JP2012083548A - Light-diffusing thermally conductive composition and light-diffusing thermally conductive molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-diffusing thermally conductive composition and a light-diffusing thermally conductive molded article which have light-diffusing properties, light transmissivity and thermal conductivity.SOLUTION: In the light-diffusing thermally conductive composition which contains a thermally conductive filler in a liquid matrix material formed by using a polymer composition as a main material and has both light-diffusing properties and light transmissivity, a difference in refractive index between the matrix material and the thermally conductive filler is in a range of 0.010-0.025 in terms of absolute value.

Description

  The present invention relates to a light diffusing heat conductive composition and a light diffusing heat conductive molded body having both light diffusibility, light transmittance and heat conductivity.

In recent years, there has been an increasing demand for backlights and illumination that have high luminance and low power consumption, and optical materials with higher light transmission and thermal conductivity are required. For example, light emitting diodes used for backlights of liquid crystal displays, illumination light sources, and the like, in particular, have high luminance types, require a heat dissipation path that efficiently releases heat generated from these light emitting elements. Normally, the luminance type has a heat dissipation path for releasing the generated heat through the lead frame and the substrate, but this heat dissipation path alone is insufficient to meet the heat dissipation requirement of the high luminance type. As a new heat dissipation path, it is conceivable to release heat from the light emitting surface of the backlight or the lens portion side of the light emitting diode.
As a technique related to this, for example, Japanese Patent Application Laid-Open No. 2010-170026 (Patent Document 1) discloses a light diffusing resin film used for a backlight and a light diffusing resin used for a lens portion.
JP-A-2005-202361 (Patent Document 2) discloses an optical material having excellent thermal conductivity.

JP 2010-170026 JP JP-A-2005-202361

  However, with the technique described in Japanese Patent Application Laid-Open No. 2010-170026 (Patent Document 1), when the filler is highly filled, it is not possible to obtain a suitable molded article with low light transmittance. Further, in the technique described in Japanese Patent Application Laid-Open No. 2005-202361 (Patent Document 2), transparent alumina or magnesium oxide having high thermal conductivity is filled, but the light transmittance decreases as the filling is high. It was difficult to achieve both thermal conductivity and transparency.

On the other hand, the heat radiating member as described above needs to take into consideration the influence of diffused light. If the material is excellent in light diffusibility and light transmittance even if the transparency is low, it has high brightness and thermal conductivity. The knowledge that a heat radiating member that achieves an excellent desired purpose could be obtained was obtained.
Then, an object of this invention is to provide the light-diffusion heat conductive composition and light-diffusion heat conductive molded object which have light diffusibility, light transmittance, and heat conductivity.

In order to achieve the above object, the following configuration is provided.
A light diffusing heat conductive composition comprising a heat conductive filler in a liquid matrix material mainly composed of a polymer composition, and having both light diffusibility and light transmissive property. A light diffusion heat conductive composition comprising a matrix material and a heat conductive filler having a relationship in which the difference between the refractive index and the refractive index of the heat conductive filler is in the range of 0.010 to 0.025 in absolute value. is there.

A light diffusion heat conductive composition containing a heat conductive filler in a liquid matrix material mainly composed of a polymer composition and having both light diffusibility and light transmittance, and the refractive index of the matrix material And a light diffusion heat conductive composition comprising a matrix material and a heat conductive filler having a relationship in which the difference in refractive index between the heat conductive filler and the heat conductive filler is in the range of 0.010 to 0.025 in absolute value. In the matrix material, the heat conductive filler can scatter light and obtain high diffusibility. Further, the light scattering property can be increased by suppressing back scattering. And if a molded object is formed with this light diffusion heat conductive composition, the light diffusion heat conductive molded object with high light transmittance and light diffusibility can be obtained.
The absolute value of the difference between the refractive index of the matrix material and the refractive index of the thermally conductive filler is from 0.010 to 0.025, more preferably from 0.010 to 0.020. This is because the total light transmittance and haze value are high, and the light diffusibility and light transmittance are more excellent.

It can be set as the light-diffusion heat conductive composition whose content of a heat conductive filler is 50 volume%-70 volume%. Even if the content of the thermally conductive filler is as high as 50% by volume to 70% by volume,
Since the absolute value of the difference in refractive index between the matrix material and the thermally conductive filler is set to 0.010 to 0.025, high diffusibility and light transmittance can be maintained. And since the heat conductive filler is highly filled with 50 volume%-70 volume%, the light-diffusion heat conductive composition with favorable heat conductivity and easy shaping | molding is realizable. When the heat conductive filler is less than 50% by volume, it is difficult to increase the heat conductivity of the molded body by the light diffusion heat conductive composition. When the heat conductive filler exceeds 70% by volume, the viscosity of the light diffusing heat conductive composition increases, and it becomes difficult to mold by a simple process. May be damaged. A more preferable content of the heat conductive filler is 60% by volume to 70% by volume.

Provided is a light diffusing heat conductive composition having both light diffusibility and light transmissive property, wherein the total light transmittance and haze value measured at a thickness of 500 μm are more than 70% and less than 100%.
Since the total light transmittance and haze value measured at a thickness of 500 μm are more than 70% and less than 100%, it is a light diffusion heat conductive composition excellent in both light diffusibility and light transmittance.
Particularly, at a predetermined temperature T, if the total light transmittance and haze value measured at a thickness of 500 μm are more than 70% and less than 100%, light diffusion excellent in both light diffusibility and light transmittance at the predetermined temperature T It becomes a heat conductive composition.

  The viscosity at 10 rpm at 25 ° C. can be 5000 mPa · s to 300,000 mPa · s. When the viscosity at 25 ° C. and 10 rpm is 5000 mPa · s to 300,000 mPa · s, the light diffusion thermal conductive composition can be applied to a wide range of uses. For example, it can be easily formed into a sheet or film. In addition, the light diffusion heat conductive composition can be poured into the gaps between the electronic components including the heating element, and even the complicated gaps can be filled with the light diffusion heat conductive moldings. In addition, the light diffusion heat conductive molded body can be brought into close contact with the heating element, and an increase in heat conduction performance can be expected. If the viscosity is less than 5000 mPa · s, the processability is good, but the blending amount of the heat conductive filler tends to decrease, and the thermal conductivity tends to be low, and if the viscosity exceeds 300000 mPa · s, the light diffusion A heat conductive composition becomes difficult to flow, and manufacture is also difficult. Moreover, when manufacturing a light-diffusion heat conductive molded object, there exists a possibility that a bubble may mix and light transmittance may be impaired.

