average thickness of the high refractive index region 101, more preferably 0.1 to 1. 25 times or less.
The average thickness of the low refractive index regions 102 and 103 is not particularly limited, but is preferably 1 μm or more and 200 μm or less, more preferably 1 μm or more and 100 μm or less, and further preferably 5 μm or more and 60 μm or less.
Thereby, the function as the low refractive index regions 102 and 103 is suitably exhibited while preventing the optical sheet 100 from becoming unnecessarily large.

FIG. 3 is a diagram schematically illustrating an example of D1 / D2 of the refractive index distribution T in the layer thickness direction of the optical sheet 100 according to the first embodiment. Here, f _max in the figure indicates the maximum value of the refractive index in the layer thickness direction.
The optical sheet 100 has a half width at half maximum of f _max in the refractive index distribution T as D1, and is closest to the center line A1 among the minimum values of the refractive index distribution T in the layer thickness direction from the center line A1 of the optical sheet 100. When the vertical distance to the point is D2, D1 / D2 is preferably 0.01 or more and 0.95 or less, more preferably 0.4 or more and 0.9 or less, and further preferably 0.6 or more and 0. .8 or less.

Here, “the point closest to the center line A1 in the minimum value of the refractive index distribution T” changes from the high refractive index region 101 to the low refractive index regions 102 and 103 as shown in FIG. This refers to the points P1 and P2 at the boundary. Since the refractive indexes of the low refractive index regions 102 and 103 do not substantially change, the boundary point where the high refractive index region 101 changes to the low refractive index regions 102 and 103 is the center of the minimum value of the refractive index distribution T. The closest point to the line A1.
When D1 / D2 in the layer thickness direction is within the above range, when the optical sheet 100 is used as an optical waveguide, the initial optical transmission performance can be further improved.

In the optical sheet 100, the difference between the maximum value and the minimum value of the refractive index distribution in the layer thickness direction is preferably 0.005 or more, more preferably 0.01 or more. Here, the maximum value of the refractive index distribution in the layer thickness direction is usually the refractive index f _max on the center line A1 shown in FIG. The minimum value of the refractive index distribution in the layer thickness direction is usually the refractive index at the point P1 or P2 in FIG.
When the difference between the maximum value and the minimum value of the refractive index distribution in the layer thickness direction is not less than the above lower limit, when the optical sheet 100 is used as an optical waveguide, the initial optical transmission performance can be further improved.

  In the optical sheet 100, the haze value measured in accordance with JIS-K7136 is preferably 5.0% or less, more preferably 1.0% or less, and further preferably 0.5% or less. According to this embodiment, the light transmission characteristic of the optical waveguide can be further improved by setting the haze value to be equal to or lower than the upper limit value.

  Moreover, the transparency of the optical sheet 100 can be specified by the transmittance measured at a wavelength of 850 nm in the layer thickness direction. The transmittance of the optical sheet 100 is preferably 80% or more, more preferably 85% or more, and further preferably 90% or more. By setting the transmittance to be equal to or higher than the lower limit, when the optical sheet 100 is used as an optical waveguide, the optical transmission characteristics can be further improved.

(Refractive index modifier)
In the optical sheet 100 according to this embodiment, it is preferable that a refractive index adjusting agent is present at least in the refractive index changing regions 107 and 111. Hereinafter, the refractive index adjusting agent will be described.

  As described above, the refractive index adjusting agent according to this embodiment is preferably a polymer having a high glass transition temperature from the viewpoint of improving the reliability of the optical sheet 100 under high temperature and high humidity. Specifically, it is a polymer having a glass transition temperature calculated by the Bicerano method of 50 ° C to 300 ° C, preferably 85 ° C to 250 ° C.

  The refractive index adjusting agent according to this embodiment is preferably a compound that is compatible with the base polymer described below. Here, “compatible with the base polymer” means that the refractive index adjusting agent is mixed with at least the base polymer and the haze value of the optical sheet 100 becomes 5.0% or less.

When a cyclic olefin-based resin is used as the base polymer, the refractive index adjuster according to the present embodiment, from the viewpoint of further improving the initial optical transmission performance of the optical sheet 100 and the reliability under high temperature and high humidity, A polymer having an alicyclic structure in the side chain is preferred. A polymer having an alicyclic structure in the side chain is excellent in compatibility with the cyclic olefin-based resin that is the base polymer, and can reduce light loss in the mixed portion. It is also possible to form a significant refractive index difference with the base polymer.
The alicyclic structure of the side chain is preferably a five-membered ring or a six-membered ring structure.

  As such a polymer having an alicyclic structure in the side chain, for example, a cyclic resin such as an acrylic resin, a methacrylic resin, a polycarbonate, a polystyrene, an epoxy resin or an oxetane resin having an alicyclic structure in the side chain. Ether resin, polyamide, polyimide, polybenzoxazole, polysilane, polysilazane, silicone resin, fluorine resin, polyolefin resin, polybutadiene, polyisoprene, polychloroprene, polyester such as polyethylene terephthalate and polybutylene terephthalate, polyethylene succinate, Examples thereof include cyclic olefin resins such as polysulfone, polyether, benzocyclobutene resin, and norbornene resin.

  Among these, acrylic resins, methacrylic resins, polycarbonates, cyclic ether resins such as epoxy resins and oxetane resins, silicone resins, polyolefin resins, polybutadiene, polyisoprene having an alicyclic structure in the side chain. It is preferable to use at least one selected from the group consisting of cyclic olefin resins such as polyether and norbornene resins.

In particular, a group consisting of cyclic olefin resins such as acrylic resins, methacrylic resins, cyclic ether resins such as epoxy resins and oxetane resins, polyolefin resins, norbornene resins having an alicyclic structure in the side chain It is preferable to use at least one selected from
Since these refractive index adjusting agents have high light transmittance, an optical sheet 100 with particularly small transmission loss can be obtained.

  Examples of the acrylic resin having an alicyclic structure in the side chain include polycyclohexyl acrylate represented by the following formula (1), isobonyl acrylate represented by the following formula (2), and the like.

