- Top of Page
The present invention relates to a novel chromene compound, a precursor thereof and use of the chromene compound.
- Top of Page
Photochromism is the reversible function of a certain compound that it changes its color swiftly upon exposure to light including ultraviolet light such as sunlight or light from a mercury lamp and returns to its original color when it is put in the dark by stopping its exposure to light. A compound having this property is called “photochromic compound” and used as a material for photochromic plastic lenses which are photochromic optical articles.
The following properties are required for the photochromic compound used for the above purpose:
(i) the degree of coloration at a visible light range before ultraviolet light is applied (to be referred to as “initial coloration” hereinafter) should be low;
(ii) the degree of coloration upon exposure to ultraviolet light (to be referred to as “color optical density” hereinafter) should be high;
(iii) the speed from the time when the application of ultraviolet light is started to the time when the color optical density reaches saturation (to be referred to as “color development sensitivity” hereinafter) should be high;
(iv) the speed from the stoppage of the application of ultraviolet light to the time when the photochromic compound returns to its original state (to be referred to as “fading speed” hereinafter) should be high;
(v) the repeat durability of this reversible function should be high; and
(vi) the solubility in a monomer composition which will become a host material after curing of the photochromic compound should be high so that its dispersibility in the host material in use becomes high.
It has been desired that the photochromic plastic lenses develop a color of a neutral tint such as grey or brown. What color is developed depends on the photochromic compound as a matter of course, which is a very important factor. When the color is to be adjusted by mixing together a plurality of photochromic compounds, there occur various problems such as a color change at the time of color development and fading (to be referred to as “color shift” hereinafter) due to the different characteristic properties of the photochromic compounds that are mixed together and a color change at the time of deterioration due to the difference in durability. To solve the above problems, a photochromic compound which by itself has two absorption wavelengths at a visible range when developing a color to develop a color of a neutral tint (to be referred to as “double peak compound” hereinafter) is important.
As the double peak compound, there are known a chromene compound represented by the following formula (A) (refer to a pamphlet of International Laid-Open WO2001/19813), a chromene compound represented by the following formula (B) or (C) (refer to a pamphlet of International Laid-Open WO2003/025638), a chromene compound represented by the following formula (D) (refer to a pamphlet of International Laid-Open WO2003/044022) and a chromene compound represented by the following formula (E) (refer to a pamphlet of International Laid-Open WO02005/028465).
DISCLOSURE OF THE INVENTION
- Top of Page
In the field of photochromic plastic lenses, the requirements for photochromic properties, especially high fading speed when a photochromic plastic lens moves from outdoors to indoors and transparency when a user wears a photochromic plastic lens indoors (little initial coloration) are becoming stronger and stronger each year. Therefore, the development of a photochromic compound which satisfies all the above requirements (i) to (vi) at a higher level than the chromene compounds of the prior art is desired. When the color is to be adjusted by mixing together a plurality of photochromic compounds, it is known that a photochromic compound which develops a yellow color is generally inferior in durability to a photochromic compound which develops another color, for example, a blue color. Therefore, a compound which has a higher yellow color optical density (having a maximum absorption wavelength at 430 to 530 nm) than a blue color optical density (having a maximum absorption wavelength at 550 to 650 nm) is desired as the double peak compound (in the double peak compound, the ratio of the yellow color optical density to the blue color optical density may be referred to as “double peak characteristic” hereinafter). In consideration of these characteristic properties, the chromene compounds of the prior art have room for the improvement of the following points.
For example, although the chromene compound represented by the above formula (A) has practical levels of color optical density and double peak characteristic, it has room for improvement as it has a low fading speed. The chromene compounds represented by the above formula (B) (C) and (D) also have room for improvement as they do not have satisfactory double peak characteristic. Further, although the chromene compound represented by the above formula (E) is excellent in double peak characteristic and has practical levels of color optical density and fading speed as it is a compound whose 7-position carbon atom is substituted by a specific aryl group, it has room for improvement as the end portion of its absorption spectrum (to be referred to as “absorption end” hereinafter) goes beyond 420 nm into the visible range with the result of large initial coloration.
Therefore, it is an object of the present invention to provide a novel photochromic compound (chromene compound) which has little initial coloration, high color optical density when it is exposed to light, high color development sensitivity, high fading speed and high durability and exhibits excellent double peak characteristic.
It is another object of the present invention to provide a naphthol compound which is an intermediate for the production of the chromene compound of the present invention.
Other objects and advantages of the present invention will become apparent from the following description.
The inventors of the present invention conducted intensive studies to attain the above objects and found the following fact. Although the double peak characteristic of a chromene compound having an indenonaphthopyran skeleton can be enhanced by increasing the electron donating abilities of the 6-position and 7-position substituents, when the electron donating abilities of the 6-position and 7-position substituents are increased, the fading speed becomes lower, the initial coloration becomes larger and the durability becomes lower in proportion to this.
Then, the inventors thought if the above disadvantage could be improved by adjusting the electron donating abilities of the 6-position and 7-position substituents while retaining the above advantage and investigated the introduction of various substituents.
They made further intensive studies and found that the above objects can be attained by a chromene compound having an indenonaphthopyran skeleton prepared by introducing a hetero ring condensed to the 6-position and the 7-position and further introducing an electron absorbing group onto the hetero ring. The present invention was accomplished based on this finding.
That is, firstly, the present invention is a chromene compound having a skeleton represented by the following formula (1):
wherein Z is a group represented by any one of the following formulas: