JP3190078B2 - Refractive index distributed microlens array and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gradient index microlens array using a polymerizable liquid crystal material and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, with the development of optical fiber, photodiode, and semiconductor laser technologies, high integration of optical components has been promoted. In addition, in order to miniaturize and highly integrate the optical lenses connecting them, instead of spherical lenses,
A microlens array using an aspheric lens or a gradient index lens has been commercialized.

[0003] Of these, aspherical lenses require extremely high precision molds and high molding techniques, and the resulting microlens arrays are very expensive. The refractive index distribution type lens is present yet name type irregularities, the optical fiber in this case, the connection between the photodiode and the semiconductor laser is easy. However, glass of inorganic both cases flop <br/> La steel click organic, it is necessary to achieve the refractive index distribution are manufactured by a very cumbersome process.

[0004] That is, specifically, materials having different refractive index, for example, or to incorporated stain to a substrate from ambient or process as or ion exchange is utilized. As a result, there is a disadvantage that reproducibility is poor.

[0005] Sato et al. Of Akita University in Japan Display '89, pp. 396-399, reported that one of the glass substrates with a transparent electrode and the glass substrate with an aluminum electrode was subjected to a horizontal orientation treatment, A substrate in which a large number of holes are formed by etching is used, and a liquid crystal having a positive dielectric anisotropy is sandwiched between the substrates.

[0006] Upon application of an electric field between the electrodes, when the applied voltage is low, acts as a convex lens microlens array, when the applied voltage is high is reported to act as a concave lens micro lens array . This is not to realize the refractive index distribution state by giving a gradient of the composition ratio as in the conventional refractive index distribution type microlens array. This is to generate an asymmetric electric field using an electrode having an asymmetric structure, thereby causing a distortion in the alignment of the liquid crystal.

[0007]

The refractive index distribution type microlens array has an advantage that the performance of the lens can be changed by the applied voltage as described above.
However, there is a disadvantage that the performance as a lens cannot be maintained unless a voltage is constantly applied. Furthermore, since significantly change the refractive index anisotropy of the liquid crystal by the temperature change, even Ru Oh disadvantage that lens performance sensitively varies with the ambient temperature.

[0008]

The present invention SUMMARY OF] has been made to solve the problems as described above, distortion Shi was caused in the arrangement of the liquid crystal external field is applied to the polymerizable liquid crystalline material
Merare, gradient index microlens array This strain is characterized by having a fixed structure by the polymerization unit, and can be polymerized between at least one of the substrate with a pair of transparent electrodes a liquid crystal material sandwiched, the pattern of the pair of electrodes and asymmetric, while applying an electric field between the substrate with the pair of electrodes, and performing polymerization of the polymerizable liquid crystalline material method for producing a gradient index microlens array, and is intended to provide a method of manufacturing a refraction index distribution type micro lens array that polymerizable liquid-crystalline materials you containing 3 to 30 wt% of the crosslinkable compound .

In the present invention, a polymerizable liquid crystal material is used, an external field is applied to the liquid crystal material to cause a distortion in the arrangement of the liquid crystal, and the distortion is fixed by a polymerization means. Thus, once manufactured, the function as a gradient index microlens array is fixed, and there is no need to apply an electric field during use. Moreover, the function as a gradient index microlens array is stably maintained over a relatively wide temperature range.

FIG. 1 is a sectional view of a gradient index microlens array according to the present invention. In FIG. 1, 1 is ITO
(In ₂ O ₃ —SnO ₂ ), a transparent electrode such as SnO ₂ ,
Denotes an opaque electrode of aluminum or the like; 3, 4 denotes a substrate of glass, plastic, or the like; 5 denotes a refractive index distribution layer in which a polymerizable liquid crystal material sandwiched between substrates having both electrodes is polymerized and fixed.