Here, n in the formula represents an integer of 20 or more.

Here, n in the formula represents an integer of 20 or more.

  Examples of the methacrylic resin having an alicyclic structure in the side chain include polycyclohexyl methacrylate represented by the following formula (3), polyisomethanyl methacrylate represented by the following formula (4), and the like.

Here, n in the formula represents an integer of 20 or more.

Here, n in the formula represents an integer of 20 or more.

  Examples of the cyclic ether resin having an alicyclic structure in the side chain include polycyclohexyl oxetane represented by the following formula (5).

Here, n in the formula represents an integer of 20 or more.

  Among these, acrylic resins having an alicyclic structure in the side chain such as polycyclohexyl acrylate represented by the above formula (1) and isobornyl polyacrylate represented by the above formula (2); A methacrylic resin having an alicyclic structure in the side chain, such as polycyclohexyl methacrylate represented by formula (4) and polyisomethanyl methacrylate represented by the above formula (4), is particularly preferred. When these refractive index adjusting agents are used as the refractive index adjusting agent according to this embodiment, it is possible to obtain the optical sheet 100 with further improved reliability under high temperature and high humidity.

The weight average molecular weight (Mw) in terms of polystyrene measured by gel permeation chromatography of the polymer used for the refractive index adjusting agent according to this embodiment is preferably 5,000 or more and 200,000 or less, more Preferably they are 10,000 or more and 100,000 or less.
When the weight average molecular weight (Mw) is within the above range, it is possible to suppress the deterioration of the light transmission characteristics even when the optical sheet 100 is left under a high temperature and high humidity for a long time. That is, when the weight average molecular weight (Mw) is within the above range, the reliability of the optical sheet 100 under high temperature and high humidity can be further improved.

(Base polymer)
The optical sheet 100 according to this embodiment preferably includes a base polymer having a higher refractive index than the refractive index adjusting agent. By including such a base polymer, the refractive index distribution of the optical sheet 100 can be changed by the distribution of the refractive index adjusting agent, and the refractive index distribution in the layer thickness direction can be GI type.
Further, as will be described later, the base polymer can react with a monomer (polymerization reaction or crosslinking reaction), and those having sufficient transparency even after the monomer is polymerized are preferably used.
Hereinafter, the base polymer will be described.

  The base polymer according to the present embodiment is selected as necessary, for example, cyclic olefin resin such as norbornene resin, acrylic resin, methacrylic resin, polycarbonate, polystyrene, epoxy resin, polyamide, polyimide, Examples include polybenzoxazole, silicone resin, and fluorine resin. The base polymer may be used alone or in combination of two or more thereof (polymer alloy, polymer blend (mixture), copolymer, etc.). By using these resins as the base polymer, an optical sheet 100 having excellent light transmission performance can be obtained.

Among these, those mainly composed of cyclic olefin resins are preferable. Since the cyclic olefin-based resin has high light transmittance, the optical sheet 100 with particularly small transmission loss can be obtained by using the cyclic olefin-based resin as the base polymer.
As the cyclic olefin-based resin, for example, those described in paragraphs 0022 to 0072 of JP2010-090328A can be used.
Among the cyclic olefin resins, it is preferable to use a norbornene resin from the viewpoints of heat resistance and transparency.
Among them, the norbornene-based resin preferably includes a norbornene repeating unit having a substituent containing a polymerizable group or a norbornene repeating unit having a substituent containing an alkyl group.

  As the repeating unit of norbornene having a substituent containing a polymerizable group, the repeating unit of norbornene having a substituent containing an epoxy group, the repeating unit of norbornene having a substituent containing a (meth) acryl group, and an alkoxysilyl group At least one of the repeating units of norbornene having a substituent containing is preferable. These polymerizable groups are preferable because of their high reactivity among various polymerizable groups.

  Moreover, if the thing containing 2 or more types of norbornene repeating units containing such a polymeric group is used, both flexibility and heat resistance can be achieved.

(Leaving group)
In addition, the base polymer may have a leaving group that is branched from the main chain and released from the main chain by the action of the acid released from the photoacid generator. Specifically, those having at least one of an —O— structure, an —Si—aryl structure, and an —O—Si— structure in the molecular structure are preferable. Such an acid leaving group is released relatively easily by the action of a cation. Due to elimination of the leaving group, the refractive index of the base polymer is lowered. For this reason, the refractive index of the region irradiated with light can be reliably reduced as compared with the unirradiated region. That is, a refractive index difference can be formed between the irradiated region and the non-irradiated region in the in-layer direction composed of the base polymer having a leaving group.

  Examples of the base polymer having such a leaving group include polymers of monocyclic monomers such as cyclohexene and cyclooctene, norbornene, norbornadiene, dicyclopentadiene, dihydrodicyclopentadiene, tetracyclododecene, and tricyclopentadiene. And cyclic olefin resins such as polymers of polycyclic monomers such as dihydrotricyclopentadiene, tetracyclopentadiene, and dihydrotetracyclopentadiene. Among these, one or more cyclic olefin resins selected from polymers of polycyclic monomers are preferably used. Thereby, the heat resistance of the base polymer can be improved.

  The difference between the refractive index adjusting agent according to the present embodiment and the refractive index of the base polymer is preferably 0.005 or more and 0 from the viewpoint of more efficiently forming the GI type refractive index distribution T in the layer thickness direction. .3 or less, more preferably 0.01 or more and 0.1 or less.

(Support film and cover film)
The optical sheet 100 according to the present embodiment may further include a support film and a cover film. The support film is disposed on the lower surface of the optical sheet 100. The cover film is disposed so as to cover the surface of the optical sheet 100.

<Optical sheet manufacturing method>
Below, the manufacturing method of the optical sheet 100 which concerns on this embodiment is demonstrated.

  The optical sheet 100 is obtained by laminating and applying a first resin composition and a second resin composition on a substrate. A first resin layer can be formed from the first resin composition, and a second resin layer can be formed from the second resin composition.

  Examples of the application method include, but are not limited to, a doctor blade method, a spin coating method, a dipping method, a table coating method, a spray method, an applicator method, a curtain coating method, and a die coating method. .