Light diffusion heat conduction containing in the matrix material a refractive index adjusting agent that makes the difference between the refractive index of the polymer composition as the main material and the refractive index of the heat conductive filler an absolute value of 0.010 to 0.025 Composition. Since the matrix material contains a refractive index adjusting agent that makes the difference between the refractive index of the polymer composition as the main material and the refractive index of the heat conductive filler in an absolute value of 0.010 to 0.025, the main material and Even if the difference between the refractive index of the polymer composition and the refractive index of the thermally conductive filler exceeds 0.025 in absolute value or smaller than 0.010, the matrix material containing the refractive index adjusting agent The difference can be set to 0.010 to 0.025 in absolute value. Therefore, even if only the polymer composition as the main material has poor light diffusibility and light transmittance, the addition of the refractive index adjusting agent can increase the light diffusibility and light transmittance.
Also, if a low-viscosity material is used as the refractive index adjusting agent, the amount of the heat conductive filler can be easily increased, and if a material that functions as a softening agent is used as the refractive index adjusting agent, the light diffusion heat conductive composition is changed. It can be made flexible and heat conductivity can be increased.

  It can be set as the light-diffusion heat conductive composition whose refractive index of a heat conductive filler is isotropic. Since the refractive index of the thermally conductive filler is isotropic, the difference from the refractive index of the matrix material can be easily adjusted to 0.010 to 0.025 regardless of the direction of the thermally conductive filler. The total light transmittance and haze value measured at a thickness of 500 μm can be more than 70% and less than 100%. Therefore, the light diffusing heat conductive composition and the light diffusing heat conductive molded body formed using the composition have high light transmittance and light diffusibility, and can be suitably used as a heat conductive member for optical applications. .

（但し、数式（１）において、ｎ’_ｍ ^２５：マトリクス材の２５℃における屈折率の中心値、α：マトリクス材の線膨張係数、(ｄｎ／ｄＴ)_ｆ：熱伝導性充填材の屈折率温度係数、ｎ_ｆ ^２５：熱伝導性充填材の２５℃における屈折率、Ｔ：所定温度、をそれぞれ表す。）によって求められるマトリクス材の２５℃における屈折率の中心値ｎ’_ｍ ^２５とマトリクス材の２５℃における実際の屈折率の差が絶対値で０．０１１〜０．０２５の範囲となる関係を有するマトリクス材と熱伝導性充填材でなる光拡散熱伝導性組成物である。 A light diffusion heat conductive composition containing a heat conductive filler in a liquid matrix material mainly composed of a polymer composition and having both light diffusibility and light transmittance at a predetermined temperature T (° C.). The difference between the refractive index of the matrix material and the refractive index of the thermally conductive filler at a predetermined temperature T is in the range of 0.010 to 0.025 in absolute value, and the following formula (1)

(However, in Equation (1), n ′ _m ^{25 is} the central value of the refractive index of the matrix material at 25 ° C., α is the linear expansion coefficient of the matrix material, and (dn / dT) _{f is} the refractive index of the thermally conductive filler. The temperature coefficient, n _f ²⁵ : Refractive index of the thermally conductive filler at 25 ° C., and T: Predetermined temperature, respectively.) The central value n ′ _m ²⁵ of the refractive index at 25 ° C. of the matrix material and the matrix material Is a light diffusion heat conductive composition comprising a matrix material and a heat conductive filler having a relationship in which the difference in the actual refractive index at 25 ° C. is in the range of 0.011 to 0.025 in absolute value.

The absolute value of the difference between the actual refractive index of the matrix material at 25 ° C. and the central value of the refractive index of the matrix material at 25 ° C. (hereinafter, also simply referred to as “central value” in this specification) obtained by Equation (1). Since 0.011 to 0.025, the absolute value of the difference between the refractive index of the matrix material and the refractive index of the thermally conductive filler at a predetermined temperature T can be set to 0.010 to 0.025. This is because the refractive index of the matrix material at 25 ° C. obtained by Equation (1) is based on the refractive index of the matrix material at the predetermined temperature T, which is the same value as the refractive index of the thermally conductive filler at the predetermined temperature T. This is because the center value is n ′ _m ²⁵ . Therefore, if the matrix material has a refractive index such that the absolute value of the difference with respect to the center value n ′ _m ²⁵ is 0.011 to 0.025, the mathematical expression (1) is calculated backward from the value of the center value at the predetermined temperature T. When the refractive index is obtained, the absolute value of the difference from the refractive index of the thermally conductive filler at the predetermined temperature T can be set to 0.010 to 0.025.

When the absolute value of the difference between the refractive index of the matrix material and the refractive index of the thermally conductive filler is 0.010 to 0.025 at the predetermined temperature T, the thermally conductive filling is performed in the matrix material at the predetermined temperature T. Light can be appropriately diffused by the material, and a light diffusing heat conductive composition having high light diffusibility and light transmittance at a predetermined temperature T can be obtained. Here, if the predetermined temperature T is a temperature at which the heating element is operating, the light diffusion heat conductive composition having high light diffusibility and light transmission at the temperature at which the heating element operates. And if a molded object is formed with this light diffusion heat conductive composition, light diffusibility and light transmittance can be maintained, and a light diffusion heat conductive molded object with high light diffusibility and light transmission can be obtained. Can do.
The absolute value of the difference between the refractive index at 25 ° C. of the matrix material and the central value of the refractive index at 25 ° C. determined by the formula (1) is in the range of 0.011 to 0.025, but is 0.011 to 0. More preferably, it is .020. It is because it will become a light-diffusion heat conductive composition and a light-diffusion heat conductive molded object with both high total light transmittance and a haze value if it is 0.011-0.020.
If the predetermined temperature T is the operating temperature T, which is the temperature when the heating element to which the light diffusing heat conductive composition and the light diffusing heat conductive molded body are affixed, or the assumed temperature when it is assumed that heat has been generated, is assumed. The light diffusibility and the light transmittance at the temperature at which the light diffusion heat conductive composition and the light diffusion heat conductive molded body are actually used or at the temperature actually used can be increased. That is, light that can increase the total light transmittance by suppressing backscattering while the heat conductive filler scatters light in the matrix material to increase the haze value while the heating element is in operation. A diffusion heat conductive composition and a light diffusion heat conductive molding can be obtained.