[0011] The electrode used in the present invention comprises a pair of substrates,
At least one is a transparent electrode. The other electrode may be a transparent electrode or an opaque electrode. In the present invention, the pair of electrodes is asymmetric, that is, has a non-identical pattern. During this, so as not provided with an electrode on the portion corresponding to the center of individual microlenses for the transmission of light of one of the electrodes. Usually, an opaque electrode is provided with an opening in a circular shape, a rectangular shape, or the like, and the other transparent electrode is often a solid pattern.

Further, as the electrode-attached substrate, in a case where itself a substrate of electrically conductive, need not greens providing a further electrode on the surface. When the substrate with electrodes is removed after the production, the opaque electrode may be a solid electrode. However, it is advantageous to leave the substrate with the electrode as a protective plate as it is even after manufacture in terms of strength and prevention of deterioration.

The polymerizable liquid crystal material used in the present invention is a liquid crystal compound which is itself a liquid crystal compound, has a functional group polymerizable by light or heat in the molecule, and is fixed at least after polymerization. Some show phases. Further, the compound itself is not a liquid crystal compound, but is a mixture of a compound having a functional group polymerizable by light or heat in the molecule and a liquid crystal compound, and is affected by the liquid crystal compound during polymerization, It may show a liquid crystal phase fixed after polymerization. Of course, a single compound or a composition may be used for these liquid crystal materials, but in general, a composition is often used to obtain desired performance.

The liquid crystal phase in the liquid crystal compound of the present invention may be any of nematic, cholesteric and smectic. The dielectric anisotropy can be used whether it is positive or negative.

The shape of the microlens may be any of a circle, an ellipse, a square, a rectangle, and the like. The size of the microlens is about 5 μm to 1 mm on the short side and about 5 μm to 1 m on the long side. Usually, one of the electrodes is an electrode having an opening of a pattern that matches the shape of the microlens. Of course, when a pair of electrodes are overlapped, the combined pattern of the two (a pattern in which the electrodes overlap) may be a portion outside the microlens. The performance of this microlens also depends on the gap and shape between the electrodes on both substrates. Generally, the larger the shape of the lens, the larger the gap.

[0016] Polymerization of the polymerizable liquid crystal material is carried out by light or heat, row Ukoto with ultraviolet light or visible light irradiation is the simple, preferred because productivity is good. In the present invention, polymerization is performed by applying an external field such as an electric field during the polymerization.
It is preferable to hold the substrate between the electrodes and to polymerize while applying an electric field because the production is easy. In addition, polymerization may be performed by applying a magnetic field. However, the use of an electric field is preferable because the generation of a magnetic field requires an expensive and large-sized apparatus and productivity is not good.

At this time, the polymerizable liquid crystal material should contain 3 to 30% by weight of a crosslinkable compound in order to obtain a stable lens which does not change its performance even when an external field such as an electric field is cut off after polymerization. Is preferred. In order to stabilize the immobilization, the amount of the crosslinkable compound is preferably set to 3 wt% or more,
The reason for setting the content to 30 wt% or less is that the relative amount of the liquid crystalline material decreases and the degree of the refractive index distribution decreases.

As the crosslinkable compound, an ordinary crosslinkable compound containing two or more multiple bonds can be used. The crosslinkable compound itself may exhibit liquid crystallinity, but from the viewpoint of economical efficiency, a non-liquid crystalline crosslinkable compound having two or more functionalities is preferable.

When photo-polymerization of the crosslinkable compound is performed, if the crosslinkable compound has a vinyl bond, radical polymerization may be performed. In the case of having an epoxy bond, it may be carried out by cationic polymerization. As the polymerization initiator,
In the case of radical polymerization, benzoin ether-based, benzophenone-based, acetophenone-based, quaternary ammonium cation / quaternary borate anion salts and the like are used. Triaryl over Rusuruhoniumu salt or the like is used as an acid generator in the case of cationic polymerization.

[0020] Specific examples of the crosslinkable compound having a vinyl bond, poly with polyol polyacrylate, polyester polyacrylate, urethane polyacrylate, epoxy polyacrylate, silicone poly acrylates <br/> DOO, the port re butadiene skeleton There are acrylates, polyacrylates having an isosinual skeleton, polyacrylates having a hydantoin skeleton, and the like.

When an electric field is applied, the applied voltage increases as the gap between the electrodes increases, and the dielectric anisotropy of the liquid crystal compound and whether the target lens of the mylo lens array is a convex lens or a concave lens . , Also change.
Generally, when the dielectric constant of the liquid crystal is positive, a low voltage is required for a convex lens and a high voltage is required for a concave lens, but about 2 to 50 V is usually sufficient.

[0022] may be the alignment treatment of the liquid crystal rather than to the electrode, it is preferable to go to assume a uniform distortion arrangement state when a voltage is applied. The alignment treatment of the liquid crystal may be either a vertical alignment treatment or a horizontal alignment treatment, and may be a so-called hybrid alignment treatment in which one electrode is vertically aligned and the other electrode is horizontally aligned. In the case of horizontal alignment processing, the alignment processing direction may be different between one electrode and the other electrode. As this alignment treatment method, known alignment treatments such as application of a vertical alignment agent, rubbing, and oblique deposition can be used.

For example, when a liquid crystal having a positive dielectric anisotropy is used and the electrodes on both sides are subjected to horizontal alignment processing and the alignment processing directions are matched, the microlens shows polarization dependence. Is the same as the alignment direction of the liquid crystal,
It is preferable to use it by arranging it perpendicular to it.

In the present invention, other monomers, oligomers, polymers and the like may be added to the polymerizable liquid crystal material in order to adjust the refractive index, the operating temperature range and the like. Further, viscosity modifiers thereto, colorants, but it may also be added additives such as dichroic dye.

The polymerizable liquid crystalline material of the present invention includes
As described above, a photocurable material is preferable, but a vinyl photocurable compound is particularly preferable, and an acrylic photocurable compound is particularly preferable . The yo Ri Specifically, terminal cyano group, an alkyl group, there is a straight chain compound having an alkoxy group or the like, for example, as a typical compound, there are compounds represented by the following general formula (1) .

[0026]

Embedded image CH _Two  = CX-CO-OR ¹  -Ph-AB-Ph-R ^Two  (1)

In the general formula (1), X is a fluorine atom, a methyl group or a hydrogen atom, and R ¹ is a group having 1 to ¹ carbon atoms.
15 alkylene group or a -CH ₂ in - oxyalkylene groups obtained by substituting some group to an oxygen atom, Ph is 1,
4 - off Eniren group, A, B each independently 1,4 - off <br/> Eniren group, -CO-O-or -CH ₂ CH ₂ - indicates, and at least one of A and B is 1,4-fe
A vinylene group, R ² is a cyano group, a chlorine atom, a fluorine atom or, optionally a linear alkyl group Moshiku be substituted with a part of the hydrogen atoms are fluorine atom, represents an alkoxy group.

[0028] The above examples are an illustration of a representative compounds, the present invention is not limited thereto, as long as it shows liquid crystallinity, 1,4 - off Enire < br /> emissions group trans-1,4 - or substituted in the other ring, such as shea Kurohekishiren group, bonding group is -CH ₂ O between the ring and the ring
It may be substituted with another bonding group such as-, -CO-, or another hydrogen atom in the ring may be substituted with a halogen atom or a cyano group.

[0029]

EXAMPLE 1 A total of 10 wt% of 2-ethylhexyl acrylate which is an acrylic photocurable monomer and polypropylene glycol diacrylate which is a bifunctional acrylic photocurable oligomer was prepared by the following formula (2) and formula (2). (3), and a liquid crystal monomer total 89 wt% of formula (4), and a photopolymerization initiator 1 wt% were mixed to obtain an uncured solution is a mixture of polymerizable liquid crystalline material.