  As the substrate, for example, a silicon substrate, a silicon dioxide substrate, a glass substrate, a polyethylene terephthalate (PET) film, or the like is used.

  The first resin composition forming the first resin layer contains at least a base polymer. The base polymer may have a leaving group. Here, the leaving group is a group that is released from the main chain by the action of an acid released from the polymerization initiator. Moreover, the first resin composition may further include a polymerization initiator that accelerates a polymerization reaction of the in-layer moving component and the in-layer moving component described later. This polymerization initiator includes a general photoacid generator that generates an acid upon irradiation with light such as actinic radiation.

  Further, the intra-layer moving component varies the refractive index in the intra-layer direction of the optical sheet 100 according to the present embodiment. The in-layer transfer component preferably contains, for example, a monomer or an oligomer. The in-layer transfer component is preferably a substance compatible with the base polymer, and more preferably a monomer compatible with the base polymer and polymerized by heat or light. In this embodiment, the monomer that is polymerized by heat or light is a photopolymerization initiator or heat generator that generates active species such as radicals, acids, and bases by light irradiation in addition to those that are polymerized by light irradiation or heat treatment. Including those polymerized by the agent.

(Monomer or oligomer)
Monomers (photopolymerizable monomers) or oligomers (photopolymerizable oligomers) that move within the layer react with each other in the irradiated region by irradiation with actinic radiation, which will be described later, and the monomers or oligomers diffuse with it. It is a compound that can cause a refractive index difference between an irradiated region and an unirradiated region in the optical sheet by moving.

  As the monomer or oligomer, those having compatibility with the base polymer and having a refractive index difference with the base polymer of 0.01 or more are preferably used.

  Such a monomer or oligomer may be a compound having a polymerizable site in the molecular structure. Examples thereof include acrylic acid (methacrylic acid) monomers, epoxy monomers, oxetane monomers, norbornene monomers, vinyl ether monomers, styrene monomers, photodimerization monomers, and oligomers thereof. One or more of these can be used in combination.

  Among these monomers or oligomers, by using the same type of monomer or oligomer as the base polymer, the monomer can be more uniformly dispersed in the base polymer. Therefore, the characteristics of the optical sheet can be homogenized.

  In addition, a monomer or oligomer having a cyclic ether group such as an oxetanyl group and an epoxy group can easily react because the ring opening of the cyclic ether group is likely to occur. Therefore, by using the monomer, the manufacturing time of the optical sheet can be shortened.

As the monomer having an oxetanyl group, for example, Aron oxetane (manufactured by Toagosei Co., Ltd.) can be used.
Further, at least a part of the monomer may be oligomerized as described above.

  Examples of the monomer and oligomer having an oxetanyl group and the monomer and oligomer having an epoxy group include those described in paragraphs 0073 to 0099 of JP 2010-090328 A.

(Polymerization initiator)
A polymerization initiator may optionally be included in the first resin composition. The polymerization initiator acts on the monomer with irradiation of actinic radiation and promotes the reaction of the monomer.

  The polymerization initiator to be used is appropriately selected according to the type of monomer polymerization reaction or crosslinking reaction. For example, radical polymerization initiators are preferably used for acrylic acid (methacrylic acid) monomers and styrene monomers. Cationic polymerization initiators are preferably used for epoxy monomers, oxetane monomers, and vinyl ether monomers.

  Examples of the radical polymerization initiator include benzophenones and acetophenones. Specifically, Irgacure 651, Irgacure 184 (above, BASF Japan Ltd. make) etc. are mentioned.

  On the other hand, examples of the cationic polymerization initiator include a Lewis acid generating type such as a diazonium salt, and a Bronsted acid generating type such as an iodonium salt and a sulfonium salt. Specific examples include Adekaoptomer SP-170 (manufactured by ADEKA Corporation), Sun-Aid SI-100L (manufactured by Sanshin Chemical Industry Co., Ltd.), Rhodorsil 2074 (manufactured by Rhodia Japan Co., Ltd.), and the like.

(Additive)
The first resin composition may further contain an additive such as a sensitizer. This sensitizer increases the sensitivity of the polymerization initiator to light, reduces the time and energy required for the activation (reaction or decomposition) of the polymerization initiator, and has a wavelength suitable for the activation of the polymerization initiator. It has a function of changing the wavelength of light.

  In addition to the sensitizer, the additive includes, for example, a catalyst precursor, a promoter, an antioxidant, an ultraviolet absorber, a light stabilizer, a silane coupling agent, a coating surface improver, a thermal polymerization inhibitor, Examples include leveling agents, surfactants, colorants, storage stabilizers, plasticizers, lubricants, fillers, inorganic particles, anti-aging agents, wettability improvers, and antistatic agents. With these various additives, the refractive index of the optical sheet 100 can be appropriately controlled.

  The second resin composition includes at least the refractive index adjusting agent according to the present embodiment and a base polymer.

  FIG. 2 shows a configuration in which three layers are laminated in the order of the second resin layer by the second resin composition, the first resin layer by the first resin composition, and the second resin layer by the second resin composition. However, the present invention is not limited to this mode, and two or more layers may be stacked.

  The concentration of various substances in the optical sheet 100 can be measured using, for example, FT-IR, TOF-SIMS line analysis, surface analysis, or the like.

  The refractive index distribution is, for example, (1) a method of observing a refractive index dependent interference fringe using an interference microscope (dual-beam interference microscope) and calculating the refractive index distribution from the interference fringe, (2) It is possible to use a method of directly measuring by a refraction near field method (RNF). Among these, the refractive near field method can employ, for example, the measurement conditions described in JP-A-5-332880. On the other hand, the interference microscope is preferably used in that the refractive index distribution can be easily measured.