The central value n ′ _m ²⁵ of the refractive index of the matrix material at 25 ° C. is the linear expansion coefficient (α) of the matrix material, the refractive index temperature coefficient ((dn / dT) _f ) of the thermally conductive filler, and the thermal conductivity. If the refractive index at 25 ° C. of the filler is known, it is expressed as a function of the predetermined temperature (T), so that a light diffusive and thermally conductive composition having high light diffusibility and light transmissivity at the desired temperature (T) is obtained. Can do.
Moreover, in order to obtain this light diffusion heat conductive composition, it can be manufactured by mixing a matrix material and a heat conductive filler, kneading and defoaming, and therefore complicated processes such as pressurization and decompression. Can be manufactured by a simple process that does not need to be repeated.

  The predetermined temperature T can be set to 50 ° C to 140 ° C. That is, a light diffusing heat conductive composition having high light diffusibility and light transmissive property can be obtained at an arbitrary temperature set at a predetermined temperature T within a range of 50 ° C. to 140 ° C. This is because at a temperature lower than 50 ° C., the heating element operating at such a low temperature hardly needs to dissipate heat, and it is less necessary to apply the light diffusion heat conductive composition and the light diffusion heat conductive molded body. In addition, at a temperature exceeding 140 ° C., it is preferable to use a material having high thermal conductivity even if light diffusibility and light transmittance are inferior to cool a heating element that generates heat to such a high temperature. This is because it is less necessary to apply the diffusion heat conductive composition and the light diffusion heat conductive molding.

  In addition, the matrix material includes a refractive index adjusting agent that adjusts the difference between the refractive index of the polymer composition as the main material and the refractive index of the thermally conductive filler at an absolute value of 0.010 to 0.025 at a predetermined temperature T. The light diffusing heat conductive composition contained in As a matrix material containing a refractive index adjusting agent, the difference in refractive index at a predetermined temperature T can be set to 0.010 to 0.025 in absolute value. Even if the light diffusibility and the light transmittance are poor, the light diffusibility and the light transmittance can be increased.

And if a molded object is formed with this light diffusion heat conductive composition, the light diffusion heat conductive molded object with high light transmittance and light diffusibility can be obtained. More preferably, the absolute value of the difference between the center value of the refractive index of the matrix material at 25 ° C. and the actual refractive index is 0.011 to 0.020.
In addition, when obtaining this light diffusion heat conductive composition, it is not necessary to repeat complicated steps such as pressurization and decompression, and a matrix material and a heat conductive filler are blended to facilitate kneading and defoaming. It can be manufactured in a process.
And this light-diffusion heat conductive composition has high heat conductivity, can obtain the solidified body with high light transmittance and light diffusibility, and can be used suitably as a heat conductive member for optical uses. .

According to the light diffusing heat conductive composition and the light diffusing heat conductive molded body of the present invention, a light diffusing heat conductive composition having high light permeability, light diffusibility, and heat conductivity can be realized. And this light-diffusion heat conductive molded object can be used suitably as a heat conductive member for optical uses.
Further, the light diffusing heat conductive composition does not need to be manufactured by repeating complicated processes such as pressurization and decompression, and a simple mixing and defoaming is performed by mixing a matrix material and a heat conductive filler. It can be manufactured in a process.

  The light-diffusion heat conductive composition and light-diffusion heat conductive molded object of this invention are demonstrated based on specific embodiment. In the following description, the operating temperature T indicates the temperature when the heating element using the light diffusing heat conductive composition and the light diffusing heat conductive molded body generates heat, or the assumed temperature when it is assumed that heat is generated. . In other words, it indicates the temperature at which the light diffusion heat conductive composition and the light diffusion heat conductive molded body are actually used, or the temperature assumed to be the temperature actually used.

Light diffusion thermal conductive composition :
The light diffusion heat conductive composition contains a heat conductive filler in a liquid and highly transparent matrix material mainly composed of a polymer composition.
The matrix material plays the role of a binder including a thermally conductive filler, and is liquid and transparent or translucent. This matrix material contains a polymer composition as a main material.
The refractive index of the matrix material is required to have a difference between the refractive index of the thermally conductive filler and the absolute value of 0.010 to 0.025. If the difference in refractive index between the matrix material and the thermally conductive filler is 0.010 to 0.025 in absolute value, a light diffusing and highly light diffusing thermally conductive composition can be realized. it can. And if a molded object is formed with this light diffusive heat conductive composition, light diffusibility and light transmittance can be maintained, and a light diffusive heat conductive molded object excellent in both light diffusibility and light transmittance can be obtained. Obtainable.
Note that high light transmittance can be defined by replacing the high total light transmittance, and high light diffusivity by high haze value.
If the difference between the absolute values is less than 0.010, the light transmitted through the matrix material is not scattered at the interface between the matrix material and the thermally conductive filler, resulting in a transparent composition with low light diffusibility. On the other hand, if it exceeds 0.025, backscattering increases and light transmittance is impaired.

In particular, in order to set the absolute value of the difference between the refractive index of the matrix material and the refractive index of the thermally conductive filler at a predetermined temperature T to 0.010 to 0.025, the actual refraction of the matrix material at 25 ° C. The absolute value of the difference may be set in the range of 0.011 to 0.025 with respect to the central value n ′ _m ²⁵ of the refractive index of the matrix material described below. Hereinafter, the center value n ′ _m ²⁵ of the refractive index of the matrix material will be described.

