SOLVENT COMPOSITION FOR WELDING OPTICAL MODULE AND CAMERA MODULE USING THE SAME

A solvent composition for welding an optical module includes a first solvent and a second solvent. The first solvent includes at least one solvent selected from a first group having a swelling ratio of 60% or more, and the second solvent includes at least one solvent selected from a second group having a swelling ratio of less than 60%.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 USC 119 (a) of Korean Patent Application No. 10-2023-0085455, filed on Jul. 3, 2023, in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference for all purposes.

BACKGROUND

The following description relates to a solvent composition for welding an optical module and a camera module using the composition.

2. Description of the Background

A camera module may include a lens. For example, a high-resolution camera module may include four or more lenses that are disposed in a lens barrel.

The camera module may include a component to prevent the lens disposed on the lens barrel from being separated. For example, the camera module may include a press-fit ring or adhesive for fixing the lens to the lens barrel.

However, a conventional adhesive for an optical module may be a UV curing adhesive, a heat curing adhesive, or a UV heat curing adhesive that may be significantly expensive per unit gram (g). In addition, curing and shrinkage of the adhesive may cause a change in the MTF of the lens or non-curing of a core, which may increase the defect rate of the camera module.

Typical bonding force (or binding force) between the press-fit ring and the lens barrel when fixing the lens through a press-fit ring is inadequate.

SUMMARY

In one general aspect, a solvent composition for welding an optical module includes a first solvent and a second solvent. The first solvent includes at least one solvent selected from a first group having a swelling ratio of 60% or more, and the second solvent includes at least one solvent selected from a second group having a swelling ratio of less than 60%.

The first solvent may be at least one of methylene chloride (MC) and tetrahydrofuran (THF), and the second solvent may be at least one of ethyl acetate (EA), methyl ethyl ketone (MEK), and acetone (AC).

The first solvent may be THF and the second solvent may be MEK.

The solvent composition may include 70 to 95% by volume of MEK and 5 to 30% by volume of THF.

A camera module includes a lens barrel accommodating a plurality of lenses, and a press-fit ring disposed in the lens barrel to support the plurality of lenses. The solvent composition may be used to couple the press-fit ring to the lens barrel.

In another general aspect, a camera module includes a plurality of lenses, a lens barrel in which an accommodation space for accommodating the plurality of lenses is formed, and a press-fit ring bonded to the lens barrel by a solvent composition including a first solvent selected from a first group having a swelling ratio of 60% or more, and a second solvent selected from a second group having a swelling ratio of less than 60%.

The first solvent may be at least one of methylene chloride (MC) and tetrahydrofuran (THF), and the second solvent may be at least one of ethyl acetate (EA), methyl ethyl ketone (MEK), and acetone (AC).

The first solvent may be THF and the second solvent may be MEK.

The solvent composition may include 70 to 95% by volume of MEK and 5 to 30% by volume of THF.

The plurality of lenses may include a first lens group including a frontmost lens disposed most adjacently to an object, and a second lens group including a rearmost lens disposed most adjacently to an image plane. The lens barrel may include a first accommodation space for accommodating the first lens group and a second accommodation space for accommodating the second lens group.

A gap maintenance member may be disposed between the first lens group and the second lens group.

In another general aspect, a solvent composition for welding an optical module includes a first solvent consisting of at least one solvent selected from a first group having a swelling ratio of 60% or more, and a second solvent consisting of at least one solvent selected from a second group having a swelling ratio of less than 60%.

Throughout the drawings and the detailed description, unless otherwise described, the same reference numerals refer to the same elements. The drawings may not be to scale, and the relative size, proportions, and depiction of elements in the drawings may be exaggerated for clarity, illustration, and convenience.

DETAILED DESCRIPTION

Hereinafter, while examples of the present disclosure will be described in detail with reference to the accompanying drawings, it is noted that examples are not limited to the same.

The camera module described herein may be installed in portable electronic products. For example, the camera module may be installed in a portable phone, laptop, and the like. However, the scope of use of the camera module, according to the present embodiment, is not limited to the electronic devices described above. For example, the camera module may be installed in all electronic devices requiring screen imaging and video recording, such as motion detection, image capture, facial recognition, iris recognition, virtual reality implementation, augmented reality implementation, and the like.

According to an embodiment, a camera module will be described with reference toFIGS.1to3.

A camera module10includes a plurality of lenses, a lens barrel300in which an accommodation space for accommodating the plurality of lenses is formed, and a press-fit ring500.

The lens may be divided into a first lens group100and a second lens group200. However, the configuration of the camera module10is not limited to the configurations described above.

For example, the camera module10may further include a filter (not shown), an image sensor (not shown), and the like. In addition, the camera module10may further include a driving means for driving the lens barrel300in an optical axis or a direction intersecting the optical axis.