  Hereinafter, an example of a procedure for measuring the refractive index distribution using an interference microscope will be described. First, the optical sheet is sliced in the cross-sectional direction (width direction) to obtain an optical sheet fragment. For example, the optical sheet is sliced to have a length of 200 to 300 μm. Next, a chamber filled with oil having a refractive index of 1.536 is produced in a space surrounded by two glass slides. And an optical sheet piece is inserted in the space in a chamber, and a measurement sample part and a blank sample part which has not put an optical sheet piece are produced. Next, using an interference microscope, the measurement sample portion and the blank sample portion are respectively irradiated with the light divided into two, and then the transmitted light is integrated to obtain an interference fringe photograph. Since the interference fringes are generated along with the refractive index distribution (phase distribution) of the optical sheet fragment, by analyzing the obtained interference fringe photograph, the refractive index distribution W in the width direction of the optical sheet fragment and / or Alternatively, the refractive index distribution T in the layer thickness direction can be obtained. When acquiring the refractive index distributions W and T, the accuracy of the refractive index distributions W and T can be increased by image analysis of a plurality of interference fringe photographs. When obtaining a plurality of interference fringe photographs, it is only necessary to change the optical path length by moving the prism in the interference microscope to obtain photographs having different interference fringe spacings and interference fringe spots. Further, when image analysis is performed on the interference fringe photograph, for example, analysis points may be set at intervals of 2.5 μm.

<Optical waveguide>
As described above, since the optical sheet 100 includes the refractive index changing regions 107 and 111 in which the refractive index continuously decreases along the layer thickness direction, high optical transmission characteristics are realized. Therefore, it can be suitably used for an optical waveguide.
When the optical sheet 100 according to the present embodiment is used in an optical waveguide, the high refractive index region 101 becomes an optical waveguide region that guides light, and as an optical wiring that transmits an optical signal from one end to the other end. Function. As described above, the refractive index changing regions 107 and 111 existing from the high refractive index region 101 to the low refractive index regions 102 and 103 function as a potential barrier against light propagating through the high refractive index region 101. Therefore, in the optical sheet 100 according to this embodiment, a potential barrier is formed by the refractive index change regions 107 and 111. Thereby, the oozing of light from the high refractive index region 101 is effectively suppressed, and high light transmission characteristics are realized.

<Other uses>
In addition, the optical sheet 100 according to the present embodiment takes advantage of the features having the refractive index change regions 107 and 111 in which the refractive index continuously decreases along the layer thickness direction, in addition to the optical waveguide. An optical film such as a rate control film and an optical compensation film; a liquid crystal display, a plasma display, a digital paper, an organic EL, an inorganic EL, a display substrate such as a rear pro, and the like.

<Electronic equipment>
The optical waveguide of this embodiment is excellent in optical transmission efficiency and long-term reliability. For this reason, by providing an optical waveguide, a highly reliable electronic device capable of performing high-quality optical communication between two points can be obtained.

Such electronic devices can be applied to electronic devices such as mobile phones, game machines, router devices, WDM devices, personal computers, televisions, home servers, and the like. In any of these electronic devices, it is necessary to transmit a large amount of data at high speed between an arithmetic device such as an LSI and a storage device such as a RAM. Therefore, by providing such an electronic device with the optical waveguide of the present embodiment, problems such as noise and signal degradation peculiar to electric wiring are eliminated, and a dramatic improvement in performance can be expected.
In addition, the amount of heat generated in the optical waveguide portion is greatly reduced compared to electrical wiring. For this reason, the electric power required for cooling can be reduced and the power consumption of the whole electronic device can be reduced.
Further, the optical waveguide of the present embodiment has small transmission loss and pulse signal dullness, and interference does not easily occur even when the number of channels is increased and the density is increased. For this reason, an optical waveguide having high density and a small area and high reliability can be obtained. By mounting the optical waveguide, the reliability of electronic equipment can be improved and the size can be reduced.

(Second Embodiment)
FIG. 4 is a perspective view showing an example of the structure of the optical sheet 200 according to the second embodiment of the present invention.
The second embodiment is the same as the first embodiment except that at least one high refractive index portion 220 and two or more low refractive index portions 230 are provided in the width direction of the optical sheet. It is. For this reason, the second embodiment will be described with a focus on differences from the first embodiment, and description of similar matters will be omitted.

<Optical sheet>
The optical sheet 200 includes at least one or more high refractive index portions 220 and two or more low refractive index portions 230 in the width direction. Low refractive index portions 230 are adjacent to both sides of the high refractive index portion 220, respectively. And the high refractive index part 220 has the GI type refractive index distribution T in the layer thickness direction similar to the optical sheet 100 of the first embodiment.
The optical sheet 200 has the same GI-type refractive index distribution T in the entire width direction of the high refractive index portion 220.

  FIG. 5 is a diagram schematically illustrating an example of a refractive index distribution with respect to a cross section taken along line XX of the optical sheet 200 illustrated in FIG. 4. (A) of FIG. 5 shows sectional drawing in the XX line of the optical sheet 200 shown in FIG. In FIG. 5B, the horizontal axis represents the refractive index, and the vertical axis represents the distance in the layer thickness direction. On the center line C2 passing vertically through the center in the width direction of the high refractive index portion 220. It is a figure which shows an example of refractive index distribution T typically.

The optical sheet 200 includes a layered high refractive index region 201 having a relatively high refractive index and a layered low refractive index region 202 having a refractive index relatively lower than that of the high refractive index region 201.
At least part of the portion from the center line A2 in the layer thickness direction toward the one surface 205 has a refractive index change region 207 in which the refractive index continuously decreases along the layer thickness direction. The refractive index adjusting agent described in the first embodiment is present at least in the refractive index changing region 207.
Further, as shown in FIG. 5, the optical sheet 200 further includes a layered low-refractive index region 203 having a refractive index relatively lower than that of the high-refractive index region 201, from the center line A <b> 2 in the layer thickness direction to the other. It is preferable to have a refractive index changing region 211 in which the refractive index continuously decreases along the layer thickness direction at least at a part of the portion toward the surface 209. When the optical sheet 200 further includes the refractive index change region 211, the refractive index distribution T includes the maximum value W in the high refractive index region 201 and the center line A2 in the layer thickness direction as shown in FIG. However, it is preferable that the shape is symmetrical.