  Since the light diffusing heat conductive composition and the light diffusing heat conductive molded body are heat radiating members attached to a heat generating body of an electronic device, they are used at a temperature higher than room temperature. However, since the refractive index temperature coefficient of the matrix material and the refractive index temperature coefficient of the thermally conductive filler are different, the absolute value of the difference between the refractive index of the matrix material and the refractive index of the thermally conductive filler at room temperature is 0. Even in the range of 011 to 0.025, at the operating temperature T, there is a difference in the refractive index between the matrix material and the thermally conductive filler. As a result, the light diffusibility or light transmittance of the light diffusion heat conductive composition and the light diffusion heat conductive molding at the operating temperature T is impaired. In order to increase the light diffusibility and light transmittance at the operating temperature T, the absolute value of the difference between the refractive index of the matrix material and the refractive index of the thermally conductive filler at the operating temperature T is set to 0.010 to 0.025. It is necessary to.

When the refractive index at the operating temperature T of the thermally conductive filler is n _f ^T and the refractive index at 25 ° C. is n _f ²⁵ , the refractive index temperature coefficient (dn / dT) _f of the thermally conductive filler is (2).
_{(Dn / dT) f = (} n f T -n f 25) / (T-25) ··· (2)

When this is transformed, the following formula (3) is obtained.
n _f ^T = n _f ²⁵ + (T−25) (dn / dT) _f (3)
That is, it is possible to calculate the refractive index n _f ^T of the heat-conducting filler in operating temperature T from the refractive index n _f ²⁵ and the refractive index temperature coefficient (dn / dT) _f at 25 ° C. of the thermally conductive filler.
The refractive index temperature coefficient (dn / dT) _f of the thermally conductive filler can be measured with a refractive index measuring apparatus (for example, “Prism Coupler SPA Series” manufactured by SAIRON TECHNOLOGY) with a temperature adjustment function. For example, in silica, (dn / dT) _f = 10 × 10 ⁻⁶ . Further, the refractive index n _f ²⁵ at 25 ° C. of the thermally conductive filler can be measured by a measuring method such as the Becke method. For example, n _f ²⁵ = 1.4585 for silica.

On the other hand, the refractive index temperature coefficient (dn / dT) _m of the matrix material can be expressed by the following mathematical formula (4).
(Dn / dT) _m = (n ′ _m ²⁵ −1) × (−3α) (4)
Here, α is defined as the linear expansion coefficient of the matrix material, and n ′ _m ²⁵ is defined as the central value of the refractive index of the matrix material at 25 ° C., but Equation (4) is the refractive index temperature coefficient (dn / dT) of the matrix material. ) Indicates that _m can be obtained based on the linear expansion coefficient of the matrix material and the refractive index of the matrix material at 25 ° C.

Further, the refractive index temperature coefficient (dn / dT) _m of the matrix material can be expressed by the following mathematical formula (5), similarly to the mathematical formula (2) representing the refractive index temperature coefficient of the thermally conductive filler.
(Dn / dT) _m = (n _m ^T −n _m ²⁵ ) / (T−25) (5)

From the equations (4) and (5), the following equation (6) can be derived.
(N _m ^T −n _m ²⁵ ) / (T−25) = (n ′ _m ²⁵ −1) × (−3α) (6)
When formula (6) is transformed, the following formula (7) is obtained.
n ′ _m ²⁵ = {n _m ^T −3α (T−25)} / {1−3α (T−25)} (7)

Here, a case where the difference in refractive index n _m ^T of the refractive index n _f ^T and the matrix material of the heat-conducting filler in the operating temperature T is 0. That is, when n _m ^T = n _f ^T and substituting the right side of equation (3), which is n _f ^T , into n _m ^T of equation (7), the following equation (1) can be derived. The central value n ′ _m ²⁵ of the refractive index of the matrix material at 25 ° C. derived by the formula (1) is the matrix material at 25 ° C. when the refractive index of the matrix material and the thermally conductive filler becomes equal at the operating temperature T. It can also be called a refractive index.

In this mathematical formula (1), the value of the linear expansion coefficient α of the matrix material can be easily measured with a thermomechanical analyzer or the like. For example, with silicone rubber, it is about 290 × 10 ⁻⁶ / ° C.
Therefore, the value of the matrix material used for the heating element operating at the operating temperature T as the center value n ′ _m ²⁵ is the linear expansion coefficient α of the matrix material, the refractive index n _f ^{25 of} the thermally conductive filler at 25 ° C., the heat The refractive index temperature coefficient (dn / dT) of the conductive filler can be obtained by calculation using Formula (1) from _f .
Then, the actual refractive index of the matrix material at 25 ° C. is such that the difference from the central value n ′ _m ²⁵ is in the range of 0.011 to 0.025 in absolute value, so that the refractive index of the matrix material at the operating temperature T And the absolute value of the difference between the refractive index of the thermally conductive filler can be in the range of 0.010 to 0.025.

In other words, by using Equation (1), the refractive index of the matrix material at 25 ° C. (the center of the matrix material at 25 ° C.) when the refractive index of the matrix material and the thermally conductive filler becomes equal under the operating temperature T. matrix 'can obtain a value) obtained by the _m ^25, the central value n' value n absolute value of the difference between the value of _m ²⁵ has a refractive index at 25 ° C. in the range of 0.011 to 0.025 If the material is set, the absolute value of the difference between the refractive index of the matrix material and the refractive index of the thermally conductive filler at the operating temperature T is measured at 0.010 without measuring the refractive index of the matrix material at the operating temperature T. It can be made into the range of -0.025. Therefore, when manufacturing the light diffusion heat conductive composition, if the refractive index at 25 ° C. is known, it is not necessary to measure the refractive index of the matrix material under the operating temperature T, and the light diffusion heat conductive composition The design efficiency can be greatly increased.

In addition to the liquid resin material, the polymer composition that is the main material of the liquid matrix material may include a resin precursor, and the resin precursor includes monomers and oligomers that react to become a resin material. included. Furthermore, since the polymer composition contains a large amount of a heat conductive filler, it is preferably liquid and has a low viscosity.
In addition to the main polymer composition, the matrix material further includes a curing agent that contributes to the curing reaction with the polymer composition, a crosslinking agent, a reaction initiator, a plasticizer, a solvent, and the like. The additive which becomes may be included. Moreover, the refractive index adjusting agent mentioned later may be included.
For example, when the viscosity of the polymer composition as the main material is high or when it is desired to reduce the hardness of the molded product after molding, a plasticizer is added, or the polymer composition as the main material is diluted with a soluble solvent. You can do it. Such an additive preferably has high light diffusibility and light transmittance, and preferably has light diffusibility and light transmittance close to a matrix material.
In addition, the said additive needs to be added in the range from which the absolute value of the difference with the central value of the refractive index in 25 degreeC of a matrix material will be 0.010-0.025.