The first lens group100may include one or more lenses. For example, the first lens group100may include a frontmost lens110disposed most adjacently to an object.

The frontmost lens110may include an optical portion112and a flange portion114. The optical portion112is configured to exhibit optical performance, and the flange portion114is configured to enable positional alignment of the lens.

For example, the optical portion112may be configured to have positive or negative refractive power, and the flange portion114may be configured to contact an adjacent lens or lens barrel300.

The optical portion112may be exposed externally of the lens barrel300. For example, the optical portion112may be partially or fully exposed through an opening of the lens barrel300, as shown inFIG.1. In contrast, the flange portion114may be configured not to be exposed through the opening of the lens barrel300.

The frontmost lens110may be disposed in an innermost portion of the lens barrel300. The frontmost lens110may contact a plurality of different inner surfaces of a first accommodation space310, to be described later.

For example, an object-side surface of the flange portion114may be in contact with an upper surface312of the first accommodation space310, and an outer peripheral surface of the flange portion114may be in contact with an inner surface314of the first accommodation space310.

Accordingly, the frontmost lens110may be aligned to match an optical axis C of the lens barrel300by being installed in the lens barrel300.

The first lens group100may include a plurality of lenses. For example, the first lens group100may further include one or more lenses in addition to the frontmost lens110.

For reference, the first lens group100, according to the present embodiment, may further include four lenses120,130,140, and150, in addition to the frontmost lens110. However, the number of lenses forming the first lens group100is not limited to five. For example, depending on the optical performance of the camera module10, the first lens group100may be comprised of less than 5 lenses or 6 or more lenses.

The lenses110,120,130,140, and150of the first lens group100may generally have larger diameters from an object side toward an image plane. For example, the second lens120may have a larger diameter than the first lens110(frontmost lens), and the third lens130may have a larger diameter than the second lens120.

However, the positions of the lenses110,120,130,140, and150and the sizes of the lenses are not necessarily proportional. For example, the fourth lens140and the third lens130may be formed to be substantially the same size. Among the lenses of the first lens group100, a lens disposed most adjacently to the second lens group200may generally have the largest diameter. For example, in the present embodiment, the fifth lens150may have a larger diameter than the first to fourth lenses110to140.

The second lens group200may include one or more lenses. For example, the second lens group200may include a rearmost lens280disposed most adjacently to an image plane. The rearmost lens280may include an optical portion282and a flange portion284.

The optical portion282is configured to exhibit optical performance, and the flange portion284is configured to enable positional alignment of the lens. For example, the optical portion282may be configured to have positive or negative refractive power, and the flange portion284may be configured to contact the lens barrel300. An outer peripheral surface of the flange portion284may be configured to be generally parallel to an optical axis C.

The lens barrel300is configured to accommodate the first lens group100and the second lens group200therein. For example, a first accommodation space310and a second accommodation space320may be formed inside the lens barrel300.

The first accommodation space310is configured to accommodate the first lens group100. For example, the first accommodation space310may be formed to have a considerable size to accommodate the lenses110,120,130,140, and150of the first lens group100.

A step may be formed in the first accommodation space310. For example, a plurality of steps may be formed in the first accommodation space310to specify accommodation positions of the first to fifth lenses110to150. These steps may be formed to have different sizes. For example, each of the steps may be formed to substantially match the size of the first to fifth lenses110to150.

The second accommodation space320is configured to accommodate a second lens group200. For example, the second accommodation space320may be formed to accommodate a rearmost lens200of the second lens group200.

The camera module10may further include a gap maintenance member400. The gap maintenance member400may be disposed between the first lens group100and the second lens group200.

For example, the gap maintenance member400may be disposed between the fifth lens150and the rearmost lens200. In this case, the gap maintenance member400may maintain a distance in an optical axis direction between the fifth lens150and the rearmost lens200to be constant.

In addition, the gap maintenance member400may serve to increase the bonding force between the rearmost lens200and the lens barrel300by acting on or transmitting a force in a direction of the image plane to the rearmost lens200.

The camera module10configured as above may improve the bonding force between the lens barrel300and the rearmost lens200so that the phenomenon of the rearmost lens200and other lenses being separated from the lens barrel300due to external impacts may be significantly reduced.

A press-fit ring500is installed to fix the rearmost lens200of the second lens group200and the lens barrel300.

The press-fit ring500may be configured in the form of an annular ring, may be installed in the lens barrel300to press-fit and fix the lens and support a lower edge portion of the lens, and may have a plurality of support portions formed to extend directly below an inner peripheral surface thereof.

The press-fit ring500and the lens barrel300are bonded to each other using solvent welding technology by applying a solvent composition600therebetween.