  When the optical sheet 200 according to the present embodiment is used for an optical waveguide, the high refractive index region 201 of the high refractive index portion 220 becomes an optical waveguide region that guides light, and the refractive index changing regions 207 and 211 are high refractive index regions. It functions as a potential barrier against light propagating through 201. Therefore, in the optical sheet 200, a potential barrier is formed by the refractive index change regions 207 and 211. Thereby, the oozing of light from the high refractive index region 201 is effectively suppressed, and high light transmission characteristics are realized.

FIG. 6 is a diagram schematically illustrating an example of a refractive index distribution with respect to a cross section taken along line XX of the optical sheet 200 illustrated in FIG. 4. FIG. 6A shows a cross-sectional view of the optical sheet 200 shown in FIG. 6B, the refractive index distribution W on the center line A2 in the layer thickness direction of the optical sheet 200 when the refractive index is taken on the vertical axis and the distance in the width direction of the optical sheet 200 is taken on the horizontal axis. It is the figure which showed typically an example.
When the optical sheet 200 according to the present embodiment is used for an optical waveguide, as shown in FIG. 6, the refractive index distribution W in the direction perpendicular to the light waveguide direction (longitudinal direction) is maximum in the in-layer direction. A refractive index including a high refractive index portion 220 having a refractive index changing region 260, 270 including a value W2 and having a refractive index continuously decreasing from the maximum value W2 toward the end faces 240, 250, and a low refractive index portion 230. A distribution is preferred. The low refractive index portion 230 may or may not have the flat portion 280 whose refractive index is not substantially changed. That is, the refractive index distribution W is also preferably a GI type (graded index) refractive index distribution W.

  Note that the refractive index continuously decreases from the maximum value W2 toward the end faces 240 and 250 when the refractive index distribution curve in the width direction is rounded and the curve is differentiable. is there.

  This refractive index distribution W contains the base polymer and the photopolymerizable monomer or photopolymerizable oligomer described in the first embodiment, which has a refractive index different from that of the base polymer, and is photopolymerizable in the base polymer. A layer composed of a material in which a monomer or a photopolymerizable oligomer is dispersed is partially irradiated with light, and the photopolymerizable monomer or photopolymerizable oligomer is moved and unevenly distributed, whereby the refractive index is within the layer. This is a distribution formed. Since the film is formed based on such a principle, the refractive index continuously changes in the refractive index distribution W.

  In addition, it is particularly preferable that the optical sheet 200 according to the present embodiment has a GI type refractive index distribution W in the entire high refractive index region 201 of the high refractive index portion 220.

  In addition, it is preferable that the optical sheet 200 maintains substantially the same GI type refractive index distribution W in the entire longitudinal direction.

  In the GI-type refractive index distribution W, at least a part or the whole of the refractive index changes continuously in a curved line. Due to this feature, the effect of collecting light near the center of the high refractive index region 201 of the high refractive index portion 220 as compared with an optical sheet having a so-called step index type (SI type) refractive index distribution in which the refractive index changes stepwise. As a result, transmission loss can be further reduced.

  According to this embodiment, the same effect as that of the first embodiment can be obtained. In addition, according to the present embodiment, since both the layer thickness direction and the width direction have the GI type refractive index distribution, the effect of collecting light near the center of the high refractive index region 201 is enhanced, and transmission loss is further reduced. Is planned.

<Optical sheet manufacturing method>
Next, a method for manufacturing the optical sheet 200 according to the present embodiment will be described focusing on differences from the first embodiment. The optical sheet 200 according to the present embodiment can be manufactured, for example, by the following method.

First, similarly to the first embodiment, a laminate is manufactured.
Next, the laminate is selectively irradiated with energy such as light (for example, ultraviolet rays). For example, actinic radiation is irradiated through a mask in which an opening is formed in the laminate.

  Examples of preferable masks include photomasks made of quartz glass or PET base materials, stencil masks, metal thin films formed by vapor deposition methods (evaporation, sputtering, etc.), etc. Among these, it is particularly preferable to use a photomask or a stencil mask. This is because a fine pattern can be formed with high accuracy, and handling is easy, which is advantageous in improving productivity.

  The actinic radiation is not limited as long as it can cause a photochemical reaction (change) to the polymerization initiator. For example, in addition to visible light, ultraviolet light, infrared light, laser light, electron beam, X-ray, etc. Can also be used. The actinic radiation is appropriately selected depending on the kind of the sensitizer when it contains a polymerization initiator, a leaving group, and a sensitizer, and is not particularly limited, but has a peak wavelength in the range of 200 to 450 nm. It is preferable that it has. Thereby, a polymerization initiator can be activated comparatively easily.

The irradiation amount of actinic radiation is preferably in the range of about 0.03~9J / cm ^2, more preferably about 0.05~6J / cm ^2, at about 0.1~3J / cm ² More preferably. In addition, the refractive index difference formed can be controlled by adjusting the irradiation amount of actinic radiation, for example, a refractive index difference can be expanded by increasing irradiation amount.

  Moreover, when using light with high directivity like a laser beam as active radiation, use of a mask may be abbreviate | omitted.

Next, heat processing is performed to a laminated body as needed. In this heat treatment, the monomer or oligomer in the irradiated region irradiated with light is further polymerized. Although the heating temperature in this heat processing is not specifically limited, It is preferable that it is 30-180 degreeC, and it is more preferable that it is 40-160 degreeC. The heating time is preferably set so that the polymerization reaction of the monomer or oligomer in the irradiated region is almost completed, specifically 0.1 to 2 hours, preferably 0.1 to 1 hour. It is more preferable that Note that this heat treatment may be performed as necessary and may be omitted.
Thus, the optical sheet 200 is obtained.

  In the present embodiment, a GI-type refractive index distribution can be formed in the stacking direction of the optical sheet 200 and a GI-type refractive index distribution can be formed in the width direction of the optical sheet 200 by the same energy irradiation process.

  The optical sheet, the optical waveguide, and the electronic device of the present invention have been described above. However, the present invention is not limited to this, and for example, an arbitrary component is added to the optical sheet or the optical waveguide. Also good.