Examples of the material of the polymer composition include liquid silicone having a vinyl group, (meth) acrylate having a functional group, and an epoxy monomer having two or more epoxy groups. Various curing agents that cause a curing reaction with the polymer composition can be used as the curing agent. For example, silicone having a Si—H group, a phthalic anhydride compound, and the like can be given. It is preferable to use a transparent or translucent curing agent as the curing agent.
Then, a liquid polymer composition can be crosslinked and cured by using a method using active energy rays such as ultraviolet rays and electron beams, a method of performing thermal polymerization by applying heat, and the like.

The refractive index adjuster is used when the difference between the refractive index of the main polymer composition and the refractive index of the thermally conductive filler is large or small, and the refractive index of the matrix material and the refractive index of the thermally conductive filler. The difference from the rate is adjusted to 0.010 to 0.025 in absolute value.
At the time of preparing the light diffusion heat conductive composition, it is added when the absolute value of the difference from the central value of the refractive index of the matrix material at 25 ° C. is less than 0.010 or more than 0.025. Thus, the difference between the actual refractive index of the matrix material at 25 ° C. and the central value of the refractive index is in the range of 0.011 to 0.025 in absolute value.

  Since there are few choices for the combination of materials in which the difference between the refractive index of the main polymer composition and the refractive index of the thermally conductive filler is 0.010 to 0.025, a refractive index adjusting agent is used. For example, light diffusion heat with high light diffusivity and light transmission, regardless of whether the difference between the refractive index of the main polymer composition and the refractive index of the thermally conductive filler is large or small. A conductive composition can be realized.

Such a refractive index adjusting agent needs to be homogeneously mixed with the polymer composition. When the refractive index of the polymer composition as the main material is larger than the refractive index of the thermally conductive filler by more than 0.025, the refractive index of the refractive index adjusting agent is the refractive index of the thermally conductive filler. Choose a smaller one. In addition, when the refractive index of the polymer composition as the main material is smaller than the refractive index of the thermally conductive filler by more than 0.025, the refractive index of the refractive index adjusting agent is the refractive index of the thermally conductive filler. Choose a larger one.
The refractive index adjuster may have a functional group that reacts with the polymer composition. A curing agent can also be used as a refractive index adjusting agent.
Examples of the refractive index adjuster include silicone resins and silicone oils other than the silicone resin when the polymer composition is a silicone resin.

As an example, a light diffusion heat conductive composition in which a liquid silicone resin is applied to a polymer composition as a main material, silica is used as a heat conductive filler, and a refractive index adjusting agent is used. An example in which the center value of the refractive index of the matrix material at 25 ° C. is determined to determine the refractive index of the matrix material will be described.
Assuming that the operating temperature T is affixed to a heating element of 100 ° C., T = 100. Linear expansion coefficient of matrix material α = 290 × 10 ⁻⁶ / ° C. (The linear expansion coefficient of the liquid silicone resin, which is a polymer composition that is the main material because it is substantially the same as the linear expansion coefficient of the liquid silicone resin that is the main material) Because the refractive index n _f ²⁵ = 1.4585 of the thermally conductive filler at 25 ° C. and the refractive index temperature coefficient of the thermally conductive filler (dn / dT) _f = 10 × 10 ⁻⁶ When the center value n ′ _m ²⁵ of the refractive index of the matrix material is calculated by substituting ## EQU1 ## into the above formula (1), it is 1.4913.
Therefore, if silicone oil or the like is added to the liquid silicone resin as a refractive index adjusting agent and the refractive index of the actual matrix material at 25 ° C. is adjusted to 1.4913 ± 0.011 to 0.025, it is refracted at 100 ° C. A light diffusing heat conductive composition having high light diffusibility and high light transmittance in which the absolute value of the difference in rate is in the range of about 0.010 to 0.025 is obtained.

  When the same calculation is performed for each temperature, the refractive index at 25 ° C. is 1.46889 ± 0.011-0.025 when the operating temperature is 50 ° C., and 1.4733 ± 0 when the operating temperature is 60 ° C. .011 to 0.025, 1.776 ± 0.011 to 0.025 at 70 ° C., 1.4821 ± 0.011 to 0.025 at 80 ° C., 1 at 90 ° C. 4821 ± 0.011-0.025, 110 ° C. at 1.4960 ± 0.011-0.025, 120 ° C. at 1.5008 ± 0.011-0.025, 130 ° C. Is adjusted to 1.5058 ± 0.011-0.025, and at 140 ° C., it is adjusted to 1.5108 ± 0.011-0.025.

As the thermally conductive filler, a filler made of an inorganic substance or an organic substance can be used. Among them, it is preferable to use an inorganic filler because of its high thermal conductivity, but it is difficult to use a metallic inorganic filler that does not transmit light.
The inorganic filler as the thermally conductive filler preferably has a refractive index at 25 ° C. of 1.38 to 1.65, more preferably 1.42 to 1.60. A matrix that can be adjusted so that the absolute value of the difference in refractive index is 0.010 to 0.025 when an inorganic filler with a refractive index at 25 ° C. of greater than 1.65 or an inorganic filler of less than 1.38 is used. Since the material is determined to some extent, the selection range of the matrix material is narrowed, and the preparation of the light diffusion heat conductive composition becomes difficult. If it is an inorganic filler with a refractive index of 1.42 to 1.60 at 25 ° C., the selection of the polymer composition and refractive index adjuster as the main material becomes easy.

  Examples of the inorganic filler having a refractive index of 1.42 to 1.60 at 25 ° C. include aluminum hydroxide, magnesium hydroxide, and silica. Here, aluminum hydroxide and magnesium hydroxide are expected to have a thermal conductivity of about 8 W / m · K when they are estimated from the thermal conductivity value of the thermally conductive molded body. Silica is crystalline and is about 8 W / m · K (10.4 W / m · K in the crystal c-axis direction, 6.2 W / m · K in the direction perpendicular to the c-axis), and 1 is non-crystalline. It has a thermal conductivity of 38 W / m · K.