According to an embodiment of the present disclosure, the solvent composition is used to assemble a lens and a lens barrel in the camera module using a simple and economical method of bonding a thermoplastic resin known as solvent welding technology. In the present disclosure, more specifically, an optimized solvent composition is applied to a bonded area between the press-fit ring and the lens barrel, softened, and then pressed together to bond the press-fit ring and the lens barrel.

Such solvent welding technology has the advantage of bonding quickly through solvent evaporation simply by heating to an appropriate temperature instead of using separate curing equipment such as UV.

Conventionally, acetone (AC) or ethyl acetate (EA) has been used as a welding solvent. When acetone and ethyl acetate are used on a product with a small diameter, it is difficult to secure an adhesive area, and there is a concern that the removal force may be insufficient.

Accordingly, the present disclosure discloses a solvent composition with superior adhesion compared to existing AC and EA so that applicability may be expanded to various models, such as a model with a small diameter or the like.

Taking this into account, in the present disclosure, first, the basic physical properties of a barrel and a press ring resin (e.g., PC series) and candidate organic solvents are evaluated to classify various solvents, and adhesion is evaluated on specimens and products to select a solvent composition for welding an optical module.

Solvent welding technology ultimately improves bonding force through increased fluidity of a polymer chain by a solvent and diffusion and rearrangement of the polymer at an interface. For this reason, selecting an appropriate solvent with high reactivity with a target polymer is a top priority.

To this end, the basic physical properties of the solvent are determined by measuring the swelling ratio of the polymer to the solvent and evaluating the spreadability of the solvent on the surface of the polymer.

It is generally known that the larger an adhesion area and dissolution power, the better the adhesion. To this end, in an embodiment, two or more solvents are mixed instead of a single solvent to secure physical properties, and adhesion evaluation for each composition is performed to select an excellent solvent.

Taking this into account, the solvent composition of an embodiment is composed of two types of solvents. In this case, the first solvent having a high swelling ratio increases swelling solubility of the resin, causing more surface dissolution of the resin, and as a result, when the solvent is removed, miscibility between the two materials increases, thereby improving adhesion.

The first solvent includes at least one solvent selected from a first group having a high swelling ratio, and the solvent of the first group has a swelling ratio of 60% or more.

In addition, the solvent of the first group may be at least one of methylene chloride (MC) and tetrahydrofuran (THF).

The second solvent includes at least one solvent selected from a second group with a low swelling ratio, and the solvent of the second group has a swelling ratio of less than 60%.

In addition, the solvent of the second group may be at least one of ethyl acetate (EA), methyl ethyl ketone (MEK), and acetone (AC).

In the five solvents AC, EA, MEK, MC, and THF, for swelling characteristics, MC>THF>MEK≈EA>AC, and for spreadability, AC>EA≈MEK>THF≈MC.

The solvent composition of this embodiment may include MEK and THF, and may include 70 to 95% by volume of MEK and 5 to 30% by volume of THF.

In this case, when a content of MEK is less than 70% by volume, a surface of a resin to be bonded may whiten, causing a problem with the appearance of the product, and when the content of MEK exceeds 95% by volume, there is little effect in improving adhesion.

A conventional lens and lens barrel are bonded using a heat-cured adhesive using UV.

Specifically, after applying the heat-curing adhesive, the heat-curing adhesive is pre-cured with UV at 3000 mj or less, and then heat-cured at 90° C. for 30 minutes to cure the adhesive. In this case, an adhesive force of 15 kgf or less can be provided.

Acetone is conventionally used as a solvent when using solvent welding technology instead of UV. Specifically, this solvent welding technology is performed by simply applying an acetone solvent to a bonded area and drying the same, and through this process, adhesion of 16 kgf may be provided.

In an embodiment of the present disclosure, the press-fit ring and the lens barrel are fixed using solvent welding technology, and the solvent composition used at this time includes a first solvent and a second solvent, the first solvent includes at least one solvent selected from a first group having a swelling ratio of 60% or more, and the second solvent includes at least one solvent selected from a second group having a swelling ratio of less than 60%.

The solvent composition configured as described above may be applied to an area to which the press-fit ring and the lens barrel are bonded and dried at a temperature within a range of 60 to 90° C. for 20 minutes, thereby obtaining adhesion of 19 kgf.

Hereinafter, it is intended to confirm an excellent effect of the solvent composition of the present disclosure by comparing the solvent composition according to the present disclosure with a conventional case of bonding a solvent using AC.

Test Example 1

To compare adhesion according to solvent characteristics, a swelling ratio and adhesion of flat specimens were measured for five types of solvents, AC, EA, MEK, THF, and MC, and are shown inFIG.4.