  Next, examples of the present invention will be described. The present invention will be described in detail based on examples and comparative examples, but the present invention is not limited thereto.

1. Production of optical waveguide (Example 1)
(1) Synthesis of base polymer 7.2 g (40.1 mmol) of hexylnorbornene (HxNB), diphenylmethylnorbornene methoxysilane in a glove box where both moisture and oxygen concentrations were controlled to 1 ppm or less and filled with dry nitrogen 12.9 g (40.1 mmol) was weighed into a 500 mL vial, 60 g of dehydrated toluene and 11 g of ethyl acetate were added, and the top was sealed with a silicon sealer.

Next, 1.56 g (3.2 mmol) of Ni catalyst and 10 mL of dehydrated toluene were weighed in a 100 mL vial, and a stirrer chip was placed and sealed, and the catalyst was thoroughly stirred to dissolve completely.
When 1 mL of this Ni catalyst solution was accurately weighed with a syringe, and quantitatively injected into the vial bottle in which the two kinds of norbornene were dissolved and stirred at room temperature for 1 hour, a marked increase in viscosity was confirmed. At this point, the stopper was removed, 60 g of tetrahydrofuran (THF) was added, and the mixture was stirred to obtain a reaction solution.
In a 100 mL beaker, 9.5 g of acetic anhydride, 18 g of hydrogen peroxide (concentration 30%) and 30 g of ion-exchanged water were added and stirred to prepare an aqueous solution of peracetic acid on the spot. Next, the total amount of this aqueous solution was added to the above reaction solution and stirred for 12 hours to reduce Ni.
Next, the treated reaction solution was transferred to a separatory funnel, the lower aqueous layer was removed, and then 100 mL of a 30% aqueous solution of isopropyl alcohol was added and vigorously stirred. The aqueous layer was removed after standing and completely separating the two layers. After repeating this water washing process three times in total, the oil layer was dropped into a large excess of acetone to reprecipitate the polymer produced, separated from the filtrate by filtration, and then in a vacuum dryer set at 60 ° C. A base polymer was obtained by heat drying for 12 hours. The molecular weight distribution of the base polymer was Mw = 100,000 and Mn = 40,000 as measured by GPC (polystyrene conversion). The molar ratio of each structural unit in the first base polymer was 50 mol% for the hexylnorbornene structural unit and 50 mol% for the diphenylmethylnorbornenemethoxysilane structural unit, as identified by NMR. The refractive index of the base polymer was 1.55.

(2) Production of first resin composition 10 g of the purified base polymer was weighed into a 100 mL glass container, and 40 g of mesitylene, 0.01 g of antioxidant Irganox 1076 (manufactured by Ciba Geigy Japan), cyclohexyl oxetane monomer ( Toa Gosei Co., Ltd. CHOX, CAS # 48333-3-25-9) 2 g, polymerization initiator (photoacid generator) Rhodosil Photoinitiator 2074 (Rhodia, CAS # 178233-72-2) (0.0125 g, ethyl acetate 0) In 1 mL), the mixture was uniformly dissolved, and then filtered through a 0.2 μm PTFE filter to obtain a clean first resin composition.

(3) Synthesis of Refractive Index Adjusting Agent 1 10 g of mesitylene is added to 10 g of cyclohexyloxetane monomer (manufactured by Toagosei Co., Ltd., CHOX, CAS # 483303-25-9) in a 100 mL eggplant flask, and an acid generator DANFABA (manufactured by Boulder Scientific Company) , CAS # 118612-00-3) was added, and the flask was immersed in a 50 ° C. warm bath for reaction. The molecular weight distribution of the polymer obtained 1 hour after the start of the reaction was Mw = 33,000 and Mn = 15,000 as measured by GPC (polystyrene conversion). Moreover, the glass transition temperature computed by the Bicerano method was 60 degreeC, and the refractive index was 1.49.

(4) Production of Second Resin Composition The refractive index modifier 1 synthesized in (3) is added to 40 parts by weight with respect to 100 parts by weight of the base polymer in the first resin composition of (2) above. Then, the mixture was filtered again with a 0.2 μm PTFE filter to obtain a clean second resin composition.

(5) Production of optical sheet Using the composition for forming an optical waveguide using the first and second resin compositions of (2) and (4) above, on a polyethersulfone (PES) film by a die coater. Multicolor extrusion was performed. As a result, a multicolor molded body having the core layer forming composition as an intermediate layer and the cladding layer forming composition as a lower layer and an upper layer was obtained. Then, the solvent was completely removed by putting in a dryer at 55 ° C. for 30 minutes. The average thickness of the obtained optical waveguide was 85 μm, the average thickness of the high refractive index region was 45 μm, and the average thickness of the low refractive index region was 20 μm.

(6) Production of optical waveguide Next, a photomask was mounted on the obtained optical sheet, and ultraviolet rays were selectively irradiated at 1300 mJ / cm ² . The mask was removed, and heating was performed at 150 ° C. for 1.5 hours in a dryer. After heating, it was confirmed that a clear waveguide pattern appeared.

(Example 2)
(1) Manufacture of optical sheet and optical waveguide As a refractive index adjusting agent, the following refractive index adjusting agent 2 is used, and the compounding amount of the synthesized refractive index adjusting agent 2 is 70 parts by weight with respect to 100 parts by weight of the base polymer. An optical waveguide was produced in the same manner as in Example 1 except for the change.

(2) Synthesis of Refractive Index Adjuster 2 After adding 30 g of cyclohexyl acrylate (Blenmer CHA, CAS # 3066-71-5, manufactured by NOF Corporation) and 67 g of mesitylene to a 100 mL eggplant flask, radical polymerization initiator V-601 (Wako Pure Chemical Industries, Ltd., CAS # 2589-57-3) A solution prepared by dissolving 0.15 g in mesitylene 2.85 g was added, and the flask was immersed in a 65 ° C. warm bath for reaction. The molecular weight distribution of the polymer obtained 4 hours after the start of the reaction was Mw = 51,000 and Mn = 23,000 as measured by GPC (polystyrene conversion). Moreover, the glass transition temperature computed by the Bicerano method was 96 degreeC, and the refractive index was 1.50.