The refractive index of the thermally conductive filler is preferably as the anisotropy is small, and it is more preferable that there is no anisotropy of the refractive index, that is, the refractive index is isotropic. If the refractive index of the thermally conductive filler is isotropic, the difference from the refractive index of the matrix material can be set to 0.010 to 0.025 regardless of the direction of the thermally conductive filler. Further, when the thermally conductive filler has an anisotropy of refractive index, the refractive index difference is in the range of 0.010 to 0.025 from both refractive index values of the maximum refractive index and the minimum refractive index. The refractive index of the matrix material is adjusted so that
The shape of the heat conductive filler is preferably substantially spherical. When a thermally conductive filler with a crushed surface having a smooth surface is used, bubbles at the interface remain without being lost, and the light transmittance may be reduced. From this point of view, spherical silica is more preferable than crushed silica.

The average particle size of the thermally conductive filler is preferably 1 μm or more. The heat conductive filler with a small average particle size has a large specific surface area, so that the viscosity of the light diffusion heat conductive composition obtained compared with the heat conductive filler with a large average particle size becomes high, and the heat conductive filling High filling of material becomes difficult. A more preferable average particle diameter of the thermally conductive filler is 4 μm or more.
Moreover, it is preferable that the largest particle diameter of a heat conductive filler is 15 micrometers or less. Since the filler having a substantially spherical shape often contains bubbles in coarse particles, there is a risk that the light transmittance may be reduced when blended with a matrix material. More preferably, it is 10 μm or less.

  It is preferable that content of a heat conductive filler is 50 volume%-70 volume% with respect to the whole light-diffusion heat conductive composition. When the heat conductive filler is less than 50% by volume, it is difficult to increase the heat conductivity of the molded body by the light diffusion heat conductive composition. When the content of the heat conductive filler exceeds 70% by volume, the viscosity of the light diffusing heat conductive composition is increased, and air bubbles easily enter, making it difficult to produce the light diffusing heat conductive composition. Because. Moreover, it is preferable to contain 60 volume%-70 volume% of heat conductive fillers from a viewpoint of improving heat conductivity.

  The initial viscosity of the light diffusing thermally conductive composition as described above is preferably 5000 mPa · s to 300,000 mPa · s at 25 ° C. and a rotation speed of 10 rpm. When the viscosity is less than 5000 mPa · s, the heat conductive composition tends to flow, the workability is poor, and the heat conductivity is difficult to increase. When the viscosity exceeds 300,000 mPa · s, the light diffusion heat conductive composition is inferior in fluidity, difficult to stir, and difficult to defoam, so that the light diffusion heat conductive molded product obtained from this light diffusion heat conductive composition is obtained. It becomes easy for bubbles to enter. Furthermore, the light diffusion heat conductive molded body tends to be hard and brittle. If the viscosity is in the range of 5000 mPa · s to 300,000 mPa · s, it can be easily formed into a sheet or film, and the light diffusion heat conductive composition is poured into the gap between the electronic components including the heating element. The light diffusing heat conductive composition can be used for a wide range of applications, such as being able to be molded.

Light diffusion heat conductive molding :
The light diffusion heat conductive molded body formed from the above light diffusion heat conductive composition preferably has a haze value (haze value) of more than 70% at an operating temperature T and a thickness of 500 μm. The haze value means the degree of unclear cloudy appearance inside or on the surface of the light diffusion heat conductive molded body. The higher the haze value, the stronger the degree of cloudy appearance is. Is high.
On the other hand, it is preferable that this light diffusion heat conductive molded object also shows the value which total light transmittance exceeds 70%. A high total light transmittance means that most of the light incident on the light diffusing thermally conductive molded body is transmitted through the light diffusing thermally conductive molded body, and light absorption by the light diffusing thermally conductive molded body. And less backscatter. A light diffusion heat conductive molded body having a haze value and a total light transmittance exceeding 70% is excellent in light diffusibility and light transmission, and can be suitably used as a heat conductive member for optical applications.

The manufacturing method of a light diffusion thermal conductive molded object is demonstrated.
First, a light diffusion heat conductive composition is prepared by mixing a matrix material and a heat conductive filler. Next, it deaerates by stirring under vacuum. And a light-diffusion heat conductive molded object is obtained by inject | pouring a light-diffusion heat conductive composition into a metal mold | die etc. and solidifying.
If the polymer composition is a thermoplastic resin that is soluble in a solvent, dissolve the thermoplastic resin in the solvent, add a refractive index adjusting agent and a thermally conductive filler, stir and cast. It can also be formed into a sheet or film.
Furthermore, the light diffusing heat conductive composition is applied to the surface of the display or the light source of the illumination, or the light diffusing heat conductive composition is poured into a gap of an electronic component including a heating element, and then the light. The diffusion heat conductive composition can be cured to form a light diffusion heat conductive molding.

Next, the present invention will be described from experimental examples.
[1. Sample Preparation] In this experimental example, the following liquid silicone A is used as the matrix material, the following amorphous spherical silica is used as the thermally conductive filler, and the above equation (when the operating temperature T is 100 ° C.) Based on 1), the center value of the refractive index of the matrix material was calculated. Then, Samples 1 to 5 shown below were prepared, in which a refractive index adjusting agent was further adjusted and added so that the difference in refractive index value with respect to the central value of the refractive index varied.
The linear expansion coefficient of the cured product of liquid silicone A used in the experiment is α = 290 × 10 ⁻⁶ / ° C., the refractive index of silica at 25 ° C. is n _f ²⁵ = 1.4585, and the refractive index of amorphous spherical silica. The rate temperature coefficient is (dn / dT) _f = 10 × 10 ⁻⁶ . By substituting this into Equation (1), the center value of the refractive index of the matrix material is calculated as n ′ _m ²⁵ = 1.4913. In addition, since the value of the linear expansion coefficient was also substantially the same for the cured products of liquid silicones B, C, D, E, and F, the optimum refractive index of the mixture was also assumed to be the same value.