[0030]

Embedded image

[0031] One of the substrate, a glass substrate with a solid ITO transparent electrode to form a polyvinyl alkenyl alcohol layer, a horizontal alignment treatment by rubbing this, to produce a glass substrate with a transparent electrode. As the other substrate, an aluminum thin film was deposited on a glass substrate, further, a hole of a number of diameter 100μm was formed by etching to form a polyvinyl sulfonyl <br/> alcohol layer, which was a horizontal alignment treatment rubbing A glass substrate with an opaque electrode was manufactured.

The substrates with these two electrodes were arranged so that the orientation treatment directions of both electrodes were parallel, and a cell having a gap of 25 μm was formed via spacer particles.
This cell was filled with the previously prepared uncured solution, and irradiated with high-pressure mercury lamp light for 1 minute while applying an alternating current of 4 V between both electrodes, thereby photocuring.

A polarizing plate was arranged on the obtained device such that the direction of the polarization axis thereof coincided with the alignment treatment direction of the liquid crystal. This shows the performance as a convex lens microlens array, and the performance as a lens hardly changed even when the temperature was 60 ° C.

[0034] In Example 1, except that indicia pressurized exchanges 20V between the electrodes was prepared in the same manner. The obtained element exhibited performance as a concave lens microlens array.

[0035]

According to the present invention, a polymerizable liquid crystal material is used, and an external field is applied thereto to cause a distortion in the arrangement of the liquid crystal, and this distortion is fixed by the polymerization means.
After the manufacture, the function as the gradient index microlens array is fixed. For this reason, the function of the microlens array is exhibited without applying an electric field during use.

Further, or to incorporated stains conventional materials of different refractive index as the substrate from ambient example, or very array regardless of laborious manner or ion exchange as simple as described above Obtained by the method. Therefore, the reproducibility is excellent.

A liquid crystal compound used in a general display device has a large change in refractive index anisotropy when the temperature changes. However, in the present invention, since the liquid crystal phase is fixed in the refractive index distribution layer by polymerization, the change in the refractive index anisotropy of the liquid crystal is small, and the refractive index distribution is stable over a relatively wide temperature range. Maintain the function as a micro lens array.

Further, since the microlens pattern can be easily changed by the electrode pattern, the production of a wide variety of products can be facilitated by changing the electrode pattern by a simple technique called etching. Also, the characteristics of the lens can be changed depending on the strength of an external field such as an applied electric field, which also facilitates multi-product production.

The present invention can be applied to various applications within a range that does not impair the effects of the present invention.

[Brief description of the drawings]

FIG. 1 is a sectional view of a gradient index microlens array according to the present invention.

[Explanation of symbols]

 1: transparent electrode 2: opaque electrode 3, 4: substrate 5: refractive index distribution layer

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yoshinori Hirai 1150 Hazawacho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Asahi Glass Co., Ltd. Examiner at Central Research Laboratory Yasumasa Yokoi (56) References JP-A-3-87720 (JP, A ) Japan Display '89 (1989) p. 396-399 (58) Field surveyed (Int.Cl. ⁷ , DB name) G02B 3/00 C09K 19/00-19/60

Claims (3)

(57) [Claims] 1. A external field to a polymerizable liquid crystal material distortion is made to occur in the applied liquid <br/> sequence of crystallization, this strain is immobilized by Tsu <br/> the polymerization unit structure And a gradient index microlens array comprising: Wherein at least one of sandwiching the polymerizable liquid crystal material between the substrates with a pair of transparent electrodes, and the pattern of the pair of electrodes and asymmetric, between the substrate with the pair of electrodes A method for producing a gradient index microlens array, comprising polymerizing the polymerizable liquid crystalline material while applying an electric field. Wherein said polymerizable liquid material is 3 to 30 wt%
Method for producing a gradient index microlens array according to the 請 Motomeko 2 you containing a crosslinkable compound.