(Example 3)
(1) Manufacture of optical sheet and optical waveguide As a refractive index adjusting agent, the following refractive index adjusting agent 3 is used, and the compounding amount of the synthesized refractive index adjusting agent 3 is 70 parts by weight with respect to 100 parts by weight of the base polymer. An optical waveguide was produced in the same manner as in Example 1 except for the change.

(2) Synthesis of Refractive Index Adjuster 3 After adding 30 g of isobornyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., CAS # 5888-33-5) and 67 g of toluene to a 100 mL eggplant flask, radical polymerization initiator V-601 (Wako Pure Chemical Industries, Ltd. make, CAS # 2589-57-3) The solution which melt | dissolved 0.15g in toluene 2.85g was added, and the flask was immersed in a 65 degreeC warm bath, and was made to react. The molecular weight distribution of the polymer obtained 4 hours after the start of the reaction was Mw = 47,000 and Mn = 19000 as measured by GPC (polystyrene conversion). Moreover, the glass transition temperature computed by the Bicerano method was 108 degreeC, and the refractive index was 1.50.

Example 4
(1) Manufacture of optical sheet and optical waveguide As a refractive index adjusting agent, the following refractive index adjusting agent 4 is used, and the compounding amount of the synthesized refractive index adjusting agent 4 is 70 parts by weight with respect to 100 parts by weight of the base polymer. An optical waveguide was produced in the same manner as in Example 1 except for the change.

(2) Synthesis of Refractive Index Adjuster 4 After adding 21.9 g of cyclohexyl methacrylate (Kyoei Chemical Co., Ltd., Light Ester CH, CAS # 101-43-9) and 49.0 g of mesitylene to a 100 mL eggplant flask, radical polymerization was started. A solution prepared by dissolving 1.00 g of Agent V-601 (manufactured by Wako Pure Chemical Industries, Ltd., CAS # 2589-57-3) in 18.96 g of mesitylene was added, and the flask was immersed in a warm bath at 80 ° C. for reaction. The molecular weight distribution of the polymer obtained 5 hours after the start of the reaction was Mw = 15.3 million and Mn = 93,000 as measured by GPC (polystyrene conversion). Moreover, the glass transition temperature computed by the Bicerano method was 119 degreeC, and the refractive index was 1.51.

(Example 5)
(1) Production of optical sheet and optical waveguide As a refractive index adjusting agent, the following refractive index adjusting agent 5 is used, and the compounding amount of the synthesized refractive index adjusting agent 5 is 90 parts by weight with respect to 100 parts by weight of the base polymer. An optical waveguide was produced in the same manner as in Example 1 except for the change.

(2) Synthesis of Refractive Index Adjusting Agent 5 1-adamantyl methacrylate (Adamantate M-104, CAS # 16887-36-8 manufactured by Idemitsu Kosan Co., Ltd.) 8.8 g and mesitylene 49.3 g were added to a 100 mL eggplant flask. Later, a solution prepared by dissolving 0.31 g of radical polymerization initiator V-601 (manufactured by Wako Pure Chemical Industries, Ltd., CAS # 2589-57-3) in 5.83 g of mesitylene was added, and the flask was immersed in a warm bath at 80 ° C. And reacted. The molecular weight distribution of the polymer obtained 5 hours after the start of the reaction was Mw = 47,000 and Mn = 22,000 as measured by GPC (polystyrene conversion). Moreover, the glass transition temperature computed by the Bicerano method was 141 degreeC, and the refractive index was 1.54.

(Example 6)
(1) Production of optical sheet and optical waveguide As a refractive index adjusting agent, the following refractive index adjusting agent 6 is used, and the blending amount of the synthesized refractive index adjusting agent 6 is 90 parts by weight with respect to 100 parts by weight of the base polymer. An optical waveguide was produced in the same manner as in Example 1 except for the change.

(2) Synthesis of Refractive Index Adjusting Agent 6 18.0 g of cyclohexyl acrylate (Blenmer CHA, CAS # 3066-71-5 manufactured by NOF Corporation) in a 100 mL eggplant flask, acrylic acid = (3-ethyloxetane-3-yl) ) After adding 2.0 g of methyl (Osaka Organic Chemical Co., Ltd. OXE-10, CAS # 41988-14-1) and 46.7 g of mesitylene, radical polymerization initiator V-601 (manufactured by Wako Pure Chemical Industries, Ltd., (CAS # 2589-57-3) A solution in which 0.50 g was dissolved in 5.0 g of mesitylene was added, and the flask was immersed in a warm bath at 80 ° C. for reaction. The molecular weight distribution of the polymer obtained 4 hours after the start of the reaction was Mw = 17,000 and Mn = 1 million as measured by GPC (polystyrene conversion). Moreover, the glass transition temperature computed by the Bicerano method was 92 degreeC, and the refractive index was 1.52.

(Example 7)
(1) Production of optical sheet and optical waveguide As a refractive index adjusting agent, the following refractive index adjusting agent 7 is used, and the compounding amount of the synthesized refractive index adjusting agent 7 is 70 parts by weight with respect to 100 parts by weight of the base polymer. An optical waveguide was produced in the same manner as in Example 1 except for the change.

(2) Synthesis of Refractive Index Adjuster 7 A 100 mL eggplant flask was charged with cyclohexyl acrylate (Blenmer CHA, CAS # 3066-71-5) manufactured by NOF Corporation, isobonyl acrylate (manufactured by Osaka Organic Chemical Co., Ltd., CAS # 5888-33-5) 4.1 g and mesitylene 46.7 g were added, and then radical polymerization initiator V-601 (manufactured by Wako Pure Chemical Industries, Ltd., CAS # 2589-57-3) 0.50 g was added to mesitylene 5 A solution dissolved in 0.0 g was added, and the flask was immersed in a warm bath at 80 ° C. for reaction. The molecular weight distribution of the polymer obtained 5 hours after the start of the reaction was Mw = 37,000 and Mn = 18,000 according to GPC measurement (polystyrene conversion). Moreover, the glass transition temperature computed by the Bicerano method was 103 degreeC, and the refractive index was 1.50.