Sample 1 : 90.0 parts by weight of liquid silicone B (manufactured by Gelest, product name: PDV-1625) as a polymer composition, and liquid silicone C (manufactured by Gelest, product name: HDP-111) as a refractive index adjusting agent 4 parts by weight, 4 parts by weight of liquid silicone E (manufactured by Gelest, trade name: DMS-H03), 2 parts by weight of liquid silicone F (manufactured by Gelest, trade name: HQM-105), and further a curing catalyst (Gelest A matrix material was prepared by adding 0.005 part by weight, manufactured by the company, trade name SIP6832.2). Next, 413 parts by weight of the above amorphous spherical silica (manufactured by Tatsumori Co., Ltd., PLV-6, average particle size 4.3 μm, refractive index 1.4585) is added to this matrix material as a thermally conductive filler, and stirred. And vacuum degassing to prepare a light diffusion heat conductive composition. In the light diffusion heat conductive composition, the heat conductive filler is 66.7 vol%.
This light diffusion heat conductive composition is applied onto a resin film, sandwiched between another resin film, stretched with a roll so as to have a constant thickness so as not to generate bubbles, The light diffusing heat conductive composition was cured by leaving it in a thermostat for 20 minutes to produce a sheet-like light diffusing heat conductive molding.
As the constant thickness, two types were used: 500 μm as a test piece for measuring total light transmittance and haze value, and 5 mm as a test piece for measuring thermal conductivity.
The light diffusing heat conductive composition and the light diffusing heat conductive molding thus obtained were used as Sample 1.

Sample 2 : Liquid silicone A (manufactured by Momentive Performance Materials, the main ingredient, trade name: XE5844 (A)) 40 parts by weight as a polymer composition and curing agent A (made by Momentive Performance Materials) , Trade name: XE5844 (B)) 80 parts by weight of a liquid mixture, 18.2 parts by weight of the above liquid silicone B as a refractive index adjusting agent, and 1.8 parts by weight of the above liquid silicone C are added. A matrix material was prepared. Next, 413 parts by weight of the silica as a heat conductive filler was added to the matrix material, and stirring and vacuum degassing were performed to prepare a light diffusion heat conductive composition.
A light diffusion heat conductive molded body was produced in the same manner as Sample 1 using this light diffusion heat conductive composition. The light diffusing heat conductive composition and the light diffusing heat conductive molding thus obtained were used as Sample 2.

Sample 3 : 10 parts by weight of the above liquid silicone A as a polymer composition, 20 parts by weight of a liquid mixture of 10 parts by weight of the curing agent A, and 72.7 parts by weight of the above liquid silicone B as a refractive index adjusting agent. The matrix material was prepared by adding 7.3 parts by weight of the liquid silicone C and 0.004 parts by weight of the curing catalyst. Next, 413 parts by weight of the above silica as a heat conductive filler was added to the matrix material, and stirring and vacuum degassing were performed to prepare a light diffusion heat conductive composition.
A light diffusion heat conductive molded body was produced in the same manner as Sample 1 using this light diffusion heat conductive composition. The light diffusing heat conductive composition and the light diffusing heat conductive molding thus obtained were used as Sample 3.

Sample 4 : 45 parts by weight of the above liquid silicone A as a polymer composition, 90 parts by weight of a liquid mixture of the above curing agent A: 45 parts by weight, and liquid silicone D (manufactured by Toray Dow Corning, A matrix material was prepared by adding 5 parts by weight of a trade name: OE-6520A) and 5 parts by weight of the curing agent D (manufactured by Toray Dow Corning, trade name: OE-6520B). Next, 413 parts by weight of the silica as a heat conductive filler was added to the matrix material, and stirring and vacuum defoaming were performed to prepare a light diffusion heat conductive composition.
A light diffusion heat conductive molded body was produced in the same manner as Sample 1 using this light diffusion heat conductive composition. The light diffusing heat conductive composition and the light diffusing heat conductive molding thus obtained were used as Sample 4.

Sample 5 : 25 parts by weight of the above liquid silicone A as a polymer composition, 50 parts by weight of a liquid mixture of the above curing agent A: 25 parts by weight, and 45.5 parts by weight of the above liquid silicone B as a refractive index adjusting agent. The liquid silicone C: 4.5 parts by weight and the curing catalyst: 0.0025 parts by weight were added to prepare a matrix material. Next, 413 parts by weight of the silica as a heat conductive filler was added to the matrix material, and stirring and vacuum defoaming were performed to prepare a light diffusion heat conductive composition.
A light diffusion heat conductive molded body was produced in the same manner as Sample 1 using this light diffusion heat conductive composition. The light diffusing heat conductive composition and the light diffusing heat conductive molding thus obtained were used as Sample 5.

[2. Test Method] For samples 1 to 5, “viscosity” of the light diffusion heat conductive composition, “refractive index at 25 ° C.” of the matrix material, “total light at temperature T” of the light diffusion heat conductive molded body "Transmissivity", "Haze value at temperature T", and "Thermal conductivity" were measured. The results are shown in Tables 1 and 2.
The temperature T is a measurement temperature in a test for measuring total line transmittance and haze described below.

Viscosity : Using a rotational viscometer (Brookfield, trade name: DV-E type, spindle No. 14), the viscosity at 25 ° C. of the light diffusion thermal conductive compositions of Sample 1 to Sample 5 was measured. Measured.
Refractive index at 25 ° C . : After the matrix materials of Sample 1 to Sample 5 before adding the thermally conductive filler are cured to produce a molded body made only of the matrix material, the refractive index at a wavelength of 589 nm at 25 ° C. Was measured using a refractometer (manufactured by Atago Co., Ltd., Abbe refractometer DR-M2).
Total light transmittance at temperature T and haze at temperature T : Test specimens for measuring total light transmittance and haze value were prepared from Sample 1 to Sample 5 which are light diffusion heat conductive molded bodies having a thickness of 500 μm. Then, using a TM double beam type haze computer HZ-2 manufactured by Suga Test Instruments Co., Ltd., all light transmission is performed at a temperature selected from 36 ° C., 65 ° C., 88 ° C. and 100 ° C. assuming the operating temperature of the heating element. The rate and haze (cloudiness value) were measured. In addition, it was set as the conditions of JISK7136 except the said temperature conditions.
More specifically, the test piece prepared from Sample 1 measured at 65 ° C. is measured at 100 ° C. prepared from Molded Product A, and the test piece measured at 100 ° C. prepared from Sample 2 is measured at 100 ° C. Test piece prepared from molded body C, sample 1 measured at 88 ° C., molded body D, sample 3 prepared from sample 3 measured at 36 ° C. Test piece measured from molded body E, sample 4 measured at 100 ° C. The test piece to be measured is molded body F, and the test piece prepared from sample 1 and measured at 100 ° C. is molded body G.
The measurement was performed using the test piece prepared from Sample 5 measured at 36 ° C. as the molded product H and the test piece prepared from Sample 4 measured at 65 ° C. as the molded product I.
Thermal conductivity : 5 mm thick test pieces for measuring thermal conductivity were prepared from Samples 1 to 5 which are light diffusion thermal conductive compositions, and each test piece was subjected to rapid thermal conductivity manufactured by Kyoto Electronics Industry Co., Ltd. Thermal conductivity was measured by a thin film measuring method using a total of QTM-500.