Five types of solvents, AC, EA, MEK, THF, and MC, are prepared for the swelling ratio. Depending on the time, 1 ml of each solvent is dispensed into 1 g of polymer pellets and waited for 10, 30, and 60 minutes. Then, the weight of the pellets is measured, and an increase and decrease in the weight before/after waiting are compared so that the swelling ratio is calculated, as shown in Equation 1 below.

The adhesion of the specimen is measured after producing a flat plate and a specimen with a diameter of 4 mm and applying and pressing five types of solvents, respectively. Specifically, 1of a solvent is applied between a contact surface of the specimen and a flat plate under a pressure of 0 to 0.1 kgf, respectively, heated and dried at 90° C. for 20 minutes, and then adhesion of each solvent is measured using a band tester.

Referring toFIG.4, it can be seen that MC and THF, having high swelling characteristics, have high adhesion when a solvent is pre-applied to an adhesive surface and compressed.

On the other hand, it can be seen that MEK, EA, and AC have relatively low swelling characteristics and good spreadability on the surface as compared to other solvents. It can be seen that MEK, EA, and AC show excellent adhesion when divided, as if shooting a water gun into a gap between specimens after compression using jetting equipment. Therefore, a solvent composition obtained by mixing two types of solvents is expected to have better adhesion than a solvent composition containing only one type of solvent.

Test Example 2

To evaluate a lens product, a solvent composition is prepared by mixing THF, which has an excellent swelling ratio, and MEK, which has excellent spreadability, and adhesion to a specimen is measured.

The solvent composition is screened for highly swellable THF at a ratio of 0, 30, 70, and 100% by volume. Then detailed evaluation is performed by changing the content of highly swellable THF to 10 to 50% by volume in the composition composed of THF and MEK.

FIG.5is a graph illustrating a change in adhesion according to an amount of THF in the mixed solvent of THF and MEK. Referring toFIG.5, it can be seen that the relatively lower the content of THF, the better the adhesion, and that the adhesion is relatively most excellent in a composition range containing 5 to 30% by volume of THF.

The removal force for a mixed solvent composition of MEK and THF is measured and compared after actual lens-barrel assembly using a solvent dispenser.

This removal force is obtained by producing a sample using an automatic dispenser, and a solvent is applied under conditions of a stroke of 54%, a line speed of 8 mm/s, and a pressure of 10 kpa. The applied sample is again pressed at 65° C. for 5 seconds at 0.1 kgf, pre-dried, and then secondarily dried at 90° C. for 20 minutes.

A press-fit ring of the sample model is designed to have a gap of −3 μm compared to a barrel. The removal force of the product is measured at a speed of 12 mm/min using a push-pull gauge.

FIG.6is a graph illustrating a comparison of removal force between adhesion using a conventional acetone solvent and adhesion using a mixed solvent of THF and MEK of the present disclosure.

Referring toFIG.6, when using an AC single solvent in the prior art, the removal force is about 11 kgf, and when using a mixed solvent in the case of the present disclosure, the removal force is about 14 kgf. It can be seen that the removal force is excellent when the MEK-THF mixed solvent composition (mixing ratio MEK:THF=9:1) of an embodiment is used compared to the conventional bonding method using an AC single solvent.

Test Example 3

After the adhesion of a lens product, whether a solvent applied through GC-MS analysis remains is evaluated.

Referring toFIG.7, as in an embodiment, after applying a mixed solvent composition of MEK and THF, even after drying at 90° C. for 20 minutes, the mixed solvent remains in a portion to which a mixed solvent applied or inside the lens barrel and is detected under heating conditions at 200° C.

Therefore, as described above, through Test Examples 1 to 3, it can be confirmed that when the press-fit ring and the lens barrel are bonded with a solvent composition in which a first solvent and a second solvent of an embodiment are mixed, excellent adhesion and removal force are obtained.

As set forth above, according to the present disclosure, a solvent composition for welding an optical module may be formed by mixing two types of solvents having different swelling ratios, and by the solvent composition for welding an optical module applied between a press-fit ring and a lens barrel, an effect of reducing a phenomenon of a lens being separated from the lens barrel due to an external impact may be improved.

When the lens is fixed by bonding the press-fit ring and the lens barrel with a solvent composition including first and second solvents of a mixed composition developed in the present disclosure as compared to a conventional acetone solvent, as a result of evaluating adhesion of a product, adhesion may be improved by about 30% as compared to the conventional acetone solvent.

Therefore, if the bonding force between the lens and the lens barrel increases, the drop reliability of an individual lens is improved, and the change in resolution in a subsequent thermal process is reduced so that an effect of reducing a defect rate during a manufacturing process of the camera module may be expected.

An aspect of the present disclosure is to provide a solvent composition for welding an optical module, which can prevent a lens from being separated from a lens barrel by improving the bonding force and removal force between the lens and lens barrel and a camera module using the same.