NEAR-INFRARED LIGHT TRANSMITTING BLACK MATERIAL

Abstract

The present invention provides a near-infrared transmitting black material that can sufficiently absorb visible light and sufficiently inhibit the absorption of near-infrared light. Provided is a near-infrared transmitting black material containing an oxazine resin.

Claims

1. A near-infrared transmitting black material comprising an oxazine resin.

2. The near-infrared transmitting black material according to claim 1, wherein the oxazine resin is a naphthoxazine resin.

3. The near-infrared transmitting black material according to claim 1, wherein the black material has a particulate shape with an average particle size of 0.02 m or larger and 10.0 m or smaller.

4. The near-infrared transmitting black material according to claim 1, wherein the black material has an average transmittance of 20% or lower in a visible light region of 400 to 800 nm wavelength and an average transmittance of 60% or higher in a near-infrared region of 900 to 2,500 nm wavelength.

5. A near-infrared transmitting ink comprising the near-infrared transmitting black material according to claim 1.

6. A near-infrared transmitting filter comprising the near-infrared transmitting black material according to claim 1.

Description

DESCRIPTION OF EMBODIMENTS

[0107] Embodiments of the present invention are more specifically described with reference to, but not limited to, examples below.

Example 1

[0108] First, 1.20 g of 1,5-dihydroxynaphthalene (1,5-DHN, available from Tokyo Chemical Industry Co., Ltd.) and 0.98 g of 1,3,5-trimethylhexahydro-1,3,5-triazine (available from Tokyo Chemical Industry Co., Ltd.) were sequentially dissolved in 50 ml of ethanol to prepare a mixed solution in ethanol.

[0109] Next, the obtained mixed solution was stirred under heat at 80 C. for 5.0 hours (rotation rate: 300 rpm). The solution was filtered through a glass filter, and the obtained particles were washed with ethanol three times and vacuum-dried at 50 C. for three hours, followed by vacuum-heating at 200 C. for 12 hours. Thus, naphthoxazine resin particles as a near-infrared transmitting black material were obtained.

[0110] Four parts by weight of the obtained black material was dispersed in 40 parts by weight of polyvinyl butyral resin, and applied to a glass slide to a thickness after drying of 30 m, followed by drying at 100 C. for two hours. Thus, a coating film was obtained.

Example 2

[0111] First, 1.0 g of 1,5-dihydroxynaphthalene (available from Tokyo Chemical Industry Co., Ltd.), 0.5 g of 40% methylamine (available from FUJIFILM Wako Pure Chemicals Co., Ltd.), and 1.0 g of a 37% formaldehyde solution (available from FUJIFILM Wako Pure Chemicals Co., Ltd.) were sequentially dissolved in 500 ml of a mixed solution of isopropanol and water (weight ratio of isopropanol to water=4:1).

[0112] Next, the obtained mixed solution was reacted at 30 C. overnight, and then stirred under heat at 80 C. for 10 hours (rotation rate: 300 rpm). The particles were collected, washed, and vacuum-dried at 50 C. for three hours, followed by heat treatment at 220 C. for 20 hours. Thus, naphthoxazine resin particles as a near-infrared transmitting black material were obtained.

[0113] A coating film was produced as in Example 1, except that the obtained black material was used.

Comparative Example 1

[0114] A coating film was produced as in Example 1, except that carbon black was used.

Evaluation Method

(1) Average Particle Size, CV Value, and Average Sphericity

[0115] The average sphericities were determined by analyzing FE-SEM images of the black materials obtained in the examples and of the carbon black used in the comparative example using image analysis software (WINROOF, Mitani Corporation).

[0116] The standard deviation was calculated for the black materials obtained in the examples. Based on the obtained values, the coefficients of variation (CV value) of the particle size were calculated.

[0117] The sphericities of the black materials obtained in the examples were determined based on the ratio of the smallest diameter to the largest diameter of particles, and the average sphericities were calculated.

(2) Average Transmittance and Lightness L*

[0118] The coating films obtained in the examples and comparative example were subjected to measurement of the reflectance spectra in the visible light region of 400 to 800 nm wavelength and in the near-infrared region of 90 to 2,500 nm wavelength using a spectrophotometer equipped with an integrating sphere (V-670, available from Jasco Corporation). The geometric average of the transmittance in each wavelength range was determined as the average value of the transmittance in each wavelength range. Thus, the average transmittance was determined.

[0119] The coating films obtained in the examples and comparative example were subjected to measurement of lightness values L* in the LAB (L*a*b*) color system using a spectrophotometer equipped with an integrating sphere (V-670, Jasco Corporation) in accordance with JIS Z 8722:2009.

TABLE-US-00001 TABLE 1 Near-infrared transmitting material Evaluation Average CV value Transmittance in visible particle of particle Average light range (%) Transmittance in near-infrared range (%) size size sphericity Wavlength (nm) Wavelength (nm) Material (m) (%) (%) L* 400 550 800 Average 850 950 1200 1800 2400 Average Example 1 Naphthoxazine 5 20 90 9.2 0.2 0.21 5.31 0.64 42.7 51.3 81.5 85.1 63.2 67.4 resin Example 2 Naphthoxazine 0.3 25 95 12.2 0.22 0.85 35 7.4 50 60.2 90.8 90.7 85.6 84.8 resin Comparative Carbon black 0.02 2.96 0.09 0.31 0.71 0.38 0.83 1.02 1.56 2.85 3.89 2.54 Example 1

INDUSTRIAL APPLICABILITY

[0120] The present invention can provide a near-infrared transmitting black material that can sufficiently absorb visible light and sufficiently inhibit the absorption of near-infrared light.