[3. Test results]
The light diffusing thermally conductive molded body as the molded body A has a small absolute value of the refractive index difference between the matrix material and the thermally conductive filler at 65 ° C. as small as 0.0059, and a high total light transmittance and low at 65 ° C. It has a haze value and exhibits high thermal conductivity.
The light diffusing thermally conductive molded body, which is the molded body B, has an absolute value of the difference in refractive index between the matrix material and the thermally conductive filler at 100 ° C. of less than 0.0087 and 0.010. It has a transmittance and a low haze value, and exhibits a high thermal conductivity. Compared with the molded product A, it is slightly cloudy and the haze value is increased.

The light diffusing thermally conductive molded body, which is the molded body C, has an absolute value of the refractive index difference between the matrix material and the thermally conductive filler at 100 ° C. of 0.0103, and has a high total light transmittance and high at 100 ° C. It has a haze value and exhibits high thermal conductivity.
The light diffusion thermal conductive molded body, which is the molded body D, has an absolute value of the refractive index difference of 0.0156 at 88 ° C. and a high total light transmittance and high at 88 ° C. It has a haze value and exhibits high thermal conductivity.
The light diffusing thermally conductive molded body, which is the molded body E, has an absolute value of a difference in refractive index of 0.0171 between the matrix material and the thermally conductive filler at 36 ° C., and has a high total light transmittance and high at 36 ° C. It has a haze value and exhibits high thermal conductivity.

The light diffusing thermally conductive molded body, which is the molded body F, has an absolute value of the difference in refractive index between the matrix material and the thermally conductive filler at 100 ° C. of 0.0182, and has a high total light transmittance and high at 100 ° C. It has a haze value and exhibits high thermal conductivity.
The light diffusion thermal conductive molded body, which is the molded body G, has an absolute value of the difference in refractive index between the matrix material and the thermal conductive filler at 100 ° C. of 0.0206. It has a high haze value and a high thermal conductivity. Since the refractive difference is a little larger than that of the molded product F, the value of the total light transmittance is a little as low as 74.9%.

The light diffusing thermally conductive molded body which is the molded body H has an absolute value of the refractive index difference between the matrix material and the thermally conductive filler at 36 ° C. larger than 0.0261 and 0.0250, and a high haze value at 36 ° C. And has a high thermal conductivity, but the total light transmittance is low.
The light diffusing thermally conductive molded body, which is molded body I, has a large refractive index difference of 0.0341 at 65 ° C. between the matrix material and the thermally conductive filler, and has a high haze value at 65 ° C. In addition, although the thermal conductivity is high, the total light transmittance is lower than that of the molded body H.

  As described above, the molded bodies C to G have excellent light diffusibility and light transmittance, but the molded bodies A and B have excellent light transmittance but low haze value. It was inferior. Moreover, although the molded object H and the molded object I were high in haze value and excellent in light diffusibility, the total line transmittance was low and it was inferior to light transmittance.

Claims (7)

A light diffusion heat conductive composition comprising a heat conductive filler in a liquid matrix material mainly composed of a polymer composition, and having both light diffusibility and light transmittance,
Light diffusion heat conduction comprising a matrix material and a thermally conductive filler having a relationship that the difference between the refractive index of the matrix material and the refractive index of the thermally conductive filler is in the range of 0.010 to 0.025 in absolute value. Sex composition.   The light-diffusing thermally conductive composition according to claim 1, wherein the content of the thermally conductive filler is 50% by volume to 70% by volume.   The light diffusive heat conductive composition according to claim 1 or 2, comprising both light diffusivity and light transmissive properties having a total light transmittance and a haze value of more than 70% and less than 100% measured at a thickness of 500 µm. .   The matrix material contains a refractive index adjuster that makes the difference between the refractive index of the polymer composition as the main material and the refractive index of the thermally conductive filler 0.010 to 0.025 in absolute value. The light diffusion thermal conductive composition according to claim 3. A light diffusion heat conductive composition containing a heat conductive filler in a liquid matrix material mainly composed of a polymer composition and having both light diffusibility and light transmittance at a predetermined temperature T (° C.). And
The difference between the refractive index of the matrix material and the refractive index of the thermally conductive filler at a predetermined temperature T is in the range of 0.010 to 0.025 in absolute value,
The following mathematical formula (1)

However, in Formula (1),
n ′ _m ²⁵ : center value of refractive index of matrix material at 25 ° C. α: linear expansion coefficient of matrix material
(dn / dT) _f : Refractive index temperature coefficient of thermally conductive filler n _f ²⁵ : Refractive index of thermally conductive filler at 25 ° C. T: Predetermined temperature, respectively.
The matrix having a relationship in which the difference between the central value n ′ _m ²⁵ of the refractive index at 25 ° C. of the matrix material and the actual refractive index at 25 ° C. of the matrix material is in the range of 0.011 to 0.025 in absolute value. The light-diffusion heat conductive composition of any one of Claims 1-4 which consists of a material and a heat conductive filler.   The light diffusion heat conductive composition according to claim 5, wherein the predetermined temperature T is 50 ° C. to 140 ° C.   The light-diffusion heat conductive molded object which is a solidified body of the light-diffusion heat conductive composition in any one of Claims 1-6.