(Comparative Example 1)
(1) Manufacture of optical sheet and optical waveguide As a refractive index adjusting agent, the following refractive index adjusting agent 8 is used, and the compounding amount of the synthesized refractive index adjusting agent 8 is 70 parts by weight with respect to 100 parts by weight of the base polymer. An optical waveguide was produced in the same manner as in Example 1 except for the change.

(2) Synthesis of Refractive Index Adjuster 8 After adding 3.4 g of methyl acrylate (manufactured by Kanto Chemical Co., Ltd., CAS # 96-33-3) and 46.7 g of mesitylene to a 100 mL eggplant flask, radical polymerization initiator V A solution prepared by dissolving 0.51 g of -601 (manufactured by Wako Pure Chemical Industries, Ltd., CAS # 2589-57-3) in 5.0 g of mesitylene was added, and the flask was immersed in a 80 ° C. warm bath to cause a reaction. The molecular weight distribution of the polymer obtained 5 hours after the start of the reaction was Mw = 29,000 and Mn = 14,000 by GPC measurement (polystyrene conversion). Moreover, the glass transition temperature computed by the Bicerano method was 35 degreeC, and the refractive index was 1.48.

(Evaluation)
The optical sheet and optical waveguide obtained in each example and comparative example were evaluated as follows. The obtained results are shown in Table 1.

(1) Haze The optical sheets obtained in each Example and Comparative Example were cut into 50 mm squares, and haze was measured. Nippon Denshoku Industries Co., Ltd. NDH5000 was used for the haze measuring apparatus. The measuring method of haze was measured based on JIS-K7136.

(2) Measurement of refractive index distribution The optical sheet was sliced in the cross-sectional direction (width direction) so as to be 200 to 300 μm to obtain an optical sheet fragment. About the cross section of the obtained optical sheet, refractive index distribution was measured with the interference microscope along the thickness direction, and the refractive index distribution of the optical sheet was obtained. The thickness up to the maximum value and the minimum value of the refractive index in the layer thickness direction was D2, and the thickness up to the half value and the minimum value of the refractive index in the layer thickness direction was D1.

(3) Transmission loss of optical waveguide The light emitted from the 850 nm VCSEL (surface emitting laser) is introduced into the optical waveguide obtained in each of the examples and comparative examples via the optical fiber of 50 μmφ, and is received by the optical fiber of 200 μmφ. The light intensity was measured. The insertion loss was calculated from the ratio with the light intensity when the fiber was connected without going through the waveguide.
The optical waveguide whose insertion loss was measured was placed in a thermo-hygrostat (manufactured by Espec Corp., LHU-113) set at 85 ° C. and 85% RH for 1000 hours. After reaching a predetermined time, the insertion loss was measured again.

DESCRIPTION OF SYMBOLS 100 Optical sheet 101 High refractive index area | region 102 Low refractive index area | region 103 Low refractive index area | region 105 One surface 107 Refractive index change area | region 109 Other surface 111 Refractive index change area | region 113 Flat part 115 Flat part 200 Optical sheet 201 High refractive index area | region 202 Low refractive index region 203 Low refractive index region 205 One surface 207 Refractive index change region 209 Other surface 211 Refractive index change region 220 High refractive index portion 230 Low refractive index portion 240 End surface 250 End surface 260 Refractive index change region 270 Refractive index Change region 280 Flat part

Claims (16)

An optical sheet comprising a layered high refractive index region having a relatively high refractive index and a layered low refractive index region having a refractive index relatively lower than that of the high refractive index region,
An optical sheet comprising a refractive index adjusting agent having a glass transition temperature calculated by the Bicerano method of 50 ° C. or higher and 300 ° C. or lower. The optical sheet according to claim 1,
An optical sheet having a polystyrene-equivalent weight average molecular weight of 5,000 or more and 200,000 or less as measured by gel permeation chromatography of the refractive index modifier. The optical sheet according to claim 1 or 2,
An optical sheet comprising a base polymer having a refractive index higher than that of the refractive index adjusting agent. In the optical sheet according to claim 3,
The optical sheet, wherein the refractive index adjuster is a compound that is compatible with the base polymer. The optical sheet according to claim 3 or 4,
An optical sheet, wherein a difference between a refractive index of the refractive index adjusting agent and a refractive index of the base polymer is 0.005 or more and 0.3 or less. The optical sheet according to any one of claims 3 to 5,
An optical sheet in which the base polymer is a cyclic olefin resin. The optical sheet according to claim 6,
The said refractive index regulator is an optical sheet which is a polymer which has an alicyclic structure in a side chain. The optical sheet according to claim 7,
The alicyclic structure of the side chain is an optical sheet having a five-membered or six-membered ring structure. The optical sheet according to any one of claims 3 to 5,
The base polymer is at least one selected from the group consisting of cyclic olefin resins, acrylic resins, methacrylic resins, polycarbonate, polystyrene, epoxy resins, polyamides, polyimides, polybenzoxazoles, silicone resins, and fluorine resins. Including an optical sheet. The optical sheet according to any one of claims 1 to 9,
The optical sheet whose haze value measured based on JIS-K7136 is 5.0% or less. In the optical sheet according to any one of claims 1 to 10,
At least part of the portion from the center line in the layer thickness direction toward one surface has a refractive index change region in which the refractive index continuously decreases along the layer thickness direction,
An optical sheet in which the refractive index adjusting agent is present at least in the refractive index changing region. The optical sheet according to claim 11,
An optical sheet, further comprising a refractive index changing region in which a refractive index continuously decreases along a layer thickness direction at least in a part from a center line in the layer thickness direction toward the other surface.   An optical waveguide comprising the optical sheet according to claim 1. The optical waveguide according to claim 13,
An optical waveguide, wherein the high refractive index region is an optical waveguide region that guides light. The optical waveguide according to claim 13 or 14,
An optical waveguide having a graded index type refractive index distribution in a direction perpendicular to the waveguide direction of light in the in-layer direction.   An electronic device comprising the optical waveguide according to claim 13.